Phenotypical and Functional Polymorphism of Liver Resident Macrophages

Histone demethylase KDM4A mediating macrophage polarization: A potential mechanism of trichloroethylene induced liver injury

Trichloroethylene (TCE) is a commonly used organic solvent in industry. Our previous studies have found that TCE can cause liver injury accompanied by macrophage polarization, but the specific mechanism is unclear. The epigenetic regulation of macrophage polarization is mainly focused on histone modification. Histone lysine demethylase 4A (KDM4A) is involved in the activation of macrophages. In this study, we used a mouse model we investigated the role of KDM4A in the livers of TCE-drinking mice and found that the expression of KDM4A, M1-type polarization indicators, and related inflammatory factors in the livers of TCE-drinking mice. In the study, BALB/c mice were randomly divided into four groups: 2.5 mg/mL TCE dose group and 5.0 mg/mL TCE dose group, the vehicle control group, and the blank control group. We found that TCE triggered M1 polarization of mouse macrophages, characterized by the expression of CD11c and robust production of inflammatory cytokines. Notably, exposure to TCE resulted in markedly increased expression of KDM4A in macrophages. Functionally, the increased expression of KDM4A significantly impaired the expression of H3K9me3 and H3K9me2 and increased the expression of H3K9me1. In addition, KDM4A potentially represents a novel epigenetic modulator, with its upregulation connected to β-catenin activation, a signal critical for the pro-inflammatory activation of macrophages. Furthermore, KDM4A inhibitor JIB-04 treatment resulted in a decrease in β-catenin expression and prevented TCE-induced M1 polarization and the expression of the pro-inflammatory cytokines TNF-α and IL-1β. These results suggest that the association of KDM4A and Wnt/β-catenin cooperatively establishes the activation and polarization of macrophages and global changes in H3K9me3/me2/me1. Our findings identify KDM4A as an essential regulator of the polarization of macrophages and the expression of inflammatory cytokines, which might serve as a potential target for preventing and treating liver injury caused by TCE.

Lipopolysaccharide modification enhances the inhibitory effect of clodronate liposomes on hepatic fibrosis by depletion of macrophages and hepatic stellate cells

Hepatic fibrosis is a complex chronic liver disease in which both macrophages and hepatic stellate cells (HSCs) play important roles. Many studies have shown that clodronate liposomes (CLD-lipos) effectively deplete macrophages. However, no liposomes have been developed that target both HSCs and macrophages. This study aimed to evaluate the therapeutic efficacy of lipopolysaccharide-coupled clodronate liposomes (LPS-CLD-lipos) and the effects of liposomes size on hepatic fibrosis. Three rat models of hepatic fibrosis were established in vivo; diethylnitrosamine (DEN), bile duct ligation (BDL), and carbon tetrachloride (CCl4). Hematoxylin and eosin staining and serological liver function indices were used to analyze pathological liver damage. Masson's trichrome and Sirius red staining were used to evaluate the effect of liposomes on liver collagen fibers. The hydroxyproline content in liver tissues was determined. In vitro cell counting kit-8 (CCK-8) and immunofluorescence assays were used to further explore the effects of LPS modification and liposomes size on the killing of macrophages and HSCs. Both in vitro and in vivo experiments showed that 200 nm LPS-CLD-lipos significantly inhibited hepatic fibrosis and the abnormal deposition of collagen fibers in the liver and improved the related indicators of liver function. Further results showed that 200 nm LPS-CLD-lipos increased the clearance of macrophages and induced apoptosis of hepatic stellate cells, significantly. The present study demonstrated that 200 nm LPS-CLD-lipos could significantly inhibit hepatic fibrosis and improve liver function-related indices and this study may provide novel ideas and directions for hepatic fibrosis treatment.

Mimicking the cellular environment does not cause monocyte-derived macrophages to become phenotypically similar to Kupffer cells

Resident macrophages of various mammalian organs are characterized by several distinctive features in their gene expression profile and phenotype, including involvement in the regulation of organ functions, as well as reduced sensitivity to proinflammatory activation factors. The reasons for the formation of such a specific phenotype remain the subject of intensive research. Some papers emphasize the role of the origin of organ macrophages. Other studies indicate that monocytes that develop in the red bone marrow are also able to form resident macrophages with a phenotype characteristic of a particular organ, but this requires appropriate microenvironmental conditions. In this article, we studied the possibility of differentiation of monocyte-derived macrophages into cells with a Kupffer-like phenotype under the influence of the main stromal components of Kupffer cells macrophage niche: Ito cells, liver sinusoid endotheliocytes and hepatocyte growth factor (HGF). It was found that Kupffer cells are characterized by several features, including increased expression of transcription factors Spic and Id3, as well as MUP family genes, Clusterin and Ngp genes. In addition, Kupffer cells were characterized by a higher proliferative activity. The expression of marker genes of Kupffer cells (i.e. Id3, Spic, Marco and Timd4) increased in monocyte-derived macrophages during coculture with Ito cells, liver sinusoid endothelial cells, macrophage colony-stimulating factor and HGF cells only by 3 days. However, the expression level of these genes was always higher in Kupffer cells. In addition, a complete coincidence of the expressed gene profile in monocyte-derived macrophages and Kupffer cells did not occur even after 3 days of culturing.

The effect of leptin on trained innate immunity and on systemic inflammation in subjects with obesity

Leptin is associated with cardiometabolic complications of obesity, such as metabolic syndrome and atherosclerosis. In obese men, the presence of metabolic syndrome is associated with higher circulating leptin and interleukin (IL)-6 concentrations and increased monocyte cytokine production capacity. Here, we investigated the effects of leptin on monocyte function and systemic inflammatory markers in obese individuals. We specifically explored whether leptin can induce long-term changes in innate immune function by inducing innate immune memory (also called trained immunity). We exposed human primary monocytes for 24 h to relevant leptin concentrations in vitro and measured cytokine production. In addition, after removing leptin, we incubated monocytes for 5 d in culture medium, and we restimulated them on day 6 to assess cytokine production capacity, phagocytosis, and foam cell formation. Direct stimulation with leptin did not induce cytokine production, but exposure to 50 ng/mL leptin augmented lipopolysaccharide- and R848-induced tumor necrosis factor α (TNF-α) production after 1 wk. In a separate in vivo study in a cohort of 302 obese subjects (body mass index [BMI] >27 kg/m2, 55 to 81 yr), we measured circulating leptin, inflammatory markers, and cytokine production upon ex vivo stimulation of isolated peripheral blood mononuclear cells. Circulating leptin concentrations positively correlated with circulating IL-1β and IL-6, which was more pronounced in men than in women. Four single nucleotide polymorphisms in the leptin gene influenced circulating IL-6 concentrations in men, suggesting a direct effect of leptin on IL-6. In conclusion, in vitro, leptin does not directly stimulate monocytes to produce cytokines, yet induces long-term monocyte hyperresponsiveness, i.e. trained immunity. In obese subjects, leptin is associated with circulating IL-6 in a sex-dependent manner. The underlying mechanisms of the sex-specific effect of leptin on innate immune cells remain to be further investigated.

