Accuracy of blood-based biomarkers for staging liver fibrosis in chronic liver disease: A systematic review supporting the AASLD Practice Guideline.

BACKGROUND AND AIMS: Blood-based biomarkers have been proposed as an alternative to liver biopsy for noninvasive liver disease assessment in chronic liver disease. Our aims for this systematic review were to evaluate the diagnostic utility of selected blood-based tests either alone, or in combination, for identifying significant fibrosis (F2-4), advanced fibrosis (F3-4), and cirrhosis (F4), as compared to biopsy in chronic liver disease. APPROACH AND RESULTS: We included a comprehensive search of databases including Ovid MEDLINE(R), EMBASE, Cochrane Database, and Scopus through to April 2022. Two independent reviewers selected 286 studies with 103,162 patients. The most frequently identified studies included the simple aspartate aminotransferase-to-platelet ratio index and fibrosis (FIB)-4 markers (with low-to-moderate risk of bias) in HBV and HCV, HIV-HCV/HBV coinfection, and NAFLD. Positive (LR+) and negative (LR-) likelihood ratios across direct and indirect biomarker tests for HCV and HBV for F2-4, F3-4, or F4 were 1.66-6.25 and 0.23-0.80, 1.89-5.24 and 0.12-0.64, and 1.32-7.15 and 0.15-0.86, respectively; LR+ and LR- for NAFLD F2-4, F3-4, and F4 were 2.65-3.37 and 0.37-0.39, 2.25-6.76 and 0.07-0.87, and 3.90 and 0.15, respectively. Overall, the proportional odds ratio indicated FIB-4 <1.45 was better than aspartate aminotransferase-to-platelet ratio index <0.5 for F2-4. FIB-4 >3.25 was also better than aspartate aminotransferase-to-platelet ratio index >1.5 for F3-4 and F4. There was limited data for combined tests. CONCLUSIONS: Blood-based biomarkers are associated with small-to-moderate change in pretest probability for diagnosing F2-4, F3-4, and F4 in viral hepatitis, HIV-HCV coinfection, and NAFLD, with limited comparative or combination studies for other chronic liver diseases.

Coffee, adenosine, and the liver.

A variety of observational studies have demonstrated that coffee, likely acting through caffeine, improves health outcomes in patients with chronic liver disease. The primary pharmacologic role of caffeine is to act as an inhibitor of adenosine receptors. Because key liver cells express adenosine receptors linked to liver injury, regeneration, and fibrosis, it is plausible that the biological effects of coffee are explained by effects of caffeine on adenosinergic signaling in the liver. This review is designed to help the reader make sense of that hypothesis, highlighting key observations in the literature that support or dispute it.

Coffee as chemoprotectant in fatty liver disease: caffeine-dependent and caffeine-independent effects.

Coffee consumption is associated with a variety of positive health outcomes in patients with chronic liver disease, including decreased liver-related mortality. The evidence for this has come from a wide variety of epidemiological studies over the past decade and remains consistent. Because coffee contains a large number of constituent molecules, many of which vary based on coffee source, roasting approach, and preparation, it has been difficult to identify the mechanisms by which coffee improves liver-related health. The caffeine hypothesis suggests that the primary active ingredient in coffee in this context is caffeine, which is an antagonist of liver adenosine receptors. However, some lines of data suggest caffeine-independent effects as well. This review examines the biological plausibility for caffeine-independent effects in the context of a recent publication in this journal.

Sortilin Deficiency Reduces Ductular Reaction, Hepatocyte Apoptosis, and Liver Fibrosis in Cholestatic-Induced Liver Injury.

