Hepatocyte-specific METTL3 ablation by Alb-iCre mice (GPT), but not by Alb-Cre mice (JAX), resulted in acute liver failure (ALF) and postnatal lethality

AIM

In 2019, to examine the functions of METTL3 in liver and underlying mechanisms, we generated mice with hepatocyte-specific METTL3 homozygous knockout (METTL3Δhep) by simultaneously crossing METTL3fl/fl mice with Alb-iCre mice (GPT) or Alb-Cre mice (JAX), respectively. In this study, we explored the potential reasons why hepatocyte-specific METTL3 homozygous disruption by Alb-iCre mice (GPT), but not by Alb-Cre mice (JAX), resulted in acute liver failure (ALF) and then postnatal lethality.

MAIN METHODS

Mice with hepatocyte-specific METTL3 knockout were generated by simultaneously crossing METTL3fl/fl mice with Alb-iCre mice (GPT; Strain No. T003814) purchased from the GemPharmatech Co., Ltd., (Nanjing, China) or with Alb-Cre mice (JAX; Strain No. 003574) obtained from The Jackson Laboratory, followed by combined-phenotype analysis. The publicly available RNA-sequencing data deposited in the NCBI Gene Expression Omnibus (GEO) database under the accession No.: GSE198512 (postnatal lethality), GSE197800 (postnatal survival) and GSE176113 (postnatal survival) were mined to explore the potential reasons why hepatocyte-specific METTL3 homozygous deletion by Alb-iCre mice (GPT), but not by Alb-Cre mice (JAX), leads to ALF and then postnatal lethality.

KEY FINDINGS

Firstly, we observed that hepatocyte-specific METTL3 homozygous deficiency by Alb-iCre mice (GPT) or by Alb-Cre mice (JAX) caused liver injury, abnormal lipid accumulation and apoptosis. Secondly, we are surprised to find that hepatocyte-specific METTL3 homozygous deletion by Alb-iCre mice (GPT), but not by Alb-Cre mice (JAX), led to ALF and then postnatal lethality. Our findings clearly demonstrated that METTL3Δhep mice (GPT), which are about to die, exhibited the severe destruction of liver histological structure, suggesting that METTL3Δhep mice (GPT) nearly lose normal liver function, which subsequently contributes to ALF, followed by postnatal lethality. Finally, we unexpectedly found that as the compensatory growth responses of hepatocytes to liver injury induced by METTL3Δhep (GPT), the proliferation of METTL3Δhep hepatocytes (GPT), unlike METTL3Δhep hepatocytes (JAX), was not evidenced by the significant increase of Ki67-positive hepatocytes, not accompanied by upregulation of cell-cycle-related genes. Moreover, GO analysis revealed that upregulated genes in METTL3Δhep livers (GPT), unlike METTL3Δhep livers (JAX), are not functionally enriched in terms associated with cell cycle, cell division, mitosis, microtubule cytoskeleton organization, spindle organization, chromatin segregation and organization, and nuclear division, consistent with the loss of compensatory proliferation of METTL3Δhep hepatocytes (GPT) observed in vivo. Thus, obviously, the loss of the compensatory growth capacity of METTL3Δhep hepatocytes (GPT) in response to liver injury might contribute to, at least partially, ALF and subsequently postnatal lethality of METTL3Δhep mice (GPT).

SIGNIFICANCE

These findings from this study and other labs provide strong evidence that these phenotypes (i.e., ALF and postnatal lethality) of METTL3Δhep mice (GPT) might be not the real functions of METTL3, and closely related with Alb-iCre mice (GPT), suggesting that we should remind researchers to use Alb-iCre mice (GPT) with caution to knockout gene in hepatocytes in vivo.

