U.S. patent application number 11/626724 was filed with the patent office on 2007-08-02 for method of enhancing neural stem cell proliferation, differentiation, and survival using pituitary adenylate cyclase activating polypeptide (pacap).
This patent application is currently assigned to STEM CELL THERAPEUTICS INC.. Invention is credited to Shigeki Ohta, Samuel Weiss.
Application Number | 20070179092 11/626724 |
Document ID | / |
Family ID | 31188575 |
Filed Date | 2007-08-02 |
United States Patent
Application |
20070179092 |
Kind Code |
A1 |
Ohta; Shigeki ; et
al. |
August 2, 2007 |
Method of Enhancing Neural Stem Cell Proliferation,
Differentiation, and Survival Using Pituitary Adenylate Cyclase
Activating Polypeptide (PACAP)
Abstract
The present invention relates to a method of increasing the
number and/or differentiation of neural stem cells and/or neural
stem cell progeny using pituitary adenylate cyclase-activating
polypeptide (PACAP). In a preferred embodiment, additional growth
factors are also utilized. The present invention can be practiced
in vivo and in vitro, rendering it useful for the treatment of
neurodegenerative disease and other neural trauma.
Inventors: |
Ohta; Shigeki; (Tokyo,
JP) ; Weiss; Samuel; (Calgary, CA) |
Correspondence
Address: |
FISH & RICHARDSON P.C.
P.O BOX 1022
Minneapolis
MN
55440-1022
US
|
Assignee: |
STEM CELL THERAPEUTICS INC.
Suite 1000 1520 4th Street, S.W.
Calgary
CA
T2R 1H5
|
Family ID: |
31188575 |
Appl. No.: |
11/626724 |
Filed: |
January 24, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10630967 |
Jul 31, 2003 |
|
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11626724 |
Jan 24, 2007 |
|
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60399390 |
Jul 31, 2002 |
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Current U.S.
Class: |
424/198.1 ;
435/325; 435/368; 514/11.5; 514/17.8; 514/18.2; 514/9.1;
514/9.6 |
Current CPC
Class: |
C12N 2501/11 20130101;
A61K 38/00 20130101; C12N 2501/115 20130101; C07K 14/57563
20130101; C12N 2501/35 20130101 |
Class at
Publication: |
514/012 ;
435/325; 435/368 |
International
Class: |
A61K 38/18 20060101
A61K038/18; C12N 5/08 20060101 C12N005/08; C12N 5/06 20060101
C12N005/06 |
Claims
1. A method for increasing neural stem cell or neural stem cell
progeny number comprising adding pituitary adenylate
cyclase-activating polypeptide (PACAP) to multipotent neural stem
cells in an amount effective to increase neural stem cell or neural
stem cell progeny number.
2. The method of claim 1, wherein the number of neural stem cells
or neural stem cell progeny is increased by enhancing
proliferation.
3. The method of claim 1, wherein the number of neural stem cells
or neural stem cell progeny is increased by enhancing survival.
4. The method of claim 1, wherein the number of neural stem cells
or neural stem cell progeny is increased by increasing secondary
neural stem cells obtained from a primary neural stem cell.
5. The method of claim 1, wherein the neural stem cells are located
in a subject.
6. The method of claim 5, wherein PACAP is added parenterally.
7. The method of claim 5, wherein the subject is a mammal.
8. The method of claim 7, wherein the subject is an adult.
9. The method of claim 7, wherein the subject is a human.
10. The method of claim 5, wherein the subject has a
neurodegenerative disease or condition or a brain injury.
11. The method of claim 10, wherein the neurodegenerative disease
or condition is Alzheimer's Disease, Parkinson's Disease, or
Huntington's Disease.
12. The method of claim 5, wherein the subject has had a
stroke.
13. The method of claim 5, wherein the increase in neural stem cell
number occurs in the subventricular zone of the subject.
14. The method of claim 1, wherein the PACAP is added to
multipotent stem cells in vitro.
15. The method of claim 1, wherein the PACAP is PACAP38.
16. The method of claim 1, wherein the PACAP is PACAP27.
17. The method claim 1, further comprising adding at least one
growth factor.
18. The method of claim 17, wherein the at least one growth factor
is fibroblast growth factor-2 (FGF-2).
19. The method of claim 18, further comprising adding heparan
sulfate.
20. The method of claim 17, wherein the at least one growth factor
is epidermal growth factor (EGF).
21. The method of claim 20, wherein the EGF is EGF51N or
EGF51Q.
22. The method of claim 17, wherein the at least one growth factor
is prolactin.
23. The method of claim 17, wherein the at least one growth factor
is added concurrently with PACAP.
24. The method of claim 17, wherein the at least one growth factor
is added sequentially with PACAP.
25. The method of claim 24, wherein the at least one growth factor
is added prior to the addition of PACAP.
26. The method of claim 24, wherein the at least one growth factor
is added after the addition of PACAP.
27. A method of increasing the number of neural stem cells or
neurospheres in a culture comprising adding pituitary adenylate
cyclase-activating polypeptide (PACAP) to a neural stem cell
culture to increase the number of neural stem cells or neurospheres
generated from the neural stem cell culture.
28. The method of claim 27, wherein the neural stem cell culture is
a primary culture.
29. The method of claim 27, wherein the neural stem cell culture is
a clonal density culture.
30. The method of claim 27, further comprising adding a growth
factor to the culture.
31. The method of claim 27, wherein the PACAP is PACAP38.
32. The method of claim 27, wherein the PACAP is PACAP27.
33. The method of claim 30, wherein the growth factor is fibroblast
growth factor-2 (FGF-2).
34. The method of claim 33, further comprising adding heparan
sulfate.
35. The method of claim 30, wherein the growth factor is epidermal
growth factor.
36. The method of claim 35, wherein the EGF is EGF51N or
EGF51Q.
37. The method of claim 30, wherein the growth factor is
prolactin.
38. A method of enhancing differentiation of neural stem cells in a
subject comprising administering pituitary adenylate
cyclase-activating polypeptide (PACAP) to the subject in an amount
sufficient to enhance differentiation of neural stem cells.
39. The method of claim 38, wherein differentiation of neural stem
cells into neurons is enhanced.
