Influence of sire fertility status on conceptus-induced transcriptomic response of the bovine endometrium

The aim of this study was to examine the effect of sire fertility status on conceptus-induced changes in the endometrial transcriptome. Holstein Friesian bulls (3 High fertility, HF, 3 Low fertility, LF) were selected from the Irish national population of AI bulls (minimum of 500 inseminations/bull) based on adjusted fertility scores (HF: +4.37% and LF: -12.7%; mean = 0%). To generate elongated conceptuses, Day 7 blastocysts produced in vitro using sperm from these six bulls were transferred in groups of 5-10 to synchronized heifers (n=7 heifers per bull; total 42 heifers). Conceptuses were recovered following slaughter on Day 15 (recovery rate: HF 59.4% vs. LF 45.0%; P<0.05). In parallel, Day 15 endometrial explants were recovered from synchronized cyclic heifers (n=4). Explants from each heifer were co-cultured for 6 h in RPMI medium with (i) nothing, control (ii) 100 ng/ml ovine recombinant interferon tau (IFNT) (iii) a single conceptus from each high fertility bull, or (iv) a single conceptus from each low fertility bull. To minimize variation, explants from the same uterus were used across all treatments, replicated across 4 heifers. After 6 h, explants were snap frozen and stored at -80°C. Extracted mRNA was subjected to RNA-seq (Illumina NextSeq 500) and the resulting data were analyzed through a bioinformatic pipeline with R software. Endometrial explants were co-cultured for 6 h in RPMI medium with (i) nothing, control (ii) 100 ng/ml ovine recombinant interferon tau (IFNT) (iii) a single conceptus from each high fertility bull, or (iv) a single conceptus from each low fertility bull.