Evidence for an involvement of regulatory T-lymphocytes (Treg cells) in tolerance of pregnancy in mares

Abstract

treatment-associated endometrial changes were seen at Day 19 than at Day 20. Cloprostenol treatment in pregnant mares markedly increased (10-100x) expression of many endometrial genes at Day 20. Of these, several genes involved in signaling (IL6, GABRP, IGFBP-1, IL1RN, CHGA, PENK), lipid metabolism (SPLA2, SCGB1A1, SAA1, EquC1), extracellular matrix modification (MMP3, HYAL4) and lipid transport (SAA1) were most increased in treated pregnant mares compared with control pregnant mares. The changes in expression of secretory phospholipase A2 (SPLA2), uteroglobin (SCGB1A1), and a lipocalin (EquC1) were also higher in non-pregnant mares than in control pregnant mares so these changes could partly reflect transition to the non-pregnant state after luteolysis. Endometrial expression of ST6GALNAC1, PLA2G6, PLA2G4, NCAM1 and GZMB were most reduced in pregnant mares in response to cloprostenol. By comparison, gene expression in Day 19 or 20 trophoblasts from control or treated mares were similar with only 14 significant differences in the 2-5 fold range observed. These included increases in serpins B2 and B10 after cloprostenol. Major alterations in proteins in uterine flush fluids and yolk-sac fluids were assessed in a separate series in which cloprostenol was administered 3 or 4 days before collection on Days 15-21. Identified proteins were ranked in relative amounts from trypsin digested peptides identified by LC/MS/MS and Scaffold 2 software performed at the Advanced Protein Technology Centre, Toronto. Proteins corresponding to SERPINA14, ANXA1, MUC6, SPLA2, and B2Mweremost increased in uterine flush fluids after cloprostenol treatment, with SERPINA14 and SPLA2 also being increased in yolk-sac fluid. By comparison, VNN2, VNN2, GZMB, CD109 and A2Mwere consistently reduced in uterine flush fluid from treated mares. These studies reveal several alterations in the endometrium and conceptus that might beharmful effectors, or biomarkers of adverse uterine conditions, useful for clarifying the mechanisms of pregnancy establishment and pregnancy failure in mares.