PSIII-8 Expression of Toll-Like Receptors in endometrium of gilts during early gestation

Abstract Interactions between the innate immune system and reproductive tissues via Toll-like receptors (TLRs) have a pivotal role in maintaining the health and fertility status of mammalian species. TLRs are pattern recognition receptors used by the innate immune system to regulate inflammation, infections, and to indicate the presence of pathogenic activity within a tissue. Recent studies have identified several TLRs present in pigs that can detect a variety of molecules. Previous data from our group has demonstrated shifts in bacterial communities within the uterus during early gestation in gilts. Therefore, the objective of this study was to quantify and compare expression of TLR1, TLR2, TLR4, TLR5, and TLR6 in endometria of gilts. These TLRs were chosen because they are located on the cell surface and recognize invading microbes. Crossbred gilts (n = 21) free of physical, health or reproductive-related issues were euthanized and hysterectomized during the preimplantation (d 11) and peri-implantation (d 15) stages of pregnancy (Pregnant d 11, n = 10; Pregnant d 15, n = 11). Samples of endometrial mucosa were collected and snap-frozen in sterile 1.5 mL tubes and stored at -80°C until analyzed. The mean relative expression of TLR-1, TLR-2, TLR-4, TLR-5, and TLR-6 mRNAs were quantified by RT-qPCR. Statistical analysis was completed using one-way ANOVA and student’s t-test for pairwise comparison in JMP 17.0 (SAS Institute; Cary, NC). All TLRs were expressed in the endometrium. Expression of TLR-4 was greater on d 11 than d 15 (1.39 ± 0.14 vs. 0.45 ± 0.13, respectively; P < 0.01), and there was a trend for expression of TLR-2 to be greater on d 11 than d 15 (1.89 ± 0.37 vs. 0.90 ± 0.35, respectively; 0.05 < P < 0.1). Expression of TLR2, TLR5, and TLR6 did not differ between d 11 and d 15 (P > 0.05). The results indicate that TLRs are not only expressed in the porcine endometrium, but they differ in expression during early gestation. Conceptus signaling and inflammation during elongation and implantation and/ or shifts in bacterial communities within the uterus may be responsible. Additionally, future work examining bacterial shifts and TLR expression during mid and late gestation may offer further insight.