Résumé :
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The interplay between macrophages and muscle precursors is known to be critical for muscle repair and regeneration. In the past, we have already reported that themurine macrophage cell line J774 can produce a macrophage-conditioned medium (MCM) that contains muscle-specific growth factors, which are capable of stimulatingthe proliferation and differentiation of rat and human primary myoblasts. MCM greatly delayed senescence of cultured myoblasts derived from normal and DMD muscles,as well as prevented spontaneous adipogenic trans-differentiation of satellite cells derived from adult rat muscle cultured at sub-clonal density. Also in the rat model,the use of MCM coupled to serial plating enhanced the proliferation of a population of round, poorly adherent, highly myogenic and multipotent cells, which could bedifferentiated into myoblasts, osteoblasts and adipocytes.We now report the extension of our analyses to murine muscles. Interestingly, our data indicate that in thiscase MCM does not have an appreciable pro-proliferative effect, although it still enhances the myogenicity of primary muscle cultures and prevents the adipogenic transdifferentiationof adult satellite cells. These findings, which were also confirmed in another species (Gallus gallus), suggest that there might be some differences in theroles carried out by macrophages in human and murine muscle regeneration. Importantly, we show that MCM allows to obtain the population of round, highly myogeniccells also in mouse, and that these calls can be transplanted with high efficiency into the muscles of dystrophic, mdx, animals. Last but not least, in vivo experiments arepresently in course to assess the possible effect of MCM treatment on the accumulation of adipose tissue in the muscles of mdx mice.
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