Collagen synthesis by human fibroblasts

We have examined the combined effects of transforming growth factor-fl (TGF-,8), serum and y-interferon (y-IFN) on collagen synthesis by fibroblasts and compared the response of fibroblast subpopulations to TGF-,6. Human diploid fibroblasts were treated with TGF-/J alone and with serum or y-IFN. Cells were labelled with radioactive amino acids, and collagen production was measured as collagenase-digestible radioactivity. Collagen mRNA was determined by a solution-hybridization assay using procollagen-al[1] cDNA clone HF 677. The results showed that either serum or TGF-,/ increased incorporation, collagen production and mRNA by fibroblasts approx. 2-fold; however, collagen synthesis relative to total protein synthesis and collagen mRNA relative to total polyadenylated [poly (A)'] RNA were not affected. Only serum activated cell growth. Collagen production increased approx. 4-fold in cells exposed to both TGF-,/ and serum, and this increase was equal to that expected for an additive effect by both components. Treatment with y-IFN decreased collagen production and collagen mRNA to 44 and 400 respectively, whereas total incorporation and poly(A)+ RNA were affected only marginally. Cells exposed simultaneously to both y-IFN and TGF-, produced less collagen and contained less mRNA than did those treated with TGF-, alone. The y-IFN decreased collagen synthesis in control and TGF-,/-treated cultures to a similar extent, and TGF-,/ increased collagen synthesis 2-fold in cells pre-treated with y-IFN. Fibroblast strains obtained in medium containing plasma-derived serum synthesized approximately half as much collagen as did cells derived from the same explant in the presence of fresh human serum, and TGF-,/ stimulated collagen production and mRNA in both cell strains. We conclude that TGF-fl, serum and y-IFN regulate collagen synthesis by independent mechanisms, and that the combined action of these components plays a s-ignificant role in regulating collagen synthesis during wound healing and tissue repair.