Histochemical study of hyaluronate in alcoholic liver disease

Hyaluronan synthesis inhibition normalizes ethanol-enhanced hepatic stellate cell activation

BACKGROUND

Chronic ethanol overconsumption promotes alcohol-associated liver disease (ALD), characterized by hepatocyte injury, inflammation, hepatic stellate cell (HSC) activation, and fibrosis. Hyaluronan (HA) concentration is greater in livers and blood from advanced ALD patients than patients with advanced non-ALD. In the liver, HSCs are the major HA producers. The relationship between ethanol, HA, and HSC activation is incompletely understood. Thus, here, we tested the hypothesis that ethanol enhances HSC activation in a HA-dependent manner.

METHODS

Liver tissue microarrays (TMAs) containing steatotic livers from donors with or without a history of alcohol consumption were used to measure HA and collagen content. Mice were fed a moderate (2%, v/v) ethanol-containing diet or pair-fed control diet for 2 days, after which they were given a single carbon tetrachloride (CCl4 ) injection. To inhibit HA synthesis, we provided 4-methylumbelliferone (4MU) daily. We used LX2 cells, a human HSC cell line, to determine the impact ethanol had on LPS responses, with or without concurrent 4MU exposure.

RESULTS

CCl4 induced liver injury, but it did not differ between ethanol or control diet fed mice with or without 4MU treatment. Ethanol feeding enhanced CCl4 -induced hepatic HA content, which was paralleled by HA synthase (Has)2 transcript abundance; 4MU treatment normalized both. Consistently, HSC activation, assessed by measuring αSMA mRNA and protein, was induced by CCl4 exposure, enhanced by ethanol feeding, and normalized by 4MU. Hepatic transcripts, but not protein, for Ccl2 were enhanced by ethanol feeding and normalized by 4MU exposure. Finally, ethanol-exposed LX2 cells made more LPS-stimulated CCL2 mRNA and protein than cells not exposed to ethanol; 4MU prevented this.

CONCLUSION

These data show that ethanol augments HSC activation through HA synthesis and enhances hepatic profibrogenic features. Therefore, targeting HSC HA production could potentially attenuate liver disease in ALD patients.

A review of the clinical utility of the Enhanced Liver Fibrosis test in multiple aetiologies of chronic liver disease

The rising incidence of chronic liver disease continues to be an increasing health burden. The morbidity and mortality associated with chronic liver disease typically occur in patients with advanced fibrosis. Hence, early identification of those at-risk is of vital importance to ensure appropriate ongoing management. Currently, tools for appropriate risk stratification remain limited. Increasing awareness of the limitations of liver biopsy has driven research into alternative non-invasive methods of fibrosis assessment including serological markers assessing functional changes. One such biomarker, the Enhanced Liver Fibrosis test, was initially validated in a cohort of 1021 patients with mixed aetiology chronic liver disease and shown to perform well. Since this pathfinder study, it has been independently validated in cohorts of hepatitis C, non-alcoholic fatty liver disease, alcoholic liver disease, primary biliary cirrhosis and primary sclerosing cholangitis. In addition to performing well as a diagnostic tool, the Enhanced Liver Fibrosis test has been shown to outperform liver biopsy in prognostic studies and is the only non-invasive marker to do so. However, questions remain regarding the use of this test, particularly regarding the possible effect age and alcohol may have on test scores. This review examines the current literature published in relation to the Enhanced Liver Fibrosis test and its clinical utility and highlights areas requiring further study.

Tissue-specific Fixation Methods Are Required for Optimal In Situ Visualization of Hyaluronan in the Ovary, Kidney, and Liver

Hyaluronan (HA) is a ubiquitous component of the extracellular matrix. The spatial-temporal localization of HA can be visualized in situ using biotinylated HA binding proteins (HABPs). This assay is sensitive to fixation conditions, and there are currently no best practices for HA detection. Thus, the goal of this study was to optimize fixation conditions for visualizing HA in the ovary, kidney, and liver through analysis of six commonly used fixatives for HA detection: Bouin's Solution, Carnoy's Solution, Ethanol-Formalin-Glacial Acetic Acid (EFG), Histochoice, Modified Davidson's Solution, and 10% Neutral Buffered Formalin. Organs were harvested from CB6F1 mice and fixed with one of the identified fixatives. Fixed organs were sectioned, and the HABP assay was performed on sections in parallel. Hematoxylin and eosin staining was also performed to visualize tissue architecture. HABP signal localization and intensity varied between fixatives. EFG and Carnoy's Solution best preserved the HA signal intensity in the ovary and liver, showing HA localization in various sub-organ structures. In the kidney, only Modified Davidson's Solution was less than optimal. Our findings demonstrate that fixation can alter the ability to detect HA in tissue macro- and microstructures, as well as localization in a tissue-specific manner, in situ.

