Clinical implications of advances in liver regeneration

From Cells to Exosomes: a Review of Non-Surgical Biotherapeutic-Based Strategies for Liver Regeneration in the Face of End-Stage Diseases

Liver diseases, such as hepatitis, cirrhosis, and liver cancer, pose significant public health challenges, ranking as the twelfth leading cause of death globally. Given the liver's critical functions in metabolism, detoxification, and biosynthesis, its impairment can lead to severe consequences, often resulting in end-stage liver failure. Although liver transplantation is regarded as the definitive intervention for advanced liver disease, factors such as a shortage of donors and potential surgical complications necessitate the investigation of non-surgical regenerative medicine alternatives. This manuscript provides a comprehensive review of innovative non-surgical therapies aimed at liver regeneration, with an emphasis on both cell-based and cell-free approaches. It examines the contributions of various stem cell populations, including mesenchymal stem cells, hematopoietic stem cells, and induced pluripotent stem cells, in facilitating liver repair through mechanisms of differentiation and paracrine signaling. Furthermore, it explores the therapeutic potential of exosomes and conditioned media derived from stem cells as biotherapeutic agents in the context of regenerative medicine. By elucidating the mechanisms that underpin liver regeneration, this study aspires to inform the development of effective therapeutic strategies to address liver diseases and slow their progression. By elucidating the underlying mechanisms of liver regeneration, this study aims to contribute to the development of effective therapeutic strategies to address liver diseases and slow their progression.

Human umbilical cord mesenchymal stem cells enhance liver regeneration and decrease collagen content in fibrosis mice after partial hepatectomy by activating Wnt/β-catenin signaling

Liver fibrosis is a critical stage in the progression of various chronic liver diseases to cirrhosis and liver cancer. Early inhibition of liver fibrosis is crucial for the treatment of liver disease. Hepatectomy, a common treatment for liver-related diseases, promotes liver regeneration. However, in the context of liver fibrosis, liver regeneration is hindered. Many studies have shown that mesenchymal stem cells (MSCs) can promote liver regeneration after partial hepatectomy (PH). However, there are few reports on the impact of MSC therapy on liver regeneration post-PH in the context of hepatic fibrosis. The objective of this study is to examine the impact of MSCs on liver regeneration following PH in the fibrotic liver and uncover the related molecular mechanisms. This study reveals that MSC therapy significantly enhances liver function and mitigates liver inflammation after PH in the context of hepatic fibrosis. MSCs also significantly promote liver regeneration and alleviate liver fibrosis. In addition, this study identifies the role of MSCs in promoting liver regeneration and alleviating liver fibrosis via the activation of Wnt/β-catenin signaling. The combination of MSCs with hepatectomy may offer a novel approach for the treatment of liver fibrotic diseases.

Liver regeneration after injury: Mechanisms, cellular interactions and therapeutic innovations

The liver possesses a distinctive capacity for regeneration within the human body. Under normal circumstances, liver cells replicate themselves to maintain liver function. Compensatory replication of healthy hepatocytes is sufficient for the regeneration after acute liver injuries. In the late stage of chronic liver damage, a large number of hepatocytes die and hepatocyte replication is blocked. Liver regeneration has more complex mechanisms, such as the transdifferentiation between cell types or hepatic progenitor cells mediated. Dysregulation of liver regeneration causes severe chronic liver disease. Gaining a more comprehensive understanding of liver regeneration mechanisms would facilitate the advancement of efficient therapeutic approaches. This review provides an overview of the signalling pathways linked to different aspects of liver regeneration in various liver diseases. Moreover, new knowledge on cellular interactions during the regenerative process is also presented. Finally, this paper explores the potential applications of new technologies, such as nanotechnology, stem cell transplantation and organoids, in liver regeneration after injury, offering fresh perspectives on treating liver disease.

Does apocynin increase liver regeneration in the partial hepatectomy model?

BACKGROUND

Hepayocyte loss may develop secondary to liver surgery and at this point liver regeneration plays a significant act in terms of liver reserve. The purpose of this research was to investigate the efficacy of apocynin on liver regeneration and preservation after partial hepatectomy in rats.

METHODS

A total of 32 rats, have been divided into 4 groups (n: 8) for hepatectomy model. Inflammatory and antiinflammatory parameters were measured from blood and liver tissue samples. In addition, the effects of apocynin were examined immunohistochemically and histopathologically from liver tissue.

RESULTS

In liver tissue samples, a significant difference has been found in glutathione peroxidase, total nitrite, catalase, oxidative stress index, total antioxidant and total oxidant status between sham and hepatectomy groups. A significant difference has been achieved between hepatectomy and posthepatectomy-Apocynin in terms of glutathione peroxidase and oxidative stress index. Total antioxidant status, oxidative stress index, and total oxidant status were significantly different only between the sham and the hepatectomy groups. Statistical differences were found between sham and hepatectomy groups and between hepatectomy and pre+post-hepatectomy-Apocynin groups in terms of serum glutathione, malondialdehyde, total nitrite, and L-Arginine. There were significant differences between the sham and hepatectomy groups, between hepatectomy and posthepatectomy-apocynin groups, between posthepatctomy-apocynin and pre+posthepatectomy-apocynin groups in terms of sinusoidal dilatation, intracytoplasmic vacuolization and glycogen loss (p < 0.001), in all histopathologic parameters except sinusoidal dilatation (p < 0.05). However, significant Ki-67 increases have been elaborated in hepatectomy, posthepatectomy-apocynin, and pre+posthepatectomy-apocynin groups compared to sham group (p < 0.001), in pre+posthepatectomy apocynin group compared to hepatectomy and posthepatectomy-apocynin groups (p < 0.001).

DISCUSSION

Histopathology, immunohistochemistry, and biochemistry results of this study revealed that apocynin has a protective effect on enhancing liver regeneration in partial hepatectomy cases in rats.

Interleukin-33 facilitates liver regeneration through serotonin-involved gut-liver axis

BACKGROUND AND AIMS

Insufficient liver regeneration causes post-hepatectomy liver failure and small-for-size syndrome. Identifying therapeutic targets to enhance hepatic regenerative capacity remains urgent. Recently, increased IL-33 was observed in patients undergoing liver resection and in mice after partial hepatectomy (PHx). The present study aims to investigate the role of IL-33 in liver regeneration after PHx and to elucidate its underlying mechanisms.

APPROACH AND RESULTS

We performed PHx in IL-33 -/- , suppression of tumorigenicity 2 (ST2) -/- , and wild-type control mice, and found deficiency of IL-33 or its receptor ST2 delayed liver regeneration. The insufficient liver regeneration could be normalized in IL-33 -/- but not ST2 -/- mice by recombinant murine IL-33 administration. Furthermore, we observed an increased level of serotonin in portal blood from wild-type mice, but not IL-33 -/- or ST2 -/- mice, after PHx. ST2 deficiency specifically in enterochromaffin cells recapitulated the phenotype of delayed liver regeneration observed in ST2 -/- mice. Moreover, the impeded liver regeneration in IL-33 -/- and ST2 -/- mice was restored to normal levels by the treatment with (±)-2,5-dimethoxy-4-iodoamphetamine, which is an agonist of the 5-hydroxytrytamine receptor (HTR)2A. Notably, in vitro experiments demonstrated that serotonin/HTR2A-induced hepatocyte proliferation is dependent on p70S6K activation.

