Activation of stem cells in hepatic diseases

Novel Therapeutic Approaches in Treatment of Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF), a clinical syndrome that can develop at any stage in the progression of cirrhotic liver disease, is characterized by an acute decompensation in liver function with associated multiorgan failure and high short-term mortality. Current evidence points to ACLF being reversible, particularly in those at the lower end of the severity spectrum. However, there are no specific treatments for ACLF, and overall outcomes remain poor. Expedited liver transplantation as a treatment option is limited by organ shortage and a lack of priority allocation for this indication. Other options are therefore urgently needed, and our improved understanding of the condition has led to significant efforts to develop novel therapies. In conclusion, this review aims to summarize the current understanding of the pathophysiological processes involved in the onset, progression, and recovery of ACLF and discuss novel therapies under development.

Efficacy of Granulocyte Colony-Stimulating Factor in Acute on Chronic Liver Failure: A Systematic Review and Survival Meta-Analysis

BACKGROUND

Acute-on-chronic liver failure (ACLF) mostly occurs when there is an acute insult to the liver in patients with pre-existing liver disease, and it is characterized by a high mortality rate. Various therapeutic approaches have been used thus far, with orthotopic liver transplantation being the only definitive cure. Clinical trials and meta-analyses have investigated the use of granulocyte colony-stimulating factor (G-CSF) to mobilize bone marrow-derived stem cells. Some studies have suggested that G-CSF may have a significant role in the management and survival of patients with ACLF. However, the results are conflicting, and the efficacy of G-CSF still needs to be confirmed.

AIM

The aim was to assess the efficacy of G-CSF in patients with ACLF.

METHODS

Electronic databases were searched until May 2023 for randomized controlled trials investigating the use of G-CSF in adult patients with ACLF. Outcome measures were the effects of G-CSF on overall survival, changes in liver disease severity scores, complications of cirrhosis, other G-CSF-related adverse effects, and all-cause mortality. The study's protocol has been registered with Prospero (CRD42023420273).

RESULTS

Five double-blind randomized controlled trials involving a total of 421 participants met the inclusion criteria. The use of G-CSF demonstrated a significant effect on overall survival (HR 0.63, 95% CI 0.41 to 0.95, and I2 48%), leading to a decreased mortality (LogOR-0.97, 95% CI -1.57 to -0.37, and I2 37.6%) and improved Model for End-Stage Liver Disease (MELD) scores (SMD -0.87, 95% CI -1.62 to -0.13, and I2 87.3%). There was no correlation between the improvement of the Child-Pugh score and the use of G-CSF(SMD -2.47, 95% CI -5.78 to 0.83, and I2 98.1%). The incidence of complications of cirrhosis did not decrease significantly with G-CSF treatment (rate ratio 0.51, 95% CI 0.26 to 1.01, and I2 90%). A qualitative synthesis showed that the use of G-CSF is safe.

CONCLUSIONS

The administration of G-CSF has demonstrated a positive impact on overall survival, liver function, and the MELD score. The presence of heterogeneity in the included studies prohibits conclusive recommendations.

In Vitro Generated Equine Hepatic-Like Progenitor Cells as a Novel Potent Cell Pool for Equine Metabolic Syndrome (EMS) Treatment

Equine metabolic syndrome (EMS) is recognized as one of the leading cause of health threatening in veterinary medicine worldwide. Recently, PTP1B inhibition has been proposed as an interesting strategy for liver insulin resistance reversion in both equines and humans, however as being a multifactorial disease, proper management of EMS horses further necessities additional interventional approaches aiming at repairing and restoring liver functions. In this study, we hypothesized that in vitro induction of Eq_ASCs hepatogenic differentiation will generate a specialized liver progenitor-like cell population exhibiting similar phenotypic characteristics and regenerative potential as native hepatic progenitor cells. Our obtained data demonstrated that Eq_ASCs-derived liver progenitor cells (Eq_HPCs) displayed typical flattened polygonal morphology with packed fragmented mitochondrial net, lowered mesenchymal CD105 and CD90 surface markers expression, and significant high expression levels of specific hepatic lineage genes including PECAM-1, ALB, AFP and HNF4A. therewith, generated Eq_HPCs exhibited potentiated stemness and pluripotency markers expression (NANOG, SOX-2 and OCT-4). Hence, in vitro generation of hepatic progenitor-like cells retaining high differentiation capacity represents a promising new approach for the establishment of cell-based targeted therapies for the restoration of proper liver functions in EMS affected horses.

Alcohol and Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is a clinical syndrome that occurs in patients with cirrhosis and is characterised by acute deterioration, organ failure and high short-term mortality. Alcohol is one of the leading causes of ACLF and the most frequently reported aetiology of underlying chronic liver disease. Among patients with alcoholic hepatitis (AH), ACLF is a frequent and severe complication. It is characterised by both immune dysfunction associated to an increased risk of infection and high-grade systemic inflammation that ultimately induce organ failure. Diagnosis and severity of ACLF determine AH prognosis, and therefore, ACLF prognostic scores should be used in severe AH with organ failure. Corticosteroids remain the first-line treatment for severe AH but they seem insufficient when ACLF is associated. Novel therapeutic targets to contain the excessive inflammatory response and reduce infection have been identified and are under investigation. With liver transplantation remaining one of the most effective therapies for severe AH and ACLF, adequate organ allocation represents a growing challenge. Hence, a clear understanding of the pathophysiology, clinical implications and management strategies of ACLF in AH is essential for hepatologists, which is narrated briefly in this review.

A review of hepatic fibrosis-associated histopathology in aged cadavers

This article reviews hepatic fibrosis-associated histopathology of aged cadavers (mean age 82 years). A study of 68 livers identified steatosis in 35.5%, central vein fibrosis in 49.2%, perisinusoidal fibrosis in 63.2%, portal tract fibrosis in 47.7%, septa formation in 44.1%, bridging fibrosis in 30.8%, and cirrhosis in 4.4% of the samples as well as one hepatocellular carcinoma and six metastatic tumors. Other studies have revealed that collagens I, III, IV, V, and VI and fibronectin constitute the matrices of fibrous central veins, perisinusoidal space, portal tracts, and septa. Elastin is rich in portal tracts and fibrous septa but absent from the perisinusoidal space. Hepatic stellate cells are ubiquitous in the liver parenchyma while myofibroblasts localize in fibrotic foci. Factor VIII-related antigen expression signals sinusoidal to systemic vascular endothelium transformation while collagen IV and laminin codistribution indicates formation of perisinusoidal membranes. Their coincidence reflects focalized capillarization of sinusoids in the aged liver. In response to fibrogenesis, hepatic progenitor cells residing in the canal of Hering in the periportal parenchyma undergo expansion and migration deep into the lobule. Concomitantly, intermediate hepatocyte-like cells increase in advanced fibrosis stages, which is possibly related to hepatic regeneration. Metabolic zonation of glutamine synthetase expands from the perivenous to non-perivenous parenchyma in fibrosis progression but its expression is lost in cirrhosis, while cytochrome P-4502E1 expression is maintained in centrilobular and midlobular zones in fibrosis progression and expressed in cirrhosis. Hence, cadaveric livers provide a platform for further investigation of hepatic histopathologies associated with the aging liver.

