SOX9 predicts progression toward cirrhosis in patients while its loss protects against liver fibrosis

SOX9 Overexpression Ameliorates Metabolic Dysfunction-associated Steatohepatitis Through Activation of the AMPK Pathway

Background and Aims

The transcription factor sex-determining region Y-related high-mobility group-box gene 9 (SOX9) plays a critical role in organ development. Although SOX9 has been implicated in regulating lipid metabolism in vitro, its specific role in metabolic dysfunction-associated steatohepatitis (MASH) remains poorly understood. This study aimed to investigate the role of SOX9 in MASH pathogenesis and explored the underlying mechanisms.

Methods

MASH models were established using mice fed either a methionine- and choline-deficient (MCD) diet or a high-fat, high-fructose diet. To evaluate the effects of SOX9, hepatocyte-specific SOX9 deletion or overexpression was performed. Lipidomic analyses were conducted to assess how SOX9 influences hepatic lipid metabolism. RNA sequencing was employed to identify pathways modulated by SOX9 during MASH progression. To elucidate the mechanism further, HepG2 cells were treated with an adenosine monophosphate-activated protein kinase (AMPK) inhibitor to test whether SOX9 acts via AMPK activation.

Results

SOX9 expression was significantly elevated in hepatocytes of MASH mice. Hepatocyte-specific SOX9 deletion exacerbated MCD-induced MASH, whereas overexpression of SOX9 mitigated high-fat, high-fructose-induced MASH. Lipidomic and RNA sequencing analyses revealed that SOX9 suppresses the expression of genes associated with lipid metabolism, inflammation, and fibrosis in MCD-fed mice. Furthermore, SOX9 deletion inhibited AMPK pathway activation, while SOX9 overexpression enhanced it. Notably, administration of an AMPK inhibitor negated the protective effects of SOX9 overexpression, leading to increased lipid accumulation in HepG2 cells.

Conclusions

Our findings demonstrate that SOX9 overexpression alleviates hepatic lipid accumulation in MASH by activating the AMPK pathway. These results highlight SOX9 as a promising therapeutic target for treating MASH.

Functional mechanisms and potential therapeutic strategies for lactylation in liver diseases

Lactylation, a novel form of lactate-mediated protein post-translational modification (PTM), has been identified as a crucial regulator of gene expression and protein function through the modification of both histone and non-histone proteins. Liver disease is frequently characterized by a reprogramming of glucose metabolism and subsequent lactate accumulation. Recent research has implicated lactylation in a diverse array of hepatic pathologies, including liver injury, non-alcoholic fatty liver disease, liver fibrosis, and hepatocellular carcinoma. Consequently, lactylation has emerged as a pivotal regulatory mechanism in liver disease pathogenesis. This review aims to elucidate the intricate regulatory and functional mechanisms underlying lactylation, synthesize recent advancements in its role in various liver diseases, and highlight its potential as a therapeutic target for future interventions in hepatic disorders.

Influence of Sex in the Development of Liver Diseases

The liver is a sexually dimorphic organ. Sex differences in prevalence, progression, prognosis, and treatment prevail in most liver diseases, and the mechanism of how liver diseases act differently among male versus female patients has not been fully elucidated. Biological sex differences in normal physiology and disease arise principally from sex hormones and/or sex chromosomes. Sex hormones contribute to the development and progression of most liver diseases, with estrogen- and androgen-mediated signaling pathways mechanistically involved. In addition, genetic factors in sex chromosomes have recently been found to contribute to the sex disparity of many liver diseases, which might explain, to some extent, the difference in gene expression pattern, immune response, and xenobiotic metabolism between men and women. Although increasing evidence suggests that sex is one of the most important modulators of disease prevalence and outcomes, at present, basic and clinical studies have long been sex unbalanced, with female subjects underestimated. As such, this review focuses on sex disparities of liver diseases and summarizes the current understanding of sex-specific mechanisms, including sex hormones, sex chromosomes, etc. We anticipate that understanding sex-specific pathogenesis will aid in promoting personalized therapies for liver disease among male versus female patients.

Identification of SOX9-related prognostic DEGs and a prediction model for hepatitis C-induced early-stage fibrosis

BACKGROUND

Hepatitis C virus (HCV) infection induces liver inflammation, activating hepatic stellate cells (HSC) and advancing fibrosis. Studies have indicated that SOX9 overexpression is closely linked to HSC activation. The study aims to identify genes associated with SOX9 and search for potential targets for detecting and treating liver fibrosis.

METHOD

The dataset GSE15654, containing 216 biopsy samples from HCV-induced early-stage cirrhosis patients, was obtained from the GEO database. Prognostic genes were identified through differential gene analysis, LASSO, and Cox regression analyses. CIBERSORT analysis quantified infiltration levels across 22 immune cell types. Constructing a prognostic prediction model using screened genes and conducting preliminary validation using qRT PCR and RNA sequencing techniques.

RESULTS

Elevated SOX9 expression correlates with unfavorable outcomes in patients with early-stage liver fibrosis induced by HCV. We identified nine SOX9-related prognostic DEGs in our study. ADAMTS2, ARHGEF5, CCT8, ERG, LBH, FRMD6, INMT, and RASGRF2 were considered risk factors in the disease progression, while DHRS4 was considered a protective factor. SOX9 expression showed a positive correlation with mast cell infiltration, whereas ARHGEF5 and FRMD6 expressions were positively associated with M0 macrophage infiltration. Our combined model surpasses the commonly used APRI and FIB4 indicators in predicting patient prognosis. The testing of clinical samples also preliminarily validated our research results.

CONCLUSION

The prognostic model based on nine SOX9-related DEGs provides an effective tool for forecasting the progression and outcomes of liver fibrosis. This study introduces a new strategy for advancing liver fibrosis prediction and treatment.

Molecular Mechanisms of Fibrosis in Cholestatic Liver Diseases and Regenerative Medicine-Based Therapies

The aim of this review is to explore the potential of new regenerative medicine approaches in the treatment of cholestatic liver fibrosis. Cholestatic liver diseases, such as primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and biliary atresia (BA), due to the accumulation of bile, often progress to liver fibrosis, cirrhosis, and liver failure. When the disease becomes severe enough to require liver transplantation. Deeply understanding the disease's progression and fibrosis formation is crucial for better diagnosis and treatment. Current liver fibrosis treatments mainly target the root causes and no direct treatment method in fibrosis itself. Recent advances in regenerative medicine offer a potential approach that may help find the ways to target fibrosis directly, offering hope for improved outcomes. We also summarize, analyze, and discuss the current state and benefits of regenerative medicine therapies such as mesenchymal stem cell (MSC) therapy, induced pluripotent stem cells (iPSCs), and organoid technology, which may help the treatment of cholestatic liver diseases. Focusing on the latest research may reveal new targets and enhance therapeutic efficacy, potentially leading to more effective management and even curative strategies for cholestatic liver diseases.

