Regeneration in acute-on-chronic liver failure - the phantom lost its camouflage

The Immunoregulatory and Regenerative Potential of Activated Human Stem Cell Secretome Mitigates Acute-on-Chronic Liver Failure in a Rat Model

Acute-on-chronic liver failure (ACLF) is a syndrome marked by sudden liver function decline and multiorgan failure, predominantly acute kidney injury (AKY), in patients with chronic liver disease. Unregulated inflammation is a hallmark of ACLF; however, the key drivers of ACLF are not fully understood. This study explores the therapeutic properties of human mesenchymal stem cell (MSC) secretome, particularly focusing on its enhanced anti-inflammatory and pro-regenerative properties after the in vitro preconditioning of the cells. We evaluated the efficacy of the systemic administration of MSC secretome in preventing liver failure and AKI in a rat ACLF model where chronic liver disease was induced using by the administration of porcine serum, followed by D-galN/LPS administration to induce acute failure. After ACLF induction, animals were treated with saline (ACLF group) or MSC-derived secretome (ACLF-secretome group). The study revealed that MSC-secretome administration strongly reduced liver histological damage in the ACLF group, which was correlated with higher hepatocyte proliferation, increased hepatic and systemic anti-inflammatory molecule levels, and reduced neutrophil and macrophage infiltration. Additionally, renal examination revealed that MSC-secretome treatment mitigated tubular injuries, reduced apoptosis, and downregulated injury markers. These improvements were linked to increased survival rates in the ACLF-secretome group, endorsing MSC secretomes as a promising therapy for multiorgan failure in ACLF.

Therapeutic potential of stem cells in regeneration of liver in chronic liver diseases: Current perspectives and future challenges

The deposition of extracellular matrix and hyperplasia of connective tissue characterizes chronic liver disease called hepatic fibrosis. Progression of hepatic fibrosis may lead to hepatocellular carcinoma. At this stage, only liver transplantation is a viable option. However, the number of possible liver donors is less than the number of patients needing transplantation. Consequently, alternative cell therapies based on non-stem cells (e.g., fibroblasts, chondrocytes, keratinocytes, and hepatocytes) therapy may be able to postpone hepatic disease, but they are often ineffective. Thus, novel stem cell-based therapeutics might be potentially important cutting-edge approaches for treating liver diseases and reducing patient' suffering. Several signaling pathways provide targets for stem cell interventions. These include pathways such as TGF-β, STAT3/BCL-2, NADPH oxidase, Raf/MEK/ERK, Notch, and Wnt/β-catenin. Moreover, mesenchymal stem cells (MSCs) stimulate interleukin (IL)-10, which inhibits T-cells and converts M1 macrophages into M2 macrophages, producing an anti-inflammatory environment. Furthermore, it inhibits the action of CD4+ and CD8+ T cells and reduces the activity of TNF-α and interferon cytokines by enhancing IL-4 synthesis. Consequently, the immunomodulatory and anti-inflammatory capabilities of MSCs make them an attractive therapeutic approach. Importantly, MSCs can inhibit the activation of hepatic stellate cells, causing their apoptosis and subsequent promotion of hepatocyte proliferation, thereby replacing dead hepatocytes and reducing liver fibrosis. This review discusses the multidimensional therapeutic role of stem cells as cell-based therapeutics in liver fibrosis.

Combination of G-CSF and a TLR4 inhibitor reduce inflammation and promote regeneration in a mouse model of ACLF

BACKGROUND & AIMS

Acute-on-chronic liver failure (ACLF) is characterised by high short-term mortality, systemic inflammation, and failure of hepatic regeneration. Its treatment is a major unmet medical need. This study was conducted to explore whether combining TAK-242, a Toll-like receptor-4 (TLR4) antagonist, with granulocyte-colony stimulating factor (G-CSF), could reduce inflammation whilst enhancing liver regeneration.

METHODS

Two mouse models of ACLF were investigated. Chronic liver injury was induced by carbon tetrachloride; lipopolysaccharide (LPS) or galactosamine (GalN) were then administered as extrahepatic or hepatic insults, respectively. G-CSF and/or TAK-242 were administered daily. Treatment durations were 24 hours and 5 days in the LPS model and 48 hours in the GalN model.

RESULTS

In a mouse model of LPS-induced ACLF, treatment with G-CSF was associated with significant mortality (66% after 48 hours vs. 0% without G-CSF). Addition of TAK-242 to G-CSF abrogated mortality (0%) and significantly reduced liver cell death, macrophage infiltration and inflammation. In the GalN model, both G-CSF and TAK-242, when used individually, reduced liver injury but their combination was significantly more effective. G-CSF treatment, with or without TAK-242, was associated with activation of the pro-regenerative and anti-apoptotic STAT3 pathway. LPS-driven ACLF was characterised by p21 overexpression, which is indicative of hepatic senescence and inhibition of hepatocyte regeneration. While TAK-242 treatment mitigated the effect on senescence, G-CSF, when co-administered with TAK-242, resulted in a significant increase in markers of hepatocyte regeneration.

