Résumé :
|
Satellite cells are the main progenitor cells for skeletal muscle growth and regeneration under physiological conditions. The difficulty of purifying these quiescent cells in sufficient number has precluded their biochemical characterization. Pax3 and Pax7 paired-box transcription factors play critical roles in skeletal myogenesis by directing progenitor cells into the myogenic programme and by ensuring their survival. In adult muscle, satellite cells are marked by the expression of Pax7 and, in a subset of muscles, also of Pax3. The generation of a Pax3GFP/+ mouse line permitted the purification of satellite cells expressing the GFP marker by flow cytometry and the demonstration of their major role in muscle repair together with their capacity to self renew as adult muscle progenitor cells in vivo. This purification procedure has opened the way for biochemical characterization of these freshly isolated Pax3GFP/+ quiescent cells. The gene expression profile of quiescent satellite cells has been established by comparison with activated cells. Activated cells were obtained in three ways: in vitro, by culturing freshly isolated cells for 3 days in growth medium, and in vivo, by isolating them from growing post-natal muscles and from mdx mice. These mice lack dystrophin, a structural protein that is mutated in Duchenne muscular dystrophy patients. In mdx mice, fibre degeneration is chronic but constantly compensated by regeneration, which results from the continuous mobilization and activation of satellite cells. This approach gives new insights into satellite cell function and regulation and should lead to the identification of novel specific markers such as those of use for isolating satellite cells from other species, including humans. Relaix F, Montarras D, Zaffran S, Gayraud-Morel B, Rocancourt D, Tajbakhsh S, Mansouri A, Cumano A, Buckingham M. (2006) Pax3 and Pax7 have distinct and overlapping functions in adult muscle progenitor cells. J.Cell Biol. 172, 91-102 Montarras D, Morgan J, Collins C, Relaix F, Zaffran S, Cumano A, Partridge T, Buckingham M. (2005). Direct isolation of satellite cells for skeletal muscle repair. Science. 309, 2064-
|