Stem cells for skeletal muscle regeneration: therapeutic potential and roadblocks FABRIZIO RINALDI, and RITA C. R. PERLINGEIRO MINNEAPOLIS, MINN

Conditions involving muscle wasting, such as muscular dystrophies, cachexia, and sarcopenia, would benefit from approaches that promote skeletal muscle regeneration. Stem cells are particularly attractive because they are able to differentiate into specialized cell types while retaining the ability to self-renew and, thus, provide a long-term response. This review will discuss recent advancements on different types of stem cells that have been attributed to be endowed with muscle regenerative potential. We will discuss the nature of these cells and their advantages and disadvantages in regards to therapy for muscular dystrophies. (Translational Research 2014;163:409–417) Abbreviations: DMD ¼ Duchenne muscular dystrophy; ES cells ¼ embryonic stem cells; iPS cells ¼ induced pluripotent stem cells; MD ¼ muscular dystrophy; MDSCs ¼ muscle-derived stem cells; MyoD ¼ myogenic differentiation antigen; Pax3 ¼ paired box homeodomain 3; Pax7 ¼ paired box homeodomain 7

M

uscular dystrophies (MDs) comprise more than 30 neuromuscular disorders of inherited origin.1 A common feature of this clinically and genetically heterogeneous group of disorders is progressive muscle weakness in particular subsets of degenerating skeletal muscles, which leads to atrophy, and frequently the confinement of affected patients to a wheelchair. The most common, Duchenne muscular dystrophy (DMD), affects one out of 5000 male live births, and is caused by mutations in the dystrophin gene that result in biochemical defects of the dystrophin-glycoprotein complex in skeletal muscle and other tissues.2,3 Affected patients lose mobility by

From the Department of Medicine, Lillehei Heart Institute, University of Minnesota, Minneapolis, Minn. Submitted for publication September 16, 2013; revision submitted November 1, 2013; accepted for publication November 7, 2013. Reprint requests: Rita C.R. Perlingeiro, PhD, Lillehei Heart Institute, University of Minnesota, 4-128 CCRB, 2231 6th St. SE, Minneapolis, MN 55455; e-mail: [email protected]. 1931-5244/$ - see front matter Ó 2014 Mosby, Inc. All rights reserved. http://dx.doi.org/10.1016/j.trsl.2013.11.006

their teenager years with eventual death because of respiratory and/or cardiac failure. Loss of skeletal muscle mass is also observed in the aging population, a process known as sarcopenia, and as a secondary effect in some cancer patients, known as cachexia. These conditions can also cause severe debilitating weakness and metabolic dysfunction.4-7 Skeletal muscle comprises about 40% of the human body mass, and it is well recognized for its robust capacity for regeneration. Seminal observations in this regard were first described in 1953 by Russian investigator A.N. Studitsky, who chopped a muscle biopsy into 1-mm3 pieces and observed remarkable new muscle formation following reimplantation of this minced muscle tissue back into the muscle bed.8 This rudimentary model was proven to be very useful to understand the initial principles of skeletal muscle regeneration. Subsequently, Carlson and Gutmann9 repeated these experiments in rats and demonstrated that the new fibers were functionally and morphologically similar to those present in normal muscle. Several years later, this model was used to investigate the impact of age on this regenerative process. Whereas young and aged minced muscle tissue regenerated well in young hosts, this was not the case in aged hosts,10,11 indicating for the first time that 409

410

Rinaldi and Perlingeiro

the environment plays an important role in skeletal muscle regeneration. Several recent reports have corroborated this observation.12-15 Based on the premise of this incredible regenerative capacity, pioneering studies initiated in the late 1980s16 and extended into the 1990s17-19 began to explore cell-based therapies to promote muscle regeneration as a potential treatment for MDs. Initially, most of these studies focused on the transplantation of adult myoblasts aiming to regenerate skeletal muscle by the fusion of those cells (donor myoblasts) with recipient’s cells to form new or hybrid fibers. Adult myoblasts were isolated from muscle biopsies and expanded ex vivo before transplantation.16-18 Despite the encouraging findings obtained using the dystrophindeficient mdx mouse model, clinical trials performed in a cohort of DMD patients were disheartening due to poor myoblast transfer efficacy and failure to improve strength in treated muscles.3,20,21 Major factors underlining this poor outcome included low ability of myoblasts to migrate beyond the injection site22,23 and poor survival of injected cells.24,25 Several research groups have been working toward the goal of overcoming these issues as well as the immune response observed in the recipient following myoblast transfer.26-29 As an alternative to poorly engrafting myoblasts, much recent interest has developed around the idea of therapy with stem cells. These cells have the ability to self-renew and to differentiate into specialized cell types, and can be primarily classified as adult and pluripotent stem cells, which differ significantly in regard to their differentiation potential and in vitro expansion capability. Adult stem cells are tissuespecific and have limited capacity to be expanded ex vivo whereas pluripotent stem cells have the ability to differentiate into any cell type of the body while possessing unlimited in vitro self-renewal. Below we review the literature on some of the most studied stem cell populations that have been ascribed with in vivo muscle regenerative potential, pointing out their advantages as well as caveats. ADULT STEM CELLS Satellite cells. Studies in the last decade have clearly proven that the regenerative ability of adult skeletal muscle is due to the satellite cell, a quiescent stem cell population of muscle precursors located between the basal lamina and sarcolemma of each myofiber.30-32 The satellite cell was first described by Mauro in 1961 using electron microscopy,33 and later by Bishoff 34 in 1986 using phase-contrast microscopy on single myofiber explants. Upon injury, satellite cells become

