Cell sources, liver support systems and liver tissue engineering: alternatives to liver transplantation

A review on the application of chitosan-based polymers in liver tissue engineering

Chitosan-based polymers have enormous structural tendencies to build bioactive materials with novel characteristics, functions, and various applications, mainly in liver tissue engineering (LTE). The specific physicochemical, biological, mechanical, and biodegradation properties give the effective ways to blend these biopolymers with synthetic and natural polymers to fabricate scaffolds matrixes, sponges, and complexes. A variety of natural and synthetic biomaterials, including chitosan (CS), alginate (Alg), collagen (CN), gelatin (GL), hyaluronic acid (HA), hydroxyapatite (HAp), polyethylene glycol (PEG), polycaprolactone (PCL), poly(lactic-co-glycolic) acid (PGLA), polylactic acid (PLA), and silk fibroin gained considerable attention due to their structure-properties relationship. The incorporation of CS within the polymer matrix results in increased mechanical strength and also imparts biological behavior to the designed PU formulations. The significant and growing interest in the LTE sector, this review aims to be a detailed exploration of CS-based polymers biomaterials for LTE. A brief explanation of the sources and extraction, properties, structure, and scope of CS is described in the introduction. After that, a full overview of the liver, its anatomy, issues, hepatocyte transplantation, LTE, and CS LTE applications are discussed.

Pluripotent Stem Cell-Derived Hepatocyte-like Cells: Induction Methods and Applications

The development of regenerative medicine provides new options for the treatment of end-stage liver diseases. Stem cells, such as bone marrow mesenchymal stem cells, embryonic stem cells, and induced pluripotent stem cells (iPSCs), are effective tools for tissue repair in regenerative medicine. iPSCs are an appropriate source of hepatocytes for the treatment of liver disease due to their unlimited multiplication capacity, their coverage of the entire range of genetics required to simulate human disease, and their evasion of ethical implications. iPSCs have the ability to gradually produce hepatocyte-like cells (HLCs) with homologous phenotypes and physiological functions. However, how to induce iPSCs to differentiate into HLCs efficiently and accurately is still a hot topic. This review describes the existing approaches for inducing the differentiation of iPSCs into HLCs, as well as some challenges faced, and summarizes various parameters for determining the quality and functionality of HLCs. Furthermore, the application of iPSCs for in vitro hepatoprotective drug screening and modeling of liver disease is discussed. In conclusion, iPSCs will be a dependable source of cells for stem-cell therapy to treat end-stage liver disease and are anticipated to facilitate individualized treatment for liver disease in the future.

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

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

Role of three-dimensional printing and artificial intelligence in the management of hepatocellular carcinoma: Challenges and opportunities

Hepatocellular carcinoma (HCC) constitutes the fifth most frequent malignancy worldwide and the third most frequent cause of cancer-related deaths. Currently, treatment selection is based on the stage of the disease. Emerging fields such as three-dimensional (3D) printing, 3D bioprinting, artificial intelligence (AI), and machine learning (ML) could lead to evidence-based, individualized management of HCC. In this review, we comprehensively report the current applications of 3D printing, 3D bioprinting, and AI/ML-based models in HCC management; we outline the significant challenges to the broad use of these novel technologies in the clinical setting with the goal of identifying means to overcome them, and finally, we discuss the opportunities that arise from these applications. Notably, regarding 3D printing and bioprinting-related challenges, we elaborate on cost and cost-effectiveness, cell sourcing, cell viability, safety, accessibility, regulation, and legal and ethical concerns. Similarly, regarding AI/ML-related challenges, we elaborate on intellectual property, liability, intrinsic biases, data protection, cybersecurity, ethical challenges, and transparency. Our findings show that AI and 3D printing applications in HCC management and healthcare, in general, are steadily expanding; thus, these technologies will be integrated into the clinical setting sooner or later. Therefore, we believe that physicians need to become familiar with these technologies and prepare to engage with them constructively.

Design and Characterization of a Bioinspired Polyvinyl Alcohol Matrix with Structural Foam-Wall Microarchitectures for Potential Tissue Engineering Applications

Traditional medical soft matrix used in a surgical treatment or in wound management was not good enough in both the structural support and interconnectivity to be applied in tissue engineering as a scaffold. Avian skeleton and feather rachises might be good reference objects to mimic in designing a scaffold material with good structural support and high interconnectivity because of its structural foam-wall microarchitectures and structural pneumaticity. In this study, a biomimetic airstream pore-foaming process was built up and the corresponding new medical soft matrix derived from polyvinyl alcohol matrix (PVAM) with air cavities inspired by avian skeleton and feather rachises was prepared. Furthermore, the resulting medical soft matrix and bovine Achilles tendon type I collagen could be employed to prepare a new collagen-containing composite matrix. Characterization, thermal stability and cell morphology of the bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix with open-cell foam-wall microarchitectures were studied for evaluation of potential tissue engineering applications. TGA, DTG, DSC, SEM and FTIR results of new bioinspired PVA matrix were employed to build up the effective system identification approach for biomimetic structure, stability, purity, and safety of target soft matrix. The bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix would be conductive to human hepatoblastoma HepG2 cell proliferation, migration, and expression which might serve as a promising liver cell culture carrier to be used in the biological artificial liver reactor.

Single cell Raman spectroscopy to identify different stages of proliferating human hepatocytes for cell therapy

Background

Cell therapy provides hope for treatment of advanced liver failure. Proliferating human hepatocytes (ProliHHs) were derived from primary human hepatocytes (PHH) and as potential alternative for cell therapy in liver diseases. Due to the continuous decline of mature hepatic genes and increase of progenitor like genes during ProliHHs expanding, it is challenge to monitor the critical changes of the whole process. Raman microspectroscopy is a noninvasive, label free analytical technique with high sensitivity capacity. In this study, we evaluated the potential and feasibility to identify ProliHHs from PHH with Raman spectroscopy.

