Efficient generation of human hepatocytes by the intrahepatic delivery of clonal human mesenchymal stem cells in fetal sheep

Optimization of methods for intrasplenic administration of human amniotic epithelial cells in order to perform safe and effective cell-based therapy for liver diseases

In animal experimental models the administration of stem cells into the spleen should ensure high effectiveness of their implantation in the liver due to a direct vascular connection between the two organs. The aim of this study was to update the methods of experimental intrasplenic cell transplantation using human amniotic epithelial cells (hAECs) which are promising cells in the treatment of liver diseases. BALB/c mice were administered intrasplenically with 0.5, 1, and 2 million hAECs by direct bolus injection (400 µl/min) and via a subcutaneous splenic port by fast (20 μl/min) and slow (10 μl/min) infusion. The port was prepared by translocating the spleen to the skin pocket. The spleen, liver, and lungs were collected at 3 h, 6 h, and 24 h after the administration of cells. The distribution of hAECs, histopathological changes in the organs, complete blood count, and biochemical markers of liver damage were assessed. It has been shown that the method of intrasplenic cell administration affects the degree of liver damage. The largest number of mice showing significant liver damage was observed after direct administration and the lowest after slow administration through a port. Liver damage increased with the number of administered cells, which, paradoxically, resulted in increased liver colonization efficiency. It was concluded that the administration of 1 × 106 hAECs by slow infusion via a subcutaneous splenic port reduces the incidence of complications at the expense of a slight decrease in the effectiveness of implantation of the transplanted cells in the liver.

Liver Disease and Cell Therapy: Advances Made and Remaining Challenges

The limited availability of organs for liver transplantation, the ultimate curative treatment for end stage liver disease, has resulted in a growing and unmet need for alternative therapies. Mesenchymal stromal cells (MSCs) with their broad ranging anti-inflammatory and immunomodulatory properties have therefore emerged as a promising therapeutic agent in treating inflammatory liver disease. Significant strides have been made in exploring their biological activity. Clinical application of MSC has shifted the paradigm from using their regenerative potential to one which harnesses their immunomodulatory properties. Reassuringly, MSCs have been extensively investigated for over 30 years with encouraging efficacy and safety data from translational and early phase clinical studies, but questions remain about their utility. Therefore, in this review, we examine the translational and clinical studies using MSCs in various liver diseases and their impact on dampening immune-mediated liver damage. Our key observations include progress made thus far with use of MSCs for clinical use, inconsistency in the literature to allow meaningful comparison between different studies and need for standardized protocols for MSC manufacture and administration. In addition, the emerging role of MSC-derived extracellular vesicles as an alternative to MSC has been reviewed. We have also highlighted some of the remaining clinical challenges that should be addressed before MSC can progress to be considered as therapy for patients with liver disease.

Mechanisms of Action of Mesenchymal Stem Cells in Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD) is currently the most common chronic liver disease worldwide. However, its pathophysiological mechanism is complicated, and currently, it has no FDA-approved pharmacological therapies. In recent years, mesenchymal stem cell (MSC) therapy has attracted increasing attention in the treatment of hepatic diseases. MSCs are multipotent stromal cells that originated from mesoderm mesenchyme, which have self-renewal and multipotent differentiation capability. Recent experiments and studies have found that MSCs have the latent capacity to be used for MAFLD treatment. MSCs have the potential to differentiate into hepatocytes, which could be induced into hepatocyte-like cells (HLCs) with liver-specific morphology and function under appropriate conditions to promote liver tissue regeneration. They can also reduce liver tissue injury and reverse the development of MAFLD by regulating immune response, antifibrotic activities, and lipid metabolism. Moreover, several advantages are attributed to MSC-derived exosomes (MSC-exosomes), such as targeted delivery, reliable reparability, and poor immunogenicity. After entering the target cells, MSC-exosomes help regulate cell function and signal transduction; thus, it is expected to become an emerging treatment for MAFLD. In this review, we comprehensively discussed the roles of MSCs in MAFLD, main signaling pathways of MSCs that affect MAFLD, and mechanisms of MSC-exosomes on MAFLD.

Autologous bone marrow-derived MSCs engineered to express oFVIII-FLAG engraft in adult sheep and produce an effective increase in plasma FVIII levels

Introduction

Hemophilia A (HA) is the most common X-linked bleeding disorder, occurring in 1 in 5,000 live male births and affecting >1 million individuals worldwide. Although advances in protein-based HA therapeutics have improved health outcomes, current standard-of-care requires infusion 2-3 times per week for life, and 30% of patients develop inhibitors, significantly increasing morbidity and mortality. There are thus unmet medical needs requiring novel approaches to treat HA.

Methods

We tested, in a highly translational large animal (sheep) model, whether the unique immunological and biological properties of autologous bone marrow (BM)-derived mesenchymal stromal cells (MSCs) could enable them to serve as cellular delivery vehicles to provide long-term expression of FVIII, avoiding the need for frequent infusions.

Results

We show that autologous BM-MSCs can be isolated, transduced with a lentivector to produce high levels of ovine (o)FVIII, extensively expanded, and transplanted into adult animals safely. The transplanted cells engraft in multiple organs, and they stably produce and secrete sufficient quantities of FVIII to yield elevated plasma FVIII levels for at least 15 weeks.

Discussion

These studies thus highlight the promise of cellular-based gene delivery approaches for treating HA.

Potential mesenchymal stem cell therapeutics for treating primary biliary cholangitis: advances, challenges, and perspectives

Primary biliary cholangitis (PBC) is a cholestatic autoimmune liver disease characterized by the gradual destruction of small intrahepatic bile ducts that eventually leads to liver cirrhosis, failure, and even carcinoma. The treatment options for PBC are limited, and the main treatment choices are the US Food and Drug Administration–approved ursodeoxycholic acid and obeticholic acid. However, many patients fail to respond adequately to these drugs and the adverse effects frequently lead to low life quality. For patients with end-stage PBC, liver transplantation remains the only effective treatment. Given their low immunogenicity, prominent immunomodulation property, differentiation potential, and tissue maintenance capacity, mesenchymal stem cells (MSCs) are emerging as new options for treating liver diseases, including PBC. Accumulating evidence from basic research to clinical studies supports the positive effects of MSC-based therapy for treating PBC. In this review, we characterized the underlying roles and mechanisms of MSCs for treating liver diseases and highlight recent basic and clinical advances in MSC-based therapy for treating PBC. Finally, the current challenges and perspectives for MSC-based therapy in clinical application are discussed, which could help accelerate the application of MSCs in clinical practice, especially for refractory diseases such as PBC.

