Targeting of αv integrin identifies a core molecular pathway that regulates fibrosis in several organs

Mechanobiology of portal hypertension

The interplay between mechanical stimuli and cellular mechanobiology orchestrates the physiology of tissues and organs in a dynamic balance characterized by constant remodelling and adaptative processes. Environmental mechanical properties can be interpreted as a complex set of information and instructions that cells read continuously, and to which they respond. In cirrhosis, chronic inflammation and injury drive liver cells dysfunction, leading to excessive extracellular matrix deposition, sinusoidal pseudocapillarization, vascular occlusion and parenchymal extinction. These pathological events result in marked remodelling of the liver microarchitecture, which is cause and result of abnormal environmental mechanical forces, triggering and sustaining the long-standing and progressive process of liver fibrosis. Multiple mechanical forces such as strain, shear stress, and hydrostatic pressure can converge at different stages of the disease until reaching a point of no return where the fibrosis is considered non-reversible. Thereafter, reciprocal communication between cells and their niches becomes the driving force for disease progression. Accumulating evidence supports the idea that, rather than being a passive consequence of fibrosis and portal hypertension (PH), mechanical force-mediated pathways could themselves represent strategic targets for novel therapeutic approaches. In this manuscript, we aim to provide a comprehensive review of the mechanobiology of PH, by furnishing an introduction on the most important mechanisms, integrating these concepts into a discussion on the pathogenesis of PH, and exploring potential therapeutic strategies.

Back to the future: targeting the extracellular matrix to treat systemic sclerosis

Fibrosis is the excessive deposition of a stable extracellular matrix (ECM); fibrotic tissue is composed principally of highly crosslinked type I collagen and highly contractile myofibroblasts. Systemic sclerosis (SSc) is a multisystem autoimmune connective tissue disease characterized by skin and organ fibrosis. The fibrotic process has been recognized in SSc for >40 years, but drugs with demonstrable efficacy against SSc fibrosis in ameliorating the lung involvement have only recently been identified. Unfortunately, these treatments are ineffective at improving the skin score in patients with SSc. Previous clinical trials in SSc have largely focused on the cross-purposing of anti-inflammatory drugs and the use of immunosuppressive drugs from the transplantation field, which address inflammatory and/or autoimmune processes. Limited examination has taken place of specific anti-fibrotic agents developed through their ability to directly target the ECM in SSc by, for example, alleviating the persistent matrix stiffness and mechanotransduction that might be required for both the initiation and maintenance of fibrosis, including in SSc. However, because of the importance of the ECM in the SSc phenotype, attempts have now been made to identify drugs that specifically target the ECM, including some drugs that are currently under consideration for the treatment of cancer.

Therapeutic modulation of the liver immune microenvironment

Inflammation is a hallmark of progressive liver diseases such as chronic viral or immune-mediated hepatitis, alcohol-associated liver disease, and NAFLD. Preclinical and clinical studies have provided robust evidence that cytokines and related cellular stress sensors in innate and adaptive immunity orchestrate hepatic disease processes. Unresolved inflammation and liver injury result in hepatic scarring, fibrosis, and cirrhosis, which may culminate in HCC. Liver diseases are accompanied by gut dysbiosis and a bloom of pathobionts, fueling hepatic inflammation. Anti-inflammatory strategies are extensively used to treat human immune-mediated conditions beyond the liver, while evidence for immunomodulatory therapies and cell therapy-based strategies in liver diseases is only emerging. The development and establishment of novel immunomodulatory therapies for chronic liver diseases has been dampened by several clinical challenges, such as invasive monitoring of therapeutic efficacy with liver biopsy in clinical trials and risk of DILI in several studies. Such aspects prevented advancements of novel medical therapies for chronic inflammatory liver diseases. New concepts modulating the liver immune environment are studied and eagerly awaited to improve the management of chronic liver diseases in the future.

Inhibition of integrin binding to ligand arg-gly-asp motif induces AKT-mediated cellular senescence in hepatic stellate cells

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) play an essential role in liver fibrogenesis. The induction of cellular senescence has been reported to inhibit HSC activation. Previously, we demonstrated that CWHM12, a small molecule arginine-glycine-aspartic acid (RGD) peptidomimetic compound, inhibits HSC activation. This study investigated whether the inhibitory effects of CWHM12 on HSCs affected cellular senescence.

METHODS

The immortalized human HSC lines, LX-2 and TWNT-1, were used to evaluate the effects of CWHM12 on cellular senescence via the disruption of RGD-mediated binding to integrins.

RESULTS

CWHM12 induces cell cycle arrest, senescence-associated beta-galactosidase activity, acquisition of senescence-associated secretory phenotype (SASP), and expression of senescence-associated proteins in HSCs. Further experiments revealed that the phosphorylation of AKT and murine double minute 2 (MDM2) was involved in the effects of CWHM12, and the inhibition of AKT phosphorylation reversed these effects of CWHM12 on HSCs.

CONCLUSIONS

Pharmacological inhibition of RGD-mediated integrin binding induces senescence in activated HSCs.

The Dual-Mode Transition of Myofibroblasts Derived from Hepatic Stellate Cells in Liver Fibrosis

Hepatic stellate cells (HSCs) are the key promoters of liver fibrosis. In response to liver-fibrosis-inducing factors, HSCs express alpha smooth muscle actin (α-SMA) and obtain myofibroblast phenotype. Collagen secretion and high expression of α-SMA with related high cell tension and migration limitation are the main characteristics of myofibroblasts. How these two characteristics define the role of myofibroblasts in the initiation and progression of liver fibrosis is worth exploring. From this perspective, we explored the correlation between α-SMA expression and collagen secretion in myofibroblasts and the characteristics of collagen deposition in liver fibrosis. Based on a reasonable hypothesis and experimental verification, we believe that the myofibroblast with the α-SMAhighcollagenhigh model do not effectively explain the initial stage and progression characteristics of liver fibrosis. Therefore, we propose a myofibroblast dual-mode transition model in fibrotic liver (DMTM model). In the DMTM model, myofibroblasts have dual modes. Myofibroblasts obtain enhanced α-SMA expression, accompanied by collagen expression inhibition in the high-concentration region of TGF-β. At the edge of the TGF-β positive region, myofibroblasts convert to a high-migration and high-collagen secretion phenotype. This model reasonably explains collagen deposition and expansion in the initial stage of liver fibrosis.

Molecular View on the iRGD Peptide Binding Mechanism: Implications for Integrin Activity and Selectivity Profiles

Receptor-selective peptides are widely used as smart carriers for specific tumor-targeted delivery. A remarkable example is the cyclic nonapeptide iRGD (CRGDKPGDC, 1) that couples intrinsic cytotoxic effects with striking tumor-homing properties. These peculiar features are based on a rather complex multistep mechanism of action, where the primary event is the recognition of RGD integrins. Despite the high number of preclinical studies and the recent success of a phase I trial for the treatment of pancreatic ductal adenocarcinoma (PDAC), there is little information available about the iRGD three-dimensional (3D) structure and integrin binding properties. Here, we re-evaluate the peptide's affinity for cancer-related integrins including not only the previously known targets αvβ3 and αvβ5 but also the αvβ6 isoform, which is known to drive cell growth, migration, and invasion in many malignancies including PDAC. Furthermore, we use parallel tempering in the well-tempered ensemble (PT-WTE) metadynamics simulations to characterize the in-solution conformation of iRGD and extensive molecular dynamics calculations to fully investigate its binding mechanism to integrin partners. Finally, we provide clues for fine-tuning the peptide's potency and selectivity profile, which, in turn, may further improve its tumor-homing properties.