Cordycepin alleviates diabetes mellitus-associated hepatic fibrosis by inhibiting SOX9-mediated Wnt/β-catenin signal axis

Diabetes mellitus can induce liver injury and easily progress to liver fibrosis. However, there is still a lack of effective treatments for diabetes-induced hepatic fibrosis. Cordycepin (COR), a natural nucleoside derived from Cordyceps militaris, has demonstrated remarkable efficacy in treating metabolic diseases and providing hepatoprotective effects. However, its protective effect and underlying mechanism in diabetes-induced liver injury remain unclear. This study utilized a high-fat diet/streptozotocin-induced diabetic mouse model, as well as LX-2 and AML-12 cell models exposed to high glucose and TGF-β1, to explore the protective effects and mechanisms of Cordycepin in liver fibrosis associated with diabetes. The results showed that COR lowered blood glucose levels, enhanced liver function, mitigated fibrosis, and suppressed HSC activation in diabetic mice. Mechanistically, COR attenuated the activation of the Wnt/β-catenin pathway by inhibiting β-catenin nuclear translocation, and β-catenin knockdown further intensified this effect. Meanwhile, COR significantly inhibited SOX9 expression in vivo and in vitro. Knockdown of SOX9 downregulated Wnt3a and β-catenin expression at the protein and gene levels to exacerbate the inhibitory action of COR on HG&TGF-β1-induced HSCs activations. These results indicate SOX9 is involved in the mechanism by which COR deactivates the Wnt/β-catenin pathway in hepatic fibrosis induced by diabetes. Moreover, prolonged half-life time, slower metabolism and higher exposure of COR were observed in diabetes-induced liver injury animal model via pharmacokinetics studies. Altogether, COR holds potential as a therapeutic agent for ameliorating hepatic injury and fibrosis in diabetes by suppressing the activation of the SOX9-mediated Wnt/β-catenin pathway.

Profibrotic role of the SOX9-MMP10-ECM biosynthesis axis in the tracheal fibrosis after injury and repair

Fibroblast activation and extracellular matrix (ECM) deposition play an important role in the tracheal abnormal repair process and fibrosis. As a transcription factor, SOX9 is involved in fibroblast activation and ECM deposition. However, the mechanism of how SOX9 regulates fibrosis after tracheal injury remains unclear. We investigated the role of SOX9 in TGF-β1-induced fibroblast activation and ECM deposition in rat tracheal fibroblast (RTF) cells. SOX9 overexpression adenovirus (Ad-SOX9) and siRNA were transfected into RTF cells. We found that SOX9 expression was up-regulated in RTF cells treated with TGF-β1. SOX9 overexpression activated fibroblasts and promoted ECM deposition. Silencing SOX9 inhibited cell proliferation, migration, and ECM deposition, induced G2 arrest, and increased apoptosis in RTF cells. RNA-seq and chromatin immunoprecipitation sequencing (ChIP-seq) assays identified MMP10, a matrix metalloproteinase involved in ECM deposition, as a direct target of SOX9, which promotes ECM degradation by increasing MMP10 expression through the Wnt/β-catenin signaling pathway. Furthermore, in vivo, SOX9 knockdown ameliorated granulation proliferation and tracheal fibrosis, as manifested by reduced tracheal stenosis. In conclusion, our findings indicate that SOX9 can drive fibroblast activation, cell proliferation, and apoptosis resistance in tracheal fibrosis via the Wnt/β-catenin signaling pathway. The SOX9-MMP10-ECM biosynthesis axis plays an important role in tracheal injury and repair. Targeting SOX9 and its downstream target MMP10 may represent a promising therapeutic approach for tracheal fibrosis.

H3K18 lactylation accelerates liver fibrosis progression through facilitating SOX9 transcription

Liver fibrosis is a significant health concern globally due to its association with severe liver conditions like cirrhosis and liver cancer. Histone lactylation has been implicated in the progression of hepatic fibrosis, but its specific role in liver fibrosis, particularly regarding H3K18 lactylation, remained unclear. To investigate this, we established in vivo and in vitro models of liver fibrosis using carbon tetrachloride (CCl4) injection in rats and stimulation of hepatic stellate cells (HSCs) with TGF-β1, respectively. We found that histone lactylation, particularly H3K18 lactylation, was upregulated in both CCl4-induced rats and TGF-β1-activated HSCs, indicating its potential involvement in liver fibrosis. Further experiments revealed that lactate dehydrogenase A (LDHA) knockdown inhibited H3K18 lactylation and had a beneficial effect on liver fibrosis by suppressing HSC proliferation, migration, and extracellular matrix (ECM) deposition. This suggests that H3K18 lactylation promotes liver fibrosis progression. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays demonstrated that H3K18 lactylation facilitated the transcription of SOX9, a transcription factor associated with fibrosis. Importantly, overexpression of SOX9 counteracted the effects of LDHA silencing on activated HSCs, indicating that SOX9 is downstream of H3K18 lactylation in promoting liver fibrosis. In summary, this study uncovers a novel mechanism by which H3K18 lactylation contributes to liver fibrosis by activating SOX9 transcription. This finding opens avenues for exploring new therapeutic strategies for hepatic fibrosis targeting histone lactylation pathways.

Diverse functions of SOX9 in liver development and homeostasis and hepatobiliary diseases

The liver is the central organ for digestion and detoxification and has unique metabolic and regenerative capacities. The hepatobiliary system originates from the foregut endoderm, in which cells undergo multiple events of cell proliferation, migration, and differentiation to form the liver parenchyma and ductal system under the hierarchical regulation of transcription factors. Studies on liver development and diseases have revealed that SRY-related high-mobility group box 9 (SOX9) plays an important role in liver embryogenesis and the progression of hepatobiliary diseases. SOX9 is not only a master regulator of cell fate determination and tissue morphogenesis, but also regulates various biological features of cancer, including cancer stemness, invasion, and drug resistance, making SOX9 a potential biomarker for tumor prognosis and progression. This review systematically summarizes the latest findings of SOX9 in hepatobiliary development, homeostasis, and disease. We also highlight the value of SOX9 as a novel biomarker and potential target for the clinical treatment of major liver diseases.

PAK1-dependent mechanotransduction enables myofibroblast nuclear adaptation and chromatin organization during fibrosis

Myofibroblasts are responsible for scarring during fibrosis. The scar propagates mechanical signals inducing a radical transformation in myofibroblast cell state and increasing profibrotic phenotype. Here, we show mechanical stress from progressive scarring induces nuclear softening and de-repression of heterochromatin. The parallel loss of H3K9Me3 enables a permissive state for distinct chromatin accessibility and profibrotic gene regulation. Integrating chromatin accessibility profiles with RNA expression provides insight into the transcription network underlying the switch in profibrotic myofibroblast states, emphasizing mechanoadaptive regulation of PAK1 as key drivers. Through genetic manipulation in liver and lung fibrosis, loss of PAK1-dependent signaling impairs the mechanoadaptive response in vitro and dramatically improves fibrosis in vivo. Moreover, we provide human validation for mechanisms underpinning PAK1-mediated mechanotransduction in liver and lung fibrosis. Collectively, these observations provide insight into the nuclear mechanics driving the profibrotic chromatin landscape in fibrosis, highlighting actomyosin-dependent mechanisms as potential therapeutic targets in fibrosis.

