Reproduction Abstracts

Introduction: Toll-like receptors (TLRs) are critical mediators of the host defence against pathogens, but may also directly influence reproduction. TLR signalling pathways have been identified in bovine granulosa cells. However, despite key diseases, such as mastitis, being associated with reduced luteal function, TLRs have not been extensively examined in the corpus luteum (CL). TLRs have also been implicated in tissue repair and remodelling processes critical to the rapid tissue changes associated with luteinisation and luteolysis. We hypothesise that the TLRs are expressed in the bovine CL and directly influence luteal function.

Methods: Bovine CL (very early haemorrhagic, early, mid, late/regressing n=3–4/stage) were collected at abattoir and morphologically staged. Total RNA was extracted, reverse transcribed and subjected to RT-PCR for TLR1-10. Subsequently, quantitative Taqman PCR was performed for the key receptors TLR2 and TLR4, using housekeeper genes (GAPDH and RPLPO) to normalise transcription levels. All reactions were prepared in triplicate. The housekeepers were tested for stability and a reference CT determined, which was used to calculate delta CT and fold-change values.

Results and discussion: This study demonstrated for the first time that the bovine ovary expresses mRNA encoding TLR1 to 10. Quantitative RT-PCR confirmed that TLR2 and TLR4 were expressed throughout the luteal phase, however no significant difference in the expression of TLR2 or TLR4 mRNA was detected between the different luteal stages (one-way ANOVA P>0.05). In addition, TLR4 mRNA was expressed more highly than TLR2 (P<0.05). The expression of TLR1-10 mRNA by the bovine CL demonstrated the potential for regulation of luteal function by members of the TLR family. Future studies will investigate how TLR signalling might impact luteal function and how this might be altered in animals with concurrent disease. (Supported by the SRF Vacation Scholarship.)