U.S. patent application number 13/940749 was filed with the patent office on 2014-01-16 for methods for expansion and analysis of cultured hematopoietic stem cells.
The applicant listed for this patent is WHITEHEAD INSTITUTE FOR BIOMEDICAL RESEARCH. Invention is credited to Harvey F. Lodish, ChengCheng Zhang.
Application Number | 20140017784 13/940749 |
Document ID | / |
Family ID | 37387977 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140017784 |
Kind Code |
A1 |
Zhang; ChengCheng ; et
al. |
January 16, 2014 |
Methods for Expansion and Analysis of Cultured Hematopoietic Stem
Cells
Abstract
Methods and kits for propagating hematopoietic stem cells are
provided. The methods comprise culturing cells in medium comprising
one or more angiopoietin-like proteins, under conditions sufficient
for expansion of HSCs. Angiopoietin-like proteins include
angiopoietin-like protein 2, angiopoietin-like protein 3,
angiopoietin-like protein 4, angiopoietin-like protein 5,
angiopoietin-like protein 7, and microfibrillar-associated
glycoprotein (Mfap4). Methods for identifying hematopoietic stem
cells are provided and isolated hematopoietic stem cells are also
provided.
Inventors: |
Zhang; ChengCheng;
(Arlington, MA) ; Lodish; Harvey F.; (Brookline,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WHITEHEAD INSTITUTE FOR BIOMEDICAL RESEARCH |
CAMBRIDGE |
MA |
US |
|
|
Family ID: |
37387977 |
Appl. No.: |
13/940749 |
Filed: |
July 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12853677 |
Aug 10, 2010 |
8506955 |
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13940749 |
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11438847 |
May 23, 2006 |
7807464 |
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12853677 |
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60753212 |
Dec 22, 2005 |
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60684147 |
May 24, 2005 |
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Current U.S.
Class: |
435/372 ;
435/405 |
Current CPC
Class: |
A61K 2035/124 20130101;
C12N 2501/105 20130101; C12N 2501/125 20130101; C12N 2501/17
20130101; A61P 7/00 20180101; C12N 5/00 20130101; A61P 37/04
20180101; A61P 31/04 20180101; C12N 2500/90 20130101; C12N 2501/145
20130101; A61P 31/18 20180101; A61P 7/06 20180101; C12N 5/0647
20130101; C12N 2501/91 20130101; A61P 7/04 20180101; C12N 2501/113
20130101 |
Class at
Publication: |
435/372 ;
435/405 |
International
Class: |
C12N 5/0789 20060101
C12N005/0789 |
Goverment Interests
GOVERNMENT FUNDING
[0002] This invention was made with support from the United States
government under grant numbers R01 DK 067356-01 and 075/P-IRFT,
awarded by the National Institutes of Health, and the United States
government has certain rights in the invention.
Claims
1-38. (canceled)
39. A kit for propagating hematopoietic stem cells (HSCs) in vitro
comprising: a) medium suitable for culturing one or more cells
comprising an HSC, b) at least one angiopoietin-like protein, and
c) at least one additional growth factor selected from the group
consisting of insulin-like growth factor (IGF), fibroblast growth
factor (FGF), thrombopoietin (TPO), and stem cell factor (SCF).
40-46. (canceled)
47. The kit of claim 39, wherein the angiopoietin-like protein is
selected from the group consisting of angiopoietin-like protein 2,
angiopoietin-like protein 3, angiopoietin-like protein 4,
angiopoietin-like protein 5, angiopoietin-like protein 7, and
Mfap4.
48. The kit of claim 39, wherein when in use, the angiopoietin-like
protein is present in the medium at a concentration of about 0.1
ng/mL to about 500 ng/mL.
49. The kit of claim 39, wherein the angiopoietin-like protein is a
recombinant protein.
50. The kit of claim 39, wherein the kit comprises SCF.
51. The kit of claim 39, wherein when in use, the additional growth
factor is present in the medium at a concentration of about 0.1
ng/mL to about 500 ng/mL.
52. The kit of claim 39, wherein the one or more cells are selected
from the group consisting of bone marrow cells, umbilical cord
blood cells, and fetal liver cells.
53. The kit of claim 39, wherein the one or more cells are human
cells.
54. The kit of claim 39, wherein the one or more cells are primary
cells.
55. The kit of claim 39, further comprising an instruction to
culture the one or more cells for at least five days.
56. A kit for propagating hematopoietic stem cells (HSCs) in vitro
comprising: a) medium suitable for culturing primary cells
comprising an HSC; b) at least one angiopoietin-like protein
selected from the group consisting of angiopoietin-like protein 2,
angiopoietin-like protein 3, angiopoietin-like protein 4,
angiopoietin-like protein 5, angiopoietin-like protein 7, and
Mfap4; and c) at least one additional growth factor selected from
the group consisting of insulin-like growth factor (IGF),
fibroblast growth factor (FGF), thrombopoietin (TPO), and stem cell
factor (SCF).
57. The kit of claim 56, wherein when in use, the angiopoietin-like
protein is present in the medium at a concentration of about 0.1
ng/mL to about 500 ng/mL
58. The kit of claim 56, wherein the angiopoietin-like protein is a
recombinant protein.
59. The kit of claim 56, wherein the kit comprises SCF.
60. The kit of claim 56, wherein when in use, the additional growth
factor is present in the medium at a concentration of about 0.1
ng/mL to about 500 ng/mL
61. The kit of claim 56, wherein the primary cells are selected
from the group consisting of bone marrow cells, umbilical cord
blood cells, and fetal liver cells.
62. The kit of claim 56, wherein the primary cells are human
cells.
63. The kit of claim 56, further comprising an instruction to
culture the one or more cells for at least five days.
64. A method of propagating hematopoietic stem cells (HSCs) in
vitro comprising: (a) providing the kit of claim 39; and (b)
culturing the one or more cells in the medium comprising the
angiopoietin-like protein and the additional growth factor.
65. A method of propagating hematopoietic stem cells (HSCs) in
vitro comprising: (a) providing the kit of claim 56; and (b)
culturing the primary cells in the medium comprising the
angiopoietin-like protein and the additional growth factor.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/853,677, filed Aug. 10, 2010, which is a
continuation of U.S. patent application Ser. No. 11/438,847, filed
May 23, 2006, now U.S. Pat. No. 7,807,464, issued on Oct. 5, 2010,
which claims the benefit of and priority to U.S. Provisional Patent
Application Ser. No. 60/753,212 filed on Dec. 22, 2005 and U.S.
Provisional Patent Application Ser. No. 60/684,147 filed on May 24,
2005, the teachings of all of which are incorporated herein in
their entireties.
BACKGROUND OF THE INVENTION
[0003] The hematopoietic stem cell (HSC) through proliferation and
differentiation gives rise to all of the cells in the hematopoietic
system. Pluripotent HSCs are considered to be ideal candidates for
disease therapy and they serve as attractive target cells for
delivery of genes and gene products. It is desirable to have access
to large amounts of such HSCs; unfortunately, hematopoietic stem
cells are present in extremely low numbers in tissues where they
are found, such as bone marrow and cord blood. Therefore, there is
a need for improved methods of ex vivo cell culture systems capable
of expanding hematopoietic cells, while maintaining stem cell
pluripotency. It is also important to be able to readily identify
cells retaining such pluripotency.
[0004] Difficulties in ex vivo expansion of HSCs have greatly
hampered their clinical utility as well as studies of their
biological properties. The identification of new protein factors
that can stimulate the self-renewal or prevent their apoptosis is
an essential way to increase the number of HSCs, including long
term HSCs (LT-HSCs) in culture.
SUMMARY
[0005] As described herein, angiopoietin-like proteins promote the
expansion of HSCs. As a result of the present invention,
hematopoietic stem cells can be expanded to greater numbers in
vitro.
[0006] The present invention includes methods of propagating
hematopoietic stem cells in vitro comprising culturing one or more
cells in culture medium comprising an angiopoietin-like protein,
wherein at least one of the cells is capable of differentiating
into one or more blood cell types. In an embodiment, a population
of cells that contains stem cells is cultured in a medium that
contains an effective amount of one or more angiopoietin-like
proteins under conditions sufficient for expansion of the cells. In
a more particular embodiment, the method of propagating
hematopoietic stem cells comprises culturing one or more primary
cells for at least five days in a serum free culture medium
comprising an angiopoietin-like protein. The angiopoietin-like
protein can be, for example, angiopoietin-like protein 2,
angiopoietin-like protein 3, angiopoietin-like protein 4,
angiopoietin-like protein 5, angiopoietin-like protein 7, or Mfap4.
In another embodiment, the method of propagating hematopoietic stem
cells comprises culturing at least one primary cell for at least
five days in a serum free culture medium comprising an
angiopoietin-like protein selected from the group consisting of
angiopoietin-like protein 2, angiopoietin-like protein 3,
angiopoietin-like protein 4, angiopoietin-like protein 5,
angiopoietin-like protein 7, or Mfap4, wherein at least one of the
primary cells is capable of differentiating into one or more blood
cell types. In still another embodiment, the method of propagating
hematopoietic stem cells comprises culturing at least one human
cell for at least five days in a serum free culture medium
comprising angiopoietin-like protein 5, wherein at least one of the
human cells is capable of differentiating into one or more blood
cell types.
[0007] Cultured stem cells of the invention include hematopoietic
stem cells, endothelial progenitor cells, bone marrow stromal stem
cells, mesenchymal stem cells, embryonic stem (ES) cells and
skeletal muscle stem cells. Hematopoietic stem cells are
particularly preferred.
[0008] HSCs can be cultured from any cell or population of cells
which contains or has the potential to develop into HSCs. The
population of cells can contain at least 0.1% hematopoietic stem
cells. In an embodiment, the one or more cells are primary cells.
Typically, primary cells are obtained directly from tissue. Methods
of obtaining primary cells are well known in the art.
[0009] In another embodiment, the one or more cells can comprise
total bone marrow, umbilical cord blood cells, mobilized peripheral
blood stem cells, or fetal liver cells. In another embodiment, the
one or more cells comprises side population (SP) cells. In still
another embodiment, the one or more cells comprises an isolated
population of SP Sca1.sup.+ CD45.sup.+ bone marrow cells. In other
embodiments, the population of cells cultured can comprise
CD34.sup.+ umbilical cord blood cells, AC133.sup.- (prominin)
umbilical cord blood cells, CD34.sup.+ mobilized peripheral blood
stem cells, or AC133.sup.+ mobilized peripheral blood stem cells.
In still another embodiment, the one or more cells can be human
bone marrow CD34.sup.+ and AC133.sup.+ cells. Other enriched
populations of hematopoietic stem cells can be used. Embryonic stem
cells can also be used.
[0010] The one or more cells can be cultured for at least five
days. In other embodiments, the one or more cells can be cultured
for at least 10 days, or for at least 2 weeks, or for at least four
weeks.
[0011] The culture medium used for culturing the cells can comprise
serum-free medium. The culture medium can comprise an effective
amount of one or more additional factor(s), such as a cytokine(s).
Suitable factors include insulin-like growth factor (IGF) and at
least one of fibroblast growth factor (FGF), thrombopoietin (TPO),
and stem cell factor (SCF), under conditions sufficient for
expansion of the cells. In certain embodiments, at least two of the
latter factors are included. In further embodiments, at least three
of the latter factors are included.
[0012] In another embodiment, the expanded HSCs retain at least
some of the pluripotency of the initial stem cells or HSCs.
Pluripotency includes stem cell activity or potential, such as the
ability to differentiate into other blood cell types or the ability
to multiply without differentiating.
[0013] In another embodiment, the methods for promoting the
expansion of hematopoietic stem cells further comprises the step of
selecting cells after culture (e.g., cultured cells) that express
at least one positive cell surface marker selected from the group
consisting of Sca-1.sup.+, IGF2-hFC.sup.+, CD31.sup.+, and
Kit.sup.+ and/or do not express at least one negative cell surface
marker selected from the group consisting of PrP, Lin, and CD62L.
In another aspect, the cultured cells express at least two positive
cell surface markers and do not express at least two negative cell
surface markers. In another aspect, the cultured cells express at
least three positive cell surface markers and do not express at
least three negative cell surface markers.
[0014] In another embodiment, the cultured cells express
Sca-1.sup.+, IGF2-hFC.sup.+, CD31.sup.+ and Kit.sup.+ and do not
express PrP, Lin, and CD62L. In another embodiment, the cultured
cells express Sca-1.sup.- and IGF2-hFC.sup.+ and do not express
PrP, Lin, and CD62L. In still another embodiment, the method for
promoting the expansion of hematopoietic stem cells comprises the
step of selecting cells after culture which specifically bind to an
angiopoietin-like protein.
[0015] An embodiment of the invention provides methods for
promoting the expansion of hematopoietic stem cells in an
individual in need of an expanded number of hematopoietic cells,
comprising administering to the individual an angiopoietin-like
protein in an amount effective to promote expansion of
hematopoietic stem cells, thereby promoting expansion of
hematopoietic cells in the individual. In an embodiment for
promoting the expansion of hematopoietic stem cells in an
individual, administration is by infusion.
[0016] In an embodiment, the individual is in need of expanded
numbers of hematopoietic cells due to the presence of a condition
including but not limited to reduced hematopoietic function,
reduced immune function, reduced neutrophil count, reduced
neutrophil mobilization, mobilization of peripheral blood
progenitor cells, sepsis, severe chronic neutropenia, bone marrow
transplants, infectious diseases, leucopenia, thrombocytopenia,
anemia, enhancing engraftment of bone marrow during
transplantation, enhancing bone marrow recovery in treatment of
radiation, chemical or chemotherapeutic induced bone marrow aplasia
or myelosuppression, and acquired immune deficiency syndrome.
[0017] The present invention also provides methods of enhancing
hematopoietic recovery in a mammal that has undergone chemotherapy,
comprising administering to the mammal an amount of an
angiopoietin-like protein effective to promote expansion of
hematopoietic stem cells in the mammal, thereby enhancing the
hematopoietic recovery in the mammal that has undergone
chemotherapy.
[0018] The present invention is drawn to methods of administering
hematopoietic stem cells to an individual. In an embodiment, the
method comprises obtaining hematopoietic stem cells from the
individual or from a donor, culturing the cells in a culture medium
comprising an angiopoietin-like protein, and transplanting the
cultured cells into the individual.
[0019] The present invention also provides methods of treating an
individual in need of a hematopoietic stem cell-based therapy,
comprising removing hematopoietic stem cells from the individual or
from a donor; culturing the cells in a culture medium containing an
amount of an angiopoietin-like protein effective to promote
expansion of hematopoietic stem cells, harvesting the cultured
cells, and transplanting the cultured cells into the
individual.
[0020] The present invention also provides methods of gene delivery
and expression in an individual, comprising removing hematopoietic
stem cells from the individual or from a donor, culturing the cells
in a culture medium containing an amount of an angiopoietin-like
protein effective to promote expansion of hematopoietic stem cells,
introducing DNA into the cultured cells, harvesting the cultured
cells, and transplanting the cultured cells into the
individual.
[0021] Another embodiment of the invention provides methods for
screening for a receptor for an angiopoietin-like protein,
comprising screening a library of candidate proteins or a library
of genes encoding candidate proteins to identify proteins which
bind to the angiopoietin-like protein and/or promote the expansion
of hematopoietic stem cells in culture, wherein a candidate protein
that binds to angiopoietin-like protein is indicative of a receptor
for angiopoietin-like protein.
