Hedgehog pathway activation parallels histologic severity of injury and fibrosis in human nonalcoholic fatty liver disease

Evaluation of the hepatic and subcutaneous adipose tissue effects of triiodothyronine treatment in an animal model of metabolic syndrome

BACKGROUND AND AIMS

Metabolic dysfunction associated steatotic liver disease (MASLD) is a metabolic liver disease and thyroid hormones (TH) may decrease liver fat and extra-hepatic fat content. We aimed to evaluate the effects of high and low dose triiodothyronine (T3) in liver and subcutaneous adipose tissue (sAT) in an animal model of Metabolic Syndrome (MS).

METHODS AND RESULTS

Four groups were evaluated: 1) ZSF1 Lean (Lean-Ctrl, n = 8); 2) ZSF1 obese (rat model of MS with MASLD, MetS, n = 13); 3) ZSF1 obese supplemented with high-dose of T3 (MetS-hT3, n = 5); and 4) ZSF1 obese supplemented with a low-dose of T3 (MetS-lT3, n = 8). Treatment with both doses of T3 decreased body weight, liver weight and perirenal fat. High-dose T3 treatment normalized the increased expression of COL3A1 in MetS group. Histologically, lipid hepatic burden in treated groups was significantly reduced. Adipocytes and adipocytes' fibrosis areas were significantly reduced by the treatment with T3. MetS-hT3 had an increased risk of arrhythmias and sudden death.

CONCLUSION

Treatment with T3 improves steatosis and fibrosis at the liver and sAT in animals with MS. High doses of T3 may not be safe due to the risk of cardiac events. Our results support new therapeutic strategies for MASLD focused on the modulation of TH.

The correlation between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) with non-alcoholic fatty liver disease: an analysis of the population-based NHANES (2017-2018)

Background/objective

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver disorders, from benign steatosis to more severe conditions like non-alcoholic steatohepatitis, with risks of progressing to fibrosis, cirrhosis, and hepatocellular carcinoma. The non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) indicates lipid metabolic dysregulation and is associated with increased risks of various diseases. This study examines the relationship between NHHR and NAFLD to evaluate NHHR as a potential predictive biomarker for NAFLD.

Methods

Data from the 2017-2018 National Health and Nutrition Examination Survey (NHANES) were used for cross-sectional analysis. After excluding individuals with incomplete data, hepatitis infections, heavy alcohol use, and those under 18, the study included 2,757 adults. The relationship between NHHR and NAFLD was analyzed using multivariable logistic regression, including subgroup analysis and interaction testing.

Results

Among the 2,757 participants (mean age 49.91 years), 44.9% had NAFLD. NHHR showed a significant positive association with NAFLD, with an unadjusted odds ratio (OR) of 1.71 and a fully adjusted OR of 1.45. Quartile analysis revealed a 228% higher prevalence of NAFLD in the highest NHHR quartile, with an OR of 3.28. This positive association was consistent across various subgroups.

Conclusion

Our findings suggest that elevated NHHR is positively correlated with the prevalence of NAFLD and possesses predictive value. We recommend that future research validate the clinical utility of NHHR, particularly for early detection of high-risk individuals and guiding personalized interventions.

Hepatic inflammation, ballooning, and pyknosis caused by LED light exposure in a mouse model, with differential effects by age and gender

Light-emitting diode (LED) is commonly used in lighting and digital devices in modern life, which delivers higher levels of blue light than other light sources. Previous work indicated that exposure to blue lights increases serum oxidative stress and affects hepatic functions in animals. However, the detailed hepatic pathogenesis caused by blue lights remains largely elusive. This study investigated the characteristics of hepatic injuries caused by LED light exposure in a mouse model. C57BL/6 mice were exposed the LED lights at 1000 lux, 12 h per day for 45 days or at 4500 lux, 1 h per day for 7 days. The mice were aged 8 weeks or 36 weeks in both genders and maintained under a 12 h light/dark cycle without alteration of diet pattern. Liver tissue sections were obtained for hematoxylin and eosin (H&E) and immunohistochemical staining. The mice with 1000 lux exposure displayed severe liver injuries, including inflammation, ballooning, and pyknosis, which were found to a lesser extent in the 4500 lux mice, and aging aggravated the hepatic injuries. The hepatocellular ballooning was found more severe in the males than the females. In contrast, the females expressed the F4/80 and TNF-α inflammatory markers more evidently. Taken together, LED light exposure may have detrimental effects on liver health, particularly in vulnerable groups such as the elderly and the females with excessive exposure to LED lights, even if they maintain a normal diet and regular light/dark cycles. The potential risk should be considered by both the clinicians and the public.

Fibrosis and Hepatocarcinogenesis: Role of Gene-Environment Interactions in Liver Disease Progression

The liver is a complex organ that performs vital functions in the body. Despite its extraordinary regenerative capacity compared to other organs, exposure to chemical, infectious, metabolic and immunologic insults and toxins renders the liver vulnerable to inflammation, degeneration and fibrosis. Abnormal wound healing response mediated by aberrant signaling pathways causes chronic activation of hepatic stellate cells (HSCs) and excessive accumulation of extracellular matrix (ECM), leading to hepatic fibrosis and cirrhosis. Fibrosis plays a key role in liver carcinogenesis. Once thought to be irreversible, recent clinical studies show that hepatic fibrosis can be reversed, even in the advanced stage. Experimental evidence shows that removal of the insult or injury can inactivate HSCs and reduce the inflammatory response, eventually leading to activation of fibrolysis and degradation of ECM. Thus, it is critical to understand the role of gene-environment interactions in the context of liver fibrosis progression and regression in order to identify specific therapeutic targets for optimized treatment to induce fibrosis regression, prevent HCC development and, ultimately, improve the clinical outcome.

Crosstalk in extrahepatic and hepatic system in NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) has emerged as the most prevalent chronic liver disease globally. Non-alcoholic steatohepatitis (NASH) represents an extremely progressive form of NAFLD, which, without timely intervention, may progress to cirrhosis or hepatocellular carcinoma. Presently, a definitive comprehension of the pathogenesis of NAFLD/NASH eludes us, and pharmacological interventions targeting NASH specifically remain constrained. The aetiology of NAFLD encompasses a myriad of external factors including environmental influences, dietary habits and gender disparities. More significantly, inter-organ and cellular interactions within the human body play a role in the development or regression of the disease. In this review, we categorize the influences affecting NAFLD both intra- and extrahepatically, elaborating meticulously on the mechanisms governing the onset and progression of NAFLD/NASH. This exploration delves into progress in aetiology and promising therapeutic targets. As a metabolic disorder, the development of NAFLD involves complexities related to nutrient metabolism, liver-gut axis interactions and insulin resistance, among other regulatory functions of extraneous organs. It further encompasses intra-hepatic interactions among hepatic cells, Kupffer cells (KCs) and hepatic stellate cells (HSCs). A comprehensive understanding of the pathogenesis of NAFLD/NASH from a macroscopic standpoint is instrumental in the formulation of future therapies for NASH.

Unveiling the role of the Hedgehog signaling pathway in chronic liver disease: Therapeutic insights and strategies

The Hedgehog (Hh) signaling plays a crucial role in adult liver repair by promoting the expansion and differentiation of hepatic progenitor cells into mature hepatocytes and cholangiocytes. Elevated Hh signaling is associated with severe chronic liver diseases, making Hh inhibitors a promising therapeutic option. Sonidegib and vismodegib, both FDA-approved Smoothened (Smo) inhibitors for basal cell carcinoma (BCC), have shown potential for application in chronic liver disorders based on clinical evidence. We highlight the vital role of the Hh pathway in metabolic dysfunction-associated steatotic liver disease (MASLD)/metabolic dysfunction-associated steatohepatitis (MASH), liver fibrosis, and hepatocellular carcinoma (HCC). Moreover, therapeutic strategies targeting the Hh pathway in chronic liver diseases have been discussed, providing a basis for improving disease management and outcomes.

