Cell therapies for liver diseases

Magnetic Nanostructures and Stem Cells for Regenerative Medicine, Application in Liver Diseases

The term "liver disease" refers to any hepatic condition that leads to tissue damage or altered hepatic function and can be induced by virus infections, autoimmunity, inherited genetic mutations, high consumption of alcohol or drugs, fat accumulation, and cancer. Some types of liver diseases are becoming more frequent worldwide. This can be related to increasing rates of obesity in developed countries, diet changes, higher alcohol intake, and even the coronavirus disease 2019 (COVID-19) pandemic was associated with increased liver disease-related deaths. Although the liver can regenerate, in cases of chronic damage or extensive fibrosis, the recovery of tissue mass is impossible, and a liver transplant is indicated. Because of reduced organ availability, it is necessary to search for alternative bioengineered solutions aiming for a cure or increased life expectancy while a transplant is not possible. Therefore, several groups were studying the possibility of stem cells transplantation as a therapeutic alternative since it is a promising strategy in regenerative medicine for treating various diseases. At the same time, nanotechnological advances can contribute to specifically targeting transplanted cells to injured sites using magnetic nanoparticles. In this review, we summarize multiple magnetic nanostructure-based strategies that are promising for treating liver diseases.

Liver Ultrasound Histotripsy: Novel Analysis of the Histotripsy Site Cell Constituents with Implications for Histotripsy Application in Cell Transplantation and Cancer Therapy

Introduction: Allogenic hepatocyte transplantation is an attractive alternative to whole-organ transplantation, particularly for the treatment of metabolic disorders and acute liver failure. However, the shortage of human donor organs for cell isolation, the low cell yield from decellularisation regimes, and low engraftment rates from portal administration of donor cells have restricted its clinical application. Using ultrasound histotripsy to provide a nidus in the liver for direct cell transplantation offers a new approach to overcoming key limitations in current cell therapy. We have analysed the liver cavity constituents to assess their potential as a site for cell delivery and implantation. Methods: Using human organ retrieval techniques, pig livers were collected from the abattoir and transported in ice-cold storage to the laboratory. Following 2 h of cold storage, the livers were flushed with organ preservation solution and placed on an organ perfusion circuit to maintain viability. Organs were perfused with Soltran™ organ preservation solution via the portal vein at a temperature of 24-30 °C. The perfusion circuit was oxygenated through equilibration with room air. Perfused livers (n=5) were subjected to ultrasound histotripsy, producing a total of 130 lesions. Lesions were generated by applying 50 pulses at 1 Hz pulse repetition frequency and 1% duty cycle using a single element 2 MHz bowl-shaped transducer (Sonic Concepts, H-148). Following histotripsy, a focal liver lesion was produced, which had a liquid centre. The fluid from each lesion was aspirated and cultured in medium (RPMI) at 37 °C in an incubator. Cell cultures were analysed at 1 and 7 days for cell viability and a live-dead assay was performed. The histotripsy sites were excised following aspiration and H&E staining was used to characterise the liver lesions. Cell morphology was determined by histology. Results: Histotripsy created a subcapsular lesion (~5 mm below the liver capsule; size ranging from 3 to 5 mm), which contained a suspension of cells. On average, 61×10⁴ cells per mL were isolated. Hepatocytes were present in the aspirate, were viable at 24 h post isolation and remained viable in culture for up to 1 week, as determined by phalloidin/DAPI cell viability stains. Cultures up to 21 days revealed metabolically active live hepatocyte. Live-dead assays confirmed hepatocyte viability at 1 week (Day 1: 12% to Day 7: 45% live cells; p < 0.0001), which retained metabolic activity and morphology, confirmed on assay and microscopy. Cell Titre-Glo^TM showed a peak metabolic activity at 1 week (average luminescence 24.6 RLU; p < 0.0001) post-culture compared with the control (culture medium alone), reduced to 1/3 of peak level (7.85 RLU) by day 21. Conclusions: Histotripsy of the liver allows isolation and culture of hepatocytes with a high rate of viability after 1 week in culture. Reproducing these findings using human livers may lead to wide clinical applications in cell therapy.

A novel agonist for the HGF receptor MET promotes differentiation of human pluripotent stem cells into hepatocyte-like cells

Hepatocyte growth factor (HGF) is the natural ligand of the MET receptor tyrosine kinase. This ligand-receptor couple is essential for the maturation process of hepatocytes. Previously, the rational design of a synthetic protein based on the assembly of two K1 domains from HGF led to the production of a potent and stable MET receptor agonist. In this study, we compared the effects of K1K1 with HGF during the differentiation of hepatocyte progenitors derived from human induced pluripotent stem cells (hiPSCs). In vitro, K1K1, in the range of 20 to 200 nM, successfully substituted for HGF and efficiently activated ERK downstream signaling. Analysis of the levels of hepatocyte markers showed typical liver mRNA and protein expression (HNF4α, albumin, alpha-fetoprotein, CYP3A4) and phenotypes. Although full maturation was not achieved, the results suggest that K1K1 is an attractive candidate MET agonist suitable for replacing complex and expensive HGF treatments to induce hepatic differentiation of hiPSCs.

Preclinical Experience of the Mayo Spheroid Reservoir Bioartificial Liver (SRBAL) in Management of Acute Liver Failure

The Spheroid Reservoir Bioartificial Liver (SRBAL) is an innovative treatment option for acute liver failure (ALF). This extracorporeal support device, which provides detoxification and other liver functions using high-density culture of porcine hepatocyte spheroids, has been reported in three randomized large animal studies. A meta-analysis of these three preclinical studies was performed to establish efficacy of SRBAL treatment in terms of survival benefit and neuroprotective effect. The studies included two hepatotoxic drug models of ALF (D-galactosamine, α-amanitin/lipopolysaccharide) or a liver resection model (85% hepatectomy) in pigs or monkeys. The SRBAL treatment was started in three different settings starting at 12 h, 24 h or 48 h after induction of ALF; comparisons were made with two similar control groups in each model. SRBAL therapy was associated with significant survival and neuroprotective benefits in all three animal models of ALF. The benefits of therapy were dose dependent with the most effective configuration of SRBAL being continuous treatment of 24 h duration and dose of 200 g of porcine hepatic spheroids. Future clinical testing of SRBAL in patients with ALF appears warranted.

Customizable Microfluidic Origami Liver-on-a-Chip (oLOC)

The design and manufacture of an origami-based liver-on-a-chip device are presented, together with demonstrations of the chip's effectiveness at recapitulating some of the liver's key in vivo architecture, physical microenvironment, and functions. Laser-cut layers of polyimide tape are folded together with polycarbonate nanoporous membranes to create a stack of three adjacent flow chambers separated by the membranes. Endothelial cells are seeded in the upper and lower flow chambers to simulate sinusoids, and hepatocytes are seeded in the middle flow chamber. Nutrients and metabolites flow through the simulated sinusoids and diffuse between the vascular pathways and the hepatocyte layers, mimicking physiological microcirculation. Studies of cell viability, metabolic functions, and hepatotoxicity of pharmaceutical compounds show that the endothelialized liver-on-a-chip model is conducive to maintaining hepatocyte functions and evaluation of the hepatotoxicity of drugs. Our unique origami approach speeds chip development and optimization, effectively simplifying the laboratory-scale fabrication of on-chip models of human tissues without necessarily reducing their structural and functional sophistication.

Biotin-streptavidin sandwich integrated PDA-ZnO@Au nanocomposite based SPR sensor for hIgG detection

SPR is a mature optical biosensor technology for detecting biomolecular interactions without fluorescence or enzyme labeling. In this paper, we acquire a sensitive SPR biosensor based on ZnO@Au nanomaterial, and the classical sandwich strategy using biotin-streptavidin for secondary signal amplification system was used to detect human IgG (hIgG). Nano-zinc oxide (ZnO) has the dual characteristics of nanocomposite and traditional zinc oxide, with large specific surface area and high chemical activity. Besides, the gold-coated ZnO nanocrystals improve the optical properties of ZnO and enlarge the loading capacity with better biocompatibility. Therefore, a sensing platform based on PDA-ZnO@Au nanomaterial was constructed on gold film modified with mercaptan. Meanwhile, the biotin-avidin system in SPR sensor field has been rapidly developed and applied. Due to the highly selection of streptavidin (SA) and biotin interact with each other, GNRs-SA-biotin-Ab₂ (GSAB-Ab₂) were constructed to obtain the secondary enhancement of SPR signal. The influences of experimental conditions were also discussed. With optimal experimental conditions, introducing GSAB-Ab₂ conjugate combined with a sandwich format, the resulting SPR biosensor provides a favourable range for hIgG determination of 0.0375-40 μg mL^-1. The minimum detection concentration of hIgG that can be obtained by this method is approximately 67-fold lower than the conventional SPR sensor based on gold film. The sensitivity of SPR biosensor is significantly improved in a certain range.

