FETAL AND POSTNATAL SERA DIFFERENTIALLY MODULATE HUMAN DERMAL FIBROBLAST PHENOTYPIC AND FUNCTIONAL FEATURES IN-VITRO

Fetal wounds heal without scar formation, fibrosis, or contracture. Co mpared with adult wounds, they are characterized by major differences in the extracellular matrix and the absence of myofibroblastic cells. The reasons for these differences are not well known and determination of factors affecting the absence of scarring in the fetus may lead to strategies for controlling adult pathological scarring. In the presen t study, we have assessed the effects of serum on the behavior of norm al human dermal fibroblasts. Using an in vitro approach, we investigat ed the effects of fetal and adult serum on cell properties such as gro wth rate, collagen synthesis, gelatinase activities, and differentiati on to myofibroblasts using biochemical, morphological, and ultrastruct ural parameters. We studied the induction of alpha-smooth muscle (alph a-SM) actin in fibroblasts, and its correlation with increased collage n gel contraction by the cells. Our results showed that, compared with FBS (fetal bovine serum), postnatal calf serum (PCS) decreased mitoge nic activity and collagenase synthesis but not collagen synthesis. Fur thermore, cells cultured with PCS differentiated to myofibroblasts wit h an increase in cell diameter, number of stress fibers, a-SM actin ex pression, and collagen gel contraction. To characterize the molecules involved in this differentiation process, the amount of transforming g rowth factor beta (TCF beta) in FBS and PCS was determined and the eff ect of neutralizing anti-TGF beta antibody was evaluated. It was deter mined that FBS contained more TGF beta than PCS, but that essentially all the TGF beta was latent in both sera. However, results obtained wi th anti-TGF beta antibody show that active TGF beta is present when hu man dermal fibroblasts are cultured with medium containing PCS. These results suggest that, in the presence of PCS but not FBS, the cells ei ther produce active TGF beta or an enzyme that is able to activate lat ent serum TGF beta. Alternatively, sera may contain two different form s of latent TGF beta, the PCS form being activated by the dermal fibro blast cells. A similar mechanism may be involved, at least in part, in skin wound healing and may underlie the appearance of myofibroblasts in postnatal wounds. (C) 1997 Wiley-Liss, Inc.