High-yield and high-purity isolation of hepatic stellate cells from normal and fibrotic mouse livers

LOX-1 rewires glutamine ammonia metabolism to drive liver fibrosis

OBJECTIVE

Liver fibrosis is a crucial condition for evaluating the prognosis of chronic liver disease. Lectin-1ike oxidized low density lipoprotein receptor-1 (LOX-1) has been shown potential research value and therapeutic targeting possibilities in different fibrotic diseases. However, the role of LOX-1 and the underlying mechanisms in liver fibrosis progression remain unclear.

METHODS

LOX-1 expression was detected in liver tissues from patients and rodents with liver fibrosis. LOX-1 knockout rats were subjected to CCl4 or methionine and choline-deficient diet (MCD) to induce liver fibrosis. Transcriptomic and metabolomics analysis were used to investigate the involvement and mechanism of LOX-1 on liver fibrosis.

RESULTS

We found that LOX-1 exacerbated liver fibrosis by promoting hepatic stellate cells (HSCs) activation. LOX-1 deletion reversed the development of liver fibrosis. We further verified that LOX-1 drove liver fibrosis by reprogramming glutamine metabolism through mediating isoform switching of glutaminase (GLS). Mechanistically, we revealed the crucial role of the LOX-1/OCT1/GLS1 axis in the pathogenesis of liver fibrosis. Moreover, LOX-1 rewired ammonia metabolism by regulating glutamine metabolism-urea cycle to drive the progression of liver fibrosis.

CONCLUSIONS

Our findings uncover the pivotal role of LOX-1 in the progression of liver fibrosis, enrich the pathological significance of LOX-1 regulation of hepatic ammonia metabolism, and provide an insight into promising targets for the therapeutic strategy of liver fibrosis, demonstrating the potential clinical value of targeting LOX-1 in antifibrotic therapy.

Multitissue single-cell analysis reveals differential cellular and molecular sensitivity between fructose and high-fat high-sucrose diets

Metabolic syndrome (MetS), a conglomerate of dysregulated metabolic traits that vary between individuals, is partially driven by modern diets high in fat, sucrose, or fructose and their interactions with host genes in metabolic tissues. To elucidate the roles of individual tissues and cell types in diet-induced MetS, we performed single-cell RNA sequencing on the hypothalamus, liver, adipose tissue, and small intestine of mice fed high-fat high-sucrose (HFHS) or fructose diets. We found that hypothalamic neurons were sensitive to fructose, while adipose progenitor cells and macrophages were responsive to HFHS. Ligand-receptor analysis revealed lipid metabolism and inflammation networks among peripheral tissues driven by HFHS, while both diets stimulated synaptic remodeling within the hypothalamus. mt-Rnr2, a top responder to both diets, mitigated diet-induced MetS by stimulating thermogenesis. Our study demonstrates that HFHS and fructose diets have differential cell type and network targets but also share regulators such as mt-Rnr2 to affect MetS risk.

Identification of a robust promoter in mouse and human hepatocytes by in vivo biopanning of a barcoded AAV library

Recombinant adeno-associated viruses (AAVs) are leading vectors for in vivo human gene therapy. An integral vector element is promoters, which control transgene expression in either a ubiquitous or cell-type-selective manner. Identifying optimal capsid-promoter combinations is challenging, especially when considering on- versus off-target expression. Here, we report a pipeline for in vivo promoter biopanning in AAV building on our AAV capsid barcoding technology and illustrate its potential by screening 53 promoters in 16 murine tissues using an AAV9 vector. Surprisingly, the 2.2-kb human glial fibrillary acidic protein (GFAP) promoter was the top hit in the liver, where it outperformed robust benchmarks such as the human α-1-antitrypsin promoter or the clinically used liver-specific promoter 1 (LP1). Analysis of hepatic cell populations revealed preferred GFAP promoter activity in hepatocytes. Notably, the GFAP promoter also surpassed the LP1 and cytomegalovirus promoters in human hepatocytes engrafted in an immune-deficient mouse. These findings establish the GFAP promoter as an exciting alternative for research and clinical applications requiring efficient and specific transgene expression in hepatocytes. Our pipeline expands the arsenal of technologies for high-throughput in vivo screening of viral vector components and is compatible with capsid barcoding, facilitating the combinatorial interrogation of complex AAV libraries.

HIF-1α/LTBP2 axis activate HSCs to promote liver fibrosis by interacting with LOXL1 via the ERK pathway

Latent Transforming Growth Factor Beta Binding Protein 2 (LTBP2) is a multi-domain exocrine protein located in the extracellular matrix (ECM) and has been implicated in fibrosis across various organs. However, its role in liver fibrosis remains inadequately understood. This study aims to elucidate the function and mechanism of LTBP2 in hepatic stellate cells (HSCs) activation and liver fibrosis. Our findings indicate that LTBP2 expression is positively correlated with liver fibrosis and is significantly elevated in fibrotic liver tissues from both human and murine models. Importantly, AAV6-mediated knockdown of LTBP2 in HSCs markedly alleviates CCl4-induced liver fibrosis by inhibiting the HSCs activation and reducing collagen deposition in mice. Gain-of-function and loss-of-function experiments confirmed that overexpression or knockdown of LTBP2 can enhance or inhibit the activation of HSCs, proliferation, migration and epithelial-mesenchymal transition (EMT) in LX-2 cells. Mechanistically, chromatin immunoprecipitation (ChIP) assays and dual-luciferase reporter gene assays revealed that Hypoxia-inducible Factor 1α (HIF-1α) promotes LTBP2 expression by directly binding to the LTBP2 promoter region. Furthermore, molecular docking and co-immunoprecipitation (Co-IP) experiments demonstrated an interaction between Lysyl Oxidase Like Protein 1 (LOXL1) and LTBP2. Rescue experiments verified that LTBP2 interacts with LOXL1 via the ERK signaling pathway to promote the activation of HSCs and EMT. Our results provide compelling evidence that the HIF-1α/LTBP2 axis facilitates the activation of HSCs and EMT by interacting with LOXL1 through ERK signaling pathway, suggesting that LTBP2 may serve as a potential therapeutic target for liver fibrosis.

Periductal fibroblasts participate in liver homeostasis, fibrosis, and tumorigenesis

Hepatic fibroblasts comprise groups of stromal cells in the liver that are phenotypically distinct from hepatic stellate cells. However, their physiology is poorly understood. By single-cell RNA sequencing, we identified Cd34 and Dpt as hepatic fibroblast-specific genes. Cd34-CreER labeled periportal-venous and periductal fibroblasts, but few pericentral-venous fibroblasts. Cd34+ fibroblasts generated ∼25% of myofibroblasts in periportal fibrosis and ∼40% of cancer-associated fibroblasts (CAFs) in intrahepatic cholangiocarcinoma (ICC). Myofibroblast formation by Cd34+ fibroblasts required Tgfbr2. Depletion of Cd34+ fibroblasts increased the frequency of the ductal epithelial cells under homeostasis and accelerated the progression of ICC. Dpt-CreER labeled periportal- and pericentral-venous fibroblasts, but much less periductal fibroblasts. Dpt+ cells generated ∼15% of myofibroblasts in periportal fibrosis, but few myofibroblasts in pericentral fibrosis or CAFs in ICC. Thus, an orthogonal combination of Cd34-CreER and Dpt-CreER dissected the fates of periductal, periportal-venous, and pericentral-venous fibroblasts. Both periductal and periportal-venous fibroblasts contribute to liver fibrosis. Periductal fibroblasts also contribute to ductal homeostasis and ICC progression.

Hepatic stellate cells control liver zonation, size and functions via R-spondin 3

Hepatic stellate cells (HSCs) have a central pathogenetic role in the development of liver fibrosis. However, their fibrosis-independent and homeostatic functions remain poorly understood1-5. Here we demonstrate that genetic depletion of HSCs changes WNT activity and zonation of hepatocytes, leading to marked alterations in liver regeneration, cytochrome P450 metabolism and injury. We identify R-spondin 3 (RSPO3), an HSC-enriched modulator of WNT signalling, as responsible for these hepatocyte-regulatory effects of HSCs. HSC-selective deletion of Rspo3 phenocopies the effects of HSC depletion on hepatocyte gene expression, zonation, liver size, regeneration and cytochrome P450-mediated detoxification, and exacerbates alcohol-associated and metabolic dysfunction-associated steatotic liver disease. RSPO3 expression decreases with HSC activation and is inversely associated with outcomes in patients with alcohol-associated and metabolic dysfunction-associated steatotic liver disease. These protective and hepatocyte-regulating functions of HSCs via RSPO3 resemble the R-spondin-expressing stromal niche in other organs and should be integrated into current therapeutic concepts.

Impact of liver fibrosis on AAV-mediated gene transfer to mouse hepatocytes

Liver fibrosis, characterized by scar tissue accumulation due to liver injury, poses significant barriers to liver-targeted gene therapy. Current clinical trials exclude patients with fibrosis, as intact liver architecture is considered essential for efficient and safe adeno-associated viral vector (AAV)-mediated gene delivery. Here, we show that liver fibrosis reduces the efficiency of hepatocyte transduction by AAV8 vectors across three mouse models with diverse fibrotic patterns. This inefficiency stems primarily from decreased vector uptake by the liver rather than loss of vector genomes due to hepatocyte turnover. Additionally, fibrosis alters blood vector clearance and redistributes AAV particles to extra-hepatic organs, such as spleen, lung, and kidney. At the cellular level, fibrosis decreases AAV genome content in hepatocytes while increasing it in non-parenchymal liver cells and splenic immune cells. Importantly, the capsid variant AAV-KP1 retains transduction efficiency in fibrotic livers, highlighting its potential for expanding gene therapy applications to fibrotic diseases.

