Mechanisms Of Liver Regeneration Research Articles

Apolipoprotein A-1 Accelerated Liver Regeneration Through Regulating Autophagy Via AMPK-ULK1 Pathway

Apolipoprotein A-1 (ApoA-1), the main apolipoprotein of high-density lipoprotein, has been well studied in the area of lipid metabolism and cardiovascular diseases. In this project, we clarify the function and mechanism of ApoA-1 in liver regeneration. Seventy percent of partial hepatectomy was applied in male ApoA-1 knockout mice and wild-type mice to investigate the effects of ApoA-1 on liver regeneration. D-4F (ApoA-1 mimetic peptide), autophagy activator, and AMPK activator were used to explore the mechanism of ApoA-1 on liver regeneration. We demonstrated that ApoA-1 levels were highly expressed during the early stage of liver regeneration. ApoA-1 deficiency greatly impaired liver regeneration after hepatectomy. Meanwhile, we found that ApoA-1 deficiency inhibited autophagy during liver regeneration. The activation of autophagy protected against ApoA-1 deficiency in inhibiting liver regeneration. Furthermore, ApoA-1 deficiency impaired autophagy through AMPK-ULK1 pathway, and AMPK activation significantly improved liver regeneration. The administration of D-4F could accelerated liver regeneration after hepatectomy. These findings suggested that ApoA-1 played an essential role in liver regeneration through promoting autophagy in hepatocytes via AMPK-ULK1 pathway. Our findings enrich the understanding of the underlying mechanism of liver regeneration and provide a potential therapeutic strategy for liver injury.

Mechanism of liver regeneration: 20-year bibliometric analyses.

Objectives: The study aims to explore the most influential countries, institutions, journals, authors, "research hotspots," and trends in the study of the mechanism of liver regeneration (MoLR) in the last 20years using bibliometric analyses. Methods: The literature associated with the MoLR was retrieved from the Web of Science Core Collection on 11 October 2022. CiteSpace 6.1.R6 (64-bit) and VOSviewer 1.6.18 were used for bibliometric analyses. Results: A total of 18,956 authors from 2,900 institutions in 71 countries/regions published 3,563 studies in different academic journals on the MoLR. The United States was the most influential country. The University of Pittsburgh was the institution from which most articles on the MoLR were published. Cunshuan Xu published the most articles on the MoLR, and George K. Michalopoulos was the most frequently co-cited author. Hepatology was the journal in which most articles on the MoLR were published and the most frequently co-cited journal in this field. The research hotspots for the MoLR were origin and subsets of hepatocytes during LR; new factors and pathways in LR regulation; cell therapy for LR; interactions between liver cells in LR; mechanism of the proliferation of residual hepatocytes and trans-differentiation between cells; and prognosis of LR. The emerging topic was the mechanism of regeneration of a severely injured liver. Conclusion: Our bibliometric analyses provide (i) a comprehensive overview of the MoLR; (ii) important clues and ideas for scholars in this field.

The pharmacology and mechanisms of traditional Chinese medicine in promoting liver regeneration: A new therapeutic option

BackgroundThe liver is renowned for its remarkable regenerative capacity to restore its structure, size and function after various types of liver injury. However, in patients with end-stage liver disease, the regenerative capacity is inhibited and liver transplantation is the only option. Considering the limitations of liver transplantation, promoting liver regeneration is suggested as a new therapeutic strategy for liver disease. Traditional Chinese medicine (TCM) has a long history of preventing and treating various liver diseases, and some of them have been proven to be effective in promoting liver regeneration, suggesting the therapeutic potential in liver diseases. PurposeThis review aims to summarize the molecular mechanisms of liver regeneration and the pro-regenerative activity and mechanism of TCM formulas, extracts and active ingredients. MethodsWe conducted a systematic search in PubMed, Web of Science and the Cochrane Library databases using "TCM", "liver regeneration" or their synonyms as keywords, and classified and summarized the retrieved literature. The PRISMA guidelines were followed. ResultsForty-one research articles met the themes of this review and previous critical studies were also reviewed to provide essential background information. Current evidences indicate that various TCM formulas, extracts and active ingredients have the effect on stimulating liver regeneration through modulating JAK/STAT, Hippo, PI3K/Akt and other signaling pathways. Besides, the mechanisms of liver regeneration, the limitation of existing studies and the application prospect of TCM to promote liver regeneration are also outlined and discussed in this review. ConclusionThis review supports TCM as new potential therapeutic options for promoting liver regeneration and repair of the failing liver, although extensive pharmacokinetic and toxicological studies, as well as elaborate clinical trials, are still needed to demonstrate safety and efficacy.