Mesenchymal Stromal/Stem Cells and Their Extracellular Vesicles Application in Acute and Chronic Inflammatory Liver Diseases: Emphasizing on the Anti-Fibrotic and Immunomodulatory Mechanisms

Various factors, including viral and bacterial infections, autoimmune responses, diabetes, drugs, alcohol abuse, and fat deposition, can damage liver tissue and impair its function. These factors affect the liver tissue and lead to acute and chronic liver damage, and if left untreated, can eventually lead to cirrhosis, fibrosis, and liver carcinoma. The main treatment for these disorders is liver transplantation. Still, given the few tissue donors, problems with tissue rejection, immunosuppression caused by medications taken while receiving tissue, and the high cost of transplantation, liver transplantation have been limited. Therefore, finding alternative treatments that do not have the mentioned problems is significant. Cell therapy is one of the treatments that has received a lot of attention today. Hepatocytes and mesenchymal stromal/stem cells (MSCs) are used in many patients to treat liver-related diseases. In the meantime, the use of mesenchymal stem cells has been studied more than other cells due to their favourable characteristics and has reduced the need for liver transplantation. These cells increase the regeneration and repair of liver tissue through various mechanisms, including migration to the site of liver injury, differentiation into liver cells, production of extracellular vesicles (EVs), secretion of various growth factors, and regulation of the immune system. Notably, cell therapy is not entirely excellent and has problems such as cell rejection, undesirable differentiation, accumulation in unwanted locations, and potential tumorigenesis. Therefore, the application of MSCs derived EVs, including exosomes, can help treat liver disease and prevent its progression. Exosomes can prevent apoptosis and induce proliferation by transferring different cargos to the target cell. In addition, these vesicles have been shown to transport hepatocyte growth factor (HGF) and can promote the hepatocytes'(one of the most important cells in the liver parenchyma) growths.

A bioinspired scaffold for rapid oxygenation of cell encapsulation systems

Inadequate oxygenation is a major challenge in cell encapsulation, a therapy which holds potential to treat many diseases including type I diabetes. In such systems, cellular oxygen (O2) delivery is limited to slow passive diffusion from transplantation sites through the poorly O2-soluble encapsulating matrix, usually a hydrogel. This constrains the maximum permitted distance between the encapsulated cells and host site to within a few hundred micrometers to ensure cellular function. Inspired by the natural gas-phase tracheal O2 delivery system of insects, we present herein the design of a biomimetic scaffold featuring internal continuous air channels endowed with 10,000-fold higher O2 diffusivity than hydrogels. We incorporate the scaffold into a bulk hydrogel containing cells, which facilitates rapid O2 transport through the whole system to cells several millimeters away from the device-host boundary. A computational model, validated by in vitro analysis, predicts that cells and islets maintain high viability even in a thick (6.6 mm) device. Finally, the therapeutic potential of the device is demonstrated through the correction of diabetes in immunocompetent mice using rat islets for over 6 months.

Implanted subcutaneous versus intraperitoneal bioscaffold seeded with hepatocyte-like cells: functional evaluation

Background and objectives

The X-linked bleeding disorder, hemophilia A, is caused by defective production of factor VIII (FVIII). Hemophilic patients require regular FVIII infusions. Recombinant factor replacement poses the safest line of therapy. However, its main drawbacks are high expenses and the higher liability for formation of inhibitors. Recent studies confirmed the ability of bone marrow-derived stem cells to secrete FVIII. This study aims to generate bioscaffold from decellularized liver and subsequently seed it with trans-differentiated human stem cells into hepatic-like cells. This scaffold can then be implanted intraperitoneally or subcutaneously to provide FVIII.

Methods

After generation of the bioscaffold, seeding of discoid scaffolds with trans-differentiated human hepatocyte-like cells was performed. Then, the generated organoid was implanted into peritoneal cavity or subcutaneous tissue of experimental rats.

Results

Serum human FVIII was significantly increased in rats subjected to subcutaneous implantation compared intraperitoneal implantation. Immunostaining for detecting Cytokeratin 19 and human anti-globulin confirmed the presence of mature human hepatocytes that were significantly increased in subcutaneous implanted scaffold compared to the intraperitoneal one.

Conclusion

Implantation of decellularized bioscaffold seeded with trans-differentiated stem cells in rats was successful to establish production of FVIII. Subcutaneous implantation showed higher FVIII levels than intraperitoneal implantation.

Preparation of cell aggregates incorporating gelatin hydrogel microspheres of sugar-responsive water solubilization

The objective of this study is to design hydrogel microspheres of a cell scaffold, which not only function as a scaffold to form cell aggregates of three-dimensional culture but also can disappear to release growth factors in the well-controlled manner by noncytotoxic stimulation in any timing. The hydrogel microspheres were prepared by a water-in-oil emulsion method from m-aminophenylboronic acid (APBA)-introduced gelatin (APBA-gelatin) with or without poly(vinyl alcohol) (PVA) mixing. Irrespective of the PVA concentration, the microspheres with the same diameter were prepared. The microspheres were water solubilized only by adding sorbitol of a sugar although the solubilization extent depended on the PVA concentration. When cocultured with the microspheres, mesenchymal stem cells formed cell aggregates homogeneously incorporating the microspheres. Upon adding sorbitol in the culture medium, mixed APBA-gelatin-PVA hydrogel microspheres disappeared with time in the cell aggregates. The microspheres containing basic fibroblast growth factor or bone morphogenetic protein-2 released the respective growth factor accompanied with the microspheres disappearance. It is concluded that the present microspheres of sugar-responsive water solubilization are promising scaffold of cell aggregates and have an ability to allow growth factors to be released in the cell aggregates when it is required.

Perspective of placenta derived mesenchymal stem cells in acute liver failure

Acute Liver failure (ALF) is a life-threatening disease and is determined by coagulopathy (with INR ≥ 1.5) and hepatic encephalopathy as a result of severe liver injury in patients without preexisting liver disease. Since there are problems with liver transplantation including lack of donors, use of immunosuppressive drugs, and high costs of this process, new therapeutic approaches alongside current treatments are needed. The placenta is a tissue that is normally discarded after childbirth. On the other hand, human placenta is a rich source of mesenchymal stem cells (MSCs), which is easily available, without moral problems, and its derived cells are less affected by age and environmental factors. Therefore, placenta-derived mesenchymal stem cells (PD-MSCs) can be considered as an allogeneic source for liver disease. Considering the studies on MSCs and their effects on various diseases, it can be stated that MSCs are among the most important agents to be used for novel future therapies of liver diseases. In this paper, we will investigate the effects of mesenchymal stem cells through migration and immigration to the site of injury, cell-to-cell contact, immunomodulatory effects, and secretory factors in ALF.

In vitro differentiation of rhesus macaque bone marrow- and adipose tissue-derived MSCs into hepatocyte-like cells

Orthotopic liver or hepatocyte transplantation is effective for the treatment of acute liver injury and end-stage chronic liver disease. However, both of these therapies are hampered by the extreme shortage of organ donors. The clinical application of cell therapy through the substitution of hepatocytes with mesenchymal stem cells (MSCs) that have been differentiated into hepatocyte-like cells (HLCs) for liver disease treatment is expected to overcome this shortage. Bone marrow and adipose tissue are two major sources of MSCs [bone marrow-derived MSCs (BM-MSCs) and adipose tissue-derived MSCs (AT-MSCs), respectively]. However, knowledge about the variability in the differentiation potential between BM-MSCs and AT-MSCs is lacking. In the present study, the hepatogenic differentiation potential of rhesus macaque BM-MSCs and AT-MSCs was compared with the evaluation of morphology, immunophenotyping profiles, differentiation potential, glycogen deposition, urea secretion and hepatocyte-specific gene expression. The results indicated that BM-MSCs and AT-MSCs shared similar characteristics in terms of primary morphology, surface markers and trilineage differentiation potential (adipogenesis, osteogenesis and chondrogenesis). Subsequently, the hepatogenic differentiation potential of BM-MSCs and AT-MSCs was evaluated by morphology, glycogen accumulation, urea synthesis and expression of hepatocyte marker genes. The results indicated that rhesus BM-MSCs and AT-MSCs had hepatogenic differentiation ability. To the best of our knowledge, this is the first report to detect the hepatogenic differentiation potential of rhesus macaque BM-MSCs and AT-MSCs. The present study provides the basis for the selection of seed cells that can trans-differentiate into HLCs for cytotherapy of acute or chronic liver injuries in either clinical or veterinary practice.

