U.S. patent application number 17/175324 was filed with the patent office on 2021-06-10 for method for scalable skeletal muscle lineage specification and cultivation.
The applicant listed for this patent is The Curators of the University of Missouri, Memphis Meats, Inc.. Invention is credited to Nicholas J. GENOVESE, R. Michael ROBERTS, Bhanu Prakash V. L. TELUGU.
Application Number | 20210171912 17/175324 |
Document ID | / |
Family ID | 1000005405936 |
Filed Date | 2021-06-10 |
United States Patent
Application |
20210171912 |
Kind Code |
A1 |
GENOVESE; Nicholas J. ; et
al. |
June 10, 2021 |
METHOD FOR SCALABLE SKELETAL MUSCLE LINEAGE SPECIFICATION AND
CULTIVATION
Abstract
The present disclosure relates to methods for enhancing cultured
meat production, such as livestock-autonomous meat production. In
certain aspects, the meat is any metazoan tissue or cell-derived
comestible product intended for use as a comestible food or
nutritional component by humans, companion animals, domesticated or
captive animals whose carcasses are intended for comestible use,
service animals, conserved animal species, animals used for
experimental purposes, or cell cultures.
Inventors: |
GENOVESE; Nicholas J.;
(Hayward, CA) ; ROBERTS; R. Michael; (Columbia,
MO) ; TELUGU; Bhanu Prakash V. L.; (College Park,
MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Memphis Meats, Inc.
The Curators of the University of Missouri |
Berkeley
Columbia |
CA
MO |
US
US |
|
|
Family ID: |
1000005405936 |
Appl. No.: |
17/175324 |
Filed: |
February 12, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15134252 |
Apr 20, 2016 |
10920196 |
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17175324 |
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PCT/US2014/063250 |
Oct 30, 2014 |
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15134252 |
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61962068 |
Oct 30, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C12N 5/0658 20130101;
C12N 2506/45 20130101; C12N 2501/415 20130101; C12N 2501/602
20130101; A23V 2002/00 20130101; C12N 2501/603 20130101; C12N
2501/999 20130101; C12N 2506/02 20130101; C12N 2501/40 20130101;
C12N 2501/72 20130101; C12N 2501/392 20130101; C12N 2501/727
20130101; C12N 2501/604 20130101; A23L 13/00 20160801; C12N 2501/60
20130101; C12N 5/10 20130101 |
International
Class: |
C12N 5/077 20060101
C12N005/077; A23L 13/00 20060101 A23L013/00; C12N 5/10 20060101
C12N005/10 |
Goverment Interests
STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND
DEVELOPMENT
[0002] This invention was made with Government support under Grant
No. R01 HD069979/00032722 awarded by the National Institutes of
Health. The Government has certain rights in the invention.
Claims
1-28. (canceled)
29. An in vitro method for producing a cultured meat product for
dietary consumption, the method comprising: providing a cell line
demonstrating the capacity for skeletal muscle tissue
specification; modifying said cell line with an inducible myogenic
transcription factor to produce a myogenic
transcription-factor-modified cell line; inducing myogenic
differentiation of said modified cell line; and culturing the
differentiated modified cell line, thereby producing a cultured
meat product for dietary consumption.
30. The method of claim 29, wherein the cell line is from a
livestock or poultry species.
31. The method of claim 30, wherein the livestock species is
porcine or bovine.
32. The method of claim 29, wherein the myogenic transcription
factor is MYOD1, MYOG, MYF5, MYF6, PAX3, PAX7, or a paralog,
ortholog, or genetic variant thereof,
33. The method of claim 29, wherein the myogenic transcription
factor is a transcriptional activation agonist of the respective
promoter recognition DNA sequences of a myogenic transcription
factor.
34. The method of claim 29, wherein the cell line is a
self-renewing cell line.
35. The method of claim 34, wherein the self-renewing cell line
comprises embryonic stem cells, induced pluripotent stem cells,
somatic cells, or extra-embryotic cells with myogenic
potential.
36. The method of claim 34, wherein the inducing step further
comprise a self-renewal sub-step and a differentiation sub-step
regulated by a double-switch mechanism.
37. The method of claim 36, wherein in the self-renewal sub-step
the undifferentiated state of the modified cell line is
maintained.
38. The method of claim 36, wherein in the differentiation
sub-step, the modified cell line is treated, and the cell line is
specified to skeletal myocytes.
39. The method of claim 38, wherein the differentiation sub-step
further comprises contacting the cell line with a reagent for
activating the canonical WNT signaling pathway to prevent cell
death and facilitate myogenic differentiation.
40. The method of claim 38, wherein the differentiation sub-step
further comprises contacting the cell line with an epigenetic
modulator to alter the chromatin structure for enhanced myogenic
gene expression.
41. The method of claim 29, wherein said inducing is carried out by
exogenous regulation to direct a differentiation processes in the
cell line.
42. The method of claim 29, wherein culturing of the differentiated
modified cell line forms myocytes and multinucleated myotubes.
43. The method of claim 42, wherein the cell line is cultured in a
low-mitogen culture medium.
44. The method of claim 42, wherein the myocytes and multinucleated
myotubes both comprise myonuclei, and wherein greater than 50% of
the total myonuclei are within the multinucleated myotubes.
45. The method of claim 42, further comprising culturing the
myocytes and multinucleated myotubes to generate skeletal muscle
fibers.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 61/962,068, filed Oct. 30, 2013, which is
incorporated herein by reference in its entirety.
INCORPORATION OF SEQUENCE LISTING
[0003] The content of the electronically submitted sequence listing
in ASCII text file (Name 52553_136621_ST25.txt; Size: 2,962 bytes;
and Date of Creation: Oct. 30, 2014) filed with the application is
incorporated herein by reference in its entirety.
BACKGROUND
[0004] The present disclosure relates to methods for enhancing
cultured meat production, such as livestock-autonomous meat
production. The conceptual promises of "cultured meat" (e.g.,
animal-autonomous meat production by in vitro cell culture, tissue
engineering, and food technology methods) include increased
production efficiency, reduced environmental impacts, expanded
culinary application utility, enhanced nutritional value,
cruelty-free production and improved food safety relative to
conventionally produced meats. Technologies, to date however, have
not advanced sufficiently to support scalable, economically
sustainable production. The current laboratory-scale cultivation of
prototype tissues has utilized primary animal components such as
animal tissues and serum, thereby largely negating the advantages
of animal-autonomous meat production. Hence, current methods fail
to resolve the animal dependence from cultured meat production
sufficiently to realize the conceptual promises of "cultured meat"
and provide a commercially advantageous product. Therefore, there
is a need to provide new and improved methods for scalable meat
cultivation from a self-renewing source in vitro for dietary
nutrition and other applications.
SUMMARY
[0005] The example embodiments provide a scalable platform for
skeletal muscle cultivation that utilizes cell lines with the
potential to differentiate as skeletal muscle. In certain aspects,
the cell lines are from livestock such as domestic cattle, pigs,
sheep, goats, camels, water buffalo, rabbits and the like. In
certain aspects, the cells lines are from poultry such as domestic
chicken, turkeys, ducks, geese, pigeons and the like. In certain
aspects, the cell lines are from common game species such as wild
deer, gallinaceous fowl, waterfowl, hare and the like. In certain
aspects, the cell lines are from aquatic species or semi-aquatic
species harvested commercially from wild fisheries or aquaculture
operations, or for sport, including certain fish, crustaceans,
mollusks, cephalopods, cetaceans, crocodilians, turtles, frogs and
the like. In certain aspects, the cell lines are from exotic,
conserved or extinct animal species. In certain aspects, the cell
lines are from any metazoan species demonstrating the capacity for
skeletal muscle tissue specification. In certain aspects, the cell
lines are for research or for therapeutic purposes, such as humans,
primates, rodents including rats and mice, and companion animals
such as dogs, cats, horses, and the like. In certain specific
aspects, the cell lines from any organisms are self-renewing stem
cell lines. In certain aspects, the selected cell line is modified
by a `genetic switch` to induce rapid and efficient conversion of
cells to skeletal muscle for cultured meat production. In an
example embodiment, the above or other aspects may be accomplished
by a method comprising modifying a selected self-renewing cell line
by a myogenic transcription factor to produce a
myogenic-transcription-factor-modified cell line, and inducing such
modified cell line by exogenous regulation to direct alternate
self-renewal or differentiation processes.