Characterization of a model of liver regeneration: Role of hedgehog signaling in experimental hepatic amoebiasis

The development of amoebic liver abscess (ALA) leads to liver necrosis, accompanied by an exacerbated inflammatory response and the formation of multiple granulomas. Adequate management of the infection through the administration of treatment and the timely response of the organ to the damage allows the injury to heal with optimal regeneration without leaving scar tissue, which does not occur in other types of damage such as viral hepatitis that may conducts to fibrosis or cirrhosis. The Hedgehog signaling pathway (Hh) is crucial in the embryonic stage, while in adults it is usually reactivated in response to acute or chronic injuries, regeneration, and wound healing. In this work, we characterized Hh in experimental hepatic amoebiasis model, with the administration of treatment with metronidazole, as well as a pathway inhibitor (cyclopamine), through histological and immunohistochemical analyses including an ultrastructure analysis through transmission electron microscopy. The results showed an increase in the percentage of lesions obtained, a decrease in the presence of newly formed hepatocytes, a generalized inflammatory response, irregular distribution of type I collagen accompanied by the presence of fibroblast-type cells and a decrease in effector cells of this pathway. These results constitute the first evidence of the association of the activation of Hh with the liver regeneration process in experimental amebiasis.

Exosome prospects in the diagnosis and treatment of non-alcoholic fatty liver disease

The growing prevalence of NAFLD and its global health burden have provoked considerable research on possible diagnostic and therapeutic options for NAFLD. Although various pathophysiological mechanisms and genetic factors have been identified to be associated with NAFLD, its treatment remains challenging. In recent years, exosomes have attracted widespread attention for their role in metabolic dysfunctions and their efficacy as pathological biomarkers. Exosomes have also shown tremendous potential in treating a variety of disorders. With increasing evidence supporting the significant role of exosomes in NAFLD pathogenesis, their theragnostic potential has become a point of interest in NAFLD. Expectedly, exosome-based treatment strategies have shown promise in the prevention and amelioration of NAFLD in preclinical studies. However, there are still serious challenges in preparing, standardizing, and applying exosome-based therapies as a routine clinical option that should be overcome. Due to the great potential of this novel theragnostic agent in NAFLD, further investigations on their safety, clinical efficacy, and application standardization are highly recommended.

Hepatocyte programmed cell death: the trigger for inflammation and fibrosis in metabolic dysfunction-associated steatohepatitis

By replacing and removing defective or infected cells, programmed cell death (PCD) contributes to homeostasis maintenance and body development, which is ubiquitously present in mammals and can occur at any time. Besides apoptosis, more novel modalities of PCD have been described recently, such as necroptosis, pyroptosis, ferroptosis, and autophagy-dependent cell death. PCD not only regulates multiple physiological processes, but also participates in the pathogenesis of diverse disorders, including metabolic dysfunction-associated steatotic liver disease (MASLD). MASLD is mainly classified into metabolic dysfunction-associated steatotic liver (MASL) and metabolic dysfunction-associated steatohepatitis (MASH), and the latter putatively progresses to cirrhosis and hepatocellular carcinoma. Owing to increased incidence and obscure etiology of MASH, its management still remains a tremendous challenge. Recently, hepatocyte PCD has been attracted much attention as a potent driver of the pathological progression from MASL to MASH, and some pharmacological agents have been proved to exert their salutary effects on MASH partly via the regulation of the activity of hepatocyte PCD. The current review recapitulates the pathogenesis of different modalities of PCD, clarifies the mechanisms underlying how metabolic disorders in MASLD induce hepatocyte PCD and how hepatocyte PCD contributes to inflammatory and fibrotic progression of MASH, discusses several signaling pathways in hepatocytes governing the execution of PCD, and summarizes some potential pharmacological agents for MASH treatment which exert their therapeutic effects partly via the regulation of hepatocyte PCD. These findings indicate that hepatocyte PCD putatively represents a new therapeutic point of intervention for MASH.

Intrahepatic hypothyroidism in MASLD: Role of liver-specific thyromimetics including resmetirom

BACKGROUND AND AIMS

Thyroid hormones are important regulators of hepatic lipid homeostasis and whole-body energy expenditure. Recent evidence suggests that euthyroid individuals with metabolic dysfunction-associated steatohepatitis (MASH) develop intrahepatic hypothyroidism that promotes progression of MASH.

METHODS

A literature search was performed with Medline (PubMed), Scopus and Google Scholar electronic databases from inception till March 2024, using the following keywords: hypothyroidism and nonalcoholic fatty liver disease; MASLD and thyroid function; intrahepatic hypothyroidism; TRβ agonists; and resmetirom. Relevant studies were extracted that described pathogenesis of MASH in the context of thyroid functions.

RESULTS

In euthyroid individuals with MASH, there is decreased conversion of prohormone thyroxine (T4) to bioactive tri-iodothyronine (T3) and increased conversion of T4 to inactive metabolite reverse T3 (rT3). Consequently, reduced levels of T3 results in impaired intrahepatic TRβ signaling, a state of intrahepatic hypothyroidism, which promotes progression of MASH. Hepatic TRβ activation leads to metabolically beneficial effects in the liver including mitochondrial fatty acid uptake and β-oxidation, mitochondrial biogenesis, increasing surface low-density lipoprotein (LDL) receptor density and lowering of circulatory LDL-cholesterol. In recent years, selective thyroid hormone mimetics that exhibit TRβ-selective binding and liver-selective uptake have been designed. Resmetirom, a liver-specific thyromimetic, improves intrahepatic TRβ signaling and in clinical trials significantly improved liver inflammation, fibrosis and lipid profile in patients with MASH.

CONCLUSIONS

In euthyroid individuals with MASH, development of intrahepatic hypothyroidism results in further progression of the disease. In clinical trials, resmetirom treatment results in a significant improvement in steatosis, inflammation and fibrosis and is the first drug approved by the US Food and Drug Administration (FDA) for the treatment of noncirrhotic MASH with moderate to advanced fibrosis.

Sonic hedgehog-heat shock protein 90β axis promotes the development of nonalcoholic steatohepatitis in mice

Sonic hedgehog (SHH) and heat shock protein 90β (HSP90β) have been implicated in nonalcoholic steatohepatitis (NASH) but their molecular mechanisms of action remain elusive. We find that HSP90β is a key SHH downstream molecule for promoting NASH process. In hepatocytes, SHH reduces HSP90β ubiquitylation through deubiquitylase USP31, thus preventing HSP90β degradation and promoting hepatic lipid synthesis. HSP90β significantly increases in NASH mouse model, leading to secretion of exosomes enriched with miR-28-5p. miR-28-5p directly targetes and decreases Rap1b levels, which in turn promotes NF-κB transcriptional activity in macrophages and stimulates the expression of inflammatory factors. Genetic deletion, pharmacological inhibition of the SHH-HSP90β axis, or delivery of miR-28-5p to macrophages in the male mice liver, impairs NASH symptomatic development. Importantly, there is a markedly higher abundance of miR-28-5p in NASH patient sera. Taken together, the SHH-HSP90β-miR-28-5p axis offers promising therapeutic targets against NASH, and serum miR-28-5p may serve as a NASH diagnostic biomarker.

High fat diet-induced downregulation of TRPV2 mediates hepatic steatosis via p21 signalling

The global prevalence and incidence of non-alcoholic fatty liver disease (NAFLD) are exhibiting an increasing trend. NAFLD is characterized by a significant accumulation of lipids, though its underlying mechanism is still unknown. Here we report that high-fat diet (HFD) feeding induced hepatic steatosis in mice, which was accompanied by a reduction in the expression and function of hepatic TRPV2. Moreover, conditional knockout of TRPV2 in hepatocytes exacerbated HFD-induced hepatic steatosis. In an in vitro model of NAFLD, TRPV2 regulated lipid accumulation in HepG2 cells, and TRPV2 activation inhibited the expression of the cellular senescence markers p21 and p16, all of which were mediated by AMPK phosphorylation. Finally, we found that administration of probenecid, a TRPV2 agonist, impaired HFD-induced hepatic steatosis and suppressed HFD-induced elevation in p21 and p16. Collectively, our findings imply that hepatic TRPV2 protects against the accumulation of lipids by modulating p21 signalling.