Multimodal evaluation of tissue-engineered cartilage

Tissue engineering (TE) has promise as a biological solution and a disease modifying treatment for arthritis. Although cartilage can be generated by TE, substantial inter- and intra-donor variability makes it impossible to guarantee optimal, reproducible results. TE cartilage must be able to perform the functions of native tissue, thus mechanical and biological properties approaching those of native cartilage are likely a pre-requisite for successful implantation. A quality-control assessment of these properties should be part of the implantation release criteria for TE cartilage. Release criteria should certify that selected tissue properties have reached certain target ranges, and should be predictive of the likelihood of success of an implant in vivo. Unfortunately, it is not currently known which properties are needed to establish release criteria, nor how close one has to be to the properties of native cartilage to achieve success. Achieving properties approaching those of native cartilage requires a clear understanding of the target properties and reproducible assessment methodology. Here, we review several main aspects of quality control as it applies to TE cartilage. This includes a look at known mechanical and biological properties of native cartilage, which should be the target in engineered tissues. We also present an overview of the state of the art of tissue assessment, focusing on native articular and TE cartilage. Finally, we review the arguments for developing and validating non-destructive testing methods for assessing TE products.

Expression of hyaluronic acid in N-nitrosodimethylamine induced hepatic fibrosis in rats

Hyaluronic acid (HA) plays prominent role in the pathogenesis of liver fibrosis. The mechanism of increased serum and liver HA during hepatic fibrosis was studied in rats. Liver injury was induced by intraperitoneal injections of N-nitrosodimethylamine (NDMA) for 7 consecutive days. A group of animals were sacrificed on everyday during injection and also on days 14 and 21 after the start of NDMA administration. The alpha-smooth muscle actin (alpha-SMA) was stained as a marker for activated stellate cells. Liver HA was studied by histochemical methods and serum HA was monitored by HA binding protein assay. CD44 was stained immunohistochemically. After the start of NDMA administration, necrosis was initiated on day 3 and massive necrosis was observed on days 5 and 7. Fibrosis was developed on day 14 and early cirrhosis was present on day 21. Staining of alpha-SMA demonstrated activated stellate cells from day 3 onwards. Serum HA peaked on day 7 and reduced afterwards. Serial liver sections stained for HA revealed excessive accumulation of HA during NDMA administration. On days 14 and 21, alpha-SMA and HA staining was remarkable in fibrotic and cirrhotic areas. CD44 staining was negative except during necrosis. It is concluded that the early elevation of serum HA is due to the increased synthesis and simultaneous release from the necrotic liver. In latter stages the increase of both serum and liver HA is contributed by the increased synthesis by the activated stellate cells and reduced clearance by the impaired sinusoidal endothelial cells.

Assessment of prognosis in alcoholic liver disease: can serum hyaluronate replace liver biopsy?

1. Only 15-20% of chronic alcohol misusers ever develop cirrhosis. 2. Currently it is not possible to predict clinically who will develop progressive fibrotic alcoholic liver disease. 3. Liver biopsy is currently the gold standard diagnostic test in alcoholic liver disease, but it has associated morbidity and mortality. 4. Serum hyaluronic acid is a simple non-invasive test that may be able to give an estimate of the severity of fibrosis in alcoholic liver disease. The full clinical assessment of alcoholic liver disease includes liver biopsy, since accurate clinical prediction of the severity of liver damage is extremely difficult in all except very advanced cases. Unfortunately, liver biopsy has an associated complication rate and is contraindicated in, or unacceptable to, some patients. A reliable non-invasive test of the severity of fibrotic disease would be clinically useful at initial clinical assessment in some patients with alcoholic liver disease. Such a test would be more useful in subsequent monitoring of disease progression, and in particular may diminish the need for follow-up liver biopsy. Serum hyaluronic acid has been put forward as such a non-invasive test. Based on current evidence, serum hyaluronic acid may well be a useful adjunctive test in the assessment of certain categories of alcoholic liver disease patients, but at present it is unlikely to displace liver biopsy as the investigation of choice in alcoholic liver disease.