40. The method of claim 38, wherein the PACAP is PACAP38.
41. The method of claim 38, wherein the PACAP is PACAP27.
42. The method of claim 38, wherein the subject is a mammal.
43. The method of claim 42, wherein the subject is an adult.
44. The method of claim 42, wherein the subject is a human.
45. The method of claim 38, further comprising administering at
least one growth factor.
46. The method of claim 45, wherein the at least one growth factor
is fibroblast growth factor-2 (FGF-2).
47. The method of claim 46, further comprising adding heparan
sulfate.
48. The method of claim 45, wherein the at least one growth factor
is epidermal growth factor (EGF).
49. The method of claim 48, wherein the EGF is EGF51N or
EGF51Q.
50. The method of claim 45, wherein the at least one growth factor
is prolactin.
51. The method claim 45, wherein the at least one growth factor is
administered to the subject prior to the administration of
PACAP.
52. The method of claim 45, wherein the at least one growth factor
is administered to the subject after the administration of
PACAP.
53. The method of claim 38, wherein the subject has a
neurodegenerative disease or condition or brain injury.
54. The method of claim 53, wherein the neurodegenerative disease
is Alzheimer's Disease, Parkinson's Disease, or Huntington's
Disease.
55. The method of claim 38, wherein the subject has had a
stroke.
56. The method of claim 38, wherein the differentiation of neural
stem cells occurs in the subventricular zone.
57. (canceled)
58. The method of claim 14, further comprising transplanting the
neural stem cells or progeny cells into a subject.
59. A method of increasing the number of neural stem cells or
neurospheres in a subject comprising transplanting into the subject
one or more neural stem cells or neurospheres generated by the
method of claim 27.
Description
RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
application Ser. No. 10/630,967, filed Jul. 31, 2003, which claims
the benefit of U.S. Provisional Application Ser. No. 60/399,390,
filed Jul. 31, 2003. The entire disclosure of each of these
priority applications is hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of enhancing
proliferation and differentiation of neural stem cells in vivo and
in vitro using pituitary adenylate cyclase-activating peptide. In a
preferred embodiment, additional growth factors are also utilized.
The present invention has applications in the treatment of
neurodegenerative diseases, such as Alzheimer's, Parkinson's, and
Huntington's Diseases.
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[0054] All of the publications, patents, and patent applications
cited in this application are hereby incorporated by reference in
their entirety to the same extent as if the disclosure of each
individual publication, patent, or patent application was
specifically and individually indicated to be incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0055] Neurogenesis in mammals is largely complete early in the
postnatal period. While it was previously thought that cells of the
adult mammalian central nervous system (CNS) have little or no
ability to undergo mitosis and generate new neurons, recent studies
have demonstrated that the mature nervous system does have some
limited capability to produce new neurons. (Craig, et al., 1996;
Rietze, et al., 2000; review in van der Kooy and Weiss, 2000).
Several mammalian species (e.g., rats) exhibit the limited ability
to generate new neurons in restricted adult brain regions such as
the dentate gyrus and olfactory bulb (Kaplan, 1981; Bayer, 1985).
However, the generation of new CNS neurons in adult primates does
not normally occur (Rakic, 1985). This relative inability to
produce new neural cells in most mammals (and especially primates)
may be advantageous for long-term memory retention; however, it is
a distinct disadvantage when the need to replace lost neuronal
cells arises due to an injury or disease.
[0056] The role of neural stem cells in the adult is to replace
cells that are lost by natural cell death, injury or disease. Until
recently, the low turnover of cells in the mammalian CNS together
with the inability of the adult mammalian CNS to generate new
neuronal cells in response to the loss of cells following an injury
or disease had led to the assumption that the adult mammalian CNS
does not contain multipotent neural stem cells. The critical
identifying feature of a stem cell is its ability to exhibit
self-renewal or to generate more of itself. The simplest definition
of a stem cell would be a cell with the capacity for
self-maintenance. A more stringent (but still simplistic)
definition of a stem cell is provided by Potten and Loeffler (1990)
who have defined stem cells as "undifferentiated cells capable of
a) proliferation, b) self-maintenance, c) the production of a large
number of differentiated functional progeny, d) regenerating the
tissue after injury, and e) a flexibility in the use of these
options."
[0057] CNS disorders encompass numerous afflictions such as
neurodegenerative diseases (e.g., Alzheimer's and Parkinson's),
acute brain injury (e.g., stroke, head injury, cerebral palsy) and
a large number of CNS dysfunctions (e.g., depression, epilepsy, and
schizophrenia). In recent years, neurodegenerative disease has
become an important concern due to the expanding elderly population
which is at the greatest risk for these disorders. These diseases,
which include Alzheimer's Disease, Parkinson's Disease,
Huntington's Disease, Multiple Sclerosis (MS), and Amyotrophic
Lateral Sclerosis, have been linked to the degeneration of neuronal
cells in particular locations of the CNS, leading to the inability
of these cells or the brain region to carry out their intended
function.
[0058] Degeneration in a brain region known as the basal ganglia
can lead to diseases with various cognitive and motor symptoms,
depending on the exact location. The basal ganglia consists of many
separate regions, including the striatum (which consists of the
caudate and putamen), the globus pallidus, the substantia nigra,
substantia innominate, ventral pallidum, nucleus basalis of
Meynert, ventral tegmental area and the subthalamic nucleus. Many
motor deficits are a result of neuronal degeneration in the basal
ganglia. Huntington's Chorea is associated with the degeneration of
neurons in the striatum, which leads to involuntary jerking
movements in the host. Degeneration of a small region called the
subthalamic nucleus is associated with violent flinging movements
of the extremities in a condition called ballismus, while
degeneration in the putamen and globus pallidus is associated with
a condition of slow writhing movements or athetosis. In the case of
Parkinson's Disease, degeneration is seen in another area of the
basal ganglia, the substantia nigra pars compacta. This area
normally sends dopaminergic connections to the dorsal striatum
which are important in regulating movement. In the case of
Alzheimer's Disease, there is a profound cellular degeneration of
the forebrain and cerebral cortex. In addition, upon closer
inspection, a localized degeneration in an area of the basal
ganglia, the nucleus basalis of Meynert, appears to be selectively
degenerated. The nucleus normally sends cholinergic projections to
the cerebral cortex which are thought to participate in cognitive
functions including memory. Other forms of neurological impairment
can occur as a result of neural degeneration, such as cerebral
palsy, or as a result of CNS trauma, such as stroke and
epilepsy.
