Transcriptional profile of endometrial TLR4 and 5 genes during the estrous cycle and uterine infection in the buffalo (Bubalus bubalis).

Endometritis is one of the leading causes of infertility in the cattle and buffalo and innate immune mechanism plays an important role in clearing the infection. In this regard, endometrial expression and function of Toll Like Receptors (TLR) are focus of investigation in the recent years. In this study, we report the transcriptional profiles of TLR4 and 5 in the buffalo endometrium during the follicular, early, mid and late luteal phases of estrous cycle and 'subclinical and clinical endometritis' and also at true anestrus (n = 10 for each stage) using RT-PCR and qRT-PCR as they are the ligands for the lipopolysaccharide and flagellin components of E.coli, the most common cause of postpartum endometritis. We found a significant positive correlation between TLR4 and 5 in all the groups (r = 0.696-0.803; P < 0.05) except late luteal phase (r = 0.522; P > 0.05). Chi-square analysis showed that the qualitative expression of endometrial TLR4 and 5 transcripts was significantly associated with the phase of estrous cycle and also with uterine infection (P < 0.05). Further, using true anestrus category as a calibrator group, relative quantitation of TLR4 and 5 revealed that the transcriptional expression of TLR4 and 5 genes were highly upregulated (24.6-83.3 folds) during endometritis conditions and moderately upregulated during mid-luteal phase (6.8-16.2) of the estrous cycle (P < 0.05). The results suggested a role of progesterone in the expression of TLR4 and 5.