Oncological transformation in vitro of hepatic progenitor cell lines isolated from adult mice

Colorectal cancer cells can transfer the oncogene KRAS to distant cells, predisposing them to malignant transformation (Genometastasis Theory). This process could contribute to liver metastasis; besides, hepatic progenitor cells (HPCs) have been found to be involved in liver malignant neoplasms. The objective of this study is to determine if mouse HPCs—Oval cells (OCs)—are susceptible to incorporate Kras GAT (G12D) mutation from mouse colorectal cancer cell line CT26.WT and if OCs with the incorporated mutation behave like malignant cells. To achieve this, three lines of OCs in different conditions were exposed to CT26.WT cells through transwell co-culture for a week. The presence of Kras^G12D and capacity to form tumors were analyzed in treated samples by droplet digital PCR and colony-forming assays, respectively. The results showed that the Kras^G12D mutation was detected in hepatic culture conditions of undifferentiated OCs and these cells were capable of forming tumors in vitro. Therefore, OCs are susceptible to malignant transformation by horizontal transfer of DNA with Kras^G12D mutation in an undifferentiated condition associated with the liver microenvironment. This study contributes to a new step in the understanding of the colorectal metastatic process.

Novel drug discovery strategies for the treatment of decompensated cirrhosis

INTRODUCTION

Disease progression in cirrhosis leads to decompensation and acute-on-chronic liver failure (ACLF), which is characterized by organ failure and high mortality. Portal hypertension and cardiovascular dysfunction trigger the development of cirrhosis-related complications whilst tissue injury and cellular metabolic dysfunction lead to organ failure. System inflammation is the overarching mechanism mediating both the transition from compensation to decompensation as well as progression to ACLF. Treatment of precipitating events and intensive organ support is the only established therapeutic strategies. Liver transplantationrepresents the only curative therapy but contraindications and organ scarcity limit its availability to only a minority of patients with end-stage liver disease. Therefore, the discovery and development of novel interventions modifying the disease course and improving patients' outcome are of utmost importance.

AREAS COVERED

This review highlights and discusses therapeutic novelties in the field of end-stage liver disease.

EXPERT OPINION

Despite decades of research, there are still no established therapies to improve the devastating prognosis of patients with end-stage liver disease. The clinical heterogeneity and complex pathogenesis will put high demands on drug discovery. Combinatorial therapies tailored to the patients' individual pattern of pathomechanisms may be the most efficient way to modify disease course.

The Current Status of Granulocyte-Colony Stimulating Factor to Treat Acute-on-Chronic Liver Failure

Patients with acute-on-chronic liver failure (ACLF) have a devastating prognosis and therapeutic options are limited. Granulocyte-colony stimulating factor (G-CSF) mobilizes immune and stem cells and possess immune-modulatory and proregenerative capacities. In this review, we aim to define the current evidence for the treatment with G-CSF in end-stage liver disease. Several smaller clinical trials in patients with different severity grades of end-stage liver disease have shown that G-CSF improves survival and reduces the rate of complications. Adequately powered multicenter European trials could not confirm these beneficial effects. In mouse models of ACLF, G-CSF increased the toll-like receptor (TLR)-mediated inflammatory response which led to an increase in mortality. Adding a TLR4 signaling inhibitor allowed G-CSF to unfold its proregenerative properties in these ACLF models. These data suggest that G-CSF requires a noninflammatory environment to exert its protective properties.

Bone Marrow-Derived Mesenchymal Stem Cells Isolated from Patients with Cirrhosis and Healthy Volunteers Show Comparable Characteristics

Background and Objectives

Autologous or allogeneic bone marrow-derived mesenchymal stem cells (BMSCs) have been applied in clinical trials to treat liver disease. However, only a few studies are comparing the characteristics of autologous MSCs from patients and allogeneic MSCs from normal subjects.

Methods and Results

We compared the characteristics of BMSCs (BCs and BPs, respectively) isolated from six healthy volunteers and six patients with cirrhosis. In passage 3 (P3), senescent population and expression of p53 and p21 were slightly higher in BPs, but the average population doubling time for P3–P5 in BPs was approximately 65.3±11.1 h, which is 18.4 h shorter than that in BCs (83.7±9.2 h). No difference was observed in the expression of CD73, CD90, or CD105 between BCs and BPs. Adipogenic differentiation slightly increased in BCs, but the expression levels of leptin, peroxisome proliferator-activated receptor γ, and CCAAT-enhancer-binding protein α did not vary between differentiated BCs and BPs. While ATP and reactive oxygen species levels were slightly lower in BPs, mitochondrial membrane potential, oxygen consumption rate, and expression of mitochondria-related genes such as cytochrome c oxidase 1 were not significantly different between BCs and BPs.

Conclusions

Taken together, there are marginal differences in the proliferation, differentiation, and mitochondrial activities of BCs and BPs, but both BMSCs from patients with cirrhosis and healthy volunteers show comparable characteristics.

Cell Therapy for Liver Disease: From Promise to Reality

Over the last decade, there has been a considerable progress in the development of cell therapy products for the treatment of liver diseases. The quest to generate well-defined homogenous cell populations with defined mechanism(s) of action has enabled the progression from use of autologous bone marrow stem cells comprising of heterogeneous cell populations to allogeneic cell types such as monocyte-derived macrophages, regulatory T cells, mesenchymal stromal cells, macrophages, etc. There is growing evidence regarding the multiple molecular mechanisms pivotal to various therapeutic effects and hence, careful selection of cell therapy product for the desired putative effects is crucial. In this review, we have presented an overview of the cell therapies that have been developed thus far, with preclinical and clinical evidence for their use in liver disease. Limitations associated with these therapies have also been discussed. Despite the advances made, there remain multiple challenges to overcome before cell therapies can be considered as viable treatment options, and these include larger scale clinical trials, scalable production of cells according to good manufacturing practice standards, pathways for delivery of cell therapy within hospital environments, and costs associated with the production.

Effect of hepato-toxins in the acceleration of hepatic fibrosis in hepatitis B mice

Chronic liver diseases such as hepatitis B viral (HBV) infection and liver fibrosis have been a major health problem worldwide. However, less research has been conducted owing to the lack of animal models. The key purpose of this study was to determine the effects of different hepatotoxins in HBV-affected liver. In this study, we successfully generated a combined liver fibrosis model by administering HBV 1.2 plasmid and thioacetamide/ethanol (TAA/EtOH). To our knowledge, this is the first study in which an increase in the liver fibrosis level is observed by the intraperitoneal administration of TAA and EtOH in drinking water after the hydrodynamic transfection of the HBV 1.2 plasmid in C3H/HeN mice. The HBV+TAA/EtOH group exhibited higher level of hepatic fibrosis than that of the control groups. The hepatic stellate cell activation in the TAA- and EtOH-administered groups was demonstrated by the elevation in the level of fibrotic markers. In addition, high levels of collagen content and histopathological results were also used to confirm the prominent fibrotic levels. We established a novel HBV mice model by hydrodynamic injection-based HBV transfection in C3H/HeN mice. C3H/HeN mice were reported to have a higher HBV persistence level than that of the C57BL/6 mouse model. All the results showed an increased fibrosis level in the HBV mice treated with TAA and EtOH; hence, this model would be useful to understand the effect of hepatotoxins on the high risk of fibrosis after HBV infection. The acceleration of liver fibrosis can occur with prolonged administration as well as the high dosage of hepatotoxins in mice.

Mesenchymal stem cells to treat liver diseases

Mesenchymal stem cells (MSCs) are being developed for stem cell therapy and can be efficiently used in regenerative medicine. To date, more than 1,000 clinical trials have used MSCs; of these, more than 80 clinical trials have targeted liver disease. MSCs migrate to damaged liver tissues, differentiate into hepatocytes, reduce liver inflammatory responses, reduce liver fibrosis, and act as antioxidants. According to the reported literature, MSCs are safe, have no side effects, and improve liver function; however, their regenerative therapeutic effects are unsatisfactory. Here, we explain, in detail, the basic therapeutic effects and recent clinical advances of MSCs. Furthermore, we discuss future research directions for improving the regenerative therapeutic effects of MSCs.