Dupuytren's Disease Is Mediated by Insufficient TGF-β1 Release and Degradation

Dupuytren's disease (DD) is a fibroproliferative disorder affecting the palmar fascia, causing functional restrictions of the hand and thereby limiting patients' daily lives. The disturbed and excessive myofibroblastogenesis, causing DD, is mainly induced by transforming growth factor (TGF)-β1. But, the extent to which impaired TGF-β1 release or TGF-β signal degradation is involved in pathologically altered myofibroblastogenesis in DD has been barely examined. Therefore, the complex in which TGF-β1 is secreted in the extracellular matrix to elicit its biological activity, and proteins such as plasmin, integrins, and matrix metalloproteinases (MMPs), which are involved in the TGF-β1 activation, were herein analyzed in DD-fibroblasts (DD-FBs). Additionally, TGF-β signal degradation via caveolin-1 was examined with 5-fluoruracil (5-FU) in detail. Gene expression analysis was performed via Western blot, PCR, and immunofluorescence analyses. As a surrogate parameter for disturbed myofibroblastogenesis, 𝛼-smooth-muscle-actin (𝛼-SMA) expression was evaluated. It was demonstrated that latency-associated peptide (LAP)-TGF-β and latent TGF-β-binding protein (LTBP)-1 involved in TGF-β-complex building were significantly upregulated in DD. Plasmin a serinprotease responsible for the TGF-β release was significantly downregulated. The application of exogenous plasmin was able to inhibit disturbed myofibroblastogenesis, as measured via 𝛼-SMA expression. Furthermore, a reduced TGF-β1 degradation was also involved in the pathological phenotype of DD, because caveolin-1 expression was significantly downregulated, and if rescued, myofibroblastogenesis was also inhibited. Therefore, our study demonstrates that a deficient release and degradation of TGF-β1 are important players in the pathological phenotype of DD and should be addressed in future research studies to improve DD therapy or other related fibrotic conditions.

Hepatic stellate cell-intrinsic role of SOCS1 in controlling hepatic fibrogenic response and the pro-inflammatory macrophage compartment during liver fibrosis

Introduction

Hepatic stellate cells (HSC) become activated, differentiate to myofibroblasts and produce extracellular fibrillar matrix during liver fibrosis. The hepatic fibrogenic response is orchestrated by reciprocal interactions between HSCs and macrophages and their secreted products. SOCS1 can regulate several cytokines and growth factors implicated in liver fibrosis. Here we investigated the role of SOCS1 in regulating HSC activation.

Methods

Mice lacking SOCS1 in HSCs (Socs1ΔHSC) were generated by crossing Socs1fl/fl and LratCre mice. Liver fibrosis was induced by carbon tetrachloride and evaluated by Sirius red staining, hydroxyproline content and immunostaining of myofibroblasts. Gene expression of pro-fibrogenic factors, cytokines, growth factors and chemokines were quantified by RT-qPCR. The phenotype and the numbers of intrahepatic leukocyte subsets were studied by flow cytometry. The impact of fibrosis on the development of diethyl nitrosamine-induced hepatocellular carcinoma was evaluated.

Results

Socs1ΔHSC mice developed more severe liver fibrosis than control Socs1fl/fl mice that was characterized by increased collagen deposition and myofibroblast differentiation. Socs1ΔHSC mice showed a significant increase in the expression of smooth muscle actin, collagens, matrix metalloproteases, cytokines, growth factors and chemokines in the liver following fibrosis induction. The fibrotic livers of Socs1ΔHSC mice displayed heightened inflammatory cell infiltration with increased proportion and numbers of Ly6ChiCCR2+ pro-inflammatory macrophages. This macrophage population contained elevated numbers of CCR2+CX3CR1+ cells, suggesting impaired transition towards restorative macrophages. Fibrosis induction following exposure to diethyl nitrosamine resulted in more numerous and larger liver tumor nodules in Socs1ΔHSC mice than in Socs1fl/fl mice.

Discussion

Our findings indicate that (i) SOCS1 expression in HSCs is a critical to control liver fibrosis and development of hepatocaellular carcinoma, and (ii) attenuation of HSC activation by SOCS1 regulates pro-inflammatory macrophage recruitment and differentiation during liver fibrosis.

Kidney fibrosis: Emerging diagnostic and therapeutic strategies

An increasing number of patients worldwide suffers from chronic kidney disease (CKD). CKD is accompanied by kidney fibrosis, which affects all compartments of the kidney, i.e., the glomeruli, tubulointerstitium, and vasculature. Fibrosis is the best predictor of progression of kidney diseases. Currently, there is no specific anti-fibrotic therapy for kidney patients and invasive renal biopsy remains the only option for specific detection and quantification of kidney fibrosis. Here we review emerging diagnostic approaches and potential therapeutic options for fibrosis. We discuss how translational research could help to establish fibrosis-specific endpoints for clinical trials, leading to improved patient stratification and potentially companion diagnostics, and facilitating and optimizing development of novel anti-fibrotic therapies for kidney patients.

Extracellular Matrix Stiffness Regulates Microvascular Stability by Controlling Endothelial Paracrine Signaling to Determine Pericyte Fate

BACKGROUND

The differentiation of pericytes into myofibroblasts causes microvascular degeneration, ECM (extracellular matrix) accumulation, and tissue stiffening, characteristics of fibrotic diseases. It is unclear how pericyte-myofibroblast differentiation is regulated in the microvascular environment. Our previous study established a novel 2-dimensional platform for coculturing microvascular endothelial cells (ECs) and pericytes derived from the same tissue. This study investigated how ECM stiffness regulated microvascular ECs, pericytes, and their interactions.

METHODS

Primary microvessels were cultured in the TGM2D medium (tubular microvascular growth medium on 2-dimensional substrates). Stiff ECM was prepared by incubating ECM solution in regular culture dishes for 1 hour followed by PBS wash. Soft ECM with Young modulus of ≈6 kPa was used unless otherwise noted. Bone grafts were prepared from the rat skull. Immunostaining, RNA sequencing, RT-qPCR (real-time quantitative polymerase chain reaction), Western blotting, and knockdown experiments were performed on the cells.

RESULTS

Primary microvascular pericytes differentiated into myofibroblasts (NG2+αSMA+) on stiff ECM, even with the TGFβ (transforming growth factor beta) signaling inhibitor A83-01. Soft ECM and A83-01 cooperatively maintained microvascular stability while inhibiting pericyte-myofibroblast differentiation (NG2+αSMA-/low). We thus defined 2 pericyte subpopulations: primary (NG2+αSMA-/low) and activated (NG2+αSMA+) pericytes. Soft ECM promoted microvascular regeneration and inhibited fibrosis in bone graft transplantation in vivo. As integrins are the major mechanosensor, we performed RT-qPCR screening of integrin family members and found Itgb1 (integrin β1) was the major subunit downregulated by soft ECM and A83-01 treatment. Knocking down Itgb1 suppressed myofibroblast differentiation on stiff ECM. Interestingly, ITGB1 phosphorylation (Y783) was mainly located on microvascular ECs on stiff ECM, which promoted EC secretion of paracrine factors, including CTGF (connective tissue growth factor), to induce pericyte-myofibroblast differentiation. CTGF knockdown or monoclonal antibody treatment partially reduced myofibroblast differentiation, implying the participation of multiple pathways in fibrosis formation.

CONCLUSIONS

ECM stiffness and TGFβ signaling cooperatively regulate microvascular stability and pericyte-myofibroblast differentiation. Stiff ECM promotes EC ITGB1 phosphorylation (Y783) and CTGF secretion, which induces pericyte-myofibroblast differentiation.

Novel approaches to target fibroblast mechanotransduction in fibroproliferative diseases

The ability of cells to sense and respond to changes in mechanical environment is vital in conditions of organ injury when the architecture of normal tissues is disturbed or lost. Among the various cellular players that respond to injury, fibroblasts take center stage in re-establishing tissue integrity by secreting and organizing extracellular matrix into stabilizing scar tissue. Activation, activity, survival, and death of scar-forming fibroblasts are tightly controlled by mechanical environment and proper mechanotransduction ensures that fibroblast activities cease after completion of the tissue repair process. Conversely, dysregulated mechanotransduction often results in fibroblast over-activation or persistence beyond the state of normal repair. The resulting pathological accumulation of extracellular matrix is called fibrosis, a condition that has been associated with over 40% of all deaths in the industrialized countries. Consequently, elements in fibroblast mechanotransduction are scrutinized for their suitability as anti-fibrotic therapeutic targets. We review the current knowledge on mechanically relevant factors in the fibroblast extracellular environment, cell-matrix and cell-cell adhesion structures, stretch-activated membrane channels, stress-regulated cytoskeletal structures, and co-transcription factors. We critically discuss the targetability of these elements in therapeutic approaches and their progress in pre-clinical and/or clinical trials to treat organ fibrosis.

Sulforaphane-driven reprogramming of gut microbiome and metabolome ameliorates the progression of hyperuricemia

INTRODUCTION

Currently, revealing how to prevent and control hyperuricemia has become an essential public health issue. Sulforaphane hasawiderangeofapplications in the management of hyperuricemia.

