Progesterone Regulation of Endometrial Gene Expression in the Early Pregnant Ovine Uterus

Establishment of pregnancy in ruminants requires blastocyst development to form an elongated filamentous conceptus that produces interferon tau (IFNT), the pregnancy recognition signal, and initiate implantation. Blastocyst growth and development is dependent upon secretions from the uterine endometrium. An early increase in post-ovulatory circulating levels of progesterone (P4) stimulates blastocyst growth and conceptus elongation in ruminants. Microarray analysis was used to identify candidate P4-regulated genes and regulatory networks in the endometrium that govern peri-implantation blastocyst/conceptus growth and development. The first study was conducted to validate effects of P4 and/or pregnancy on expression of candidate genes identified by microarray analysis. The genes included: ANGPTL3, CHGA, CLEC4E, CXCL14, EFNA1, EFNB1, FABP3, IFNG, IL6, LGALS3, PTH, RBP4, SLIT2, SLIT3, and VWF. Early P4 treatment up-regulated CXCL14 gene expression in Day 9 ovine endometrium compared to control endometrium, and FABP3, IFNG, IL6 and LGALS3 in Day 12 early P4-treated ovine endometrium. Expression of ANGPTL3, CHGA, CXCL14, EFNA1, EFNB1, LGALS3 and RBP4 was affected by day of pregnancy. Treatment of ewes with P4+RU486 (P4 receptor antagonist) reduced expression of ANGPTL3, CHGA, EFNA1, EFNB1, FABP3, IFNG, IL6, LGALS3, RBP4, and SLIT2, SLIT3 and VWF in comparison to Day 12 P4-treated endometrium. The second study evaluated expression of genes identified by microarray analysis in endometrium from pregnant and cyclic ewes. Genes evaluated included those from the first study. ANGPTL3, CHGA, CXCL14, EFNA1, EFNB1, IFNG, LGALS3, PTH, RBP4, SLIT2, SLIT3 and VWF were affected by day, status and/or their interaction between Days 10 and 16. Of note, FABP3 increased 21-fold between Days 14 to 18 of pregnancy, and IL6 increased 37-fold between Days 14 to 20 of pregnancy. In situ hybridization analysis detected FABP3 mRNA in both luminal and superficial glandular epithelia of pregnant ewes and trophectoderm, whereas IL6 mRNA was detected in immune cells within uterine luminal epithelium and glandular epithelium and trophectoderm. Collectively, these results identify candidate genes encoding for biologically active molecules that regulate growth and development of the ovine conceptus during the peri-implantation period of pregnancy