Serum Levels of Granulocyte-Macrophage-colony-stimulating Factor and Stem-cell Factor During Liver Regeneration after Partial Hepatectomy in Humans

BACKGROUND

Multiple biological functions have been recognized regarding Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) and Stem Cell Factor (SCF).

AIM

To evaluate the serum changes of GM-CSF and SCF in patients undergoing surgical resection for liver tumor, in the regenerative phase after surgery in order to identify the possible relationship with the patient, tumor or surgical variables.

METHODS

Thirty-two consecutive patients (50% male, median age 66), undergoing hepatic resection of liver neoplasm, were evaluated. The liver tumor was Hepatocellular Carcinoma (HCC) in 44% of cases. Other tumors were cholangiocarcinoma and metastasis. Serum levels of GM-CSF and SCF were assessed at baseline and 2 days, 7 days and 4 weeks after surgery. Personal and clinical patient data were also recorded. The statistical analysis was carried out using t-test for unpaired data or ANOVA (repeated measure) for continuous variables and Fisher test for discrete variables.

RESULTS

GM-CSF levels remained constant after surgery and were compared to baseline values. SCF levels, on the other hand, increased during the time, after surgery. The evaluation of SCF levels (fold increase) according to surgical, patient and tumor variables evidenced some differences. At day 7 and week 4, SCF levels were statistically increased: i) in patients undergoing a large resection in comparison with others (p<0.05); ii) in patients non-cirrhotic in comparison with cirrhotic ones (p=0.02) and finally; iii) in patients with non-HCC tumor in comparison with HCC ones (p=0.02).

CONCLUSION

During liver regeneration in humans, SCF serum levels are increased allowing to hypothesize a possible role of this chemokine during tissue growth and remodeling.

Tannic acid and vitamin E loaded PLGA nanoparticles ameliorate hepatic injury in a chronic alcoholic liver damage model via EGFR-AKT-STAT3 pathway

Aim: Tannic acid and vitamin E loaded-poly D, L-lactide-co-glycolic acid (PLGA) nanoparticles (NP) were developed to achieve hepatoprotection in alcoholic liver disease mice model. Materials & methods: PLGA NPs were formed by emulsion solvent evaporation and characterized and delivered to mice. Histology studies were performed, serum enzyme levels of AST, ALT and inflammatory cytokines were checked using ELISA kits. Confocal microscopy and western blot analysis were utilized to determine protein expression levels, and docking studies were performed for interaction analysis. Results: PLGA NPs provided hepatoprotection by reducing inflammatory load, preventing reactive oxygen species generation and apoptosis, as well as by inhibiting the EGFR-AKT-STAT3 pathway. Conclusion: PLGA NPs of tannic acid and vitamin E could be a future medication for alcoholic liver disease treatment.

IL-8 induces transdifferentiation of mature hepatocytes toward the cholangiocyte phenotype

The adult mammalian liver exhibits a remarkable regenerative capacity, with different modes of regeneration according to the type and extent of injury. Hepatocyte–cholangiocyte biphenotypic liver progenitor cell populations appear under conditions of excessive injury. It has been reported that mature hepatocytes can transdifferentiate toward a cholangiocyte phenotype and be a cellular source of progenitor cell populations. Here, we determined that among various plasma cytokines, interleukin (IL)‐8 levels were significantly elevated in acute liver failure and severe acute liver injury patients. In vitro assays revealed that administration of IL‐8 homologues increases the expression of Sry HMG box protein 9 (SOX9). In liver biopsies of acute liver injury patients, we observed the appearance of SOX9‐positive biphenotypic hepatocytes accompanied by elevation of plasma IL‐8 levels. Our results suggest that IL‐8 regulates the phenotypic conversion of mature hepatocytes toward a cholangiocyte phenotype.

Interleukin (IL)‐8 treated mouse mature hepatocytes expressed Sry HMG box protein 9 (SOX9), a bile duct‐associated marker. In liver biopsies of acute liver injury patients, SOX9‐positive biphenotypic hepatocytes appeared in the liver parenchyma which is accompanied by elevation of plasma IL‐8 levels. Our results suggest that IL‐8 regulates the phenotypic conversion of mature hepatocytes toward a cholangiocyte phenotype.

Cellular and functional loss of liver endothelial cells correlates with poor hepatocyte regeneration in acute-on-chronic liver failure

BACKGROUND AND AIM

Acute hepatic insult triggers regeneration. If acute-on-chronic liver failure (ACLF) patients have a poorer regenerative response than acute liver failure (ALF) patients, and if so, the mechanisms underlying this, are not well understood.

METHODS

We investigated the status of hepatocyte proliferation, hepatic progenitor cell (HPC) mediated regeneration, non-parenchymal cells (through immunohistochemistery), cytokines and growth factors (cytokine bead array) in liver and peripheral blood of ACLF (n = 29) and ALF (n = 17) patients. Liver endothelial cells, mesenchymal cells and Kupffer cells were isolated from explant livers and analysis of regenerative factors was done by qRT-PCR.

RESULTS

Unlike ALF, the ACLF livers showed decreased hepatocyte proliferation (p < 0.001) and profound ductular-reaction with increased CK19 + hepatocytes (p < 0.0001). However, only decrease in Ki67+ hepatocytes was associated with 28 day mortality in ACLF (p < 0.001; HR = 0.78; 95% CI 0.69-0.88). In both groups, increase in plasma hepatocyte growth factor (HGF) (OR = 21.87 p = 0.002;), macrophage colony stimulating factor (MCSF) (OR = 21.73; p = 0.002) and stromal derived factor (SDF1)(OR = 10.2; p = 0.001) were associated with hepatocyte proliferation and decreased (> fivefolds) levels were associated with poor hepatocyte regeneration in ACLF patients. ACLF livers showed decrease in endothelial cells (p < 0.01) and expression of regenerative angiocrine factors C-X-C chemokine receptor type 7 (CXCR7), Inhibitor of DNA Binding 1(IDI) and HGF compared to ALF. In co-culture, while ALF liver mesenchymal stromal cells (LMSCs) induced the expression of CXCR7, IDI and HGF in human umbilical cord endothelial cells (HUVECs), the ACLF LMSCs were defective and showed decreased production of SDF-1, HGF and MCSF compared to ALF.

CONCLUSIONS

Decrease in hepatic endothelial cells and their regenerative angiocrine functions indicated by defective CXCR7-ID1 dependent HGF expression underlie the poor hepatocyte proliferation in ACLF compared to ALF patients. A robust hepatocyte self-replication is lacking in the livers of ACLF patients and is associated with poor survival.

Development and validation of a primate model for liver fibrosis

INTRODUCTION

Many liver diseases involve liver fibrosis. Most preclinical studies of liver fibrosis are carried out in small animals such as rodents, and thus lack direct potential for extrapolation to human diseases. The aim of the current study was to develop a primate model for liver fibrosis with greater relevance to translational research.

METHODS

Liver fibrosis was induced in adult male healthy rhesus monkeys using repeated CCl₄ treatment (40% in olive oil, 1.5 ml/kg once every 3 days via peritoneal injection, subcutaneous injection or gastric gavage). Liver biopsy was conducted at various time points for histologic examination. Blood samples were taken for standard liver function test.

RESULTS

Gastric gavage was the optimal approach for establishing stably liver fibrosis without animal loss due to toxicity. The progression of fibrosis appeared to involve epithelial to mesenchymal transition and hepatic ductular reaction.

CONCLUSION

Repeated CCl₄ gavage in rhesus monkeys results in stable liver fibrosis. Such a model may be an effective platform for future studies of human liver fibrosis.