Dietary Galactose Increases the Expression of Mitochondrial OXPHOS Genes and Modulates the Carbohydrate Oxidation Pathways in Mouse Intestinal Mucosa

BACKGROUND

Prolonged lactation provides substantial health benefits, possibly because of galactose as part of milk sugar lactose. Isocaloric replacement of dietary glucose [16 energy%(en%)] with galactose within a normal diet (64en% carbohydrates) during a 3-wk postweaning period provided substantial benefits on short- and long-term physiologic and metabolic parameters at the whole-body level and liver in female mice, which might be attributable to intestinal function.

OBJECTIVES

This study aimed to investigate if partial dietary replacement of glucose with galactose alters intestinal metabolism underlying hepatic health effects.

METHODS

Proximal intestinal mucosa gene profiles in female mice were analyzed using RNAseq technology, validated, and correlated with hepatic health parameters.

RESULTS

Transcriptome analysis revealed that the presence of galactose primarily affected the pathways involved in energy metabolism. A consistently higher expression was observed in the subset of mitochondrial transcripts (78 of 80, all P.adj < 0.1). Oxidative phosphorylation (OXPHOS) represented the most upregulated process (all top 10 pathways) independent of the total mitochondrial mass (P = 0.75). Moreover, galactose consistently upregulated carbohydrate metabolism pathways, specifically glycolysis till acetyl-CoA production and fructose metabolism. Also, the expression of transcripts involved in these pathways was negatively correlated with circulating serum amyloid A3 protein, a marker of hepatic inflammation [R (-0.61, -0.5), P (0.002, 0.01)]. Accordingly, CD163+ cells were decreased in the liver. Additionally, the expression of key fructolytic enzymes in the small intestinal mucosa was negatively correlated with triglyceride accumulation in the liver [R (-0.45, -0.4), P (0.03, 0.05)].

CONCLUSIONS

To our knowledge, our results show for the first time the role of galactose as an OXPHOS activator in vivo. Moreover, the concept of intestinal cells acting as the body's metabolic gatekeeper is strongly supported, as they alter substrate availability and thereby contribute to the maintenance of metabolic homeostasis, protecting other organs, as evidenced by their potential ability to shield the liver from the potentially detrimental effects of fructose.

Biochemical and molecular inducers and modulators of M2 macrophage polarization in clinical perspective

Macrophages as innate immune cells with great plasticity are of great interest for cell therapy. There are two main macrophage populations - pro- and anti-inflammatory cells also known as M1 and M2. High potential in cancer research contributed to the in-depth study of the molecular processes leading to the polarization of macrophages into the M1 phenotype, and much less attention has been paid to anti-inflammatory M2 macrophages, which can be successfully used in cell therapy of inflammatory diseases. This review describes ontogenesis of macrophages, main functions of pro- and and-inflammatory cells and four M2 subpopulations characterized by different functionalities. Data on agents (cytokines, microRNAs, drugs, plant extracts) that may induce M2 polarization through the changes in microenvironment, metabolism, and efferocytosis are summarized. Finally, recent attempts at stable macrophage polarization using genetic modifications are described. This review may be helpful for researchers concerned with the problem of M2 macrophage polarization and potential use of these anti-inflammatory cells for the purposes of regenerative medicine.

Exploratory study of macrophage polarization and spatial distribution in colorectal cancer liver metastasis: a pilot study

Background

The liver is the most typical site of metastatic disease for patients with colorectal cancer (CRC), and up to half the patients with CRC will develop colorectal liver metastasis (CLM). Studying the tumor microenvironment, particularly macrophages and their spatial distribution, can give us critical insight into treatment.

Methods

Ten CLMs (five treatment-naïve and five post-neoadjuvant chemotherapy) were stained with multiplex immunofluorescence panels against cytokeratins, CD68, Arg1, CD206, CD86, CD163, PD-L1, and MRP8-14. Densities of cell phenotypes and their spatial distribution in the tumor center and the normal liver-tumor interface were correlated with clinicopathological variables.

Results

M2 macrophages were the predominant subtype in both the tumor center and the periphery, with a relatively higher density at the periphery. The larger tumors, more than 3.9 cm, were associated with higher densities of total CD68+ macrophages and CD68+CD163+ CD206neg and CD68+CD206+ CD163neg M2 macrophage subtypes. Total macrophages in the tumor periphery demonstrated significantly greater proximity to malignant cells than did those in the tumor center (p=0.0371). The presence of higher than median CD68+MRP8-14+CD86neg M1 macrophages in the tumor center was associated with poor overall survival (median 2.34 years) compared to cases with lower than median M1 macrophages at the tumor center (median 6.41 years) in univariate analysis.

Conclusion

The dominant polarization of the M2 macrophage subtype could drive new therapeutic approaches in CLM patients.

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.

Activation of Kupffer cells in NAFLD and NASH: mechanisms and therapeutic interventions

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are emerging as the leading causes of liver disease worldwide. These conditions can lead to cirrhosis, liver cancer, liver failure, and other related ailments. At present, liver transplantation remains the sole treatment option for end-stage NASH, leading to a rapidly growing socioeconomic burden. Kupffer cells (KCs) are a dominant population of macrophages that reside in the liver, playing a crucial role in innate immunity. Their primary function includes phagocytosing exogenous substances, presenting antigens, and triggering immune responses. Moreover, they interact with other liver cells during the pathogenesis of NAFLD, and this crosstalk may either delay or exacerbate disease progression. Stimulation by endogenous signals triggers the activation of KCs, resulting in the expression of various inflammatory factors and chemokines, such as NLRP3, TNF-α, IL-1B, and IL-6, and contributing to the inflammatory cascade. In the past 5 years, significant advances have been made in understanding the biological properties and immune functions of KCs in NAFLD, including their interactions with tissue molecules, underlying molecular mechanisms, signaling pathways, and relevant therapeutic interventions. Having a comprehensive understanding of these mechanisms and characteristics can have enormous potential in guiding future strategies for the prevention and treatment of NAFLD.

The effect of miR-155-5p on M1 polarization of Kupffer cells and immune response during liver transplantation through regulating the expression of KDM5D

BACKGROUND

To explore the effect and its specific mechanism of miR-155-5p on M1 polarization of Kupffer cells (KCs) and immune response in liver transplantation (LT) through KDM5D.

