CELLULAR-LOCALIZATION OF GP46 AT THE HUMAN FETAL-MATERNAL INTERFACE

gp46 is a collagen-binding heat-shock glycoprotein with a possible rol e in the biosynthesis of collagen as well as in cell differentiation a nd fusion. In this study, the relative levels of gp46 protein and its mRNA transcript were examined, as well as the mRNA levels of collagen types I and IV in first trimester and term human placental tissues. We stern blot analysis revealed substantially higher levels of gp46 in fi rst trimester placentae than in term placentae. Similarly elevated lev els of type TV collagen transcript were detected in first trimester re lative to term tissues. Interestingly, the levels of gp46 and type I c ollagen mRNA remained unchanged. Immunohistochemical analysis of first trimester tissues demonstrated intense gp46 staining in mononucleated villous and estravillous cytotrophoblasts, decidual cells and in the villous connective tissue stroma. Syncytiotrophoblast in the same tiss ues also exhibited gp46 staining but at a reduced intensity. In chorio nic villi of term placentae, faint gp46 staining was only observed in the syncytiotrophoblast layer. However, as in the first trimester plac entae, intense labelling was evident in the estravillous cytotrophobla sts and decidual cells of these tissues. These results suggest a devel opmental regulation of gp46 expression at the fetal-maternal interface during pregnancy and suggest a possible functional link between gp46 and collagen type IV during gestation. (C) 1997 W. B. Saunders Company Ltd.