The long-term treatment of injured, aging, or pathological skeletal muscle using stem cell therapy requires an abundant source of skeletal muscle progenitors (SMP) that are capable of self-replenishment. While adult SMPs-known as satellite cells and marked by PAX7 expression-can be collected from healthy donors, these satellite cells have limited replication potential once extracted, and may have difficulties providing sufficient numbers for therapy. Therefore, we sought to utilize the near-unlimited replication potential of human embryonic stem cells (hESC) to generate large quantities of SMPs in vitro. We developed a 50-day directed hESC differentiation that produced cultures with up to 90% myogenic identity; roughly 43 ± 4% become PAX7+ SMPs, and 47 ± 3% of cells become skeletal myocytes. We also performed gene expression profiling on our differentiating cultures to better understand in vitro skeletal myogenesis, and to better characterize in vitro hESC-derived SMPs, which remain poorly understood relative to adult satellite cells. 50-day cultures shared gene expression profiles more similar to quiescent rather than activated satellite cells, featuring a number of genes related to FOS/JUN, NOTCH, and TGFB-signaling. Day 50 cultures also expressed surface proteins known to mark adult or embryonic SMPs: CD82, CXCR4, ERBB3, NGFR, and PDGFRA. Transplanting 50-day cultures into cardiotoxin or BaCl2 injured immunodeficient murine muscle showed donor human cells persisted within the host muscle for 1 - 2 months post-injection; however, donor cells were confined to the interstitial space and did not contribute to host myofibers or the satellite cell niche. Together, these studies provide a tool for generating large quantities of embryonic skeletal muscle, and a gene expression resource that can provide insight into signaling factors that might improve or accelerate SMP development, or provide putative new surface receptors that may isolate embryonic SMPs better suited for in vivo transplantation.

A discussion of all the key issues in the use of human pluripotent stem cells for treating degenerative diseases or for replacing tissues lost from trauma. On the practical side, the topics range from the problems of deriving human embryonic stem cells and driving their differentiation along specific lineages, regulating their development into mature cells, and bringing stem cell therapy to clinical trials. Regulatory issues are addressed in discussions of the ethical debate surrounding the derivation of human embryonic stem cells and the current policies governing their use in the United States and abroad, including the rules and conditions regulating federal funding and questions of intellectual property.

Recent scientific breakthroughs, celebrity patient advocates, and conflicting religious beliefs have come together to bring the state of stem cell researchâ€"specifically embryonic stem cell researchâ€"into the political crosshairs. President Bush's watershed policy statement allows federal funding for embryonic stem cell research but only on a limited number of stem cell lines. Millions of Americans could be affected by the continuing political debate among policymakers and the public. Stem Cells and the Future of Regenerative Medicine provides a deeper exploration of the biological, ethical, and funding questions prompted by the therapeutic potential of undifferentiated human cells. In terms accessible to lay readers, the book summarizes what we know about adult and embryonic stem cells and discusses how to go about the transition from mouse studies to research that has therapeutic implications for people. Perhaps most important, Stem Cells and the Future of Regenerative Medicine also provides an overview of the moral and ethical problems that arise from the use of embryonic stem cells. This timely book compares the impact of public and private research funding and discusses approaches to appropriate research oversight. Based on the insights of leading scientists, ethicists, and other authorities, the book offers authoritative recommendations regarding the use of existing stem cell lines versus new lines in research, the important role of the federal government in this field of research, and other fundamental issues.

This volume covers all aspects of embryonic stem cell differentiation, including mouse embryonic stem cells, mouse embryonic germ cells, monkey and human embryonic stem cells, and gene discovery.* Early commitment steps and generation of chimeric mice* Differentiation to mesoderm derivatives* Gene discovery by manipulation of mouse embryonic stem cells