Methods

Raman spectra were collected at least 600 single spectrum for PHH and ProliHHs at different stages (Passage 1 to Passage 4). Linear discriminant analysis and a two-layer machine learning model were used to analyze the Raman spectroscopy data. Significant differences in Raman bands were validated by the associated conventional kits.

Results

Linear discriminant analysis successfully classified ProliHHs at different stages and PHH. A two-layer machine learning model was established and the overall accuracy was at 84.6%. Significant differences in Raman bands have been found within different ProliHHs cell groups, especially changes at 1003 cm⁻¹, 1206 cm⁻¹ and 1440 cm⁻¹. These changes were linked with reactive oxygen species, hydroxyproline and triglyceride levels in ProliHHs, and the hypothesis were consistent with the corresponding assay results.

Conclusions

In brief, Raman spectroscopy was successfully employed to identify different stages of ProliHHs during dedifferentiation process. The approach can simultaneously trace multiple changes of cellular components from somatic cells to progenitor cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02619-9.

Regenerative Medicine of Liver: Promises, Advances and Challenges

Liver tissue engineering is a rapidly developing field which combines the novel use of liver cells, appropriate biochemical factors, and engineering principles, in order to replace or regenerate damaged liver tissue or the organ. The aim of this review paper is to critically investigate different possible methods to tackle issues related with liver diseases/disorders mainly using regenerative medicine. In this work the various regenerative treatment options are discussed, for improving the prognosis of chronic liver disorders. By reviewing existing literature, it is apparent that the current popular treatment option is liver transplantation, although the breakthroughs of stem cell-based therapy and bioartificial liver technology make them a promising alternative.

Progress of 3D Bioprinting in Organ Manufacturing

Three-dimensional (3D) bioprinting is a family of rapid prototyping technologies, which assemble biomaterials, including cells and bioactive agents, under the control of a computer-aided design model in a layer-by-layer fashion. It has great potential in organ manufacturing areas with the combination of biology, polymers, chemistry, engineering, medicine, and mechanics. At present, 3D bioprinting technologies can be used to successfully print living tissues and organs, including blood vessels, skin, bones, cartilage, kidney, heart, and liver. The unique advantages of 3D bioprinting technologies for organ manufacturing have improved the traditional medical level significantly. In this article, we summarize the latest research progress of polymers in bioartificial organ 3D printing areas. The important characteristics of the printable polymers and the typical 3D bioprinting technologies for several complex bioartificial organs, such as the heart, liver, nerve, and skin, are introduced.

Xenogeneic stem cell transplantation: Research progress and clinical prospects

Organ transplantation is the ultimate treatment for end-stage diseases such as heart and liver failure. However, the severe shortage of donor organs has limited the organ transplantation progress. Xenogeneic stem cell transplantation provides a new strategy to solve this problem. Researchers have shown that xenogeneic stem cell transplantation has significant therapeutic effects and broad application prospects in treating liver failure, myocardial infarction, advanced type 1 diabetes mellitus, myelosuppression, and other end-stage diseases by replacing the dysfunctional cells directly or improving the endogenous regenerative milieu. In this review, the sources, problems and solutions, and potential clinical applications of xenogeneic stem cell transplantation will be discussed.

Tissue Engineering Strategies for Cancer-Related Lymphedema

Tissue engineering has witnessed remarkable advancement in various fields of medicine and has the potential of revolutionizing the management of lymphedema. Combining approaches of biotechnology with the evolving understanding of lymphangiogenesis may offer promising treatment modalities for patients suffering from lymphedema. The strategies to lymphatic vessels tissue engineer can be grouped into four main categories: Delivery of chemokines, cytokines, and other growth factors to induce lymphangiogenesis; cell-based approach using lymphatic endothelial cells or stem-cells; scaffold-based tissue engineering; or a combination of these. This review will summarize the current approach to cancer-related lymphedema and advances in lymphatic tissue engineering strategies and the challenges facing the regeneration of lymphatic vasculature, particularly in an oncologic setting.

The Role of the Microenvironment in Controlling the Fate of Bioprinted Stem Cells

The field of tissue engineering and regenerative medicine has made numerous advances in recent years in the arena of fabricating multifunctional, three-dimensional (3D) tissue constructs. This can be attributed to novel approaches in the bioprinting of stem cells. There are expansive options in bioprinting technology that have become more refined and specialized over the years, and stem cells address many limitations in cell source, expansion, and development of bioengineered tissue constructs. While bioprinted stem cells present an opportunity to replicate physiological microenvironments with precision, the future of this practice relies heavily on the optimization of the cellular microenvironment. To fabricate tissue constructs that are useful in replicating physiological conditions in laboratory settings, or in preparation for transplantation to a living host, the microenvironment must mimic conditions that allow bioprinted stem cells to proliferate, differentiate, and migrate. The advances of bioprinting stem cells and directing cell fate have the potential to provide feasible and translatable approach to creating complex tissues and organs. This review will examine the methods through which bioprinted stem cells are differentiated into desired cell lineages through biochemical, biological, and biomechanical techniques.

Three dimensional polyvinyl alcohol scaffolds modified with collagen for HepG2 cell culture

The creation of in vitro functional hepatic tissue simulating micro environmental niche of the native liver is a keen area of research due to its demand in bioartificial liver. However, it is still unclear how to maintain benign cell function while achieving the sufficient cell quantity. In this work, we aim to prepare a novel scaffold for the culture of HepG2 cells, a liver cell line, by modifying polyvinyl alcohol (PVA) scaffold with collagen (COL). PVA is a kind of synthetic biostable polymer with high hydrophilicity in the human body, has been widely used in the biomedical field. However, the use of PVA is limited in cell cultures due to lack of biologically active functional groups. In this study, amino silane (KH-550), glutaraldehyde and native type I collagen were used to modify three-dimensional PVA scaffold to establish a suitable composite scaffold for hepatocyte culture. Three types of composite scaffolds were prepared for different collagen content, named as PVA/COL (0.2%), PVA/COL (0.5%) and PVA/COL (0.8%), respectively. The composite scaffolds were characterized by SEM, XPS, FTIR, MS, porosity estimation and water contact angle measurement. The PVA/COL (0.8%) scaffolds had the highest collagen content of 12.13%. The composite scaffold showed high porosity with interconnected pores. Furthermore, the biocompatibility between HepG2 cells and scaffolds was evaluated by the ability of cell proliferation, albumin secretion, as well as urea synthesis. The coating of collagen on PVA scaffolds promoted hydrophilicity and HepG2 cell adhesion. Additionally, enhanced cell proliferation, increased albumin secretion and urea synthesis were observed in HepG2 cells growing on collagen-coated three-dimensional PVA scaffolds.