Translational Research April 2014

activated, giving rise to proliferating myoblasts, which then fuse to existing muscle fibers or to other myoblasts to form new myofibers to repair muscle damage.35-39 Meanwhile, a small subset of satellite cells does not undergo differentiation but retains the ability to return to a quiescent state and thus preserve the satellite cell pool.4,30,40,41 In addition to their typical localization, a hallmark of these cells is the expression of Pax7, a paired box homeodomaincontaining transcription factor32,42 necessary for the maintenance of the muscle stem cell compartment in adult mice32,42-44 as well proliferation following injury45 and, consequently, being indispensable for adult skeletal muscle regeneration.46 There is evidence for heterogeneity within the satellite cell compartment, with a subset of satellite cells having greater potential to engraft the satellite cell compartment.45,47,48 It took about 50 years from their initial identification in the early 1960s for pure preparations of mouse satellite cells to be isolated and tested for their regenerative potential.30,31 One group took the approach of transplanting single muscle fibers, which demonstrated that each myofiber, containing 7 or fewer satellite cells, could generate over 100 new myofibers in engrafted muscles.30 The other approach made use of a transgenic reporter mouse for Pax3, a paralog of Pax7, which allowed for the direct isolation of Pax31 (green fluorescent protein1) muscle satellite cells by flow cytometry.31 Cells isolated from adult skeletal muscles displayed homogenous expression of Pax7, and contributed to both fiber repair and to the muscle satellite cell compartment following their transplantation into dystrophic mice.31 Subsequently Sacco et al demonstrated that intramuscular transplantation of a single luciferase-expressing muscle stem cell, isolated from Myf5 reporter mice, resulted in extensive proliferation and contribution to muscle fibers. In addition, these authors showed that Pax7(1)luciferase(1) mononuclear cells could be readily re-isolated, providing evidence for the self-renewal of this cell population.49 Satellite cells have also been characterized phenotypically by the expression of several surface markers, such as M-cadherin,50 CD34,51 syndecan-3/4,52 a7b1integrin,53,54 and the chemokine receptor CXCR4,55 among others.56-59 The first report making use of surface markers to isolate muscle precursor cells was published in 2004, in which the authors used a combination of negative and positive selection to discern muscle activity among different cell fractions.60 In vitro and in vivo myogenic potential was found within the CD45-Sca-1-Mac-1-CXCR41b1integrin1CD341.60,61 In 2009, Tanaka et al62 documented that the Sca-11/ABCG21/Syndecan-41 cell

Translational Research Volume 163, Number 4

subpopulation expresses Pax7 and participates in muscle regeneration in vivo, as showed by myofiber and satellite cell engraftment. The generation of reporter mouse models for Pax763,64 has enabled better characterization of the satellite cell compartment, not only in terms of their regulation but also functionality.47,65-67 In a recent report, Arpke et al68 have confirmed the potency of satellite cells since the transplantation of as few as 900 Pax71 satellite cells resulted in clearly measurable improvement of muscle function in dystrophic mice. In summary, a lot has been learned about satellite cells in the last decade, and these promising findings confirm that satellite cells represent a potent cell source for skeletal muscle regeneration. Challenges to be circumvented are the optimization of protocols to isolate human satellite cells because the surface markers identified in the mouse are not necessarily applicable to the human counterparts. To date, investigators have used antibodies to neural cell adhesion molecule (N-CAM) to identify satellite cells in human tissues.69-72 Perhaps the greatest challenge in applying these cells in the clinical setting is to obtain enough cells for transplantation since activation and in vitro expansion diminishes their engraftment ability.31 Strategies that allow for the in vitro expansion of satellite cells would be desirable. Muscle-derived stem cells. A population known as muscle derived stem cells (MDSCs) has been identified in the mouse muscle interstitial space.73 These cells, isolated based on their adhesion characteristics using the preplating method, can be expanded in vitro for up to 30 passages while maintaining myogenic potential.24,74 Because satellite cells are nonadherent, it is likely that MDSC preparations include satellite cells. Upon transplantation into dystrophic mice, MDSCs contribute to muscle regeneration following their local24,74 or systemic injection,75 although there is currently no evidence that these preparations can improve function in treated muscles.76 Recently, 2 studies have documented the isolation of human MDSCs based on their delayed adherence to collagencoated plates.77,78 These cells were able to differentiate in vitro but after injection into the gastrocnemius muscles of mdx/SCID mice, engraftment levels were not robust.77 Mesoangioblasts/pericytes. Mesoangioblasts, first identified as an embryonic population of vesselassociated stem cells isolated in the dorsal aorta,79 were reported to have the ability to differentiate into most mesodermal cell types, including skeletal muscle.80 Mesoangioblasts have been shown to express some of the markers commonly associated with satellite cells, such as M-cadherin, CD34, and

Rinaldi and Perlingeiro

411

Myf5, however, distinctively from satellite cells, these cells can be grown extensively in culture.79 Intraarterial transplantation studies using mouse and dog models of MD demonstrated that these cells engraft substantially, restoring normal muscle morphology and improving muscle function.81,82 With these encouraging results, the same authors evolved their studies to human muscle samples and came to the conclusion that pericytes are the human equivalent of the mouse mesoangioblasts.83 These cells are found in the muscle microvasculature, are proliferative, display muscle regenerative potential, and express pericyte markers (ie, NG2 proteoglycan and alkaline phosphatase) but not endothelial markers.83 Such as their mouse counterparts, pericytes have been shown to generate new myofibers as well as to assume satellite cell position and express Pax7 after intraarterial injection into immunodeficient mdx mice.84 Genetic correction has been successfully applied to mesoangioblasts isolated from dystrophic donors.81,85 Based on these encouraging results, there is an ongoing phase I/II clinical trial focused on the use of allogeneic human leukocyte antigen-identical mesoangioblasts to treat pediatric patients affected by DMD (EudraCT no. 2011-000176-33). A major caveat when moving to larger numbers of patient samples is the variability in the in vitro scalability of pericytes.86 As one would expect, they seem to have a finite lifespan in culture, which is inversely correlated with age. Thus, obtaining enough cell material to systemically treat a patient may be challenging. PLURIPOTENT STEM CELLS Embryonic stem cells. Embryonic stem (ES) cells, first isolated from the inner cell mass of blastocyst-stage preimplantation mouse embryos,87,88 are pluripotent and, thus, endowed with the ability to differentiate into all 3 germ layers, mesoderm, ectoderm, and endoderm, and importantly, are able to be maintained indefinitely in the undifferentiated stage in the presence of specific culture conditions. Almost 20 years later, human ES cells were isolated from fertilized human embryos,89 providing the rationale for investigators to pursue differentiation methods to study lineage-specific cell populations and to envision a potential therapeutic application for these cells. While several lineages are easily recapitulated during the in vitro differentiation of ES cells, such as blood,90-93 cardiac muscle,94 and endothelial,95 skeletal muscle has proven to be more difficult. Although early gene expression studies of embryoid bodies and their outgrowths suggested a temporal expression of myogenic regulatory factors, detection of differentiated