Unlocking the post-transplant microenvironment for successful islet function and survival

Islet transplantation (IT) offers the potential to restore euglycemia for patients with type 1 diabetes mellitus (T1DM). Despite improvements in islet isolation techniques and immunosuppressive regimes, outcomes remain suboptimal with UK five-year graft survivals (5YGS) of 55% and most patients still requiring exogenous insulin after multiple islet infusions. Native islets have a significant non-endocrine component with dense extra-cellular matrix (ECM), important for islet development, cell survival and function. Collagenase isolation necessarily disrupts this complex islet microenvironment, leaving islets devoid of a supporting framework and increasing vulnerability of transplanted islets. Following portal venous transplantation, a liver injury response is potentially induced, which typically results in inflammation and ECM deposition from liver specific myofibroblasts. The impact of this response may have important impact on islet survival and function. A fibroblast response and ECM deposition at the kidney capsule and eye chamber alongside other implantation sites have been shown to be beneficial for survival and function. Investigating the implantation site microenvironment and the interactions of transplanted islets with ECM proteins may reveal therapeutic interventions to improve IT and stem-cell derived beta-cell therapy.

Construction of a neural network diagnostic model for renal fibrosis and investigation of immune infiltration characteristics

Background

Recently, the incidence rate of renal fibrosis has been increasing worldwide, greatly increasing the burden on society. However, the diagnostic and therapeutic tools available for the disease are insufficient, necessitating the screening of potential biomarkers to predict renal fibrosis.

Methods

Using the Gene Expression Omnibus (GEO) database, we obtained two gene array datasets (GSE76882 and GSE22459) from patients with renal fibrosis and healthy individuals. We identified differentially expressed genes (DEGs) between renal fibrosis and normal tissues and analyzed possible diagnostic biomarkers using machine learning. The diagnostic effect of the candidate markers was evaluated using receiver operating characteristic (ROC) curves and verified their expression using Reverse transcription quantitative polymerase chain reaction (RT-qPCR). The CIBERSORT algorithm was used to determine the proportions of 22 types of immune cells in patients with renal fibrosis, and the correlation between biomarker expression and the proportion of immune cells was studied. Finally, we developed an artificial neural network model of renal fibrosis.

Results

Four candidate genes namely DOCK2, SLC1A3, SOX9 and TARP were identified as biomarkers of renal fibrosis, with the area under the ROC curve (AUC) values higher than 0.75. Next, we verified the expression of these genes by RT-qPCR. Subsequently, we revealed the potential disorder of immune cells in the renal fibrosis group through CIBERSORT analysis and found that immune cells were highly correlated with the expression of candidate markers.

Conclusion

DOCK2, SLC1A3, SOX9, and TARP were identified as potential diagnostic genes for renal fibrosis, and the most relevant immune cells were identified. Our findings provide potential biomarkers for the diagnosis of renal fibrosis.

Cellular and Molecular Mechanisms of Liver Fibrosis in Patients with NAFLD

The expression of immune- and cancer-related genes was measured in liver biopsies from 107 NAFLD patients. The strongest difference in overall gene expression was between liver fibrosis stages F3 and F4, with 162 cirrhosis-associated genes identified. Strong correlations with fibrosis progression from F1 to F4 were observed for 91 genes, including CCL21, CCL2, CXCL6, and CCL19. In addition, the expression of 21 genes was associated with fast progression to F3/F4 in an independent group of eight NAFLD patients. These included the four chemokines, SPP1, HAMP, CXCL2, and IL-8. A six-gene signature including SOX9, THY-1, and CD3D had the highest performance detecting the progressors among F1/F2 NAFLD patients. We also characterized immune cell changes using multiplex immunofluorescence platforms. Fibrotic areas were strongly enriched in CD3+ T cells compared to CD68+ macrophages. While the number of CD68+ macrophages increased with fibrosis severity, the increase in CD3+ T-cell density was more substantial and progressive from F1 to F4. The strongest correlation with fibrosis progression was observed for CD3+CD45R0+ memory T cells, while the most significant increase in density between F1/F2 and F3/F4 was for CD3+CD45RO+FOXP3+CD8- and CD3+CD45RO-FOXP3+CD8- regulatory T cells. A specific increase in the density of CD68+CD11b+ Kupffer cells with liver fibrosis progression was also observed.

Mechanosensation to inflammation: Roles for YAP/TAZ in innate immune cells

Innate immune cells are responsible for eliminating foreign infectious agents and cellular debris, and their ability to perceive, respond to, and integrate biochemical and mechanical cues from their microenvironment eventually determines their behavior. In response to tissue injury, pathogen invasion, or a biomaterial implant, immune cells activate many pathways to initiate inflammation in the tissue. In addition to common inflammatory pathways, studies have demonstrated the role of the mechanosensitive proteins and transcriptional coactivators YAP and TAZ (YAP/TAZ) in inflammation and immunity. We review our knowledge of YAP/TAZ in controlling inflammation and immunity in innate immune cells. Furthermore, we discuss the roles of YAP/TAZ in inflammatory diseases, wound healing, and tissue regeneration and how they integrate mechanical cues with biochemical signaling during disease progression. Last, we comment on possible approaches that can be exploited to harness the therapeutic potential of YAP/TAZ in inflammatory diseases.

Wilms Tumor 1-Driven Fibroblast Activation and Subpleural Thickening in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease that is often fatal due to the formation of irreversible scar tissue in the distal areas of the lung. Although the pathological and radiological features of IPF lungs are well defined, the lack of insight into the fibrogenic role of fibroblasts that accumulate in distinct anatomical regions of the lungs is a critical knowledge gap. Fibrotic lesions have been shown to originate in the subpleural areas and extend into the lung parenchyma through processes of dysregulated fibroproliferation, migration, fibroblast-to-myofibroblast transformation, and extracellular matrix production. Identifying the molecular targets underlying subpleural thickening at the early and late stages of fibrosis could facilitate the development of new therapies to attenuate fibroblast activation and improve the survival of patients with IPF. Here, we discuss the key cellular and molecular events that contribute to (myo)fibroblast activation and subpleural thickening in IPF. In particular, we highlight the transcriptional programs involved in mesothelial to mesenchymal transformation and fibroblast dysfunction that can be targeted to alter the course of the progressive expansion of fibrotic lesions in the distal areas of IPF lungs.