CONCLUSION

The combination of TAK-242 and G-CSF inhibits inflammation, promotes hepatic regeneration and prevents mortality in models of ACLF; thus, this combination could be a potential treatment option for ACLF.

LAY SUMMARY

Acute-on-chronic liver failure is associated with severe liver inflammation and poor short-term survival. Therefore, effective treatments are urgently needed. Herein, we have shown, using mouse models, that the combination of granulocyte-colony stimulating factor (which can promote liver regeneration) and TAK-242 (which inhibits a receptor that plays a key role in inflammation) could be effective for the treatment of acute-on-chronic liver failure.

Prospect of Animal Models for Acute-on-chronic Liver Failure: A Mini-review

Acute-on-chronic liver failure (ACLF) is a clinical syndrome that develops in patients with chronic liver diseases following a precipitating event and associated with a high mortality rate due to systemic multiorgan failure. Establishing a suitable and stable animal model to precisely elucidate the molecular basis of ACLF pathogenesis is essential for the development of effective early diagnostic and treatment strategies. In this context, this article provides a concise and inclusive review of breakthroughs in ACLF animal model development.

Cirrhosis-Based Acute-on-Chronic Liver Failure Is Marked by Inflammation and Impaired Liver Regeneration Despite Stat3 Activation

Background and Aims

Acute-on-chronic liver failure (ACLF) is associated with excessive systemic inflammation, cell death, and organ failures. Yet, little is known about the hepatic histopathology of ACLF. Here, we assessed the histopathology and regenerative capacity of the liver in ACLF with or without cirrhosis.

Methods

Liver specimens of patients with compensated cirrhosis (N = 37), acute decompensation (N = 40), and ACLF with (N = 18) or without (N = 10) cirrhosis were assessed for morphological features and the pro-regenerative Stat3 pathway.

Results

ACLF was associated with high levels of lobular inflammation, tissue necrosis, and apoptosis. In patients with cirrhosis, the percentage of pStat3-positive hepatocytes was increasing with disease severity (3.5%/10.4%/21% for compensated cirrhosis/acute decompensation/cirrhosis-ACLF; P < .001), but lower in noncirrhotic ACLF vs cirrhosis-ACLF (21% vs 13%; P = .02). A distinct pattern of the expression of the proliferation marker Ki-67, a downstream effector marker of pStat3, was observed. Ki-67-positive hepatocytes were more frequent in patients with cirrhosis-ACLF compared to compensated cirrhosis or acute decompensation (4.9% vs 1.3% vs 1.8%; P < .05), but much lower in cirrhosis-ACLF vs noncirrhotic ACLF (4.9% vs 13.5%; P = .01). The ratio of Ki-67-positive to pStat3-positive hepatocytes was lowest in cirrhosis-ACLF and predicted 3-month transplant-free survival accurately (area under the curve = 0.95, P < .00001).

Conclusion

Our study identifies hepatic inflammation and Stat3 activation as hallmarks of ACLF. In cirrhosis-ACLF, Stat3 activation does not appear to translate in effective liver regeneration, which is distinct from noncirrhotic ACLF.

Animal models applied to acute-on-chronic liver failure: Are new models required to understand the human condition?

The liver is a multifaceted organ; its location and detoxifying function expose this organ to countless injuries. Acute-on-chronic failure liver (ACLF) is a severe syndrome that affects the liver due to acute decompensation in patients with chronic liver disease. An infection environment, ascites, increased liver enzymes and prothrombin time, encephalopathy and fast-evolving multiorgan failure, leading to death, usually accompany this. The pathophysiology remains poorly understand. In this context, animal models become a very useful tool in this regard, as understanding; the disease may be helpful in developing novel therapeutic methodologies for ACLF. However, although animal models display several similarities to the human condition, they do not represent all ACLF manifestations, resulting in significant challenges. An initial liver cirrhosis framework followed by the induction of an acute decompensation by administering lipopolysaccharide and D-GaIN, potentiating liver damage supports the methodologies applied to induce experimental ACLF. The entire methodology has been described mostly for rats. Nevertheless, a quick PubMed database search indicates about 30 studies concerning ACFL models and over 1000 regarding acute liver failure models. These findings demonstrate the clear need to establish easily reproducible ACFL models to elucidate questions about this quickly established and often fatal syndrome.