412

Rinaldi and Perlingeiro

myogenic cells was elusive.96 Similarly, early transplantation studies of mouse and human differentiating ES cells were not highly promising in terms of the myogenic potential of isolated cells.97,98 In the first study, mouse EBs had to be cocultured with primary muscle precursor cells for 4 days prior to transplantation in dystrophic mice.97 In the second study, the authors transplanted human ES cells taken through a mesenchymal differentiation protocol into immunodeficient mice and detected a few myogenic cells as shown by staining for human nuclear antigen and laminin.98 In this multistep differentiation protocol, gene expression of Pax7 and myogenic differentiation antigen (MyoD) was not observed until 30 days in culture or longer. In 2008, Darabi et al99 proposed that the poor skeletal muscle formation observed in ES cell cultures was due to the fact that key embryonic structures (ie, somite, neural tube, notochord) and thus inductive signals necessary for proper patterning of paraxial mesoderm and subsequent activation of the myogenic program are not well recapitulated during EB differentiation. By using transient expression of Pax399 or Pax7100 during early mesoderm development, these authors showed that it is possible to bypass inefficient mesoderm patterning. This approach allowed for the in vitro generation of large quantities of early embryonic skeletal myogenic progenitors, whose transplantation into dystrophic mice resulted in high levels of myofiber and satellite cell engraftment that was accompanied by improvement in muscle force generation.99-102 Following these encouraging results, attempts have been made toward generating paraxial mesoderm and subsequent skeletal muscle without genetic modification.103,104 It has been demonstrated that serum-free ES-derived monolayers cultured with bone morphogenetic protein 4 for a short period and then incubated with lithium chloride promoted the differentiation of myogenic progenitor cells from paraxial mesoderm, although transplantation potential has not yet been documented.104 Another approach relied on the purification of satellite-like cells from differentiating mouse ES cells using a SM/C-2.6 antibody,105 which had been previously identified in quiescent satellite cells.106 The engraftment ability of SM/C-2.61 cells purified from differentiating mouse ES cells was demonstrated in mdx mice using serial transplantations.105 Despite the potential application of the findings discussed above, major limitations with ES cells are their potential rejection due to immunologic mismatch and the ethical concerns associated with their utilization in the clinics. These particular hurdles have been circumvented with the discovery of reprogramming somatic cells to an induced pluripotent state by the introduction

Translational Research April 2014

of Oct4, Klf4, Sox2, and c-Myc,107-111 as detailed below. Induced pluripotent stem cells. Induced pluripotent stem (iPS) cells have been shown by several investigators to behave very similarly to ES cells in terms of pluripotency,107-116 and the generation of patientspecific iPS cell lines that could be used for autologous transplantation following appropriate in vitro differentiation has attracted great interest. A mandatory requirement for the potential therapeutic application of iPS cells is the generation of abundant tissue-specific, tumor-free, cell populations that are able to integrate and properly function in the host following transplantation. Strategies used to generate skeletal muscle from mouse ES cells were then validated with mouse iPS cells. Mizuno et al117 used the SM/C-2.6 antibody to purify iPS-derived satellite-like cells, while Darabi et al118 applied controlled expression of Pax7 during EB differentiation of mouse iPS cells, along with purification for PDGFaR1Flk-1- paraxial mesoderm, as shown for mouse ES cells.99 The generation of functional human skeletal myogenic progenitors from pluripotent cells has recently been accomplished using the Pax7 induction protocol.119 In this study, the authors demonstrated the feasibility of generating large quantities of human ESand iPS-derived early skeletal myogenic progenitors, which had the ability to promote robust regeneration and to improve the force generation of engrafted muscles upon transplantation into immunodeficient dystrophic mice. These cells were also shown to contribute to the satellite cell pool, and accordingly durable engraftment was observed in a long-term cohort of treated mice (46 weeks) that were devoid of teratoma or abnormal cell growth.119 MyoD and Myf5 have also been used to pattern mesoderm from human pluripotent cells.120,121 In the case of MyoD, modified cells participated in muscle regeneration by fusing efficiently with existing muscle fibers following their transplantation into Rag/mdx mice.120 Also in 2012, another study described a stepwise culture method for the expansion of mesenchymal cells from human EBs, which differentiated into mature myotubes in vitro, a process that took 64 days in culture. Transplantation of these myogenic mesenchymal cells, isolated at day 49, into pre-irradiated and cardiotoxin-injured muscles of immunodeficient mice resulted in engraftment as shown by the presence of human nuclei.122 To date the SM/C-2.6 antibody used to purify myogenic progenitors from differentiating mouse ES and iPS cells105,117 has not been shown to recognize the human counterparts. Potential for the genetic correction of disease-specific iPS cells. The encouraging results discussed above

Translational Research Volume 163, Number 4

Rinaldi and Perlingeiro

413

Fig 1. Schematic representation of the stem populations described in this review.