Sortilin, a member of the vacuolar protein sorting 10 domain receptor family, traffics newly synthesized proteins from the trans-Golgi network to secretory pathways, endosomes, and cell surface. Sortilin-trafficked molecules, including IL-6 and acid sphingomyelinase (aSMase), mediate cholangiocyte proliferation and liver inflammation, hepatic stellate cell activation, hepatocyte apoptosis, and fibrosis. Based on these sortilin-regulated functions, we investigated its role in biliary damage leading to hepatocellular injury and fibrosis. Sortilin-/- mice displayed impaired inflammation and ductular reaction 3 days after bile duct ligation (BDL), as demonstrated by reduced cholangiocyte proliferation and activation and reduced serum IL-6. Interestingly, liver fibrosis was reduced in Sortilin-/- mice after both BDL and carbon tetrachloride treatment, in line with attenuated in vitro activation of Sortilin-/- hepatic stellate cells. Sortilin-/- hepatic aSMase activity was reduced in the BDL and carbon tetrachloride models and accompanied by reduced in vivo hepatocyte apoptosis. In addition, wild type (WT), but not Sortilin-/- hepatocytes, had increased aSMase-dependent susceptibility to bile acid-induced apoptosis in vitro. Mechanistically, short-term IL-6 neutralization in bile duct-ligated WT mice decreased hepatic inflammation and reactive cholangiocyte-derived cytokines and chemokines, without affecting fibrosis, whereas pharmacological inhibition of aSMase activity was not sufficient to attenuate hepatic fibrosis. Only combined IL-6 and aSMase inhibition significantly reduced fibrosis in bile duct-ligated WT mice. We conclude that sortilin regulates cholestatic liver damage and fibrosis via effects on both aSMase activity and serum IL-6.

Transforming Growth Factors α and ß Are Essential for Modeling Cholangiocarcinoma Desmoplasia and Progression in a Three-Dimensional Organotypic Culture Model.

To gain insight into the cellular and molecular interactions mediating the desmoplastic reaction and aggressive malignancy of mass-forming intrahepatic cholangiocarcinoma (ICC), we modeled ICC desmoplasia and progression in vitro. A unique three-dimensional (3D) organotypic culture model was established; within a dilute collagen-type I hydrogel, a novel clonal strain of rat cancer-associated myofibroblasts (TDFSM) was co-cultured with a pure rat cholangiocarcinoma cell strain (TDECC) derived from the same ICC type as TDFSM. This 3D organotypic culture model reproduced key features of desmoplastic reaction that closely mimicked those of the in situ tumor, as well as promoted cholangiocarcinoma cell growth and progression. Our results supported a resident liver mesenchymal cell origin of the TDFSM cells, which were not neoplastically transformed. Notably, 3D co-culturing of TDECC cells with TDFSM cells provoked the formation of a dense fibrocollagenous stroma in vitro that was associated with significant increases in both proliferative TDFSM myofibroblastic cells and TDECC cholangiocarcinoma cells accumulating within the gel matrix. This dramatic desmoplastic ICC-like phenotype, which was not observed in the TDECC or TDFSM controls, was highly dependent on transforming growth factor (TGF)-ß, but not promoted by TGF-α. However, TGF-α was determined to be a key factor for promoting cholangiocarcinoma cell anaplasia, hyperproliferation, and higher malignant grading in this 3D culture model of desmoplastic ICC.

Junctional adhesion molecules JAM-B and JAM-C promote autoimmune-mediated liver fibrosis in mice.

Fibrosis remains a serious health concern in patients with chronic liver disease. We recently reported that chemically induced chronic murine liver injury triggers increased expression of junctional adhesion molecules (JAMs) JAM-B and JAM-C by endothelial cells and de novo synthesis of JAM-C by hepatic stellate cells (HSCs). Here, we demonstrate that biopsies of patients suffering from primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) or autoimmune hepatitis (AIH) display elevated levels of JAM-C on portal fibroblasts (PFs), HSCs, endothelial cells and cholangiocytes, whereas smooth muscle cells expressed JAM-C constitutively. Therefore, localization and function of JAM-B and JAM-C were investigated in three mouse models of autoimmune-driven liver inflammation. A PBC-like disease was induced by immunization with 2-octynoic acid-BSA conjugate, which resulted in the upregulation of both JAMs in fibrotic portal triads. Analysis of a murine model of PSC revealed a role of JAM-C in PF cell-cell adhesion and contractility. In mice suffering from AIH, endothelial cells increased JAM-B level and HSCs and capsular fibroblasts became JAM-C-positive. Most importantly, AIH-mediated liver fibrosis was reduced in JAM-B-/- mice or when JAM-C was blocked by soluble recombinant JAM-C. Interestingly, loss of JAM-B/JAM-C function had no effect on leukocyte infiltration, suggesting that the well-documented function of JAMs in leukocyte recruitment to inflamed tissue was not effective in the tested chronic models. This might be different in patients and may even be complicated by the fact that human leukocytes express JAM-C. Our findings delineate JAM-C as a mediator of myofibroblast-operated contraction of the liver capsule, intrahepatic vasoconstriction and bile duct stricture. Due to its potential to interact heterophilically with endothelial JAM-B, JAM-C supports also HSC/PF mural cell function. Together, these properties allow JAM-B and JAM-C to actively participate in vascular remodeling associated with liver/biliary fibrosis and suggest them as valuable targets for anti-fibrosis therapies.

