Hepatocyte transplantation: clinical experience and potential for future use

Human Amniotic Epithelial Cell Transplantation is Safe and Well Tolerated in Patients with Compensated Cirrhosis: A First-in-Human Trial

Placenta-derived human amniotic epithelial cells (hAEC) exhibit anti-inflammatory and anti-fibrotic effects in cirrhosis models. We conducted a first-in-human phase I clinical trial to assess the safety and tolerability of hAEC in adults with compensated cirrhosis. We examined increasing and repeated doses of hAEC in 9 patients in 3 cohorts. Cohort 1 patients received 0.5 × 106/kg hAEC in one IV infusion. Cohort 2 patients received 1 × 106/kg hAEC in one IV infusion. The patients in cohort 3 received 1 × 106/kg hAEC on days 0 and 28. Here, we report follow-up to post-infusion day 56 (D56), during which no serious adverse events occurred. Six patients experienced no study-related adverse events, while 3 patients reported mild (grade 1) headaches that were possibly infusion-related. A transient decrease in serum platelet count occurred in all patients, which returned to baseline screening values by day 5. FIB-4 values to assess fibrosis were significantly lower at D56. Although not statistically significant, serum AST levels and liver stiffness measurements at D56 were lower than those at baseline. The hepatic venous pressure gradient, a measure of portal hypertension, declined in 4 patients, did not change in 3 patients, and increased in 2 patients. In conclusion, intravenous infusion of allogeneic hAEC in patients with compensated cirrhosis at the doses used in this study was safe and well tolerated, with no difference observed between 1 and 2 doses. Decreased hepatic inflammation, liver stiffness, and portal hypertension support larger studies aimed at identifying patients who may benefit from this therapy. Clinical Trial registration: The trial was prospectively entered on the Australian Clinical Trials Registry (ANZCTR12616000437460).

Cell therapy in end-stage liver disease: replace and remodel

Liver disease is prevalent worldwide. When it reaches the end stage, mortality rises to 50% or more. Although liver transplantation has emerged as the most efficient treatment for end-stage liver disease, its application has been limited by the scarcity of donor livers. The lack of acceptable donor organs implies that patients are at high risk while waiting for suitable livers. In this scenario, cell therapy has emerged as a promising treatment approach. Most of the time, transplanted cells can replace host hepatocytes and remodel the hepatic microenvironment. For instance, hepatocytes derived from donor livers or stem cells colonize and proliferate in the liver, can replace host hepatocytes, and restore liver function. Other cellular therapy candidates, such as macrophages and mesenchymal stem cells, can remodel the hepatic microenvironment, thereby repairing the damaged liver. In recent years, cell therapy has transitioned from animal research to early human studies. In this review, we will discuss cell therapy in end-stage liver disease treatment, especially focusing on various cell types utilized for cell transplantation, and elucidate the processes involved. Furthermore, we will also summarize the practical obstacles of cell therapy and offer potential solutions.

Human amniotic epithelial stem cells: Hepatic differentiation and regenerative properties in liver disease treatment

The placenta and the extraembryonic tissues represent a valuable source of cells for regenerative medicine. In particular, the amniotic membrane possesses cells with stem cells characteristics that have attracted research attention. Human amniotic epithelial cells (hAECs) have unique and desirable features that position them over other stem cells, not only because of the unlimited potential supplied of, the easy access to placental tissues, and the minimal ethical and legal barriers associated, but also due to the embryonic stem cells markers expression and their ability to differentiate into the three germ layers. In addition, they are non-tumorigenic and have immunomodulatory and anti-inflammatory properties. Hepatic failure is one of the major causes of morbidity and mortality worldwide. Organ transplantation is the best way to treat acute and chronic liver failure, but there are several associated obstacles. Stem cells have been highlighted as alternative hepatocytes source because of their potential for hepatogenic differentiation. HAECs, in particular, have some properties that make them suitable for hepatocyte differentiation. In this work, we review the general characteristics of the epithelial stem cells isolated from human amniotic membrane as well as their ability to differentiate to hepatic cells. We also revise their regenerative properties, with the focus on their potential application in the liver disease treatment.

Cotransplantation With Adipose Tissue-derived Stem Cells Improves Engraftment of Transplanted Hepatocytes

BACKGROUND

Hepatocyte transplantation is expected to be an alternative therapy to liver transplantation; however, poor engraftment is a severe obstacle to be overcome. The adipose tissue-derived stem cells (ADSCs) are known to improve engraftment of transplanted pancreatic islets, which have many similarities to the hepatocytes. Therefore, we examined the effects and underlying mechanisms of ADSC cotransplantation on hepatocyte engraftment.

METHODS

Hepatocytes and ADSCs were cotransplanted into the renal subcapsular space and livers of syngeneic analbuminemic rats, and the serum albumin level was quantified to evaluate engraftment. Immunohistochemical staining and fluorescent staining to trace transplanted cells in the liver were also performed. To investigate the mechanisms, cocultured supernatants were analyzed by a multiplex assay and inhibition test using neutralizing antibodies for target factors.

RESULTS

Hepatocyte engraftment at both transplant sites was significantly improved by ADSC cotransplantation ( P < 0.001, P < 0.001). In the renal subcapsular model, close proximity between hepatocytes and ADSCs was necessary to exert this effect. Unexpectedly, ≈50% of transplanted hepatocytes were attached by ADSCs in the liver. In an in vitro study, the hepatocyte function was significantly improved by ADSC coculture supernatant ( P < 0.001). The multiplex assay and inhibition test demonstrated that hepatocyte growth factor, vascular endothelial growth factor, and interleukin-6 may be key factors for the abovementioned effects of ADSCs.

CONCLUSIONS

The present study revealed that ADSC cotransplantation can improve the engraftment of transplanted hepatocytes. This effect may be based on crucial factors, such as hepatocyte growth factor, vascular endothelial growth factor, and interleukin-6, which are secreted by ADSCs.

Short-term inhalation of isoflurane improves the outcomes of intraportal hepatocyte transplantation

Clinical hepatocyte transplantation (HTx) is only performed without general anesthesia, while inhalation anesthetics are usually used in animal experiments. We hypothesized that isoflurane may be a possible reason for the discrepancy between the results of animal experiments and the clinical outcomes of HTx. Syngeneic rat hepatocytes (1.0 × 10⁷) were transplanted to analbuminemic rats with (ISO group) and without (AW group) isoflurane. The serum albumin, AST, ALT, LDH levels and several inflammatory mediators were analyzed. Immunohistochemical staining and ex vivo imaging were also performed. The serum albumin levels of the ISO group were significantly higher in comparison to the AW group (p < 0.05). The serum AST, ALT, LDH levels of the ISO group were significantly suppressed in comparison to the AW group (p < 0.0001, respectively). The serum IL-1β, IL-10, IL-18, MCP-1, RNTES, Fractalkine and LIX levels were significantly suppressed in the ISO group. The ischemic regions of the recipient livers in the ISO group tended to be smaller than the AW group; however, the distribution of transplanted hepatocytes in the liver parenchyma was comparable between the two groups. Isoflurane may at least in part be a reason for the discrepancy between the results of animal experiments and the clinical outcomes of HTx.