Digital twin demonstrates significance of biomechanical growth control in liver regeneration after partial hepatectomy

Partial liver removal is an important therapy option for liver cancer. In most patients within a few weeks, the liver is able to fully regenerate. In some patients, however, regeneration fails with often severe consequences. To better understand the control mechanisms of liver regeneration, experiments in mice were performed, guiding the creation of a spatiotemporal 3D model of the regenerating liver. The model represents cells and blood vessels within an entire liver lobe, a macroscopic liver subunit. The model could reproduce the experimental data only if a biomechanical growth control (BGC)-mechanism, inhibiting cell cycle entrance at high compression, was taken into account and predicted that BGC may act as a short-range growth inhibitor minimizing the number of proliferating neighbor cells of a proliferating cell, generating a checkerboard-like proliferation pattern. Model-predicted cell proliferation patterns in pigs and mice were found experimentally. The results underpin the importance of biomechanical aspects in liver growth control.

Treatment with hepatocyte transplantation in a novel mouse model of persistent liver failure

Background and AimCell-based transplantation therapy using hepatocytes, hepatic stem cells, hepatocyte-like cells induced from stem cells, etc. is thought to be an attractive alternative to liver transplantation, and have been studied to date. For its clinical application, however, it is extremely important to develop a model that reproduces the pathological conditions with indication for treatment and enables the study for the ideal treatment strategy. MethodsThe transgenic mice which express the thymidine kinase (TK) gene of human herpes simplex virus (HSV) in their hepatocytes with normal immunity has been developed (designated as HSVtk). After ganciclovir (GCV) administration which injure TK-expressing hepatocytes, the primary hepatocytes (PHs) isolated from green fluorescent protein (GFP) transgenic mouse (GFP-tg) were transplanted to HSVtk intrasplenically, and replacement index (RI) with transplanted PHs in the liver, liver histology, and mRNA expressions in the liver were analyzed up to 8 weeks after transplantation. ResultsHSVtk without PH transplantation after GCV administration developed persistent liver failure with degenerated hepatocytes, persistent elevation of ALT and hepatic p16 mRNA levels, suggesting the existence of cellular senescence in the base of the disease. When autologous GFP-PHs were transplanted to HSVtk, the transplanted cells were successfully engrafted in the liver. Eight weeks after transplantation, serum ALT levels and liver histology were almost normalized, while RIs varied from 19.8 to 73.8%. Since the hepatic p16 mRNA levels were decreased significantly in these mice, the senescence of hepatocytes associated with liver injury was thought to be resolved. On the other hand, allogenic GFP-PHs transplanted to HSVtk were eliminated as early as 1 week after transplantation. In these mice, hepatic p16 mRNA levels were significantly increased at 8 weeks after transplantation, suggesting the aggravation of hepatocyte senescence. FK506 administration to HSVtk protected the transplanted hepatocytes with allogenic background from rejection at 2 weeks after transplantation, but the condition of mice and the senescent status in the liver seemed worsened. ConclusionsThe mouse model with HSVtk/GCV system was useful for studying the mechanism of liver regeneration and the immune rejection responses in the hepatocyte transplantation treatment. It may also be utilized to develop the effective remedies to avoid immune rejection.

Analysis of CCN Functions in Liver Regeneration After Partial Hepatectomy.