Liver regeneration and alcoholic liver disease

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

Regulated differentiation of stem cells into an artificial 3D liver as a transplantable source

End-stage liver disease is one of the leading causes of death around the world. Since insufficient sources of transplantable liver and possible immune rejection severely hinder the wide application of conventional liver transplantation therapy, artificial three-dimensional (3D) liver culture and assembly from stem cells have become a new hope for patients with end-stage liver diseases, such as cirrhosis and liver cancer. However, the induced differentiation of single-layer or 3D-structured hepatocytes from stem cells cannot physiologically support essential liver functions due to the lack of formation of blood vessels, immune regulation, storage of vitamins, and other vital hepatic activities. Thus, there is emerging evidence showing that 3D organogenesis of artificial vascularized liver tissue from combined hepatic cell types derived from differentiated stem cells is practical for the treatment of end-stage liver diseases. The optimization of novel biomaterials, such as decellularized matrices and natural macromolecules, also strongly supports the organogenesis of 3D tissue with the desired complex structure. This review summarizes new research updates on novel differentiation protocols of stem cell-derived major hepatic cell types and the application of new supportive biomaterials. Future biological and clinical challenges of this concept are also discussed.

Pluripotent-Stem-Cell-Derived Hepatic Cells: Hepatocytes and Organoids for Liver Therapy and Regeneration

The liver is a very complex organ that ensures numerous functions; it is thus susceptible to multiple types of damage and dysfunction. Since 1983, orthotopic liver transplantation (OLT) has been considered the only medical solution available to patients when most of their liver function is lost. Unfortunately, the number of patients waiting for OLT is worryingly increasing, and extracorporeal liver support devices are not yet able to counteract the problem. In this review, the current and expected methodologies in liver regeneration are briefly analyzed. In particular, human pluripotent stem cells (hPSCs) as a source of hepatic cells for liver therapy and regeneration are discussed. Principles of hPSC differentiation into hepatocytes are explored, along with the current limitations that have led to the development of 3D culture systems and organoid production. Expected applications of these organoids are discussed with particular attention paid to bio artificial liver (BAL) devices and liver bio-fabrication.

Tissue Engineering in Liver Regenerative Medicine: Insights into Novel Translational Technologies

Organ and tissue shortage are known as a crucially important public health problem as unfortunately a small percentage of patients receive transplants. In the context of emerging regenerative medicine, researchers are trying to regenerate and replace different organs and tissues such as the liver, heart, skin, and kidney. Liver tissue engineering (TE) enables us to reproduce and restore liver functions, fully or partially, which could be used in the treatment of acute or chronic liver disorders and/or generate an appropriate functional organ which can be transplanted or employed as an extracorporeal device. In this regard, a variety of techniques (e.g., fabrication technologies, cell-based technologies, microfluidic systems and, extracorporeal liver devices) could be applied in tissue engineering in liver regenerative medicine. Common TE techniques are based on allocating stem cell-derived hepatocyte-like cells or primary hepatocytes within a three-dimensional structure which leads to the improvement of their survival rate and functional phenotype. Taken together, new findings indicated that developing liver tissue engineering-based techniques could pave the way for better treatment of liver-related disorders. Herein, we summarized novel technologies used in liver regenerative medicine and their future applications in clinical settings.

HGF Gene Delivering Alginate/Galactosylated Chitosan Sponge Scaffold for Three-Dimensional Coculture of Hepatocytes/3T3 Cells

Gene delivery from tissue engineering scaffold is a novel strategy in regulating long-term growth and function of cells in vitro culture. In this study, a hepatocyte growth factor plasmid/polyetherimide (pHGF/PEI) polyplex delivering alginate (AL)/galactosylated chitosan (GC) (pHGF/PEI-AL/GC) sponge scaffold was prepared for the in vitro coculture of hepatocytes/3T3 cells. The pHGF/PEI polyplex released for 6 days in the sponge scaffold with weight ratio of AL/GC being 3:1 and fixed amount of pHGF being 40 μg (24-well scaffold). In addition, the 3T3 cells culturing in the pHGF/PEI-AL/GC sponge scaffold could be continually transfected and expressed the exogenous HGF for 6 days. Furthermore, the albumin secretion and urea synthesis of hepatocytes were significantly enhanced when cocultured with 3T3 cells in the pHGF/PEI-AL/GC sponge scaffold compared with that in the AL/GC sponge without pHGF. In summary, the preparation of AL/GC sponge scaffold delivering pHGF/PEI polyplex is a critical significance for maintaining the long-term survival and function of primary hepatocytes in vitro.

The Effect of Vascular Endothelial Growth Factor on Bone Marrow Mesenchymal Stem Cell Engraftment in Rat Fibrotic Liver upon Transplantation

Background

According to existing related experiments and research reports, stem cell transplantation therapy has been shown to have a positive effect on the recovery of liver fibrosis/cirrhosis, but for some reason, this therapy still cannot be widely used in clinical work. One of the reasons that cannot be ignored is the low quantity of exogenous stem cells transplanted into the liver in vivo. Thus, we investigated whether the use of the vascular endothelial growth factor (VEGF) can increase the number of stem cell transplants and improve the efficacy of stem cell transplantation therapy.