Mesenchymal stem cell homing to improve therapeutic efficacy in liver disease

Mesenchymal stem cell (MSC) transplantation, as an alternative strategy to orthotopic liver transplantation, has been evaluated for treating end-stage liver disease. Although the therapeutic mechanism of MSC transplantation remains unclear, accumulating evidence has demonstrated that MSCs can regenerate tissues and self-renew to repair the liver through differentiation into hepatocyte-like cells, immune regulation, and anti-fibrotic mechanisms. Multiple clinical trials have confirmed that MSC transplantation restores liver function and alleviates liver damage. A sufficient number of MSCs must be home to the target tissues after administration for successful application. However, inefficient homing of MSCs after systemic administration is a major limitation in MSC therapy. Here, we review the mechanisms and clinical application status of MSCs in the treatment of liver disease and comprehensively summarize the molecular mechanisms of MSC homing, and various strategies for promoting MSC homing to improve the treatment of liver disease.

The Clinical Trials of Mesenchymal Stromal Cells Therapy

Mesenchymal stromal cells (MSCs) are a heterogeneous population of adult stem cells, which are multipotent and possess the ability to differentiate/transdifferentiate into mesodermal and nonmesodermal cell lineages. MSCs display broad immunomodulatory properties since they are capable of secreting growth factors and chemotactic cytokines. Safety, accessibility, and isolation from patients without ethical concern make MSCs valuable sources for cell therapy approaches in autoimmune, inflammatory, and degenerative diseases. Many studies have been conducted on the application of MSCs as a new therapy, but it seems that a low percentage of them is related to clinical trials, especially completed clinical trials. Considering the importance of clinical trials to develop this type of therapy as a new treatment, the current paper is aimed at describing characteristics of MSCs and reviewing relevant clinical studies registered on the NIH database during 2016-2020 to discuss recent advances on MSC-based therapeutic approaches being used in different diseases.

Investigating Optimal Autologous Cellular Platforms for Prenatal or Perinatal Factor VIII Delivery to Treat Hemophilia A

Patients with the severe form of hemophilia A (HA) present with a severe phenotype, and can suffer from life-threatening, spontaneous hemorrhaging. While prophylactic FVIII infusions have revolutionized the clinical management of HA, this treatment is short-lived, expensive, and it is not available to many A patients worldwide. In the present study, we evaluated a panel of readily available cell types for their suitability as cellular vehicles to deliver long-lasting FVIII replacement following transduction with a retroviral vector encoding a B domain-deleted human F8 transgene. Given the immune hurdles that currently plague factor replacement therapy, we focused our investigation on cell types that we deemed to be most relevant to either prenatal or very early postnatal treatment and that could, ideally, be autologously derived. Our findings identify several promising candidates for use as cell-based FVIII delivery vehicles and lay the groundwork for future mechanistic studies to delineate bottlenecks to efficient production and secretion of FVIII following genetic-modification.

Mesenchymal stem cell-based treatment in autoimmune liver diseases: underlying roles, advantages and challenges

Autoimmune liver disease (AILD) is a series of chronic liver diseases with abnormal immune responses, including autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC). The treatment options for AILD remain limited, and the adverse side effects of the drugs that are typically used for treatment frequently lead to a low quality of life for AILD patients. Moreover, AILD patients may have a poor prognosis, especially those with an incomplete response to first-line treatment. Mesenchymal stem cells (MSCs) are pluripotent stem cells with low immunogenicity and can be conveniently harvested. MSC-based therapy is emerging as a promising approach for treating liver diseases based on their advantageous characteristics of immunomodulation, anti-fibrosis effects, and differentiation to hepatocytes, and accumulating evidence has revealed the positive effects of MSC therapy in AILD. In this review, we first summarize the mechanisms, safety, and efficacy of MSC treatment for AILD based on work in animal and clinical studies. We also discuss the challenges of MSC therapy in clinical applications. In summary, although promising data from preclinical studies are now available, MSC therapy is currently far for being applied in clinical practice, thus developing MSC therapy in AILD is still challenging and warrants further research.

Therapeutic effect and safety of stem cell therapy for chronic liver disease: a systematic review and meta-analysis of randomized controlled trials

Background

Stem cell therapy is becoming an emerging therapeutic option for chronic liver disease (CLD). However, whether stem cell therapy is more effective than conventional treatment remains questionable. We performed a large-scale meta-analysis of randomized controlled trials (RCTs) to evaluate the therapeutic effects and safety of stem cell therapy for CLD.

Methods

We systematically searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov databases for the period from inception through March 16, 2020. Primary outcomes were all-cause mortality and adverse events related to stem cell therapy. Secondary outcomes included the model for end-stage liver disease score, total bilirubin, albumin, alanine aminotransferase, prothrombin activity, and international normalized ratio. The standardized mean difference (SMD) and odds ratio (OR) with 95% confidence interval (CI) were calculated using a random-effects model.

Results

Twenty-four RCTs were included and the majority of these studies showed a high risk of bias. The meta-analysis indicated that compared with conventional treatment, stem cell therapy was associated with improved survival and liver function including the model of end-stage liver disease score, total bilirubin, and albumin levels. However, it had no obvious beneficial effects on alanine aminotransferase level, prothrombin activity, and international normalized ratio. Subgroup analyses showed stem cell therapy conferred a short-term survival benefit for patients with acute-on-chronic liver failure (ACLF), a single injection was more effective than multiple injections, hepatic arterial infusion was more effective than intravenous infusion, and bone marrow-derived stem cells were more effective than those derived from the umbilical cord. Thirteen trials reported adverse events related to stem cell therapy, but no serious adverse events were reported.

Conclusions

Stem cell therapy is a safe and effective therapeutic option for CLD, while patients with ACLF benefit the most in terms of improved short-term survival. A single injection administration of bone marrow-derived stem cells via the hepatic artery has superior therapeutic effects.

Space of Disse: a stem cell niche in the liver

Recent evidence indicates that the plasticity of preexisting hepatocytes and bile duct cells is responsible for the appearance of intermediate progenitor cells capable of restoring liver mass after injury without the need of a stem cell compartment. However, mesenchymal stem cells (MSCs) exist in all organs and are associated with blood vessels which represent their perivascular stem cell niche. MSCs are multipotent and can differentiate into several cell types and are known to support regenerative processes by the release of immunomodulatory and trophic factors. In the liver, the space of Disse constitutes a stem cell niche that harbors stellate cells as liver resident MSCs. This perivascular niche is created by extracellular matrix proteins, sinusoidal endothelial cells, liver parenchymal cells and sympathetic nerve endings and establishes a microenvironment that is suitable to maintain stellate cells and to control their fate. The stem cell niche integrity is important for the behavior of stellate cells in the normal, regenerative, aged and diseased liver. The niche character of the space of Disse may further explain why the liver can become an organ of extra-medullar hematopoiesis and why this organ is frequently prone to tumor metastasis.