[0006] In certain aspects, the self-renewing cell line is selected
from a group consisting of embryonic stem cells, induced
pluripotent stem cells, somatic cell lines, or extra-embryotic cell
lines with myogenic potential. In certain aspects, the cell line is
derived from species intended for dietary consumption.
Illustrative, non-limiting examples of myogenic transcription
factors include, alone or in combination, MYOD1, MYOG, MYF5, MYF6,
PAX3, PAX7, paralogs, orthologs, genetic variants thereof, or
transcriptional activation agonists of the respective promoter
recognition DNA sequences of the myogenic transcription factors as
further described herein.
[0007] In certain specific aspects, an inducible MyoD transcription
factor may be used as the differentiation lineage specifier. In
certain specific aspects, the porcine induced pluripotent cell line
02K may be employed as the self-renewing cell line. In one specific
aspect the method comprises modifying a 02K stem cell line with an
inducible MyoD transcription factor to produce a
myogenic-transcription-factor-modified 02KM cell line, and inducing
such 02KM cell line by exogenous regulation to direct self-renewal
or differentiation processes. The aforementioned modifying step can
further comprise modifying the cell line with a chromosomally
integrated vector constitutively expressing an inducible fusion of
the MYOD1 transcription factor and an ESR1 ligand binding domain
from a constitutively active promoter region. For example, the
inducible activity of the translated fusion transcript (e.g.,
MyoDER), can be conditionally activated in the presence of the ESR1
agonist (e.g., 17-.beta. Estradiol (E2)).
[0008] In certain aspects, the inducing step can further comprise
the self-renewal sub-step and the differentiation sub-step
regulated by a double-switch mechanism. In the self-renewal
sub-step, the modified cell line undifferentiated ground-state is
preserved, such as in the presence of doxycycline (DOX), whereby
the cell line is maintained in a stem cell self-renewal state by
the induced expression of the pluripotency transgenes POU5F1 and
KLF4. In the differentiation sub-step, the modified cell line is
treated, such as with E2 in the absence of DOX, whereas the cell
line is efficiently specified to skeletal myocytes, i.e., the
myogenic lineage, by the inducible MyoD transcription factor,
resulting in characteristic elongated cells with spindle-like
morphology. When further cultured in low-mitogen culture medium,
the derivative myocytes can fuse into multinucleated myotubes,
precursors to skeletal muscle fibers. Following extended culture in
low-mitogen medium, the multinucleated myotubes mature into
skeletal muscle fibers capable of terminal differentiation, as
evidenced by increased expression of MYOG, DES, MYHC; fusion; and
development of sarcomeric myofibrils with contractile potential.
The differentiation sub-step can further comprise adding certain
reagents in the culture medium for activating the canonical WNT
signaling pathway to prevent cell death and facilitate myogenic
differentiation, and adding epigenetic modulators to the culture
medium to alter the chromatin structure for enhanced myogenic gene
expression.
[0009] Certain aspects of the disclosure employ genetically
enhanced cells for unlimited renewal capacity and efficient
conversation to skeletal muscle, the predominant tissue lineage
constituting non-offal meat products, in serum-free culture medium.
When coupled with a scalable tissue engineering approach, such
methods can revolutionize the way meat is produced and marketed for
consumers by enabling cultivation of animal tissue in unlimited
quantities for animal-autonomous cultured meat production.
Additional applications contemplated include in vivo
xeno-transplantation use and in vitro models for drug screening,
developmental physiology, and developmental biology.
[0010] Further features and advantages of the disclosure, as well
as the structure and operation of various embodiments of the
disclosure, are described in detail below with reference to any
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
[0011] FIG. 1 shows a MyoDER DNA sequence.
[0012] FIG. 2 is a schematic illustration of a method comprising a
double-switch regulation mechanism for expansion of the
undifferentiated cell line, or skeletal muscle lineage
specification.
[0013] FIG. 3 is a schematic illustration showing a double-switch
mechanism applied to the myogenic modified 02KM cell line regulated
by DOX or E2.
[0014] FIG. 4A is a schematic illustration of the selectable MyoDER
transgene expression cassette. Arrows and boxes respectively
indicate promoter and gene sequences.
[0015] FIG. 4B shows Western blot image detection of MyoDER
transgene expression in blastidicin-selected 02K by an anti-MYOD1
antibody. Transgene expression cassette modified 02K is designated
as 02KM. TUBA (alpha-tubulin) is detected as an internal loading
control.
[0016] FIG. 5 is an image showing 02KM cells exhibiting stable,
compact-colony morphology in self-renewal conditions as the
parental 02K cell line.
[0017] FIG. 6 is a panel of images showing 02KM cultured on
Poly-D-Lysine+Laminin+MATRIGEL coated dishes +/-0.25 .mu.M
5-Aza-Cytidine (5AC) for phenol-free self-renewal medium (SRM)
under 5% O.sub.2 for three days followed with or without 17-.beta.
Estradiol (E2) induction of the MyoDER fusion protein under 20%
O.sub.2 for two days in phenol red-free myogenic induction medium
(MIM) supplemented with 3 .mu.M CHIR99021. C. Phase-contrast images
of 02KM on E2-induction day 2.
[0018] FIG. 7 shows Western blot analysis of MYOD1 (MyoD), MYF5
(Myf5), and MYOG (myogenin) in differentiated 02KM cell lysates
harvested following indicated 2-day E2 induction regimens. MyoDER
migration: .about.75 kD. Expected endogenous MYOD1 migration: 45-50
kD.
[0019] FIG. 8 shows images of immuno fluorescent detection of
myocyte cell surface marker NCAM (Alexa568) and nuclei (DAPI) in
5AC-exposed 02KM cultures prior to, and following, a 2-day 10 .mu.M
E2 induction time-course.
[0020] FIG. 9 shows a panel of phase-contrast images of i. ground
state undifferentiated 02K colonies cultured on Poly-D
Lysine+Gelatin+Laminin under 5% O.sub.2 in SRM, ii.-vi. adherent
colonies differentiating from the ground state, as shown in panel
i. for two days in differentiation medium (DM) under 20% O.sub.2
supplemented with ii. 0 .mu.M, iii. 1 .mu.M, iv. 3 .mu.M, v. 6
.mu.M or vi. 9 .mu.M CHIR99021. Non-adherant colonies were
prevalent as embryoid bodies in cultures exposed to 6 .mu.M (vii.)
or 9 .mu.M (viii.) CHIR99021.
[0021] FIG. 10 shows a bar graph illustrating adherent 02K cell
population change during differentiation. Percentages represent the
ratio of adherent cells enumerated in cultures following two days
in the presence of CHIR99021 at the concentrations indicated (shown
in FIG. 9, panels ii.-vi.) relative to the adherent cells
enumerated prior to differentiation from the ground-state (shown in
FIG. 9, panel i.). n=3 for each enumerated culture condition.
[0022] FIG. 11 shows a bar graph of flow cytometric analysis of
Annexin V labeled cells. Undifferentiated 02K colonies were
cultured under 20% O.sub.2 in differentiation medium the presence
of 0, 1, 3 or 6 .mu.M CHIR99021 for one day prior to analysis.
[0023] FIG. 12 shows Western Blot analysis of relative CTNNB1
(.beta.-catenin) levels and phosphorylation (p-CTNNB1) at GSK3P
substrates serine 33, 37 and threonine 41 in cultures
differentiated from the ground-state (as shown in FIG. 9) in the
presence of CHIR99021 at the concentrations indicated. Cultures
were exposed to 50 nM Calyculin A and 30 .mu.M MG-132 for 3 hours
prior to harvest to stabilize detectable levels of p-CTNNB1 for
comparative analysis.
[0024] FIG. 13A shows a graph illustrating the densitomentric
ratios of p-CTNNB1/CTNNB1 bands as shown in FIG. 12.
[0025] FIG. 13B shows a graph illustrating the densitometric ratios
of CTNNB 1/TUBA bands as shown in FIG. 12.
[0026] FIG. 14 shows an image illustrating the differentiation
marker time-course Western blot analysis. Expression levels of
pluripotency markers, POU5F1 and KLF4, and the pre-myogenic
paraxial mesoderm marker PAX3 in 02K cultures differentiated from
the ground state in the presence of CHIR99021.
