Effect of Transforming Growth Factor-β on Decorin and β1 Integrin Expression During Muscle Development in Chickens

Abstract

Myoblast-extracellular matrix interactions play a pivotal role in skeletal muscle development. Transforming growth factor-β (TGF-β) is a key regulator of muscle cell proliferation and differentiation. The level of TGF-β expressed will affect the concentration of the extracellular matrix proteoglycan decorin and the cell surface β1 integrin subunit. The decorin proteoglycan is a regulator of cell growth as well as the organization of the extracellular matrix. The β1 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-β expression as it relates to decorin and β1 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-β2 and TGF-β4 with increased expression of decorin and decreased β1 integrin during myogenic satellite cell proliferation and differentiation. Normal satellite cell cultures were treated with the addition of exogenous TGF-β during differentiation to determine if the altered expression of LSN decorin and β1 integrin was associated with TGF-β expression. The addition of exogenous TGF-β decreased decorin expression during differentiation and reduced β1 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-β, but the addition of exogenous TGF-β did affect both decorin and β1 integrin expression. These data, therefore, suggested that TGF-β 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.