Demonstration of competence and progression activities for human fibroblasts

Human embryonic lung fibroblasts (HEL) completed 4.5 population doublings in 6 days when maintained in DMEM supplemented with 10% human whole blood serum (WBS), plasma-derived serum (PDS) or defibrinogenated plasma containing 10 mM CaCl₂. Plasma in the absence of additional calcium promoted less growth. Sera and plasma chromatographed through carboxymethyl Sephadex (CMS) supported only one population doubling. Increased growth resulting in three doublings was observed in CMS-treated WBS or PDS supplemented with commercially prepared platelet-derived growth factor (PDGF). The magnitude of this PDGF response was dependent on serum concentration. A significant increase in the proportion of cells incorporating [³H]thymidine was observed in confluent cultures exposed to PDGF prior to incubation in WBS-CMS or PDS-CMS indicating competence and progression activities for human fibroblasts. In contrast, cells maintained in the presence of plasma-CMS failed to grow in response to PDGF. Factors bound to CMS columns restored growth-promoting activity to PDGF-supplemented WBS-CMS, PDS-CMS and plasma-CMS. However, growth-promoting CMS-bound components from plasma were lost during dialysis through membranes excluding materials above 12000 MW.