Intrahepatic Administration of Human Liver Stem Cells in Infants with Inherited Neonatal-Onset Hyperammonemia: A Phase I Study

Large-Scale Expansion of Human Liver Stem Cells Using Two Different Bioreactor Systems

The assessment of human liver stem cells (HLSCs) as cell therapeutics requires scalable, controlled expansion processes. We first focused on defining appropriate process parameters for HLSC expansion such as seeding density, use of antibiotics, optimal cell age and critical metabolite concentrations in conventional 2D culture systems. For scale-up, we transferred HLSC expansion to multi-plate and stirred-tank bioreactor systems to determine their limitations. A seeding density of 4000 cells cm-2 was needed for efficient expansion. Although growth was not significantly affected by antibiotics, the concentrations of lactate and ammonia were important. A maximum expansion capacity of at least 20 cumulative population doublings (cPDs) was observed, confirming HLSC growth, identity and functionality. For the expansion of HLSCs in the multi-plate bioreactor system Xpansion (XPN), the oxygen supply strategy was optimized due to a low kLa of 0.076 h-1. The XPN bioreactor yielded a final mean cell density of 94 ± 8 × 103 cells cm-2, more than double that of the standard process in T-flasks. However, in the larger XPN50 device, HLSC density reached only 28 ± 0.9 × 103 cells cm-2, while the glucose consumption rate increased 8-fold. In a fully-controlled 2 L stirred-tank bioreactor (STR), HLSCs expanded at a comparable rate to the T-flask and XPN50 processes in a homogeneous microenvironment using advanced process analytical technology. Ultimately, the scale-up of HLSCs was successful using two different bioreactor systems, resulting in sufficient numbers of viable, functional and undifferentiated HLSCs for therapeutic applications.

Extracellular Vesicles Derived from Human Liver Stem Cells Counteract Chronic Kidney Disease Development and Cardiac Dysfunction in Remnant Kidney Murine Model: The Possible Involvement of Proteases

Fibrosis is a marker of chronic kidney disease (CKD) and consists of the accumulation of the extracellular matrix (ECM) components, causing the progressive deterioration of kidney function. Human liver stem cells (HLSCs) have anti-fibrotic activity, and HLSC-derived extracellular vesicles (EVs) mediate this effect. Herein, we evaluated the ability of HLSC-EVs to reverse renal and cardiac alterations in a murine model of partial nephrectomy (PNx) that mimics human CKD development. Furthermore, we investigated the contribution of extracellular matrix remodeling-related proteases to the anti-fibrotic effect of HLSC-EVs. PNx was performed by ligation of both poles of the left kidney, followed one week later by the removal of the right kidney. EV treatment started 4 weeks after the nephrectomy, when renal and cardiac alternations were already established, and mice were sacrificed at week eight. HLSC-EV treatment improved renal function and morphology, significantly decreasing interstitial fibrosis, glomerular sclerosis, and capillary rarefaction. This improvement was confirmed by the decreased expression of pro-fibrotic genes. Moreover, EV treatment improved cardiac function and reduced cardiac fibrosis. HLSC-EVs shuttled different proteases with ECM remodeling activity, and matrix metalloproteinase 1 (MMP-1) was involved in their anti-fibrotic effect on renal tissue. HLSC-EV treatment interferes with CKD development and ameliorates cardiomyopathy in PNx mice.

In vitro characterization of 3D culture-based differentiation of human liver stem cells