Downregulation of augmenter of liver regeneration impairs the therapeutic efficacy of liver epithelial progenitor cells against acute liver injury by enhancing mitochondrial fission

Cell-based therapeutic approaches have been proven to be effective strategies for the treatment of acute liver injury (ALI). However, widespread application of these procedures is limited by several key issues, including rapid loss of stemness in vitro, aberrant differentiation into undesirable cell types, and low engraftment in vivo. In this study, liver epithelial progenitor cells (LEPCs) were characterized and transfected with augmenter of liver regeneration (ALR). The results revealed that in ALI mice with CCl₄ , the transplantation of ALR-bearing LEPCs into the liver markedly protected mice against ALI by decreasing the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), thus relieving hepatic tissue injury and attenuating inflammatory infiltration. Mechanistically, the knockdown of ALR in LEPCs activated the phosphorylation of dynamin-related protein 1 (Drp1) at the S616 site and thereby enhanced mitochondrial fission. In contrast, the transfection of ALR into LEPCs significantly inhibited Drp1 phosphorylation, thereby favoring the maintenance of mitochondrial integrity and the preservation of adenosine triphosphate contents in LEPCs. Consequently, the ALR-bearing LEPCs transplanted into ALI mice exhibited substantially greater homing ability to the injured liver via the SDF-1/CXCR4 axis than that of LEPCs-lacking ALR. In conclusion, we demonstrated that the transplantation of ALR-transfected LEPCs protected mice against CCl₄ -induced ALI, thus offering immense curative potential in the clinic.

Endoderm and Hepatic Progenitor Cells Engraft in the Quiescent Liver Concurrent with Intrinsically Activated Epithelial-to-Mesenchymal Transition

Stem cell transplantation to the liver is a promising therapeutic strategy for a variety of disorders. Hepatocyte transplantation has short-term efficacy but can be problematic due to portal hypertension, inflammation, and sinusoidal thrombosis. We have previously transplanted small mouse endoderm progenitor (EP) cells to successfully reverse a murine model of hemophilia B, and labeling these cells with iron nanoparticles renders them responsive to magnetic fields, which can be used to enhance engraftment. The mechanisms mediating progenitor cell migration from the sinusoidal space to the hepatocyte compartment are unknown. Here we find human EP and hepatic progenitor (HP) cells can be produced from human embryonic stem cells with high efficiency, and they also readily uptake iron nanoparticles. This provides a simple manner through which one can readily identify transplanted cells in vivo using electron microscopy, shortly after delivery. High resolution imaging shows progenitor cell morphologies consistent with epithelial-to-mesenchymal transition (EMT) mediating invasion into the hepatic parenchyma. This occurs in as little as 3 h, which is considerably faster than observed when hepatocytes are transplanted. We confirmed activated EMT in transplanted cells in vitro, as well as in vivo 24 h after transplantation. We conclude that EMT naturally occurs concurrent with EP and HP cell engraftment, which may mediate the rate, safety, and efficacy of early cell engraftment in the undamaged quiescent liver.

Stem cells and COVID-19: are the human amniotic cells a new hope for therapies against the SARS-CoV-2 virus?

A new coronavirus respiratory disease (COVID-19) caused by the SARS-CoV-2 virus, surprised the entire world, producing social, economic, and health problems. The COVID-19 triggers a lung infection with a multiple proinflammatory cytokine storm in severe patients. Without effective and safe treatments, COVID-19 has killed thousands of people, becoming a pandemic. Stem cells have been suggested as a therapy for lung-related diseases. In particular, mesenchymal stem cells (MSCs) have been successfully tested in some clinical trials in patients with COVID-19. The encouraging results positioned MSCs as a possible cell therapy for COVID-19. The amniotic membrane from the human placenta at term is a valuable stem cell source, including human amniotic epithelial cells (hAECs) and human mesenchymal stromal cells (hAMSCs). Interestingly, amnion cells have immunoregulatory, regenerative, and anti-inflammatory properties. Moreover, hAECs and hAMSCs have been used both in preclinical studies and in clinical trials against respiratory diseases. They have reduced the inflammatory response and restored the pulmonary tissue architecture in lung injury in vivo models. Here, we review the existing data about the stem cells use for COVID-19 treatment, including the ongoing clinical trials. We also consider the non-cellular therapies that are being applied. Finally, we discuss the human amniotic membrane cells use in patients who suffer from immune/inflammatory lung diseases and hypothesize their possible use as a successful treatment against COVID-19.

Fetal liver stem cell transplantation for liver diseases

Stem cell transplantation exhibited a promising lifesaving therapy for various end-stage liver diseases and could serve as a salvaging bridge until curative methods can be performed. In past decades, mature hepatocytes, liver progenitor cells, mesenchymal stem cells and induced pluripotent stem cells have been practiced in above settings. However, long-term survival rates and continuous proliferation ability of these cells in vivo are unsatisfactory, whereas, fetal liver stem cells (FLSCs), given their unique superiority, may be the best candidate for stem cell transplantation technique. Recent studies have revealed that FLSCs could be used as an attractive genetic therapy or regenerative treatments for inherited metabolic or other hepatic disorders. In this study, we reviewed current status and advancements of FLSCs-based treatment.

Agonist c-Met Monoclonal Antibody Augments the Proliferation of hiPSC-derived Hepatocyte-Like Cells and Improves Cell Transplantation Therapy for Liver Failure in Mice

Rationale: Hepatocyte-like cells (HLCs) derived from human induced pluripotent stem cells (hiPSCs) have been developed to address the shortage of primary human hepatocytes (PHHs) for therapeutic applications. However, the in vivo repopulation capacity of HLCs remains limited. This study investigated the roles of agonist antibody activating the c-Met receptor in promoting the in vivo proliferation and repopulation of engrafted PHHs and/or HLCs in mice with liver injuries due to different causes.

Methods: An agonist c-Met receptor antibody (5D5) was used to treat PHHs and hiPSC-HLCs in both cell culture and hepatocyte-engrafted immunodeficient mice mimicking various inherited and acquired liver diseases. The promoting roles and potential influence on the hepatic phenotype of the 5D5 regimen in cell transplantation-based therapeutic applications were systematically evaluated.

Results: In hiPSC-HLC cell cultures, 5D5 treatment significantly stimulated c-Met receptor downstream signalling pathways and accelerated cell proliferation in dose-dependent and reversible manners. In contrast, only slight but nonsignificant promotion was observed in 5D5-treated PHHs. In vivo administration of 5D5 greatly promoted the expansion of implanted hiPSC-HLCs in fumarylacetoacetate hydrolase (Fah) deficient mice, resulting in significantly increased human albumin levels and high human liver chimerism (over 40%) in the transplanted mice at week 8 after transplantation. More importantly, transplantation of hiPSC-HLCs in combination with 5D5 significantly prolonged animal survival and ameliorated liver pathological changes in mice with acute and/or chronic liver injuries caused by Fas agonistic antibody treatment, carbon tetrachloride treatment and/or tyrosinemic stress.

Conclusion: Our results demonstrated that the proliferation of hiPSC-HLCs can be enhanced by antibody-mediated modulation of c-Met signalling and facilitate hiPSC-HLC-based therapeutic applications for life-threatening liver diseases.

Stem cell characteristics and the therapeutic potential of amniotic epithelial cells

Multiple stem cell types can be isolated from the human placenta. Recent advances in stem cell biology have revealed that human amniotic epithelial cells (hAECs) are one of the perinatal stem cells which possess embryonic stem cell-like differentiation capability and adult stem cell-like immunomodulatory properties. Unlike other types of placental stem cells, hAECs are derived from pluripotent epiblasts and maintain multilineage differentiation potential throughout gestation. Similar to mesenchymal stem cells, hAECs are also able to modulate the local immune response. These, and other properties, make hAECs attractive for cellular therapy. This review article summarizes current knowledge of stem cell characteristics and immunomodulatory properties of amniotic epithelial cells and aims to advance our understanding towards the goal of novel therapy development.