OBJECTIVE

The study objective was to verify the uric acid-lowering effects and the regulation of the gut-kidney axis mediated by sulforaphane and identify host-microbial co-metabolites in hyperuricemia.

METHODS

A hyperuricemia model was established by administering feedstuffs with 4% potassium oxonate and 20% yeast. Forty male Sprague-Dawley rats were randomly divided into the normal control, hyperuricemia, allopurinol, and sulforaphane groups. Animals were treated by oral gavage for six consecutive weeks, and then phenotypic parameters, metabolomic profiling, and metagenomicsequencing were performed.

RESULTS

Sulforaphane could lower uric acid by decreasing urate synthesis and increasing renal urate excretion in hyperuricemic rats (P＜0.05). We identified succinic acid and oxoglutaric acid as critical host-gut microbiome co-metabolites. Moreover, sulforaphane improved the diversity of microbial ecosystems and functions, as well as metabolic control of the kidney. Notably, sulforaphane exerted its renoprotective effect through epigenetic modification of Nrf2 and interaction between gut microbiota and epigenetic modification in hyperuricemic rats.

CONCLUSION

We revealed that sulforaphane could ameliorate the progression of hyperuricemia by reprogramming the gut microbiome and metabolome. Our findings may provide a good means for efficiently preventing and treating hyperuricemia.

Hepatic inflammatory responses in liver fibrosis

Chronic liver diseases such as nonalcoholic fatty liver disease (NAFLD) or viral hepatitis are characterized by persistent inflammation and subsequent liver fibrosis. Liver fibrosis critically determines long-term morbidity (for example, cirrhosis or liver cancer) and mortality in NAFLD and nonalcoholic steatohepatitis (NASH). Inflammation represents the concerted response of various hepatic cell types to hepatocellular death and inflammatory signals, which are related to intrahepatic injury pathways or extrahepatic mediators from the gut-liver axis and the circulation. Single-cell technologies have revealed the heterogeneity of immune cell activation concerning disease states and the spatial organization within the liver, including resident and recruited macrophages, neutrophils as mediators of tissue repair, auto-aggressive features of T cells as well as various innate lymphoid cell and unconventional T cell populations. Inflammatory responses drive the activation of hepatic stellate cells (HSCs), and HSC subsets, in turn, modulate immune mechanisms via chemokines and cytokines or transdifferentiate into matrix-producing myofibroblasts. Current advances in understanding the pathogenesis of inflammation and fibrosis in the liver, mainly focused on NAFLD or NASH owing to the high unmet medical need, have led to the identification of several therapeutic targets. In this Review, we summarize the inflammatory mediators and cells in the diseased liver, fibrogenic pathways and their therapeutic implications.

Friend or foe? The elusive role of hepatic stellate cells in liver cancer

Liver fibrosis is a substantial risk factor for the development and progression of liver cancer, which includes hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA). Studies utilizing cell fate mapping and single-cell transcriptomics techniques have identified quiescent perisinusoidal hepatic stellate cells (HSCs) as the primary source of activated collagen-producing HSCs and liver cancer-associated fibroblasts (CAFs) in HCC and liver metastasis, complemented in iCCA by contributions from portal fibroblasts. At the same time, integrative computational analysis of single-cell, single-nucleus and spatial RNA sequencing data have revealed marked heterogeneity among HSCs and CAFs, with distinct subpopulations displaying unique gene expression signatures and functions. Some of these subpopulations have divergent roles in promoting or inhibiting liver fibrogenesis and carcinogenesis. In this Review, we discuss the dual roles of HSC subpopulations in liver fibrogenesis and their contribution to liver cancer promotion, progression and metastasis. We review the transcriptomic and functional similarities between HSC and CAF subpopulations, highlighting the pathways that either promote or prevent fibrosis and cancer, and the immunological landscape from which these pathways emerge. Insights from ongoing studies will yield novel strategies for developing biomarkers, assessing prognosis and generating new therapies for both HCC and iCCA prevention and treatment.

Integrated single-cell RNA sequencing analysis reveals a mesenchymal stem cell-associated signature for estimating prognosis and drug sensitivity in gastric cancer

BACKGROUND

Mesenchymal stem cells (MSCs) play an important role in regulating all stages of the immune response, angiogenesis, and transformation of matrix components in the tumor microenvironment. The aim of this study was to identify the prognostic value of MSC-related signatures in patients with gastric cancer (GC).

METHODS

MSC marker genes were identified by analyzing single-cell RNA sequencing (scRNA-seq) data for GC from the Gene Expression Omnibus (GEO) database. Using bulk sequencing data from the Cancer Genome Atlas-Stomach adenocarcinoma (TCGA-STAD), as a training cohort, and data from GEO, as a validation cohort, we developed a risk model consisting of MSC prognostic signature genes, and classified GC patients into high- and low-MSC risk subgroups. Multifactorial Cox regression was used to evaluate whether MSC prognostic signature was an independent prognostic factor. An MSC nomogram was constructed combining clinical information and risk grouping. Subsequently, we evaluated the effect of MSC prognostic signature on immune cell infiltration, antitumor drugs and immune checkpoints and verified the expression of MSC prognostic signature by in vitro cellular assays.

RESULTS

In this study, 174 MSC marker genes were identified by analyzing scRNA-seq data. We identified seven genes (POSTN, PLOD2, ITGAV, MMP11, SDC2, MARCKS, ANXA5) to construct MSC prognostic signature. MSC prognostic signature was an independent risk factor in the TCGA and GEO cohorts. GC patients in the high-MSC risk group had worse prognoses. In addition, the MSC nomogram has a high clinical application value. Notably, the MSC signature can induce the development of a poor immune microenvironment. GC patients in the high MSC-risk group were more sensitive to anticancer drugs and tended to have higher levels of immune checkpoint markers. In qRT-PCR assays, the MSC signature was more highly expressed in GC cell lines.

CONCLUSIONS

The MSC marker gene-based risk signature developed in this study can not only be used to predict the prognosis of GC patients, but also has the potential to reflect the efficacy of antitumor therapies.

Endothelial cell plasticity in kidney fibrosis and disease

Renal endothelial cells demonstrate an impressive remodeling potential during angiogenic sprouting, vessel repair or while transitioning into mesenchymal cells. These different processes may play important roles in both renal disease progression or regeneration while underlying signaling pathways of different endothelial cell plasticity routes partly overlap. Angiogenesis contributes to wound healing after kidney injury and pharmaceutical modulation of angiogenesis may home a great therapeutic potential. Yet, it is not clear whether any differentiated endothelial cell can proliferate or whether regenerative processes are largely controlled by resident or circulating endothelial progenitor cells. In the glomerular compartment for example, a distinct endothelial progenitor cell population may remodel the glomerular endothelium after injury. Endothelial-to-mesenchymal transition (EndoMT) in the kidney is vastly documented and often associated with endothelial dysfunction, fibrosis, and kidney disease progression. Especially the role of EndoMT in renal fibrosis is controversial. Studies on EndoMT in vivo determined possible conclusions on the pathophysiological role of EndoMT in the kidney, but whether endothelial cells really contribute to kidney fibrosis and if not what other cellular and functional outcomes derive from EndoMT in kidney disease is unclear. Sequencing data, however, suggest no participation of endothelial cells in extracellular matrix deposition. Thus, more in-depth classification of cellular markers and the fate of EndoMT cells in the kidney is needed. In this review, we describe different signaling pathways of endothelial plasticity, outline methodological approaches and evidence for functional and structural implications of angiogenesis and EndoMT in the kidney, and eventually discuss controversial aspects in the literature.

Mechanical stiffness promotes skin fibrosis through Piezo1-mediated arginine and proline metabolism

The increased mechanics of fibrotic skin tissue continuously regulate fibroblast functions such as survival and differentiation. Although all these processes consume metabolites, it is unclear whether and how cells adapt their metabolic activity to increased matrix stiffness. Here, we show that transferring mouse dermal fibroblasts from soft to stiff substrates causes an up-regulation of arginine and proline metabolism. Increased matrix stiffness stimulates the expression and activity of key metabolic enzymes, leading to the synthesis of L-proline, a major source of collagen. In addition, the novel mechanosensitive channel Piezo1 was identified as a key regulator of arginine and proline metabolism in fibroblasts under increased stiffness. Consistently, targeting Piezo1 to dermal fibroblasts in vivo effectively reduces fibrosis and arginine-proline metabolism in mouse skin. Therefore, mechanical stiffness is a critical environmental cue for fibroblast metabolism and skin fibrosis progression.

