A comparison of human amnion tissue and amnion cells in primary culture by morphological and biochemical criteria.

Abstract

Prostaglandins, which are believed to mediate the initiation or maintenance of human labor or both, are synthesized from arachidonic acid. We have shown previously that the arachidonic acid content of two glycerophospholipids (diacyl phosphatidylethanolamine and phosphatidylinositol) in amnion tissue obtained during early labor is decreased compared with that in amnion tissue obtained before labor commenced. We and others have demonstrated that amnion tissue synthesizes prostaglandin E2 from exogenous and endogenous arachidonic acid. Thus, the amnion may be a source of prostaglandins involved in the initiation of parturition. We have investigated whether amnion cells in monolayer culture could be utilized as an in vitro model system for the study of glycerophospholipid and arachidonic acid metabolism in amnion. Several morphological biochemical, and enzymatic characteristics of amnion cells in culture were compared with those of amnion tissue. Morphologically, the amnion cells in culture and amnion tissue are similar. The lipid composition and arachidonic acid content of lipid fractions of amnion cells in culture and of amnion tissue also are similar. The specific activities of phospholipases A2 and C, the enzymes that initiate and thus probably regulate the release of arachidonic acid from phosphatidylethanolamine and phosphatidylinositol, are lower in amnion cells in culture than in amnion tissue obtained from term placentas. The specific activities of diacylglycerol lipase, monoacylglycerol lipase, and diacylglycerol kinase, enzymes that catalyze the release of arachidonic acid from diacylglycerol produced by the action of phospholipase C on phosphatidylinositol, are similar in amnion cells in culture and in amnion tissue. Therefore, we conclude that, based on morphology, lipid composition and enzymatic activities amnion cells in primary culture seem to be an appropriate in vitro model system for the investigation of the regulation of arachidonic acid metabolism in amnion.