Real-time in vivo confocal laser endomicroscopic imaging of equine endometrium: Preliminary observations and feasibility study.

Overview

• This study explores the use of confocal laser endomicroscopy (CLE), a real-time microscopic imaging technique, to assess the equine endometrium (lining of the uterus) in live mares.
• It aims to establish the feasibility of CLE for this purpose and determine the optimal dose of fluorescein sodium, a contrast agent, for effective imaging.

Introduction and Background

• Endometrial health is critical for reproductive success in broodmares, affecting fertility and pregnancy outcomes.
• Current diagnostic methods rely mainly on taking tissue biopsies and performing histopathology, which is invasive and limited to small or single site assessments.
• Confocal laser endomicroscopy (CLE) is an advanced endoscopic imaging technology that allows real-time microscopic visualization of tissues in vivo by using a fiber optic probe combined with fluorescent contrast agents.
• In human medicine, intravenous fluorescein sodium is commonly used to induce fluorescence and enhance tissue contrast for CLE imaging.

Study Goals and Methods

• The study had two primary goals:
  • Evaluate the use of CLE for real-time imaging of the equine endometrium in live mares.
  • Determine the optimal dose of intravenously injected fluorescein sodium to produce clear, high-contrast images at the cellular level.
• Forty-four mares were imaged in vivo using CLE.
• Images obtained via CLE were compared with traditional histopathological analysis of biopsied endometrial tissue to validate findings.
• Fluorescein sodium was administered intravenously at varying doses; the study identified 4 mg/kg as the optimal concentration, which corresponds to 0.04 mL/kg of a 10% fluorescein sodium solution.
• The safety of intravenous fluorescein sodium administration was evaluated; no adverse reactions were observed.

Findings and Imaging Observations

• CLE allowed rapid visualization of multiple regions of the endometrium with real-time microscopic detail.
• Tissue architecture:
  • Distinct patterns of endometrial tissue structure were identifiable.
  • The integrity of the luminal epithelium could be assessed, including detection of ulcerations.
  • Exocytosed inflammatory cells were visible on the epithelial surface.
• Endometrial gland parameters:
  • Distribution and density of glands could be evaluated.
  • Shape and epithelial height of these glands were also assessed.
• Vascular structures:
  • Blood vessels were clearly outlined in images, highlighting the vascular network.
• Inflammation and fibrosis:
  • Inflammatory cells and fibrotic changes in the interstitial tissue were discernible.
• Variation in image quality across different mares was noted, possibly influenced by the stage of the estrous cycle.

Significance and Advantages

• CLE offers a novel, minimally invasive method to obtain “virtual biopsies”—live microscopic images that can provide detailed histological information without needing tissue removal.
• This technique facilitates surveying multiple uterine regions during one procedure, potentially providing a more comprehensive assessment than traditional single-site biopsy histology.
• It may improve diagnostic accuracy and help tailor treatment strategies for equine reproductive health by identifying subtle endometrial changes in real time.
• The established fluorescein sodium protocol ensures safe administration with effective image contrast, supporting potential clinical adoption.

Conclusion

• The study demonstrates the feasibility of using CLE with intravenous fluorescein sodium to perform real-time, in vivo microscopic imaging of the equine endometrium.
• This promising technology could complement or eventually reduce reliance on invasive biopsies in evaluating the uterine health of mares.
• Further research may be needed to refine imaging protocols, explore the influence of estrous cycle stages, and validate diagnostic accuracy across a larger population.