Hepatocellular Ballooning is Due to Highly Pronounced Glycogenosis Potentially Associated with Steatosis and Metabolic Reprogramming

Background and Aims

Hepatocellular ballooning is a common finding in chronic liver disease, mainly characterized by rarefied cytoplasm that often contains Mallory-Denk bodies (MDB). Ballooning has mostly been attributed to degeneration but its striking resemblance to glycogenotic/steatotic changes characterizing preneoplastic hepatocellular lesions in animal models and chronic human liver diseases prompts the question whether ballooned hepatocytes (BH) are damaged cells on the path to death or rather viable cells, possibly involved in neoplastic development.

Methods

Using specimens from 96 cirrhotic human livers, BH characteristics were assessed for their glycogen/lipid stores, enzyme activities, and proto-oncogenic signaling cascades by enzyme- and immunohistochemical approaches with serial paraffin and cryostat sections.

Results

BH were present in 43.8% of cirrhotic livers. Particularly pronounced excess glycogen storage of (glycogenosis) and/or lipids (steatosis) were characteristic, ground glass features and MDB were often observed. Decreased glucose-6-phosphatase, increased glucose-6-phosphate dehydrogenase activity and altered immunoreactivity of enzymes involved in glycolysis, lipid metabolism, and cholesterol biosynthesis were discovered. Furthermore, components of the insulin signaling cascade were upregulated along with insulin dependent glucose transporter glucose transporter 4 and the v-akt murine thymoma viral oncogene homolog/mammalian target of rapamycin signaling pathway associated with de novo lipogenesis.

Conclusions

BH are hallmarked by particularly pronounced glycogenosis with facultative steatosis, many of their features being reminiscent of metabolic aberrations documented in preneoplastic hepatocellular lesions in experimental animals and chronic human liver diseases. Hence, BH are not damaged entities facing death but rather viable cells featuring metabolic reprogramming, indicative of a preneoplastic nature.

Digital pathology for nonalcoholic steatohepatitis assessment

Histological assessment of nonalcoholic fatty liver disease (NAFLD) has anchored knowledge development about the phenotypes of the condition, their natural history and their clinical course. This fact has led to the use of histological assessment as a reference standard for the evaluation of efficacy of drug interventions for nonalcoholic steatohepatitis (NASH) - the more histologically active form of NAFLD. However, certain limitations of conventional histological assessment systems pose challenges in drug development. These limitations have spurred intense scientific and commercial development of machine learning and digital approaches towards the assessment of liver histology in patients with NAFLD. This research field remains an area in rapid evolution. In this Perspective article, we summarize the current conventional assessment of NASH and its limitations, the use of specific digital approaches for histological assessment, and their application to the study of NASH and its response to therapy. Although this is not a comprehensive review, the leading tools currently used to assess therapeutic efficacy in drug development are specifically discussed. The potential translation of these approaches to support routine clinical assessment of NAFLD and an agenda for future research are also discussed.

Hedgehog Signaling: Implications in Liver Pathophysiology

The purpose of this review is to summarize current knowledge about the role of the Hedgehog signaling pathway in liver homeostasis and disease. Hedgehog is a morphogenic signaling pathway that is active in development. In most healthy tissues, pathway activity is restricted to stem and/or stromal cell compartments, where it enables stem cell self-renewal and tissue homeostasis. Aberrant over-activation of Hedgehog signaling occurs in many cancers, including hepatocellular and cholangio-carcinoma. The pathway is also activated transiently in stromal cells of injured tissues and orchestrates normal wound healing responses, including inflammation, vascular remodeling, and fibrogenesis. In liver, sustained Hedgehog signaling in stromal cells plays a major role in the pathogenesis of cirrhosis. Hedgehog signaling was thought to be silenced in healthy hepatocytes. However, recent studies show that targeted disruption of the pathway in hepatocytes dysregulates lipid, cholesterol, and bile acid metabolism, and promotes hepatic lipotoxicity, insulin resistance, and senescence. Hepatocytes that lack Hedgehog activity also produce a secretome that activates Hedgehog signaling in cholangiocytes and neighboring stromal cells to induce inflammatory and fibrogenic wound healing responses that drive progressive fibrosis. In conclusion, Hedgehog signaling must be precisely controlled in adult liver cells to maintain liver health.

Inflammatory signaling in NASH driven by hepatocyte mitochondrial dysfunctions

Liver steatosis, inflammation, and variable degrees of fibrosis are the pathological manifestations of nonalcoholic steatohepatitis (NASH), an aggressive presentation of the most prevalent chronic liver disease in the Western world known as nonalcoholic fatty liver (NAFL). Mitochondrial hepatocyte dysfunction is a primary event that triggers inflammation, affecting Kupffer and hepatic stellate cell behaviour. Here, we consider the role of impaired mitochondrial function caused by lipotoxicity during oxidative stress in hepatocytes. Dysfunction in oxidative phosphorylation and mitochondrial ROS production cause the release of damage-associated molecular patterns from dying hepatocytes, leading to activation of innate immunity and trans-differentiation of hepatic stellate cells, thereby driving fibrosis in NASH.

Enhancement of biochemical and genomic pathways through lycopene-loaded nano-liposomes: Alleviating insulin resistance, hepatic steatosis, and autophagy in obese rats with non-alcoholic fatty liver disease: Involvement of SMO, GLI-1, and PTCH-1 genes

Non-alcoholic fatty liver (NAFL) is a prevalent hepatic disorder of global significance that can give rise to severe complications. This research endeavor delves into the potential of nano-liposomal formulated Lycopene (Lip-Lyco) in averting the development of obesity and insulin resistance, both of which are major underlying factors contributing to NAFL. The investigation further scrutinizes the impact of Lip-Lyco on intricate cellular pathways within the liver tissue of rats induced with NAFL, specifically focusing on the progression of steatosis and fibrosis. To establish an obesity-NAFL model, twenty rats were subjected to a high-fat diet (HFD) for a duration of twelve weeks, after which they received an oral treatment of Lip-Lyco (10mg/kg) for an additional eight weeks. Another group of sixteen non-obese rats were subjected to treatment with or without Lip-Lyco, serving as a control for comparison. Results: The rats on a hypercaloric diet had high body mass index (BMI) and insulin resistance, reflected in disturbed serum adipokines and lipid profiles. Oxidative stress, inflammation, and apoptosis were evident in hepatic tissue, and the autophagic process in hepatocytes was inhibited. Additionally, the hedgehog pathway was activated in the liver tissue of NAFL group. Lip-Lyco was found to counteract all these aspects of NAFL pathogenesis. Lip-Lyco exhibited antioxidant, anti-inflammatory, hypoglycemic, antiapoptotic, autophagy-inducing, and Hedgehog signaling inhibitory effects. This study concludes that Lip-Lyco, a natural compound, has promising therapeutic potential in combating NAFLdisease. However, more experimental and clinical studies are required to confirm the effectiveness of lycopene in treating NAFLdisease.

Study on inflammation and fibrogenesis in MAFLD from 2000 to 2022: a bibliometric analysis

Chronic inflammation and fibrosis are significant factors in the pathogenesis of metabolic-associated fatty liver disease (MAFLD). In this study, we conducted a bibliometric analysis of publications on inflammation and fibrogenesis in MAFLD, with a focus on reporting publication trends. Our findings indicate that the USA and China are the most productive countries in the field, with the University of California San Diego being the most productive institution. Over the past 23 years, Prof. Diehl AM has published 25 articles that significantly contributed to the research community. Notably, the research focus of the field has shifted from morbid obesity and adiponectin to metabolic syndrome, genetics, and microbiome. Our study provides a comprehensive and objective summary of the historical characteristics of research on inflammation and fibrogenesis in MAFLD, which will be of interest to scientific researchers in this field.

