Ultrastructural changes in the equine colonic mucosa after ischaemia and reperfusion.

The research deals with the morphological changes that take place in the epithelium of a horse’s colonic mucosa due to ischaemia and reperfusion, and how the cells of the immune system respond to the damage.

Objective and Methodology

• The study was conducted to understand the changes in the ultrastructure of the epithelium, which forms the inner lining of the equine colon, following ischaemia (restriction in blood supply) and reperfusion (restoration of blood supply), and how the immune cells respond to this injury.
• Ischaemia was triggered in a 40 cm segment of the pelvic flexure in six horses for an hour and was followed by four hours of reperfusion.
• Biopsies were taken from the mucosa prior to and post ischaemia, and after 1, 2 and 4 hours of reperfusion.
• The biopsies were fixed and treated with various substances, followed by embedding in epon, a type of resin used in electron microscopy.
• Light microscopy was used to evaluate morphological changes in toluidine blue-stained semithin sections, while transmission electron microscopy was used to study ultrastructural changes in thin sections stained with uranyl acetate/lead citrate.

Results and Findings

• Ischaemia caused changes like swelling of the epithelial cells and their organelles, loosening of tight junctions, detachment of cells from the basement membrane, early apoptosis (programmed cell death) and single cell necrosis.
• Ischaemia also triggered autophagy, a process where the body destroys its own cells to provide nutrients in conditions of starvation, in the affected epithelial cells.
• During the reperfusion phase, the evidence pointed to apoptosis, regeneration of the epithelium, and restoration of the cell junctions at the top.
• There were vacuoles, which are tiny cavities in the cell containing fluid, which looked like they were involved in phagocytic activity. They contained cellular debris and bacteria, indicating their role in fighting off the injury.
• There were spaces formed between the cells (paracellular) and under the epithelium (subepithelial), and an influx of neutrophils, lymphocytes and eosinophils, which are types of white blood cells that fight against infections and injury, into the epithelium.
• Macrophages, which engulf and digest cellular debris and pathogens, in the area under the epithelium, and neutrophils inside the lumen, showed escalated phagocytic activity.

Conclusion

• Ischaemia resulted in ultrastructural damage to the epithelial lineage in the colon, however, the cells demonstrated recovery during the reperfusion phase.
• The study concluded that Transmission Electron Microscopy (TEM) can effectively exhibit subtle ultrastructural damage and recovery after ischaemia and reperfusion in the equine colon.