Genetic Loss of HIF-Prolyl-Hydroxylase 1, but Not Pharmacological Inhibition, Mitigates Hepatic Fibrosis

Liver fibrosis is characterized by excessive deposition of extracellular matrix due to chronic inflammation of the liver. Hepatic stellate cells (HSCs) become activated and produce increased amounts of extracellular matrix. Loss of HIF-prolyl-hydroxylase 1 (PHD1) attenuates HSC activation and fibrotic tissue remodeling in a murine model of biliary liver fibrosis. Herein, the protective effect of PHD1 deficiency (PHD1-/-) in an additional (toxic) model of liver fibrosis was validated and the effect of dimethyloxalylglycine (DMOG), a pan-HIF-prolyl-hydroxylase inhibitor, on the development of liver fibrosis, was evaluated. Liver fibrosis was induced utilizing carbon tetrachloride in wild-type (WT) and PHD1-/- mice treated with either vehicle or DMOG. To assess fibrosis development, expression of profibrotic genes in the livers was analyzed by Sirius red staining. When compared with WT mice, PHD1-/- mice developed less-severe liver fibrosis. DMOG treatment did not prevent this liver fibrosis. PHD1-/- mice had fewer α-SMA+ cells and less macrophage infiltration compared with WT mice. Expression of profibrogenic and proinflammatory genes was reduced in livers from carbon tetrachloride-exposed PHD1-/- mice. In vitro analyses of PHD1-deficient human HSCs revealed attenuated mRNA levels of profibrotic genes, as well as impaired migration and invasion. Although PHD1 deficiency attenuated activation of HSCs, pharmacologic PHD inhibition did not ameliorate fibrosis development. These data indicate that selective PHD1 inhibitors could prove effective in preventing and treating liver fibrosis.

Neutrophil extracellular traps promote MASH fibrosis by metabolic reprogramming of HSC

BACKGROUND AND AIMS

Metabolic dysfunction-associated steatohepatitis (MASH) fibrosis is a reversible stage of liver disease accompanied by inflammatory cell infiltration. Neutrophils extrude a meshwork of chromatin fibers to establish neutrophil extracellular traps (NETs), which play important roles in inflammatory response regulation. Our previous work demonstrated that NETs promote HCC in MASH. However, it is still unknown if NETs play a role in the molecular mechanisms of liver fibrosis.

APPROACH AND RESULTS

Following 12 weeks of Western diet/carbon tetrachloride, MASH fibrosis was identified in C57BL/6 mice with increased NET formation. However, NET depletion using DNase I treatment or mice knocked out for peptidyl arginine deaminase type IV significantly attenuated the development of MASH fibrosis. NETs were demonstrated to induce HSCs activation, proliferation, and migration through augmented mitochondrial and aerobic glycolysis to provide additional bioenergetic and biosynthetic supplies. Metabolomic analysis revealed markedly an altered metabolic profile upon NET stimulation of HSCs that were dependent on arachidonic acid metabolism. Mechanistically, NET stimulation of toll-like receptor 3 induced cyclooxygenase-2 activation and prostaglandin E2 production with subsequent HSC activation and liver fibrosis. Inhibiting cyclooxygenase-2 with celecoxib reduced fibrosis in our MASH model.

CONCLUSIONS

Our findings implicate NETs playing a critical role in the development of MASH hepatic fibrosis by inducing metabolic reprogramming of HSCs through the toll-like receptor 3/cyclooxygenase-2/cyclooxygenase-2 pathway. Therefore, NET inhibition may represent an attractive treatment target for MASH liver fibrosis.

Engineered EVs from LncEEF1G - overexpressing MSCs promote fibrotic liver regeneration by upregulating HGF release from hepatic stellate cells

Fibrosis is a disease that negatively affects liver regeneration, resulting in severe complications after liver surgery. However, there is still no clinically effective treatment for promoting fibrotic liver regeneration because the underlying hepatocellular mechanism remains poorly understood. Through microRNA microarrays combined with the application of AAV6, we found that high expression of miR-181a-5p in activated hepatic stellate cells (HSCs) suppressed the expression of hepatic growth factor (HGF) and partially contributed to impaired regeneration potential in mice with hepatic fibrosis that had undergone two-thirds partial hepatectomy. As nanotherapeutics, mesenchymal stem-cell-derived extracellular vesicles (MSC-EVs) have been verified as effective treatments for liver regeneration. Here we observe that MSC-EVs can also promote fibrotic liver regeneration via enriched lncEEF1G, which acts as a competing endogenous RNA to directly sponge miR-181a-5p, leading to the upregulated expression of HGF in HSCs. Finally, engineered MSC-EVs with high expression of lncEEF1G (lncEEF1GOE-EVs) were constructed, suggesting greater potential for this model. In summary, our findings indicate that lncEEF1GOE-EVs have a nanotherapeutic effect on promoting regeneration of fibrotic livers by modulating the miR-181a-5p/HGF pathway in HSCs, which highlights the potential of extracellular vesicle engineering technology for patients with hepatic fibrosis who have undergone hepatic surgery. Engineered mesenchymal stem cells that overexpress lncEEF1G can secrete extracellular vesicles that are rich in lncEEF1G (lncEEF1GOE-EVs). Upon injection of lncEEF1GOE-EVs into a fibrotic 70% partial hepatectomy mouse model, lncEEF1G competitively binds to miR-181a-5p in hepatic stellate cells, preventing the interaction between miR-181a-5p and the messenger RNA of hepatocyte growth factor. This consequently leads to an increase in the secretion of hepatocyte growth factor and the promotion of hepatocyte proliferation.

The Impact of Toll-Like Receptor 5 on Liver Function in Age-Related Metabolic Disorders

Toll-like receptor 5 (TLR5) plays a critical role beyond its traditional function in innate immunity, significantly impacting metabolic regulation and liver health. Previously, we reported that TLR5 activation extends the healthspan and lifespan of aging mice. This study demonstrates that TLR5 deficiency leads to pronounced metabolic abnormalities with age, primarily affecting liver metabolic functions rather than intestinal inflammation. Comprehensive RNA sequencing analysis revealed that TLR5 deficiency induces gene expression changes in liver tissue similar to those caused by the methionine-choline deficient (MCD) diet, particularly affecting lipid metabolism and circadian rhythm-related genes. TLR5 knockout (TLR5 KO) mice displayed an increased propensity for liver fibrosis and lipid accumulation under the MCD diet, exacerbating liver pathology. Both hepatocytes and hepatic stellate cells in TLR5 KO mice were functionally impacted, leading to metabolic dysfunction and fibrosis. These findings suggest that TLR5 could be a significant target for addressing metabolic diseases that arise and worsen with aging. Furthermore, understanding the mechanisms by which TLR5 activation extends healthspan could provide valuable insights into therapeutic strategies for enhancing longevity and managing age-related metabolic disorders.

Ghrelin alleviates liver fibrosis by triggering HSCs ferroptosis via regulating injured hepatocyte-derived exosomal LncMALAT1/GPX4 pathway

Ghrelin reduced the profibrotic effect of IHC-Exo in liver fibrosis by regulating lncMALAT1/GPX4 pathway mediated HSCs ferroptosis. Triggering HSCs ferroptosis via GHR-IHC-Exo may become a novel strategy to alleviate the progression of liver fibrosis. Liver fibrosis is the end stage of the continuous progression of a variety of chronic liver diseases. With the continuous action of various pathogenic factors, hepatic stellate cells in the liver are activated and produce a large amount of collagen fibers that are deposited in the liver, resulting in obvious damage to liver tissue and leading to cirrhosis and even liver cancer, which seriously affects human health. However, there are still clear and effective drugs approved for the treatment of liver fibrosis, so it is important to explore the possible mechanisms of liver fibrosis treatment. In previous studies, researchers found that exosomes secreted by injured hepatocytes promote the progression of liver fibrosis. In our study, we found that the role of exosomes in promoting liver fibrosis progression was attenuated after pretreatment with Ghrelin. This provides an important theoretical basis for the use of Ghrelin in the treatment of liver fibrosis.

Cellular Crosstalk Promotes Hepatic Progenitor Cell Proliferation and Stellate Cell Activation in 3D Co-culture

BACKGROUND & AIMS

Following liver damage, ductular reaction often coincides with liver fibrosis. Proliferation of hepatic progenitor cells is observed in ductular reaction, whereas activated hepatic stellate cells (HSCs) are the main drivers of liver fibrosis. These observations may suggest a functional interaction between these 2 cell types. Here, we report on an in vitro co-culture system to examine these interactions and validate their co-expression in human liver explants.

METHODS

In a 3D organoid co-culture system, we combined freshly isolated quiescent mouse HSCs and fluorescently labeled progenitor cells (undifferentiated intrahepatic cholangiocyte organoids), permitting real-time observation of cell morphology and behavior. After 7 days, cells were sorted based on the fluorescent label and analyzed for changes in gene expression.