The role and mechanisms of macrophage polarization and hepatocyte pyroptosis in acute liver failure

Acute liver failure (ALF) is a severe liver disease caused by disruptions in the body's immune microenvironment. In the early stages of ALF, Kupffer cells (KCs) become depleted and recruit monocytes derived from the bone marrow or abdomen to replace the depleted macrophages entering the liver. These monocytes differentiate into mature macrophages, which are activated in the immune microenvironment of the liver and polarized to perform various functions. Macrophage polarization can occur in two directions: pro-inflammatory M1 macrophages and anti-inflammatory M2 macrophages. Controlling the ratio and direction of M1 and M2 in ALF can help reduce liver injury. However, the liver damage caused by pyroptosis should not be underestimated, as it is a caspase-dependent form of cell death. Inhibiting pyroptosis has been shown to effectively reduce liver damage induced by ALF. Furthermore, macrophage polarization and pyroptosis share common binding sites, signaling pathways, and outcomes. In the review, we describe the role of macrophage polarization and pyroptosis in the pathogenesis of ALF. Additionally, we preliminarily explore the relationship between macrophage polarization and pyroptosis, as well as their effects on ALF.

Isolation, culture, and delivery considerations for the use of mesenchymal stem cells in potential therapies for acute liver failure

Acute liver failure (ALF) is a high-mortality syndrome for which liver transplantation is considered the only effective treatment option. A shortage of donor organs, high costs and surgical complications associated with immune rejection constrain the therapeutic effects of liver transplantation. Recently, mesenchymal stem cell (MSC) therapy was recognized as an alternative strategy for liver transplantation. Bone marrow mesenchymal stem cells (BMSCs) have been used in clinical trials of several liver diseases due to their ease of acquisition, strong proliferation ability, multipotent differentiation, homing to the lesion site, low immunogenicity and anti-inflammatory and antifibrotic effects. In this review, we comprehensively summarized the harvest and culture expansion strategies for BMSCs, the development of animal models of ALF of different aetiologies, the critical mechanisms of BMSC therapy for ALF and the challenge of clinical application.

Etiology of viral induced acute liver failure and defensins as potential therapeutic agents in ALF treatment

Acute liver failure (ALF) is a rare and severe disease, which, despite continuous advances in medicine, is still characterized by high mortality (65-85%). Very often, a liver transplant is the only effective treatment for ALF. Despite the implementation of prophylactic vaccinations in the world, the viral background of ALF is still a problem and leads to many deaths. Depending on the cause of ALF, it is sometimes possible to reverse this condition with appropriate therapies, which is why the search for effective antiviral agents seems to be a very desirable direction of research. Defensins, which are our natural antimicrobial peptides, have a very high potential to be used as therapeutic agents for infectious liver diseases. Previous studies on the expression of human defensins have shown that increased expression of human α and β-defensins in HCV and HBV infections is associated with a better response to treatment. Unfortunately, conducting clinical trials for ALF is very difficult due to the severity of the disease and the low incidence, therefore animal models are important for the development of new therapeutic strategies. One of the best animal models that has real reference to research on acute liver failure (ALF) is rabbit hemorrhagic disease in rabbits caused by the Lagovirus europaeus virus. So far, there have been no studies on the potential of defensins in rabbits infected with Lagovirus europaeus virus.

Extracorporeal blood purification in patients with liver failure: Considerations for the low-and-middle income countries of Latin America

Severe liver failure is common in Low-and-Medium Income Countries (LMIC) and is associated with a high morbidity, mortality and represents an important burden to the healthcare system. In its most severe state, liver failure is a medical emergency, that requires supportive care until either the liver recovers or a liver transplant is performed. Frequently the patient requires intensive support until their liver recovers or they receive a liver transplant. Extracorporeal blood purification techniques can be employed as a strategy for bridging to transplantation or recovery. The most common type of extracorporeal support provided to these patients is kidney replacement therapy (KRT), as acute kidney injury is very common in these patients and KRT devices more readily available. However, because most of the substances that the liver clears are lipophilic and albumin-bound, they are not cleared effectively by KRT. Hence, there has been much effort in developing devices that more closely resemble the clearance function of the liver. This article provides a review of various non-biologic extracorporeal liver support devices that can be used to support these patients, and our perspective keeping in mind the needs and unique challenges present in the LMIC of Latin America.

