Dysregulated Epithelial Shedding Promotes Early Intestinal Hyperpermeability Following Major Burn Injury

Background: Major burn injury triggers systemic inflammation and metabolic responses beyond the skin. Early intestinal barrier failure can amplify post-burn inflammation and organ dysfunction, yet the dynamic epithelial lesions that generate focal leakage in vivo remain unclear. We characterized villus-tip epithelial shedding, epithelial gap formation, and tracer leak sites early after burn using intravital multiphoton fluorescence microscopy. Methods: Male C57BL/6 mice were assigned to Control or Burn groups (30–35% total body surface area full-thickness burn; n=6/group). Intestinal permeability was assessed at 2, 4, and 6 hours post-injury using luminal fluorescein isothiocyanate–dextran (4 kilodaltons) with portal venous sampling. Distal-ileum intravital imaging was performed 330–420 minutes post-injury (1-minute intervals). Ten villi per mouse were quantified for shedding duration and prevalence, condensation-first versus extrusion-first sequence, epithelial gap density, goblet-cell proportion, and focal luminal tracer leak sites. Results: Major burn shortened shedding duration and increased shedding prevalence during the 90-minute observation (p<0.05), with a shift toward a condensation-first pattern and fewer extrusion-first events (p<0.05). Burn increased epithelial gap density and goblet-cell proportion (p<0.05). Portal serum fluorescein isothiocyanate–dextran concentrations were elevated at 6 hours (p<0.05), and imaging localized tracer penetration to discrete post-shedding epithelial defects, consistent with incomplete sealing. Conclusions: Major burn rapidly disrupts intestinal barrier integrity through accelerated stress-associated shedding, increased gap formation, and focal leak sites. These time-resolved structural lesions provide an in vivo substrate for early hyperpermeability and suggest a time-critical window for gut-directed interventions to mitigate downstream post-burn complications.