bring about the possibility of generating MD patientspecific iPS cells that could be used for autologous transplantation, following proper genetic correction. Proof-of-principle studies in this direction were recently reported by Filareto et al123 using mouse dystrophic iPS cells. In this study, the authors generated iPS cells from fibroblasts obtained from dystrophin/utrophin double knockout mice, which display a severe phenotype that much resembles the human DMD pathology.124,125 Dystrophic iPS cells were corrected by insertion of the micro-utrophin (mUTRN) gene, which has been shown to ameliorate the dystrophic phenotype,126-129 using the sleeping beauty transposon system. Transplantation of mUTRNcorrected iPS-derived skeletal myogenic progenitors, generated using the Pax3 induction approach,99 into double knockout mice resulted in substantial engraftment, as evidenced by the presence of donorderived utrophin1 myofibers and satellite cells, as well as improved muscle strength.123 As discussed above, although mesoangioblasts/ pericytes have reported in vitro expansion potential, obtaining enough cell material from adult patients has proven to be more challenging. Tedesco et al130 have

recently used a protocol to derive mesoangioblast/ mesenchymal-like cells from iPSCs derived from healthy individuals and from patients affected by limb-girdle 2d type MD. Mesoangioblast/mesenchymal-like cells, generated from iPS cells, were expanded, corrected with a lentiviral vector encoding the human a-sarcoglycan gene (SGCA), and subsequently differentiated into myogenic cells following MyoD modification. Transplantation of genetically corrected cells resulted in engraftment and functional amelioration of the dystrophic phenotype upon their intramuscular or intra-arterial injection into a-sarcoglycan-null immunodeficient mice.130 CONCLUSIONS

In this review, we covered stem cell types (Fig. 1) that have been most studied within the last decade in terms of regenerative capacity for the potential treatment of neuromuscular disorders. As pointed out, each cell type presents its own advantages and limitations. Currently, bona-fide satellite cells cannot be used until approaches are developed to expand these cells in vitro. This may be accomplished in the near future, as we gain more mechanistic insight on the signaling

414

Rinaldi and Perlingeiro

pathways that regulate satellite cell self-renewal. Ongoing clinical trials with mesoangioblasts/pericytes have indicated no side effects for these cell preparations so far, although data on efficacy have not been reported yet. As discussed above, in vitro expansion of these cells may be an issue for older patients. iPS cell technology provides an exciting opportunity for cell-based therapies. However, several safety concerns need to be overcome before they can be considered for clinical applications,131,132 including (1) the development of an efficient integration-free method for their generation as well as for the subsequent derivation of skeletal myogenic progenitors, (2) safe gene correction strategies, and (3) purification of target cells to avoid the presence of tumor-forming undifferentiated ES and iPS cells to eliminate the risk of the transplanted cells to generate tumors in the host. Another important aspect to keep in mind in terms of stem cell transplantation for neuromuscular disorders is the method for delivering the cells. Because the skeletal muscle is the largest organ of the human body, and in most conditions, multiple muscle groups are affected, local intramuscular cell injection is not a feasible strategy. Thus, it is critical that selected stem cell preparations have efficient and selective skeletal muscle homing ability following systemic delivery. ACKNOWLEDGMENTS

This project was supported by National Institutes of Health grants R01 AR055299 and RC1AR058118 as well as funding from the Muscular Dystrophy Association (#238127). All authors have read the journal’s policy on disclosure of potential conflicts of interest. The authors declare no potential conflicts of interest. REFERENCES

1. Emery AE. The muscular dystrophies. Lancet 2002;359: 687–95. 2. Emery AE. Population frequencies of inherited neuromuscular diseases—a world survey. Neuromuscul Disord 1991;1:19–29. 3. Mendell JR, Kissel JT, Amato AA, et al. Myoblast transfer in the treatment of Duchenne’s muscular dystrophy. N Engl J Med 1995;333:832–8. 4. Glass DJ. Signaling pathways perturbing muscle mass. Curr Opin Clin Nutr Metab Care 2010;13:225–9. 5. Acharyya S, Butchbach ME, Sahenk Z, et al. Dystrophin glycoprotein complex dysfunction: a regulatory link between muscular dystrophy and cancer cachexia. Cancer Cell 2005;8:421–32. 6. Janssen I, Heymsfield SB, Ross R. Low relative skeletal muscle mass (sarcopenia) in older persons is associated with functional impairment and physical disability. J Am Geriatr Soc 2002;50: 889–96. 7. Grounds MD. Age-associated changes in the response of skeletal muscle cells to exercise and regeneration. Ann NY Acad Sci 1998;854:78–91.