[0059] In addition to neurodegenerative diseases, brain injuries
often result in the loss of neurons, the inappropriate functioning
of the affected brain region, and subsequent behavior
abnormalities. Probably the largest area of CNS dysfunction (with
respect to the number of affected people) is not characterized by a
loss of neural cells but rather by an abnormal functioning of
existing neural cells. This may be due to inappropriate firing of
neurons, or the abnormal synthesis, release, and/or processing of
neurotransmitters. These dysfunctions may be the result of well
studied and characterized disorders such as depression and
epilepsy, or less understood disorders such as neurosis and
psychosis.
[0060] Demyelination of central and peripheral neurons occurs in a
number of pathologies and leads to improper signal conduction
within the nervous system. Myelin is a cellular sheath, formed by
glial cells, that surrounds axons and axonal processes that
enhances various electrochemical properties and provides trophic
support to the neuron. Myelin is formed by Schwann cells in the
peripheral nervous system and by oligodendrocytes in the central
nervous system. Among the various demyelinating diseases, MS is the
most notable.
[0061] To date, treatment for CNS disorders has been primarily via
the administration of pharmaceutical compounds. Unfortunately, this
type of treatment has been fraught with many complications
including limited ability to transport drugs across the blood-brain
barrier and drug-tolerance acquired by patients to whom these drugs
are administered long-term. For instance, partial restoration of
dopaminergic activity in Parkinson's patients has been achieved
with levodopa, which is a dopamine precursor able to cross the
blood-brain barrier. However, patients become tolerant to the
effects of levodopa, and therefore, steadily increasing dosages are
needed to maintain its effects. In addition, there are a number of
side effects associated with levodopa such as increased and
uncontrollable movement.
[0062] Recently, the concept of neurological tissue grafting has
been applied to the treatment of neurological diseases such as
Parkinson's Disease. Neural grafts may avert the need not only for
constant drug administration, but also for complicated drug
delivery systems which arise due to the blood-brain barrier.
However, there are limitations to this technique as well. First,
cells used for transplantation which carry cell surface molecules
of a differentiated cell from another host can induce an immune
reaction in the host. In addition, the cells must be at a stage of
development where they are able to form normal neural connections
with neighboring cells. For these reasons, initial studies on
neurotransplantation centered on the use of fetal cells. Several
studies have shown improvements in patients with Parkinson's
Disease after receiving implants of fetal CNS tissue. Implantation
of embryonic mesencephalic tissue containing dopamine cells into
the caudate and putamen of human patients was shown by Freed et al.
(1992) to offer long-term clinical benefit to some patients with
advanced Parkinson's Disease. Similar success was shown by Spencer
et al. (1992). Widner et al. (1992) have shown long-term functional
improvements in patients with
N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced
Parkinsonism that received bilateral implantation of fetal
mesencephalic tissue. Perlow et al. (1979) describe the
transplantation of fetal dopaminergic neurons into adult rats with
chemically induced nigrostriatal lesions. These grafts showed good
survival, axonal outgrowth and significantly reduced the motor
abnormalities in the host animals. A further discussion of tissue
transplantation techniques and drawbacks can be found in U.S. Pat.
No. 6,294,346 B1.
[0063] While the studies noted above are encouraging, the use of
large quantities of aborted fetal tissue for the treatment of
diseases raises ethical considerations and political obstacles.
There are other considerations as well. Fetal CNS tissue is
composed of more than one cell type, and thus is not a well-defined
source of tissue. In addition, there are serious doubts as to
whether an adequate and constant supply of fetal tissue would be
available for transplantation. For example, in the treatment of
MPTP-induced Parkinsonism (Widner, 1992) tissue from 6 to 8 fresh
fetuses were required for implantation into the brain of a single
patient. There is also the added problem of the potential for
contamination during fetal tissue preparation. Moreover, the tissue
may already be infected with a bacteria or virus, thus requiring
expensive diagnostic testing for each fetus used However, even
diagnostic testing might not uncover all infected tissue. For
example, the successful diagnosis of HIV-free tissue is not
guaranteed because antibodies to the virus are generally not
present until several weeks after infection.
[0064] While currently available transplantation approaches
represent a significant improvement over other available treatments
for neurological disorders, they suffer from significant drawbacks.
The inability in the prior art of the transplant to fully integrate
into the host tissue, and the lack of availability of neuronal
cells in unlimited amounts from a reliable source for grafting are,
perhaps, the greatest limitations of neurotransplantation. A
well-defined, reproducible source of neural cells is currently
available. It has been discovered that multipotent neural stem
cells, capable of producing progeny that differentiate into neurons
and glia, exist in adult mammalian neural tissue. (Reynolds and
Weiss, 1992). Methods have been provided for the proliferation of
these stem cells to provide large numbers of neural cells that can
differentiate into neurons and glia (See, e.g., U.S. Pat. No.
5,750,376, and International Application No. WO 93/01275). Various
factors can be added to neural cell cultures to influence the
make-up of the differentiated progeny of multipotent neural stem
cell, as disclosed in published PCT application WO 94/10292.
Additional methods for directing the differentiation of stem cell
progeny were disclosed in U.S. Pat. No. 6,165,783 utilizing
erythropoietin and various growth factors.
[0065] Thus, it can be seen that a need exists for the repair of
damaged neural tissue in a relatively non-invasive fashion, by
inducing neural cells to proliferate and differentiate into
neurons, astrocytes, and oligodendrocytes in vivo, averting the
need for transplantation. Additional methods for increasing the
number of neural stem cells and their progeny in vitro are also
desirable both for research and for transplantation. As the adult
nervous system possesses limited capacity for reproducing new
neurons, it is particularly desirable to be able to enhance
proliferation of neural stem cells in order to be able to replace
lost or damaged neurons.
SUMMARY OF THE INVENTION
[0066] Accordingly, a major object of the present invention is to
provide both in vivo and in vitro techniques of enhancing neural
stem cell proliferation and/or survival and/or differentiation. The
present inventors have now found that PACAP can enhance neural stem
cell proliferation, survival, and differentiation both in vitro and
in vivo in embryonic and adult tissue.