Identification of key genes related to immune infiltration in cirrhosis via bioinformatics analysis

Cirrhosis is the most common subclass of liver disease worldwide and correlated to immune infiltration. However, the immune-related molecular mechanism underlying cirrhosis remains obscure. Two gene expression profiles GSE89377 and GSE139602 were investigated to identify differentially expressed genes (DEGs) related to cirrhosis. Enrichment analysis for DEGs was conducted. Next, the immune infiltration of DEGs was evaluated using CIBERSORT algorithm. The hub DEGs with tight connectivity were identified using the String and Cytoscape databases, and the expression difference of these hub genes between normal liver and cirrhosis samples was determined. Moreover, in order to evaluate the discriminatory ability of hub genes and obtained the area under the receiver operating characteristic curve values in the GSE89377 and GSE139602 datasets. Finally, the association between hub DEGs and immune cell infiltration was explored by Spearman method. Among the 299 DEGs attained, 136 were up-regulated and 163 were down-regulated. Then the enrichment function analysis of DEGs and CIBERSORT algorithm showed significant enrichment in immune and inflammatory responses. And four hub DEGs (ACTB, TAGLN, VIM, SOX9) were identified, which also showed a diagnostic value in the GSE89377 and GSE 139,602 datasets. Finally, the immune infiltration analysis indicated that, these hub DEGs were highly related to immune cells. This study revealed key DEGs involved in inflammatory immune responses of cirrhosis, which could be used as biomarkers for diagnosis or therapeutic targets of cirrhosis.

Knockdown of SOX9 alleviates tracheal fibrosis through the Wnt/β-catenin signaling pathway

Trachealfibrosis is an important cause of tracheal stenosis without effective treatments, and new drug targets need to be developed. The role of SOX9 in the injury and repair of the trachea is unknown; this study aims to investigate the role of SOX9 in the regulation of tracheal fibrosis based on clinical samples from patients with tracheal injury and a model of tracheal fibrosis produced by tracheal brushing in rats. The results showed that the expressions of SOX9 and mesenchymal and ECM-related indicators were increased in the injury and fibrosis of the trachea in patients and rats. Serum SOX9 levels exhibited a sensitivity of 83.87% and specificity of 90% in distinguishing patients with tracheal fibrosis from healthy volunteers when the cut‑off value was 13.24 ng/ml. Knockdown SOX9 can markedly inhibit granulation tissue proliferation, reduce inflammation and ECM deposition, promote epithelial regeneration and granulation tissue apoptosis, and attenuate the tracheal fibrosis after injury. Additionally, RNA sequencing showed that the proliferation, migration, and ECM deposition of tracheal granulation tissue were related to the activation of Wnt pathway, activation of the β-catenin, and p-GSK3β after injury can be inhibited by the knockdown of SOX9. In summary, SOX9 is upregulated in tracheas fibrosis and may be a novel factor to promote tracheal fibrosis progression. Inhibiting SOX9 may be used to prevent and treat tracheal fibrosis in the future. KEY MESSAGE : The expression of SOX9 is upregulated the process of injury and repair of the tracheal fibrosis. Knocking down SOX9 can attenuate tracheal fibrosis after injury by inhibiting inflammation response, granulation tissue proliferation, ECM deposition, and promoting granulation tissue apoptosis. The Wnt/β-catenin-SOX9 axis is activated during tracheal injury and fibrosis, and inhibition of SOX9 can partially alleviate tracheal fibrosis. SOX9 may act as a new diagnostic and therapeutic target in patients with tracheal fibrosis in the future.

Cellular and transcriptional heterogeneity in the intrahepatic biliary epithelium

Epithelial tissues comprise heterogeneous cellular subpopulations, which often compartmentalize specialized functions like absorption and secretion to distinct cell types. In the liver, hepatocytes and biliary epithelial cells (BECs; also called cholangiocytes) are the two major epithelial lineages and play distinct roles in (1) metabolism, protein synthesis, detoxification, and (2) bile transport and modification, respectively. Recent technological advances, including single cell transcriptomic assays, have shed new light on well-established heterogeneity among hepatocytes, endothelial cells, and immune cells in the liver. However, a "ground truth" understanding of molecular heterogeneity in BECs has remained elusive, and the field currently lacks a set of consensus biomarkers for identifying BEC subpopulations. Here, we review long-standing definitions of BEC heterogeneity as well as emerging studies that aim to characterize BEC subpopulations using next generation single cell assays. Understanding cellular heterogeneity in the intrahepatic bile ducts holds promise for expanding our foundational mechanistic knowledge of BECs during homeostasis and disease.

MicroRNA-15a inhibits hepatic stellate cell activation and proliferation via targeting SRY-box transcription factor 9

Accumulating research have indicated that microRNAs are associated with the progression of hepatic fibrosis (HF). Nevertheless, the biological role and function of microRNA (miR)-15a in HF are still unknown. Our data revealed that miR-15a expression was decreased in TGF-β1-treated LX-2 cells and CCl₄-induced mouse model. Additionally, miR-15a could directly target the 3’‑untranslated region of SRY-box transcription factor 9 (SOX9) to inhibit its expression. miR-15a overexpression attenuated the viability and invasion, but enhanced apoptosis in LX-2 cells. However, miR-15a knockdown had the opposite effects. Interestingly, SOX9 overexpression reversed the changes in cell viability, invasion and apoptosis mediated by miR-15a overexpression. Moreover, the miR-15a overexpression-mediated collagen I and alpha smooth muscle actin (a-SMA) downregulation were reversed by SOX9 overexpression. Overall, miR-15a could inhibit LX-2 cell viability and HF pathogenesis by targeting SOX9 in vitro and in vivo.

In vivo partial cellular reprogramming enhances liver plasticity and regeneration

Mammals have limited regenerative capacity, whereas some vertebrates, like fish and salamanders, are able to regenerate their organs efficiently. The regeneration in these species depends on cell dedifferentiation followed by proliferation. We generate a mouse model that enables the inducible expression of the four Yamanaka factors (Oct-3/4, Sox2, Klf4, and c-Myc, or 4F) specifically in hepatocytes. Transient in vivo 4F expression induces partial reprogramming of adult hepatocytes to a progenitor state and concomitantly increases cell proliferation. This is indicated by reduced expression of differentiated hepatic-lineage markers, an increase in markers of proliferation and chromatin modifiers, global changes in DNA accessibility, and an acquisition of liver stem and progenitor cell markers. Functionally, short-term expression of 4F enhances liver regenerative capacity through topoisomerase2-mediated partial reprogramming. Our results reveal that liver-specific 4F expression in vivo induces cellular plasticity and counteracts liver failure, suggesting that partial reprogramming may represent an avenue for enhancing tissue regeneration.

Yap-Sox9 signaling determines hepatocyte plasticity and lineage-specific hepatocarcinogenesis

BACKGROUND & AIMS

Primary liver tumors comprise distinct subtypes. A subset of intrahepatic cholangiocarcinoma (iCCA) can arise from cell fate reprogramming of mature hepatocytes in mouse models. However, the underpinning of cell fate plasticity during hepatocarcinogenesis is still poorly understood, hampering therapeutic development for primary liver cancer. As YAP activation induces liver tumor formation and cell fate plasticity, we investigated the role of Sox9, a transcription factor downstream of Yap activation that is expressed in biliary epithelial cells (BECs), in Yap-induced cell fate plasticity during hepatocarcinogenesis.

