Jacqueline Jozefonvicz

Lipid composition of cultured endothelial cells in relation to their growth

Human endothelial cells in culture were examined in different growth conditions. The human endothelial cell line, EA.hy 926 cell line, was used and cells were studied either in exponential growth phase, at confluence, or growth-arrested by serum deprivation. Phospholipids were separated and analyzed by high-performance thin-layer chromatography, and their fatty acids were quantified by gas-liquid chromatography. No significant differences in the phospholipid distributions were found between exponentially growing and confluent endothelial cells in which phosphatidylcholine (PC) represented the major phospholipid. In comparison, serum-deprived cells exhibited higher proportions of sphingomyelin and lower content of PC. We also found that among the total lipids, cholesterol level for dividing endothelial cells was lower than for cells growth-arrested either by serum deprivation or by contact inhibition at confluence. The global fatty acid distribution was not affected by the growth conditions. Thus, oleate (18∶1n−9 and 18∶1n-7), palmitate (C16∶0), and stearate (C18∶0) were the main components of endothelial cell membranes. However, the fatty acid distributions obtained from each phospholipid species differed with the growth status. Altogether, the data indicated that subtle modulations of endothelial cell metabolism appear upon cell growth. The resulting membrane-dependent cellular functions such as cholesterol transport and receptor activities can be expected to be relevant for lipid trafficking within the vessel wall in vitro and in vivo.

Randomness and Biospecificity : Random Copolymers are Endowed with Biospecific Properties

Biocompatible polymers should induce appropriate response from the host living bodies. Therefore they should be able to deliver appropriate messages. Biospecific random copolymers obtained by random substitution with suitable chemical groups of polymers like crosslinked polystyrene are biomaterials capable of mimicking the natural messenger molecules of a living system. The biospecific activities of the random copolymers depend on the overall chemical composition of the final product. Indeed, random copolymers endowed with antigen-like abilities have been synthesized. We recently developped a detailed analysis of the chemical structure of the specific sites responsible for the “factor VIII — like antigen” or “DNA-like antigen” properties of polystyrene derivatives synthesized by random derivatization. As a consequence, it appears that biospecificity is a continuous function of randomness from purely statistical distribution of chemical functional groups to the strictly defined chemical structure of ligand receptor molecules in living system.