Value of extracorporeal artificial liver support in pediatric acute liver failure: A single-center experience of over 10 years

PURPOSE

Acute liver failure (ALF) is a life-threatening disease characterized by rapid-onset liver dysfunction, coagulopathy, and encephalopathy in patients without chronic liver disease. Today, the combined application of continuous veno-venous hemodiafiltration (CVVHDF) and plasma exchange (PEX), which are forms of supportive extracorporeal therapy (SECT), with conventional liver therapy in ALF is recommended. This study aims to retrospectively analyze the effects of combined SECT in pediatric patients with ALF.

MATERIALS AND METHODS

We retrospectively analyzed 42 pediatric patients, followed in the liver transplantation intensive care unit. The patients had ALF and received PEX supportive therapy with combined CVVHDF. The biochemical lab values of the results for the patients before the first combined SECT and after the last combined SECT were analyzed comparatively.

RESULTS

Of the pediatric patients included in our study, 20 were girls and 22 were boys. Liver transplantation was performed in 22 patients, and 20 patients recovered without transplantation. After the discontinuation of combined SECT, all patients had significantly lower serum liver function test results (total bilirubin, alanine transaminase, aspartate transaminase), ammonia, and prothrombin time/international normalized ratio levels than the previous levels (p < 0.01). Hemodynamic parameters (i.e., mean arterial pressure) also improved significantly.

DISCUSSION AND CONCLUSION

Combined CVVHDF and PEX treatment significantly improved biochemical parameters and clinical findings, including encephalopathy, in pediatric patients with ALF. PEX therapy combined with CVVHDF is a proper supportive therapy for bridging or recovery.

A non-human primate model of acute liver failure suitable for testing liver support systems

Acute hepatic failure is associated with high morbidity and mortality for which the only definitive therapy is liver transplantation. Some fraction of those who undergo emergency transplantation have been shown to recover native liver function when transplanted with an auxiliary hepatic graft that leaves part of the native liver intact. Thus, transplantation could have been averted with the development and use of some form of hepatic support. The costs of developing and testing liver support systems could be dramatically reduced by the availability of a reliable large animal model of hepatic failure with a large therapeutic window that allows the assessment of efficacy and timing of intervention. Non-lethal forms of hepatic injury were examined in combination with liver-directed radiation in non-human primates (NHPs) to develop a model of acute hepatic failure that mimics the human condition. Porcine hepatocyte transplantation was then tested as a potential therapy for acute hepatic failure. After liver-directed radiation therapy, delivery of a non-lethal hepatic ischemia-reperfusion injury reliably and rapidly generated liver failure providing conditions that can enable pre-clinical testing of liver support or replacement therapies. Unfortunately, in preliminary studies, low hepatocyte engraftment and over-immune suppression interfered with the ability to assess the efficacy of transplanted porcine hepatocytes in the model. A model of acute liver failure in NHPs was created that recapitulates the pathophysiology and pathology of the clinical condition, does so with reasonably predictable kinetics, and results in 100% mortality. The model allowed preliminary testing of xenogeneic hepatocyte transplantation as a potential therapy.

Case Report: A Case of Epstein-Barr Virus-Associated Acute Liver Failure Requiring Hematopoietic Cell Transplantation After Emergent Liver Transplantation

Hepatic manifestations of Epstein-Barr virus (EBV) infection are relatively common, mild, and self-limiting. Although fulminant hepatic failure has been reported in a few cases, the contributing factors are unclear. This report discusses a pediatric case of EBV-associated acute liver failure that required urgent liver transplantation; however, liver damage continued to progress post-liver replacement. Monoclonal CD8+ T cells that preferentially infiltrated the native and transplanted liver were positive for EBV-encoded small RNA, suggesting a pathophysiology similar to that of EBV-associated hemophagocytic lymphohistiocytosis and chronic active EBV infection. Therefore, subsequent chemotherapy and hematopoietic cell transplantation was conducted, which led to cure. This is the first case of EBV-associated acute liver failure that relapsed post-liver transplant. As such, it sheds light on an under-recognized clinical entity: liver-restricted hyperinflammation caused by EBV-infected monoclonal CD8+ T cells. This phenomenon needs to be recognized and differentiated from hepatitis/hepatic failure caused by EBV-infected B cells, which has a relatively benign clinical course.

