Lysyl oxidase activity contributes to collagen stabilization during liver fibrosis progression and limits spontaneous fibrosis reversal in mice

Fibulin-1 deficiency alleviates liver fibrosis by inhibiting hepatic stellate cell activation via the p38 MAPK pathway

Elastin stabilization has been correlated with the reversibility of fibrosis. Fibulin-1 can participate in elastin assembly, which promotes its stabilization. However, the role of Fibulin-1 in liver fibrosis remains unknown. Here, we performed a proteomics analysis to identify notable changes in Fibulin-1 expression during continuous fibrosis progression and regression. Fibulin-1 expression was dramatically increased in the plasma of patients with cirrhosis as well as in liver fibrosis models and hepatic stellate cells (HSCs) treated with TGF-β1, and significant accumulation of Fibulin-1 was observed in chronic hepatitis B (CHB)- and metabolic dysfunction-associated steatohepatitis (MASH)-related cirrhosis. Functional studies demonstrated that Fibulin-1 silencing inhibited HSC activation, while the opposite effects were observed for Fibulin-1 overexpression in vitro. Furthermore, transcriptomic analysis revealed that Fibulin-1 mediated p38 MAPK pathway activation, which was confirmed by the addition of a p38 MAPK inhibitor. More importantly, Fibulin-1 depletion in a CCl4-induced liver fibrosis model substantially ameliorated fibrosis progression, which was accompanied by decreased profibrogenic gene expression and decreased levels of insoluble elastin. Moreover, activation of the p38 MAPK pathway was inhibited in vivo. The expression of Fibulin-1D, rather than Fibulin-1C, was elevated during liver fibrogenesis, which suggested a major role for Fibulin-1D in liver fibrosis. Next, we established Fibulin-1D/elastin-coated culture models with LX-2 cells. LX-2 cells with extracellular elastin and Fibulin-1D deposition showed more significant profibrotic phenotypic alterations than those with elastin alone. Fibulin-1 deficiency alleviated liver fibrosis by reducing insoluble elastin and HSC activation, and finally, the p38 MAPK pathway might be involved in the effect of Fibulin-1 on HSCs.

Therapeutic potential of heat-killed Lactobacillus reuteri against bile acid-induced male reproductive toxicity

Exposure of testicular tissue to supraphysiological concentrations of bile acids can lead to infertility. This study aimed to investigate the protective effects of heat-killed Lactobacillus reuteri (L. reuteri) against male reproductive toxicity induced by bile duct ligation (BDL). Thirty-two male Wistar rats were randomly assigned to four groups (N = 8): control normal (CN), sham-control (SC), BDL-control (underwent BDL surgery), and BDL + heat-killed L. reuteri (received probiotic supplementation for 7 days before and 21 days after BDL). At the end of the study, reproductive parameters, including sex hormones, sperm characteristics, oxidative stress markers, antioxidant status, and inflammatory gene expression in testicular tissue, were analyzed. Additionally, histological assessments of the testis and epididymis were performed. The administration of heat-killed L. reuteri significantly improved sperm viability (p ≤ 0.05) and luteinizing hormone levels (p ≤ 0.05) while reducing total oxidative status, carbonyl protein, and oxidative stress index (p ≤ 0.05) compared to the BDL-control group. Moreover, nitric oxide levels were significantly increased (p ≤ 0.05) in the probiotic-treated group. The expression levels of TNF-α and IL-6 were notably downregulated (p ≤ 0.05), indicating reduced testicular inflammation. Histological analysis demonstrated significant improvements in epithelial height, spermatogenic epithelial area ratio, lumen diameter, and lumen area (p ≤ 0.05) in the probiotic-treated group. These findings suggest that heat-killed L. reuteri alleviates cholestasis-related male reproductive toxicity through its antioxidant and anti-inflammatory effects.

Mechanical forces in the tumor microenvironment: roles, pathways, and therapeutic approaches

Tumors often exhibit greater stiffness compared to normal tissues, primarily due to increased deposition within the tumor stroma. Collagen, proteoglycans, laminin, and fibronectin are key components of the extracellular matrix (ECM), interacting to facilitate ECM assembly. Enhanced fiber density and cross-linking within the ECM result in elevated matrix stiffness and interstitial fluid pressure, subjecting tumors to significant physical stress during growth. This mechanical stress is transduced intracellularly via integrins, the Rho signaling pathway, and the Hippo signaling pathway, thereby promoting tumor invasion. Additionally, mechanical pressure fosters glycolysis in tumor cells, boosting energy production to support metastasis. Mechanical cues also regulate macrophage polarization, maintaining an inflammatory microenvironment conducive to tumor survival. In summary, mechanical signals within tumors play a crucial role in tumor growth and invasion. Understanding these signals and their involvement in tumor progression is essential for advancing our knowledge of tumor biology and enhancing therapeutic approaches.

Hot and cold fibrosis: The role of serum biomarkers to assess immune mechanisms and ECM-cell interactions in human fibrosis

Fibrosis is a pathological condition characterised by excessive accumulation of extracellular matrix (ECM) components, particularly collagens, leading to tissue scarring and organ dysfunction. In fibrosis, an imbalance between collagen synthesis (fibrogenesis) and degradation (fibrolysis) results in the deposition of fibrillar collagens disrupting the structural integrity of the ECM and, consequently, tissue architecture. Fibrosis is associated with a wide range of chronic diseases, including cirrhosis, kidney fibrosis, pulmonary fibrosis, and autoimmune diseases. Recently, the concept of "hot" and "cold" fibrosis has emerged, referring to the immune status within fibrotic tissues and the nature of fibrogenic signalling. Hot fibrosis is characterised by active immune cell infiltration and inflammation, while cold fibrosis is associated with auto- and paracrine myofibroblast activation, immune cell exclusion and quiescence. In this article, we explore the relationship between hot and cold fibrosis, the role of various types of collagens and their biologically active fragments in modulating the immune system, and how serological ECM biomarkers can help improve our understanding of the disease-relevant interactions between immune and mesenchymal cells in fibrotic tissues. Additionally, we draw lessons from immuno-oncology research in solid tumours to shed light on potential strategies for fibrosis treatment and highlight the advantage of having a "hot fibrotic environment" to treat fibrosis by enhancing collagen degradation through modulation of the immune system.

NUDT21 regulates lysyl oxidase-like 2(LOXL2) to influence ECM protein cross-linking in silica-induced pulmonary fibrosis

Silicosis is a disease caused by prolonged exposure to silica dust. It is the most typical, rapidly progressive, and fatal form of pneumoconiosis. Currently, there is no specific medication available for the treatment of silicosis. LOXL2 is a copper-dependent lysine oxidase whose main function is to catalyze the cross-linking of extracellular matrix components, particularly collagen and elastin. However, few researchers have investigated the role of LOXL2 in the pathogenesis of silicosis. In this study, we demonstrated that LOXL2 is upregulated in silica-inhaled mouse lung tissue and in a TGF-β-induced fibroblast model. In vitro, we confirmed that LOXL2 functions to promote ECM deposition by binding directly to collagen and elastin. We then used scavenger receptor cysteine-rich (SRCR) domains to show that LOXL2 can induce fibrosis independently of its enzymatic activity. Furthermore, we discovered that NUDT21, the LOXL2 upstream regulatory mechanism of LOXL2, alters LOXL2's 3'UTR usage by substituting alternative polyadenylation (APA), thereby modulating LOXL2 expression. By injecting LOXL2 siRNA-loaded liposomes into the tail vein of mice in the silica dust-treated mouse pulmonary fibrosis model, the severity of lung fibrosis was significantly reduced. In this context, LOXL2 is regulated by NUDT21 and may affect pulmonary fibrosis by influencing the cross-linking of ECM proteins. Our research provides a scientific basis for the development of new anti-fibrosis treatment strategies.

Impact of heterogeneity in liver matrix and intrahepatic cells on the progression of hepatic fibrosis

Liver fibrosis is a disease with a high prevalence worldwide. The development of hepatic fibrosis results from a combination of factors within the liver, such as extracellular matrix (ECM) deposition, hepatic stellate cells (HSCs) activation, collagen cross-linking, and inflammatory response. Heterogeneity in fibrotic liver is the result of a combination of heterogeneity in the intrahepatic microenvironment as well as heterogeneous expression of fibrosis-associated enzymes and cells, complicating the study of the mechanisms underlying the progression of liver fibrosis. The role of this heterogeneity on the crosstalk between cells and matrix and on the fibrotic process is worth exploring. In this paper, we will describe the phenomenon and mechanism of heterogeneity of liver matrix and intrahepatic cells in the process of hepatic fibrosis and discuss the crosstalk between heterogeneous factors on the development of fibrosis. The elucidation of heterogeneity is important for a deeper understanding of the pathological mechanisms of liver fibrosis as well as for clinical diagnosis and targeted therapies.