Secretome of senescent hepatic stellate cells favors malignant transformation from nonalcoholic steatohepatitis-fibrotic progression to hepatocellular carcinoma

Background: Hepatic fibrosis is a premalignant lesion, and how injured hepatocytes transform into malignancy in a fibrotic microenvironment is poorly understood. Senescence is one of major fates of activated hepatic stellate cells (HSCs). Paucity of literature is available regarding the influence of senescent HSCs on behavior of steatotic hepatocytes. Methods: Senescent HSCs were identified in a murine model of nonalcoholic steatohepatitis (NASH)-fibrosis-hepatocellular carcinoma (HCC) and human NASH-HCC specimens. Secretome of senescent HSCs was analyzed by label-free mass-spectrum (NanoRPLC-MS/MS) and verified quantitatively. Results: Senescent HSCs were increased along with the progression from nonalcoholic fatty liver (NAFL), NASH to NASH-fibrosis, and reached a peak at the stage of advanced fibrosis and then decreased when hepatocellular dysplasia or HCC was developed. Critical components affecting proliferation, epithelial-mesenchymal transition (EMT) or migration were identified from secretome of senescent HSCs, and may activate morphogenic hedgehog or oncogenic Wnt signaling pathways to accelerate malignant transformation of steatotic or dysplastic hepatocytes. Primary hepatocytes stimulated with conditioned medium from senescent HSCs, in co-culture or co-cultured in 3D spheroids with senescent HSCs exhibited an enhanced proliferating or EMT profile. Conclusion: Senescent HSCs secreted a characterized protein profile favoring malignant transformation of steatotic or dysplastic hepatocytes through activating morphogenic hedgehog or oncogenic Wnt signaling pathways in the progression from NASH to malignancy.

Ductular reaction in non-alcoholic fatty liver disease: When Macbeth is perverted

Non-alcoholic fatty liver disease (NAFLD) or metabolic (dysfunction)-associated fatty liver disease is the leading cause of chronic liver diseases defined as a disease spectrum comprising hepatic steatosis, non-alcoholic steatohepatitis (NASH), liver fibrosis, cirrhosis, and hepatic carcinoma. NASH, characterized by hepatocyte injury, steatosis, inflammation, and fibrosis, is associated with NAFLD prognosis. Ductular reaction (DR) is a common compensatory reaction associated with liver injury, which involves the hepatic progenitor cells (HPCs), hepatic stellate cells, myofibroblasts, inflammatory cells (such as macrophages), and their secreted substances. Recently, several studies have shown that the extent of DR parallels the stage of NASH and fibrosis. This review summarizes previous research on the correlation between DR and NASH, the potential interplay mechanism driving HPC differentiation, and NASH progression.

Differential Lipidomics, Metabolomics and Immunological Analysis of Alcoholic and Non-Alcoholic Steatohepatitis in Mice

Non-alcoholic steatohepatitis (NASH) and alcoholic steatohepatitis (ASH) are the leading causes of liver disease worldwide. To identify disease-specific pathomechanisms, we analyzed the lipidome, metabolome and immune cell recruitment in livers in both diseases. Mice harboring ASH or NASH had comparable disease severities regarding mortality rate, neurological behavior, expression of fibrosis marker and albumin levels. Lipid droplet size was higher in NASH than ASH and qualitative differences in the lipidome were mainly based on incorporation of diet-specific fatty acids into triglycerides, phosphatidylcholines and lysophosphatidylcholines. Metabolomic analysis showed downregulated nucleoside levels in both models. Here, the corresponding uremic metabolites were only upregulated in NASH suggesting stronger cellular senescence, which was supported by lower antioxidant levels in NASH as compared to ASH. While altered urea cycle metabolites suggest increased nitric oxide synthesis in both models, in ASH, this depended on increased L-homoarginine levels indicating a cardiovascular response mechanism. Interestingly, only in NASH were the levels of tryptophan and its anti-inflammatory metabolite kynurenine upregulated. Fittingly, high-content immunohistochemistry showed a decreased macrophage recruitment and an increased polarization towards M2-like macrophages in NASH. In conclusion, with comparable disease severity in both models, higher lipid storage, oxidative stress and tryptophan/kynurenine levels were seen in NASH, leading to distinct immune responses.

Peroxisome Proliferator-Activated Receptor-γ as a Target and Regulator of Epigenetic Mechanisms in Nonalcoholic Fatty Liver Disease

Peroxisome proliferator-activated receptor-γ (PPARγ) belongs to the superfamily of nuclear receptors that control the transcription of multiple genes. Although it is found in many cells and tissues, PPARγ is mostly expressed in the liver and adipose tissue. Preclinical and clinical studies show that PPARγ targets several genes implicated in various forms of chronic liver disease, including nonalcoholic fatty liver disease (NAFLD). Clinical trials are currently underway to investigate the beneficial effects of PPARγ agonists on NAFLD/nonalcoholic steatohepatitis. Understanding PPARγ regulators may therefore aid in unraveling the mechanisms governing the development and progression of NAFLD. Recent advances in high-throughput biology and genome sequencing have greatly facilitated the identification of epigenetic modifiers, including DNA methylation, histone modifiers, and non-coding RNAs as key factors that regulate PPARγ in NAFLD. In contrast, little is still known about the particular molecular mechanisms underlying the intricate relationships between these events. The paper that follows outlines our current understanding of the crosstalk between PPARγ and epigenetic regulators in NAFLD. Advances in this field are likely to aid in the development of early noninvasive diagnostics and future NAFLD treatment strategies based on PPARγ epigenetic circuit modification.

Activation of the hedgehog signaling pathway is associated with the promotion of cell proliferation and epithelial-mesenchymal transition in chronic rhinosinusitis with nasal polyps

PURPOSE

To investigate the pathogenesis of the hedgehog (Hh) signaling pathway activated by inflammation in the development of chronic rhinosinusitis with nasal polyps (CRSwNP).

METHODS

The 82 people including CRSwNP patients (case group) and nasal septal deviation patients (control group) were recruited. The samples in the case group were collected and classified into two groups: mucosal tissue of nasal polyps (NP group) and mucosal tissue adjacent to nasal polyps (NM group), the samples were collected from the control group as CM group. Clinical characteristics were assessed. Hematoxylin and eosin (H&E) and immunohistochemical (IHC) staining were performed to detect eosinophils (EOS), the expression of the key genes of the pathway and epithelial-mesenchymal transition (EMT) markers in the samples.

RESULTS

There were significant differences in the nasal obstruction visual analog scale (VAS) score, rhinorrhea VAS score, percentage of blood EOS, blood EOS absolute counts and tissue EOS counts in the case group compared with the control group (P < 0.05). The EOS level and expression levels of PTCH1, SMO, Gli1, Gli2, Ki67 and vimentin were higher in NP group than in the other two groups (P < 0.05). E-cadherin expression was decreased in NP group (P < 0.05). A positive correlation between PTCH1 expression and CRSwNP Lund-Mackay score in NP group.

CONCLUSIONS

Our results indicated that the activation of Hh signaling pathway might promote cell proliferation and EMT occurrence, ultimately leading to the development of CRSwNP, which might provide a new target for treatment.

Hepatic Stellate Cells: Dictating Outcome in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a fast growing, chronic liver disease affecting ∼25% of the global population. Nonalcoholic fatty liver disease severity ranges from the less severe simple hepatic steatosis to the more advanced nonalcoholic steatohepatitis (NASH). The presence of NASH predisposes individuals to liver fibrosis, which can further progress to cirrhosis and hepatocellular carcinoma. This makes hepatic fibrosis an important indicator of clinical outcomes in patients with NASH. Hepatic stellate cell activation dictates fibrosis development during NASH. Here, we discuss recent advances in the analysis of the profibrogenic pathways and mediators of hepatic stellate cell activation and inactivation, which ultimately determine the course of disease in nonalcoholic fatty liver disease/NASH.