Human-relevant preclinical in vitro models for studying hepatobiliary development and liver diseases using induced pluripotent stem cells

IMPACT STATEMENT

In this review, we address the potential of human-induced pluripotent stem cell-based hepatobiliary differentiation technology as a means to study human liver development and cell fate determination, and to model liver diseases in an effort to develop a new human-relevant preclinical platform for drug development.

Therapeutic Potential of Autologous Adipose-Derived Stem Cells for the Treatment of Liver Disease

Currently, the most effective therapy for liver diseases is liver transplantation, but its use is limited by organ donor shortage, economic reasons, and the requirement for lifelong immunosuppression. Mesenchymal stem cell (MSC) transplantation represents a promising alternative for treating liver pathologies in both human and veterinary medicine. Interestingly, these pathologies appear with a common clinical and pathological profile in the human and canine species; as a consequence, dogs may be a spontaneous model for clinical investigations in humans. The aim of this work was to characterize canine adipose-derived MSCs (cADSCs) and compare them to their human counterpart (hADSCs) in order to support the application of the canine model in cell-based therapy of liver diseases. Both cADSCs and hADSCs were successfully isolated from adipose tissue samples. The two cell populations shared a common fibroblast-like morphology, expression of stemness surface markers, and proliferation rate. When examining multilineage differentiation abilities, cADSCs showed lower adipogenic potential and higher osteogenic differentiation than human cells. Both cell populations retained high viability when kept in PBS at controlled temperature and up to 72 h, indicating the possibility of short-term storage and transportation. In addition, we evaluated the efficacy of autologous ADSCs transplantation in dogs with liver diseases. All animals exhibited significantly improved liver function, as evidenced by lower liver biomarkers levels measured after cells transplantation and evaluation of cytological specimens. These beneficial effects seem to be related to the immunomodulatory properties of stem cells. We therefore believe that such an approach could be a starting point for translating the results to the human clinical practice in future.

Cytokinome of adult-derived human liver stem/progenitor cells: immunological and inflammatory features

Background

Being non-immunogenic and capable of achieving major metabolic liver functions, adult-derived human liver stem/progenitor cells (ADHLSCs) are of special interest in the field of liver cell therapy. The cytokine repertoire of engrafted cells may have critical impacts on the immune response balance, particularly during cell transplantation.

Methods

In this work, we analyzed the cytokinome of ADHLSCs during hepatogenic differentiation (HD) following stimulation with a mixture of inflammatory cytokines (I) in vitro and compared it to that of mature hepatocytes.

Results

Independent of their hepatic state, ADHLSCs showed no constitutive expression of pro-inflammatory cytokines, which were significantly induced by inflammation (IL-1β, IL-6, IL-8, TNFα, CCL5, IL-12a, IL-12b, IL-23p19, IL-27p28 and EBI-3). IL1-RA and IDO-1, as immunoregulatory cytokines, were highly induced in undifferentiated ADHLSCs, whereas TGF-β was downregulated by both hepatic and inflammatory events. Interestingly, TDO-1 was exclusively expressed in ADHLSCs after hepatic differentiation and enhanced by inflammatory cytokines. Compared to mature hepatocytes, hepatic-differentiated ADHLSCs showed significantly different cytokine expression patterns.

Conclusions

By establishing the cytokinome of ADHLSCs and highlighting their immunological and inflammatory features, we can enhance our knowledge about the safety and efficiency of the transplantation strategy.

Conditioned Media Derived from Human Adipose Tissue Mesenchymal Stromal Cells Improves Primary Hepatocyte Maintenance

Objective

Recent advances in cell therapy have encouraged researchers to provide an alternative for treatment and restoration of damaged liver through using hepatocytes. However, these cells quickly lose their functional capabilities in vitro. Here, we aim to use the secretome of mesenchymal stromal cells (MSCs) to improve in vitro maintenance conditions for hepatocytes.

Materials and Methods

In this experimental study, following serum deprivation, human adipose tissue-derived MSCs (hAT-MSCs) were cultured for 24 hours under normoxic (N) and hypoxic (H) conditions. Their conditioned media (CM) were subsequently collected and labeled as N-CM (normoxia) and H-CM (hypoxia). Murine hepatocytes were isolated by perfusion of mouse liver with collagenase, and were cultured in hepatocyte basal (William’s) medium supplemented with 4% N-CM or H-CM. Untreated William’s and hepatocyte-specific media (HepZYM) were used as controls. Finally, we evaluated the survival and proliferation rates, as well as functionality and hepatocyte-specific gene expressions of the cells.

Results

We observed a significant increase in viability of hepatocytes in the presence of N-CM and H-CM compared to HepZYM on day 5, as indicated by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)- 2H-tetrazolium) assay. Indocyanine green (ICG) uptake of hepatocytes in the H-CM and HepZYM groups on days 3 and 5 also suggested that H-CM maintained the hepatocytes at about the same level as the hepatocyte-specific medium. The HepZYM group had significantly higher levels of albumin (Alb) and urea secretion compared to the other groups (P<0.0001). However, there were no significant differences in cytochrome activity and cytochrome gene expression profiles among these groups. Finally, we found a slightly, but not significantly higher concentration of vascular endothelial growth factor (VEGF) in the H-CM group compared to the N-CM group (P=0.063).

Conclusion

The enrichment of William’s basal medium with 4% hAT-MSC-H-CM improved some physiologic parameters in a primary hepatocyte culture.

Vascularized microfluidic organ-chips for drug screening, disease models and tissue engineering

Vascularization of micro-tissues in vitro has enabled formation of tissues larger than those limited by diffusion with appropriate nutrient/gas exchange as well as waste elimination. Furthermore, angiocrine signaling from the vasculature may be essential in mimicking organ-level functions in these micro-tissues. In drug screening applications, the presence of an appropriate blood-organ barrier in the form of a vasculature and its supporting cells (pericytes, appropriate stromal cells) may be essential to reproducing organ-scale drug delivery pharmacokinetics. Cutting-edge techniques including 3D bioprinting and in vitro angiogenesis and vasculogenesis could be applied to vascularize a range of tissues and organoids. Herein, we describe the latest developments in vascularization and prevascularization of micro-tissues and provide an outlook on potential future strategies.

Leveraging Engineering of Cells for Drug Delivery

Cell therapy has become a momentum-gathering treatment strategy for a variety of diseases, including cancer, diabetes, hemophilia, and cardiomyopathy. However, clinical applications of conventional cell therapies have often been compromised by rapid decline in viability and function of the transplanted cells due to host recognition and subsequent foreign body rejection. Along this line, cell engineering technologies such as cell encapsulation within microcapsules and immobilization in porous scaffolds have been implemented to address the immunosuppression concerns. As a recent emerging research topic, drawing inspiration from the ways that natural cells interact with the body has opened new avenues for cell engineering, such as direct modification of whole cells with synthetic materials and "top-down" integration of biological membranes with micro/nanomaterials, which aim to alleviate immune response while harnessing the complex biological functions of cells. In this Account, we summarize our recent contribution to the field of cell engineering methodologies, with which we have demonstrated their promising applications for cancer immunotherapy, targeted drug delivery, and blood glucose regulation. For example, inspired by the inherent ability of platelets to accumulate at wound sites and interact with circulating tumor cells, we exploited a targeted checkpoint antibody delivery strategy for treatment of postsurgical cancer recurrence and metastatic spread by covalent binding of platelets' cell surfaces with a monoclonal antibody against programmed-death ligand 1 (aPDL1). Without interfering with the platelets' surgical-site homing property, the conjugated aPDL1 could be triggered to release in the form of microparticles after in situ activation. As an extension, we then engineered the platelet membrane to cloak nanoparticles for anticancer drug delivery, mimicking the targeting capability of the source cells while possessing prolonged circulation lifetime and insignificant immunogenicity. At the same time, we also found that the subcellular compartment membrane-derived particulates exhibited high specificity toward homotypic cells, by which enhanced intracellular drug delivery was achieved. Moreover, by taking advantage of the reversible interaction between glucose-derivative-modified insulin and the red blood cell membrane, we constructed a glucose-responsive smart insulin delivery system for long-term maintenance of blood glucose levels within a normal range. Recently, by virtue of painless microneedle patches as convenient cell engineering platforms, a minimally invasive intradermal antitumor vaccine was invented by integrating whole-tumor lysis into near-infrared light-illuminated microneedle patches. The microneedle patches also showed promise in combining with conventional cell encapsulation techniques, by which an externally positioned β-cell engineering strategy was proposed for diabetes treatment. The results presented in this Account demonstrate distinct approaches to the development and application of cell engineering strategies for drug delivery.