Methods

Using a Sprague-Dawley rat liver fibrosis model, we transplanted into fibrosis liver allograft bone marrow mesenchymal stem cells (BMSCs) which were labelled with chlormethylbenzamido-1,1-dioctadecyl-3,3,3′3′-tetramethylin-docarbocyamine (CM-DiI) or injected VEGF adenovirus solution through the tail vein or conducted the above two operations simultaneously. The cell surface receptor profile of BMSC was examined by flow cytometry and immunofluorescence staining. Hepatic sinusoidal vascular leakage was measured with Evan's blue dye assay. Paraffin section staining, immunofluorescent staining, RT-qPCR (quantitative reverse transcription polymerase chain reaction), and Western blot were used to evaluate hepatic pathological changes and physiology function.

Result

The in vivo study indicated that, comparing with other groups of rats, the rats with combined treatment of BMSC transplantation and VEGF injection exhibited obvious reduction in liver fibrosis. Evan's blue dye assay suggests that after injecting with VEGF adenovirus solution, the rat's hepatic sinusoidal permeability would be increased. We confirmed the expression of very late antigen-4 (VLA4, integrin α₄β₁) on rat BMSCs and the elevated expression of vascular adhesion molecule-1 (VCAM-1) in the hepatic sinusoidal endothelial cells. In addition, the analysis of CM-DiI-labeled BMSCs showed that the BMSC+VEGF group exhibited better cell engraftment and that the engrafted cells were mainly distributed in the hepatic parenchyma. Furthermore, compared with the other situation, it is best to reconstitute the liver secretion and regeneration function of rats after combined application of VEGF and BMSC.

Conclusion

We showed that VEGF promotes the engraftment of BMSCs in liver fibrosis, enhances liver regeneration, and improves liver function. These outcomes may be related to the increasing hepatic sinusoidal endothelium permeability and VCAM-1-increased expression.

Graphene-based 3D scaffolds in tissue engineering: fabrication, applications, and future scope in liver tissue engineering

Tissue engineering embraces the potential of recreating and replacing defective body parts by advancements in the medical field. Being a biocompatible nanomaterial with outstanding physical, chemical, optical, and biological properties, graphene-based materials were successfully employed in creating the perfect scaffold for a range of organs, starting from the skin through to the brain. Investigations on 2D and 3D tissue culture scaffolds incorporated with graphene or its derivatives have revealed the capability of this carbon material in mimicking in vivo environment. The porous morphology, great surface area, selective permeability of gases, excellent mechanical strength, good thermal and electrical conductivity, good optical properties, and biodegradability enable graphene materials to be the best component for scaffold engineering. Along with the apt microenvironment, this material was found to be efficient in differentiating stem cells into specific cell types. Furthermore, the scope of graphene nanomaterials in liver tissue engineering as a promising biomaterial is also discussed. This review critically looks into the unlimited potential of graphene-based nanomaterials in future tissue engineering and regenerative therapy.

Naturally-Derived Biomaterials for Tissue Engineering Applications

Naturally-derived biomaterials have been used for decades in multiple regenerative medicine applications. From the simplest cell microcarriers made of collagen or alginate, to highly complex decellularized whole-organ scaffolds, these biomaterials represent a class of substances that is usually first in choice at the time of electing a functional and useful biomaterial. Hence, in this chapter we describe the several naturally-derived biomaterials used in tissue engineering applications and their classification, based on composition. We will also describe some of the present uses of the generated tissues like drug discovery, developmental biology, bioprinting and transplantation.

Micro‑dimpled surface atelocollagen maintains primary human hepatocytes in culture and may promote their functionality compared with collagen coat culture

Primary human hepatocytes (PHHs) are the gold standard for drug development procedures; however, maintaining functional PHHs in vitro is challenging in conventional collagen-coated cultures. In the present study, we developed a new scaffold comprising high amounts (≥1 mg/cm²) of atelocollagen exposed to ultraviolet radiation to induce cross-linking and improve stability. Scanning and transmission electron microscopy revealed a micro-dimpled surface (MDS) scaffold composed of randomly arranged atelocollagen fibrils. The scaffold was therefore designated as MDS atelocollagen. PHHs cultured on MDS atelocollagen were round with a compact cytoplasm and exhibited enhanced levels of albumin (ALB) secretion and cytochrome P450 (CYP) 3A4 activity. The expression of hepatocyte-related genes, such as serum proteins, drug metabolism-related CYPs, and nuclear receptors, was enhanced in cells cultured on MDS atelocollagen, but not in those cultured on conventional atelocollagen. Moreover, the abnormal gene expression of cell adhesion molecules observed in conventional atelocollagen culture was suppressed when the cells were grown on MDS atelocollagen, thereby suggesting a cell behavior similar to that of in vivo hepatocytes. These results suggest that MDS atelocollagen functionally preserves PHHs while conserving the simplicity of conventional PHH atelocollagen-coated cultures.

Human hepatocellular adenoma as a promising cell source for bioartificial liver systems

The present study assessed human hepatocellular adenoma (HCA) as a potential source of biological material for bioartificial liver (BAL) systems. The histological characteristics of HCA tissues from 8 patients were examined using hematoxylin and eosin staining. The glycogen synthesis capacity of HCA cells was assessed using Periodic Acid-Schiff (PAS) staining and the expression of genes involved in liver function were examined using immunohistochemical staining (IHC) and reverse transcription-quantitative PCR analysis. Primary cells from HCA tissues were subsequently isolated and cultured in vitro. Cells within HCA tissues from 8 patients exhibited a polygonal shape, similar to that of cells in adjacent normal liver tissues. PAS staining of HCA tissues indicated the capacity of these cells to synthesize and store glycogen. Furthermore, IHC and PCR analyses revealed that the expression of liver function genes in HCA tissues were similar to those observed within normal adjacent liver tissues. Primary cells isolated from HCA tissues exhibited an irregular polygonal shape and positive in vitro growth. The current study demonstrated that HCA tissues exhibit histological and functional characteristics matching those of normal human liver tissue and may therefore be a promising alternative to hepatocytes as a source of biological material for BAL systems.