Hic-5 antisense oligonucleotide inhibits advanced hepatic fibrosis and steatosis in vivo

Background & Aims

Chronic liver diseases, including metabolic dysfunction-associated steatohepatitis (MASH), pose a significant global health burden. Progressive liver fibrosis can lead to severe outcomes; however, there is a lack of effective therapies targeting advanced fibrosis. Hydrogen peroxide-inducible clone-5 (Hic-5), an adaptor protein in focal adhesion, is critical for promoting liver fibrosis in hepatic stellate cells. This study investigated its clinical applicability by examining hepatic Hic-5 expression in human fibrotic tissues, exploring its association with MASH, and assessing the therapeutic potential of antisense oligonucleotides (ASOs) targeting Hic-5 in a MASH mouse model.

Methods

Hepatic Hic-5 expression in human fibrotic tissues underwent pathological image analysis and single-cell RNA sequencing. ASOs targeting Hic-5 were developed and tested using in vitro cell models. An in vivo MASH mouse model was used to evaluate the effects of anti-Hic-5 ASOs on advanced fibrosis and steatosis.

Results

Hepatic Hic-5 expression increased with the progression of fibrosis, particularly in advanced stages. Single-cell RNA sequencing revealed Hic-5 expression primarily in hepatic stellate cells. In MASH-associated fibrosis, Hic-5 expression correlated with the expression of fibrotic genes. In the MASH mouse model, hepatic Hic-5 expression increased with disease progression. Anti-Hic-5 ASOs effectively suppressed Hic-5 expression in vitro and attenuated advanced fibrosis and steatosis in vivo, indicating their therapeutic potential.

Conclusions

Hepatic Hic-5 expression is associated with advanced liver fibrosis and MASH. Anti-Hic-5 ASOs are promising therapeutic interventions for MASH accompanied by advanced fibrosis. These findings provide valuable insights into potential clinical treatments for advanced liver fibrosis.

Impact and implications

This study investigated the role of Hic-5 in liver fibrosis and steatohepatitis, highlighting its potential as a therapeutic target. We developed an antisense oligonucleotide (ASO) that was particularly transportable to the liver, and targeted Hic-5. Anti-Hic-5 ASO exhibited therapeutic efficacy for liver fibrosis and steatosis in vivo, indicating its therapeutic potential for liver fibrosis and steatosis. ASOs have already achieved dramatic therapeutic effects as approved nucleic acid drugs. Thus, anti-Hic-5 ASO is expected to lead the direct generation of seed compounds for the clinical development of drugs for liver fibrosis and steatosis.

Non-invasive fibrosis markers are useful in predicting the presence of varices in compensated cirrhosis and variceal bleeding in decompensated cirrhosis

This study aims to investigate the effectiveness of non-invasive fibrosis markers in predicting varices in compensated advanced chronic liver disease patients and variceal bleeding in decompensated cirrhotic patients. Between 1 July 2020-2021, 137 newly diagnosed cirrhosis patients (67 females/70 males; mean age: 53.35) were included in the study. The diagnosis of cirrhosis was made based on clinical, laboratory, imaging, and, if available, biopsy findings. Laboratory and clinical parameters, including lysyl oxidase-like protein 2 (LOXL2), were recorded for all patients. Commonly used noninvasive fibrosis scores were calculated, and endoscopies were performed to assess varices. All patients were followed up for 12 months, and variceal bleeding events were recorded. Parameters that could predict the presence of varices and variceal bleeding were identified using appropriate statistical methods. Out of the 137 cirrhotic patients, 55 were in the compensated stage and 82 were in the decompensated stage. Varices were detected in 36 (65%) of the compensated cirrhotic patients. It was found that a variceal score derived from spleen size and the ELF score could be used to predict varices (AUC: 0.83). Variceal bleeding developed in 26 (31%) of the patients with decompensated cirrhosis. It was determined that a scoring system derived from albumin, spleen size, LOXL2 level, and the Lok index could be used to predict variceal bleeding in this patient group (AUC: 0.845). This study demonstrates that, besides device-dependent examinations, non-invasive fibrosis scores and various serum parameters can predict varices and variceal bleeding in cirrhotic patients.

LOXL2 inhibition ameliorates pulmonary artery remodeling in pulmonary hypertension

Conduit pulmonary arterial stiffening and the resultant increase in pulmonary vascular impedance have emerged as an important underlying driver of pulmonary arterial hypertension (PAH). Given that matrix deposition is central to vascular remodeling, we evaluated the role of the collagen cross-linking enzyme lysyl oxidase like 2 (LOXL2) in this study. Human pulmonary artery smooth muscle cells (PASMCs) subjected to hypoxia showed increased LOXL2 secretion. LOXL2 activity and expression were markedly higher in primary PASMCs isolated from the pulmonary arteries of the rat Sugen 5416 + hypoxia (SuHx) model of severe pulmonary hypertension (PH). Similarly, LOXL2 protein and mRNA levels were increased in the pulmonary arteries (PA) and lungs of rats with PH (SuHx and monocrotaline (MCT) models). Pulmonary arteries (PAs) isolated from the rats with PH exhibited hypercontractility to phenylephrine and attenuated vasorelaxation elicited by acetylcholine, indicating severe endothelial dysfunction. Tensile testing revealed a significant increase in PA stiffness in PH. Treatment with PAT-1251, a novel small-molecule LOXL2 inhibitor, improved active and passive properties of the PA ex vivo. There was an improvement in right heart function as measured by right ventricular pressure volume loops in vivo with PAT-1251. Importantly, PAT-1251 treatment ameliorated PH, resulting in improved pulmonary artery pressures, right ventricular remodeling, and survival. Hypoxia-induced LOXL2 activation is a causal mechanism in pulmonary artery stiffening in PH and pulmonary artery mechanical and functional decline. LOXL2 inhibition with PAT-1251 could be a promising approach to improve pulmonary artery pressures, right ventricular elastance, cardiac relaxation, and survival in PAH.NEW & NOTEWORTHY Pulmonary arterial stiffening contributes to the progression of PAH and the deterioration of right heart function. This study shows that LOXL2 is upregulated in rat models of PH. LOXL2 inhibition halts pulmonary vascular remodeling and improves PA contractility, endothelial function, and PA pressure, resulting in prolonged survival. Thus, LOXL2 is an important mediator of PA remodeling and stiffening in PH and a promising target to improve PA pressures and survival in PH.

Evaluating ECM stiffness and liver cancer radiation response via shear-wave elasticity in 3D culture models

BACKGROUND

The stiffness of the tumor microenvironment (TME) directly influences cellular behaviors. Radiotherapy (RT) is a common treatment for solid tumors, but the TME can impact its efficacy. In the case of liver cancer, clinical observations have shown that tumors within a cirrhotic, stiffer background respond less to RT, suggesting that the extracellular matrix (ECM) stiffness plays a critical role in the development of radioresistance.

METHODS

This study explored the effects of ECM stiffness and the inhibition of lysyl oxidase (LOX) isoenzymes on the radiation response of liver cancer in a millimeter-sized three-dimensional (3D) culture. We constructed a cube-shaped ECM-based millimeter-sized hydrogel containing Huh7 human liver cancer cells. By modulating the collagen concentration, we produced two groups of samples with different ECM stiffnesses to mimic the clinical scenarios of normal and cirrhotic livers. We used a single-transducer system for shear-wave-based elasticity measurement, to derive Young's modulus of the 3D cell culture to investigate how the ECM stiffness affects radiosensitivity. This is the first demonstration of a workflow for assessing radiation-induced response in a millimeter-sized 3D culture.

RESULTS

Increased ECM stiffness was associated with a decreased radiation response. Moreover, sonoporation-assisted LOX inhibition with BAPN (β-aminopropionitrile monofumarate) significantly decreased the initial ECM stiffness and increased RT-induced cell death. Inhibition of LOX was particularly effective in reducing ECM stiffness in stiffer matrices. Combining LOX inhibition with RT markedly increased radiation-induced DNA damage in cirrhotic liver cancer cells, enhancing their response to radiation. Furthermore, LOX inhibition can be combined with sonoporation to overcome stiffness-related radioresistance, potentially leading to better treatment outcomes for patients with liver cancer.

CONCLUSIONS

The findings underscore the significant influence of ECM stiffness on liver cancer's response to radiation. Sonoporation-aided LOX inhibition emerges as a promising strategy to mitigate stiffness-related resistance, offering potential improvements in liver cancer treatment outcomes.

Atlas of mildly and highly insoluble matrisome driving liver fibrosis

The excessive deposition and cross-linking of core matrisome components typically result in abnormal remodeling of the extracellular matrix (ECM), leading to increased liver stiffness and worsening liver fibrosis. Exploring the biochemical properties of the ECM scaffold can deepen our understanding of the pathological mechanisms driving liver fibrosis and potentially facilitate the identification of therapeutic targets. While traditional sodium dodecyl sulfate (SDS)-based liver decellularization followed by proteomics can uncover the matrisome components within the ECM scaffold, it lacks the ability to reveal physicochemical characteristics like solubility. In our present study, using adult mouse liver as an example, we introduced a novel two-step workflow that combines our previously enhanced SDS (ESDS) decellularization with the conventional SDS method, enabling the identification of matrisome members with mild and/or high solubilities. Through this approach, we visualized the atlas of the mildly and highly insoluble matrisome contents in the adult mouse liver, as well as the regulatory network of highly insoluble matrisome that largely governs liver stiffness. Given the strong correlation between increased matrisome insolubility and heightened ECM stiffness, we believe that this methodology holds promise for future research focused on liver stiffness.

