抄録
[Introduction] We previously reported that the bovine endometrium expresses Toll-like receptor 2 (TLR2) which reacts to sperm signals in uterine glands to induce immune reactions using a sperm-endometrial ex vivo culture model. Now we investigated the expression of TLR2 in bull sperm and their role in activating the innate immune responses in the endometrium. [Materials and methods] Immunofluorescence staining was done to observe the localization of TLR2 in bull sperm. Frozen-thawed bull sperm were swim-up and treated with TLR1/2 antagonist (TLR2 ant. (+)) or without antagonist (TLR2 ant. (-)). CASA and flow cytometry evaluations were conducted to investigate the effects of TLR1/2 antagonist on sperm characteristics. The endometrial explants were incubated with JC1 labeled sperm, and sperm-uterine interaction was observed using fluorescence microscopy. [Results] TLR2 is localized in the posterior segment of the sperm head in both TLR2 ant. (-)/(+) sperm. Sperm motility parameters, plasma membrane integrity, acrosomal integrity, and high mitochondrial membrane potential were not affected by the antagonist treatment. TLR2 ant. (+) sperm entered and remained within the uterine glands by a lower number than TLR2 ant. (-) sperm. TLR2 ant. (+) sperm did not increase the mRNA expressions of TNFA, IL1B, and PGES in explants, whereas TLR2 ant. (-) sperm induced these genes. Both TLR2 ant. (-)/(+) sperm upregulated the mRNA expressions of IL8 and TLR2. Results suggest that TLR2 ant. (+) sperm induce a weaker immune response in the endometrium. Collectively, TLR2 is localized in bull sperm and regulates sperm sensing with TLR2 in uterine glands to trigger the immune responses in the endometrium.