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

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

Liver tissue engineering: From implantable tissue to whole organ engineering

The term “liver tissue engineering” summarizes one of the ultimate goals of modern biotechnology: the possibility of reproducing in total or in part the functions of the liver in order to treat acute or chronic liver disorders and, ultimately, create a fully functional organ to be transplanted or used as an extracorporeal device. All the technical approaches in the area of liver tissue engineering are based on allocating adult hepatocytes or stem cell‐derived hepatocyte‐like cells within a three‐dimensional structure able to ensure their survival and to maintain their functional phenotype. The hosting structure can be a construct in which hepatocytes are embedded in alginate and/or gelatin or are seeded in a pre‐arranged scaffold made with different types of biomaterials. According to a more advanced methodology termed three‐dimensional bioprinting, hepatocytes are mixed with a bio‐ink and the mixture is printed in different forms, such as tissue‐like layers or spheroids. In the last decade, efforts to engineer a cell microenvironment recapitulating the dynamic native extracellular matrix have become increasingly successful, leading to the hope of satisfying the clinical demand for tissue (or organ) repair and replacement within a reasonable timeframe. Indeed, the preclinical work performed in recent years has shown promising results, and the advancement in the biotechnology of bioreactors, ex vivo perfusion machines, and cell expansion systems associated with a better understanding of liver development and the extracellular matrix microenvironment will facilitate and expedite the translation to technical applications. (Hepatology Communications 2018;2:131–141)

Immuno-biological comparison of hepatic stellate cells in a reverted and activated state

Human hepatic stellate cells (HSCs) demonstrated great immunological plasticity with important consequences for liver cell therapy. Activated HSCs (aHSCs) are in vitro reverted (rHSCs) to a quiescent-like phenotype with potential benefit to reduce liver fibrosis. The goal of this study is to establish and compare the immunological profile of activated and in vitro reverted HSCs and to investigate the impact of inflammatory priming on the immunobiology of both HSCs populations. The distribution of inflammatory primed activated and reverted HSCs across the different phases of the cell cycle is assessed by flow cytometry. In addition, Flow analysis was done to assess the expression level of neuronal, endothelial and stromal markers, cell adhesion molecules, human leucocyte antigens, co-stimulatory molecules, immunoregulatory molecules and natural killer ligands. Our results showed that the cell cycle distribution of both HSCs populations is significantly modulated by inflammation. Accordingly, activated HSC that were in G1 phase switch to S- and G2 phases when exposed to inflammation, while reverted HSCs mostly redistribute into sub-G0 phase. In a HSC state dependent manner, inflammatory priming modulated the expression of the stromal marker CD90, biological receptors (CD95 and CD200R), cell adhesion molecules (CD29, CD54, CD58, CD106 and CD166), human leucocyte antigen HLA-G, co-stimulatory molecules (CD40 and CD252), as well as the immunoregulatory molecules (CD200 and CD274). In conclusion, the immunologic profile of HSCs is significantly modulated by their activation state and inflammation and is important for the development of novel HSC liver cell-based therapy.

Paracrine Effects of Bone Marrow Mononuclear Cells in Survival and Cytokine Expression after 90% Partial Hepatectomy

Acute liver failure is a complex and fatal disease. Cell-based therapies are a promising alternative therapeutic approach for liver failure due to relatively simple technique and lower cost. The use of semipermeable microcapsules has become an interesting tool for evaluating paracrine effects in vivo. In this study, we aimed to assess the paracrine effects of bone marrow mononuclear cells (BMMC) encapsulated in sodium alginate to treat acute liver failure in an animal model of 90% partial hepatectomy (90% PH). Encapsulated BMMC were able to increase 10-day survival without enhancing liver regeneration markers. Gene expression of Il-6 and Il-10 in the remnant liver was markedly reduced at 6 h after 90% PH in animals receiving encapsulated BMMC compared to controls. This difference, however, was neither reflected by changes in the number of CD68+ cells nor by serum levels of IL6. On the other hand, treated animals presented increased caspase activity and gene expression in the liver. Taken together, these results suggest that BMMC regulate immune response and promote apoptosis in the liver after 90% PH by paracrine factors. These changes ultimately may be related to the higher survival observed in treated animals, suggesting that BMMC may be a promising alternative to treat acute liver failure.

Regenerative Medicine and the Biliary Tree

Despite decades of basic research, biliary diseases remain prevalent, highly morbid, and notoriously difficult to treat. We have, however, dramatically increased our understanding of biliary developmental biology, cholangiocyte pathophysiology, and the endogenous mechanisms of biliary regeneration and repair. All of this complex and rapidly evolving knowledge coincides with an explosion of new technological advances in the area of regenerative medicine. New breakthroughs such as induced pluripotent stem cells and organoid culture are increasingly being applied to the biliary system; it is only a matter of time until new regenerative therapeutics for the cholangiopathies are unveiled. In this review, the authors integrate what is known about biliary development, regeneration, and repair, and link these conceptual advances to the technological breakthroughs that are collectively driving the emergence of a new global field in biliary regenerative medicine.

Generation of functional hepatocytes from human spermatogonial stem cells

To generate functional human hepatocytes from stem cells and/or extra-hepatic tissues could provide an important source of cells for treating liver diseases. Spermatogonial stem cells (SSCs) have an unlimited plasticity since they can dedifferentiate and transdifferentiate to other cell lineages. However, generation of mature and functional hepatocytes from human SSCs has not yet been achieved. Here we have for the first time reported direct transdifferentiation of human SSCs to mature and functional hepatocytes by three-step induction using the defined condition medium. Human SSCs were first transdifferentiated to hepatic stem cells, as evidenced by their morphology and biopotential nature of co-expressing hepatocyte and cholangiocyte markers but not hallmarks for embryonic stem cells. Hepatic stem cells were further induced to differentiate into mature hepatocytes identified by their morphological traits and strong expression of CK8, CK18, ALB, AAT, TF, TAT, and cytochrome enzymes rather than CK7 or CK19. Significantly, mature hepatocytes derived from human SSCs assumed functional attributes of human hepatocytes, because they could produce albumin, remove ammonia, and uptake and release indocyanine green. Moreover, expression of β-CATENIN, HNF4A, FOXA1 and GATA4 was upregulated during the transdifferentiation of human SSCs to mature hepatocytes. Collectively, human SSCs could directly transdifferentiate to mature and functional hepatocytes. This study could offer an invaluable source of human hepatocytes for curing liver disorders and drug toxicology screening and provide novel insights into mechanisms underlying human liver regeneration.

Hedgehog Signaling Overcomes an EZH2-Dependent Epigenetic Barrier to Promote Cholangiocyte Expansion

BACKGROUND & AIMS

Developmental morphogens play an important role in coordinating the ductular reaction and portal fibrosis occurring in the setting of cholangiopathies. However, little is known about how membrane signaling events in ductular reactive cells (DRCs) are transduced into nuclear transcriptional changes to drive cholangiocyte maturation and matrix deposition. Therefore, the aim of this study was to investigate potential mechanistic links between cell signaling events and epigenetic regulators in DRCs.

