Increased chymase in livers with autoimmune disease: colocalization with fibrosis

Chymase, one of the proteases contained in human mast cells, promotes myocardial and renal interstitial fibrosis by converting angiotensin I to II (AII). We previously established a method for measuring chymase in liver tissue and examined the relationship between chymase and fibrosis in chronic hepatitis. In the present study, chymase was determined in liver specimens affected by autoimmune hepatitis (AIH, n=10) or primary biliary cirrhosis (PBC, n=12). To investigate spatial relationships between hepatic fibrosis and human chymase, mast cell distribution in the specimens was determined immunohistochemically using anti-chymase antibody. The mean amounts of chymase in livers with AIH and PBC were 11.56+/-10.64 and 11.67+/-9.96 ng/mg respectively. Hepatic chymase in AIH and PBC was significantly more abundant than in acute hepatitis (AH, 2.72+/-2.23 ng/mg, n=10; p<0.05). When sections from patients with AIH and PBC were immunostained for chymase, immunoreactive mast cells were detected in portal areas and sinusoidal walls, coinciding with zones of fibrosis. Thus chymase appears to be involved in hepatic fibrosis in AIH and PBC.