Longitudinal assessment of strength and body composition in a mouse model of chronic alcohol-related myopathy

BACKGROUND

Excessive, chronic alcohol consumption can result in muscle atrophy and weakness (i.e., alcoholic myopathy) that impairs the quality of life. However, the precise mechanisms responsible for ethanol's detrimental impact on skeletal muscle have not been fully elucidated, in part due because the time course of disease development and progression are not well established. Therefore, we examined muscle strength and body composition longitudinally using an established preclinical mouse model of chronic alcoholic myopathy.

METHODS

To establish a time course of chronic alcoholic myopathy, we fed High Drinking in the Dark (HDID) female mice (n = 7) 20% ethanol for ~32 weeks (following a 2-week ethanol ramping period). We assessed in vivo isometric contractility of the left ankle dorsiflexor and lean mass via NMR every 4 weeks. Outcomes were compared with age-matched control HDID mice that did not consume ethanol (n = 8).

RESULTS

At study completion, mice who consumed ethanol were 12% weaker than control mice (p = 0.015). Compared to baseline, consuming ethanol resulted in an acute transient reduction in dorsiflexion torque at Week 4 (p = 0.032) that was followed by a second, more sustained reduction at Week 20 (p < 0.001). Changes in lean mass paralleled those of dorsiflexor torque, with ~40% of the variance in dorsiflexor torque being explained by the variance in lean mass of the ethanol group (p < 0.001). Dorsiflexor torque normalized to lean mass (mN·m/g lean mass) did not differ between the ethanol and control groups from Weeks 4 to 32 (p ≥ 0.498).

CONCLUSIONS

These results indicate that reductions in muscle mass and strength due to chronic, excessive ethanol intake are dynamic, not necessarily linear, processes. Moreover, the findings confirm that ethanol-induced weakness is primarily driven by muscle atrophy (i.e., loss of muscle quantity). Future studies should consider how chronic alcoholic myopathy develops and progresses rather than identifying changes after it has been diagnosed.

[Biomechanical properties of epithelial mesenchymal transition in idiopathic pulmonary fibrosis]

Idiopathic pulmonary fibrosis (IPF) is a progressive scar-forming disease with a high mortality rate that has received widespread attention. Epithelial mesenchymal transition (EMT) is an important part of the pulmonary fibrosis process, and changes in the biomechanical properties of lung tissue have an important impact on it. In this paper, we summarize the changes in the biomechanical microenvironment of lung tissue in IPF-EMT in recent years, and provide a systematic review on the effects of alterations in the mechanical microenvironment in pulmonary fibrosis on the process of EMT, the effects of mechanical factors on the behavior of alveolar epithelial cells in EMT and the biomechanical signaling in EMT, in order to provide new references for the research on the prevention and treatment of IPF.

Axon guidance genes control hepatic artery development

Earlier data on liver development demonstrated that morphogenesis of the bile duct, portal mesenchyme and hepatic artery is interdependent, yet how this interdependency is orchestrated remains unknown. Here, using 2D and 3D imaging, we first describe how portal mesenchymal cells become organised to form hepatic arteries. Next, we examined intercellular signalling active during portal area development and found that axon guidance genes are dynamically expressed in developing bile ducts and portal mesenchyme. Using tissue-specific gene inactivation in mice, we show that the repulsive guidance molecule BMP co-receptor A (RGMA)/neogenin (NEO1) receptor/ligand pair is dispensable for portal area development, but that deficient roundabout 2 (ROBO2)/SLIT2 signalling in the portal mesenchyme causes reduced maturation of the vascular smooth muscle cells that form the tunica media of the hepatic artery. This arterial anomaly does not impact liver function in homeostatic conditions, but is associated with significant tissular damage following partial hepatectomy. In conclusion, our work identifies new players in development of the liver vasculature in health and liver regeneration.

Fibroblasts in liver cancer: functions and therapeutic translation

Accumulation of fibroblasts in the premalignant or malignant liver is a characteristic feature of liver cancer, but has not been therapeutically leveraged despite evidence for pathophysiologically relevant roles in tumour growth. Hepatocellular carcinoma is a largely non-desmoplastic tumour, in which fibroblasts accumulate predominantly in the pre-neoplastic fibrotic liver and regulate the risk for hepatocellular carcinoma development through a balance of tumour-suppressive and tumour-promoting mediators. By contrast, cholangiocarcinoma is desmoplastic, with cancer-associated fibroblasts contributing to tumour growth. Accordingly, restoring the balance from tumour-promoting to tumour-suppressive fibroblasts and mediators might represent a strategy for hepatocellular carcinoma prevention, whereas in cholangiocarcinoma, fibroblasts and their mediators could be leveraged for tumour treatment. Importantly, fibroblast mediators regulating hepatocellular carcinoma development might exert opposite effects on cholangiocarcinoma growth. This Review translates the improved understanding of tumour-specific, location-specific, and stage-specific roles of fibroblasts and their mediators in liver cancer into novel and rational therapeutic concepts.

Unraveling the activation process and core driver genes of HSCs during cirrhosis by single-cell transcriptome

Worldwide, cirrhosis is a common cause of death, manifesting itself as fibrosis of the liver tissue. When the liver is damaged, the liver produces fibrotic, proliferative myofibroblasts, which are formed by the differentiation of activated hepatic stellate cells. There are no effective antifibrotic treatment options. To deeply explore the activation process of hepatic stellate cells (HSCs) and to discover better therapeutic target genes, single-cell RNA sequencing data on 13 non-cirrhotic liver tissue samples and 10 cirrhotic liver tissue samples were analyzed. We identified activated HSCs from the mesenchymal cell population with high expression of ACTA2. By pseudo-time analysis, we found that the key genes for the differentiation of HSCs into myofibroblasts were C3, CCDC80, COL1A1, COL3A1, DCN, FBLN1, IGFBP3, MXRA5, SERPINE1, and MYH11. Then, we found that the main regulators of HSCs from inactive to activated state were NTF3, NTRK3, NTRK2, JAG1, NOTCH3, ESAM, and CD46 by cell-cell communication analysis. In addition, we found that the top2 hub genes of activated HSCs were CRIP1 and ACTA2. The experimental results show that the top2 hub genes were significantly overexpressed in cirrhotic samples. Our work dissected key intercellular regulators and core driver genes during hepatic stellate cell activation during cirrhosis through single-cell transcriptome data analysis, providing a research strategy to discover rational therapeutic targets for cirrhosis and some important information for gene targeting therapy.

Cellular mechanotransduction in health and diseases: from molecular mechanism to therapeutic targets

Cellular mechanotransduction, a critical regulator of numerous biological processes, is the conversion from mechanical signals to biochemical signals regarding cell activities and metabolism. Typical mechanical cues in organisms include hydrostatic pressure, fluid shear stress, tensile force, extracellular matrix stiffness or tissue elasticity, and extracellular fluid viscosity. Mechanotransduction has been expected to trigger multiple biological processes, such as embryonic development, tissue repair and regeneration. However, prolonged excessive mechanical stimulation can result in pathological processes, such as multi-organ fibrosis, tumorigenesis, and cancer immunotherapy resistance. Although the associations between mechanical cues and normal tissue homeostasis or diseases have been identified, the regulatory mechanisms among different mechanical cues are not yet comprehensively illustrated, and no effective therapies are currently available targeting mechanical cue-related signaling. This review systematically summarizes the characteristics and regulatory mechanisms of typical mechanical cues in normal conditions and diseases with the updated evidence. The key effectors responding to mechanical stimulations are listed, such as Piezo channels, integrins, Yes-associated protein (YAP) /transcriptional coactivator with PDZ-binding motif (TAZ), and transient receptor potential vanilloid 4 (TRPV4). We also reviewed the key signaling pathways, therapeutic targets and cutting-edge clinical applications of diseases related to mechanical cues.