Proliferation and survival of human amniotic epithelial cells during their hepatic differentiation

Stem cells derived from placental tissues are an attractive source of cells for regenerative medicine. Amniotic epithelial cells isolated from human amnion (hAECs) have desirable and competitive characteristics that make them stand out between other stem cells. They have the ability to differentiate toward all three germ layers, they are not tumorigenic and they have immunosuppressive properties. Although liver transplantation is the best way to treat acute and chronic hepatic failure patients, there are several obstacles. Recently, stem cells have been spotlighted as alternative source of hepatocytes because of their potential for hepatogenic differentiation. In this work, we aimed to study the proliferation and survival of the hAECs during their hepatic differentiation. We have also analyzed the changes in pluripotency and hepatic markers. We differentiated amniotic cells applying a specific hepatic differentiation (HD) protocol. We determined by qRT-PCR that hAECs express significant levels of SOX-2, OCT-4 and NANOG during at least 15 days in culture and these pluripotent markers diminish during HD. SSEA-4 expression was reduced during HD, measured by immunofluorescence. Morphological characteristics became more similar to hepatic ones in differentiated cells and representative hepatic markers significantly augmented their expression, measured by qRT-PCR and Western blot. Cells achieved a differentiation efficiency of 75%. We observed that HD induced proliferation and promoted survival of hAECs, during 30 days in culture, evaluated by ³H-thymidine incorporation and MTT assay. HD also promoted changes in hAECs cell cycle. Cyclin D1 expression increased, while p21 and p53 levels were reduced. Immunofluorescence analysis showed that Ki-67 expression was upregulated during HD. Finally, ERK 1/2 phosphorylation, which is intimately linked to proliferation and cell survival, augmented during all HD process and the inhibition of this signaling pathway affected not only proliferation but also differentiation. Our results suggest that HD promotes proliferation and survival of hAECs, providing important evidence about the mechanisms governing their hepatic differentiation. We bring new knowledge concerning some of the optimal transplantation conditions for these hepatic like cells.

In Vitro Generated Hepatocyte-Like Cells: A Novel Tool in Regenerative Medicine and Drug Discovery

Hepatocyte-like cells (HLCs) are generated from either various human pluripotent stem cells (hPSCs) including induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs), or direct cell conversion, mesenchymal stem cells as well as other stem cells like gestational tissues. They provide potential cell sources for biomedical applications. Liver transplantation is the gold standard treatment for the patients with end stage liver disease, but there are many obstacles limiting this process, like insufficient number of donated healthy livers. Meanwhile, the number of patients receiving a liver organ transplant for a better life is increasing. In this regard, HLCs may provide an adequate cell source to overcome these shortages. New molecular engineering approaches such as CRISPR/ Cas system applying in iPSCs technology provide the basic principles of gene correction for monogenic inherited metabolic liver diseases, as another application of HLCs. It has been shown that HLCs could replace primary human hepatocytes in drug discovery and hepatotoxicity tests. However, generation of fully functional HLCs is still a big challenge; several research groups have been trying to improve current differentiation protocols to achieve better HLCs according to morphology and function of cells. Large-scale generation of functional HLCs in bioreactors could make a new opportunity in producing enough hepatocytes for treating end-stage liver patients as well as other biomedical applications such as drug studies. In this review, regarding the biomedical value of HLCs, we focus on the current and efficient approaches for generating hepatocyte-like cells in vitro and discuss about their applications in regenerative medicine and drug discovery.

A Rational Strategy for the Use of Amniotic Epithelial Stem Cell Therapy for Liver Diseases

Stem cell-based therapies hold the potential to alleviate the burden of many serious diseases, including those of the liver. Among the different types of stem cells, human placenta-derived stem cells are potentially one of the most clinically applicable stem cells because of their tissue-specific advantages. They are a readily available cell source that can be procured in a noninvasive manner, and there are few ethical concerns regarding their use. Recent studies have demonstrated that the amniotic epithelium contains stem cells that possess four unique and advantageous properties; human amniotic epithelial cells (hAECs) have low immunogenicity, secrete several immune regulatory molecules, possess the potential to differentiate into all three germ layers, and contain abundant lysosomes allowing them to secrete lysosomal enzymes. This perspective article provides an overview of the beneficial properties of hAECs and proposes a rational strategy for translating placental stem cells toward clinical application for various liver diseases.

SIGNIFICANCE

This article provides an overview of the beneficial properties of one type of human placental stem cell and proposes a rational strategy for translating placental stem cells toward clinical application for various liver diseases.

Improvement of Infusion Process in Cell Transplantation: Effect of Shear Stress on Hepatocyte Viability Under Horizontal and Vertical Syringe Orientation

Improving cell viability and function are important for enhancing the clinical results of cell transplantation. The relationship between cell viability and shear stress remains unexplained, and sedimentation effects during the infusion process are important to the hepatocyte transplantation process. In the present study, the relationship between cell viability and shear stress in the presence of sedimentation effect was investigated using a microchannel simulating the cell transplantation process under several shear stress conditions. Horizontal and vertical syringe orientations were employed to investigate the sedimentation effect. The vertical syringe orientation resulted in lower viability loss than the horizontal orientation. In summary, removing a sedimentation effect is important to improving cell viability by preventing high shear stress.

Effect of bone marrow-derived mesenchymal stem cells on hepatic fibrosis in a thioacetamide-induced cirrhotic rat model

Background

Cirrhosis is a long-term consequence of chronic hepatic injury with fibrosis. No effective therapy is currently available for decompensated cirrhosis except liver transplantation. Hence, we investigated the effect of bone marrow-derived mesenchymal stem cells (BM-MSCs) on hepatic fibrosis in a thioacetamide (TAA)-induced cirrhotic rat model.

Methods

The BM-MSCs were injected directly into the right liver lobe twice, at 6 and 8 weeks during the 12-week TAA administration, in thioacetamide (TAA)-induced cirrhotic rats model, and hepatic fibrosis was evaluated. At 12 weeks, the effect of BM-MSCs on hepatic fibrosis was analyzed histomorphologically using the Laennec fibrosis scoring system, and the collagen proportionate area was quantified. Cirrhosis-related factors, such as transforming growth factor β1 (TGF-β1), type 1 collagen (collagen-1), α-smooth muscle actin (α-SMA), and P-Smad3/Smad3 expression levels, were evaluated using real-time polymerase chain reaction and western blot assays.

Results

According to the Laennec fibrosis scoring system, histological improvement was observed in hepatic fibrosis after BM-MSC treatment (P <0.01). The percentage of the collagen proportionate area decreased from 16.72 ± 5.51 to 5.06 ± 1.27 after BM-MSC treatment (P <0.01). The content of hepatic hydroxyproline was significantly lower in the BM-MSC treated group (46.25 ± 13.19) compared to the untreated cirrhotic group (85.81 ± 17.62; P <0.01). BM-MSC administration significantly decreased TGF-β1, collagen-1, and α-SMA expression in TAA-induced cirrhotic rats (P <0.01). We also confirmed P-Smad3/Smad3, downstream effectors of the TGF-β1 signaling pathway, and found that MSC transplantation inhibited Smad3 phosphorylation.

Conclusions

BM-MSC treatment attenuated hepatic fibrosis in rats with TAA-induced cirrhosis, raising the possibility of the clinical use of BM-MSCs in the treatment of cirrhosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-014-0198-6) contains supplementary material, which is available to authorized users.

Rapid and sensitive assessment of human hepatocyte functions

Transplantation of human hepatocytes (HTx) has gained recognition as a bridge to, or an alternative to, orthotopic liver transplantation for patients with acute liver failure or genetic defects in liver function. Although the quality of the hepatocytes used for cell transplantation is critical, no consensus exists on protocols to assess the function of hepatocytes prior to HTx. Application of this cell therapy in clinical practice could be aided by fast and reliable assays to evaluate the functional competence of isolated hepatocytes prior to clinical transplantation. Traditional assays for measuring metabolic functions in primary hepatocytes frequently involve highly technical equipment, time-consuming methods, and large numbers of cells. We describe a novel approach for the rapid assessment of the metabolic capabilities of human hepatocytes. This report details simple procedures to evaluate 11 endpoints from cells isolated from human liver that can be performed by a single operator within approximately 2 h of isolation. Longer term cultured hepatocytes were also analyzed to determine if the results from the 2-h tests were predictive of long-term hepatic function. The assays simultaneously measure five cytochrome P450 activities, one phase II activity, plating efficiency, and ammonia metabolism in addition to viability and cell yield. The assays require fewer than 20 million cells and can be completed using commonly available and inexpensive laboratory equipment. The protocol details methods that can be used in a time frame that would allow analysis of hepatic functions in freshly isolated hepatocytes prior to their use for clinical transplantation.