Fibrosis in tissue engineering and regenerative medicine: treat or trigger?

Fibrosis is a life-threatening pathological condition resulting from a dysfunctional tissue repair process. There is no efficient treatment and organ transplantation is in many cases the only therapeutic option. Here we review tissue engineering and regenerative medicine (TERM) approaches to address fibrosis in the cardiovascular system, the kidney, the lung and the liver. These strategies have great potential to achieve repair or replacement of diseased organs by cell- and material-based therapies. However, paradoxically, they might also trigger fibrosis. Cases of TERM interventions with adverse outcome are also included in this review. Furthermore, we emphasize the fact that, although organ engineering is still in its infancy, the advances in the field are leading to biomedically relevant in vitro models with tremendous potential for disease recapitulation and development of therapies. These human tissue models might have increased predictive power for human drug responses thereby reducing the need for animal testing.

The influence of the ratio of liver cells and bone marrow in the implantable cell-engineering structures of the liver on the recovery efficiency of functional and morphological parameters in chronic liver failure

Aim:to determinate the most effective liver cells and multipotent mesenchymal stromal cells of bone marrow (MMSC BM) ratio into implantable cell engineering constructions (CECs) used for chronic liver failure (CLF) correcting.

Materials and methods.For creating liver CECs it was used a biopolymer implant – a composition of a heterogeneous collagen-containing gel (BMCG) (Sphero®GEL trademark) containing viable liver cells and MMSC BM in the following ratios – 1 : 1; 5 : 1 and 10 : 1 respectively. CECs with different ratios of liver cells and MMSC BM were implanted into liver of rats in which chronic liver failure (CLF), was modeled by using CCl4. The effectiveness of the regulatory effects of CECs (with different cell ratios) on regenerative processes in livers were assessed by using biochemical, morphological and morphometric methods at different periods after their implantation.

Results.Corrective effect of CECs with different cell composition on biochemical and morphological parameters of livers at chronic liver failure was established. During studying the liver CECs with various cell ratios of liver cells and MMSC BM (1 : 1; 5 : 1 and 10 : 1 respectively), it was found that the most optimal ratio of cells into the CECs is 5 : 1, because at this ratio of cells, there were a more distinct normalization of the morphological and functional liver parameters within 365 days after modeling CLF and maintenance of the structural homeostasis into the CECs. Themselves, which allows predicting their long-term regulatory effect on the liver tissue in CLF and maintaining its normal structural and functional state.

Conclusion.The effective correction of chronic liver failure can be carried out by using the implanted liver CECs, in which donor liver cells and MMSC BM where presented in ratios – 1 : 1; 5 : 1 and 10 : 1. But analysis of prolonged correction of liver morphological and functional parameters at CECs using it was allow to recommend the preferences using of CECs with ratio 5 : 1, because prolonged preservation of structural homeostasis into these CECs makes possible to prognosticate their prolonged regulatory action on the liver tissue at CLF, especially for recipients on a waiting list for liver transplantation.

Lymphatic Tissue Engineering and Regeneration

The lymphatic system is a major circulatory system within the body, responsible for the transport of interstitial fluid, waste products, immune cells, and proteins. Compared to other physiological systems, the molecular mechanisms and underlying disease pathology largely remain to be understood which has hindered advancements in therapeutic options for lymphatic disorders. Dysfunction of the lymphatic system is associated with a wide range of disease phenotypes and has also been speculated as a route to rescue healthy phenotypes in areas including cardiovascular disease, metabolic syndrome, and neurological conditions. This review will discuss lymphatic system functions and structure, cell sources for regenerating lymphatic vessels, current approaches for engineering lymphatic vessels, and specific therapeutic areas that would benefit from advances in lymphatic tissue engineering and regeneration.

Bioengineering Organs for Blood Detoxification

For patients with severe kidney or liver failure the best solution is currently organ transplantation. However, not all patients are eligible for transplantation and due to limited organ availability, most patients are currently treated with therapies using artificial kidney and artificial liver devices. These therapies, despite their relative success in preserving the patients' life, have important limitations since they can only replace part of the natural kidney or liver functions. As blood detoxification (and other functions) in these highly perfused organs is achieved by specialized cells, it seems relevant to review the approaches leading to bioengineered organs fulfilling most of the native organ functions. There, the culture of cells of specific phenotypes on adapted scaffolds that can be perfused takes place. In this review paper, first the functions of kidney and liver organs are briefly described. Then artificial kidney/liver devices, bioartificial kidney devices, and bioartificial liver devices are focused on, as well as biohybrid constructs obtained by decellularization and recellularization of animal organs. For all organs, a thorough overview of the literature is given and the perspectives for their application in the clinic are discussed.

3D-printed gelatin scaffolds of differing pore geometry modulate hepatocyte function and gene expression

Three dimensional (3D) printing is highly amenable to the fabrication of tissue-engineered organs of a repetitive microstructure such as the liver. The creation of uniform and geometrically repetitive tissue scaffolds can also allow for the control over cellular aggregation and nutrient diffusion. However, the effect of differing geometries, while controlling for pore size, has yet to be investigated in the context of hepatocyte function. In this study, we show the ability to precisely control pore geometry of 3D-printed gelatin scaffolds. An undifferentiated hepatocyte cell line (HUH7) demonstrated high viability and proliferation when seeded on 3D-printed scaffolds of two different geometries. However, hepatocyte specific functions (albumin secretion, CYP activity, and bile transport) increases in more interconnected 3D-printed gelatin cultures compared to a less interconnected geometry and to 2D controls. Additionally, we also illustrate the disparity between gene expression and protein function in simple 2D culture modes, and that recreation of a physiologically mimetic 3D environment is necessary to induce both expression and function of cultured hepatocytes.