Characterization of human stem cell-derived hepatic stellate cells and liver sinusoidal endothelial cells during extended in vitro culture

Background: There is a significant need for predictive and stable in vitro human liver representations for disease modeling and drug testing. Hepatic stellate cells (HSCs) and liver sinusoidal endothelial cells (LSECs) are important non-parenchymal cell components of the liver and are hence of relevance in a variety of disease models, including hepatic fibrosis. Pluripotent stem cell- (PSC-) derived HSCs (scHSCs) and LSECs (scLSECs) offer an attractive alternative to primary human material; yet, the suitability of scHSCs and scLSECs for extended in vitro modeling has not been characterized. Methods: In this study, we describe the phenotypic and functional development of scHSCs and scLSECs during 14 days of 2D in vitro culture. Cell-specific phenotypes were evaluated by cell morphology, immunofluorescence, and gene- and protein expression. Functionality was assessed in scHSCs by their capacity for intracellular storage of vitamin A and response to pro-fibrotic stimuli induced by TGF-β. scLSECs were evaluated by nitric oxide- and factor VIII secretion as well as endocytic uptake of bioparticles and acetylated low-density lipoprotein. Notch pathway inhibition and co-culturing scHSCs and scLSECs were separately tested as options for enhancing long-term stability and maturation of the cells. Results and Conclusion: Both scHSCs and scLSECs exhibited a post-differentiation cell type-specific phenotype and functionality but deteriorated during extended culture with PSC line-dependent variability. Therefore, the choice of PSC line and experimental timeframe is crucial when designing in vitro platforms involving scHSCs and scLSECs. Notch inhibition modestly improved long-term monoculture in a cell line-dependent manner, while co-culturing scHSCs and scLSECs provides a strategy to enhance phenotypic and functional stability.

Cell Adhesion Molecules in Fibrotic Diseases

Mechanisms underlying the pathogenesis of tissue fibrosis remain incompletely understood. Emerging evidence suggests that cell adhesion molecules (CAMs) are critical in fibrotic progression in many organs, including lung, kidney, skin, and liver. CAMs promote cell-cell and cell-extracellular matrix (ECM) interactions to maintain tissue architecture and normal function in homeostasis. However, dysregulated expression and function of CAMs can lead to chronic inflammation and tissue fibrosis. The major families of CAMs include integrins, cadherins, selectins, and immunoglobulins. Here, we review the role of the CAMs in fibrosis development across various organs with a focus on integrins and cadherins, and discuss their respective roles in the development of pulmonary fibrosis.

Myocardin-related transcription factor contributes to renal fibrosis through the regulation of extracellular microenvironment surrounding fibroblasts

Fibroblast accumulation and extracellular matrix (ECM) deposition are common critical steps for the progression of organ fibrosis, but the precise molecular mechanisms remain to be fully investigated. We have previously demonstrated that lysophosphatidic acid contributes to organ fibrosis through the production of connective tissue growth factor (CTGF) via actin cytoskeleton-dependent signaling, myocardin-related transcription factor family (MRTF) consisting of MRTF-A and MRTF-B-serum response factor (SRF) pathway. In this study, we investigated the role of the MRTF-SRF pathway in the development of renal fibrosis, focusing on the regulation of ECM-focal adhesions (FA) in renal fibroblasts. Here we showed that both MRTF-A and -B were required for the expressions of ECM-related molecules such as lysyl oxidase family members, type I procollagen and fibronectin in response to transforming growth factor (TGF)-β1 . TGF-β1 -MRTF-SRF pathway induced the expressions of various components of FA such as integrin α subunits (αv , α2 , α11 ) and β subunits (β1 , β3 , β5 ) as well as integrin-linked kinase (ILK). On the other hand, the blockade of ILK suppressed TGF-β1 -induced MRTF-SRF transcriptional activity, indicating a mutual relationship between MRTF-SRF and FA. Myofibroblast differentiation along with CTGF expression was also dependent on MRTF-SRF and FA components. Finally, global MRTF-A deficient and inducible fibroblast-specific MRTF-B deficient mice (MRTF-AKO BiFBKO mice) are protected from renal fibrosis with adenine administration. Renal expressions of ECM-FA components and CTGF as well as myofibroblast accumulation were suppressed in MRTF-AKO BiFBKO mice. These results suggest that the MRTF-SRF pathway might be a therapeutic target for renal fibrosis through the regulation of components forming ECM-FA in fibroblasts.

Strategic outline of interventions targeting extracellular matrix for promoting healthy longevity

The extracellular matrix (ECM), composed of interlinked proteins outside of cells, is an important component of the human body that helps maintain tissue architecture and cellular homeostasis. As people age, the ECM undergoes changes that can lead to age-related morbidity and mortality. Despite its importance, ECM aging remains understudied in the field of geroscience. In this review, we discuss the core concepts of ECM integrity, outline the age-related challenges and subsequent pathologies and diseases, summarize diagnostic methods detecting a faulty ECM, and provide strategies targeting ECM homeostasis. To conceptualize this, we built a technology research tree to hierarchically visualize possible research sequences for studying ECM aging. This strategic framework will hopefully facilitate the development of future research on interventions to restore ECM integrity, which could potentially lead to the development of new drugs or therapeutic interventions promoting health during aging.

Liquid Biopsy at the Frontier of Kidney Diseases: Application of Exosomes in Diagnostics and Therapeutics

In the era of precision medicine, liquid biopsy techniques, especially the use of urine analysis, represent a paradigm shift in the identification of biomarkers, with considerable implications for clinical practice in the field of nephrology. In kidney diseases, the use of this non-invasive tool to identify specific and sensitive biomarkers other than plasma creatinine and the glomerular filtration rate is becoming crucial for the diagnosis and assessment of a patient's condition. In recent years, studies have drawn attention to the importance of exosomes for diagnostic and therapeutic purposes in kidney diseases. Exosomes are nano-sized extracellular vesicles with a lipid bilayer structure, composed of a variety of biologically active substances. In the context of kidney diseases, studies have demonstrated that exosomes are valuable carriers of information and are delivery vectors, rendering them appealing candidates as biomarkers and drug delivery vehicles with beneficial therapeutic outcomes for kidney diseases. This review summarizes the applications of exosomes in kidney diseases, emphasizing the current biomarkers of renal diseases identified from urinary exosomes and the therapeutic applications of exosomes with reference to drug delivery and immunomodulation. Finally, we discuss the challenges encountered when using exosomes for therapeutic purposes and how these may affect its clinical applications.

NO-sensitive guanylyl cyclase discriminates pericyte-derived interstitial from intra-alveolar myofibroblasts in murine pulmonary fibrosis

BACKGROUND

The origin of αSMA-positive myofibroblasts, key players within organ fibrosis, is still not fully elucidated. Pericytes have been discussed as myofibroblast progenitors in several organs including the lung.

METHODS

Using tamoxifen-inducible PDGFRβ-tdTomato mice (PDGFRβ-CreER^T2; R26tdTomato) lineage of lung pericytes was traced. To induce lung fibrosis, a single orotracheal dose of bleomycin was given. Lung tissue was investigated by immunofluorescence analyses, hydroxyproline collagen assay and RT-qPCR.

RESULTS

Lineage tracing combined with immunofluorescence for nitric oxide-sensitive guanylyl cyclase (NO-GC) as marker for PDGFRβ-positive pericytes allows differentiating two types of αSMA-expressing myofibroblasts in murine pulmonary fibrosis: (1) interstitial myofibroblasts that localize in the alveolar wall, derive from PDGFRβ⁺ pericytes, express NO-GC and produce collagen 1. (2) intra-alveolar myofibroblasts which do not derive from pericytes (but express PDGFRβ de novo after injury), are negative for NO-GC, have a large multipolar shape and appear to spread over several alveoli within the injured areas. Moreover, NO-GC expression is reduced during fibrosis, i.e., after pericyte-to-myofibroblast transition.

CONCLUSION

In summary, αSMA/PDGFRβ-positive myofibroblasts should not be addressed as a homogeneous target cell type within pulmonary fibrosis.