Mesenchymal Stem Cells: A Potential Therapeutic Strategy for Neurodegenerative Diseases

Neurodegenerative disease is a kind of chronic, progressive nervous system disease characterized by neuron degeneration or apoptosis. Current treatments cannot prevent the development of the disease. Possible alternative treatments include cell therapy, especially with the use of mesenchymal stem cells (MSCs). MSCs are pluripotent stem cells with capacities for self-renewal and multidirectional differentiation. MSCs may serve as a reliable source of neural cells for potential cell replacement therapy or regenerative medicine treatment. Here, we summarized the therapeutic mechanisms of MSCs and how they can contribute to the development of treatments for neurodegenerative diseases.

In vitro efficacy of liver microenvironment in bone marrow mesenchymal stem cell differentiation

Bone marrow-derived mesenchymal stem cells (BM-MSCs) represent an interesting alternative to liver or hepatocyte transplantation to treat liver injuries. Many studies have reported that MSCs can treat several diseases, including liver damage, just by injection into the bloodstream, without evidence of differentiation. The improvements were attributed to the organotrophic factors, low immunogenicity, immunomodulatory, and anti-inflammatory effects of MSCs, rather than their differentiation. The aim of the present study was to answer the question of whether the presence of BM-MSCs in the hepatic microenvironment will lead to their differentiation to functional hepatocyte-like cells. The hepatic microenvironment was mimicked in vitro by culture for 21 d with liver extract. The resulted cells expressed marker genes of the hepatic lineage including AFP, CK18, and Hnf4a. Functionally, they were able to detoxify ammonia into urea, to store glycogen as observed by PAS staining, and to synthesize glucose from pyruvate/lactate mixture. Phenotypically, the expression of MSC surface markers CD90 and CD105 decreased by differentiation. This evidenced differentiation into hepatocyte-like cells was accompanied by a downregulation of the stem cell marker genes sox2 and Nanog and the cell cycle regulatory genes ANAPC2, CDC2, Cyclin A1, and ABL1. The present results suggest a clear differentiation of BM-MSCs into functional hepatocyte-like cells by the extracted liver microenvironment. This differentiation is confirmed by a decrease in the stemness and mitotic activities. Tracking transplanted BM-MSCs and proving their in vivo differentiation remains to be elucidated.

Liver regeneration and alcoholic liver disease

Alcoholic liver diseases (ALD) are a wide spectrum of liver diseases caused by excessive alcohol consumption, from steatosis to cirrhosis. The pathogenesis of ALD is insufficiently understood, but mainly involves oxidative stress, inflammation, bacterial translocation, cell death, and impaired regeneration. Despite numerous attempts to improve patient prognosis, the treatment of advanced ALD is still based on abstinence, brief exposure to corticosteroids, or liver transplantation. However, poor response to corticosteroids and the shortage of liver donors leaves patients helpless towards the end stages. Advances in basic research have contributed to a better understanding of ALD pathophysiology, which offers new options for treatment. In recent years, several therapies related to liver regeneration have been tested with promising prospects, including molecule-induced liver regeneration, stem cell transplantation, and full-function 3D artificial liver assembly. This review discusses mechanisms underlying ALD that can be considered therapeutic targets for regeneration-based treatments.

Defining the Optimal FVIII Transgene for Placental Cell-Based Gene Therapy to Treat Hemophilia A

The delivery of factor VIII (FVIII) through gene and/or cellular platforms has emerged as a promising hemophilia A treatment. Herein, we investigated the suitability of human placental cells (PLCs) as delivery vehicles for FVIII and determined an optimal FVIII transgene to produce/secrete therapeutic FVIII levels from these cells. Using three PLC cell banks we demonstrated that PLCs constitutively secreted low levels of FVIII, suggesting their suitability as a transgenic FVIII production platform. Furthermore, PLCs significantly increased FVIII secretion after transduction with a lentiviral vector (LV) encoding a myeloid codon-optimized bioengineered FVIII containing high-expression elements from porcine FVIII. Importantly, transduced PLCs did not upregulate cellular stress or innate immunity molecules, demonstrating that after transduction and FVIII production/secretion, PLCs retained low immunogenicity and cell stress. When LV encoding five different bioengineered FVIII transgenes were compared for transduction efficiency, FVIII production, and secretion, data showed that PLCs transduced with LV encoding hybrid human/porcine FVIII transgenes secreted substantially higher levels of FVIII than did LV encoding B domain-deleted human FVIII. In addition, data showed that in PLCs, myeloid codon optimization is needed to increase FVIII secretion to therapeutic levels. These studies have identified an optimal combination of FVIII transgene and cell source to achieve clinically meaningful levels of secreted FVIII.

Therapeutic Mesenchymal Stromal Cells for Immunotherapy and for Gene and Drug Delivery

Mesenchymal stromal cells (MSCs) possess several fairly unique properties that, when combined, make them ideally suited for cellular-based immunotherapy and as vehicles for gene and drug delivery for a wide range of diseases and disorders. Key among these are: (1) their relative ease of isolation from a variety of tissues; (2) the ability to be expanded in culture without a loss of functionality, a property that varies to some degree with tissue source; (3) they are relatively immune-inert, perhaps obviating the need for precise donor/recipient matching; (4) they possess potent immunomodulatory functions that can be tailored by so-called licensing in vitro and in vivo; (5) the efficiency with which they can be modified with viral-based vectors; and (6) their almost uncanny ability to selectively home to damaged tissues, tumors, and metastases following systemic administration. In this review, we summarize the latest research in the immunological properties of MSCs, their use as immunomodulatory/anti-inflammatory agents, methods for licensing MSCs to customize their immunological profile, and their use as vehicles for transferring both therapeutic genes in genetic disease and drugs and genes designed to destroy tumor cells.

Xenotransplantation: Progress Along Paths Uncertain from Models to Application

For more than a century, transplantation of tissues and organs from animals into man, xenotransplantation, has been viewed as a potential way to treat disease. Ironically, interest in xenotransplantation was fueled especially by successful application of allotransplantation, that is, transplantation of human tissue and organs, as a treatment for a variety of diseases, especially organ failure because scarcity of human tissues limited allotransplantation to a fraction of those who could benefit. In principle, use of animals such as pigs as a source of transplants would allow transplantation to exert a vastly greater impact than allotransplantation on medicine and public health. However, biological barriers to xenotransplantation, including immunity of the recipient, incompatibility of biological systems, and transmission of novel infectious agents, are believed to exceed the barriers to allotransplantation and presently to hinder clinical applications. One way potentially to address the barriers to xenotransplantation is by genetic engineering animal sources. The last 2 decades have brought progressive advances in approaches that can be applied to genetic modification of large animals. Application of these approaches to genetic engineering of pigs has contributed to dramatic improvement in the outcome of experimental xenografts in nonhuman primates and have encouraged the development of a new type of xenograft, a reverse xenograft, in which human stem cells are introduced into pigs under conditions that support differentiation and expansion into functional tissues and potentially organs. These advances make it appropriate to consider the potential limitation of genetic engineering and of current models for advancing the clinical applications of xenotransplantation and reverse xenotransplantation.

Mesenchymal stem cells prolong survival and prevent lethal complications in a porcine model of fulminant liver failure

BACKGROUND

Fulminant liver failure (FLF) is a life-threatening disease.

