IMMUNOLOCALIZATION OF COLLAGEN TYPE-I AND LAMININ IN THE UTERUS ON DAYS 5 TO 8 OF EMBRYO IMPLANTATION IN THE RAT

This study investigated the immunohistochemical distribution of collag en type I and laminin during remodeling of the uterine extracellular m atrix in response to embryo implantation in the rat. Collagen type I w as found to be virtually absent around the embryo on the evening of da y 5 of pregnancy. On days 6 to 8 of pregnancy the areas of primary and secondary decidualized tissue contained very little collagen in contr ast to the outer nondecidualized stroma and myometrial tissues in whic h the staining patterns did not appear to alter. Day 8 of pregnancy wa s also notable for the appearance of collagen type I at the site of th e developing placenta. Localization of laminin corresponded to areas o f basement membrane and was associated with the redistribution of bloo d vasculature during implantation. By day 7 laminin staining was dimin ished in the basal areas of the lumenal epithelium around the implanti ng embryo. Laminin was also located in a punctate fashion at the margi ns of the primary decidual cells on day 6 of pregnancy, but by days 7 and 8 this staining pattern was no longer evident. This study has prov ided further evidence for a decline in a major fibrillar collagen duri ng natural decidualization and also revealed a localized and transient expression of laminin in association with the differentiation of cell s during primary decidual formation. (C) 1993 Wiley-Liss, Inc.