Comprehensive analysis of biological landscape of oxidative stress-related genes in diabetic erectile dysfunction

Oxidative stress plays a pivotal role in the pathogenesis of diabetic erectile dysfunction, while specific mechanisms have not been illuminated. The study aims to reveal the genetic expression patterns of oxidative stress in diabetic erectile dysfunction. Transcriptome data of diabetic erectile dysfunction and oxidative stress-related genes (OSRGs) in the Gene Expression Omnibus database were downloaded and analyzed based on differential expression. Functional enrichment analyses were conducted to clarify the biological functions. A protein interaction framework was established, and significant gene profiles were validated in the cavernous endothelial cells, clinical patients, and rat models. A miRNA-OSRGs network was predicted and validated. The results were analyzed using Student's t-test. The analysis screened 203 differentially expressed OSRGs (p < 0.05), which had a close association with oxidoreductase activities, glutathione metabolism, and autophagy. A four-gene signature comprised of EPS8L2 (p = 0.044), GSTA3 (p = 0.015), LOX (p < 0.001) and MGST1 (p = 0.002) was well validated and regarded as the hub OSRGs. Compared with the control group, notable increases and decreases were observed in the expressions of GSTA3 (3.683 ± 0.636 vs. 0.416 ± 0.507) and LOX (2.104 ± 1.895 vs. 18.804 ± 2.751) in the validated diabetic erectile dysfunction group. The hub OSRGs-related miRNAs participated in smooth muscle cell proliferation. Besides, miR-125a-3p (p = 0.034) and miR-138-2-3p (p = 0.012) were validated as promising oxidative stress-related miRNA biomarkers. Our findings revealed the genetic alternations of oxidative stress in diabetic erectile dysfunction. These results will be instructive to explore the molecular landscape and the potential treatment for diabetic erectile dysfunction.

Metabolic dysfunction-associated liver disease and diabetes: Matrix remodeling, fibrosis, and therapeutic implications

Metabolic dysfunction-associated liver disease (MASLD) and steatohepatitis (MASH) are becoming the most common causes of chronic liver disease in the United States and worldwide due to the obesity and diabetes epidemics. It is estimated that by 2030 close to 100 million people might be affected and patients with type 2 diabetes are especially at high risk. Twenty to 30% of patients with MASLD can progress to MASH, which is characterized by steatosis, necroinflammation, hepatocyte ballooning, and in advanced cases, fibrosis progressing to cirrhosis. Clinically, it is recognized that disease progression in diabetic patients is accelerated and the role of various genetic and epigenetic factors, as well as cell-matrix interactions in fibrosis and stromal remodeling, have recently been recognized. While there has been great progress in drug development and clinical trials for MASLD/MASH, the complexity of these pathways highlights the need to improve diagnosis/early detection and develop more successful antifibrotic therapies that not only prevent but reverse fibrosis.

Hepatic Extracellular Matrix and Its Role in the Regulation of Liver Phenotype

The hepatic extracellular matrix (ECM) is most accurately depicted as a dynamic compartment that comprises a diverse range of players that work bidirectionally with hepatic cells to regulate overall homeostasis. Although the classic meaning of the ECM referred to only proteins directly involved in generating the ECM structure, such as collagens, proteoglycans, and glycoproteins, the definition of the ECM is now broader and includes all components associated with this compartment. The ECM is critical in mediating phenotype at the cellular, organ, and even organismal levels. The purpose of this review is to summarize the prevailing mechanisms by which ECM mediates hepatic phenotype and discuss the potential or established role of this compartment in the response to hepatic injury in the context of steatotic liver disease.

Advances in Noninvasive Molecular Imaging Probes for Liver Fibrosis Diagnosis

Liver fibrosis is a wound-healing response to chronic liver injury, which may lead to cirrhosis and cancer. Early-stage fibrosis is reversible, and it is difficult to precisely diagnose with conventional imaging modalities such as magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and ultrasound imaging. In contrast, probe-assisted molecular imaging offers a promising noninvasive approach to visualize early fibrosis changes in vivo, thus facilitating early diagnosis and staging liver fibrosis, and even monitoring of the treatment response. Here, the most recent progress in molecular imaging technologies for liver fibrosis is updated. We start by illustrating pathogenesis for liver fibrosis, which includes capillarization of liver sinusoidal endothelial cells, cellular and molecular processes involved in inflammation and fibrogenesis, as well as processes of collagen synthesis, oxidation, and cross-linking. Furthermore, the biological targets used in molecular imaging of liver fibrosis are summarized, which are composed of receptors on hepatic stellate cells, macrophages, and even liver collagen. Notably, the focus is on insights into the advances in imaging modalities developed for liver fibrosis diagnosis and the update in the corresponding contrast agents. In addition, challenges and opportunities for future research and clinical translation of the molecular imaging modalities and the contrast agents are pointed out. We hope that this review would serve as a guide for scientists and students who are interested in liver fibrosis imaging and treatment, and as well expedite the translation of molecular imaging technologies from bench to bedside.

Non-invasive biomarkers prognostic of decompensation events in NASH cirrhosis: a systematic literature review

Liver cirrhosis due to nonalcoholic steatohepatitis (NASH) is a life-threatening condition with increasing incidence world-wide. Although its symptoms are unspecific, it can lead to decompensation events such as ascites, hepatic encephalopathy, variceal hemorrhage, and hepatocellular carcinoma (HCC). In addition, an increased risk for cardiovascular events has been demonstrated in patients with NASH. Pharmacological treatments for NASH cirrhosis are not yet available, one of the reasons being the lack in surrogate endpoints available in clinical trials of NASH cirrhosis. The feasibility of non-invasive prognostic biomarkers makes them interesting candidates as possible surrogate endpoints if their change following treatment would result in better outcomes for patients in future clinical trials of NASH cirrhosis. In this systematic literature review, a summary of the available literature on the prognostic performance of non-invasive biomarkers in terms of cardiovascular events, liver-related events, and mortality is outlined. Due to the scarcity of data specific for NASH cirrhosis, this review includes studies on NAFLD whose evaluation focuses on cirrhosis. Our search strategy identified the following non-invasive biomarkers with prognostic value in studies of NASH patients: NAFLD fibrosis score (NFS), Fibrosis-4 (FIB-4), aspartate aminotransferase (AST) to platelet ratio index (APRI), enhanced liver fibrosis (ELF™), BARD (BMI, AST/ALT (alanine aminotransferase) ratio, diabetes), Hepamet Fibrosis Score (HFS), liver enzymes (AST + ALT), alpha-fetoprotein, platelet count, neutrophil to lymphocyte ratio (NLR), Lysyl oxidase-like (LOXL) 2, miR-122, liver stiffness, MEFIB (liver stiffness measured with magnetic resonance elastography (MRE) + FIB-4), and PNPLA3 GG genotype. The aim of the present systematic literature review is to provide the reader with a summary of the non-invasive biomarkers with prognostic value in NASH cirrhosis and give an evaluation of their utility as treatment monitoring biomarkers in future clinical trials.

An Integrative Transcriptome Subtraction Strategy to Identify Human lncRNAs That Specifically Play a Role in Activation of Human Hepatic Stellate Cells

Fibrotic liver features excessive deposition of extracellular matrix (ECM), primarily produced from "activated" hepatic stellate cells (HSCs). While targeting human HSCs (hHSCs) in fibrosis therapeutics shows promise, the overall understanding of hHSC activation remains limited, in part because it is very challenging to define the role of human long non-coding RNAs (lncRNAs) in hHSC activation. To address this challenge, we identified another cell type that acts via a diverse gene network to promote fibrogenesis. Then, we identified the lncRNAs that were differentially regulated in activated hHSCs and the other profibrotic cell. Next, we conducted concurrent analysis to identify those lncRNAs that were specifically involved in fibrogenesis. We tested and confirmed that transdifferentiation of vascular smooth muscle cells (VSMCs) represents such a process. By overlapping TGFβ-regulated lncRNAs in multiple sets of hHSCs and VSMCs, we identified a highly selected list of lncRNA candidates that could specifically play a role in hHSC activation. We experimentally characterized one human lncRNA, named CARMN, which was significantly regulated by TGFβ in all conditions above. CARMN knockdown significantly reduced the expression levels of a panel of marker genes for hHSC activation, as well as the levels of ECM deposition and hHSC migration. Conversely, gain of function of CARMN using CRISPR activation (CRISPR-a) yielded the completely opposite effects. Taken together, our work addresses a bottleneck in identifying human lncRNAs that specifically play a role in hHSC activation and provides a framework to effectively select human lncRNAs with significant pathophysiological role.

