Muscle progenitor cell proliferation during passive stretch of unweighted soleus in dystrophin deficient mice

Dystrophin, subsarcolemmal protein communicating muscle fiber cytoskeleton to extracellular matrix, is believed to be involved in mechanical signal transduction. The experiment was carried out to assess the role of dystrophin in passive stretch-induced preventing unloaded muscle fiber atrophy and possible linkage between this protein and muscle progenitor (satellite cells) proliferation activity. The study was performed on two months old C57 black and mdx (dystrophin-deficient) mice. Passive stretch resulted in attenuating atrophy development in two fiber types of both C57 black and mdx mice. Altered dystrophin synthesis in mdx mice had virtually no effect on passive stretch preventive action. Thus the hypothesis about dystrophin key role in mediating stretch-induced hypertrophy effects didn't find its confirmation concerning gravitational unloading atrophy. Chronic hindlimb unloading downregulated SC proliferative activity in soleus muscle, passive stretch drastically increased proliferation both in C57 and mdx mice. Thus we observed no relationship between altered dystrophin synthesis and satellite cell proliferation activity in soleus muscle under conditions of simulated microgravity and concurrent passive stretch.