Introduction: The lack of functional hepatocytes poses a significant challenge for drug safety testing and therapeutic applications due to the inability of mature hepatocytes to expand and their tendency to lose functionality in vitro. Previous studies have demonstrated the potential of Human Liver Stem Cells (HLSCs) to differentiate into hepatocyte-like cells within an in vitro rotary cell culture system, guided by a combination of growth factors and molecules known to regulate hepatocyte maturation. In this study, we employed a matrix multi-assay approach to comprehensively characterize HLSC differentiation. Methods: We evaluated the expression of hepatic markers using qRT-PCR, immunofluorescence, and Western blot analysis. Additionally, we measured urea and FVIII secretion into the supernatant and developed an updated indocyanine green in vitro assay to assess hepatocyte functionality. Results: Molecular analyses of differentiated HLSC aggregates revealed significant upregulation of hepatic genes, including CYP450, urea cycle enzymes, and uptake transporters exclusively expressed on the sinusoidal side of mature hepatocytes, evident as early as 1 day post-differentiation. Interestingly, HLSCs transiently upregulated stem cell markers during differentiation, followed by downregulation after 7 days. Furthermore, differentiated aggregates demonstrated the ability to release urea and FVIII into the supernatant as early as the first 24 h, with accumulation over time. Discussion: These findings suggest that a 3D rotation culture system may facilitate rapid hepatic differentiation of HLSCs. Despite the limitations of this rotary culture system, its unique advantages hold promise for characterizing HLSC GMP batches for clinical applications.

Current status and future directions of liver transplantation for metabolic liver disease in children

Orthotopic liver transplantation (OLT) in the care of children with inborn errors of metabolism (IEM) is well established and represent the second most common indication for pediatric liver transplantation in most centers worldwide, behind biliary atresia. OLT offers cure of disease when a metabolic defect is confined to the liver, but may still be transformative on a patient's quality of life reducing the chance of metabolic crises causing neurological damage in children be with extrahepatic involvement and no "functional cure." Outcomes post-OLT for inborn errors of metabolism are generally excellent. However, this benefit must be balanced with consideration of a composite risk of morbidity, and commitment to a lifetime of post-transplant chronic disease management. An increasing number of transplant referrals for children with IEM has contributed to strain on graft access in many parts of the world. Pragmatic evaluation of IEM referrals is essential, particularly pertinent in cases where progression of extra-hepatic disease is anticipated, with long-term outcome expected to be poor. Decision to proceed with liver transplantation is highly individualized based on the child's dynamic risk-benefit profile, their family unit, and their treating multidisciplinary team. Also to be considered is the chance of future treatments, such as gene therapies, emerging in the medium term.

Expression and function of the urea cycle in widely-used hepatic cellular models

The group of rare metabolic defects termed urea cycle disorders (UCDs) occur within the ammonia elimination pathway and lead to significant neurocognitive sequelae for patients surviving decompensation episodes. Besides orthotopic liver transplantation, curative options are lacking for UCDs, with dietary management being the gold clinical standard. Novel therapeutic approaches are essential for UCDs; however, such effort presupposes preclinical testing in cellular models that effectively capture disease manifestation. Several cellular and animal models exist and aim to recapitulate the broad phenotypic spectrum of UCDs; however, the majority of those lack extensive molecular and biochemical characterization. The development of cellular models is emerging since animal models are extremely time and cost consuming, and subject to ethical considerations, including the 3R principle that endorses animal welfare over unchecked preclinical testing. The aim of this study was to compare the extent of expression and functionality of the urea cycle in two commercial hepatoma-derived cell lines, induced pluripotent stem cell hepatocytes (iPSC-Heps), primary human hepatocytes (PHHs) and human liver cell preparations. Using immunoblotting, immunocytochemistry, and stable isotope tracing of the urea cycle metabolites, we identified that the hepatoma-derived, 2-week differentiated HepaRG cells are urea cycle proficient and behave as cellular alternatives to PHHs. Furthermore, HepaRG cells were superior to iPSC-Heps, which are known to exhibit batch-to-batch variabilities in terms of hepatic maturity and enzyme expression. Finally, HepG2 cells lack the urea cycle enzymes ornithine transcarbamylase and arginase 1, the transporter ORNT1, which limits their suitability as model for the study of UCDs.