Reactive Oxygen Species-Responsive Nanoparticles Toward Extracellular Matrix Normalization for Pancreatic Fibrosis Regression

Pancreatic fibrosis (PF) is primarily characterized by aberrant production and degradation modes of extracellular matrix (ECM) components, resulting from the activation of pancreatic stellate cells (PSCs) and the pathological cross-linking of ECM mediated by lysyl oxidase (LOX) family members. The excessively deposited ECM increases matrix stiffness, and the over-accumulated reactive oxygen species (ROS) induces oxidative stress, which further stimulates the continuous activation of PSCs and advancing PF; challenging the strategy toward normalizing ECM homeostasis for the regression of PF. Herein, ROS-responsive and Vitamin A (VA) decorated micelles (named LR-SSVA) to reverse the imbalanced ECM homeostasis for ameliorating PF are designed and synthesized. Specifically, LR-SSVA selectively targets PSCs via VA, thereby effectively delivering siLOXL1 and resveratrol (RES) into the pancreas. The ROS-responsive released RES inhibits the overproduction of ECM by eliminating ROS and inactivating PSCs, meanwhile, the decreased expression of LOXL1 ameliorates the cross-linked collagen for easier degradation by collagenase which jointly normalizes ECM homeostasis and alleviates PF. This research shows that LR-SSVA is a safe and efficient ROS-response and PSC-targeted drug-delivery system for ECM normalization, which will propose an innovative and ideal platform for the reversal of PF.

Inhibition of lysyl oxidase by pharmacological intervention and genetic manipulation alleviates epilepsy-associated cognitive disorder

Epilepsy-associated cognitive disorder (ECD), a prevalent comorbidity in epilepsy patients, has so far uncharacterized etiological origins. Our prior work revealed that lysyl oxidase (Lox) acted as a novel contributor of ferroptosis, a recently discovered cell death mode in the regulation of brain function. However, the role of Lox-mediated ferroptosis in ECD remains unknown. ECD mouse model was established 2 months later following a single injection of kainic acid (KA) for. After chronic treatment with KA, mice were treated with different doses (30 mg/kg, 100 mg/kg and 300 mg/kg) of Lox inhibitor BAPN. Additionally, hippocampal-specific Lox knockout mice was also constructed and employed to validate the role of Lox in ECD. Cognitive functions were assessed using novel object recognition test (NOR) and Morris water maze test (MWM). Protein expression of phosphorylated cAMP-response element binding (CREB), a well-known molecular marker for evaluation of cognitive performance, was also detected by Western blot. The protein distribution of Lox was analyzed by immunofluorescence. In KA-induced ECD mouse model, ferroptosis process was activated according to upregulation of 4-HNE protein and a previously discovered ferroptosis in our group, namely, Lox was remarkably increased. Pharmacological inhibition of Lox by BAPN at the dose of 100 mg/kg significantly increased the discrimination index following NOR test and decreased escape latency as well as augmented passing times within 60 s following MWM test in ECD mouse model. Additionally, deficiency of Lox in hippocampus also led to pronounced improvement of deficits in ECD model. These findings indicate that the ferroptosis regulatory factor, Lox, is activated in ECD. Ablation of Lox by either pharmacological intervention or genetic manipulation ameliorates the impairment in ECD mouse model, which suggest that Lox serves as a promising therapeutic target for treating ECD in clinic.

Crosstalk of lysyl oxidase-like 1 and lysyl oxidase prolongs their half-lives and regulates liver fibrosis through Notch signal

BACKGROUND

Lysyl oxidase (LOX) family members (LOX and LOXL1 to 4) are crucial copper-dependent enzymes responsible for cross-linking collagen and elastin. Previous studies have revealed that LOX and LOXL1 are the most dramatically dysregulated LOX isoforms during liver fibrosis. However, the crosstalk between them and the underlying mechanisms involved in the profibrotic behaviors of HSCs, as well as the progression of liver fibrosis, remain unclear.

METHODS

pCol9GFP-HS4,5Tg mice, Loxl1fl/flGfapCre mice, human HSC line, and primary HSCs were enrolled to study the dysregulation pattern, profibrotic roles, and the potential mechanisms of LOX and LOXL1 interaction involved in the myofibroblast-like transition of HSCs and liver fibrogenesis.

RESULTS

LOX and LOXL1 were synergistically upregulated during liver fibrogenesis, irrespective of etiology, together orchestrating the profibrotic behaviors of HSCs. LOX and LOXL1 coregulated in HSCs, whereas LOXL1 dominated in the coregulation loop. Interestingly, the interaction between LOXL1 and LOX prolonged their half-lives, specifically enhancing the Notch signal-mediated myofibroblast-like transition of HSCs. Selective disruption of Loxl1 in Gfap+ HSCs deactivated the Notch signal, inhibited HSC activation, and relieved carbon tetrachloride-induced liver fibrosis.

CONCLUSIONS

Our current study confirmed the synergistic roles and the underlying mechanisms of LOXL1 and LOX crosstalk in the profibrotic behaviors of HSCs and liver fibrosis progression, providing experimental evidence for further clear mechanism-based anti-LOXL1 strategy development in the therapy of liver fibrosis.

Assessing Heterogeneity in the N-Telopeptides of Type I Collagen by Mass Spectrometry

Collagen cross-links created by the lysyl oxidase and lysyl hydroxylase families of enzymes are a significant contributing factor to the biomechanical strength and rigidity of tissues, which in turn influence cell signaling and ultimately cell phenotype. In the clinic, the proteolytically liberated N-terminal cross-linked peptide of collagen I (NTX) is used as a biomarker of bone and connective tissue turnover, which is altered in several disease processes. Despite the clinical utility of these collagen breakdown products, the majority of the cross-linked peptide species have not been identified in proteomic datasets. Here we evaluate several parameters for the preparation and identification of these peptides from the collagen I-rich Achilles tendon. Our refined approach involving chemical digestion for protein solubilization coupled with mass spectrometry allows for the identification of the NTX cross-links in a range of modification states. Based on the specificity of the enzymatic cross-linking reaction we utilized follow-up variable modification searches to facilitate identification with a wider range of analytical workflows. We then applied a spectral library approach to identify differences in collagen cross-links in bovine pulmonary hypertension. The presented method offers unique opportunities to understand extracellular matrix remodeling events in development, aging, wound healing, and fibrotic disease that modulate collagen architecture through lysyl-hydroxylase and lysyl-oxidase enzymes.

Copper chelation reduces early collagen deposition and preserves saliva secretion in irradiated salivary glands

Radiation therapy is a first-line treatment for head and neck cancer; however, it typically leads to hyposalivation stemming from fibrosis of the salivary gland. Current strategies to restore glandular function are dependent on the presence of residual functional salivary gland tissue, a condition commonly not met in patients with extensive fibrotic coverage of the salivary gland resulting from radiation therapy. Fibrosis is defined by the pathological accumulation of connective tissue (i.e., extracellular matrix) and excessive deposition of crosslinked (fibrillar) collagen that can impact a range of tissues and given that collagen crosslinking is necessary for fibrosis formation, inhibiting this process is a reasonable focus for developing anti-fibrotic therapies. Collagen crosslinking is catalyzed by the lysyl oxidase family of secreted copper-dependent metalloenzymes, and since that copper is an essential cofactor in all lysyl oxidase family members, we tested whether localized delivery of a copper chelator into the submandibular gland of irradiated mice could suppress collagen deposition and preserve the structure and function of this organ. Our results demonstrate that transdermal injection of tetrathiomolybdate into salivary glands significantly reduced the early deposition of fibrillar collagen in irradiated mice and preserved the integrity and function of submandibular gland epithelial tissue. Together, these studies identify copper metabolism as a novel therapeutic target to control radiation induced damage to the salivary gland and the current findings further indicate the therapeutic potential of repurposing clinically approved copper chelators as neoadjuvant treatments for radiation therapy.

