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

Involvement of TLR7 and TLR8 in conceptus development and establishment of pregnancy in sheep

Toll-like receptors (TLRs) belong to the innate immune system and regulate inflammatory events that affect mammalian reproduction. In Study 1, we demonstrated that abundance of ovine TLR1–TLR9 mRNAs in the uterus differs due to reproductive status (TLR2, TLR3, TLR7, and TLR8) and the day of the estrous cycle and pregnancy (TLR1–TLR3, TLR5–TLR7, and TLR9). Expression of TLR7 and TLR8 proteins was localized primarily to uterine epithelia and stroma and regulated in a temporal manner. In Study 2, we determined that ovine conceptuses express TLR7 and TLR8 on all days studied and that expression of the envelope protein of ovine endogenous retrovirus (enJSRV-Env) declined in conceptus trophectoderm from Day 13 to Day 16 of pregnancy. In Study 3, loss-of-function experiments were conducted in vivo using morpholino antisense oligonucleotides (MAOs) injected into the uterine lumen to block synthesis of TLR7 and TLR8 proteins, individually and jointly. Conceptuses were recovered on Day 16 to assess their morphology. MAO-treated conceptuses were developmentally retarded, produced less interferon tau (IFNT), and had fewer binucleate cells (BNCs) compared with MAO-Controls. Moreover, expression of enJSRV-Env mRNA in MAO-TLR7 conceptuses was greater than that for MAO-Control and MAO-TLR8 conceptuses, but similar to MAO-TLR7/TLR8 conceptuses. Results of this study indicated differences in TLR1–TLR9 expression due to reproductive status and the day of the estrous cycle and pregnancy. TLR7 and TLR8 also influence development, enJSRV-Env abundance, secretion of IFNT, and formation of BNCs by conceptuses. These findings corroborate our hypothesis that TLR7 and TLR8 mediate pathways whereby enJSRV-Env regulates key peri-implantation events in conceptus development and differentiated functions of trophectoderm cells.</jats:p

Placental development during early pregnancy in sheep: vascular growth and expression of angiogenic factors in maternal placenta

Placental vascular development (angiogenesis) is critical for placental function and thus for normal embryonic/fetal growth and development. Specific environmental factors or use of assisted reproductive techniques may result in poor placental angiogenesis, which may contribute to embryonic losses and/or fetal growth retardation. Uterine tissues were collected on days 14, 16, 18, 20, 22, 24, 26, 28, and 30 after mating and on day 10 after estrus (nonpregnant controls) to determine vascular development and expression of several factors involved in the regulation of angiogenesis in the endometrium. Compared with controls, several measurements of endometrial vascularity increased (P&lt;0.001) including vascular labeling index (LI; proportion of proliferating cells), the tissue area occupied by capillaries, area per capillary (capillary size), total capillary circumference per unit of tissue area, and expression of factor VIII (marker of endothelial cells), but capillary number decreased (P&lt;0.001). Compared with controls, mRNA for placental growth factor, vascular endothelial growth factor receptors, angiopoietins (ANGPT) 1 and 2, ANGPT receptorTEK, endothelial nitric oxide synthase, and hypoxia-inducible factor 1α increased (P&lt;0.05) during early pregnancy. Vascular LI was positively correlated (P&lt;0.05) with several measurements of vascularity and with mRNA expression of angiogenic factors. These data indicate that endometrial angiogenesis, manifested by increased vascularity and increased expression of several factors involved in the regulation of angiogenesis, is initiated very early in pregnancy. This more complete description of early placental angiogenesis may provide the foundation for determining whether placental vascular development is altered in compromised pregnancies.</jats:p

Placental development during early pregnancy in sheep: cell proliferation, global methylation, and angiogenesis in the fetal placenta

To characterize early fetal placental development, gravid uterine tissues were collected from pregnant ewes every other day from day 16 to 30 after mating. Determination of 1) cell proliferation was based on Ki67 protein immunodetection; 2) global methylation was based on 5-methyl-cytosine (5mC) expression and mRNA expression for DNA methyltransferases (DNMTs)1,3a, and3b; and 3) vascular development was based on smooth muscle cell actin immunolocalization and on mRNA expression of several factors involved in the regulation of angiogenesis in fetal membranes (FMs). Throughout early pregnancy, the labeling index (proportion of proliferating cells) was very high (21%) and did not change. Expression of 5mC and mRNA forDNMT3bdecreased, but mRNA forDNMT1and3aincreased. Blood vessels were detected in FM on days 18–30 of pregnancy, and their number per tissue area did not change. The patterns of mRNA expression for placental growth factor, vascular endothelial growth factor, and their receptorsFLT1andKDR; angiopoietins 1 and 2 and their receptorTEK; endothelial nitric oxide synthase and the NO receptorGUCY13B; and hypoxia inducing factor 1 α changed in FM during early pregnancy. These data demonstrate high cellular proliferation rates, and changes in global methylation and mRNA expression of factors involved in the regulation of DNA methylation and angiogenesis in FM during early pregnancy. This description of cellular and molecular changes in FM during early pregnancy will provide the foundation for determining the basis of altered placental development in pregnancies compromised by environmental, genetic, or other factors.</jats:p