Translational Research April 2014

8. Studitsky AN. Types of new formation of cells from living substance in processes of histogenesis and regeneration. Zhur Obsch Biol 1953;4:177–97. 9. Carlson BM, Gutmann E. Development of contractile properties of minced muscle regenerates in the rat. Exp Neurol 1972;36: 239–49. 10. Carlson BM, Faulkner JA. Muscle transplantation between young and old rats: age of host determines recovery. Am J Physiol 1989;256:C1262–6. 11. Zacks SI, Sheff MF. Age-related impeded regeneration of mouse minced anterior tibial muscle. Muscle Nerve 1982; 5:152–61. 12. Brack AS, Conboy MJ, Roy S, et al. Increased Wnt signaling during aging alters muscle stem cell fate and increases fibrosis. Science 2007;317:807–10. 13. Carlson ME, Conboy MJ, Hsu M, et al. Relative roles of TGFbeta1 and Wnt in the systemic regulation and aging of satellite cell responses. Aging Cell 2009;8:676–89. 14. Chakkalakal JV, Jones KM, Basson MA, Brack AS. The aged niche disrupts muscle stem cell quiescence. Nature 2012;490: 355–60. 15. Conboy IM, Conboy MJ, Wagers AJ, Girma ER, Weissman IL, Rando TA. Rejuvenation of aged progenitor cells by exposure to a young systemic environment. Nature 2005;433:760–4. 16. Partridge TA, Morgan JE, Coulton GR, Hoffman EP, Kunkel LM. Conversion of mdx myofibres from dystrophinnegative to -positive by injection of normal myoblasts. Nature 1989;337:176–9. 17. Brussee V, Tardif F, Roy B, Goulet M, Sebille A, Tremblay JP. Successful myoblast transplantation in fibrotic muscles: no increased impairment by the connective tissue. Transplantation 1999;67:1618–22. 18. Gussoni E, Blau HM, Kunkel LM. The fate of individual myoblasts after transplantation into muscles of DMD patients. Nat Med 1997;3:970–7. 19. Gussoni E, Pavlath GK, Lanctot AM, et al. Normal dystrophin transcripts detected in Duchenne muscular-dystrophy patients after myoblast transplantation. Nature 1992;356:435–8. 20. Partridge T, Lu QL, Morris G, Hoffman E. Is myoblast transplantation effective? Nat Med 1998;4:1208–9. 21. Tremblay JP, Malouin F, Roy R, et al. Results of a triple blind clinical study of myoblast transplantations without immunosuppressive treatment in young boys with Duchenne muscular dystrophy. Cell Transplant 1993;2:99–112. 22. Guerette B, Skuk D, Celestin F, et al. Prevention by anti-LFA-1 of acute myoblast death following transplantation. J Immunol 1997;159:2522–31. 23. Skuk D, Caron NJ, Goulet M, Roy B, Tremblay JP. Resetting the problem of cell death following muscle-derived cell transplantation: detection, dynamics and mechanisms. J Neuropath Exp Neur 2003;62:951–67. 24. Qu Z, Balkir L, van Deutekom JC, Robbins PD, Pruchnic R, Huard J. Development of approaches to improve cell survival in myoblast transfer therapy. J Cell Biol 1998;142:1257–67. 25. Fan Y, Maley M, Beilharz M, Grounds M. Rapid death of injected myoblasts in myoblast transfer therapy. Muscle Nerve 1996;19:853–60. 26. Skuk D, Paradis M, Goulet M, Chapdelaine P, Rothstein DM, Tremblay JP. Intramuscular transplantation of human postnatal myoblasts generates functional donor-derived satellite cells. Mol Ther 2010;18:1689–97. 27. Hill E, Boontheekul T, Mooney DJ. Regulating activation of transplanted cells controls tissue regeneration. Proc Natl Acad Sci U S A 2006;103:2494–9.

Translational Research Volume 163, Number 4

28. Hill E, Boontheekul T, Mooney DJ. Designing scaffolds to enhance transplanted myoblast survival and migration. Tissue Eng 2006;12:1295–304. 29. Goudenege S, Lamarre Y, Dumont N, et al. Laminin-111: a potential therapeutic agent for Duchenne muscular dystrophy. Mol Ther 2010;18:2155–63. 30. Collins CA, Olsen I, Zammit PS, et al. Stem cell function, selfrenewal, and behavioral heterogeneity of cells from the adult muscle satellite cell niche. Cell 2005;122:289–301. 31. Montarras D, Morgan J, Collins C, et al. Direct isolation of satellite cells for skeletal muscle regeneration. Science 2005;309: 2064–7. 32. Seale P, Sabourin LA, Girgis-Gabardo A, Mansouri A, Gruss P, Rudnicki MA. Pax7 is required for the specification of myogenic satellite cells. Cell 2000;102:777–86. 33. Mauro A. Satellite cell of skeletal muscle fibers. J Biophys Biochem Cytol 1961;493–5. 34. Bischoff R. A satellite cell mitogen from crushed adult muscle. Dev Biol 1986;115:140–7. 35. Buckingham M, Bajard L, Chang T, et al. The formation of skeletal muscle: from somite to limb. J Anat 2003;202:59–68. 36. Montarras D, L’Honore A, Buckingham M. Lying low but ready for action: the quiescent muscle satellite cell. FEBS J 2013;280: 4036–50. 37. Zammit PS, Golding JP, Nagata Y, Hudon V, Partridge TA, Beauchamp JR. Muscle satellite cells adopt divergent fates: a mechanism for self-renewal? J Cell Biol 2004;166:347–57. 38. Halevy O, Piestun Y, Allouh MZ, et al. Pattern of Pax7 expression during myogenesis in the posthatch chicken establishes a model for satellite cell differentiation and renewal. Dev Dyn 2004;231:489–502. 39. Olguin HC, Olwin BB. Pax-7 up-regulation inhibits myogenesis and cell cycle progression in satellite cells: a potential mechanism for self-renewal. Dev Biol 2004;275: 375–88. 40. Cox DM, Du M, Marback M, et al. Phosphorylation motifs regulating the stability and function of myocyte enhancer factor 2A. J Biol Chem 2003;278:15297–303. 41. Rosenblatt JD, Lunt AI, Parry DJ, Partridge TA. Culturing satellite cells from living single muscle fiber explants. In Vitro Cell Dev Biol Anim 1995;31:773–9. 42. Oustanina S, Hause G, Braun T. Pax7 directs postnatal renewal and propagation of myogenic satellite cells but not their specification. Embo J 2004;23:3430–9. 43. Kuang S, Charge SB, Seale P, Huh M, Rudnicki MA. Distinct roles for Pax7 and Pax3 in adult regenerative myogenesis. J Cell Biol 2006;172:103–13. 44. Relaix F, Montarras D, Zaffran S, et al. Pax3 and Pax7 have distinct and overlapping functions in adult muscle progenitor cells. JCell Biol 2006;172:91–102. 45. Kuang SH, Kuroda K, Le Grand F, Rudnicki MA. Asymmetric self-renewal and commitment of satellite stem cells in muscle. Cell 2007;129:999–1010. 46. Sambasivan R, Yao R, Kissenpfennig A, et al. Pax7-expressing satellite cells are indispensable for adult skeletal muscle regeneration. Development 2011;138:3647–56 47. Rocheteau P, Gayraud-Morel B, Siegl-Cachedenier I, Blasco MA, Tajbakhsh S. A subpopulation of adult skeletal muscle stem cells retains all template DNA strands after cell division. Cell 2012;148:112–25. 48. Troy A, Cadwallader AB, Fedorov Y, Tyner K, Tanaka KK, Olwin BB. Coordination of satellite cell activation and selfrenewal by par-complex-dependent asymmetric activation of p38 alpha/beta MAPK. Cell Stem Cell 2012;11:541–53.