METHODS

Using directed differentiation of induced pluripotent stem cells (iPSC), isolated DRCs, and in vivo models, we examine the mechanisms whereby sonic hedgehog (Shh) overcomes an epigenetic barrier in biliary precursors and promotes both cholangiocyte maturation and deposition of fibronectin (FN).

RESULTS

We demonstrate, for the first time, that Gli1 influences the differentiation state and fibrogenic capacity of iPSC-derived hepatic progenitors and isolated DRCs. We outline a novel pathway wherein Shh-mediated Gli1 binding in key cholangiocyte gene promoters overcomes an epigenetic barrier conferred by the polycomb protein, enhancer of zeste homolog 2 (EZH2) and initiates the transcriptional program of cholangiocyte maturation. We also define previously unknown functional Gli1 binding sites in the promoters of cytokeratin (CK)7, CK19, and FN. Our in vivo results show that EZH2 KO mice fed the choline-deficient, ethanolamine supplemented (CDE) diet have an exaggerated cholangiocyte expansion associated with more robust ductular reaction and increased peri-portal fibrosis.

CONCLUSION

We conclude that Shh/Gli1 signaling plays an integral role in cholangiocyte maturation in vitro by overcoming an EZH2-dependent epigenetic barrier and this mechanism also promotes biliary expansion in vivo.

Cell Therapy for Liver Disease Using Bioimaging Rats

Advances in stem cell research suggest that cell therapy is a potential alternative to liver transplantation. The use of individualized and minimally invasive cell therapy is desirable to avoid rejection and reduce patient burden. While allo-hepatocyte transplantation has been performed for metabolic hepatic disease, auto-bone marrow transplantation (BMT) has shifted toward mesenchymal stem cells (MSCs) transplantation for liver cirrhosis. In this article, an overview of cell transplantation research for liver disease is provided through our recent rat studies. We have developed various kinds of rat imaging models and have evaluated the effect of cell therapy for liver disease. Bone marrow cells (BMCs) of the Alb-DsRed2 rat were transplanted via the portal vein (PV) in acute and chronic liver damage models. The number of Alb-DsRed2⁺ albumin-producing cells increased, and the size of the cells increased in the chronic liver damage model as well as in the acute liver damage model. Luciferase transgenic (luc-Tg) rat hepatocytes were transplanted into the hepatectomized LEW rat via the PV. Luminescence intensity lasted for 2 months in the hepatectomized rat. BMCs obtained from green fluorescent protein (GFP) Tg rats were transplanted repeatedly via the PV using an implanted catheter with a port. Repeated BMT via the PV reduced the liver fibrosis. Adipocyte-derived MSCs from the luc-Tg rat were transplanted into the hepatectomized rat model via the PV after ischemic reperfusion. MSCs inhibited hepatocyte apoptosis and promoted liver regeneration. Transplanting the optimal number of cells by an effective and safe way is important for clinical application. Bioimaging rats are a powerful tool for cell transplantation research because it makes observation of the in vivo kinetics of transplanted cells possible. Cell transplantation research using bioimaging rats contributes greatly to evaluating effective methods of cell therapy.

Differentiation of human foreskin fibroblast-derived induced pluripotent stem cells into hepatocyte-like cells

The aim of this study was to investigate the differentiation potential of induced pluripotent stem cells (iPSCs) derived from human foreskin fibroblasts (HFFs) into hepatocyte-like cells (HLCs). The iPSCs were firstly induced by transduction of OCT4, SOX2, KLF4, and c-MYC into HFFs using retrovirus. Afterwards, expressions of pluripotency factors were identified by semiquantitative reverse transcription-polymerase chain reaction and immunofluorescence staining, and karyotype, embryoid, and teratoma were observed by microscope. Then, iPSCs were gradually differentiated into endoderm cells, hepatic progenitor cells, and mature HLCs by special culture medium. During this process, differentiation efficiency into each kind of cells was evaluated by detecting SOX17, HNF4a, and ALB using flow cytometry, respectively. Besides, enzyme-linked immunosorbent assay was conducted to detect the secretion of ALB in iPSC-induced HLCs and quantitative reverse transcription-polymerase chain reaction was performed to detect the expression levels of hepatocyte-specific genes. The iPSCs were successfully induced by HFFs, which exhibited typical embryonic stem cells morphology, positive alkaline phosphatase staining, normal diploid karyotype, and positive expression of various pluripotency factors. Meanwhile, spherical embryoid and teratoma with 3 germ layers were formed by iPSCs. The iPSCs were consecutively induced into endoderm cells, hepatic progenitor cells and mature HLCs, and the differentiation efficiency was 55.7 ± 2.9%, 45.7 ± 4.8%, and 35.0 ± 3.9%, respectively. Besides, the secretion of ALB and expression of various hepatocyte-specific genes was highly detected in iPSC-induced HLCs. The iPSCs were successfully derived from HFFs and then differentiated into HLCs, which proved a new source for hepatocyte transplantation.

HIGHLIGHTS

HFFs were successfully induced into iPSCs by transduction of OCT4, SOX2, KLF4, and c-MYC. Positive expressions of various pluripotency factors were exhibited in HFFs-induced iPSCs. The iPSCs were consecutively induced into endoderm cells, hepatic progenitor cells, and mature HLCs. Various hepatocyte-specific genes were highly expressed in iPSC-induced HLCs.

Human Hepatic HepaRG Cells Maintain an Organotypic Phenotype with High Intrinsic CYP450 Activity/Metabolism and Significantly Outperform Standard HepG2/C3A Cells for Pharmaceutical and Therapeutic Applications

Conventional in vitro human hepatic models for drug testing are based on the use of standard cell lines derived from hepatomas or primary human hepatocytes (PHHs). Limited availability, interdonor functional variability and early phenotypic alterations in PHHs restrict their use, whilst standard cell lines such as HepG2 lack a substantial and variable set of liver‐specific functions such as CYP450 activity. Alternatives include the HepG2‐derivative C3A cells selected as a more differentiated and metabolically active hepatic phenotype. Human HepaRG cells are an alternative organotypic co‐culture model of hepatocytes and cholangiocytes reported to maintain in vivo‐like liver‐specific functions, including intact Phase I–III drug metabolism. In this study, we compared C3A and human HepaRG cells using phenotypic profiling, CYP450 activity and drug metabolism parameters to assess their value as hepatic models for pre‐clinical drug testing or therapeutics. Compared with C3As, HepaRG co‐cultures exhibit a more organotypic phenotype, including evidence of hepatic polarity with the strong expression of CYP3A4, the major isoform involved in the metabolism of over 60% of marketed drugs. Significantly greater CYP450 activity and expression of CYP1A2, CYP2E1 and CYP3A4 genes in HepaRG cells (comparable with that of human liver tissue) was demonstrated. Moreover, HepaRG cells also preferentially expressed the hepatic integrin α₅β₁ – an important modulator of cell behaviour including growth and survival, differentiation and polarity. Drug metabolite profiling of phenacetin (CYP1A2) and testosterone (CYP3A4) using LC‐MS/MS and HPLC, respectively, revealed that HepaRGs had more intact (Phase I–II) metabolism profile. Thus, HepaRG cells significantly outperform C3A cells for the potential pharmaceutical and therapeutic applications.

Heparin-gelatin mixture improves vascular reconstruction efficiency and hepatic function in bioengineered livers

Whole organ decellularization is a cell removal process that creates a natural extracellular matrix for use in transplantation. A lack of an intact endothelial layer in the vascular network of decellularized organs results in blood clotting even with anti-coagulation treatment. Furthermore, shear stress caused by blood flow may affect reseeded parenchymal cells. We hypothesized that a heparin-gelatin mixture (HG) can act as an antithrombotic coating reagent and induce attachment and migration of endothelial cells (ECs) on vascular wall surfaces within decellularized livers, with subsequent parenchymal cell function enhancement. Portal vein (PV) perfusion was performed for right lateral lobe decellularization of porcine livers. We tested if HG-precoating of isolated decellularized PV could increase EC attachment and migration. Additionally, we coated PV and hepatic artery walls in decellularized liver with HG, and then repopulated it with ECs and maintained it under vascular flow in a bioreactor for 10days. Re-endothelialized scaffolds were perfused with porcine blood for thrombogenicity evaluation. We then co-cultured hepatocellular carcinoma (HepG2) cells and ECs to evaluate the effect of endothelialization on parenchymal cells. Finally, we transplanted these scaffolds heterotopically in pigs. HG improved ECs' ability to migrate and adhere to vessel discs. ECs efficiently covered the vascular compartments within decellularized scaffolds and maintained function and proliferation after HG-precoating. No thrombosis was observed after 24h blood perfusion in HG-precoated scaffolds, indicating an efficiently endothelialized vascular tree. HepG2 cells displayed a higher function in scaffolds endothelialized after HG-precoating compared to uncoated scaffolds in vitro and after in vivo transplantation. Our results lay the groundwork for engineering human-sized whole-liver scaffolds for clinical applications.

