Ballooned hepatocytes in steatohepatitis: The value of keratin immunohistochemistry for diagnosis☆
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.
Section snippets
Tissues
Formaldehyde (8% buffered formaldehyde solution)-fixed and paraffin-embedded liver biopsies and surgical material were retrieved from the biobank of the Institute of Pathology of the Medical University of Graz. The protocol was approved by the Local Ethics Committee in accordance with the ethical guidelines of the Helsinki Declaration of 1975, as revised in 1983.
Light microscopy
Dewaxed tissue sections (3 μm thick) were stained with hematoxylin and eosin (H&E) and the chromotrope aniline blue (CAB) connective
Results
Steatohepatitis of both alcoholic and non-alcoholic aetiology was characterized in H&E stained sections by appearance of enlarged and rounded hepatocytes with lightly stained reticular cytoplasm, enlarged nuclei and prominent nucleoli. Most of these hepatocytes contained MDBs (Fig. 1A). Regardless of their MDB content, ballooned liver cells showed loss or at least marked diminution of cytoplasmic K8/18 immunostaining, even with disappearance of the usually more pronounced and stable
Discussion
Hepatocellular ballooning is one of the histological hallmarks of steatohepatitis and a key feature of recently described semiquantitative grading systems of this disease [24], [25], [26]. However, poor intra-observer and inter-observer agreement for the assessment of hepatocyte ballooning has proven to be a major obstacle to reproducibility [26], [27]. Our immunohistochemical study was undertaken to evaluate K8/18 expression in ballooned hepatocytes in steatohepatitis and compare the findings
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The authors who have taken part in the research of this paper declared that they do not have a relationship with the manufacturers of the materials involved either in the past or present and they did not receive funding from the manufacturers to carry out their research. They did not receive funding from any source to carry out this study.