STATEMENT OF SIGNIFICANCE

Three dimensional (3D) printing provides tissue engineers the ability spatially pattern cells and materials in precise geometries, however the biological effects of scaffold geometry on soft tissues such as the liver have not been rigorously investigated. In this manuscript, we describe a method to 3D print gelatin into well-defined repetitive geometries that show clear differences in biological effects on seeded hepatocytes. We show that a relatively simple and widely used biomaterial, such as gelatin, can significantly modulate biological processes when fabricated into specific 3D geometries. Furthermore, this study expands upon past research into hepatocyte aggregation by demonstrating how it can be manipulated to enhance protein function, and how function and expression may not precisely correlate in 2D models.

Tissue engineering; strategies, tissues, and biomaterials

Current tissue regenerative strategies rely mainly on tissue repair by transplantation of the synthetic/natural implants. However, limitations of the existing strategies have increased the demand for tissue engineering approaches. Appropriate cell source, effective cell modification, and proper supportive matrices are three bases of tissue engineering. Selection of appropriate methods for cell stimulation, scaffold synthesis, and tissue transplantation play a definitive role in successful tissue engineering. Although the variety of the players are available, but proper combination and functional synergism determine the practical efficacy. Hence, in this review, a comprehensive view of tissue engineering and its different aspects are investigated.

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.

Regenerative Medicine Applications of Mesenchymal Stem Cells

A major research challenge is to develop therapeutics that assist with healing damaged tissues and organs because the human body has limited ability to restore the majority of these tissues and organs to their original state. Tissue engineering (TE) and regenerative medicine (RM) promises to offer efficient therapeutic biological strategies that use mesenchymal stem cells (MSCs). MSCs possess the capability for self-renewal, multilineage differentiation, and immunomodulatory properties that make them attractive for clinical applications. They have been extensively investigated in numerous preclinical and clinical settings in an attempt to overcome their challenges and promote tissue regeneration and repair. This review explores the exciting opportunities afforded by MSCs, their desirable properties as cellular therapeutics in RM, and implicates their potential use in clinical practice. Here, we attempt to identify challenges and issues that determine the clinical efficacy of MSCs as treatment for skeletal and non-skeletal tissues.

3D bioprinting using stem cells

Recent advances have allowed for three-dimensional (3D) printing technologies to be applied to biocompatible materials, cells and supporting components, creating a field of 3D bioprinting that holds great promise for artificial organ printing and regenerative medicine. At the same time, stem cells, such as human induced pluripotent stem cells, have driven a paradigm shift in tissue regeneration and the modeling of human disease, and represent an unlimited cell source for tissue regeneration and the study of human disease. The ability to reprogram patient-specific cells holds the promise of an enhanced understanding of disease mechanisms and phenotypic variability. 3D bioprinting has been successfully performed using multiple stem cell types of different lineages and potency. The type of 3D bioprinting employed ranged from microextrusion bioprinting, inkjet bioprinting, laser-assisted bioprinting, to newer technologies such as scaffold-free spheroid-based bioprinting. This review discusses the current advances, applications, limitations and future of 3D bioprinting using stem cells, by organ systems.

Adipose-derived stromal cells resemble bone marrow stromal cells in hepatocyte differentiation potential in vitro and in vivo

AIM

To investigate whether mesenchymal stem cells (MSCs) from adipose-derived stromal cells (ADSCs) and bone marrow stromal cells (BMSCs) have similar hepatic differentiation potential.

METHODS

Mouse ADSCs and BMSCs were isolated and cultured. Their morphological and phenotypic characteristics, as well as their multiple differentiation capacity were compared. A new culture system was established to induce ADSCs and BMSCs into functional hepatocytes. Reverse transcription polymerase chain reaction, Western blot, and immunofluorescence analyses were performed to identify the induced hepatocyte-like cells. CM-Dil-labeled ADSCs and BMSCs were then transplanted into a mouse model of CCl₄-induced acute liver failure. Fluorescence microscopy was used to track the transplanted MSCs. Liver function was tested by an automatic biochemistry analyzer, and liver tissue histology was observed by hematoxylin and eosin (HE) staining.

RESULTS

ADSCs and BMSCs shared a similar morphology and multiple differentiation capacity, as well as a similar phenotype (with expression of CD29 and CD90 and no expression of CD11b or CD45). Morphologically, ADSCs and BMSCs became round and epithelioid following hepatic induction. These two cell types differentiated into hepatocyte-like cells with similar expression of albumin, cytokeratin 18, cytokeratin 19, alpha fetoprotein, and cytochrome P450. Fluorescence microscopy revealed that both ADSCs and BMSCs were observed in the mouse liver at different time points. Compared to the control group, both the function of the injured livers and HE staining showed significant improvement in the ADSC- and BMSC-transplanted mice. There was no significant difference between the two MSC groups.

CONCLUSION

ADSCs share a similar hepatic differentiation capacity and therapeutic effect with BMSCs in an acute liver failure model. ADSCs may represent an ideal seed cell type for cell transplantation or a bio-artificial liver support system.

Concise Review: Bioprinting of Stem Cells for Transplantable Tissue Fabrication

Bioprinting is a quickly progressing technology, which holds the potential to generate replacement tissues and organs. Stem cells offer several advantages over differentiated cells for use as starting materials, including the potential for autologous tissue and differentiation into multiple cell lines. The three most commonly used stem cells are embryonic, induced pluripotent, and adult stem cells. Cells are combined with various natural and synthetic materials to form bioinks, which are used to fabricate scaffold‐based or scaffold‐free constructs. Computer aided design technology is combined with various bioprinting modalities including droplet‐, extrusion‐, or laser‐based bioprinting to create tissue constructs. Each bioink and modality has its own advantages and disadvantages. Various materials and techniques are combined to maximize the benefits. Researchers have been successful in bioprinting cartilage, bone, cardiac, nervous, liver, and vascular tissues. However, a major limitation to clinical translation is building large‐scale vascularized constructs. Many challenges must be overcome before this technology is used routinely in a clinical setting. Stem Cells Translational Medicine2017;6:1940–1948

Comparison of Reprogramming Methods for Generation of Induced-Oligodendrocyte Precursor Cells

Direct conversion by trans-differentiation is of growing interest in cell therapy for incurable diseases. The efficiency of cell reprogramming and functionality of converted cells are important considerations in cell transplantation therapy. Here, we compared two representative protocols for the generation of induced-oligodendrocyte progenitor cells (iOPCs) from mouse and rat fibroblasts. Then, we showed that induction of Nkx6.2, Olig2, and Sox10 (NOS) was more effective in mouse fibroblasts and that induction of Olig2, Sox10, and Zfp536 (OSZ) was more effective at reprogramming iOPCs from rat fibroblasts. However, OSZ-iOPCs did not show greater proliferation than NOS-induced cells. Because the efficiency of iOPCs generation appears to differ between cell species depending on transcription factors and culture conditions, it is important to select appropriate methods for efficient reprogramming.

