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Phosphatidyl choline and the growth in serum‐free medium of vascular endothelial and smooth muscle cells, and corneal endothelial cells

Liposomes made by sonication of egg yolk phosphatidyl choline support the proliferation of low‐density bovine vascular and corneal endothelial cells, and vascular smooth muscle cells maintained on basement laminacoated dishes and exposed to a defined medium supplemented with transferrin. The optimal growth‐promoting effect of phosphatidyl choline was observed at concentrations of 25 μg/ml for low‐density cultures of vascular smooth muscle cells, and 100 μg/ml for vascular and corneal endothelial cells. The growth rate and final cell density of vascular endothelial cells exposed to a synthetic medium supplemented with transferrin and either high‐density lipoproteins or phosphatidyl choline has been compared. Although cultures exposed to phosphatidyl choline reached a final cell density similar to that of cultures exposed to high‐density lipoproteins, they had a longer average doubling time (17 h vs. 12 h) during their logarithmic growth phase and a shorter lifespan (17 generations vs. 30 generations). Similar observations were made in the case of vascular smooth muscle cells or bovine corneal endothelial cells maintained in medium supplemented with transferrin, fibroblast growth factor (FGF) or epidermal growth factor (EGF), and insulin and exposed to either high‐density lipoproteins or phosphatidyl choline. Since phosphatidyl choline can, for the most part, replace highdensity lipoproteins in supporting the proliferation of various cell types, it is likely that the growth stimulating signal conveyed by high‐density lipoproteins is associated with its polar lipid fraction, which is composed mostly of phosphatidyl cholines.