[0067] The present invention provides a method for increasing
neural stem cell and/or neural stem cell progeny number comprising
adding pituitary adenylate cyclase-activating polypeptide (PACAP)
to multipotent neural stem cells in an amount effective to increase
neural stem cells and/or neural stem cell progeny number. In one
embodiment, PACAP38 is used. In another embodiment, PACAP27 is
used. In one embodiment, the number of neural stem cells and/or
neural stem cell progeny is increased by enhancing proliferation.
In an alternative embodiment, the number of neural stem cells
and/or progeny is increased by enhancing survival. In another
alternative, the number of neural stem cells and/or progeny is
increased by increasing the number of secondary neural stem cells
obtained from a primary neural stem cell.
[0068] In one embodiment, the neural stem cells are located in a
subject. Preferably, the subject is a mammal, particularly a human.
Even more preferably, the subject is an adult. In one embodiment,
the subject is suffering from a neurodegenerative disease or brain
injury. In a preferred embodiment, the subject is suffering from
Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, or
stroke. The number of neural stem cells and/or progeny are
preferably increased in the subventricular zone of the subject. In
one embodiment, the neural stem cells and/or progenitor cells which
are derived from neural stem cells are transplanted into the
subject.
[0069] In a preferred embodiment, at least one growth factor is
added in addition to PACAP. In a particularly preferred embodiment,
the growth factor is fibroblast growth factor-2 (FGF-2), with or
without heparan sulfate. In another particularly preferred
embodiment, the growth factor is epidermal growth factor, EGF. In
still another preferred embodiment, prolactin is used.
[0070] In one embodiment the growth factor is added to the cells
concurrently with PACAP. In another embodiment, the growth factor
is added sequentially with the PACAP. In a particularly preferred
embodiment, the PACAP is added prior to the growth factor. In
another particularly preferred embodiment, PACAP is added after the
growth factor.
[0071] Another aspect of the present invention provides a method of
increasing the number of neural stem cells and/or neurospheres
comprising adding PACAP to a neural stem cell culture to increase
the number of neural stem cells and/or neurospheres generated from
the neural stem cell culture. In one embodiment, PACAP38 is used.
In another embodiment, PACAP27 is used. In a preferred embodiment,
the neural stem cell culture is a primary culture or a clonal
density culture. In another embodiment, the method further
comprises adding a growth factor to the neural stem cell culture.
In a preferred embodiment the growth factor is FGF-2, with or
without heparan sulfate. In another preferred embodiment, the
growth factor is EGF. In still another preferred embodiment, the
growth factor is prolactin.
[0072] In yet another aspect, the present invention provides a
method of enhancing proliferation and/or differentiation and/or
survival of neural stem cells in a subject comprising administering
PACAP to the subject in an amount sufficient to enhance
proliferation and/or differentiation and/or survival of neural stem
cells. In one embodiment, PACAP38 is used. In another embodiment,
PACAP27 is used. In one embodiment, the differentiation into
neurons is increased.
[0073] In a preferred embodiment, the subject is a mammal. In more
preferred embodiment, the mammal is an adult. In a particularly
preferred embodiment, the mammal is a human. In a preferred
embodiment, at least one growth factor is administered. In
particularly preferred embodiment, the growth factor is FGF-2 (with
or without heparan sulfate), EGF, or prolactin.
[0074] In one embodiment, the subject is suffering from a
neurodegenerative disease or brain injury. In a particularly
preferred embodiment, the subject is suffering from Alzheimer's
Disease, Parkinson's Disease, Huntington's Disease, or stroke. In a
preferred embodiment, the proliferation and/or differentiation
and/or survival of neural stem cells occurs in the subventricular
zone. In a particularly preferred embodiment, the multipotent
neural stem cells and/or progenitor cells which are derived from
said multipotent neural stem cells are transplanted into said
subject.
[0075] In one embodiment, the growth factor is administered
concurrently with PACAP. In another embodiment, the growth factor
is administered consecutively with PACAP. In a particularly
preferred embodiment, the growth factor is administered prior to
PACAP. In another embodiment, the growth factor is administered
after PACAP.
BRIEF DESCRIPTION OF THE DRAWINGS
[0076] FIG. 1. Pituitary adenylate cyclase-activating (PACAP)
enhanced neural stem cell survival in vitro. Embryonic day 14
ganglionic eminences (E14 GE) were dissociated and plated at 150
cells/ml in the indicated growth factor conditions. The number of
neurospheres was counted after 10 days. Data are expressed relative
to the number obtained with epidermal growth factor (EGF) alone
(100%). PACAP increased the number of neurospheres obtained with
either EGF or fibroblast growth factor (FGF)+heparan sulfate (HS).
Delayed addition of PACAP did not increase neurosphere number,
indicating that PACAP acts as a survival factor. (*p<0.05,
n=3).
[0077] FIG. 2. PACAP increased neural stem cell self-renewal in
vitro. Primary E14 neurospheres were grown in the indicated
conditions, dissociated, and replated in the presence of either EGF
or FGF+HS. Neurospheres were counted and data were normalized to
either EGF or FGF+HS alone. PACAP increased the number of secondary
neurospheres obtained with either EGF or FGF+HS. (*p<0.05,
n=3).
[0078] FIG. 3. PACAP enhanced in vitro neurogenesis by neural stem
cells. Primary E14 neurospheres were grown in the indicated
conditions for seven days and then processed for
immunocytochemistry to count the number of B-tubulin immunopositive
neurons. Data were normalized to either EGF or FGF+HS alone (100%).
PACAP increased the number of neurons in all conditions.
(*p<0.01, n=3).
[0079] FIG. 4. PACAP infusion stimulated increased proliferation in
the adult subventricular zone (SVZ) in vivo. PACAP was infused into
the lateral ventricles for six days with an osmotic minipump,
followed by a series of BrdU injections. Brains were processed for
immunocytochemistry. PACAP increased proliferation in the adult
SVZ. (**p<0.05, n=4).