Extracellular vesicles carry microRNA-195 to intrahepatic cholangiocarcinoma and improve survival in a rat model.

The cancer microenvironment plays a central role in cancer development, growth, and homeostasis. This paradigm suggests that cancer fibroblasts support cancers, probably in response to stimuli received from the cancer cells. We aimed at investigating whether extracellular vesicles (EVs) can shuttle microRNA (miR) species between cancer-associated fibroblasts (CAFs) and cancer cells. To this end, we extracted EVs according to published protocols. EVs were studied for their miR content by quantitative reverse-transcription polymerase chain reaction. EVs were transfected with select miR species and utilized in vitro as well as in vivo in a rat model of cholangiocarcinoma (CCA). We found that miR-195 is down-regulated in CCA cells, as well as in adjoining fibroblasts. Furthermore, we report that EVs shuttle miR-195 from fibroblasts to cancer cells. Last, we show that fibroblast-derived EVs, loaded with miR-195, can be administered in a rat model of CCA, concentrate within the tumor, decrease the size of cancers, and improve survival of treated rats. CONCLUSION: EVs play a salient role in trafficking miR species between cancer cells and CAFs in human CCA. Understanding of these mechanisms may allow devising of novel therapeutics. (Hepatology 2017;65:501-514).

Coffee Consumption and Prevention of Cirrhosis: In Support of the Caffeine Hypothesis.

Coffee is acknowledged as the most widely used drug worldwide. Coffee is also a foodstuff, so its use is often used to satisfy dietary urges. When used as a drug, coffee is normally consumed as a stimulant rather than to treat or prevent particular diseases. Recently, coffee consumption has been inversely related to progression of liver fibrosis to cirrhosis and even hepatocellular carcinoma. Experiments in cellular and animal models have provided biological plausibility for coffee as an antifibrotic agent in the liver. A recent article examined one of the key questions regarding the antifibrotic role of coffee-specifically what is the primary antifibrotic agent in coffee? This article briefly reviews the relevant issues with regard to coffee as an antifibrotic agent for patients with chronic liver disease.

An Elf2-like transcription factor acts as repressor of the mouse ecto-5'-nucleotidase gene expression in hepatic myofibroblasts.

Hepatic fibrosis represents a pathological wound healing and tissue repair process triggered in response to chronic liver injury. A heterogeneous population of activated non-parenchymal liver cells, known as liver myofibroblasts, functions as the effector cells in hepatic fibrosis. Upon activation, liver myofibroblasts become fibrogenic, acquiring contractile properties and increasing collagen production capacity, while developing enhanced sensitivity to endogenous molecules and factors released in the local microenvironment. Hepatic extracellular adenosine is a bioactive small molecule, increasingly recognized as an important regulator of liver myofibroblast functions, and an important mediator in the pathogenesis of liver fibrosis overall. Remarkably, ecto-5'-nucleotidase/Nt5e/Cd73 enzyme, which accounts for the dominant adenosine-generating activity in the extracellular medium, is expressed by activated liver myofibroblasts. However, the molecular signals regulating Nt5e gene expression in liver myofibroblasts remain poorly understood. Here, we show that activated mouse liver myofibroblasts express Nt5e gene products and characterize the putative Nt5e minimal promoter in the mouse species. We describe the existence of an enhancer sequence upstream of the mouse Nt5e minimal promoter and establish that the mouse Nt5e minimal promoter transcriptional activity is negatively regulated by an Elf2-like Ets-related transcription factor in activated mouse liver myofibroblasts.

The Cholangiocyte Adenosine-IL-6 Axis Regulates Survival During Biliary Cirrhosis.

