Ballooned hepatocytes in steatohepatitis: The value of keratin immunohistochemistry for diagnosis

Background/Aims

Hepatocyte “ballooning” is an often used but ill defined term in liver pathology to designate a special form of liver cell degeneration associated with cell swelling and enlargement found particularly in steatohepatitis. Alterations of the intermediate filament cytoskeleton of the hepatocyte may contribute to the pathogenesis of this microscopic change. Ballooning degeneration is considered a hallmark of steatohepatitis, but enlarged hepatocytes may also be observed in a variety of other acute and chronic liver diseases.

Methods

The intermediate filament cytoskeleton was investigated using keratin 8 and 18 immunohistochemistry in liver diseases associated with enlarged or ballooned hepatocytes.

Results

Keratin 8/18 immunostaining was drastically reduced or lost in the cytoplasm of ballooned hepatocytes in alcoholic and non-alcoholic steatohepatitis, chronic cholestatic conditions, ischemia/reperfusion injury and in ballooned hepatocytes in chronic hepatitis C cases with concurrent steatohepatitis. In contrast, substantial decrease or loss of keratin 8/18 immunostaining was not noted in cases of acute hepatitis, giant cell hepatitis, chronic hepatitis B, or autoimmune hepatitis.

Conclusions

Loss of keratin 8/18 immunostaining can serve as an objective marker of a specific type of ballooning degeneration of hepatocytes. Oxidative stress may be a common denominator in the pathogenesis of keratin filament alterations in these conditions.

Introduction

“Ballooning” is a frequently used yet ill-defined term in liver morphology indicating hepatocyte degeneration associated with enlargement, swelling, rounding and characteristic reticulated cytoplasm [1]. The term has been applied to hepatocytes in acute viral hepatitis, autoimmune hepatitis, alcoholic and non-alcoholic steatohepatitis, neonatal giant cell hepatitis, Wilson’s disease, toxic liver damage and ischemia/reperfusion injury of liver allografts [1], [2], [3], [4]. Size and shape of hepatocytes may be determined by the amount of intracellular organelles and other cytoplasmic components, fluid retention, cytoskeletal architecture, or a combination of these factors [5], [6], [7], [8], [9]. Due to its scaffold-like properties the intermediate filament (IF) cytoskeleton plays a major role in the stabilization and topographical organization of a cell and its organelles. In hepatocytes IFs consist of the type I keratin (K) 18 and the type II K8 noncovalently assembled in an equimolar ratio as heteropolymers [10], [11], [12]. Alterations of the hepatocyte IF cytoskeleton have been reported in alcoholic and non-alcoholic steatohepatitis, Wilson’s disease and other types of copper toxicosis, primary biliary cirrhosis, hepatocellular neoplasms and related animal models, e.g. the chronically dicarboxy-diethoxy-dihydrocollidine-fed mouse, in which immunohistochemical analysis using antibodies against K 8 and 18 revealed a disturbance, decrease or even loss of the IF network staining particularly in enlarged (“ballooned”) hepatocytes [3], [10], [13], [14], [15].

The aim of this study was to utilize immunohistochemistry to investigate the detectable expression of the keratin (K) IF cytoskeleton and the oxidative stress induced sequestosome 1/p62 (p62) and ubiquitin proteins in various non-neoplastic liver diseases associated with enlarged liver cells in order to relate IF cytoskeleton alterations to the hepatocyte phenotype in specific disease processes and to explore whether K immunostaining could provide more objective criteria for diagnosis of hepatocyte ballooning.