Regulatory T cells (Tregs) in liver fibrosis

Fragile Treg cells: Traitors in immune homeostasis?

Regulatory T (Treg) cells play a key role in maintaining immune tolerance and tissue homeostasis. However, in some disease microenvironments, Treg cells exhibit fragility, which manifests as preserved FoxP3 expression accompanied by inflammation and loss of immunosuppression. Fragile Treg cells are formatively, phenotypically and functionally diverse in various diseases, further complicating the role of Treg cells in the immunotherapeutic response and offering novel targets for disease treatment by modulating specific Treg subsets. In this review, we summarize findings on fragile Treg cells to provide a framework for characterizing the formation and role of fragile Treg cells in different diseases, and we discuss how this information may guide the development of more specific Treg-targeted immunotherapies.

Roles and therapeutic targeting of dendritic cells in liver fibrosis

Liver fibrosis is a common pathological condition marked by excessive accumulation of extracellular matrix proteins, resulting in irreversible cirrhosis and cancer. Dendritic cells (DCs) act as the crucial component of hepatic immunity and are believed to affect fibrosis by regulating the proliferation and differentiation of hepatic stellate cells (HSCs), a key mediator of fibrogenesis, and by interplaying with immune cells in the liver. This review concisely describes the process of fibrogenesis, and the phenotypic and functional characteristics of DCs in the liver. Besides, it focuses on the interaction between DCs and HSCs, T cells, and natural killer (NK) cells, as well as the dual roles of DCs in liver fibrosis, for the sake of exploring the potential of targeting DCs as a therapeutic strategy for the disease.

Unraveling the hepatic stellate cells mediated mechanisms in aging's influence on liver fibrosis

Aging enhances numerous processes that compromise homeostasis and pathophysiological processes. Among these, activated HSCs play a pivotal role in advancing liver fibrosis. This research delved into how aging impacts liver fibrosis mechanisms. The study involved 32 albino rats categorized into four groups: Group I (young controls), Group II (young with liver fibrosis), Group III (old controls), and Group IV (old with liver fibrosis). Various parameters including serum ALT, adiponectin, leptin, and cholesterol levels were evaluated. Histopathological analysis was performed, alongside assessments of TGF-β, FOXP3, and CD133 gene expressions. Markers of fibrosis and apoptosis were the highest in group IV. Adiponectin levels significantly decreased in Group IV compared to all other groups except Group II, while cholesterol levels were significantly higher in liver fibrosis groups than their respective control groups. Group III displayed high hepatic expression of desmin, α-SMA, GFAP and TGF- β and in contrast to Group I. Increased TGF-β and FOXP3 gene expressions were observed in Group IV relative to Group II, while CD133 gene expression decreased in Group IV compared to Group II. In conclusion, aging modulates immune responses, impairs regenerative capacities via HSC activation, and influences adipokine and cholesterol levels, elevating the susceptibility to liver fibrosis.

Association between serum vitamin D concentration and liver fibrosis in diabetes mellitus patients: a cross-sectional study from the NHANES database

AIM

Liver fibrosis (LF) is a common complication of diabetes mellitus (DM). Studies have found that vitamin D (VD), as a modifiable factor has been reported to be associated with LF. The relationship between serum VD concentration and LF in DM patients has rarely been reported. The aim of this study was to assess the association between serum VD concentration and LF in DM patients.

METHODS

In this cross-sectional study, data of DM patients aged ≥ 45 years were extracted from the National Health and Nutrition Examination Survey (NHANES 2017-2018). Serum VD concentration was measured by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Vibration controlled transient elastography (VCTE) was used to measure liver stiffness. Covariates included sociodemographic information, lifestyles, laboratory data, diseases history were extracted from the database. The weighted univariable and multivariable logistic regression models were utilized to explore the association between serum VD concentration and LF in DM patients, and were described as odds ratio (ORs) and 95% confidence intervals (CIs). Subgroup analyses based on BMI, liver steatosis, hypertension and dyslipidemia were further assessed the association.

RESULTS

A total of 799 patients were included, of which 188 (23.53%) had LF. Higher serum VD concentration was associated with the lower odds of LF (OR = 0.33, 95% CI 0.19-0.59) and advanced LF (OR = 0.31, 95% CI 0.17-0.55) in DM patients after adjustment for race, liver steatosis, BMI, smoking, drinking, AST, ALT and physical activity, especially in patients with liver steatosis (OR = 0.28, 95% CI 0.13-0.59) and dyslipidemia (OR = 0.31, 95% CI 0.14-0.66), respectively.