[0022] The present invention also provides methods of identifying
hematopoietic stem cells. In an embodiment, the method comprises
screening for cells which bind to at least one angiopoietin-like
protein. In another embodiment, the screening for hematopoietic
stem cells further comprises selecting cells expressing at least
one positive cell surface marker and/or not expressing at least one
negative cell surface marker as described above.
[0023] The present invention also includes kits for identifying
hematopoietic stem cells. The kit includes at least one detectably
labeled angiopoietin-like protein. The angiopoietin-like protein
can be labeled with any suitable detectable label such as an
epitope, a fluorescent dye, or a radioactive label. Suitable
epitopes include FLAG tags, myc tags and other epitopes for which
specific antibodies can be made or are available. Suitable
fluorescent dyes include, for example, fluorescein, rhodamine, Cy3,
and Cy5. Suitable radiolabels include, for example, .sup.125I,
.sup.32P, and .sup.35S. Methods for using detectable labels such as
epitope tags, fluorescent dyes, and radiolabels are well known in
the art.
[0024] Kits for propagating hematopoietic stem cells ex vivo (e.g.,
in vitro) are also provided. The kit can comprise medium suitable
for culturing HSCs, one or more angiopoietin-like proteins, and
optionally includes instructions for expanding hematopoietic stem
cells in vitro.
[0025] The various embodiments described herein can be
complimentary and can be combined or used together in a manner
understood by the skilled person in view of the teachings contained
herein.
BRIEF DESCRIPTION OF FIGURES
[0026] FIG. 1 upper panel shows a schematic of the plasmid
expressing the human Angptl2 protein fused to a FLAG epitope at the
C-terminus, and the bottom panel shows a Western blot of the 48 h
conditioned medium of 293T cells transfected by pcDNA3.1(-) (lane
1) or pcDNA3.1(-) encoding FLAG-Angptl2 (lane 2), probed with
antibodies against FLAG epitope.
[0027] FIG. 2 shows micrographs of FACS sorted bone marrow SP
Sca-1.sup.+ CD45.sup.+ cells in various serum-free culture
conditions, with and without Angptl2.
[0028] FIG. 3A is a bar graph showing bar percent repopulation 3
weeks, 4 months, and 9 months after transplant with twenty freshly
isolated CD45.2 bone marrow SP Sca-1.sup.+ CD45.sup.+ cells
cotransplanted with 1.times.10.sup.5 CD45.1 competitors in the
absence of prior culturing (bars 1, 6, and 11) or cultured as
indicated.
[0029] FIG. 3B top panel shows representative FACS plots of
peripheral blood mononuclear cells from one mouse at 9 months
post-transplant (cells from bar 15 of FIG. 3A) (the number in each
quadrant is the percentage of cells in each quadrant); the bottom
panel shows the summary of data from all mice in bars 13 and 15 of
FIG. 3A.
[0030] FIG. 3C top panel shows representative FACS plots of
peripheral blood mononuclear cells from one mouse at 4 months after
a secondary transplantation; the bottom panel shows the summary of
data from all mice at 4 months after a secondary transplantation of
mouse bone marrow represented in bars 8 and 10 of FIG. 3A.
[0031] FIG. 4A shows a silver stain of 16 ng of purified E.
coli-expressed Angptl2 (lane 2), and 2.5 ng of purified
mammalian-expressed FLAG-Angptl2 protein (purified from an
anti-FLAG column, lane 3) fractioned by SDS-PAGE.
[0032] FIG. 4B shows a Western blot of the purified Angptl2 (right
lane) and control (left lane) probed with anti-FLAG antibody.
[0033] FIG. 4C shows a Western blot of the purified Angptl2 (right
lane) and control BSA (left lane) probed with anti-Angptl2 mAb.
[0034] FIG. 5 is a bar graph showing that purified Angptl2 is a
growth factor for HSCs.
[0035] FIG. 6 left panel shows a Western blot of 48 hour
conditioned medium of 293T cells transfected by pcDNA3.1(-) (lane
1), FLAG-hAngptl2 coiled-coil domain (lane 2), or FLAG-hAngptl2
fibrinogen-like domain (lane 3), probed with antibodies against
hAngptl2; the right panel is a bar graph showing percent
repopulation 3 months and 6 months after transplant with twenty
CD45.2 bone marrow SP Sca-1.sup.+ CD45.sup.- cells cultured for 5 d
in serum-free mock-transfected 293T cell conditioned STIF medium
(bars 1 and 6); in the same medium with 100 ng/ml E. coli-expressed
full-length Angptl2 (bars 2 and 7); and in the same medium with 100
ng/ml mammalian-expressed full-length Angptl2 (bars 3 and 8).
[0036] FIG. 7A is a graph showing percent of mice repopulated with
the indicated number of BM SP CD45.sup.+Sca-1.sup.+ cells.
[0037] FIG. 7B is a graph showing percent of mice repopulated with
the indicated number of BM SP CD45.sup.+Sca-1.sup.+ cells after
culturing for 10 d in serum-free conditioned STIF medium containing
100 ng/ml of purified Angptl2.
[0038] FIG. 7C is a graph showing percent of mice repopulated with
the indicated number of BM SP CD45.sup.+Sca-1.sup.+ cells after
culturing for 10 d in serum-free conditioned STIF medium containing
100 ng/ml of purified Angptl3.
[0039] FIG. 8 is a bar graph showing that purified Angptl3,
Angptl5, and Angptl7 are growth factors for hematopoietic stem
cells.
[0040] FIG. 9 is a bar graph showing that Angptl2-coiled coil
domain, Angptl4, and Mfap4 expressed in 293T cell conditioned
medium stimulated the proliferation of hematopoietic stem
cells.
[0041] FIG. 10A left panel shows a silver stain of purified
bacterially-expressed hAngptl7 (lane 2), purified wheat germ in
vitro transcribed GST-hAngptl5 (lane 3), purified
mammalian-expressed hAngptl4 (lane 4), and purified sf21-expressed
mAngptl3 (lane 5) fractioned by SDS-PAGE; the right panel shows a
bar graph of percent repopulation 4 weeks, 3 months, or 6 months
after transplant with twenty CD45.2 bone marrow SP Sca-1.sup.+
CD45.sup.+ cells cultured for 5 d in serum-free unconditioned STIF
medium (bars 1, 6, and 11), or cultured in the same medium with 100
ng/ml purified insect-expressed mAngptl3 (bars 2, 7, and 12), or
cultured in the same medium with 100 ng/ml purified hAngptl4 (bars
3, 8, and 13), or cultured in the same medium with 100 ng/ml
purified GST-hAngptl5 (bars 4, 9, and 14), or cultured in the same
medium with 1 .mu.g/ml purified bacterially-expressed hAngptl7
(bars 5, 10, and 15).
[0042] FIG. 10B left panel shows a Western blot of 48 hour
conditioned medium of 293T cells transfected by pcDNA3.1(-) (lane
1), pcDNA3.1 encoding FLAG-hMfap4 (lane 2), or pcDNA3.1 encoding
FLAG-hFgl1 (lane 3), and probed with an antibody specific for the
FLAG epitope; the right panel shows a bar graph of percent
repopulation 3 months or 6 months after transplant with twenty
CD45.2 bone marrow SP Sca-1.sup.+ CD45.sup.+ cells cultured for 5 d
in serum-free mock transfected conditioned STIF medium (bars 1 and
4), in conditioned STIF medium from 293T cells transfected by
pcDNA3.1 encoding FLAG-hFgl1 (bars 2 and 5), or conditioned STIF
medium from 293T cells transfected by PCDNA3.1 encoding FLAG-hMfap4
(bars 3 and 6).
[0043] FIG. 11A is a bar graph showing average relative expression
of Angptl2 (left panel) or Angptl3 (right panel) mRNA in cells
having the indicated phenotype (FL is fetal liver).
[0044] FIG. 11B is a bar graph showing average relative expression
of Angptl2 mRNA in adult mouse bone marrow hematopoietic cells and
adult mouse bone marrow cells having the indicated phenotype.
[0045] FIG. 11C is a bar graph showing average relative expression
of Angptl3 mRNA in adult mouse bone marrow hematopoietic cells and
adult mouse bone marrow having the indicated phenotype.
[0046] FIG. 12A is a bar graph showing percent repopulation 3 weeks
or 4 months after transplant with freshly isolated adult CD45.2 BM
cells that either bind Angptl2 or not, as indicated; demonstrating
that freshly isolated HSCs bind Angptl2.
[0047] FIG. 12B is a bar graph showing percent repopulation 3 weeks
or 3 months after transplant with adult CD45.2 BM cells cultured in
serum-free medium with SCF, TPO, IGF-2, and FGF-1 for 4 d and that
bind Angptl2 or not, as indicated; demonstrating that 4-day
cultured HSCs bind Angptl2.
[0048] FIG. 13 is a graph showing percent repopulation in NOD/SCID
recipient mice two months after transplant with human cord blood
cells cultured for the indicated number of days in medium
supplemented with the indicated growth factors.
[0049] FIG. 14 is a schematic diagram of hematopoietic stem cell
self renewal and differentiation into different blood cell
types.
[0050] FIG. 15 shows the amino acid sequences for exemplary
angiopoietin-like proteins.
DETAILED DESCRIPTION
[0051] As described herein, freshly isolated HSCs as well as
cultured HSCs bind to angiopoietin-like proteins. In addition, as
described herein, angiopoietin-like proteins promote the expansion
of hematopoietic stem cells. The present invention is directed to
hematopoietic stem cells, methods for propagating or expanding
hematopoietic stem cells, and methods of using the propagated
hematopoietic stem cells.
Ex vivo Cultures of Hematopoietic Stem Cells
[0052] The present invention provides methods for promoting the
expansion of hematopoietic stem cells (HSCs) in culture (e.g., in
vitro or ex vivo). The cell or cells to be cultured can include any
cell that is capable of differentiating into one or more blood cell
types. Exemplary blood cell types are shown in FIG. 14 and include
phagocytic immune cells (e.g., granulocytes), monocytes (e.g.,
macrophage precursor cells), macrophages, eosiniphils,
erythrocytes, platelet forming cells (e.g., megakaryocytes), T
lymphocytes, B lymphocytes, and natural killer (NK) cells. Suitable
cell(s) can also be capable of self renewal, that is, capable of
propagating or increasing in number and remaining at the same
developmental stage as the parent cell.
[0053] Suitable cell(s) can be isolated, for example, from any
known source of hematopoietic stem cells, including, but not
limited to, bone marrow, mobilized peripheral blood (MPB), fetal
liver, and umbilical cord blood. Umbilical cord blood is discussed,
for instance, in Issaragrishi et al., N. Engl. J. Med. 332:367-369
(1995). Bone marrow cells can be obtained from a source of bone
marrow, including but not limited to, ilium (e.g., from the hip
bone via the iliac crest), tibia, femora, vertebrate, or other bone
cavities. Other sources of stem cells include, but are not limited
to, ES cells, embryonic yolk sac, fetal liver, and fetal
spleen.
[0054] The cell or cells can be subjected to methods of further
enrichment for hematopoietic stem cells. Means for isolating
hematopoietic stem cells using specific stem cell markers are known
to those skilled in the art.
[0055] The one or more cells and the hematopoietic cells of the
invention can be derived from any suitable animal, e.g., human,
non-human primates, porcine or murine. In one preferred embodiment,
the cells are human cells.
[0056] For isolation of bone marrow, an appropriate solution can be
used to flush the bone, including, but not limited to, salt
solution, optionally supplemented with fetal calf serum (FCS) or
other naturally occurring factors, in conjunction with an
acceptable buffer. In an embodiment, the buffer is at low
concentration, generally from about 5 to about 25 mM. Convenient
buffers include, but are not limited to, HEPES, phosphate buffers
and lactate buffers. Bone marrow can also be aspirated from the
bone in accordance with conventional techniques.
[0057] Regarding lineage specific markers, the absence or low
expression of lineage specific markers can be identified by the
lack of binding of antibodies specific to the lineage specific
markers, useful in so-called "negative selection". The source of
cells for use in the methods of the present invention can be
subjected to negative selection techniques to remove those cells
that express lineage specific markers and retain those cells which
are lineage negative ("Lin.sup.-"). Lin.sup.- generally refers to
cells which lack markers such as those associated with T cells
(such as CD2, 3, 4 and 8), B cells (such as B220, CD48, CD10, 19
and 20), myeloid cells (such as Mac-1, Gr-1, CD14, 15, 16 and 33),
natural killer ("NK") cells (such as CD244, CD2, 16 and 56), RBC
(such as Ter119, and glycophorin A), megakaryocytes (CD41), mast
cells, eosinophils or basophils. Methods of negative selection are
known in the art. Lineage specific markers also include CD38,
HLA-DR and CD71. As used herein, "Lin.sup.-" refers to a cell
population selected based on the lack of expression of at least one
lineage specific marker.
[0058] Various techniques can be employed to separate the cells by
initially removing cells of dedicated lineage or having a
particular phenotype. Monoclonal antibodies are particularly useful
for identifying markers associated with particular cell lineages,
stages of differentiation, or particular phenotypes. The antibodies
can be attached to a solid support to allow for crude separation.
The separation techniques employed should maximize the retention of
viable cells in the fraction to be collected. Various techniques of
different efficacy can be employed to obtain "relatively crude"
separations. Such separations are up to 10%, usually not more than
about 5%, of the total cells present not having the marker can
remain with the cell population to be retained. In certain
embodiments, not more than about 1% of the total cells present in
the population of retained cells do not have the marker. The
particular technique employed will depend upon efficiency of
separation, associated cytotoxicity, ease and speed of performance,
and necessity for sophisticated equipment and/or technical
skill.
[0059] Procedures for separation can include, but are not limited
to, physical separation, magnetic separation, using antibody-coated
magnetic beads, affinity chromatography, cytotoxic agents joined to
a monoclonal antibody or used in conjunction with a monoclonal
antibody, including, but not limited to, complement and cytotoxins,
and "panning" with antibody attached to a solid matrix, e.g.,
plate, elutriation or any other convenient technique. In certain
embodiments, one uses a high throughput technique to rapidly screen
and separate different cells.
[0060] The use of physical separation techniques include, but are
not limited to, those based on differences in physical (density
gradient centrifugation and counter-flow centrifugal elutriation),
cell surface (lectin and antibody affinity), and vital staining
properties (mitochondria-binding dye rho123 and DNA-binding dye
Hoechst 33342). These procedures are well known to those of skill
in this art.
[0061] Techniques providing accurate and rapid separation include,
but are not limited to, flow cytometry (e.g., fluorescence
activated cell sorting), which can have varying degrees of
sophistication, e.g., a plurality of color channels, low angle and
obtuse light scattering detecting channels, impedance channels,
etc. Cells also can be selected by flow cytometry based on light
scatter characteristics, where stem cells are selected based on low
side scatter and low to medium forward scatter profiles. Cytospin
preparations show the enriched stem cells to have a size between
mature lymphoid cells and mature granulocytes.
[0062] For example, in a first separation step, anti-CD34 can be
labeled with a first fluorochrome, while the antibodies for the
various dedicated lineages, can be conjugated to a fluorochrome
with different and distinguishable spectral characteristics from
the first fluorochrome. While each of the lineages can be separated
in more than one "separation" step, desirably the lineages are
separated at the same time as one is positively selecting for HSCs.
The cells can be selected and isolated from dead cells, by
employing dyes associated with dead cells (including but not
limited to, propidium iodide (PI)). The particular order of
separation is not critical to this invention.
