Abstract
Following parturition, bacterial contamination of the uterus is common in dairy cattle, which can develop into uterine diseases such as metritis or endometritis. Postpartum uterine diseases are associated with reduced fertility even after the resolution of disease. The mechanisms responsible for reduced fertility in these animals are unknown but likely involve the endometrium and/or conceptus. Here we hypothesized that the transcriptomes of the endometrium and conceptus would be altered 41 d after induced uterine infection. Non-lactating, multiparous Holstein cows (n = 32) were subjected to estrus synchronization, and three days after ovulation (d 0) received an intrauterine infusion of either Escherichia coli and Trueperella pyogenes or saline as a control. Bacterial infusion acutely increased rectal temperature and vaginal discharge score. On d 14 relative to intrauterine infusion, estrus was synchronized again in preparation for transfer of d 7 blastocyst stage embryos on d 32. On d 41 (corresponding to d 16 of pregnancy), the uterus was flushed to collect any conceptus, and the endometrium was sampled by cytobrush. Total RNA was isolated from the conceptus (bacteria, n = 3; saline, n = 4) and endometrium (bacteria, n = 2; saline, n = 4) of pregnant cows and subjected to sequencing. In the conceptus, bacterial infusion altered the expression of 128 transcripts (FDR < 0.1), of which 80 were downregulated and 48 were upregulated compared to the saline group. Differentially expressed transcripts of the conceptus included upregulated IFNT2, BMP6 and PAG11, and downregulated JUN, JUND, ETS2, GATA2, TGFA and EGFR, compared to the saline group. Differentially expressed transcripts of the conceptus were associated with canonical pathways including transcriptional regulation by AP-2 transcription factors and BMP signaling, while upstream regulators of differentially expressed transcripts included IL1-β, TNF-α and lipopolysaccharide. Despite a small number of endometrial samples, bacterial infusion altered the expression of 10 transcripts (FDR < 0.1), of which 6 were downregulated and 4 were upregulated compared to the saline group. Differentially expressed transcripts of the endometrium included downregulated LAP, THBD and C4BPA, and upregulated IL1R2 and TRPV5, compared to the saline group. Due to the low number of differentially expressed transcripts, no canonical pathways were identified in the endometrium, but the G-protein subunit GNB2 and the selectin SELP were identified as predicted upstream regulators of differentially expressed transcripts in the endometrium. This work indicates that the transcriptomes of the endometrium and conceptus of d 16 pregnant cows are altered many weeks after induced uterine infection, and will better inform our understanding of the mechanisms of reduced fertility in dairy cattle after disease resolution.