METHODS

Lethal FLF was induced by ischemia-reperfusion (I-R) injury in mini-pigs, and MSCs were infused via splenic vein after reperfusion.

RESULTS

Accumulated survival within 28 days was significantly improved by MSCs (P = 0.0348). Notably, MSCs maintained blood-gas homeostasis in the first 24 hours and prevented FLF-induced elevation of prothrombin time, international normalized ratio, and creatinine and ammonia levels in the first 3 days. With MSCs, serum levels of liver enzymes gradually decreased after 3 days, and platelet count was back to normal at 1 week of FLF. MSCs promoted liver regeneration within 2 weeks and differentiated into functional hepatocytes at 2-4 weeks after transplantation, evidenced by increase in Ki67-positive cells, detectable human hepatocyte growth factor, human vascular endothelial growth factor, human hepatocyte-specific antigen, and human albumin-expressing cells in the liver at different time points. Reactive oxidative species (ROS) were accumulated after FLF and eliminated at 4 weeks after MSC transplantation.

CONCLUSIONS

Together, MSCs prolong the survival and prevent lethal sequelae of I-R injury-induced FLF by maintenance of liver-function homeostasis and rescue of ROS in the acute stage and by homing and differentiation into hepatocytes in the subacute stage.

Mesenchymal stem cells to treat type 1 diabetes

What is clear is we are in the era of the stem cell and its potential in ameliorating human disease. Our perspective is generated from an in vivo model in a large animal that offers significant advantages (complete transplantation tolerance, large size and long life span). This review is an effort to meld our preclinical observations with others for the reader and to outline potential avenues to improve the present outlook for patients with diabetes. This effort exams the history or background of stem cell research in the laboratory and the clinic, types of stem cells, pluripotency or lack thereof based on a variety of pre-clinical investigations attempting endocrine pancreas recovery using stem cell transplantation. The focus is on the use of hematopoietic and mesenchymal stem cells. This review will also examine recent clinical experience following stem cell transplantation in patients with type 1 diabetes.

A human bone marrow mesodermal-derived cell population with hemogenic potential

The presence, within the human bone marrow, of cells with both endothelial and hemogenic potential has been controversial. Herein, we identify, within the human fetal bone marrow, prior to establishment of hematopoiesis, a unique APLNR+, Stro-1+ cell population, co-expressing markers of early mesodermal precursors and/or hemogenic endothelium. In adult marrow, cells expressing similar markers are also found, but at very low frequency. These adult-derived cells can be extensively culture expanded in vitro without loss of potential, they preserve a biased hemogenic transcriptional profile, and, upon in vitro induction with OCT4, assume a hematopoietic phenotype. In vivo, these cells, upon transplantation into a fetal microenvironment, contribute to the vasculature, and generate hematopoietic cells that provide multilineage repopulation upon serial transplantation. The identification of this human somatic cell population provides novel insights into human ontogenetic hematovascular potential, which could lead to a better understanding of, and new target therapies for, malignant and nonmalignant hematologic disorders.

Mesenchymal stromal cell therapy for liver diseases

The therapeutic potential of mesenchymal stromal cells (MSCs) in the treatment of liver fibrosis is predominantly based on their immunosuppressive properties, and their ability to secrete various trophic factors. This potential has been investigated in clinical and preclinical studies. Although the therapeutic mechanisms of MSC transplantation are still not fully characterised, accumulating evidence has revealed that various trophic factors secreted by MSCs play key therapeutic roles in regeneration by alleviating inflammation, apoptosis, and fibrosis as well as stimulating angiogenesis and tissue regeneration in damaged liver. In this review, we summarise the safety, efficacy, potential transplantation routes and therapeutic effects of MSCs in patients with liver fibrosis. We also discuss some of the key strategies to enhance the functionality of MSCs, which include sorting and/or priming with factors such as cytokines, as well as genetic engineering.

In Vitro Pluripotent Stem Cell Differentiation to Hepatocyte Ceases Further Maturation at an Equivalent Stage of E15 in Mouse Embryonic Liver Development

Hepatocyte-like cells (HLCs) can be derived from pluripotent stem cells (PSCs) by sequential treatment of chemical cues to mimic the microenvironment of embryonic liver development. However, these HLCs do not reach the full maturity level of primary hepatocytes. In this study, we carried out a meta-analysis of cross-species transcriptome data of in vitro differentiation of human PSCs to HLCs and in vivo mouse embryonic liver development to identify the developmental stage at which HLC maturation was blocked at. Systematic variations were found associated with the data source and removed by batch correction. Using principal component analysis, HLCs from different stages of differentiation were aligned with mouse embryonic liver development chronologically. A "unified developmental time" (DT) scale was developed after aligning in vitro HLC differentiation and in vivo embryonic liver development. HLCs were found to cease further maturation at an equivalent stage of mouse embryonic day (E)13-15. Genes with discordant time dynamics were identified by aligning in vivo and in vitro data set onto a common DT scale. These genes may be targets of genetic intervention for enhancing the maturity of PSC-derived HLCs.

Evaluation of Cytotoxic and Genotoxic Effects of Extremely Low-frequency Electromagnetic Field on Mesenchymal Stromal Cells

Background

Interest in the use of extremely low-frequency (ELF) electromagnetic field (EMF) for the treatment of pain and inflammation is increasing due to the ability of this promising therapy to compete with pharmaceuticals without the adverse effects caused by drugs. However, there continues to be concerns regarding cytotoxic and genotoxic effects that may occur as a result of exposure to EMF.

Objective

To investigate this concern, we tested the effect of our known therapeutic 5 Hz, 0.4 milliTesla (mT) EMF on a human mesenchymal stromal cell (hMSC) line to determine whether ELF-EMF exposure would cause cytotoxic or genotoxic effects.

Methods

Treated samples along with controls were exposed to 5 Hz, 0.4 mT ELF-EMF for 20 min/day, 3×/week for 2 weeks and then assayed for cell viability, proliferation rates, and chromosome breaks.

Results

Cytogenetic analysis of the viability and proliferation rates along with analysis of morphological genome stability showed no cytotoxicity, and no chromosome breaks per karyotype analysis—therefore no genotoxicity.

Conclusion

Exposure to an ELF-EMF of 5 Hz, 0.4 mT for 20 min/day, 3×/week for 2 weeks does not cause cytotoxic or genotoxic effects in hMSCs.