Preoperative hepatocyte transplantation improves the survival of rats with nonalcoholic steatohepatitis-related cirrhosis after partial hepatectomy

Liver failure after liver resection for cirrhosis is a critical problem, and no effective therapy except liver transplantation is currently available. The objective of this study was to examine whether hepatocyte transplantation (HT) reduces the poststandard liver resection mortality rate of rats with nonalcoholic steatohepatitis (NASH)-related cirrhosis. Liver resection for hepatocellular carcinoma (HCC) combined with NASH-related cirrhosis has become increasingly common. We developed a rat model of acute liver failure after two-thirds partial hepatectomy (PH) for NASH-related cirrhosis. The mechanism by which HT improved the survival of the model rats was examined in short- and long-term investigations. Female DPPIV(-) recipient F344 rats were fed the choline-deficient l-amino acid (CDAA)-defined diet for 12 weeks. Some of the rats were transplanted with male F344 DPPIV(+) rat hepatocytes 24 h before undergoing PH. The overall post-PH survival of each group was evaluated, and short- and long-term pathological and molecular biological evaluations were also performed. Overall survival was significantly longer in the HT group than the non-HT group (7-day survival rates: 46.7% and 7.7%, respectively). Compared with the recipient livers of the non-HT group, numerous Ki-67(+) hepatocytes and few TUNEL(+) hepatocytes were observed in the livers of the HT group. At 6 months after the HT, the DPPIV(+) hepatocytes had partially replaced the recipient liver and formed hepatocyte clusters in the spleen. Preoperative HT might improve the survival of rats with NASH-related cirrhosis after PH by preventing the host hepatocytes from accelerating their growth and falling into apoptosis.

Histological improvement following administration of autologous bone marrow-derived mesenchymal stem cells for alcoholic cirrhosis: a pilot study

BACKGROUND

In experimental models, bone marrow-derived mesenchymal stem cells (BM-MSCs) have the capacity to differentiate into hepatocytes and exhibit antifibrotic effects. However, there have been no studies in humans with alcoholic cirrhosis.

AIM

The aim of this study was to elucidate the antifibrotic effect of BM-MSCs in patients with alcoholic cirrhosis, as a phase II clinical trial.

METHODS

Twelve patients (11 males, 1 female) with baseline biopsy-proven alcoholic cirrhosis who had been alcohol free for at least 6 months were enrolled. BM-MSCs were isolated from each patient's BM and amplified for 1 month, and 5 × 10(7) cells were then injected twice, at weeks 4 and 8, through the hepatic artery. One patient was withdrawn because of ingestion of alcohol. Finally, 11 patients completed the follow-up biopsy and laboratory tests at 12 weeks after the second injection. The primary outcome was improvement in the patients' histological features.

RESULTS

According to the Laennec fibrosis system, histological improvement was observed in 6 of 11 patients (54.5%). The Child-Pugh score improved in ten patients (90.9%) and the levels of transforming growth factor-β1, type 1 collagen and α-smooth muscle actin significantly decreased (as assessed by real-time reverse transcriptase polymerase chain reaction) after BM-MSCs therapy (P < 0.05). No significant complications or side effects were observed during this study.

CONCLUSIONS

Bone marrow-derived mesenchymal stem cells therapy in alcoholic cirrhosis induces a histological and quantitative improvement of hepatic fibrosis.

Therapeutic potential of placenta-derived stem cells for liver diseases: current status and perspectives

Over the last decade, there has been a growing interest in the human placenta as a unique source of stem cells. The placenta is a fetal organ that is normally discarded following delivery. Therefore, it is readily available as a source of cells without the ethical concerns normally associated with embryonic stem cells. These cells also carry less risk for age- and environmental-related DNA damage. In addition to these practical advantages of placenta-derived cells, amniotic epithelial cells possess unique stem cell-like biological characteristics. In contrast to other parts of the placenta, cells from the amniotic epithelium are derived from pluripotent epiblasts and possess the ability to differentiate into all three germ layers. From a translational perspective, amnion-derived stem cells are very attractive candidates for clinical application. These cells are genetically stable and do not demonstrate tumorigenicity upon transplantation, and may be endowed with immunomodulatory and/or anti-inflammatory properties. These unique characteristics have made amniotic epithelial cells attractive for use as stem cell-based therapies for liver disease. Human and rodent amniotic epithelial cells have already demonstrated their therapeutic efficacy in multiple animal models. Although the detailed mechanism by which the transplanted cells generate a therapeutic effect is not yet totally understood, these dramatic results have generated significant interest for consideration of these amnion-derived stem cells for clinical applications. This review covers recent findings of the therapeutic potential of amnion-derived stem cells for liver diseases, and provides perspectives for future developments.

Blockade of endothelial G(i) protein enhances early engraftment in intraportal cell transplant to mouse liver

The limited availability of liver donors and recent progress in cell therapy technologies has centered interest on cell transplantation as a therapeutic alternative to orthotopic liver transplant for restoring liver function. Following transplant by intraportal perfusion, the main obstacle to cell integration in the parenchyma is the endothelial barrier. Transplanted cells form emboli in the portal branches, inducing ischemia and reperfusion injury, which cause disruption of endothelial impermeability and activate the immune system. Approximately 95% of transplanted cells fail to implant and die within hours by anoikis or are destroyed by the host immune system. Intravascular perfusion of Bordetella pertussis toxin (PTx) blocks endothelial G(i) proteins and acts as a reversible inducer of actin cytoskeleton reorganization, leading to interruption of cell confluence in vitro and increased vascular permeability in vivo. PTx treatment of the murine portal vascular tree 2 h before intraportal perfusion of embryonic stem cells facilitated rapid cell engraftment. By 2 h postperfusion, the number of implanted cells in treated mice was more than fivefold greater than in untreated controls, a difference that was maintained to at least 30 days posttransplant. We conclude that prior to cell transplant, PTx blockade of the G(i) protein pathway in liver endothelium promotes rapid, efficient cell implantation in liver parenchyma, and blocks chemokine receptor signaling, an essential step in early activation of the immune system.

New potential cell source for hepatocyte transplantation: discarded livers from metabolic disease liver transplants

Domino liver transplantation is a method used to increase the number of liver grafts available for orthotopic liver transplantation (OLT). Reports indicate that livers from patients with metabolic liver disease can be safely transplanted into select recipients if the donor's defect and the recipient's metabolic needs are carefully considered. The liver of patients with many types of metabolic liver disease is morphologically and biochemically normal, except for the mutation that characterizes that disease. Other biochemical functions normally performed by the liver are present and presumably "normal" in these hepatocytes. Hepatocytes were isolated from the liver of 35 organ donors and 35 liver tissues taken at OLT from patients with liver disease were analyzed for 9 different measures of viability and function. The data indicate that cells isolated from some diseased livers performed as well or better than those isolated from organ donors with respect to viability, cell yield, plating efficiency and in assays of liver function, including drug metabolism, conjugation reactions and ammonia metabolism. Cells from metabolic diseased livers rapidly and efficiently repopulated a mouse liver upon transplantation.

CONCLUSIONS

As with domino liver transplantation, domino cell transplantation deserves consideration as method to extend the pool of available organs and cells for transplantation.