A novel mechanistic approach for the anti-fibrotic potential of rupatadine in rat liver via amendment of PAF/NF-ĸB p65/TGF-β1 and hedgehog/HIF-1α/VEGF trajectories

Hepatic fibrosis is one of the major worldwide health concerns which requires tremendous research due to the limited outcomes of the current therapies. The present study was designed to assess, for the first time, the potential therapeutic effect of rupatadine (RUP) in diethylnitrosamine (DEN)-induced liver fibrosis and to explore its possible mechanistic actions. For the induction of hepatic fibrosis, rats were treated with DEN (100 mg/kg, i.p.) once weekly for 6 consecutive weeks, and on the 6th week, RUP (4 mg/kg/day, p.o.) was administered for 4 weeks. Treatment with RUP ameliorated changes in body weights, liver indices, liver function enzymes, and histopathological alterations induced by DEN. Besides, RUP amended oxidative stress, which led to the inhibition of PAF/NF-κB p65-induced inflammation, and, subsequently, prevention of TGF-β1 elevation and HSCs activation as indicated by reduced α-SMA expression and collagen deposition. Moreover, RUP exerted significant anti-fibrotic and anti-angiogenic effects by suppressing Hh and HIF-1α/VEGF signaling pathways. Our results highlight, for the first time, a promising anti-fibrotic potential of RUP in rat liver. The molecular mechanisms underlying this effect involve the attenuation of PAF/NF-κB p65/TGF-β1 and Hh pathways and, subsequently, the pathological angiogenesis (HIF-1α/VEGF).

Screening of Biomarkers in Liver Tissue after Bariatric Surgery Based on WGCNA and SVM-RFE Algorithms

As the most common chronic liver disease around the world, nonalcoholic fatty liver disease (NAFLD) has a close connection with obesity, diabetes, and metabolic syndrome. Bariatric surgery (BS) is considered to be the most effective treatment for NAFLD. However, the regulatory mechanism of hepatic lipid metabolism after BS remains poorly elucidated. By analyzing two transcriptome datasets regarding liver tissues after BS, namely, GSE83452 and GSE106737, we acquired 110 differentially expressed genes (DEGs). By further analysis of DEGs in terms of the weighted gene coexpression network analysis (WGCNA) and support vector machine-recursive feature elimination (SVM-RFE) algorithms, we identified four crucial genes participating in the regulation of hepatic lipid metabolism: SRGN, THEMIS2, SGK1, and FPR3. In addition, the results of gene set enrichment analysis (GSEA) showed that BS can activate immune-related regulatory pathways and change immune cell infiltration levels. Finally, through cellular level studies, we found that the silencing of SRGN affects the expression of SREBP-1, SIRT1, and FAS during adipogenesis in the liver and the formation of lipid droplets in the liver. In summary, the immune system in the liver is activated after BS, and SRGN participates in the regulation of hepatic lipid metabolism.

Cardiovascular and lipid-lowering effects of a marine lipoprotein extract in a high-fat diet-induced obesity mouse model

Obesity is a major health challenge worldwide, with implications for diabetes, hypertension and cardiovascular disease (CVD). Regular consumption of dark-meat fish is linked to a lower incidence of CVD and associated metabolic disorders due to the presence of long-chain omega-3 fatty acid ethyl esters in fish oils. The aim of the present study was to determine whether a marine compound like a sardine lipoprotein extract (RCI-1502), regulates fat accumulation in the heart of a high-fat diet-induced (HFD) mouse model of obesity. To investigate its effects in the heart and liver, we conducted a randomized, 12-week placebo-controlled study in which we analyzed the expression of vascular inflammation markers, obesity biochemical patterns and related CVD pathologies. Male HFD-fed mice treated with a RCI-1502-supplemented diet showed reduced body weight, abdominal fat tissue and pericardial fat pad mass density without systemic toxicity. RCI-1502 significantly reduced triacylglyceride, low-density lipoprotein and total-cholesterol concentrations in serum, but increased HDL-cholesterol levels. Our data show that RCI-1502 is beneficial for reducing obesity associated with a long-term HFD, possibly by exerting a protective effect on lipidic homeostasis, indicated also by histopathological analysis. These results collectively indicate that RCI-1502 acts as a cardiovascular therapeutic nutraceutical agent, which modulates fat-induced inflammation and improves metabolic health.

Fatty Liver Disease-Alcoholic and Non-Alcoholic: Similar but Different

In alcohol-induced liver disease (ALD) and in non-alcoholic fatty liver disease (NAFLD), there are abnormal accumulations of fat in the liver. This phenomenon may be related to excessive alcohol consumption, as well as the combination of alcohol consumption and medications. There is an evolution from simple steatosis to steatohepatitis, fibrosis and cirrhosis leading to hepatocellular carcinoma (HCC). Hepatic pathology is very similar regarding non-alcoholic fatty liver disease (NAFLD) and ALD. Initially, there is lipid accumulation in parenchyma and progression to lobular inflammation. The morphological changes in the liver mitochondria, perivenular and perisinusoidal fibrosis, and hepatocellular ballooning, apoptosis and necrosis and accumulation of fibrosis may lead to the development of cirrhosis and HCC. Medical history of ethanol consumption, laboratory markers of chronic ethanol intake, AST/ALT ratio on the one hand and features of the metabolic syndrome on the other hand, may help in estimating the contribution of alcohol intake and the metabolic syndrome, respectively, to liver steatosis.

Hepatocyte Smoothened Activity Controls Susceptibility to Insulin Resistance and Nonalcoholic Fatty Liver Disease

BACKGROUND & AIMS

Nonalcoholic steatohepatitis (NASH), a leading cause of cirrhosis, strongly associates with the metabolic syndrome, an insulin-resistant proinflammatory state that disrupts energy balance and promotes progressive liver degeneration. We aimed to define the role of Smoothened (Smo), an obligatory component of the Hedgehog signaling pathway, in controlling hepatocyte metabolic homeostasis and, thereby, susceptibility to NASH.

METHODS

We conditionally deleted Smo in hepatocytes of healthy chow-fed mice and performed metabolic phenotyping, coupled with single-cell RNA sequencing (RNA-seq), to characterize the role of hepatocyte Smo in regulating basal hepatic and systemic metabolic homeostasis. Liver RNA-seq datasets from 2 large human cohorts were also analyzed to define the relationship between Smo and NASH susceptibility in people.

RESULTS

Hepatocyte Smo deletion inhibited the Hedgehog pathway and promoted fatty liver, hyperinsulinemia, and insulin resistance. We identified a plausible mechanism whereby inactivation of Smo stimulated the mTORC1-SREBP1c signaling axis, which promoted lipogenesis while inhibiting the hepatic insulin cascade. Transcriptomics of bulk and single Smo-deficient hepatocytes supported suppression of insulin signaling and also revealed molecular abnormalities associated with oxidative stress and mitochondrial dysfunction. Analysis of human bulk RNA-seq data revealed that Smo expression was (1) highest in healthy livers, (2) lower in livers with NASH than in those with simple steatosis, (3) negatively correlated with markers of insulin resistance and liver injury, and (4) declined progressively as fibrosis severity worsened.

CONCLUSIONS

The Hedgehog pathway controls insulin sensitivity and energy homeostasis in adult livers. Loss of hepatocyte Hedgehog activity induces hepatic and systemic metabolic stress and enhances susceptibility to NASH by promoting hepatic lipoxicity and insulin resistance.

Cerebrolysin Use in Patients with Liver Damage-A Translational Study

The treatment of acute life-threatening events in patients suffering from chronic pathologies is problematic, as physicians need to consider multisystemic drug effects. Regarding Cerebrolysin, a Sonic Hedgehog signaling pathway amplifier and one of the few approved neurotrophic treatments for stroke patients, concerns of excessive Hedgehog pathway activation that could accelerate NAFLD progression to cirrhosis seem valid. We investigated stroke patients treated with Cerebrolysin that presented elevated levels of aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT). We also investigated the efficiency of Cerebrolysin in reversing the neurogenesis inhibition within the hippocampus in a mouse model of NAFLD by evaluating behavior and histological outcomes. NeuN, BrdU and Iba1 positive signals in the cortex and hippocampus of the animals were also observed. Clinically, Cerebrolysin improved AST levels in a majority of stroke patients with hepatic damage. The same treatment in an experimental setup was able to reverse anxiety-like behavior in MCD mice, reducing their freezing time from 333.61 ± 21.81 s in MCD animals to 229.17 ± 26.28 in treated ones. The use of Cerebrolysin did not improve short-term memory nor rescued cell multiplication in the hippocampus after MCD food intake. Understanding the neuroprotective and neurotrophic effects that drugs have on NAFLD patients can significantly contribute to a suitable therapeutic approach.