Corrigendum: PCRRT Expert Committee ICONIC position paper on prescribing kidney replacement therapy in critically sick children with acute liver failure

[This corrects the article DOI: 10.3389/fped.2021.833205.].

Human umbilical cord mesenchymal stem cells ameliorate acute liver failure by inhibiting apoptosis, inflammation and pyroptosis

Background

Human umbilical cord mesenchymal stem cells (UC-MSCs) are multipotent progenitor cells representing an attractive therapeutic tool for tissue damage and inflammation owing to their unique immunomodulatory properties. This study was designed to determine the protective effects and underlying mechanisms of UC-MSCs on acute liver failure (ALF).

Methods

ALF was induced in mice by intraperitoneal injection of D-galactosamine (D-GalN) and lipopolysaccharide (LPS). Mice were intravenously injected with 1×10⁶ UC-MSCs one hour before or six hours after D-GalN/LPS injection. Liver function was valued by serum biochemical parameters and hematoxylin-eosin staining. Inflammatory cytokine and chemokine levels were measured by real-time PCR, and inflammatory cells infiltration was observed by immunofluorescence staining. Hepatocyte apoptosis and pyroptosis related proteins were detected by western blot. Murine macrophage Raw264.7 in the presentation of LPS was treated with the UC-MSCs condition medium (UC-MSCs-CM), and then the levels of inflammatory cytokines and NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome in Raw264.7 were measured.

Results

UC-MSCs significantly reduced the mortality, decreased serum alanine aminotransferase and aspartate aminotransferase levels, and improved the pathological damage. Moreover, UC-MSCs inhibited inflammatory cytokine and chemokine levels, especially TNF-α, interleukins-6 (IL-6), IL-1β, monocyte chemoattractant protein (MCP-1), CC-chemokines ligand 2 (CCL2), C-X-C motif ligand 2 (CXCL2), and reduced macrophage, neutrophil and T lymphocyte infiltration into the liver tissue. UC-MSCs also attenuated hepatocyte apoptosis, as evidenced by decreased TUNEL positive cells, increased Bcl-xl/Bax protein ratio and downregulated cleaved caspase 3 levels. NLRP3 inflammasome activation, IL-1β maturation and cleaved caspase1 were suppressed by UC-MSC administration. Furthermore, the UC-MSCs-CM reduced the levels of inflammatory cytokines and the activation of NLRP3 inflammasome in Raw264.7.

Conclusions

Our results demonstrated that UC-MSCs exerted therapeutic effects on ALF by inhibiting apoptosis, inflammation, and pyroptosis.

PCRRT Expert Committee ICONIC Position Paper on Prescribing Kidney Replacement Therapy in Critically Sick Children With Acute Liver Failure

Management of acute liver failure (ALF) and acute on chronic liver failure (ACLF) in the pediatric population can be challenging. Kidney manifestations of liver failure, such as hepatorenal syndrome (HRS) and acute kidney injury (AKI), are increasingly prevalent and may portend a poor prognosis. The overall incidence of AKI in children with ALF has not been well-established, partially due to the difficulty of precisely estimating kidney function in these patients. The true incidence of AKI in pediatric patients may still be underestimated due to decreased creatinine production in patients with advanced liver dysfunction and those with critical conditions including shock and cardiovascular compromise with poor kidney perfusion. Current treatment for kidney dysfunction secondary to liver failure include conservative management, intravenous fluids, and kidney replacement therapy (KRT). Despite the paucity of evidence-based recommendations concerning the application of KRT in children with kidney dysfunction in the setting of ALF, expert clinical opinions have been evaluated regarding the optimal modalities and timing of KRT, dialysis/replacement solutions, blood and dialysate flow rates and dialysis dose, and anticoagulation methods.