Histopathological and Ultrastructural Changes after Electroporation in Pig Liver Using Parallel-Plate Electrodes and High-Performance Generator

Irreversible electroporation (IRE) has gained attention as a new non-thermal therapy for ablation with important benefits in terms of homogeneous treatment and fast recovery. In this study, a new concept of high voltage generator is used, enabling irreversible electroporation treatment in large tissue volume using parallel plates. Unlike currently available generators, the proposed versatile structure enables delivering high-voltage high-current pulses. To obtain homogeneous results, 3-cm parallel-plates electrodes have also been designed and implemented. IRE ablation was performed on six female pigs at 2000 V/cm electric field, and the results were analysed after sacrifice three hours, three days and seven days after ablation. Histopathological and ultrastructural studies, including transmission and scanning electron microscopy, were carried out. The developed high-voltage generator has proved to be effective for homogeneous IRE treatment using parallel plates. The destruction of the membrane of the hepatocytes and the alterations of the membranes of the cellular organelles seem incompatible with cell death by apoptosis. Although endothelial cells also die with electroporation, the maintenance of vascular scaffold allows repairing processes to begin from the third day after IRE as long as the blood flow has not been interrupted. This study has opened new direction for IRE using high performance generators and highlighted the importance of taking into account ultrastructural changes after IRE by using electron microscopy analysis.

Tracking iron oxide labelled mesenchymal stem cells(MSCs) using magnetic resonance imaging (MRI) in a rat model of hepatic cirrhosis

Homing and tumor attenuation potential of BM-MSCs labelled with superparamagnetic iron-oxide nanoparticles (SPIONs) in a rat model of hepatic cirrhosis was evaluated. Rat BM-MSCs were derived, characterized and labelled with SPIONs (200 nm; 25 mg Fe/ml). Hepatic cirrhosis was induced in Wistar rats (n=30; 10/group) with carbon tetrachloride (CCl4; 0.3 mL/kg body weight) injected twice a week for 12 weeks. Group-I was administered vehicle (castor-oil) alone; Group-II received two doses of unlabelled BM-MSCs (3x106 cells) and Group-III received two doses of SPIONs labelled BM-MSCs (3x106 cells) via tail vein injection (0.5 ml) at weekly intervals. All animals were sacrificed after two weeks for histological, radiological and biochemical analysis. Derived BM-MSCs demonstrated MSCs related CD markers. Histology confirmed induction of hepatic cirrhosis with CCL4. Levels of alanine-aminotransferase, aspartate-aminotransferase,alkaline-phosphatase and gamma glutamyl-transferase returned to normal levels following treatment with BM-MSCs. Uptake and homing of SPIONs labelled BM-MSCs, and reduction in the size of cirrhotic nodules were confirmed using transmission electron microscopy and magnetic resonance imaging respectively. BM-MSCs reduced the pathological effects of CCL4 induced hepatic cirrhosis and labelling BMMSCs with SPIONs were non-toxic and enabled efficient tracking using non-invasive methods.

Immunomodulatory Functions of Mesenchymal Stem Cells in Tissue Engineering

The inflammatory response to chronic injury affects tissue regeneration and has become an important factor influencing the prognosis of patients. In previous stem cell treatments, it was revealed that stem cells not only have the ability for direct differentiation or regeneration in chronic tissue damage but also have a regulatory effect on the immune microenvironment. Stem cells can regulate the immune microenvironment during tissue repair and provide a good "soil" for tissue regeneration. In the current study, the regulation of immune cells by mesenchymal stem cells (MSCs) in the local tissue microenvironment and the tissue damage repair mechanisms are revealed. The application of the concepts of "seed" and "soil" has opened up new research avenues for regenerative medicine. Tissue engineering (TE) technology has been used in multiple tissues and organs using its biomimetic and cellular cell abilities, and scaffolds are now seen as an important part of building seed cell microenvironments. The effect of tissue engineering techniques on stem cell immune regulation is related to the shape and structure of the scaffold, the preinflammatory microenvironment constructed by the implanted scaffold, and the material selection of the scaffold. In the application of scaffold, stem cell technology has important applications in cartilage, bone, heart, and liver and other research fields. In this review, we separately explore the mechanism of MSCs in different tissue and organs through immunoregulation for tissue regeneration and MSC combined with 3D scaffolds to promote MSC immunoregulation to repair damaged tissues.

Liver Macrophage Depletion Ameliorates The Effect of Mesenchymal Stem Cell Transplantation in a Murine Model of Injured Liver

Mesenchymal stem cells (MSCs) therapy show different levels of effectiveness in the context of different types of liver damage, suggesting that the microenvironment of the injured liver is a key determinant for effective stem cell therapy. The objective was to assess the modulatory effect of hepatic stem cell niche components on the transplanted MSCs during liver injury induced by carbon tetrachloride (CCl₄). Superparamagnetic iron oxide (SPIO)-labeled human MSCs were injected intravenously into mice treated with CCl₄ and subjected to hepatic macrophage-depletion. Liver tissues were collected at different intervals post transplantation for subsequent histopathological, morphometric, immunohistochemical, gene expression and ultrastructural studies. The homing of the transplanted MSCs was evidenced by tracing them within the niche by iron staining and immunohistochemical studies. MSCs differentiated into hepatocyte-like cells and intimal smooth muscle cells as evidenced by their expression of human albumin and α-smooth muscle actin with a concomitant increase in the level of mouse hepatocyte growth factor. A post transplantation reduction in the liver fibro-inflammatory reaction was found and was promoted by liver macrophages depletion. Thus, it could be concluded from the present study that prior manipulation of the microenvironment is required to improve the outcome of the transplanted cells.

HBV induces different responses of the hepatocytes and oval cells during HBV-related hepatic cirrhosis

Although hepatitis B virus (HBV)-related cirrhosis and hepatocellular carcinoma (HCC) cause a sever health problem worldwide, the underlying mechanisms are still elusive. This study aimed to investigate the responses of different cell types isolated from HBV transgenic mice. A cross-sectional set of hepatocytes and oval cells were obtained from HBV transgenic and control mice. Flow cytometry, immunohistochemistry and microarray were applied to investigate the cell biology of the hepatocytes and oval cells. Our results showed that HBV induced the proliferation of both cell oval cells and hepatocytes, and induced cell death of HBV hepatocytes while had minimal effects on oval cells. Further molecular and pathways analysis identified some genes and signaling pathways may be responsible for the different responses between oval cells and hepatocytes. In addition, analyses of selectively ten genes by IHC staining in human samples were consistent with microarray data. In summary, HBV transgenic mice is a useful model for studying the biological behaviors of oval cells affected by HBV and HBV-cirrhosis. Also, our results help better understand the mechanisms of HBV induced cirrhosis, and provide novel progenitor markers or prognostic/therapeutic markers.

Calcium Signaling in Liver Injury and Regeneration

The liver fulfills central roles in metabolic control and detoxification and, as such, is continuously exposed to a plethora of insults. Importantly, the liver has a unique ability to regenerate and can completely recoup from most acute, non-iterative insults. However, multiple conditions, including viral hepatitis, non-alcoholic fatty liver disease (NAFLD), long-term alcohol abuse and chronic use of certain medications, can cause persistent injury in which the regenerative capacity eventually becomes dysfunctional, resulting in hepatic scaring and cirrhosis. Calcium is a versatile secondary messenger that regulates multiple hepatic functions, including lipid and carbohydrate metabolism, as well as bile secretion and choleresis. Accordingly, dysregulation of calcium signaling is a hallmark of both acute and chronic liver diseases. In addition, recent research implicates calcium transients as essential components of liver regeneration. In this review, we provide a comprehensive overview of the role of calcium signaling in liver health and disease and discuss the importance of calcium in the orchestration of the ensuing regenerative response. Furthermore, we highlight similarities and differences in spatiotemporal calcium regulation between liver insults of different etiologies. Finally, we discuss intracellular calcium control as an emerging therapeutic target for liver injury and summarize recent clinical findings of calcium modulation for the treatment of ischemic-reperfusion injury, cholestasis and NAFLD.

