Expression Profile Of Immune Tolerance Related Genes In Porcine Endometrium During The Early And Mid-gestations

The litter size of pig is a low hereditary trait, and combining marker assisted selection (MAS) with the traditional breeding method is an effective way to improve this trait. Many studies have demonstrated that high embryonic death during the early and mid-gestation is the main cause of small litter size.During the process of embryos implantation and growth, many immune cells are recruited on the endometrium surface, and they express a lot of immune factors, which suggest that materno-fetal immune tolerance play an import role on maintaining embryos implantation and normal growth.The Chinese Meishan pig is a prolific breed with averarge 3-4 more piglets/litter than the western breed Yorkshire, but they have the same number of embryos with Yorkshire pigs before implantation, which means embryonic death during gestation is the main cause for their difference in litter size. In this study, we investigated the expression of immune genes in the purebred Meishan and Yorkshire sows’endometrium samples on gestational day 15 (gd15),26 (gd26) and 50 (gd50) (n=2 pigs/day/status). The main results are listed as follows:(1) We identified the differentially expressed immune genes between breeds at the same stages (M15 vs Y15, M26 vs Y26, M50 vs Y50) as well as between different gestation stages within Meishan and Yorkshire breeds (gd26 vs gd15, gd50 vs gd26), and the gene number was 96,67 and 139, respectively.(2) Both in Meishan and Yorkshire pigs, the difference of immune genes’expression is mainly at gd26 vs gd15. The immune genes showing higher expression at gd15 are mainly cytokines, growth factors, adhesion related molecules main effect is to increase the embryos implanted ability and endometrial attached accept ability, promoting groupings of complete attached. However, the genes with lower expression at gdl5 are mainly inflammation factors and cell invasion factors, which play an important role in reducing immune rejection and inhibiting blastocyte excessive invasion.(3) Between the two breeds, there were 56 and 40 immune genes showing differential expression at gd26 and gd50, respectively. The genes showing higher exprssion in Yorkshire pigs at these two stages are mainly involved in apoptosis and inflammation response. Only 19 immune genes were differentially expressed between Meishan and Yorkshire pigs at gd15, which suggested that there was little difference between Meishan and Yorkshire pigs at the beginning of embryo implantation. but the raising difference of endometriumal environment after implantation resulted in the litter size disparity. (4)In order to ensure the accuracy of microarray data, we used GeNorm program to choose appropriate control genes for Q-PCR from 6 candidate genes. The stability of gene is:TBP1, p-actin> GAPDH>RPL32>SUZ12> ZNF131.