Changes in fibrillin-1 in the endometrium during the early stages of pregnancy in mice

Blastocyst reception and implantation require various adaptations of the uterine microenvironment. We have previously shown that in mice, remodeling of the extracellular matrix begins early in pregnancy, characterized by synthesis, degradation and alteration of collagen fibrillogenesis, accompanied by pregnancy stage-dependent expression of glycosaminoglycans and proteoglycans. Fibrillin-1 is a matrix glycoprotein that participates in the formation of elastic fibers and promotes cell adhesion through its integrin- binding domain. In the present study, we used light microscope immunohistochemistry to analyze the distribution of fibrillin-1 in the endometrial stroma of mice during estrous and diestrous, as well as in the pre- and postimplantation periods. Fibrillin-1 was found among endometrial fibroblasts and decidual cells, respectively, in the pre- and postimplantation periods. However, fibrillin-1 organization and distribution in the various regions of the endometrial stroma were found to be pregnancy stage dependent. Fibrillin-1 was also abundant in the basement membrane regions of blood vessels, as well as in the luminal and glandular epithelia. Fibrillin-1 at the maternal-fetal interface and in Reichert's membrane of embryos at up to 6 days of development might facilitate embryo expansion and fixation. Changes in the fibrillin-1 expression during the peri-implantation period suggest that fibrillin-1 plays a role in preparing the endometrium for embryo implantation. Copyright (c) 2007 S. Karger AG, Basel.