METHODS

To evaluate the function of Sox9 in YAP-induced hepatocarcinogenesis in vivo, we used several genetic mouse models of inducible hepatocyte-specific YAP activation with simultaneous Sox9 removal. Cell fate reprogramming was determined by lineage tracing and immunohistochemistry. The molecular mechanism underlying Yap and Sox9 function in hepatocyte plasticity was investigated by transcription and transcriptomic analyses of mouse and human liver tumors.

RESULTS

Sox9, a marker of liver progenitor cells (LPCs) and BECs, is differentially required in YAP-induced stepwise hepatocyte programming. While Sox9 has a limited role in hepatocyte dedifferentiation to LPCs, it is required for BEC differentiation from LPCs. YAP activation in Sox9-deficient hepatocytes resulted in more aggressive HCC with enhanced Yap activity at the expense of iCCA-like tumors. Furthermore, we showed that 20% of primary human liver tumors were associated with a YAP activation signature, and tumor plasticity is highly correlated with YAP activation and SOX9 expression.

CONCLUSION

Our data demonstrated that Yap-Sox9 signaling determines hepatocyte plasticity and tumor heterogeneity in hepatocarcinogenesis in both mouse and human liver tumors. We identified Sox9 as a critical transcription factor required for Yap-induced hepatocyte cell fate reprogramming during hepatocarcinogenesis.

LAY SUMMARY

Sox9, a marker of liver progenitor cells and bile duct lining cells, is a downstream target of YAP protein activation. Herein, we found that YAP activation in hepatocytes leads to a transition from mature hepatocytes to liver progenitor cells and then to bile duct lining cells. Sox9 is required in the second step during mouse hepatocarcinogenesis. We also found that human YAP and SOX9 may play similar roles in liver cancers.

Expression of Protein SOX9 in Biliary Atresia

OBJECTIVES

Biliary atresia (BA) is still an enigmatic disease. Deeper knowledge of its pathophysiology could help develop better treatments. SOX9 regulates bile duct development, liver regeneration and fibrosis; therefore, it could be determinant in characterizing BA liver damage. Aim: To study if there is a SOX9 expression pattern in liver biopsies from BA patients.

METHODS

Liver biopsies from BA patients (group BA), from age-matched infants without primary hepatic disease (group Control), and from patients with other liver conditions (group OLC) were compared. Expression of SOX9 was checked for: amount, intensity of immunoreaction, localization within ductular structures, perifibrotic epithelial cells, and lobular cells. The scores were added to create a scale from 0 to 11 that allowed group comparison. SOX9 Scale and liver survival were also looked for a correlation.

RESULTS

All BA cases had a score >4, while all controls scored <4. OLC livers scored 1 to 8 (3.5 ± 2.0) (P < 0.001 between all groups). A cut-off at 4 had 100% sensitivity and 88.24% specificity to differentiate BA from Controls and from OLC (area under receiver operating characteristic curve: 0.9989 (95% confidence interval: 0.9964-1.000). Strong expression of SOX9 was observed mainly in the nuclei of proliferated ductules of portal spaces and fibrotic bridges. SOX9 Scale score could not be related to liver survival in this study.

CONCLUSION

In BA livers, SOX9 is mainly expressed in reactive ductular epithelium, following a pattern significantly different from that seen in non-BA patients; thus, SOX9 Scale may have a role in the diagnosis of BA.

Evaluation of SOX9-Positive Hepatocytes in Human Liver Specimens and Mature Mouse Hepatocytes

The liver has a remarkable regenerative capacity with different modes of regeneration according to the type and extent of an injury. It has been reported that mature hepatocytes could transdifferentiate into a cholangiocyte phenotype. Sry HMG box protein 9 (SOX9) is one of the earliest biliary markers that regulate bile duct development. We have found that SOX9-positive biphenotypic hepatocytes appear in severe acute liver injury patients' liver specimens accompanied by an elevation in plasma interleukin-8 levels. In vitro assays revealed that interleukin-8 homologs induce the expression of SOX9 in mature mouse hepatocytes. Here, we describe the methods used to detect SOX9-positive hepatocytes in human liver specimens and to induce SOX9-positive hepatocytes in mature mouse hepatocytes.

Dysregulated overexpression of Sox9 induces fibroblast activation in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal fibrotic lung disease associated with unremitting fibroblast activation including fibroblast-to-myofibroblast transformation (FMT), migration, resistance to apoptotic clearance, and excessive deposition of extracellular matrix (ECM) proteins in the distal lung parenchyma. Aberrant activation of lung-developmental pathways is associated with severe fibrotic lung disease; however, the mechanisms through which these pathways activate fibroblasts in IPF remain unclear. Sry-box transcription factor 9 (Sox9) is a member of the high-mobility group box family of DNA-binding transcription factors that are selectively expressed by epithelial cell progenitors to modulate branching morphogenesis during lung development. We demonstrate that Sox9 is upregulated via MAPK/PI3K-dependent signaling and by the transcription factor Wilms' tumor 1 in distal lung-resident fibroblasts in IPF. Mechanistically, using fibroblast activation assays, we demonstrate that Sox9 functions as a positive regulator of FMT, migration, survival, and ECM production. Importantly, our in vivo studies demonstrate that fibroblast-specific deletion of Sox9 is sufficient to attenuate collagen deposition and improve lung function during TGF-α-induced pulmonary fibrosis. Using a mouse model of bleomycin-induced pulmonary fibrosis, we show that myofibroblast-specific Sox9 overexpression augments fibroblast activation and pulmonary fibrosis. Thus, Sox9 functions as a profibrotic transcription factor in activating fibroblasts, illustrating the potential utility of targeting Sox9 in IPF treatment.

A Novel Sox9/lncRNA H19 Axis Contributes to Hepatocyte Death and Liver Fibrosis

Sox9 has been previously characterized as a transcription factor responsible for the extracellular matrix production during liver fibrosis. However, the deregulation and functional role of hepatocyte Sox9 in the progression of liver fibrosis remains elusive. Here, we found a significant increase of Sox9 in the hepatocytes isolated from CCl4-induced fibrotic liver and showed that antisense oligoribonucleotides depletion of Sox9 was sufficient to attenuate CCl4-induced liver fibrosis. Notably, the increase of Sox9 in hepatocyte was associated with the upregulation of long noncoding RNA H19 in both in vitro and in vivo systems. Mechanistic studies revealed that Sox9 induced H19 by binding to a conserved promoter region of H19. In vitro, hepatocyte injury triggered the increase of Sox9/H19 axis, whereas silence of H19 greatly alleviated the H2O2-induced hepatocyte apoptosis, suggesting that H19 functions as a downstream effector of Sox9 signaling and is involved in hepatocyte apoptosis. In animal experiments, inhibition of H19 alleviated the activation of hepatic stellate cells and reduced the extent of liver fibrosis, whereas ectopic expression of H19 abolished the inhibitory effects of Sox9 depletion on liver fibrosis, suggesting that the profibrotic effect of hepatocyte Sox9 depends on H19. Finally, we investigated the clinical relevance of Sox9/H19 axis to liver fibrosis and identified the increase of Sox9/H19 axis in liver cirrhosis patients. In conclusion, our findings link Sox9/H19 axis to the intrinsic mechanisms of hepatocyte apoptosis and may represent a hitherto unknown paradigm in hepatocyte injury associated with the progression of liver fibrosis.