Participation of liver stem cells in cholangiocarcinogenesis after aflatoxin B1 exposure of glutathione S-transferase A3 knockout mice

Aflatoxin B1, arguably the most potent human carcinogen, induces liver cancer in humans, rats, trout, ducks, and so on, but adult mice are totally resistant. This resistance is because of a detoxifying enzyme, mouse glutathione S-transferase A3, which binds to and inactivates aflatoxin B1 epoxide, preventing the epoxide from binding to DNA and causing mutations. Glutathione S-transferase A3 or its analog has not been detected in any of the sensitive species, including humans. The generation of a glutathione S-transferase A3 knockout (represented as KO or -/-) mice has allowed us to study the induction of liver cancer in mice by aflatoxin B1. In contrast to the induction of hepatocellular carcinomas in other species, aflatoxin B1 induces cholangiocarcinomas in GSTA3-/- mice. In other species and in knockout mice, the induction of liver cancer is preceded by extensive proliferation of small oval cells, providing additional evidence that oval cells are bipolar stem cells and may give rise to either hepatocellular carcinoma or cholangiocarcinoma depending on the nature of the hepatocarcinogen and the species of animal. The recent development of mouse oval cell lines in our laboratory from aflatoxin B1-treated GSTA3-/- mice should provide a new venue for study of the properties and potential of putative mouse liver stem cells.

Current Perspectives Regarding Stem Cell-Based Therapy for Liver Cirrhosis

Liver cirrhosis is a major cause of mortality and a common end of various progressive liver diseases. Since the effective treatment is currently limited to liver transplantation, stem cell-based therapy as an alternative has attracted interest due to promising results from preclinical and clinical studies. However, there is still much to be understood regarding the precise mechanisms of action. A number of stem cells from different origins have been employed for hepatic regeneration with different degrees of success. The present review presents a synopsis of stem cell research for the treatment of patients with liver cirrhosis according to the stem cell type. Clinical trials to date are summarized briefly. Finally, issues to be resolved and future perspectives are discussed with regard to clinical applications.

Characterization of liver injury, oval cell proliferation and cholangiocarcinogenesis in glutathione S-transferase A3 knockout mice

We recently generated glutathione S-transferase (GST) A3 knockout (KO) mice as a novel model to study the risk factors for liver cancer. GSTA3 KO mice are sensitive to the acute cytotoxic and genotoxic effects of aflatoxin B1 (AFB1), confirming the crucial role of GSTA3 in resistance to AFB1. We now report histopathological changes, tumor formation, biochemical changes and gender response following AFB1 treatment as well as the contribution of oxidative stress. Using a protocol of weekly 0.5 mg AFB1/kg administration, we observed extensive oval (liver stem) cell (OC) proliferation within 1-3 weeks followed by microvesicular lipidosis, megahepatocytes, nuclear inclusions, cholangiomas and small nodules. Male and female GSTA3 KO mice treated with 12 and 24 weekly AFB1 injections followed by a rest period of 12 and 6 months, respectively, all had grossly distorted livers with macro- and microscopic cysts, hepatocellular nodules, cholangiomas and cholangiocarcinomas and OC proliferation. We postulate that the prolonged AFB1 treatment leads to inhibition of hepatocyte proliferation, which is compensated by OC proliferation and eventually formation of cholangiocarcinoma (CCA). At low-dose AFB1, male KO mice showed less extensive acute liver injury, OC proliferation and AFB1-DNA adducts than female KO mice. There were no significant compensatory changes in KO mice GST subunits, GST enzymatic activity, epoxide hydrolase, or CYP1A2 and CYP3A11 levels. Finally, there was a modest increase in F2-isoprostane and isofuran in KO mice that confirmed putative GSTA3 hydroperoxidase activity in vivo for the first time.

Taurocholate Induces Biliary Differentiation of Liver Progenitor Cells Causing Hepatic Stellate Cell Chemotaxis in the Ductular Reaction: Role in Pediatric Cystic Fibrosis Liver Disease

Cystic fibrosis liver disease (CFLD) in children causes progressive fibrosis leading to biliary cirrhosis; however, its cause(s) and early pathogenesis are unclear. We hypothesized that a bile acid-induced ductular reaction (DR) drives fibrogenesis. The DR was evaluated by cytokeratin-7 immunohistochemistry in liver biopsies, staged for fibrosis, from 60 children with CFLD, and it demonstrated that the DR was significantly correlated with hepatic fibrosis stage and biliary taurocholate levels. To examine the mechanisms involved in DR induction, liver progenitor cells (LPCs) were treated with taurocholate, and key events in DR evolution were assessed: LPC proliferation, LPC biliary differentiation, and hepatic stellate cell (HSC) chemotaxis. Taurocholate induced a time-dependent increase in LPC proliferation and expression of genes associated with cholangiocyte differentiation (cytokeratin 19, connexin 43, integrin β4, and γ-glutamyltranspeptidase), whereas the hepatocyte specification marker HNF4α was suppressed. Functional cholangiocyte differentiation was demonstrated via increased acetylated α-tubulin and SOX9 proteins, the number of primary cilia⁺ LPCs, and increased active γ-glutamyltranspeptidase enzyme secretion. Taurocholate induced LPCs to release MCP-1, MIP1α, and RANTES into conditioned medium causing HSC chemotaxis, which was inhibited by anti-MIP1α. Immunofluorescence confirmed chemokine expression localized to CK7⁺ DR and LPCs in CFLD liver biopsies. This study suggests that taurocholate is involved in initiating functional LPC biliary differentiation and the development of the DR, with subsequent induction of chemokines that drive HSC recruitment in CFLD.

The diversity and plasticity of adult hepatic progenitor cells and their niche

The liver is a unique organ for homoeostasis with regenerative capacities. Hepatocytes possess a remarkable capacity to proliferate upon injury; however, in more severe scenarios liver regeneration is believed to arise from at least one, if not several facultative hepatic progenitor cell compartments. Newly identified pericentral stem/progenitor cells residing around the central vein is responsible for maintaining hepatocyte homoeostasis in the uninjured liver. In addition, hepatic progenitor cells have been reported to contribute to liver fibrosis and cancers. What drives liver homoeostasis, regeneration and diseases is determined by the physiological and pathological conditions, and especially the hepatic progenitor cell niches which influence the fate of hepatic progenitor cells. The hepatic progenitor cell niches are special microenvironments consisting of different cell types, releasing growth factors and cytokines and receiving signals, as well as the extracellular matrix (ECM) scaffold. The hepatic progenitor cell niches maintain and regulate stem cells to ensure organ homoeostasis and regeneration. In recent studies, more evidence has been shown that hepatic cells such as hepatocytes, cholangiocytes or myofibroblasts can be induced to be oval cell-like state through transitions under some circumstance, those transitional cell types as potential liver-resident progenitor cells play important roles in liver pathophysiology. In this review, we describe and update recent advances in the diversity and plasticity of hepatic progenitor cell and their niches and discuss evidence supporting their roles in liver homoeostasis, regeneration, fibrosis and cancers.