The remarkable regenerative capability of the liver has long been appreciated. Upon significant loss of liver tissue, the remnant liver can grow rapidly to restore the original liver mass through a combination of hepatocyte proliferation and hypertrophy to maintain homeostasis. Experimentally, 2/3 partial hepatectomy in mice has been used extensively as a model to dissect the molecular mechanism of liver regeneration and the genetic networks involved. Herein, we describe the protocols for partial hepatectomy and analyses of pertinent CCN protein functions.

Hepatocyte Transplantation Rebalances Cytokines for Hepatic Regeneration in Rats with Ataxia Telangiectasia Mutated Pathway-Related Acute Liver Failure

Inadequate DNA damage response related to ataxia telangiectasia mutated gene restricts hepatic regeneration in acute liver failure. Resolving mechanistic gaps in liver damage and repair requires additional animal models that are unconstrained by ultrarapid and unpredictable mortalities or substantial divergences from human pathology. This study used Fischer 344 rats primed with the antitubercular drug, rifampicin, plus phenobarbitone, and monocrotaline, a DNA adduct-forming alkaloid. Rifampicin and monocrotaline can cause liver failure in people. This regimen resulted in hepatic oxidative stress, necrosis, DNA double-strand breaks, liver test abnormalities, altered serum cytokine expression, and mortality. Healthy donor hepatocytes were transplanted ectopically in the peritoneal cavity to study whether they could supply metabolic support and rebalance inflammatory or protective cytokines affecting liver regeneration events. Hepatocyte transplantation increased candidate cytokine levels (granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, interferon-γ, IL-10, and IL-12), leading to Atm, Stat3, and Akt signaling in hepatocytes and nonparenchymal cells, lowering of inflammation, and improvements in intermediary metabolism, DNA repair, and hepatocyte proliferation. Such control of DNA damage and inflammation, along with stimulation of hepatic growth, offers paradigms for cell signaling to restore hepatic homeostasis and regeneration in acute liver failure. Further studies of molecular pathways of high pathobiological impact will advance the knowledge of liver regeneration.

RNA-seq transcriptome profiling of liver regeneration in mice identifies the miR-34b-5p/phosphoinositide-dependent protein kinase 1 axis as a potential target for hepatocyte proliferation

Characterized by compensatory hyperplasia dependent on hepatocyte proliferation, the liver will initiate regeneration after partial hepatectomy (PH) and acute or chronic injuries. A variety of genes and noncoding RNAs play pivotal roles in these cell proliferation and growth processes. However, it is still unclear how competition endogenous RNAs (ceRNAs) modulate cellular activities during each phase of liver regeneration, and the specific mechanisms of posttranscriptional gene expression regulation in hepatocyte proliferation remain to be elucidated. To investigate the mechanism of liver regeneration through RNA-seq profiling and to determine the role of miR-34b-5p/PDK1 on hepatocyte proliferation, we established a 2/3 PH mouse model for whole transcriptome profiling based on high-throughput sequencing techniques. We subsequently constructed a lncRNA-miRNA-mRNA ceRNA regulatory network through integrative analyses of RNA interactions. Finally, plasmid transfection in NCTC 1469 cells, dual luciferase reporter gene assay, quantitative real-time PCR, western blotting, Cell Counting Kit-8, and EdU-DNA synthesis cell proliferation assay were used to demonstrate the role of the miR-34b-5p/PDK1 axis in hepatocyte proliferation in vitro. A total of 1443 mRNAs (962 up, 481 down), 48 miRNAs (35 up, 13 down), and 1955 lncRNAs (986 up, 969 down) were identified as significantly differentially expressed. We then successfully constructed a ceRNA regulatory network consisting of 7 lncRNAs, 15 miRNAs, and 347 mRNAs based on the predicted inverse interactions among ceRNAs. Additionally, miR-34b-5p/PDK1 was predicted to be closely related to hepatocyte proliferation. We further demonstrated that miR-34b-5p could bind specifically to the 3′-untranslated region (3′-UTR) of PDK1 using the dual luciferase reporter assay. Ectopic overexpression of miR-34b-5p significantly reduced the mRNA and protein expression of PDK1, while it markedly inhibited the proliferation of mouse NCTC 1469 cells in vitro. In contrast, knocking down miR-34b-5p exhibited the inverse effects on PDK1 expression and hepatocyte proliferation. Through analyzing the ceRNA network during mouse liver regeneration, this study reveals that miR-34b-5p can inhibit hepatocyte proliferation through negatively regulating PDK1 and may be a potential pharmacological intervention target.

