Proliferative behaviour of fibroblasts in plasma-rich culture medium

We examined the proliferative behaviour in tertiary culture cells of human skin fibroblasts (HSF) as well as cells of the rat 3Y1 diploid fibroblast line placed on a plastic substratum in a nutrient-rich medium containing high concentrations of platelet-poor plasma (PPP). Autochthonous human PPP was used for the HSF cells and heat-treated (at 56 degrees C for 30 min) bovine PPP was used for the 3Y1 cells. In both types of cells, the saturation cell density rose with increasing PPP concentration and reached a plateau at 30–90% PPP. When the cells were cultivated in serum, the saturation densities were the same as those with the same concentrations of corresponding PPP in both the HSF and 3Y1 cells. When the cells were arrested at a saturation cell density in a medium containing 10% PPP and then were refed with a fresh medium containing 90% PPP, DNA synthesis and cell division occurred in both types of fibroblasts. This effect was either reduced in the HSF cells or enhanced in the 3Y1 cells by the addition of platelet lysate. TGF-beta 1 added to the fresh medium containing 90% PPP also inhibited the induction of DNA synthesis in the HSF cells but not in the 3Y1 cells. The inhibitory effect of the platelet lysate was neutralized by anti-TGF-beta 1 IgG. On the other hand, PDGF added to the fresh medium had no effect on either type of cells. These results suggest that cultured fibroblasts are capable of proliferating on a plastic substratum under fluid conditions that essentially reflect the fluid environment of the body, as long as sufficient nutrients are supplied. Platelet lysate represses the proliferation of HSF cells, possibly through the inhibitory effect of TGF-beta 1, and promotes the proliferation of 3Y1 cells by growth factor(s) other than PDGF and TGF-beta 1.