Fibrotic Events in the Progression of Cholestatic Liver Disease

Cholestatic liver diseases including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are associated with active hepatic fibrogenesis, which can ultimately lead to the development of cirrhosis. However, the exact relationship between the development of liver fibrosis and the progression of cholestatic liver disease remains elusive. Periductular fibroblasts located around the bile ducts seem biologically different from hepatic stellate cells (HSCs). The fibrotic events in these clinical conditions appear to be related to complex crosstalk between immune/inflammatory mechanisms, cytokine signalling, and perturbed homeostasis between cholangiocytes and mesenchymal cells. Several animal models including bile duct ligation (BDL) and the Mdr2-knockout mice have improved our understanding of mechanisms underlying chronic cholestasis. In the present review, we aim to elucidate the mechanisms of fibrosis in order to help to identify potential diagnostic and therapeutic targets.

SOX9 is required for kidney fibrosis and activates NAV3 to drive renal myofibroblast function

Renal fibrosis is a common end point for kidney injury and many chronic kidney diseases. Fibrogenesis depends on the sustained activation of myofibroblasts, which deposit the extracellular matrix that causes progressive scarring and organ failure. Here, we showed that the transcription factor SOX9 was associated with kidney fibrosis in humans and required for experimentally induced kidney fibrosis in mice. From genome-wide analysis, we identified Neuron navigator 3 (NAV3) as acting downstream of SOX9 in kidney fibrosis. NAV3 increased in abundance and colocalized with SOX9 after renal injury in mice, and both SOX9 and NAV3 were present in diseased human kidneys. In an in vitro model of renal pericyte transdifferentiation into myofibroblasts, we demonstrated that NAV3 was required for multiple aspects of fibrogenesis, including actin polymerization linked to cell migration and sustained activation of the mechanosensitive transcription factor YAP1. In summary, our work identifies a SOX9-NAV3-YAP1 axis involved in the progression of kidney fibrosis and points to NAV3 as a potential target for pharmacological intervention.

Sox9EGFP Defines Biliary Epithelial Heterogeneity Downstream of Yap Activity

BACKGROUND & AIMS

Defining the genetic heterogeneity of intrahepatic biliary epithelial cells (BECs) is challenging, and tools for identifying BEC subpopulations are limited. Here, we characterize the expression of a Sox9^EGFP transgene in the liver and demonstrate that green fluorescent protein (GFP) expression levels are associated with distinct cell types.

METHODS

Sox9^EGFP BAC transgenic mice were assayed by immunofluorescence, flow cytometry, and gene expression profiling to characterize in vivo characteristics of GFP populations. Single BECs from distinct GFP populations were isolated by fluorescence-activated cell sorting, and functional analysis was conducted in organoid forming assays. Intrahepatic ductal epithelium was grown as organoids and treated with a Yes-associated protein (Yap) inhibitor or bile acids to determine upstream regulation of Sox9 in BECs. Sox9^EGFP mice were subjected to bile duct ligation, and GFP expression was assessed by immunofluorescence.

RESULTS

BECs express low or high levels of GFP, whereas periportal hepatocytes express sublow GFP. Sox9^EGFP+ BECs are differentially distributed by duct size and demonstrate distinct gene expression signatures, with enrichment of Cyr61 and Hes1 in GFP^high BECs. Single Sox9^EGFP+ cells form organoids that exhibit heterogeneous survival, growth, and HNF4A activation dependent on culture conditions, suggesting that exogenous signaling impacts BEC heterogeneity. Yap is required to maintain Sox9 expression in biliary organoids, but bile acids are insufficient to induce BEC Yap activity or Sox9 in vivo and in vitro. Sox9^EGFP remains restricted to BECs and periportal hepatocytes after bile duct ligation.

CONCLUSIONS

Our data demonstrate that Sox9^EGFP levels provide readout of Yap activity and delineate BEC heterogeneity, providing a tool for assaying subpopulation-specific cellular function in the liver.

Chronic Disruption of the Late Cholesterol Synthesis Leads to Female-Prevalent Liver Cancer

Simple Summary

Hepatocellular carcinoma is a disease with a variety of molecular triggers and is usually reported to prevail in males. However, after the menopause, the disease is also increasing in the female population. Herein, we discovered that chronic depletion of cholesterol synthesis due to the knock-out of the gene Cyp51 from this pathway leads to female prevalent hepatocarcinogenesis in aging mice. There is a high similarity between our mouse model and the situation in humans. Multiple deregulated pathways of hepatocarcinogenesis are shared. A female-dependent metabolic reprogramming leading to this type of liver cancer is exposed for the first time and reflects on deregulated cholesterol synthesis as the metabolic trigger. These data are of crucial importance. Despite the higher overall prevalence of hepatocellular carcinoma in males, we need tools and biomarkers to further stratify patients and offer better diagnosis and treatment options to both sexes.

Abstract

While the role of cholesterol in liver carcinogenesis remains controversial, hepatocellular carcinoma generally prevails in males. Herein, we uncover pathways of female-prevalent progression to hepatocellular carcinoma due to chronic repression of cholesterogenic lanosterol 14α-demethylase (CYP51) in hepatocytes. Tumors develop in knock-out mice after year one, with 2:1 prevalence in females. Metabolic and transcription factor networks were deduced from the liver transcriptome data, combined by sterol metabolite and blood parameter analyses, and interpreted with relevance to humans. Female knock-outs show increased plasma cholesterol and HDL, dampened lipid-related transcription factors FXR, LXRα:RXRα, and importantly, crosstalk between reduced LXRα and activated TGF-β signalling, indicating a higher susceptibility to HCC in aging females. PI3K/Akt signalling and ECM-receptor interaction are common pathways that are disturbed by sex-specific altered genes. Additionally, transcription factors (SOX9)2 and PPARα were recognized as important for female hepatocarcinogenesis, while overexpressed Cd36, a target of nuclear receptor RORC, is a new male-related regulator of ECM-receptor signalling in hepatocarcinogenesis. In conclusion, we uncover the sex-dependent metabolic reprogramming of cholesterol-related pathways that predispose for hepatocarcinogenesis in aging females. This is important in light of increased incidence of liver cancers in post-menopausal women.

Hepatic stellate cell autophagy inhibits extracellular vesicle release to attenuate liver fibrosis

BACKGROUND & AIMS

Autophagy plays a crucial role in hepatic homeostasis and its deregulation has been associated with chronic liver disease. However, the effect of autophagy on the release of fibrogenic extracellular vesicles (EVs) by platelet-derived growth factor (PDGF)-stimulated hepatic stellate cells (HSCs) remains unknown. Herein, we aimed to elucidate the role of autophagy, specifically relating to fibrogenic EV release, in fibrosis.

METHODS

In vitro experiments were conducted in primary human and murine HSCs as well as LX2 cells. Small EVs were purified by differential ultracentrifugation. Carbon tetrachloride (CCl₄) or bile duct ligation (BDL) were used to induce fibrosis in our mouse model. Liver lysates from patients with cirrhosis or healthy controls were compared by RNA sequencing.