Exposure of the Bone Marrow Microenvironment to Simulated Solar and Galactic Cosmic Radiation Induces Biological Bystander Effects on Human Hematopoiesis

The stem cell compartment of the hematopoietic system constitutes one of the most radiosensitive tissues of the body and leukemias represent one of the most frequent radiogenic cancers with short latency periods. As such, leukemias may pose a particular threat to astronauts during prolonged space missions. Control of hematopoiesis is tightly governed by a specialized bone marrow (BM) microenvironment/niche. As such, any environmental insult that damages cells of this niche would be expected to produce pronounced effects on the types and functionality of hematopoietic/immune cells generated. We recently reported that direct exposure of human hematopoietic stem cells (HSC) to simulated solar energetic particle (SEP) and galactic cosmic ray (GCR) radiation dramatically altered the differentiative potential of these cells, and that simulated GCR exposures can directly induce DNA damage and mutations within human HSC, which led to leukemic transformation when these cells repopulated murine recipients. In this study, we performed the first in-depth examination to define changes that occur in mesenchymal stem cells present in the human BM niche following exposure to accelerated protons and iron ions and assess the impact these changes have upon human hematopoiesis. Our data provide compelling evidence that simulated SEP/GCR exposures can also contribute to defective hematopoiesis/immunity through so-called "biological bystander effects" by damaging the stromal cells that comprise the human marrow microenvironment, thereby altering their ability to support normal hematopoiesis.

Mesenchymal stem cells: potential application for the treatment of hepatic cirrhosis

Nowadays, orthotopic liver transplantation is considered the most efficient approach to the end stage of chronic hepatic cirrhosis. Because of the limitations of orthotopic liver transplantation, stem cells are an attractive therapeutic option. Mesenchymal stem cells (MSCs) especially show promise as an alternative treatment for hepatic cirrhosis in animal models and during clinical trials. Nevertheless, the homing of transplanted MSCs to the liver occurs in limited numbers. Therefore, we review the strategies for enhancing the homing of MSCs, mainly via the delivery routes, optimizing cell culture conditions, stimulating the target sites, and genetic modification.

Cell fusion in the liver, revisited

There is wide agreement that cell fusion is a physiological process in cells in mammalian bone, muscle and placenta. In other organs, such as the cerebellum, cell fusion is controversial. The liver contains a considerable number of polyploid cells: They are commonly believed to originate by genome endoreplication, although the contribution of cell fusion to polyploidization has not been excluded. Here, we address the topic of cell fusion in the liver from a historical point of view. We discuss experimental evidence clearly supporting the hypothesis that cell fusion occurs in the liver, specifically when bone marrow cells were injected into mice and shown to rescue genetic hepatic degenerative defects. Those experiments-carried out in the latter half of the last century-were initially interpreted to show “transdifferentiation”, but are now believed to demonstrate fusion between donor macrophages and host hepatocytes, raising the possibility that physiologically polyploid cells, such as hepatocytes, could originate, at least partially, through homotypic cell fusion. In support of the homotypic cell fusion hypothesis, we present new data generated using a chimera-based model, a much simpler model than those previously used. Cell fusion as a road to polyploidization in the liver has not been extensively investigated, and its contribution to a variety of conditions, such as viral infections, carcinogenesis and aging, remains unclear.

Evaluating Interaction of Cord Blood Hematopoietic Stem/Progenitor Cells with Functionally Integrated Three-Dimensional Microenvironments

Despite advances in ex vivo expansion of cord blood‐derived hematopoietic stem/progenitor cells (CB‐HSPC), challenges still remain regarding the ability to obtain, from a single unit, sufficient numbers of cells to treat an adolescent or adult patient. We and others have shown that CB‐HSPC can be expanded ex vivo in two‐dimensional (2D) cultures, but the absolute percentage of the more primitive stem cells decreases with time. During development, the fetal liver is the main site of HSPC expansion. Therefore, here we investigated, in vitro, the outcome of interactions of primitive HSPC with surrogate fetal liver environments. We compared bioengineered liver constructs made from a natural three‐dimensional‐liver‐extracellular‐matrix (3D‐ECM) seeded with hepatoblasts, fetal liver‐derived (LvSt), or bone marrow‐derived stromal cells, to their respective 2D culture counterparts. We showed that the inclusion of cellular components within the 3D‐ECM scaffolds was necessary for maintenance of HSPC viability in culture, and that irrespective of the microenvironment used, the 3D‐ECM structures led to the maintenance of a more primitive subpopulation of HSPC, as determined by flow cytometry and colony forming assays. In addition, we showed that the timing and extent of expansion depends upon the biological component used, with LvSt providing the optimal balance between preservation of primitive CB HSPC and cellular differentiation. Stem Cells Translational Medicine2018;7:271–282

Boosting Hematopoietic Engraftment after in Utero Transplantation through Vascular Niche Manipulation

In utero hematopoietic stem/progenitor cell transplantation (IUHSCT) has only been fully successful in the treatment of congenital immunodeficiency diseases. Using sheep as a large animal model of IUHSCT, we demonstrate that administration of CD146⁺CXCL12⁺VEGFR2⁺ or CD146⁺CXCL12⁺VEGFR2⁻ cells prior to, or in combination with, hematopoietic stem/progenitor cells (HSC), results in robust CXCL12 production within the fetal marrow environment, and significantly increases the levels of hematopoietic engraftment. While in the fetal recipient, donor-derived HSC were found to reside within the trabecular bone, the increased expression of VEGFR2 in the microvasculature of CD146⁺CXCL12⁺VEGFR2⁺ transplanted animals enhanced levels of donor-derived hematopoietic cells in circulation. These studies provide important insights into IUHSCT biology, and demonstrate the feasibility of enhancing HSC engraftment to levels that would likely be therapeutic in many candidate diseases for IUHSCT.

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After IUHSCT, HSC engraft in the trabecular bone of the metaphysis

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CD146^++(+/−) cells engraft in diaphysis and make hematopoiesis-supporting cytokines

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Donor cell-derived CXCL12 and VEGFR2 significantly increase HSC engraftment

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IUHSCT of CD146⁺CXCL12⁺VEGFR2⁺ cells prior to HSC could be curative in several diseases

Role of mesenchymal stem cells, their derived factors, and extracellular vesicles in liver failure

Liver failure is a severe clinical syndrome with a poor prognosis. Mesenchymal stem cell (MSC) transplantation has emerged as a new intervention in treating liver failure. It is conventionally recognized that MSCs exert their therapeutic effect mainly through transdifferentiation. Recently, published articles have shown that MSCs work in liver failure by secreting trophic and immunomodulatory factors as well as extracellular vesicles (EVs) before transdifferentiation. In particular,MSC-derived EVs have shown similar curative effects as MSCs. Here we review the role of MSCs as well as their derived factors and EVs in liver failure and discuss the use of MSC-derived EVs instead of intact MSCs in treating liver failure.

Quantitative evaluation of human bone mesenchymal stem cells rescuing fulminant hepatic failure in pigs

OBJECTIVE

Stem cell transplantation provides a promising alternative for the treatment of fulminant hepatic failure (FHF). However, it lacks fundamental understanding of stem cells' activities. Our objective was to clarify stem cell-recipient interactions for overcoming barriers to clinical application.

