Inhibition of proliferation in 8-week-old mdx XXXX muscle fibroblasts in vitro.

@entity1 @entity1555 @entity19 @entity39
Our purpose is to understand why mdx muscle does not show the progressive degeneration observed in @entity1 @entity1555 ( @entity1555 ) muscle. In the @entity19 , the regenerative process compensates for the @entity39 of the muscle fibers, particularly during the acute phase of the disease (5-9 weeks). In @entity1555 muscle, there is a gradual failure of the regenerative process and the muscle fibers are replaced by connective and fatty tissue. We propose that distinct properties of mdx and @entity1555 muscle fibroblasts could be one of the reasons for the differences between the mdx and @entity1555 phenotypes. We found that fibroblasts taken from @entity1 @entity1555 and control muscle had similar in vitro proliferative capacities. The proliferation rate of @entity19 muscle fibroblasts decreased during the acute phase of the disease, and inhibition was complete in fibroblasts from 8-week-old mdx @entity19 . Moreover, the medium conditioned by these cells inhibited fibroblast proliferation. The effect was specific for fibroblasts, since this conditioned medium stimulated myoblast proliferation, as did control fibroblast-conditioned medium. These results suggest that 8-week-old mdx @entity19 muscle fibroblasts produce an inhibitor of their own proliferation and a growth factor specific for myoblasts in vitro. If these factors are secreted in vivo, the growth inhibitory factory may stop fibroblast proliferation whereas the mitogenic activity could stimulate satellite cell proliferation, thus favouring muscle regeneration.