RESULTS

In vitro, PDGF and its downstream molecule SHP2 (Src homology 2-containing protein tyrosine phosphatase 2) inhibited autophagy and increased HSC-derived EV release. We used this PDGF/SHP2 model to further investigate how autophagy affects fibrogenic EV release. RNA sequencing identified an mTOR (mammalian target of rapamycin) signaling molecule that was regulated by SHP2 and PDGF. Disruption of mTOR signaling abolished PDGF-dependent EV release. Activation of mTOR signaling induced the release of multivesicular body-derived exosomes (by inhibiting autophagy) and microvesicles (by activating ROCK1 signaling). These mTOR-dependent EVs promoted in vitro HSC migration. To assess the importance of this mechanism in vivo, SHP2 was selectively deleted in HSCs, which attenuated CCl_4- or BDL-induced liver fibrosis. Furthermore, in the CCl₄ model, mice receiving circulating EVs derived from mice with HSC-specific Shp2 deletion had less fibrosis than mice receiving EVs from control mice. Correspondingly, SHP2 was upregulated in patients with liver cirrhosis.

CONCLUSION

These results demonstrate that autophagy in HSCs attenuates liver fibrosis by inhibiting the release of fibrogenic EVs.

LAY SUMMARY

During liver fibrosis and cirrhosis, activated hepatic stellate cells (HSCs) are the key cell type responsible for fibrotic tissue deposition. Recently, we demonstrated that activated HSCs release nano-sized vesicles enriched with fibrogenic proteins. In the current study, we unveil the mechanism by which these fibrogenic vesicles are released, moving a step closer to the long-term goal of therapeutically targeting this process.

IL-8 induces transdifferentiation of mature hepatocytes toward the cholangiocyte phenotype

The adult mammalian liver exhibits a remarkable regenerative capacity, with different modes of regeneration according to the type and extent of injury. Hepatocyte–cholangiocyte biphenotypic liver progenitor cell populations appear under conditions of excessive injury. It has been reported that mature hepatocytes can transdifferentiate toward a cholangiocyte phenotype and be a cellular source of progenitor cell populations. Here, we determined that among various plasma cytokines, interleukin (IL)‐8 levels were significantly elevated in acute liver failure and severe acute liver injury patients. In vitro assays revealed that administration of IL‐8 homologues increases the expression of Sry HMG box protein 9 (SOX9). In liver biopsies of acute liver injury patients, we observed the appearance of SOX9‐positive biphenotypic hepatocytes accompanied by elevation of plasma IL‐8 levels. Our results suggest that IL‐8 regulates the phenotypic conversion of mature hepatocytes toward a cholangiocyte phenotype.

Interleukin (IL)‐8 treated mouse mature hepatocytes expressed Sry HMG box protein 9 (SOX9), a bile duct‐associated marker. In liver biopsies of acute liver injury patients, SOX9‐positive biphenotypic hepatocytes appeared in the liver parenchyma which is accompanied by elevation of plasma IL‐8 levels. Our results suggest that IL‐8 regulates the phenotypic conversion of mature hepatocytes toward a cholangiocyte phenotype.

The Roles of Notch Signaling in Liver Development and Disease

The Notch signaling pathway plays major roles in organ development across animal species. In the mammalian liver, Notch has been found critical in development, regeneration and disease. In this review, we highlight the major advances in our understanding of the role of Notch activity in proper liver development and function. Specifically, we discuss the latest discoveries on how Notch, in conjunction with other signaling pathways, aids in proper liver development, regeneration and repair. In addition, we review the latest in the role of Notch signaling in the pathogenesis of liver fibrosis and chronic liver disease. Finally, recent evidence has shed light on the emerging connection between Notch signaling and glucose and lipid metabolism. We hope that highlighting the major advances in the roles of Notch signaling in the liver will stimulate further research in this exciting field and generate additional ideas for therapeutic manipulation of the Notch pathway in liver diseases.

miR-1-3p suppresses proliferation of hepatocellular carcinoma through targeting SOX9

Background

Liver cancer was the fourth leading cause of cancer-related death in 2015. Hepatocellular carcinoma (HCC) is the most common type of liver cancer. miR-1-3p plays important roles in cancer, including prostate, bladder, lung cancer, and colorectal carcinoma. The function of miR-1-3p in HCC remains poorly understood.

Methods

qRT-PCR was performed to detect the miR-1-3p expression in HCC cell lines (HCCLM3, Hep3B, Bel-7404, SMMC-7721) and the normal human hepatic cell line (LO2). HCCLM3 and Bel-7404 cells were transfected with miR-1-3p mimic or scramble control followed by water-soluble tetrazolium salt (WST-1) assay. Western bolt analysis was performed to determine the protein levels. TargetScan7.1 (http://www.targetscan.org/vert_71/) was used to predict the potential targets of miR-1-3p. SRY (sex determining region Y)-box 9 (SOX9), which has been previously shown to play an important role in HCC, was found to be a target of miR-1-3p. Luciferase reporter assay was used to explore the targeting of miR-1-3p on SOX9. For in vivo tumorigenesis assay, HCCLM3 cells with stable overexpression of miR-1-3p or control plasmid were injected subcutaneously into the flank of the SCID mice and animals were monitored for tumor growth.

Results

miR-1-3p was significantly downregulated in HCC cell lines (HCCLM3, Hep3B, Bel-7404, and SMMC-7721) compared to normal human hepatic cell line (LO2). Overexpression of miR-1-3p significantly inhibited the proliferation and induced apoptosis in HCCLM3 and Bel-7474 cells. SOX9 was a direct target of miR-1-3p in HCC cells. Inhibition of SOX9 significantly inhibited the proliferation of HCCLM3 and Bel-7474 cells. In vivo, overexpression of miR-1-3p decreased tumor volume in a xenograft model.

Conclusion

These results highlight the role of miR-1-3p in HCC. Overexpression of miR-1-3P inhibited the proliferation of HCC at least partly due to the regulation of SOX9. miR-1-3p may be a promising therapeutic candidate for HCC.

Liver Fibrosis Conventional and Molecular Imaging Diagnosis Update

Liver fibrosis is a serious, life-threatening disease with high morbidity and mortality that result from diverse causes. Liver biopsy, considered the "gold standard" to diagnose, grade, and stage liver fibrosis, has limitations in terms of invasiveness, cost, sampling variability, inter-observer variability, and the dynamic process of fibrosis. Compelling evidence has demonstrated that all stages of fibrosis are reversible if the injury is removed. There is a clear need for safe, effective, and reliable non-invasive assessment modalities to determine liver fibrosis in order to manage it precisely in personalized medicine. However, conventional imaging methods used to assess morphological and structural changes related to liver fibrosis, including ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), are only useful in assessing advanced liver disease, including cirrhosis. Functional imaging techniques, including MR elastography (MRE), US elastography, and CT perfusion are useful for assessing moderate to advanced liver fibrosis. MRE is considered the most accurate noninvasive imaging technique, and US elastography is currently the most widely used noninvasive means. However, these modalities are less accurate in early-stage liver fibrosis and some factors affect the accuracy of these techniques. Molecular imaging is a target-specific imaging mechanism that has the potential to accurately diagnose early-stage liver fibrosis. We provide an overview of recent advances in molecular imaging for the diagnosis and staging of liver fibrosis which will enable clinicians to monitor the progression of disease and potentially reverse liver fibrosis. We compare the promising technologies with conventional and functional imaging and assess the utility of molecular imaging in precision and personalized clinical medicine in the early stages of liver fibrosis.