Disruption of Prostaglandin F2α Receptor Signaling Attenuates Fibrotic Remodeling and Alters Fibroblast Population Dynamics in A Preclinical Murine Model of Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronic parenchymal lung disease characterized by repetitive alveolar cell injury, myofibroblast proliferation, and excessive extracellular matrix deposition for which unmet need persists for effective therapeutics. The bioactive eicosanoid, prostaglandin F2α, and its cognate receptor FPr (Ptfgr) are implicated as a TGFβ1 independent signaling hub for IPF. To assess this, we leveraged our published murine PF model (IER - SftpcI73T) expressing a disease-associated missense mutation in the surfactant protein C (Sftpc) gene. Tamoxifen treated IER-SftpcI73T mice develop an early multiphasic alveolitis and transition to spontaneous fibrotic remodeling by 28 days. IER-SftpcI73T mice crossed to a Ptgfr null (FPr-/-) line showed attenuated weight loss and gene dosage dependent rescue of mortality compared to FPr+/+ cohorts. IER-SftpcI73T/FPr-/- mice also showed reductions in multiple fibrotic endpoints for which administration of nintedanib was not additive. Single cell RNA sequencing, pseudotime analysis, and in vitro assays demonstrated Ptgfr expression predominantly within adventitial fibroblasts which were reprogrammed to an "inflammatory/transitional" cell state in a PGF2α/FPr dependent manner. Collectively, the findings provide evidence for a role for PGF2α signaling in IPF, mechanistically identify a susceptible fibroblast subpopulation, and establish a benchmark effect size for disruption of this pathway in mitigating fibrotic lung remodeling.

Hepatic stellate cells maintain liver homeostasis through paracrine neurotrophin-3 signaling that induces hepatocyte proliferation

Organ size is maintained by the controlled proliferation of distinct cell populations. In the mouse liver, hepatocytes in the midlobular zone that are positive for cyclin D1 (CCND1) repopulate the parenchyma at a constant rate to preserve liver mass. Here, we investigated how hepatocyte proliferation is supported by hepatic stellate cells (HSCs), pericytes that are in close proximity to hepatocytes. We used T cells to ablate nearly all HSCs in the murine liver, enabling the unbiased characterization of HSC functions. In the normal liver, complete loss of HSCs persisted for up to 10 weeks and caused a gradual reduction in liver mass and in the number of CCND1+ hepatocytes. We identified neurotrophin-3 (Ntf-3) as an HSC-produced factor that induced the proliferation of midlobular hepatocytes through the activation of tropomyosin receptor kinase B (TrkB). Treating HSC-depleted mice with Ntf-3 restored CCND1+ hepatocytes in the midlobular region and increased liver mass. These findings establish that HSCs form the mitogenic niche for midlobular hepatocytes and identify Ntf-3 as a hepatocyte growth factor.

Combinatorial Microgels for 3D ECM Screening and Heterogeneous Microenvironmental Culture of Primary Human Hepatic Stellate Cells

Non-alcoholic fatty liver disease affects 30% of the United States population and its progression can lead to non-alcoholic steatohepatitis (NASH), which can result in cirrhosis and hepatocellular carcinoma. NASH is characterized by a highly heterogeneous liver microenvironment created by the fibrotic activity of hepatic stellate cells (HSCs). While HSCs have been widely studied in 2D, further advancements in physiologically-relevant 3D culture platforms for the in vitro modeling of these heterogeneous environments are needed. In this study, we have demonstrated the use of stiffness-variable, ECM protein-conjugated polyethylene glycol microgels as 3D cell culture scaffolds to modulate HSC activation. We further employed these microgels as a high throughput ECM screening system to identify HSC matrix remodeling and metabolic activities in distinct heterogeneous microenvironmental conditions. In particular, 6 kPa fibronectin microgels were shown to significantly increase HSC matrix remodeling and metabolic activities in single or multiple component microenvironments. Overall, heterogeneous microenvironments consisting of multiple distinct ECM microgels promoted a decrease in HSC matrix remodeling and metabolic activities compared to homogeneous microenvironments. We envision this ECM screening platform being adapted to a broad number of cell types to aid the identification of ECM microenvironments that best recapitulate the desired phenotype, differentiation, or drug efficacy.

An inducible model for genetic manipulation and fate-tracing of PDGFRβ-expressing fibrogenic cells in the liver

Myofibroblasts are the source of extracellular matrix protein during liver fibrogenesis. Fibroblasts, hepatic stellate cells (HSCs) and vascular smooth muscle cells are mesenchymal subpopulations in the liver that are characterized by the expression of PDGFRβ and contribute to the pool of these myofibroblasts. Conditional knockout models are important to better understand the function of specific liver cell populations including mesenchymal cells. While there is a limited number of constitutive mouse models for liver mesenchymal cell specific transgene expression, there is no established model for inducible gene targeting in HSCs or PDGFRβ-expressing mesenchymal cell populations in the liver. To address this, we investigated whether the tamoxifen inducible PDGFRβ-P2A-CreER^T2 mouse can be used as a reliable tool to specifically express transgens in liver mesenchymal cells. Our data demonstrate, that PDGFRβ-P2A-CreER^T2 specifically and efficiently marks over 90% of retinoid positive HSCs in healthy and fibrotic liver in mice upon tamoxifen injection, and that those cells give rise to Col1a1-expressing myofibroblasts in different models of liver fibrosis. Together with a negligible background recombination of only about 0.33%, this confirms that the PDGFRβ-P2A-CreER^T2 mouse is nearly as efficient as established constitutive LratCre and PDGFRβ-Cre mouse models for recombination in HSCs, and that it is a powerful model for mesenchymal liver cell studies that require an inducible Cre approach.

Stretch regulates alveologenesis and homeostasis via mesenchymal Gαq/11-mediated TGFβ2 activation

Alveolar development and repair require tight spatiotemporal regulation of numerous signalling pathways that are influenced by chemical and mechanical stimuli. Mesenchymal cells play key roles in numerous developmental processes. Transforming growth factor-β (TGFβ) is essential for alveologenesis and lung repair, and the G protein α subunits Gαq and Gα11 (Gαq/11) transmit mechanical and chemical signals to activate TGFβ in epithelial cells. To understand the role of mesenchymal Gαq/11 in lung development, we generated constitutive (Pdgfrb-Cre+/-;Gnaqfl/fl;Gna11-/-) and inducible (Pdgfrb-Cre/ERT2+/-;Gnaqfl/fl;Gna11-/-) mesenchymal Gαq/11 deleted mice. Mice with constitutive Gαq/11 gene deletion exhibited abnormal alveolar development, with suppressed myofibroblast differentiation, altered mesenchymal cell synthetic function, and reduced lung TGFβ2 deposition, as well as kidney abnormalities. Tamoxifen-induced mesenchymal Gαq/11 gene deletion in adult mice resulted in emphysema associated with reduced TGFβ2 and elastin deposition. Cyclical mechanical stretch-induced TGFβ activation required Gαq/11 signalling and serine protease activity, but was independent of integrins, suggesting an isoform-specific role for TGFβ2 in this model. These data highlight a previously undescribed mechanism of cyclical stretch-induced Gαq/11-dependent TGFβ2 signalling in mesenchymal cells, which is imperative for normal alveologenesis and maintenance of lung homeostasis.

Unraveling the Emerging Niche Role of Hepatic Stellate Cell-derived Exosomes in Liver Diseases

Hepatic stellate cells (HSCs) play an essential role in various liver diseases, and exosomes are critical mediators of intercellular communication in local and distant microenvironments. Cellular crosstalk between HSCs and surrounding multiple tissue-resident cells promotes or inhibits the activation of HSCs. Substantial evidence has revealed that HSC-derived exosomes are involved in the occurrence and development of liver diseases through the regulation of retinoid metabolism, lipid metabolism, glucose metabolism, protein metabolism, and mitochondrial metabolism. HSC-derived exosomes are underpinned by vehicle molecules, such as mRNAs and microRNAs, that function in, and significantly affect, the processes of various liver diseases, such as acute liver injury, alcoholic liver disease, nonalcoholic fatty liver disease, viral hepatitis, fibrosis, and cancer. As such, numerous exosomes derived from HSCs or HSC-associated exosomes have attracted attention because of their biological roles and translational applications as potential targets for therapeutic targets. Herein, we review the pathophysiological and metabolic processes associated with HSC-derived exosomes, their roles in various liver diseases and their potential clinical application.

