Impact of alginate type and bead diameter on mass transfers and the metabolic activities of encapsulated C3A cells in bioartificial liver applications

Serum-free alginate-C2C12 cells microcapsule as a model of alternative animal protein source

Due to the climate change crisis, and environmental impacts of the traditional meat sector, the production of artificial animal protein based on in vitro cell culture technology is proposed as an alternative. Furthermore, since traditional animal serum-supplemented cultures pose scientific challenges such as batch variation and contamination risks, artificial animal protein cultures are currently in urgent need of not only serum-free cultures, but also microcarrier culture systems for scalability. However, serum-free microcarrier-based culture system for the differentiation of muscle cells is not available to date. Therefore, we established an edible alginate microcapsules culture system for the differentiation of C2C12 cells in serum-free conditions. Furthermore, metabolites related to central carbon metabolism were profiled based on targeted metabolomics using mass spectrometry. The C2C12 cells cultured in alginate microcapsules displayed high viability throughout 7 days and successfully differentiated within 4 days in serum and serum-free cultures except for AIM-V cultures, which was confirmed by CK activity and MHC immunostaining. Lastly, to the best of our knowledge, this is the first report to compare metabolite profiles between monolayer and alginate microcapsule culture systems. Alginate microcapsule culture showed higher levels of intracellular glycolysis and TCA cycle intermediates, lactate, and the contribution of essential amino acids compared to the monolayer culture. We believe our serum-free alginate microcapsule culture system is adaptable to different species of muscle cells and contributes to future food technology as a proof of concept for the scalability of alternative animal protein source production.

Encapsulation of Concentrated Solution Obtained by Block Freeze Concentration in Calcium Alginate and Corn Starch Calcium Alginate Hydrogel Beads

A model (sucrose and gallic acid) solution was concentrated by block freeze concentration (BFC) at three centrifugation cycles, and the solutions were encapsulated in calcium alginate and corn starch calcium alginate hydrogel beads. Static and dynamic tests determined the rheological behavior, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) established thermal and structural properties, and the release kinetics was evaluated under in vitro simulated digestion experiment. The highest efficiency encapsulation value was close to 96%. As the concentrated solution increased in terms of solutes and gallic acid, the solutions were fitted to the Herschel-Bulkley model. Moreover, from the second cycle, the solutions exhibited the highest values of storage modulus (G') and loss modulus (G″), contributing to form a more stable encapsulation. The FTIR and DSC results demonstrated strong interactions between corn starch and alginate, establishing a good compatibility and stability in the bead formation. The kinetic release model under in vitro conditions was fitted to the Korsmeyer-Peppas model, demonstrating the significant stability of the model solutions inside the beads. Therefore, the present study proposes a clear and precise definition for the elaboration of liquid foods obtained by BFC and its incorporation inside an edible material that facilitates the controlled release in specific sites.

Microencapsulated Hepatocytes Differentiated from Human Induced Pluripotent Stem Cells: Optimizing 3D Culture for Tissue Engineering Applications

Liver cell therapy and in vitro models require functional human hepatocytes, the sources of which are considerably limited. Human induced pluripotent stem cells (hiPSCs) represent a promising and unlimited source of differentiated human hepatocytes. However, when obtained in two-dimensional (2D) cultures these hepatocytes are not fully mature and functional. As three-dimensional culture conditions offer advantageous strategies for differentiation, we describe here a combination of three-dimensional (3D) approaches enabling the successful differentiation of functional hepatocytes from hiPSCs by the encapsulation of hiPSC-derived hepatoblasts in alginate beads of preformed aggregates. The resulting encapsulated and differentiated hepatocytes (E-iHep-Orgs) displayed a high level of albumin synthesis associated with the disappearance of α-fetoprotein (AFP) synthesis, thus demonstrating that the E-iHep-Orgs had reached a high level of maturation, similar to that of adult hepatocytes. Gene expression analysis by RT-PCR and immunofluorescence confirmed this maturation. Further functional assessments demonstrated their enzymatic activities, including lactate and ammonia detoxification, as well as biotransformation activities of Phase I and Phase II enzymes. This study provides proof of concept regarding the benefits of combining three-dimensional techniques (guided aggregation and microencapsulation) with liver differentiation protocols as a robust approach to generate mature and functional hepatocytes that offer a permanent and unlimited source of hepatocytes. Based on these encouraging results, our combined conditions to produce mature hepatocytes from hiPSCs could be extended to liver tissue engineering and bioartificial liver (BAL) applications at the human scale for which large biomasses are mandatory.

