Inflammatory proteins as novel diagnostic biomarkers for endometritis in mare

Equine endometritis is a costly, prevalent, and challenging disease for equine practitioners to diagnose, with clinical implications ranging from subfertility to infertility. Currently, gold standard diagnostic test is endometrial biopsy subjected to Kenney-Doig grades; however, time to receive results can be variable. Objective was to test for inflammatory proteins that are previously validated as equine diagnostic biomarkers in uterine low volume lavage (LVL) fluid of mares. We hypothesized that these inflammatory proteins would substantially increase in LVL fluid of mares with documented evidence of endometritis or poor biopsy grade. Light breed mares (n = 29) 3 - 22 years old were used. Each mare had an LVL (250 ml) followed by endometrial biopsy. Endometrial cytology was performed from LVL and biopsy evaluation was graded by a board-certified veterinary pathologist. Mares were either assigned to endometritis group (n = 12), or healthy group (n = 17) based on endometrial cytology (> 1% PMNs), and/or poor endometrial biopsy score (IIB/III). LVL was utilized in a multiplex bead assay (Luminex Corp. Austin, TX) to quantify levels of following biomarkers: IFNγ, IL1β, IL10, IL17, sCD14, TNFα, chemokine (C-C motif) ligand 2 (CCL2), CCL3, CCL5, and CCL11. Data were analyzed by STATA (College Station, TX). Since data were not normally distributed, a Mann-Whitney U test was performed to compare levels of inflammatory markers between healthy and endometritis mares, with significance set at p value < 0.05. Following inflammatory markers were higher in LVL from mares with endometritis compared to healthy mares: IFN-γ (p = 0.0094), IL17 (p = 0.0296), CCL2 (p = 0.0196), and CCL3 (p = 0.0118). These 4 biomarkers are all proinflammatory cytokines, which orchestrate response of various leukocytes to endometrial changes. Further studies with a larger population are warranted; however, we suggest that proinflammatory markers identified may serve as potential diagnostic markers for endometritis in equine uterine fluid samples. Use of LVL samples for detection of inflammatory biomarkers could provide a less invasive and efficient diagnostic test to practitioners during busy breeding season.

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.

Keywords: Biomarkers, endometritis, equine, low volume lavage