Lipid droplets and associated proteins in viral hepatitis

Background and aims:

Chronic hepatitis C (HCV) and B (HBV) are major risk factors for the development of liver cirrhosis, favouring the development of hepatocellular carcinoma (HCC). The lipid metabolism plays a major role in the pathogenesis of HCV-infection, as HCV is known to require lipid droplets (LDs) for the production of infectious virus particles. Amphiphilic proteins of the perilipin/PAT-family decorate the surface of LDs and determine their formation, maintenance and degradation. In mammals, the perilipin-family consists of 5 members, with perilipins 1 and 2 being constitutively expressed at LDs. Aim of this project was to further the understanding of LD-histopathology in chronic hepatitis.

Material and methods:

Liver biopsies of 231 HCV-patients were immunohistochemically stained for perilipins 1 and 2, scored and correlated with clinical parameters. In addition, a collective of 27 liver biopsies of patients with HBV infection, 10 with autoimmune hepatitis and 15 with liver metastases were investigated as control.

Results:

As expected, in liver biopsies of chronic hepatitis C, staining intensity of perilipin 1 and 2 correlated with the degree of steatosis. Steatosis was not significantly correlated with HCV virus load, yet in confirmation of the literature, steatosis was highest in HCV genotype 3 especially when compared to genotypes 1a and b. Interestingly, besides significant steatosis in most of the liver biopsies with chronic hepatitis B and C as measured by conventional histology and immunohistochemical perilipin stains, also in 36% of the HCV liver biopsies and in 48% of the HBV liver biopsies, perilipin-positive clusters of hepatocytes with focally increased microvesicular steatosis were observed that were only visible in perilipin immunohistochemistry. In RNA-chromogen-in situ hybridization against HCV, neither a clear correlation with infected hepatocytes was found, nor a correlation of perilipin-positive clusters with HBs or HBc-positive clusters in liver biopsies of patients with chronic hepatitis B, although clusters sometimes overlapped. Therefore, we checked the presence of these clusters also in other chronic liver diseases. In autoimmune hepatitis and non-neoplastic livers of patients resected for liver metastases, perilipin-positive clusters could also be noted in varying amounts. Statistically, a correlation (Pearson) between the percentage share of perilipin clusters and the perilipin 2 score was noted. The steatosis judged by H&E staining and the percentage share of perilipin clusters also correlated. GPT (p < 0.001) as well as GOT levels (p < 0.001) correlated positively with the percentage share of perilipin clusters.

Conclusion:

The finding of microvesicular steatotic foci is not only a pathologic feature of viral hepatitis, but appears to be a focal metabolic dysregulation, the significance of which will need further investigations to unravel whether it constitutes a reactive/degenerative or even (early) preneoplastic process. Ribback and coauthors already described clear-cell foci which may match to the steatotic foci, although in our hands, the foci were not visible by conventional histology. Importantly, larger steatotic foci may be detected by radiology and may constitute a differential diagnosis to other primary or secondary liver lesions.

This project contains data of an unfinished dissertation of Selina Schelbert.