[0027] FIG. 15 shows images of terminal differentiation of 02KM
myocytes differentiated in the absence (left panel) or presence
(right panel) of 5-Aza-Cytidine (5AC). Note the myocyte derivatives
with flattened morphology in the left panel (-5 AC) in contrast to
the elongated, multinucleated myotubes in the left panel (+5
AC).
[0028] FIG. 16 shows Annexin V labeling of apoptotic cells prior
to, and following 24 h transition of cultures, as in FIG. 9, panels
i-ii.
[0029] FIG. 17A shows Western blot detection of full-length CPP32
(.about.32 kD procaspase 3a) and the large cleaved fragment
(.about.17 kD cleaved-caspase 3a) in ground-state colonies prior to
(Oh) and following (12-48 h) differentiation milieu transition
(12-48 h).
[0030] FIG. 17B shows Western blot detection of full-length CPP32
and the cleaved fragment in colonies following 42 h transition to
the differentiation milieu in the presence of CHIR99021 levels
indicated.
[0031] FIG. 18 shows outgrowth morphology of embryoid bodies formed
in a differentiation milieu containing 6 .mu.M CHIR99021 for two
days and following transfer to a Poly-D Lysine+Laminin+MATRIGEL
coated substrate for one (d3, left panel) or three (d5, right
panel) additional days.
[0032] FIG. 19A shows Western Blot of lysates from unmodified piPSC
cultured in the absence of 3i, DOX, hLIF and E2 in differentiation
milieu containing KOSR.
[0033] FIG. 19B shows Western Blot of lysates from MyoDER-modified
piPSC cultured in the presence of DOX, LIF and 3i. MYODER-modified
piPSC were cultured 3 days in self-renewal or expansion milieu.
[0034] FIG. 20A is a schematic of the 02KM expansion and induction
regimens, followed by the terminal differentiation regimen.
[0035] FIG. 20B shows myotube morphology and conformation.
Post-induction (d2), piPSC developed as elongated, anisotropic,
refractive myotubes when exposed to 5AC during the expansion and
induction regimens.
[0036] FIG. 20C shows uniform expression of myosin heavy chain by
d6.
[0037] FIG. 20D shows myotube multinucleation. Left panel: enlarged
image of d4 terminal differentiation cultures. Bracketed arrows
indicate multiple nuclei within a single myotube. Right panel:
myonuclei distribution by myotube ploidy by propidium iodide
labeling and flow cytometry analysis. n=3 with standard deviation
shown.
[0038] FIG. 20E Western blots show increasing expression of desmin
(DES) and myogenin (MYOG) over the 8 d course.
[0039] FIG. 20F shows cell-cycle withdrawal concomitant with
terminal differentiation.
[0040] FIG. 20G shows Transmission Electron Microscopy of d6
myotubes. Sarcomeric structural units were aligned in single {left
panels) and staggered, parallel rows {right panel).
[0041] FIG. 21A shows asynchronous, single-cell transient cycles
{left, middle and right panels) were observed in spontaneously
contracting d6 myotube subpopulations.
[0042] FIG. 2IB shows FOV activation and synchronization of calcium
transient cycles by 1.0 Hz field stimulation in d6 myotubes.
[0043] FIG. 21C shows FOV calcium transient activation of d6
myotubes by 10 mM caffeine.
[0044] FIG. 2ID: single-cell analysis of calcium transient
activation in a d7 myotubes by 100 nM acetylcholine.
DETAILED DESCRIPTION
[0045] To the extent necessary to provide descriptive support, the
subject matter and/or text of the appended claims is incorporated
herein by reference in their entirety. It will be understood by all
readers of this written description that the exemplary embodiments
described and claimed herein may be suitably practiced in the
absence of any recited feature, element or step that is, or is not,
specifically disclosed herein.
[0046] Throughout this disclosure, the term "a" or "an" entity
refers to one or more of that entity; for example, "a
polynucleotide," is understood to represent one or more
polynucleotides. A s such, the terms "a" (or "an"), "one or more,"
and "at least one" can be used interchangeably herein.
[0047] Furthermore, "and/or" where used herein is to be taken as
specific disclosure of each of the two specified features or
components with or without the other. Thus, the term "and/or" as
used in a phrase such as "A and/or B" herein is intended to include
"A and B," "A or B," "A" (alone), and "B" (alone). Likewise, the
term "and/or" as used in a phrase such as "A, B, and/or C" is
intended to encompass each of the following aspects: A, B, and C;
A, B, or C; A or C; A or B; B or C; A and C; A and B; B and C; A
(alone); B (alone); and C (alone).
[0048] It is understood that wherever aspects are described herein
with the language "comprising," otherwise analogous aspects
described in terms of "consisting of and/or "consisting essentially
of are also provided.
[0049] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to whom this disclosure is directed. For
example, the Concise Dictionary of Biomedicine and Molecular
Biology, Juo, Pei-Show, 2nd ed., 2002, CRC Press; The Dictionary of
Cell and Molecular Biology, 3rd ed., 1999, Academic Press; and the
Oxford Dictionary Of Biochemistry And Molecular Biology, Revised,
2000, Oxford University Press, provide one of skill with a general
dictionary of many of the terms used in this disclosure.
[0050] Units, prefixes, and symbols are denoted in their Systeme
International de Unites (SI) accepted form. Numeric ranges are
inclusive of the numbers defining the range. Unless otherwise
indicated, nucleic acid sequences are written 5' to 3' and amino
acid sequences are written left to right in amino to carboxy
orientation. The headings provided herein are not limitations of
the various aspects of the disclosure, which can be had by
reference to the specification as a whole.
[0051] All methods described herein can be performed in any
suitable order unless otherwise indicated herein.
[0052] No language or terminology in this specification should be
construed as indicating any non-claimed element as essential or
critical.
[0053] Recitation of ranges of values herein are merely intended to
serve as a shorthand method of referring individually to each
separate value falling within the range, unless otherwise indicated
herein, and each separate value is incorporated into the
specification as if it were individually recited herein. Where a
specific range of values is provided, it is understood that each
intervening value is intended to be included therein, and all
smaller subranges are also included.
[0054] Provided herein are new and improved methods for generating
functional skeletal muscle, for cultivating meat such as engineered
tissue or other comestible product, from a cell source in vitro.
Such methods are contemplated, for example, for
livestock-autonomous meat production, wherein meat is any metazoan
tissue or cell-derived comestible product intended for use as a
comestible food or nutritional component by humans, companion
animals, domesticated or captive animals whose carcasses are
intended for comestible use, service animals, conserved animal
species, animals used for experimental purposes, or cell
cultures.
[0055] Also provided are in vitro-produced animal tissues, such as
muscle tissue, made by any of the various aspects disclosed herein.
In certain aspects, the cell source is a stem cell source, for
example, a self-renewable stem cell line. Certain aspect of the
methods employ a myogenic, inducible transgene-modified
self-renewable cell line derived from an intended species. In
certain aspects, the intended species can be any edible species
including livestock and poultry species. In certain aspects, the
intended species are livestock species such as domestic cattle,
pigs, sheep, goats, camels, water buffalo, rabbits and the like. In
certain aspects, the intended species are poultry species such as
domestic chicken, turkeys, ducks, geese, pigeons and the like. In
certain aspects, the intended species are common game species such
as wild deer, gallinaceous fowl, waterfowl, hare and the like. In
certain aspects, the intended species are aquatic species or
semi-aquatic species harvested commercially from wild fisheries or
aquaculture operations, or for sport, including certain fish,
crustaceans, mollusks, cephalopods, cetaceans, crocodilians,
turtles, frogs and the like. In certain aspects, the intended
species are exotic, conserved or extinct animal species. In certain
aspects, the intended species are any metazoan species
demonstrating the capacity for skeletal muscle tissue
specification. In certain aspects, the intended species are for
research or for therapeutic purposes, such as humans, primates,
rodents including rats and mice, and companion animals such as
dogs, cats, horses, and the like.
[0056] In certain aspects, the cell line is regulated by a
double-switch mechanism to either maintain the cell line in
self-renewal process or direct myogenic differentiation.
[0057] A parent/host cell line of aspects disclosed herein has the
properties of being immortal (self-renewing) and having the
potential to differentiate, reprogram, specify or otherwise convert
to skeletal muscle lineage, such as following regimens comprising
one or more components that direct myogenic conversion. Three
classes of stem cell may be employed as cell sources for scalable
cultivation: (1) lineage-restricted primary adult progenitor stem
cell isolations, (2) lineage-restricted immortalized cell lines,
and (3) pluripotent stem cells lines. It has been determined that
each of these approaches has advantages and disadvantages in
serving as a cell source for cultured meat production.