STATEMENT OF SIGNIFICANCE

A major obstacle to successful organ bioengineering is vasculature reconstruction to avoid thrombosis and deliver nutrients through blood to the whole scaffold after in vivo transplantation. Although many attempts have been made to construct endothelial cell layers on the vascular network within decellularized organs, complete coverage has not be achieved. Here, we describe an effective approach for endothelial cell seeding to reconstruct a patent vascular tree within decellularized livers by coating the vasculature using heparin-gelatin mixture. Our results have demonstrate that enhancement of endothelial cell attachment by heparin-gelatin treatment could improve vascular patency and parenchymal cell function in vitro and in vivo. These results represent a significant advancement toward bioengineering functional liver tissue that maintains vascular patency for transplantation.

Hepatocyte cell therapy in liver disease

Liver disease is a leading cause of morbidity and mortality. Liver transplantation remains the only proven treatment for end-stage liver failure but is limited by the availability of donor organs. Hepatocyte cell therapy, either with bioartificial liver devices or hepatocyte transplantation, may help address this by delaying or preventing liver transplantation. Early clinical studies have shown promising results, however in most cases, the benefit has been short lived and so further research into these therapies is required. Alternative sources of hepatocytes, including stem cell-derived hepatocytes, are being investigated as the isolation of primary human hepatocytes is limited by the same shortage of donor organs. This review summarises the current clinical experience of hepatocyte cell therapy together with an overview of possible alternative sources of hepatocytes. Current and future areas for research that might lead towards the realisation of the full potential of hepatocyte cell therapy are discussed.

A Patient-Inspired Ex Vivo Liver Tissue Engineering Approach with Autologous Mesenchymal Stem Cells and Hepatogenic Serum

Design and development of ex vivo bioengineered liver tissue substitutes intended for subsequent in vivo implantation has been considered therapeutically relevant to treat many liver diseases that require whole-organ replacement on a long-term basis. The present study focus on patient-inspired ex vivo liver tissue engineering strategy to generate hepatocyte-scaffold composite by combining bone marrow mesenchymal stem cells (BMSCs) derived from cardiac failure patients with secondary hyperbilirubinemia as primers of hepatic differentiation and hepatocyte growth factor (HGF)-enriched sera from same individuals as hepatic inducer. A biodegradable and implantable electrospun fibrous mesh of poly-l-lactic acid (PLLA) and gelatin is used as supporting matrix (average fiber diameter = 285 ± 64 nm, porosity = 81 ± 4%, and average pore size = 1.65 ± 0.77 μm). The fibrous mesh supports adhesion, proliferation, and hepatic commitment of patient-derived BMSCs of adequate stemness using HGF-enriched sera generating metabolically competent hepatocyte-like cells, which is comparable to the hepatic induction with defined recombinant growth factor cocktail. The observed results confirm the combinatorial effects of nanofiber topography and biochemical cues in guiding hepatic specification of BMSCs. The fibrous mesh-hepatocyte construct developed in this study using natural growth factors and BMSCs of same individual is promising for future therapeutic applications in treating damaged livers.

Improvement of Liver Cell Therapy in Rats by Dietary Stearic Acid

BACKGROUND

Stearic acid is known as a potent anti-inflammatory lipid. This fatty acid has profound and diverse effects on liver metabolism. The aim of this study was to investigate the effect of stearic acid on markers of hepatocyte transplantation in rats with acetaminophen (APAP)-induced liver damage.

METHODS

Wistar rats were randomly assigned to 10-day treatment. Stearic acid was administered to the rats with APAP-induced liver damage. The isolated liver cells were infused intraperitoneally into rats. Blood samples were obtained to evaluate the changes in the serum liver enzymes, including activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) and the level of serum albumin. To assess the engraftment of infused hepatocytes, rats were euthanized, and the liver DNA was used for PCR using sex-determining region Y (SRY) primers.

RESULTS

The levels of AST, ALT and ALP in the serum of rats with APAP-induced liver injury were significantly increased and returned to the levels in control group by day six. The APAP-induced decrease in albumin was significantly improved in rats through cell therapy, when compared with that in the APAP-alone treated rats. SRY PCR analysis showed the presence of the transplanted cells in the liver of transplanted rats.

CONCLUSION

Stearic acid-rich diet in combination with cell therapy accelerates the recovering of hepatic dysfunction in a rat model of liver injury.

A robust model of natural hepatitis C infection using hepatocyte-like cells derived from human induced pluripotent stem cells as a long-term host

BACKGROUND

Hepatitis C virus (HCV) could induce chronic liver diseases and hepatocellular carcinoma in human. The use of primary human hepatocyte as a viral host is restrained with the scarcity of tissue supply. A culture model restricted to HCV genotype 2a (JFH-1) has been established using Huh7-derived hepatocyte. Other genotypes including the wild-type virus could not propagate in Huh7, Huh7.5 and Huh7.5.1 cells.

METHODS

Functional hepatocyte-like cells (HLCs) were developed from normal human iPS cells as a host for HCV infection. Mature HLCs were identified for selective hepatocyte markers, CYP450s, HCV associated receptors and HCV essential host factors. HLCs were either transfected with JFH-1 HCV RNA or infected with HCV particles derived from patient serum. The enhancing effect of α-tocopherol and the inhibitory effects of INF-α, ribavirin and sofosbuvir to HCV infection were studied. The HCV viral load and HCV RNA were assayed for the infection efficiency.

RESULTS

The fully-developed HLCs expressed phase I, II, and III drug-metabolizing enzymes, HCV associated receptors (claudin-1, occludin, CD81, ApoE, ApoB, LDL-R) and HCV essential host factors (miR-122 and SEC14L2) comparable to the primary human hepatocyte. SEC14L2, an α-tocopherol transfer protein, was expressed in HLCs, but not in Huh7 cell, had been implicated in effective HCVser infection. The HLCs permitted not only the replication of HCV RNA, but also the production of HCV particles (HCVcc) released to the culture media. HLCs drove higher propagation of HCVcc derived from JFH-1 than did the classical host Huh7 cells. HLCs infected with either JFH-1 or wild-type HCV expressed HCV core antigen, NS5A, NS5B, NS3 and HCV negative-stand RNA. HLCs allowed entire HCV life cycle derived from either JFH-1, HCVcc or wild-type HCV (genotype 1a, 1b, 3a, 3b, 6f and 6n). Further increasing the HCVser infection in HLCs was achieved by incubating cell with α-tocopherol. The supernatant from infected HLCs could infect both naïve HLC and Huh7 cell. Treating infected HLC with INF-α and ribavirin decreased HCV RNA in both the cellular fraction and the culture medium. The HLCs reacted to HCVcc or wild-type HCV infection by upregulating TNF-α, IL-28B and IL-29.

CONCLUSIONS

This robust cell culture model for serum-derived HCV using HLCs as host cells provides a remarkable system for investigating HCV life cycle, HCV-associated hepatocellular carcinoma development and the screening for new anti HCV drugs.

Immunological aspects of liver cell transplantation

Within the field of regenerative medicine, the liver is of major interest for adoption of regenerative strategies due to its well-known and unique regenerative capacity. Whereas therapeutic strategies such as liver resection and orthotopic liver transplantation (OLT) can be considered standards of care for the treatment of a variety of liver diseases, the concept of liver cell transplantation (LCTx) still awaits clinical breakthrough. Success of LCTx is hampered by insufficient engraftment/long-term acceptance of cellular allografts mainly due to rejection of transplanted cells. This is in contrast to the results achieved for OLT where long-term graft survival is observed on a regular basis and, hence, the liver has been deemed an immune-privileged organ. Immune responses induced by isolated hepatocytes apparently differ considerably from those observed following transplantation of solid organs and, thus, LCTx requires refined immunological strategies to improve its clinical outcome. In addition, clinical usage of LCTx but also related basic research efforts are hindered by the limited availability of high quality liver cells, strongly emphasizing the need for alternative cell sources. This review focuses on the various immunological aspects of LCTx summarizing data available not only for hepatocyte transplantation but also for transplantation of non-parenchymal liver cells and liver stem cells.