[0063] The cells obtained as described above can be used
immediately or frozen at liquid nitrogen temperatures and stored
for long periods of time, being thawed and capable of being reused.
Once thawed, the cells can be expanded by use of the methods
described herein.
[0064] HSCs can be expanded by culturing one or more cells in an
expansion container and in a volume of a suitable medium. Cells
populations highly enriched in stem cells and methods for obtaining
them are described in WO 95/05843; WO 95/03693 and WO 95/08105. In
a preferred embodiment the one or more cells comprises a population
of cells that is substantially enriched in hematopoietic stem
cells. In another embodiment, the population of cells is
substantially free of stromal cells.
[0065] The cells can be cultured such that the culture well
contains about 1-100 cells per well. Where the population of cells
is bone marrow, the cells can be cultured at a density of about
1.times.10.sup.2 cells to about 1.times.10.sup.7 cells/mL of
medium. In another embodiment, the cells cells can be cultured at a
density of about 1.times.10.sup.5 cells to about 1.times.10.sup.6
cells/mL of medium. In another embodiment, the population of cells
comprises Side Population (SP) bone marrow cells. The SP bone
marrow cells can be cultured at lower density, for example from
about 1.times.10.sup.2 to 5.times.10.sup.3 cells/ml. In a separate
aspect, the population of cells can be derived from mobilized
peripheral blood. The mobilized peripheral blood cells can be
cultured at a density of about 20,000 cells/mL to about 50,000
cells/mL; in another embodiment, the mobilized peripheral blood
cells is cultured at a density of about 50,000 cells/mL.
[0066] Any suitable expansion container, flask, or appropriate tube
such as a 12, 24 or 96 well plate, 12.5 cm.sup.2 T flask or
gas-permeable bag can be used in the method of this invention. Such
culture containers are commercially available from Falcon, Corning
or Costar. As used herein, "expansion container" also is intended
to include any chamber or container for expanding cells whether or
not free standing or incorporated into an expansion apparatus.
[0067] Various media can be used for the expansion of the stem
cells including Dulbecco's MEM, IMDM, X-Vivo 15 (serum-depleted,
Cambrex), RPMI-1640 and StemSpan (Stem Cell Technologies). In
another embodiment, the cell culture medium is serum free. One
serum free medium which can be used in the methods of the invention
is serum free StemSpan (Stem Cell Technologies). In another
embodiment, the medium is supplemented with 10 .mu.g/ml
heparin.
[0068] The media formulations for expansion of HSCs contain
concentrations of one or more angiopoietin-like proteins in a range
from about 0.1 ng/mL to about 500 ng/mL. In another embodiment,
from about 1 ng/mL to about 100 ng/mL of one or more
angiopoietin-like proteins is used. In another embodiment, from
about 10 ng/ml to 50 ng/ml of one or more angiopoietin-like
proteins is used. Other useful concentrations of angiopoietin-like
proteins can be readily determined by one of ordinary skill in the
art using the teachings contained herein.
[0069] In another aspect, in addition to the angiopoietin-like
protein of the invention, the media formulations for expansion of
HSCs are supplemented with cytokines, including but not limited to
fibroblast growth factor (FGF) (e.g. FGF-1 or FGF-2), insulin
growth factor (e.g. IGF-2, or IGF-1), thrombopoietin (TPO), and
stem cell factor (SCF). As indicated above, the concentrations of
cytokines range from about 0.1 ng/mL to about 500 ng/mL. In another
embodiment, from about 1 ng/mL to about 200 ng/mL of a cytokine is
used. In another embodiment, from about 10 ng/ml to 100 ng/ml of a
cytokine is used. In another embodiment, the cytokines for use in
the invention are FGF-1, TPO, IGF-2, and SCF. In still another
embodiment the SCF is present at 10 ng/ml concentration, TPO at 20
ng/ml concentration, IGF-2 at 20 ng/ml concentration and FGF-1 at
10 ng/ml concentration. Other cytokines may be added, alone or in
combination, and include but are not limited to G-CSF, GM-CSF,
IL-1.alpha., and IL-11. Other useful concentrations of cytokines
can be readily determined by one of ordinary skill in the art using
the teachings contained herein.
Transplantation
[0070] The expanded cultured hematopoietic stem cells of the
invention can be used for a variety of applications, including
transplantation, sometimes referred to as cell-based therapies or
cell replacement therapies, such as bone marrow transplants, gene
therapies, tissue engineering, and in vitro organogenesis.
[0071] Hematopoietic progenitor cell expansion for bone marrow
transplantation is a potential application of human bone marrow
cultures. Human autologous and allogeneic bone marrow
transplantation are currently used as therapies for diseases such
as leukemia, lymphoma, and other life-threatening diseases. For
these procedures, however, a large amount of donor bone marrow must
be removed to ensure that there are enough cells for engraftment.
The methods of the present invention circumvent this problem.
Methods of transplantation are known to those skilled in the
art.
[0072] Expanded hematopoietic stem cells are particularly suited
for reconstituting hematopoietic cells in a subject or for
providing cell populations enriched in desired hematopoietic cell
types. This method involves administering by standard means, such
as intravenous infusion or mucosal injection, the expanded cultured
cells to a patient.
[0073] The discovery that cells may be expanded ex vivo and
administered intravenously provides the means for systemic
administration. For example, bone marrow-derived stem cells may be
isolated with relative ease and the isolated cells may be cultured
according to methods of the present invention to increase the
number of cells available. Intravenous administration also affords
ease, convenience and comfort at higher levels than other modes of
administration. In certain applications, systemic administration by
intravenous infusion is more effective overall. In another
embodiment, the stem cells are administered to an individual by
infusion into the superior mesenteric artery or celiac artery. The
cells may also be delivered locally by irrigation down the
recipient's airway or by direct injection into the mucosa of the
intestine.
[0074] After isolating the cells, the cells can be cultured for a
period of time sufficient to allow them to expand to desired
numbers, without any loss of desired functional characteristics.
For example cells can be cultured from 1 day to over a year. In
another embodiment, cells are cultured for 3 to 30 days. In another
embodiment, cells are cultured for 4 to 14 days. In yet another
embodiment, cells can be cultured for at least 7 days.
[0075] Between 10.sup.5 and 10.sup.13 cells per 100 kg person are
administered per infusion. In another embodiment, about
1.times.10.sup.8 to about 5.times.10.sup.12 cells are infused
intravenously per 100 kg person. In another embodiment, between
about 1.times.10.sup.9 and 5.times.10.sup.11 cells are infused
intravenously per 100 kg person. For example, dosages such as
4.times.10.sup.9 cells per 100 kg person and 2.times.10.sup.11
cells can be infused per 100 kg person.
[0076] In some embodiments, a single administration of cells is
provided. In other embodiments, multiple administrations are used.
Multiple administrations can be provided over periodic time periods
such as an initial treatment regime of 3 to 7 consecutive days, and
then repeated at other times.
[0077] With respect to cells as administered to a patient, an
effective amount may range from as few as several hundred or fewer
to as many as several million or more. In specific embodiments, an
effective amount may range from 10.sup.3 to 10.sup.8. It will be
appreciated that the number of cells to be administered will vary
depending on the specifics of the disorder to be treated, including
but not limited to size or total volume/surface area to be treated,
as well as proximity of the site of administration to the location
of the region to be treated, among other factors familiar to the
medicinal biologist.
[0078] The terms effective period (or time) and effective
conditions refer to a period of time or other controllable
conditions (e.g., temperature, humidity for in vitro methods),
necessary or preferred for an agent or pharmaceutical composition
to achieve its intended result.
[0079] The term pharmaceutically acceptable carrier (or medium),
which may be used interchangeably with the term biologically
compatible carrier or medium, refers to reagents, cells, compounds,
materials, compositions, and/or dosage forms which are, within the
scope of sound medical judgment, suitable for use in contact with
the tissues of human beings and animals without excessive toxicity,
irritation, allergic response, or other complication commensurate
with a reasonable benefit/risk ratio. As described in greater
detail herein, pharmaceutically acceptable carriers suitable for
use in the present invention include liquids, semi-solid (e.g.,
gels) and solid materials (e.g., cell scaffolds). As used herein,
the term biodegradable describes the ability of a material to be
broken down (e.g., degraded, eroded, dissolved) in vivo. The term
includes degradation in vivo with or without elimination (e.g., by
resorption) from the body. The semi-solid and solid materials may
be designed to resist degradation within the body
(non-biodegradable) or they may be designed to degrade within the
body (biodegradable, bioerodable). A biodegradable material may
further be bioresorbable or bioabsorbable, e.g., it may be
dissolved and absorbed into bodily fluids (water-soluble implants
are one example), or degraded and ultimately eliminated from the
body, either by conversion into other materials or by breakdown and
elimination through natural pathways.
[0080] Several terms are used herein with respect to
transplantation therapies, also known as cell-based therapies or
cell replacement therapy. The terms autologous transfer, autologous
transplantation, autograft and the like refer to treatments wherein
the cell donor is also the recipient of the cell replacement
therapy. The terms allogeneic transfer, allogeneic transplantation,
allograft and the like refer to treatments wherein the cell donor
is of the same species as the recipient of the cell replacement
therapy, but is not the same individual. A cell transfer in which
the donor's cells have been histocompatibly matched with a
recipient is sometimes referred to as a syngeneic transfer. The
terms xenogeneic transfer, xenogeneic transplantation, xenograft
and the like refer to treatments wherein the cell donor is of a
different species than the recipient of the cell replacement
therapy.
[0081] The expanded hematopoietic cells can be used for
reconstituting the full range of hematopoietic cells in an
immunocompromised host following therapies such as, but not limited
to, radiation treatment and chemotherapy. Such therapies destroy
hematopoietic cells either intentionally or as a side-effect of
bone marrow transplantation or the treatment of lymphomas,
leukemias and other neoplastic conditions, e.g., breast cancer.
[0082] Expanded hematopoietic cells are also useful as a source of
cells for specific hematopoietic lineages. The maturation,
proliferation and differentiation of expanded hematopoietic cells
into one or more selected lineages may be effected through
culturing the cells with appropriate factors including, but not
limited to, erythropoietin (EPO), colony stimulating factors, e.g.,
GM-CSF, G-CSF, or M-CSF, SCF, interleukins, e.g., IL-1, -2, -3, -4,
-5, -6, -7, -8, -13, etc., or with stromal cells or other cells
which secrete factors responsible for stem cell regeneration,
commitment, and differentiation.
Drug Discovery
[0083] Expanded hematopoietic cells of the invention are useful for
identifying culture conditions or biological modifiers such as
growth factors which promote or inhibit such biological responses
of stem cells as self-regeneration, proliferation, commitment,
differentiation, and maturation. In this way one may also identify,
for example, receptors for these biological modifiers, agents which
interfere with the interaction of a biological modifier and its
receptor, and polypeptides, antisense polynucleotides, small
molecules, or environmental stimuli affecting gene transcription or
translation.
[0084] For example, the present invention makes it possible to
prepare relatively large numbers of hematopoietic stem cells for
use in assays for the differentiation of stem cells into various
hematopoietic lineages. These assays may be readily adapted in
order to identify substances such as factors which, for example,
promote or inhibit stem cell self-regeneration, commitment, or
differentiation.
[0085] The invention provides methods to identify receptors for the
angiopoietin-like proteins. Receptors for these orphan ligands have
not yet been identified.
[0086] Accordingly, the invention provides methods for screening
for a receptor for an angiopoietin-like protein, comprising
screening a library of candidate proteins or a library of genes
encoding candidate proteins to identify proteins which bind to the
angiopoietin-like protein and/or promote the expansion of
hematopoietic stem cells in culture. In an embodiment, a library of
candidate genes is introduced into and expressed in cells that do
not normally bind to the angiopoietin-like protein of interest.
These cells can then be exposed to one or more angiopoietin-like
proteins. Cells that bind to the angiopoietin-like protein and/or
expand upon exposure to the angiopoietin-like protein are
indicative of cells that contain an angiopoietin-like protein
receptor. The cells that bind or expand in the presence of the
angiopoietin-like protein can be isolated, and the transfected gene
can be isolated from the cells.
Gene Cloning Strategies
[0087] One may also use the expanded cells of the invention to
identify and clone genes whose expression is associated with
proliferation, commitment, differentiation, and maturation of stem
cells or other hematopoietic cells, e.g., by subtractive
hybridization or by expression cloning using monoclonal antibodies
specific for target antigens associated with these biological
events or characteristic of a hematopoietic cell type.
Gene Delivery and Expression
[0088] As described above hematopoietic stem cells are also
important targets for gene delivery and expression in a subject.
One such embodiment is sometimes referred to as gene therapy.
[0089] According to the invention, the cultured expanded cells can
be further genetically altered prior to reintroducing the cells
into an individual for gene therapy, to introduce a gene whose
expression has therapeutic effect on the individual. Methods for
introducing genes into the cultured cells are provided in detail
below.
[0090] In some aspects of the invention, individuals can be treated
by supplementing, augmenting and/or replacing defective and/or
damaged cells with cells that express a therapeutic gene. The cells
may be derived from cells of a normal matched donor or stem cells
from the individual to be treated (i.e., autologous). By
introducing normal genes in expressible form, individuals suffering
from such a deficiency can be provided the means to compensate for
genetic defects and eliminate, alleviate or reduce some or all of
the symptoms.
[0091] Expression vectors may be introduced into and expressed in
autologous or allogeneic expanded hematopoietic cells, or the
genome of cells may be modified by homologous or non-homologous
recombination by methods known in the art. In this way, one may
correct genetic defects in an individual or provide genetic
capabilities naturally lacking in stem cells. For example, diseases
including, but not limited to, .beta.-thalassemia, sickle cell
anemia, adenosine deaminase deficiency, recombinase deficiency, and
recombinase regulatory gene deficiency may be corrected in this
fashion. Diseases not associated with hematopoietic cells may also
be treated, e.g., diseases related to the lack of secreted proteins
including, but not limited to hormones, enzymes, and growth
factors. Inducible expression of a gene of interest under the
control of an appropriate regulatory initiation region will allow
production (and secretion) of the protein in a fashion similar to
that in the cell which normally produces the protein in nature.
[0092] Similarly, one may express in expanded hematopoietic cells a
ribozyme, antisense RNA or protein to inhibit the expression or
activity of a particular gene product. Drug resistance genes
including, but not limited to, the multiple drug resistance (MDR)
gene, may also be introduced into cells, e.g., to enable them to
survive drug therapy. For hematotrophic pathogens, such as HIV or
HTLV-I, and HTLV II, the cells can be genetically modified to
produce an antisense RNA, ribozyme, or protein which would prevent
the proliferation of a pathogen in hematopoietic stem cells or
differentiated cells arising from the stem cells. One may also
disable or modulate the expression of a particular genetic sequence
by methods known in the art, including, but not limited to,
directly substituting, deleting, or adding DNA by homologous
recombination or indirectly by antisense sequences.
Transduction of Hematopoietic Stem Cell Cultures
[0093] The expanded hematopoietic stem cells of the invention can
be genetically modified. The introduction of the gene into the
hematopoietic stem cell can be by standard techniques, e.g.
infection, transfection, transduction or transformation. Examples
of modes of gene transfer include e.g., naked DNA, CaPO.sub.4
precipitation, DEAE dextran, electroporation, protoplast fusion,
lipofection, cell microinjection, and viral vectors,
adjuvant-assisted DNA, gene gun, catheters, etc. In another
embodiment, a viral vector is used.
