The evidence-based multifaceted roles of hepatic stellate cells in liver diseases: A concise review

Cellular interactions in self-directed immune-mediated liver diseases

The lymphocyte population must traverse a complex path throughout their journey to the liver. The signals which these cells must detect, including cytokines, chemokines and other soluble factors, steer their course towards further crosstalk with other hepatic immune cells, hepatocytes and biliary epithelial cells. A series of specific chemokine receptors and adhesion molecules drive not only the recruitment, migration, and retention of these cells within the liver, but also their localisation. Perturbation of these interactions and failure of self-recognition drive the development of several autoimmune liver diseases. We also describe check point-induced liver injury. Immune cell internalisation into hepatocytes (emperipolesis) in autoimmune hepatitis and into biliary epithelial cells (intra-epithelial lymphocyte) in primary biliary cholangitis are typical features in autoimmune liver diseases. Finally, we describe emerging immune-based therapies, including regulatory T cell, anti-cytokine and anti-chemokine therapies, cytokine supplementation (e.g. interleukin-2), as well as co-inhibitory molecule manipulation, including T-cell engagers, and discuss their potential application in the treatment of autoimmune liver diseases.

Hepatic stellate cells: balancing homeostasis, hepatoprotection and fibrogenesis in health and disease

In the past decades, the pathogenic role of hepatic stellate cells (HSCs) in the development of liver fibrosis and its complications has been deeply characterized, rendering HSCs a primary target for antifibrotic therapies. By contrast, the beneficial roles of HSCs in liver homeostasis and liver disease are only beginning to emerge, revealing critical regulatory and fibrosis-independent functions in hepatic zonation, metabolism, injury, regeneration and non-parenchymal cell identity. Here, we review how HSC mediators, such as R-spondin 3, hepatocyte growth factor and bone morphogenetic proteins, regulate critical and homeostatic liver functions in health and disease via cognate receptors in hepatocytes, Kupffer cells and endothelial cells. We highlight how the balance shifts from protective towards fibropathogenic HSC mediators during the progression of chronic liver disease (CLD) and the impact of this shifted balance on patient outcomes. Notably, the protective roles of HSCs are not accounted for in current therapeutic concepts for CLD. We discuss the concept that reverting the HSC balance from fibrogenesis towards hepatoprotection might represent a novel holistic treatment approach to inhibit fibrogenesis and restore epithelial health in CLD simultaneously.

Reduction of alternative polarization of macrophages by short-term activated hepatic stellate cell-derived small extracellular vesicles

BACKGROUND

Activated hepatic stellate cells (HSCs) induce alternative (M2) polarization of macrophages and contribute to the progression of fibrosis and hepatocellular carcinoma (HCC). However, the effects of small extracellular vesicles released by HSCs (HSC-sEVs) during activation remain largely unknown.

METHODS

The aim of this study was to investigate the role of extracellular vesicles released by HSCs (HSC-sEVs) at different stages of activation in macrophage polarization. The effects of sEVs from short-term activated and long-term activated HSCs on liver macrophages was studied. Small RNA sequencing analyses were performed to obtain differential miRNAs transported by the short-term and long-term activated HSC- sEVs. The in vivo effects of short-term activated HSC-sEV-specific miRNA on liver macrophage and liver fibrosis were confirmed in a CCl4-induced liver injury mouse model. To study the tumor suppressive effects of the macrophages educated by short-term activated HSC-sEV-specific miRNA, human hepatoma cells were mixed and subcutaneously cotransplanted with miR-99a-5p mimic-pretreated macrophages.

RESULTS

We found that consistent with activated HSCs, long-term activated HSC-sEVs (14dHSC-sEVs) induce bone marrow-derived monocytes (MOs) toward an M2 phenotype, but short-term activated HSC-sEVs (3dHSC-sEVs) induce the resident macrophages (Kupffer cells, KCs) toward a classically activated (M1) phenotype. We identified five 3dHSC-sEV-specific miRNAs, including miR-99a-5p. In vitro and in vivo experiments support that miR-99a-5p negatively regulates alternative polarization of macrophages, decreases collagen deposition in chronic liver injury model, and suppresses the progression of hepatoma in a xenograft model partially by targeting CD93.

CONCLUSION

Collectively, our work reveals an unexpected proinflammatory role of 3dHSC-sEVs, preliminarily explores the underlying mechanism, and evaluates the therapeutic potential of 3dHSC-sEV-specific miR-99a-5p for liver fibrosis and tumorigenesis.

Extracellular calreticulin regulates fibrogenic and immunogenic properties of hepatic stellate cells

Liver fibrosis is a persistent damage repair response triggered by various etiological factors, resulting in an excessive accumulation of extracellular matrix (ECM). Activated hepatic stellate cells (HpSCs) are the primary source of ECM proteins. Therefore, specifically targeting HpSCs has become a crucial approach for treating liver fibrosis. Calreticulin (CRT) is a molecular chaperone mainly located in the endoplasmic reticulum (ER), regulating protein folding and calcium homeostasis. Recently, CRT has gained much attention for its role outside the ER, particularly at the cell surface and extracellular space, acting as an immunomodulatory protein. The current study investigates the role of extracellular CRT in hepatic injury and its effects on HpSCs. Elevated levels of circulating CRT were observed in mouse models of liver injury, suggesting that hepatic injury may trigger CRT release. Extracellular CRT was found to moderately inhibit HpSC viability and induce morphological changes. Additionally, CRT treatment led to a decrease in α-smooth muscle actin and an upregulation of matrix metalloproteinase-2 and -9, indicating a potential fibrolytic effect. Immunomodulatory activities of CRT were also noted, as it increased cytokine expression in both macrophages and HpSCs. These effects were partially mediated through low-density lipoprotein receptor-related protein 1 (LRP1), as evidenced by altered cytokine expression upon co-treatment with a known LRP1 ligand receptor-associated protein (RAP). Overall, this study elucidates the complex role of extracellular CRT in liver injury and its potential impact on HpSC behavior and immune responses.

