Synthesis and release of fatty acids by human trophoblast cells in culture

Abstract

In order to determine whether placental cells can synthesize and release fatty acids, trophoblast cells from term human placentas were established in monolayer culture. The cells continued to secrete placental lactogen and progesterone and maintained specific activities of critical enzymes of triacylglycerol and phosphatidylcholine biosynthesis for 24 to 72 hr in culture. Fatty acid was rapidly synthesized from [14C]acetate and released by the cells. Palmitoleic, palmitic, and oleic acids were the major fatty acids synthesized from [14C]acetate and released. Small amounts of lauric, myristic, and stearic acids were also identified. [14C]acetate was also incorporated into cellular triacylglycerol, phospholipid, and cholesterol, but radiolabeled free fatty acid did not accumulate intracellularly. In a pulse-chase experiment, cellular glycerolipids were labeled with [1-14C]oleate; trophoblast cells then released 14C-labeled fatty acid into the media as the cellular content of labeled phospholipid and triacylglycerol decreased without intracellular accumulation of free fatty acid. Twenty percent of the 14C-label lost from cellular glycerolipid could not be recovered as a chloroform-extractable product, suggesting that some of the hydrolyzed fatty acid had been oxidized. These data indicate that cultured placenta trophoblast cells can release fatty acids that have either been synthesized de novo or that have been hydrolyzed from cellular glycerolipids. Trophoblast cells in monolayer culture should provide an excellent model for molecular studies of placental fatty acid metabolism and release.