CONCLUSIONS

High serum VD concentration may have a potential benefit for maintain the liver health in DM patients.

Role of T cells in liver metastasis

The liver is a major metastatic site (organ) for gastrointestinal cancers (such as colorectal, gastric, and pancreatic cancers) as well as non-gastrointestinal cancers (such as lung, breast, and melanoma cancers). Due to the innate anatomical position of the liver, the apoptosis of T cells in the liver, the unique metabolic regulation of hepatocytes and other potential mechanisms, the liver tends to form an immunosuppressive microenvironment and subsequently form a pre-metastatic niche (PMN), which can promote metastasis and colonization by various tumor cells(TCs). As a result, the critical role of immunoresponse in liver based metastasis has become increasingly appreciated. T cells, a centrally important member of adaptive immune response, play a significant role in liver based metastases and clarifying the different roles of the various T cells subsets is important to guide future clinical treatment. In this review, we first introduce the predisposing factors and related mechanisms of liver metastasis (LM) before introducing the PMN and its transition to LM. Finally, we detail the role of different subsets of T cells in LM and advances in the management of LM in order to identify potential therapeutic targets for patients with LM.

Tyrosol attenuates NASH features by reprogramming the hepatic immune milieu

Nonalcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease, and no drugs have been approved for its therapy. Among plant-derived molecules, phenolic compounds of extra virgin olive oil like tyrosol (Tyr) had demonstrated multiple beneficial actions for liver health, including the modulation of inflammation in fibrosis. This study aims at assessing the protective effect and mechanism of Tyr in invitro and in vivo models of NASH, with a focus on the hepatic immune microenvironment and extrahepatic manifestations. The effect of Tyr was evaluated in cellular models of NASH, obtained by co-culturing palmitic and oleic acid-treated HepG2 cells with THP1-derived M1 macrophages and LX2 cells, and in a mouse model of NASH induced by a high fructose-high fat diet combined to CCl4 treatment. In vitro Tyr reduced fatty acid (FA) accumulation in HepG2 cells and displayed a beneficial effect on LX2 activation and macrophage differentiation. In vivo, beside reducing steatosis and fibrosis in NASH animals, Tyr prevented inflammation, as demonstrated by the reduction of hepatic inflammatory foci, and immune cells like CD86+ macrophages (p < 0.05), CD4+ (p < 0.05) and T helper effector CD4+ FoxP3- CD62L-lymphocytes (p < 0.05). Also, the prooxidant enzyme NOX1 and the mRNA expression of TGF-β1 and IL6 (p < 0.05) were reduced by Tyr. Notably, in Tyr-treated animals, a significant increase of CD4+ FoxP3+ Treg cells (p < 0.05) was observed, involved in regenerative pathways. Moreover, Tyr attenuated the fatigue and anxious behavior observed in NASH mice. In conclusion, Tyr effectively reduced NASH-related steatosis, fibrosis, oxidative stress, and inflammation, displaying a beneficial effect on the hepatic immune infiltrate, indicating its possible development as a therapeutic agent for NASH due to its multifaceted mechanism.

Immune regulation and therapeutic application of T regulatory cells in liver diseases

CD4+ CD25+ FOXP3+ T regulatory cells (Tregs) are a subset of the immunomodulatory cell population that can inhibit both innate and adaptive immunity by various regulatory mechanisms. In hepatic microenvironment, proliferation, plasticity, migration, and function of Tregs are interrelated to the remaining immune cells and their secreted cytokines and chemokines. In normal conditions, Tregs protect the liver from inflammatory and auto-immune responses, while disruption of this crosstalk between Tregs and other immune cells may result in the progression of chronic liver diseases and the development of hepatic malignancy. In this review, we analyze the deviance of this protective nature of Tregs in response to chronic inflammation and its involvement in inducing liver fibrosis, cirrhosis, and hepatocellular carcinoma. We will also provide a detailed emphasis on the relevance of Tregs as an effective immunotherapeutic option for autoimmune diseases, liver transplantation, and chronic liver diseases including liver cancer.