The generation of hepatocytes from mesenchymal stem cells and engraftment into the liver

PURPOSE OF REVIEW

Liver transplantation is the ultimate therapeutic option for the treatment of end-stage liver diseases, which, however, is restricted by the shortage of donor organs. Instead hepatocyte transplantation seemed to be a way out, but again marginal donor livers for the isolation of primary human hepatocytes are scarce. The hepatocyte differentiation capacity of mesenchymal stem cells might open a new cell resource to generate hepatocyte-like cells for therapeutical use.

RECENT FINDINGS

Apart from their potency of hepatocyte differentiation mesenchymal stem cells display pleiotropic biological features including modulation of immunogenicity, anti-inflammatory and anti-apoptotic as well as pro-proliferative impact at the site of tissue or organ lesions. They are mobilized from the bone marrow and migrate to the liver along chemoattractive gradients thus contributing to the humoral and cellular response in tissue repair. The cause of different liver diseases is varying depending on, for example, viral, toxic, nutritional, neoplastic challenges. As known from animal studies mesenchymal stem cells seem to have a beneficial impact on liver regeneration and tissue repair under a variety of liver disease conditions.

SUMMARY

Their versatile biological features render mesenchymal stem cells an alternate cell resource for the treatment of liver diseases. It is important to know the mechanisms of integration of transplanted cells into the recipient tissue and to understand the communication between donor cells and the host tissue on the molecular level in order to support efficacy of cell transplantation and thus optimize the therapeutical outcome.

Improved amino acid, bioenergetic metabolite and neurotransmitter profiles following human amnion epithelial cell transplant in intermediate maple syrup urine disease mice

Orthotopic liver transplant (OLT) significantly improves patient outcomes in maple syrup urine disease (MSUD; OMIM: 248600), yet organ shortages point to the need for alternative therapies. Hepatocyte transplantation has shown both clinical and preclinical efficacy as an intervention for metabolic liver diseases, yet the availability of suitable livers for hepatocyte isolation is also limited. Conversely, human amnion epithelial cells (hAEC) may have utility as a hepatocyte substitute, and they share many of the characteristics of pluripotent embryonic stem cells while lacking their safety and ethical concerns. We reported that like hepatocytes, transplantation of hAEC significantly improved survival and lifespan, normalized body weight, and significantly improved branched-chain amino acid (BCAA) levels in sera and brain in a transgenic murine model of intermediate maple syrup urine disease (imsud). In the current report, we detail the neural and peripheral metabolic improvements associated with hAEC transplant in imsud mice, including amino acids associated with bioenergetics, the urea cycle, as well as the neurotransmitter systems for serotonin, dopamine, and gamma-aminobutyric acid (GABA). This stem cell therapy results in significant global correction of the metabolic profile that characterizes the disease, both in the periphery and the central nervous system, the target organ for toxicity in iMSUD. The significant correction of the disease phenotype, coupled with the theoretical benefits of hAEC, particularly their lack of immunogenicity and tumorigenicity, suggests that human amnion epithelial cells deserve serious consideration for clinical application to treat metabolic liver diseases.

Placental stem cell correction of murine intermediate maple syrup urine disease

There is improved survival and partial metabolic correction of a mouse intermediate maple syrup urine disease (iMSUD) model after allogenic hepatocyte transplantation, confirming that a small number of enzyme-proficient liver-engrafted cells can improve phenotype. However, clinical shortages of suitable livers for hepatocyte isolation indicate a need for alternative cell sources. Human amnion epithelial cells (hAECs) share stem cell characteristics without the latter's safety and ethical concerns and differentiate to hepatocyte-like cells. Eight direct hepatic hAEC transplantations were performed in iMSUD mice over the first 35 days beginning at birth; animals were provided a normal protein diet and sacrificed at 35 and 100 days. Treatment at the neonatal stage is clinically relevant for MSUD and may offer a donor cell engraftment advantage. Survival was significantly extended and body weight was normalized in iMSUD mice receiving hAEC transplantations compared with untreated iMSUD mice, which were severely cachectic and died ≤28 days after birth. Branched chain α-keto acid dehydrogenase enzyme activity was significantly increased in transplanted livers. The branched chain amino acids leucine, isoleucine, valine, and alloisoleucine were significantly improved in serum and brain, as were other large neutral amino acids.

CONCLUSION

Placental-derived stem cell transplantation lengthened survival and corrected many amino acid imbalances in a mouse model of iMSUD. This highlights the potential for their use as a viable alternative clinical therapy for MSUD and other liver-based metabolic diseases.

Therapeutic potentials occurring during the early differentiation process of mesenchymal stem cells in a rats model with thioacetamide-induced liver fibrosis

BACKGROUNDS/AIMS

Mesenchymal stem cells (MSCs) have the capacity to differentiate into hepatocytes, The purpose of this study is to investigate the MSCs' differentiation process and therapeutic potentials by comparing isolated MSCs with HGF-treated MSCs in rat's model with thiacetamide (TAA)-induced cirrhosis.

METHODS

Male Sprague-Dawley (SD) rats, weighing 100-150 g were used in this study. To induce liver fibrosis, recipient rats were taken with 0.04% thioacetamide (TAA) in the drinking water (400 mg TAA/L) for 8 weeks. The rats underlying liver cirrhosis were divided into 3 groups according to the transplanted materials, compared to normal saline as control (I) and isolated MSCs (II) HGF-treated MSCs.

RESULTS

Severe hepatic fibrosis and hepatocyte destruction were detected in the control group. Less hepatic cirrhosis and collagen formation, more hepatocyte regeneration and glycogen storage were detected in isolated MSCs compared to HGF-treated MSCs group, Distribution of red autofluorescence is mainly localized near the sinusoids in isolated MSCs, scattered away the sinusoids in HGF-treated MSCs group. MSCs transdifferentiated into CK-19 postive Oval cells and then to albulmin-producing hepatocytes, HGF treated MSCs differentiated into hepatocyte without the intermediate oval cells phase. HGF treated MSCs became the CK18-positive, MSCs became CD 90-positive.

CONCLUSIONS

Significant hepatocyte differentiation occurred in not HGF-treated MSCs but isolated MSCs group unexpectedly. These results suggest that the beneficial effect of MSCs on in rat's model with TAA-induced cirrhosis may occur during early differentiation course of MSCs. Mature hepatocyte itself has a little effect on the accelerated differentiation and functional capacity of hepatic lineage cell-line.

Direct oxygen supply with polydimethylsiloxane (PDMS) membranes induces a spontaneous organization of thick heterogeneous liver tissues from rat fetal liver cells in vitro

Oxygen is a vital nutrient for growth and maturation of in vitro cells (e.g., adult hepatocytes). We previously demonstrated that direct oxygenation through a polydimethylsiloxane (PDMS) membrane increases the oxygen supply to cell cultures and improves hepatocyte functions. In this study, we removed limits on oxygen supply to fetal rat liver cells through the use of direct oxygenation through a PDMS membrane to investigate in vitro growth and maturation. We chose fetal liver cells because they are considered a feasible source of liver progenitor cells for regenerative medicine therapy due to their highly efficient maturation and proliferation. Cells from 17-day-old pregnant rats were cultured under 5% and 21% oxygen atmospheres. Some cells were first cultured under 5% oxygen, and then switched to a 21% oxygen atmosphere. When oxygen supply was enhanced by a PDMS membrane, the rat fetal liver cells organized into a complex tissue composed of an epithelium of hepatocytes above a mesenchyme-like tissue. The thickness of this supportive tissue was directly correlated to oxygen concentration and was thicker under 5% oxygen. When cultures were switched from 5% to 21% oxygen, lumen-containing structures were formed in the thick mesenchymal-like tissue and the albumin secretion rate increased. In addition, cells adapted their glycolytic activity to the oxygen concentrations. This system promoted the formation of a functional and organized thick tissue suitable for use in regenerative medicine.

