Do you see what I see? The role of quality histopathology in scientific study

Variation in diagnostic NAFLD/NASH read-outs in paired liver samples from rodent models

INTRODUCTION

In animal models of non-alcoholic fatty liver disease (NAFLD), assessment of disease severity and treatment effects of drugs rely on histopathological scoring of liver biopsies. However, little is known about the sampling variation in liver samples from animal models of NAFLD, even though several histopathological hallmarks of the disease are known to be affected by sampling variation in patients. The aim of this study was to assess the sampling variation in multiple paired liver biopsies from three commonly used diet-induced rodent models of NAFLD.

METHODS

Eight male C57BL/6 mice, 8 male Sprague Dawley rats and 16 female Hartley guinea pigs were fed a NAFLD-inducing high-fat diet for 16 weeks (mice and rats), 20 or 24 weeks (guinea pigs). After the initial diet period, liver sections were sampled and subsequently assessed by histopathological scoring and biochemical analyses.

RESULTS

Fibrosis was heterogeneously distributed throughout the liver in mice, manifesting as both intra- and interlobular statistically significant differences. Hepatic triglyceride content showed interlobular differences in mice, and both intra- and interlobular differences in guinea pigs (24-week time point) all of which were statistically significant. Also, hepatic cholesterol content was subject to significant intra-lobular sampling variation in mice, and hepatic glycogen content differed significantly between lobes in mice and guinea pigs.

DISCUSSION

Dependent on animal model, both histopathological and biochemical end-points differed between sampling sites in the liver. Based on these findings, we recommend that sample site location is highly standardized and properly reported in order to minimize potential sampling variation and to optimize reproducibility and meaningful comparisons of preclinical studies of NAFLD.

Liver steatosis in Polish children assessed by medicolegal autopsies

BACKGROUND

Cases of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are increasing in the pediatric population. Their growing prevalence coincides with the obesity epidemic. Assessment of the incidence requires liver biopsies on a representative population sample, which are hampered by the absence of indications for invasive examination on children without clinical symptoms. The aim of the current study was to assess the incidence of liver steatosis in the population of children up to 18 years old from Lower Silesia.

METHODS

We retrospectively reviewed 342 medico-legal autopsy reports from 2000 to 2009. We separated a group of 256 children whose death was caused by trauma. Liver steatosis was diagnosed according to the results of histopathological examinations and typical macroscopic imaging.

RESULTS

In the 265 children who died from trauma, liver steatosis was reported in 11 (4.2%) children (6 boys) aged between 6 months and 18 years old. Six of the 11 children (54.5%) were found to be overweight. In all 342 children, steatosis was found in 18 (5.3%) children (13 boys), while NASH was diagnosed in 1 (0.3%). Excess body weight was observed in 55.6% (10/18) of children with steatosis.

CONCLUSIONS

Liver steatosis can occur at any age, even in infancy. Being overweight is a very important risk factor. Gross examination of the liver is insufficient for the diagnosis of steatosis because of its lower sensitivity and specificity. Verification of liver steatosis requires reference histopathological examination.

The controlled attenuation parameter (CAP): a novel tool for the non-invasive evaluation of steatosis using Fibroscan

Steatosis is a reversible and benign condition. However, in a few cases, steatosis is associated with inflammation and hepatocyte changes, and is then defined as steato-hepatitis. Steatosis can also be a co-factor in many chronic liver diseases that can lead to fibrosis and cirrhosis. Although an important parameter, until now, evaluation of steatosis by non-invasive methods has remained challenging. In this paper, we report on the use of a novel non-invasive methodology called a controlled attenuation parameter (CAP). This is based on signals acquired by the Fibroscan, which was developed to specifically assess liver steatosis concomitant to liver stiffness measurements (LSM). CAP's performance from published articles and communications is also reported.

