Résumé :
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Communication n° 514 After birth, adult skeletal muscle growth and repair are mediated by a population of cells, normally mitotically quiescent and located under the basal lamina of the myofibers, called satellite cells. In response to muscle damage, resident satellite cells are activated, proliferate and then differentiate to form new muscle fibres. Numerous recent reports have suggested the presence of additional sources of myogenic cells distinct from satellite cells. Observations in mice have indicated that adult skeletal muscle may contain rare multipotent progenitors that can give rise to myogenic and hematopoietic lineages. Moreover, bone-marrow derived progenitors have been reported to participate to the formation of myofibers and satellite cells. We have investigated the myogenic potential of human muscle-derived and circulating hematopoieitc stem cells (HSC) based on the expression of CD34 and AC133. The efficiency of these cell populations to participate to muscle regeneration was evaluated in an ex vivo model, the RAG-/- gammaC-/- C5-/- mouse in which degeneration of the Tibialis Anterior (TA) is induced by cryoinjury. Human cells were injected into the regenerating TA and muscles were analysed 2 months post-injection. Human nuclei were visualised using a human-specific antibody directed against lamin A/C, while fibres containing human proteins were identified with an anti human spectrin antibody. Our preliminary results demonstrate a difference in the behaviour of the AC133+/CD34+ population isolated from muscle or peripheric blood: the AC133+/CD34+ muscle population demonstrated a better regenerative capacity when compared to the blood AC133+/CD34+. Other experiments will be addressed to assess the in vitro myogenic potential of human circulating HSCs when cocultured in a myogenic environment.
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