Liver tissue engineering utilizing hepatocytes propagated in mouse livers in vivo

Recent advances in tissue engineering technologies have highlighted the ability to create functional liver systems using isolated hepatocytes in vivo. Considering the serious shortage of donor livers that can be used for hepatocyte isolation, it has remained imperative to establish a hepatocyte propagation protocol to provide highly efficient cell recovery allowing for subsequent tissue engineering procedures. Donor primary hepatocytes were isolated from human α-1 antitrypsin (hA1AT) transgenic mice and were transplanted into the recipient liver of urokinase-type plasminogen activator-severe combined immunodeficiency (uPA/SCID) mice. Transplanted donor hepatocytes actively proliferated within the recipient liver of the uPA/SCID mice. At week 8 or later, full repopulation of the uPA/SCID livers with the transplanted hA1AT hepatocytes were confirmed by blood examination and histological assessment. Proliferated hA1AT hepatocytes were recovered from the recipient uPA/SCID mice, and we generated hepatocyte sheets using these recovered hepatocytes for subsequent transplantation into the subcutaneous space of mice. Stable persistency of the subcutaneously engineered liver tissues was confirmed for up to 90 days, which was the length of our present study. These new data demonstrate the feasibility in propagating murine hepatocytes prior to the development of hepatic cells and bioengineered liver systems. The ability to regenerate and expand hepatocytes has potential clinical value whereby procurement of small amounts of tissue could be expanded to sufficient quantities prior to their use in hepatocyte transplantation or other hepatocyte-based therapies.

Phenotypic and functional heterogeneity of human bone marrow- and amnion-derived MSC subsets

Bone marrow-derived mesenchymal stromal/stem cells (MSCs) are nonhematopoietic cells that are able to differentiate into osteoblasts, adipocytes, and chondrocytes. In addition, they are known to participate in niche formation for hematopoietic stem cells and to display immunomodulatory properties. Conventionally, these cells are functionally isolated from tissue based on their capacity to adhere to the surface of culture flasks. This isolation procedure is hampered by the unpredictable influence of secreted molecules, the interactions between cocultured hematopoietic and other unrelated cells, and by the arbitrarily selected removal time of nonadherent cells before the expansion of MSCs. Finally, functionally isolated cells do not provide biological information about the starting population. To circumvent these limitations, several strategies have been developed to facilitate the prospective isolation of MSCs based on the selective expression, or absence, of surface markers. In this report, we summarize the most frequently used markers and introduce new targets for antibody-based isolation procedures of primary bone marrow- and amnion-derived MSCs.

Hepatogenic differentiation of mesenchymal stem cells in a rat model of thioacetamide-induced liver cirrhosis

Implantation of bone-marrow-derived MSCs (mesenchymal stem cells) has emerged as a potential treatment modality for liver failure, but in vivo differentiation of MSCs into functioning hepatocytes and its therapeutic effects have not yet been determined. We investigated MSC differentiation process in a rat model of TAA (thioacetamide)-induced liver cirrhosis. Male Sprague-Dawley rats were administered 0.04% TAA-containing water for 8 weeks, MSCs were injected into the spleen for transsplenic migration into the liver, and liver tissues were examined over 3 weeks. Ingestion of TAA for 8 weeks induced micronodular liver cirrhosis in 93% of rats. Injected MSCs were diffusely engrafted in the liver parenchyma, differentiated into CK19 (cytokeratin 19)- and thy1-positive oval cells and later into albumin-producing hepatocyte-like cells. MSC engraftment rate per slice was measured as 1.0-1.6%. MSC injection resulted in apoptosis of hepatic stellate cells and resultant resolution of fibrosis, but did not cause apoptosis of hepatocytes. Injection of MSCs treated with HGF (hepatocyte growth factor) in vitro for 2 weeks, which became CD90-negative and CK18-positive, resulted in chronological advancement of hepatogenic cellular differentiation by 2 weeks and decrease in anti-fibrotic activity. Early differentiation of MSCs to progenitor oval cells and hepatocytes results in various therapeutic effects, including repair of damaged hepatocytes, intracellular glycogen restoration and resolution of fibrosis. Thus, these results support that the in vivo hepatogenic differentiation of MSCs is related to the beneficial effects of MSCs rather than the differentiated hepatocytes themselves.

Live cell-imaging perfusion culture system of liver sinusoidal endothelial cells to mimic stem cell engraftment in liver

Hepatocyte and various hepatic stem cell transplantations have been studied as alternative therapies to orthotopic liver transplantation for liver injury. The engraftment of transplanted cells into the parenchyma requires transmigration through sinusoidal endothelial cells (SECs), the only cellular barrier. In this study, we constructed a SEC-imaging perfusion culture system that mimics sinusoids with respect to hemorheologic properties. SECs were successfully maintained for 24 hours. Human liver stem cells (HLSCs) were used as a model of transplanted cells for in vitro engraftment to SECs under perfusion culture conditions. Conditions of high shear stress perfusion with 0.34 dyne/cm(2) significantly reduced cell adhesion in contrast to lower shear stress conditions of 0.1 and 0.03 dyne/cm(2). Among the biologic perfusion fluids, namely, fetal bovine serum (FBS), pig plasma, and 5% human albumin solution, HLSCs showed significantly greater attachment to SECs when perfused with FBS, which is well known to contain abundant amounts of adhesion molecules. This biomimetic SEC perfusion culture system may provide a useful tool to study engraftment mechanisms and to evaluate the effects of various enhancers as an alternative to animal models.

Immediate intraportal transplantation of human bone marrow mesenchymal stem cells prevents death from fulminant hepatic failure in pigs

The effectiveness of human bone marrow mesenchymal stem cell (hBMSC) transplantation to treat acute and chronic liver injury has been demonstrated in animal models and in a few nonrandomized clinical trials. However, no studies have investigated hBMSC transplantation in the treatment of fulminant hepatic failure (FHF), especially in large animal (pig) models. The aim of this study was to demonstrate the safety, effectiveness, and underlying mechanism of hBMSC transplantation for treating FHF in pigs through the intraportal route. Human BMSCs (3 × 10(7) ) were transplanted into pigs with FHF via the intraportal route or peripheral vein immediately after D-galactosamine injection, and a sham group underwent intraportal transplantation (IPT) without cells (IPT, peripheral vein transplantation [PVT], and control groups, respectively, n = 15 per group). All of the animals in the PVT and control groups died of FHF within 96 hours. In contrast, 13 of 15 animals in the IPT group achieved long-term survival (>6 months). Immunohistochemistry demonstrated that transplanted hBMSC-derived hepatocytes in surviving animals were widely distributed in the hepatic lobules and the liver parenchyma from weeks 2 to 10. Thirty percent of the hepatocytes were hBMSC-derived. However, the number of transplanted cells decreased significantly at week 15. Only a few single cells were scattered in the regenerated liver lobules at week 20, and the liver tissues exhibited a nearly normal structure.

CONCLUSION

Immediate IPT of hBMSCs is a safe and effective treatment for FHF. The transplanted hBMSCs may quickly participate in liver regeneration via proliferation and transdifferentiation into hepatocytes during the initial stage of FHF. This method can possibly be used in future clinical therapy.