[0058] Lineage-Restricted Primary Adult Progenitor Stem Cell
Isolations. These include adult progenitor cells committed to
lineages constituting meat products such as skeletal muscle.
Skeletal muscle progenitor cells include, but are not limited, to
satellite cells, myoblasts and myocytes. Their advantages include:
i) primary adult progenitor cells are restricted to specific
lineages and require little or no in vitro specification to desired
lineages; and ii) primary adult progenitor cells do not require
genetic modification for lineage specification. Their disadvantages
include: i) they must either be harvested from a freshly
slaughtered animal carcass or procured from an invasive biopsy.
Either method conveys dependence on livestock and compromises the
benefit of livestock-autonomous production to the extent that
livestock are used in the process; ii) primary cell isolation is a
highly inefficient process. The desired cells comprise a fraction
of the source tissue. A subtraction of the desired cells survive
the isolation process. Desired cell lineages must be isolated from
mixed populations of surviving cells, requiring additional
purification and expansion steps; iii) primary adult progenitor
cells are subject to the `Hayflick Limit`, wherein cells can divide
only limited number of times before they lose their capacity to
proliferate. Moreover, primary adult progenitor cells lose their
ability to terminally differentiate in a manner concordant with
extended passage. Thus, additional cells must be procured from
primary cell isolations, thereby limiting cultivation scalability
from a single isolation; and iv) primary cell culture of lineages
of tissues applicable to cultured meat production, such as skeletal
muscle, are anchorage dependent-limiting methods for volumetric
scalability of cultures. In suspension culture, these cells may be
susceptible to cell death by anoikis.
[0059] Lineage-Restricted Immortalized Cell Lines. These are
lineage-committed primary cells that are genetically altered to
self-renew indefinitely while retaining their capacity to
terminally differentiate or lineage-restricted. Their advantages
include: i) "perpetually self-renewing" (i.e. not subject to the
`Hayflick Limit`) and can expand indefinitely for scalable and
livestock-autonomous cultivation; ii) restricted to specific
lineages and require little or no further in vitro specification.
Their disadvantages include: i) immortalized, lineage-restricted
cell lines from certain species with the capacity to differentiate
along lineages applicable to cultured meat production (e.g.
skeletal muscle) may require development; ii) cultures of
lineage-committed cell lines are anchorage dependent, limiting
scalability. In suspension culture, lineage-committed cell lines
may be susceptible to cell death by anoikis; and iii) cellular
transformation(s) enabling `immortalization` necessitates genetic
modification. The necessary genetic modifications that immortalize
applicable primary cell populations without interfering with their
capacity to terminally differentiate are not well
characterized.
[0060] Pluripotent Stem Cells Lines: Pluripotent stem cell lines
include embryonic stem cells or induced pluripotent stem cells
(iPSC) that maintain the capacity to self-renew in the
undifferentiated state, or alternately differentiate to any tissue
lineage. Their advantages include: i) in general, pluripotent stem
cell lines proliferate at a higher rate than primary or
immortalized lineage-restricted cell lines, reducing the time
required for biomass expansion in production processes; ii)
pluripotent stem cells may be cultivated as embryoid bodies in
suspension culture, thereby enhancing culture scalability per unit
of culture volume. Moreover, embryoid bodies may be cultured as
`bio-ink` compatible with micromold and bioprinting tissue assembly
methods; and iii) like immortalized lineage-restricted cell lines,
pluripotent stem cells are not subject to the `Hayflick Limit` and
can expand indefinitely for scalable, livestock-autonomous
cultivation. Their disadvantages include: i) authentic embryonic
stem cell lines derived from certain species may require
development; ii) methods for reprogramming and self-renewal of iPSC
may be transgene-dependent. Hence, iPSC pluripotency may require
genetic modification for induction and self-renewal of the
undifferentiated state. Efficient iPSC differentiation requires
mechanisms for silencing the transgenes used for reprogramming and
maintenance of the undifferentiated state mutually exclusive to the
differentiated state to avoid conflicting transcription network
activation disadvantageous to desired lineage specification; and
iii) relative to lineage-restricted primary adult progenitor stem
cells and immortalized cell lines, pluripotent stem cells, in
general, require additional lineage specification steps to develop
and enrich the desired lineage specification.
[0061] Other parental/host cells lines in addition to the three
stem cell classifications provided above are also contemplated
herein. For example, induced trophoblast cell lines (representing
non-pluripotent, non-somatic immortalized cells of extra-embryonic
type), whose myogenic potential was established previously by the
teratoma assay, may be suitable for myogenic conversion as well.
For example, somatic cell lines partially reprogrammed to
pluripotency may possess myogenic potential but fail to form
teratomas representing three embryonic germ layers. For example,
though their existence is controversial, STAP cell lines
(stimulus-triggered acquisition of pluripotency) may be myo-potent
and self-renewing.
[0062] 02K cell line. The 02K cell line is an induced pluripotent
stem cell line established from the inner cell mass of a
pre-implantation porcine embryo. The 02K cell line has been studied
and it was discovered that the self-renewal state of 02K can be
maintained by transcriptional activation of POU5F1 and KLF4
transgenes by doxycycline (i.e. DOX) using a `Tet-On` induction
system.
[0063] MYOD1 transcription factor. MYOD1 (i.e. MyoD) is a dominant
regulator of skeletal muscle lineage commitment. The MyoDER
construct has been described previously, consisting of a genetic
fusion of the murine MYOD1 gene and the sequence encoding the
ligand binding domain of the human estrogen receptor a, shown in
FIG. 1 (SEQ ID NO: 1). In FIG. 1, the MyoDER consists of a genetic
fusion between the murine MYODI gene at the Nar I restriction
endonuclease digest site with the ligand binding domain coding
sequence of the ESR1 (i.e. human estrogen receptor a) nucleotides
844-1781. Non-specified and Cla 1 linker sequences are also
present. The myogenic specification activity of the MyoDER fusion
construct is post-translationally induced by addition of the
estrogen receptor a ligand, 17P-Estradiol (i.e., E2). In the
absence of the 17P-estradiol, MyoDER remains in an inactive state.
The MyoDER construct is herein referred to as "inducible MyoD."
[0064] Referring now to FIG. 2, one aspect is cell-stock-expansion,
i.e., expansion of the cell line in self-renewal conditions
necessary for the maintenance of cell stocks for continued scalable
cultivation. Another aspect is the
lineage-specification/differentiation, i.e., inducing myogenic
lineage differentiation for further tissue cultivation process.
Thus, certain aspects may be summarized as comprising two main
steps: i) modifying a selected self-renewing cell line with a
myogenic transcription factor to produce an
myogenic-transcription-factor-modified cell line, and ii) inducing
such modified cell line by exogenous regulation to maintain in
self-renewal process or advance to differentiation process. As used
herein, "modifying" a cell line with an myogenic transcription
factor refers to inserting a nucleic acid vector or construct
operably encoding a myogenic transcription factor (such as by
transfection, transduction, transformation, and the like) into the
cell line, wherein the modified cell line expresses the myogenic
transcription factor. In certain aspects, the inserted myogenic
transcription factor is inducibly-expressed to produce an
inducible-myogenic transcription factor cell modified cell line. As
used herein, "inducibly," "inducible," and the like refers to any
genetically engineered approaches that may be used to exogenously
regulate the activities of a gene product such as a myogenic
transcription factor. Inducible approaches include, but are not
limited to, regulation of myogenic transcription factor activity by
ligand inducible transcription factor technology (e.g., tet-on,
tet-off, RheoSwitch), site-directed recombination technology (e.g.,
Cre-LoxP, flp-FRT), transposon technology (e.g. Sleeping Beauty,
PiggyBac), ligand binding receptor fusion technology (e.g.,
estrogen, progesterone, androgen, thyroid hormone, glucocorticoid
hormone, tamoxifen ligand agonists), and transient transfection of
extrachromosomal expression vectors bearing a myogenic
transcription factor gene. In certain aspects, the nucleic acid
construct or vector is chromosomally integrated into the modified
cell line. Representative examples of self-renewing cell lines
include those selected from a group consisting of embryonic stem
cells, induced pluripotent stem cells, and immortal
lineage-restricted cell lines. In certain aspects, such
self-renewing cell lines are derived from species intended for
dietary consumption or for research or for therapeutic purposes.