Extracellular Vesicles in Liver Transplantation: Current Evidence and Future Challenges

Extracellular vesicles (EVs) are emerging as a promising field of research in liver disease. EVs are small, membrane-bound vesicles that contain various bioactive molecules, such as proteins, lipids, and nucleic acids and are involved in intercellular communication. They have been implicated in numerous physiological and pathological processes, including immune modulation and tissue repair, which make their use appealing in liver transplantation (LT). This review summarizes the current state of knowledge regarding the role of EVs in LT, including their potential use as biomarkers and therapeutic agents and their role in graft rejection. By providing a comprehensive insight into this emerging topic, this research lays the groundwork for the potential application of EVs in LT.

Genetic background and clinical characteristics of infantile hyperammonemia

Background

This study was conducted to analyze the genetic spectrum and clinical characteristics of infantile hyperammonemia.

Methods

Between January 2016 and June 2020, we retrospectively enrolled infantile hyperammonemia patients with definitive genetic diagnosis at the Children's Hospital of Fudan University. Based on the age of hyperammonemia onset, patients were grouped into neonatal and post-neonatal subgroups to compare their genetic and clinical features.

Results

Collectively, 136 pathogenic or likely pathogenic variants of the 33 genes were identified. Fourteen genes were reported with hyperammonemia (42%, 14/33), with SLC25A13 and MUT being the top two detected genes. In contrast, 19 genes, which have not been previously reported with hyperammonemia, were detected (58%, 19/33), in which JAG1 and ABCC8 were the most frequently mutated genes. Compared with post-neonatal hyperammonemia, neonatal patients with hyperammonemia presented with higher rates of organic acidemia (P=0.001) and fatty acid oxidation disorder (P=0.006), but a lower rate of cholestasis (P<0.001). Patients with neonatal hyperammonemia had a higher ratio of peak plasma ammonia level ≥500 µmol/L (P=0.003) and were more likely to receive precision medicine (P=0.027); however, they had a refractory clinical course (P=0.001) and poorer prognosis than the infantile group.

Conclusions

There were significant differences in the genetic spectrum, clinical features, clinical course, and outcomes between infants with different hyperammonemia onset ages.

Cell and cell-derivative-based therapy for liver diseases: current approaches and future promises

INTRODUCTION

According to the recent updates from World Health Organization, liver diseases are the 12th most common cause of mortality. Currently, orthotopic liver transplantation (OLT) is the most effective and the only treatment for end-stage liver diseases. Owing to several shortcomings like finite numbers of healthy organ donors, lifelong immunosuppression, and complexity of the procedure, cell and cell-derivatives therapies have emerged as a potential therapeutic alternative for liver diseases. Various cell types and therapies have been proposed and their therapeutic effects evaluated in preclinical or clinical studies, including hepatocytes, hepatocyte-like cells (HLCs) derived from stem cells, human liver stem cells (HLSCs), combination therapies with various types of cells, organoids, and implantable cell-biomaterial constructs with synthetic and natural polymers or even decellularized extracellular matrix (ECM).

AREAS COVERED

In this review, we highlighted the current status of cell and cell-derivative-based therapies for liver diseases. Furthermore, we discussed future prospects of using HLCs, liver organoids, and their combination therapies.

EXPERT OPINION

Promising application of stem cell-based techniques including iPSC technology has been integrated into novel techniques such as gene editing, directed differentiation, and organoid technology. iPSCs offer promising prospects to represent novel therapeutic strategies and modeling liver diseases.

State-of-the-Art and Future Directions in Organ Regeneration with Mesenchymal Stem Cells and Derived Products during Dynamic Liver Preservation

Transplantation is currently the treatment of choice for end-stage liver diseases but is burdened by the shortage of donor organs. Livers from so-called extended-criteria donors represent a valid option to overcome organ shortage, but they are at risk for severe post-operative complications, especially when preserved with conventional static cold storage. Machine perfusion technology reduces ischemia-reperfusion injury and allows viability assessment of these organs, limiting their discard rate and improving short- and long-term outcomes after transplantation. Moreover, by keeping the graft metabolically active, the normothermic preservation technique guarantees a unique platform to administer regenerative therapies ex vivo. With their anti-inflammatory and immunomodulatory properties, mesenchymal stem cells are among the most promising sources of therapies for acute and chronic liver failure, but their routine clinical application is limited by several biosafety concerns. It is emerging that dynamic preservation and stem cell therapy may supplement each other if combined, as machine perfusion can be used to deliver stem cells to highly injured grafts, avoiding potential systemic side effects. The aim of this narrative review is to provide a comprehensive overview on liver preservation techniques and mesenchymal stem cell-based therapies, focusing on their application in liver graft reconditioning.