CONCLUSIONS

Our study identified that IL-33 is pro-regenerative in a noninjurious model of liver resection. The underlying mechanism involved IL-33/ST2-induced increase of serotonin release from enterochromaffin cells to portal blood and subsequent HTR2A/p70S6K activation in hepatocytes by serotonin. The findings implicate the potential of targeting the IL-33/ST2/serotonin pathway to reduce the risk of post-hepatectomy liver failure and small-for-size syndrome.

Predicting liver regeneration following major resection

Breakdown of synthesis, excretion and detoxification defines liver failure. Post-hepatectomy liver failure (PHLF) is specific for liver resection and a rightfully feared complication due to high lethality and limited therapeutic success. Individual cytokine and growth factor profiles may represent potent predictive markers for recovery of liver function. We aimed to investigate these profiles in post-hepatectomy regeneration. This study combined a time-dependent cytokine and growth factor profiling dataset of a training (30 patients) and a validation (14 patients) cohorts undergoing major liver resection with statistical and predictive models identifying individual pathway signatures. 2319 associations were tested. Primary hepatocytes isolated from patient tissue samples were stimulated and their proliferation was analysed through DNA content assay. Common expression trajectories of cytokines and growth factors with strong correlation to PHLF, morbidity and mortality were identified despite highly individual perioperative dynamics. Especially, dynamics of EGF, HGF, and PLGF were associated with mortality. PLGF was additionally associated with PHLF and complications. A global association-network was calculated and validated to investigate interdependence of cytokines and growth factors with clinical attributes. Preoperative cytokine and growth factor signatures were identified allowing prediction of mortality following major liver resection by regression modelling. Proliferation analysis of corresponding primary human hepatocytes showed associations of individual regenerative potential with clinical outcome. Prediction of PHLF was possible on as early as first postoperative day (POD1) with AUC above 0.75. Prediction of PHLF and mortality is possible on POD1 with liquid-biopsy based risk profiling. Further utilization of these models would allow tailoring of interventional strategies according to individual profiles.

Geometrical model of lobular structure and its importance for the liver perfusion analysis

A convenient geometrical description of the microvascular network is necessary for computationally efficient mathematical modelling of liver perfusion, metabolic and other physiological processes. The tissue models currently used are based on the generally accepted schematic structure of the parenchyma at the lobular level, assuming its perfect regular structure and geometrical symmetries. Hepatic lobule, portal lobule, or liver acinus are considered usually as autonomous functional units on which particular physiological problems are studied. We propose a new periodic unit-the liver representative periodic cell (LRPC) and establish its geometrical parametrization. The LRPC is constituted by two portal lobulae, such that it contains the liver acinus as a substructure. As a remarkable advantage over the classical phenomenological modelling approaches, the LRPC enables for multiscale modelling based on the periodic homogenization method. Derived macroscopic equations involve so called effective medium parameters, such as the tissue permeability, which reflect the LRPC geometry. In this way, mutual influences between the macroscopic phenomena, such as inhomogeneous perfusion, and the local processes relevant to the lobular (mesoscopic) level are respected. The LRPC based model is intended for its use within a complete hierarchical model of the whole liver. Using the Double-permeability Darcy model obtained by the homogenization, we illustrate the usefulness of the LRPC based modelling to describe the blood perfusion in the parenchyma.

Establishing a 3D In Vitro Hepatic Model Mimicking Physiologically Relevant to In Vivo State

Three-dimensional (3D) bioprinting is a promising technology to establish a 3D in vitro hepatic model that holds great potential in toxicological evaluation. However, in current hepatic models, the central area suffers from hypoxic conditions, resulting in slow and weak metabolism of drugs and toxins. It remains challenging to predict accurate drug effects in current bioprinted hepatic models. Here, we constructed a hexagonal bioprinted hepatic construct and incorporated a spinning condition with continuous media stimuli. Under spinning conditions, HepG2 cells in the bioprinted hepatic construct exhibited enhanced proliferation capacity and functionality compared to those under static conditions. Additionally, the number of spheroids that play a role in boosting drug-induced signals and responses increased in the bioprinted hepatic constructs cultured under spinning conditions. Moreover, HepG2 cells under spinning conditions exhibited intensive TGFβ-induced epithelial-to-mesenchymal transition (EMT) and increased susceptibility to acetaminophen (APAP)-induced hepatotoxicity as well as hepatotoxicity prevention by administration of N-acetylcysteine (NAC). Taken together, the results of our study demonstrate that the spinning condition employed during the generation of bioprinted hepatic constructs enables the recapitulation of liver injury and repair phenomena in particular. This simple but effective culture strategy facilitates bioprinted hepatic constructs to improve in vitro modeling for drug effect evaluation.

Astragaloside IV Suppresses Hepatic Proliferation in Regenerating Rat Liver after 70% Partial Hepatectomy via Down-Regulation of Cell Cycle Pathway and DNA Replication

Astragaloside IV (AS-IV) is one of the major bio-active ingredients of huang qi which is the dried root of Astragalus membranaceus (a traditional Chinese medicinal plant). The pharmacological effects of AS-IV, including anti-oxidative, anti-cancer, and anti-diabetic effects have been actively studied, however, the effects of AS-IV on liver regeneration have not yet been fully described. Thus, the aim of this study was to explore the effects of AS-IV on regenerating liver after 70% partial hepatectomy (PHx) in rats. Differentially expressed mRNAs, proliferative marker and growth factors were analyzed. AS-IV (10 mg/kg) was administrated orally 2 h before surgery. We found 20 core genes showed effects of AS-IV, many of which were involved with functions related to DNA replication during cell division. AS-IV down-regulates MAPK signaling, PI3/Akt signaling, and cell cycle pathway. Hepatocyte growth factor (HGF) and cyclin D1 expression were also decreased by AS-IV administration. Transforming growth factor β1 (TGFβ1, growth regulation signal) was slightly increased. In short, AS-IV down-regulated proliferative signals and genes related to DNA replication. In conclusion, AS-IV showed anti-proliferative activity in regenerating liver tissue after 70% PHx.

CDK5RAP3 Deficiency Restrains Liver Regeneration after Partial Hepatectomy Triggering Endoplasmic Reticulum Stress

CDK5 regulatory subunit-associated protein 3 (CDK5RAP3) plays a crucial role in mammalian liver development and hepatic function by controlling hepatocyte proliferation and differentiation, glucose and lipid metabolism, UFMylation, and endoplasmic reticulum homeostasis. However, the role of CDK5RAP3 in liver regeneration remains unknown. A liver-specific Cdk5rap3 knockout (CKO) mouse model was used to study the function of CDK5RAP3 during liver regeneration induced by standard two-thirds partial hepatectomy (PHx). Twenty-four hours after PHx, the liver-to-body weight ratio was markedly higher in CKO mice than in wild-type mice. However, this ratio did not increase significantly and gradually over time after PHx in CKO mice. Hepatocyte proliferation was significantly delayed in CKO mice compared with wild-type mice. Meanwhile, CDK5RAP3 deficiency increased lipid accumulation, impaired glycogen synthesis, and lowered blood glucose levels after PHx. Critically, the absence of CDK5RAP3 seemed to promote an inflammatory response and induce apoptosis at a late stage of liver regeneration. In addition, CDK5RAP3 deficiency disrupted UFMylation homeostasis and aggravated endoplasmic reticulum stress in hepatocytes after PHx. Taken together, these data suggest that CDK5RAP3 enhances liver regeneration, at least partially via controlling cell cycle and glucose and lipid metabolism.