Rinaldi and Perlingeiro

415

49. Sacco A, Doyonnas R, Kraft P, Vitorovic S, Blau HM. Selfrenewal and expansion of single transplanted muscle stem cells. Nature 2008;456:502–6. 50. Irintchev A, Zeschnigk M, Starzinski-Powitz A, Wernig A. Expression pattern of M-cadherin in normal, denervated, and regenerating mouse muscles. Dev Dyn 1994;199:326–37. 51. Beauchamp JR, Heslop L, Yu DS, et al. Expression of CD34 and Myf5 defines the majority of quiescent adult skeletal muscle satellite cells. J Cell Biol 2000;151:1221–34. 52. Cornelison DD, Wilcox-Adelman SA, Goetinck PF, Rauvala H, Rapraeger AC, Olwin BB. Essential and separable roles for Syndecan-3 and Syndecan-4 in skeletal muscle development and regeneration. Genes Dev 2004;18:2231–6. 53. Burkin DJ, Kaufman SJ. The alpha7beta1 integrin in muscle development and disease. Cell Tissue Res 1999;296:183–90. 54. Gnocchi VF, White RB, Ono Y, Ellis JA, Zammit PS. Further characterisation of the molecular signature of quiescent and activated mouse muscle satellite cells. PloS One 2009;4:e5205. 55. Ratajczak MZ, Majka M, Kucia M, et al. Expression of functional CXCR4 by muscle satellite cells and secretion of SDF-1 by muscle-derived fibroblasts is associated with the presence of both muscle progenitors in bone marrow and hematopoietic stem/progenitor cells in muscles. Stem Cells 2003;21:363–71. 56. Meech R, Gonzalez KN, Barro M, et al. Barx2 is expressed in satellite cells and is required for normal muscle growth and regeneration. Stem Cells 2012;30:253–65. 57. Volonte D, Liu Y, Galbiati F. The modulation of caveolin-1 expression controls satellite cell activation during muscle repair. FASEB J 2005;19:237–9. 58. Fukada S, Uezumi A, Ikemoto M, et al. Molecular signature of quiescent satellite cells in adult skeletal muscle. Stem Cells 2007;25:2448–59. 59. Cornelison DD, Wold BJ. Single-cell analysis of regulatory gene expression in quiescent and activated mouse skeletal muscle satellite cells. Dev Biol 1997;191:270–83. 60. Sherwood RI, Christensen JL, Conboy IM, et al. Isolation of adult mouse myogenic progenitors: functional heterogeneity of cells within and engrafting skeletal muscle. Cell 2004;119: 543–54. 61. Cerletti M, Jurga S, Witczak CA, et al. Highly efficient, functional engraftment of skeletal muscle stem cells in dystrophic muscles. Cell 2008;134:37–47. 62. Tanaka KK, Hall JK, Troy AA, Cornelison DDW, Majka SM, Olwin BB. Syndecan-4-expressing muscle progenitor cells in the SP engraft as satellite cells during muscle regeneration. Cell Stem Cell 2009;4:217–25. 63. Bosnakovski D, Xu Z, Li W, et al. Prospective isolation of skeletal muscle stem cells with a Pax7 reporter. Stem Cells 2008;26: 3194–204. 64. Sambasivan R, Gayraud-Morel B, Dumas G, et al. Distinct regulatory cascades govern extraocular and pharyngeal arch muscle progenitor cell fates. Dev Cell 2009;16:810–21. 65. Gilbert PM, Havenstrite KL, Magnusson KE, et al. Substrate elasticity regulates skeletal muscle stem cell self-renewal in culture. Science 2010;329:1078–81. 66. Bentzinger CF, Wang YX, von Maltzahn J, Soleimani VD, Yin H, Rudnicki MA. Fibronectin regulates Wnt7a signaling and satellite cell expansion. Cell Stem Cell 2013;12:75–87. 67. Kawabe Y, Wang YX, McKinnell IW, Bedford MT, Rudnicki MA. Carm1 regulates Pax7 transcriptional activity through MLL1/2 recruitment during asymmetric satellite stem cell divisions. Cell Stem Cell 2012;11:333–45. 68. Arpke RW, Darabi R, Mader TL, et al. A new immunodystrophin-deficient model, the NSG-Mdx mouse, provides

416

69.

70.

71.

72.

73.

74.

75.

76.

77.

78.

79.

80.

81.

82.

83.

84.

85.

86.