METHODS

Primary KCs were isolated from Wistar rats and identified by cell culture, ink-swallowing test and flow cytometry. The cells identified as KCs were induced into LT acute rejection (AR) model cells by LPS/IFN-γ, flow cytometry was used for cell sorting and apoptosis detection. Enzyme-linked immunosorbent assay (ELISA) kit was used to detect the levels of inflammatory factors, macrophages and liver function markers. RT-qPCR detected the expression of miR-155-5p and KDM5D mRNA. The protein expression of KDM5D was detected by Western blot. Dual luciferase reporter gene experiment verified the targeting relationship between miR-155-5p and KDM5D.

RESULTS

The separated KCs adhered after being cultured for 24 h, had pseudopodia and phagocytosis, and the proportion of F4/80 positive cells was more than 90%. The expression of miR-155-5p was increased in LPS/IFN-γ-induced KCs. And knockdown of miR-155-5p inhibited H3K4me3 and H3K27me3 of TNF-α promoter, M1 polarization of KCs and the immune response of AR model cells by upregulating KDM5D. In animal experiments, knockdown of miR-155-5p was found to inhibit liver damage and immune response in rats with allogeneic orthotopic LT.

CONCLUSION

These results confirmed that miR-155-5p inhibited M1 polarization of KCs induced by LPS/IFN-γ, thereby alleviating AR and liver function impairment after LT by upregulating KDM5D.

CAFs secrete CXCL12 to accelerate the progression and cisplatin resistance of colorectal cancer through promoting M2 polarization of macrophages

The purpose of this study was to investigate the effect of the interaction between tumor-associated fibroblasts (CAFs) and macrophage polarization on colorectal cancer (CRC) progression. Clinical tissue samples of CRC and health volunteers were collected to isolate normal fibroblasts (NFs) and CAFs. LoVo, HCT116, or THP-1 cells were co-cultured with NFs or CAFs. Immunofluorescence and western blot detected the expression of related markers. MTT assay measured cell viability and IC50. Cell proliferation and metastasis were detected through colony formation and transwell assays. CRC mice models were constructed by injection of HCT116 cells, with IHC assessing C-X-C Motif Chemokine Ligand 12 (CXCL12) expression. The proliferation, migration, invasion, and cisplatin (DDP) resistance of CRC cells were apparently increased after co-culture with CAFs. Compared to NFs, CAFs have a markedly higher ability to recruit macrophages and promote macrophages M2 polarization by secreting CXCL12. Further experiments affirmed that CXCL12 secreted by CAFs boosted proliferation, migration, invasion, and DDP resistance of CRC cells via induction of the M2 polarization of macrophages. In vivo experiments confirmed that CAFs promoted the progression of CRC and DDP resistance by affecting M2 polarization through CXCL12. CAFs recruit macrophages and secrete CXCL12 to induce M2 polarization of macrophages, thus mediating cell function and DDP resistance of CRC.

Combination treatment of mannose and GalNAc conjugated small interfering RNA protects against lethal Marburg virus infection

Marburg virus (MARV) infection results in severe viral hemorrhagic fever with mortalities up to 90%, and there is a pressing need for effective therapies. Here, we established a small interfering RNA (siRNA) conjugate platform that enabled successful subcutaneous delivery of siRNAs targeting the MARV nucleoprotein. We identified a hexavalent mannose ligand with high affinity to macrophages and dendritic cells, which are key cellular targets of MARV infection. This ligand enabled successful siRNA conjugate delivery to macrophages both in vitro and in vivo. The delivered hexa-mannose-siRNA conjugates rendered substantial target gene silencing in macrophages when supported by a mannose functionalized endosome release polymer. This hexa-mannose-siRNA conjugate was further evaluated alongside our hepatocyte-targeting GalNAc-siRNA conjugate, to expand targeting of infected liver cells. In MARV-Angola-infected guinea pigs, these platforms offered limited survival benefit when used as individual agents. However, in combination, they achieved up to 100% protection when dosed 24 h post infection. This novel approach, using two different ligands to simultaneously deliver siRNA to multiple cell types relevant to infection, provides a convenient subcutaneous route of administration for treating infection by these dangerous pathogens. The mannose conjugate platform has potential application to other diseases involving macrophages and dendritic cells.

The immune-related circRNA-miRNA-mRNA ceRNA regulatory network in the liver of turbot (Scophthalmus maximus L.) induced by Vibrio anguillarum

Recently, Vibrio anguillarum, a Gram-negative pathogenic bacterium, has been becoming a major constraint on the development of the turbot aquaculture industry because of its characteristics of worldwide distribution, broad host range and potentially devastating impacts. Although the functions of protein-coding mRNAs in the immune response against bacterial infection have been reported, as well as several non-coding RNAs (ncRNAs), such as circular RNAs (circRNAs) and microRNAs (miRNAs), the relationships between mRNAs and ncRNAs in the immune system of turbot liver are still limited during bacterial infection. In present study, the comprehensive analyses of whole-transcriptome sequencing were conducted in turbot liver infected by V. anguillarum. The differential expression was analyzed in the data of circRNAs, miRNAs, and mRNAs. The interactions of miRNA-circRNA pairs and miRNA-mRNA pairs were predicted basing on the negative regulatory relationships between miRNAs and their target circRNAs\mRNAs. The circRNA-related ceRNA regulatory networks were constructed for the analyses of regulated mechanism in turbot immune system. Subsequently, the RT-qPCR was carried out to verify the results of sequencing. Finally, we identified 31 circRNAs, 53 miRNAs and 948 mRNAs with differential expression. Gene set enrichment analyses using Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways showed that innate immunity was principally activated at the early stages of infection, while adaptive immunity was activated after 24 h. Finally, 65 circRNA-miRNA-mRNA pathways were constructed, based on the hypothesis of ceRNA regulatory networks. In conclusion, our findings provide new insights on the underlying immune response to bacterial infection and identify novel target genes for the prevention and control of disease in turbot.

Ultrastructural evidence of four types of lipofuscins in the melanomacrophagic centers in hepatocytes of zebrafish (Denio rerio)

Melanomacrophagic centers (MMCs) were studied in the hepatocytes of zebrafish using transmission electron microscope (TEM). The MMCs with irregular or amoeboid nucleus were located in the hepatocytes adjacent to the bile canaliculi. Several engulfed structures were present in the cytoplasm of MMCs. The most frequent observation was the presence of mitochondria, ranging in size from small to giant, with distorted shape and inconspicuous cristae. Occasionally the fragments of erythrocytes were found. The rough endoplasmic reticulum (rER) showed whirling around the mitochondria and lipid droplets, forming membrane-like structures. The damaged mitochondria were invaded by the lysosomes, and this was covered by a membrane led to the formation of lipofuscin. Four different types of lipofuscins were observed; namely, (1) granular with/without vacuoles of high electron-density, (2) homogenous surrounded by indistinct limiting membrane, (3) lamellated structures similar to inner matrix and cristae of mitochondria, and, (4) compound structure made by the combinations of first 3 types, (granular and homogenous, granular and lamellated, homogenous and lamellated). The present evidence suggests that MMCs in the hepatocytes of zebrafish perform continuous functions of removal of the damaged cellular organelles. The lipofuscin formation work in coordination with the cellular players of immune system and remove pathogens and maintain the internal homeostasis of cells.

