Electron Microscopic Study of Patients with Ulcerative Colitis by Colonosocopic Biopsy

Purpose: Ulcerative colitis (UC) is a chronic inflammatory disorder primarily affecting the colon mucosa. Typical pathologic findings include widespread crypt architectural distortion (cryptitis, crypt abscess, and crypt atrophy), heavy, diffuse lamina propria cell infiltration, and basal plasmacytosis. However, only few studies have been performed on the ultrastructural changes of patients with UC by transmission electron microscopy. The aims of this study were to examine ultrastructural changes in colon of patients with UC and to evaluate the differences in ultrastructural changes according to the severity of UC. Methods: A total of 5 patients diagnosed with UC received colonoscopy. During the examination, biopsy of each segment was performed for light microscopic examination. Two pieces of inflamed mucosa and the corresponding non-inflamed mucosa from the left colitis were obtained by colonoscopy for electron microscopic examination. For pancolitis, two pieces of the most severe inflamed mucosa were obtained. Results: All patients were male; the mean age was 38±5 years. According to the endoscopic severity, mild degree was found in 2 patients, moderate in 1 patient, and severe in 2 patients. The extents of the colon involvement were left colitis in 2 patients and pancolitis in 3 patients. In mild UC, mitochondrial swelling in the colonocyte was prominent in the inflamed mucosa compared to that in non-inflamed mucosa. In lamina propria, plasma cells were predominant, and mitochondrial swelling and dilated endoplasmic reticulum were noticeable in the inflamed mucosa. In moderate UC, mitochondrial swelling and autophagic vacuole of the colonocyte were observed in the epithelial layer, mitochondrial swelling and dilated endoplasmic reticulum of plasma cells, and phagocytosing macrophage were found at the lamina propria. In severe UC, multiple autophagosomes of mitochondria in the colonocyte were detected, and intercellular space was remarkably narrowed. Mitochondrial degeneration with autophagosomes was also found in the goblet cells of the epithelial layer. In lamina propria, increased plasma cells showed multiple autophagosomes of mitochondria and dilated rough endoplasmic reticulum. Mitochondrial degeneration within the macrophages, eosinophils, and lymphocytes were also found. Conclusion: As UC developed from mild to severe, the ultrastructural changes of mitochondria in epithelial layer and lamina propria were generally definitive. In mild UC, mitochondrial swelling and enlarged endoplasmic reticulum were found in colonocyte and plasma cells. In severe UC, the mitochondria degeneration and autophagy were noticeable in the colonocyte, goblet cell, and plasma cells.