Directly induced hepatogenic cells derived from human fibroblast ameliorate liver fibrosis

Recently, reprogramming technology has emerged as a fascinating tool to generate specific tissue cells. In this study, we tested the hypothesis that ultrasound-directed cellular reprogramming can generate fibroblasts into hepatogenic cells. We directly induced human dermal fibroblasts (HDFs) into hepatocyte-like cells mediated by environmental transition-guided cellular reprogramming (h/entr) using ultrasound. We confirmed the characteristics of h/entr by the expression levels of hepatocyte specific RNA and proteins. The effects of h/entr on the activation of hepatic stellate cells were analyzed using conditioned medium (CM). h/entr were transplanted into mice with acute liver fibrosis and the therapeutic effects and mechanism of liver fibrosis were determined. h/entr exhibited high levels of hepatocyte specific genes, hepatogenic (hepatocyte growth factor [HGF], colony-stimulating factor 3 [CSF-3]) and anti-inflammatory (interleukin 10 [IL-10]) factors. h/entr CM suppressed the activation of hepatic stellate cells in vitro. Transplantation of h/entr significantly delayed liver fibrosis and improved liver function. Transplantation of h/entr accelerates liver regeneration, and human albumin expressing h/entr and human Alu gene were detected in the mouse livers. This report suggests that directly induced h/entr could be one of the highly effective therapeutic options for the treatment of liver cirrhotic disease.

Clinical Outcome of Residual Liver Volume and Hepatic Steatosis After Right-Lobe Living-Donor Hepatectomy

Background

We examine how residual liver volume (RLV) and hepatic steatosis (HS) of living liver donors affect the regeneration process and clinical outcomes.

Material/Methods

We longitudinally studied 58 donors who underwent right-lobe hepatectomy during the period February 2014 to February 2015 at a single medical institution. The patients were classified based on RLV (30–35%, 35–40%, 40–50%) subgroups and HS (<10%, 10–30%, 30–50%) subgroups. Clinical parameters such as clinical outcome, liver volumetric recovery (LVR,%) rate and remnant left-liver (RLL,%) growth rate were collected for analysis.

Results

The clinical features of postoperative peak total bilirubin (p=.024) were significant in the 3 RLV subgroups. Body mass index (p=.017), preoperative alanine transaminase (p<.001), and pleural effusion (p=.038) were significant in the 3 HS subgroups. The LVR rate and RLL growth rate equations showed significant variation in regeneration among the 3 RLV subgroups. The LVR rate and RLL growth rate equations did not show significant variation in regeneration among the 3 HS subgroups.

Conclusions

Hyperbilirubinemia was a risk factor in the small-RLV group, and a large amount of pleural effusion was a risk factor in the steatosis 30–50% group. Hepatic steatosis subgroups did not show significantly different degrees of regeneration. The safety of living donors was a major concern while we compiled the extended living-donor criteria presented in this paper.

Small-molecule-mediated reprogramming: a silver lining for regenerative medicine

Techniques for reprogramming somatic cells create new opportunities for drug screening, disease modeling, artificial organ development, and cell therapy. The development of reprogramming techniques has grown exponentially since the discovery of induced pluripotent stem cells (iPSCs) by the transduction of four factors (OCT3/4, SOX2, c-MYC, and KLF4) in mouse embryonic fibroblasts. Initial studies on iPSCs led to direct-conversion techniques using transcription factors expressed mainly in target cells. However, reprogramming transcription factors with a virus risks integrating viral DNA and can be complicated by oncogenes. To address these problems, many researchers are developing reprogramming methods that use clinically applicable small molecules and growth factors. This review summarizes research trends in reprogramming cells using small molecules and growth factors, including their modes of action.

The reprogramming of cells using small molecules to generate viable, safe stem-cell populations could transform stem-cell therapies, disease modeling and artificial organ development. Existing ways of reprogramming cells to generate stem cells carry risks, because the methods used often involve using viral DNA components or oncogenes, genes with the potential to turn cells into tumour cells. Safer, inexpensive alternatives are sought by scientists, and the efficient reprogramming of cells using small molecules and growth factors shows promise. Dongho Choi and co-workers at Hanyang University College of Medicine in Seoul, South Korea, reviewed recent research highlighting how small molecules including chemical compounds, plant derivatives and certain approved drugs are being used effectively to create different stem-cell populations. Recent successes are also contributing valuable insights into how stem cells differentiate into different cell types.

Severe polycystic liver diseases: hepatectomy or waiting for liver transplantation?: Two case reports

INTRODUCTION

Choice of treatment in patients with symptomatic polycystic liver diseases (PLD) remains controversial. Various surgical procedures aiming at eliminating symptomatic cysts are widely used in mild and advanced PLD patients, but liver transplantation is currently recommended as the only curative treatment especially in severe cases.

PATIENT CONCERNS

Case 1: A 51-year-old male was admitted for severe eating disorder and dyspnea for 2 months. He had been diagnosed as PLD, PKD, and hypertension for 9 years, with only antihypertensive drug therapy. No significant family history could be traced.Case 2: A 54-year-old female was admitted to our hospital for ventosity during nearly 5 years. She had been diagnosed as PLD and hypertension for 22 years, for which only aspiration-sclerotherapy therapy was performed for multiple times. Both her mother and sister were diagnosed with PLD previously.

DIAGNOSIS

They were diagnosed as PLD by medical history, family history, and computed tomography scan (multiple cysts dispersively presenting in the liver).

INTERVENTIONS

The 2 patients underwent hepatectomy with fenestration, and were well recovered with no mortality.

OUTCOMES

While case 1 only experienced relief of symptoms, case 2 experienced massive growth of hepatic parenchyma, which indicated positive prognosis and showed the possibility to avoid or at least postpone liver transplantation for a long time, considering the lack of liver parenchyma is one of the main reason for urgency of liver transplantation.

CONCLUSION

Here we described subradical polycystic hepatectomy, a special form of hepatectomy with fenestration modified by us, as a safe and effective treatment to potentially achieve long-term effects in PLD patients.

Beneficial and Deleterious Effects of Female Sex Hormones, Oral Contraceptives, and Phytoestrogens by Immunomodulation on the Liver

The liver is considered the laboratory of the human body because of its many metabolic processes. It accomplishes diverse activities as a mixed gland and is in continuous cross-talk with the endocrine system. Not only do hormones from the gastrointestinal tract that participate in digestion regulate the liver functions, but the sex hormones also exert a strong influence on this sexually dimorphic organ, via their receptors expressed in liver, in both health and disease. Besides, the liver modifies the actions of sex hormones through their metabolism and transport proteins. Given the anatomical position and physiological importance of liver, this organ is evidenced as an immune vigilante that mediates the systemic immune response, and, in turn, the immune system regulates the hepatic functions. Such feedback is performed by cytokines. Pro-inflammatory and anti-inflammatory cytokines are strongly involved in hepatic homeostasis and in pathological states; indeed, female sex hormones, oral contraceptives, and phytoestrogens have immunomodulatory effects in the liver and the whole organism. To analyze the complex and interesting beneficial or deleterious effects of these drugs by their immunomodulatory actions in the liver can provide the basis for either their pharmacological use in therapeutic treatments or to avoid their intake in some diseases.

