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BackgroundThe steroid hormone environment in healthy horses seems to have a significant impact on the efficiency of their uterine immune response. The objective of this study was to characterize the changes in gene expression in the equine endometrium in response to the introduction of bacterial pathogens and the influence of steroid hormone concentrations on this expression.MethodsEndometrial biopsies were collected from five horses before and 3 h after the inoculation of Escherichia coli once in oestrus (follicle >35 mm in diameter) and once in dioestrus (5 days after ovulation) and analysed using high-throughput RNA sequencing techniques (RNA-Seq).ResultsComparison between time points revealed that 2422 genes were expressed at significantly higher levels and 2191 genes at significantly lower levels 3 h post inoculation in oestrus in comparison to pre-inoculation levels. In dioestrus, the expression of 1476 genes was up-regulated and 383 genes were down-regulated post inoculation. Many immune related genes were found to be up-regulated after the introduction of E. coli. These include pathogen recognition receptors, particularly toll-like receptors TLR2 and 4 and NOD-like receptor NLRC5. In addition, several interleukins including IL1B, IL6, IL8 and IL1ra were significantly up-regulated. Genes for chemokines, including CCL 2, CXCL 6, 9, 10, 11 and 16 and those for antimicrobial peptides, including secretory phospholipase sPLA2, lipocalin 2, lysozyme and equine β-defensin 1, as well as the gene for tissue inhibitor for metalloproteinases TIMP-1 were also up-regulated post inoculation.ConclusionThe results of this study emphasize the complexity of an effective uterine immune response during acute endometritis and the tight balance between pro- and anti-inflammatory factors required for efficient elimination of bacteria. It is one of the first high-throughput analyses of the uterine inflammatory response in any species and several new potential targets for treatment of inflammatory diseases of the equine uterus have been identified.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2139-3) contains supplementary material, which is available to authorized users.

Persistent mating-induced endometritis (PMIE) severely decreases fertility in horses. The aim of the present study was to evaluate differences between horses susceptible to PMIE and a control group in terms of the expression of selected immune response and effector genes, and the effects of oestrous cycle stage on this expression. Endometrial biopsies from 18 uterine samples of mares in the control group (eight in dioestrus, 10 in oestrus) and 16 PMIE-susceptible mares (four in dioestrus, 12 in oestrus) were analysed by quantitative real-time reverse transcription-polymerase chain reaction. Genes for pathogen recognition receptors Toll-like receptor 2 (TLR2) and NLR family CARD domain containing 5 (NLRC5), as well as tissue-specific inhibitor of metalloproteinase 1 (TIMP1), C-X-C motif chemokine ligand (CXCL) 9, CXCL10 and CXCL11 and uteroferrin were expressed at similar levels in the control group and in susceptible mares. Genes for C-C motif chemokine ligand 2 (CCL2) and the antimicrobial peptides secreted phospholipase A2 (sPLA2), lipocalin 2 and lactoferrin were all expressed at higher levels in susceptible compared with control mares. The expression of genes for the antimicrobial peptides equine β-defensin 1 (EBD1), lysozyme (LYZ) and secretory leukoprotease inhibitor (SLPI) was also higher in susceptible than control mares. The diagnostic sensitivity of assays for EBD1, LYZ and SLP1 gene expression to detect susceptibility to PMIE was estimated to be 100%, 94% and 100% respectively, with specificities of 83%, 78% and 78% respectively. When all three tests were positive, the specificity increased to 94%, with an overall sensitivity of 94%. The present study has yielded insights into pathophysiological changes in mares susceptible to PMIE and identified robust diagnostic markers (EBD1, LYZ and SLPI) for susceptibility to this disease.

TUA was effective for reduction of twin pregnancy in mares, with best results achieved before gestational day 43.

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