Histopathology of nonalcoholic fatty liver disease

Histological analysis of liver biopsies remains a standard against which other methods of assessment for the presence and amount of hepatic injury due to nonalcoholic fatty liver disease (NAFLD) are measured. Histological evaluation remains the sole method of distinguishing steatosis from advanced forms of NAFLD, i.e. nonalcoholic steatohepatitis (NASH) and fibrosis. Included in the lesions of NAFLD are steatosis, lobular and portal inflammation, hepatocyte injury in the forms of ballooning and apoptosis, and fibrosis. However, patterns of these lesions are as distinguishing as the lesions themselves. Liver injury in adults and children due to NAFLD may have different histological patterns. In this review, the rationale for liver biopsy, as well as the histopathological lesions, the microscopically observable patterns of injury, and the differential diagnoses of NAFLD and NASH are discussed.

Nonalcoholic fatty liver disease/nonalcoholic steatohepatitis: histological diagnostic criteria and scoring systems

Nonalcoholic fatty liver disease (NAFLD) is recognized as the most common cause of chronic liver disease in western countries. NAFLD is etiologically associated with systemic and hepatic insulin resistance and is considered by many as the hepatic manifestation of the metabolic syndrome. NAFLD has a wide histological spectrum ranging from 'simple' steatosis to nonalcoholic steatohepatitis (NASH), which may progress to cirrhosis. Hepatocellular carcinoma may occur in NASH-related cirrhosis. The diagnosis of NAFLD/NASH is based on clinico-pathological criteria. Currently available noninvasive tests for the diagnosis of NASH lack specificity and sensitivity, so liver biopsy, despite its limitations, still remains the 'golden standard' for confirming or excluding NASH in a patient with chronically-elevated liver enzymes and image-detected steatosis. This review examines the currently used criteria for the histopathological diagnosis of NAFLD/NASH in adults and children and the relevant histological scoring systems.

Histopathology of non-alcoholic fatty liver disease

Current imaging methodologies can detect steatosis with increasing accuracy but cannot detect inflammation or pre-cirrhotic fibrosis or remodeling of the liver parenchyma. Imaging also cannot assess types or localization of hepatic steatosis. With the increased use of rodents to study NAFLD/NASH, careful analysis or reading highlights the fact that liver tissue evaluations reported in many of the popular animal models of NAFLD/NASH often do not imitate many of the significant aspects of the human disease, despite similar terminology applied by investigators. This review will focus on the findings in human disease.

Clinical correlates of histopathology in pediatric nonalcoholic steatohepatitis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver disease in American children. Noninvasive means to discriminate between NAFLD and nonalcoholic steatohepatitis (NASH) might diminish the requirement for liver biopsy or predict those at increased risk for progression.

METHODS

Data obtained prospectively from children (age, 6-17 y) enrolled in the NASH Clinical Research Network were analyzed to identify clinical-pathologic correlates of pediatric NAFLD. All participants underwent liver biopsy within 6 months of clinical data that were reviewed by a central pathology committee.

RESULTS

A total of 176 children (mean age, 12.4 y; 77% male) were eligible for inclusion. By using ordinal logistic regression analysis, increasing aspartate aminotransferase (AST) level (odds ratio [OR], 1.017 per U/L; 95% confidence interval [CI], 1.004-1.031) and gamma-glutamyltransferase level (OR, 1.016 per U/L; 95% CI, 1.000-1.033) were associated independently with increasing severity of NASH. Increasing AST level (OR, 1.015 per U/L; 95% CI, 1.006-1.024), increasing white blood cell count (OR, 1.22 per 1000/mm(3); 95% CI, 1.07-1.38), and decreasing hematocrit (OR, 0.87 per %; 95% CI, 0.79-0.96) were associated independently with increasing severity of fibrosis. Area under the receiver operator characteristic curve for a model with AST and alanine aminotransferase was 0.75 (95% CI, 0.66-0.84) and 0.74 (95% CI, 0.63-0.85) for distinguishing steatosis from more advanced forms of NASH and bridging fibrosis from lesser degrees of fibrosis, respectively.

CONCLUSIONS

Certain components of routine laboratory tests are predictive of NAFLD pattern and fibrosis severity, but do not have adequate discriminate power to replace liver biopsy in evaluating pediatric NAFLD.