[0094] Polynucleotides are inserted into vector genomes using
methods well known in the art. For example, insert and vector DNA
can be contacted, under suitable conditions, with a restriction
enzyme to create complementary ends on each molecule that can pair
with each other and be joined together with a ligase.
Alternatively, synthetic nucleic acid linkers can be ligated to the
termini of restricted polynucleotide. These synthetic linkers
contain nucleic acid sequences that correspond to a particular
restriction site in the vector DNA. Additionally, an
oligonucleotide containing a termination codon and an appropriate
restriction site can be ligated for insertion into a vector
containing, for example, some or all of the following: a selectable
marker gene, such as the neomycin gene for selection of stable or
transient transfectants in mammalian cells; enhancer/promoter
sequences from the immediate early gene of human CMV for high
levels of transcription; transcription termination and RNA
processing signals from SV40 for mRNA stability; SV40 polyoma
origins of replication and ColE1 for proper episomal replication;
versatile multiple cloning sites; and T7 and SP6 RNA promoters for
in vitro transcription of sense and antisense RNA. Other means are
well known and available in the art.
[0095] Modification of hematopoietic stem cells can comprise the
use of an expression cassette created for either constitutive or
inducible expression of the introduced transgene. Such an
expression cassette can include regulatory elements such as a
promoter, an initiation codon, a stop codon, and a polyadenylation
signal. It is necessary that these elements be operable in the stem
cells or in cells that arise from the stem cells after infusion
into an individual. Moreover, it is necessary that these elements
be operably linked to the nucleotide sequence that encodes the
protein such that the nucleotide sequence can be expressed in the
stem cells and thus the protein can be produced. Initiation codons
and stop codons are generally considered to be part of a nucleotide
sequence that encodes the protein.
[0096] A variety of promoters can be used for expression of the
transgene. Promoters that can be used to express the gene are well
known in the art. Promoters include cytomegalovirus (CMV)
intermediate early promoter, a viral LTR such as the Rous sarcoma
virus LTR, HIV-LTR, HTLV-1 LTR, the simian virus 40 (SV40) early
promoter, E. coli lac UV5 promoter and the herpes simplex tk virus
promoter. For example, one can use a tissue specific promoter, i.e.
a promoter that functions in some tissues but not in others. Such
promoters include EF2 responsive promoters, etc. Examples of
promoters that may be used to cause expression of the introduced
sequence in specific cell types include Granzyme A for expression
in T-cells and NK cells, the CD34 promoter for expression in stem
and progenitor cells, the CD8 promoter for expression in cytotoxic
T-cells, and the CD11b promoter for expression in myeloid
cells.
[0097] Regulatable promoters can be used. Such systems include
those using the lac repressor from E. coli as a transcription
modulator to regulate transcription from lac operator-bearing
mammalian cell promoters (Brown, M. et al., Cell, 49:603-612
(1987)), those using the tetracycline repressor (tetR) (Gossen, M.,
and Bujard, H., Proc. Natl. Acad. Sci. USA 89:5547-5551 (1992);
Yao, F. et al., Human Gene Therapy, 9:1939-1950 (1998); Shockelt,
P., et al., Proc. Natl. Acad. Sci. USA, 92:6522-6526 (1995)). Other
systems include FK506 dimer, VP16 or p65 using astradiol, RU486,
diphenol murislerone or rapamycin. Inducible systems are available
from Invitrogen, Clontech and Ariad. Systems using a repressor with
the operon can be used in the invention. Regulation of transgene
expression in target cells represents a critical aspect of gene
therapy. For example, the lac repressor from Escherichia coli can
function as a transcriptional modulator to regulate transcription
from lac operator-bearing mammalian cell promoters (M. Brown et
al., Cell, 49:603-612 (1987); Gossen and Bujard (1992); M. Gossen
et al., Natl. Acad. Sci. USA, 89:5547-5551 (1992)) combined the
tetracycline repressor (tetR) with the transcription activator
(VP16) to create a tetR-mammalian cell transcription activator
fusion protein, tTa (tetR-VP16), with the tetO-bearing minimal
promoter derived from the human cytomegalovirus (hCMV) major
immediate-early promoter to create a tetR-tet operator system to
control gene expression in mammalian cells. Yao and colleagues (F.
Yao et al., Human Gene Therapy, supra) demonstrated that the
tetracycline repressor (tetR) alone, rather than the tetR-mammalian
cell transcription factor fusion derivatives can function as potent
trans-modulator to regulate gene expression in mammalian cells when
the tetracycline operator is properly positioned downstream for the
TATA element of the CMVIE promoter. One particular advantage of
this tetracycline inducible switch is that it does not require the
use of a tetracycline repressor-mammalian cells transactivator or
repressor fusion protein, which in some instances can be toxic to
cells (M. Gossen et al., Natl. Acad. Sci. USA, 89:5547-5551 (1992);
P. Shockett et al., Proc. Natl. Acad. Sci. USA, 92:6522-6526
(1995)), to achieve its regulatable effects.
[0098] The effectiveness of some inducible promoters increases over
time. In such cases one can enhance the effectiveness of such
systems by inserting multiple repressors in tandem, e.g. TetR
linked to a TetR by an IRES. Alternatively, one can wait at least 3
days before screening for the desired function. While some
silencing may occur, it is minimized given the large number of
cells being used, for example if at least 1.times.10.sup.4 to about
1.times.10.sup.7 cells are used, the effect of silencing is
minimal. One can enhance expression of desired proteins by known
means to enhance the effectiveness of this system. For example,
using the Woodchuck Hepatitis Virus Posttranscriptional Regulatory
Element (WPRE). See Loeb, V. E., et al., Human Gene Therapy
10:2295-2305 (1999); Zufferey, R., et al., J. of Virol.
73:2886-2892 (1999); Donello, J. E., et al., J. of Virol.
72:5085-5092 (1998).
[0099] Examples of polyadenylation signals useful to practice the
present invention include but are not limited to human collagen I
polyadenylation signal, human collagen II polyadenylation signal,
and SV40 polyadenylation signal.
[0100] The exogenous genetic material that includes the transgene
operably linked to the regulatory elements may remain present in
the cell as a functioning cytoplasmic molecule, a functioning
episomal molecule or it may integrate into the cell's chromosomal
DNA. Exogenous genetic material may be introduced into cells where
it remains as separate genetic material in the form of a plasmid.
Alternatively, linear DNA, which can integrate into the chromosome,
may be introduced into the cell. When introducing DNA into the
cell, reagents, which promote DNA integration into chromosomes, may
be added. DNA sequences, which are useful to promote integration,
may also be included in the DNA molecule. Alternatively, RNA may be
introduced into the cell.
[0101] Selectable markers can be used to monitor uptake of the
desired gene into the hematopoietic stem cells of the invention.
These marker genes can be under the control of any promoter or an
inducible promoter. These are well known in the art and include
genes that change the sensitivity of a cell to a stimulus such as a
nutrient, an antibiotic, etc. Genes include those for neo, puro,
and tk, multiple drug resistance (MDR), etc. Other genes express
proteins that can readily be screened for such as green fluorescent
protein (GFP), blue fluorescent protein (BFP), luciferase, and
LacZ.
[0102] The HSC cells can be transduced with a therapeutic gene. For
example, the transduction can be via a viral vector such as a
retroviral vector (e.g. as described in for example, WO 94/29438,
WO 97/21824 and WO 97/21825) or a pox viral vector. When
transduction is ex vivo, the transduced cells are subsequently
administered to the recipient. Thus, the invention encompasses
treatment of diseases amenable to gene transfer into HSCs, by
administering the gene ex vivo or in vivo by the methods disclosed
herein. For example, diseases including, but not limited to, .beta.
thalassemia, sickle cell anemia, adenosine deaminase deficiency,
recombinase deficiency, recombinase regulatory gene deficiency,
etc. can be corrected by introduction of a therapeutic gene. Other
indications of gene therapy are introduction of drug resistance
genes to enable normal stem cells to have an advantage and be
subject to selective pressure during chemotherapy. Suitable drug
resistance genes include, but are not limited to, the gene encoding
the multidrug resistance (MDR) protein.
[0103] Diseases other than those associated with hematopoietic
cells can also be treated by genetic modification, where the
disease is related to the lack of a particular secreted product
including, but not limited to, hormones, enzymes, interferons,
growth factors, or the like. By employing an appropriate regulatory
initiation region, inducible production of the deficient protein
can be achieved, so that production of the protein will parallel
natural production, even though production will be in a different
cell type from the cell type that normally produces such protein.
It is also possible to insert a ribozyme, antisense or other
message to inhibit particular gene products or susceptibility to
diseases, particularly hematolymphotropic diseases.
[0104] As used herein, therapeutic gene can be an entire gene or
only the functionally active fragment of the gene capable of
compensating for the deficiency in the patient that arises from the
defective endogenous gene. Therapeutic gene also encompasses
antisense oligonucleotides or genes useful for antisense
suppression and ribozymes for ribozyme-mediated therapy.
Therapeutic genes that encode dominant inhibitory oligonucleotides
and peptides as well as genes that encode regulatory proteins and
oligonucleotides also are encompassed by this invention. Generally,
gene therapy will involve the transfer of a single therapeutic gene
although more than one gene may be necessary for the treatment of
particular diseases. The therapeutic gene can be a normal, i.e.
wild-type, copy of the defective gene or a functional homolog. In a
separate embodiment, the therapeutic gene is a dominant inhibiting
mutant of the wild-type. More than one gene can be administered per
vector or alternatively, more than one gene can be delivered using
several compatible vectors. Depending on the genetic defect, the
therapeutic gene can include the regulatory and untranslated
sequences. For gene therapy in human patients, the therapeutic gene
will generally be of human origin although genes from other closely
related species that exhibit high homology and biologically
identical or equivalent function in humans may be used, if the gene
product does not induce an adverse immune reaction in the
recipient. For example, a primate insulin gene whose gene product
is capable of converting glucose to glycogen in humans would be
considered a functional equivalent of the human gene. The
therapeutic gene suitable for use in treatment will vary with the
disease. For example, a suitable therapeutic gene for treating
sickle cell anemia is a normal copy of the globin gene. A suitable
therapeutic gene for treating SCID is the normal ADA gene.
General Considerations
[0105] For each of the embodiments described herein, a number of
variations can be made as described below, without departing from
the scope of the invention.
[0106] The term "about" in the context of numerical values and
ranges refers to values or ranges that approximate or are close to
the recited values or ranges such that the invention can perform as
intended, such as having a desired rate, amount, degree or extent
of stem cell activity, as is apparent from the teachings contained
herein. Thus, this term encompasses values beyond those simply
resulting from systematic error.
[0107] Angiopoietin-like protein (Angptl) can be any member of a
family of secreted glycosylated proteins that are similar in
structure to angiopoietins (Oike et al., Int. J. Hematol. 80:21-8
(2004)). Similar to angiopoietins, angiopoietin-like proteins
contain an N-terminal coiled-coil domain and a C-terminal
fibrinogen-like domain. Unlike angiopoietins, angiopoietin-like
proteins do not bind to the tyrosine kinase receptor Tie2.
Angiopoietin-like proteins include angiopoietin-like proteins 2, 3,
4, 5, 6, and 7. Angiopoietin-like proteins also include
microfibrillar-associated glycoprotein 4 (Mfap4), and analogs and
equivalents thereof. Angptl2 has been described by Kim, I. et al. J
Biol Chem 274, 26523-8 (1999)). In addition, angiopoietin-like
proteins are available commercially (R&D Systems, Abnova Corp).
Angiopoietin-like proteins 2, 3, 4, 5, 7, and Mfap4 are
preferred.
[0108] Exemplary angiopoietin-like proteins are provided, for
example in GenBank as Accession Number AAH12368 (human Angptl2
precursor; SEQ ID NO: 3) Accession Number AAH58287 (human Angptl3
precursor; SEQ ID NO: 4) Accession Number AAH23647 (human Angptl4;
SEQ ID NO: 5) and Accession Number AAH49170 (human Angptl5; SEQ ID
NO: 6). SEQ ID NOs: 3 through 6 are shown in FIG. 15. Other
suitable angiopoietin-like proteins share at least 60% sequence
homology with any one of SEQ ID NOs: 4 to 6. In other embodiments,
suitable angiopoietin-like proteins share at least 70% or at least
80% or at least 90% sequence homology with SEQ ID NOs: 4 to 6. An
exemplary sequence for Angptl7 is found in GenBank Accession No.
AAH01881. An exemplary sequence for Mfap4 is found in GenBank
Accession No. NP.sub.--002395. The exemplary sequences of Angptl
proteins having the GenBank Accession Nos. provided above are
hereby incorporated by reference. In addition to
naturally-occurring Angptl sequences, the skilled artisan will
further appreciate that suitable Angptl proteins include those
proteins that have changes in the naturally occurring amino acid
sequence wherein the altered Angptl sequence retains functional
ability of the Angptl protein. Suitable alterations include changes
to or elimination of non-essential amino acid residues as well as
conservative amino acid changes (e.g., replacing an amino acid
residue with an amino acid residue having a similar side
chain).
[0109] Suitable equivalents for angiopoietin-like protein include
proteins and polypeptides having similar biological activity to
these factors as wild-type or purified angiopoietin-like proteins
(e.g., recombinantly produced). Suitable analogs of
angiopoietin-like proteins include fragments retaining the desired
activity and related molecules. One preferred analog is a fragment
of the angiopoietin-like protein containing the coiled coil domain.
For example, the coiled coil domain of angiopoietin-like protein 2.
As shown herein, the coiled coil domain stimulates HSC expansion.
Another analog is the fibrinogen-like domain. Fragments of Angptls
such as the coiled-coil domain and the fibrinogen-like domain may
be easier to express and to purify compared to full-length protein.
Molecules capable of binding the corresponding angiopoietin-like
protein receptor and initiating one or more biological actions
associated with angiopoietin-like protein binding to its receptor
are also within the scope of the invention.
[0110] The angiopoietin-like protein can be naturally produced or
can be produced by expressing a gene encoding the angiopoietin-like
protein in a suitable host using any suitable expression method.
The host can be, for example, bacteria, yeast, or cell culture. The
cell culture can be, for example, insect cell culture, or mammalian
cell culture. The angiopoietin-like protein can be glycosylated. In
another embodiment, the angiopoietin-like protein is glycosylated
in the same or substantially the same manner as the naturally
occurring angiopoietin-like protein.
[0111] As described herein, hematopoietic stem cells have the
ability to differentiate into any of several types of blood cells,
including red blood cells, white blood cells, including lymphoid
cells and myeloid cells. As described herein, HSCs include
hematopoietic cells having long-term engrafting potential in vivo.
Long term engrafting potential (e.g., long term hematopoietic stem
cells) can be determined using animal models or in vitro
models.
[0112] Animal models for long-term engrafting potential of
candidate human hematopoietic stem cell populations include the
non-obese diabetic/severe combined immunodeficiency mouse
(NOD/SCID) model, the SCID-hu bone model (Kyoizumi et al. (1992)
Blood 79:1704; Murray et al. (1995) Blood 85(2) 368-378) and the in
utero sheep model (Zanjani et al. (1992) J. Clin. Invest. 89:1179).