Rinaldi and Perlingeiro

evidence for functional improvement following allogeneic satellite cell transplantation. Stem Cells 2013;31:1611–20. Dreyer HC, Blanco CE, Sattler FR, Schroeder ET, Wiswell RA. Satellite cell numbers in young and older men 24 hours after eccentric exercise. Muscle Nerve 2006;33: 242–53. Maier F, Bornemann A. Comparison of the muscle fiber diameter and satellite cell frequency in human muscle biopsies. Muscle Nerve 1999;22:578–83. Kadi F, Charifi N, Denis C, Lexell J. Satellite cells and myonuclei in young and elderly women and men. Muscle Nerve 2004; 29:120–7. Crameri RM, Langberg H, Magnusson P, et al. Changes in satellite cells in human skeletal muscle after a single bout of high intensity exercise. J Physiol 2004;558:333–40. Qu-Petersen Z, Deasy B, Jankowski R, et al. Identification of a novel population of muscle stem cells in mice: potential for muscle regeneration. J Cell Biol 2002;157:851–64. Deasy BM, Jankowski RJ, Huard J. Muscle-derived stem cells: characterization and potential for cell-mediated therapy. Blood Cells Mol Dis 2001;27:924–33. Torrente Y, Tremblay JP, Pisati F, et al. Intraarterial injection of muscle-derived CD34(1)Sca-1(1) stem cells restores dystrophin in mdx mice. J Cell Biol 2001;152:335–48. Mueller GM, O’Day T, Watchko JF, Ontell M. Effect of injecting primary myoblasts versus putative muscle-derived stem cells on mass and force generation in mdx mice. Hum Gene Ther 2002; 13:1081–90. Chirieleison SM, Feduska JM, Schugar RC, Askew Y, Deasy BM. Human muscle-derived cell populations isolated by differential adhesion rates: phenotype and contribution to skeletal muscle regeneration in Mdx/SCID mice. Tissue Eng Pt A 2012;18:232–41. Lavasani M, Lu A, Thompson SD, Robbins PD, Huard J, Niedernhofer LJ. Isolation of muscle-derived stem/progenitor cells based on adhesion characteristics to collagen-coated surfaces. Methods Mol Biol 2013;976:53–65. De Angelis L, Berghella L, Coletta M, et al. Skeletal myogenic progenitors originating from embryonic dorsal aorta coexpress endothelial and myogenic markers and contribute to postnatal muscle growth and regeneration. The J Cell Biol 1999;147: 869–78. Minasi MG, Riminucci M, De Angelis L, et al. The mesoangioblast: a multipotent, self-renewing cell that originates from the dorsal aorta and differentiates into most mesodermal tissues. Development 2002;129:2773–83. Sampaolesi M, Blot S, D’Antona G, et al. Mesoangioblast stem cells ameliorate muscle function in dystrophic dogs. Nature 2006;444:574–9. Sampaolesi M, Torrente Y, Innocenzi A, et al. Cell therapy of alpha-sarcoglycan null dystrophic mice through intra-arterial delivery of mesoangioblasts. Science 2003;301:487–92. Dellavalle A, Sampaolesi M, Tonlorenzi R, et al. Pericytes of human skeletal muscle are myogenic precursors distinct from satellite cells. Nat Cell Biol 2007;9:255–67. Dellavalle A, Maroli G, Covarello D, et al. Pericytes resident in postnatal skeletal muscle differentiate into muscle fibres and generate satellite cells. Nat Commun 2011;2:499. Tedesco FS, Hoshiya H, D’Antona G, et al. Stem cell-mediated transfer of a human artificial chromosome ameliorates muscular dystrophy. Sci Transl Med 2011;3:96ra78. Quattrocelli M, Palazzolo G, Floris G, et al. Intrinsic cell memory reinforces myogenic commitment of pericyte-derived iPSCs. J Pathol 2011;223:593–603.

Translational Research April 2014

87. Evans MJ, Kaufman MH. Establishment in culture of pluripotential cells from mouse embryos. Nature 1981;292:154–6. 88. Martin GR. Isolation of a pluripotent cell line from early mouse embryos cultured in medium conditioned by teratocarcinoma stem cells. Proc Natl Acad Sci U S A 1981;78:7634–8. 89. Thomson JA, Itskovitz-Eldor J, Shapiro SS, et al. Embryonic stem cell lines derived from human blastocysts. Science 1998; 282:1145–7. 90. Wiles MV, Keller G. Multiple hematopoietic lineages develop from embryonic stem (ES) cells in culture. Development 1991; 111:259–67. 91. Kennedy M, Firpo M, Choi K, et al. A common precurson for primitive erythropoiesis and definitive haematopoiesis. Nature 1997;386:488–93. 92. Kaufman DS, Woll PS, Martin CH, Linehan JL, Tian X. CD341 cells derived from human embryonic stem cells demonstrate hematopoietic stem cell potential in vitro and in vivo. Blood 2004; 104:163a. 93. M€uller M, Fleischmann BK, Selbert S, et al. Selection of ventricular-like cardiomyocytes from ES cells in vitro. FASEB J 2000;14:2540–8. 94. Klug MG, Soonpaa MH, Koh GY, Field LJ. Genetically selected cardiomyocytes from differentiating embronic stem cells form stable intracardiac grafts. J Clin Invest 1996;98: 216–24. 95. Vittet D, Prandini MH, Berthier R, et al. Embryonic stem cells differentiate in vitro to endothelial cells through successive maturation steps. Blood 1996;88:3424–31. 96. Rohwedel J, Maltsev V, Bober E, Arnold HH, Hescheler J, Wobus AM. Muscle cell differentiation of embryonic stem cells reflects myogenesis in vivo: developmentally regulated expression of myogenic determination genes and functional expression of ionic currents. Dev Biol 1994;164:87–101. 97. Bhagavati S, Xu W. Generation of skeletal muscle from transplanted embryonic stem cells in dystrophic mice. Biochem Biophys Res Commun 2005;333:644–9. 98. Barberi T, Bradbury M, Dincer Z, Panagiotakos G, Socci ND, Studer L. Derivation of engraftable skeletal myoblasts from human embryonic stem cells. Nat Med 2007;13:642–8. 99. Darabi R, Gehlbach K, Bachoo RM, et al. Functional skeletal muscle regeneration from differentiating embryonic stem cells. Nat Med 2008;14:134–43. 100. Darabi R, Santos FNC, Filareto A, et al. Assessment of the myogenic stem cell compartment following transplantation of Pax3/Pax7-induced embryonic stem cell-derived progenitors. Stem Cells 2011;29:777–90. 101. Darabi R, Baik J, Clee M, Kyba M, Tupler R, Perlingeiro RC. Engraftment of embryonic stem cell-derived myogenic progenitors in a dominant model of muscular dystrophy. Exp Neurol 2009;220:212–6. 102. Filareto A, Darabi R, Perlingeiro RCR. Engraftment of ESderived myogenic progenitors in a severe mouse model of muscular dystrophy. J Stem Cell Res Ther 2012;220:212–6. 103. Sakurai H, Okawa Y, Inami Y, Nishio N, Isobe K. Paraxial mesodermal progenitors derived from mouse embryonic stem cells contribute to muscle regeneration via differentiation into muscle satellite cells. Stem Cells 2008;26:1865–73. 104. Sakurai H, Inami Y, Tamamura Y, Yoshikai T, SeharaFujisawa A, Isobe K. Bidirectional induction toward paraxial mesodermal derivatives from mouse ES cells in chemically defined medium. Stem Cell Res 2009;3:157–69. 105. Chang H, Yoshimoto M, Umeda K, et al. Generation of transplantable, functional satellite-like cells from mouse embryonic stem cells. FASEB J 2009;23:1907–19.