Functional genetics-directed identification of novel pharmacological inhibitors of FAS- and TNF-dependent apoptosis that protect mice from acute liver failure

shRNA-mediated gene-silencing technology paired with cell-based functional readouts reveals potential targets directly, providing an opportunity to identify drugs against the target without knowing the precise role of the target in the pathophysiological processes of interest. By screening a lentiviral shRNA library targeting for major components of human signaling pathways and known drug targets, we identified and validated both canonical as well as 52 novel mediators of FAS and TNF ligand-induced apoptosis. Presence of potential therapeutic targets among these mediators was confirmed by demonstration of in vivo activity of siRNAs against four identified target candidates that protected mice from acute liver failure (ALF), a life-threatening disease with known involvement of death receptor (DR)-mediated apoptosis. Network-based modeling was used to predict small-molecule inhibitors for several candidate apoptosis mediators, including somatostatin receptor 5 (SSTR5) and a regulatory subunit of PP2A phosphatase, PPP2R5A. Remarkably, pharmacological inhibition of either SSTR5 or PPP2R5A reduced apoptosis induced by either FASL or TNF in cultured cells and dramatically improved survival in several mouse models of ALF. These results demonstrate the utility of loss-of-function genetic screens and network-based drug-repositioning methods for expedited identification of targeted drug candidates and revealed pharmacological agents potentially suitable for treatment of DR-mediated pathologies.

MicroRNA Regulates Hepatocytic Differentiation of Progenitor Cells by Targeting YAP1

MicroRNA expression profiling in human liver progenitor cells following hepatocytic differentiation identified miR-122 and miR-194 as the microRNAs most strongly upregulated during hepatocytic differentiation of progenitor cells. MiR-194 was also highly upregulated following hepatocytic differentiation of human embryonic stem cells (hESCs). Overexpression of miR-194 in progenitor cells accelerated their differentiation into hepatocytes, as measured by morphological features such as canaliculi and expression of hepatocytic markers. Overexpression of miR-194 in hESCs induced their spontaneous differentiation, a phenotype accompanied with accelerated loss of the pluripotent factors OCT4 and NANOG and decrease in mesoderm marker HAND1 expression. We then identified YAP1 as a direct target of miR-194. Inhibition of YAP1 strongly induced hepatocytic differentiation of progenitor cells and YAP1 overexpression reversed the miR-194-induced hepatocytic differentiation of progenitor cells. In conclusion, we identified miR-194 as a potent inducer of hepatocytic differentiation of progenitor cells and further identified YAP1 as a mediator of miR-194's effects on hepatocytic differentiation and liver progenitor cell fate. Stem Cells 2016;34:1284-1296.

Stem Cells in Aggregate Form to Enhance Chondrogenesis in Hydrogels

There are a variety of exciting hydrogel technologies being explored for cartilage regenerative medicine. Our overall goal is to explore whether using stem cells in an aggregate form may be advantageous in these applications. 3D stem cell aggregates hold great promise as they may recapitulate the in vivo skeletal tissue condensation, a property that is not typically observed in 2D culture. We considered two different stem cell sources, human umbilical cord Wharton’s jelly cells (hWJCs, currently being used in clinical trials) and rat bone marrow-derived mesenchymal stem cells (rBMSCs). The objective of the current study was to compare the influence of cell phenotype, aggregate size, and aggregate number on chondrogenic differentiation in a generic hydrogel (agarose) platform. Despite being differing cell sources, both rBMSC and hWJC aggregates were consistent in outperforming cell suspension control groups in biosynthesis and chondrogenesis. Higher cell density impacted biosynthesis favorably, and the number of aggregates positively influenced chondrogenesis. Therefore, we recommend that investigators employing hydrogels consider using cells in an aggregate form for enhanced chondrogenic performance.

Adipose-derived stem cells: A candidate for liver regeneration

The scarcity of donor livers and the impracticality of hepatocyte transplantation represent the biggest obstacles for the treatment of liver failure. Adipose-derived stem cells, with their ability to differentiate into the hepatic lineage, provide a reliable alternative cell source with clear ethical and practical advantages. Moreover, adipose-derived stem cells can effectively repair liver damage by the dominant indirect pattern and increase the number of hepatocytes by the secondary direct pattern. In recent years, the development of the indirect pattern, which mainly includes immunomodulatory and trophic effects, has become a hot topic in the field of cell engineering. Therefore, adipose-derived stem cells are considered to be ideal therapeutic stem cells for human liver regeneration. In this article, we reviewed the advantages of adipose-derived stem cells in liver regeneration, and explore their underlying mechanisms.

Long Term Liver Engraftment of Functional Hepatocytes Obtained from Germline Cell-Derived Pluripotent Stem Cells

One of the major hurdles in liver gene and cell therapy is availability of ex vivo-expanded hepatocytes. Pluripotent stem cells are an attractive alternative. Here, we show that hepatocyte precursors can be isolated from male germline cell-derived pluripotent stem cells (GPSCs) using the hepatoblast marker, Liv2, and induced to differentiate into hepatocytes in vitro. These cells expressed hepatic-specific genes and were functional as demonstrated by their ability to secrete albumin and produce urea. When transplanted in the liver parenchyma of partially hepatectomised mice, Liv2-sorted cells showed regional and heterogeneous engraftment in the injected lobe. Moreover, approximately 50% of Y chromosome-positive, GPSC-derived cells were found in the female livers, in the region of engraftment, even one month after cell injection. This is the first study showing that Liv2-sorted GPSCs-derived hepatocytes can undergo long lasting engraftment in the mouse liver. Thus, GPSCs might offer promise for regenerative medicine.

Pivotal preclinical trial of the spheroid reservoir bioartificial liver

BACKGROUND & AIMS

The neuroprotective effect of the spheroid reservoir bioartificial liver (SRBAL) was evaluated in a porcine model of drug-overdose acute liver failure (ALF).

METHODS

Healthy pigs were randomized into three groups (standard therapy (ST) alone, ST+No-cell device, ST+SRBAL device) before placement of an implantable intracranial pressure (ICP) monitor and a tunneled central venous catheter. One week later, pigs received bolus infusion of the hepatotoxin D-galactosamine and were followed for up to 90h.

RESULTS

At 48h, all animals had developed encephalopathy and biochemical changes confirming ALF; extracorporeal treatment was initiated and pigs were observed up to 90h after drug infusion. Pigs treated with the SRBAL, loaded with porcine hepatocyte spheroids, had improved survival (83%, n=6) compared to ST alone (0%, n=6, p=0.003) and No-cell device therapy (17%, n=6, p=0.02). Ammonia detoxification, peak levels of serum ammonia and peak ICP, and pig survival were influenced by hepatocyte cell dose, membrane pore size and duration of SRBAL treatment. Hepatocyte spheroids remained highly functional with no decline in mean oxygen consumption from initiation to completion of treatment.

CONCLUSIONS

The SRBAL improved survival in an allogeneic model of drug-overdose ALF. Survival correlated with ammonia detoxification and ICP lowering indicating that hepatocyte spheroids prevented the cerebral manifestations of ALF (brain swelling, herniation, death). Further investigation of SRBAL therapy in a clinical setting is warranted.

Cell-based therapy approaches: the hope for incurable diseases

Cell therapies aim to repair the mechanisms underlying disease initiation and progression, achieved through trophic effect or by cell replacement. Multiple cell types can be utilized in such therapies, including stem, progenitor or primary cells. This review covers the current state of cell therapies designed for the prominent disorders, including cardiovascular, neurological (Parkinson's disease, amyotrophic lateral sclerosis, stroke, spinal cord injury), autoimmune (Type 1 diabetes, multiple sclerosis, Crohn's disease), ophthalmologic, renal, liver and skeletal (osteoarthritis) diseases. Various cell therapies have reached advanced clinical trial phases with potential marketing approvals in the near future, many of which are based on mesenchymal stem cells. Advances in pluripotent stem cell research hold great promise for regenerative medicine. The information presented in this review is based on the analysis of the cell therapy collection detailed in LifeMap Discovery(®) (LifeMap Sciences Inc., USA) the database of embryonic development, stem cell research and regenerative medicine.