Epithelial response to injury is critical to the pathogenesis of biliary cirrhosis, and IL-6 has been suggested as a mediator of this phenomenon. Several liver cell types can secrete IL-6 following activation by various signaling molecules including circulating adenosine. The aims of this study were to assess whether adenosine can induce IL-6 secretion by cholangiocytes via the A2b adenosine receptor (A2bAR) and to determine the effect of A2bAR-sensitive IL-6 release on injury response in biliary cirrhosis. Human normal cholangiocyte H69 cells were used for in vitro studies to determine the mechanism by which adenosine and the A2bAR induce release of IL-6. In vivo, control and A2bAR-deficient mice were used to determine the roles of A2bAR-sensitive IL-6 release in biliary cirrhosis induced by common bile duct ligation (BDL). Additionally, the response to exogenous IL-6 was assessed in C57BL/6 and A2bAR-deficient mice. Adenosine induced IL-6 mRNA expression and protein secretion via A2bAR activation. Although activation of A2bAR induced cAMP and intracellular Ca2+ signals, only the Ca2+ signals were linked to IL-6 upregulation. After BDL, A2bAR-deficient mice have impaired survival, which is further impaired by exogenous IL-6; however, decreased survival is not due to changes in fibrosis and no changes in inflammatory cells. Exogenous IL-6 is associated with the increased presence of bile infarcts. Extracellular adenosine induces cholangiocyte IL-6 release via the A2bAR. This signaling pathway is important in the pathogenesis of injury response in biliary cirrhosis but does not alter fibrosis. Adenosine upregulates IL-6 release by cholangiocytes via the A2bAR in a calcium-sensitive fashion. Mice deficient in A2bAR experience impaired survival after biliary cirrhosis induced by common bile duct ligation independent of changes in fibrosis.

Strategies and endpoints of antifibrotic drug trials: Summary and recommendations from the AASLD Emerging Trends Conference, Chicago, June 2014.

There is an urgent need to develop antifibrotic therapies for chronic liver disease, and clarify which endpoints in antifibrotic trials will be acceptable to regulatory agencies. The American Association for the Study of Liver Diseases sponsored an endpoints conference to help accelerate the efficient testing of antifibrotic agents and develop recommendations on clinical trial design for liver fibrosis. In this review, we summarize the salient and novel elements of this conference and provide directions for future clinical trial design. The article follows the structure of the conference and is organized into five areas: (1) antifibrotic trial design; (2) preclinical proof-of-concept studies; (3) pharmacological targets, including rationale and lessons to learn; (4) rational drug design and development; and (5) consensus and recommendations on design of clinical trials in liver fibrosis. Expert overviews and collaborative discussions helped to summarize the key unmet needs and directions for the future, including: (1) greater clarification of at-risk populations and study groups; (2) standardization of all elements of drug discovery and testing; (3) standardization of clinical trial approaches; (4) accelerated development of improved noninvasive markers; and (5) need for exploration of potential off-target toxicities of future antifibrotic drugs.

Expression of mediators of purinergic signaling in human liver cell lines.

Purinergic signaling regulates a diverse and biologically relevant group of processes in the liver. However, progress of research into functions regulated by purinergic signals in the liver has been hampered by the complexity of systems probed. Specifically, there are multiple liver cell subpopulations relevant to hepatic functions, and many of these have been effectively modeled in human cell lines. Furthermore, there are more than 20 genes relevant to purinergic signaling, each of which has distinct functions. Hence, we felt the need to categorize genes relevant to purinergic signaling in the best characterized human cell line models of liver cell subpopulations. Therefore, we investigated the expression of adenosine receptor, P2X receptor, P2Y receptor, and ecto-nucleotidase genes via RT-PCR in the following cell lines: LX-2, hTERT, FH11, HepG2, Huh7, H69, and MzChA-1. We believe that our findings will provide an excellent resource to investigators seeking to define functions of purinergic signals in liver physiology and liver disease pathogenesis.

Diagnostic Accuracy of Transient Elastography in Hepatosteatosis in Youth With Obesity.

