Microstructural and ultrastructural changes in the healing process of bile duct trauma

Objective: To explore the mechanism of benign biliary stricture caused by bile duct trauma. Methods: A model of trauma of the common bile duct was established in 28 dogs and then repaired. The anastomotic tissues were taken on 3 days, 1 week, 3 weeks, 3 months, and 6 months respectively after operation and examined by using light microscopy and electromicroscopy. Macrophage, transforming growth factor beta 1 (TGF-β1) and α-smooth muscle actin (α-SMA) were studied immunohistochemically. Results: The mucosal epithelium of the common bile duct restored poorly, chronic inflammation lasted for a long time, fibroblasts proliferated actively, extracellular matrix overdeposited, and myofibroblasts functioned actively during the whole healing process. Immunohistochemical test showed a high expression of macrophage, TGF-β1 and α-SMA during the healing process lasting a long duration. Macrophages were found in the lamina propria under mucosa, TGF-β1 in the granular tissue, fibroblasts and endothelial cells of blood vessels, while α-SMA in the myofibroblasts and smooth muscle tissue. Conclusions: The healing of the bile duct is in the mode of overhealing. Myofibroblast is the main cause for contracture of scar and stricture of the bile duct. The high expression of macrophage, TGF-β1 and α-SMA is closely related to active proliferation of fibroblasts, extracellular matrix overdeposition and scar contracture of the bile duct.