Animal models applied to acute-on-chronic liver failure: Are new models required to understand the human condition?

The liver is a multifaceted organ; its location and detoxifying function expose this organ to countless injuries. Acute-on-chronic failure liver (ACLF) is a severe syndrome that affects the liver due to acute decompensation in patients with chronic liver disease. An infection environment, ascites, increased liver enzymes and prothrombin time, encephalopathy and fast-evolving multiorgan failure, leading to death, usually accompany this. The pathophysiology remains poorly understand. In this context, animal models become a very useful tool in this regard, as understanding; the disease may be helpful in developing novel therapeutic methodologies for ACLF. However, although animal models display several similarities to the human condition, they do not represent all ACLF manifestations, resulting in significant challenges. An initial liver cirrhosis framework followed by the induction of an acute decompensation by administering lipopolysaccharide and D-GaIN, potentiating liver damage supports the methodologies applied to induce experimental ACLF. The entire methodology has been described mostly for rats. Nevertheless, a quick PubMed database search indicates about 30 studies concerning ACFL models and over 1000 regarding acute liver failure models. These findings demonstrate the clear need to establish easily reproducible ACFL models to elucidate questions about this quickly established and often fatal syndrome.

Transcriptomics reveals immune-metabolism disorder in acute-on-chronic liver failure in rats

Liver tissue transcriptomics of liver cirrhosis (LC)–based acute-on-chronic liver failure (ACLF) rats reveal immune-metabolism disorder as the core mechanism underlying ACLF development and prognosis.

Acute-on-chronic liver failure (ACLF) is clinical syndrome with high mortality rate. This study aimed to perform detailed transcriptomic analysis in liver cirrhosis–based ACLF rats to elucidate ACLF pathogenesis. ACLF was induced by combined porcine serum with D-galactosamine and lipopolysaccharide. Gene expression profile of liver tissues from ACLF rats was generated by transcriptome sequencing to reveal the molecular mechanism. ACLF rats successfully developed with typical characteristics. Total of 2,354/3,576 differentially expressed genes were identified when ACLF was compared to liver cirrhosis and normal control, separately. The functional synergy analysis revealed prominent immune dysregulation at ACLF stage, whereas metabolic disruption was significantly down-regulated. Relative proportions of innate immune–related cells showed significant elevation of monocytes and macrophages, whereas adaptive immune–related cells were reduced. The seven differentially expressed genes underlying the ACLF molecular mechanisms were externally validated, among them THBS1, IL-10, and NR4A3 expressions were confirmed in rats, patient transcriptomics, and liver biopsies, verifying their potential value in the ACLF pathogenesis. This study indicates immune-metabolism disorder in ACLF rats, which may provide clinicians new targets for improving intervention strategies.

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.

Yi-Qi-Jian-Pi Formula Suppresses RIPK1/RIPK3-Complex-Dependent Necroptosis of Hepatocytes Through ROS Signaling and Attenuates Liver Injury in Vivo and in Vitro

Acute-on-chronic liver failure (ACLF) is described as a characteristic of acute jaundice and coagulation dysfunction. Effective treatments for ACLF are unavailable and hence are urgently required. We aimed to define the effect of Yi-Qi-Jian-Pi Formula (YQJPF) on liver injury and further examine the molecular mechanisms. In this study, we established CCl₄-, LPS-, and d-galactosamine (D-Gal)-induced ACLF rat models in vivo and LPS- and D-Gal-induced hepatocyte injury models in vitro. We found that YQJPF significantly ameliorates liver injury in vivo and in vitro that is associated with the regulation of hepatocyte necroptosis. Specifically, YQJPF decreased expression of receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3) and pseudokinase mixed lineage kinase domain-like (MLKL) to inhibit the migration of RIPK1 and RIPK3 into necrosome. YQJPF also reduces the expression of inflammatory cytokines IL-6, IL-8, IL-1β, and TNF-α, which were regulated by RIPK3 mediates cell death. RIPK1 depletion was found to enhance the protective effect of YQJPF. Furthermore, we showed that YQJPF significantly downregulates the mitochondrial reactive oxygen species (ROS) production and mitochondrial depolarization, with ROS scavenger, 4-hydroxy-TEMPO treatment recovering impaired RIPK1-mediated necroptosis and reducing the expression of IL-6, IL-8, IL-1β, and TNF-α. In summary, our study revealed the molecular mechanism of protective effect of YQJPF on hepatocyte necroptosis, targeting RIPK1/RIPK3-complex-dependent necroptosis via ROS signaling. Overall, our results provided a novel perspective to indicate the positive role of YQJPF in ACLF.