Of mice and women: toward a mouse model of autoimmune hepatitis

Plasma proteomic analysis of autoimmune hepatitis in an improved AIH mouse model

Background

The prevalence of autoimmune hepatitis (AIH) is increasing, and its early clinical diagnosis is difficult. The pathogenesis of AIH remains unclear, and AIH-related studies are largely limited because of lack of suitable mouse models.

Methods

To obtain a good tool for research on AIH, we first established an improved immune-mediated mouse model that can mimic the pathological process of AIH as in the human body, through repeated injections of human cytochrome P450 2D6 (CYP2D6) plasmid. Next, a proteomic analysis based on isobaric tag (IBT) technology was performed to detect the differentially expressed proteins (DEPs), and related biological functions and pathways in the plasma of AIH and normal mice. Finally, we performed enzyme-linked immunosorbent assay (ELISA) to further confirm the most abundant DEP in the plasma of patients with AIH.

Results

Autoantibodies and the characteristic pathology of AIH were observed in our mouse model. Inflammatory infiltration also increased in the livers of AIH mice over time and plateaued by day 42 post the first injection. Chronic hepatitis was most severe on day 35 with the development of fibrosis as well, and the plasma of AIH mice were collected for proteomic analysis. A total of 176 DEPs were found in this experiment, of which 148 DEPs were up-regulated and 28 DEPs were down-regulated. Thirty significant Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways (P < 0.05) were detected. Arginine biosynthesis was found to be the most significant pathway involved in the AIH process. During the Gene Ontology (GO) analysis, most DEPs were found to be involved in the binding, cellular, and metabolic processes. Using ELISA, the most overexpressed DEP, serum amyloid A 1 (SAA1), was confirmed to be increased specifically in the plasma of patients with AIH compared to other chronic hepatitis. Different plasma levels of SAA1 were also found related to different grades of inflammation and stages of fibrosis in the liver of patients with AIH.

Conclusions

Our study is the first to describe the proteomics analysis of a true sense of AIH mouse model, which is beneficial for a better understanding of AIH pathogenesis and identifying potential biomarkers for its clinical diagnosis.

Hepatobiliary pathology

PURPOSE OF REVIEW

Publications concerning liver histopathology in fatty liver disease and chronic hepatitis C, iron and copper overload, and liver transplantation from the past year have been surveyed to highlight useful concepts and diagnostic information.

RECENT FINDINGS

Two microscopic forms of pediatric nonalcoholic steatohepatitis have been described: type 1 in which hepatocyte ballooning and/or pericellular fibrosis accompany the steatosis; and type 2 which has portal tract inflammation and/or fibrosis as the salient accompanying feature. In chronic hepatitis C, the ductular reaction appears to be a major factor associated with fibrosis. In patients transplanted for hepatitis C virus-related cirrhosis, immunostaining of post-transplant liver biopsies for alpha-smooth muscle actin (i.e. in activated hepatic stellate cells) may identify those individuals at risk for severe recurrence. Clinicopathological papers on several forms of non-HFE hemochromatosis were published and Wilson's disease was described in individuals of 60 years or more in age. Cholestasis in childhood was expertly reviewed and histopathologic precursor lesions of hepatocellular carcinoma were also examined in a comprehensive article.

SUMMARY

Recent publications with impact on liver biopsy interpretation include a morphologic classification of nonalcoholic steatohepatitis in childhood, the differential diagnosis of childhood cholestasis and pathogenetic factors involved in fibrogenesis in chronic hepatitis C.

Cost-effectiveness of pharmacotherapy for autoimmune hepatitis

In > 80% of patients with autoimmune hepatitis, steroid therapy alone or in combination with azathioprine results in disease remission. Treatment response results in reversal of fibrosis and excellent long-term survival in many patients, whereas untreated patients may expect a 10-year survival of < 30%. The use of azathioprine monotherapy (2 mg/kg/day) has gained widespread acceptance in maintaining remission in clinical practice. Although all patients with autoimmune hepatitis may not need treatment, particularly those with mild disease, alternative strategies are required in patients who have failed to achieve remission on standard therapy of steroids with or without azathioprine, or patients with azathioprine-induced drug toxicity. In such circumstances, the use of salvage therapy in the form of ciclosporin, tacrolimus or mycophenolate mofetil may be warranted. Liver transplantation is the treatment of choice for patients who present with subacute liver failure or decompensated cirrhosis. Salvage therapy results in an exponential rise in cost with each increment in therapeutic escalation. As an alternative to standard therapy, it has also been suggested that novel therapies such as ciclosporin, tacrolimus or mycophenolate mofetil be initiated to achieve remission. However, a > 10-fold cost differential exists between the charges associated with more potent immunosuppression and standard therapy. Therefore, in evaluating novel immunosuppression in autoimmune hepatitis, it behoves clinicians not only to consider end points pertaining to efficacy, but also end points pertaining to cost-effectiveness. Moreover, the exact role of pharmacogenomics and genotyping of thiopurine methyltransferase in patients with autoimmune hepatitis needs to be fully defined.