Selective inhibition of hepatic stellate cell and fibroblast-derived LOXL1 attenuates BDL- and Mdr2-/--induced cholestatic liver fibrosis

Lysyl oxidase-like 1 (LOXL1) proteins are amine oxidases that play a crucial role in extracellular matrix remodeling due to their collagen cross-linking and intracellular functions. The role of LOXL1 in cholestatic liver fibrosis remains unexplored. We measured LOXL1 expression in two murine models of cholestasis [Mdr2 knockout (Mdr2-/-) and bile duct ligation (BDL)]. We used adeno-associated virus (AAV) serotype 6-mediated hepatic delivery against LOXL1 (AAV2/6-shLoxl1) to investigate the therapeutic efficacy of targeting LOXL1 in cholestatic liver fibrosis. NIH-3T3 murine fibroblasts were used to investigate the function and regulatory mechanisms of LOXL1 in vitro. LOXL1 expression was significantly upregulated in Mdr2-/- and BDL mice compared with their corresponding controls, predominantly in collagen-rich fibrous septa and portal areas. AAV2/6-shLoxl1 significantly reduced LOXL1 levels in Mdr2-/- and BDL mice, mainly in desmin-positive hepatic stellate cells (HSCs) and fibroblasts. Concomitant with reduced LOXL1 expression, there was reduced ductular reaction, inflammation, and fibrosis in both Mdr2-/- and BDL mice. In addition, Loxl1 intervention decreased Ki-67-positive cells in the desmin-positive areas in both Mdr2-/- and BDL mice. Overexpression of LOXL1 significantly promoted fibroblast proliferation by activating the platelet-derived growth factor receptor and extracellular signal-regulated kinase signaling pathways in vitro. Our findings demonstrated that selective inhibition of LOXL1 derived from HSCs/fibroblasts attenuated cholestatic liver/biliary fibrosis, inflammation, ductal reaction, and HSC/fibroblast proliferation. Based on our findings, LOXL1 could be a potential therapeutic target for cholestatic fibrosis.NEW & NOTEWORTHY Selectively, inhibition of HSC/fibroblasts-derived LOXL1 by AAV2/6-shLoxl1 could reduce collagen deposition, HSC/fibroblasts proliferation, and cholestatic liver fibrosis progression. In addition, overexpression of LOXL1 significantly promoted HSC/fibroblast proliferation by activating the PDGFRß/PI3K and ERK signaling pathways in vitro.

Evaluation of the flavonol-rich fraction of Rosa damascena in an animal model of liver fibrosis by targeting the expression of fibrotic cytokines, antioxidant/oxidant ratio and collagen cross-linking

INTRODUCTION

The flavonoid-rich fraction of Rosa damascena (FRFRD) contains antioxidant and active compounds. Therefore, this study aimed to investigate the role of FRFRD, rich in quercetin and kaempferol, in liver fibrosis induced by CCl4.

MATERIALS AND METHODS

The FRFRD fraction was separated and standardized by High-Performance Liquid Chromatography (HPLC) based on the levels of quercetin and kaempferol. Liver fibrosis was induced over CCl4 over 12 weeks in 30 male Wistar rats, and three concentrations of FRFRD were administered to them during the last four weeks. Subsequently, after evaluation of liver serum markers and fibrotic parameters, the relative expression of transforming growth factor-beta-1 (TGF-β1), platelet-derived growth factor (PDGF), and lysyl oxidase homolog 2 (Loxl2) genes were assessed, along with the measurement of lysyl oxidase activity and oxidative markers.

RESULTS

Fibrotic markers demonstrated progressive recovery of liver damage in the treated group compared to the non-treatment group (p < 0.01). These results were accompanied by a significant decrease in the expression of TGF-β1, PDGF, and Loxl2 genes, as well as, a reduction in lysyl oxidase activity (p < 0.001). The antioxidant effects of the treatment were observed through a significant decrease in malondialdehyde (MDA) levels and an increase in catalase enzyme (CAT) and glutathione peroxidase (GPx) activity in the treatment group compared to the fibrotic group (p < 0.01).

CONCLUSION

The flavonoid-rich fraction of Rosa damascena ameliorates liver damage by affecting collagen cross-linking and lowering oxidative and inflammatory levels.

Current investigations for liver fibrosis treatment: between repurposing the FDA-approved drugs and the other emerging approaches

Long-term liver injuries lead to hepatic fibrosis, often progressing into cirrhosis, liver failure, portal hypertension, and hepatocellular carcinoma. There is currently no effective therapy available for liver fibrosis. Thus, continuous investigations for anti-fibrotic therapy are ongoing. The main theme of anti-fibrotic investigation during recent years is the rationale-based selection of treatment molecules according to the current understanding of the pathology of the disease. The research efforts are mainly toward repurposing current FDA-approved drugs targeting etiological molecular factors involved in developing liver fibrosis. In parallel, investigations also focus on experimental small molecules with evidence to hinder or reverse the fibrosis. Natural compounds, immunological, and genetic approaches have shown significant encouraging effects. This review summarizes the efficacy and safety of current under-investigation antifibrosis medications targeting various molecular targets, as well as the properties of antifibrosis medications, mainly in phase II and III clinical trials.

Advanced glycation end-products as mediators of the aberrant crosslinking of extracellular matrix in scarred liver tissue

The extracellular matrix of cirrhotic liver tissue is highly crosslinked. Here we show that advanced glycation end-products (AGEs) mediate crosslinking in liver extracellular matrix and that high levels of crosslinking are a hallmark of cirrhosis. We used liquid chromatography-tandem mass spectrometry to quantify the degree of crosslinking of the matrix of decellularized cirrhotic liver samples from patients and from two mouse models of liver fibrosis and show that the structure, biomechanics and degree of AGE-mediated crosslinking of the matrices can be recapitulated in collagen matrix crosslinked by AGEs in vitro. Analyses via cryo-electron microscopy and optical tweezers revealed that crosslinked collagen fibrils form thick bundles with reduced stress relaxation rates; moreover, they resist remodelling by macrophages, leading to reductions in their levels of adhesion-associated proteins, altering HDAC3 expression and the organization of their cytoskeleton, and promoting a type II immune response of macrophages. We also show that rosmarinic acid inhibited AGE-mediated crosslinking and alleviated the progression of fibrosis in mice. Our findings support the development of therapeutics targeting crosslinked extracellular matrix in scarred liver tissue.

LOXL2 inhibition ameliorates pulmonary artery remodeling in pulmonary hypertension

Background

Conduit pulmonary arterial stiffening and the resultant increase in pulmonary vascular impedance has emerged as an important underlying driver of pulmonary arterial hypertension (PAH). Given that matrix deposition is central to vascular remodeling, we evaluated the role of the collagen crosslinking enzyme lysyl oxidase like 2 (LOXL2) in this study.

Methods and Results

Human pulmonary artery smooth muscle cells (PASMCs) subjected to hypoxia showed increased LOXL2 secretion. LOXL2 activity and expression were markedly higher in primary PASMCs isolated from pulmonary arteries of the rat Sugen 5416 + hypoxia (SuHx) model of severe PH. Similarly, LOXL2 protein and mRNA levels were increased in pulmonary arteries (PA) and lungs of rats with PH (SuHx and monocrotaline (MCT) models). Pulmonary arteries (PAs) isolated from rats with PH exhibited hypercontractility to phenylephrine and attenuated vasorelaxation elicited by acetylcholine, indicating severe endothelial dysfunction. Tensile testing revealed a a significant increase in PA stiffness in PH. Treatment with PAT-1251, a novel small-molecule LOXL2 inhibitor, improved active and passive properties of the PA ex vivo. There was an improvement in right heart function as measured by right ventricular pressure volume loops in-vivo with PAT-1251. Importantly PAT-1251 treatment ameliorated PH, resulting in improved pulmonary artery pressures, right ventricular remodeling, and survival.

Conclusion

Hypoxia induced LOXL2 activation is a causal mechanism in pulmonary artery stiffening in PH, as well as pulmonary artery mechanical and functional decline. LOXL2 inhibition with PAT-1251 is a promising approach to improve pulmonary artery pressures, right ventricular elastance, cardiac relaxation, and survival in PAH.

New & Noteworthy

Pulmonary arterial stiffening contributes to the progression of PAH and the deterioration of right heart function. This study shows that LOXL2 is upregulated in rat models of PH. LOXL2 inhibition halts pulmonary vascular remodeling and improves PA contractility, endothelial function and improves PA pressure, resulting in prolonged survival. Thus, LOXL2 is an important mediator of PA remodeling and stiffening in PH and a promising target to improve PA pressures and survival in PH.

Unaltered hepatic wound healing response in male rats with ancestral liver injury

The possibility that ancestral environmental exposure could result in adaptive inherited effects in mammals has been long debated. Numerous rodent models of transgenerational responses to various environmental factors have been published but due to technical, operational and resource burden, most still await independent confirmation. A previous study reported multigenerational epigenetic adaptation of the hepatic wound healing response upon exposure to the hepatotoxicant carbon tetrachloride (CCl4) in male rats. Here, we comprehensively investigate the transgenerational effects by repeating the original CCl4 multigenerational study with increased power, pedigree tracing, F2 dose-response and suitable randomization schemes. Detailed pathology evaluations do not support adaptive phenotypic suppression of the hepatic wound healing response or a greater fitness of F2 animals with ancestral liver injury exposure. However, transcriptomic analyses identified genes whose expression correlates with ancestral liver injury, although the biological relevance of this apparent transgenerational transmission at the molecular level remains to be determined. This work overall highlights the need for independent evaluation of transgenerational epigenetic inheritance paradigms in mammals.