How the mechanical microenvironment of stem cell growth affects their differentiation: a review

Stem cell differentiation is of great interest in medical research; however, specifically and effectively regulating stem cell differentiation is still a challenge. In addition to chemical factors, physical signals are an important component of the stem cell ecotone. The mechanical microenvironment of stem cells has a huge role in stem cell differentiation. Herein, we describe the knowledge accumulated to date on the mechanical environment in which stem cells exist, which consists of various factors, including the extracellular matrix and topology, substrate stiffness, shear stress, hydrostatic pressure, tension, and microgravity. We then detail the currently known signalling pathways that stem cells use to perceive the mechanical environment, including those involving nuclear factor-kB, the nicotinic acetylcholine receptor, the piezoelectric mechanosensitive ion channel, and hypoxia-inducible factor 1α. Using this information in clinical settings to treat diseases is the goal of this research, and we describe the progress that has been made. In this review, we examined the effects of mechanical factors in the stem cell growth microenvironment on stem cell differentiation, how mechanical signals are transmitted to and function within the cell, and the influence of mechanical factors on the use of stem cells in clinical applications.

Clinical Application of Induced Hepatocyte-like Cells Produced from Mesenchymal Stromal Cells: A Literature Review

Liver disease is a leading cause of mortality worldwide, resulting in 1.3 million deaths annually. The vast majority of liver disease is caused by metabolic disease (i.e., NASH) and alcohol-induced hepatitis, and to a lesser extent by acute and chronic viral infection. Furthermore, multiple insults to the liver is becoming common due to the prevalence of metabolic and alcohol-related liver diseases. Despite this rising prevalence of liver disease, there are few treatment options: there are treatments for viral hepatitis C and there is vaccination for hepatitis B. Aside from the management of metabolic syndrome, no direct liver therapy has shown clinical efficacy for metabolic liver disease, there is very little for acute alcohol-induced liver disease, and liver transplantation remains the only effective treatment for late-stage liver disease. Traditional pharmacologic interventions have failed to appreciably impact the pathophysiology of alcohol-related liver disease or end-stage liver disease. The difficulties associated with developing liver-specific therapies result from three factors that are common to late-stage liver disease arising from any cause: hepatocyte injury, inflammation, and aberrant tissue healing. Hepatocyte injury results in tissue damage with inflammation, which sensitizes the liver to additional hepatocyte injury and stimulates hepatic stellate cells and aberrant tissue healing responses. In the setting of chronic liver insults, there is progressive scarring, the loss of hepatocyte function, and hemodynamic dysregulation. Regenerative strategies using hepatocyte-like cells that are manufactured from mesenchymal stromal cells may be able to correct this pathophysiology through multiple mechanisms of action. Preclinical studies support their effectiveness and recent clinical studies suggest that cell replacement therapy can be safe and effective in patients with liver disease for whom there is no other option.

The Potential Clinical Use of Stem/Progenitor Cells and Organoids in Liver Diseases

The liver represents the most important metabolic organ of the human body. It is evident that an imbalance of liver function can lead to several pathological conditions, known as liver failure. Orthotropic liver transplantation (OLT) is currently the most effective and established treatment for end-stage liver diseases and acute liver failure (ALF). Due to several limitations, stem-cell-based therapies are currently being developed as alternative solutions. Stem cells or progenitor cells derived from various sources have emerged as an alternative source of hepatic regeneration. Therefore, hematopoietic stem cells (HSCs), mesenchymal stromal cells (MSCs), endothelial progenitor cells (EPCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are also known to differentiate into hepatocyte-like cells (HPLCs) and liver progenitor cells (LPCs) that can be used in preclinical or clinical studies of liver disease. Furthermore, these cells have been shown to be effective in the development of liver organoids that can be used for disease modeling, drug testing and regenerative medicine. In this review, we aim to discuss the characteristics of stem-cell-based therapies for liver diseases and present the current status and future prospects of using HLCs, LPCs or liver organoids in clinical trials.

