Author ORCID Identifier
https://orcid.org/0009-0004-9126-010
Date Available
8-20-2027
Year of Publication
2025
Document Type
Master's Thesis
Degree Name
Master of Science (MS)
College
Agriculture, Food and Environment
Department/School/Program
Veterinary Science
Faculty
Dr. Emma Adam
Faculty
Dr. Hossam El-Sheikh Ali
Faculty
Dr. Mats Troedsson
Abstract
Persistent breeding-induced endometritis (PBIE) is a major cause of subfertility in mares, characterized by prolonged post-breeding inflammation and delayed uterine clearance, both of which impair embryo survival. Despite its clinical significance, the molecular and immunological mechanisms underlying susceptibility to PBIE remain incompletely understood. This study aimed to compare endometrial transcriptomic profiles, histopathological features, and cytokine concentrations in low-volume uterine lavage (LVL) among mares classified as resistant (R), intermediate (I), or susceptible (S) to PBIE based on uterine clearance time, to elucidate the molecular basis of susceptibility. LVL samples and endometrial biopsies were collected 24 hours post-breeding from mares classified as resistant (clearance ≤48 h; n = 8), intermediate (48 h < clearance ≤96 h; n = 5), or susceptible (clearance >96 h; n = 8). Cytokine analysis of LVL revealed significantly elevated IL-6 and IL-8, and reduced G-CSF and IL-1α concentrations in S mares (P < 0.05), indicating a sustained inflammatory response. Receiver operating characteristic (ROC) analysis showed that IL-1α and G-CSF were the most accurate biomarkers for distinguishing S mares from R and I groups at 24 hours after insemination (AUC = 0.86 and 0.84, respectively; P < 0.05). These cytokines also accurately predicted pregnancy status at day 14 (AUC = 0.83 and 0.84, respectively; P < 0.05). Histopathological assessment revealed significantly higher eosinophil counts and density (per mm²) in endometrial biopsies from S mares (P = 0.01), with both parameters demonstrating high predictive accuracy for susceptibility (AUC = 0.88 and 0.87, respectively; P < 0.05). Transcriptomic analysis identified 543 and 425 differentially expressed genes (DEGs) in S vs. R and S vs. I comparisons, respectively. Susceptible mares showed upregulation of genes involved in inflammatory signaling (e.g., TNFα, CARD9, NOD1), smooth muscle contraction (e.g., MYH11, ACTG2, MYLK), extracellular matrix remodeling (e.g., LOXL2, MMP7, LTBP1/2), and oxidative stress (e.g., CRYAB, MAPK8, TFAM). Upstream regulator analysis identified 33 and 9 key regulators in the S vs. R and S vs. I comparisons, respectively (P < 0.05). Notably, HAMP, MYH11, and KCNH2 emerged as shared hub genes in weighted gene co-expression network analysis (WGCNA), suggesting central roles in PBIE pathogenesis. This integrative analysis highlights key immune, histological, and molecular signatures associated with PBIE susceptibility. These findings advance our understanding of PBIE pathophysiology and offer potential biomarkers and therapeutic targets to improve reproductive outcomes in PBIE susceptible mares.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2025.449
Funding Information
This study was supported by the Gluck Equine Research Foundation in 2025, the Gluck Equine Research Center Wallace Fund in 2025, and the Lincoln Memorial University Summer Research Grant in 2023.
Recommended Citation
Thompson, Jaden R., "IMMUNOLOGICAL, HISTOLOGICAL, AND TRANSCRIPTOMIC INSIGHTS INTO EQUINE PERSISTENT BREEDING-INDUCED ENDOMETRITIS (PBIE)" (2025). Theses and Dissertations--Veterinary Science. 73.
https://uknowledge.uky.edu/gluck_etds/73
Included in
Immunopathology Commons, Large or Food Animal and Equine Medicine Commons, Other Animal Sciences Commons