Identification of Key Biomarkers and Immune Infiltration in Liver Tissue after Bariatric Surgery

Background

Few drugs are clearly available for nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH); nevertheless, mounting studies have provided sufficient evidence that bariatric surgery is efficient for multiple metabolic diseases, including NAFLD and NASH, while the molecular mechanisms are still poorly understood.

Methods

The mRNA expression profiling of GSE48452 and GSE83452 were retrieved and obtained from the Gene Expression Omnibus (GEO) database. The limma package was employed for identifying differentially expressed genes (DEGs), followed by clusterProfiler for performing Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, and GSEA software for performing GSEA analyses. The PPI network analyses were constructed using Metascape online analyses. WGCNA was also utilized to identify and verify the hub genes. CIBERSORT tools contributed to the analysis of immune cell infiltration of liver diseases.

Results

We identify coexpressed differential genes including 10 upregulated and 55 downregulated genes in liver tissue after bariatric surgery. GO and KEGG enrichment analyses indicated that DEGs were remarkably involved in the immune response. GSEA demonstrated that DEGs were markedly enriched in the immune response before surgery, while most were enriched in metabolism after surgery. Seven genes were screened through the MCC algorithm and KME values, including SRGN, CD53, EVI2B, MPEG1, NCKAP1L, LCP1, and TYROBP. The mRNA levels of these genes were verified in the Attie Lab Diabetes Database, and only LCP1 was found to have significant differences and correlation with certain immune cells.

Conclusion

Our knowledge of the mechanisms by which bariatric surgery benefits the liver and the discovery of LCP1 is expected to serve as potential biomarkers or therapeutic targets for NAFLD and NASH.

Hedgehog Signaling: Linking Embryonic Lung Development and Asthmatic Airway Remodeling

The development of the embryonic lung demands complex endodermal-mesodermal interactions, which are regulated by a variety of signaling proteins. Hedgehog (Hh) signaling is vital for lung development. It plays a key regulatory role during several morphogenic mechanisms, such as cell growth, differentiation, migration, and persistence of cells. On the other hand, abnormal expression or loss of regulation of Hh signaling leads to airway asthmatic remodeling, which is characterized by cellular matrix modification in the respiratory system, goblet cell hyperplasia, deposition of collagen, epithelial cell apoptosis, proliferation, and activation of fibroblasts. Hh also targets some of the pathogens and seems to have a significant function in tissue repairment and immune-related disorders. Similarly, aberrant Hh signaling expression is critically associated with the etiology of a variety of other airway lung diseases, mainly, bronchial or tissue fibrosis, lung cancer, and pulmonary arterial hypertension, suggesting that controlled regulation of Hh signaling is crucial to retain healthy lung functioning. Moreover, shreds of evidence imply that the Hh signaling pathway links to lung organogenesis and asthmatic airway remodeling. Here, we compiled all up-to-date investigations linked with the role of Hh signaling in the development of lungs as well as the attribution of Hh signaling in impairment of lung expansion, airway remodeling, and immune response. In addition, we included all current investigational and therapeutic approaches to treat airway asthmatic remodeling and immune system pathway diseases.

Complexity of ballooned hepatocyte feature recognition: Defining a training atlas for artificial intelligence-based imaging in NAFLD

BACKGROUND & AIMS

Histologically assessed hepatocyte ballooning is a key feature discriminating non-alcoholic steatohepatitis (NASH) from steatosis (NAFL). Reliable identification underpins patient inclusion in clinical trials and serves as a key regulatory-approved surrogate endpoint for drug efficacy. High inter/intra-observer variation in ballooning measured using the NASH CRN semi-quantitative score has been reported yet no actionable solutions have been proposed.

METHODS

A focused evaluation of hepatocyte ballooning recognition was conducted. Digitized slides were evaluated by 9 internationally recognized expert liver pathologists on 2 separate occasions: each pathologist independently marked every ballooned hepatocyte and later provided an overall non-NASH NAFL/NASH assessment. Interobserver variation was assessed and a 'concordance atlas' of ballooned hepatocytes generated to train second harmonic generation/two-photon excitation fluorescence imaging-based artificial intelligence (AI).

RESULTS

The Fleiss kappa statistic for overall interobserver agreement for presence/absence of ballooning was 0.197 (95% CI 0.094-0.300), rising to 0.362 (0.258-0.465) with a ≥5-cell threshold. However, the intraclass correlation coefficient for consistency was higher (0.718 [0.511-0.900]), indicating 'moderate' agreement on ballooning burden. 133 ballooned cells were identified using a ≥5/9 majority to train AI ballooning detection (AI-pathologist pairwise concordance 19-42%, comparable to inter-pathologist pairwise concordance of between 8-75%). AI quantified change in ballooned cell burden in response to therapy in a separate slide set.

CONCLUSIONS

The substantial divergence in hepatocyte ballooning identified amongst expert hepatopathologists suggests that ballooning is a spectrum, too subjective for its presence or complete absence to be unequivocally determined as a trial endpoint. A concordance atlas may be used to train AI assistive technologies to reproducibly quantify ballooned hepatocytes that standardize assessment of therapeutic efficacy. This atlas serves as a reference standard for ongoing work to refine how ballooning is classified by both pathologists and AI.

LAY SUMMARY

For the first time, we show that, even amongst expert hepatopathologists, there is poor agreement regarding the number of ballooned hepatocytes seen on the same digitized histology images. This has important implications as the presence of ballooning is needed to establish the diagnosis of non-alcoholic steatohepatitis (NASH), and its unequivocal absence is one of the key requirements to show 'NASH resolution' to support drug efficacy in clinical trials. Artificial intelligence-based approaches may provide a more reliable way to assess the range of injury recorded as "hepatocyte ballooning".

Hepatic stellate cell activation by TGFβ induces hedgehog signaling and endoplasmic reticulum stress simultaneously

Activation of hepatic stellates (HSCs) is known as the major cause of initiation and progression of liver fibrosis. A wide array of events occurs during HSC activation including induction of hedgehog (Hh) signaling and endoplasmic reticulum (ER) stress. Targeting HSC activation may provide promising insights into liver fibrosis treatment. In this regard, establishing in vitro models which can mimic the molecular pathways of interest is very important. We aimed to activate HSC in which Hh signaling and ER stress are stimulated simultaneously. We used 5 ng/ml TGFβ to activate LX-2 cells, HSC cell line. Gene expression analysis using qRT-PCR, immunostaining and immunoblotting were performed to show HSC activation associated markers. Furthermore, the migration capacity of the TGFβ treated cells is evaluated. The results demonstrated that major fibrogenic markers including collagen1a, lysyl oxidase, and tissue inhibitor of matrix metalloproteinase 1 genes are up-regulated significantly. In addition, our immunofluorescence and immunoblotting results showed that protein levels of GLI-2 and XBP1, were enhanced. Moreover, we found that TGFβ treatment reduced the migration of LX-2 cells. Our results are compatible with high throughput data analysis with respect to differentially expressed genes of activated HSC compared to the quiescent ones. Moreover, our findings suggest that quercetin can reduce fibrogenic markers of activated HSCs as well as osteopontin expression, a target gene of hedgehog signaling.

The Potential Role of Cellular Senescence in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) represents an increasing global health burden. Cellular senescence develops in response to cellular injury, leading not only to cell cycle arrest but also to alterations of the cellular phenotype and metabolic functions. In this review, we critically discuss the currently existing evidence for the involvement of cellular senescence in NAFLD in order to identify areas requiring further exploration. Hepatocyte senescence can be a central pathomechanism as it may foster intracellular fat accumulation, fibrosis and inflammation, also due to secretion of senescence-associated inflammatory mediators. However, in some non-parenchymal liver cell types, such as hepatic stellate cells, senescence may be beneficial by reducing the extracellular matrix deposition and thereby reducing fibrosis. Deciphering the detailed interaction between NAFLD and cellular senescence will be essential to discover novel therapeutic targets halting disease progression.

