Résumé :
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Fibrosis, characterized by excessive accumulation of extracellular matrix (ECM), is a hallmark of muscle biopsies in several muscular dystrophies such as Congenital (CMD) or Duchenne Muscular Dystrophies (DMD). Cell therapy trials have shown that increased connective tissue hindered the dispersion and incorporation of grafted cells into regenerating myofibers. Consequently, the success of this therapeutic strategy depends on the comprehension of molecular mechanisms leading to dysregulation of the balance between production and/or hydrolysis of ECM components. The involvement of Transforming Growth Factor beta (TGF?) in fibrotic processes is well established. Other factors, among which Connective Tissue Growth Factor (CTGF), have equally been implicated. This protein, member of the CCN family (Cyr61/Ctgf/Nov), appears to be involved in the development of fibrosis in various pathological situations. It was shown to act as a downstream mediator of TGF? but could also act through a TGF? independent mechanism. In dystrophic muscles, the role played by CTGF in the fibrotic process is emerging and remains to be fully assessed. In this study, we have examined the consequences of exposing myogenic cells to CTGF. At first, we have investigated the production of endogenous CTGF by myogenic cells and its regulation during myogenesis in vitro. Then, we have overexpressed human-CTGF in myoblasts to explore its effect on cell proliferation and differentiation and compared them to control cells. Stably transfected clones were screened for h-CTGF expression by western blotting and quantitative real time Q-PCR has confirmed CTGF overexpression. The effect of CTGF on myoblast proliferation was quantified using the Neutral Red assay. Myogenic differentiation was evaluated by comparing the fusion capacity of clones overexpressing the protein versus their control clones. Data on CTGF expression, regulation and the functional consequences resulting from myoblasts exposure to CTGF will be presented.
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