Dysregulation of Liver Regeneration by Hepatitis B Virus Infection: Impact on Development of Hepatocellular Carcinoma.

Simple SummaryLiver regeneration after injury or partial removal is a complicated and critical process that can be affected by several factors such as hepatitis B virus (HBV) or intracellular signaling pathways. Understanding regeneration repressive mechanisms provides insight to encounter these inhibitory factors and prevent further complications including liver cancer. Here we summarized pathways of liver regeneration and pointed out in detail, the different mechanisms that may dysregulate this process during HBV infection. In addition, other intracellular factors and pathways related to the regulation of liver regeneration have been recapped. The overall information provided here can be beneficial for understanding the method of preventing and treatment of liver failure due to the defective regeneration.The liver is unique in its ability to regenerate in response to damage. The complex process of liver regeneration consists of multiple interactive pathways. About 2 billion people worldwide have been infected with hepatitis B virus (HBV), and HBV causes 686,000 deaths each year due to its complications. Long-term infection with HBV, which causes chronic inflammation, leads to serious liver-related diseases, including cirrhosis and hepatocellular carcinoma. HBV infection has been reported to interfere with the critical mechanisms required for liver regeneration. In this review, the studies on liver tissue characteristics and liver regeneration mechanisms are summarized. Moreover, the inhibitory mechanisms of HBV infection in liver regeneration are investigated. Finally, the association between interrupted liver regeneration and hepatocarcinogenesis, which are both triggered by HBV infection, is outlined. Understanding the fundamental and complex liver regeneration process is expected to provide significant therapeutic advantages for HBV-associated hepatocellular carcinoma.

Mechanism of Liver Regeneration During ALPPS.

Liver cancer is one of the most lethal malignant tumors in the world, and surgical resection is the main treatment for liver cancer. Liver failure due to insufficient residual liver volume is a fatal complication after hepatectomy. How to effectively increase the residual liver volume after hepatectomy and improve the safety of hepatectomy has always been a problem to be solved in liver surgery. Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) effectively reduces the occurrence of liver failure due to insufficient residual liver volume after hepatectomy, thereby increasing the probability of radical resection by inducing rapid proliferation of residual liver tissue. However, the molecular mechanism of residual liver tissue regeneration after primary ALPPS (combined liver partition and portal vein ligation) remains unclear. Here, we found that lots of circular RNAs (circRNAs) are upregulated after ALPPS in pig liver cells; then, we identified the orthologous circRNA in humans and pigs to detect their function in liver regeneration. The results showed that loss of circ-0067724 and circ-0016213 could suppress liver cell proliferation. Together, these findings suggest that circ-0067724 and circ-0016213 play an important role in liver cell proliferation, and this may help us to find new strategies to promote liver regeneration.

A new liver regeneration molecular mechanism involving hepatic stellate cells, Kupffer cells, and glucose-regulated protein 78 as a new hepatotrophic factor.

To overcome liver failure, we focused on liver regeneration mechanisms by the activation of hepatic stellate cells (HSCs) and Kupffer cells (KCs). It is known that the HSC-secreted Mac-2-binding protein glycan isomer (M2BPGi) activates KC in the fibrotic liver. However, its importance for liver regeneration of the HSCs/M2BPGi/KCs axis after hepatectomy is still unknown. The aim of this study was to clarify whether the HSC-derived M2BPGi can activate KCs after hepatectomy, and elucidate the new molecular mechanism of liver regeneration. We examined the effect of M2BPGi on human hepatocytes and KCs, and explored secretory factors from M2BPGi-activated KCs using proteomics. Furthermore, the effect on liver regeneration of glucose-regulated protein 78 (GRP78) as one of the M2BPGi-related secreted proteins was examined in vitro and in murine hepatectomy models. Although M2BPGi had no hepatocyte-promoting effect, M2BPGi promoted the production of GRP78 in KCs. The KC-driven GRP78 promoted hepatocyte proliferation. GRP78 administration facilitated liver regeneration after 70% hepatectomy and increased the survival rate after 90% hepatectomy in mice. The M2BPGi-activated KCs secrete GRP78, which facilitates liver regeneration and improves the survival in a lethal mice model. Our data suggest that the new hepatotrophic factor GRP78 may be a promising therapeutic tool for lethal liver failure.

