Differential mRNA expression of luteal TLR2, TLR4, TLR7, and interleukin-8 across canine reproductive states

Toll-like receptors (TLRs) are essential components of both innate and adaptive immunity, influencing various physiological and pathological processes. It is also known that immune system components are present in the corpus luteum (CL) and regulate its functions. This study aimed to, for the first time, examine the mRNA expression levels of TLR2, TLR4, TLR7, and interleukin-8 (IL-8) in canine luteal tissue samples collected during early diestrus (EDI) (n=5), early pregnancy (EPR) (n=5), and pyometra (PYO) (n=5), a pathological condition in which the CL remains active. The luteal tissue samples were obtained via ovariohysterectomy and analyzed using real-time quantitative polymerase chain reaction (RT-qPCR). It was found that the mRNA expression levels of TLR2, TLR7, and IL-8 were highest in the PYO group (p<0.05). However, no significant difference was observed in TLR4 mRNA expression between groups (p>0.05). This study reveals distinct expression profiles of TLRs and IL-8 in canine luteal tissue under different physiological and pathological states. In conclusion, pyometra may induce changes in the mRNA expression patterns of TLRs and IL-8 in canine luteal tissues. Further research involving protein-level analyses with larger sample sizes is necessary to better understand the roles of these molecules in the regulation of luteal function.