Collagen and collagenases in mare’s endometrium with endometrosis.

Overview

• This study investigates changes in collagen deposition and related gene expression in the uterus (endometrium) of mares suffering from endometrosis, a fibrotic uterine disease.
• The research identifies specific molecular markers and enzymes involved in tissue remodeling and fibrosis progression, which could improve diagnosis and treatment strategies for this condition in horses.

Background and Purpose

• Endometrosis is a degenerative, primarily fibrotic disease affecting the mare’s endometrium, characterized by irreversible changes and altered tissue remodeling.
• Tissue remodeling involves changes in the extracellular matrix (ECM), where collagen plays a key role in maintaining endometrial structure but also in fibrosis development.
• The balance between matrix metalloproteinases (MMPs)—enzymes that break down ECM proteins—and their tissue inhibitors (TIMPs) is crucial to tissue remodeling and fibrosis.
• The study aimed to quantify collagen deposits and examine gene expression of collagen types II (COL-2) and III (COL-3), MMPs (MMP-1 and MMP-2), TIMP-2, and tumor necrosis factor alpha (TNF-α) in mares with varying severity of endometrial fibrosis.

Methodology

• A total of 34 endometrial samples from mares were collected and classified into three categories:
  • Category I: Healthy endometrium (n=12)
  • Category II: Moderate fibrosis (n=12)
  • Category III: Severe fibrosis (n=10)
• Collagen quantification was performed using picrosirius red (PSR) staining, a technique that highlights collagen fibers under a microscope.
• Gene expression analyses were conducted to measure mRNA levels of COL-2, COL-3, MMP-1, MMP-2, TIMP-2, and TNF-α using appropriate molecular biology methods.

Key Findings

• Collagen Deposition: Collagen content increased progressively with fibrosis severity:
  • Category I: 11.72% collagen
  • Category II: 17.76% collagen
  • Category III: 24.15% collagen
• The increase was statistically significant indicating fibrosis-associated collagen accumulation.
• Gene Expression Patterns:
  • COL-2 expression was highest in moderately fibrotic tissue (Category II), suggesting its involvement in early or intermediate fibrotic remodeling stages.
  • MMP-1 expression increased in moderate fibrosis (Category II) compared to severe fibrosis (Category III), implying a role in normal or reparative remodeling rather than in advanced fibrosis.
  • MMP-2 expression was higher in severe fibrosis (Category III), indicating it may contribute to fibrogenesis or advanced tissue remodeling.
  • TIMP-2 levels were lower in severe fibrosis (Category III), suggesting reduced inhibition of MMP-2, potentially facilitating fibrotic ECM remodeling.
  • TNF-α, a pro-inflammatory cytokine, showed elevated expression in moderate fibrosis (Category II), highlighting the involvement of inflammation in fibrosis progression.

Interpretation and Implications

• PSR staining is validated as a useful tool to objectively quantify collagen deposition in equine endometrial tissue during fibrosis evaluation.
• MMP-1 may be involved in maintaining normal tissue remodeling, acting more during early or moderate fibrosis stages.
• MMP-2’s increased expression in severe fibrosis, alongside lower TIMP-2, suggests a dysregulated ECM breakdown and deposition promoting fibrotic progression.
• COL-2 and TNF-α act as biological markers that correlate with fibrosis severity and inflammatory responses, respectively, making them potential targets for diagnostics or therapeutic monitoring.
• The findings contribute to understanding molecular mechanisms underlying endometrosis and support the future development of antifibrotic treatments aimed at preventing or reversing endometrial fibrosis in mares.
• Overall, this research enhances the potential for improved diagnosis, prognosis, and treatment of uterine fibrosis to support mare reproductive health.