IMMUNOHISTOCHEMICAL IDENTIFICATION OF THE RECEPTOR FOR UROKINASE PLASMINOGEN-ACTIVATOR ASSOCIATED WITH FIBRIN DEPOSITION IN NORMAL AND ECTOPIC HUMAN PLACENTA

The receptor for urokinase plasminogen activator (uPAR) is a key molec ule in cell surface-directed plasminogen activation. uPAR binds urokin ase plasminogen activator (uPA) and thereby focuses plasminogen activa tion on the cell surface. Plasmin dissolves fibrin deposits and facili tates cell migration during tissue repair processes by degrading the e xtracellular matrix. During human implantation and placental developme nt, plasmin is considered important for both trophoblast migration/inv asion and for fibrin surveillance. This study examined the expression of uPAR in normal and ectopic human placentae by immunohistochemistry. In first and third trimester normal placentae as well as in tubal ect opic placental tissues, a high uPAR expression was seen in the trophob last associated with deposits of fibrin-type fibrinoid. Extravillous t rophoblast of the basal plate, of the cell islands, and of the cell co lumns was also positive for uPAR in the first trimester whereas at ter m the expression of the protein was decreased. Moreover, uPAR immunost aining was observed in decidual cells throughout normal gestation and in endometrial tissues of patients with ectopic pregnancies. These fin dings suggest that uPAR participates in placental development and in t rophoblast invasion particularly in the first trimester of pregnancy a nd that uPAR is involved in repair mechanisms of the trophoblast and f ibrin surveillance. (C) 1998 W. B. Saunders Company Ltd.