Enhanced quorum sensing capacity via regulating microenvironment to facilitate stress resistance of probiotic in alginate-based microcapsules

Alginate-based microcapsule has becoming a promising carrier for probiotic encapsulation due to the improved stress resistant ability. Besides the physical protection of microcapsules, bacterial quorum sensing (QS) is another prominent factor affecting microbial stress resistance in microcapsules. In the present study, Vibrio harveyi cells were entrapped and proliferated into cell aggregates in alginate-based microcapsules. The microenvironment composed of cells and biomacromolecules was regulated by the diameter, alginate concentration and core state of microcapsule. Then the effect of microenvironment on bacterial QS capacity was investigated, including bioluminescence, autoinducers (AIs) production and QS related genes expression. The highest diameter of 1200 μm and highest alginate concentration of 2.0 % w/v under the investigation range presented strongest QS capacity, and the maintenance of hydrogel core could enhance bacterial QS. Moreover, the mechanism analysis revealed that the formed biofilm on the surface of cell aggregates hampered the outward transfer of AIs, and the local AIs inside the cell aggregates induced stronger bacteria QS by close-range interaction. As a whole, these findings are helpful to guide the technological development and optimization of microencapsulated probiotics with stronger stress resistance, and the potential application in food, dairy, wastewater treatment and biosensor.

Bioartificial livers: a review of their design and manufacture

Acute liver failure (ALF) is a rapidly progressive disease with high morbidity and mortality rates. Liver transplantation and artificial liver support systems, such as artificial livers (ALs) and bioartificial livers (BALs), are the two major therapies for ALF. Compared to ALs, BALs are composed of functional hepatocytes that provide essential liver functions, including detoxification, metabolite synthesis, and biotransformation. Furthermore, BALs can potentially provide effective support as a form of bridging therapy to liver transplantation or spontaneous recovery for patients with ALF. In this review, we systematically discussed the currently available state-of-the-art designs and manufacturing processes for BAL support systems. Specifically, we classified the cell sources and bioreactors that are applied in BALs, highlighted the advanced technologies of hepatocyte culturing and bioreactor fabrication, and discussed the current challenges and future trends in developing next generation BALs for large scale clinical applications.

Development of Surgically Transplantable Parathyroid Hormone-Releasing Microbeads

Hypoparathyroidism is an endocrine disorder that occurs because of the inability to produce parathyroid hormone (PTH) effectively. Previously, we reported the efficacy of tonsil-derived mesenchymal stem cells (TMSCs) differentiated into parathyroid-like cells for the treatment of hypoparathyroidism. Here, we investigated the feasibility of three-dimensional structural microbeads fabricated with TMSCs and alginate, a natural biodegradable polymer, to treat hypoparathyroidism. Alginate microbeads were fabricated by dropping a 2% (w/v) alginate solution containing TMSCs into a 5% CaCl2 solution and then differentiated into parathyroid-like cells using activin A and sonic hedgehog for 7 days. The protein expression of PTH, a specific marker of the parathyroid gland, was significantly higher in differentiated alginate microbeads with TMSCs (Al-dT) compared with in undifferentiated alginate microbeads with TMSCs. For in vivo experiments, we created the hypoparathyroidism animal model by parathyroidectomy (PTX) and implanted alginate microbeads in the dorsal interscapular region. The PTX rats with Al-dT (PTX+Al-dT) showed the highest survival rate and weight change and a gradual increase in serum intact PTH levels. We also detected a higher expression of PTH in retrieved tissues of PTX+Al-dT using immunofluorescence analysis. This study demonstrates that alginate microbeads are potential a new tool as a surgically scalable therapy for treating hypoparathyroidism.