Found in translation-Fibrosis in metabolic dysfunction-associated steatohepatitis (MASH)

Metabolic dysfunction-associated steatohepatitis (MASH) is a severe form of liver disease that poses a global health threat because of its potential to progress to advanced fibrosis, leading to cirrhosis and liver cancer. Recent advances in single-cell methodologies, refined disease models, and genetic and epigenetic insights have provided a nuanced understanding of MASH fibrogenesis, with substantial cellular heterogeneity in MASH livers providing potentially targetable cell-cell interactions and behavior. Unlike fibrogenesis, mechanisms underlying fibrosis regression in MASH are still inadequately understood, although antifibrotic targets have been recently identified. A refined antifibrotic treatment framework could lead to noninvasive assessment and targeted therapies that preserve hepatocellular function and restore the liver's architectural integrity.

Lysyl oxidase like-2 in fibrosis and cardiovascular disease

Fibrosis is an important and essential reparative response to injury that, if left uncontrolled, results in the excessive synthesis, deposition, remodeling, and stiffening of the extracellular matrix, which is deleterious to organ function. Thus, the sustained activation of enzymes that catalyze matrix remodeling and cross linking is a fundamental step in the pathology of fibrotic diseases. Recent studies have implicated the amine oxidase lysyl oxidase like-2 (LOXL2) in this process and established significantly elevated expression of LOXL2 as a key component of profibrotic conditions in several organ systems. Understanding the relationship between LOXL2 and fibrosis as well as the mechanisms behind these relationships can offer significant insights for developing novel therapies. Here, we summarize the key findings that demonstrate the link between LOXL2 and fibrosis and inflammation, examine current therapeutics targeting LOXL2 for the treatment of fibrosis, and discuss future directions for experiments and biomedical engineering.

Combination Therapy of Lox Inhibitor and Stimuli-Responsive Drug for Mechanochemically Synergistic Breast Cancer Treatment

Chemotherapy based on small molecule drugs, hormones, cycline kinase inhibitors, and monoclonal antibodies has been widely used for breast cancer treatment in the clinic but with limited efficacy, due to the poor specificity and tumor microenvironment (TME)-caused diffusion barrier. Although monotherapies targeting biochemical cues or physical cues in the TME have been developed, none of them can cope with the complex TME, while mechanochemical combination therapy remains largely to be explored. Herein, a combination therapy strategy based on an extracellular matrix (ECM) modulator and TME-responsive drug for the first attempt of mechanochemically synergistic treatment of breast cancer is developed. Specifically, based on overexpressed NAD(P)H quinone oxidoreductase 1 (NQO1) in breast cancer, a TME-responsive drug (NQO1-SN38) is designed and it is combined with the inhibitor (i.e., β-Aminopropionitrile, BAPN) for Lysyl oxidases (Lox) that contributes to the tumor stiffness, for mechanochemical therapy. It is demonstrated that NQO1 can trigger the degradation of NQO1-SN38 and release SN38, showing nearly twice tumor inhibition efficiency compared with SN38 treatment in vitro. Lox inhibition with BAPN significantly reduces collagen deposition and enhances drug penetration in tumor heterospheroids in vitro. It is further demonstrated that the mechanochemical therapy showed outstanding therapeutic efficacy in vivo, providing a promising approach for breast cancer therapy.

Multiple Roles of LOXL2 in the Progression of Hepatocellular Carcinoma and Its Potential for Therapeutic Targeting

LOXL2, a copper-dependent amine oxidase, has emerged as a promising therapeutic target in hepatocellular carcinoma (HCC). Increased LOXL2 expression in HCC has been linked with an aggressive phenotype and represents a poor prognostic factor. Here, we focus on the mechanisms through which LOXL2 orchestrates multiple oncogenic functions in HCC development. We performed a review of the current knowledge on the roles LOXL2 performs in the modulation of the HCC tumor microenvironment, formation of premetastatic niches, and epithelial-mesenchymal transition. We also highlighted the complex interplay between LOXL2 and hypoxia, angiogenesis, and vasculogenic mimicry in HCC. At the end of the review, we summarize the current LOXL2 inhibitors and discuss their potential in HCC precision treatment.

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.

Mesenchymal stem cell-derived exosomal miR-27b-3p alleviates liver fibrosis via downregulating YAP/LOXL2 pathway

Lysyl oxidase-like 2 (LOXL2) is an extracellular copper-dependent enzyme that plays a central role in fibrosis by catalyzing the crosslinking and deposition of collagen. Therapeutic LOXL2 inhibition has been shown to suppress liver fibrosis progression and promote its reversal. This study investigates the efficacy and underlying mechanisms of human umbilical cord-derived exosomes (MSC-ex) in LOXL2 inhibition of liver fibrosis. MSC-ex, nonselective LOX inhibitor β-aminopropionitrile (BAPN), or PBS were administered into carbon tetrachloride (CCl4)-induced fibrotic livers. Serum LOXL2 and collagen crosslinking were assessed histologically and biochemically. MSC-ex's mechanisms on LOXL2 regulation were investigated in human hepatic stellate cell line LX-2. We found that systemic administration of MSC-ex significantly reduced LOXL2 expression and collagen crosslinking, delaying the progression of CCl4-induced liver fibrosis. Mechanically, RNA-sequencing and fluorescence in situ hybridization (FISH) indicated that miR-27b-3p was enriched in MSC-ex and exosomal miR-27b-3p repressed Yes-associated protein (YAP) expression by targeting its 3' untranslated region in LX-2. LOXL2 was identified as a novel downstream target gene of YAP, and YAP bound to the LOXL2 promoter to positively regulate transcription. Additionally, the miR-27b-3p inhibitor abrogated the anti-LOXL2 abilities of MSC-ex and diminished the antifibrotic efficacy. miR-27b-3p overexpression promoted MSC-ex mediated YAP/LOXL2 inhibition. Thus, MSC-ex may suppress LOXL2 expression through exosomal miR-27b-3p mediated YAP down-regulation. The findings here may improve our understanding of MSC-ex in liver fibrosis alleviation and provide new opportunities for clinical treatment.

Estrogen-related receptor γ (ERRγ) is a key regulator of lysyl oxidase gene expression in mouse hepatocytes

Lysyl oxidase (LOX), the copper-dependent extracellular enzyme, plays a critical role in the regulation of protein cross-linking in the extracellular matrix (ECM). It is also involved in liver regeneration and liver fibrosis. However, the mechanism of LOX regulation in mouse hepatocytes is still unclear. Here, we identify a molecular mechanism showing that orphan nuclear receptor estrogen-related receptor γ (ERRγ) regulates LOX gene expression in the presence of the pro-inflammatory cytokine, interleukin 6 (IL6). IL6 significantly stimulated the expression of ERRγ and LOX in mouse hepatocytes. Overexpression of ERRγ increased LOX mRNA and protein levels. Moreover, knockdown of ERRγ attenuated IL6-mediated LOX gene expression at mRNA and protein levels. Overexpression of ERRγ or IL6 treatment upregulated LOX gene promoter activity, while knockdown of ERRγ decreased the IL6-induced LOX promoter activity. Furthermore, GSK5182, a specific ERRγ inverse agonist, inhibited the induction effect of IL6 on LOX promoter activity and gene expression in mouse hepatocytes. Overall, our study elucidates the mechanism involved in the LOX gene regulation by nuclear receptor ERRγ in response to IL6 in mouse hepatocytes, suggesting that, in conditions such as chronic inflammation, IL6 may contribute to liver fibrosis via inducing LOX gene expression. Thus, LOX gene regulation by the inverse agonist of ERRγ can be applied to improve liver fibrosis.

Mechanical homeostasis imbalance in hepatic stellate cells activation and hepatic fibrosis

Chronic liver disease or repeated damage to hepatocytes can give rise to hepatic fibrosis. Hepatic fibrosis (HF) is a pathological process of excessive sedimentation of extracellular matrix (ECM) proteins such as collagens, glycoproteins, and proteoglycans (PGs) in the hepatic parenchyma. Changes in the composition of the ECM lead to the stiffness of the matrix that destroys its inherent mechanical homeostasis, and a mechanical homeostasis imbalance activates hepatic stellate cells (HSCs) into myofibroblasts, which can overproliferate and secrete large amounts of ECM proteins. Excessive ECM proteins are gradually deposited in the Disse gap, and matrix regeneration fails, which further leads to changes in ECM components and an increase in stiffness, forming a vicious cycle. These processes promote the occurrence and development of hepatic fibrosis. In this review, the dynamic process of ECM remodeling of HF and the activation of HSCs into mechanotransduction signaling pathways for myofibroblasts to participate in HF are discussed. These mechanotransduction signaling pathways may have potential therapeutic targets for repairing or reversing fibrosis.