Resident macrophages of the lung and liver: The guardians of our tissues

Resident macrophages play a unique role in the maintenance of tissue function. As phagocytes, they are an essential first line defenders against pathogens and much of the initial characterization of these cells was focused on their interaction with viral and bacterial pathogens. However, these cells are increasingly recognized as contributing to more than just host defense. Through cytokine production, receptor engagement and gap junction communication resident macrophages tune tissue inflammatory tone, influence adaptive immune cell phenotype and regulate tissue structure and function. This review highlights resident macrophages in the liver and lung as they hold unique roles in the maintenance of the interface between the circulatory system and the external environment. As such, we detail the developmental origin of these cells, their contribution to host defense and the array of tools these cells use to regulate tissue homeostasis.

Premature Macrophage Activation by Stored Red Blood Cell Transfusion Halts Liver Regeneration Post-Partial Hepatectomy in Rats

Liver resection is a common treatment for various conditions and often requires blood transfusions to compensate for operative blood loss. As partial hepatectomy (PHx) is frequently performed in patients with a pre-damaged liver, avoiding further injury is of paramount clinical importance. Our aim was to study the impact of red blood cell (RBC) resuscitation on liver regeneration. We assessed the impact of RBC storage time on liver regeneration following 50% PHx in rats and explored possible contributing molecular mechanisms using immunohistochemistry, RNA-Seq, and macrophage depletion. The liver was successfully regenerated after PHx when rats were transfused with fresh RBCs (F-RBCs). However, in rats resuscitated with stored RBCs (S-RBCs), the regeneration process was disrupted, as detected by delayed hepatocyte proliferation and lack of hypertrophy. The delayed regeneration was associated with elevated numbers of hemorrhage-activated liver macrophages (Mhem) secreting HO-1. Depletion of macrophages prior to PHx and transfusion improved the regeneration process. Gene expression profiling revealed alterations in numerous genes belonging to critical pathways, including cell cycle and DNA replication, and genes associated with immune cell activation, such as chemokine signaling and platelet activation and adhesion. Our results implicate activated macrophages in delayed liver regeneration following S-RBC transfusion via HO-1 and PAI-1 overexpression.

Constructing biomimetic liver models through biomaterials and vasculature engineering

The occurrence of various liver diseases can lead to organ failure of the liver, which is one of the leading causes of mortality worldwide. Liver tissue engineering see the potential for replacing liver transplantation and drug toxicity studies facing donor shortages. The basic elements in liver tissue engineering are cells and biomaterials. Both mature hepatocytes and differentiated stem cells can be used as the main source of cells to construct spheroids and organoids, achieving improved cell function. To mimic the extracellular matrix (ECM) environment, biomaterials need to be biocompatible and bioactive, which also help support cell proliferation and differentiation and allow ECM deposition and vascularized structures formation. In addition, advanced manufacturing approaches are required to construct the extracellular microenvironment, and it has been proved that the structured three-dimensional culture system can help to improve the activity of hepatocytes and the characterization of specific proteins. In summary, we review biomaterials for liver tissue engineering, including natural hydrogels and synthetic polymers, and advanced processing techniques for building vascularized microenvironments, including bioassembly, bioprinting and microfluidic methods. We then summarize the application fields including transplant and regeneration, disease models and drug cytotoxicity analysis. In the end, we put the challenges and prospects of vascularized liver tissue engineering.

Monocyte‐derived macrophages: The supplements of hepatic macrophage in Echinococcus multilocularis infected mice

Background

Alveolar echinococcosis is a potentially lethal zoonosis caused by the cestode Echinococcus multilocularis. This study is to investigate the dynamic changes of monocytes, macrophages, and related cytokines in animal models of persistent infection of E. multilocularis.

Methods

An infection model was established by intraperitoneal injection of a protoscolex suspension. The pathological changes of liver were observed by HE staining. The percentage of Ly6C^hi and Ly6C^lo Monocytes in peripheral blood was detected by flow cytometry. The distribution and expression of CX3CL1, CX3CR1, iNOS, CD163, and CD11b in the liver were detected by immunohistochemistry. The mRNA expression of tumor necrosis factor‐α (TNF‐α) and Arg1 in the liver was detected by quantitative reverse transcription polymerase chain reaction. The expression of INF‐γ, interleukin‐17 (IL‐17), IL‐4, and IL‐10 in peripheral blood was detected by enzyme‐linked immunosorbent assay.

Results

Hematoxylin‐eosin(HE) staining showed that significant lesions appeared in the later stages of infection in the liver. The proportion of Ly6C^hi monocytes in the peripheral blood of the experimental group mice decreased after a brief rise, Ly6C^lo monocytes decreased first and then increased. The expression of CX3CL1, CX3CR1, CD11b, CD163, and iNOS in the mice liver of the experimental group was increased. The expression level of TNF‐α and Arg1 mRNA in the liver of the experimental group mice increased. The expression level of IFN‐γ, IL‐17, IL‐4, and IL‐10 increased with the duration of infection.

Conclusions

Monocytes as a supplement to hepatic macrophage, monocytes and kupffer cells may both participate in Th1 and Th2 immune responses by differentiating into M1 or M2 at different stages of E. multilocularis infection.

The Phylogeny, Ontogeny, and Organ-specific Differentiation of Macrophages in the Developing Intestine

Macrophages are large highly motile phagocytic leukocytes that appear early during embryonic development and have been conserved during evolution. The developmental roles of macrophages were first described nearly a century ago, at about the time these cells were being identified as central effectors in phagocytosis and elimination of microbes. Since then, we have made considerable progress in understanding the development of various subsets of macrophages and the diverse roles these cells play in both physiology and disease. This article reviews the phylogeny and the ontogeny of macrophages with a particular focus on the gastrointestinal tract, and the role of these mucosal macrophages in immune surveillance, innate immunity, homeostasis, tissue remodeling, angiogenesis, and repair of damaged tissues. We also discuss the importance of these macrophages in the inflammatory changes in neonatal necrotizing enterocolitis (NEC). This article presents a combination of our own peer-reviewed clinical and preclinical studies, with an extensive review of the literature using the databases PubMed, EMBASE, and Scopus.

