Reciprocal actions of platelet-secreted TGF-β1 on the production of VEGF and HGF by human tendon cells

Background: Autologous platelet-rich matrices can be an aid in surgery by promoting and accelerating tissue healing because of the release of growth factors including transforming growth factor (TGF)-beta 1 and platelet-derived growth factor (PDGF) from platelet a-granules. Methods: PDGF and TGF-beta 1 were quantified in supernatants collected from platelet-rich matrices prepared in vitro (n = 45 donors) and they correlated with the number of platelets and showed a constant ratio (p < 0.05). Tendon cells in culture were exposed to the supernatants (n = 4 donors) from either platelet-rich or platelet-poor matrices, differing in their content of platelet-secreted molecules. These treatments were modified by either neutralizing or adding PDGF or TGF-beta 1. Effects were compared in terms of proliferation, procollagen I, vascular enclothelial growth factor (VEGF), and hepatocyte growth factor (HGF) production. Results: PDGF was a partial contributor to cell proliferation, whereas exogenous TGF-beta 1 acted as a negative modulator (p < 0.05). The production of type I collagen was similar regardless of differences in the concentration of TGF-beta 1. Moreover, addition of exogenous TGF-beta 1 promoted a significant increase in collagen synthesis only in the absence of other platelet-released substances (p < 0.05). Exogenous TGF-beta 1 increased the synthesis of VEGF and simultaneously abolished the production of HGF. Furthermore, antibody mediated neutralization of TGF-beta 1 induced a decrease in VEGF synthesis and concomitantly a substantial production of HGF (p < 0.05). Conclusion: The balance between TGF-beta 1 and the pools of platelet-secreted molecules may have important therapeutic implications in the control of angiogenesis and fibrosis.