Amphiregulin alleviated concanavalin A-induced acute liver injury via IL-22

OBJECTIVES

Amphiregulin (Areg), a glycoprotein from the epidermal growth factor receptor (EGFR) ligand family, has a well-documented protective role against tissue injury; however, its effects on immune-mediated liver injury are still unclear. Here, we used a concanavalin A (ConA)-induced acute liver hepatitis model to explore the effects of Areg on immune-mediated acute liver injury.

MATERIALS AND METHODS

Some C57BL/6 mice were administered ConA at a dose of 20 mg/kg (model mice), and some received 5 µg of Areg (treated mice). Then, their survival rates over 36 h were analyzed. After 5 h of treatment, liver function, hepatic histology, and apoptosis in liver tissue were investigated, and cytokine expression and neutrophil infiltration and activity in the liver were detected. Moreover, the protective effects of Areg were also evaluated without IL-22 in vivo.

RESULTS

Our results showed that Areg administration increased acute liver failure (ALF) mouse survival, restored liver function, and alleviated liver damage. Interestingly, Areg administration increased IL-22 production in hepatic T cells and upregulated IL-22 concentrations in the serum and liver, whereas IL-22 neutralization completely abolished the therapeutic effect of Areg. Meanwhile, Areg administration was concomitant with increased expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL, which are important in the hepatoprotective mechanism of IL-22.

CONCLUSIONS

Areg showed direct protective effects against ConA-induced acute liver injury, which suggests the potential therapeutic application of Areg in immune-mediated ALF.

The role of Neu1 in the protective effect of dipsacoside B on acetaminophen-induced liver injury

Background

Pharmacological induction of autophagy can protect against acetaminophen (APAP) induced acute liver failure (ALF) by removing APAP adducts (APAP-AD), but its mechanism is not well understood. Hepatoprotective effect of saponins from traditional Chinese medicine has attracted widespread attention from all over the world. The content of saponins in Lonicerae Flos (Shanyinhua in Chinese) is up to 15–25%. Dipsacoside B (DB) is a common bioactive ingredient of different Shanyinhua, but its hepatoprotective effect and mechanism are still unknown. The present investigation aimed to study the benefit of DB in APAP-induced hepatotoxicity mouse model and different cell model.

Methods

Mice were treated with DB by intraperitoneal injection 1 h before treated with 500 mg/kg APAP, which caused ALF after 4 h. HepG2 cells were treated with DB for 1 h before treated with 10 mM APAP for 12 h. Hepatotoxicity was assessed via ALT and AST. Neuraminidase 1 (Neu1), lysosomal autophagy marker LC3 and P62 were examined by western blot. Neu1 activity was assayed using its substrate 2-(4-methylumbelliferyl)-D-N-acetylneuraminic acid. Apoptosis level was examined by TUNEL and caspase 3 activity. Molecular docking was used to predict the interaction between DB and protein Neu1.

Results

Our results demonstrated that pretreatment with 0.5 μM DB (in vitro) and 50 mg/kg DB (in vivo) respectively reversed increased level of AST and ALT induced by APAP. Histopathological examinations showed reduced necrosis and apoptosis in the liver of DB-treated APAP mice. DB promoted the removal of APAP-AD by lysosomal autophagy. These effects were associated with significant decrease in the level of Neuraminidase 1 (Neu1), a negative regulator of lysosomal exocytosis. Molecular docking results showed that DB could bind to Neu1 protein (binding energy =−7.86 kcal/mol). Akt/mTOR-mediated autophagy and inhibition of apoptosis may be the main mechanisms for the hepatoprotective effects of DB in acetaminophen-induced liver injury.

Conclusions

These data indicate that DB alleviated hepatotoxicity caused by APAP at least in part via Neu1 inhibition, Akt/mTOR pathway is involved in the detoxification effect of DB on acetaminophen-induced hepatotoxicity.

