LOCALIZATION OF PROSTAGLANDIN-H SYNTHASE TYPE-2 PROTEIN AND MESSENGER-RNA IN TERM HUMAN FETAL MEMBRANES AND DECIDUA

Prostaglandin (PG) production by human fetal membranes (amnion and cho rion laeve) may be important in the onset and progression of labour, c ervical ripening and membrane rupture. Prostaglandin H synthase (PGHS) is a key enzyme in PG formation and has two isoforms, a constitutive form (PGHS-1) and an inducible form (PGHS-2). The present study examin ed the cellular distribution of the PGHS-2 enzyme and PGHS-2 mRNA in t erm human fetal membranes and decidua prior to and following labour, u sing immunohistochemistry and in situ hybridization with an S-35-label led oligonucleotide probe. The PGHS-2 protein was found to be localize d in amnion epithelial cells and chorion laeve trophoblast, but was ab sent or at low levels in the decidual stroma in most tissues, although cells surrounding some of the blood vessels in the decidua did expres s PGHS-2. In situ hybridization demonstrated that PGHS-2 mRNA had a si milar distribution and was localized to amnion epithelial cells, cells in the amnion-chorion mesenchyme, chorion laeve trophoblast and, occa sionally, to cells surrounding blood vessels in the decidua. Of partic ular note was the high mRNA expression in some cells and low expressio n in other cells, particularly in the chorion, and the low level of PG HS-2 mRNA in decidua. There was no observable difference in the cellul ar localization of PGHS-2 protein or PGHS-2 mRNA in tissues obtained p rior to and following labour. The studies indicate that, at term, the inducible form of PGHS, PGHS-2, is expressed at a high level in fetal tissues in a number of different cell types rather than in the materna l decidua.