Changes in extracellular matrix components and cytokeratins in the endometrium during goat implantation.

Tissue remodelling within the endometrium is necessary for successful implantation and placentation. These processes require changes in the extracellular matrix (ECM) components and modifications of the uterine luminal epithelium. These changes have been studied in species with invasive forms of implantation but there have been few reports characterizing the biochemical modifications of the ECM and cytoskeletal proteins in the ruminant endometrium during implantation. The distribution of type I and IV collagens, laminin, the beta1 integrin subunit and cytokeratins 8, 18 and 19 in the caprine endometrium during the oestrous cycle and early pregnancy (days 15-21) were investigated by immunofluorescence microscopy. No major differences were observed between endometrial tissue from cyclic or pregnant goats before implantation, which starts by day 18. Intense type I collagen staining was detected throughout the uterine caruncular and intercaruncular stroma. Type IV collagen and laminin were constitutive in the basal lamina of the luminal and glandular epithelia and vascular endothelium. Uterine epithelial cells expressed the beta1 integrin subunit and cytokeratins 8, 18 and 19. As implantation proceeded, immunolabelling of the ECM proteins became undetectable in the endometrium adherent to the trophoblast. Conversely, the uterine epithelial cells lost beta1 integrins and cytokeratins 8, 18 and 19. In the uterine compartments not in contact with the trophoblast, immunostaining remained unaltered. These data suggest a local control of protease activity within the endometrium and demonstrate major changes in the epithelial phenotype of the uterine cells during trophoblast adhesion in ruminants.