RESULTS

In the 3D co-culture system, the proliferation of progenitor cells is enhanced, and HSCs are activated, recapitulating the cellular events observed in the patient liver. Both effects in 3D co-culture require close contact between the 2 different cell types. HSC activation during 3D co-culture differs from quiescent (3D mono-cultured) HSCs and activated HSCs on plastic (2D mono-culture). Upregulation of a cluster of genes containing Aldh1a2, Cthrc1, and several genes related to frizzled binding/Wnt signaling were exclusively observed in 3D co-cultured HSCs. The localized co-expression of specific genes was confirmed by spatial transcriptomics in human liver explants.

CONCLUSION

An in vitro 3D co-culture system provides evidence for direct interactions between HSCs and progenitor cells, which are sufficient to drive responses that are similar to those seen during ductular reaction and fibrosis. This model paves the way for further research into the cellular basis of liver pathology.

Alleviation of liver fibrosis by inhibiting a non-canonical ATF4-regulated enhancer program in hepatic stellate cells

Liver fibrosis is a critical liver disease that can progress to more severe manifestations, such as cirrhosis, yet no effective targeted therapies are available. Here, we identify that ATF4, a master transcription factor in ER stress response, promotes liver fibrosis by facilitating a stress response-independent epigenetic program in hepatic stellate cells (HSCs). Unlike its canonical role in regulating UPR genes during ER stress, ATF4 activates epithelial-mesenchymal transition (EMT) gene transcription under fibrogenic conditions. HSC-specific depletion of ATF4 suppresses liver fibrosis in vivo. Mechanistically, TGFβ resets ATF4 to orchestrate a unique enhancer program for the transcriptional activation of pro-fibrotic EMT genes. Analysis of human data confirms a strong correlation between HSC ATF4 expression and liver fibrosis progression. Importantly, a small molecule inhibitor targeting ATF4 translation effectively mitigates liver fibrosis. Together, our findings identify a mechanism promoting liver fibrosis and reveal new opportunities for treating this otherwise non-targetable disease.

A perfusion-independent high-throughput method to isolate liver sinusoidal endothelial cells

Liver sinusoidal endothelial cells (LSECs) critically regulate homeostatic liver function and liver pathogenesis. However, the isolation of LSECs remains a major technological bottleneck in studying molecular mechanisms governing LSEC functions. Current techniques to isolate LSECs, relying on perfusion-dependent liver digestion, are cumbersome with limited throughput. We here describe a perfusion-independent high-throughput procedure to isolate LSECs with high purity. Indifferently from previous perfusion-independent approaches, chopped liver tissue was incubated in the digestion mix for 30 minutes with intermittent mixing with a serological pipette. This led to the safeguarding of LSEC integrity and yielded 10 ± 1.0 million LSECs per adult mouse liver, which is far higher than previous perfusion-independent protocols and comparable yield to established perfusion-dependent protocols for isolating LSECs. Combining magnetic and fluorescence-activated cell sorting (FACS), LSECs from different zones of the hepatic sinusoid can now be isolated in high numbers in less than two hours for downstream applications including proteomics. Our protocol enables the isolation of LSECs from fibrotic liver tissues from mice and healthy liver tissues from higher vertebrate species (pigs), where traditional perfusion-based digestion protocols have very limited application. In conclusion, these technical advancements reduce post-mortem changes in the LSEC state and aid in reliable investigation of LSEC functions.

AdipoRon mitigates liver fibrosis by suppressing serine/glycine biosynthesis through ATF4-dependent glutaminolysis

AdipoRon has been validated for its ability to reverse liver fibrosis, yet the underlying mechanisms remain to be thoroughly investigated. Collagen, predominantly synthesized and secreted in hepatic stellate cells (HSCs), relies on glycine as a crucial constituent. Activating transcription factor 4 (ATF4) serves as a pivotal transcriptional regulator in amino acid metabolism. Therefore, our objective is to explore the impact of AdipoRon on ATF4-mediated endoplasmic reticulum stress and amino acid metabolism in HSCs. We induced liver fibrosis in mice through intraperitoneal injection of CCl4 and administered AdipoRon (50 mg/kg) via gavage. In vitro studies were predominantly conducted using LX-2 cells. Our findings demonstrated that AdipoRon effectively suppressed ATF4-mediated endoplasmic reticulum stress in HSCs and assumed a crucial role in hindering serine/glycine biosynthesis. Interestingly, this inhibitory effect of AdipoRon on serine/glycine biosynthesis is regulated by PSAT1-mediated glutaminolysis, resulting in a subsequent decrease in collagen synthesis within HSCs. This study provides potential mechanistic insights into the treatment of liver fibrosis with AdipoRon.

A natural small molecule alleviates liver fibrosis by targeting apolipoprotein L2

Liver fibrosis is an urgent clinical problem without effective therapies. Here we conducted a high-content screening on a natural Euphorbiaceae diterpenoid library to identify a potent anti-liver fibrosis lead, 12-deoxyphorbol 13-palmitate (DP). Leveraging a photo-affinity labeling approach, apolipoprotein L2 (APOL2), an endoplasmic reticulum (ER)-rich protein, was identified as the direct target of DP. Mechanistically, APOL2 is induced in activated hepatic stellate cells upon transforming growth factor-β1 (TGF-β1) stimulation, which then binds to sarcoplasmic/ER calcium ATPase 2 (SERCA2) to trigger ER stress and elevate its downstream protein kinase R-like ER kinase (PERK)-hairy and enhancer of split 1 (HES1) axis, ultimately promoting liver fibrosis. As a result, targeting APOL2 by DP or ablation of APOL2 significantly impairs APOL2-SERCA2-PERK-HES1 signaling and mitigates fibrosis progression. Our findings not only define APOL2 as a novel therapeutic target for liver fibrosis but also highlight DP as a promising lead for treatment of this symptom.

Pemigatinib suppresses liver fibrosis and subsequent osteodystrophy in mice

BACKGROUND

Liver fibrosis could lead to serious secondary diseases, including osteodystrophy. The interaction between liver and bone has not been fully elucidated, thus existing therapies for osteodystrophy secondary to liver fibrosis are often ineffective. FGF23 was initially found as an endocrine regulator of phosphate homeostasis, but recently, its involvement in fibrosis has been suggested. In this study, we hypothesized that the FGF23 level increases with liver injury, which in turn induces liver fibrosis and osteodystrophy.

METHODS

Liver fibrosis model mice were generated via carbon tetrachloride administration and bile duct ligation. Fibrosis was assessed using Masson trichrome staining and hydroxyproline assay. The bone structure was evaluated using dual-energy x-ray absorptiometry and microcomputed tomography. Human HSC lines LX-2 and primary rat HSCs were used for in vitro analyses.

RESULTS

Carbon tetrachloride-induced and bile duct ligation-induced liver injury increased the serum FGF23 level compared with that in control mice. RNA sequencing analysis of FGF23-treated LX-2 showed that FGF23 promotes the production of matrisome, which helps in forming the extracellular matrix. The FGF receptor antagonist pemigatinib alleviated carbon tetrachloride-induced and bile duct ligation-induced liver fibrosis and the deleterious alterations in bone density and microstructure in mice.

CONCLUSIONS

The serum FGF23 level increased with liver injury, and FGF23 promoted liver fibrosis. Moreover, pemigatinib alleviated liver fibrosis and hepatic osteodystrophy. These findings suggest that FGF23 mediates the communication between the liver and bone and that FGF23 may be a new therapeutic target for liver fibrosis and subsequent osteodystrophy.

Strategic Optimization of the Middle Domain IIIA in RBP-Albumin IIIA-IB Fusion Protein to Enhance Productivity and Thermostability

The protein therapeutics market, including antibody and fusion proteins, has experienced steady growth over the past decade, underscoring the importance of optimizing amino acid sequences. In our previous study, we developed a fusion protein, R31, which combines retinol-binding protein (RBP) with albumin domains IIIA and IB, linked by a sequence (AAAA), and includes an additional disulfide bond (N227C-V254C) in IIIA. This fusion protein effectively inhibited hepatic stellate cell activation. In this study, we further optimized the sequence. The G176K mutation at the C-terminus of RBP altered the initiation site of the first α-helix in domain IIIA, shifting it from P182 to K176, and promoted polar interactions between K176 and adjacent residues, enhancing the rigidity of the RBP/IIIA interface. The introduction of an additional disulfide bond (V231C/Y250C) connecting helices 3 and 4 in IIIA resulted in a three-fold increase in productivity and a 2 °C improvement in thermal stability compared to R31. Furthermore, combining the G176K mutation with V231C/Y250C further enhanced both productivity and anti-fibrotic activity. These findings suggest that the enhanced stability of domain IIIA, conferred by V231C/Y250C, along with the increased rigidity of the RBP/IIIA interface, optimizes interdomain distance and alignment, facilitating proper protein folding.

