Proteomic profile of the ipsilateral and contralateral uterine horns around the time of blastocyst transfer

Abstract

Commercial cattle breeding programs worldwide continue to experience challenges related to low efficacy and productivity despite advances in assisted reproductive techniques (ART) becoming mainstream, such as embryo transfer. One such challenge is the variability in available embryo culturing media and how these can be optimised to better replicate the natural in vivo uterine environment. Another is the technical and financial difficulty in recognising which uterine horn is associated with a corpus luteum (ipsilateral uterine horn) for embryo transfer, which is essential for ART given the significantly improved pregnancy rates when embryos are transferred to the ipsilateral as opposed to the contralateral uterine horn. The present project used a label-free quantitative liquid-chromatography mass spectrometry approach to identify the molecular functions relevant to embryo development occurring in uterine fluid on days 5 and 6 after oestrus and identify potential corpus luteum biomarkers in bovine (Bos taurus indicus) uterine fluid on day 7 after oestrus (typical day of blastocyst transfer).

The proteomic profile of the ipsilateral uterine horn on days 5 and 6 were found to be distinct, with 594 proteins being particular to day 5 and 1151 proteins being particular to day 6. Despite the differences in proteomic composition, biosynthesis and metabolism of amino acids and energy production were identified as the predominant molecular functions occurring in uterine fluid on days 5 and 6 after oestrus. 14 candidate biomarkers were identified on day 7 after oestrus, 11 of which (ALDH1A3, ALPL, TXLNA, CDK1, SERPINE2, HSPB6, F11R/JAM-A, MVB12A, RAC3, SPARCL1, TPP1) were present only in the ipsilateral uterine horn and 3 (MUC16, PGM5, TLNRD1) were only present in the contralateral uterine horn.The results of the present project could be expected to inform future research that would dramatically improve ART pregnancy outcomes in cattle and other species.