Lysyl oxidase-like 2 processing by factor Xa modulates its activity and substrate preference

Lysyl oxidase-like 2 (LOXL2) has been identified as an essential mediator of extracellular matrix (ECM) remodeling in several disease processes including cardiovascular disease. Thus, there is growing interest in understanding the mechanisms by which LOXL2 is regulated in cells and tissue. While LOXL2 occurs both in full length and processed forms in cells and tissue, the precise identity of the proteases that process LOXL2 and the consequences of processing on LOXL2's function remain incompletely understood. Here we show that Factor Xa (FXa) is a protease that processes LOXL2 at Arg-338. Processing by FXa does not affect the enzymatic activity of soluble LOXL2. However, in situ in vascular smooth muscle cells, LOXL2 processing by FXa results in decreased cross-linking activity in the ECM and shifts substrate preference of LOXL2 from type IV collagen to type I collagen. Additionally, processing by FXa increases the interactions between LOXL2 and prototypical LOX, suggesting a potential compensatory mechanism to preserve total LOXs activity in the vascular ECM. FXa expression is prevalent in various organ systems and shares similar roles in fibrotic disease progression as LOXL2. Thus, LOXL2 processing by FXa could have significant implications in pathologies where LOXL2 is involved.

Kidney fibrosis: from mechanisms to therapeutic medicines

Chronic kidney disease (CKD) is estimated to affect 10-14% of global population. Kidney fibrosis, characterized by excessive extracellular matrix deposition leading to scarring, is a hallmark manifestation in different progressive CKD; However, at present no antifibrotic therapies against CKD exist. Kidney fibrosis is identified by tubule atrophy, interstitial chronic inflammation and fibrogenesis, glomerulosclerosis, and vascular rarefaction. Fibrotic niche, where organ fibrosis initiates, is a complex interplay between injured parenchyma (like tubular cells) and multiple non-parenchymal cell lineages (immune and mesenchymal cells) located spatially within scarring areas. Although the mechanisms of kidney fibrosis are complicated due to the kinds of cells involved, with the help of single-cell technology, many key questions have been explored, such as what kind of renal tubules are profibrotic, where myofibroblasts originate, which immune cells are involved, and how cells communicate with each other. In addition, genetics and epigenetics are deeper mechanisms that regulate kidney fibrosis. And the reversible nature of epigenetic changes including DNA methylation, RNA interference, and chromatin remodeling, gives an opportunity to stop or reverse kidney fibrosis by therapeutic strategies. More marketed (e.g., RAS blockage, SGLT2 inhibitors) have been developed to delay CKD progression in recent years. Furthermore, a better understanding of renal fibrosis is also favored to discover biomarkers of fibrotic injury. In the review, we update recent advances in the mechanism of renal fibrosis and summarize novel biomarkers and antifibrotic treatment for CKD.

Collagen is More Abundant and Structurally Altered in Lichen Sclerosus

OBJECTIVE

To test the hypothesis that genital skin and male urethra affected by lichen sclerosus (LS) has increased collagen content and altered collagen structure.

METHODS

We used picrosirius red to stain and image collagen in human urethral, vulvar, and foreskin specimens with and without LS. Using Image J software, we quantified and compared (1) collagen content (using 2o metrics: collagen proportionate area [CPA] and collagen fiber count), (2) collagen fiber length and width, and (3) collagen structure using the texture analysis technique gray level co-localization matrix (GLCM) with respect to LS status and tissue type.

RESULTS

We analyzed 23 LS specimens (vulva n=9, urethra n=7, foreskin n=7) and 29 non-LS specimens (vulva n=9, urethra n=7, foreskin n=13). Fiber count and CPA were significantly higher in all LS specimens compared to non-LS specimens (CPA: mean±SD 0.971±0.03 vs 0.948±0.02, P < .007; fiber count: mean±SD = 2906±127 vs 2509±78 fibers; P = .003). Collagen fiber width and length were similar with respect to LS status. GLCM analysis showed decreased inverse difference moment and increased entropy in LS tissues indicative of less homogeneous and more disorganized tissue structure (P<.001).

CONCLUSION

LS tissues have greater collagen content compared to non-LS tissues. Quantitative assessment of collagen organization, using GLCM, revealed less homogeneity and more disorganization of collagen in LS compared to non-LS tissues. Taken together, our findings suggest that alterations in physical tissue properties seen in LS may be due to both increased collagen abundance and altered structure.

17α-estradiol, a lifespan-extending compound, attenuates liver fibrosis by modulating collagen turnover rates in male mice

Estrogen signaling is protective against chronic liver diseases, although men and a subset of women are contraindicated for chronic treatment with 17β-estradiol (17β-E2) or combination hormone replacement therapies. We sought to determine if 17α-estradiol (17α-E2), a naturally occurring diastereomer of 17β-E2, could attenuate liver fibrosis. We evaluated the effects of 17α-E2 treatment on collagen synthesis and degradation rates using tracer-based labeling approaches in male mice subjected to carbon tetrachloride (CCl4)-induced liver fibrosis. We also assessed the effects of 17α-E2 on markers of hepatic stellate cell (HSC) activation, collagen cross-linking, collagen degradation, and liver macrophage content and polarity. We found that 17α-E2 significantly reduced collagen synthesis rates and increased collagen degradation rates, which was mirrored by declines in transforming growth factor β1 (TGF-β1) and lysyl oxidase-like 2 (LOXL2) protein content in liver. These improvements were associated with increased matrix metalloproteinase 2 (MMP2) activity and suppressed stearoyl-coenzyme A desaturase 1 (SCD1) protein levels, the latter of which has been linked to the resolution of liver fibrosis. We also found that 17α-E2 increased liver fetuin-A protein, a strong inhibitor of TGF-β1 signaling, and reduced proinflammatory macrophage activation and cytokines expression in the liver. We conclude that 17α-E2 reduces fibrotic burden by suppressing HSC activation and enhancing collagen degradation mechanisms. Future studies will be needed to determine if 17α-E2 acts directly in hepatocytes, HSCs, and/or immune cells to elicit these benefits.

Identification of hub biomarkers and exploring the roles of immunity, M6A, ferroptosis, or cuproptosis in rats with diabetic erectile dysfunction

BACKGROUND

Currently, patients with diabetic erectile dysfunction (DMED) were not satisfied with the effects of first-line phosphodiesterase type 5 inhibitors (PDE5Is). Hence, this paper was designed to mine hub biomarkers in DMED and explore its potential mechanisms.

METHODS

Gene expression matrix of DMED was downloaded from the gene expression omnibus (GEO; GSE2457) dataset. The top 20 genes were selected based on the connectivity degrees in protein-protein interaction (PPI) network. Functional enrichment analysis was utilized to reveal DMED-related signaling pathways. We also explored the roles of immunity, m6A, ferroptosis, or cuproptosis in DMED and constructed Sprague Dawley (SD) rats DMED model to verify gene expressions by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Based on the threshold, a total of 122 differently expressed genes (DEGs) were identified in DMED, including 39 up-regulated and 83 down-regulated genes. Functional enrichment analysis implied that these DEGs were significantly enriched in peroxisome proliferator-activated receptors, ferroptosis, hypoxia-inducible factor 1 signaling pathways, and so on. SD rats DMED model was also successfully established by us and validated by intracavernous pressure/mean arterial pressure, Masson's trichrome staining, and immunohistochemical analysis. We further verified the expression of these top 20 genes from the PPI network by qRT-PCR in the SD rats DMED model and finally identified Sparc, Lox, Srebf1, and Mmp3 as hub biomarkers (all p < 0.05). As for immunity and cuproptosis, our analysis indicated that DMED had nothing to do with them (all p > 0.05). Actually, DMED was markedly associated with m6A regulators and ferroptosis.

CONCLUSIONS

We identified Sparc, Lox, Srebf1, and Mmp3 as potential hub biomarkers in the SD rats DMED model for future drug development and found its significant associations with m6A regulators and ferroptosis, but not with immunity or cuproptosis.

Scar-Degrading Endothelial Cells as a Treatment for Advanced Liver Fibrosis

Deposition of extracellular matrix (ECM) in the liver is an important feature of liver cirrhosis. Recovery from liver cirrhosis is physiologically challenging, partially due to the ECM in scar tissue showing resistance to cell-mediated degradation by secreted matrix metalloproteinases (MMPs). Here, a cell-mediated ECM-degradation screening system (CEDSS) in vitro is constructed for high-throughput searching for cells with tremendous degradation ability. ECM-degrading liver sinusoidal endothelial cells (dLSECs) are screened using CEDSS, which exhibit 17 times the ability to degrade collagen when compared to other cells. The degradation ability of dLSECs is mediated by the upregulation of MMP9. In particular, mRNA expression of MMP9 shows an 833-fold increase in dLSECs compared to normal endothelial cells (nLSECs), and MMP9 is regulated by transcription factor c-Fos. In vivo, single intrasplenic injection of dLSECs alleviates advanced liver fibrosis in mice, while intraperitoneal administration of liver-targeting peptide-modified dLSECs shows enhanced fibrosis-targeting effects. Degradative human umbilical vein endothelial cells (dHUVECs) prove their enhanced potential of clinical translation. Together, these results highlight the potential of ECM-degrading endothelial cells in alleviating advanced liver fibrosis, thus providing remarkable insights in the development of ECM-targeting therapeutics.