Prevent and Reverse Metabolic Dysfunction-Associated Steatohepatitis and Hepatic Fibrosis via mRNA-Mediated Liver-Specific Antibody Therapy

Chronic exposure of the liver to multiple insults culminates in the development of metabolic dysfunction-associated steatohepatitis (MASH), a complicated metabolic syndrome characterized by hepatic steatosis and inflammation, typically accompanied by progressive fibrosis. Despite extensive clinical evaluation, there remain challenges in MASH drug development, which are primarily due to unsatisfactory efficacy and limited specificity. Strategies to address the unmet medical need for MASH with fibrosis before it reaches the irreversible stage of decompensated cirrhosis are critically needed. Herein, we developed an mRNA-mediated liver-specific antibody therapy for MASH and hepatic fibrosis using a targeted lipid nanoparticle (LNP) delivery system. When encapsulated with IL-11 single-chain variable fragment (scFv)-encoded mRNA, the targeted AA3G LNP (termed mIL11-scFv@AA3G) specifically accumulated in the liver and secreted IL-11 scFv to neutralize overexpressed IL-11 in hepatic environments, thus inhibiting the IL-11 signaling pathway in hepatocytes and hepatic stellate cells. As a preventative regimen, systemic administration of mIL11-scFv@AA3G reversed MASH and prevented the progression to fibrosis in a murine model of early MASH. Notably, mIL11-scFv@AA3G exhibited superior efficacy compared to systemic administration of IL-11 scFv alone, attributed to the sustained antibody expression in the liver, which lasted 18-fold longer than that of IL-11 scFv. When tested in the MASH model with fibrosis, mIL11-scFv@AA3G effectively ameliorated steatosis and resolved fibrosis and inflammation. These findings present a versatile LNP platform targeting liver cell subtypes for the sustained expression of therapeutic antibodies to treat MASH and fibrosis. The developed mRNA-mediated liver-specific antibody therapy offers a promising approach for addressing MASH and holds the potential for expansion to various other diseases.

Hepatic Stellate Cell Membrane-Camouflaged Nanoparticles for Targeted Delivery of an Antifibrotic Agent to Hepatic Stellate Cells with Enhanced Antifibrosis Efficacy

Liver fibrosis is characterized by the excessive accumulation of extracellular matrix proteins primarily produced by activated hepatic stellate cells (HSCs). The activation of HSCs plays a pivotal role in driving the progression of liver fibrosis. Achieving specific targeted delivery of antifibrotic agents toward activated HSCs remains a formidable challenge. Here, we developed an HSC membrane-camouflaged nanosystem, named HSC-PLGA-BAY, for the precise delivery of the antifibrosis agent BAY 11-7082 to activated HSCs in the treatment of liver fibrosis. The designed HSC-PLGA-BAY nanosystem exhibited selective targeting toward activated HSCs, with internalization mediated by homologous cell adhesion molecules from the HSC membrane, namely integrins and N-cadherin. Furthermore, our findings demonstrate that treatment with HSC-PGA-BAY significantly increased apoptosis of activated HSCs and ameliorated liver fibrosis progression in a bile duct ligation (BDL)-induced fibrotic mice model. Collectively, the HSCs-targeted therapeutic platform holds promising potential as an effective strategy for liver fibrosis treatment.

NiCo identifies extrinsic drivers of cell state modulation by niche covariation analysis

Cell states are modulated by intrinsic driving forces such as gene expression noise and extrinsic signals from the tissue microenvironment. The distinction between intrinsic and extrinsic cell state determinants is essential for understanding the regulation of cell fate in tissues during development, homeostasis and disease. The rapidly growing availability of single-cell resolution spatial transcriptomics makes it possible to meet this challenge. However, available computational methods to infer topological tissue domains, spatially variable genes, or ligand-receptor interactions are limited in their capacity to capture cell state changes driven by crosstalk between individual cell types within the same niche. We present NiCo, a computational framework for integrating single-cell resolution spatial transcriptomics with matched single-cell RNA-sequencing reference data to infer the influence of the spatial niche on the cell state. By applying NiCo to mouse embryogenesis, adult small intestine and liver data, we demonstrate the ability to predict novel niche interactions that govern cell state variation underlying tissue development and homeostasis. In particular, NiCo predicts a feedback mechanism between Kupffer cells and neighboring stellate cells dampening stellate cell activation in the normal liver. NiCo provides a powerful tool to elucidate tissue architecture and to identify drivers of cellular states in local niches.

OPN-Mediated Crosstalk Between Hepatocyte E4BP4 and Hepatic Stellate Cells Promotes MASH-Associated Liver Fibrosis

Stressed hepatocytes promote liver fibrosis through communications with hepatic stellate cells (HSCs) during chronic liver injury. However, intra-hepatocyte players that facilitate such cell-to-cell communications are largely undefined. It is previously reported that hepatocyte E4BP4 is potently induced by ER stress and hepatocyte deletion of E4bp4 protects mice from high-fat diet-induced liver steatosis. Here how hepatocyte E4bp4 deficiency impacts the activation of HSCs and the progression toward MASH-associated liver fibrosis is examined. Hepatic E4BP4 is increased in mouse models of NASH diet- or CCl4-induced liver fibrosis. Hepatocyte-specific E4bp4 deletion protected mice against NASH diet-induced liver injury, inflammation, and fibrosis without impacting liver steatosis. Hepatocyte E4BP4 overexpression activated HSCs in a medium transfer experiment, whereas hepatocyte E4bp4 depletion did the opposite. RNA-Seq analysis identified the pro-fibrogenic factor OPN as a critical target of E4BP4 within hepatocytes. Antibody neutralization or shRNA depletion of Opn abrogated hepatocyte E4BP4-induced HSC activation. E4BP4 interacted with and stabilized YAP, an established activator of OPN. Loss of hepatic Yap blocked OPN induction in the liver of Ad-E4bp4-injected mice. Hepatocyte E4BP4 induces OPN via YAP to activate HSCs and promote liver fibrosis during diet-induced MASH. Inhibition of the hepatocyte E4BP4-OPN pathway could offer a novel therapeutic avenue for treating MASLD/MASH.

Hepatic Stellate Cell-mediated Increase in CCL5 Chemokine Expression after X-ray Irradiation Determined In Vitro and In Vivo

Radiation exposure causes hepatitis which induces hepatic steatosis and fibrosis. Although hepatic stellate cells (HSCs) have been considered potential pathological modulators for the development of hepatitis due to viral and microbial infections, their involvement in radiation-induced hepatitis is yet to be determined. This study aimed to clarify the relationship between radiation exposure and expressions of inflammatory cytokines and chemokines in HSCs in vitro and in vivo. HSCs were obtained from 1-week-old mice, known to be highly sensitive to radiation-induced hepatocellular carcinoma, using a newly established method combining liver perfusion, cell dissociation, and density gradient centrifugation, followed by magnetic negative selection of hematopoietic and endothelial cells with anti-CD45.2 and CD146 antibodies. The isolated HSCs were confirmed by the expression of desmin and glial fibrillary acidic protein (GFAP). We demonstrated that primary cultured HSCs, exposed to X-ray irradiation (0, 1.9, and 3.8 Gy) and cultured for 3 and 7 days, produced elevated levels of C-C motif chemokine ligand 5 (CCL5, also known as RANTES) inflammatory chemokine in a dose-dependent manner. An in vivo immunofluorescence method confirmed that increased CCL5 signals were observed in GFAP-positive HSCs in mouse livers 7 days after whole-body X-ray irradiation (1.9 and 3.8 Gy). Adequate expression of C-C motif chemokine receptor 5 (Ccr5), a receptor for CCL5, was also detected using real-time PCR in the liver of both irradiated and non-irradiated mice. Taken together, our data suggest that HSCs may drive hepatitis via CCL5/CCR5 axis in the liver under radiation-induced stress. Furthermore, this newly established experimental protocol can help evaluate the expression of other inflammatory cytokines in primary cultures of HSCs isolated from infant mice.

FoxD1 expression identifies a distinct subset of hepatic stellate cells involved in liver fibrosis

Hepatic stellate cells (HSCs) are pericytes of the liver responsible for liver fibrosis and cirrhosis, which are the end stages of chronic liver diseases. TGF-β activates HSCs, leading to the differentiation of myofibroblasts in the process of liver fibrosis. While the heterogeneity of HSCs is appreciated in the fibrotic liver, it remains elusive which HSC subsets mainly contribute to fibrosis. Here, we show that the expression of the pericyte marker FoxD1 specifically marks a subset of HSCs in FoxD1-fate tracer mice. HSCs fate-mapped by FoxD1 were preferentially localized in the portal and peripheral areas of both the homeostatic and fibrotic liver induced by carbon tetrachloride. Furthermore, the deletion of Cbfβ, which is necessary for TGF-β signaling, in FoxD1-expressing cells ameliorated liver fibrosis. Thus, we identified an HSC subset that preferentially responds to liver injuries.

SIRT7 protects against liver fibrosis by suppressing stellate cell activation via TGF-β/SMAD2/3 pathway

BACKGROUND

SIRT7 is a class III HDACs deacetylase which plays critical roles in various biological processes. Aberrant SIRT7 expression is associated with tumorigenesis and disease progression while role of SIRT7 in hepatic fibrosis remain elusive.

METHODS

SIRT7 expression was examined in fibrotic liver sample via WB and IHC. Myeloid cell-specific knockout (SIRT7MKO) mice were generated by crossing SIRT7flox/flox mice with LysM-Cre mice. Primary hepatic stellate cells (HSCs) was isolated to examine stellate cells activation. SIRT7 and SMAD2/3 interaction were analyzed by immunoprecipitation. SB525334 was used to prevent SMAD2/3 phosphorylation.

RESULTS

SIRT7 expression was decreased during chronic liver disease progression but was increased in liver cancer. IHC staining indicated that SIRT7 was primarily expressed in non-parenchymal cells in both fibrotic and cirrhotic liver. Knockout SIRT7 in myeloid cells resulted in significant elevation of serum ALT and liver fibrosis, but mildly affected hepatic inflammation after CCl4 treatment. We further observed significant elevation of elevation of stellate cell activation and SMAD2/3 activation in SIRT7MKO mice. By using primary HSCs and stellate cell line, we confirmed that SIRT7 interacted with SMAD2/3, induced its deacetylation and was critical in regulation of SMAD2/3 activation and stellate cell activation upon TGF-β stimulation. Pharmacological inhibition of SMAD2/3 reversed the hyperactivation of SIRT7MKO HSCs after TGF-β stimulation, and abolished stellate cell activation and liver fibrosis in SIRT7MKO mice.

