Connective tissue growth factor and progressive fibrosis in biliary atresia

Abstract

Connective tissue growth factor (CTGF) is a newly described protein that stimulates transforming growth factor-β1 (TGF-β1). We evaluated the expression of CTGF mRNA in operative biopsy specimens from biliary atresia (BA) patients and normal controls to assess the role of CTGF in BA. Liver biopsy specimens were taken from BA patients at the time of portoenterostomy (n=22) and compared with specimens taken from normal controls (n=6). In situ hybridization was used to stain CTGF mRNA in all specimens. The distribution of collagen type IV (C-IV) was also assessed in the same specimens as an indicator of the severity of fibrosis present at the time of biopsy. Results were analyzed to determine whether there was any correlation between CTGF and C-IV and outcome. Of the 22 postoperative BA patients, eventual outcome was good in 17 (group I), and five (group II) subsequently required liver transplantation. Control specimens (n=6) had no apparent CTGF mRNA expression, and median C-IV positive immunoreactivity was 1.23±0.25%. CTGF mRNA was weakly expressed in hepatic stellate cells (HSC) and hepatocytes in specimens from group I, and median C-IV-positive immunoreactivity was 3.18±0.86%. However, in specimens from group II, there was increased CTGF mRNA in HSC and hepatocytes. Median C-IV-positive immunoreactivity was 6.31±0.96%. There was a significant correlation between CTGF mRNA intensity and the amount of C-IV, which implies that CTGF expression reflects prognosis. This study provides the first evidence that CTGF is strongly expressed in BA, in particular in HSC and hepatocytes, suggesting that they may be a source of CTGF. The strong correlation with C-IV indicates that CTGF plays a major role in the pathogenesis of progressive fibrosis in BA.