Epithelial barrier defects in ulcerative colitis: characterization and quantification by electrophysiological imaging

Area of Science:

• Gastroenterology
• Epithelial Biology
• Ion Transport

Background:

• Ulcerative colitis (UC) involves epithelial barrier defects, including lesions and apoptosis, leading to increased colonic ion permeability.
• Mechanisms include local leaks and generalized tight junction alterations.

Purpose of the Study:

• To quantify the contribution of epithelial lesions, apoptosis, and tight junction changes to increased colonic ion permeability in UC.

Main Methods:

• Used conductance scanning with a microelectrode probe to map spatial current distribution in sigmoid colon.
• Identified local leaks and correlated them with structural changes in H&E-stained sections.

Main Results:

• Overall colonic conductivity significantly increased with UC severity.
• Local leaks, not just generalized permeability, were the primary cause of increased conductivity.
• Leaks were associated with epithelial apoptosis in mild UC and erosion/ulcer lesions in severe UC.

Conclusions:

• In early UC, apoptotic foci create leaks in otherwise intact epithelium.
• Erosions and ulcers are highly conductive in severe UC.
• Local leaks account for 19% (mild) to 65% (moderate-to-severe) of increased epithelial conductivity in UC.