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Objective: To explore the formation mechanism of benign biliary stricture. Methods: A model of trauma ofcommon bile duct was established in 28 dogs and then repaired. The anasomosis tissues were taken on the 1st week

3rd week and the 3rd month

6th month respectively after operation and examined by using light microscopy and elec-tromicroscopy. Macrophage

TGF-β

1

and α-SMA were studied immunohistochemically. Results: The mucosal epitheli-um of common bile duct restored poorly

chronic inflammation lasted for a long time

fibroblasts proliferated actively

extracellular matrix overdeposited; and myofibroblasts functioned actively and existed during the whole healing process.Immunohistochemical test showed a high expression of macrophage

TGF-β

1

and α-SMA during healing process lastinga long duration. Macrophages were found in the lamina propria under mucosa

TGF-β

1

in the granulation tissue

fibro-blasts and endothelial cells of blood vesssels

while α-SMA in the myofiroblasts and smooth muscle