Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 30, 2007
Publication Date: July 20, 2007
Citation: Miles, J., Vallet, J. 2007. Differential gene regulation of estrogen receptor 1 and 2 in the porcine endometrium during the pre-implantation period of pregnancy [abstract]. Biology of Reproduction. Special Issue:127. Technical Abstract: During elongation of the pig embryo (gestational day 12), the conceptus synthesizes and secretes estrogen, which serves as the key molecule for maternal recognition of pregnancy and also modulates the production of proteins and growth factors within the uterus. In mammals, the physiological responses of estrogen are mediated through estrogen binding to two known estrogen receptors (ESR), ESR1 and 2 (formerly known as ER alpha and beta, respectively). The objective of the current study was to characterize ESR1 and 2 mRNA expression in porcine endometrial tissue during the estrous cycle and pre-implantation period of pregnancy. Total RNA was isolated from endometrial tissue at Day 10, 13, and 15 of the estrous cycle (n = 3 per day of cycle) and at Day 10, 12, 14, and 16 of gestation (n = 4 per day of gestation). Gene expression for ESR1 and 2 was measured via real-time rtPCR and data were analyzed by analysis of variance using GLM procedures. Heterogeneity of regression analysis was performed to evaluate the effects of status (i.e., estrous cycle vs. pregnancy) and day-by-status interactions on the expression of ESR1 and 2 mRNA. In pregnant endometrial tissues, ESR1 mRNA expression was greater (P = 0.001) at Day 10 of gestation (2.26 ± 0.12 relative quantity [RQ]; LS means ± SEM) compared with Day 12, 14, and 16 of gestation (1.73 ± 0.12 RQ, 1.54 ± 0.12 RQ, and 1.34 ± 0.12 RQ, respectively). Similarly, expression of ESR1 mRNA in cyclic endometrium tended (P = 0.07) to be greater at Day 10 of the cycle (2.26 ± 0.23 RQ) compared with Day 15 of the cycle (1.28 ± 0.23 RQ) with endometrial tissues at Day 13 of the cycle (1.80 ± 0.23 RQ) demonstrating an intermediate level of ESR1 mRNA expression. Heterogeneity of regression indicated that expression of ESR1 mRNA was not different (P = 0.44) between the estrous cycle and pregnancy and no day-by-status interaction was detected for ESR1 mRNA. In pregnant endometrial tissues, ESR2 mRNA expression was greater (P < 0.0001) at Day 14 and 16 of gestation (8.52 ± 0.58 RQ and 8.43 ± 0.58 RQ, respectively) compared with Day 10 and 12 of gestation (3.08 ± 0.58 RQ and 3.53 ± 0.58 RQ, respectively). Expression of ESR2 mRNA was not different (P = 0.29) in the endometrium at Day 10, 13, or 15 of the estrous cycle (2.96 ± 0.95 RQ, 4.26 ± 0.95 RQ, and 5.30 ± 0.95 RQ, respectively). Heterogeneity of regression indicated a day-by-status interaction (P = 0.07) suggesting that ESR2 mRNA was greater during pregnancy compared with the estrous cycle. These findings demonstrate differential gene expression for ESR1 and 2 mRNA during the pre-implantation period of pregnancy and suggest that ESR2 may play a role in mediating the response of the endometrium to estrogen during pregnancy.