Context: Steatotic liver disease is common but overlooked in childhood obesity; diagnostic methods are invasive or expensive. Objective: We sought to determine the diagnostic accuracy of vibration-controlled transient elastography (VCTE) compared with magnetic resonance imaging (MRI) in adolescents with obesity and high risk for hepatosteatosis. Methods: Baseline data in 3 clinical trials enrolling adolescents with obesity were included (NCT03919929, NCT03717935, NCT04342390). Liver fat was assessed using MRI fat fraction and VCTE-based controlled attenuation parameter (CAP). Hepatosteatosis was defined as MRI fat fraction ≥5.0%. The area under the receiver-operating characteristic curves (AUROCs) for CAP against MRI was calculated, and optimal CAP using the Youden index for hepatosteatosis diagnosis was determined. Results: Data from 82 adolescents (age 15.6 ± 1.4 years, body mass index 36.5 ± 5.9 kg/m2, 81% female) were included. Fifty youth had hepatosteatosis by MRI (fat fraction 9.3% ; 95% CI 6.7, 14.0), and 32 participants did not have hepatosteatosis (fat fraction 3.1%; 95% CI 2.2, 3.9; P < .001). The hepatosteatosis group had higher mean CAP compared with no hepatosteatosis (293 dB/m; 95% CI 267, 325 vs 267 dB/m; 95% CI 248, 282; P = .0120). A CAP of 281 dB/m had the highest sensitivity (60%) and specificity (74%) with AUROC of 0.649 (95% CI 0.51-0.79; P = .04) in the entire cohort. In a subset of participants with polycystic ovary syndrome (PCOS), a CAP of 306 dB/m had the highest sensitivity (78%) and specificity (52%) and AUROC of 0.678 (95% CI 0.45-0.90; P = .108). Conclusion: CAP of 281 dB/m has modest diagnostic performance for hepatosteatosis compared with MRI in youth with significant obesity. A higher CAP in youth with PCOS suggests that comorbidities might affect optimal CAP in hepatosteatosis diagnosis.

CXCL12 induces hepatic stellate cell contraction through a calcium-independent pathway.

Liver fibrosis, with subsequent development of cirrhosis and ultimately portal hypertension, results in the death of patients with end-stage liver disease if liver transplantation is not performed. Hepatic stellate cells (HSCs), central mediators of liver fibrosis, resemble tissue pericytes and regulate intrahepatic blood flow by modulating pericapillary resistance. Therefore, HSCs can contribute to portal hypertension in patients with chronic liver disease (CLD). We have previously demonstrated that activated HSCs express functional chemokine receptor, CXCR4, and that receptor engagement by its ligand, CXCL12, which is increased in patients with CLD, leads to further stellate cell activation in a CXCR4-specific manner. We therefore hypothesized that CXCL12 promotes HSC contraction in a CXCR4-dependent manner. Stimulation of HSCs on collagen gel lattices with CXCL12 led to gel contraction and myosin light chain (MLC) phosphorylation, which was blocked by addition of AMD3100, a CXCR4 small molecule inhibitor. These effects were further mediated by the Rho kinase pathway since both Rho kinase knockdown or Y-27632, a Rho kinase inhibitor, blocked CXCL12 induced phosphorylation of MLC and gel contraction. BAPTA-AM, a calcium chelator, had no effect, indicating that this pathway is calcium sensitive but not calcium dependent. In conclusion, CXCL12 promotes stellate cell contractility in a predominantly calcium-independent fashion. Our data demonstrates a novel role of CXCL12 in stellate cell contraction and the availability of small molecule inhibitors of the CXCL12/CXCR4 axis justifies further investigation into its potential as therapeutic target for portal hypertension.

Effects of short-term supervised exercise training on liver fat in adolescents with obesity: a randomized controlled trial.