Representative examples of myogenic transcription factors include,
used alone or in combination, MYOD1, MYOG, MYF5, MYF6, PAX3, PAX7,
paralogs, orthologs, genetic variants thereof, or transcriptional
activation agonists of the respective promoter recognition DNA
sequences of the myogenic transcription factors disclosed
herein.
[0065] Reference is made now to FIG. 3, which includes exemplary
schematic illustrations of the double-switch mechanism of the
myogenic modified 02KM cell line regulated by DOX or E2. As shown
in FIG. 3, during the 02KM stem cell self-renewal process, the
expression of the pluripotency transgenes POU5F1 and KLF4 is
induced in the presence of DOX in the self-renewal medium (SRM),
while such expression is repressed when DOX is absent. Similarly,
during the 02KM myogenic differentiation process, myogenic
differentiation is activated by the inducible MyoD transgene in the
presence of E2 in the myogenic induction medium (MIM), while such
directed differentiation is inactive when E2 is absent.
[0066] Certain aspects provide differentiation/specification
methods comprising additional reagents other than E2 in the MIM to
prevent cell death and to modulate the epigenetic state of
chromatin. For example, a Glyogen Synthase Kinase-3P (GSK3P)
inhibitor can be added to the SRM and MIM to activate the canonical
WNT signaling pathway, in turn, enhance myogenic differentiation
and reduce cell death at the time of DOX withdrawal. Without being
limited by theory, in certain aspects, the epigenetic modular
alters the chromatin activation by myogenic transcription factors
and/or enhances expression of myogenic transcription factors, such
as MYF5.
[0067] It is understood that GSK3P inhibition includes targeting
with small-molecules. Gene editing is also a promising approach to
enhance skeletal muscle specification by WNT signaling activation.
For example, GSK3P may be inhibited in the host/parental cell line
by mutating the GSK3P alleles either by sequence-specific insertion
or deletion technology (i.e. Zinc-Finger Nuclease, TALEN, CRISPR).
Mutating the endogenous promotor region can be used to repress
expression of GSK3p. Alternately, the GSK3P open reading frame may
be deleted or mutated using the same methods to abolish GSK3P
activity. Likewise, the downstream phosphorylation target of GSK3P,
beta-catenin (CTNNB1) may be mutated at the codons coding for
residues phosphorylated by GSK3P, thereby preventing
phosphorylation of CTNNB1 by GSK3P, resulting in a constitutively
active, stable CTNNB1. Such "gene-editing" methods would reduce the
cost of GSK3P inhibition by small-molecule targeting and
potentially improve the safety profile of the meat product, as
additional chemicals would not be required to inhibit GSK3P during
the process. It is contemplated that a third approach to
Wnt-signaling inhibition includes the use of anti-sense nucleic
acid inhibitors to GSK3P or other factors antagonistic to the WNT
pathway. These may include RNA interference methods using
sequence-targeting shRNA or miRNA.
[0068] Certain specific aspects provide for use of a GSK3P
inhibitor to promote cell survival, for example at the time of DOX
withdrawal. One illustrative example of a GSK3P inhibitor is
CHIR99021. Additional representative GSK3P inhibitors may include,
without limitation: lithium chloride, BIO, SB216763, CHIR-98014,
TWS1 19, Tideglusib, IM-12, 1-Azakenpullone, AR-A014418, and
SB415286. Without being bound by theory, it is believed that
concomitant with DOX, both self-renewal of undifferentiated cells
is maintained by a WNT signaling pathway involving the inhibition
of GSK3p.
[0069] Without being bound by theory or limited by any specific
representative example, it was observed that simultaneous
withdrawal of both DOX and the GSK3P inhibitor CHIR99021 from the
culture medium supplemented with N-2 and B-27 serum replacements
precipitates massive cell death of differentiating 02K parental
line within 48 h hours. Withdrawal of DOX in the presence of
CHIR99021 enabled survival of the differentiating 02K. Death by
differentiating 02K cells in the absence of a GSK3P inhibitor and
reciprocal survival in the presence thereof was confirmed by
morphology, cell adhesion assay, cleaved caspase-3 accumulation,
and Annexin V labeling. In the parental 02K cell line, inhibition
of GSK3P concordantly resulted in the stabilization and activation
of its phosphorylation substrate, CTNNB1, the downstream positive
effector of the canonical WNT signaling pathway. WNT signaling
plays crucial roles in both mesoderm specification from the
undifferentiated ground-state pluripotency, pre-myogenic enrichment
from unpatterned mesoderm and terminal differentiation of committed
myocytes both in vivo and in vitro. In agreement, extended culture
of the 02K line in the absence of DOX, and in the presence of a
GSK3P inhibitor, supported differentiation toward the pre-myogenic
paraxial mesoderm, as evidenced by the expression of PAX3 and
concomitant loss of POU5F1 and KLF4 expression. Furthermore, in
combination with 5AC, the GSK3P inhibitor enhanced expression of
the myogenic transcription factor MYF5 in differentiating 02K.
Moreover, a GSK3P inhibitor, such as CHIR99021, enhanced the
terminal differentiation of the myogenic murine C2C12 cell line
into multi-nucleated myotubes, as shown in Table 1.
[0070] Table 1 lists the influences of extracellular matrix
effectors (i.e. Gelatin, Poly-D-Lysine, Laminin, MATRIGEL) and
soluble factors (E2, CHIR99021) on the terminal differentiation of
the murine C2C12 myoblast by assessment of the size and extent of
myotube formation proceeding a 5-day differentiation time course.
(Cultures were scored from [*****], indicating robust myotube
formation to [-] indicating non-detectable myotube formation.)
TABLE-US-00001 TABLE 1 Influence of Extracellular Matrix effectors
and Soluble factors on the terminal differentiation. +5 .mu.M E2,
Basal +3 .mu.M +3 .mu.M Medium +5 .mu.M E2 CHIR CHIR Gelatin *** **
*** ** Gelatin + Poly-D *** * * -- Lysine Laminin + *** * ** **
MATRIGEL + Poly-D Lysine Laminin + *** * **** ** MATRIGEL Laminin
*** * *** * MATRIGEL *** ** ***** ***
[0071] In certain aspects due to its multifunction: (1) suppressing
cell death following DOX withdraw, (2) supporting differentiation
toward the pre-myogenic state, (3) enhancing myogenic
specification, and (4) enhancing terminal differentiation, a GSK3P
inhibitor when retained in the culture medium during
differentiation (in the absence of DOX), is deemed compatible with
the inducible myogenic transcription factor directed lineage
specification and subsequent terminal differentiation conditions by
derivative myocytes. For example, CHIR99021 was retained in the
02KM cultures following DOX withdrawal during subsequent E2-induced
lineage-specification and terminal differentiation processes.