Translational Research Volume 163, Number 4

106. Fukada S, Higuchi S, Segawa M, et al. Purification and cellsurface marker characterization of quiescent satellite cells from murine skeletal muscle by a novel monoclonal antibody. Exp Cell Res 2004;296:245–55. 107. Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell 2006;126:663–76. 108. Wernig M, Meissner A, Foreman R, et al. In vitro reprogramming of fibroblasts into a pluripotent ES-cell-like state. Nature 2007; 448:318–24. 109. Okita K, Ichisaka T, Yamanaka S. Generation of germlinecompetent induced pluripotent stem cells. Nature 2007;448: 313–7. 110. Maherali N, Sridharan R, Xie W, et al. Directly reprogrammed fibroblasts show global epigenetic remodeling and widespread tissue contribution. Cell Stem Cell 2007;1:55–70. 111. Takahashi K, Tanabe K, Ohnuki M, et al. Induction of pluripotent stem cells from adult human fibroblasts by defined factors. Cell 2007;131:861–72. 112. Park IH, Zhao R, West JA, et al. Reprogramming of human somatic cells to pluripotency with defined factors. Nature 2008; 451:141–6. 113. Yu J, Vodyanik MA, Smuga-Otto K, et al. Induced pluripotent stem cell lines derived from human somatic cells. Science 2007;318:1917–20. 114. Blelloch R, Venere M, Yen J, Ramalho-Santos M. Generation of induced pluripotent stem cells in the absence of drug selection. Cell Stem Cell 2007;1:245–7. 115. Byrne JA, Pedersen DA, Clepper LL, et al. Producing primate embryonic stem cells by somatic cell nuclear transfer. Nature 2007;450:497–502. 116. Park IH, Arora N, Huo H, et al. Disease-specific induced pluripotent stem cells. Cell 2008;134:877–86. 117. Mizuno Y, Chang H, Umeda K, et al. Generation of skeletal muscle stem/progenitor cells from murine induced pluripotent stem cells. FASEB J 2010;24:2245–53. 118. Darabi R, Pan W, Bosnakovski D, Baik J, Kyba M, Perlingeiro RC. Functional myogenic engraftment from mouse iPS cells. Stem Cell Rev Rep 2011;7:948–57. 119. Darabi R, Arpke RW, Irion S, et al. Human ES- and iPS-derived myogenic progenitors restore dystrophin and improve contractility upon transplantation in dystrophic mice. Cell Stem Cell 2012;10:610–9. 120. Goudenege S, Lebel C, Huot NB, et al. Myoblasts derived from normal hESCs and dystrophic hiPSCs efficiently fuse with exist-

Rinaldi and Perlingeiro

121.

122.

123.

124.

125.

126.

127.

128.

129.

130.

131. 132.

417

ing muscle fibers following transplantation. Mol Ther 2012;20: 2153–67. Iacovino M, Bosnakovski D, Fey H, et al. Inducible cassette exchange: a rapid and efficient system enabling conditional gene expression in embryonic stem and primary cells. Stem Cells 2011;29:1580–8. Awaya T, Kato T, Mizuno Y, et al. Selective development of myogenic mesenchymal cells from human embryonic and induced pluripotent stem cells. PloS One 2012;7: e51638. Filareto A, Parker S, Darabi R, et al. An ex vivo gene therapy approach to treat muscular dystrophy using inducible pluripotent stem cells. Nat Commun 2013;4:1549. Deconinck AE, Rafael JA, Skinner JA, et al. Utrophin-dystrophin-deficient mice as a model for Duchenne muscular dystrophy. Cell 1997;90:717–27. Grady RM, Teng H, Nichol MC, Cunningham JC, Wilkinson RS, Sanes JR. Skeletal and cardiac myopathies in mice lacking utrophin and dystrophin: a model for Duchenne muscular dystrophy. Cell 1997;90:729–38. Odom GL, Gregorevic P, Allen JM, Finn E, Chamberlain JS. Microutrophin delivery through rAAV6 increases lifespan and improves muscle function in dystrophic dystrophin/utrophindeficient mice. Mol Ther 2008;16:1539–45. Sonnemann KJ, Heun-Johnson H, Turner AJ, Baltgalvis KA, Lowe DA, Ervasti JM. Functional substitution by TATutrophin in dystrophin-deficient mice. PLoS Med 2009;6: e1000083. Tinsley JM, Potter AC, Phelps SR, Fisher R, Trickett JI, Davies KE. Amelioration of the dystrophic phenotype of mdx mice using a truncated utrophin transgene. Nature 1996;384: 349–53. Tinsley J, Deconinck N, Fisher R, et al. Expression of full-length utrophin prevents muscular dystrophy in mdx mice. Nat Med 1998;4:1441–4. Tedesco FS, Gerli MF, Perani L, et al. Transplantation of genetically corrected human iPSC-derived progenitors in mice with limb-girdle muscular dystrophy. Science Transl Med 2012;4: 140ra89. Fong CY, Gauthaman K, Bongso A. Teratomas from pluripotent stem cells: a clinical hurdle. J Cell Biochem 2010;111:769–81. Fu W, Wang SJ, Zhou GD, Liu W, Cao Y, Zhang WJ. Residual undifferentiated cells during differentiation of induced pluripotent stem cells in vitro and in vivo. Stem Cells Dev 2012;21: 521–9.