PS2-9. Expression of Genes Associated with the Retinol Biosynthesis Pathway in Endometria of Cyclic and Pregnant Gilts.

Abstract During gestation, the endometrium undergoes extensive molecular and cellular changes that support conceptus elongation, implantation, and placentation. Vitamin A (retinol) is an essential fat-soluble vitamin with important roles in tissue development and reproduction. Therefore, the objective of this study was to characterize the expression of genes associated with the retinol biosynthesis pathway in endometrial tissue from cyclic and pregnant gilts. Crossbred gilts (n = 38) were housed in groups on solid concrete floors with ad libitum water access and fed 2.0 kg per day of a standard gestation diet formulated to meet micronutrient requirements. Gilts were humanely euthanized on either Day (D)11 (n = 10; elongation), 15 (n = 11; implantation), 60 (n = 6; mid-gestation) or 90 (n = 6; late-gestation) of pregnancy, or D15 of the estrous cycle (n = 5; diestrus). Immediately following euthanasia, the gilts were ovariohysterectomized and endometrial mucosa was collected and snap frozen in sterile 1.5 mL tubes and stored at −80 °C until analyzed. Mean relative expression of alcohol dehydrogenase 1C (ADH1C), aldehyde dehydrogenase 1 family member 1A (ALDH1A1), lecithin retinol acyltransferase (LRAT), retinol binding protein 2 (RBP2), and retinol binding protein 4 (RBP4) was quantified by RT-qPCR. Gene expression changes were normalized to ribosomal protein L7 (RPL7). Normality of the distribution of data was assessed using the Anderson-Darling test (P > 0.05). Outliers were identified and excluded. Transformations were carried out to achieve a normal distribution and expression of ADH1C, ALDH1A1, and RBP4 mRNAs were analyzed using PROC GLM. Expression of LRAT and RBP2 mRNAs remained non-normally distributed and analyzed using the nonparametric Kruskal-Wallis test in PROC NPAR1WAY. Expression of ADH1C tended to be less in cyclic gilts compared to pregnant gilts on D11 and D90 (−1.24 ± 0.50 vs. 0.15 ± 0.34 and 0.72 ± 0.50, respectively; P = 0.08). Expression of ALDH1A1 mRNA was greater on D60 compared to cyclic, D11, and D15 gilts (0.70 ± 0.14 vs. −0.23 ± 0.16, −0.06 ± 0.11, and −0.63 ± 0.11, respectively; P < 0.001). RBP4 mRNA expression was greater on D11 compared to cyclic, D15 and D90 (0.21 ± 0.10 vs. −0.35 ± 0.13, −0.18 ± 0.09, and −0.64 ± 0.12, respectively; P < 0.001). Expression of LRAT mRNA differed by day (P < 0.001), with greatest expression on D60 than D11 and D15 (1.35 ± 0.13 vs. −0.53 ± 0.15 and −0.44 ± 0.12, respectively; P = 0.03 and P = 0.04) and D90 compared to D15 (0.46 ± 0.21 vs. −0.44 ± 0.12; P = 0.04). There were no differences in expression of RBP2 mRNA among days (P > 0.05). These findings indicate that retinol biosynthesis in the porcine endometrium changes dynamically throughout gestation in support of conceptus development and uterine remodeling.