Gene expression profiling of early primary biliary cirrhosis: possible insights into the mechanism of action of ursodeoxycholic acid

Objectives: Primary biliary cirrhosis (PBC) is a poorly understood disease, both in terms of its pathogenesis and the mechanism of action of its most common treatment, ursodeoxycholic acid (UDCA). We used gene expression profiling to compare liver tissue from treatment-naive and UDCA-treated patients in order to outline some of the molecular changes associated with PBC and its treatment. Patients and Experimental Design: Liver biopsy specimens from non-cirrhotic, treatment-naive (n=11) patients were compared with biopsies from UDCA-treated patients (n=20) and with 10 normal, healthy female controls. Gene expression was determined using a 19K cDNA microarray. In order to determine whether the observed changes in gene expression levels were specific to PBC or generic to liver damage overall, PBC samples were also compared with chronically diseased [48 hepatitis C virus (HCV), 18 hepatitis B virus (HBV)] and acutely stressed liver tissue (25 liver biopsies taken after reperfusion of liver transplant grafts). Results: We found a gene signature specific to PBC (P <= 0.012), containing biologically plausible genes (221 genes with adjusted P <= 0.05). Differences in the expression of selected genes were confirmed using real-time polymerase chain reaction. When gene expression from non-cirrhotic UDCA-treated (n=20) and UDCA-naive liver tissue was compared, we found a striking downregulation of a number of genes involved in protein biosynthetic pathways. Conclusions: These studies highlight the genes associated with both treatment-naive and UDCA-treated PBC, and suggest that the effects of UDCA are mediated, at least in part, via a modulation of protein biosynthesic pathways.