Expression of alpha5beta1 integrin and fibronectin during early pregnancy in pigs

The implantation in pig is superficial and non-invasive, involving phases of apposition, adhesion and attachment of conceptuses to endometrial surface epithelium. The role of integrins and ECM proteins is suggested. In the study, the expression of beta5beta1 integrin and FN on conceptus trophectoderm and endometrium during implantation and early pregnancy was investigated. The immunohistochemical localization of alpha5beta1 integrin and FN was performed on formalin-fixed, paraffin-embedded tissue sections using the ABC method. The results indicate that both conceptus and uterus expressed alpha5beta1 integrin and FN during early porcine pregnancy. The most intensive staining for alpha5beta1 integrin and FN was found in conceptus trophectoderm and endometrial surface epithelium in all investigated periods. During placentation the immunohistochemical staining for both alpha5beta1 integrin and FN was increased in trophectoderm and all endometrial structures. Since placenta in pigs is non-invasive, it can be suggested that both alpha5beta1 integrin and FN participate in molecular events leading to successful implantation and placentation in species with true epitheliochorial placenta.