Detection of fibronectin during porcine placentation
The porcine placenta is epitheliochorial, diffuse, folded, decidual, and non-invasive. Fibronectin (FN) is a dimeric glycoprotein present in the extracellular matrix of most animal tissues; it plays a major role in cell adhesion, migration, implantation and embryogenesis. The aim of this study was to investigate the expression of FN in the maternal-fetal interface during porcine placentation. Placental tissue samples from sows (n = 12) at 17, 32, 60, and 107 d of gestation (dg) and non-pregnant uterus samples (n = 4) were collected. The detection of FN was performed by indirect immunoperoxidase and the FN area immunolabeled was determined with the software Image Pro-Plus® 3.0. The most intensive staining for FN was found in the conceptus´ trophectoderm, particularly in the apical membrane on 17, 32, and 60 dg; staining was weaker in the surface of the uterine epithelium on the same days. FN did not express itself in the glandular epithelium until 107 dg. No significant difference was found in the trophoblast as to the percentage of the immuno-staining area until day 60 of gestation when it decreased. In the endometrial luminal epithelium, significant differences were found in the area positive to FN during placentation. These results suggest that FN might be involved in the molecular mechanisms that take part in the adhesion and attachment of the epithelia that makes up the maternal-fetal interface during porcine placentation.