Nanostructured lipid carriers containing chitosan or sodium alginate for co-encapsulation of antioxidants and an antimicrobial agent for potential application in wound healing

The high incidence and costs of chronic wounds in the elderly have motivated the search for innovations to improve product performance and the healing process while reducing costs. In this study, bioadhesive nanostructured lipid carriers (NLC) were developed for the co-encapsulation of compounds with antioxidant (α-tocopherol and quercetin) and antimicrobial (tea tree oil) activity for management of wounds. The NLC was produced with shea butter and argan oil, and modified with sodium alginate or chitosan to confer bioadhesive properties. Spherical nanoparticles of ~307-330 nm and zeta potential varying from -21.2 to +11.8 mV were obtained. Thermal analysis demonstrated that the lipid matrix reduced tea tree oil thermal loss (~1.8-fold). Regardless of the type of polysaccharide employed, the NLCs promoted cutaneous localization of antioxidants in damaged (subjected to incision) skin, with a ~74 to 180-fold higher delivery into the skin compared to percutaneous delivery. This result is consistent with the similar bioadhesive properties of chitosan or sodium alginate-modified NLC. Nanoencapsulation of tea tree oil did not preclude its antimicrobial effects against susceptible and resistant strains of S. aureus and P. aeruginosa, while co-encapsulation of antioxidants increased the NLC-induced fibroblasts migration, supporting their potential usefulness for management of wounds.

Evaluation of anti-tumor effects of crocin on a novel 3D tissue-engineered tumor model based on sodium alginate/gelatin microbead

Crocin, as one of the biologically active components of saffron, has anti-inflammatory, anti-oxidant, anti-depressant and auxiliary anti-tumor effects. Studies have shown that crocin could promote breast cancer cell apoptosis. However, conventional methods are mainly based on two-dimensional (2D) cell culture models, which are difficult to reproduce the tumor environment in vivo due to space constraints. In this study, we prepared a three-dimensional (3D) cell model in vitro based on sodium alginate/gelatin to evaluate the inhibitory effect of crocin on MCF-7 cells, which could bridge the gap in crocin drug evaluation between 2D and 3D cell model in vitro. Different from the 2D culture, the cells were found to aggregate in a spherical shape in the 3D microgel beads. And the CCK-8 assay showed that the growth of MCF-7 cells exposed to crocin was inhibited in a time-related and concentration-related manner. Compared with 2D culture (IC₅₀ that MCF-7 cells treated with crocin at 24 h, 48 h, 72 h: 3.68, 2.55 and 1.53 mg/mL, respectively), the IC₅₀ value of 3D culture (IC₅₀ that MCF-7 cells treated with crocin at 24 h, 48 h, 72 h: 10.12, 6.89 and 6.64 mg/mL, respectively) was significantly increased by 2.77, 2.70, 4.34 times, respectively. Besides, live/dead staining and scanning electron microscope (SEM) revealed that the 2D cultured cells shrank and ruptured after crocin treatment, and the number of living cells was considerably reduced; the size of the cell colonies in the 3D microgel beads decreased.

Effect of nanoemulsion modification with chitosan and sodium alginate on the topical delivery and efficacy of the cytotoxic agent piplartine in 2D and 3D skin cancer models

Due to the limited options for topical management of skin cancer, this study aimed at developing and evaluating nanoemulsions (NE) for topical delivery of the cytotoxic agent piplartine (piperlongumine). NEs were modified with chitosan or sodium alginate, and the effects on the physicochemical properties, piplartine delivery and formulation efficacy were evaluated. The nanoemulsion droplets displayed similar size (96-112 nm), but opposite charge; the polysaccharides improved piplartine penetration into and across the skin (1.3-1.9-fold) in a similar manner, increasing the ratio "drug in the skin/receptor phase" by 1.4-1.5-fold compared to the plain NE and highlighting their relevance for cutaneous localization. Oleic acid addition to the chitosan-containing NE further increased drug penetration (~1.9-2.0-fold), as did increases in drug content from 0.5 to 1%. The cytotoxicity of piplartine was ~2.8-fold higher when the drug was incorporated in the chitosan-containing NE compared to its solution (IC50 = 14.6 μM) against melanoma cells. The effects of this nanocarrier on 3D melanoma tissues were concentration-related; at 1%, piplartine elicited marked epidermis destruction. These results support the potential applicability of the chitosan-modified nanoemulsion containing piplartine as a new strategy for local management of skin cancer.

