NAD(P)H oxidase in human fetal membrane chorion laeve trophoblasts with or without chorioamnionitis: ultrastructural enzyme histochemical study

We examined the subcellular localizations of NAD(P)H oxidase, a reactive oxygen species (ROS)-producing enzyme, in fetal membrane chorion laeve trophoblasts from preterm or term pregnant women with or without chorioamnionitis (CAM). Ultrastructural enzyme histochemistry for NAD(P)H oxidase was used. In fetal membranes without CAM, approximately one quarter of the chorion laeve trophoblasts (25.6%) showed NAD(P)H oxidase activity on their surface plasma membranes and microvillous membranes. In mild CAM, the proportion of these NAD(P)H oxidase-positive cells significantly increased, reaching about half (51.0%). Enzyme activity appeared on the plasma and microvillous membranes and also on both phagosomal membranes and intracellular vesico-tubular structures. Appearance of NAD(P)H oxidase on surface plasma membranes, phagosomal membranes, and vesico-tubular structures is strong cytochemical evidence of phagocytic cell activation. These observations indicate that chorion laeve trophoblasts possess NAD(P)H oxidase activity, and therefore that fetal membranes themselves have ROS-generating capacity. Further, in fetal membrane inflammation, chorion laeve trophoblasts exhibited enzyme distribution characteristic of activated professional phagocytes. Similar to phagocytes infiltrating to the intrauterine environment, chorion laeve trophoblast NAD(P)H oxidase may play a role both in the defence of chorioamnion against infection and in the pathogenesis or pathophysiology of CAM-related preterm delivery.