This study investigated the effect of cyclic mechanical stretching on the collagen gene expression and protein synthesis of human patellar tendon fibroblasts (HPTFs). We hypothesized that cyclic mechanical stretching of HPTFs would increase collagen synthesis via transforming growth factor-beta 1 (TGF-β1). To test the hypothesis, the tendon fibroblasts were cultured on microgrooved surfaces of silicone dishes under serum-free conditions. The cells were subjected to cyclic uniaxial stretching with a constant frequency and duration (0.5Hz, 4hr), and one of three stretching magnitudes (no stretch, 4%, and 8%) followed by 4 hours of rest. It was found that the gene and protein expression of both collagen type I and TGF-β1 were significantly increased in a stretching-magnitude dependent manner, whereas collagen type III gene and protein levels were not significantly changed. The exogenous addition of antibody to TGF-β1 eliminated the stretching-induced increase in collagen type I protein synthesis. The results therefore confirmed our working hypothesis and suggest that mechanical stretching of tendon fibroblasts can lead to matrix remodeling by modulating the collagen production of tendon fibroblasts, a process at least particially mediated by TGF-β1.

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