Extracellular matrix proteoglycan decorin-mediated myogenic satellite cell responsiveness to transforming growth factor-beta1 during cell proliferation and differentiation Decorin and transforming growth factor-beta1 in satellite cells.

Transforming growth factor-beta1 (TGF-beta1) is a potent inhibitor of muscle cell proliferation and differentiation. Decorin, a small proteoglycan in the extracellular matrix, binds to TGF-beta1 and modulates the activity of TGF-beta1 during muscle cell growth and development. However, its interaction with TGF-beta1 and involvement in myogenesis is not well characterized. In the present study, chicken myogenic satellite cells, myogenic precursors for muscle growth and repair, were isolated from the pectoralis major muscle and used to investigate the biological function of TGF-beta1 and decorin during myogenesis. The over-expression of decorin in satellite cells significantly increased cell proliferation, compared to the control cells. Consistent with this result, reducing decorin expression decreased cell proliferation, which suggests a decorin-mediated mechanism is involved in the regulation of myogenic satellite cell proliferation. Satellite cells over-expressing decorin were less sensitive to TGF-beta1 during proliferation, which indicates that decorin may sequester TGF-beta1 leading to increased proliferation. During satellite cell differentiation, the over-expression of decorin induced differentiation by increasing the muscle specific creatine kinase concentration. However, the addition of TGF-beta1 diminished decorin-mediated cell responsiveness to TGF-beta1 during differentiation. Taken together, these results suggest that decorin induces myogenic satellite cell proliferation and differentiation by regulating cellular responsiveness to TGF-beta1. An alternative TGF-beta1-independent pathway may be involved in the regulation of satellite cells by decorin.