The versatility of macrophage heterogeneity in liver fibrosis

Liver fibrosis is a highly conserved wound healing response to liver injury, characterized by excessive deposition of extracellular matrix (ECM) in the liver which might lead to loss of normal functions. In most cases, many types of insult could damage hepatic parenchymal cells like hepatocytes and/or cholangiocytes, and persistent injury might lead to initiation of fibrosis. This process is accompanied by amplified inflammatory responses, with immune cells especially macrophages recruited to the site of injury and activated, in order to orchestrate the process of wound healing and tissue repair. In the liver, both resident macrophages and recruited macrophages could activate interstitial cells which are responsible for ECM synthesis by producing a variety of cytokines and chemokines, modulate local microenvironment, and participate in the regulation of fibrosis. In this review, we will focus on the main pathological characteristics of liver fibrosis, as well as the heterogeneity on origin, polarization and functions of hepatic macrophages in the setting of liver fibrosis and their underlying mechanisms, which opens new perspectives for the treatment of liver fibrosis.

3,5,3'-Triiodothyronine-Loaded Liposomes Inhibit Hepatocarcinogenesis Via Inflammation-Associated Macrophages

Background

Hepatocellular carcinoma (HCC) is inflammation-related cancer. Persistent inflammatory injury of the liver is an important factor mediating the occurrence and development of liver cancer. Hepatic macrophages play an important role in the inflammatory microenvironment, which mediates tumor immune escape, tumor growth, and metastasis. Previous studies have suggested that L-3,5,3-triiodothyronine (T3) can regulate inflammation; however, its use is associated with serious cardiac side effects, and its role in hepatocarcinogenesis remains unclear. In this study, we aimed to develop an effective T3 delivery system with reduced cardiac toxicity and to explore its effects on HCC occurrence.

Methods

T3 liposomes (T3-lipo) were prepared using the thin-film hydration method, and their characteristics, including particle size, polydispersity index, zeta potential, encapsulation efficiency, drug loading, drug release, and stability, were evaluated in vitro. We assessed the effect of T3-lipo on hepatocarcinogenesis in diethylnitrosamine (DEN)–induced primary HCC in rats and examined the biodistribution of T3 and T3-lipo by high-performance liquid chromatography–mass spectrometry. Furthermore, we explored the potential molecular mechanism of T3-lipo in hepatocarcinogenesis by immunohistochemistry and immunofluorescence analyses, Bio-Plex assays, real-time polymerase chain reaction analysis, and Western blotting assays.

Results

Compared with T3, T3-lipo had an enhanced inhibitory effect on hepatocarcinogenesis and reduced cardiac side effects in DEN-induced primary HCC in rats. Mechanistically, T3-lipo were absorbed by hepatic macrophages and regulated the secretion of inflammatory cytokines in macrophages by inhibiting inflammatory signaling pathways.

Conclusions

T3-lipo may suppress hepatocarcinogenesis by regulating the inflammatory microenvironment in the liver and reduce the cardiac side effects meanwhile.

Recovered Hepatocytes Promote Macrophage Apoptosis through CXCR4 after Acetaminophen-Induced Liver Injury in Mice

Acetaminophen (APAP) overdose is the main cause of acute liver failure in Western countries. The mechanism of APAP hepatotoxicity is associated with centrilobular necrosis which initiates infiltration of neutrophils, monocytes, and other leukocytes to the area of necrosis. While it has been recognized that this infiltration of immune cells plays a critical role in promoting liver repair, mechanism of immune cell clearance that is important for resolution of inflammation and the return to normal homeostasis are not well characterized. CXCR4 is a chemokine receptor expressed on hepatocytes as well as neutrophils, monocytes, and hematopoietic stem cells. CXCR4 function is dependent on its selective expression on different cell types and thus can vary depending on the pathophysiology. This study aimed to investigate the crosstalk between hepatocytes and macrophages through CXCR4 to promote macrophage apoptosis after APAP overdose. C57BL/6J mice were subjected to APAP overdose (300 mg/kg). Flow cytometry and immunohistochemistry were used to determine the mode of cell death of macrophages and expression pattern of CXCR4 during the resolution phase of APAP hepatotoxicity. The impact of CXCR4 in regulation of macrophage apoptosis and liver recovery was assessed after administration of a monoclonal antibody against CXCR4. RNAseq analysis was performed on flow cytometry sorted CXCR4+ macrophages at 72 h to confirm the apoptotic cell death of macrophages. Our data indicate that the inflammatory response is resolved by recovering hepatocytes through induction of CXCR4 on macrophages, which triggers their cell death by apoptosis at the end of the recovery phase.

Hepatic Macrophage Types Cluster with Disease Etiology in Chronic Liver Disease and Differ Compared to Normal Liver: Implications for Their Biologic and Diagnostic Role

Introduction. Macrophages are phenotypically heterogeneous cells that play a vital role in hepatic fibrogenesis. We aimed to compare the macrophage profiles between normal livers and those with various chronic liver diseases in the precirrhotic fibrosis stage. Methods. Immunohistochemistry was performed for three macrophage markers (CD163, CD68, and IBA1) on 48 liver biopsies. Digital image analysis and automated cell count were used to calculate the densities of immunostained cells in two selected regions of interest: the periportal region and the perivenous region. Results. The absolute and relative densities of the macrophage phenotypes in relationship with zones and etiologies showed four distinct patterns by hierarchical cluster analysis: (1) no significant increase in the macrophage densities in either periportal or perivenous regions - nonalcoholic steatohepatitis; (2) significant increase in the selected macrophage densities in both periportal and perivenous regions - Hepatitis C; (3) significant increase in the macrophage densities only in periportal region - alcoholic liver disease, primary sclerosing cholangitis, and primary biliary cholangitis; and (4) significant increase in the densities of all types of macrophages in both periportal and perivenous regions - autoimmune hepatitis. Conclusions. There are distinct macrophage phenotypic and zonal geographic signatures correlating to etiologies of chronic liver disease in the precirrhotic stage.

Inflammation: A New Look at an Old Problem

Pro-inflammatory stress is inherent in any cells that are subject to damage or threat of damage. It is defined by a number of universal components, including oxidative stress, cellular response to DNA damage, unfolded protein response to mitochondrial and endoplasmic reticulum stress, changes in autophagy, inflammasome formation, non-coding RNA response, formation of an inducible network of signaling pathways, and epigenetic changes. The presence of an inducible receptor and secretory phenotype in many cells is the cause of tissue pro-inflammatory stress. The key phenomenon determining the occurrence of a classical inflammatory focus is the microvascular inflammatory response (exudation, leukocyte migration to the alteration zone). This same reaction at the systemic level leads to the development of life-critical systemic inflammation. From this standpoint, we can characterize the common mechanisms of pathologies that differ in their clinical appearance. The division of inflammation into alternative variants has deep evolutionary roots. Evolutionary aspects of inflammation are also described in the review. The aim of the review is to provide theoretical arguments for the need for an up-to-date theory of the relationship between key human pathological processes based on the integrative role of the molecular mechanisms of cellular and tissue pro-inflammatory stress.