CONCLUSION

Our findings revealed previously unidentified role of SIRT7 in regulating HSCs activation via modulating TGF-β/SMAD2/3 signaling pathway. Targeting SIRT7 might offer novel therapeutic option against liver fibrosis.

Delivery of Synthetic Interleukin-22 mRNA to Hepatocytes via Lipid Nanoparticles Alleviates Liver Injury

Hepatocellular injury, a pivotal contributor to liver diseases, particularly hepatitis, lacks effective pharmacological treatments. Interleukin-22 (IL-22), crucial for liver cell survival, shows potential in treating liver diseases by regulating repair and regeneration through signal transducer and activator of transcription 3 (STAT3) activation. However, the short half-life and off-target effects limit its clinical applications. To address these issues, lipid nanoparticles are employed to deliver synthetic IL-22 mRNA (IL-22/NP) for in situ IL-22 expression in hepatocytes. The study reveals that IL-22/NP exhibits liver-targeted IL-22 expression, with increased IL-22 levels detected in the liver as early as 3 h postintravenous injection, lasting up to 96 h. Furthermore, IL-22/NP activates STAT3 signaling in an autocrine or paracrine manner to upregulate downstream factors Bcl-xL and CyclinD1, inhibiting hepatocyte apoptosis and promoting cell proliferation. The therapeutic efficacy of IL-22/NP is demonstrated in both chronic and acute liver injury models, suggesting IL-22 mRNA delivery as a promising treatment strategy for hepatitis and liver diseases involving hepatocellular injury.

Modulation of Notch signaling pathway in activated hepatic stellate cells does not ameliorate the outcome of liver fibrosis in carbon tetrachloride and DDC-feeding models

Background

Recent research suggests a possible role of Notch signaling pathway in development of liver fibrosis, but exact cellular and molecular mechanisms are still not well defined. Methods: We modulated Notch signaling in activated hepatic stellate cells/myofibroblasts using the model of inducible activation or inhibition of Notch signaling selective for αSMA positive cells in murine models of toxic fibrosis induced by CCl4 and cholestatic fibrosis induced by DDC supplemented feeding.

Results

Our results confirm that Notch signaling pathway is activated in both CCL4 and DDC model of liver fibrosis and that αSMA positive myofibroblasts are of activated hepatic stellate cells origin. However, neither the inhibition of canonical Notch signaling (in tamoxifen treated αSMACreER/RBP-Jfl/fl mice) nor its overactivation (in tamoxifen treated αSMACreER/NICD1 mice) changed the degree of liver fibrosis in comparison to the control groups in either of the investigated models. Furthermore, after the withdrawal of the fibrogenic treatment the degree of resolution of fibrosis was similar between the animals with Notch overactivation and controls. In addition to genetic manipulation, we investigated the effect of antibodies against NOTCH1 and NOTCH2 on the development of liver fibrosis. Treatment with antibodies had effects on thymus and spleen respectively, but failed to ameliorate liver fibrosis. In conclusion, our data demonstrate that modulation of Notch activity in activated HSC is not sufficient to change the outcome of liver fibrosis. The results obtained with inhibitory antibodies further demonstrate limitations of targeting Notch 1 and 2 receptors as antifibrotic therapy. Notch pathway remains a potential target for the treatment of liver fibrosis, but future studies should be directed to Notch 3 signaling and/or targeting different populations of cells.

Vitamin D receptor attenuates carbon tetrachloride-induced liver fibrosis via downregulation of YAP

Liver fibrosis is characterized by the excessive accumulation of extracellular matrix proteins, which can lead to cirrhosis and liver cancer. Metabolic dysfunction-associated steatosis liver diseases are common causes of liver fibrosis, sharing a similar pathogenesis with carbon tetrachloride (CCl₄) exposure. This process involves the activation of hepatic stellate cells (HSCs) into myofibroblasts. However, the detailed mechanism and effective treatment strategies require further investigation. In this study, we uncovered a negative correlation between VDR expression and YAP within HSCs. Subsequently, we demonstrated that VDR exerted a downregulatory influence on YAP transcriptional activity in HSCs. Intriguingly, activation VDR effectively inhibited the culture induced activation of primary HSCs by suppressing the transcriptional activity of early YAP. Furthermore, in vivo results manifested that hepatic-specific deletion of YAP/TAZ ameliorates CCl4-induced liver fibrosis, and nullified the antifibrotic efficacy of VDR. Importantly, a YAP inhibitor rescued the exacerbation of liver fibrosis induced by hepatic-specific VDR knockout. Moreover, the combined pharmacological of VDR agonist and YAP inhibitor demonstrated a synergistic effect in diminishing CCl4-induced liver fibrosis, primary HSCs activation and hepatic injury in vivo. These effects were underpinned by their collective ability to inhibit HSC activation through AMPK activation, consequently curbing ATP synthesis and HSCs proliferation. In conclusion, our results not only revealed the inhibition of VDR on YAP-activated liver stellate cells but also identified a synergistic effect of VDR agonist and YAP inhibitor in an AMPKα-dependent manner, providing a practical foundation for integration of multi-targeted drugs in the therapy of CCl4-induced hepatic fibrosis.

Kisspeptin Alleviates Human Hepatic Fibrogenesis by Inhibiting TGFβ Signaling in Hepatic Stellate Cells

The peptide hormone kisspeptin attenuates liver steatosis, metabolic dysfunction-associated steatohepatitis (MASH), and fibrosis in mouse models by signaling via the kisspeptin 1 receptor (KISS1R). However, whether kisspeptin impacts fibrogenesis in the human liver is not known. We investigated the impact of a potent kisspeptin analog (KPA) on fibrogenesis using human precision-cut liver slices (hPCLS) from fibrotic livers from male patients, in human hepatic stellate cells (HSCs), LX-2, and in primary mouse HSCs. In hPCLS, 48 h and 72 h of KPA (3 nM, 100 nM) treatment decreased collagen secretion and lowered the expression of fibrogenic and inflammatory markers. Immunohistochemical studies revealed that KISS1R is expressed and localized to HSCs in MASH/fibrotic livers. In HSCs, KPA treatment reduced transforming growth factor b (TGFβ)-the induced expression of fibrogenic and inflammatory markers, in addition to decreasing TGFβ-induced collagen secretion, cell migration, proliferation, and colony formation. Mechanistically, KISS1R signaling downregulated TGFβ signaling by decreasing SMAD2/3 phosphorylation via the activation of protein phosphatases, PP2A, which dephosphorylates SMAD 2/3. This study revealed for the first time that kisspeptin reverses human hepatic fibrogenesis, thus identifying it as a new therapeutic target to treat hepatic fibrosis.

Conditional deletion of CEACAM1 in hepatic stellate cells causes their activation

OBJECTIVES

Hepatic CEACAM1 expression declines with advanced hepatic fibrosis stage in patients with metabolic dysfunction-associated steatohepatitis (MASH). Global and hepatocyte-specific deletions of Ceacam1 impair insulin clearance to cause hepatic insulin resistance and steatosis. They also cause hepatic inflammation and fibrosis, a condition characterized by excessive collagen production from activated hepatic stellate cells (HSCs). Given the positive effect of PPARγ on CEACAM1 transcription and on HSCs quiescence, the current studies investigated whether CEACAM1 loss from HSCs causes their activation.

METHODS

We examined whether lentiviral shRNA-mediated CEACAM1 donwregulation (KD-LX2) activates cultured human LX2 stellate cells. We also generated LratCre + Cc1fl/fl mutants with conditional Ceacam1 deletion in HSCs and characterized their MASH phenotype. Media transfer experiments were employed to examine whether media from mutant human and murine HSCs activate their wild-type counterparts.

RESULTS

LratCre + Cc1fl/fl mutants displayed hepatic inflammation and fibrosis but without insulin resistance or hepatic steatosis. Their HSCs, like KD-LX2 cells, underwent myofibroblastic transformation and their media activated wild-type HSCs. This was inhibited by nicotinic acid treatment which blunted the release of IL-6 and fatty acids, both of which activate the epidermal growth factor receptor (EGFR) tyrosine kinase. Gefitinib inhibition of EGFR and its downstream NF-κB/IL-6/STAT3 inflammatory and MAPK-proliferation pathways also blunted HSCs activation in the absence of CEACAM1.

CONCLUSIONS

Loss of CEACAM1 in HSCs provoked their myofibroblastic transformation in the absence of insulin resistance and hepatic steatosis. This response is mediated by autocrine HSCs activation of the EGFR pathway that amplifies inflammation and proliferation.