Cholangiocytes act as facultative liver stem cells during impaired hepatocyte regeneration

Following liver injury, regeneration occurs through self-replication of hepatocytes. In severe liver injury, hepatocyte proliferation is impaired, a feature of human chronic liver disease1,2. It is contested whether other liver cell types can regenerate hepatocytes3–5. Here, we use two independent systems to impair hepatocyte proliferation during liver injury to evaluate the contribution of non-hepatocytes to parenchymal regeneration. Firstly, loss of β1-Integrin in hepatocytes with liver injury triggered a ductular reaction of cholangiocyte origin, and ~25% of hepatocytes being derived from a non-hepatocyte origin. Secondly cholangiocytes were lineage traced with concurrent inhibition of hepatocyte proliferation by β1-Integrin knockdown or p21 over-expression, resulting in the significant emergence of cholangiocyte derived hepatocytes. We describe a model of combined liver injury and inhibition of hepatocyte proliferation that causes physiologically significant levels of regeneration of functional hepatocytes from biliary cells.

Negligible Oval Cell Proliferation Following Ischemia-Reperfusion Injury With and Without Partial Hepatectomy

BACKGROUND

Hepatic oval cells proliferate to replace hepatocytes and restore liver function when hepatocyte proliferation is compromised or inadequate. Exposure to chemical carcinogens, severe liver steatosis, and partial hepatectomy has been used in animal models to demonstrate the role of oval cells in liver regeneration. Ischemia-reperfusion injury (IRI) causes hepatocellular damage and death in the absence of confounding chemical toxicity; however, oval cell induction by IRI has not been demonstrated in vivo. We examine oval cell induction following partial IRI.

METHODS

Wistar rats were subjected to 2 IRI protocols: 70% warm liver ischemia for 30 minutes followed by reperfusion or 70% warm liver ischemia for 30 minutes with partial hepatectomy of the nonischemic lobes followed by reperfusion. Liver injury was monitored by serum alanine aminotransferase (ALT) at 1 day and 7 days of reperfusion. Oval cell proliferation was monitored by indirect immunofluorescence staining using the surface markers BD.2 and Thy-1. Cellular proliferation was quantified by 5-ethynyl-2'-deoxyuridine (EdU) incorporation in vivo.

RESULTS

Serum ALT elevation was only observed at the 1-day time point in the IRI with partial hepatectomy model. Oval cell marker expression was restricted to the biliary structures in both the ischemic and the nonischemic control lobes. Oval cell induction, measured by changes in the frequency of BD.2 and Thy-1 expression and EdU incorporation, was not significantly altered by IRI.

CONCLUSION

In both mild and moderate IRI models, we did not find evidence of oval cell induction or proliferation. EdU staining was restricted to hepatocytes, suggesting that liver regeneration following IRI is mediated by hepatocyte proliferation.

Liver regeneration - mechanisms and models to clinical application

Liver regeneration has been studied for many decades and the mechanisms underlying regeneration of the normal liver following resection or moderate damage are well described. A large number of factors extrinsic (such as bile acids and circulating growth factors) and intrinsic to the liver interact to initiate and regulate liver regeneration. Less well understood, and more clinically relevant, are the factors at play when the abnormal liver is required to regenerate. Fatty liver disease, chronic scarring, prior chemotherapy and massive liver injury can all inhibit the normal programme of regeneration and can lead to liver failure. Understanding these mechanisms could enable the rational targeting of specific therapies to either reduce the factors inhibiting regeneration or directly stimulate liver regeneration. Although animal models of liver regeneration have been highly instructive, the clinical relevance of some models could be improved to bridge the gap between our in vivo model systems and the clinical situation. Likewise, modern imaging techniques such as spectroscopy will probably improve our understanding of whole-organ metabolism and how this predicts the liver's regenerative capacity. This Review describes briefly the mechanisms underpinning liver regeneration, the models used to study this process, and discusses areas in which failed or compromised liver regeneration is clinically relevant.

Environmental Ligands of the Aryl Hydrocarbon Receptor and Their Effects in Models of Adult Liver Progenitor Cells

The toxicity of environmental and dietary ligands of the aryl hydrocarbon receptor (AhR) in mature liver parenchymal cells is well appreciated, while considerably less attention has been paid to their impact on cell populations exhibiting phenotypic features of liver progenitor cells. Here, we discuss the results suggesting that the consequences of the AhR activation in the cellular models derived from bipotent liver progenitors could markedly differ from those in hepatocytes. In contact-inhibited liver progenitor cells, the AhR agonists induce a range of effects potentially linked with tumor promotion. They can stimulate cell cycle progression/proliferation and deregulate cell-to-cell communication, which is associated with downregulation of proteins forming gap junctions, adherens junctions, and desmosomes (such as connexin 43, E-cadherin, β-catenin, and plakoglobin), as well as with reduced cell adhesion and inhibition of intercellular communication. At the same time, toxic AhR ligands may affect the activity of the signaling pathways contributing to regulation of liver progenitor cell activation and/or differentiation, such as downregulation of Wnt/β-catenin and TGF-β signaling, or upregulation of transcriptional targets of YAP/TAZ, the effectors of Hippo signaling pathway. These data illustrate the need to better understand the potential role of liver progenitors in the AhR-mediated liver carcinogenesis and tumor promotion.

Upregulation of hydroxysteroid sulfotransferase 2B1b promotes hepatic oval cell proliferation by modulating oxysterol-induced LXR activation in a mouse model of liver injury

Hydroxysteroid sulfotransferase 2B1b (SULT2B1b) sulfates cholesterol and oxysterols. Hepatic oval cells (HOCs), thought to be progenitor cells, can be triggered in chemically injured livers. The present study focused on the role of SULT2B1b in HOC proliferation after liver injury. Our experiments revealed that the expression of SULT2B1b was increased dramatically in a chemical-induced liver injury model, mainly in HOCs. Upon challenge with a hepatotoxic diet containing 0.1 % 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC), SULT2B1^-/- mice presented alleviated liver injury and less HOC proliferation compared with wild-type (WT) mice, and these findings were verified by serum analysis, histopathology, immunofluorescence staining, RNA-seq, and Western blotting. HOCs derived from SULT2B1^-/- mice showed lower proliferative capability than those from WT mice. SULT2B1b overexpression promoted growth of the WB-F344 hepatic oval cell line, whereas SULT2B1b knockdown inhibited growth of these cells. The IL-6/STAT3 signaling pathway also was promoted by SULT2B1b. Liquid chromatography and mass spectrometry indicated that the levels of 22-hydroxycholesterol, 25-hydroxycholesterol, and 24,25-epoxycholesterol were higher in the DDC-injured livers of SULT2B1^-/- mice than in livers of WT mice. The above oxysterols are physiological ligands of liver X receptors (LXRs), and SULT2B1b suppressed oxysterol-induced LXR activation. Additional in vivo and in vitro experiments demonstrated that LXR activation could inhibit HOC proliferation and the IL-6/STAT3 signaling pathway, and these effects could be reversed by SULT2B1b. Our data indicate that upregulation of SULT2B1b might promote HOC proliferation and aggravate liver injury via the suppression of oxysterol-induced LXR activation in chemically induced mouse liver injury.

