Influence of calcium concentration in the medium on the cell proliferation and glycosaminoglycan synthesis of human diploid skin fibroblasts in culture

Effect of calcium on cell proliferation and extracellular matrix synthesis in arterial smooth muscle cells and dermal fibroblasts

The effect of calcium on cell proliferation and connective tissue formation was studied in cultured vascular smooth muscle cells (SMC) and dermal fibroblasts. Calcium deficiency caused a modest decrease in proliferation of smooth muscle cells but this effect was small compared to that previously observed with fibroblasts. Synthesis of connective tissue components was affected differently in the two cell types. Biosynthesis of proteoglycans was assessed by metabolic labeling of their glycosaminoglycan side chains. Different levels of extracellular calcium did not affect proteoglycan production by fibroblasts, but it was significantly reduced in smooth muscle cells incubated in calcium-deficient medium. Both smooth muscle cells and fibroblasts were able to produce appreciable amounts of collagen in the complete absence of calcium and in both cell types collagen synthesis was increased when calcium was present. Fibroblasts, however, showed a much smaller response to calcium than did smooth muscle cells. In fibroblasts the maximum rate of collagen synthesis was achieved in a narrow range of calcium concentration which was slightly below that found commonly in the tissue culture medium. By contrast, in smooth muscle cells the rate of collagen synthesis increased greatly when calcium was present and this elevated rate persisted even when the cells were exposed to high levels of extracellular calcium. We conclude that these findings may be of significance to the development of atherosclerotic lesions.