Repopulation of Human Origin Hepatocyte Progenitor-Like Cell Line, THLE-5b, in the SCID Mouse Liver under p21-Mediated Cell Growth-Arresting Conditions

The in vivo repopulation of hepatocytes depends on donor cell growth potential and recipient conditioning. We herein demonstrate the successful cell transplantation of a human hepatocyte cell line, THLE-5b, into the SCID mouse liver by means of a rather mild conditioning using a 55% hepatectomy and p21 transfection. Adult human liver-derived cells, THLE-5b, are SV40 T antigen-immortalized epithelial cells. A phenotypic examination of THLE-5b showed they expressed hepatic stem cell markers such as EpCAM, OCT3/4, and Thy-1, thus indicating the immature nature of the cells. A three-dimensional aggregate culture of THLE-5b showed a higher expression level of liver-specific genes such as albumin, α1-antitrypsin, and CYP3A4, thus suggesting that THLE-5b possess the capability to differentiate into hepatocytes. In a cell transplantation experiment, the cell cycle regulator p21 was transfected with adenoviral vector into the SCID mouse liver. On the next day, 8 × 105 cells of GFP-transfected THLE-5b were injected intrasplenically, together with the intraperitoneal administration of anti-asialo GM1 antibodies. The following day, a partial hepatectomy was performed. The GFP-THLE-5b cells were observed to have migrated and become integrated into the liver parenchyma 14 days after transplantation. The present protocol is thus considered to be a novel experimental model to elucidate the mechanism of hepatocyte repopulation and to develop efficient stem cell therapy in the liver.

The nude mouse as model for liver deficiency study and treatment and xenotransplantation

We aimed at reviewing the various uses of Nude mouse for the development of liver deficiency models and evaluation of efficacy of hepatic cell xenotransplantation. The first part records the large range of liver deficiency models that can be developed in Nude mice: surgical partial hepatectomy, acute toxic liver deficiency, chronic cirrhosis, and transgenic liver injury. The second part tackles the outcome of rat hepatocyte as well as human cell transplantation, both mature hepatocyte and hepatic progenitor, into Nude mouse submitted to liver injury. Results are discussed and compared to other available immunodeficient mouse models. The issue of humanized liver creation is also addressed. Altogether, these results show that Nude mouse appears to be a suitable small animal model to expand our insight into liver cell engraftment and regeneration.

Development and application of purified tissue dissociation enzyme mixtures for human hepatocyte isolation

Human hepatocyte transplantation is gaining acceptance for the treatment of liver diseases. However, the reagents used to isolate hepatocytes from liver tissue are not standardized and show lot-to-lot variability in enzyme activity and endotoxin contamination. For clinical application, highly purified reagents are preferable to crude digest preparations. A purified tissue dissociating enzyme (TDE) preparation (CIzyme(TM) purified enzymes) was developed based on the enzyme compositions found in a superior lot of collagenase previously used by our group for human hepatocyte isolation. The performance of this enzyme preparation was compared to collagenase type XI on 110 liver cases by assessing hepatocyte yield, viability, and seven other functional assays that included plating efficiency, basal and induced CYP450 activities, phase II conjugation activity, and ammonia metabolism. No statistically significant difference was observed between these TDEs when they were used to isolate hepatocytes from liver resections or organ donor tissue on 54 hepatocyte isolations with type XI enzyme and 56 isolations using CIzyme(TM). These results show that a highly purified and defined TDE preparation can be formulated that provides excellent performance with respect to viability, yield, and functional activity of the isolated cells. In addition to reproducible formulation, these purified enzyme products have only 2-3% of the endotoxin of crude enzyme preparations. These results show that purified enzymes such as CIzyme(TM) will be a safe and effective for the isolation of human hepatocytes for clinical transplants.

Enhanced growth and hepatic differentiation of fetal liver epithelial cells through combinational and temporal adjustment of soluble factors

Fetal liver epithelial cells (FLEC) are valuable for liver cell therapy and tissue engineering, but methods for culture and characterization of these cells are not well developed. This work explores the influence of multiple soluble factors on FLEC, with the long-term goal of developing an optimal culture system to generate functional liver tissue. Our comparative analysis suggests hepatocyte growth factor (HGF) is required throughout the culture period. In the presence of HGF, addition of oncostatin M (OSM) at culture initiation results in concurrent growth and maturation, while constant presence of protective agents like ascorbic acid enhances cell survival. Study observations led to the development of a culture medium that provided optimal growth and hepatic differentiation conditions. FLEC expansion was observed to be approximately twofold of that under standard conditions, albumin secretion rate was 2-3 times greater than maximal values obtained with other media, and the highest level of glycogen accumulation among all conditions was observed with the developed medium. Our findings serve to advance culture methods for liver progenitors in cell therapy and tissue engineering applications.

Amnion-derived stem cells: in quest of clinical applications

In the promising field of regenerative medicine, human perinatal stem cells are of great interest as potential stem cells with clinical applications. Perinatal stem cells could be isolated from normally discarded human placentae, which are an ideal cell source in terms of availability, the fewer number of ethical concerns, less DNA damage, and so on. Numerous studies have demonstrated that some of the placenta-derived cells possess stem cell characteristics like pluripotent differentiation ability, particularly in amniotic epithelial (AE) cells. Term human amniotic epithelium contains a relatively large number of stem cell marker-positive cells as an adult stem cell source. In this review, we introduce a model theory of why so many AE cells possess stem cell characteristics. We also describe previous work concerning the therapeutic applications and discuss the pluripotency of the AE cells and potential pitfalls for amnion-derived stem cell research.

Autologous serum improves yield and metabolic capacity of monocyte-derived hepatocyte-like cells: possible implication for cell transplantation

Hepatocyte-transplantation is a therapeutic approach for diverse acute and chronic liver diseases. As availability of primary cells is limited, there is an increasing demand for hepatocyte-like cells (e.g., neohepatocytes generated from peripheral blood monocytes). The aim of this study was to evaluate the effects of six different human AB sera, fetal calf serum, or autologous serum on production of neohepatocytes. The yield and quality of neohepatocytes varied considerably depending on the different sera. Using autologous sera for the whole production process we constantly generated the highest amount of cells with the highest metabolic activity for phase I (e.g., CYP1A1/2, CYP3A4) and phase II enzymes (e.g., glutathione-S-transferase). Moreover, similar effects were seen examining glucose and urea metabolism. Especially, glucose-6-phosphatase and PAS staining showed distinct serum-dependent differences. The role of macrophage activation was investigated by measuring the secretion of TNF-α, TGF-β, and RANKL, MMP activity, as well as mRNA levels of different interleukins in programmable cells of monocytic origin (PCMO). Our data clearly demonstrate that the use of autologous serum reduced initial macrophage activation in PCMOs and subsequently improved both yield and function of differentiated neohepatocytes. The autologous approach presented here might also be useful in other stem cell preparation processes where cell activation during generation shall be kept to a minimum.

Amniotic membrane application reduces liver fibrosis in a bile duct ligation rat model

Biliary fibrosis and resultant cirrhosis are among the most common outcomes of chronic liver diseases. Currently, liver transplantation remains the only effective treatment. In seeking alternative therapeutic approaches, we focused on the potential use of the human amniotic membrane (AM). Indeed, AM has gained increasing importance for its antiscarring, anti-inflammatory, and wound-healing properties, as well as for the multipotent differentiation ability and immunomodulatory features of AM-derived cells. Intriguingly, we have recently demonstrated that placenta-derived cells reduce lung fibrosis in bleomycin-treated mice, and that AM patches reduce postischemic cardiac injury in rats. Hence, we have now investigated the effects of human AM on biliary fibrosis induced in rats through the bile duct ligation (BDL) procedure. A fragment of human AM was applied onto the liver surface after BDL and the effects on fibrosis establishment and progression were evaluated at different time points in comparison with fibrosis progression in control BDL rats. The degree of liver fibrosis was first assessed by the semiquantitative Knodell scoring system and, thereafter, by digital image morphometric analysis to quantify the area occupied by ductular reaction, activated myofibroblasts, and collagen deposition. We demonstrated a significant reduction in the severity of BDL-induced fibrosis in AM-treated rats. Indeed, while fibrosis progressed rapidly in control BDL rats, leading to cirrhosis within 6 weeks, AM-treated rats showed confined fibrosis at the portal/periportal area with no signs of cirrhosis, and a reduction in collagen deposition to about 50% of levels observed in control BDL rats. In addition, the AM was able to significantly slow the gradual progression of the ductular reaction and reduce, at all time points, the area occupied by activated myofibroblasts. These findings suggest that human AM, when applied as a patch onto the liver surface, might inhibit fibrosis progression in BDL-injured livers, and could protect against hepatic damage associated with fibrotic degeneration.