Interaction of TWEAK with Fn14 leads to the progression of fibrotic liver disease by directly modulating hepatic stellate cell proliferation

Tumour necrosis factor‐like weak inducer of apoptosis (TWEAK) and its receptor fibroblast growth factor‐inducible 14 (Fn14) have been associated with liver regeneration in vivo. To further investigate the role of this pathway we examined their expression in human fibrotic liver disease and the effect of pathway deficiency in a murine model of liver fibrosis. The expression of Fn14 and TWEAK in normal and diseased human and mouse liver tissue and primary human hepatic stellate cells (HSCs) were investigated by qPCR, western blotting and immunohistochemistry. In addition, the levels of Fn14 in HSCs following pro‐fibrogenic and pro‐inflammatory stimuli were assessed and the effects of exogenous TWEAK on HSCs proliferation and activation were studied in vitro. Carbon tetrachloride (CCl₄) was used to induce acute and chronic liver injury in TWEAK KO mice. Elevated expression of both Fn14 and TWEAK were detected in acute and chronic human liver injury, and co‐localized with markers of activated HSCs. Fn14 levels were low in quiescent HSCs but were significantly induced in activated HSCs, which could be further enhanced with the profibrogenic cytokine TGFβin vitro. Stimulation with recombinant TWEAK induced proliferation but not further HSCs activation. Fn14 gene expression was also significantly up‐regulated in CCl₄ models of hepatic injury whereas TWEAK KO mice showed reduced levels of liver fibrosis following chronic CCl₄ injury. In conclusion, TWEAK/Fn14 interaction leads to the progression of fibrotic liver disease via direct modulation of HSCs proliferation, making it a potential therapeutic target for liver fibrosis. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

EGFR Signaling in Liver Diseases

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase that is activated by several ligands leading to the activation of diverse signaling pathways controlling mainly proliferation, differentiation, and survival. The EGFR signaling axis has been shown to play a key role during liver regeneration following acute and chronic liver damage, as well as in cirrhosis and hepatocellular carcinoma (HCC) highlighting the importance of the EGFR in the development of liver diseases. Despite the frequent overexpression of EGFR in human HCC, clinical studies with EGFR inhibitors have so far shown only modest results. Interestingly, a recent study has shown that in human HCC and in mouse HCC models the EGFR is upregulated in liver macrophages where it plays a tumor-promoting function. Thus, the role of EGFR in liver diseases appears to be more complex than what anticipated. Further studies are needed to improve the molecular understanding of the cell-specific signaling pathways that control disease development and progression to be able to develop better therapies targeting major components of the EGFR signaling network in selected cell types. In this review, we compiled the current knowledge of EGFR signaling in different models of liver damage and diseases, mainly derived from the analysis of HCC cell lines and genetically engineered mouse models (GEMMs).

TGF-β1 Induces the Dual Regulation of Hepatic Progenitor Cells with Both Anti- and Proliver Fibrosis

Transforming growth factor-beta 1 (TGF-β1) plays a central role in hepatic progenitor cells- (HPCs-) mediated liver repair and fibrosis. However, different effects of TGF-β1 on progenitor cells have not been described. In this study, both in vitro (HPCs cocultured with hepatic stellate cells (HSCs) in transwells) and in vivo (CCl₄-injured liver fibrosis rat) systems were used to evaluate the impacts. We found that HPCs pretreated with TGF-β1 for 12 hours inhibited the activation of HSCs, while sensitization for 48 hours increased the activation of HSCs. Consistent with these in vitro results, the in vivo fibrosis rat model showed the same time-dependent dual effect of TGF-β1. Regression of liver fibrosis as well as normalization of serum aminotransferase and albumin levels was detected in the rats transplanted with HPCs pretreated with TGF-β1 for 12 hours. In contrast, severe liver fibrosis and elevated collagen-1 levels were detected in the rats transplanted with HPCs pretreated with TGF-β1 for 48 hours. Furthermore, the TGF-β1-pretreated HPCs were shown to deactivate HSCs via enhancing SERPINE1 expression. Inhibition of SERPINE1 reversed the deactivation response in a dose-dependent manner.

Dysregulated YAP1/TAZ and TGF-β signaling mediate hepatocarcinogenesis in Mob1a/1b-deficient mice

Mps One Binder Kinase Activator (MOB)1A/1B are core components of the Hippo pathway that coactivate large tumor suppressor homolog (LATS) kinases. Mob1a/1b double deficiency in mouse liver (LMob1DKO) results in hyperplasia of oval cells and immature cholangiocytes accompanied by inflammatory cell infiltration and fibrosis. More than half of mutant mice die within 3 wk of birth. All survivors eventually develop liver cancers, particularly combined hepatocellular and cholangiocarcinomas (cHC-CCs) and intrahepatic cholangiocellular carcinomas (ICCs), and die by age 60 wk. Because this phenotype is the most severe among mutant mice lacking a Hippo signaling component, MOB1A/1B constitute the critical hub of Hippo signaling in mammalian liver. LMob1DKO liver cells show hyperproliferation, increased cell saturation density, hepatocyte dedifferentiation, enhanced epithelial-mesenchymal transition and cell migration, and elevated transforming growth factor beta(TGF-β)2/3 production. These changes are strongly dependent on Yes-Associated Protein-1 (Yap1) and partially dependent on PDZ-binding motif (Taz) and Tgfbr2, but independent of connective tissue growth factor (Ctgf). In human liver cancers, YAP1 activation is frequent in cHC-CCs and ICCs and correlates with SMAD family member 2 activation. Drug screening revealed that antiparasitic macrocyclic lactones inhibit YAP1 activation in vitro and in vivo. Targeting YAP1/TAZ with these drugs in combination with inhibition of the TGF-β pathway may be effective treatment for cHC-CCs and ICCs.

Mesenchymal stem cell therapy for cirrhosis: Present and future perspectives

Cirrhosis occurs as a result of various chronic liver injuries, which may be caused by viral infections, alcohol abuse and the administration of drugs and chemicals. Recently, bone marrow cells (BMCs), hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) have been used for developing treatments for cirrhosis. Clinical trials have investigated the therapeutic potential of BMCs, HSCs and MSCs for the treatment of cirrhosis based on their potential to differentiate into hepatocytes. Although the therapeutic mechanisms of BMC, HSC and MSC treatments are still not fully characterized, the evidence thus far has indicated that the potential therapeutic mechanisms of MSCs are clearer than those of BMCs or HSCs with respect to liver regenerative medicine. MSCs suppress inflammatory responses, reduce hepatocyte apoptosis, increase hepatocyte regeneration, reverse liver fibrosis and enhance liver functionality. This paper summarizes the clinical studies that have used BMCs, HSCs and MSCs in patients with liver failure or cirrhosis. We also present the potential therapeutic mechanisms of BMCs, HSCs and MSCs for the improvement of liver function.

EGF Suppresses the Initiation and Drives the Reversion of TGF-β1-induced Transition in Hepatic Oval Cells Showing the Plasticity of Progenitor Cells

Transforming growth factor-β1 (TGF-β1) induces hepatic progenitors to tumor initiating cells through epithelial-mesenchymal transition (EMT), thus raising an important drawback for stem cell-based therapy. How to block and reverse TGF-β1-induced transition is crucial for progenitors' clinical application and carcinogenic prevention. Rat adult hepatic progenitors, hepatic oval cells, experienced E-cadherin to N-cadherin switch and changed to α-smooth muscle actin (α-SMA) positive cells after TGF-β1 incubation, indicating EMT. When TGF-β1 plus EGF were co-administrated to these cells, EGF dose-dependently suppressed the cadherin switch and α-SMA expression. Interestingly, if EGF was applied to TGF-β1-pretreated cells, the cells that have experienced EMT could return to their epithelial phenotype. Abruption of EGF receptor revealed that EGF exerted its blockage and reversal effects through phosphorylation of ERK1/2 and Akt. These findings suggest an important attribute of EGF on opposing and reversing TGF-β1 effects, indicating the plasticity of hepatic progenitors.

Isolation and Expansion of Hepatic Stem-like Cells from a Healthy Rat Liver and their Efficient Hepatic Differentiation of under Well-defined Vivo Hepatic like Microenvironment in a Multiwell Bioreactor

BACKGROUND

Currently, undifferentiated cells are found in all tissue and term as local stem cells which are quiescent in nature and less in number under normal healthy conditions but activate upon injury and repair the tissue or organs via automated activating mechanism. Due to very scanty presence of local resident somatic local stem cells in healthy organs, isolation and expansion of these adult stems is an immense challenge for medical research and cell based therapy. Particularly organ like liver, there is an ongoing controversy about existence of liver stem cells.