For a review of animal models of human hematopoiesis, see Srour et
al. (1992) J. Hematother. 1:143-153 and the references cited
therein. An in vitro model for stem cells is the long-term
culture-initiating cell (LTCIC) assay, based on a limiting dilution
analysis of the number of clonogenic cells produced in a stromal
co-culture after 5 to 8 weeks (Sutherland et al. (1990) Proc. Nat'l
Acad. Sci. 87:3584-3588). The LTCIC assay has been shown to
correlate with another commonly used stem cell assay, the
cobblestone area forming cell (CAFC) assay, and with long-term
engrafting potential in vivo (Breems et al. (1994) Leukemia
8:1095).
[0113] As used herein, expansion or propagation includes any
increase in cell number. Expansion includes, for example, an
increase in the number of hematopoietic stem cells over the number
of HSCs present in the cell population used to initiate the
culture. Expansion can also include increased survival of existing
cells, such as hematopoietic stem cells. The term survival refers
to the ability to continue to remain alive or function.
[0114] The cell or cells used to inoculate the cell culture may be
derived from any source including bone marrow, both adult and
fetal, cytokine or chemotherapy mobilized peripheral blood, fetal
liver, bone marrow or umbilical cord blood. Isolated fractions of
cells can be used. For example, a purified "side population" (SP)
cells obtained from bone marrow or other sources can be used. Other
enriched populations of HSCs can also be used. Methods for
isolating enriched populations of HSCs are known to those in the
art, e.g. methods for obtaining SP cells are described in Goodell
et al., J. Exp. Med. 183, 1797-806 (Apr. 1, 1996).
[0115] Separation of stem cells from a cell population can be
performed by any number of methods, including cell sorters, (e.g.,
fluorescence activated cell sorters) magnetic beads, and packed
columns. Exemplary of a highly enriched stem cell population is a
population having the CD34.sup.+Thy.sup.-1.sup.+LIN.sup.- phenotype
as described in U.S. Pat. No. 5,061,620. A population of this
phenotype will typically have an average CAFC frequency of
approximately 1/20 (Murray et al. (1995) supra; Lansdorp et al., J.
Exp. Med. 177:1331 (1993)). It will be appreciated by those of
skill in the art that the enrichment provided in any stem cell
population will be dependent both on the selection criteria used as
well as the purity achieved by the given selection techniques.
Methods for isolating highly enriched populations of hematopoietic
stem cells are further provided in U.S. patent application Ser. No.
5,681,559. The population of cells can be from any suitable animal.
The cells can be derived from a mammal. Suitable mammals include
human, non-human primate, cow, horse, dog, cat, mouse and the like.
In an embodiment, the cells are human cells, in still another
embodiment, the cells are murine cells.
[0116] The method of the invention can be used to stimulate the
expansion of any stem cells which expand in the presence of an
angiopoietin-like protein, including other types of adult stem
cells such as endothelial progenitor cells (Shi, Q. et al. (1998),
Blood. 92, 362-367), bone marrow stromal stem cells (Owen, M.
(1988), J. Cell Science Supp. 10, 63-76), mesenchymal stem cells
(Pittenger, M. F. and Marshak, D. R. (2001), Marshak, D. R.,
Gardner, D. K., and Gottlieb, D. eds. Cold Spring Harbor, New York:
Cold Spring Harbor Laboratory Press 349-374), and skeletal muscle
stem cells (Gussoni, E., et al. (1999), Nature. 401, 390-394),
embryonic stem cells, as well as others. In another embodiment, the
stem cells are endothelial progenitor cells, which are believed to
share the same precursor--hemangioblasts--as HSCs.
[0117] As used herein, the term cytokine refers to any one of the
numerous factors that exert a variety of effects on cells, for
example, inducing growth or proliferation or preventing cell death.
Non-limiting examples of additional cytokines which may be used in
combination in the practice of the present invention include,
interleukin-2 (IL-2), interleukin 3 (IL-3), interleukin 6 (IL-6)
including soluble IL-6 receptor, interleukin 12 (IL12), G-CSF,
granulocyte-macrophage colony stimulating factor (GM-CSF),
interleukin 1 alpha (IL-1.alpha.), interleukin 11 (IL-11),
MIP-1.alpha., leukemia inhibitory factor (LIF), and flt3 ligand.
The present invention also includes culture conditions in which one
or more cytokine is specifically excluded from the medium.
Cytokines are commercially available from several vendors such as,
for example, Amgen (Thousand Oaks, Calif.), R & D Systems
(Minneapolis, Minn.) and Immunex (Seattle, Wash.).
[0118] Cytokines useful to promote expansion of hematopoeitic stem
cells in methods of the invention include fibroblast growth factor
(FGF) (e.g. FGF-1 or FGF-2), insulin growth factor (e.g. IGF-2, or
IGF-1) thrombopoietin (TPO), and stem cell factor (SCF).
Accordingly, in another embodiment, the media includes at least two
of FGF, IGF, TPO and SCF or analogs and equivalents thereof.
Equivalents thereof include molecules having similar biological
activity to these factors (i.e. FGF, TPO, IGF and SCF) as wild-type
or purified cytokines (e.g., recombinantly produced). Analogs
include fragments retaining the desired activity and related
molecules. For example, TPO is a ligand of the mp1 receptor, thus
molecules capable of binding the mp1 receptor and initiating one or
more biological actions associated with TPO binding to mp1 are also
within the scope of the invention. An example of a TPO mimetic is
found in Cwirla et. al., Science 276:1696 (1997).
[0119] Culturing includes incubating cells in a suitable medium in
vitro. It is understood that the descendants of a cell grown in
culture may not be completely identical (either morphologically,
genetically, or phenotypically) to the parent cell. Suitable media
that can be used for culturing HSCs are known to those in the art.
Illustrative media include HEPES, Dulbecco's MEM, IMDM RPMI-1640,
and StemSpan (Stem Cell Technologies) that can be supplemented with
a variety of different nutrients, heparin, antibiotics, growth
factors, cytokines, etc. Suitable conditions comprise culturing at
33.degree. to 39.degree. C., and preferably around 37.degree. C.
The effect of oxygen concentration on culturing HSCs is known in
the art, for example, see Cipolleschi et al. (1993), Blood
82:2031-7. HSCs can be cultured in an oxygen concentration of 1 to
10%. In another embodiment, the oxygen concentration is 1 to 5%,
for example, 1% oxygen. In another embodiment, the HSCs are
cultured under hypoxic conditions. Media can be replaced throughout
the culture period. In another embodiment, half of the medium is
replaced twice per week with fresh media. The cells can be cultured
from 3 to 30 days. In another embodiment, the population of cells
including HSCs is cultured for at least four weeks. In another
embodiment, the population of cells including HSCs is cultured for
up to two weeks. In another embodiment, the population of cells
including HSCs is cultured for 7 to 14 days. In another embodiment,
the population of cells including HSCs is cultured for 10 days.
[0120] An effective amount is an amount sufficient to effect
beneficial or desired results. An effective amount can be
administered in one or more administrations. For purposes of this
invention, an effective amount of the angiopoietin-like protein
and/or cytokine used herein is an amount that is sufficient to
promote expansion of hematopoietic stem cells. In another
embodiment, an effective amount of the various cytokines
individually may be from about 0.1 ng/mL to about 500 ng/mL. In
another embodiment, from about 1 ng/mL to about 200 ng/mL can be
used. In another embodiment, from about 10 ng/ml to 100 ng/ml of
the cytokines can be used.
[0121] An isolated or purified population of cells is substantially
free of cells and materials with which it is associated in nature.
For example, isolated hematopoietic stem cells comprise a
population of cells that is at least 50% hematopoietic stem cells,
or at least 70% hematopoietic stem cells, or at least 80%
hematopoietic stem cells. In yet another embodiment, an isolated or
purified population of hematopoietic stem cells comprises at least
90% hematopoietic stem cells, or is 100% hematopoietic stem cells.
Substantially free of stromal cells can comprise a cell population
which, when placed in a culture system as described herein, does
not form an adherent cell layer.
[0122] A subject or individual is a vertebrate. In an embodiment,
the individual is a mammal. Mammals include, but are not limited
to, humans, non-human primates, mice, cows, horses, dogs, cats and
the like. In a preferred embodiment, the mammal is a human.
[0123] The expanded hematopoietic cells of the invention can be
genetically modified. As used herein, a genetic modification can
include any addition, deletion or disruption to the nucleotide
sequence of a cell. The methods of this invention are intended to
encompass any method of gene transfer into hematopoietic stem
cells, including but not limited to viral mediated gene transfer,
liposome mediated transfer, transformation, transfection and
transduction, e.g., viral mediated gene transfer such as the use of
vectors based on DNA viruses such as adenovirus, adeno-associated
virus and herpes virus, as well as retroviral based vectors. Other
non limiting examples of vectors include non-viral vectors such as
DNA/liposome complexes, and targeted viral protein DNA complexes.
To enhance delivery of non viral vectors to a cell, the nucleic
acid or proteins can be conjugated to antibodies or binding
fragments thereof which bind cell surface antigens, e.g.,
Sca-1.sup.+, IGF2-hFC.sup.+, and CD31.sup.+. Where freshly isolated
HSCs are used, additional suitable surfaced markers include
endoglin.sup.- and CD150.sup.+. Liposomes that also comprise a
targeting antibody or fragment thereof can be used in the methods
of this invention.
[0124] As used herein, the terms transgene, heterologous gene,
exogenous genetic material, exogenous gene, and nucleotide sequence
encoding the gene are used interchangeably and are meant to refer
to genomic DNA, cDNA, synthetic DNA and RNA, mRNA and antisense DNA
and RNA which is introduced into the hematopoietic stem cell. The
exogenous genetic material may be heterologous or an additional
copy or copies of genetic material normally found in the individual
or animal. When cells are to be used as a component of a
pharmaceutical composition in a method for treating human diseases,
conditions or disorders, the exogenous genetic material that is
used to transform the cells may also encode proteins selected as
therapeutics used to treat the individual and/or to make the cells
more amenable to transplantation.
[0125] A viral vector is defined as a recombinantly produced virus
or viral particle that comprises a polynucleotide to be delivered
into a host cell, either in vivo, ex vivo or in vitro. Examples of
viral vectors include retroviral vectors such as lentiviral
vectors; adenovirus vectors; adeno-associated virus vectors and the
like. In aspects where gene transfer is mediated by a retroviral
vector, a vector construct refers to the polynucleotide comprising
the retroviral genome or part thereof, and a therapeutic gene.
[0126] The following example is not intended to limit the present
invention in any way.
EXAMPLE
Materials and Methods
[0127] Animals
[0128] C57 BL/6 CD45.2 and CD45.1 mice were purchased from the
Jackson Laboratory or the National Cancer Institute and were
maintained at the Whitehead Institute animal facility. All animal
experiments were performed with the approval of M.I.T. Committee on
Animal Care.
[0129] FACS Sorting
[0130] Donor bone marrow cells were isolated from 8 to 10 week old
C57BL/6 CD45.2 mice. To sort SP Sca-1.sup.+ CD45.sup.+ cells, adult
mouse bone marrow SP cells (stained as previously described (Zhang,
C. C. & Lodish, H. F. Blood 103, 2513-21 (2004) and Zhang, C.
C. & Lodish, H. F. Blood 105, 4314-20 (2005)) were further
stained with anti-Sca-1-PE and anti-CD45-FITC followed by cell
sorting on a MoFlo.RTM. sorter.
[0131] To sort cells that bind or that do not bind to Angptl2,
1.times.10.sup.6 bone marrow cells were resuspended in 1 ml
conditioned medium, containing .about.1 .mu.g/ml FLAG-Angptl2 or
FLAG-hFc-Angptl2 as determined by Western blotting, at 4.degree. C.
for 30 min, followed by staining with APC-anti-FLAG M2 or anti-hFc
IgG1-PE antibody, respectively. The conditioned medium from
mock-transfected cells was used as control.
[0132] DNA Array Experiments and Analyses
[0133] Total RNA and cRNA were prepared for hybridization to
Affymetrix U74Bv2 and U74Cv2 mouse chips according to the
manufacturer's instructions. Briefly, total RNA was isolated with
TRIzol. 15 .mu.g of total RNA was used for first strand and second
strand cDNA synthesis, followed by in vitro transcription using
Ambion T7 MegaScript Kit to produce biotinylated cRNAs. Fragmented
cRNAs were then hybridized to Affymetrix U74Bv2 and U74Cv2 mouse
chips at 45.degree. C. for 16 h. Arrays were washed, stained, and
scanned. Microarray data was analyzed by Microarray Suite.
Background elements which were not detected in the array of fetal
liver CD3.sup.+ cell samples (defined as perfect match
hybridization not significantly different from mismatch control
signal intensity according to Microarray Suite analysis) were
filtered out. An arbitrary raw value of 50 was allocated for genes
whose expression levels were undetectable or whose scan readouts
were below 50 in arrays of splenic CD3.sup.+ or fetal liver
Gr-1.sup.+ cell samples, in order to facilitate calculation of the
fold changes. Array measurements for all samples were then
normalized with arrays hybridized with cRNAs prepared from the
control cells by using the median of the hybridization signals of
all genes. Transcripts in fetal liver CD3.sup.+ cells that had a
normalized value >2.0 were selected. For each candidate
transcript, its refseq nucleotide ID was retrieved from the
Affymetrix data center, followed by transfer into the Refseq
protein sequence ID. The protein sequence was then obtained using
batch entrez from the NCBI Entrez database. The signal peptides
were predicted using the SignalP web server (on the world wide web
at cbs.dtu.dk/services/SignalP/), based on both Neural networks and
Hidden Markov models (Nielsen, H., Engelbrecht, J., Brunak, S.
& von Heijne, G. Protein Eng 10, 1-6 (1997), and Bendtsen, J.
D., Nielsen, H., von Heijne, G. & Brunak, S. J Mol Biol 340,
783-95 (2004)). Candidate proteins with signal peptides expressed
in fetal liver CD3.sup.+ cells at a level greater than two-fold
that of adult CD3.sup.+ and fetal liver Gr-1.sup.+ cells were
selected for further study.
[0134] Production of Coiled-Coil Domain and Fibrinogen-Like Domain
of Angptl2
[0135] The DNA encoding human Angptl2 fused with FLAG peptide
sequence at the c terminus was constructed as Flag-Angptl2. Human
Angptl2 and Pro 100-Lys 330 of human IgG1 Fc sequences were linked
by a DNA sequence encoding IEGRMD linker peptide (SEQ ID NO.: 1) to
form Angptl2-hFc. The whole fragment was inserted into pcDNA3.1,
downstream of CMV promoter. The plasmid was transfected into 293T
cells using lipofectamine 2000 (Invitrogen) and conditioned medium
at 48 hour after transfection was collected. The conditioned medium
with about 1 .mu.g/ml of IGF-2-hFc determined by western blotting
was used in the subsequent staining of bone marrow cells.
[0136] Similar to constructing FLAG-hAngptl2, a cDNA encoding the
coiled-coil domain or fibrinogen-like domain of human Angptl2
fragments was generated. The former contained hAngptl2 amino acids
Arg 1-Lys 249 and the latter Arg 1-Pro 76 fused to Arg 276-His 493.
Both were fused at the C-terminus with a FLAG epitope. FLAG tagged
human Fgl1 or human Mfap4 were also constructed with a FLAG fused
at the C-terminus of the encoded proteins. These plasmids were
transfected into 293T cells and the conditioned medium were
collected similar to the procedure for producing FLAG-Angptl2.
