Pure Platelet-Derived Growth Factor Stimulates Human Fibroblasts to Proliferate in Plasma-Free Culture
Platelet-derived growth factor (PDGF) is released from platelets when they aggregate (1). It stimulates connective tissue cells to proliferate in vitro (2–5) and has been ascribed a role in wound healing (6) and in the pathogenesis of atherosclerosis (7). Data concerning the role of PDGF in the cell cycle are conflicting. For 3T3 cell cultures PDGF alone is not capable of inducing DNA synthesis but induces a state of “competence” to respond to other hormones which stimulates “progression” through G1(8–10). Others have found that PDGF alone is sufficient for stimulation of proliferation of normal human glial cells (2). In this study, we have investigated the role of PDGF in the cell cycle of human skin fibroblasts, a cell type which expresses a high number of PDGF receptors (11). We have found that human fetal or neonatal fibroblasts are able to initiate DNA synthesis and divide in serum-free culture in the absence of added growth factors. When this spontaneous proliferation is inhibited by increased cellular density, reduced cell spreading or subphysiologic extracellular Ca2+ concentrations, PDGF becomes mitogenic. In addition, proliferation in the absence of PDGF, EGF or other hormones which usually are added to serum-free culture systems seems to be a feature specific for fetal or neonatal fibroblasts; their adult counterparts have an obligatory requirement for exogenous growth factors.
KeywordsTitanium Agarose Palladium Petn
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