Gene expression of type I and type III collagen by mechanical stretch in anterior cruciate ligament cells

Mechanical stretch affects the healing and remodeling process of the anterior cruciate ligament (ACL) after surgery in important ways. In this study, the effects of mechanical stress on gene expression of type I and III collagen by cultured human ACL cells and roles of transforming growth factor (TGF)-beta1 in the regulation of mechanical strain-induced gene expression were investigated. Uniaxial cyclic stretch was applied on ACL cells at 10 cycles/min with 10% length stretch for 24 h. mRNA expression of the type I and type III collagen was increased by the cyclic stretch. TGF-beta1 protein in the cell culture supernatant was also increased by the stretch. In the presence of anti-TGF-beta1 antibody, stretch-induced increase in type I and type III mRNA expression was markedly ablated. The results suggest that the stretch-induced mRNA expression of the type I and type III collagen is mediated via an autocrine mechanism of TGF-beta1 released from ligament cells.