Generation of functional human hepatocytes in vitro: current status and future prospects

Liver and hepatocyte transplantation are the only effective therapies for late-stage liver diseases, in which the liver loses its regenerative capacity. However, there is a shortage of donors. As a potential alternative approach, functional hepatocytes were recently generated from various cell sources. Analysis of drug metabolism in the human liver is important for drug development. Consequently, cells that metabolize drugs similar to human primary hepatocytes are required. This review discusses the current challenges and future perspectives concerning hepatocytes and hepatic progenitor cells that have been reprogrammed from various cell types, focusing on their functions in transplantation models and their ability to metabolize drugs.

Roles of hepatic stellate cells in acute liver failure: From the perspective of inflammation and fibrosis

Acute liver failure (ALF) usually results in hepatocellular dysfunction and coagulopathy and carries a high mortality rate. Hepatic stellate cells (HSCs) are famous for their role in liver fibrosis. Although some recent studies revealed that HSCs might participate in the pathogenesis of ALF, the accurate mechanism is still not fully understood. This review focuses on the recent advances in understanding the functions of HSCs in ALF and revealed both protective and promotive roles during the pathogenesis of ALF: HSC activation participates in the maintenance of cell attachment and the architecture of liver tissue via extracellular matrix production and assists liver regeneration by producing growth factors; and HSC inflammation plays a role in relaying inflammation signaling from sinusoids to parenchyma via secretion of inflammatory cytokines. A better understanding of roles of HSCs in the pathogenesis of ALF may lead to improvements and novel strategies for treating ALF patients.

Mesenchymal Stem Cells for Liver Regeneration in Liver Failure: From Experimental Models to Clinical Trials

The liver centralizes the systemic metabolism and thus controls and modulates the functions of the central and peripheral nervous systems, the immune system, and the endocrine system. In addition, the liver intervenes between the splanchnic and systemic venous circulation, determining an abdominal portal circulatory system. The liver displays a powerful regenerative potential that rebuilds the parenchyma after an injury. This regenerative mission is mainly carried out by resident liver cells. However, in many cases this regenerative capacity is insufficient and organ failure occurs. In normal livers, if the size of the liver is at least 30% of the original volume, hepatectomy can be performed safely. In cirrhotic livers, the threshold is 50% based on current practice and available data. Typically, portal vein embolization of the part of the liver that is going to be resected is employed to allow liver regeneration in two-stage liver resection after portal vein occlusion (PVO). However, hepatic resection often cannot be performed due to advanced disease progression or because it is not indicated in patients with cirrhosis. In such cases, liver transplantation is the only treatment possibility, and the need for transplantation is the common outcome of progressive liver disease. It is the only effective treatment and has high survival rates of 83% after the first year. However, donated organs are becoming less available, and mortality and the waiting lists have increased, leading to the initiation of living donor liver transplantations. This type of transplant has overall complications of 38%. In order to improve the treatment of hepatic injury, much research has been devoted to stem cells, in particular mesenchymal stem cells (MSCs), to promote liver regeneration. In this review, we will focus on the advances made using MSCs in animal models, human patients, ongoing clinical trials, and new strategies using 3D organoids.

The role of extracellular matrix on liver stem cell fate: A dynamic relationship in health and disease

The liver stem cell niche is a specialized and dynamic microenvironment with biomechanical and biochemical characteristics that regulate stem cell behavior. This is feasible due to the coordination of a complex network of secreted factors, small molecules, neural, blood inputs and extracellular matrix (ECM) components involved in the regulation of stem cell fate (self-renewal, survival, and differentiation into more mature phenotypes like hepatocytes and cholangiocytes). In this review, we describe and summarize all the major components that play essential roles in the liver stem cell niche, in particular, growth factor signaling and the biomechanical properties of the ECM.

CD11b+Ly6G+ myeloid-derived suppressor cells promote liver regeneration in a murine model of major hepatectomy

Liver regeneration depends on sequential activation of pathways and cells involving the remaining organ in recovery of mass. Proliferation of parenchyma is dependent on angiogenesis. Understanding liver regeneration-associated neovascularization may be useful for development of clinical interventions. Myeloid-derived suppressor cells (MDSCs) promote tumor angiogenesis and play a role in developmental processes that necessitate rapid vascularization. We therefore hypothesized that the MDSCs could play a role in liver regeneration. Following partial hepatectomy, MDSCs were enriched within regenerating livers, and their depletion led to increased liver injury and postoperative mortality, reduced liver weights, decreased hepatic vascularization, reduced hepatocyte hypertrophy and proliferation, and aberrant liver function. Gene expression profiling of regenerating liver-derived MDSCs demonstrated a large-scale transcriptional response involving key pathways related to angiogenesis. Functionally, enhanced reactive oxygen species production and angiogenic capacities of regenerating liver-derived MDSCs were confirmed. A comparative analysis revealed that the transcriptional response of MDSCs during liver regeneration resembled that of peripheral blood MDSCs during progression of abdominal tumors, suggesting a common MDSC gene expression profile promoting angiogenesis. In summary, our study shows that MDSCs contribute to early stages of liver regeneration possibly by exerting proangiogenic functions using a unique transcriptional program.-Nachmany, I., Bogoch, Y., Sivan, A., Amar, O., Bondar, E., Zohar, N., Yakubovsky, O., Fainaru, O., Klausner, J. M., Pencovich, N. CD11b⁺Ly6G⁺ myeloid-derived suppressor cells promote liver regeneration in a murine model of major hepatectomy.

Small molecule-mediated reprogramming of human hepatocytes into bipotent progenitor cells

BACKGROUND & AIMS

Currently, much effort is directed towards the development of new cell sources for clinical therapy using cell fate conversion by small molecules. Direct lineage reprogramming to a progenitor state has been reported in terminally differentiated rodent hepatocytes, yet remains a challenge in human hepatocytes.

METHODS

Human hepatocytes were isolated from healthy and diseased donor livers and reprogrammed into progenitor cells by 2 small molecules, A83-01 and CHIR99021 (AC), in the presence of EGF and HGF. The stemness properties of human chemically derived hepatic progenitors (hCdHs) were tested by standard in vitro and in vivo assays and transcriptome profiling.

RESULTS

We developed a robust culture system for generating hCdHs with therapeutic potential. The use of HGF proved to be an essential determinant of the fate conversion process. Based on functional evidence, activation of the HGF/MET signal transduction system collaborated with A83-01 and CHIR99021 to allow a rapid expansion of progenitor cells through the activation of the ERK pathway. hCdHs expressed hepatic progenitor markers and could self-renew for at least 10 passages while retaining a normal karyotype and potential to differentiate into functional hepatocytes and biliary epithelial cells in vitro. Gene expression profiling using RNAseq confirmed the transcriptional reprogramming of hCdHs towards a progenitor state and the suppression of mature hepatocyte transcripts. Upon intrasplenic transplantation in several models of therapeutic liver repopulation, hCdHs effectively repopulated the damaged parenchyma.

CONCLUSION

Our study is the first report of successful reprogramming of human hepatocytes to a population of proliferating bipotent cells with regenerative potential. hCdHs may provide a novel tool that permits expansion and genetic manipulation of patient-specific progenitors to study regeneration and the repair of diseased livers.

LAY SUMMARY

Human primary hepatocytes were reprogrammed towards hepatic progenitor cells by a combined treatment with 2 small molecules, A83-01 and CHIR99021, and HGF. Chemically derived hepatic progenitors exhibited a high proliferation potential and the ability to differentiate into hepatocytes and biliary epithelial cells both in vitro and in vivo. This approach enables the generation of patient-specific hepatic progenitors and provides a platform for personal and stem cell-based regenerative medicine.