DNMT3a-mediated methylation of PSTPIP2 enhances inflammation in alcohol-induced liver injury via regulating STAT1 and NF-κB pathway

Alcohol-induced liver injury (ALI) is associated with inflammatory responses regulated by macrophages. Activation of macrophages plays a crucial role in ALI while DNA methylation-regulated gene silencing is associated with inflammation processes in macrophages. Proline-Serine-Threonine Phosphatase Interacting Protein 2 (PSTPIP2), which belongs to the Fes/CIP4 homology-Bin/Amphiphysin/Rvs domain family of proteins and plays a role in macrophages. Previous studies have shown that Pstpip2 can be methylated. Herein, its expression was found to be significantly downregulated in primary liver macrophages isolated from EtOH-fed mice and EtOH-induced RAW264.7 cells. Overexpression of PSTPIP2 using liver-specific recombinant AAV serotype 9 (rAAV9)-PSTPIP2 in EtOH-fed mice dramatically alleviated liver injury and inflammatory responses. In addition, silencing of PSTPIP2 aggravated the alcohol-induced inflammatory response in vitro. Mechanistically, PSTPIP2 might affect macrophage-induced inflammatory responses by regulating the STAT1 and NF-κB signaling pathways. The downregulation of PSTPIP2 in ALI may be associated with DNA methylation. Methylation-specific PCR and western blotting analyses showed that EtOH induced abnormal DNA methylation patterns and increased the protein expression levels of DNMT1, DNMT3a, and DNMT3b. The chromatin immunoprecipitation assay showed that DNMT3a could directly bind to the Pstpip2 promoter and act as a principal regulator of PSTPIP2 expression. Moreover, silencing of DNMT3a significantly restored the EtOH-induced low expression of PSTPIP2 and inhibited EtOH-induced inflammation. Overall, these findings provide a detailed understanding of the possible functions and mechanisms of PSTPIP2 in ALI, thus providing new substantive research to elucidate the pathogenesis of ALI and investigate potential targeted treatment strategies.

The iNKT Cell-Macrophage Axis in Homeostasis and Disease

Invariant natural killer T (iNKT) cells are CD1d-restricted, lipid-reactive T cells that exhibit preponderant immunomodulatory properties. The ultimate protective or deleterious functions displayed by iNKT cells in tissues are known to be partially shaped by the interactions they establish with other immune cells. In particular, the iNKT cell–macrophage crosstalk has gained growing interest over the past two decades. Accumulating evidence has highlighted that this immune axis plays central roles not only in maintaining homeostasis but also during the development of several pathologies. Hence, this review summarizes the reported features of the iNKT cell–macrophage axis in health and disease. We discuss the pathophysiological significance of this interplay and provide an overview of how both cells communicate with each other to regulate disease onset and progression in the context of infection, obesity, sterile inflammation, cancer and autoimmunity.

Lymphotoxin-β-receptor (LTβR) signaling on hepatocytes is required for liver regeneration after partial hepatectomy

Lymphotoxin-β-receptor deficient (LTβR-/-) and Tumor Necrosis Factor Receptor p55 deficient (TNFRp55-/-) mice show defects in liver regeneration (LR) after partial hepatectomy (PHx) with significantly increased mortality. LTβR and TNFRp55 belong to the core members of the TNF/TNFR superfamily. Interestingly, combined failure of LTβR and TNFRp55 signaling after PHx leads to a complete defect in LR. Here, we first addressed the question which liver cell population crucially requires LTβR signaling for efficient LR. To this end, mice with a conditionally targeted LTβR allele (LTβRfl/fl) were crossed to AlbuminCre and LysozymeMCre mouse lines to unravel the function of the LTβR on hepatocytes and monocytes/macrophages/Kupffer cells, respectively. Analysis of these mouse lines clearly reveals that LTβR is required on hepatocytes for efficient LR while no deficit in LR was found in LTβRfl/fl × LysMCre mice. Second, the molecular basis for the cooperating role of LTβR and TNFRp55 signaling pathways in LR was investigated by transcriptome analysis of etanercept treated LTβR-/- (LTβR-/-/ET) mice. Bioinformatic analysis and subsequent verification by qRT-PCR identified novel target genes (Cyclin-L2, Fas-Binding factor 1, interferon-related developmental regulator 1, Leucyl-tRNA Synthetase 2, and galectin-4) that are upregulated by LTβR/TNFRp55 signaling after PHx and fail to be upregulated after PHx in LTβR-/-/ET mice.

The response of two polar monocyte subsets to inflammation

Macrophages are a central component of innate immunity that play an important role in the defense of the organism. Macrophages are highly plastic and are activated by interaction with other cells and environmental factors. In this work, we study the effect of lipopolysaccharide on macrophages derived from the two most polar (CD14+ and CD16+ monocytes) as well as the intermediate subset of blood monocytes from healthy donors and assess what happens to the subset most prone to polarization on the transcriptomic and proteomic level. It has been shown that, according to primary pro-inflammatory polarization markers, their cytokine profile, and their phagocytic activity, macrophages derived from CD14+ monocytes exhibit higher sensitivity to inducers of pro-inflammatory polarization. Flow cytometry analysis revealed increased levels of CD86, while secretome analysis demonstrated significant increase of pro-inflammatory and anti-inflammatory cytokines observed in CD14+-derived macrophages, as compared to CD16+-derived macrophages in conditioned media. Assessment of the transcriptome and proteome of CD14+-derived macrophages with further bioinformatic analysis identified the most significant differences after polarization towards the pro-inflammatory phenotype. Immune-, membrane-, IFN-γ-, cytokine-, and defense-associated pathways were found significantly prevalent, while downregulated pathways were represented by RNA binding-, housekeeping-, exocytosis-, intracellular transport-, peptide and amide metabolic-related signaling. This data could be useful for macrophage-based cell therapeutics of cancer, as it provides additional background for the manipulation of donor monocytes intended for back transplantation.

Macrophage polarization by MSC-derived CXCL12 determines tumor growth

BACKGROUND

Phenotypic and functional heterogeneity of macrophages is known to be the main reason for their ability to regulate inflammation and promote tumorigenesis. Mesenchymal stem cells (MSCs) are one of the principal cells commonly found in the tumor stromal niche, with capability of macrophage phenotypic switching. The objective of this study was to evaluate the role of C-X-C motif chemokine ligand 12 (CXCL12) produced by marrow-derived MSCs in the phenotypic and functional pattern of bone marrow-derived macrophages (BMDMs).

METHODS

First, the CRISPR/Cas9 system was used for the CXCL12 gene knock-out in MSCs. Then, coculture systems were used to investigate the role of MSCsCXCL12-/- and MSCsCXCL12+/+ in determination of macrophage phenotype. To further analyze the role of the MSC-derived CXCL12 niche, cocultures of 4T1 mammary tumor cells and macrophages primed with MSCsCXCL12-/- or MSCsCXCL12+/+ as well as in-vivo limiting dilution assays were performed.