Vitamin D3 reverses immune tolerance and enhances the cytotoxicity of effector T cells in coal pneumoconiosis

Coal worker's pneumoconiosis (CWP) is a common occupational disease that coal miners are highly susceptible due to long-term exposure to coal dust particles (CDP). CWP can induce the accumulation of immune cells surrounding the bronchioles and alveoli in the lungs, resulting in pulmonary fibrosis and compromised immune function. Using single-cell RNA sequencing (scRNA-Seq), our previous studies disclose that CDP exposure triggers heterogeneity of transcriptional profiles in mouse pneumoconiosis, while Vitamin D3 (VitD3) supplementation reduces CDP-induced cytotoxicity; however, the mechanism by which how VitD3 regulates immune status in coal pneumoconiosis remains unclear. In this study, we elucidated the heterogeneity of pulmonary lymphocytes in mice exposed to CDP and demonstrated the therapeutic efficacy of VitD3 using scRNA-Seq dataset. The validation of key lymphocyte markers and their functional molecules was performed using immunofluorescence. The results demonstrated that VitD3 increased the number of naive T cells by modulating CD4 + T cell differentiation and decreased the number of Treg cells in CDP-exposed mice, thereby enhancing the cytotoxic activity of CD8 + effector T cells. These effects markedly alleviated lung fibrosis and symptoms. Taken together, the mechanism by which VitD3 regulates the functions of lymphocytes in CWP provides a new perspective for further research on the prevention and treatment of CWP.

Transmission-Blocking Vaccines against Schistosomiasis Japonica

Control of schistosomiasis japonica, endemic in Asia, including the Philippines, China, and Indonesia, is extremely challenging. Schistosoma japonicum is a highly pathogenic helminth parasite, with disease arising predominantly from an immune reaction to entrapped parasite eggs in tissues. Females of this species can generate 1000-2200 eggs per day, which is about 3- to 15-fold greater than the egg output of other schistosome species. Bovines (water buffalo and cattle) are the predominant definitive hosts and are estimated to generate up to 90% of parasite eggs released into the environment in rural endemic areas where these hosts and humans are present. Here, we highlight the necessity of developing veterinary transmission-blocking vaccines for bovines to better control the disease and review potential vaccine candidates. We also point out that the approach to producing efficacious transmission-blocking animal-based vaccines before moving on to human vaccines is crucial. This will result in effective and feasible public health outcomes in agreement with the One Health concept to achieve optimum health for people, animals, and the environment. Indeed, incorporating a veterinary-based transmission vaccine, coupled with interventions such as human mass drug administration, improved sanitation and hygiene, health education, and snail control, would be invaluable to eliminating zoonotic schistosomiasis.

Integrated analysis reveals crosstalk between pyroptosis and immune regulation in renal fibrosis

Purpose

The pathogenesis of renal fibrosis (RF) involves intricate interactions between profibrotic processes and immune responses. This study aimed to explore the potential involvement of the pyroptosis signaling pathway in immune microenvironment regulation within the context of RF. Through comprehensive bioinformatics analysis and experimental validation, we investigated the influence of pyroptosis on the immune landscape in RF.

Methods

We obtained RNA-seq datasets from Gene Expression Omnibus (GEO) databases and identified Pyroptosis-Associated Regulators (PARs) through literature reviews. Systematic evaluation of alterations in 27 PARs was performed in RF and normal kidney samples, followed by relevant functional analyses. Unsupervised cluster analysis revealed distinct pyroptosis modification patterns. Using single-sample gene set enrichment analysis (ssGSEA), we examined the correlation between pyroptosis and immune infiltration. Hub regulators were identified via weighted gene coexpression network analysis (WGCNA) and further validated in a single-cell RNA-seq dataset. We also established a unilateral ureteral obstruction-induced RF mouse model to verify the expression of key regulators at the mRNA and protein levels.

Results

Our comprehensive analysis revealed altered expression of 19 PARs in RF samples compared to normal samples. Five hub regulators, namely PYCARD, CASP1, AIM2, NOD2, and CASP9, exhibited potential as biomarkers for RF. Based on these regulators, a classifier capable of distinguishing normal samples from RF samples was developed. Furthermore, we identified correlations between immune features and PARs expression, with PYCARD positively associated with regulatory T cells abundance in fibrotic tissues. Unsupervised clustering of RF samples yielded two distinct subtypes (Subtype A and Subtype B), with Subtype B characterized by active immune responses against RF. Subsequent WGCNA analysis identified PYCARD, CASP1, and NOD2 as hub PARs in the pyroptosis modification patterns. Single-cell level validation confirmed PYCARD expression in myofibroblasts, implicating its significance in the stress response of myofibroblasts to injury. In vivo experimental validation further demonstrated elevated PYCARD expression in RF, accompanied by infiltration of Foxp3+ regulatory T cells.