DETAILED DESCRIPTION OF THE INVENTION
[0080] The present invention relates to a method of increasing the
number of neural stem cells or neural stem cell progeny by adding
PACAP and optionally one or more growth factors to neural stem
cells and/or progeny. The numbers of neural stem cell and neural
stem cell progeny may be increased by a variety of mechanisms,
including increasing proliferation, increasing survival, and
increasing the number of secondary neurospheres that can be derived
from primary neurospheres. These methods may be practiced both in
vivo and in vitro. With regard to in vitro methods, the number of
neural stem cells and/or neurospheres can be increased by
exogenously adding PACAP to neural stem cell cultures.
[0081] Additionally, the present invention provides for a method of
enhancing the differentiation of neural stem cells in a subject. In
particular PACAP can increase the differentiation of neural stem
cells into neurons. The present invention has important
implications for the treatment and research of neurodegenerative
diseases and brain injury.
[0082] Prior to describing the invention in further detail, the
terms used in this application are defined as follows unless
otherwise indicated.
[0083] As used herein, the term "multipotent neural stem cell" (or
more simply, neural stem cell) refers to an undifferentiated cell
which is capable of self-maintenance. Thus, in essence, a stem cell
is capable of dividing without limit. "Progenitor cells" are
non-stem cell progeny of a multipotent neural stem cell. A
distinguishing feature of a progenitor cell is that, unlike a stem
cell, it has limited proliferative ability and thus does not
exhibit self-maintenance. It is committed to a particular path of
differentiation and will, under appropriate conditions, eventually
differentiate. A neuronal progenitor cell is capable of a limited
number of cell divisions before giving rise to differentiated
neurons. A glial progenitor cell likewise is capable of a limited
number of cell divisions before giving rise to astrocytes or
oligodendrocytes. A neural stem cell is multipotent because its
progeny include both neuronal and glial progenitor cells and thus
is capable of giving rise to neurons, astrocytes, and
oligodendrocytes. Multipotent stem cell progeny thus include
neuronal precursor cells, glial precursor cells, neurons, and glial
cells.
[0084] A "neurosphere" is a group of cells derived from a single
neural stem cell as the result of clonal expansion. Primary
neurospheres are generated by plating as primary cultures brain
tissue which contains neural stem cells. The method for culturing
neural stem cells to form neurospheres has been described in, e.g.,
U.S. Pat. No. 5,750,376. Secondary neurospheres can be generated by
dissociating primary neurospheres and allowing the individual
dissociated cells to form neurospheres again.
[0085] "PACAP" or "pituitary adenylate cyclase activating
polypeptide" is a polypeptide hormone that activates adenylate
cyclase. The native mammalian PACAP is a 38 or 27 amino acid
polypeptide hormone which is released by the hypothalamus. As used
herein, "PACAP" encompasses polypeptides which share substantial
sequence similarity with either form of the native mammalian PACAP
and possess a biological activity of the native mammalian PACAP.
Having a biological activity of native mammalian PACAP means having
at least one activity of a native mammalian PACAP, such as binding
to one or more of the same receptors as the native mammalian PACAP
binds and/or stimulating adenylate cyclase. Preferably, the PACAP
binds to one of more of the same receptors as the native mammalian
PACAP. PACAP can be isolated from the pituitary or can be
synthesized using genetic engineering or chemical synthetic
techniques.
[0086] A polypeptide which shares "substantial sequence similarity"
with a native mammalian PACAP is at least about 30% identical with
native mammalian PACAP at the amino acid level. The PACAP is
preferably about 40%, more preferably about 60%, yet more
preferably at least about 70%, and most preferably, at least about
80% identical with the native mammalian PACAP at the amino acid
level. Thus, the term PACAP encompasses PACAP analogs which are
deletional, insertional, or substitutional mutants of the native
mammalian PACAP. Furthermore, the term PACAP encompasses PACAPs
from other species and the naturally occurring and synthetic
variants thereof. Particularly useful are the analogs and variants
disclosed in, e.g., U.S. Pat. Nos. 5,128,242; 5,198,542; 5,208,320;
5,326,860; 5,623,050; 5,801,147; and 6,242,563.
[0087] "Percent identity" or "% identity" refers to the percentage
of amino acid sequence in a protein or polypeptide which are also
found in a second sequence when the two sequences are aligned.
Percent identity can be determined by any methods or algorithms
established in the art, such as LALIGN or BLAST.
[0088] By "growth factor" is meant a substance that affects the
growth of a cell or an organism, including proliferation,
differentiation, and increases in cell size. A growth factor is a
polypeptide which shares substantial sequence identity with a
native mammalian growth factor and possesses a biological activity
of the native mammalian growth factor. In a preferred embodiment,
the native mammalian growth factor is a native human growth factor.
Having a biological activity of a native mammalian growth factor
means having at least one activity of a native mammalian growth
factor, such as binding to the same receptor as a particular native
mammalian growth factor binds and/or eliciting proliferation and/or
differentiation and/or changes in cell size. Preferably, the growth
factor binds to the same receptor as a particular native mammalian
growth factor. This includes functional variants of the native
mammalian growth factor.
[0089] A polypeptide which shares "substantial sequence similarity"
with the native mammalian growth factor is at least about 30%
identical to the native mammalian growth factor at the amino acid
level. The growth factor is preferably at least about 40%, more
preferably at least about 60%, and most preferably about 60%
identical to the native mammalian growth factor at the amino acid
level. Thus, the term growth factor encompasses analogs which are
deletional, insertional, or substitutional mutants of a native
mammalian growth factor. Furthermore, the term growth factor
encompasses the growth factors from other species and naturally
occurring and synthetic variants thereof. Exemplary growth factors
include platelet-derived growth factor (PDGF), epidermal growth
factor (EGF), erythropoeitin, insulin-like growth factor-1 and -2
(IGF-1, IGF-2), transforming growth factors .alpha. and .beta.
(TGF-.alpha., TGF-.beta.), acidic and basic fibroblast growth
factors (a-FGF/FGF-2, b-FGF/FGF-2), interleukins 1, 2, 6, and 8
(IL-1, IL-2, IL-6, IL-8), nerve growth factor (NGF), brain-derived
neurotrophic factor (BDNF), neurotrophin-3 (NT-3), interleukin-3,
hematopoietic colony stimulating factors (CSFs), amphiregulin,
interferon-.gamma. (INF-.gamma.), thyrotropin releasing hormone
(TRH), and prolactin.