Preclinical characterization of alginate-poly-L-lysine encapsulated HepaRG for extracorporeal liver supply

We recently demonstrated that HepaRG cells encapsulated into 1.5% alginate beads are capable of self-assembling into spheroids. They adequately differentiate into hepatocyte-like cells, with hepatic features observed at Day 14 post-encapsulation required for external bioartificial liver applications. Preliminary investigations performed within a bioreactor under shear stress conditions and using a culture medium mimicking acute liver failure (ALF) highlighted the need to reinforce beads with a polymer coating. We demonstrated in a first step that a poly-l-lysine coating improved the mechanical stability, without altering the metabolic activities necessary for bioartificial liver applications (such as ammonia and lactate elimination). In a second step, we tested the optimized biomass in a newly designed perfused dynamic bioreactor, in the presence of the medium model for pathological plasma for 6 h. Performances of the biomass were enhanced as compared to the steady configuration, demonstrating its efficacy in decreasing the typical toxins of ALF. This type of bioreactor is easy to scale up as it relies on the number of micro-encapsulated cells, and could provide an adequate hepatic biomass for liver supply. Its design allows it to be integrated into a hybrid artificial/bioartificial liver setup for further clinical studies regarding its impact on ALF animal models.

Alginate/Pluronic F127-based encapsulation supports viability and functionality of human dental pulp stem cell-derived insulin-producing cells

BACKGROUND

Current approach for diabetes treatment remained several adverse events varied from gastrointestinal to life-threatening symptoms. Regenerative therapy regarding Edmonton protocol has been facing serious limitations involving protocol efficiency and safety. This led to the study for alternative insulin-producing cell (IPC) resource and transplantation platform. In this study, evaluation of encapsulated human dental pulp-derived stem cell (hDPSC)-derived IPCs by alginate (ALG) and pluronic F127-coated alginate (ALGPA) was performed.

RESULTS

The results showed that ALG and ALGPA preserved hDPSC viability and allowed glucose and insulin diffusion in and out. ALG and ALGPA-encapsulated hDPSC-derived IPCs maintained viability for at least 336 h and sustained pancreatic endoderm marker (NGN3), pancreatic islet markers (NKX6.1, MAF-A, ISL-1, GLUT-2 and INSULIN), and intracellular pro-insulin and insulin expressions for at least 14 days. Functional analysis revealed a glucose-responsive C-peptide secretion of ALG- and ALGPA-encapsulated hDPSC-derived IPCs at 14 days post-encapsulation.

CONCLUSION

ALG and ALGPA encapsulations efficiently preserved the viability and functionality of hDPSC-derived IPCs in vitro and could be the potential transplantation platform for further clinical application.

Small-Scale Fluidized Bed Bioreactor for Long-Term Dynamic Culture of 3D Cell Constructs and in vitro Testing

With the increasing interest in three-dimensional (3D) cell constructs that better represent native tissues, comes the need to also invest in devices, i.e., bioreactors, that provide a controlled dynamic environment similar to the perfusion mechanism observed in vivo. Here a laboratory-scale fluidized bed bioreactor (sFBB) was designed for hydrogel (i.e., alginate) encapsulated cells to generate a dynamic culture system that produced a homogenous milieu and host substantial biomass for long-term evolution of tissue-like structures and “per cell” performance analysis. The bioreactor design, conceptualized through scale-down empirical similarity rules, was initially validated through computational fluid dynamics analysis for the distributor capacity of homogenously dispersing the flow with an average fluid velocity of 4.596 × 10^–4 m/s. Experimental tests then demonstrated a consistent fluidization of hydrogel spheres, while maintaining shape and integrity (606.9 ± 99.3 μm diameter and 0.96 shape factor). It also induced mass transfer in and out of the hydrogel at a faster rate than static conditions. Finally, the sFBB sustained culture of alginate encapsulated hepatoblastoma cells for 12 days promoting proliferation into highly viable (>97%) cell spheroids at a high final density of 27.3 ± 0.78 million cells/mL beads. This was reproducible across multiple units set up in parallel and operating simultaneously. The sFBB prototype constitutes a simple and robust tool to generate 3D cell constructs, expandable into a multi-unit setup for simultaneous observations and for future development and biological evaluation of in vitro tissue models and their responses to different agents, increasing the complexity and speed of R&D processes.