Serum hyaluronate correlates with histological progression in alcoholic liver disease

OBJECTIVES

Chronic alcohol consumption may lead to the development of liver cirrhosis. Serum concentrations of hyaluronate were suggested as a predictor in chronic liver disease, but its power to distinguish between severity of fibrosis and inflammation had not been assessed. In order to evaluate hyaluronate as a marker to detect early stages of alcoholic liver disease and to establish a possible correlation with hepatic histology, serum concentrations were measured by radioimmunoassay in 87 patients with biopsy-proven fatty liver, fatty liver and mild fibrosis, fatty liver and inflammation, severe fibrosis and inflammation, and cirrhosis, and in 12 non-alcoholic control subjects. In addition, serum hyaluronate was determined in 40 non-cirrhotic alcoholic patients with either a normal serum aspartate aminotransferase (AST) or an AST elevated at least two-fold.

RESULTS

Serum hyaluronate increased significantly with advanced stages of alcoholic liver disease, while levels in patients with fatty liver were elevated only slightly without reaching significance. Hyaluronate correlated well with histological stage and was highly sensitive for detecting fibrosis in general and perivenular fibrosis as an indicator of progression to cirrhosis. Hyaluronate levels were not influenced by AST levels.

CONCLUSION

Serum hyaluronate is a good predictor of the presence of even moderate hepatic fibrosis in alcoholic liver disease, justifying its clinical use to assess morphological alterations of the liver in alcoholics.

Biochemical markers for alcohol consumption

A variety of laboratory tests are available to assist in the diagnosis of alcohol consumption and related disorders. The levels of intake at which laboratory results become abnormal vary from person to person. Laboratory tests are particularly useful in settings where cooperativeness is suspected or when a history is not available. Several biochemical and hematological tests, such as γ-glutamyltransferase (GGT) activity, aspartate aminotransferase (AST) activity, high-density lipoprotein cholesterol (HDL-C) content of serum, and erythrocyte mean corpuscular volume (MCV) are established markers of alcohol intake. Their validity as markers is based largely on correlations with recent intake at a single time point and on decreases in elevated values when heavy drinkers abstain from alcohol. These readily available laboratory tests provide important prognostic information and should be integral part of the assessment of persons with hazardous alcohol consumption. There are several other markers with considerable potential for more accurate reflection of recent alcohol intake. These include carbohydrate deficient transferrin, β-hexosaminidase, acetaldehyde adducts and the urinary ratio of serotonin metabolites, 5-hydroxytryptophol and 5-hydroxyindoleacetic acid. These markers provide hope for more sensitive and specific aids to diagnosis and improved monitoring for intake.

Alcoholic liver disease

Important mechanisms responsible for alcohol-induced liver injury include mitochondrial damage and loss of ATP, formation of acetaldehyde-and other aldehyde-protein adducts, release of reactive oxygen species (ROS) from mitochondrial electron transfer chain, CYP2E1 , and activated Kupffer cells (KCs); weakening of antioxidant defense systems; and increased intestinal permeability with endotoxemia. Endotoxin interacts with ethanol and/or acetaldehyde, and such interaction leads to a complex cascade of autocrine and paracrine pathways that involve the release of cytokines (proinflammatory, anti-inflammatory, and mutagenic), chemokines, and eicosanoids. These pathways are mediated by activation of KCs, induction of proliferation, and other phenotype changes in hepatic stellate cells (HSCs) leading to transformation to myofibroblasts (the latter is responsible for fibrogenesis, chemotaxis, and contractility, therefore contributing to portal hypertension, angiogenic response, and release of additional cytokines), and stimulation of sinusoidal cells (SECs) to release adhesive molecules and cytokines. Recent data implicate a likely role of apoptosis as a mechanism of hepatocyte cell death in alcoholic liver disease.