Deficiency of apoptosis-stimulating protein two of p53 promotes liver regeneration in mice by activating mammalian target of rapamycin

Although liver regeneration has been intensively studied in various ways, the mechanisms underlying liver regeneration remain elusive. Apoptosis-stimulating protein two of p53 (ASPP2) was discovered as a binding partner of p53 and plays an important role in regulating cell apoptosis and growth. However, the role of ASPP2 in hepatocyte proliferation and liver regeneration has not been reported. The expression profile of ASPP2 was measured in a mouse model with 70% partial hepatectomy (PHX). Liver regeneration and hepatocyte proliferation were detected in wild-type (ASPP2+/+) and ASPP2 haploinsufficient (ASPP2+/-) mice with PHX. The mammalian target of rapamycin (mTOR) and autophagy pathways were analyzed in the ASPP2+/+ and ASPP2+/- mice with PHX. After rapamycin or 3-methyladenine (3-MA) treatment, hepatocyte proliferation and liver regeneration were analyzed in the ASPP2+/+ and ASPP2+/- mice with PHX. ASPP2 expression was shown to be upregulated at the early stage and downregulated at the late stage. Compared to the ASPP2+/+ mice, liver regeneration was enhanced in ASPP2+/- mice with 70% PHX. In addition, compared to the ASPP2+/+ mice, the mTORC1 pathway was significantly upregulated and the autophagic pathway was downregulated in ASPP2+/-mice with 70% PHX. Inhibition of the mTORC1 pathway significantly suppressed liver regeneration in ASPP2+/- mice with 70% PHX. In contrast, disruption of the autophagic pathway further enhanced liver regeneration in ASPP2+/- mice with 70% PHX. ASPP2 deficiency can promote liver regeneration through activating the mTORC1 pathway, which further regulates downstream molecules, such as those related to autophagy and p70S6K expression in mouse model post-PHX.

Nonintegrating Direct Conversion Using mRNA into Hepatocyte-Like Cells

Recently, several researchers have reported that direct reprogramming techniques can be used to differentiate fibroblasts into hepatocyte-like cells without a pluripotent intermediate step. However, the use of viral vectors for conversion continues to pose important challenges in terms of genome integration. Herein, we propose a new method of direct conversion without genome integration with potential clinical applications. To generate hepatocyte-like cells, mRNA coding for the hepatic transcription factors Foxa3 and HNF4α was transfected into mouse embryonic fibroblasts. After 10-12 days, the fibroblasts converted to an epithelial morphology and generated colonies of hepatocyte-like cells (R-iHeps). The generated R-iHeps expressed hepatocyte-specific marker genes and proteins, including albumin, alpha-fetoprotein, HNF4α, CK18, and CYP1A2. To evaluate hepatic function, indocyanine green uptake, periodic acid-Schiff staining, and albumin secretion were assessed. Furthermore, mCherry-positive R-iHeps were engrafted in the liver of Alb-TRECK/SCID mice, and we confirmed FAH enzyme expression in Fah1RTyrc/RJ models. In conclusion, our data suggest that the nonintegrating method using mRNA has potential for cell therapy.

Portal venous velocity affects liver regeneration after right lobe living donor hepatectomy

OBJECTIVES

We investigated whether chronological changes in portal flow and clinical factors play a role in the liver regeneration (LR) process after right donor-hepatectomy.

MATERIALS AND METHODS

Participants in this prospective study comprised 58 donors who underwent right donor-hepatectomy during the period February 2014 to February 2015 at a single medical institution. LR was estimated using two equations: remnant left liver (RLL) growth (%) and liver volumetric recovery (LVR) (%). Donors were classified into an excellent regeneration (ER) group or a moderate regeneration (MR) group based on how their LR on postoperative day 7 compared to the median value.

RESULTS

Multivariate analysis revealed that low residual liver volume (OR = .569, 95% CI: .367- .882) and high portal venous velocity in the immediate postoperative period (OR = 1.220, 95% CI: 1.001-1.488) were significant predictors of LR using the RLL growth equation; high portal venous velocity in the immediate postoperative period (OR = 1.325, 95% CI: 1.081-1.622) was a significant predictor of LR using the LVR equation. Based on the two equations, long-term LR was significantly greater in the ER group than in the MR group (p < .001).

CONCLUSION

Portal venous velocity in the immediate postoperative period was an important factor in LR. The critical time for short-term LR is postoperative day 7; it is associated with long-term LR in donor-hepatectomy.

Low-Power Laser Irradiation (LPLI): A Clinical Point of View on a Promising Strategy to Improve Liver Regeneration

The capacity of the liver to regenerate is an important clinical issue after major hepatectomies and makes the difference between life and death in some cases of post-operative malfunction when the liver remnant is too small or has an impaired regenerative capacity. Several approaches have been tested to stimulate hepatic regeneration after post-operative hepatic failure syndrome; however, they have produced controversial results. A quick, simple, and harmless method that can be used intraoperatively and capable of promoting an increased regenerative capacity of the remaining liver would be very welcome. Thus, based on the data in the literature, we presented low-power laser irradiation (LPLI) as a quick, simple, and harmless method to improve liver regeneration after major hepatectomies. This article highlights the current evidence about the effects of LPLI on liver regeneration, and also suggests laser therapy as an important tool for regenerative stimulation in clinical practice.

Associating liver partition and portal vein ligation versus 2-stage hepatectomy: A meta-analysis

BACKGROUND

The aim of this study was to conduct a meta-analysis comparing associating liver partition and portal vein ligation (ALPPS) with conventional 2-stage hepatectomy (TSH) in terms of clinical outcomes and to determine the feasibility and safety of ALPPS.

METHODS

A comprehensive search strategy was adopted to search the PubMed, Embase, Cochrane Library, and China Biology Medicine disc databases for studies comparing ALPPS and TSH. The search was broadened by looking up the reference lists of the retrieved articles. A meta-analysis was performed using the statistical software RevMan (v 5.3; Cochrane Collaboration).

RESULTS

A total of 7 studies involving 561 patients (ALPPS group, 136 patients; TSH group, 425 patients) were included in the present study, all of which were observational studies. Compared with TSH, ALPPS was associated with high completion rates of both stages [odds ratio (OR): 10.68, 95% confidence interval (95% CI): 3.26-34.97, P < .0001]. No significant differences were found in other outcomes such as complications of the first (OR: 4.04, 95% CI: 0.81-20.27, P = .09) and second surgical stage (OR: 1.59, 95% CI: 0.71-3.57, P = .26), liver failure (OR: 0.76, 95% CI: 0.29-1.98, P = .58) and the 90-day mortality rate (OR: 2.20, 95% CI: 1.00-4.84, P = .05).

CONCLUSION

ALPPS is associated with lower noncompletion rate and had similar perioperative outcomes relative to TSH. However, only retrospective observational studies were included in this meta-analysis, which may have limited the strength of the evidence. High-quality, large-scale studies are required to further evaluate the outcomes of ALPPS.

The multiple functions of melatonin in regenerative medicine

Melatonin research has been experiencing hyper growth in the last two decades; this relates to its numerous physiological functions including anti-inflammation, oncostasis, circadian and endocrine rhythm regulation, and its potent antioxidant activity. Recently, a large number of studies have focused on the role of melatonin in the regeneration of cells or tissues after their partial loss. In this review, we discuss the recent findings on the molecular involvement of melatonin in the regeneration of various tissues including the nervous system, liver, bone, kidney, bladder, skin, and muscle, among others.