DESIGN

We used an in-house large-animal (pig) model of FHF rescue by human bone marrow mesenchymal stem cells (hBMSCs) and profiled the cells' activities. The control and transplantation groups of pigs (n=15 per group) both received a D-galactosamine (D-Gal) injection (1.5 g/kg). The transplantation group received hBMSCs via intraportal vein infusion (3×10⁶ cells/kg) immediately after D-Gal administration. The stem cell-recipient interactions were quantitatively evaluated by biochemical function, cytokine array, metabolite profiling, transcriptome sequencing and immunohistochemistry.

RESULTS

All pigs in the control group died within an average of 3.22 days, whereas 13/15 pigs in the transplantation group lived >14 days. The cytokine array and metabolite profiling analyses revealed that hBMSC transplantation suppressed D-Gal-induced life-threatening cytokine storms and stabilised FHF within 7 days, while human-derived hepatocytes constituted only ∼4.5% of the pig hepatocytes. The functional synergy analysis of the observed profile changes indicated that the implanted hBMSCs altered the pigs' cytokine responses to damage through paracrine effects. Delta-like ligand 4 was validated to assist liver restoration in both pig and rat FHF models.

CONCLUSIONS

Our results delineated an integrated model of the multifaceted interactions between stem cells and recipients, which may open a new avenue to the discovery of single molecule-based therapeutics that simulate stem cell actions.

Targeted introduction and effective expression of hFIX at the AAVS1 locus in mesenchymal stem cells

Hemophilia B occurs due to a deficiency in human blood coagulation factor IX (hFIX). Currently, no effective treatment for hemophilia B has been identified, and gene therapy has been considered the most appropriate treatment. Mesenchymal stem cells (MSCs) have homing abilities and low immunogenicity, and therefore they may be potential cell carriers for targeted drug delivery to lesional tissues. The present study constructed an adeno‑associated virus integration site 1 (AAVS1)‑targeted vector termed AAVS1‑green fluorescent protein (GFP)‑hFIX and a zinc finger nuclease (ZFN) expression vector. Nucleofection was used to co‑transfect the targeting vector and the ZFN expression vector into human MSCs. The GFP‑positive cells were selected using flow cytometry. Site‑specific integration clones were obtained following the monoclonal culture, subsequent detections were performed using polymerase chain reaction and Southern blotting. Following the confirmation of stem cell traits of the site‑specific integration MSCs, the in vivo and in vitro expression levels of hFIX were detected. The results demonstrated that the hFIX gene was successfully transfected into the AAVS1 locus in human MSCs. The clones with the site‑specific integration retained stem cell traits of the MSCs. In addition, hFIX was effectively expressed in vivo and in vitro. No significant differences in expression levels were identified among the individual clones. In conclusion, the present study demonstrated that the exogenous gene hFIX was effectively expressed following site‑specific targeting into the AAVS1 locus in MSCs; therefore, MSCs may be used as potential cell carriers for gene therapy of hemophilia B.

Mesenchymal stem cell subpopulations: phenotype, property and therapeutic potential

Mesenchymal stem cells (MSC) are capable of differentiating into cells of multiple cell lineages and have potent paracrine effects. Due to their easy preparation and low immunogenicity, MSC have emerged as an extremely promising therapeutic agent in regenerative medicine for diverse diseases. However, MSC are heterogeneous with respect to phenotype and function in current isolation and cultivation regimes, which often lead to incomparable experimental results. In addition, there may be specific stem cell subpopulations with definite differentiation capacity toward certain lineages in addition to stem cells with multi-differentiation potential. Recent studies have identified several subsets of MSC which exhibit distinct features and biological activities, and enhanced therapeutic potentials for certain diseases. In this review, we give an overview of these subsets for their phenotypic, biological and functional properties.

In utero stem cell transplantation and gene therapy: rationale, history, and recent advances toward clinical application

Recent advances in high-throughput molecular testing have made it possible to diagnose most genetic disorders relatively early in gestation with minimal risk to the fetus. These advances should soon allow widespread prenatal screening for the majority of human genetic diseases, opening the door to the possibility of treatment/correction prior to birth. In addition to the obvious psychological and financial benefits of curing a disease in utero, and thereby enabling the birth of a healthy infant, there are multiple biological advantages unique to fetal development, which provide compelling rationale for performing potentially curative treatments, such as stem cell transplantation or gene therapy, prior to birth. Herein, we briefly review the fields of in utero transplantation (IUTx) and in utero gene therapy and discuss the biological hurdles that have thus far restricted success of IUTx to patients with immunodeficiencies. We then highlight several recent experimental breakthroughs in immunology, hematopoietic/marrow ontogeny, and in utero cell delivery, which have collectively provided means of overcoming these barriers, thus setting the stage for clinical application of these highly promising therapies in the near future.

Multipotent mesenchymal stromal cells: A promising strategy to manage alcoholic liver disease

Chronic alcohol consumption is a major cause of liver disease. The term alcoholic liver disease (ALD) refers to a spectrum of mild to severe disorders including steatosis, steatohepatitis, cirrhosis, and hepatocellular carcinoma. With limited therapeutic options, stem cell therapy offers significant potential for these patients. In this article, we review the pathophysiologic features of ALD and the therapeutic mechanisms of multipotent mesenchymal stromal cells, also referred to as mesenchymal stem cells (MSCs), based on their potential to differentiate into hepatocytes, their immunomodulatory properties, their potential to promote residual hepatocyte regeneration, and their capacity to inhibit hepatic stellate cells. The perfect match between ALD pathogenesis and MSC therapeutic mechanisms, together with encouraging, available preclinical data, allow us to support the notion that MSC transplantation is a promising therapeutic strategy to manage ALD onset and progression.

Therapeutic Potential of HGF-Expressing Human Umbilical Cord Mesenchymal Stem Cells in Mice with Acute Liver Failure

Human umbilical cord-derived mesenchymal stem cells (UCMSCs) are particularly attractive cells for cellular and gene therapy in acute liver failure (ALF). However, the efficacy of this cell therapy in animal studies needs to be significantly improved before it can be translated into clinics. In this study, we investigated the therapeutic potential of UCMSCs that overexpress hepatocyte growth factor (HGF) in an acetaminophen-induced acute liver failure mouse model. We found that the HGF-UCMSC cell therapy protected animals from acute liver failure by reducing liver damage and prolonging animal survival. The therapeutic effect of HGF-UCMSCs was associated with the increment in serum glutathione (GSH) and hepatic enzymes that maintain redox homeostasis, including γ-glutamylcysteine synthetase (γ-GCS), superoxide dismutase (SOD), and catalase (CAT). Immunohistochemical staining confirmed that HGF-UCMSCs were mobilized to the injured areas of the liver. Additionally, HGF-UCMSCs modulated apoptosis by upregulating the antiapoptotic Bcl2 and downregulating proapoptotic genes, including Bax and TNFα. Taken together, these data suggest that ectopic expression of HGF in UCMSCs protects animals from acetaminophen-induced acute liver failure through antiapoptosis and antioxidation mechanisms.