Use of Nucleoside Modified mRNA Encoding Regenerative Factors Encapsulated with Lipid Nanoparticles to Alleviate Acute and Chronic Murine Liver Diseases

The remarkable ability of the liver to regenerate by proliferation of mature hepatocytes constitutes the first mechanism of repair commonly named the hepatocyte‐driven regeneration. Yet, during chronic liver injury or acute severe hepatocyte death, proliferation of mature cells becomes exhausted. In these cases, alternative precursors of hepatocytes that derive from cholangiocytes have been identified in both human and rodent diseased livers. They are presently growing evidence of conversion of these cholangiocytes into hepatocytes as defined as the cholangiocyte‐driven regeneration. Despite these two mechanisms of liver repair, end stage liver disease remains the 12th most common cause of death in the United States, begging for therapeutic strategies to harness mechanisms of liver regeneration. Here we demonstrate that delivery via nucleoside modified mRNA complexed to lipid nanoparticles (mRNA‐LNP) to the liver of the key hepatocyte mitogen hepatocyte growth factor (HGF) and epidermal growth factor (EGF) enhance hepatocyte‐driven repair, while delivery of vascular endothelial growth factor A (VEGFA) mRNA‐LNP promotes cholangiocyte‐driven repair. We confirm specific hepatotropism of mRNA‐LNP via intravenous injection of firefly luciferase encoding mRNA‐LNP, with protein expression lasting about 3 days. In the liver, virtually all hepatocytes are transfected along with a subpopulation of endothelial and Kupffer cells. In homeostasis, HGF mRNA‐LNP efficiently induce hepatocyte proliferation. In a chronic liver injury mouse model recapitulating non‐alcoholic fatty liver disease, injections of both HGF and EGF mRNA‐LNP sharply reverse steatosis and accelerate restoration of liver function. Likewise, HGF and EGF mRNA‐LNP accelerate liver regeneration after acetaminophen‐induced acute liver injury with rapid return to baseline alanine transaminase (ALT) levels. Transient delivery of VEGFA in acute and chronic injured mouse livers via mRNA‐LNP induces robust cholangiocyte conversion to hepatocytes as well as reversion of steatosis and fibrosis. This study introduces mRNA‐LNP as a potentially translatable safe therapeutic intervention to harness both hepatocyte‐ and cholangiocyte‐driven liver regeneration to ultimately treat human acute and chronic liver diseases.

Liver regeneration: Cellular origin and molecular mechanisms.

The liver is known as an organ with high proliferation potential. Clarifying the cellular origin and deepening the understanding of liver regeneration mechanisms will help provide new directions for the treatment of liver disease. With the development and application of lineage tracing technology, the specific distribution and dynamic changes of hepatocyte subpopulations in homeostasis and liver injury have been illustrated. Self-replication of hepatocytes is responsible for the maintenance of liver function and mass under homeostasis. The compensatory proliferation of remaining hepatocytes is the main mechanism of liver regeneration following acute and chronic liver injury. Transdifferentiation between hepatocytes and cholangiocytes has been recognized upon severe chronic liver injury. Wnt/β-catenin, Hippo/YAP and Notch signalling play essential roles in the maintenance of homeostatic liver and hepatocyte-to-cholangiocyte conversion under liver injury. In this review, we summarized the recent studies on cell origin of newly generated hepatocytes and the underlying mechanisms of liver regeneration in homeostasis and liver injury.

