Purification and characterization of an endothelial cell-viability maintaining factor from fetal bovine serum

Serum is an essential requirement for the growth and long-term survival of human endothelial cells, even in the presence of such defined elements such as polypeptide growth factors and hormones. A polypeptide from fetal bovine serum was isolated and characterized on the basis of long-term survival of human endothelial cells in serum-free culture. The endothelial cell viability maintaining factor has been purified to homogeneity by a combination of polyethylene glycol precipitation, hydroxylapatite, gel permeation and reverse-phase high performance liquid chromatography. The final purified endothelial cell viability maintaining factor has a molecular weight of 65,000 (reduced) and has been identified as bovine apolipoprotein H by amino-terminal amino acid sequence analysis and Western blot analysis. Endothelial cell viability maintaining factor improved a long-term viability of human endothelial cells at maximal concentrations of 2.5-5 micrograms protein/ml in serum-free medium.