REGULATION OF FIBROBLAST PROLIFERATION IN 3-DIMENSIONAL COLLAGEN GEL MATRIX

Fibroblasts in vivo reside in a three-dimensional (3-D) matrix. The 3- D culture method using collagen gels provides valuable information, bu t it also has some practical difficulties. In particular, the changes caused by the contraction of gels and the occasional abrupt detachment from the underlying surface have made extended culture difficult. In this study, the 3-D culture method was modified in order to observe th e cells with minimal change of substrata for longer periods. The proli feration characteristics of fibroblasts cultured in gels in response t o fetal calf serum (FCS), to two defined growth factors, insulin and p latelet-derived growth factor (PDGF), and to a growth inhibitory facto r, prostaglandin E(2) (PGE(2)), were evaluated with this system in com parison with monolayer cultured fibroblasts. The DNA content of fibrob lasts cultured both in gels and on dishes increased in response to FCS in a concentration-dependent manner. The proliferation of gel-culture d fibroblasts, however, was lower than that of dish-cultured cells, an d higher concentrations of serum were necessary for proliferation. The response of gel-cultured cells to PDGF was also less than that of dis h-cultured cells. In addition, fibroblasts cultured in gel culture did not respond to insulin, while the fibroblasts on dishes responded to insulin in a concentration-dependent manner. In contrast to the reduce d response to growth stimulators, PGE(2) inhibited proliferation in ge l culture and in monolayer culture similarly. The reduced responsivene ss to growth stimulation but equivalent response to growth inhibition may account for reduced proliferation of fibroblasts in 3-D culture.