RESULTS

Our results revealed that the expression of IL-4, IL-10, TGF-β and CD206 as M2 markers was significantly increased in macrophages co-cultured with MSCsCXCL12+/+ , whereas the expression of IL-6, TNF-α and iNOS was conversely decreased. The number and size of multicellular tumor spheroids were remarkably higher when 4T1 cells were cocultured with MSCCXCL12+/+-induced M2 macrophages. We also found that the occurrence of tumors was significantly higher in coinjection of 4T1 cells with MSCCXCL12+/+-primed macrophages. Tumor initiating cells were significantly decreased after coinjection of 4T1 cells with macrophages pretreated with MSCsCXCL12-/-.

CONCLUSIONS

In conclusion, our findings shed new light on the role of MSC-derived CXCL12 in macrophage phenotypic switching to M2, affecting their function in tumorigenesis.

Macro- and microtranscriptomic evidence of the monocyte recruitment to regenerating liver after partial hepatectomy in mouse model

Macrophages are important regulators of liver repair. Participation of migratory monocytes/macrophages in regeneration of hepatic tissues after resection remains disputable. In mouse the resection promotes migration of Ly6C+CD11b+ monocytes/macrophages to the remnant liver accompanied by a reduction in its CD206 + macrophage content. Macrophage proliferation within the liver reaches maximum on day 3 after the surgery. Corresponding macro- and microtranscriptomic profiles of macrophages in regeneration liver cannot be unambiguously defined as pro- or anti-inflammatory. Their typical features include elevated expression of leukocyte chemoattractant factors, and many of the differentially expressed sequences are related to the control of cell growth and metabolic processes in the liver. These findings revealed essential roles of immigration of monocytes/macrophages and macrophages proliferation in maintenance of macrophage populations in the mouse liver during its recovery from a massive resection.

Endometriosis and Cancer: Exploring the Role of Macrophages

Endometriosis and cancer have much in common, notably their burgeoning of cells in hypoxic milieus, their invasiveness, and their capacity to trigger remodeling, vascularization, and innervation of other tissues. An important role in these processes is played by permissive microenvironments inhabited by a variety of stromal and immune cells, including macrophages. Remarkable phenotypical plasticity of macrophages makes them a promising therapeutic target; some key issues are the range of macrophage phenotypes characteristic of a particular pathology and the possible manners of its modulation. In both endometriosis and cancer, macrophages guard the lesions from immune surveillance while promoting pathological cell growth, invasion, and metastasis. This review article focuses on a comparative analysis of macrophage behaviors in endometriosis and cancer. We also highlight recent reports on the experimental modulation of macrophage phenotypes in preclinical models of endometriosis and cancer.

In Vivo and In Vitro Characterization of Primary Human Liver Macrophages and Their Inflammatory State

Liver macrophages (LMs) play a central role in acute and chronic liver pathologies. Investigation of these processes in humans as well as the development of diagnostic tools and new therapeutic strategies require in vitro models that closely resemble the in vivo situation. In our study, we sought to gain further insight into the role of LMs in different liver pathologies and into their characteristics after isolation from liver tissue. For this purpose, LMs were characterized in human liver tissue sections using immunohistochemistry and bioinformatic image analysis. Isolated cells were characterized in suspension using FACS analyses and in culture using immunofluorescence staining and laser scanning microscopy as well as functional assays. The majority of our investigated liver tissues were characterized by anti-inflammatory LMs which showed a homogeneous distribution and increased cell numbers in correlation with chronic liver injuries. In contrast, pro-inflammatory LMs appeared as temporary and locally restricted reactions. Detailed characterization of isolated macrophages revealed a complex disease dependent pattern of LMs consisting of pro- and anti-inflammatory macrophages of different origins, regulatory macrophages and monocytes. Our study showed that in most cases the macrophage pattern can be transferred in adherent cultures. The observed exceptions were restricted to LMs with pro-inflammatory characteristics.

Targeting macrophages in cancer immunotherapy

Immunotherapy is regarded as the most promising treatment for cancers. Various cancer immunotherapies, including adoptive cellular immunotherapy, tumor vaccines, antibodies, immune checkpoint inhibitors, and small-molecule inhibitors, have achieved certain successes. In this review, we summarize the role of macrophages in current immunotherapies and the advantages of targeting macrophages. To better understand and make better use of this type of cell, their development and differentiation characteristics, categories, typical markers, and functions were collated at the beginning of the review. Therapeutic strategies based on or combined with macrophages have the potential to improve the treatment efficacy of cancer therapies.

Evolution of Regeneration in Animals: A Tangled Story

The evolution of regenerative capacity in multicellular animals represents one of the most complex and intriguing problems in biology. How could such a seemingly advantageous trait as self-repair become consistently attenuated by the evolution? This review article examines the concept of the origin and nature of regeneration, its connection with the processes of embryonic development and asexual reproduction, as well as with the mechanisms of tissue homeostasis. The article presents a variety of classical and modern hypotheses explaining different trends in the evolution of regenerative capacity which is not always beneficial for the individual and notably for the species. Mechanistically, these trends are driven by the evolution of signaling pathways and progressive restriction of differentiation plasticity with concomitant advances in adaptive immunity. Examples of phylogenetically enhanced regenerative capacity are considered as well, with appropriate evolutionary reasoning for the enhancement and discussion of its molecular mechanisms.

Macrophage Modification Strategies for Efficient Cell Therapy

Macrophages, important cells of innate immunity, are known for their phagocytic activity, capability for antigen presentation, and flexible phenotypes. Macrophages are found in all tissues and therefore represent an attractive therapeutic target for the treatment of diseases of various etiology. Genetic programming of macrophages is an important issue of modern molecular and cellular medicine. The controllable activation of macrophages towards desirable phenotypes in vivo and in vitro will provide effective treatments for a number of inflammatory and proliferative diseases. This review is focused on the methods for specific alteration of gene expression in macrophages, including the controllable promotion of the desired M1 (pro-inflammatory) or M2 (anti-inflammatory) phenotypes in certain pathologies or model systems. Here we review the strategies of target selection, the methods of vector delivery, and the gene editing approaches used for modification of macrophages.