Focal adhesion kinase promotes aerobic glycolysis in hepatic stellate cells via the cyclin D1/c-Myc/MCT-1 pathway to induce liver fibrosis

Hepatic stellate cells (HSCs) transdifferentiate into myofibroblasts during liver fibrosis and exhibit increased glycolysis. Phosphorylated focal adhesion kinase (FAK) (pY397-FAK) promotes monocarboxylate transporter 1 (MCT-1) expression in HSCs to increase aerobic glycolysis and cause liver fibrosis. A combined multiomics analysis of C57BL/6 mice with tetrachloromethane (CCl4)-induced liver fibrosis was performed to identify the downstream FAK signaling pathway. The effect of the FAK inhibitor PF562271 on CCl4-induced liver fibrosis was explored by immunofluorescence of liver tissues. The migration, proliferation and aerobic glycolysis of LX-2 cells after stimulation and activation by transforming growth factor beta-1 (TGF-β1) or suppression by PF562271 was assessed in vitro. Multiomics analysis of a successfully generated CCl4-induced liver fibrosis mouse model was performed. FAK and cyclin D1 were significantly enriched in mice with CCl4-induced liver fibrosis. In vivo, the MCT-1 and alpha smooth muscle actin (α-SMA) levels were increased in mice with CCl4-induced liver fibrosis, and MCT-1 and α-SMA expression decreased after PF562271 treatment. In vitro, PF562271 alleviated TGF-β1-induced LX-2 activation. LX-2 cells showed diminished migration, proliferation, and aerobic glycolysis after PF562271 intervention. FAK promotes aerobic glycolysis in LX-2 cells through the cyclin D1/c-Myc/MCT-1 pathway, thereby increasing liver fibrosis.

Tenascin C-Guided Nanosystem for Precision Delivery of Obeticholic Acid in Liver Fibrosis Therapy

Objective: Liver fibrosis, a hallmark of chronic liver diseases, is characterized by excessive extracellular matrix (ECM) deposition and scar tissue formation. Current antifibrotic nanomedicines face significant limitations, including poor penetration into fibrotic tissue, rapid clearance, and suboptimal therapeutic efficacy. The dense fibrotic ECM acts as a major physiological barrier, necessitating the development of a targeted delivery strategy to achieve effective therapeutic outcomes. Methods: We designed a liposomal delivery system functionalized with the GBI-10 aptamer and encapsulating obeticholic acid (OCA lips@Apt) to enhance selective delivery to fibrotic liver tissue while minimizing systemic toxicity. Results: Both in vitro and in vivo studies demonstrated that the aptamer-modified OCA liposomes effectively treated hepatic fibrosis through dual mechanisms: modulation of abnormal bile acid metabolism and attenuation of inflammation. The targeted delivery system leveraged the overexpression of Tenascin-C (TnC), a key ECM component in fibrotic tissues, for precise localization and enhanced endocytosis via the exposed cationic liposome surface. Conclusions: The OCA lips@Apt nanodrug demonstrated superior therapeutic efficacy with minimal off-target effects, offering a promising strategy to overcome critical barriers in liver fibrosis treatment. By precisely targeting the fibrotic ECM and modulating key pathological pathways, this TnC-guided liposomal delivery system provides a significant advancement in antifibrotic nanomedicine.

Nano-encapsulation of drugs to target hepatic stellate cells: Toward precision treatments of liver fibrosis

Liver fibrosis is characterized by excessive extracellular matrix (ECM) deposition triggered by hepatic stellate cells (HSCs). As central players in fibrosis progression, HSCs are the most important therapeutic targets for antifibrotic therapy. However, owing to the limitations of systemic drug administration, there is still no suitable and effective clinical treatment. In recent years, nanosystems have demonstrated expansive therapeutic potential and evolved into a clinical modality. In liver fibrosis, nanosystems have undergone a paradigm shift from targeting the whole liver to locally targeted modifying processes. Nanomedicine delivered to HSCs has significant potential in managing liver fibrosis, where optimal management would benefit from targeted delivery, personalized therapy based on the specific site of interest, and minor side effects. In this review, we present a brief overview of the role of HSCs in the pathogenesis of liver fibrosis, summarize the different types of nanocarriers and their specific delivery applications in liver fibrosis, and highlight the biological barriers associated with the use of nanosystems to target HSCs and approaches available to solve this issue. We further discuss in-depth all the molecular target receptors overexpressed during HSC activation in liver fibrosis and their corresponding ligands that have been used for drug or gene delivery targeting HSCs.

Targeting uridine diphosphate glucuronosyltransferase 1A1 in liver disease: Current research and future directions

The current letter to the editor pertains to the manuscript entitled 'Uridine diphosphate glucuronosyltransferase 1A1 prevents the progression of liver injury'. Increased levels of uridine diphosphate glucuronosyltransferase 1A1 during liver injury could mitigate damage by reducing endoplasmic reticulum stress, oxidative stress, and dysregulated lipid metabolism, impeding hepatocyte apoptosis and necroptosis.