Safety of Intraperitoneal Injection of Adipose Tissue-Derived Autologous Mesenchymal Stem Cells in Cats

Background

Chronic inflammatory diseases are common in cats and mesenchymal stem cells (MSC) are a promising therapeutic approach for management of these disorders. The purpose of this study was to evaluate the safety of intraperitoneal injection of MSC in cats.

Hypothesis

Intrapertioneal injection of autologous MSC in cats is safe.

Animals

Ten healthy adult purpose‐bred cats.

Methods

Mesenchymal stem cells were isolated from subcutaneous adipose tissue collected during ovariohysterectomy and characterized for expression of CD90, CD105 and CD44 and trilineage differentiation. Three weeks postoperatively a complete blood count, serum chemistry profile, urinalysis, and abdominal ultrasound were performed. Five cats then received 1 × 10⁶ of autologous MSC/kg of body weight intraperitoneally with ultrasound guidance; 5 additional cats were sham injected. Cats were monitored for 6 weeks with daily physical examinations and weekly clinicopathological evaluations. Abdominal ultrasonography was repeated at weeks 1 and 5 after injection.

Results

Serious adverse effects were not observed in any MSC‐injected cat. Two animals developed transient lethargy and decreased activity. Jejunal lymph node size was increased in MSC‐injected cats compared to controls at weeks 1 (1.38 ± 0.25 versus 0.88 ± 0.25 cm²; P = .036) and 5 (1.75 ± 0.82 versus 0.79 ± 0.12 cm²; P = .047). A hyperechoic renal segmental cortical lesion was observed in 1 MSC‐injected cat.

Conclusions and Clinical Relevance

Intraperitoneal MSC injection was well tolerated with only mild, self‐limiting adverse effects being observed in 2 cats. This route provides a safe means of administration for cell‐based treatment in cats.

Sheep CD34+ amniotic fluid cells have hematopoietic potential and engraft after autologous in utero transplantation

Unmatched allogeneic in utero stem cell transplantation (IUSCT) produces poor engraftment unless the fetus has congenital immunodeficiency, probably because of maternal and fetal immune responses to injected cells. We studied the functional hematopoietic potential of transduced green fluorescent protein (GFP+) sheep amniotic fluid (AF) stem cells, before and after autologous IUSCT. CD34+ cells were selected from first trimester sheep AF, transduced overnight, and injected intravenously into NOD-SCID-gamma (NSG) mice. At 3 months, primary recipient bone marrow (BM) was injected into secondary NSG recipients. GFP+ cells were detected in the hematopoietic organs and peripheral blood of primary and secondary recipients at 3 months. Autologous IUSCT (transduced GFP+CD34+AF) was performed in fetal sheep. Six months postnatally, lamb BM was injected into secondary NSG recipients. GFP+ cells were detected in the peripheral blood of primary and secondary recipients. This confirms the hematopoietic potential of AF stem cells supporting the concept of autologous IUSCT to treat congenital hematopoietic disease.

Bile acids induce hepatic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSC) have the potential to differentiate into multiple cell lineages and their therapeutic potential has become obvious. In the liver, MSC are represented by stellate cells which have the potential to differentiate into hepatocytes after stimulation with growth factors. Since bile acids can promote liver regeneration, their influence on liver-resident and bone marrow-derived MSC was investigated. Physiological concentrations of bile acids such as tauroursodeoxycholic acid were able to initiate hepatic differentiation of MSC via the farnesoid X receptor and transmembrane G-protein-coupled bile acid receptor 5 as investigated with knockout mice. Notch, hedgehog, transforming growth factor-β/bone morphogenic protein family and non-canonical Wnt signalling were also essential for bile acid-mediated differentiation, whereas β-catenin-dependent Wnt signalling was able to attenuate this process. Our findings reveal bile acid-mediated signalling as an alternative way to induce hepatic differentiaion of stem cells and highlight bile acids as important signalling molecules during liver regeneration.

In Vitro and In Vivo Hepatic Differentiation of Adult Somatic Stem Cells and Extraembryonic Stem Cells for Treating End Stage Liver Diseases

The shortage of liver donors is a major handicap that prevents most patients from receiving liver transplantation and places them on a waiting list for donated liver tissue. Then, primary hepatocyte transplantation and bioartificial livers have emerged as two alternative treatments for these often fatal diseases. However, another problem has emerged. Functional hepatocytes for liver regeneration are in short supply, and they will dedifferentiate immediately in vitro after they are isolated from liver tissue. Alternative stem-cell-based therapeutic strategies, including hepatic stem cells (HSCs), embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs), are more promising, and more attention has been devoted to these approaches because of the high potency and proliferation ability of the cells. This review will focus on the general characteristics and the progress in hepatic differentiation of adult somatic stem cells and extraembryonic stem cells in vitro and in vivo for the treatment of end stage liver diseases. The hepatic differentiation of stem cells would offer an ideal and promising source for cell therapy and tissue engineering for treating liver diseases.

Repeated versus single transplantation of mesenchymal stem cells in carbon tetrachloride-induced liver injury in mice

Despite its numerous limitations, liver transplants are the only definite cure for end-stage liver disease. Various stem cell populations may contribute to liver regeneration, of which there is accumulating evidence of the contribution of mesenchymal stem cells (MSCs). This study examines the hypothesis that repeated infusions of human bone marrow-derived MSCs (hBMMSCs)can improve liver injury in an experimental model. MSCs were intravenously transplanted into immunosuppressed mice with carbon tetrachloride (CCl(4))-induced liver fibrosis. Transplanting 3x10(6) MSCs in three divided doses improved survival,liver fibrosis and necrosis compared with injection of the same number of MSCs in a single dose. This was accompanied by increased influence on the expression of the fibrogenic/fibrolytic related genes Col1a1, Timp1 and Mmp13 in the repeated transplant group. Repeat administration of MSCs was three times more effective in homing of PKH-tagged transplanted cells 3 weeks post-transplant compared with the single transplant group. The benefits of repeated transplants may be of considerable significance in clinical trials on liver failure.

Cell therapy for liver diseases: current medicine and future promises

Liver diseases are a major health problem worldwide since they usually represent the main causes of death in most countries, causing excessive costs to public health systems. Nowadays, there are no efficient current therapies for most hepatic diseases and liver transplant is infrequent due to the availability of organs, cost and risk of transplant rejection. Therefore, alternative therapies for liver diseases have been developed, including cell-based therapies. Stem cells (SCs) are characterized by their self-renewing capacity, unlimited proliferation and differentiation under certain conditions into tissue- or organ-specific cells with special functions. Cell-based therapies for liver diseases have been successful in experimental models, showing anti-inflammatory, antifibrogenic and regenerative effects. Nowadays, clinical trials using SCs for liver pathologies are increasing in number, and those that have reached publication have achieved favorable effects, encouraging us to think that SCs will have a potential clinical use in a short time.