Immobilised Chlorella vulgaris as An Alternative for The Enhancement of Microalgae Oil and Biodiesel Production

Microalgae are a promising alternative for biodiesel production and a valuable source of fatty acid methyl ester (FAME). In this research, Chlorella vulgaris has been chosen as the suitable microalgae because this species was able to produce highest oils for biodiesel processing. Previously, sodium alginate (SA) was used to entrap the microalgae in the culturing process due to its low toxicity and high transparency. However, SA have some disadvantages such as bead disruption which leading to the loss of microalgae cell. Therefore, this research has been conducted to evaluate the oil production of immobilised Chlorella vulgaris using different matric systems at different ratios which are 0.3:1, 1:1 and 2:1. Currently, six matric systems have been developed, they are SA as a control, a combination of SA and chitosan (SA+CT), SA and carrageenan (SA+CR), SA and gelatin (SA+GT), SA and calcium alginate (SA+CA), and SA and sodium carboxymethylcellulose (SA+CMC). The microalgae was first cultivated, harvested and extracted to produce oil, prior to use in the transesterification process. The SA+GT showed the highest oil yield with 59.14% and a total FAME of 0.56 mg/g. The FAME profile of oil extracted microalgae showed high potential for biodiesel production as it consisted of palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3). The results proved that the combination of SA+GT had improved the oil yield and fatty acid composition as compared to the other matric systems, which may have useful application for the biodiesel industry. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Assessment of biological functions for C3A cells interacting with adverse environments of liver failure plasma

BACKGROUND

For its better differentiated hepatocyte phenotype, C3A cell line has been utilized in bioartificial liver system. However, up to now, there are only a few of studies working at the metabolic alternations of C3A cells under the culture conditions with liver failure plasma, which mainly focus on carbohydrate metabolism, total protein synthesis and ureagenesis. In this study, we investigated the effects of acute liver failure plasma on the growth and biological functions of C3A cells, especially on CYP450 enzymes.

METHODS

C3A cells were treated with fresh DMEM medium containing 10% FBS, fresh DMEM medium containing 10% normal plasma and acute liver failure plasma, respectively. After incubation, the C3A cells were assessed for cell viabilities, lactate dehydrogenase leakage, gene transcription, protein levels, albumin secretion, ammonia metabolism and CYP450 enzyme activities.

RESULTS

Cell viabilities decreased 15%, and lactate dehydrogenase leakage had 1.3-fold elevation in acute liver failure plasma group. Gene transcription exhibited up-regulation, down-regulation or stability for different hepatic genes. In contrast, protein expression levels for several CYP450 enzymes kept constant, while the CYP450 enzyme activities decreased or remained stable. Albumin secretion reduced about 48%, and ammonia accumulation increased approximately 41%.

CONCLUSIONS

C3A cells cultured with acute liver failure plasma showed mild inhibition of cell viabilities, reduction of albumin secretion, and increase of ammonia accumulation. Furthermore, CYP450 enzymes demonstrated various alterations on gene transcription, protein expression and enzyme activities.

HepaRG Self-Assembled Spheroids in Alginate Beads Meet the Clinical Needs for Bioartificial Liver

In liver tissue engineering, cell culture in spheroids is now well recognized to promote the maintenance of hepatic functions. However, the process leading to spheroids formation is time consuming, costly, and not easy to scale-up for further use in human bioartificial liver (BAL) applications. In this study, we encapsulated HepaRG cells (precursors of hepatocyte-like cells) in 1.5% alginate beads without preforming spheroids. Starting from a given hepatic biomass, we analyzed cell differentiation and metabolic performance for further use in a fluidized-bed BAL. We observed that cells self-rearranged as aggregates within the beads and adequately differentiated over time, in the absence of any differentiating factors classically used. On day 14 postencapsulation, cells displayed a wide range of hepatic features necessary for the treatment of a patient in acute liver failure. These activities include albumin synthesis, ammonia and lactate detoxification, and the efficacy of the enzymes involved in the xenobiotic metabolism (such as CYP1A1/2). Impact statement It has been recognized that culturing cells in spheroids (SPHs) is advantageous as they better reproduce the three-dimensional physiological microenvironment. This approach can be exploited in bioartificial liver applications, where obtaining a functional hepatic biomass is the major challenge. Our study describes an original method for culturing hepatic cells in alginate beads that makes possible the autonomous formation of SPHs after 3 days of culture. In turn, the cells differentiate adequately and display a wide range of hepatic features. They are also capable of treating a pathological plasma model. Finally, this setup can easily be scaled-up to treat acute liver failure.