Engineered lipid nanoparticles enable therapeutic gene silencing of GTSE1 for the treatment of liver fibrosis

Liver fibrosis is characterized by abnormal accumulation of extracellular matrix proteins, disrupting normal liver function. Despite its significant health impact, effective treatments remain limited. Here, we present the development of engineered lipid nanoparticles (LNPs) for targeted RNA therapeutic delivery in the liver. We investigated the therapeutic potential of modulating the G2 and S-phase expressed 1 (GTSE1) protein for treating liver fibrosis. Through screening, we identified P138Y LNP as a potent candidate with superior delivery efficiency and lower toxicity. Using these engineered LNPs, we successfully delivered siGTSE1 to hepatocytes, significantly reducing collagen accumulation and restoring liver function in a fibrosis animal model. Additionally, GTSE1 downregulation altered miRNA expression and upregulated hepatocyte nuclear factor 4 alpha (HNF4α). These findings suggest that therapeutic gene silencing of GTSE1 is a promising strategy for treating liver fibrosis by regenerating liver phenotypes and functions.

Early activation of hepatic stellate cells induces rapid initiation of retinyl ester breakdown while maintaining lecithin:retinol acyltransferase (LRAT) activity

Lecithin:retinol acyltransferase (LRAT) is the main enzyme producing retinyl esters (REs) in quiescent hepatic stellate cells (HSCs). When cultured on stiff plastic culture plates, quiescent HSCs activate and lose their RE stores in a process similar to that in the liver following tissue damage, leading to fibrosis. Here we validated HSC cultures in soft gels to study RE metabolism in stable quiescent HSCs and investigated RE synthesis and breakdown in activating HSCs. HSCs cultured in a soft gel maintained characteristics of quiescent HSCs, including the size, amount and composition of their characteristic large lipid droplets. Quiescent gel-cultured HSCs maintained high expression levels of Lrat and a RE storing phenotype with low levels of RE breakdown. Newly formed REs are highly enriched in retinyl palmitate (RP), similar to freshly isolated quiescent HSCs, which is associated with high LRAT activity. Comparison of these quiescent gel-cultured HSCs with activated plastic-cultured HSCs showed that although during early activation the total RE levels and RP-enrichment are reduced, levels of RE formation are maintained and mediated by LRAT. Loss of REs was caused by enhanced RE breakdown in activating HSCs. Upon prolonged culturing, activated HSCs have lost their LRAT activity and produce small amounts of REs by DGAT1. This study reveals unexpected dynamics in RE metabolism during early HSC activation, which might be important in liver disease as early stages are reversible. Soft gel cultures provide a promising model to study RE metabolism in quiescent HSCs, allowing detailed molecular investigations on the mechanisms for storage and release.

Inhibition of heme-thiolate monooxygenase CYP1B1 prevents hepatic stellate cell activation and liver fibrosis by accumulating trehalose

Activation of extracellular matrix-producing hepatic stellate cells (HSCs) is a key event in liver fibrogenesis. We showed that the expression of the heme-thiolate monooxygenase cytochrome P450 1B1 (CYP1B1) was elevated in human and mouse fibrotic livers and activated HSCs. Systemic or HSC-specific ablation and pharmacological inhibition of CYP1B1 attenuated HSC activation and protected male but not female mice from thioacetamide (TAA)-, carbon tetrachloride (CCl4)-, or bile duct ligation (BDL)-induced liver fibrosis. Metabolomic analysis revealed an increase in the disaccharide trehalose in CYP1B1-deficient HSCs resulting from intestinal suppression of the trehalose-metabolizing enzyme trehalase, whose gene we found to be a target of RARα. Trehalose or its hydrolysis-resistant derivative lactotrehalose exhibited potent antifibrotic activity in vitro and in vivo by functioning as an HSC-specific autophagy inhibitor, which may account for the antifibrotic effect of CYP1B1 inhibition. Our study thus reveals an endobiotic function of CYP1B1 in liver fibrosis in males, mediated by liver-intestine cross-talk and trehalose. At the translational level, pharmacological inhibition of CYP1B1 or the use of trehalose/lactotrehalose may represent therapeutic strategies for liver fibrosis.

Apoptotic vesicles (apoVs) derived from fibroblast-converted hepatocyte-like cells effectively ameliorate liver fibrosis

Liver fibrosis is a serious global health issue for which effective treatment remains elusive. Chemical-induced hepatocyte-like cells (ciHeps) have emerged as an appealing source for cell transplantation therapy, although they present several challenges such as the risk of lung thromboembolism or hemorrhage. Apoptotic vesicles (apoVs), small membrane vesicles generated during the apoptosis process, have gained attention for their role in regulating various physiological and pathological processes. In this study, we generated ciHep-derived apoVs (ciHep-apoVs) and investigated their therapeutic potential in alleviating liver fibrosis. Our findings revealed that ciHep-apoVs induced the transformation of macrophages into an anti-inflammatory phenotype, effectively suppressed the activity of activated hepatic stellate cells (aHSCs), and enhanced the survival of hepatocytes. When intravenously administered to mice with liver fibrosis, ciHep-apoVs were primarily engulfed by macrophages and myofibroblasts, leading to a reduction in liver inflammation and fibrosis. Proteomic and miRNA analyses showed that ciHep-apoVs were enriched in various functional molecules that modulate crucial cellular processes, including metabolism, signaling transduction, and ECM-receptor interactions. ciHep-apoVs effectively suppressed aHSCs activity through the synergistic inhibition of glycolysis, the PI3K/AKT/mTOR pathway, and epithelial-to-mesenchymal transition (EMT) cascades. These findings highlight the potential of ciHep-apoVs as multifunctional nanotherapeutics for liver fibrosis and provide insights into the treatment of other liver diseases and fibrosis in other organs.

Osr1-mediated mesothelial transition of liver mesenchymal cells exacerbates fibrotic liver damage

In chronic liver diseases, hepatic stellate cells (HSCs) are induced to form the myofibroblasts responsible for scar formation, leading to liver fibrosis and cirrhosis. Here, single-cell RNA sequencing with in vivo lineage tracing in nonalcoholic steatohepatitis (NASH) model mice reveals a subpopulation of HSCs transitioning back to a state resembling their developmental precursors, mesothelial cells (MCs), after liver injury. These damage-associated intermediates between HSCs and MCs (DIHMs) can be traced with a dual recombinase system by labeling Krt19-expressing cells within prelabeled Pdgfrb+ HSCs, and DIHMs highly express inflammation- and fibrosis-associated genes. Cre and Dre-inducible depletion of DIHMs by administering diphtheria toxin reduces liver fibrosis and alleviates liver damage in NASH model mice. Importantly, knockdown of Osr1, a zinc finger transcription factor of the OSR gene family, can block DIHM induction in vitro. Conditional knockout Osr1 in Pdgfrb-expressing mesenchymal cells in NASH model mice can reduce liver fibrosis in vivo. Our study collectively uncovers an injury-induced developmental reversion process wherein HSCs undergo what we call a mesenchymal-to-mesothelial transition, which can be targeted to develop interventions to treat chronic liver diseases.

MafG/MYH9-LCN2 axis promotes liver fibrosis through inhibiting ferroptosis of hepatic stellate cells

Hepatic stellate cells (HSCs) secrete extracellular matrix for collagen deposition, contributing to liver fibrosis. Ferroptosis is a novel type of programmed cell death induced by iron overload-dependent lipid peroxidation. Regulation of ferroptosis in hepatic stellate cells (HSCs) may have therapeutic potential for liver fibrosis. Here, we found that Maf bZIP transcription factor G (MafG) was upregulated in human and murine liver fibrosis. Interestingly, MafG knockdown increased HSCs ferroptosis, while MafG overexpression conferred resistance of HSCs to ferroptosis. Mechanistically, MafG physically interacted with non-muscle myosin heavy chain IIa (MYH9) to transcriptionally activate lipocalin 2 (LCN2) expression, a known suppressor for ferroptosis. Site-directed mutations of MARE motif blocked the binding of MafG to LCN2 promoter. Re-expression of LCN2 in MafG knockdown HSCs restored resistance to ferroptosis. In bile duct ligation (BDL)-induced mice model, we found that treatment with erastin alleviated murine liver fibrosis by inducing HSC ferroptosis. HSC-specific knowdown MafG based on adeno-associated virus 6 (AAV-6) improved erastin-induced HSC ferroptosis and alleviation of liver fibrosis. Taken together, MafG inhibited HSCs ferroptosis to promote liver fibrosis through transcriptionally activating LCN2 expression. These results suggest that MafG/MYH9-LCN2 signaling pathway could be a novel targets for the treatment of liver fibrosis.

In vitro osteoclast differentiation enhanced by hepatocyte supernatants from high-fat diet mice

Non-alcoholic fatty liver disease (NAFLD) is associated with abnormal bone metabolism, potentially mediated by elevated levels of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-ɑ) and interleukin 6 (IL-6). This study aims to investigate the direct regulatory effects of liver tissues on osteoblast and osteoclast functions in vitro, focusing on the liver-bone axis in NAFLD. Twelve-week-old C57BL/6 mice were fed either a control diet or a high-fat diet (HFD) for 12 weeks. Bone structural parameters were assessed using microCT. Primary hepatocyte cultures were established from control and HFD-fed C57BL/6 mice, as well as IL-6-/- and TNF-α-/- mice. The supernatants from these hepatocyte cultures were used to induce differentiation in bone marrow cell-derived osteoblasts and osteoclasts in vitro. Results showed that mice on a HFD exhibited increased lipid infiltration in liver and bone marrow tissues, alongside reduced bone mass. Moreover, the supernatants from hepatocyte cultures from mice on a HFD displayed elevated TNF-α and IL-6 levels. These supernatants, particularly those derived from HFD-fed and IL-6-/- mice, significantly enhanced osteoclast differentiation in vitro. In contrast, supernatants from TNF-α-/- mice did not significantly affect osteoblast or osteoclast differentiation in vitro. In conclusions, this current study suggested that fatty liver tissues may negatively impact bone metabolism. Additionally, knockout of TNF-α and IL-6 genes revealed distinct influence on osteoblast and osteoclast functions, highlighting the complex interplay between live pathology and bone health.