Conclusions

Our findings suggest that pyroptosis plays a pivotal role in orchestrating the immune microenvironment of RF. This study provides valuable insights into the pathogenesis of RF and highlights potential targets for future therapeutic interventions.

Crosstalk between fibroblasts and immunocytes in fibrosis: From molecular mechanisms to clinical trials

BACKGROUND

The impact of fibroblasts on the immune system provides insight into the function of fibroblasts. In various tissue microenvironments, multiple fibroblast subtypes interact with immunocytes by secreting growth factors, cytokines, and chemokines, leading to wound healing, fibrosis, and escape of cancer immune surveillance. However, the specific mechanisms involved in the fibroblast-immunocyte interaction network have not yet been fully elucidated.

MAIN BODY AND CONCLUSION

Therefore, we systematically reviewed the molecular mechanisms of fibroblast-immunocyte interactions in fibrosis, from the history of cellular evolution and cell subtype divisions to the regulatory networks between fibroblasts and immunocytes. We also discuss how these communications function in different tissue and organ statuses, as well as potential therapies targeting the reciprocal fibroblast-immunocyte interplay in fibrosis. A comprehensive understanding of these functional cells under pathophysiological conditions and the mechanisms by which they communicate may lead to the development of effective and specific therapies targeting fibrosis.

Gingival mesenchymal stem cell therapy, immune cells, and immunoinflammatory application

MSC-based therapeutic strategies have proven to be incredibly effective. Robust self-renewal, multilineage differentiation, and potential for tissue regeneration and disease treatments are all features of MSCs isolated from oral tissue. Human exfoliated deciduous teeth, dental follicles, dental pulp, apical papilla SCs, and alveolar bone are the primary sources of oral MSC production. The early immunoinflammatory response is the first stage of the healing process. Oral MSCs can interact with various cells, such as immune cells, revealing potential immunomodulatory regulators. They also have strong differentiation and regeneration potential. Therefore, a ground-breaking strategy would be to research novel immunomodulatory approaches for treating disease and tissue regeneration that depend on the immunomodulatory activities of oral MSCs during tissue regeneration.

Role of the immune system in liver transplantation and its implications for therapeutic interventions

Liver transplantation (LT) stands as the gold standard for treating end-stage liver disease and hepatocellular carcinoma, yet postoperative complications continue to impact survival rates. The liver's unique immune system, governed by a microenvironment of diverse immune cells, is disrupted during processes like ischemia-reperfusion injury posttransplantation, leading to immune imbalance, inflammation, and subsequent complications. In the posttransplantation period, immune cells within the liver collaboratively foster a tolerant environment, crucial for immune tolerance and liver regeneration. While clinical trials exploring cell therapy for LT complications exist, a comprehensive summary is lacking. This review provides an insight into the intricacies of the liver's immune microenvironment, with a specific focus on macrophages and T cells as primary immune players. Delving into the immunological dynamics at different stages of LT, we explore the disruptions after LT and subsequent immune responses. Focusing on immune cell targeting for treating liver transplant complications, we provide a comprehensive summary of ongoing clinical trials in this domain, especially cell therapies. Furthermore, we offer innovative treatment strategies that leverage the opportunities and prospects identified in the therapeutic landscape. This review seeks to advance our understanding of LT immunology and steer the development of precise therapies for postoperative complications.

Triptolide attenuates CCL4-induced liver fibrosis by regulating the differentiation of CD4+ T cells in mice

Liver fibrosis is a major global health issue, and immune dysregulation is a main contributor. Triptolide is a natural immunosuppressive agent with demonstrated effectiveness in ameliorating liver fibrosis, but whether it exerts anti-liver fibrotic effects via immunoregulation remains obscure. In this study, first, by employing a CCL4-induced liver fibrosis mouse model, we demonstrated that triptolide could alleviate pathological damage to liver tissue and attenuate liver function damaged by CCL4. In addition, triptolide inhibited the expression of liver fibrotic markers such as hydroxyproline, collagen type IV, hyaluronidase, laminin, and procollagen type III, and the protein expression of α-SMA in CCL4-induced liver fibrosis. Second, with the help of network pharmacology, we predicted that triptolide's anti-liver fibrotic effects might occur through the regulation of Th17, Th1, and Th2 cell differentiation, which indicated that triptolide might mitigate liver fibrosis via immunoregulation. Finally, multiplex immunoassays and flow cytometry were adopted to verify this prediction. The results suggested that triptolide could reverse the aberrant expression of inflammatory cytokines caused by CCL4 and regulate the differentiation of Th1, Th2, Th17, and Treg cells. In conclusion, triptolide could attenuate CCL4-induced liver fibrosis by regulating the differentiation of CD4+ T cells. The results obtained in this study extended the application of triptolide and introduced a new mechanism of triptolide's anti-liver fibrotic effects.