Effects of concentration variation on the physical properties of alginate-based substrates and cell behavior in culture

Nowadays alginate capsules exhibit good biocompatibility and high permeability for nutrients and metabolic wastes making them appealing biomaterial for therapeutic cell encapsulation. Further study of the characteristics of alginate beads which are highly dependent on various environmental conditions to create an optimum microenvironment for cells is also critical. Thus, in this study, the effect of concentration variation on the physical properties of alginate-based beads and entrapped-cells behavior was analyzed. Results showed that the increase of Ca ions concentration brought about the decrease of the average diameter, prolongation of dissolution time, reduction of permeability and swelling, and a rise of crosslinking extent and shrinkage of capsules; while raising sodium alginate concentration had an opposite effect on the diameter and shrinkage. Moreover, the addition of gelatin enhanced the penetration and swelling and slowed down the shrinkage of capsules. And MC3T3-E1 cells enclosed in the particles in which the concentration of calcium chloride, sodium alginate and gelatin was 2.5%, 2.0% and 0.5% (w/v %) had preferable abilities of proliferation and higher expression of alkaline phosphatase. Overall, the ability to tailor this system to support in vitro growth of MC3T3-E1 cells might have significance for the future use of other cell types in regenerative medicine.

Optogenetic control of iPS cell-derived neurons in 2D and 3D culture systems using channelrhodopsin-2 expression driven by the synapsin-1 and calcium-calmodulin kinase II promoters

Development of an optogenetically controllable human neural network model in three-dimensional (3D) cultures can provide an investigative system that is more physiologically relevant and better able to mimic aspects of human brain function. Light-sensitive neurons were generated by transducing channelrhodopsin-2 (ChR2) into human induced pluripotent stem cell (hiPSC) derived neural progenitor cells (Axol) using lentiviruses and cell-type specific promoters. A mixed population of human iPSC-derived cortical neurons, astrocytes and progenitor cells were obtained (Axol-ChR2) upon neural differentiation. Pan-neuronal promoter synapsin-1 (SYN1) and excitatory neuron-specific promoter calcium-calmodulin kinase II (CaMKII) were used to drive reporter gene expression in order to assess the differentiation status of the targeted cells. Expression of ChR2 and characterisation of subpopulations in differentiated Axol-ChR2 cells were evaluated using flow cytometry and immunofluorescent staining. These cells were transferred from 2D culture to 3D alginate hydrogel functionalised with arginine-glycine-aspartate (RGD) and small molecules (Y-27632). Improved RGD-alginate hydrogel was physically characterised and assessed for cell viability to serve as a generic 3D culture system for human pluripotent stem cells (hPSCs) and neuronal cells. Prior to cell encapsulation, neural network activities of Axol-ChR2 cells and primary neurons were investigated using calcium imaging. Results demonstrate that functional activities were successfully achieved through expression of ChR2- by both the CaMKII and SYN1 promoters. The RGD-alginate hydrogel system supports the growth of differentiated Axol-ChR2 cells whilst allowing detection of ChR2 expression upon light stimulation. This allows precise and non-invasive control of human neural networks in 3D.

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.

Ameliorating effect of encapsulated hepatocyte-like cells derived from umbilical cord in high mannuronic alginate scaffolds on acute liver failure in rats

OBJECTIVES

In this study, effects of encapsulated umbilical cord stem cells (UCSCs)-derived hepatocyte-like cells (HLCs) in high mannuronic alginate scaffolds was investigated on CCl4-induced acute liver failure (ALF) in rats.

MATERIAL AND METHODS

UCSCs were encapsulated in high mannuronic alginate scaffolds. Then the UCSCs differentiated into HLCs for treatment of CCl4-induced ALF in rats. Thirty rats randomly divided into 5 groups: Intoxicated group received only CCl4 to induce ALF. In other groups including cell-free, UCSCs and HLCs, alginate scaffolds were transplanted into the liver 4 days after CCl4 injection. Biochemical markers including albumin (ALB), blood urea nitrogen (BUN), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were evaluated. Histological changes and gene expression of ALB, alpha-fetoprotein (AFP), and cytokeratin 18 (CK-18) were also assessed.