[0137] Western Blots
[0138] Purified proteins or crude proteins in conditioned medium
were analyzed by electrophoresis on 4 to 12% NuPage Bis-Tris
polyacrylamide gels (Invitrogen), and proteins were electroblotted
onto nitrocellulose membranes. The membranes were probed with the
horseradish peroxidase-conjugated anti-FLAG M2 monoclonal antibody
(Sigma; at 1:5000 dilution) or a combination of human
Angptl2-specific primary monoclonal antibodies (in FIG. 1: 1
.mu.g/ml of clone 239829; in FIG. 15A: 1 .mu.g/ml of 239809.11,
239813.111, 239816.111, 239819.111, 239829.111, 239830.11,
239833.11, 239834.11, and 239835.111, all gifts from R&D
Systems), incubated with the horseradish peroxidase-conjugated
goat-anti-mouse antibody (at 1:2000 dilution) and detected by
chemiluminescence with the ECL kit (Amersham, Arlington Heights,
Ill.).
[0139] Real Time PCR
[0140] Total RNA was isolated from indicated fetal liver or bone
marrow cell populations. First-strand cDNA was synthesized using
SuperScript II RT (Invitrogen). Samples were analyzed in triplicate
25 .mu.l reactions (300 nM of primers, 12.5 .mu.l of Master mix),
which was adapted from the standard protocol provided in SyBR Green
PCR Master Mix and RT-PCR Protocol provided by Applied Biosystems.
Primers were purchased from Qiagen (QT00151179 for Angptl2 and
QT00110824 for Angptl3). The default PCR protocol was used on an
Applied Biosystems Prism 7000 Sequence Detection System. The mRNA
level of Angptl2 and Angptl3 in each population was normalized to
the level of 18S RNA transcripts present in the same sample.
[0141] Angiopoietin-Like Proteins
[0142] FLAG-hAngptl2, the coiled-coil domain of hAngptl2,
FLAG-tagged fibrinogen-like domain of hAngptl2, FLAG-hAngptl4,
FLAG-hFgl1, and FLAG-hMfap4, were all produced by transient
transfection of 293T cells using Lipofectamine 2000 (Invitrogen).
After transfection, the cells were cultured overnight in IMDM with
10% FBS, and then washed with IMDM before being cultured in
serum-free StemSpan medium (StemCell Technology) for another 24 h.
The conditioned medium was harvested and used in experiments in
FIGS. 1, 2, and 5b. Medium from mock-transfected cells was always
used as a negative control. Serum-free conditioned medium cultured
mock-transfected 293T cells for 4 h before addition of purified
Angptl2 or Angptl3 was used in the experiments in FIG. 3. To purify
FLAG-Angptl2 and FLAG-Angptl4, the corresponding
plasmid-transfected 293T cells were cultured in IMDM with 10% FBS
for 48 h or 72 h and the conditioned medium was collected for
anti-FLAG affinity purification.
[0143] Purified mouse angiopoietin-like protein 3 (mAngptl3) was
produced in sf21 cells using a baculovirus expression system, and
was a gift from R&D Systems. GST-hAngptl5, a fusion protein of
GST and human angiopoietin-like protein 5 (hAngptl5) and produced
by a cell-free wheat germ in vitro transcription/translation
system, was purchased from Abnova Corporation, Taiwan.
Bacterially-expressed hAngptl2 and hAngptl7 were gifts from R&D
Systems.
[0144] Production of Tagged-Angptl2 and other FLAG-Tagged
Proteins
[0145] The cDNA encoding human Angptl2 (Kim, I. et al. J Biol Chem
274, 26523-8 (1999)) fused with a FLAG peptide sequence (as
FLAG-hAngptl2) or with Pro 100-Lys 330 of human IgG1 Fc sequence
followed by FLAG (as FLAG-hFc-hAngptl2) at the C-terminus was
constructed. The DNA was inserted into the pcDNA3.1 (-) vector
(Invitrogen) downstream of the CMV promoter. Plasmids were
transfected into 293T cells using lipofectamine 2000 (Invitrogen)
and the serum-containing conditioned medium was collected at 48 h
and 72 h after transfection.
[0146] Purification of FLAG-Angptl2 and FLAG-Angptl4
[0147] Serum-free conditioned medium as detailed above was
harvested after 48-72 h from FLAG-hAngptl2 or FLAG-hAngptl4
transfected 293T cells. One tablet/50 ml of the Complete Protease
Inhibitor Cocktail (Roche), 5 .mu.g/ml PMSF, and 100 mM NaCl were
added, and the medium was applied to an anti-FLAG epitope
immunoaffinity column (Anti-FLAG M2 affinity Gel, Sigma), using 500
.mu.l of resin per 500 ml of conditioned medium. The column was
subsequently washed 10 times with a total of 100 volumes of TBS (50
mM Tris, pH 7.4, 150 mM NaCl) and the FLAG-hAngptl2 or
FLAG-hAngptl4 was eluted with 0.1 mg/ml FLAG peptide (N-DYKDDDDK-C;
SEQ ID NO.: 2) dissolved in TBS.
[0148] Cell Culture
[0149] Twenty BM SP Sca-1.sup.+ CD45.sup.+ cells isolated from 6 to
9 or 8 to 10 week old C57BL/6 CD45.2 mice were plated in 100 or 160
.mu.l of StemSpan serum-free medium (StemCell Technologies)
supplemented with 10 .mu.g/ml heparin (Sigma), 10 ng/ml mouse SCF,
20 ng/ml mouse TPO, 20 ng/ml mouse IGF-2 (all from R&D
Systems), and 10 ng/ml human FGF-1 (Invitrogen), with or without
the indicated amounts of angiopoietin-like proteins. In some
experiments, the cells were plated in one well of a U-bottom
96-well plate (3799; Corning). As indicated in the individual
experiments and detailed above, some of these proteins had been
purified, and others were added from the conditioned medium of
transfected 293T cells. Medium from mock-transfected cells was
always used as a negative control. After 3 to 10 d of culture as
indicated, the cells were harvested for competitive
transplantation. Unconditioned serum-free medium supplemented with
10 .mu.g/ml heparin, 10 ng/ml mouse SCF, 20 ng/ml mouse TPO, 20
ng/ml mouse IGF-2, and 10 ng/ml human FGF-1 is termed unconditioned
STIF medium, and the conditioned medium collected from 293T cells
which was then supplemented with the above cytokines is termed
conditioned STIF medium. For the purpose of competitive
transplantation, cells from at least 6 culture wells were pooled
and mixed with competitor cells before the indicated numbers of
cells were transplanted into each mouse.
[0150] Competitive Reconstitution Analysis
[0151] The indicated numbers of CD45.2 donor cells were mixed with
1.times.10.sup.5 or 2.times.10.sup.5 freshly isolated CD45.1
competitor bone marrow cells, and the mixture injected
intravenously via the retro-orbital route into each of a group of 6
to 9 week old CD45.1 mice previously irradiated with a total dose
of 10 Gy. To measure reconstitution of transplanted mice,
peripheral blood was collected at the indicated times
post-transplant and the presence of CD45.1.sup.+ and CD45.2.sup.+
cells in lymphoid and myeloid compartments were measured as
described (Zhang, C. C. & Lodish, H. F. Blood 103, 2513-21
(2004) and Zhang, C. C. & Lodish, H. F. Blood 105, 4314-20
(2005)). Briefly, peripheral blood cells were collected by
retro-orbital bleeding, followed by lysis of red blood cells and
staining with anti-CD45.2-FITC, and anti-CD45.1-PE, or
anti-Thy1.2-PE (for T-lymphoid lineage), anti-B220-PE (for
B-lymphoid lineage), anti-Mac-1-PE, anti-Gr-1-PE (cells costaining
with anti-Mac-1 and anti-Gr-1 were deemed the myeloid lineage), or
anti-Ter119-PE (for erythroid lineage) monoclonal antibodies (BD
Pharmingen). The "Percent repopulation" shown in all Figures except
FIGS. 1c and 1d was based on the staining results of
anti-CD45.2-FITC and anti-CD45.1-PE. In all cases FACS analysis of
the above listed lineages was also performed to confirm
multilineage reconstitution. Calculation of CRUs in limiting
dilution experiments was conducted using L-Calc software (StemCell
Technologies) (Zhang, C. C. & Lodish, H. F. Blood 105, 4314-20
(2005)).
[0152] Primary Human Cells
[0153] Primary human cord blood cells were purchased from Cambrex
(Poietics.TM. Mononuclear cells from Human Cord Blood, Cat
#2C-150A). Cells were plated at 10.sup.6 cells/ml of StemSpan
serum-free medium (StemCell Technologies) supplemented with 10
.mu.g/ml heparin (Sigma), 10 ng/ml mouse SCF, 20 ng/ml mouse TPO,
20 ng/ml mouse IGF-2 (all from R&D Systems), and 10 ng/ml human
FGF-1 (Invitrogen), and with 100 ng/ml Angptl3 or Angptl5. Medium
volume was increased by adding fresh medium at day 5, 8, 12, and 15
to maintain cell densities at 5.times.10.sup.5 to
1.5.times.10.sup.6 cells/ml.
[0154] Transplant into NOD/SCID Mice
[0155] Cultured progeny from human mononuclear cord blood cells
were collected at the indicated days and injected into sub-lethally
irradiated (350 rad) NOD-SCID mice (purchased from Jackson). Two
months after transplantation, bone marrow nucleated cells from
transplanted animals were analyzed by flow cytometry for the
presence of human CD45.sup.+ cells. Mice were considered to be
positive for human HSC engraftment when at least 0.1% CD45.sup.-
human cells were detected among mouse bone marrow cells.
Results
[0156] Fetal Liver CD3.sup.+ Cells Express Angptl2 and Angptl3
[0157] Secreted or membrane proteins that are specifically
expressed in E15 mouse fetal liver CD3.sup.+ cells but not in two
cell populations--adult CD3.sup.+ cells and fetal liver Gr-1.sup.+
cells--that do not support HSC maintenance or expansion in culture
were identified by microarray analysis (Table 1).
TABLE-US-00001 TABLE 1 FLCD3.sup.+ SpnCD3.sup.+ FLGr-1.sup.+ Fold
Fold (raw) (raw) (raw) (1)/(2) (1)/(3) Name GI NP (1) (2) (3)
(Normalized) (Normalized) claudin 13 10048432 NP_065250 4184.2 26.6
10.7 96.5 96.5 RIKEN cDNA 21313426 NP_084345 1774.3 21.2 8.7 42.3
42.3 4432416J03 chemokine 12963823 NP_076274 936.2 18.7 8.0 20.7
20.7 (C--X--C motif) ligand 7 angiopoietin-like 31560520 NP_036053
583.2 4.2 5.8 13.8 13.8 2 popeye domain 11612497 NP_071713 581.6
4.5 3.7 9.5 9.5 containing 2 expressed 31981988 NP_705768 470.0 3.2
3.8 9.3 9.3 sequence C85492 RIKEN cDNA 34304038 NP_899082 375.1 7.5
3.3 8.0 8.0 2210020M01 QIL 1 protein 23346595 NP_694792 281.5 2.2
2.2 5.8 5.8 RIKEN cDNA 22122497 NP_666132 277.8 3.8 3.5 4.7 4.7
C730027E14 RIKEN cDNA 28077025 NP_083209 237.7 3.1 4.1 5.3 5.3
1300010M03 RIKEN cDNA 28077031 NP_083166 214.4 2.3 2.6 3.8 3.8
4931414P19 claudin 14 34328494 NP_062373 208.5 2.9 26.4 4.8 4.8
chemokine (C--C 9625035 NP_062523 201.1 1.9 37.1 3.2 3.2 motif)
ligand 24 RIKEN cDNA 27370416 NP_766508 182.0 2.6 2.9 4.3 4.3
1100001I19 angiopoietin-like 33469117 NP_038941 171.6 2.0 15.5 3.3
3.3 3 neuritin 1 23956286 NP_705757 60.2 1.8 3.9 3.0 3.0
[0158] Both angiopoietin-like 2 (Angptl2) and angiopoietin-like 3
(Angptl3) were found to be secreted proteins specifically expressed
in this stem cell supportive population (Table 1, FIG. 11A). These
proteins are also found to be expressed in adult bone marrow (BM)
cells including the SP CD45.sup.+ Sca-1.sup.+ highly enriched HSC
population (FIG. 11B and FIG. 11C). These two proteins have not
previously been implicated in HSC biology.
[0159] Freshly Isolated and 4 Day Cultured Bone Marrow HSCs Bind to
Angptl2
[0160] Fusion proteins of Angptl2 with the human IgG Fc fragment or
FLAG peptide were generated. When these fusion proteins were used
to isolate populations of freshly isolated or cultured bone marrow
cells that can or cannot bind Angptl2, and followed by
reconstitution analysis of them, it was found that Angptl2 is
capable of binding to the majority of freshly isolated BM HSCs
(FIG. 12A), and to all 4 day cultured HSCs (FIG. 12B). This
demonstrates that a receptor for Angptl2 is expressed on most
freshly isolated HSCs and all cultured HSCs.
[0161] In the experiment shown in FIG. 12A, freshly isolated adult
CD45.2 bone marrow cells were incubated at 4.degree. C. for 30 min
with conditioned medium from control transfected 293T cells or
cells transfected with the Angptl2-hFc--expression vector; the
latter medium contained 1 .mu.g/ml Angptl2-hFc. Cells were then
stained with anti-human IgG1-PE. On average 12.8% of total bone
marrow cells bind to Angptl2-hFc and 5.3% of 4 day cultured bone
marrow cells bind to Angptl2. 5.times.10.sup.4 positively stained
cells and the same number of negatively stained cells were
transplanted together with 2.times.10.sup.5 CD45.1 competitor cells
into lethally irradiated CD45.1 mice (n=4-5). Peripheral blood
cells were analyzed for the presence of CD45.2.sup.+ cells in
lymphoid and myeloid compartments at 3 weeks and 4 months after
transplant.
[0162] In the experiment shown in FIG. 12B, adult CD45.2 bone
marrow cells were cultured in serum-free medium with SCF, TPO,
IGF-2, and FGF-1 as described (Reya, T. et al. Nature 423, 409-14
(2003)) for 4 days. The cells were then stained with
Flag-Angptl2--containing medium (.about.1 .mu.g/ml Flag-Angptl2) as
the same as described in FIG. 3. 5.3% of total cells bind to
Angiopoietin-FLAG. 1300 positively stained cells and 8000
negatively stained cells were transplanted together with
2.times.10.sup.5 CD45.1 competitor cells into lethally irradiated
CD45.1 mice (n=4). Peripheral blood cells were analyzed for the
presence of CD45.2.sup.+ cells in lymphoid and myeloid compartments
at 3 weeks and 3 months after transplant.
[0163] Angptl2 and Angptl3 Stimulate Ex Vivo Expansion of HSCs
[0164] A plasmid containing the entire coding sequence for human
Angptl2 with a FLAG tag fused at the C-terminus in the eukaryotic
expression vector pcDNA3.1(-) (FLAG-Angptl2) was constructed.
Following transient transfection of 293T cells, the culture
supernatant contained secreted FLAG-Angptl2 migrating with the
expected .about.60 kD size (FIG. 1). As shown herein, the majority
of freshly isolated LT-HSCs and all LT-HSCs cultured for 4 d bound
this hormone (FIG. 12).