Fibroblast Growth Factor-21 ameliorates hepatic encephalopathy by activating the STAT3-SOCS3 pathway to inhibit activated hepatic stellate cells

Neurological dysfunction, one of the consequences of acute liver failure (ALF), and also referred to as hepatic encephalopathy (HE), contributes to mortality posing challenges for clinical management. FGF21 has been implicated in the inhibition of cognitive decline and fibrogenesis. However, the effects of FGF21 on the clinical and molecular presentations of HE has not been elucidated. HE was induced by fulminant hepatic failure using thioacetamide (TAA) in male C57BL/6J mice while controls were injected with saline. For two consecutive weeks, mice were treated intraperitoneally with FGF21 (3 mg/kg) while controls were treated with saline. Cognitive, neurological, and activity function scores were recorded. Serum, liver, and brain samples were taken for analysis of CCL5 and GABA by ELISA, and RT qPCR was used to measure the expressions of fibrotic and pro-inflammatory markers. We report significant improvement in both cognitive and neurological scores by FGF21 treatment after impairment by TAA. GABA and CCL5, key factors in the progression of HE were also significantly reduced in the treatment group. Furthermore, the expression of fibrotic markers such as TGFβ and Col1 were also significantly downregulated after FGF21 treatment. TNFα and IL-6 were significantly reduced in the liver while in the brain, TNFα and IL-1 were downregulated. However, both in the liver and the brain, IL-10 was significantly upregulated. FGF21 inhibits CXCR4/CCL5 activation and upregulates the production of IL-10 in the damaged liver stimulating the production pro-inflammatory cytokines and apoptosis of hepatic stellate cells through the STAT3-SOCS3 pathway terminating the underlying fibrosis in HE.

Pediatric Liver Disease Patients and Secondary Glycosylation Abnormalities

Background: Isoelectric focusing (IEF) of serum transferrin (Tf) is still the method of choice for diagnosis of congenital disorders of glycosylation (CDG). An abnormal glycosylation is also a known phenomenon in adult liver disease patients. The aim of this study was to characterize glycosylation disturbances in pediatric patients with primary liver disease. However, there are no reports of this phenomenon in children. Materials and Methods: Between 1995 and 2019, circa 2,000 serum Tf isoform analyses have been performed in children with primary liver diseases; some of them underwent subsequent analyses. We enrolled in this study 19 patients who developed an acute liver injury (ALI)/failure (ALF) or exhibited a chronic liver disease (CLD) and were evaluated and listed for liver transplantation (LTx) or had just undergone this procedure, and secondary abnormal serum Tf isoform profile. Results: Among 12 patients with ALI/ALF, 10 had an increased percentage of asialo-, monosialo-, and disialo-Tf isoforms. All patients with CLD had an increased percentage of asialo- and monosialo-Tf isoform. Two patients diagnosed with recurrent ALF had very specific serum Tf profile with a huge increase in the asialo- and monosialo-Tf isoform. On follow-up analyses (available in some patients), serum Tf IEF profile normalized in parallel to normalization of liver function tests, spontaneously or during treatment, including glucocorticosteroids in AIH, LTx in CLD. Conclusions: All pediatric patients with primary liver disease had increased asialo-Tf as well as monosialo-Tf isoforms. None of them had elevated percentage of trisialo-Tf isoform.

Immune-mediated liver injury of the cancer therapeutic antibody catumaxomab targeting EpCAM, CD3 and Fcγ receptors