Immunoprofiling of Adult-Derived Human Liver Stem/Progenitor Cells: Impact of Hepatogenic Differentiation and Inflammation

Adult-derived human liver stem/progenitor cells (ADHLSCs) are, nowadays, developed as therapeutic medicinal product for the treatment of liver defects. In this study, the impact of hepatogenic differentiation and inflammation priming on the ADHLSCs' immune profile was assessed in vitro and compared to that of mature hepatocytes. The constitutive immunological profile of ADHLSCs was greatly different from that of hepatocytes. Differences in the expression of the stromal markers CD90 and CD105, adhesion molecules CD44 and CD49e, immunoregulatory molecules CD73 and HO-1, and NK ligands CD112 and CD155 were noted. While they globally preserved their immunological profile in comparison to undifferentiated counterparts, differentiated ADHLSCs showed a significant downregulation of CD200 expression as in hepatocytes. This was mainly induced by signals issued from EGF and OSM. On the other hand, the impact of inflammation was quite similar for all studied cell populations with an increased expression level of CD54 and CD106 and induction of that of CD40 and CD274. In conclusion, our immune profiling study suggests CD200 as a key factor in regulating the immunobiology of differentiated ADHLSCs. A better understanding of the molecular and physiological events related to such marker could help in designing the optimal conditions for an efficient therapeutic use of ADHLSCs.

Construction of three-dimensional vascularized functional human liver tissue using a layer-by-layer cell coating technique

The creation of artificial liver tissue is an active area of research due to the shortage of donors for liver transplantation. Here we investigated whether a simple and efficient cell coating technique developed in our laboratory could be used to generate functional vascularized liver tissue. This technique creates three-dimensional tissue by loading cells sterically onto other cells that have been coated with layer-by-layer (LbL) nanofilms of fibronectin and gelatin, two extracellular matrix proteins. We used this technique to construct homogenous, dense, well-vascularized liver tissue from cryopreserved human primary hepatocytes, human umbilical vein endothelial cells, and normal human dermal fibroblasts. Using LbL cell coating technique resulted in higher cellular function in terms of human albumin production (P < 0.01) and cytochrome P450 activity (P < 0.01) in vitro. Furthermore, after being transplanted subcutaneously into NOD/SCID mice, the vascularized liver tissue showed greater albumin production in the early stage than non-vascularized tissue or a hepatocyte suspension (P < 0.01). Histological examination demonstrated that compare to non-vascularized tissue, there were many less-morphologically changed and intact hepatocytes in the vascularized tissue. This cell coating technique would be applicable to the generation of vascularized functional liver tissue for regenerative medicine in the future.

Preparation and characterization of a chitosan/galactosylated hyaluronic acid/heparin scaffold for hepatic tissue engineering

Cell culture microenvironment and hepatocyte-specific three-dimensional tissue-engineering scaffold play important roles for bioartificial liver devices. In the present study, highly porous sponge scaffolds composed of chitosan (CS) and galactosylated hyaluronic acid (GHA, galactose moieties were covalently coupled with hyaluronic acid through ethylenediamine), were prepared by freezing-drying technique. Because the growth factors specifically bind to heparin with a high affinity and biological stability of the growth factors are modulated by heparin. Heparin was added into CS/GHA scaffold under mild conditions. The effects of heparin on the morphology, structure, porosity, mechanical properties of the CS/GHA/heparin scaffold were studied. CS/GHA scaffold containing heparin maintains the porous structure and good mechanical properties. Furthermore, addition of heparin with the growth factors into the scaffold resulted in a significantly improved the microenvironment of cell growth and prolonged liver functions of the hepatocytes such as albumin secretion, urea synthesis and ammonia elimination. These results indicate that this CS/GHA/heparin scaffold is a potential candidate for liver tissue engineering.

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

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

Concise Review: Liver Regenerative Medicine: From Hepatocyte Transplantation to Bioartificial Livers and Bioengineered Grafts

Donor organ shortage is the main limitation to liver transplantation as a treatment for end-stage liver disease and acute liver failure. Liver regenerative medicine may in the future offer an alternative form of therapy for these diseases, be it through cell transplantation, bioartificial liver (BAL) devices, or bioengineered whole organ liver transplantation. All three strategies have shown promising results in the past decade. However, before they are incorporated into widespread clinical practice, the ideal cell type for each treatment modality must be found, and an adequate amount of metabolically active, functional cells must be able to be produced. Research is ongoing in hepatocyte expansion techniques, use of xenogeneic cells, and differentiation of stem cell-derived hepatocyte-like cells (HLCs). HLCs are a few steps away from clinical application, but may be very useful in individualized drug development and toxicity testing, as well as disease modeling. Finally, safety concerns including tumorigenicity and xenozoonosis must also be addressed before cell transplantation, BAL devices, and bioengineered livers occupy their clinical niche. This review aims to highlight the most recent advances and provide an updated view of the current state of affairs in the field of liver regenerative medicine. Stem Cells 2017;35:42-50.

