Differentiation of Murine Embryonic Stem Cells in Skeletal Muscles of Mice
Possible myogenic differentiation of SSEA-1- and OCT-4-positive murine embryonic stem cells (ESCs) and embryoid bodies (EBs) was studied in vitro and in vivo. In vitro, ESC- or EB-derived ESCs (EBs/ESCs) showed only traces of Pax 3 and 7 expression by immunocytochemistry and Pax 3 expression by immunoblot. By RT-PCR, myogenic determinant molecules (myf5, myoD, and myogenin) were expressed by EBs/ESCs but not by ESCs. However, in such cultures, very rare contracting myotubes were still present. Suspensions of LacZ-labeled ESCs or EBs were injected into anterior tibialis muscles (ATM) of different cohorts of mice for the study of their survival and possible myogenic differentiation. The different cohorts of mice included isogenic adult 129/Sv, nonisogenic CD1 and mdx, as well as mdx immunosuppressed with 2.5 mg/kg daily injections of tacrolimus. Ten to 90 days postinjections, the injected ATM of nonisogenic mice did not contain cells positive for LacZ, SSEA-1, OCT-4, or embryonic myosin heavy chain. The ATM of intact mdx mice contained very rare examples of muscle fibers positive for dystrophin and/or embryonic myosin heavy chain. In the ATM of the isogenic normal and the immunosuppressed mdx mice, as expected, large teratomas developed containing the usual diverse cell types. In some teratomas of immunosuppressed mdx mice, small pockets of muscle fibers expressed dystrophin and myosin heavy chain. Our studies indicated that in muscles of animals nonisogenic with the used ESCs, only very rare ESCs survived with myogenic differentiation. These studies also indicated that ESCs will not undergo significant, selective, and preferential myogenic differentiation in vitro or in vivo in any of the models studied. It is probable that this strain of murine ESC requires some experimentally induced alteration of its gene expression profile to secure significant myogenicity and suppress tumorogenicity.
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Cell Transplantation publishes original, peer-reviewed research and review articles on the subject of cell transplantation and its application to human diseases. To ensure high-quality contributions from all areas of transplantation, separate section editors and editorial boards have been established. Articles deal with a wide range of topics including physiological, medical, preclinical, tissue engineering, and device-oriented aspects of transplantation of nervous system, endocrine, growth factor-secreting, bone marrow, epithelial, endothelial, and genetically engineered cells, among others. Basic clinical studies and immunological research papers are also featured. To provide complete coverage of this revolutionary field, Cell Transplantation will report on relevant technological advances, and ethical and regulatory considerations of cell transplants. Cell Transplantation is now an Open Access journal starting with volume 18 in 2009, and therefore there will be an inexpensive publication charge, which is dependent on the number of pages, in addition to the charge for color figures. This will allow work to be disseminated to a wider audience and also entitle the corresponding author to a free PDF, as well as prepublication of an unedited version of the manuscript.
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