Extracellular Targets to Reduce Excessive Scarring in Response to Tissue Injury

Excessive scar formation is a hallmark of localized and systemic fibrotic disorders. Despite extensive studies to define valid anti-fibrotic targets and develop effective therapeutics, progressive fibrosis remains a significant medical problem. Regardless of the injury type or location of wounded tissue, excessive production and accumulation of collagen-rich extracellular matrix is the common denominator of all fibrotic disorders. A long-standing dogma was that anti-fibrotic approaches should focus on overall intracellular processes that drive fibrotic scarring. Because of the poor outcomes of these approaches, scientific efforts now focus on regulating the extracellular components of fibrotic tissues. Crucial extracellular players include cellular receptors of matrix components, macromolecules that form the matrix architecture, auxiliary proteins that facilitate the formation of stiff scar tissue, matricellular proteins, and extracellular vesicles that modulate matrix homeostasis. This review summarizes studies targeting the extracellular aspects of fibrotic tissue synthesis, presents the rationale for these studies, and discusses the progress and limitations of current extracellular approaches to limit fibrotic healing.

An integrated view of anti-inflammatory and antifibrotic targets for the treatment of NASH

Successful development of treatments for non-alcoholic fatty liver disease (NAFLD) and its progressive form, non-alcoholic steatohepatitis (NASH) has been challenging. Because NASH and fibrosis lead to NAFLD progression towards cirrhosis and to clinical outcomes, approaches have either sought to attenuate metabolic dysregulation and cell injury, or directly target the inflammation and fibrosis that ensue. Targets for reducing the activation of inflammatory cascades include nuclear receptor agonists (thyroid hormone receptor-beta, e.g. resmetirom, peroxisome proliferator-activated receptor [PPAR], e.g. lanifibranor, farnesoid X receptor [FXR], e.g. obeticholic acid), modulators of lipotoxicity (e.g. aramchol, acetyl-CoA carboxylase inhibitors) or modification of genetic variants (e.g. PNPLA3 gene silencing). Extrahepatic inflammatory signals from circulation, adipose tissue or gut are targets of hormonal agonists (e.g. glucagon-like peptide-1 [GLP-1] like semaglutide, fibroblast growth factor [FGF]-19 or FGF21), microbiota or lifestyle (weight loss, diet, exercise) interventions. Stress signals and hepatocyte death activate immune responses engaging innate (macrophages, lymphocytes) and adaptive (auto-aggressive T-cells) mechanisms. Therapies seek to blunt immune cell activation, recruitment (chemokine receptor inhibitors) and responses (e.g. galectin 3 inhibition, anti-platelet drugs). The disease-driving pathways of NASH converge to elicit fibrosis, which is reversible. The activation of hepatic stellate cells (HSC) into matrix-producing myofibroblasts can be inhibited by antagonizing soluble factors (e.g. integrins, cytokines), cellular crosstalk (e.g. with macrophages), and agonizing nuclear receptor signaling (e.g. FXR or PPAR agonists). In advanced fibrosis, cell therapy with restorative macrophages or reprogrammed T-cells (e.g., CAR T) may accelerate repair through HSC deactivation or killing, or by enhancing matrix degradation. Heterogeneity of disease - either due to genetics or divergent disease drivers - is an obstacle to defining effective drugs for all patients with NASH that will be incrementally overcome.

Chronic Expression of a Clinical SFTPC Mutation Causes Murine Lung Fibrosis with Idiopathic Pulmonary Fibrosis Features

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive fibrotic interstitial lung disease. A barrier to developing more effective therapies for IPF is the dearth of preclinical models that recapitulate the early pathobiology of this disease. Intratracheal bleomycin, the conventional preclinical murine model of IPF, fails to reproduce the intrinsic dysfunction to the alveolar epithelial type 2 cell (AEC2) that is believed to be a proximal event in the pathogenesis of IPF. Murine fibrosis models based on SFTPC (Surfactant Protein C gene) mutations identified in patients with interstitial lung disease cause activation of the AEC2 unfolded protein response and endoplasmic reticulum stress-an AEC2 dysfunction phenotype observed in IPF. Although these models achieve spontaneous fibrosis, they do so with precedent lung injury and thus are challenged to phenocopy the general clinical course of patients with IPF-gradual progressive fibrosis and loss of lung function. Here, we report a refinement of a murine Sftpc mutation model to recapitulate the clinical course, physiological impairment, parenchymal cellular composition, and biomarkers associated with IPF. This platform provides the field with an innovative model to understand IPF pathogenesis and index preclinical therapeutic candidates.

BORIS variant SF2(C2/A4) promotes the malignant development of liver cancer by activating epithelial-mesenchymal transition and hepatic stellate cells

The underlying mechanisms of metastasis and recurrence of liver cancer remain largely unknown. Here, we found that Brother of the Regulator of Imprinted Sites (BORIS) variant SF2(C2/A4) was highly expressed in high metastatic potential hepatocellular carcinoma (HCC) cells and clinical tumor samples, related to the formation of satellite nodules. Its over expression promoted self-renewal, the expression of tumor stem cell markers, chemoresistance, wound healing rate, invasion and metastasis of HepG2 and Hep3B cells; reinforced epithelial-mesenchymal transition (EMT), decreased the expression of E-cadherin and increased N-cadherin and Vimentin. Subcellular localization experiment showed that BORIS SF2(C2/A4) was localized in nucleus and cytoplasm. Further double luciferase reporter gene experiment confirmed that it bound to TWIST1 gene promoter and significantly increased latter expression. BORIS SF2(C2/A4) knock down induced apoptosis of HCCLM3 and PLC/PRF/5 cells, and increased the protein content of cleaved caspase 3. Additionally, BORIS SF2(C2/A4) over expression increased the expression of fibroblast growth factor 2 (FGF2) in HepG2 and Hep3B cells. FGF2 expressed higher in HCC tumor tissues than in paired peri-tumor tissues, and its expression was positively correlated with BORIS SF2(C2/A4). Interestingly, high expression of FGF2 is also associated with the formation of satellite nodules. Moreover, using the medium from BORIS SF2(C2/A4) overexpressed cell lines to coculture hepatic stellate cell (HSCs) line LX-2, the latter could be activated and increased the expression of CD90 and PIGF, which is consistent with the effect of adding bFGF alone. These results indicate that BORIS SF2(C2/A4) plays a role in deterioration of liver cancer by regulating TWIST1 to induce EMT, and by FGF2 to activate HSCs.

Activated fibroblasts in cancer: Perspectives and challenges

Activated fibroblasts in tumors, or cancer-associated fibroblasts (CAFs), have become a popular research area over the past decade. As important players in many aspects of tumor biology, with functions ranging from collagen deposition to immunosuppression, CAFs have been the target of clinical and pre-clinical studies that have revealed their potential pro- and anti-tumorigenic dichotomy. In this review, we describe the important role of CAFs in the tumor microenvironment and the technological advances that made these discoveries possible, and we detail the models that are currently available for CAF investigation. Additionally, we present evidence to support the value of encompassing CAF investigation as a future therapeutic avenue alongside immune and cancer cells while highlighting the challenges that must be addressed for successful clinical translation of new findings.

Smooth muscle αv integrins regulate vascular fibrosis via CD109 downregulation of TGF-β signalling

Aims

α_v integrins are implicated in fibrosis in a number of organs through their ability to activate TGF-β. However their role in vascular fibrosis and collagen accumulation is only partially understood. Here we have used α_v conditional knockout mice and cell lines to determine how α_v contributes to vascular smooth muscle cell (VSMC) function in vascular fibrosis and the role of TGF-β in that process.

Methods and results

Angiotensin II (Ang II) treatment causes upregulation of α_v and β₃ expression in the vessel wall, associated with increased collagen deposition. We found that deletion of α_v integrin subunit from VSMCs (α_v ^SMKO) protected mice against angiotensin II-induced collagen production and assembly. Transcriptomic analysis of the vessel wall in α_v ^SMKO mice and controls identified a significant reduction in expression of fibrosis and related genes in α_v ^SMKO mice. In contrast, α_v ^SMKO mice showed prolonged expression of CD109, which is known to affect TGF-β signalling. Using cultured mouse and human VSMCs, we showed that overexpression of CD109 phenocopied knockdown of α_v integrin, attenuating collagen expression, TGF-β activation, and Smad2/3 signalling in response to angiotensin II or TGF-β stimulation. CD109 and TGF-β receptor were internalized in early endosomes.

Conclusion

We identify a role for VSMC α_v integrin in vascular fibrosis and show that α_v acts in concert with CD109 to regulate TGF-β signalling.

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.

