11-BETA-HYDROXYSTEROID DEHYDROGENASE EXPRESSION IN FIRST-TRIMESTER HUMAN TROPHOBLASTS

This study evaluated the levels and the enzymatic characteristics of 1 1 beta-hydroxysteroid dehydrogenase activity (11 beta-HSD) of chorioni c villi isolated from first trimester human placenta. The results demo nstrated a predominant expression of the NAD-dependent dehydrogenase i soform (11 beta HSD2) over the NADP-dependent oxoreductase (11 beta-HS D1). Thus, in tissue homogenates exogenous NAD increased the conversio n of corticosterone to 11-dehydrocorticosterone of about 14-fold while NADP was ineffective. There was no conversion of 11-dehydrocorticoste rone to corticosterone either with NADH or NADPH demonstrating the lac k of reductase activity. In keeping with these results, RT-PCR analysi s indicated a mRNA for 11 beta-HSD2 in villous tissue while 11 beta-HS D1 mRNA levels were undetectable. In addition, immunohistochemical sta ining localized the 11 beta-HSD2 protein to syncytiotrophoblasts and c ell columns of the chorionic villi. These results suggest roles for th e trophoblast-associated 11 beta-HSD2 oxidative activity in modulating the exposure of the embryo to active glucocorticoids in the early ges tation and in regulating trophoblasts invasion of the uterine wall. (C ) 1998 Elsevier Science Ireland Ltd. All rights reserved.