[0072] However, though the aforementioned GSK3P
inhibitor-supplemented culture regimen supported cell survival and
myogenic lineage specification by 02KM to differentiated cells with
distinctive myocyte-like spindle morphology, the derivative cells
failed to terminally differentiate into refractive elongated
myotubes. Therefore, a epigenetic modulator was used to enhance the
expression of myogenic genes in cells otherwise non-permissive to
myogenesis and enhance terminal differentiation of lineage
committed myoctes to mature myofibers. To enable terminal
differentiation of 02KM, cells were cultured in the presence of
5-Aza-Cytidine (5AC) for 72 hours preceding DOX withdrawal, for 48
hours during E2 induction, followed by a terminal differentiation
period up to 6 additional days. In 02KM derived myocytes cultured
in the presence of 5AC, MYF5 expression was enhanced and cells
exhibited a refractive myofibril morphology, whereas myocytes
derived in the absence of 5AC expressed reduced MYF5 and exhibited
an flattened morphology atypical to mature myofibrils. This
distinction may explained by the enhanced expression of the
myogenic transcription factor MYF5 observed only in the 5AC-exposed
02KM prior to and following 48 hours of DOX withdrawal
[0073] In conjunction with enrichment of the lower molecular
weight, non-phosphorylated myogenin isoform, known to be the active
transactivator, the morphological distinction among these cultures
may be explained by MYF5 expression enhanced by 5AC exposure. It is
understood that epigenetic modulation entails alteration of
chromatin structure influencing transcription factor binding and
targeted transcriptional activation by altering the DNA methylation
patterns and post-translational modification of
nucleosome-associated histones. It is understood that epigenetic
modulation may entail small-molecule agonists or antagonists
targeting epigenetic pathways or expressed proteins comprising
epigenetic machinery. One illustrative example of a small-molecule
epigenetic modulator is 5-Aza-Cytidine (5AC). Additional
representative examples of small molecule epigenetic modulators
include 5-Aza-2'-deoxycytidine, RG108, Scriptaid, sodium butyrate,
trichostatin A, Suberoylanilide Hydroxamic Acid, MS-275, CI-994,
BML-210, M344, MGCD0103, PXD101, LBH-589, Tubastatin A, NSC3825,
NCH-51, NSC-3852, HNHA, BML-281, CBHA, Salermide, Pimelic
Diphenylamide, ITF-2357, PCI-24781, APHA Compound 8, Droxinostat,
and SB-939. Representative examples of proteins involved in
epigenetic modulation include histone deacetylase paralogs, histone
acetyltransferase paralogs, tet-methycytosine dioxygenase paralogs,
histone demethylase paralogs, histone methyltransferase paralogs,
and DNA methyltransferase paralogs, histones, and subunits of
chromatin remodeling complexes including Mi-2/NuRD (and its
components such as methyl-CpG-binding domain protein 3 (MBD2)) and
SWI/SNF (and its components such as BAF60 and BAF60C). It is
further understood that respective activities of protein epigenetic
modulators may be influenced by representative modalities such as
targeting by small-molecule factors, over-expression of a
respective exogenous transcript, anti-sense RNA-targeted respective
transcript degradation, RNAi, and targeted mutation at the genetic
locus.
[0074] The following disclosed embodiments are merely
representative. Thus, specific structural, functional, and
procedural details disclosed in the following examples are not to
be interpreted as limiting.
Examples
Methods
[0075] 02KM cell line. The 02KM cell line was derived from the
parental 02K cell line by lentiviral insertion of a
blastidicin-selectable transgene cassette containing the MyoDER
open reading frame sequence (ORF). As referred to in this example
section, 02K cells/cell line and piPSC cells are used
interchangeably. The lentiviral vector, illustrated in FIG. 4A, was
prepared by cloning the MyoDER ORF (Addgene #13494) downstream of
the CMV promoter of the pLentiCMVBlast destination vector (Addgene
#17451) between the attR1 and attR2 recombination sites from an
pENTR/D-TOPO entry vector (Life Technologies #K2435-20) clone
containing the PCR-amplifted MyoDER ORF. To prepare the lentiviral
supernatant, 293FT cells were co-transfected with the prepared
pLentiCMVBlast[MyoDER] plasmid, the pMD2.G envelope plasmid
(Addgene #12259) and the psPAX2 packaging plasmid (Addgene #12260)
using the PolyJet transfection reagent (Signagen # SL100688). 02K
was transduced with pseudovirus concentrated from the 293FT
supernatant. Transduced 02K were cultured in phenol-red free
culture medium and selected four days with 10 .mu.g/mL blasticidin
followed by two additional days with 15 .mu.g/mL blasticidin.
Selected cells were designated as 02KM. Expression of MyoDER in the
02KM stock was verified by Western blot, FIG. 4B
[0076] 0.2KM stem cell stock expansion in presence DOX. 02KM stem
cell renewal milieu was conducted as for the parental 02K line,
with the following exception: phenol-red free formulations of
DMEM/F-12 and neurobasal medium were substituted for the phenol-red
containing formulations to avert pleotropic agonistic effects on
MyoDER (i.e. activation). The 02KM cell stock self-renewal medium
(SRM) consisted of the following components: phenol-red-free
neurobasal medium (Life Technologies #12348-017), phenol-red free
DMEM-F12 (Life Technologies #11039-021), IX non-essential amino
acids (Sigma-Aldrich #M7145), 0.5.times. Glutamax (Life
Technologies #35050061), 0.000007% .beta.-Mercaptoethanol,
0.5.times.N2 Supplement (Life Technologies #17502048),
0.5.times.B27 Supplement Minus Vitamin A (Life Technologies
#12587010), 0.1 mg/mL Bovine Serum Albumin, 2 .mu.g/mL doxacycline
hyclate (i.e. DOX), 10 ng/mL human leukemia inhibitory factor
(hLIF, Millipore #LIF1050), 3 .mu.M CHIR99021, 0.8 .mu.M PD032591
and 0.1 .mu.M PD 173074. Herein forth, the three inhibitors
CHIR99021, PD032591 and PD 173074 are collectively regarded as
`3i`. Alternatively, N-2 and B-27 serum replacements were
substituted using 15% KnockOut Serum Replecement (KOSR; Life
Technologies #A15870). 02KM maintained by enzymatic dissociation of
colonies and passages of cells onto culture dishes coated with
poly-D lysine and murine laminin in phenol-free SRM under
5%>O.sub.2 every 3 d. In these self-renewal conditions, 02KM
maintained compact, stem cell-like morphology as the parental 02K
line, as shown in FIG. 5.
[0077] CHIR99021 inhibition 1 cell death. Differentiation of the
parental 02K line in the absence of SRM culture medium components
that support self-renewal hLIF, DOX, CHIR99021, PD032591 and PD
173074, and KOSR resulted in massive cell death as determined by
(1) phase contrast microscopy as shown in FIG. 9, panels i.-ii.,
(2) CPP32 cleavage, as shown in FIG. 17A, and (3) Annexin V
labeling shown in FIG. 16. However, a culture medium formulation
including CHIR99021, when retained in the SRM basal medium in the
absence of hLIF, DOX, PD032591 and PD173074, supported both cell
survival during differentiation as determined by (1) phase-contrast
microscopy, as shown in FIG. 9, panels iii.-viii., (2) cell
adhesion assay, as shown in FIG. 10, (3) CPP32 cleavage inhibition
as shown in FIG. 17B, and (4) Annexin V labeling, as shown in FIG.
11. Moreover, CHIR99021 exposure during primordial differentiation
stabilizes and modulates the phosphorylation status of the GSK3P
substrate, CTNNB1, as shown in FIGS. 12, 13A and 13B, the
phospho-regulated downstream effector of the canonical WNT
signaling pathway known to direct mesodermal differentiation during
embryonic lineage specification, myogenic enrichment of mesodermal
progenitors, and terminal differentiation of skeletal myocytes.
Congruent with these findings, CHIR99021 supplemented basal medium
supported pre-myogenic paraxial mesoderm lineage specification of
differentiating 02K, as shown in FIG. 14 and when included in
low-mitogen differentiation cultures (2% horse serum/DMEM) of the
myogenic murine C2C12 cell line, enhanced terminal differentiation
into skeletal myotubes, listed in Table. 1. As CHIR99021 repressed
cell death, supported differentiation toward paraxial mesoderm by
the differentiating 02K cell line and enhanced terminal
differentiation by the C2C12 cell line, precedent was established
to retain the compound in all culture stages. Hence, 3 .mu.M
CHIR99021 was retained in the culture medium during expansion,
induction and terminal differentiation steps (FIG. 20A) unless
stated otherwise.
[0078] 02KM myogenic induction. 02KM cells were seeded onto culture
dishes coated with poly-D lysine, murine laminin and MATRIGEL at a
density of 4.1.times.10.sup.3 cells/cm.sup.2 and cultured under 5%
O.sub.2 in self-renewal medium for 3 d. To facilitate
differentiation, cultures were transferred to a 20% O.sub.2 basal
differentiation milieu, designated by withdrawal of PD032591, PD
173074, DOX, hLIF and .beta.-mercaptoethanol. To conditionally
induce the expressed MyoDER protein, 10 .mu.M E2 was added to the
medium. E2-directed myogenic lineage specification following 2 d
induction culture was confirmed by (1) adoption of spindle-like
morphology characteristic of skeletal myocytes in treated cultures,
as shown in FIG. 6, (2) expression of endogenous the MYOG skeletal
muscle transcription factor, as shown in FIG. 7 and (3) uniform
expression of the skeletal myocyte cell surface marker, NCAM, as
shown in FIG. 8.
