title: Deep sequencing of the uterine immune response to bacteria during the equine oestrous cycle.
abstract: BACKGROUND
  The 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.
  
  
  METHODS
  Endometrial 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).
  
  
  RESULTS
  Comparison 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 sPLA 2, 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, 250 Princes Highway, Werribee, VIC, 3030, Australia. christina.marth@unimelb.edu.au.
authors.forename: Christina D
authors.initials: CD
authors.lastname: Marth
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, 250 Princes Highway, Werribee, VIC, 3030, Australia. nyoung@unimelb.edu.au.
authors.forename: Neil D
authors.initials: ND
authors.lastname: Young
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, 250 Princes Highway, Werribee, VIC, 3030, Australia. l.glenton@student.unimelb.edu.au.
authors.forename: Lisa Y
authors.initials: LY
authors.lastname: Glenton
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853-6401, USA. drewnoden@gmail.com.
authors.forename: Drew M
authors.initials: DM
authors.lastname: Noden
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, 250 Princes Highway, Werribee, VIC, 3030, Australia. glenfb@unimelb.edu.au.
authors.forename: Glenn F
authors.initials: GF
authors.lastname: Browning
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, 250 Princes Highway, Werribee, VIC, 3030, Australia. krekeler@unimelb.edu.au.
authors.forename: Natali
authors.initials: N
authors.lastname: Krekeler
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics / Q000378:metabolism; D018925:Chemokines / Q000235:genetics / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004716:Endometritis / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D004717:Endometrium / Q000276:immunology* / Q000378:metabolism; D004927:Escherichia coli Infections / Q000276:immunology / Q000662:veterinary*; D030762:Estrous Cycle / Q000235:genetics*; D005260:Female; D015870:Gene Expression; D012739:Gonadal Steroid Hormones; D059014:High-Throughput Nucleotide Sequencing; D006734:Horse Diseases / Q000235:genetics / Q000276:immunology* / Q000382:microbiology*; D006736:Horses; D020782:Matrix Metalloproteinases / Q000235:genetics / Q000378:metabolism
chemical_list: D023181:Antimicrobial Cationic Peptides; D018925:Chemokines; D016207:Cytokines; D012739:Gonadal Steroid Hormones; D020782:Matrix Metalloproteinases