[0090] It should be noted that variants or analogs of these agents,
which share a substantial identity with a native mammalian growth
factor listed above and are capable of binding to a receptor of the
native mammalian growth factor can be used in the present
application. For example, EGF variants or analogs, which share a
substantial identity with a native mammalian EGF and are capable of
binding to a receptor of a native mammalian growth factor, can be
used in the present application. These EGF variants and analogs
include, but are not limited to, the recombinant modified EGF
having a deletion of the two C-terminal amino acids and a neutral
amino acid substitution at position 51, such as asparagine,
glutamine, serine, or alanine (particularly EGF51N or EGF51Q,
having asparagine (N) or glutamine (Q) at position 51,
respectively; WO 03/040310); the EGF mutein (EGF-X16) in which the
His residue at position 16 is replaced with a neutral or acidic
amino acid (U.S. Pat. No. 6,191,106); the 52-amino acid deletion
mutant of EGF which lacks the amino terminal residue of the native
EGF (EGF-D); the EGF deletion mutant in which the amino terminal
residue as well as the two C-terminal residues (Arg-Leu) are
deleted (EGF-B); the EGF-D in which the Met residue at position 21
is oxidized (EGF-C); the EGF-B in which the Met residue at position
21 is oxidized (EGF-A); heparin-binding EGF-like growth factor
(HB-EGF); betacellulin; amphiregulin; neuregulin; or a fusion
protein comprising any of the above. Other useful EGF analogs or
variants are described in WO 03/040310, and U.S. Pat. Nos.
6,191,106 and 5,547,935.
[0091] Specifically included as prolactins are the naturally
occurring prolactin variants, prolactin-related protein, placental
lactogens, S179D-human prolactin (Bernichtein et al., 2001),
prolactins from various mammalian species, including, but not
limited to, human, other primates, rat mouse, sheep, pig, and
cattle, and the prolactin mutants described in U.S. Pat. Nos.
6,429,186 and 5,955,346.
[0092] To "enhance" neural stem cell proliferation,
differentiation, or survival means to increase the amount or rate
of these parameters in the presence of the substance compared to
the amount or rate in the absence of the substance. For example,
PACAP enhances proliferation of neural stem cells by increasing the
number of mitotic cells in a population of neural stem cells
compared to the number of mitotic cells in the absence of
PACAP.
[0093] A "neurodegenerative disease or condition" is a disease or a
medical condition associated with neuron loss or dysfunction.
Examples of neurodegenerative diseases or conditions include
neurodegenerative diseases, brain injuries or CNS dysfunctions.
Neurodegenerative diseases include, e.g., Alzheimer's Disease,
Multiple Sclerosis, Huntington's Disease, Amyotrophic Lateral
Sclerosis, and Parkinson's Disease. Brain injuries include, e.g.,
injuries to the nervous system due to surgery, stroke, and physical
accidents. CNS dysfunctions include, e.g., depression, epilepsy,
neurosis, and psychosis.
[0094] "Treating or ameliorating" means the reduction or complete
removal of the symptoms of a disease or medical condition.
[0095] An "effective amount" is an amount of a therapeutic agent
sufficient to achieve the intended purpose. For example, an
effective amount of a growth factor or PACAP to enhance the
proliferation of neural stem cells is an amount sufficient, in vivo
or in vitro, to result in an enhancement in proliferation of neural
stem cells over the speed or number of cells in the absence of the
growth factor or PACAP. An effective amount of a growth factor or
PACAP to treat or ameliorate a neurodegenerative disease or
condition is an amount of the growth factor or PACAP sufficient to
reduce or remove the symptoms of the neurodegenerative disease or
condition. The effective amount of a given therapeutic agent will
vary with factors such as the nature of the agent, the route of
administration, the size and species of the animal or subject to
receive the therapeutic agent, and the purpose of administration.
The effective amount in each individual case may be determined
empirically by a skilled artisan according to established methods
in the art.
DETAILED DESCRIPTION
[0096] PACAP was first discovered from the hypothalami of sheep as
a peptide promoting adenylate cyclase activity of the pituitary
gland. (Miyata et al., 1989; U.S. Pat. No. 5,128,242). The
particular PACAP first isolated was a peptide consisting of 38
amino acid residues called PACAP38. However, a 27 amino acid
variant of PACAP was also discovered (PACAP27). Both peptides are
relatively equal in the ability to stimulate adenylate cyclase. The
expression of a PACAP of similar structure to that isolated from
sheep was found in humans, suggesting an important evolutionary
role due to conservation. (Kimura et al., 1990; Arimura et al.,
1998; Vaudry et al., 2000).
[0097] PACAP peptides have been found in a number of diverse
tissues, including the brain, pituitary gland, the testes, and the
adrenal gland. (Arimura et al., 1991). Several PACAPs have been
found and described in various publications, including U.S. Pat.
No. 5,128,242 and EPO Publication No. 0467279A3). The genes for the
PACAP38 and PACAP27 peptides have been isolated as described in
U.S. Pat. No. 5,326,860 and U.S. Pat. No. 5,521,069. PACAP
receptors have been described, e.g., in U.S. Pat. No. 6,399,316 B1.
At least three types of PACAP receptors have been identified.
(Arimura et al, 1998). PACAP type 1 (PAC.sub.1-R) receptors are
expressed at high levels in the brain but low levels in the rest of
the body. Type I PACAP receptors may stimulate adenylate cyclase
(AC), phospholipase C (PLC), mitogen-activated protein kinase
(MAPK), and calcium mobilization. (Christophe, 1993; Hashimoto et
al., 1993; Arimura et al., 1998; D. Vaudry et al., 2000). Exemplary
agonists and antagonists for the PACAP type I receptors are
disclosed in U.S. Pat. No. 6,017,533.
[0098] The role of PACAP in the nervous system has been studied
over the past decade. PACAP has been identified in numerous brain
regions, including the hypothalamus, the nucleus accumbens, septum,
cerebral cortex, midbrain, pons, medulla oblongata, amygdala,
globus pallidus, thalamus, and posterior pituitary. (Arimura et
al., 1998). It is now recognized that PACAP plays many diverse
roles in the brain, including neurotrophic factor,
neurotransmitter, neuromodulator, and neuroprotective agent. (For
review, see Arimura et al., 1998; also Carey et al., 2002; Yuhara
et al., 2001; Otto et al., 2001; Hansel et al., 2001; Arimura et
al., 1994; Waschek, 1996; Lindholm et al., 1998). For example,
PACAP can decrease mitosis in embryonic rat cortical precursors.