Foie gras and liver regeneration: a fat dilemma

The liver has a unique ability of regenerating after injuries or partial loss of its mass. The mechanisms responsible for liver regeneration - mostly occurring when the hepatic tissue is damaged or functionally compromised by metabolic stress - have been studied in considerable detail over the last few decades, because this phenomenon has both basic-biology and clinical relevance. More specifically, recent interest has been focusing on the widespread occurrence of abnormal nutritional habits in the Western world that result in an increased prevalence of non-alcoholic fatty liver disease (NAFLD). NAFLD is closely associated with insulin resistance and dyslipidemia, and it represents a major clinical challenge. The disease may progress to steatohepatitis with persistent inflammation and progressive liver damage, both of which will compromise regeneration under conditions of partial hepatectomy in surgical oncology or in liver transplantation procedures. Here, we analyze the impact of ER stress and SIRT1 in lipid metabolism and in fatty liver pathology, and their consequences on liver regeneration. Moreover, we discuss the fine interplay between ER stress and SIRT1 functioning when contextualized to liver regeneration. An improved understanding of the cellular and molecular intricacies contributing to liver regeneration could be of great clinical relevance in areas as diverse as obesity, metabolic syndrome and type 2 diabetes, as well as oncology and transplantation.

Shaping the future of liver surgery: Implementation of experimental insights into liver regeneration

Background

While liver surgery has become a safe and feasible operation technique, the incidence of postoperative liver dysfunction still remains a central problem. Approximately 10% of patients undergoing liver resection were shown to develop liver dysfunction, which is associated with an increased risk of morbidity and mortality. Yet, to date there is no effective treatment option for postoperative liver dysfunction available. The development of postoperative liver dysfunction was linked to a disruption in the liver's potential to regenerate. Thus, it is importance to elucidate the underlying mechanisms of liver regeneration and to find potential therapeutic targets for the treatment of patients with postoperative liver dysfunction.

Methods

A review of the literature was carried out.

Results

We report on potential future interventions for improvement of liver regeneration after surgical resection. Moreover, we evaluate the benefits and drawbacks of hepatic progenitor cell therapy and hematopoietic stem cell therapy. However, the most significant improvement seems to come from molecular targets. Indeed, von Willebrand factor and its pharmacologic manipulation are among the most promising therapeutic targets to date. Furthermore, using the example of platelet-based therapy, we stress the potentially adverse effects of treatments for postoperative liver dysfunction.

Conclusion

The present review reports on the newest advances in the field of regenerative science, but also underlines the need for more research in the field of postoperative liver regeneration, especially in regard to translational studies.

Three-Dimensional Bioprinting of Hepatic Structures with Directly Converted Hepatocyte-Like Cells

Three-dimensional (3D) bioprinting technology is a promising new technology in the field of bioartificial organ generation with regard to overcoming the limitations of organ supply. The cell source for bioprinting is very important. Here, we generated 3D hepatic scaffold with mouse-induced hepatocyte-like cells (miHeps), and investigated whether their function was improved after transplantation in vivo. To generate miHeps, mouse embryonic fibroblasts (MEFs) were transformed with pMX retroviruses individually expressing hepatic transcription factors Hnf4a and Foxa3. After 8-10 days, MEFs formed rapidly growing hepatocyte-like colonies. For 3D bioprinting, miHeps were mixed with a 3% alginate hydrogel and extruded by nozzle pressure. After 7 days, they were transplanted into the omentum of Jo2-treated NOD Scid gamma (NSG) mice as a liver damage model. Real-time polymerase chain reaction and immunofluorescence analyses were conducted to evaluate hepatic function. The 3D bioprinted hepatic scaffold (25 × 25 mm) expressed Albumin, and ASGR1 and HNF4a expression gradually increased for 28 days in vitro. When transplanted in vivo, the cells in the hepatic scaffold grew more and exhibited higher Albumin expression than in vitro scaffold. Therefore, combining 3D bioprinting with direct conversion technology appears to be an effective option for liver therapy.

A phase I study on stereotactic body radiotherapy of liver metastases based on functional treatment planning using positron emission tomography with 2-[18F]fluoro-2-deoxy-d-galactose

BACKGROUND AND PURPOSE

The galactose analog 2-[¹⁸F]fluoro-2-deoxy-d-galactose (FDGal) is used for quantification of regional hepatic metabolic capacity by functional positron emission tomography computerized tomography (PET/CT). In the present study, FDGal PET/CT was used for functional treatment planning (FTP) of stereotactic body radiotherapy (SBRT) of liver metastases with the aim of minimizing radiation dose to the best functioning liver tissue.

MATERIAL AND METHODS

Fourteen patients referred for SBRT had FDGal PET/CT performed before and one month after the treatment. The planning CT and the FDGal PET/CT images were deformable co-registered.

RESULTS

A reduction in the mean dose of approximately 2 Gy to the best functioning sub-volumes was obtained. One patient developed grade 2 acute morbidity and no patients experienced grade 3 or higher acute morbidities. The regional hepatic metabolic function post-treatment was linearly correlated to the regional radiation dose and for each 10-Gy increase in dose (γ_10Gy), the metabolic function was reduced by 12%. A 50% reduction was seen at 22.9 Gy in 3 fractions (CI 95%: 16.7-30.4 Gy).

CONCLUSION

The clinical study demonstrates the feasibility for FTP in patients with liver metastases and it was possible to minimize the radiation dose to the best functioning liver tissue.

Establishment of Hepatocellular Cancer Induced Pluripotent Stem Cells Using a Reprogramming Technique

Background/Aims

Cancer is known to be a disease by many factors. However, specific results of reprogramming by pluripotency-related transcription factors remain to be scarcely reported. Here, we verified potential effects of pluripotent-related genes in hepatocellular carcinoma cancer cells.

Methods

To better understand reprogramming of cancer cells in different genetic backgrounds, we used four liver cancer cell lines representing different states of p53 (HepG2, Hep3B, Huh7 and PLC). Retroviral-mediated introduction of reprogramming related genes (KLF4, Oct4, Sox2, and Myc) was used to induce the expression of proteins related to a pluripotent status in liver cancer cells.

Results

Hep3B cells (null p53) exhibited a higher efficiency of reprogramming in comparison to the other liver cancer cell lines. The reprogrammed Hep3B cells acquired similar characteristics to pluripotent stem cells. However, loss of stemness in Hep3B-iPCs was detected during continual passage.

Conclusions

We demonstrated that reprogramming was achieved in tumor cells through retroviral induction of genes associated with reprogramming. Interestingly, the reprogrammed pluripotent cancer cells (iPCs) were very different from original cancer cells in terms of colony shape and expressed markers. The induction of pluripotency of liver cancer cells correlated with the status of p53, suggesting that different expression level of p53 in cancer cells may affect their reprogramming.