[0079] 5AC effects. 5AC exposure prior to, during, and following
E2-mediated induction of `MyoDER` was introduced to enable
terminal-differentiation of 02KM from myocytes into refractive,
filamentous myotubes. The murine C2C12 cell line was used as
positive control to screen for optimal conditions for terminal
differentiation by 02KM. These conditions included: a MATRIGEL
extracellular matrix and CHIR99021 supplementation in the absence
of E2, as listed in Table 1. However, 02KM-derived myocytes
passaged onto MATRIGEL-coated culture dishes in differentiation
medium without E2 (the conditions determined optimal for C2C12
terminal differentiation) failed to establish refractive myotubes,
as shown in FIG. 15 and FIG. 20B. Hence, the gene expression
program in the 02KM-derived myocytes was not sufficient to enable
terminal differentiation as per the established conditions. 5AC, a
small-molecule epigenetic modulator, was determined previously to
enable skeletal muscle transcription in cell lines non-permissive
to myogenesis. Moreover, 5AC exposure was further determined to
enhance terminal differentiation by the C2C12 cell line. Hence, 250
nM 5AC, the highest dose tolerated by undifferentiated 02KM, was
included during in the proliferative 02KM expansion and induction
regimens, as shown in FIG. 20A.
[0080] Terminal Differentiation. Following 2 d E2 induction,
cultures were either terminally differentiated in situ, or passaged
to MATRIGEL-coated culture dished in terminal differentiation
medium (TDM) at 1.56.times.10.sup.5 cells/cm.sup.2 for terminal
differentiation. TDM was formulated from the same components as
MIM, except for the following modifications: withdrawal of E2,
addition of 4 .mu.M A 83-01, and 100 nM IGF-1. N-2 and B-27
supplements were used exclusively as serum replacements. Cultures
were differentiated for up to 6 d following under 20% O.sub.2
following induction regimens (FIG. 20A). Cultures exposed to 5AC
during expansion and induction regimens formed refractive,
anisotropic myotubes during the terminal differentiation regimen,
shown in FIG. 20B. FIG. 20C shows uniform expression of myosin
heavy chain by d6, and FIG. 20E shows increasing expression of
desmin (DES) and myogenin (MYOG) over the 8 d course. Myotube
polyploidy was observed during terminal differentiation, as shown
in FIG. 20D, left panel. The relative distribution of myonuclei in
d8 myotubes according to ploidy is shown in FIG. 20D, right panel.
Relative prevalence of S-phase nuclei in the renewal milieu (d3
colonies), expansion milieu (dO cultures, FIG. 20A), and terminal
differentiation milieu (d8 cultures, FIG. 20A), as shown in FIG.
20F, indicated cell cycle withdrawal following terminal
differentiation. Contractile potential of terminally
differentiating skeletal muscle myotubes was validated by (1)
structural development of well-organized sarcomeres, as shown in
FIG. 20G; (2) asynchronous spontaneous contraction, as shown in
FIG. 21A; (3) contractile stimulation and synchronization by field
stimulation, as shown in FIG. 2IB; (4) caffeine-stimulated
contraction, as shown in FIG. 21C; and (5) acetylcholine-stimulated
contraction, as shown in FIG. 2ID.
Results
[0081] An axis of apoptosis and differentiation is modulated by
CHIR99021. FIG. 9 shows phase-contrast images of ground-state piPSC
colonies cultured under 5% O.sub.2 in the self-renewal milieu (i.)
and following 48 h under 20% O.sub.2 in the absence of DOX, LIF and
3i, (ii.). FIG. 16 shows Annexin V labeling of apoptotic cells
prior to, and following 24 h transition of cultures. FIG. 17A shows
Western blot detection of full-length CPP32 (.about.32 kD
procaspase 3a) and the large cleaved fragment (.about.17 kD
cleaved-caspase 3a) in ground-state colonies prior to (Oh) and
following (12-48 h) differentiation milieu transition (12-48 h).
FIG. 9 shows phase contrast images of adherent cultures (iii, iv,
vi, and vi) and non-adherent embryoid body cultures (vii and viii)
following 48 h culture in differentiation milieu supplemented with
CHIR99021 as indicated. FIG. 10 shows adherent cell percentage of
differentiation milieu cultures supplemented with the CHIR99021 as
indicated for 48 h relative to ground-state (i.e. Oh) cultures,
normalized to 100%. *non-adherent cells viable as embryoid bodies.
n=3 for each culture condition. FIG. 11 shows Annexin V labeling of
apoptotic cells following 24 h transition of cultures to
differentiation milieu supplemented with CHIR99021 as indicated.
FIG. 17B shows Western blot detection of full-length CPP32 and the
cleaved fragment in colonies following 42 h transition to the
differentiation milieu in the presence of CHIR99021 levels
indicated. TUBA is detected an internal protein loading
control.
[0082] CHIR99021 stabilizes CTNNB1 and supports differentiation
from the ground state. FIG. 12 shows Western blot detection of
CTNNB1 and p-CTNNB1 (total and phospho-S33,37, T41 .beta.-catenin,
respectively) following 24 h differentiation milieu transition in
the presence of CHIR99021, as indicated. TUBA detected as an
internal protein loading control. FIG. 13A indicates ratios of
p-CTNNB1/CTNNB1 bands. FIG. 13B indicates ratios of CTNNB1/TUBA
bands. FIGS. 13A and 13B represent densitometric quantitation from
Western Blots as shown in FIG. 12; n=3. FIG. 18 shows outgrowth
morphology of embryoid bodies formed in a differentiation milieu
containing 6 .mu.M CHIR99021 for two days and following transfer to
a Poly-D Lysine+Laminin+MATRIGEL coated substrate for one (d3, left
panel) or three (d5, right panel) additional days. FIG. 14 shows
Western blot analysis of PAX3, POU5F1 and KLF4 expression in
ground-state milieu (dO) and differentiation milieu cultures
(d1-d5) according to one regimen aspect described elsewhere herein.
TUBA detection is shown as an internal protein loading control.
[0083] 5-Aza-cytidine and MyoDER activation of endogenous MRFs.
piPSC modification with an integrated MyoDER expression cassette.
FIG. 4A shows a Blasticidin (BLAST)-selectable MyoDER expression
cassette. Arrows and boxes indicate promoter and gene sequences,
respectively. FIG. 4B shows Western blot detection of MyoDER in the
unmodified (02K) and MyoDER expression cassette-modified (02KM)
piPSC line. MyoDER was detected with an antibody raised against a
MyoD peptide. FIG. 7 shows Western blot detection of MyoDER (-75
kD), MYF5 and MYOG following 2 d piPSC induction. Endogenous MYOD1
(-45 kD, expected) was not detected. 02KM were seeded onto poly-D
lysine+Martigel+murine laminin coated culture dishes and cultured
with hLIF, 3i & DOX for three days in the presence (i.e.
expansion, FIG. 20A) or absence of 5AC, followed by respective
transition to a -/+5AC differentiation milieu supplemented with E2
(i.e. 17.beta. estradiol) and 3 .mu.M CHIR99021 for two days.
Double Arrow: Partially resolved MYOG isoforms. FIGS. 19A and 19B.
Determinants of MYF5 activation: Western blot analyses. FIG. 19A,
following three days of culture on poly-d-lysine+laminin+MATRIGEL,
unmodified piPSC were cultured 2 d in the absence of 3i, DOX, hLIF
and E2 in differentiation milieu supplemented with 5AC (as in FIG.
7) and CHIR99021 as indicated. In the absence of CHIR99021, the 17
kD cleaved caspase isoform was not observed in the KOSR
supplemented differentiation milieu, as in contrast to observations
in the N-2 and B-27 supplemented differentiation milieu (FIG. 17A,
FIG. 19A). 5AC-enhanced activation of endogenous MYF5 expression
was dependent upon simultaneous CHIR99021 exposure, as shown in
FIG. 19A. FIG. 19B shows MYF5 activation in the presence of DOX,
LIF and 3i. MYODER-modified piPSC were cultured 3 days in
self-renewal or expansion milieu. In the presence of DOX and
CHIR99021, 5AC exposure supported detectable MYF5 expression
levels, as shown in FIG. 19B, after 3 days of expansion culture. In
contrast MYF5 was not detected following 3 days of renewal culture
(-5AC), as shown in FIG. 19B. TUBA is detected as an internal
protein loading control. FIG. 6 shows the morphology of selected
piPSC cultures following lineage specification induction culture
regimens (FIG. 20A) described elsewhere herein. FIG. 8 shows
immunocytoflourescent detection of nuclei (DAPI) and NCAM in
piPSC-MyoDER cultures prior to (dO, left panel) and following (d2,
right panel) 10 .mu.M E2 exposure, in the presence of 5AC.