(Lu and DiCicco-Bloom, 1997). In contrast, transfection of
embryonic rat cortical cells with a splice variant of PAC.sub.1-R
resulted in increased proliferation.
[0099] In the present invention, methods of increasing neural stem
cell number, survival, self-renewal, proliferation, and
differentiation were discovered. As discussed in more detail in the
Example below, PACAP is able to elicit these effects both in vivo
and in vitro.
[0100] In addition to PACAP, other growth factors such as those
described above can be used to augment the effects of PACAP. In
particular, FGF (optionally with heparan sulfate) and EGF are
particularly preferred embodiments. However, other growth factors,
such as prolactin, are also useful. The PACAP may be administered
sequentially or simultaneously with the other growth factor. The
growth factor may be administered or added either before or after
the administration or addition of PACAP.
[0101] For in vivo administration, compositions containing PACAP
and/or other growth factors can be delivered via any route known in
the art, such as orally, or parenterally, e.g., intravascularly,
intramuscularly, transdermally, subcutaneously, or
intraperitoneally. In a preferred embodiment, the composition is
administered parenterally. The composition may be delivered
directly into the CNS. Direct administration into the CNS can be
accomplished via delivery into a ventricle, such as the lateral
ventricle. However, PACAP is known to cross the blood-brain-barrier
(Banks, 1993), making direct CNS administration unnecessary.
[0102] According to embodiments of the invention, PACAP may be
administered in vivo to treat subjects suffering from
neurodegenerative diseases, brain injuries, or CNS dysfunctions.
Alzheimer's Disease, Huntington's Disease, and Parkinson's Disease,
inter alia, may be treated according to various embodiments of the
invention. Alternatively, the subject may be suffering from a
stroke. Because of the prevalence of neurodegenerative diseases in
adults, the preferred subject is an adult human. However, it is
contemplated that younger subjects may also suffer from
neurodegenerative disease, or more commonly, traumatic brain
injury, and thus will benefit from the present invention.
Additionally, while humans are particularly preferred subject,
other species, such as those kept as pets, may also be treated
according to an embodiment of the invention. Subjects may be
treated with PACAP, and optionally, other growth factors, or neural
stem cells may be exogenously treated and then transplanted into
subject. A combination of these approaches is also possible.
[0103] For in vitro practice of the present invention, multipotent
neural stem cells can be obtained from embryonic, juvenile, or
adult mammalian neural tissue (e.g. mouse and other rodents, and
humans and other primates) or from other sources as described in
PCT application WO 93/01275 and U.S. Pat. Nos. 5,750,376 and
6,294,346 B1.
[0104] In the absence of substrates that promote cell adhesion
(e.g., ionically charged surfaces such as poly-L-lysine and
poly-L-ornithine coated and the like), multipotent neural stem cell
proliferation can be detected by the formation of clusters of
undifferentiated neural cells termed "neurospheres", which after
several days in culture, lift off the floor of the culture dish and
float in suspension. Each neurosphere results from the
proliferation of a single multipotent neural stem cell and is
comprised of daughter multipotent neural stem cells and neural
progenitor cells. The neurospheres can be dissociated to form a
suspension of undifferentiated neural cells and transferred to
fresh growth-factor containing medium. This re-initiates
proliferation of the stem cells and the formation of new
neurospheres. In this manner, an unlimited number of
undifferentiated neural stem cell progeny can be produced by the
continuous culturing and passaging of the cells in suitable culture
conditions.
[0105] The ability to manipulate the fate of the differentiative
pathway of the multipotent neural stem cell progeny to produce more
neuronal progenitor cells and neurons is beneficial. Cell cultures
that contain a higher percentage of neuronal progenitor cells
and/or neurons will be useful for screening the effects of various
drugs and other agents on neuronal cells. Methods for screening the
effect of drugs on cell cultures are well known in the art and are
also disclosed in U.S. Pat. Nos. 5,750,376 and 6,294,346 B1.
[0106] Cell cultures with an enriched neuronal-progenitor cell
and/or neuron population can be used for transplantation to treat
various neurological injuries, diseases or disorders. The neuronal
progenitor cells or neurons or a combination thereof can be
harvested and transplanted into a patient needing neuronal
augmentation. Neuronal progenitor cells are particularly suitable
for transplantation because they are still undifferentiated and,
unlike differentiated neurons, there are no branched processes
which can be damaged during transplantation procedures. Once
transplanted, the neuronal progenitor cells differentiate in situ
into new, functioning neurons. Suitable transplantation methods are
known in the art and are disclosed in U.S. Pat. Nos. 5,750,376 and
6,294,346 B1.
[0107] Alternatively, a patient's endogenous multipotent neural
stem cells could be induced to proliferate, differentiate, or
survive in situ by administering to the patient a composition
comprising PACAP and optionally one or more growth factors which
instructs the neural stem cells to proliferate and to produce
neuronal progenitor cells which eventually differentiate into
neurons and to enhance differentiation and survival. Suitable
methods for administering a composition to a patient which induces
the in situ proliferation of the patient's stem cells are disclosed
in U.S. Pat. Nos. 5,750,376 and 6,294,346 B1.
EXAMPLES
PACAP Regulates Neural Stem Cell Fate In Vitro and In Vivo
PACAP Receptor Expression.
[0108] As the PACAP receptor (PAC.sub.1-R) is expressed in the
forebrain germinal zone of the rat throughout early development, it
is believed to play a role in regulating neural stem cells.
Receptor expression was examined both in vitro and in vivo at
various stages. Primary embryonic neural stem cells were isolated
from the E14 ganglionic eminences as previously described (Reynolds
and Weiss, 1992). Using Reverse-transcriptase PCR (RT-PCR)
analysis, PACAP and PAC.sub.1-R were found to be expressed in the
embryonic day 14 murine ganglionic eminence (E14 GE). PAC.sub.1-R
was also expressed in E14 EGF-generated neurospheres, further
indicating a role in neural stem cell regulation.