Kupffer cells depletion alters cytokine expression and delays liver regeneration after Radio-frequency-assisted Liver Partition with Portal Vein Ligation

Radio-frequency-assisted Liver Partition with Portal Vein Ligation (RALPP) induces comparable hypertrophy of the liver remnant compared to Associating Liver Partition and Portal vein ligation for Staged hepatectomy (ALPPS) in humans. However, whether it is significantly improved compared to ALPPS is unclear, and the underlying mechanisms of liver regeneration after RALPP need to further investigate. The present study was to develop an animal model mimicking RALPP and explore mechanisms of liver regeneration. The mice in RALPP group received liver radiofrequency ablation and 90% portal vein ligation (PVL), followed by resection of the targeted liver within two days after the first surgery. The mice in ALPPS group underwent 90% PVL combined with parenchyma transection. Controls received liver radiofrequency ablation (RAF group) or PVL (PVL group) or small left lateral lobe (LLL group) resection alone. Liver regeneration was assessed by liver weight and proliferation-associated molecules. The role of Kupffer cells (KCs) in liver regeneration was investigated after RALPP. The results showed that RALPP induced comparable liver regeneration compared to ALPPS, but with less liver injury and mortality in mice. RALPP led to over-expression of TNF-α and IL-6 in the circulating plasma compared with PVL. KCs infiltrating in liver tissues was a characteristic of mice in the RALPP group. KCs depletion markedly depressed cytokine expression and delayed liver regeneration after RALPP. These results suggested that RALPP in mice induced accelerated liver regeneration similar to ALPPS, but safer than ALPPS. KCs depletion altered cytokine expression and delayed liver regeneration after RALPP.

Liver Regeneration in Chronic Liver Injuries: Basic and Clinical Applications Focusing on Macrophages and Natural Killer Cells.

Background & AimsLiver regeneration is a necessary but complex process involving multiple cell types besides hepatocytes. Mechanisms underlying liver regeneration after partial hepatectomy and acute liver injury have been well-described. However, in patients with chronic and severe liver injury, the remnant liver cannot completely restore the liver mass and function, thereby involving liver progenitor-like cells (LPLCs) and various immune cells.ResultsMacrophages are beneficial to LPLCs proliferation and the differentiation of LPLCs to hepatocytes. Also, cells expressing natural killer (NK) cell markers have been studied in promoting both liver injury and liver regeneration. NK cells can promote LPLC-induced liver regeneration, but the excessive activation of hepatic NK cells may lead to high serum levels of interferon-γ, thus inhibiting liver regeneration.ConclusionsThis review summarizes the recent research on 2 important innate immune cells, macrophages and NK cells, in LPLC-induced liver regeneration and the mechanisms of liver regeneration during chronic liver injury, as well as the latest macrophage- and NK cell-based therapies for chronic liver injury. These novel findings can further help identify new treatments for chronic liver injury, saving patients from the pain of liver transplantations.

Liver regeneration after extensive hepatectomy in rats: effect of preoperative chemotherapy with intravenous 5-fluorouracil.

To evaluate the effect of preoperative intravenous chemotherapy with 5-fluorouracil on liver regeneration in an experimental model of major hepatectomy in rats. Wistar rats were divided into two groups of 20 animals each and submitted to 70% hepatectomy 24 h after intravenous injection of 5-fluorouracil 20 mg/kg (fluorouracil group, FG) or 0.9% saline (control group, CG). After hepatectomy, each group was subdivided into two subgroups of 10 animals each according to the day of sacrifice (24 h or 7 days). Liver weight during regeneration, liver regeneration rate using Kwon formula, and the immunohistochemical markers proliferating cell nuclear antigen (PCNA) and Ki-67 were used to assess liver regeneration. At early phase (24 h after hepatectomy) it was demonstrated the negative effect of 5-fluorouracil on liver regeneration when assessed by Kwon formula (p < 0.0001), PCNA analysis (p = 0.02). With regeneration process complete (7 days), it was possible to demonstrate the sustained impairment of chemotherapy with 5-fluorouracil on hepatocytes regeneration phenomenon when measured by Kwon formula (p = 0.009), PCNA analysis (p = 0.0001) and Ki-67 analysis (0.001). Preoperative chemotherapy with intravenous 5-fluorouracil negatively affected the mechanisms of liver regeneration after major hepatectomy in rats.