RNA nanotherapeutics with fibrosis overexpression and retention for MASH treatment

Metabolic dysfunction-associated steatohepatitis (MASH) poses challenges for targeted delivery and retention of therapeutic proteins due to excess extracellular matrix (ECM). Here we present a new approach to treat MASH, termed "Fibrosis overexpression and retention (FORT)". In this strategy, we design (1) retinoid-derivative lipid nanoparticle (LNP) to enable enhanced mRNA overexpression in fibrotic regions, and (2) mRNA modifications which facilitate anchoring of therapeutic proteins in ECM. LNPs containing carboxyl-retinoids, rather than alcohol- or ester-retinoids, effectively deliver mRNA with over 10-fold enhancement of protein expression in fibrotic livers. The carboxyl-retinoid rearrangement on the LNP surface improves protein binding and membrane fusion. Therapeutic proteins are then engineered with an endogenous collagen-binding domain. These fusion proteins exhibit increased retention in fibrotic lesions and reduced systemic toxicity. In vivo, fibrosis-targeting LNPs encoding fusion proteins demonstrate superior therapeutic efficacy in three clinically relevant male-animal MASH models. This approach holds promise in fibrotic diseases unsuited for protein injection.

Yes-associated protein inhibition ameliorates carbon tetrachloride-induced acute liver injury in mice by reducing VDR

Carbon tetrachloride (CCl4) has a wide range of toxic effects, especially causing acute liver injury (ALI), in which rapid compensation for hepatocyte loss ensures liver survival, but proliferation of surviving hepatocytes (known as endoreplication) may imply impaired residual function. Yes-associated protein (YAP) drives hepatocytes to undergo endoreplication and ploidy, the underlying mechanisms of which remain a mystery. In the present study, we uncover during CCl4-mediated ALI accompanied by increased hepatocytes proliferation and YAP activation. Notably, bioinformatics analyses elucidate that hepatic-specific deletion of YAP substantially ameliorated CCl4-induced hepatic proliferation, effectively decreased the vitamin D receptor (VDR) expression. Additionally, a mouse model of acute liver injury substantiated that inhibition of YAP could suppress hepatocytes proliferation via VDR. Furthermore, we also disclosed that the VDR agonist nullifies CCl4-induced ALI alleviated by the YAP inhibitor in vivo. Importantly, hepatocytes were isolated from mice, and it was spotlighted that the anti-proliferative impact of the YAP inhibitor was abolished by the activation of VDR within these hepatocytes. Similarly, primary hepatic stellate cells (HSCs) were isolated and it was manifested that YAP inhibitor suppressed HSC activation via VDR during acute liver injury. Our findings further elucidate the YAP's role in ALI and may provide new avenues for protection against CCl4-drived acute liver injury.

Tricetin protects against liver fibrosis through promoting autophagy and Nrf2 signaling in hepatic stellate cells

AIMS

The study aims to investigate the role and underlying mechanisms of tricetin in regulating hepatic stellate cells (HSCs) activation.

MAIN METHODS

We treated human hepatic stellate cells line LX-2 and freshly isolated primary mouse hepatic stellate cells (mHSCs) with tricetin, pharmacological inhibitors and siRNAs, western blot, immunofluorescence, quantitative PCR were used to evaluate the expression of fibrotic markers, autophagy levels and Nrf2 (nuclear factor E2-related factor 2) signaling.

KEY FINDINGS

Herein, we demonstrated that tricetin strongly attenuated the proliferation, migration, lipid droplets (LDs) loss and fibrotic markers Col 1a1 (type I α 1 collagen) and α-SMA (α-smooth muscle actin) expression in LX-2 cells. Moreover, tricetin time- and dose-dependently provoked autophagic formation in LX-2 cells. Autophagy inhibition by pharmacological intervention or genetic ATG5 (autophagy related 5) silencing facilitated tricetin-induced downregulation of profibrotic markers in LX-2 cells. Additionally, tricetin treatment reduced reactive oxygen species (ROS) accumulation, promoted Nrf2 signaling in LX-2 cells and pretreatment with ROS scavenger NAC partially reversed tricetin-induced autophagy and enhanced tricetin-mediated HSCs inactivation. Nrf2 silencing partially reversed tricetin-mediated inhibition of α-SMA expression. Finally, utilizing primary mouse hepatic stellate cells (mHSCs), we demonstrated that tricetin also induced autophagy activation, repressed TGF-β1-induced LDs loss and fibrotic marker expression and pretreatment with CQ further sensitized these effects.

SIGNIFICANCE

Our study indicates that tricetin's actions may represent an effective strategy to treat liver fibrosis and help identify novel therapeutic targets, especially in combination with autophagy inhibitors.

Delivery Strategy to Enhance the Therapeutic Efficacy of Liver Fibrosis via Nanoparticle Drug Delivery Systems

Liver fibrosis (LF) is a pathological repair reaction caused by a chronic liver injury that affects the health of millions of people worldwide, progressing to life-threatening cirrhosis and liver cancer without timely intervention. Due to the complexity of LF pathology, multiple etiological characteristics, and the deposited extracellular matrix, traditional drugs cannot reach appropriate targets in a time-space matching way, thus decreasing the therapeutic effect. Nanoparticle drug delivery systems (NDDS) enable multidrug co-therapy and develop multifactor delivery strategies targeting pathological processes, showing great potential in LF therapy. Based on the pathogenesis and the current clinical treatment status of LF, we systematically elucidate the targeting mechanism of NDDS used in the treatment of LF. Subsequently, we focus on the progress of drug delivery applications for LF, including combined delivery for the liver fibrotic pathological environment, overcoming biological barriers, precise intracellular regulation, and intelligent responsive delivery for the liver fibrotic microenvironment. We hope that this review will inspire the rational design of NDDS for LF in the future in order to provide ideas and methods for promoting LF regression and cure.

Self-organizing ovarian somatic organoids preserve cellular heterogeneity and reveal cellular contributions to ovarian aging

Ovarian somatic cells are essential for reproductive function, but no existing ex vivo models recapitulate the cellular heterogeneity or interactions within this compartment. We engineered a novel ovarian somatic organoid model by culturing a stroma-enriched fraction of mouse ovaries in scaffold-free agarose micromolds. Ovarian somatic organoids self-organized, maintained diverse cell populations, produced extracellular matrix, and secreted hormones. Organoids generated from reproductively old mice exhibited reduced aggregation and growth compared to young counterparts, as well as differences in cellular composition. Interestingly, matrix fibroblasts from old mice demonstrated upregulation of pathways associated with the actin cytoskeleton and downregulation of cell adhesion pathways, indicative of increased cellular stiffness which may impair organoid aggregation. Cellular morphology, which is regulated by the cytoskeleton, significantly changed with age and in response to actin depolymerization. Moreover, actin depolymerization rescued age-associated organoid aggregation deficiency. Overall, ovarian somatic organoids have advanced fundamental knowledge of cellular contributions to ovarian aging.

Hepatic Surf4 Deficiency Impairs Serum Amyloid A1 Secretion and Attenuates Liver Fibrosis in Mice

Liver fibrosis is a severe global health problem. However, no effective antifibrotic drugs have been approved. Surf4 is primarily located in the endoplasmic reticulum (ER) and mediates the transport of secreted proteins from the ER to the Golgi apparatus. Knockout of hepatic Surf4 (Surf4 LKO) in mice impairs very-low-density lipoprotein secretion without causing overt liver damage. Here, we found that collagen levels are significantly reduced in the liver of Surf4 LKO mice compared with control Surf4 flox mice, as demonstrated by proteomics, Western blot, and quantitative reverse transcription polymerase chain reaction. Therefore, this study aims to investigate whether and how hepatic Surf4 affects liver fibrosis. We observed that CCl4-induced liver fibrosis is significantly lower in Surf4 LKO mice than in Surf4 flox mice. Mechanistically, hepatic Surf4 deficiency reduces serum amyloid A1 (SAA1) secretion and hepatic stellate cell (HSC) activation. Surf4 coimmunoprecipitates and colocalizes with SAA1. Lack of hepatic Surf4 significantly reduces SAA1 secretion from hepatocytes, and SAA1 activates cultured human HSCs (LX-2 cells). Conditioned medium (CM) from Surf4-deficient primary hepatocytes activates LX-2 cells to a much lesser extent than CM from Surf4 flox primary hepatocytes, and this reduced effect is restored by the addition of recombinant SAA1 to CM from Surf4-deficient hepatocytes. Knockdown of SAA1 in primary hepatocytes or TLR2 in LX-2 cells significantly reduces LX-2 activation induced by CM from Surf4 flox hepatocytes but not from Surf4 LKO hepatocytes. Furthermore, knockdown of SAA1 significantly ameliorates liver fibrosis in Surf4 flox mice but does not further reduce liver fibrosis in Surf4 LKO mice. We also observe substantial expression of Surf4 and SAA1 in human fibrotic livers. Therefore, hepatic Surf4 facilitates SAA1 secretion, activates HSCs, and aggravates liver fibrosis, suggesting that hepatic Surf4 and SAA1 may serve as treatment targets for liver fibrosis.