Hereditary Angioedema as a Metabolic Liver Disorder: Novel Therapeutic Options and Prospects for Cure

Hereditary angioedema (HAE) is a rare autosomal dominant disorder caused by mutations of the SERPING1 or the Factor 12 genes. It is potentially fatal, particularly if not identified at an early stage. Apart from androgens, which are contraindicated in children and in pregnant women, a range of effective, albeit very expensive treatments have recently become available for HAE patients. The cost of these new treatments is beyond the reach of most developing countries. At this time, there is no cure for the disorder. In spite of mutations of the SERPING1 gene, autoimmunity and infections are not prominent features of the condition. Here, we present the argument that HAE should be viewed primarily as a metabolic liver disorder. This conceptual paradigm shift will stimulate basic research and may facilitate new therapeutic approaches to HAE outlined in this paper. We suggest several novel potential treatment options for HAE from the perspectives of clinical immunology, molecular biology, and liver transplantation. Many of these offer the prospect of curing the disorder. The effectiveness of these options is rapidly improving in many cases, and their risks are decreasing. Given the very high costs of treating HAE, some of these curative options may become feasible in the next decade.

Extracellular Matrix Functionalization and Huh-7.5 Cell Coculture Promote the Hepatic Differentiation of Human Adipose-Derived Mesenchymal Stem Cells in a 3D ICC Hydrogel Scaffold

In this study, we constructed a microporous hydrogel scaffold with hexagonally packed interconnected cavities and extracellular matrix (ECM)-functionalized interior surface, and systematically investigated the hepatic differentiation of human adipose-derived mesenchymal stem cells (hAD-MSCs) under the influence of three key factors: three-dimensional (3D) geometry, ECM presence, and coculture with hepatocyte-derived cell line. Results confirmed that (i) hepatic differentiation of hAD-MSC is more efficient in a 3D microporous scaffold than in 2D monolayer culture; (ii) the presence of both ECM components (fibronectin and collagen-I) in the scaffold is superior to collagen-I only, highlighting the importance of fibronectin; and (iii) coculture with Huh-7.5 hepatocyte-derived cells promoted liver-specific functions of the hAD-MSC-derived hepatocytes. The optimized differentiation process only took 21 days to complete, a time length that is shorter or at least comparable to previous reports, and more importantly, yielded an albumin production more than 10-fold higher than conventional 2D culture. Our approach of optimizing hAD-MSC hepatic differentiation could provide a potential solution to the challenges such as hepatocyte transplantation or the establishment of human physiologically relevant liver models in vitro.

Recent advances in bioprinting techniques: approaches, applications and future prospects

Bioprinting technology shows potential in tissue engineering for the fabrication of scaffolds, cells, tissues and organs reproducibly and with high accuracy. Bioprinting technologies are mainly divided into three categories, inkjet-based bioprinting, pressure-assisted bioprinting and laser-assisted bioprinting, based on their underlying printing principles. These various printing technologies have their advantages and limitations. Bioprinting utilizes biomaterials, cells or cell factors as a "bioink" to fabricate prospective tissue structures. Biomaterial parameters such as biocompatibility, cell viability and the cellular microenvironment strongly influence the printed product. Various printing technologies have been investigated, and great progress has been made in printing various types of tissue, including vasculature, heart, bone, cartilage, skin and liver. This review introduces basic principles and key aspects of some frequently used printing technologies. We focus on recent advances in three-dimensional printing applications, current challenges and future directions.

Enrichment of Pluripotent Stem Cell-Derived Hepatocyte-Like Cells by Ammonia Treatment

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are potential resources for the regeneration of defective organs, including the liver. However, some obstacles must be overcome before this becomes reality. Undifferentiated cells that remain following differentiation have teratoma-forming potential. Additionally, practical applications require a large quantity of differentiated cells, so the differentiation process must be economical. Here we describe a DNA microarray-based global analysis of the gene expression profiles of differentiating human pluripotent stem cells. We identified differences and commonalities among six human pluripotent stem cell lines: the hESCs KhES1, KhES2, KhES3, and H1, and the iPSCs 201B7 and 243G1. Embryoid bodies (EBs) formed without requiring supplementation with inducing factors. EBs also expressed some liver-specific metabolic genes including the ammonia-metabolizing enzymes glutamine synthetase and carbamoyl-phosphate synthase 1. Real-time PCR analysis revealed hepatocyte-like differentiation of EBs treated with ammonia in Lanford medium. Analysis of DNA microarray data suggested that hepatocyte-like cells were the most abundant population in ammonia-treated cells. Furthermore, expression levels of undifferentiated pluripotent stem cell markers were drastically reduced, suggesting a reduced teratoma-forming capacity. These results indicate that treatment of EBs with ammonia in Lanford medium may be an effective inducer of hepatic differentiation in absence of expensive inducing factors.

Acute-on-chronic liver failure in cirrhosis

The definition of acute-on-chronic liver failure (ACLF) remains contested. In Europe and North America, the term is generally applied according to the European Association for the Study of the Liver-Chronic Liver Failure (EASL-CLIF) Consortium guidelines, which defines this condition as a syndrome that develops in patients with cirrhosis and is characterized by acute decompensation, organ failure and high short-term mortality. One-third of patients who are hospitalized for acute decompensation present with ACLF at admission or develop the syndrome during hospitalization. ACLF frequently occurs in a closed temporal relationship to a precipitating event, such as bacterial infection or acute alcoholic, drug-induced or viral hepatitis. However, no precipitating event can be identified in approximately 40% of patients. The mechanisms of ACLF involve systemic inflammation due to infections, acute liver damage and, in cases without precipitating events, probably intestinal translocation of bacteria or bacterial products. ACLF is graded into three stages (ACLF grades 1-3) on the basis of the number of organ failures, with higher grades associated with increased mortality. Liver and renal failures are the most common organ failures, followed by coagulation, brain, circulatory and respiratory failure. The 28-day mortality rate associated with ACLF is 30%. Depending on the grade, ACLF can be reversed using standard therapy in only 16-51% of patients, leaving a considerable proportion of patients with ACLF that remains steady or progresses. Liver transplantation in selected patients with ACLF grade 2 and ACLF grade 3 increases the 6-month survival from 10% to 80%.