Targeting Periostin Expression Makes Pancreatic Cancer Spheroids More Vulnerable to Natural Killer Cells

Pancreatic cancer (PaCa) characteristically has a dense tumor microenvironment, which results in poor patient prognosis. Pancreatic stellate cells (PSCs) are the most abundant cells in the PaCa microenvironment and the principal source of collagen. Periostin, a matricellular protein, is produced specifically by PSCs and promotes the aggressiveness of PaCa cells by facilitating extracellular collagen assembly. Here, we aimed to decrease extracellular collagen assembly by suppressing periostin, thereby increasing the cytotoxic activity of natural killer (NK) cells. Periostin expression was suppressed in PSCs (called PSC-P) using CRISPR-Cas9. PaCa cells (BxPC-3) were co-cultured with PSC and PSC-P cells in a 3D environment to form tumor spheroids mimicking the tumor microenvironment. The extracellular collagen production of spheroids was evaluated by Masson's trichrome staining. The cytotoxic activity of NK-92 cells was analyzed by flow cytometry and confocal microscopy via CD107a staining. Cell death in BxPC-3 cells was evaluated by measuring Annexin-V and PI positivity using flow cytometry. As a result, periostin suppression decreased extracellular collagen and increased the infiltration of NK-92 cells into spheroids, and induced cell death in PaCa cells. In conclusion, we suggest that periostin might be a therapeutic target for PaCa and further analysis is warranted using in vivo models for proof-of-concept.

Regulators, functions, and mechanotransduction pathways of matrix stiffness in hepatic disease

The extracellular matrix (ECM) provides physical support and imparts significant biochemical and mechanical cues to cells. Matrix stiffening is a hallmark of liver fibrosis and is associated with many hepatic diseases, especially liver cirrhosis and carcinoma. Increased matrix stiffness is not only a consequence of liver fibrosis but is also recognized as an active driver in the progression of fibrotic hepatic disease. In this article, we provide a comprehensive view of the role of matrix stiffness in the pathological progression of hepatic disease. The regulators that modulate matrix stiffness including ECM components, MMPs, and crosslinking modifications are discussed. The latest advances of the research on the matrix mechanics in regulating intercellular signaling and cell phenotype are classified, especially for hepatic stellate cells, hepatocytes, and immunocytes. The molecular mechanism that sensing and transducing mechanical signaling is highlighted. The current progress of ECM stiffness's role in hepatic cirrhosis and liver cancer is introduced and summarized. Finally, the recent trials targeting ECM stiffness for the treatment of liver disease are detailed.

Fibroblast Activation Protein Activates Macrophages and Promotes Parenchymal Liver Inflammation and Fibrosis

BACKGROUND & AIMS

Fibroblast activation protein (FAP) is expressed on activated fibroblast. Its role in fibrosis and desmoplasia is controversial, and data on pharmacological FAP inhibition are lacking. We aimed to better define the role of FAP in liver fibrosis in vivo and in vitro.

METHODS

FAP expression was analyzed in mice and patients with fibrotic liver diseases of various etiologies. Fibrotic mice received a specific FAP inhibitor (FAPi) at 2 doses orally for 2 weeks during parenchymal fibrosis progression (6 weeks of carbon tetrachloride) and regression (2 weeks off carbon tetrachloride), and with biliary fibrosis (Mdr2-/-). Recombinant FAP was added to (co-)cultures of hepatic stellate cells (HSC), fibroblasts, and macrophages. Fibrosis- and inflammation-related parameters were determined biochemically, by quantitative immunohistochemistry, polymerase chain reaction, and transcriptomics.

RESULTS

FAP+ fibroblasts/HSCs were α-smooth muscle actin (α-SMA)-negative and located at interfaces of fibrotic septa next to macrophages in murine and human livers. In parenchymal fibrosis, FAPi reduced collagen area, liver collagen content, α-SMA+ myofibroblasts, M2-type macrophages, serum alanine transaminase and aspartate aminotransferase, key fibrogenesis-related transcripts, and increased hepatocyte proliferation 10-fold. During regression, FAP was suppressed, and FAPi was ineffective. FAPi less potently inhibited biliary fibrosis. In vitro, FAP small interfering RNA reduced HSC α-SMA expression and collagen production, and FAPi suppressed their activation and proliferation. Compared with untreated macrophages, FAPi regulated macrophage profibrogenic activation and transcriptome, and their conditioned medium attenuated HSC activation, which was increased with addition of recombinant FAP.

CONCLUSIONS

Pharmacological FAP inhibition attenuates inflammation-predominant liver fibrosis. FAP is expressed on subsets of activated fibroblasts/HSC and promotes both macrophage and HSC profibrogenic activity in liver fibrosis.

A comprehensive and mechanistic review on protective effects of kaempferol against natural and chemical toxins: Role of NF-κB inhibition and Nrf2 activation

Different toxins, including chemicals and natural, can be entered from various routes and influence human health. Herbal medicines and their active components can attenuate the toxicity of agents via multiple mechanisms. For example, kaempferol, as a flavonoid, can be found in fruits and vegetables, and has an essential role in improving disorders such as cardiovascular disorders, neurological diseases, cancer, pain, and inflammation situations. The beneficial effects of kaempferol may be related to the inhibition of oxidative stress, attenuation of inflammatory factors such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), cyclooxygenase-2 (COX-2) and nuclear factor ĸB (NF-ĸB) as well as the modulation of apoptosis and mitogen-activated protein kinase (MAPK) signaling pathways. This flavonoid boasts a wide spectrum of toxin targeting effects in tissue fibrosis, inflammation, and oxidative stress thus shows promising protective effects against natural and chemical toxin induced hepatotoxicity, nephrotoxicity, cardiotoxicity, neurotoxicity, lung, and intestinal in the in vitro and in vivo setting. The most remarkable aspect of kaempferol is that it does not focus its efforts on just one organ or one molecular pathway. Although its significance as a treatment option remains questionable and requires more clinical studies, it seems to be a low-risk therapeutic option. It is crucial to emphasize that kaempferol's poor bioavailability is a significant barrier to its use as a therapeutic option. Nanotechnology can be a promising way to overcome this challenge, reviving optimism in using kaempferol as a viable treatment agent against toxin-induced disorders.

Adipose-derived mesenchymal stem cell-secreted extracellular vesicles alleviate non-alcoholic fatty liver disease via delivering miR-223-3p

Increasing studies have identified the potential of mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) in non-alcoholic fatty liver disease (NAFLD) treatment. Hence, we further focused on the potential of adipose-derived MSC (ADSC)-EVs in NAFLD by delivering miR-223-3p. The uptake of isolated ADSC-EVs by hepatocytes was assessed, and the expression of miR-223-3p in ADSC-EVs and hepatocytes was characterized. It was established that miR-223-3p, enriched in ADSC-EVs, could be delivered by ADSC-EVs into hepatocytes. Using co-culture system and gain-of-function approach, we evaluated the effect of ADSC-EVs carrying miR-223-3p on lipid accumulation and liver fibrosis in pyrrolizidine alkaloids (PA)-induced hepatocytes and a high-fat diet-induced NAFLD mouse model. Bioinformatics websites and dual-luciferase reporter gene assay were performed to determine the interactions between miR-223-3p and E2F1, which was further validated by rescue experiments. ADSC-EVs containing miR-223-3p displayed suppressive effects on lipid accumulation and liver fibrosis through E2F1 inhibition, since E2F1 was demonstrated as a target gene of miR-223-3p. The protective role of ADSC-EVs by delivering miR-223-3p was then confirmed in the mouse model. Collectively, this study elucidated that ADSC-EVs delayed the progression NAFLD through the delivery of anti-fibrotic miR-223-3p and subsequent E2F1 suppression, which may suggest miR-223-3p-loaded ADSC-EVs to be a potential therapeutic approach for NAFLD.

The role of hepatic microenvironment in hepatic fibrosis development

AIM

Fibrosis is a common pathological feature of most types of chronic liver injuries. There is no specific treatment for liver fibrosis at present. The liver microenvironment, which fosters the survival and activity of liver cells, plays an important role in maintaining the normal structure and physiological function of the liver. The aim of this review is to deeply understand the role of the liver microenvironment in the dynamic and complicated development of liver fibrosis.

METHODS

After searching in Elsevier ScienceDirect, PubMed and Web of Science databases using 'liver fibrosis' and 'microenvironment' as keywords, studies related to microenvironment in liver fibrosis was compiled and examined.

RESULTS

The homeostasis of the liver microenvironment is disrupted during the development of liver fibrosis, affecting liver cell function, causing various types of cell reactions, and changing the cell-cell and cell-matrix interactions, eventually affecting fibrosis formation.

CONCLUSION

Liver microenvironment may be important for identifying potential therapeutic targets, and restoring microenvironment homeostasis may be an important strategy for promoting the reversal of liver fibrosis.KEY MESSAGESThe homeostasis of the liver microenvironment is disrupted in liver fibrosis;A pro-fibrotic microenvironment is formed during the development of liver fibrosis;Restoring microenvironment homeostasis may be an important strategy for promoting the reversal of liver fibrosis.