Routes of Stem Cell Administration

Stem cells are very promising for the treatment of a plethora of human diseases. Numerous clinical studies have been conducted to assess the safety and efficacy of various stem cell types. Factors that ensure successful therapeutic outcomes in patients are cell-based parameters such as source, viability, and number, as well as frequency and timing of intervention and disease stage. Stem cell administration routes should be appropriately chosen as these can affect homing and engraftment of the cells and hence reduce therapeutic effects, or compromise safety, resulting in serious adverse events. In this chapter, we will describe the use of stem cells in organ repair and regeneration, in particular, the liver and the available routes of cell delivery in the clinic for end-stage liver diseases. Factors affecting homing and engraftment of stem cells for each administration route will be discussed.

Stem cells in neonatal diseases: An overview

Preterm birth and its common complications are major causes of infant mortality and long-term morbidity. Despite great advances in understanding the pathogenesis of neonatal diseases and improvements in neonatal intensive care, effective therapies for the prevention or treatment for these conditions are still lacking. Stem cell (SC) therapy is rapidly emerging as a novel therapeutic tool for several diseases of the newborn with encouraging pre-clinical results that hold promise for translation to the bedside. The utility of different types of SCs in neonatal diseases is being explored. SC therapeutic efficacy is closely associated with its secretome-conditioned media and SC-derived extracellular vesicles, and a subsequent paracrine action in response to tissue injuries. In the current review, we summarize the pre-clinical and clinical studies of SCs and its secretome in diverse preterm and term birth-related diseases, thereby providing new insights for future therapies in neonatal medicine.

Extracellular Vesicles Derived from Human Liver Stem Cells Attenuate Chronic Kidney Disease Development in an In Vivo Experimental Model of Renal Ischemia and Reperfusion Injury

The potential therapeutic effect of extracellular vesicles (EVs) that are derived from human liver stem cells (HLSCs) has been tested in an in vivo model of renal ischemia and reperfusion injury (IRI), that induce the development of chronic kidney disease (CKD). EVs were administered intravenously immediately after the IRI and three days later, then their effect was tested at different time points to evaluate how EV-treatment might interfere with fibrosis development. In IRI-mice that were sacrificed two months after the injury, EV- treatment decreased the development of interstitial fibrosis at the histological and molecular levels. Furthermore, the expression levels of pro-inflammatory genes and of epithelial-mesenchymal transition (EMT) genes were significantly reverted by EV-treatment. In IRI-mice that were sacrificed at early time points (two and three days after the injury), functional and histological analyses showed that EV-treatment induced an amelioration of the acute kidney injury (AKI) that was induced by IRI. Interestingly, at the molecular level, a reduction of pro-fibrotic and EMT-genes in sacrificed IRI-mice was observed at days two and three after the injury. These data indicate that in renal IRI, treatment with HLSC-derived EVs improves AKI and interferes with the development of subsequent CKD by modulating the genes that are involved in fibrosis and EMT.

Human Liver Stem Cell-Derived Extracellular Vesicles Target Hepatic Stellate Cells and Attenuate Their Pro-fibrotic Phenotype