SOX9 regulated matrix proteins are increased in patients serum and correlate with severity of liver fibrosis

Extracellular matrix (ECM) deposition and resultant scar play a major role in the pathogenesis and progression of liver fibrosis. Identifying core regulators of ECM deposition may lead to urgently needed diagnostic and therapetic strategies for the disease. The transcription factor Sex determining region Y box 9 (SOX9) is actively involved in scar formation and its prevalence in patients with liver fibrosis predicts progression. In this study, transcriptomic approaches of Sox9-abrogated myofibroblasts identified >30% of genes regulated by SOX9 relate to the ECM. Further scrutiny of these data identified a panel of highly expressed ECM proteins, including Osteopontin (OPN), Osteoactivin (GPNMB), Fibronectin (FN1), Osteonectin (SPARC) and Vimentin (VIM) as SOX9 targets amenable to assay in patient serum. In vivo all SOX-regulated targets were increased in human disease and mouse models of fibrosis and decreased following Sox9-loss in mice with parenchymal and biliary fibrosis. In patient serum samples, SOX9-regulated ECM proteins were altered in response to fibrosis severity, whereas comparison with established clinical biomarkers demonstrated superiority for OPN and VIM at detecting early stages of fibrosis. These data support SOX9 in the mechanisms underlying fibrosis and highlight SOX9 and its downstream targets as new measures to stratify patients with liver fibrosis.

Inhibiting the integrated stress response pathway prevents aberrant chondrocyte differentiation thereby alleviating chondrodysplasia

The integrated stress response (ISR) is activated by diverse forms of cellular stress, including endoplasmic reticulum (ER) stress, and is associated with diseases. However, the molecular mechanism(s) whereby the ISR impacts on differentiation is incompletely understood. Here, we exploited a mouse model of Metaphyseal Chondrodysplasia type Schmid (MCDS) to provide insight into the impact of the ISR on cell fate. We show the protein kinase RNA-like ER kinase (PERK) pathway that mediates preferential synthesis of ATF4 and CHOP, dominates in causing dysplasia by reverting chondrocyte differentiation via ATF4-directed transactivation of Sox9. Chondrocyte survival is enabled, cell autonomously, by CHOP and dual CHOP-ATF4 transactivation of Fgf21. Treatment of mutant mice with a chemical inhibitor of PERK signaling prevents the differentiation defects and ameliorates chondrodysplasia. By preventing aberrant differentiation, titrated inhibition of the ISR emerges as a rationale therapeutic strategy for stress-induced skeletal disorders.

SOX9 predicts progression toward cirrhosis in patients while its loss protects against liver fibrosis

Fibrosis and organ failure is a common endpoint for many chronic liver diseases. Much is known about the upstream inflammatory mechanisms provoking fibrosis and downstream potential for tissue remodeling. However, less is known about the transcriptional regulation in vivo governing fibrotic matrix deposition by liver myofibroblasts. This gap in understanding has hampered molecular predictions of disease severity and clinical progression and restricted targets for antifibrotic drug development. In this study, we show the prevalence of SOX9 in biopsies from patients with chronic liver disease correlated with fibrosis severity and accurately predicted disease progression toward cirrhosis. Inactivation of Sox9 in mice protected against both parenchymal and biliary fibrosis, and improved liver function and ameliorated chronic inflammation. SOX9 was downstream of mechanosignaling factor, YAP1. These data demonstrate a role for SOX9 in liver fibrosis and open the way for the transcription factor and its dependent pathways as new diagnostic, prognostic, and therapeutic targets in patients with liver fibrosis.

Melatonin Protects against Lung Fibrosis by Regulating the Hippo/YAP Pathway

Idiopathic pulmonary fibrosis (IPF) is a progressive, fibrotic interstitial pneumonia with high mortality. Melatonin, a hormone predominantly secreted by the pineal gland, has been reported to participate in the process of IPF. However, the mechanisms underlying the effect of melatonin in pulmonary fibrosis have not been elucidated to date. This study was designed to evaluate the anti-fibrotic role of melatonin in pulmonary fibrosis and to elucidate the potential mechanisms. We observed that melatonin markedly attenuated bleomycin (BLM)-induced experimental lung fibrosis in mice and inhibited TGF-β1-induced fibrogenesis in lung fibroblasts. Additionally, we determined that luzindole, a melatonin receptor inhibitor, reduced the anti-fibrotic effect of melatonin. Further studies showed that melatonin alleviated the translocation of YAP1 from cytoplasm to nucleus, a key downstream effector of the Hippo pathway, in vivo and in vitro by interacting with its receptor. Taken together, our results suggest that melatonin prevents lung fibrosis by inhibiting YAP1 and indicate that melatonin replacement could be a novel strategy for the treatment of lung fibrosis.

Early onset of disc degeneration in SM/J mice is associated with changes in ion transport systems and fibrotic events

Intervertebral disc degeneration (IDD) causes back pain and sciatica, affecting quality of life and resulting in high economic/social burden. The etiology of IDD is not well understood. Along with aging and environmental factors, genetic factors also influence the onset, progression and severity of IDD. Genetic studies of risk factors for IDD using human cohorts are limited by small sample size and low statistical power. Animal models amenable to genetic and functional studies of IDD provide desirable alternatives. Despite differences in size and cellular content as compared to human intervertebral discs (IVDs), the mouse is a powerful model for genetics and assessment of cellular changes relevant to human biology. Here, we provide evidence for early onset disc degeneration in SM/J relative to LG/J mice with poor and good tissue healing capacity respectively. In the first few months of life, LG/J mice maintain a relatively constant pool of notochordal-like cells in the nucleus pulposus (NP) of the IVD. In contrast, chondrogenic events are observed in SM/J mice beginning as early as one-week-old, with progressive fibrotic changes. Further, the extracellular matrix changes in the NP are consistent with IVD degeneration. Leveraging on the genomic data of two parental and two recombinant inbred lines, we assessed the genetic contribution to the NP changes and identified processes linked to the regulation of ion transport systems. Significantly, "transport" system is also in the top three gene ontology (GO) terms from a comparative proteomic analysis of the mouse NP. These findings support the potential of the SM/J, LG/J and their recombinant inbred lines for future genetic and biological analysis in mice and validation of candidate genes and biological relevance in human cohort studies. The proteomic data has been deposited to the ProteomeXchange Consortium via the PRIDE [1] partner repository with the dataset identifier PXD008784.