Mechanism of benign biliary stricture: a morphological and immunohistochemical study.

Aim: To explore the mechanism of benign biliary stricture.

Methods: A model of trauma of bile duct was established in 28 dogs. The anastomosed tissues were resected and examined by light and electron microscopes on day 3, in wk 1, 3 and mo 3, 6 after operation. CD68, TGF-beta1 and alpha-SMA were examined by immunohistochemical staining, respectively.

Results: The mucosal epithelium of the bile duct was slowly recovered, chronic inflammation lasted for a long time, fibroblasts proliferated actively, extracellular matrix was over-deposited. Myofibroblasts functioned actively and lasted through the whole process. The expression of macrophages in lamina propria under mucosa, TGF-beta1 in granulation tissue, fibroblasts and endothelial cells of blood vessels, alpha-SMA in myofibroblasts were rather strong from the 1st wk to the 6th mo after operation.

Conclusion: The type of healing occurring in bile duct belongs to overhealing. Myofibroblasts are the main cause for scar contracture and stricture of bile duct. High expressions of CD68, TGF-beta1 and alpha-SMA are closely related to the active proliferation of fibroblasts, extracellular matrix over-deposition and scar contracture of bile duct.