Transforming growth factor beta-1 (TGF-β1) stimulates collagen synthesis in cultured rainbow trout cardiac fibroblasts.

Cold acclimation of rainbow trout, Oncorhynchus mykiss , causes collagen to increase within the extracellular matrix (ECM) of the myocardium, while warm acclimation has the opposite effect. The mechanism responsible for this remodelling response is not known. In mammals, transforming growth factor beta-1 (TGF-β1) stimulates collagen deposition within the myocardial ECM. Therefore, we hypothesized that TGF-β1 regulates trout myocardial ECM turnover and predicted that TGF-β1 would induce collagen deposition in cultured rainbow trout cardiac fibroblasts. We found that treatment of trout cardiac fibroblasts with 15 ng ml-1 human recombinant TGF-β1 caused an increase in total collagen at 48 and 72 h and an increase in collagen type I protein after 7 days. We also found that TGF-β1 treatment caused an increase in the transcript abundance of tissue inhibitor of metalloproteinase 2 ( timp-2 ) and matrix metalloproteinase 9 ( mmp-9 ) at 24 h. Cells treated with TGF-β1 also had lower levels of the gene transcript for mmp-2 after 48 h and higher levels of the gene transcript for collagen type I α1 ( col1a1 ) after 72 h. These changes in gene expression suggest that the increase in collagen deposition is due to a decrease in the activity of matrix metalloproteinases and an increase in collagen synthesis. Together, these results indicate that TGF-β1 is a regulator of ECM composition in cultured trout cardiac fibroblasts and suggest that this cytokine may play a role in regulating collagen content in the trout heart during thermal acclimation.