[0084] Terminal Myogenesis of Lineage-Specified piPSC. Prior to
terminal differentiation, cultures were expanded for 3 days in the
presence of 5AC, induced for 2 days in the presence of E2 &
5AC, and terminally differentiated in the absence of 5AC & E2
as shown in FIG. 20A. FIG. 20B shows myotube morphology and
conformation. Post-induction (d2), piPSC developed as elongated,
anisotropic, refractive myotubes. Where 5AC was not included in the
expansion and induction steps, cells exhibited a flattened,
non-refractive morphology. FIG. 20C and FIG. 20E show terminal
myogenesis protein expression. DO and D6 cultures were stained for
myosin heavy chain (MyHC) isoforms with a pan-MyHC monoclonal
antibody, clone MF20. FIG. 20D shows myotube multinucleation. Left
panel: enlarged image of d4 terminal differentiation cultures.
Bracketed arrows indicate multiple nuclei within a single myotube.
Right panel: myonuclei distribution by myotube ploidy by propidium
iodide labeling and flow cytometry analysis. n=3 with standard
deviation shown. FIG. 20E shows Western blot analyses. MyoD
(MYOD1), myogenin (MYOG) and desmin (DES) expression, dO-d8. TUBA
is detected as an internal protein loading control. FIG. 20F shows
cell-cycle withdrawal coinciding with terminal differentiation. d3
modified piPSC renewal, expansion cultures and d8 terminal
differentiation cultures were labeled with EdU, and the S-phase
fraction was determined by flow cytometry. n=3 with standard
deviation shown. FIG. 20G: Transmission Electron Microscopy, d6
myotubes. Sarcomeric structural units were aligned in single {left
panels) and staggered, parallel rows {right panel).
[0085] Spontaneous and Stimuli-Induced Calcium Transient Activity
in piPSC-derived myotubes. To quantify contraction cycles, myotube
cultures were stained with Fluo-4 AM calcium dye, washed, and image
sequences were captured by confocal microscopy. Dynamic signaling
events of an entire field of view (FOV) or single cells were traced
and plotted over the imaging course. [s]=seconds. FIG. 21A shows
representative asynchronous, single-cell transient cycles {left,
middle and right panels) were observed in spontaneously contracting
d6 myotube subpopulations. FIG. 2IB shows FOV activation and
synchronization of calcium transient cycles by 1.0 Hz field
stimulation in d6 myotubes. FIG. 21C shows FOV calcium transient
activation of d6 myotubes by 10 mM caffeine. FIG. 2ID: single-cell
analysis of representative calcium transient activation in a d7
myotubes by 100 nM acetylcholine.
Discussion
[0086] In summary, it has been discovered that certain aspects of
the exemplary embodiments described in this disclosure demonstrate
one or more of the following unexpected advantages for cultured
meat applications: [0087] (i) Rapid Cell Proliferation Rate; [0088]
(ii) Rapid Differentiation: With as little as 48 hours of
17P-estradiol induced MyoDER activation and doxycycline withdrawal,
the 02KM cell line differentiates to the myogenic lineage, in
vitro. No lengthy differentiation procedures required; [0089] (iii)
Efficient Differentiation: The CHIR99021/5AC/MyoDER-directed
lineage specification ensures extensive high-fidelity conversion to
functional skeletal myocytes. No cell sorting is required; [0090]
(iv) Infinite Self-Renewal: Self-renewal of undifferentiated 02KM
is tightly enforced supported in the self-renewal milieu; [0091]
(v) Self-Renewal and Terminal Differentiation in Serum-Free Medium:
Self-renewal and terminal myogenic differentiation of the 02KM line
were both validated in serum-free medium; [0092] (vi) Compatible
with Suspension Culture Systems as Embryoid Bodies: In the
pluripotent state, the parental 02K and modified 02KM are resistant
to anoikis and may be cultivated into embryoid bodies from single
cells in suspension culture. 02KM-derived embryoid bodies may be
compatible with multicelluar spheroid assembly technologies such as
bioprinting and mircomolds for cultured meat production; and [0093]
(vii) Autologous Contraction: 02KM terminally differentiated as
skeletal muscle exhibits sarcomeric maturation and autologous
contraction. Hence, external stimulation (e.g. mechanical tension,
acetylcholine receptor activation, electrical stimulation) may not
be necessary to promote myofiber maturation.
[0094] While the invention has been described in connection with
example embodiments thereof, it will be understood that the
inventive method is capable of further modifications. This patent
application is intended to cover any variations, uses, or
adaptations of the invention following, in general, the principles
of the invention and including such departures from the present
disclosure as come within known or customary practice within the
art to which the invention pertains and as may be applied to the
essential features herein before set forth and as follows in scope
of the appended claims.
Sequence CWU 1
1
111905DNAArtificial SequenceSynthetic fusion 1atggagcttc tatcgccgcc
actccgggac atagacttga caggccccga cggctctctc 60tgctcctttg agacagcaga
cgacttctat gatgacccgt gtttcgactc accagacctg 120cgcttttttg
aggacctgga cccgcgcctg gtgcacatgg gagccctcct gaaaccggag
180gagcacgcac acttccctac tgcggtgcac ccaggcccag gcgctcgtga
ggatgagcat 240gtgcgcgcgc ccagcgggca ccaccaggcg ggtcgctgct
tgctgtgggc ctgcaaggcg 300tgcaagcgca agaccaccaa cgctgatcgc
cgcaaggccg ccaccatgcg cgagcgccgc 360cgcctgagca aagtgaatga
ggccttcgag acgctcaagc gctgcacgtc cagcaacccg 420aaccagcggc
tacccaaggt ggagatcctg cgcaacgcca tccgctacat cgaaggtctg
480caggctctgc tgcgcgacca ggacgccgcg ccccctggcg attctgctgg
agacatgaga 540gctgccaacc tttggccaag cccgctcatg atcaaacgct
ctaagaagaa cagcctggcc 600ttgtccctga cggccgacca gatggtcagt
gccttgttgg atgctgagcc ccccatactc 660tattccgagt atgatcctac
cagacccttc agtgaagctt cgatgatggg cttactgacc 720aacctggcag
acagggagct ggttcacatg atcaactggg cgaagagggt gccaggcttt
780gtggatttga ccctccatga tcaggtccac cttctagaat gtgcctggct
agagatcctg 840atgattggtc tcgtctggcg ctccatggag cacccaggga
agctactgtt tgctcctaac 900ttgctcttgg acaggaacca gggaaaatgt
gtagagggca tggtggagat cttcgacatg 960ctgctggcta catcatctcg
gttccgcatg atgaatctgc agggagagga gtttgtgtgc 1020ctcaaatcta
ttattttgct taattctgga gtgtacacat ttctgtccag caccctgaag
1080tctctggaag agaaggacca tatccaccga gtcctggaca agatcacaga
cactttgatc 1140cacctgatgg ccaaggcagg cctgaccctg cagcagcagc
accagcggct ggcccagctc 1200ctcctcatcc tctcccacat caggcacatg
agtaacaaag gcatggagca tctgtacagc 1260atgaagtgca agaacgtggt
gcccctctat gacctgctgc tggagatgct ggacgcccac 1320cgcctacatg
cgcccactag ccgtggaggg gcatccgtgg aggagacgga ccaaagccac
1380ttggccactg cgggctctac ttcatcgcat tccttgcaaa agtattacat
cacgggggag 1440gcagagggtt tccctgccac agctatcgcc gctgccttct
acgcacctgg accgctgccc 1500ccaggccgtg gcagcgagca ctacagtggc
gactcagatg catccagccc gcgctccaac 1560tgctctgatg gcatgatgga
ttacagcggc cccccaagcg gcccccggcg gcagaatggc 1620tacgacaccg
cctactacag tgaggcggcg cgcgagtcca ggccagggaa gagtgcggct
1680gtgtcgagcc tcgactgcct gtccagcata gtggagcgca tctccacaga
cagccccgct 1740gcgcctgcgc tgcttttggc agatgcacca ccagagtcgc
ctccgggtcc gccagagggg 1800gcatccctaa gcgacacaga acagggaacc
cagaccccgt ctcccgacgc cgcccctcag 1860tgtcctgcag gctcaaaccc
caatgcgatt tatcaggtgc tttga 1905
* * * * *