Future Approaches and Therapeutic Modalities for Acute Liver Failure

Decreased miR-17-92 cluster correlates with senescence features, disrupted oxidative homeostasis, and impaired therapeutic efficacy of mesenchymal stem cells

Aging and replicative cellular senescence are associated with the reduced therapeutic potential of mesenchymal stem cells (MSCs) on a variety of diseases. This study aimed to determine the mechanism in MSC senescence and further explore a modification strategy to reverse senescence-associated cell dysfunction to improve the therapeutic efficacy of MSCs on acute liver failure (ALF). We found that the adipose tissue-derived MSCs from old mice (oAMSCs) exhibited senescence phenotypes and showed reduced therapeutic efficacy in lipopolysaccharide and D-galactosamine-induced ALF, as shown by the increased hepatic necrosis, liver histology activity index scores, serum liver function indicator levels, and inflammatory cytokine levels. The expression of miR-17-92 cluster members, especially miR-17 and miR-20a, was obviously decreased in oAMSCs and replicatively senescent AMSCs, and was consistent with the decreased oncogene c-Myc level during AMSC senescence and may mediate c-Myc stemness addiction. Further experiments revealed that c-Myc-regulated miR-17-92 expression contributed to increased p21 expression and redox system dysregulation during AMSC senescence. Furthermore, modification of AMSCs with the two key miRNAs in the miR-17-92 cluster mentioned above reversed the senescence features of oAMSCs and restored the therapeutic effect of senescent AMSCs on ALF. In conclusion, the cellular miR-17-92 cluster level is correlated with AMSC senescence and can be used both as an index for evaluating and as a modification target for improving the therapeutic potential of AMSCs.NEW & NOTEWORTHY We reported for the first time that c-Myc-regulated miR-17-92 contributed to increased p21 expression and redox system dysregulation during AMSC senescence and was associated with the reduced therapeutic effects of senescent AMSCs on ALF. Moreover, modifying the expression of the miR-17-92 cluster members, especially miR-17 and/or miR-20a, could reverse AMSC senescence. Thus, miR-17-92 cluster can be used both as an index for evaluating and as a modification strategy for improving the therapeutic potential of AMSCs.

Future Approaches and Therapeutic Modalities for Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) results from an acute decompensation of cirrhosis due to exogenous insult. The condition is characterized by a severe systemic inflammatory response, inappropriate compensatory anti-inflammatory response, multisystem extrahepatic organ failure, and high short-term mortality. Here, the authors evaluate the current status of potential treatments for ACLF and assess their efficacy and therapeutic potential.

Cell therapy in end-stage liver disease: replace and remodel

Liver disease is prevalent worldwide. When it reaches the end stage, mortality rises to 50% or more. Although liver transplantation has emerged as the most efficient treatment for end-stage liver disease, its application has been limited by the scarcity of donor livers. The lack of acceptable donor organs implies that patients are at high risk while waiting for suitable livers. In this scenario, cell therapy has emerged as a promising treatment approach. Most of the time, transplanted cells can replace host hepatocytes and remodel the hepatic microenvironment. For instance, hepatocytes derived from donor livers or stem cells colonize and proliferate in the liver, can replace host hepatocytes, and restore liver function. Other cellular therapy candidates, such as macrophages and mesenchymal stem cells, can remodel the hepatic microenvironment, thereby repairing the damaged liver. In recent years, cell therapy has transitioned from animal research to early human studies. In this review, we will discuss cell therapy in end-stage liver disease treatment, especially focusing on various cell types utilized for cell transplantation, and elucidate the processes involved. Furthermore, we will also summarize the practical obstacles of cell therapy and offer potential solutions.

Chrysophanol-8-O-glucoside protects mice against acute liver injury by inhibiting autophagy in hepatic stellate cells and inflammatory response in liver-resident macrophages