[0165] In the experiment shown in FIG. 2, twenty CD45.2 bone marrow
SP Sca-1.sup.+ CD45.sup.+ cells were seeded into each well of a
96-well U-bottom plate, in serum-free conditioned medium collected
from mock transfected 293T cells (S/F: serum-free medium, SCF:
serum-free medium with 10 ng/ml SCF, S+T: serum-free medium with 10
ng/ml SCF and 20 ng/ml TPO, S+T+I+F: serum-free medium with 10
ng/ml SCF, 20 ng/ml TPO, 20 ng/ml IGF-2, and 10 ng/ml FGF-1), or in
serum-free conditioned medium from 293T cells transfected with
Flag-Angptl2 (S/F+Angptl2: serum-free medium with .about.100 ng/ml
Angptl2, S+A: serum-free medium with 10 ng/ml SCF and .about.100
ng/ml Angptl2, S+T+A: serum-free medium with 10 ng/ml SCF, 20 ng/ml
TPO, and .about.100 ng/ml Angptl2, S+T+I+F+A: serum-free medium
with 10 ng/ml SCF, 20 ng/ml TPO, 20 ng/ml IGF-2, 10 ng/ml FGF-1,
and .about.100 ng/ml Angptl2). Images shown were taken after 3 days
of culture, under a phase-contrast microscope.
[0166] A representative of two independent experiments (FIG. 3A)
shows that Angptl2 is a stimulator of ex vivo expansion of LT-HSCs.
In this study Angptl2 was not purified but was contained in the
conditioned medium of 293T cells transfected with a FLAG-Angptl2
expression vector; conditioned medium from mock-transfected cells
served as a negative control. When 20 adult BM SP CD45.sup.+
Sca-1.sup.- cells, a highly enriched HSC population (Camargo, F.
D., Green, R., Capetanaki, Y., Jackson, K. A. & Goodell, M. A.
Nat Med 9, 1520-7 (2003)), were cultured for 5 d in serum-free
medium supplemented with SCF, essentially all long-term (LT)-HSC
activity was lost, measured by competitive reconstitution (FIG. 3A,
compare bars 7 and 12 to bars 6 and 11, respectively). After
culture in the same medium with SCF and 100 ng/ml FLAG-Angptl2 for
5 d, LT-HSC activity was dramatically increased (compare bars 8 and
13 to bars 7 and 12, respectively). Similarly, HSCs cultured for 10
d in the presence of SCF, TPO, IGF-2, FGF-1 and Angptl2 achieved a
tremendous increase of LT-HSC activity compared to culture in the
same medium without Angptl2 (compare bars 10 and 15 to bars 9 and
14, respectively). Stem cells cultured in the presence of Angptl2
repopulated both lymphoid and myeloid lineages of the primary
recipients at 9 months post-transplant (FIG. 3B) as well as in
secondary transplanted mice (FIG. 3C), indicating a net expansion
of LT-HSCs. After 9 months following transplants all mice were
healthy and no tumors were observed. Addition of 100 ng/ml
FLAG-Angptl2 also caused an increase in expansion of ST-HSC
activity, measured at 3 weeks post-transplant (compare bar 3 with
2, and 5 with 4).
[0167] Importantly, culturing highly enriched HSCs in serum-free
medium containing SCF, TPO, IGF-2, and FGF-1 was found to result in
an 8-fold increase of LT-HSC numbers (Zhang, C. C. & Lodish, H.
F. Blood 105, 4314-20 (2005)). An additional increase in the extent
of HSC expansion by adding Angptl2 was observed. Therefore, Angptl2
is a novel growth factor for HSCs, whose effect is synergistic with
other HSC growth factors.
[0168] To isolate pure recombinant Angptl2, conditioned medium from
FLAG-Angptl2 transfected 293T cells was collected and the
FLAG-tagged protein was purified by immunoaffinity chromatography
using an immobilized monoclonal antibody specific for the FLAG
epitope. SDS-PAGE of the eluted fraction showed two major bands,
one at the position expected for the full-length FLAG-Angptl2
(.about.60 kDa), and the other a smaller peptide of .about.36 kDa
(FIG. 4A, lane 3). The mammalian-expressed full-length FLAG-Angptl2
had a higher molecular weight than bacterially-expressed Angptl2
(compare lane 3 to lane 2), consistent with a previous result that
mammalian-expressed Angptl2 is glycosylated (Kim, I. et al. J Biol
Chem 274, 26523-8 (1999)). Western blotting with an anti-FLAG M2
antibody, which recognizes the C-terminal FLAG epitope, stained
both bands (FIG. 4B) as did an Angptl2-specific monoclonal antibody
(FIG. 4C). Thus the FLAG-Angptl2 underwent partial proteolysis
during purification.
[0169] As shown in FIG. 5, purified mammalian-expressed Angptl2
stimulated the proliferation of hematopoietic stem cells. Twenty
CD45.2 bone marrow SP Sca-1.sup.+ CD45.sup.+ cells were cultured
for 10 days in serum-free medium with 10 ng/ml SCF, 20 ng/ml TPO,
20 ng/ml IGF-2, and 10 ng/ml FGF-1, or in the same medium with 100
ng/ml purified Flag-Angptl2 (as in FIG. 4). Then the cells were
cotransplanted with 1.times.10.sup.5 CD45.1 competitors into CD45.1
recipients (n=5). Engraftment 3 weeks (left panel) and 2 months
(right panel) post-transplant were shown.
[0170] The limiting dilution competitive repopulation assay in FIG.
7 shows that culture of purified HSCs with Angptl2 or Angptl3,
together with other growth factors, results in a greater than
20-fold expansion of LT-HSC numbers. The frequency of long-term
repopulating cells (CRU) in freshly isolated BM SP CD45.sup.+
Sca-1.sup.+ cells is 1 per 23 at 3 months post-transplant (95%
confidence interval for mean: 1/15 to 1/35, n=25; FIG. 7A, bottom
line) or 1 in 39 at 6 months post-transplant (95% confidence
interval for mean: 1/24 to 1/63; FIG. 7A, top line). That is, as
calculated from Poisson statistics, injection of on average of 23
or 39 freshly isolated BM SP CD45.sup.+ Sca-1.sup.- cells is
sufficient to repopulate 63% (=1-1/e) of transplanted mice. After
the cells were cultured for 10 d in serum-free conditioned STIF
medium with Angptl2, the number of cells was too few to be counted
reliably. However, based on the number of cells initially added to
the culture, the CRU of the cultured cells was 1/1.1 at 3 months
post-transplant (FIG. 7B, bottom line; 95% confidence interval for
mean: 1/0.5 to 1/2.3, n=30) or 1/1.6 at 6 months post-transplant
(FIG. 7B, top line; 95% confidence interval for mean: 1/1.1 to
1/2.3). In other words, injection of the cultured progeny of only
1.1 or 1.6 freshly isolated BM SP CD45.sup.+ Sca-1.sup.+ cells is
sufficient to repopulate 63% of the mice. Thus the data in FIG. 7B
shows that the number of LT-HSCs (6 months post-transplant)
increases 24 fold (=39/1.6) after culture.
[0171] The same strategy was used to measure the effect of purified
Angptl3. The CRU of the cultured cells was 1/0.7 at 3 months
post-transplant (FIG. 7C, bottom line; 95% confidence interval for
mean: 1/0.3 to 1/1.7, n=24) or 1/1.3 at 6 months post-transplant
(FIG. 7C, top line; 95% confidence interval for mean: 1/0.9 to
1/2.0), again relative to the number of cells initially added to
the culture. Therefore, culture of BM SP CD45.sup.+ Sca-1.sup.+
cells in the presence of purified Angptl3 for 10 d results in a 30
(=39/1.3) fold expansion of repopulating LT-HSCs (6 months
post-transplant).
[0172] Expansion of HSC activity by Angptl3, like that by Angptl2,
was highly reproducible. In two additional experiments, progenies
of 20 BM SP CD45.sup.+ Sca-1.sup.+ cells after 10 d of culture in
serum-free conditioned STIF medium with 100 ng/ml Angptl3 showed
65.3%.+-.4.0% and 73.1%.+-.3.1% (n=5) of engraftments respectively
at 4 months post-transplant. Thus the culture system consistently
achieved dramatic increases of the repopulation activities of HSCs.
FIG. 6 shows that mammalian cell-specific posttranslational
modifications of Angptl2 facilitate its stimulation of ex vivo HSC
expansion. Confirming the result in FIG. 3A, addition of 100 ng/ml
mammalian-expressed Angptl2 significantly increased HSC activity
after culture (FIG. 6, compare bars 3 and 8 to bars 1 and 6,
respectively). By contrast, 100 ng/ml bacterially-expressed Angptl2
was unable to stimulate HSC expansion over STIF medium alone (FIG.
6, compare bars 2 and 7 to bars 1 and 6, respectively). This
suggests that some mammalian-specific modification, presumably
glycosylation (see FIG. 4A, lanes 2 and 3), positively correlates
with the ability of Angptl2 to stimulate LT-HSC expansion. The
coiled-coil domain of Angptl2 also stimulated ex vivo HSC expansion
(right panel of FIG. 6, compare bars 4 and 9 to bars 1 and 6,
respectively).
[0173] Several Angptl Family Members Stimulate HSC Expansion.
[0174] Angptl2 and Angptl3 belong to a family of angiopoietin-like
proteins (Oike, Y., Yasunaga, K. & Suda, T. Int J Hematol 80,
21-8 (2004)). FIG. 5 shows that several members of this family,
like Angptl2 and Angptl3, are capable of stimulating HSC expansion
in culture. The effects of purified Angptl3, Angptl5, or Angptl7,
as well as the coiled-coil domain of Angptl2, Angptl4, or
Microfibrillar-associated glycoprotein 4 (Mfap4) in 293T
conditioned medium were tested for stimulation of ex vivo expansion
of HSCs. All these factors support the increase of HSC activity
after culture.
[0175] As shown in FIG. 8, Angptl2-coiled coil domain, Angptl4, and
Mfap4 expressed in 293T cell conditioned medium stimulated the
proliferation of hematopoietic stem cells. Twenty CD45.2 bone
marrow SP Sca-1.sup.+ CD45.sup.+ cells were cultured for 5 days in
serum-free mock transfected conditioned medium with 10 ng/ml SCF,
20 ng/ml TPO, 20 ng/ml IGF-2, 10 ng/ml FGF-1 (lanes 1 and 8), in
conditioned medium with the same factors and full-length Angptl2
(lanes 2 and 9), Angptl2 coiled-coil domain (lanes 3 and 10),
Angptl2 fibrinogen-like domain (lanes 4 and 11), Angptl4 (lanes 5
and 12), Fibrinogen-like 1 (lanes 6 and 13), or
Microfibril-associated glycoprotein 4 (lanes 7 and 14). The cells
were then cotransplanted with 1.times.10.sup.5 CD45.1 competitors
into CD45.1 recipients (n=5). Engraftment 2 weeks (left panel) and
1 month (right panel) post-transplant are shown.
[0176] FLAG-tagged Angptl4 was generated by transient transfection
of 293T cells followed by immunoaffinity purification using an
immobilized anti-FLAG monoclonal antibody. In addition, purified
Angptl3 (produced in sf21 cells using a baculovirus system),
GST-fused Angptl5 (produced by a cell-free wheat germ in vitro
transcription/translational system), and Angptl7 (produced by a
bacterial expression system) (left panel, FIG. 10A) were
obtained.
[0177] Bone marrow SP Sca-1.sup.+ CD45.sup.+ cells were cultured
for 5 d in serum-free unconditioned STIF medium, in the presence of
100 ng/ml of Angptl3, Angptl4, Angptl5, or 1 .mu.g/ml of Angptl7
(FIG. 10A). Addition of Angptl3 to the culture stimulated both
ST-HSC and LT-HSC expansion (FIG. 10A, compare bars 2, 7, and 12 to
bars 1, 6, and 11, respectively). A significant increase of both
ST- and LT-HSC activities was also observed after culture with
Angptl5, and also 1 .mu.g/ml of bacterially-expressed Angptl7
(compare bars 1, 6, and 11 to bars 4, 9, and 14, as well as bars 5,
10, and 15, respectively). Angptl 4 stimulated at least some HSC
activity when tested at 2 weeks and 1 month post transplant (FIG.
9). However, 100 ng/ml Angptl4 was ineffective in stimulating HSC
expansion at 3 months and 6 months (FIG. 10, compare bars 3, 8, and
13).
[0178] The effects of two orthologs of Angptls,
microfibrillar-associated glycoprotein 4 (Mfap4) (Zhao, Z. et al.
Hum Mol Genet 4, 589-97 (1995)) and fibrinogen-like 1 (Fgl1)
(Yamamoto, T. et al. Biochem Biophys Res Commun 193, 681-7 (1993))
were also tested. Both full-length proteins were FLAG-tagged and
generated by transient transfection of 293T cells. They were
secreted into the medium and detected by Western blotting (FIG.
10B, left panel). Both .about.100 ng/ml FLAG-Mfap4 and FLAG-Fgl1
were applied to HSCs directly in the serum-free conditioned STIF
medium (FIG. 10B). Competitive reconstitution analysis demonstrated
that Mfap4 did stimulate ex vivo expansion of BM SP Sca-1.sup.+
CD45.sup.+ LT-HSCs after a 5 d culture whilst Fgl1 did not (FIG.
10B).
[0179] Angptl 5 Stimulates HSC Activity in Human Cord Blood
Cells
[0180] As demonstrated in FIG. 13, culturing primary human cord
blood cells in STIF medium supplemented with Angptl5 resulted in an
approximately 3 fold increase in frequency of SCID mouse
repopulating activity.
[0181] In conclusion, angiopoietin-like proteins are shown to be
important novel growth factors for HSCs, including human HSCs. The
stimulation of ex vivo expansion of HSCs by angiopoietin-like
proteins most likely results from a direct effect of the hormone on
these cells. As described herein, that the majority of freshly
isolated LT-HSCs and all LT-HSCs cultured for 4 d bound Angptl2;
thus the unknown receptor(s) of Angptl2 is expressed on cultured
HSCs. Furthermore, the cultures described herein contained only 20
highly enriched HSCs in 160 .mu.l of medium. Because of this low
cell density, it is unlikely that any accessory cell(s) in this
population respond to Angptl2 by producing sufficient amounts of
other growth factors to stimulate HSC expansion.
[0182] A simple serum-free culture system for bone marrow HSCs
using saturating levels of SCF, TPO, IGF-2, and FGF-1 was
developed; during 10 d of culture of highly enriched HSCs an 8-fold
increase in numbers of LT-HSCs was observed. (Zhang, C. C. &
Lodish, H. F. Blood 105, 4314-20 (2005)). SCF, IGF-2, and FGF-1 all
activate receptor protein-tyrosine kinases, whilst TPO signals
through a member of the cytokine receptor superfamily that requires
a Janus Kinase to activate intracellular signal transduction
pathways. As demonstrated herein, addition of any of several
members of the Angptl family--specifically Angptl2, Angptl3,
Angptl, 4, Angptl5, and Angptl7, as well as Mfap4--result in a
further increase in HSC activities. This suggests that the Angptls
activate signal transduction pathways in addition to those
activated by SCF, TPO, IGF-2, or FGF-1. As demonstrated herein, at
least Angptl2 and Angptl3 are produced by HSC supportive mouse
fetal liver CD3.sup.+ cells; therefore, both Angptl2 and Angptl3
may normally function in vivo to stimulate expansion of fetal
liver, and perhaps also adult, HSCs. As demonstrated by FIG. 13,
Angptl5 stimulates human HSCs, demonstrating that Angptls are also
an important growth factor family for human HSCs. Therefore,
Angptls are useful for ex vivo expansion of HSCs. In addition,
these factors are useful for ex vivo expansion of these cells as
part of an HSC transplantation or gene therapy protocol.
