Proteomic analysis of the endometrium during early pregnancy in the domestic pig.

Reproductive processes in domestic pigs have been studied extensively. Pigs are one of the main sources of meat for human consumption and are an established model for investigations into mammalian, including human, reproductive physiology. Studies of the uterus during early pregnancy will lead to a better understanding of mechanisms governing pregnancy. Proteomics provides the possibility to explore endometrial functions in an unbiased way. The aim of the study was to compare endometrium harvested from Days 12-13 and 15-16 of pregnancy with the corresponding days of the oestrous cycle. We identified endometrial proteins that are unique to the early stages of pregnancy (Days 12-13 and 15-16). Twenty-one proteins were identified that were uniquely expressed on the selected days of pregnancy or the oestrous cycle. Out of 21 identified proteins, 14 referred to the pregnancy periods. Systemic analysis of the identified proteins revealed cell adhesion and cytoskeletal organisation as two of the major functions, both of which are important for the establishment and maintenance of pregnancy. Thrombospondin 1 expression was validated using western blotting analysis and the results suggest its involvement in the adhesiveness of the embryo during the peri-implantation period in pigs.