Acute liver failure (ALF) is an unfavorable condition characterized by the rapid loss of liver function and high mortality. Chrysophanol-8-O-glucoside (CPOG) is an anthraquinone derivative isolated from rhubarb. This study aims to evaluate the protective effect of CPOG on lipopolysaccharide (LPS)/D-GalN-induced ALF and its underlying mechanisms. LPS/D-GalN-induced mice ALF model and LPS treatment model in RAW 264.7 and LX2 cells were established. It was found that CPOG ameliorated LPS/D-GalN-induced liver injury and improved mortality as indicated by Hematoxylin-eosin (H&E) staining. Molecularly, qPCR and ELISA results showed that CPOG alleviated LPS/D-GalN-induced release of alanine aminotransferase and aspartate transaminase and the secretion of TNF-α and IL-1β in vivo. LPS/D-GalN-induced intracellular ROS production was also attenuated by CPOG in liver tissue. Further, CPOG attenuated ROS generation and inhibited the expression of p-IκB and p-p65 as well as the expression of TNF-α and IL-1β stimulated by LPS in RAW 264.7 cells. In addition, CPOG alleviated LPS-induced up-regulation of LC3B, p62, ATG5 and Beclin1 by attenuating ROS production and inhibiting MAPK signaling in LX2 cells. Taken together, our data indicated that the CPOG protected against LPS/D-GalN-induced ALF by inhibiting oxidative stress, inflammation response and autophagy. These findings suggest that CPOG could be potential drug for the treatment of ALF in clinic.

The therapeutic potential of exosomes derived from different cell sources in liver diseases

Exosomes are small nanovesicles with a size of approximately 40-120 nm that are secreted from cells. They are involved in the regulation of cell homeostasis and mediate intercellular communication. In addition, they carry proteins, nucleic acids, and lipids that regulate the biological activity of receptor cells. Recent studies have shown that exosomes perform important functions in liver diseases. This review will focus on liver diseases (drug-induced liver injury, hepatic ischemia-reperfusion injury, liver fibrosis, acute liver failure, and hepatocellular carcinoma) and summarize the therapeutic potential of exosomes from different cell sources in liver disease.

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.

UMSCs Attenuate LPS/D-GalN-induced Acute Liver Failure in Mice by Down-regulating the MyD88/NF-κB Pathway

BACKGROUND AND AIMS

Acute liver failure (ALF) is an inflammatory process of acute liver cell injury. Mesenchymal stem cells (MSCs) are undifferentiated, primitive cells with anti-inflammatory, anti-apoptotic, and multi-directional differentiation abilities. This study aimed to explore the therapeutic mechanism of umbilical cord (U)MSCs in ALF.

METHODS

D-galactosamine (D-GalN) combined with lipopolysaccharide (LPS) was used to establish an ALF model. After model establishment, UMSCs were injected via the tail vein. After UMSC transplantation, the number of mouse deaths was monitored every 12 h. A fully automatic biochemical analyzer was used to detect changes in biochemical analysis. Pathological changes was observed by stained with hematoxylin and eosin.The expression of My D88 was detected by immunohistochemical analysis, quantitative reverse transcription, and western blotting. The expression of NF-κB was detected by quantitative reverse transcription, western blotting.The expression of Bcl-2,Bax were detected by quantitative reverse transcription, western blotting.The expression of TNF-α, IL-1β, IL-6 were detected by enzyme-linked immunosorbent assay.

RESULTS

The 48-h survival rate of the UMSC-treated group was significantly higher than that of the LPS/D-GalN-exposed group. After 24 h of LPS/D-GalN exposure, UMSCs reduced serum alanine aminotransferase and aspartate aminotransferase levels and improved the liver structure. Western blot and real-time fluorescence quantitative nucleic acid amplification analyses showed that UMSCs decreased MyD88 expression, thereby inhibiting LPS/GalN-induced phosphorylation and degradation of inhibitor of nuclear factor (NF)-κB (IκB). Additionally, NF-κB p65 underwent nuclear translocation, inhibiting the production of the inflammatory factors interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α and played a protective role in ALF by down-regulating the pro-apoptotic gene Bax and up-regulating the anti-apoptotic gene Bcl-2. In summary, these findings indicate that UMSCs play a protective role in LPS/GalN-induced acute liver injury via inhibition of the MyD88 pathway and subsequent inhibition of NF-κB-mediated cytokine production.

CONCLUSIONS

Through the above mechanisms, UMSCs can effectively reduce LPS/D-GalN-induced ALF, reduce mouse mortality, and restore damaged liver function and damaged liver tissue.