Aurora kinase A regulates liver regeneration through macrophages polarization and Wnt/β-catenin signalling.

Liver regeneration is a complex process regulated by a variety of cells, cytokines and biological pathways. Aurora kinase A (AURKA) is a serine/threonine kinase that plays a role in centrosome maturation and spindle formation during the cell division cycle. The purpose of this study was to further explore the mechanism of AURKA on liver regeneration and to identify new possible targets for liver regeneration. The effect and mechanism of AURKA on liver regeneration were studied using a 70% hepatectomy model. Human liver organoids were used as an in vitro model to investigate the effect of AURKA on hepatocyte proliferation. AURKA inhibition significantly reduced the level of β-catenin protein by reducing the phosphorylation level of glycogen synthase kinase-3β (GSK-3β), leading to the inhibition of liver regeneration. Further studies showed that AURKA co-localized and interacted with GSK-3β in the cytoplasm of hepatocytes. When phosphorylation of GSK-3β was enhanced, the total GSK-3β level remained unchanged, while AURKA was not affected, and β-catenin protein levels were increased. In addition, AURKA inhibition affected the formation and proliferation of human liver organoids. Furthermore, AURKA inhibition led to the polarization of M1 macrophages and the release of interleukin-6 and Tumour necrosis factor α, which also led to reduced liver regeneration and increased liver injury. These results provide more details on the mechanism of liver regeneration and suggest that AURKA is an important regulator of this mechanism.

A modified animal model of hepatic regeneration induced by hilar bile duct ligation

Mechanisms of the proliferation of liver are mainly studied in animal model of liver regeneration after partial hepatectomy (PH). However, the PH model involves complex regeneration mechanisms, including hemodynamic factors, cytokines, growth factors, and metabolites. Among liver metabolites, bile acid (BA) is a key signaling molecule that regulates liver regeneration. This study aimed to establish a new type of rapid liver hyperplasia model induced mainly by bile acid pathway through hepatoenteral circulation with hilar bile duct ligation (HBDL). We first established the HBDL model by ligating the bile duct of all hepatic lobes but the right lateral lobe in rabbits and compared with the PVL model and sham operation group. Changes in the liver lobe and hemodynamics were observed. Liver function and the bile acid level were also analyzed. Then we verified the HBDL model in mice. Liver function and the levels of bile acids and cytokines were tested. The protein and mRNA levels of FXR, FGF15, CYP7A1 and FoxM1b in liver tissue were also analyzed. After hilar ligation of the biliary tract, the unligated liver lobes proliferated significantly. Compared with those in the sham group, the volume and weight of the unligated right lateral lobe of the liver in the HBDL group and the PVL group increased significantly (P < 0.05). Transient liver function impairment occurred both in the HBDL group and PVL group in the rabbit model as well as the mouse models. The bile acid levels in the HBDL groups of the rabbit model and mouse model increased significantly within first week after surgery (P < 0.05). The immunohistochemistry results confirmed the proliferation of hepatocytes in the unligated liver lobe. Compared with those in the sham group, the levels of FXR, FGF15 and FoxM1b in the HBDL group were significantly increased (P < 0.05), while the expression of CYP7A1 was inhibited. Compared with those in the HBDL group, the postoperative hemodynamic changes in the PVL group were significant (P < 0.05). The levels of IL-6 and TNF-α in the HBDL group were higher than those in the sham group. The HBDL model is simple to establish and exhibits good surgical tolerance. The model has definite proliferative effect and strong specificity of bile acid pathway. This is an ideal animal model to study the mechanism of liver regeneration through bile acid pathway.

Liver Organoids: Formation Strategies and Biomedical Applications.