The Bile Acid Receptor GPBAR1 Modulates CCL2/CCR2 Signaling at the Liver Sinusoidal/Macrophage Interface and Reverses Acetaminophen-Induced Liver Toxicity

Drug-induced liver injury caused by acetaminophen (acetyl-para-aminophenol [APAP]) is the main cause of acute liver failure and liver transplantation in several Western countries. Whereas direct toxicity exerted by APAP metabolites is a key determinant for early hepatocytes injury, the recruitment of cells of innate immunity exerts a mechanistic role in disease progression, determining the clinical outcomes. GPBAR1 is a G protein-coupled receptor for secondary bile acids placed at the interface between liver sinusoidal cells and innate immunity. In this report, using genetic and pharmacological approaches, we demonstrate that whereas Gpbar1 gene deletion worsens the severity of liver injury, its pharmacological activation by 6β-ethyl-3a,7b-dihydroxy-5b-cholan-24-ol rescues mice from liver injury caused by APAP. This protective effect was supported by a robust attenuation of liver recruitment of monocyte-derived macrophages and their repolarization toward an anti-inflammatory phenotype. Macrophage depletion by gadolinium chloride pretreatment abrogated disease development, whereas their reconstitution by spleen-derived macrophage transplantation restored the sensitivity to APAP in a GPBAR1-dependent manner. RNA sequencing analyses demonstrated that GPBAR1 agonism modulated the expression of multiple pathways, including the chemokine CCL2 and its receptor, CCR2. Treating wild-type mice with an anti-CCL2 mAb attenuated the severity of liver injury. We demonstrated that negative regulation of CCL2 production by GPBAR1 agonism was promoter dependent and involved FOXO1. In conclusion, we have shown that GPBAR1 is an upstream modulator of CCL2/CCR2 axis at the sinusoidal cell/macrophage interface, providing a novel target in the treatment of liver damage caused by APAP.

IL-4 Alleviates Ischaemia-Reperfusion Injury by Inducing Kupffer Cells M2 Polarization via STAT6-JMJD3 Pathway after Rat Liver Transplantation

Background

Liver ischaemia-reperfusion injury (IRI) remains a problem in liver transplantation. Interleukin-4 (IL-4) has been found to reduce liver IRI, but the exact mechanism remains unclear.

Methods

Donor livers were infused with recombinant IL-4 or normal saline during cold storage, and the hepatocellular apoptosis and the inflammatory response were detected. The effect of IL-4 treatment on Kupffer cells (KCs) polarization and expression of the STAT6-JMJD3 pathway was evaluated in vivo and in vitro. KCs in donor livers were depleted by clodronate liposome treatment or JMJD3 was inhibited by GSK-J4 before liver transplantation to determine whether the protective effect of IL-4 treatment was dependent on KCs.

Results

IL-4 treatment decreased sALT and sAST levels and alleviated hepatocellular apoptosis and inflammation at 6 h after liver transplantation. IL-4 treatment induced KCs alternatively activated (M2) polarization in vitro. KCs in donor livers were depleted by clodronate liposome treatment or JMJD3 was inhibited by GSK-J4 before liver transplantation to determine whether the protective effect of IL-4 treatment was dependent on KCs. in vivo and in vitro. KCs in donor livers were depleted by clodronate liposome treatment or JMJD3 was inhibited by GSK-J4 before liver transplantation to determine whether the protective effect of IL-4 treatment was dependent on KCs.

Conclusions

IL-4 treatment-induced KCs M2 polarization was dependent on the STAT6-JMJD3 pathway and protected liver grafts from IRI after liver transplantation.

Kupffer Cells: Important Participant of Hepatic Alveolar Echinococcosis

Aims: Kupffer cells (KCs) are the liver-resident macrophages and play a leading role in the regulation of liver homeostasis in physiological conditions and in pathology. The study aims to investigate the anti-echinococcosis effect of KCs and the effects of hepatic stellate cells (HSCs) activation in the progression of liver fibrosis in hepatic alveolar echinococcosis (hepatic AE).

Methods: Hematoxylin—eosin (H&E) and Masson staining were used to assess the pathological inflammatory changes and collagen deposition, respectively. Immunohistochemistry and qRT-PCR were used to detect the number of aggregates of KCs, the expression of cytokines and activation of HSCs.

Results: In the close group, H&E staining showed that the normal lobular structure was destroyed and inflammatory infiltration around the lesion could be observed, and Masson staining showed that blue collagen fibers were clearly deposited near the portal area. IHC showed that KCs surface markers CD68 and CD163, cytokine iNOS and Arg-1 were positively expressed in the vicinity of inflammatory lesions. qRT-PCR indicated that TNF-α, IL-10, and TGF-β1 secreted by KCs were significantly higher than those in the distance group (P < 0.01). It is worth noticing that the expression levels of anti-inflammatory cytokines were slightly higher than that of pro-inflammatory cytokines. Both IHC and qRT-PCR results showed that HSCs activation markers, the expression of α-SMA and Desmin significantly increased.

Conclusions: Our research indicates that KCs have immune-protective effect of anti-echinococcosis and promote liver fiber repair, and it also suggests that they have potential therapeutic value for patients with hepatic AE.

Are Liver Pericytes Just Precursors of Myofibroblasts in Hepatic Diseases? Insights from the Crosstalk between Perivascular and Inflammatory Cells in Liver Injury and Repair

Cirrhosis, a late form of liver disease, is characterized by extensive scarring due to exacerbated secretion of extracellular matrix proteins by myofibroblasts that develop during this process. These myofibroblasts arise mainly from hepatic stellate cells (HSCs), liver-specific pericytes that become activated at the onset of liver injury. Consequently, HSCs tend to be viewed mainly as myofibroblast precursors in a fibrotic process driven by inflammation. Here, the molecular interactions between liver pericytes and inflammatory cells such as macrophages and neutrophils at the first moments after injury and during the healing process are brought into focus. Data on HSCs and pericytes from other tissues indicate that these cells are able to sense pathogen- and damage-associated molecular patterns and have an important proinflammatory role in the initial stages of liver injury. On the other hand, further data suggest that as the healing process evolves, activated HSCs play a role in skewing the initial proinflammatory (M1) macrophage polarization by contributing to the emergence of alternatively activated, pro-regenerative (M2-like) macrophages. Finally, data suggesting that some HSCs activated during liver injury could behave as hepatic progenitor or stem cells will be discussed.

Macrophages in Zebrafish Models of Liver Diseases

Hepatic macrophages are key components of the liver immunity and consist of two main populations. Liver resident macrophages, known as Kupffer cells in mammals, are crucial for maintaining normal liver homeostasis. Upon injury, they become activated to release proinflammatory cytokines and chemokines and recruit a large population of inflammatory monocyte-derived macrophages to the liver. During the progression of liver diseases, macrophages are highly plastic and have opposing functions depending on the signaling cues that they receive from the microenvironment. A comprehensive understanding of liver macrophages is essential for developing therapeutic interventions that target these cells in acute and chronic liver diseases. Mouse studies have provided the bulk of our current knowledge of liver macrophages. The emergence of various liver disease models and availability of transgenic tools to visualize and manipulate macrophages have made the teleost zebrafish (Danio rerio) an attractive new vertebrate model to study liver macrophages. In this review, we summarize the origin and behaviors of macrophages in healthy and injured livers in zebrafish. We highlight the roles of macrophages in zebrafish models of alcoholic and non-alcoholic liver diseases, hepatocellular carcinoma, and liver regeneration, and how they compare with the roles that have been described in mammals. We also discuss the advantages and challenges of using zebrafish to study liver macrophages.