Current understanding of mesenchymal stem cells in liver diseases

Liver diseases caused by various factors have become a significant threat to public health worldwide. Liver transplantation has been considered as the only effective treatment for end-stage liver diseases; however, it is limited by the shortage of donor organs, postoperative complications, long-term immunosuppression, and high cost of treatment. Thus, it is not available for all patients. Recently, mesenchymal stem cells (MSCs) transplantation has been extensively explored for repairing hepatic injury in various liver diseases. MSCs are multipotent adult progenitor cells originated from the embryonic mesoderm, and can be found in mesenchymal tissues including the bone marrow, umbilical cord blood, adipose tissue, liver, lung, and others. Although the precise mechanisms of MSC transplantation remain mysterious, MSCs have been demonstrated to be able to prevent the progression of liver injury and improve liver function. MSCs can self-renew by dividing, migrating to injury sites and differentiating into multiple cell types including hepatocytes. Additionally, MSCs have immune-modulatory properties and release paracrine soluble factors. Indeed, the safety and effectiveness of MSC therapy for liver diseases have been demonstrated in animals. However, pre-clinical and clinical trials are largely required to confirm its safety and efficacy before large scale clinical application. In this review, we will explore the molecular mechanisms underlying therapeutic effects of MSCs on liver diseases. We also summarize clinical advances in MSC-based therapies.

Selonsertib, a potential drug for liver failure therapy by rescuing the mitochondrial dysfunction of macrophage via ASK1-JNK-DRP1 pathway

Background

Acute liver failure (ALF) is associated with a high mortality rate, and there are still no effective treatments except liver transplantation and artificial liver therapies. This study aimed to determine the effects, therapeutic window and mechanisms of selonsertib, a selective inhibitor of ASK1, for ALF therapy.

Results

Lipopolysaccharide and d-galactosamine (LPS/GalN) were used to simulate ALF. We found that selonsertib pretreatment significantly ameliorated ALF, as determined by reduced hepatic necrosis and serum alanine aminotransferase, aspartate aminotransferase and inflammatory cytokine levels. However, selonsertib is only effective early after LPS/GalN administration, and the limited therapeutic window is related to the activation and mitochondrial translocation of JNK and DRP1. Further experiments revealed that selonsertib could alleviate LPS-induced mitochondrial damage in macrophages by evaluating the mitochondrial membrane potential and mitochondrial permeability transition pore opening in macrophages. Selonsertib also suppressed the release of inflammatory cytokines from macrophages by reducing DRP1-mediated mitochondrial dysfunction, which was confirmed by using mdivi, a specific DRP1 inhibitor.

Conclusions

Selonsertib protected against LPS/GalN-induced ALF by attenuating JNK-mediated DRP1 mitochondrial translocation and then rescuing mitochondrial damage in macrophages and may have therapeutic potential for early ALF patients.

Sex-linked differences in the course of thioacetamide-induced acute liver failure in Lewis rats

Acute liver failure (ALF) is a clinical syndrome with high mortality rate, resulting from widespread hepatocyte damage. Its pathophysiological background is still poorly understood and preclinical studies evaluating pathophysiology and new potential therapeutic measures are needed. The model of ALF induced by administration of thioacetamide (TAA) in Lewis rats is recommended as optimal; however, the limitation of previous studies was that they were performed predominantly in male rats. In view of the growing recognition that sex as a biological variable should be taken into consideration in preclinical research, we examined its role in the development of TAA-induced ALF in Lewis rats. We found that, first, intact male Lewis rats showed lower survival rate than their female counterparts, due to augmented liver injury documented by higher plasma ammonia, and bilirubin levels and alanine aminotransferase activity. Second, in female rats castration did not alter the course of TAA-induced ALF whereas in the male gonadectomy improved the survival rate and attenuated liver injury, reducing it to levels observed in their female counterparts. In conclusion, we found that Lewis rats show a remarkable sexual dimorphism with respect to TAA-induced ALF, and male rats display dramatically poorer prognosis as compared with the females. We showed that testosterone is responsible for the deterioration of the course of TAA-induced ALF in male rats. In most general terms, our findings indicate that in the preclinical studies of the pathophysiology and treatment of ALF (at least of the TAA-induced form) the sex-linked differences should be seriously considered.

