Inflammatory responses to induced infectious endometritis in mares resistant or susceptible to persistent endometritis

Mette Christoffersen, Elizabeth Woodward, Anders M. Bojesen, Stine Jacobsen, Morten R. Petersen, Mats H.T. Troedsson, Henrik Lehn-Jensen

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75 Scopus citations

Abstract

Background: The objective of the study was to evaluate the gene expression of inflammatory cytokines (interleukin [IL]-1β, IL-6, IL-8, IL-10, tumor necrosis factor [TNF]-α, IL-1 receptor antagonist [ra] and serum amyloid A (SAA) in endometrial tissue and circulating leukocytes in response to uterine inoculation of 10 5 colony forming units (CFU) Escherichia coli in mares. Before inoculation, mares were classified as resistant or susceptible to persistent endometritis based on their uterine inflammatory response to infusion of 10 9 killed spermatozoa and histological assessment of the endometrial quality. Endometrial biopsies were obtained 3, 12, 24 and 72 hours (h) after bacterial inoculation and blood samples were obtained during the 7 day period post bacterial inoculation. Expression levels of cytokines and SAA were determined by quantitative real-time reverse transcriptase PCR (qRT-PCR).Results: Compared to levels in a control biopsy (obtained in the subsequent estrous), resistant mares showed an up-regulation of IL-1β, IL-6, IL-8 and TNF-α at 3 h after E. coli inoculation, while susceptible mares showed increased gene expression of IL-6 and IL-1ra. Susceptible mares had a significant lower gene expression of TNF-α,IL-6 and increased expression of IL-1ra 3 h after E. coli inoculation compared to resistant mares. Susceptible mares showed a sustained and prolonged inflammatory response with increased gene expression levels of IL-1β, IL-8, IL-1ra and IL-1β:IL-1ra ratio throughout the entire study period (72 h), whereas levels in resistant mares returned to estrous control levels by 12 hours. Endometrial mRNA transcripts of IL-1β and IL-1ra were significantly higher in mares with heavy uterine bacterial growth compared to mares with no/mild growth.All blood parameters were unaffected by intrauterine E. coli infusion, except for a lower gene expression of IL-10 at 168 h and an increased expression of IL-1ra at 48 h observed in susceptible mares compared to resistant mares.Conclusions: The current investigation suggests that endometrial mRNA transcripts of pro-inflammatory cytokines in response to endometritis are finely regulated in resistant mares, with initial high expression levels followed by normalization within a short period of time. Susceptible mares had a prolonged expression of pro-inflammatory cytokines, supporting the hypothesis that an unbalanced endometrial gene expression of inflammatory cytokines might play an important role in the pathogenesis of persistent endometritis.

Original languageEnglish
Article number41
JournalBMC Veterinary Research
Volume8
DOIs
StatePublished - Mar 29 2012

Bibliographical note

Funding Information:
The authors would like to thank Dr. Kirsten Scoggin at the Maxwell H. Gluck Equine Research Center for laboratory support and Dr. Kerstin Skovgaard at the National Veterinary Institute, Denmark for providing primers for IL-1ra for the gene expression analyses. We would also thank Mr. Lynn Ennis, Mr. Kevin Gallagher and the University of Kentucky’s Maine Chance Farm for the management and care of the horses. This study was financially supported by Koller Endowment for Equine research and development, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington.

Keywords

  • Cytokines
  • Infectious endometritis
  • Serum amyloid A
  • Susceptibility

ASJC Scopus subject areas

  • General Veterinary

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