Expression of transforming growth factor β isoforms and their roles in tendon healing

Transforming growth factor beta (TGF-beta) plays active roles in tendon healing. However, the differential effects of TGF-beta isoforms on tendon healing have not been investigated. In cultured tendon fibroblasts, we tested the effects of TGF-beta 1, beta 2, and beta 3 on the mRNA levels of COL1A1 and COL3A1 by quantitative real-time polymerase chain reaction. We also investigated the expression of TGF-beta isoforms, TGF-beta receptors, procollagen Type I and Type III in a rat model of tendon healing. We found that TGF-beta 3 exhibited the highest potency in stimulating COL1A1 and COL3A1. TGF-beta 1 exerted antagonistic effects to TGF-beta 2 and beta 3. All TGF-beta isoforms and procollagen Type I were confined to the edges of the healing tendon at day 28 postinjury. Our results indicated that interaction of TGF-beta isoforms exist in the regulation of collagen synthesis in tendon fibroblasts. Their effects may be further complicated by uneven spatial distribution of TGF-beta and TGF-beta receptors in healing tendons.