Liver fibrosis occurs in response to chronic liver injury and is characterized by an excessive deposition of extracellular matrix. Activated hepatic stellate cells are primarily responsible for this process. A possible strategy to counteract the development of hepatic fibrosis could be the reversion of the activated phenotype of hepatic stellate cells. Extracellular vesicles (EVs) are nanosized membrane vesicles involved in intercellular communication. Our previous studies have demonstrated that EVs derived from human liver stem cells (HLSCs), a multipotent population of adult stem cells of the liver with mesenchymal-like phenotype, exert in vivo anti-fibrotic activity in the liver. However, the mechanism of action of these EVs remains to be determined. We set up an in vitro model of hepatic fibrosis using a human hepatic stellate cell line (LX-2) activated by transforming growth factor-beta 1 (TGF-β1). Then, we investigated the effect of EVs obtained from HLSCs and from human bone marrow-derived mesenchymal stromal cells (MSCs) on activated LX-2. The incubation of activated LX-2 with HLSC-EVs reduced the expression level of alpha-smooth muscle actin (α-SMA). Conversely, MSC-derived EVs induced an increase in the expression of pro-fibrotic markers in activated LX-2. The analysis of the RNA cargo of HLSC-EVs revealed the presence of several miRNAs involved in the regulation of fibrosis and inflammation. Predictive target analysis indicated that several microRNAs (miRNAs) contained into HLSC-EVs could possibly target pro-fibrotic transcripts. In particular, we demonstrated that HLSC-EVs shuttled miR-146a-5p and that treatment with HLSC-EVs increased miR-146a-5p expression in LX-2. In conclusion, this study demonstrates that HLSC-EVs can attenuate the activated phenotype of hepatic stellate cells and that their biological effect may be mediated by the delivery of anti-fibrotic miRNAs, such as miR-146a-5p.

Hyperammonemia in Inherited Metabolic Diseases

Ammonia is a neurotoxic compound which is detoxified through liver enzymes from urea cycle. Several inherited or acquired conditions can elevate ammonia concentrations in blood, causing severe damage to the central nervous system due to the toxic effects exerted by ammonia on the astrocytes. Therefore, hyperammonemic patients present potentially life-threatening neuropsychiatric symptoms, whose severity is related with the hyperammonemia magnitude and duration, as well as the brain maturation stage. Inherited metabolic diseases caused by enzymatic defects that compromise directly or indirectly the urea cycle activity are the main cause of hyperammonemia in the neonatal period. These diseases are mainly represented by the congenital defects of urea cycle, classical organic acidurias, and the defects of mitochondrial fatty acids oxidation, with hyperammonemia being more severe and frequent in the first two groups mentioned. An effective and rapid treatment of hyperammonemia is crucial to prevent irreversible neurological damage and it depends on the understanding of the pathophysiology of the diseases, as well as of the available therapeutic approaches. In this review, the mechanisms underlying the hyperammonemia and neurological dysfunction in urea cycle disorders, organic acidurias, and fatty acids oxidation defects, as well as the therapeutic strategies for the ammonia control will be discussed.

Human Liver Stem Cells: A Liver-Derived Mesenchymal Stromal Cell-Like Population With Pro-regenerative Properties

Human liver stem cells (HLSCs) were described for the first time in 2006 as a new stem cell population derived from healthy human livers. Like mesenchymal stromal cells, HLSCs exhibit multipotent and immunomodulatory properties. HLSCs can differentiate into several lineages under defined in vitro conditions, such as mature hepatocytes, osteocytes, endothelial cells, and islet-like cell organoids. Over the years, HLSCs have been shown to contribute to tissue repair and regeneration in different in vivo models, leading to more than five granted patents and over 15 peer reviewed scientific articles elucidating their potential therapeutic role in various experimental pathologies. In addition, HLSCs have recently completed a Phase 1 study evaluating their safety post intrahepatic injection in infants with inherited neonatal onset hyperammonemia. Even though a lot of progress has been made in understanding HLSCs over the past years, some important questions regarding the mechanisms of action remain to be elucidated. Among the mechanisms of interaction of HLSCs with their environment, a paracrine interface has emerged involving extracellular vesicles (EVs) as vehicles for transferring active biological materials. In our group, the EVs derived from HLSCs have been studied in vitro as well as in vivo. Our attention has mainly been focused on understanding the in vivo ability of HLSC–derived EVs as modulators of tissue regeneration, inflammation, fibrosis, and tumor growth. This review article aims to discuss in detail the role of HLSCs and HLSC-EVs in these processes and their possible future therapeutic applications.

