Type of Inflammation Differentially Affects Expression of Interleukin 1β and 6, Tumor Necrosis Factor-α and Toll-Like Receptors in Subclinical Endometritis in Mares.
Authors: Siemieniuch Marta J, Szóstek Anna Z, Gajos Katarzyna, Kozdrowski Roland, Nowak Marcin, Okuda Kiyoshi
Journal: PloS one
Summary
# Editorial Summary: Subclinical Endometritis and Immune Response in Mares Subclinical endometritis (SE) represents a significant cause of reproductive failure in mares, yet the immune mechanisms underlying this condition remain incompletely understood. Researchers examined endometrial tissue from 82 warmblood mares to compare gene expression and protein production of key inflammatory markers (IL-1β, IL-6, TNF-α and toll-like receptors) across healthy controls, chronic endometritis, and subacute suppurative endometritis cases. The severity of inflammation proved critical: whilst gene expression for all four markers increased across diseased groups, only mares with subacute suppurative endometritis showed significantly elevated concentrations of the inflammatory cytokines IL-6 and TNF-α in cultured endometrial tissue—suggesting that smouldering chronic inflammation may not fully activate the innate immune response in the same way. Immunolocalisation confirmed that epithelial cells lining the endometrial lumens and glands, along with stromal tissue, are the primary producers of these immune mediators, indicating these tissue types drive the inflammatory cascade. For practitioners managing subfertile mares, these findings suggest that the degree of inflammation severity dictates the immunological response; subclinical cases may progress insidiously without overt clinical signs precisely because innate immune activation remains incomplete, which has implications for diagnostic thresholds and intervention timing in breeding programmes.
Read the full abstract on PubMed
Practical Takeaways
- •Subclinical endometritis severity varies: subacute suppurative endometritis shows full activation of immune markers while chronic endometritis does not, suggesting different treatment approaches may be warranted based on inflammation type
- •Mares presenting with reduced conception rates or embryo loss warrant endometrial assessment, as subclinical inflammation can impair fertility without obvious clinical signs
- •Understanding that endometrial epithelial and stromal cells actively drive immune response may inform future therapeutic strategies targeting inflammatory pathways rather than just bacterial elimination
Key Findings
- •mRNA expression of TLR2, IL-1β, IL-6, TLR4 and TNF-α was significantly upregulated in mares with subacute suppurative endometritis (SSE) compared to healthy controls (P<0.01 to P<0.0001)
- •IL-6 and TNF-α protein concentrations were elevated only in SSE mares, not in chronic endometritis, suggesting inflammation type determines cytokine activation
- •TNF-α and TLR2/4 immunolocalization was confirmed in endometrial epithelial, glandular and stromal cells in both healthy and diseased endometria
- •severity of endometrial inflammation correlates with activation of innate immunity mechanisms including toll-like receptor and pro-inflammatory cytokine expression