Do plasma and serum have different abilities to promote cell growth?

The abilities of plasma and serum to support the growth of vascular smooth muscle cells maintained on uncoated tissue culture dishes or dishes coated with an extracellular matrix (ECM) have been compared. Vascular smooth muscle cells maintained on plastic dishes and exposed to plasma proliferate poorly; when exposed to serum they proliferate actively. Addition of fibroblast growth factor (FGF) incrases the growth rate of the cultures in both cases. In contrast, when vascular smooth muscle cells are maintained on an ECM, they proliferate equally well exposed to either plasma or serum. Because the cultures had an average doubling time (15 hr) that was already at a minimum, FGF no longer had an effect on vascular smooth muscle cell proliferation. These results raise the possibility that the lack of response of vascular smooth muscle cells, as well as that of other cell types in vitro, to plasma factors is not an intrinsic property of the cells but is rather due to the substrate upon which the cells rest. Because cells maintained on an ECM respond to plasma factors, it is likely that the close contact of the cells with the ECM restores their sensitivity to physiological factors present in plasma.