The immunotherapeutic catumaxomab targets EpCAM positive cancers and is approved for the treatment of peritoneal carcinomatosis. To assess the safety of intravenous applications a phase 1 clinical trial was initiated. Treatment of EpCAM positive tumor patients with catumaxomab caused dose dependent hepatitis as evidenced by significant elevations in serum alanine- and aspartate aminotransferases, bilirubin, γGT and induction of the acute phase C-reactive protein (CRP) and the cytokines IL6 and IL8. The first patient receiving 10μg catumaxomab experienced fatal acute liver failure which led to the termination of the study. Immmunopathology revealed catumaxomab to bind via its Fc-fragment to FcγR-positive Kupffer cells to stimulate CRP, chemokine and cytokine release. The observed CD3+T-cell margination at activated hepatic macrophages exacerbated T-cell mediated cytotoxicity. Strikingly, the combined Kupffer/T-cell responses against liver cells did not require hepatocytes to be EpCAM-positive. Catumaxomab's off-target activity involved T-cell mediated lysis of the granzyme B cell death pathway and the molecular interaction of hepatic sinusoidal macrophages with T-cells induced cytolytic hepatitis. Although the bile ducts were surrounded by densely packed lymphocytes these rarely infiltrated the ducts to suggest an intrahepatic cholestasis as the cause of hyperbilirubinaemia. Lastly, evidence for the programming of memory T-cells was observed with one patient that succumbed to his cancer six weeks after the last catumaxomab infusion. In conclusion, our study exemplifies off-target hepatotoxicity with molecularly targeted therapy and highlights the complexities in the clinical development of immunotherapeutic antibodies.

Porcine Adipose-Derived Mesenchymal Stem Cells Retain Their Stem Cell Characteristics and Cell Activities While Enhancing the Expression of Liver-Specific Genes after Acute Liver Failure

Acute liver failure (ALF) is a kind of complicated syndrome. Furthermore, adipose-derived mesenchymal stem cells (ADMSCs) can serve as a useful cell resource for autotransplantation due to their abundance and micro-invasive accessability. However, it is unknown how ALF will influence the characteristics of ADMSCs and whether ADMSCs from patients suffering from end-stage liver diseases are potential candidates for autotransplantation. This study was designed to compare various properties of ALF-derived ADMSCs with normal ADMSCs in pig models, with regard to their cellular morphology, cell proliferative ability, cell apoptosis, expression of surface antigens, mitochondrial and lysosomal activities, multilineage potency, and expression of liver-specific genes. Our results showed that ALF does not influence the stem cell characteristics and cell activities of ADMSCs. Intriguingly, the expression levels of several liver-specific genes in ALF-derived ADMSCs are higher than in normal ADMSCs. In conclusion, our findings indicate that the stem cell characteristics and cell activities of ADMSCs were not altered by ALF and these cells can serve as a new source for regenerative medicine.

Immune mechanisms in acetaminophen-induced acute liver failure

An overdose of acetaminophen (N-acetyl-p-aminophenol, APAP), also termed paracetamol, can cause severe liver damage, ultimately leading to acute liver failure (ALF) with the need of liver transplantation. APAP is rapidly taken up from the intestine and metabolized in hepatocytes. A small fraction of the metabolized APAP forms cytotoxic mitochondrial protein adducts, leading to hepatocyte necrosis. The course of disease is not only critically influenced by dose of APAP and the initial hepatocyte damage, but also by the inflammatory response following acetaminophen-induced liver injury (AILI). As revealed by mouse models of AILI and corresponding translational studies in ALF patients, necrotic hepatocytes release danger-associated-molecular patterns (DAMPs), which are recognized by resident hepatic macrophages, Kupffer cell (KC), and neutrophils, leading to the activation of these cells. Activated hepatic macrophages release various proinflammatory cytokines, such as TNF-α or IL-1β, as well as chemokines (e.g., CCL2) thereby further enhancing inflammation and increasing the influx of immune cells, like bone-marrow derived monocytes and neutrophils. Monocytes are mainly recruited via their receptor CCR2 and aggravate inflammation. Infiltrating monocytes, however, can mature into monocyte-derived macrophages (MoMF), which are, in cooperation with neutrophils, also involved in the resolution of inflammation. Besides macrophages and neutrophils, distinct lymphocyte populations, especially γδ T cells, are also linked to the inflammatory response following an APAP overdose. Natural killer (NK), natural killer T (NKT) and T cells possibly further perpetuate inflammation in AILI. Understanding the complex interplay of immune cell subsets in experimental models and defining their functional involvement in disease progression is essential to identify novel therapeutic targets for human disease.