Protective Effects of Human Liver Stem Cell-Derived Extracellular Vesicles in a Mouse Model of Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion injury (IRI) is observed in liver transplantation and hepato-biliary surgery and is associated with an inflammatory response. Human liver stem cell-derived extracellular vesicles (HLSC-EV) have been demonstrated to reduce liver damage in different experimental settings by accelerating regeneration and by modulating inflammation. The aim of the present study was to investigate whether HLSC-EV may protect liver from IRI in a mouse experimental model. Segmental IRI was obtained by selective clamping of intrahepatic pedicles for 90 min followed by 6 h of reperfusion. HLSC-EV were administered intravenously at the end of the ischemic period and histopathological and biochemical alterations were evaluated in comparison with controls injected with vehicle alone. Intra liver localization of labeled HLSC-EV was assessed by in in vivo Imaging System (IVIS) and the internalization into hepatocytes was confirmed by fluorescence analyses. As compared to the control group, administration of 3 × 10⁹ particles (EV1 group) significantly reduced alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) release, necrosis extension and cytokines expression (TNF-α, CCL-2 and CXCL-10). However, the administration of an increased dose of HLSC-EV (7.5 × 10⁹ particles, EV2 group) showed no significant improvement in respect to controls at enzyme and histology levels, despite a significantly lower cytokine expression. In conclusion, this study demonstrated that 3 × 10⁹ HLSC-EV were able to modulate hepatic IRI by preserving tissue integrity and by reducing transaminases release and inflammatory cytokines expression. By contrast, a higher dose was ineffective suggesting a restricted window of biological activity.

Differentiation of Cells Isolated from Afterbirth Tissues into Hepatocyte-Like Cells and Their Potential Clinical Application in Liver Regeneration

Toxic, viral and surgical injuries can pose medical indications for liver transplantation. The number of patients waiting for a liver transplant still increases, but the number of organ donors is insufficient. Hepatocyte transplantation was suggested as a promising alternative to liver transplantation, however, this method has some significant limitations. Currently, afterbirth tissues seem to be an interesting source of cells for the regenerative medicine, because of their unique biological and immunological properties. It has been proven in experimental animal models, that the native stem cells, and to a greater extent, hepatocyte-like cells derived from them and transplanted, can accelerate regenerative processes and restore organ functioning. The effective protocol for obtaining functional mature hepatocytes in vitro is still not defined, but some studies resulted in obtaining functionally active hepatocyte-like cells. In this review, we focused on human stem cells isolated from placenta and umbilical cord, as potent precursors of hepatocyte-like cells for regenerative medicine. We summarized the results of preclinical and clinical studies dealing with the introduction of epithelial and mesenchymal stem cells of the afterbirth origin to the liver failure therapy. It was concluded that the use of native afterbirth epithelial and mesenchymal cells in the treatment of liver failure could support liver function and regeneration. This effect would be enhanced by the use of hepatocyte-like cells obtained from placental and/or umbilical stem cells.

Evolving Cell-Based and Cell-Free Clinical Strategies for Treating Severe Human Liver Diseases

Liver diseases represent a major global health issue, and currently, liver transplantation is the only viable alternative to reduce mortality rates in patients with end-stage liver diseases. However, scarcity of donor organs and risk of recidivism requiring a re-transplantation remain major obstacles. Hence, much hope has turned towards cell-based therapy. Hepatocyte-like cells obtained from embryonic stem cells or adult stem cells bearing multipotent or pluripotent characteristics, as well as cell-based systems, such as organoids, bio-artificial liver devices, bioscaffolds and organ printing are indeed promising. New approaches based on extracellular vesicles are also being investigated as cell substitutes. Extracellular vesicles, through the transfer of bioactive molecules, can modulate liver regeneration and restore hepatic function. This review provides an update on the current state-of-art cell-based and cell-free strategies as alternatives to liver transplantation for patients with end-stage liver diseases.