Functional life-long maintenance of engineered liver tissue in mice following transplantation under the kidney capsule

The ability to engineer biologically active cells and tissue matrices with long-term functional maintenance has been a principal focus for investigators in the field of hepatocyte transplantation and liver tissue engineering. The present study was designed to determine the efficacy and temporal persistence of functional engineered liver tissue following transplantation under the kidney capsule of a normal mouse. Hepatocytes were isolated from human alpha-1 antitrypsin (hA1AT) transgenic mouse livers. Hepatocytes were subsequently transplanted under the kidney capsule space in combination with extracellular matrix components (Matrigel) for engineering liver tissues. The primary outcome of interest was to assess the level of engineering liver tissue function over the experimental period, which was 450 days. Long-term survival by the engineered liver tissue was confirmed by measuring the serum level of hA1AT in the recipient mice throughout the experimental period. In addition, administration of chemical compounds at day 450 resulted in the ability of the engineered liver tissue to metabolize exogenously circulating compounds and induce drug-metabolizing enzyme production. Moreover, we were able to document that the engineered tissues could retain their native regenerative potential similar to that of naïve livers. Overall, these results demonstrated that liver tissues could be engineered at a heterologous site while stably maintaining its functionality for nearly the life span of a normal mouse.

Feeder-independent continuous culture of the PICM-19 pig liver stem cell line

The PICM-19 pig liver stem cell line is a bipotent cell line, i.e., capable of forming either bile ductules or hepatocyte monolayers in vitro, that was derived from the primary culture of pig embryonic stem cells. The cell line has been strictly feeder-dependent in that cell replication, morphology, and function were lost if the cells were cultured without STO feeder cells. A method for the feeder-independent continuous culture of PICM-19 cells (FI-PICM-19) is presented. PICM-19 cells were maintained and grown without feeder cells on collagen I-coated tissue culture plastic for 26 passages (P26) with initial split ratios of 1:3 that diminished to split ratios of less than 1:2 after passage 16. Once plated, the FI-PICM-19 cells were overlaid with a 1:12 to 1:50 dilution of Matrigel or related extracellular matrix product. Growth of the cells was stimulated by daily refeedings with STO feeder-cell conditioned medium. The FI-PICM-19 cells grew to an approximate confluence of 50% prior to each passage at 2-wk intervals. Growth curve analysis showed their average cell number doubling time to be ~96 h. Morphologically, the feeder-independent cells closely resembled PICM-19 cells grown on feeder cells, and biliary canalicui were present at cell-to-cell junctions. However, no spontaneous multicellular ductules formed in the monolayers of FI-PICM-19 cells. Ultrastructural subcellular features of the FI-PICM-19 cells were similar to those of PICM-19 cells cultured on feeder cells. The FI-PICM-19 cells produced a spectrum of serum proteins and expressed many liver/hepatocyte-specific genes. Importantly, cytochrome P450 (EROD) activity, ammonia clearance, and urea production were maintained by the feeder-independent cells. This simple method for the propagation of the PICM-19 cell line without feeder cells should simplify the generation and selection of functional mutants within the population and enhances the cell line's potential for use in toxicological/pharmacological screening assays and for use in an artificial liver device.

Isolation and culture of adult human liver progenitor cells: in vitro differentiation to hepatocyte-like cells

Highly differentiated normal human hepatocytes represent the gold standard cellular model for basic and applied research in liver physiopathology, pharmacology, toxicology, virology, and liver biotherapy. Nowadays, although livers from organ donors or medically required resections represent the current sources of hepatocytes, the possibility to generate hepatocytes from the differentiation of adult and embryonic stem cells represents a promising opportunity. The aim of this chapter is to describe our experience with the isolation from adult human liver and culture of non-parenchymal epithelial cells. Under appropriate conditions, these cells differentiate in vitro in hepatocyte-like cells and therefore appear to behave as liver progenitor cells.

Pig liver xenotransplantation as a bridge to allotransplantation: which patients might benefit?

Acute liver failure is a potentially devastating clinical syndrome that, without liver transplantation (Tx), is associated with high mortality. Rapid deterioration in clinical status and a shortage of deceased human organs prohibits liver Tx in many patients. Bridging to liver Tx has been attempted by various approaches, for example, bioartificial liver support, extracorporeal pig liver perfusion, and hepatocyte Tx, but none of these approaches has convincingly improved patient survival. The orthotopic Tx of a genetically engineered pig liver could theoretically provide successful bridging. Immediate availability, perfect metabolic condition, adequate size-match and hepatocyte mass, and freedom from potentially pathogenic microorganisms could be assured. The advantages and disadvantages of bridging by pig liver Tx compared with other approaches are discussed. The selection of patients for an initial clinical trial of pig liver Tx would be similar to that of various prior trials in patients experiencing rapid and severe deterioration in liver function. The ability to give truly informed consent for a pig bridging procedure at the time of listing for liver Tx renders the patient with acute-on-chronic liver failure or primary allograft failure is a preferable candidate for this procedure than a patient who is admitted urgently with acute (fulminant) liver failure in whom consent may not be possible. Although several barriers to successful pig organ xenoTx remain, for example, coagulation dysfunction between pig and primate, if these can be resolved by further genetic engineering of the organ-source pigs, a pig liver may prove life saving to patients dying rapidly of liver failure.

Direct hepatic differentiation of mouse embryonic stem cells induced by valproic acid and cytokines

AIM: To develop a protocol for direct hepatic lineage differentiation from early developmental progenitors to a population of mature hepatocytes.

METHODS: Hepatic progenitor cells and then mature hepatocytes from mouse embryonic stem (ES) cells were obtained in a sequential manner, induced by valproic acid (VPA) and cytokines (hepatocyte growth factor, epidermal growth factor and insulin). Morphological changes of the differentiated cells were examined by phase-contrast microscopy and electron microscopy. Reverse transcription polymerase chain reaction and immunocytochemical analyses were used to evaluate the gene expression profiles of the VPA-induced hepatic progenitors and the hepatic progenitor-derived hepatocytes. Glycogen storage, cytochrome P450 activity, transplantation assay, differentiation of bile duct-like structures and tumorigenic analyses were performed for the functional identification of the differentiated cells. Furthermore, FACS and electron microscopy were used for the analyses of cell cycle profile and apoptosis in VPA-induced hepatic differentiated cells.

RESULTS: Based on the combination of VPA and cytokines, mouse ES cells differentiated into a uniform and homogeneous cell population of hepatic progenitor cells and then matured into functional hepatocytes. The progenitor population shared several characteristics with ES cells and hepatic stem/progenitor cells, and represented a novel progenitor cell between ES and hepatic oval cells in embryonic development. The differentiated hepatocytes from progenitor cells shared typical characteristics with mature hepatocytes, including the patterns of gene expression, immunological markers, in vitro hepatocyte functions and in vivo capacity to restore acute-damaged liver function. In addition, the differentiation of hepatic progenitor cells from ES cells was accompanied by significant cell cycle arrest and selective survival of differentiating cells towards hepatic lineages.

CONCLUSION: Hepatic cells of different developmental stages from early progenitors to matured hepatocytes can be acquired in the appropriate order based on sequential induction with VPA and cytokines.