Association of NK Cells with the Severity of Fibrosis in Patients with Chronic Hepatitis C

Some NK cell subpopulations may be involved in the modulation of fibrogenesis in the liver. The aim of the study was to evaluate the relationship between the number and phenotype of NK cell subsets in peripheral blood (PB) and total NK cell percentage, population density and the degree of liver fibrosis of patients infected with hepatitis C virus (HCV+). The study group consisted of 56 HCV+ patients, divided into two subgroups: patients with mild or moderate fibrosis and patients with advanced liver fibrosis or cirrhosis (F ≥ 3 in METAVIR classification). The preparations were stained with H-E and AZAN staining. NK cells were targeted with anti-CD56 antibody and identified automatically in situ using the DakoVision system. Assessment of different NK cell subsets in PB was performed with the flow cytometry technique. In the PB of HCV+ patients with advanced liver fibrosis, there was a lower proportion of CD62L+; CD62L+/CD94++; CD27+; CD127+/CD27+ and CXCR3+/CD27+ NK subsets, as compared to patients with mild/moderate liver fibrosis. The results also showed no association between total PB NK cell level and total intrahepatic NK cell population density between patients with mild/moderate fibrosis and with advanced liver fibrosis. However, positive correlations between the PB levels of CD94+ and CD62L+ NK cell subsets and the intrahepatic total NK cell percentage and population density in the liver, irrespectively to the extent of fibrosis, were observed. Additionally, positive correlation was found between the PB CXCR3+/CD94+ NK cell percentages and intrahepatic NK cell percentages in patients with advanced hepatic fibrosis. Lower blood availability of specific NK subsets in patients with chronic type C hepatitis might be a cause of progression of liver fibrosis via insufficient control over hepatic stellate cells.

Immune and Non-Immune Inflammatory Cells Involved in Autoimmune Fibrosis: New Discoveries

Fibrosis is an important health problem and its pathogenetic activation is still largely unknown. It can develop either spontaneously or, more frequently, as a consequence of various underlying diseases, such as chronic inflammatory autoimmune diseases. Fibrotic tissue is always characterized by mononuclear immune cells infiltration. The cytokine profile of these cells shows clear proinflammatory and profibrotic characteristics. Furthermore, the production of inflammatory mediators by non-immune cells, in response to several stimuli, can be involved in the fibrotic process. It is now established that defects in the abilities of non-immune cells to mediate immune regulation may be involved in the pathogenicity of a series of inflammatory diseases. The convergence of several, not yet well identified, factors results in the aberrant activation of non-immune cells, such as epithelial cells, endothelial cells, and fibroblasts, that, by producing pro-inflammatory molecules, exacerbate the inflammatory condition leading to the excessive and chaotic secretion of extracellular matrix proteins. However, the precise cellular mechanisms involved in this process have not yet been fully elucidated. In this review, we explore the latest discoveries on the mechanisms that initiate and perpetuate the vicious circle of abnormal communications between immune and non-immune cells, responsible for fibrotic evolution of inflammatory autoimmune diseases.

Cellular and Molecular Mechanisms of Liver Fibrosis in Patients with NAFLD

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

Preclinical Models and Promising Pharmacotherapeutic Strategies in Liver Fibrosis: An Update

Liver fibrosis represents one of the greatest challenges in medicine. The fact that it develops with the progression of numerous diseases with high prevalence (NAFLD, viral hepatitis, etc.) makes liver fibrosis an even greater global health problem. Accordingly, it has received much attention from numerous researchers who have developed various in vitro and in vivo models to better understand the mechanisms underlying fibrosis development. All these efforts led to the discovery of numerous agents with antifibrotic properties, with hepatic stellate cells and the extracellular matrix at the center of these pharmacotherapeutic strategies. This review focuses on the current data on numerous in vivo and in vitro models of liver fibrosis and on various pharmacotherapeutic targets in the treatment of liver fibrosis.