Roles of Macrophages and Exosomes in Liver Diseases

Exosomes are small discoid extracellular vesicles (EVs) originating from endosomes that are 30-150 nm in diameter and have a double lipid layer. They participate in the immune response, cell migration, cell differentiation, and tumor invasion and mediate intercellular communication, regulating the biological activity of receptor cells through the proteins, nucleic acids, and lipids that they carry. Exosomes also play vital roles in the diagnosis and treatment of liver diseases. Macrophages, which show unique phenotypes and functions in complex microenvironments, can be divided into M1 and M2 subtypes. M1 macrophages function in immune surveillance, and M2 macrophages downregulate the immune response. Recent studies have shown that macrophages are involved in non-alcoholic fatty liver disease, liver fibrosis, and hepatocellular carcinoma. Moreover, several studies have demonstrated that liver diseases are associated with exosomes derived from or transferred to macrophages. This review focuses on the participation of macrophages and exosomes in liver diseases.

Pharmacological stimulation of Wnt/beta-catenin signaling pathway attenuates the course of thioacetamide-induced acute liver failure

Acute liver failure (ALF) is known for extremely high mortality rate, the result of widespread damage of hepatocytes. Orthotopic liver transplantation is the only effective therapy but its application is limited by the scarcity of donor organs. Given the importance in the liver biology of Wnt/beta-catenin signaling pathway, we hypothesized that its stimulation could enhance hepatocyte regeneration and attenuate the course of thioacetamide (TAA)-induced ALF in Lewis rats. Chronic treatment with Wnt agonist was started either immediately after hepatotoxic insult ("early treatment") or when signs of ALF had developed ("late treatment"). Only 23 % of untreated Lewis rats survived till the end of experiment. They showed marked increases in plasma alanine aminotransferase (ALT) activity and bilirubin and ammonia (NH3) levels; plasma albumin decreased significantly. "Early" and "late" Wnt agonist treatment raised the final survival rate to 69 % and 63 %, respectively, and normalized ALT, NH3, bilirubin and albumin levels. In conclusion, the results show that treatment with Wnt agonist attenuates the course of TAA-induced ALF in Lewis rats, both with treatment initiated immediately after hepatotoxic insult and in the phase when ALF has already developed. Thus, the pharmacological stimulation of Wnt/beta-catenin signaling pathway can present a new approach to ALF treatment.

Inducing differentiation of human urine-derived stem cells into hepatocyte-like cells by coculturing with human hepatocyte L02 cells

OBJECTIVES

To investigate the possibility of inducing differentiation of human urine-derived stem cells (hUSCs) into hepatocyte-like cells by coculturing with human hepatocyte L02 cells in vitro.

METHODS

HUSCs were isolated from fresh urine samples collected from healthy adult volunteers by centrifugation. Cells were observed under an inverted phase contrast microscope, and proliferative activity was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Stem cell surface markers were detected by flow cytometry. HUSCs were induced to differentiate into hepatocyte-like cells by coculturing with human hepatocyte L02 cells, which were confirmed by cellular morphology, messenger RNA expression of albumin (ALB), α-fetoprotein (AFP) and hepatocyte cytochrome P450 (CYP450) analyzed with quantitative reverse transcription polymerase chain reaction and the expression of glycogen detected by glycogen staining kits at 5, 10, and 15 days after coculturing.

RESULTS

HUSCs from urine were successfully isolated and cultured in vitro. At passages 3, the growth curve of hUSCs was S-shaped with good proliferation activity. Mesenchymal stem cell surface markers CD44 and CD90 were detected positive by flow cytometry. CD31 for endothelial cells and CD34 for hematopoietic stem cell markers were not detected. HUSCs gained the cellular morphology and function of hepatocyte cells including higher expression of several hepatocyte-specific genes such as ALB and some CYP450, lower expression of AFP and positive glycogen expression (P <  .05) in coculturing with human hepatocyte L02 cells for 10-15d.

CONCLUSIONS

HUSCs can be induced to differentiate into hepatocyte-like cells by coculturing with human hepatocyte L02 cells for a certain number of days.