Bile acids and stellate cells

Hepatic stellate cells are mainly known for their contribution to fibrogenesis in chronic liver diseases, but their identity and function in normal liver remain unclear. They were recently identified as liver-resident mesenchymal stem cells (MSCs), which can differentiate not only into adipocytes and osteocytes, but also into liver epithelial cells such as hepatocytes and bile duct cells as investigated in vitro and in vivo. During hepatic differentiation, stellate cells and other MSCs transiently develop into liver progenitor cells with epithelial characteristics before hepatocytes are established. Transplanted stellate cells from the liver and pancreas are able to contribute to liver regeneration in stem cell-based liver injury models and can also home into the bone marrow, which is in line with their classification as MSCs. There is experimental evidence that bile acids support liver regeneration and are able to activate signaling pathways in hepatic stellate cells. For this reason, it is important to analyze the influence of bile acids on developmental fate decisions of hepatic stellate cells and other MSC populations.

Effect of allogeneic umbilical cord mesenchymal stem cell transplantation in a rat model of hepatic cirrhosis

OBJECTIVE

To determine the effects of human umbilical cord mesenchymal stem cell (UCMSC) transplantation, alone or in combination with tanshinone IIA (Tan IIA) on hepatic cirrhosis in rats.

METHODS

A rat model of cirrhosis was established. Rats were divided into control, UCMSC, and UCSMC plus Tan IIA groups. Rats in the UCMSC group were injected via the tail vein with 0.2 mL Dil-labeled UCMSC suspension. Intraperitoneal Tan IIA injections (20 mg/kg) were started on the day of UCMSC transplantation in the UCMSC plus Tan IIA group, and continued for 7 consecutive days thereafter. Rats were sacrificed 1 day, 3 days, 1 month, and 3 months after transplantation and the numbers of Dil-labeled UCMSCs colonizing the liver were determined. Albumin (ALB) and alanine aminotransferase (ALT) levels were measured in venous blood, and mRNA and protein expression levels of human ALB and cytokeratin (CK)-18 in liver tissues were determined by reverse transcription-polymerase chain reaction and western blotting, respectively.

RESULTS

Serum ALT levels were significantly lower and serum ALB levels significantly higher in rats in the UCMSC group compared with the control group (P < 0.05). Hepatic CK-18 and ALB mRNA and protein expression levels increased after transplantation, and were significantly higher in the UCMSC plus Tan IIA group compared with the UCMSC group (P < 0.05).

CONCLUSION

Human UCMSCs transplanted into rats with liver cirrhosis can grow and differentiate into hepatocyte-like cells resulting in improved liver function in vivo. Tan IIA further influenced transplantation outcomes.

Use of mesenchymal stem cells to treat liver fibrosis: Current situation and future prospects

Progressive liver fibrosis is a major health issue for which no effective treatment is available, leading to cirrhosis and orthotopic liver transplantation. However, organ shortage is a reality. Hence, there is an urgent need to find alternative therapeutic strategies. Cell-based therapy using mesenchymal stem cells (MSCs) may represent an attractive therapeutic option, based on their immunomodulatory properties, their potential to differentiate into hepatocytes, allowing the replacement of damaged hepatocytes, their potential to promote residual hepatocytes regeneration and their capacity to inhibit hepatic stellate cell activation or induce their apoptosis, particularly via paracrine mechanisms. The current review will highlight recent findings regarding the input of MSC-based therapy for the treatment of liver fibrosis, from in vitro studies to pre-clinical and clinical trials. Several studies have shown the ability of MSCs to reduce liver fibrosis and improve liver function. However, despite these promising results, some limitations need to be considered. Future prospects will also be discussed in this review.

Hemophilia A: an ideal disease to correct in utero

Hemophilia A (HA) is the most frequent inheritable defect of the coagulation proteins. The current standard of care for patients with HA is prophylactic factor infusion, which is comprised of regular (2-3 times per week) intravenous infusions of recombinant or plasma-derived FVIII to maintain hemostasis. While this treatment has greatly increased the quality of life and lengthened the life expectancy for many HA patients, its high cost, the need for lifelong infusions, and the fact that it is unavailable to roughly 75% of the world's HA patients make this type of treatment far from ideal. In addition, this lifesaving therapy suffers from a high risk of treatment failure due to immune response to the infused FVIII. There is thus a need for novel treatments, such as those using stem cells and/or gene therapy, which have the potential to mediate long-term correction or permanent cure following a single intervention. In the present review, we discuss the clinical feasibility and unique advantages that an in utero approach to treating HA could offer, placing special emphasis on a new sheep model of HA we have developed and on the use of mesenchymal stromal cells (MSC) as cellular vehicles for delivering the FVIII gene.

Hepatic stellate cells contribute to progenitor cells and liver regeneration

Retinoid-storing hepatic stellate cells (HSCs) have recently been described as a liver-resident mesenchymal stem cell (MSC) population; however, it is not clear whether these cells contribute to liver regeneration or serve as a progenitor cell population with hepatobiliary characteristics. Here, we purified HSCs with retinoid-dependent fluorescence-activated cell sorting from eGFP-expressing rats and transplanted these GFP(+) HSCs into wild-type (WT) rats that had undergone partial hepatectomy in the presence of 2-acetylaminofluorene (2AAF) or retrorsine, both of which are injury models that favor stem cell-based liver repair. Transplanted HSCs contributed to liver regeneration in host animals by forming mesenchymal tissue, progenitor cells, hepatocytes, and cholangiocytes and elevated direct bilirubin levels in blood sera of GUNN rats, indicating recovery from the hepatic bilirubin-handling defect in these animals. Transplanted HSCs engrafted within the bone marrow (BM) of host animals, and HSC-derived cells were isolated from BM and successfully retransplanted into new hosts with injured liver. Cultured HSCs transiently adopted an expression profile similar to that of progenitor cells during differentiation into bile acid-synthesizing and -transporting hepatocytes, suggesting that stellate cells represent a source of liver progenitor cells. This concept connects seemingly contradictory studies that favor either progenitor cells or MSCs as important players in stem cell-based liver regeneration.

Hepatic progenitor cells in liver regeneration: current advances and clinical perspectives

When there is a massive loss of hepatocytes and/or an inhibition in the proliferative capacity of the mature hepatocytes, activation of a dormant cell population of resident hepatic progenitor cells (HPCs) occurs. Depending on the type of liver damage HPCs generate new hepatocytes and biliary cells to repopulate the liver placing them as potential candidates for cell therapy in human liver failure. Liver injury specific mechanisms through which HPCs differentiate towards mature epithelial cell types are recently become understood. Such new insights will enable us not only to direct HPCs behaviour for therapeutic purposes, but also to develop clinically feasible methods for in vivo differentiation of other stem cell types towards functional hepatocytes. This review aimed to provide the current improved knowledge of the role of HPCs niche and its signals in directing the behaviour and fate of HPCs and to translate this basic knowledge of HPCs activation/differentiation into its clinical applications.