Loss of Hilnc prevents diet-induced hepatic steatosis through binding of IGF2BP2

The Hedgehog (Hh) signalling pathway plays a critical role in regulating liver lipid metabolism and related diseases. However, the underlying mechanisms are poorly understood. Here, we show that the Hh signalling pathway induces a previously undefined long non-coding RNA (Hilnc, Hedgehog signalling-induced long non-coding RNA), which controls hepatic lipid metabolism. Mutation of the Gli-binding sites in the Hilnc promoter region (Hilnc^BM/BM) decreases the expression of Hilnc in vitro and in vivo. Hilnc^BM/BM and Hilnc-knockout mice are resistant to diet-induced obesity and hepatic steatosis through attenuation of the peroxisome proliferator-activated receptor signalling pathway, as Hilnc directly interacts with IGF2BP2 to enhance Pparγ mRNA stability. Furthermore, we identify a potential functional human homologue of Hilnc, h-Hilnc, which has a similar function in regulating cellular lipid metabolism. These findings uncover a critical role of the Hh-Hilnc-IGF2BP2 signalling axis in lipid metabolism and suggest a potential therapeutic target for the treatment of diet-induced hepatic steatosis.

Zonation in NASH - A key paradigm for understanding pathophysiology and clinical outcomes

Non-alcoholic fatty liver disease (NAFLD) exists as a spectrum ranging from simple steatosis to histologically defined hepatocyte injury and inflammatory changes that define steatohepatitis (NASH), and increase risk for fibrosis. Although zonal differences in NASH have not been systematically studied, periportal involvement has been associated with worse metabolic outcomes and more hepatic fibrosis as compared to pericentral disease. These data suggest that hepatic zonation of disease may influence the diversity of clinical presentations. Similarly, several randomized clinical trials suggest a differential response based on zonation of disease, with preferential effects on periportal (cysteamine) or pericentral disease (obeticholic acid, pioglitazone). Intriguingly, morphogenic pathways known to affect zonal development and maintenance - WNT/β-Catenin, Hedgehog, HIPPO/Yap/TAZ and Notch - have been implicated in NASH pathogenesis, and nuclear hormone receptors downstream of potential NASH therapeutics show zonal preferences. In this review, we summarize these data and propose that patient-specific activation of these pathways may explain the variability in clinical presentation, and the zone-specific response observed in clinical trials.

Dysregulation of the ESRP2-NF2-YAP/TAZ axis promotes hepatobiliary carcinogenesis in non-alcoholic fatty liver disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD), the hepatic correlate of the metabolic syndrome, is a major risk factor for hepatobiliary cancer (HBC). Although chronic inflammation is thought to be the root cause of all these diseases, the mechanism whereby it promotes HBC in NAFLD remains poorly understood. Herein, we aim to evaluate the hypothesis that inflammation-related dysregulation of the ESRP2-NF2-YAP/TAZ axis promotes HB carcinogenesis.

METHODS

We use murine NAFLD models, liver biopsies from patients with NAFLD, human liver cancer registry data, and studies in liver cancer cell lines.

RESULTS

Our results confirm the hypothesis that inflammation-related dysregulation of the ESRP2-NF2-YAP/TAZ axis promotes HB carcinogenesis, supporting a model whereby chronic inflammation suppresses hepatocyte expression of ESRP2, an RNA splicing factor that directly targets and activates NF2, a tumor suppressor that is necessary to constrain YAP/TAZ activation. The resultant loss of NF2 function permits sustained YAP/TAZ activity that drives hepatocyte proliferation and de-differentiation.

CONCLUSION

Herein, we report on a novel mechanism by which chronic inflammation leads to sustained activation of YAP/TAZ activity; this imposes a selection pressure that favors liver cells with mutations enabling survival during chronic oncogenic stress.

LAY SUMMARY

Non-alcoholic fatty liver disease (NAFLD) increases the risk of hepatobiliary carcinogenesis. However, the underlying mechanism remains unknown. Our study demonstrates that chronic inflammation suppresses hepatocyte expression of ESRP2, an adult RNA splicing factor that activates NF2. Thus, inactive (fetal) NF2 loses the ability to activate Hippo kinases, leading to the increased activity of downstream YAP/TAZ and promoting hepatobiliary carcinogenesis in chronically injured livers.

Pathophysiological communication between hepatocytes and non-parenchymal cells in liver injury from NAFLD to liver fibrosis

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial disease that encompasses a spectrum of pathological conditions, ranging from simple steatosis (NAFL), nonalcoholic steatohepatitis (NASH), fibrosis/cirrhosis which can further progress to hepatocellular carcinoma and liver failure. The progression of NAFL to NASH and liver fibrosis is closely associated with a series of liver injury resulting from lipotoxicity, oxidative stress, redox imbalance (excessive nitric oxide), ER stress, inflammation and apoptosis that occur sequentially in different liver cells which ultimately leads to the activation of liver regeneration and fibrogenesis, augmenting collagen and extracellular matrix deposition and promoting liver fibrosis and cirrhosis. Type 2 diabetes is a significant risk factor in NAFLD development by accelerating liver damage. Here, we overview recent findings from human study and animal models on the pathophysiological communication among hepatocytes (HCs), Kupffer cells (KCs), hepatic stellate cells (HSCs) and liver sinusoidal endothelial cells (LSECs) during the disease development. The mechanisms of crucial signaling pathways, including Toll-like receptor, TGFβ and hedgehog mediated hepatic injury are also discussed. We further highlight the potentials of precisely targeting hepatic individual cell-type using nanotechnology as therapeutic strategy for the treatment of NASH and liver fibrosis.

Extra- and Intra-Cellular Mechanisms of Hepatic Stellate Cell Activation

Hepatic fibrosis is characterized by the pathological accumulation of extracellular matrix (ECM) in the liver resulting from the persistent liver injury and wound-healing reaction induced by various insults. Although hepatic fibrosis is considered reversible after eliminating the cause of injury, chronic injury left unchecked can progress to cirrhosis and liver cancer. A better understanding of the cellular and molecular mechanisms controlling the fibrotic response is needed to develop novel clinical strategies. It is well documented that activated hepatic stellate cells (HSCs) is the most principal cellular players promoting synthesis and deposition of ECM components. In the current review, we discuss pathways of HSC activation, emphasizing emerging extra- and intra-cellular signals that drive this important cellular response to hepatic fibrosis. A number of cell types and external stimuli converge upon HSCs to promote their activation, including hepatocytes, liver sinusoidal endothelial cells, macrophages, cytokines, altered ECM, hepatitis viral infection, enteric dysbiosis, lipid metabolism disorder, exosomes, microRNAs, alcohol, drugs and parasites. We also discuss the emerging signaling pathways and intracellular events that individually or synergistically drive HSC activation, including TGFβ/Smad, Notch, Wnt/β-catenin, Hedgehog and Hippo signaling pathways. These findings will provide novel potential therapeutic targets to arrest or reverse fibrosis and cirrhosis.

Procyanidin B2 alleviates liver injury caused by cold stimulation through Sonic hedgehog signalling and autophagy

Procyanidin B2 (PB2), a naturally occurring flavonoid abundant in a wide range of fruits, has been shown to exert antioxidant, anti‐inflammatory and anticancer properties. However, the role of PB2 in the prevention of cold stimulation (CS)‐induced liver injury. The present study was undertaken to determine the effects of PB2 on liver injury induced by cold stimulation and its potential molecular mechanisms. The present study results showed that treatment with PB2 significantly reduced CS‐induced liver injury by alleviating histopathological changes and serum levels of alanine transaminase and aspartate transaminase. Moreover, treatment with PB2 inhibited secretion of inflammatory cytokines and oxidative stress in cold‐stimulated mice. PB2 reduced cold stimulation‐induced inflammation by inhibiting TLR4/NF‐κB and Txnip/NLRP3 signalling. Treatment with PB2 reduced oxidative stress by activating Nrf‐2/Keap1, AMPK/GSK3β signalling pathways and autophagy. Furthermore, simultaneous application of Shh pathway inhibitor cyclopamine proved that PB2 targets the Hh pathway. More importantly, co‐treatment with PB2 and cyclopamine showed better efficacy than monotherapy. In conclusion, our findings provide new evidence that PB2 has protective potential against CS‐induced liver injury, which might be closely linked to the inhibition of Shh signalling pathway.