Development and characterization of human-induced pluripotent stem cell-derived cholangiocytes

Cholangiocytes are the target of a heterogeneous group of liver diseases known as the cholangiopathies. An evolving understanding of the mechanisms driving biliary development provides the theoretical underpinnings for rational development of induced pluripotent stem cell (iPSC)-derived cholangiocytes (iDCs). Therefore, the aims of this study were to develop an approach to generate iDCs and to fully characterize the cells in vitro and in vivo. Human iPSC lines were generated by forced expression of the Yamanaka pluripotency factors. We then pursued a stepwise differentiation strategy toward iDCs, using precise temporal exposure to key biliary morphogens, and we characterized the cells, using a variety of morphologic, molecular, cell biologic, functional, and in vivo approaches. Morphology shows a stepwise phenotypic change toward an epithelial monolayer. Molecular analysis during differentiation shows appropriate enrichment in markers of iPSC, definitive endoderm, hepatic specification, hepatic progenitors, and ultimately cholangiocytes. Immunostaining, western blotting, and flow cytometry demonstrate enrichment of multiple functionally relevant biliary proteins. RNA sequencing reveals that the transcriptome moves progressively toward that of human cholangiocytes. iDCs generate intracellular calcium signaling in response to ATP, form intact primary cilia, and self-assemble into duct-like structures in three-dimensional culture. In vivo, the cells engraft within mouse liver, following retrograde intrabiliary infusion. In summary, we have developed a novel approach to generate mature cholangiocytes from iPSCs. In addition to providing a model of biliary differentiation, iDCs represent a platform for in vitro disease modeling, pharmacologic testing, and individualized, cell-based, regenerative therapies for the cholangiopathies.

Noninvasive 3-dimensional imaging of liver regeneration in a mouse model of hereditary tyrosinemia type 1 using the sodium iodide symporter gene

Cell transplantation is a potential treatment for the many liver disorders that are currently only curable by organ transplantation. However, one of the major limitations of hepatocyte (HC) transplantation is an inability to monitor cells longitudinally after injection. We hypothesized that the thyroidal sodium iodide symporter (NIS) gene could be used to visualize transplanted HCs in a rodent model of inherited liver disease: hereditary tyrosinemia type 1. Wild-type C57Bl/6J mouse HCs were transduced ex vivo with a lentiviral vector containing the mouse Slc5a5 (NIS) gene controlled by the thyroxine-binding globulin promoter. NIS-transduced cells could robustly concentrate radiolabeled iodine in vitro, with lentiviral transduction efficiencies greater than 80% achieved in the presence of dexamethasone. Next, NIS-transduced HCs were transplanted into congenic fumarylacetoacetate hydrolase knockout mice, and this resulted in the prevention of liver failure. NIS-transduced HCs were readily imaged in vivo by single-photon emission computed tomography, and this demonstrated for the first time noninvasive 3-dimensional imaging of regenerating tissue in individual animals over time. We also tested the efficacy of primary HC spheroids engrafted in the liver. With the NIS reporter, robust spheroid engraftment and survival could be detected longitudinally after direct parenchymal injection, and this thereby demonstrated a novel strategy for HC transplantation. This work is the first to demonstrate the efficacy of NIS imaging in the field of HC transplantation. We anticipate that NIS labeling will allow noninvasive and longitudinal identification of HCs and stem cells in future studies related to liver regeneration in small and large preclinical animal models.

Hepatocyte transplantation attenuates the course of acute liver failure induced by thioacetamide in Lewis rats

Acute liver failure (ALF) is a clinical syndrome resulting from widespread damage of hepatocytes, with extremely high mortality rate. Urgent orthotopic liver transplantation was shown to be the most effective therapy for ALF but this treatment option is limited by scarcity of donor organs. Therefore, hepatocyte transplantation (Tx) has emerged as a new therapeutical measure for ALF, however, the first clinical applications proved unsatisfactory. Apparently, extensive preclinical studies are needed. Our aim was to examine if hepatocytes isolated from transgenic "firefly luciferase" Lewis rats into the recipient liver would attenuate the course of thioacetamide (TAA)-induced ALF in Lewis rats. Untreated Lewis rats after TAA administration showed a profound decrease in survival rate; no animal survived 54 h. The rats showed marked increases in plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, in plasma level of bilirubin and ammonia (NH(3)), and in a significant decrease in plasma albumin. Hepatocyte Tx attenuated the course of TAA-induced ALF Lewis rats which was reflected by improved survival rate and reduced degree of liver injury showing as lowering of elevated plasma ALT, AST, NH(3) and bilirubin levels and increasing plasma albumin. In addition, bioluminescence imaging analyses have shown that in the TAA-damaged livers the transplanted hepatocyte were fully viable throughout the experiment. In conclusion, the results show that hepatocyte Tx into the liver can attenuate the course of TAA-induced ALF in Lewis rats. This information should be considered in attempts to develop new therapeutic approaches to the treatment of ALF.

Proceedings: moving toward cell-based therapies for liver disease

Despite available medical therapy and organ transplantation, a significant unmet medical need remains for the treatment of liver failure, end-stage liver disease, and liver-based inborn errors of metabolism. Liver cell transplantation has the potential to address this need; however, the field is in search of a suitable cell therapeutic. The ability to reproducibly generate a well-characterized source of engraftable and functional liver cells has continued to be a challenge. Recent progress with tissue-derived stem/progenitor cells and pluripotent stem cell-derived cells now offers the field the opportunity to address this challenge.

Implications of differential stress response activation following non-frozen hepatocellular storage

Hepatocytes are critical for numerous cell therapies and in vitro investigations. A limiting factor for their use in these applications is the ability to process and preserve them without loss of viability or functionality. Normal rat hepatocytes (NHEPs) and human hepatoma (C3A) cells were stored at either 4°C or 37°C to examine post-processing stress responses. Resveratrol and salubrinal were used during storage to determine how targeted molecular stress pathway modulation would affect cell survival. This study revealed that storage outcome is dependent upon numerous factors including: cell type, storage media, storage length, storage temperature, and chemical modulator. These data implicate a molecular-based stress response that is not universal but is specific to the set of conditions under which cells are stored. Further, these findings allude to the potential for targeted protection or destruction of particular cell types for numerous applications, from diagnostic cell selection to cell-based therapy. Ultimately, this study demonstrates the need for further in-depth molecular investigations into the cellular stress response to bioprocessing and preservation.

Efficient large-scale generation of functional hepatocytes from mouse embryonic stem cells grown in a rotating bioreactor with exogenous growth factors and hormones

Introduction

Embryonic stem (ES) cells are considered a potentially advantageous source of hepatocytes for both transplantation and the development of bioartificial livers. However, the efficient large-scale generation of functional hepatocytes from ES cells remains a major challenge, especially for those methods compatible with clinical applications.

Methods

In this study, we investigated whether a large number of functional hepatocytes can be differentiated from mouse ES (mES) cells using a simulated microgravity bioreactor. mES cells were cultured in a rotating bioreactor in the presence of exogenous growth factors and hormones to form embryoid bodies (EBs), which then differentiated into hepatocytes.

Results

During the rotating culture, most of the EB-derived cells gradually showed the histologic characteristics of normal hepatocytes. More specifically, the expression of hepatic genes and proteins was detected at a higher level in the differentiated cells from the bioreactor culture than in cells from a static culture. On further growing, the EBs on tissue-culture plates, most of the EB-derived cells were found to display the morphologic features of hepatocytes, as well as albumin synthesis. In addition, the EB-derived cells grown in the rotating bioreactor exhibited higher levels of liver-specific functions, such as glycogen storage, cytochrome P450 activity, low-density lipoprotein, and indocyanine green uptake, than did differentiated cells grown in static culture. When the EB-derived cells from day-14 EBs and the cells’ culture supernatant were injected into nude mice, the transplanted cells were engrafted into the recipient livers.

Conclusions

Large quantities of high-quality hepatocytes can be generated from mES cells in a rotating bioreactor via EB formation. This system may be useful in the large-scale generation of hepatocytes for both cell transplantation and the development of bioartificial livers.