Progress and prospects of circular RNAs in Hepatocellular carcinoma: Novel insights into their function

Hepatocellular carcinoma (HCC) is one of the most predominant subjects of liver malignancies, which arouses global concern in the recent years. Advanced studies have found that Circular RNAs (circRNAs) are differentially expressed in HCC, with its regulatory capacity in HCC pathogenesis and metastasis. However, the underlying mechanism remains largely unknown. In this review, we summarized the functions and mechanisms of those aberrantly expressed circRNAs in HCC tissues. We hope to enlighten more comprehensive studies on the detailed mechanisms of circRNAs and explore their potential values in clinic applications. It revealed that hsa_circ_0004018 can be used as a potential biomarker in HCC diagnosis, with its superior sensitivity to alpha-fetoprotein (AFP). Notably, the correlation of circRNA abundance in the proliferation of liver regeneration (LR) has recently been clarified and different circRNA profiles served as candidates for nonalcoholic steatohepatitis (NASH) diagnosis also be discussed. Therefore, the improved understanding of circRNAs in HCC pathogenesis and metastasis proposed a novel basis for the early diagnosis in HCC patients, which provides a useful resource to explore the pathogenesis of HCC.

Generation of Multilayered 3D Structures of HepG2 Cells Using a Bio-printing Technique

Background/Aims

Chronic liver disease is a major widespread cause of death, and whole liver transplantation is the only definitive treatment for patients with end-stage liver diseases. However, many problems, including donor shortage, surgical complications and cost, hinder their usage. Recently, tissue-engineering technology provided a potential breakthrough for solving these problems. Three-dimensional (3D) printing technology has been used to mimic tissues and organs suitable for transplantation, but applications for the liver have been rare.

Methods

A 3D bioprinting system was used to construct 3D printed hepatic structures using alginate. HepG2 cells were cultured on these 3D structures for 3 weeks and examined by fluorescence microscopy, histology and immunohistochemistry. The expression of liver-specific markers was quantified on days 1, 7, 14, and 21.

Results

The cells grew well on the alginate scaffold, and liver-specific gene expression increased. The cells grew more extensively in 3D culture than two-dimensional culture and exhibited better structural aspects of the liver, indicating that the 3D bioprinting method recapitulates the liver architecture.

Conclusions

The 3D bioprinting of hepatic structures appears feasible. This technology may become a major tool and provide a bridge between basic science and the clinical challenges for regenerative medicine of the liver.

Three-dimensional (3D) printing of mouse primary hepatocytes to generate 3D hepatic structure

Purpose

The major problem in producing artificial livers is that primary hepatocytes cannot be cultured for many days. Recently, 3-dimensional (3D) printing technology draws attention and this technology regarded as a useful tool for current cell biology. By using the 3D bio-printing, these problems can be resolved.

Methods

To generate 3D bio-printed structures (25 mm × 25 mm), cells-alginate constructs were fabricated by 3D bio-printing system. Mouse primary hepatocytes were isolated from the livers of 6–8 weeks old mice by a 2-step collagenase method. Samples of 4 × 10⁷ hepatocytes with 80%–90% viability were printed with 3% alginate solution, and cultured with well-defined culture medium for primary hepatocytes. To confirm functional ability of hepatocytes cultured on 3D alginate scaffold, we conducted quantitative real-time polymerase chain reaction and immunofluorescence with hepatic marker genes.

Results

Isolated primary hepatocytes were printed with alginate. The 3D printed hepatocytes remained alive for 14 days. Gene expression levels of Albumin, HNF-4α and Foxa3 were gradually increased in the 3D structures. Immunofluorescence analysis showed that the primary hepatocytes produced hepatic-specific proteins over the same period of time.

Conclusion

Our research indicates that 3D bio-printing technique can be used for long-term culture of primary hepatocytes. It can therefore be used for drug screening and as a potential method of producing artificial livers.

Administration of multipotent mesenchymal stromal cells restores liver regeneration and improves liver function in obese mice with hepatic steatosis after partial hepatectomy

Background

The liver has the remarkable capacity to regenerate in order to compensate for lost or damaged hepatic tissue. However, pre-existing pathological abnormalities, such as hepatic steatosis (HS), inhibits the endogenous regenerative process, becoming an obstacle for liver surgery and living donor transplantation.

Recent evidence indicates that multipotent mesenchymal stromal cells (MSCs) administration can improve hepatic function and increase the potential for liver regeneration in patients with liver damage. Since HS is the most common form of chronic hepatic illness, in this study we evaluated the role of MSCs in liver regeneration in an animal model of severe HS with impaired liver regeneration.

Methods

C57BL/6 mice were fed with a regular diet (normal mice) or with a high-fat diet (obese mice) to induce HS. After 30 weeks of diet exposure, 70% hepatectomy (Hpx) was performed and normal and obese mice were divided into two groups that received 5 × 10⁵ MSCs or vehicle via the tail vein immediately after Hpx.

Results

We confirmed a significant inhibition of hepatic regeneration when liver steatosis was present, while the hepatic regenerative response was promoted by infusion of MSCs. Specifically, MSC administration improved the hepatocyte proliferative response, PCNA-labeling index, DNA synthesis, liver function, and also reduced the number of apoptotic hepatocytes.

These effects may be associated to the paracrine secretion of trophic factors by MSCs and the hepatic upregulation of key cytokines and growth factors relevant for cell proliferation, which ultimately improves the survival rate of the mice.

Conclusions

MSCs represent a promising therapeutic strategy to improve liver regeneration in patients with HS as well as for increasing the number of donor organs available for transplantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0469-y) contains supplementary material, which is available to authorized users.

Cellular Mechanisms of Liver Regeneration and Cell-Based Therapies of Liver Diseases

The emerging field of regenerative medicine offers innovative methods of cell therapy and tissue/organ engineering as a novel approach to liver disease treatment. The ultimate scientific foundation of both cell therapy of liver diseases and liver tissue and organ engineering is delivered by the in-depth studies of the cellular and molecular mechanisms of liver regeneration. The cellular mechanisms of the homeostatic and injury-induced liver regeneration are unique. Restoration of the mass of liver parenchyma is achieved by compensatory hypertrophy and hyperplasia of the differentiated parenchymal cells, hepatocytes, while expansion and differentiation of the resident stem/progenitor cells play a minor or negligible role. Participation of blood-borne cells of the bone marrow origin in liver parenchyma regeneration has been proven but does not exceed 1-2% of newly formed hepatocytes. Liver regeneration is activated spontaneously after injury and can be further stimulated by cell therapy with hepatocytes, hematopoietic stem cells, or mesenchymal stem cells. Further studies aimed at improving the outcomes of cell therapy of liver diseases are underway. In case of liver failure, transplantation of engineered liver can become the best option in the foreseeable future. Engineering of a transplantable liver or its major part is an enormous challenge, but rapid progress in induced pluripotency, tissue engineering, and bioprinting research shows that it may be doable.