In Vivo Real-Time Imaging of Extracellular Vesicles in Liver Regeneration via Aggregation-Induced Emission Luminogens

Extracellular vesicles (EVs) attract much attention in liver pathology because they regulate cell-cell communication and many pathophysiological events by transferring their cargos. Monitoring and understanding the in vivo fate and therapeutic capacity of these EVs is critical for the development and optimization of EV-based diagnosis and therapy. Herein, we demonstrate the use of an aggregation-induced emission luminogen, DPA-SCP, for the real-time tracking of EVs derived from human placenta-derived mesenchymal stem cells (MSCs) and their therapeutic effects in a mouse acute liver injury (ALI) model. In vitro, DPA-SCP does not alter the inherent characteristics of MSC-derived EVs and shows extremely low toxicity. Moreover, DPA-SCP exhibited superior labeling efficiency and tracking capability to the most popular commercial EV trackers, PKH26 and DiI. In vivo, DPA-SCP precisely and quantitatively tracked the behaviors of EVs for 7 days in the mouse ALI model without influencing their regenerative capacity and therapeutic efficacy. The therapeutic effects of EVs may attribute to their ability for reducing inflammatory cell infiltration, enhancing cell survival and antiapoptotic effects. In conclusion, DPA-SCP with an AIE signature serves as a favorable and safe tracker for in vivo real-time imaging of EVs in liver regeneration.

SKLB023 protects mice against acute liver injury by inhibiting proinflammatory cytokine production in both T cells and macrophages

Acute liver failure is a severe clinical syndrome accompanied with excessive inflammatory response. Our previous study demonstrated that SKLB023, a novel thiazolidinedione derivative, showed potent anti-inflammatory activity in rheumatoid arthritis. The purpose of the present study is to evaluate the protective effect of SKLB023 on lipopolysaccharide (LPS)/D-GalN-induced liver failure and to explore the underlying molecular mechanisms. Our results showed that SKLB023 significantly improved mortality and liver injury as indicated by reduced serum levels of aminotransferases and alleviated pathological damage. Additionally, SKLB023 decreased the percentage of activated T cells and macrophages as well as the serum levels of cytokines in vivo. Furthermore, SKLB023 decreased levels of TNF-α and IL-6 secreted from liver macrophages (Kupffer cells) stimulated by LPS in vitro. Our results indicated that the protective effects of SKLB023 were associated with its significant impact on the inflammatory cytokines, which were produced by both T cells and macrophages.

A novel thiazolidinedione derivative SKLB023 offers a potent therapeutic strategy for the treatment of acute liver failure.

AMSC-derived exosomes alleviate lipopolysaccharide/d-galactosamine-induced acute liver failure by miR-17-mediated reduction of TXNIP/NLRP3 inflammasome activation in macrophages

Background

Mesenchymal stem cell (MSC)-derived exosome administration has been considered as a novel cell-free therapy for liver diseases through cell-cell communication. This study was aimed to determine the effects and mechanisms of AMSC-derived exosomes (AMSC-Exo) for acute liver failure (ALF) treatment.

Methods

AMSC-Exo were intravenously administrated into the mice immediately after lipopolysaccharide and D-galactosamine (LPS/GalN)-exposure and their effects were evaluated by liver histological and serum biochemical analysis. To elucidate its mechanisms in ALF therapy, the expression levels of miRNAs and inflammasome-related genes in macrophages were evaluated by qPCR and Western blot analysis, respectively. The exosomes from miR-17-knockdowned AMSCs (AMSC-Exo^miR-17-KD) were used for further determine the role of miR-17 in AMSC-Exo-based therapy.

Findings

AMSC-Exo administration significantly ameliorated ALF as determined by reduced serum alanine aminotransferase and aspartate aminotransferase levels and hepatic inflammasome activation. Further experiments revealed that AMSC-Exo were colocalized with hepatic macrophages and could reduce inflammatory factor secretion by suppressing inflammasome activation in macrophages. Moreover, miR-17, which can suppress NLRP3 inflammasome activation by targeting TXNIP, was abundant in AMSC-Exo cargo. While, the therapeutic effects of AMSC-Exo^miR-17-KD on ALF were significantly abolished as they could not effectively suppress TXNIP expression and consequent inflammasome activation in vitro and in vivo.

Interpretation: Exosome-shuttled miR-17 plays an essential role in AMSC-Exo therapy for ALF by targeting TXNIP and suppressing inflammasome activation in hepatic macrophages. AMSC-Exo-based therapy may present as a promising approach for TXNIP/NLRP3 inflammasome-related inflammatory liver diseases.

Fund

Key R&D projects of Zhejiang province (2018C03019) and National Natural Science Fund (81470851 and 81500616).