The Foxo1-YAP-Notch1 axis reprograms STING-mediated innate immunity in NASH progression

Innate immune activation is critical for initiating hepatic inflammation during nonalcoholic steatohepatitis (NASH) progression. However, the mechanisms by which immunoregulatory molecules recognize lipogenic, fibrotic, and inflammatory signals remain unclear. Here, we show that high-fat diet (HFD)-induced oxidative stress activates Foxo1, YAP, and Notch1 signaling in hepatic macrophages. Macrophage Foxo1 deficiency (Foxo1M-KO) ameliorated hepatic inflammation, steatosis, and fibrosis, with reduced STING, TBK1, and NF-κB activation in HFD-challenged livers. However, Foxo1 and YAP double knockout (Foxo1/YAPM-DKO) or Foxo1 and Notch1 double knockout (Foxo1/Notch1M-DKO) promoted STING function and exacerbated HFD-induced liver injury. Interestingly, Foxo1M-KO strongly reduced TGF-β1 release from palmitic acid (PA)- and oleic acid (OA)-stimulated Kupffer cells and decreased Col1α1, CCL2, and Timp1 expression but increased MMP1 expression in primary hepatic stellate cells (HSCs) after coculture with Kupffer cells. Notably, PA and OA challenge in Kupffer cells augmented LIMD1 and LATS1 colocalization and interaction, which induced YAP nuclear translocation. Foxo1M-KO activated PGC-1α and increased nuclear YAP activity, modulating mitochondrial biogenesis. Using chromatin immunoprecipitation (ChIP) coupled with massively parallel sequencing (ChIP-Seq) and in situ RNA hybridization, we found that NICD colocalizes with YAP and targets Mb21d1 (cGAS), while YAP functions as a novel coactivator of the NICD, which is crucial for reprogramming STING function in NASH progression. These findings highlight the importance of the macrophage Foxo1-YAP-Notch1 axis as a key molecular regulator that controls lipid metabolism, inflammation, and innate immunity in NASH.

Concanavalin-A-Induced Acute Liver Injury in Mice

Acute liver injury is a life-threatening disease. Although immune responses are involved in the development and exacerbation of acute liver injury, the cellular and molecular mechanisms are not fully understood. Intravenous administration of the plant lectin concanavalin A (ConA) is widely used as a model of acute liver injury. ConA triggers T cell activation and cytokine production by crosslinking glycoproteins, including the T cell receptor, leading to the infiltration of myeloid cells into the liver and the subsequent amplification of inflammation in the liver. Thus, the pathogenesis of ConA-induced acute liver injury is considered a model of immune-mediated acute liver injury or autoimmune hepatitis in humans. However, the severity of the liver injury and the analyses of immune cells and non-hematopoietic cells in the liver following ConA injection are significantly influenced by the experimental conditions. This article outlines protocols for ConA-induced acute liver injury in mice and evaluation methods for liver injury, immune cells, and non-hematopoietic cells in the liver. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Induction of acute liver injury by ConA injection Basic Protocol 2: Evaluation of inflammatory cytokines in mouse plasma Basic Protocol 3: Preparation of liver sections and histological analysis of liver injury Basic Protocol 4: Preparation of liver immune cells Basic Protocol 5: Preparation of hepatocytes, endothelial cells, and hepatic stellate cells Basic Protocol 6: Flow cytometry of immune and non-hematopoietic liver cells Basic Protocol 7: Flow cytometric sorting of endothelial cells and hepatic stellate cells Basic Protocol 8: Quantitative reverse transcription polymerase chain reaction.

Ba-Qi-Rougan formula alleviates hepatic fibrosis by suppressing hepatic stellate cell activation via the MSMP/CCR2/PI3K pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The Ba-Qi-Rougan formula (BQRGF) is a traditional and effective compound prescription from Traditional Chinese Medicine (TCM) utilized in treating hepatic fibrosis (HF).

AIM OF THE STUDY

We aimed to evaluate the therapeutic efficacy of BQRGF on HF and explore the underlying mechanisms of action.

MATERIALS AND METHODS

UPLC-Q-TOF-MS technology was employed to identify the material basis of BQRGF. Mice with carbon tetrachloride (CCl4)-induced HF received BQRGF at three doses (3.87, 7.74, and 15.48 g/kg per day). We examined serum and liver biochemical indicators and liver histology to assess the therapeutic impact. Primary mouse cells were isolated and utilized for experimental analysis. MSMP expression levels were examined in vitro and in vivo experimental models, including human and mouse tissue. Furthermore, lentivirus and small interfering RNA (siRNA) transfections were employed to manipulate microseminoprotein (MSMP) expression in LO2 cells (human normal liver cells). These manipulated LO2 cells were then co-cultured with LX2 human hepatic stellate cells (HSCs). Through the modulation of MSMP expression in co-cultured cells, administering recombinant MSMP (rMSMP) with or without BQRGF-medicated serum, and using specific pathway inhibitors or agonists in LX2 cells, we elucidated the underlying mechanisms.

RESULTS

A total of 48 compounds were identified from BQRGF, with 12 compounds being absorbed into the bloodstream and 9 compounds being absorbed into the liver. Four weeks of BQRGF treatment in the HF mouse model led to significant improvements in biochemical and molecular assays and histopathology, particularly in the medium and high-dose groups. These improvements included a reduction in the level of liver injury and fibrosis-related factors. MSMP levels were elevated in human and mouse fibrotic liver tissues, and this increase was mitigated in HF mice treated with BQRGF. Moreover, primary cells and co-culture studies revealed that BQRGF reduced MSMP expression, decreased the expression of the hepatic stellate cell (HSC) activation markers, and suppressed critical phosphorylated protein levels in the CCR2/PI3K/AKT pathway. These findings were further validated using CCR2/PI3K/AKT signaling inhibitors and agonists in MSMP-activated LX2 cells.

CONCLUSIONS

Collectively, our results suggest that BQRGF combats HF by diminishing MSMP levels and inhibiting MSMP-induced HSC activation through the CCR2/PI3K/AKT pathway.

Calreticulin regulates hepatic stellate cell activation through modulating TGF-beta-induced Smad signaling

Liver fibrosis is characterized by excessive deposition of extracellular matrix (ECM) as a wound healing process. Activated hepatic stellate cells (HpSCs) are the major producer of the ECM and play a central role in liver fibrogenesis. It has been widely accepted that elimination of activated HpSCs or reversion to a quiescent state can be a feasible strategy for resolving the disease, further highlighting the urgent need for novel therapeutic targets. Calreticulin (CRT) is a molecular chaperone that normally resides in the endoplasmic reticulum (ER), important in protein folding and trafficking through the secretory pathway. CRT also plays a critical role in calcium (Ca2+) homeostasis, with its Ca2+ storage capacity. In the current study, we aimed to demonstrate its function in directing HpSC activation. In a mouse liver injury model, CRT was up-regulated in HpSCs. In cellular experiments, we further showed that this activation was through modulating the canonical TGF-β signaling. As down-regulation of CRT in HpSCs elevated intracellular Ca2+ levels through a form of Ca2+ influx, named store-operated Ca2+ entry (SOCE), we examined whether moderating SOCE affected TGF-β signaling. Interestingly, blocking SOCE had little effect on TGF-β-induced gene expression. In contrast, inhibition of ER Ca2+ release using the inositol trisphosphate receptor inhibitor 2-APB increased TGF-β signaling. Treatment with 2-APB did not alter SOCE but decreased intracellular Ca2+ at the basal level. Indeed, adjusting Ca2+ concentrations by EGTA or BAPTA-AM chelation further enhanced TGF-β-induced signaling. Our results suggest a crucial role of CRT in the liver fibrogenic process through modulating Ca2+ concentrations and TGF-β signaling in HpSCs, which may provide new information and help advance the current discoveries for liver fibrosis.

CD44 expression on murine hepatic stellate cells promotes the induction of monocytic and polymorphonuclear myeloid-derived suppressor cells

In chronic inflammation, regulatory immune cells, such as regulatory T cells and myeloid-derived suppressor cells, can develop. Local signals in the inflamed tissue, such as cytokines and eicosanoids, but also contact-dependent signals, can promote myeloid-derived suppressor cell development. In the liver, hepatic stellate cells may provide such signals via the expression of CD44. Myeloid-derived suppressor cells generated in the presence of hepatic stellate cells and anti-CD44 antibodies were functionally and phenotypically analyzed. We found that both monocytic and polymorphonuclear myeloid-derived suppressor cells generated in the presence of αCD44 antibodies were less suppressive toward T cells as measured by T-cell proliferation and cytokine production. Moreover, both monocytic and polymorphonuclear myeloid-derived suppressor cells were phenotypically altered. Monocytic myeloid-derived suppressor cells mainly changed their expression of CD80 and CD39, and polymorphonuclear myeloid-derived suppressor cells showed altered expression of CD80/86, PD-L1, and CCR2. Moreover, both polymorphonuclear and monocytic myeloid-derived suppressor cells lost expression of Nos2 messenger RNA, whereas monocytic myeloid-derived suppressor cells showed reduced expression of TGFb messenger RNA and polymorphonuclear myeloid-derived suppressor cells reduced expression of Il10 messenger RNA. In summary, the presence of CD44 in hepatic stellate cells promotes the induction of both monocytic and polymorphonuclear myeloid-derived suppressor cells, although the mechanisms by which these myeloid-derived suppressor cells may increase suppressive function due to interaction with CD44 are only partially overlapping.