OBJECTIVE: The objective of this study was to quantify the effects of a 4-week, supervised, high-intensity interval training (HIIT) on intrahepatic triglyceride content (IHTG, percentage), cardiorespiratory fitness (CRF), and cardiometabolic markers in adolescents with obesity. METHODS: A total of 40 adolescents (age 13-18 y, BMI 36.7 ± 5.8 kg/m2 ) at risk for metabolic dysfunction-associated steatotic liver disease (MASLD) based on obesity and elevated Fibroscan measured controlled attenuation parameter (CAP) scores were randomized to HIIT three times a week for 4 weeks (n = 34) or observation (control; n = 6). Liver magnetic resonance imaging proton-density fat-fraction (MRI-PDFF), CAP, oral glucose tolerance test, serum alanine aminotransferase, dual-energy x-ray absorptiometry, and CRF tests were performed before and after intervention. Within- and between-group differences were compared. RESULTS: A total of 13 (38%) and 4 (66%) children had MASLD by MRI-PDFF (IHTG ≥ 5%) in the HIIT and control groups, respectively. The implemented HIIT protocol had no impact on CRF or IHTG (baseline 5.26%, Δ = -0.31 percentage points, 95% CI: -0.77 to 0.15; p = 0.179), but it decreased the 2-h glucose concentration (baseline 116 mg/dL, Δ = -11 mg/dL; 95% CI: -17.6 to -5.5; p < 0.001). When limiting the analysis to participants with MASLD (n = 17), HIIT decreased IHTG (baseline 8.81%, Δ = -1.05 percentage points, 95% CI: -2.08 to -0.01; p = 0.048). Between-group comparisons were not different. CONCLUSIONS: The implemented exercise protocol did not reduce IHTG, but it led to modest improvement in markers of cardiometabolic health.

Advances in cholangiocyte immunobiology.

Cholangiocytes, or bile duct epithelia, were once thought to be the simple lining of the conduit system comprising the intra- and extrahepatic bile ducts. Growing experimental evidence demonstrated that cholangiocytes are in fact the first line of defense of the biliary system against foreign substances. Experimental advances in recent years have unveiled previously unknown roles of cholangiocytes in both innate and adaptive immune responses. Cholangiocytes can release inflammatory modulators in a regulated fashion. Moreover, they express specialized pattern-recognizing molecules that identify microbial components and activate intracellular signaling cascades leading to a variety of downstream responses. The cytokines secreted by cholangiocytes, in conjunction with the adhesion molecules expressed on their surface, play a role in recruitment, localization, and modulation of immune responses in the liver and biliary tract. Cholangiocyte survival and function is further modulated by cytokines and inflammatory mediators secreted by immune cells and cholangiocytes themselves. Because cholangiocytes act as professional APCs via expression of major histocompatibility complex antigens and secrete antimicrobial peptides in bile, their role in response to biliary infection is critical. Finally, because cholangiocytes release mediators critical to myofibroblastic differentiation of portal fibroblasts and hepatic stellate cells, cholangiocytes may be essential in the pathogenesis of biliary cirrhosis.

Activated hepatic stellate cells upregulate transcription of ecto-5'-nucleotidase/CD73 via specific SP1 and SMAD promoter elements.

Adenosine is a potent modulator of liver fibrosis and inflammation. Adenosine has been shown to regulate such diverse activities as chemotaxis, contraction, and matrix production in hepatic stellate cells (HSC). Ecto-5'-nucleotidase/CD73 [EC 3.1.3.5] is the rate-limiting enzyme in adenosine production. Cd73-deficient mice are resistant to experimental liver fibrosis and have impaired adenosine generation. However, cell-specific expression and regulation of CD73 within the fibrotic liver have not been defined. In particular, prior evidence demonstrating that liver myofibroblasts, the cells believed to be responsible for matrix formation in the liver, express CD73 is lacking. Thus we tested the hypothesis that HSC and portal fibroblasts (PF), cells that undergo differentiation into liver myofibroblasts, express CD73 in a regulated fashion. We found that CD73 is weakly expressed in quiescent HSC and PF but is markedly upregulated at the transcriptional level in myofibroblastic HSC and PF. We furthermore found that CD73 protein and its functional activity are strongly increased in fibrous septa in rats subjected to experimental fibrosis. To determine the mechanism for the upregulation of Cd73 gene, we cloned the rat Cd73 promoter and then used serial truncation and site-directed mutagenesis to identify key regulatory elements. We identified two consensus SP1 motifs and one SMAD binding site, each of which was necessary for Cd73 gene upregulation. In conclusion, activated HSC upregulate Cd73 gene expression, via specific SP1 and SMAD promoter elements, after myofibroblastic differentiation. The ecto-5'-nucleotidase/CD73 enzyme is a novel cellular marker of activated liver myofibroblasts in vivo and in vitro and thus represents a promising molecular target for antifibrotic therapies in liver diseases.