Résumé :
|
Together with other extracellular matrix and membrane-associated components that contribute to the cellular environment of muscle cells, proteoglycans (PG) have been implicated in numerous physiological and pathological processes including regulation of enzymes and growth factor bioavailability, cellular growth and differentiation. The known effects of PG are mainly due to the sulphated glycosaminoglycan (GAG), namely dermatan sulphate/chondroitin sulphate (DS/CS) and heparan sulphate (HS). It is generally accepted that unique tissue specific HS sequences are generated by biosynthetic enzymes that produce this type of molecules, key regulators of cell signaling. It is therefore of special interest to analyze the spatio-temporal pattern of GAG expression during skeletal muscle regeneration. We have used a crush-induced muscle regeneration model that generates differences in rat fast EDL and slow Soleus regenerating muscles. Using a simple sensitive method of GAG concentration measurement developed in our laboratory, GAGs were quantitated during regeneration of these muscles. The study was further extended to in vitro differentiation of primary cultures of satellite cells. Different GAG epitopes were visualized using specific antibodies applied on regenerating muscle sections and on myoblasts differentiating in vitro. We have demonstrated changes in the composition of GAG extracted from EDL and Soleus muscles during regeneration. In both muscle types, total GAG amounts were collapsed one day after crush, then increased during muscle repair. HS that was less abundant than DS/CS during the first week after crush, and became the most important GAG species starting at the second week of muscle reconstruction. Similar changes in GAG composition were observed during in vitro satellite cell differentiation. Time-dependent specificities were revealed that depended on muscle of origin (EDL or Soleus), in both in vivo and in vitro studies. We propose that changes in GAG environment of myogenic cells might alter signalling events associated to myogenesis.
|