Stereological analysis of size and density of hepatocytes in the porcine liver

The porcine liver is frequently used as a large animal model for verification of surgical techniques, as well as experimental therapies. Often, a histological evaluation is required that include measurements of the size, nuclearity or density of hepatocytes. Our aims were to assess the mean number-weighted volume of hepatocytes, the numerical density of hepatocytes, and the fraction of binuclear hepatocytes (BnHEP) in the porcine liver, and compare the distribution of these parameters among hepatic lobes and macroscopic regions of interest (ROIs) with different positions related to the liver vasculature. Using disector and nucleator as design-based stereological methods, the morphometry of hepatocytes was quantified in seven healthy piglets. The samples were obtained from all six hepatic lobes and three ROIs (peripheral, paracaval and paraportal) within each lobe. Histological sections (thickness 16 μm) of formalin-fixed paraffin-embedded material were stained with the periodic acid-Schiff reaction to indicate the cell outlines and were assessed in a series of 3-μm-thick optical sections. The mean number-weighted volume of mononuclear hepatocytes (MnHEP) in all samples was 3670 ± 805 μm³ (mean ± SD). The mean number-weighted volume of BnHEP was 7050 ± 2550 μm³ . The fraction of BnHEP was 4 ± 2%. The numerical density of all hepatocytes was 146 997 ± 15 738 cells mm^-3 of liver parenchyma. The porcine hepatic lobes contained hepatocytes of a comparable size, nuclearity and density. No significant differences were identified between the lobes. The peripheral ROIs of the hepatic lobes contained the largest MnHEP with the smallest numerical density. The distribution of a larger MnHEP was correlated with a larger volume of BnHEP and a smaller numerical density of all hepatocytes. Practical recommendations for designing studies that involve stereological evaluations of the size, nuclearity and density of hepatocytes in porcine liver are provided.

Functional comparison of human embryonic stem cells and induced pluripotent stem cells as sources of hepatocyte-like cells

Pluripotent stem cells can differentiate into many cell types including mature hepatocytes, and can be used in the development of new drugs, treatment of diseases, and in basic research. In this study, we established a protocol leading to efficient hepatic differentiation, and compared the capacity to differentiate into the hepatocyte lineage of human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs). Optimal combinations of cytokines and growth factors were added to embryoid bodies produced by both types of cell. Differentiation of the cells was assessed with optical and electron microscopes, and hepatic-specific transcripts and proteins were detected by quantitative reverse transcription polymerase chain reaction and immunocytochemistry, respectively. Both types of embryoid body produced polygonal hepatocyte-like cells accompanied by time-dependent up regulation of genes for α-fetoprotein, albumin (ALB), asialoglycoprotein1, CK8, CK18, CK19, CYP1A2, and CYP3A4, which are expressed in fetal and adult hepatocytes. Both types of cell displayed functions characteristic of mature hepatocytes such as accumulation of glycogen, secretion of ALB, and uptake of indocyanine green. And these cells are transplanted into mouse model. Our findings indicate that hESCs and hiPSCs have similar abilities to differentiate into hepatocyte in vitro using the protocol developed here, and these cells are transplantable into damaged liver.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s13770-016-0094-y and is accessible for authorized users.

Prediction of postoperative liver regeneration from clinical information using a data-led mathematical model

Although the capacity of the liver to recover its size after resection has enabled extensive liver resection, post-hepatectomy liver failure remains one of the most lethal complications of liver resection. Therefore, it is clinically important to discover reliable predictive factors after resection. In this study, we established a novel mathematical framework which described post-hepatectomy liver regeneration in each patient by incorporating quantitative clinical data. Using the model fitting to the liver volumes in series of computed tomography of 123 patients, we estimated liver regeneration rates. From the estimation, we found patients were divided into two groups: i) patients restored the liver to its original size (Group 1, n = 99); and ii) patients experienced a significant reduction in size (Group 2, n = 24). From discriminant analysis in 103 patients with full clinical variables, the prognosis of patients in terms of liver recovery was successfully predicted in 85-90% of patients. We further validated the accuracy of our model prediction using a validation cohort (prediction = 84-87%, n = 39). Our interdisciplinary approach provides qualitative and quantitative insights into the dynamics of liver regeneration. A key strength is to provide better prediction in patients who had been judged as acceptable for resection by current pragmatic criteria.

An updated systematic review of the evolution of ALPPS and evaluation of its advantages and disadvantages in accordance with current evidence

The main obstacle to achieving an R0 resection after a major hepatectomy is inability to preserve an adequate future liver remnant (FLR) to avoid postoperative liver failure (PLF). Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) is a novel technique for resecting tumors that were previously considered unresectable, and this technique results in a vast increase in the volume of the FLR in a short period of time. However, this technique continues to provoke heated debate because of its high mortality and morbidity.The evolution of ALPPS and its advantages and disadvantages have been systematically reviewed and evaluated in accordance with current evidence. Electronic databases (PubMed and Medline) were searched for potentially relevant articles from January 2007 to January 2016.ALPPS has evolved into various modified forms. Some of these modified techniques have reduced the difficulty of the procedure and enhanced its safety. Current evidence indicates that the advantages of ALPPS are rapid hypertrophy of the FLR, the feasibility of the procedure, and a higher rate of R0 resection in comparison to other techniques. However, ALPPS is associated with worse major complications, more deaths, and early tumor recurrence.Hepatobiliary surgeons should carefully consider whether to perform ALPPS. Some modified forms of ALPPS have reduced the mortality and morbidity of the procedure, but they cannot be recommended over the original procedure currently. Portal vein embolization (PVE) is still the procedure of choice for patients with a tumor-free FLR, and ALPPS could be used as a salvage procedure when PVE fails. More persuasive evidence needs to be assembled to determine whether ALPPS or two-stage hepatectomy (TSH) is better for patients with a tumor involving the FLR. Evidence with regard to long-term oncological outcomes is still limited. More meticulous comparative studies and studies of the 5-year survival rate of ALPPS could ultimately help to determine the usefulness of ALPPS. Indications and patient selection for the procedure need to be determined.

The Role of IL-1 Family Members and Kupffer Cells in Liver Regeneration

Interleukin-1 (IL-1) family and Kupffer cells are linked with liver regeneration, but their precise roles remain unclear. IL-1 family members are pleiotropic factors with a range of biological roles in liver diseases, inducing hepatitis, cirrhosis, and hepatocellular carcinoma, as well as liver regeneration. Kupffer cells are the main source of IL-1 and IL-1 receptor antagonist (IL-1Ra), the key members of IL-1 family. This systemic review highlights a close association of IL-1 family members and Kupffer cells with liver regeneration, although their specific roles are inconclusive. Moreover, IL-1 members are proposed to induce effects on liver regeneration through Kupffer cells.

MicroRNA-21 Contributes to Liver Regeneration by Targeting PTEN

Background

Multiple microRNAs (miRNAs, miRs), including miR-21, have been documented to be critical regulators of liver regeneration, but the mechanism underlying their roles in hepatocyte proliferation and cell cycle progression is still far from understood.

Material/Methods

miR-21 levels were determined using qRT-PCRs in mouse livers at 48 h after 70% partial hepatectomy (PH-48 h). Cell proliferation was determined by use of a cell-counting kit-8 (CCK-8), EdU incorporation staining, and flow cytometry. Phosphatase and tensin homolog (PTEN) expressions were determined using qRT-PCR and Western blot analysis. PTEN siRNA was used to perform the rescue experiment.

Results

A marked upregulation of miR-21 was observed in mouse livers at 48 h after 70% partial hepatectomy (PH-48 h) compared to 0 h after PH (PH-0 h). Overexpression of miR-21 was associated with increased proliferation and a rapid G1-to-S phase transition of the cell cycle in BNL CL.2 normal liver cells in vitro. In addition, we showed that PTEN expression was inversely correlated with miR-21 in BNL CL.2 cells and demonstrated that PTEN expression is lower in mouse livers at PH-48 h. Moreover, the presence of PTEN siRNA significantly abolished the suppressive effect of miR-21 inhibitor on hepatocyte proliferation.

Conclusions

miR-21 overexpression contributes to liver regeneration and hepatocyte proliferation by targeting PTEN. Upregulation of miR-21 might be a useful therapeutic strategy to promote liver regeneration.