The liver is the most important digestive organ in the body. Several studies have explored liver biology and diseases related to the liver. However, most of these studies have only explored liver development, mechanism of liver regeneration and pathophysiology of liver diseases mainly based on two-dimensional (2D) cell lines and animal models. Traditional 2D cell lines do not represent the complex three-dimensional tissue architecture whereas animal models are limited by inter-species differences. These shortcomings limit understanding of liver biology and diseases. Liver organoid technology is effective in elucidating structural and physiological characteristics and basictissue-level functions of liver tissue. In this review, formation strategies and a wide range of applications in biomedicine of liver organoid are summarized. Liver organoids are derived from single type cell culture, such as induced pluripotent stem cells (iPSCs), adult stem cells, primary hepatocytes, and primary cholangiocytes and multi-type cells co-culture, such as iPSC-derived hepatic endoderm cells co-cultured with mesenchymal stem cells and umbilical cord-derived endothelial cells. In vitrostudies report that liver organoids are a promising model for regenerative medicine, organogenesis, liver regeneration, disease modelling, drug screening and personalized treatment. Liver organoids are a promising in vitro model for basic research and for development of clinical therapeutic interventions for hepatopathy.

Diploid hepatocytes promote compensatory liver regeneration following acetaminophen induced acute liver injury

Background Acetaminophen (APAP) is a commonly used analgesic that can be safely used at doses under 4 g/day. When taken in excess, APAP causes acute liver injury, which leads to acute liver failure and death. APAP overdose leads to 56,000 emergency room visits and 26,000 hospitalizations annually and is the leading cause of acute liver failure in the United States. The only available pharmacological treatment, N-acetyl cysteine, is effective within hours of overdose. The only other treatment option is orthotopic liver transplantation, and this is limited by the availability of donor organs. Considering the paucity of therapeutic options, there is an urgent need to understand mechanisms of liver regeneration and repair. Most mammalian somatic cells are diploid and contain pairs of each chromosome, but there are also polyploid cells, such as hepatocytes that contain additional sets of chromosomes. Polyploid hepatocytes are among the best described, and in adult humans and mice comprise more than 25% and 90%, respectively, of the hepatocyte population. The cellular and molecular mechanisms that regulate polyploidy have been well-characterized; however, it is poorly understood if diploid and polyploid hepatocytes play specialized roles in liver injury and repair. Methods Our lab recently found that diploid hepatocytes are inherently more proliferative than polyploid hepatocytes. Additionally, we can specifically study diploid hepatocytes using mice lacking E2f7 and E2f8 in the liver (referred to as “LKO” mice), which are functionally normal, but livers are depleted of polyploid hepatocytes. Considering that liver regeneration affects the outcome of APAP-medicated injury, we asked if LKO mice enriched with highly proliferative diploid hepatocytes would respond differently than control livers. We fasted LKO and control mice for 16 hours, injected intraperitoneally with 300 mg/kg (the LD50 dose) APAP and harvested livers after 0.5, 3, 6, 12, 24, 48, 72 and 96 hours. We used these tissues to investigate differences in liver injury, necrosis, and proliferation. Results Liver injury enzymes, alanine aminotransferase (ALT) and aspartate aminotransferase (AST), were higher in control mice compared to LKO mice beginning at 3 hours. Necrotic liver tissue was abundant in control mice and was markedly reduced in LKO mice. We also measured more apoptotic, TUNEL positive hepatocytes in control mice. We next assessed the proliferation response after APAP-induced liver injury by staining tissues for PCNA which was induced by 6 hours in LKO mice compared to 24 hours in control mice. We treated wild-type 19-day old hepatocytes with 5 mM APAP for 12, 24, and 36 hours in vitro and found that diploid hepatocytes proliferate more readily compared to polyploids as marked by BrdU incorporation. Finally, we found higher doses of APAP eliminate the advantages seen in LKO mice. Conclusion Based on these data, diploid hepatocytes appear to be the main contributors of early-stage compensatory regeneration following APAP-mediated liver injury. These data suggest that, compared to polyploid hepatocytes, diploids initiate and drive liver healing/regeneration after acute injury.