METHODS

Herein, Hepatic stem cells population was identified during culture of primary hepatocyte cells upon immediate isolation of primary hepatocyte cells. These liver stem cells has been expanded extensively and differentiated into primary hepatocytes under defined culture conditions in a nanostructured self assembling peptides modular bioreactor that mimic the state of art of liver microenvironment and compared with Matrigel as a positive control. Nanostructured self assembling peptides were used a defined extracellular matrix and Matrigel was used for undefined extracellular matrix. Proliferation of hepatic stem cells was investigated by two strategies. First strategy is to provide high concentration of hepatocyte growth factor (HGF) and second strategy is to evaluate the role of recombinant human erythropoietin (rHuEPO) in presence of trauma/ischemia cytokines (IL-6, TNF-α). Expansion to hepatic differentiation is observed by morphological analysis and was evaluated for the expression of hepatocyte-specific genes using RT-PCR and biochemical methods.

RESULTS

Hepatocyte-specific genes are well expressed at final stage (day 21) of differentiation period. The differentiated hepatocytes exhibited functional hepatic characteristics such as albumin secretion, urea secretion and cytochrome P450 expression. Additionally, immunofluorescence analysis revealed that hepatic stem cells derived hepatocytes exhibited mature hepatocyte markers (albumin, CK-19, CPY3A1, alpha 1-antitrypsin). Expansion and hepatic differentiation was efficiently in nanostructured self assembling peptides without such batch to batch variation while there was much variation in Matrigel coated bioreactor. In conclusion, the results of the study suggest that the nanostructured self assembling peptides coated bioreactor supports expansion as well as hepatic differentiation of liver stem cells which is superior than Matrigel.

CONCLUSION

This defined microenvironment conditions in bioreactor module can be useful for research involving bioartificial liver system, stem cell research and engineered liver tissue which could contribute to regenerative cell therapies or drug discovery and development.

Cell therapy for liver disease: From liver transplantation to cell factory

Work over several decades has laid solid foundations for the advancement of liver cell therapy. To date liver cell therapy in people has taken the form of hepatocyte transplantation for metabolic disorders with a hepatic basis, and for acute or chronic liver failure. Although clinical trials using various types of autologous cells have been implemented to promote liver regeneration or reduce liver fibrosis, clear evidence of therapeutic benefits have so far been lacking. Cell types that have shown efficacy in preclinical models include hepatocytes, liver sinusoidal endothelial cells, mesenchymal stem cells, endothelial progenitor cells, and macrophages. However, positive results in animal models have not always translated through to successful clinical therapies and more realistic preclinical models need to be developed. Studies defining the optimal repopulation by transplanted cells, including routes of cell transplantation, superior engraftment and proliferation of transplanted cells, as well as optimal immunosuppression regimens are required. Tissue engineering approaches to transplant cells in extrahepatic locations have also been proposed. The derivation of hepatocytes from pluripotent or reprogrammed cells raises hope that donor organ and cell shortages could be overcome in the future. Critical hurdles to be overcome include the production of hepatocytes from pluripotent cells with equal functional capacity to primary hepatocytes and long-term phenotypic stability in vivo.

Galectin-3 regulates hepatic progenitor cell expansion during liver injury

OBJECTIVE

Following chronic liver injury or when hepatocyte proliferation is impaired, ductular reactions containing hepatic progenitor cells (HPCs) appear in the periportal regions and can regenerate the liver parenchyma. HPCs exist in a niche composed of myofibroblasts, macrophages and laminin matrix. Galectin-3 (Gal-3) is a β-galactoside-binding lectin that binds to laminin and is expressed in injured liver in mice and humans.

DESIGN

We examined the role of Gal-3 in HPC activation. HPC activation was studied following dietary induced hepatocellular (choline-deficient ethionine-supplemented diet) and biliary (3,5-diethoxycarbonyl-1,4-dihydrocollidine supplemented diet) injury in wild type and Gal-3(-/-) mice.

RESULTS

HPC proliferation was significantly reduced in Gal-3(-/-) mice. Gal-3(-/-) mice failed to form a HPC niche, with reduced laminin formation. HPCs isolated from wild type mice secrete Gal-3 which enhanced adhesion and proliferation of HPCs on laminin in an undifferentiated form. These effects were attenuated in Gal3(-/-) HPCs and in wild type HPCs treated with the Gal-3 inhibitor lactose. Gal-3(-/-) HPCs in vitro showed increased hepatocyte function and prematurely upregulated both biliary and hepatocyte differentiation markers and regulated cell cycle genes leading to arrest in G0/G1.

CONCLUSIONS

We conclude that Gal-3 is required for the undifferentiated expansion of HPCs in their niche in injured liver.

Impact of microenvironment and stem-like plasticity in cholangiocarcinoma: molecular networks and biological concepts

Clinical complexity, anatomic diversity and molecular heterogeneity of cholangiocarcinoma (CCA) represent a major challenge in the assessment of effective targeted therapies. Molecular and cellular mechanisms underlying the diversity of CCA growth patterns remain a key issue of clinical concern. Crucial questions comprise the nature of the CCA-origin, the initial target for cellular transformation as well as the relationship with the cancer stem cells (CSC) concept. Additionally, since CCA often develops in the context of an inflammatory milieu (cirrhosis and cholangitis), the stromal compartment or tumour microenvironment (TME) likely promotes initiation and progression of this malignancy, contributing to its heterogeneity. This review will emphasize the dynamic interplay between stem-like intrinsic and TME-extrinsic pathways, which may represent novel options for multi-targeted therapies in CCA.

Liver X receptor α (LXRα/NR1H3) regulates differentiation of hepatocyte-like cells via reciprocal regulation of HNF4α

BACKGROUND & AIMS

Hepatocyte-like cells, differentiated from different stem cell sources, are considered to have a range of possible therapeutic applications, including drug discovery, metabolic disease modelling, and cell transplantation. However, little is known about how stem cells differentiate into mature and functional hepatocytes.

METHODS

Using transcriptomic screening, a transcription factor, liver X receptor α (NR1H3), was identified as increased during HepaRG cell hepatogenesis; this protein was also upregulated during embryonic stem cell and induced pluripotent stem cell differentiation.

RESULTS

Overexpressing NR1H3 in human HepaRG cells promoted hepatic maturation; the hepatocyte-like cells exhibited various functions associated with mature hepatocytes, including cytochrome P450 (CYP) enzyme activity, secretion of urea and albumin, upregulation of hepatic-specific transcripts and an increase in glycogen storage. Importantly, the NR1H3-derived hepatocyte-like cells were able to rescue lethal fulminant hepatic failure using a non-obese diabetic/severe combined immunodeficient mouse model.

CONCLUSIONS

In this study, we found that NR1H3 accelerates hepatic differentiation through an HNF4α-dependent reciprocal network. This contributes to hepatogenesis and is therapeutically beneficial to liver disease.

Effect of liver regeneration on malignant hepatic tumors

Liver regeneration after major surgery may activate occult micrometastases and facilitate tumor growth, leading to liver tumor recurrence. Molecular changes during liver regeneration can provide a microenvironment that stimulates intrahepatic tumor propagation through alterations in cellular signaling pathways, where activation and proliferation of mature hepatocytes, hepatic progenitor cells, non-parenchymal liver cells might favor both liver regeneration and tumor growth. This review highlights recent advances of tumor growth and development in the regenerating liver, possible mechanisms and clinical implications.