Effect of transforming growth factor-beta on decorin and beta1 integrin expression during muscle development in chickens.

Myoblast-extracellular matrix interactions play a pivotal role in skeletal muscle development. Transforming growth factor-beta (TGF-beta) is a key regulator of muscle cell proliferation and differentiation. The level of TGF-beta expressed will affect the concentration of the extracellular matrix proteoglycan decorin and the cell surface beta1 integrin subunit. The decorin proteoglycan is a regulator of cell growth as well as the organization of the extracellular matrix. The beta1 integrin plays a role in muscle cell attachment, migration, and the formation of multinucleated myotubes. In the current study, chicken myogenic satellite cells isolated from the pectoralis major muscle from the chicken genetic muscle weakness, low score normal (LSN), and normal pectoralis major muscle were used to investigate TGF-beta expression as it relates to decorin and beta1 integrin mRNA expression. The LSN muscle defect is characterized by altered myotube formation and sarcomere structure, and the satellite cells have reduced proliferation and differentiation. The mRNA expression was measured by real-time quantitative reverse transcription PCR. The LSN condition has elevated expression of TGF-beta2 and TGF-beta4 with increased expression of decorin and decreased beta1 integrin during myogenic satellite cell proliferation and differentiation. Normal satellite cell cultures were treated with the addition of exogenous TGF-beta during differentiation to determine if the altered expression of LSN decorin and beta1 integrin was associated with TGF-beta expression. The addition of exogenous TGF-beta decreased decorin expression during differentiation and reduced beta1 integrin expression at 24 and 48 h of differentiation. These results suggested that alteration of decorin expression in the LSN myogenic satellite cells may occur by a mechanism involving factors in addition to TGF-beta, but the addition of exogenous TGF-beta did affect both decorin and beta1 integrin expression. These data, therefore, suggested that TGF-beta might play a pivotal role in chicken skeletal muscle formation through modulation of the expression of both extracellular matrix molecules and cellular receptors important in the control of cell migration and growth regulation.