SYNTHESIS AND SECRETION OF MATRIX-DEGRADING METALLOPROTEASES BY HUMANSKELETAL-MUSCLE SATELLITE CELLS

The expression of matrix-degrading metalloproteases (MMPs) by human sk eletal muscle satellite cells was investigated by zymography of cell c ulture media and by Northern blot analysis of mRNA prepared from satel lite cells, Zymography in gelatin substrate gels revealed that satelli te cells constitutively synthesize and secrete 72 kDa gelatinase (MMP- 2), In addition, treatment of satellite cell cultures with phorbol est er resulted in an induction of 92 kDa gelatinase (MMP-9) activity, On casein substrate gels, little or no proteolytic activity was detectabl e in control or phorbol ester treated satellite cell cultures, suggest ing that compared to fibroblasts, satellite cells secrete little or no interstitial collagenase (MMP-1) or stromelysin (MMP-3) activity, Nor thern blotting, however, revealed that there is detectable expression of mRNA transcripts encoding MMP-1 in satellite cell cultures, and tha t increased accumulation of MMP-1 mRNA transcripts occurs upon treatme nt of these cells with phorbol ester. In contrast, no constitutive, or induced expression of transcripts encoding MMP-3 was detectable in sa tellite cells. These findings show that satellite cells can synthesize and secrete selected members of the MMP family and suggest that skele tal muscle cells may participate directly in remodelling of the extrac ellular matrix during myogenesis and the regeneration of skeletal musc le. (C) 1995 Wiley-Liss, Inc.