[0109] The expression of PAC.sub.1-R was confirmed by Western blot
analysis using ECL Plus (Amersham Biosciences). Anti-PAC.sub.1-R
(1:1000) was obtained as a gift from Dr. Arimura. Western blots
demonstrated that PAC.sub.1-R receptor protein expression was found
in E14 and adult neurospheres, E14 ganglionic eminence, and the
adult olfactory bulb and subventricular zone (data not shown).
Immunohistochemistry was performed using TSA Fluorescence System
(Perkin Elmer). Indirect immunocytochemistry showed PAC.sub.1-R
immunoreactive cells in embryonic and adult neurospheres, in the
E14 mouse GE and in the adult SVZ (data not shown). Because
PAC.sub.1-R expression was observed in these various tissues in
vitro and in vivo. PACAP may play an important role in regulating
development and function of neural stem cells and/or neural stem
cell progeny.
In Vitro Effects of PACAP.
[0110] General Methods.
[0111] Cell Culture: Primary embryonic neural stem cells were
isolated from E14 ganglionic eminence as previously described
(Reynolds and Weiss, 1992). Neurospheres were grown in the presence
of EGF (20 ng/ml) or FGF-2 (20 ng/ml)+heparan sulfate (2 .mu.g/ml)
growth medium. Passaged neural stem cells were grown at a clonal
density (150 cells/ml).
[0112] Single Cell Dissociation Assay: Single neurospheres (200 mm)
were dissociated mechanically and then plated in a 96 well plate
and incubated for 10 days in vitro in the presence of growth
factors.
[0113] Differentiation of Neurospheres: Neurospheres were plated
onto poly-L-ornithine coated coverslips in serum-free medium and
subjected to immunocytochemistry after 5 days in vitro. The number
of .beta.-III tubulin-positive cells were counted.
PACAP Enhances Neural Stein Cell Survival.
[0114] E14 GE were dissociated and plated at 150 cells/ml in EGF,
EGF+PACAP, FGF+HS, or FGF+HS+PACAP. The number of neurospheres were
counted after 10 days. As shown in FIG. 1, the addition of PACAP
significantly increased the number of primary neurospheres
generated in response to FGF-2. PACAP also increased the number of
primary neurospheres generated in response to EGF, but to a lesser
extent than that observed with FGF-2. The addition of PACAP
increased neurosphere number when added at the beginning of the
culture period, but not when delayed until 5 days in vitro,
indicating the PACAP enhances neural stem cell survival.
PACAP Increases Neural Stein Cell Self-Renewal.
[0115] Primary E14 neurospheres were grown in the indicated
conditions in FIG. 2, then dissociated and replated in the presence
of either EGF or FGF+HS and the number of secondary neurospheres
was counted. Data were normalized to the numbers of secondary
neurospheres generated from primary neurospheres grown in the
absence of PACAP. As shown in FIG. 2, the number of secondary
neurospheres generated by single primary neurospheres grown in the
presence of PACAP significantly increased, indicating that PACAP
enhances neural stem cell expansion/self-renewal.
[0116] PACAP Enhances in vitro Neurogenesis by Neural Stem
Cells.
[0117] Primary E14 neurospheres were grown in either EGF or FGF
media in the presence or absence of PACAP for seven days,
differentiated for five days in vitro in basal media, and then
processed immunocytochemistry to determine the number of 13-tubulin
immunopositive neurons. Data were normalized to those obtained with
either EGF or FGF+HS alone (100%). As shown in FIG. 3, PACAP
significantly increased the number of neurons generated, indicating
that PACAP enhances neurogenesis. Furthermore, neurogenesis was
enhanced independently of PACAP's effect on survival, because an
increase was observed even when PACAP addition was delayed until
after five days in vitro (PACAP at 5 DIV in FIG. 3).
[0118] PACAP Stimulates Akt and STAT5 Phosphorylation in Cultured
Neural Stem Cells.
[0119] To examine the possible mechanisms of PACAP action on neural
stem cells, the effects of PACAP on Akt and STAT5 phosphorylation
were investigated. Immunoblots were performed with anti-STAT5
(1:1000, Santa Cruz Biotechnology), anti-phospho-STAT5 (1:1000;
Cell Signaling Technology), anti-Akt and anti-phospho-Akt (1:1000;
Cell Signaling Technology). Western blot analysis (data not shown)
demonstrated that PACAP induced a rapid increase (within 1 to 2
hours) in phosphorylation of Akt, which is believed to be
associated with cell survival. PACAP also stimulated STAT5
phosphorylation, which was previously shown to be important in
neural stem cell neurogenesis. The effects of PACAP on Akt and
STAT5 phosphorylation may be critical in mediating actions on
neural stem cell survival and neurogenesis.
[0120] In Vivo Effects of PACAP.
[0121] As noted above, examination of the expression of PAC.sub.1-R
in the adult brain revealed abundant expression in the forebrain
subventricular zone (SVZ). To examine the actions of the peptide in
vivo, CD-1 mice (6-7 weeks of age) were implanted with osmotic
minipumps (Alzet 1007D) filled with either human PACAP (American
peptide Company, 165 .mu.g/ml) or vehicle alone (0.9% saline
containing 1 mg/ml mouse serum albumin). The cannulae were placed
in the right lateral ventricle. Each animal was infused for 6 days
and injected with BrdU every two hours for ten hours and killed 0.5
hours after the last injection. Brains were processed for
immunohistochemistry as described previously (Shingo et al., 2001)
and BrdU+ cells were counted in serial sections of the SVZ.
[0122] As shown in FIG. 4, the number of BrdU incorporating cells
was significantly increased in animals receiving PACAP infusions
relative to control vehicle infused animals. Thus, PACAP increased
proliferation in the adult forebrain SVZ.
[0123] Accordingly, the data discussed above demonstrate multiple,
novel roles for PACAP in the regulation of both embryonic and adult
neural stem cell populations and demonstrate the utility of PACAP
for the treatment of neurodegenerative disease, brain injury, and
CNS dysfunction.
[0124] Although the present invention has been described in detail
with reference to examples above, it is understood that various
modifications can be made without departing from the spirit of the
invention, and would be readily known to the skilled artisan.
* * * * *