Non-Parenchymal Cells and the Extracellular Matrix in Hepatocellular Carcinoma in Non-Alcoholic Fatty Liver Disease

Hepatocellular carcinoma (HCC) in the setting of non-alcoholic fatty liver disease (NAFLD)-related cirrhosis and even in the pre-cirrhotic state is increasing in incidence. NAFLD-related HCC has a poor clinical outcome as it is often advanced at diagnosis due to late diagnosis and systemic treatment response is poor due to reduced immune surveillance. Much of the focus of molecular research has been on the pathological changes in hepatocytes; however, immune cells, hepatic stellate cells, liver sinusoidal endothelial cells and the extracellular matrix may play important roles in the pathogenesis of NAFLD-related HCC as well. Here, we review the role of non-parenchymal cells in the liver in the pathogenesis of HCC in the context of NAFLD-NASH, with a particular focus on the innate and the adaptive immune system, fibrogenesis and angiogenesis. We review the key roles of macrophages, hepatic stellate cells (HSCs), T cells, natural killer (NK) cells, NKT cells and liver sinusoidal endothelial cells (LSECs) and the role of the extracellular matrix in hepatocarcinogenesis within the steatotic milieu.

TGFβ instructs mTORC2 to activate PKCβII for increased TWIST1 expression in proximal tubular epithelial cell injury

The plasticity of proximal tubular epithelial cells in response to TGFβ contributes to the expression of TWIST1 to drive renal fibrosis. The mechanism of TWIST1 expression is not known. We show that both PI3 kinase and its target mTORC2 increase TGFβ-induced TWIST1 expression. TGFβ enhances phosphorylation on Ser-660 in the protein kinase C βII (PKCβII) hydrophobic motif site. Remarkably, phosphorylation-deficient PKCβIIS660A, kinase-dead PKCβII, and PKCβII knockdown blocked TWIST1 expression by TGFβ. Inhibition of TWIST1 arrested TGFβ-induced tubular cell hypertrophy and the expression of fibronectin, collagen I (α2), and α-smooth muscle actin. By contrast, TWIST1 overexpression induced these pathologies. Interestingly, the inhibition of PKCβII reduced these phenomena, which were countered by the expression of TWIST1. These results provide the first evidence for the involvement of the mTORC2-PKCβII axis in TWIST1 expression to promote tubular cell pathology.

Acid Ceramidase Deficiency: Bridging Gaps between Clinical Presentation, Mouse Models, and Future Therapeutic Interventions

Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME) are ultra-rare, autosomal-recessive, acid ceramidase (ACDase) deficiency disorders caused by ASAH1 gene mutations. Currently, 73 different mutations in the ASAH1 gene have been described in humans. These mutations lead to reduced ACDase activity and ceramide (Cer) accumulation in many tissues. Presenting as divergent clinical phenotypes, the symptoms of FD vary depending on central nervous system (CNS) involvement and severity. Classic signs of FD include, but are not limited to, a hoarse voice, distended joints, and lipogranulomas found subcutaneously and in other tissues. Patients with SMA-PME lack the most prominent clinical signs seen in FD. Instead, they demonstrate muscle weakness, tremors, and myoclonic epilepsy. Several ACDase-deficient mouse models have been developed to help elucidate the complex consequences of Cer accumulation. In this review, we compare clinical reports on FD patients and experimental descriptions of ACDase-deficient mouse models. We also discuss clinical presentations, potential therapeutic strategies, and future directions for the study of FD and SMA-PME.

The Angiogenesis Inhibitor Isthmin-1 (ISM1) Is Overexpressed in Experimental Models of Glomerulopathy and Impairs the Viability of Podocytes

Focal segmental glomerulosclerosis (FSGS) is a major cause of end-stage renal disease and remains without specific treatment. To identify new events during FSGS progression, we used an experimental model of FSGS associated with nephroangiosclerosis in rats injected with L-NAME (N_ω-nitro-L-arginine methyl ester). After transcriptomic analysis we focused our study on the role of Isthmin-1 (ISM1, an anti-angiogenic protein involved in endothelial cell apoptosis. We studied the renal expression of ISM1 in L-NAME rats and other models of proteinuria, particularly at the glomerular level. In the L-NAME model, withdrawal of the stimulus partially restored basal ISM1 levels, along with an improvement in renal function. In other four animal models of proteinuria, ISM1 was overexpressed and localized in podocytes while the renal function was degraded. Together these facts suggest that the glomerular expression of ISM1 correlates directly with the progression-recovery of the disease. Further in vitro experiments demonstrated that ISM1 co-localized with its receptors GRP78 and integrin αvβ5 on podocytes. Treatment of human podocytes with low doses of recombinant ISM1 decreased cell viability and induced caspase activation. Stronger ISM1 stimuli in podocytes dropped mitochondrial membrane potential and induced nuclear translocation of apoptosis-inducing factor (AIF). Our results suggest that ISM1 participates in the progression of glomerular diseases and promotes podocyte apoptosis in two different complementary ways: one caspase-dependent and one caspase-independent associated with mitochondrial destabilization.

New tools to study the interaction between integrins and latent TGFβ1

Transforming growth factor beta (TGFβ) 1 regulates cell differentiation and proliferation in different physiological settings, but is also involved in fibrotic progression and protects tumors from the immune system. Integrin αVβ6 has been shown to activate latent TGFβ1 by applying mechanical forces onto the latency-associated peptide (LAP). While the extracellular binding between αVβ6 and LAP1 is well characterized, less is known about the cytoplasmic adaptations that enable αVβ6 to apply such forces. Here, we generated new tools to facilitate the analysis of this interaction. We combined the integrin-binding part of LAP1 with a GFP and the Fc chain of human IgG. This chimeric protein, sLAP1, revealed a mechanical rearrangement of immobilized sLAP1 by αVβ6 integrin. This unique interaction was not observed between sLAP1 and other integrins. We also analyzed αVβ6 integrin binding to LAP2 and LAP3 by creating respective sLAPs. Compared to sLAP1, integrin αVβ6 showed less binding to sLAP3 and no rearrangement. These observations indicate differences in the binding of αVβ6 to LAP1 and LAP3 that have not been appreciated so far. Finally, αVβ6-sLAP1 interaction was maintained even at strongly reduced cellular contractility, highlighting the special mechanical connection between αVβ6 integrin and latent TGFβ1.

Mechanical stress regulates the mechanotransduction and metabolism of cardiac fibroblasts in fibrotic cardiac diseases

Fibrotic cardiac diseases are characterized by myocardial fibrosis that results in maladaptive cardiac remodeling. Cardiac fibroblasts (CFs) are the main cell type responsible for fibrosis. In response to stress or injury, intrinsic CFs develop into myofibroblasts and produce excess extracellular matrix (ECM) proteins. Myofibroblasts are mechanosensitive cells that can detect changes in tissue stiffness and respond accordingly. Previous studies have revealed that some mechanical stimuli control fibroblast behaviors, including ECM formation, cell migration, and other phenotypic traits. Further, metabolic alteration is reported to regulate fibrotic signaling cascades, such as the transforming growth factor-β pathway and ECM deposition. However, the relationship between metabolic changes and mechanical stress during fibroblast-to-myofibroblast transition remains unclear. This review aims to elaborate on the crosstalk between mechanical stress and metabolic changes during the pathological transition of cardiac fibroblasts.

Ganoderma lucidum: Current advancements of characteristic components and experimental progress in anti-liver fibrosis

Ganoderma lucidum (G. lucidum, Lingzhi) is a well-known herbal medicine with a variety of pharmacological effects. Studies have found that G. lucidum has pharmacological effects such as antioxidant, antitumor, anti-aging, anti-liver fibrosis, and immunomodulation. The main active components of G. lucidum include triterpenoids, polysaccharides, sterols, peptides and other bioactive components. Among them, the triterpenoids and polysaccharide components of G. lucidum have a wide range of anti-liver fibrotic effects. Currently, there have been more reviews and studies on the antioxidant, antitumor, and anti-aging properties of G. lucidum. Based on the current trend of increasing number of liver fibrosis patients in the world, we summarized the role of G.lucidum extract in anti-liver fibrosis and the effect of G. lucidum extract on liver fibrosis induced by different pathogenesis, which were discussed and analyzed. Research and development ideas and references are provided for the subsequent application of G. lucidum extracts in anti-liver fibrosis treatment.