(138) Expression of Toll-Like Receptors in the Endometrium of Pregnant and Cyclic Gilts

Kyle J. Hickman¹, Dallas R. Soffa, ¹Molly S. Smith¹, Brooke E. McAnally¹ Joe W. Cain², Heewon Seo², Fuller W. Bazer¹, Greg A. Johnson², Jeffrey G. Wiegert¹, Rebecca K. Poole¹   

¹Department of Animal Science, Texas A&M University, College Station, USA

²Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, USA

Abstract Text:

Mammalian reproductive tissues utilize the innate immune system to maintain tissue health necessary for fertility and Toll-like receptors (TLRs) play a pivotal role in these interactions. Toll-like receptors are pattern recognition receptors (PRRs) used by the innate immune system to regulate inflammation and infection, and signal 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 results from our group demonstrated shifts in bacterial communities within the uterus during gestation in gilts. Therefore, the objective of this study was to quantify and compare the expression of TLR1, TLR2, TLR4, TLR5, and TLR6 in endometria from gilts. Duroc x Landrace x Yorkshire gilts (n=38) free of physical, health or reproductive-related issues were euthanized and hysterectomized on either Day 11 (n = 11; peri-implantation), 15 (n = 10; implantation), 60 (n =6; mid-gestation) or 90 (n = 6; late-gestation) of pregnancy, as well as Day 15 (n = 5; cyclic) of the estrous cycle. Endometrial tissue was collected and snap-frozen in sterile 1.5 mL tubes and stored at -80°C until further analysis. The relative expression of mRNAs for TLR1, TLR2, TLR4, TLR5, and TLR6 were quantified by RT-qPCR. Immunolocalization of TLRs were detected by immunofluorescence staining. Statistical analysis was completed using one-way ANOVA and Tukey-Kramer test for pairwise comparison in JMP 17.0. All TLRs were expressed in the uterine endometrium. TLR1 showed greater expression on Day 90 than Day 15 (2.55 ± 0.14 vs. 0.89 ± 0.33, respectively; P < 0.05). Expression of TLR4 was greater in endometria from cyclic gilts compared to Days 11 and 15 of pregnancy (P < 0.01). TLR6 expression was greater on Day 90 than all other days of gestation (P < 0.01). Expression of TLR2 and TLR5 did not differ by pregnancy status (P > 0.05). Immunoreactive TLR1 and TLR4 were detected in trophectoderm and apical portion of uterine epithelium on Day 15 of gestation, while no immunoreactivity was detected in cyclic gilts. The results indicate that TLR’s are not only expressed in the porcine endometrium, but their levels of expression change throughout gestation. We hypothesize that some of these changes in expression are associated with signals sent from the trophectoderm of the conceptus (embryo and associated membranes) during conceptus elongation and implantation and/or shifts in bacterial communities within the endometrium during fetal growth.