[0183] It is to be understood that the description, specific
examples and data, while indicating exemplary embodiments, are
given by way of illustration and are not intended to limit the
present invention. Various changes and modifications within the
present invention will become apparent to the skilled artisan from
the discussion, disclosure and data contained herein, and thus are
considered part of the invention.
Sequence CWU 1
1
616PRTArtificial SequenceDescription of Artificial Sequence
Synthetic linker peptide 1Ile Glu Gly Arg Met Asp 1 5
28PRTArtificial SequenceDescription of Artificial Sequence
Synthetic linker peptide 2Asp Tyr Lys Asp Asp Asp Asp Lys 1 5
3493PRTHomo sapiens 3Met Arg Pro Leu Cys Val Thr Cys Trp Trp Leu
Gly Leu Leu Ala Ala 1 5 10 15 Met Gly Ala Val Ala Gly Gln Glu Asp
Gly Phe Glu Gly Thr Glu Glu 20 25 30 Gly Ser Pro Arg Glu Phe Ile
Tyr Leu Asn Arg Tyr Lys Arg Ala Gly 35 40 45 Glu Ser Gln Asp Lys
Cys Thr Tyr Thr Phe Ile Val Pro Gln Gln Arg 50 55 60 Val Thr Gly
Ala Ile Cys Val Asn Ser Lys Glu Pro Glu Val Leu Leu 65 70 75 80Glu
Asn Arg Val His Lys Gln Glu Leu Glu Leu Leu Asn Asn Glu Leu 85 90
95 Leu Lys Gln Lys Arg Gln Ile Glu Thr Leu Gln Gln Leu Val Glu Val
100 105 110 Asp Gly Gly Ile Val Ser Glu Val Lys Leu Leu Arg Lys Glu
Ser Arg 115 120 125 Asn Met Asn Ser Arg Val Thr Gln Leu Tyr Met Gln
Leu Leu His Glu 130 135 140 Ile Ile Arg Lys Arg Asp Asn Ala Leu Glu
Leu Ser Gln Leu Glu Asn 145 150 155 160Arg Ile Leu Asn Gln Thr Ala
Asp Met Leu Gln Leu Ala Ser Lys Tyr 165 170 175 Lys Asp Leu Glu His
Lys Tyr Gln His Leu Ala Thr Leu Ala His Asn 180 185 190 Gln Ser Glu
Ile Ile Ala Gln Leu Glu Glu His Cys Gln Arg Val Pro 195 200 205 Ser
Ala Arg Pro Val Pro Gln Pro Pro Pro Ala Ala Pro Pro Arg Val 210 215
220 Tyr Gln Pro Pro Thr Tyr Asn Arg Ile Ile Asn Gln Ile Ser Thr Asn
225 230 235 240Glu Ile Gln Ser Asp Gln Asn Leu Lys Val Leu Pro Pro
Pro Leu Pro 245 250 255 Thr Met Pro Thr Leu Thr Ser Leu Pro Ser Ser
Thr Asp Lys Pro Ser 260 265 270 Gly Pro Trp Arg Asp Cys Leu Gln Ala
Leu Glu Asp Gly His Asp Thr 275 280 285 Ser Ser Ile Tyr Leu Val Lys
Pro Glu Asn Thr Asn Arg Leu Met Gln 290 295 300 Val Trp Cys Asp Gln
Arg His Asp Pro Gly Gly Trp Thr Val Ile Gln 305 310 315 320Arg Arg
Leu Asp Gly Ser Val Asn Phe Phe Arg Asn Trp Glu Thr Tyr 325 330 335
Lys Gln Gly Phe Gly Asn Ile Asp Gly Glu Tyr Trp Leu Gly Leu Glu 340
345 350 Asn Ile Tyr Trp Leu Thr Asn Gln Gly Asn Tyr Lys Leu Leu Val
Thr 355 360 365 Met Glu Asp Trp Ser Gly Arg Lys Val Phe Ala Glu Tyr
Ala Ser Phe 370 375 380 Arg Leu Glu Pro Glu Ser Glu Tyr Tyr Lys Leu
Arg Leu Gly Arg Tyr 385 390 395 400His Gly Asn Ala Gly Asp Ser Phe
Thr Trp His Asn Gly Lys Gln Phe 405 410 415 Thr Thr Leu Asp Arg Asp
His Asp Val Tyr Thr Gly Asn Cys Ala His 420 425 430 Tyr Gln Lys Gly
Gly Trp Trp Tyr Asn Ala Cys Ala His Ser Asn Leu 435 440 445 Asn Gly
Val Trp Tyr Arg Gly Gly His Tyr Arg Ser Arg Tyr Gln Asp 450 455 460
Gly Val Tyr Trp Ala Glu Phe Arg Gly Gly Ser Tyr Ser Leu Lys Lys 465
470 475 480Val Val Met Met Ile Arg Pro Asn Pro Asn Thr Phe His 485
490 4460PRTHomo sapiens 4Met Phe Thr Ile Lys Leu Leu Leu Phe Ile
Val Pro Leu Val Ile Ser 1 5 10 15 Ser Arg Ile Asp Gln Asp Asn Ser
Ser Phe Asp Ser Leu Ser Pro Glu 20 25 30 Pro Lys Ser Arg Phe Ala
Met Leu Asp Asp Val Lys Ile Leu Ala Asn 35 40 45 Gly Leu Leu Gln
Leu Gly His Gly Leu Lys Asp Phe Val His Lys Thr 50 55 60 Lys Gly
Gln Ile Asn Asp Ile Phe Gln Lys Leu Asn Ile Phe Asp Gln 65 70 75
80Ser Phe Tyr Asp Leu Ser Leu Gln Thr Ser Glu Ile Lys Glu Glu Glu
85 90 95 Lys Glu Leu Arg Arg Thr Thr Tyr Lys Leu Gln Val Lys Asn
Glu Glu 100 105 110 Val Lys Asn Met Ser Leu Glu Leu Asn Ser Lys Leu
Glu Ser Leu Leu 115 120 125 Glu Glu Lys Ile Leu Leu Gln Gln Lys Val
Lys Tyr Leu Glu Glu Gln 130 135 140 Leu Thr Asn Leu Ile Gln Asn Gln
Pro Glu Thr Pro Glu His Pro Glu 145 150 155 160Val Thr Ser Leu Lys
Thr Phe Val Glu Lys Gln Asp Asn Ser Ile Lys 165 170 175 Asp Leu Leu
Gln Thr Val Glu Asp Gln Tyr Lys Gln Leu Asn Gln Gln 180 185 190 His
Ser Gln Ile Lys Glu Ile Glu Asn Gln Leu Arg Arg Thr Ser Ile 195 200
205 Gln Glu Pro Thr Glu Ile Ser Leu Ser Ser Lys Pro Arg Ala Pro Arg
210 215 220 Thr Thr Pro Phe Leu Gln Leu Asn Glu Ile Arg Asn Val Lys
His Asp 225 230 235 240Gly Ile Pro Ala Glu Cys Thr Thr Ile Tyr Asn
Arg Gly Glu His Thr 245 250 255 Ser Gly Met Tyr Ala Ile Arg Pro Ser
Asn Ser Gln Val Phe His Val 260 265 270 Tyr Cys Asp Val Ile Ser Gly
Ser Pro Trp Thr Leu Ile Gln His Arg 275 280 285 Ile Asp Gly Ser Gln
Asn Phe Asn Glu Thr Trp Glu Asn Tyr Lys Tyr 290 295 300 Gly Phe Gly
Arg Leu Asp Gly Glu Phe Trp Leu Gly Leu Glu Lys Ile 305 310 315
320Tyr Ser Ile Val Lys Gln Ser Asn Tyr Val Leu Arg Ile Glu Leu Glu
325 330 335 Asp Trp Lys Asp Asn Lys His Tyr Ile Glu Tyr Ser Phe Tyr
Leu Gly 340 345 350 Asn His Glu Thr Asn Tyr Thr Leu His Leu Val Ala
Ile Thr Gly Asn 355 360 365 Val Pro Asn Ala Ile Pro Glu Asn Lys Asp
Leu Val Phe Ser Thr Trp 370 375 380 Asp His Lys Ala Lys Gly His Phe
Asn Cys Pro Glu Gly Tyr Ser Gly 385 390 395 400Gly Trp Trp Trp His
Asp Glu Cys Gly Glu Asn Asn Leu Asn Gly Lys 405 410 415 Tyr Asn Lys
Pro Arg Ala Lys Ser Lys Pro Glu Arg Arg Arg Gly Leu 420 425 430 Ser
Trp Lys Ser Gln Asn Gly Arg Leu Tyr Ser Ile Lys Ser Thr Lys 435 440
445 Met Leu Ile His Pro Thr Asp Ser Glu Ser Phe Glu 450 455
4605406PRTHomo sapiens 5Met Ser Gly Ala Pro Thr Ala Gly Ala Ala Leu
Met Leu Cys Ala Ala 1 5 10 15 Thr Ala Val Leu Leu Ser Ala Gln Gly
Gly Pro Val Gln Ser Lys Ser 20 25 30 Pro Arg Phe Ala Ser Trp Asp
Glu Met Asn Val Leu Ala His Gly Leu 35 40 45 Leu Gln Leu Gly Gln
Gly Leu Arg Glu His Ala Glu Arg Thr Arg Ser 50 55 60 Gln Leu Ser
Ala Leu Glu Arg Arg Leu Ser Ala Cys Gly Ser Ala Cys 65 70 75 80Gln
Gly Thr Glu Gly Ser Thr Asp Leu Pro Leu Ala Pro Glu Ser Arg 85 90
95 Val Asp Pro Glu Val Leu His Ser Leu Gln Thr Gln Leu Lys Ala Gln
100 105 110 Asn Ser Arg Ile Gln Gln Leu Phe His Lys Val Ala Gln Gln
Gln Arg 115 120 125 His Leu Glu Lys Gln His Leu Arg Ile Gln His Leu
Gln Ser Gln Phe 130 135 140 Gly Leu Leu Asp His Lys His Leu Asp His
Glu Val Ala Lys Pro Ala 145 150 155 160Arg Arg Lys Arg Leu Pro Glu
Met Ala Gln Pro Val Asp Pro Ala His 165 170 175 Asn Val Ser Arg Leu
His Arg Leu Pro Arg Asp Cys Gln Glu Leu Phe 180 185 190 Gln Val Gly
Glu Arg Gln Ser Gly Leu Phe Glu Ile Gln Pro Gln Gly 195 200 205 Ser
Pro Pro Phe Leu Val Asn Cys Lys Met Thr Ser Asp Gly Gly Trp 210 215
220 Thr Val Ile Gln Arg Arg His Asp Gly Ser Val Asp Phe Asn Arg Pro
225 230 235 240Trp Glu Ala Tyr Lys Ala Gly Phe Gly Asp Pro His Gly
Glu Phe Trp 245 250 255 Leu Gly Leu Glu Lys Val His Ser Ile Thr Gly
Asp Arg Asn Ser Arg 260 265 270 Leu Ala Val Gln Leu Arg Asp Trp Asp
Gly Asn Ala Glu Leu Leu Gln 275 280 285 Phe Ser Val His Leu Gly Gly
Glu Asp Thr Ala Tyr Ser Leu Gln Leu 290 295 300 Thr Ala Pro Val Ala
Gly Gln Leu Gly Ala Thr Thr Val Pro Pro Ser 305 310 315 320Gly Leu
Ser Val Pro Phe Ser Thr Trp Asp Gln Asp His Asp Leu Arg 325 330 335
Arg Asp Lys Asn Cys Ala Lys Ser Leu Ser Gly Gly Trp Trp Phe Gly 340
345 350 Thr Cys Ser His Ser Asn Leu Asn Gly Gln Tyr Phe Arg Ser Ile
Pro 355 360 365 Gln Gln Arg Gln Lys Leu Lys Lys Gly Ile Phe Trp Lys
Thr Trp Arg 370 375 380 Gly Arg Tyr Tyr Pro Leu Gln Ala Thr Thr Met
Leu Ile Gln Pro Met 385 390 395 400Ala Ala Glu Ala Ala Ser 405
6388PRTHomo sapiens 6Met Met Ser Pro Ser Gln Ala Ser Leu Leu Phe
Leu Asn Val Cys Ile 1 5 10 15 Phe Ile Cys Gly Glu Ala Val Gln Gly
Asn Cys Val His His Ser Thr 20 25 30 Asp Ser Ser Val Val Asn Ile
Val Glu Asp Gly Ser Asn Ala Lys Asp 35 40 45 Glu Ser Lys Ser Asn
Asp Thr Val Cys Lys Glu Asp Cys Glu Glu Ser 50 55 60 Cys Asp Val
Lys Thr Lys Ile Thr Arg Glu Glu Lys His Phe Met Cys 65 70 75 80Arg
Asn Leu Gln Asn Ser Ile Val Ser Tyr Thr Arg Ser Thr Lys Lys 85 90
95 Leu Leu Arg Asn Met Met Asp Glu Gln Gln Ala Ser Leu Asp Tyr Leu
100 105 110 Ser Asn Gln Val Asn Glu Leu Met Asn Arg Val Leu Leu Leu
Thr Thr 115 120 125 Glu Val Phe Arg Lys Gln Leu Asp Pro Phe Pro His
Arg Pro Val Gln 130 135 140 Ser His Gly Leu Asp Cys Thr Asp Ile Lys
Asp Thr Ile Gly Ser Val 145 150 155 160Thr Lys Thr Pro Ser Gly Leu
Tyr Ile Ile His Pro Glu Gly Ser Ser 165 170 175 Tyr Pro Phe Glu Val
Met Cys Asp Met Asp Tyr Arg Gly Gly Gly Trp 180 185 190 Thr Val Ile
Gln Lys Arg Ile Asp Gly Ile Ile Asp Phe Gln Arg Leu 195 200 205 Trp
Cys Asp Tyr Leu Asp Gly Phe Gly Asp Leu Leu Gly Glu Phe Trp 210 215
220 Leu Gly Leu Lys Lys Ile Phe Tyr Ile Val Asn Gln Lys Asn Thr Ser
225 230 235 240Phe Met Leu Tyr Val Ala Leu Glu Ser Glu Asp Asp Thr
Leu Ala Tyr 245 250 255 Ala Ser Tyr Asp Asn Phe Trp Leu Glu Asp Glu
Thr Arg Phe Phe Lys 260 265 270 Met His Leu Gly Arg Tyr Ser Gly Asn
Ala Gly Asp Ala Phe Arg Gly 275 280 285 Leu Lys Lys Glu Asp Asn Gln
Asn Ala Met Pro Phe Ser Thr Ser Asp 290 295 300 Val Asp Asn Asp Gly
Cys Arg Pro Ala Cys Leu Val Asn Gly Gln Ser 305 310 315 320Val Lys
Ser Cys Ser His Leu His Asn Lys Thr Gly Trp Trp Phe Asn 325 330 335
Glu Cys Gly Leu Ala Asn Leu Asn Gly Ile His His Phe Ser Gly Lys 340
345 350 Leu Leu Ala Thr Gly Ile Gln Trp Gly Thr Trp Thr Lys Asn Asn
Ser 355 360 365 Pro Val Lys Ile Lys Ser Val Ser Met Lys Ile Arg Arg
Met Tyr Asn 370 375 380 Pro Tyr Phe Lys 385
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