Résumé :
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Communication n° 101. Heparin affin regulatory peptide is a heparin binding growth factor (HARP). It belongs to a family of molecule whose biological function in myogenesis has been suspected without formal demonstration. In the present study, we investigated the expression and the distribution of HARP and its mRNA during rat Soleus muscle regeneration using a crushed-induced regeneration model, and also during differentiation of muscle satellite cells grown in primary cultures. We have shown that HARP mRNA and protein expressions were both increased during the regeneration process with a peak at day 5 after muscle crushing when new myotubes are formed. Then, in the regenerated myofibers, 15 days after crushing, expression level of HARP was reduced. In situ hybridization and immunohistochemical studies showed that activated myoblasts expressed HARP at day 2 after crushing. Five days after muscle lesion, HARP was localised in newly formed myotubes as well as in prefused activated myoblasts. In vitro experiments performed with primary cultures of rat satellite cells indicated that HARP expression level increased during the differentiation process to peak at fusion of myoblasts into myotubes. In addition, fusion was prevented in the presence of HARP antibody. This study demonstrated the presence of HARP in fusing myogenic cells and suggested that this growth factor play a key role in the myogenic differentiation process.
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