NAFLD: Reporting Histologic Findings in Clinical Practice

The role of liver biopsy in NASH has evolved along with the increased recognition of the significance of this disease, and the unmet medical need it presents. Drug development and clinical trials are rapidly growing, as are noninvasive tests for markers of steatosis, inflammation, injury, and fibrosis. Liver biopsy evaluation remains necessary for both drug development and clinical trials as the most specific means of diagnosis and patient identification for appropriate intervention. This White Paper, sponsored by the American Association for the Study of Liver Disease NASH Task Force, is a focused review of liver biopsy evaluation in fatty liver disease in subjects with presumed NAFLD for practicing clinical hepatologists and pathologists. The goal is to provide succinct and specific means for reporting the histopathologic elements of NASH, distinguishing NASH from nonalcoholic fatty liver without steatohepatitis, and from alcohol-associated steatohepatitis when possible. The discussion includes the special situations of NASH in advanced fibrosis or cirrhosis, and in the pediatric population. Finally, there is discussion of semiquantitative methods of evaluation of lesions of "disease activity" and fibrosis. Tables are presented for scoring and a suggested model for final reporting. Figures are presented to highlight the histopathologic elements of NASH.

Hepatic Stellate Cell Activation and Inactivation in NASH-Fibrosis-Roles as Putative Treatment Targets?

Hepatic fibrosis is the primary predictor of mortality in patients with non-alcoholic steatohepatitis (NASH). In this process, the activated hepatic stellate cells (HSCs) constitute the principal cells responsible for the deposition of a fibrous extracellular matrix, thereby driving the hepatic scarring. HSC activation, migration, and proliferation are controlled by a complex signaling network involving growth factors, lipotoxicity, inflammation, and cellular stress. Conversely, the clearance of activated HSCs is a prerequisite for the resolution of the extracellular fibrosis. Hence, pathways regulating the fate of the HSCs may represent attractive therapeutic targets for the treatment and prevention of NASH-associated hepatic fibrosis. However, the development of anti-fibrotic drugs for NASH patients has not yet resulted in clinically approved therapeutics, underscoring the complex biology and challenges involved when targeting the intricate cellular signaling mechanisms. This narrative review investigated the mechanisms of activation and inactivation of HSCs with a focus on NASH-associated hepatic fibrosis. Presenting an updated overview, this review highlights key cellular pathways with potential value for the development of future treatment modalities.

Silencing of CD147 inhibits hepatic stellate cells activation related to suppressing aerobic glycolysis via hedgehog signaling

Hepatic stellate cells (HSCs) activation is a key step that promotes hepatic fibrosis. Emerging evidence suggests that aerobic glycolysis is one of its important metabolic characteristics. Our previous study has reported that CD147, a glycosylated transmembrane protein, contributes significantly to the activation of HSCs. However, whether and how it is involved in the aerobic glycolysis of HSCs activation is unknown. The objective of the present study was to validate the effect of CD147 in HSCs activation and the underlying molecular mechanism. Our results showed that the silencing of CD147 decreased the expression of α-smooth muscle-actin (α-SMA) and collagen I at both mRNA and protein levels. Furthermore, CD147 silencing decreased the glucose uptake, lactate production in HSCs, and repressed the lactate dehydrogenase (LDH) activity, the expression of hexokinase 2 (HK2), glucose transporter 1 (Glut1). The effect of galloflavin, a well-defined glycolysis inhibitor, was similar to CD147 siRNA. Mechanistically, CD147 silencing suppressed glycolysis-associated HSCs activation through inhibiting the hedgehog signaling. Moreover, the hedgehog signaling agonist SAG could rescue the above effect of CD147 silencing. In conclusion, CD147 silencing blockade of aerobic glycolysis via suppression of hedgehog signaling inhibited HSCs activation, suggesting CD147 as a novel therapeutic target for hepatic fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-021-00460-9.

Extracellular Vesicles as Inflammatory Drivers in NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent chronic liver disease in most parts of the world affecting one-third of the western population and a growing cause for end-stage liver diseases such as hepatocellular carcinoma (HCC). Majorly driven by obesity and diabetes mellitus, NAFLD is more of a multifactorial disease affected by extra-hepatic organ crosstalk. Non-alcoholic fatty liver (NAFL) progressed to non-alcoholic steatohepatitis (NASH) predisposes multiple complications such as fibrosis, cirrhosis, and HCC. Although the complete pathogenic mechanisms of this disease are not understood, inflammation is considered as a key driver to the onset of NASH. Lipotoxicity, inflammatory cytokines, chemokines, and intestinal dysbiosis trigger both hepatic and systemic inflammatory cascades simultaneously activating immune responses. Over a few years, extracellular vesicles studied extensively concerning the pathobiology of NAFLD indicated it as a key modulator in the setting of immune-mediated inflammation. Exosomes and microvesicles, the two main types of extracellular vesicles are secreted by an array of most mammalian cells, which are involved mainly in cell-cell communication that are unique to cell type. Various bioactive cargoes containing extracellular vesicles derived from both hepatic and extrahepatic milieu showed critical implications in driving steatosis to NASH reaffirming inflammation as the primary contributor to the whole process. In this mini-review, we provide brief insights into the inflammatory mediators of NASH with special emphasis on extracellular vesicles that acts as drivers of inflammation in NAFLD.

Maladaptive regeneration - the reawakening of developmental pathways in NASH and fibrosis

With the rapid expansion of the obesity epidemic, nonalcoholic fatty liver disease is now the most common chronic liver disease, with almost 25% global prevalence. Nonalcoholic fatty liver disease ranges in severity from simple steatosis, a benign 'pre-disease' state, to the liver injury and inflammation that characterize nonalcoholic steatohepatitis (NASH), which in turn predisposes individuals to liver fibrosis. Fibrosis is the major determinant of clinical outcomes in patients with NASH and is associated with increased risks of cirrhosis and hepatocellular carcinoma. NASH has no approved therapies, and liver fibrosis shows poor response to existing pharmacotherapy, in part due to an incomplete understanding of the underlying pathophysiology. Patient and mouse data have shown that NASH is associated with the activation of developmental pathways: Notch, Hedgehog and Hippo-YAP-TAZ. Although these evolutionarily conserved fundamental signals are known to determine liver morphogenesis during development, new data have shown a coordinated and causal role for these pathways in the liver injury response, which becomes maladaptive during obesity-associated chronic liver disease. In this Review, we discuss the aetiology of this reactivation of developmental pathways and review the cell-autonomous and cell-non-autonomous mechanisms by which developmental pathways influence disease progression. Finally, we discuss the potential prognostic and therapeutic implications of these data for NASH and liver fibrosis.

Functional Analysis of Induced Human Ballooned Hepatocytes in a Cell Sheet-Based Three Dimensional Model

BACKGROUND

Ballooned hepatocytes (BH) are a key histological hallmark of nonalcoholic steatohepatitis (NASH), yet their consequences for liver-specific functions are unknown.

METHODS

In our previous study, an experimental model of human induced-BHs (iBH) has been successfully developed based on cell sheet technology. This study aimed to determine the functions of iBHs in the primary human hepatocyte/normal human dermal fibroblast (PHH/NHDF) co-culture cell sheets. Normal hepatocytes in the PHH/3T3-J2 co-culture cell sheets were set as a control, since 3T3-J2 murine embryonic fibroblasts have exhibited previously long term maintenance of PHH functions.

RESULTS

It was found that, albumin secretion was not affected in iBHs, but urea synthesis as well as cytochrome P450 enzyme (CYP) activities including CYP1A2 and CYP3A4, were significantly reduced in iBHs. Besides, loss of bile canaliculi was observed in iBHs. These findings are consistent with clinical studies of human NASH. In addition, PHH/NHDF cell sheets demonstrated two fold higher TGF-β1 secretion compared with PHH/3T3-J2 cell sheets. Furthermore, treatment with a TGF-β inhibitor and a semi-synthetic bile acid analogue (obeticholic acid, phase 3 trial of NASH therapy) ameliorated the histological appearance of established iBHs.

CONCLUSION

In summary, this study demonstrates the priority of iBHs in recapitulating not only histology but also clinically relevant hepatic dysfunctions in human NASH and suggests TGF-β and bile acid related signal pathway may play important roles in the formation of iBHs.