RESULTS

Expression of CK-18 significantly increased in HLCs compared to the UCSCs in vitro. This indicates that UCSCs can effectively differentiate into the HLCs. In CCl4-intoxicated group, BUN, AST and ALT levels, and histological criteria, such as infiltration of inflammatory cells, accumulation of reticulocytes, nuclear pyknosis of hepatocyte and sinusoidal dilation, significantly increased. In this group, ALB secretion significantly decreased, while AFP expression significantly increased. Both UCSCs and HLCs encapsulated in alginate scaffolds effectively attenuated biochemical tests, improved liver cytoarchitecture, increased expression of ALB and reduced AFP expression.

CONCLUSION

Finding of the present study indicated that encapsulation of UCSCs or HLCs in alginate mannuronic scaffolds effectively improve CCl4-induced ALF.

Development and validation of a bioartificial liver device with fluidized bed bioreactors hosting alginate-encapsulated hepatocyte spheroids

Acute and acute-on-chronic liver failure are associated to high mortality when transplantation is not possible. The lack of donors has resulted in an important demand for liver support devices. This paper describes the design and validation of a new bioartificial liver (BAL) device including fluidized bed bioreactors hosting alginate-encapsulated hepatocytes spheroids. To ensure the efficacy of the BAL and the safety of the patients, a complex extracorporeal circulation was designed to be compatible with a commercial medical device, the Prismaflex(®) monitor, already used in intensive care units. Preclinical studies on large animal show that the treatment was well tolerated in terms of hemodynamics considerations. A method using non adhesive coating in petri dish led to the production of large amount of viable spheroids in vitro that were further encapsulated to follow up bioartificial liver activity during four days.

A clinical-scale BioArtificial Liver, developed for GMP, improved clinical parameters of liver function in porcine liver failure

Liver failure, whether arising directly from acute liver failure or from decompensated chronic liver disease is an increasing problem worldwide and results in many deaths. In the UK only 10% of individuals requiring a liver transplant receive one. Thus the need for alternative treatments is paramount. A BioArtificial Liver machine could temporarily replace the functions of the liver, buying time for the patient's liver to repair and regenerate. We have designed, implemented and tested a clinical-scale BioArtificial Liver machine containing a biomass derived from a hepatoblastoma cell-line cultured as three dimensional organoids, using a fluidised bed bioreactor, together with single-use bioprocessing equipment, with complete control of nutrient provision with feedback BioXpert recipe processes, and yielding good phenotypic liver functions. The methodology has been designed to meet specifications for GMP production, required for manufacture of advanced therapy medicinal products (ATMPs). In a porcine model of severe liver failure, damage was assured in all animals by surgical ischaemia in pigs with human sized livers (1.2-1.6 kg liver weights). The BioArtificial liver (UCLBAL) improved important prognostic clinical liver-related parameters, eg, a significant improvement in coagulation, reduction in vasopressor requirements, improvement in blood pH and in parameters of intracranial pressure (ICP) and oxygenation.

Hydrogel elasticity and microarchitecture regulate dental-derived mesenchymal stem cell-host immune system cross-talk

The host immune system (T-lymphocytes and their pro-inflammatory cytokines) has been shown to compromise bone regeneration ability of mesenchymal stem cells (MSCs). We have recently shown that hydrogel, used as an encapsulating biomaterial affects the cross-talk among host immune cells and MSCs. However, the role of hydrogel elasticity and porosity in regulation of cross-talk between dental-derived MSCs and immune cells is unclear. In this study, we demonstrate that the modulus of elasticity and porosity of the scaffold influence T-lymphocyte-dental MSC interplay by regulating the penetration of inflammatory T cells and their cytokines. Moreover, we demonstrated that alginate hydrogels with different elasticity and microporous structure can regulate the viability and determine the fate of the encapsulated MSCs through modulation of NF-kB pathway. Our in vivo data show that alginate hydrogels with smaller pores and higher elasticity could prevent pro-inflammatory cytokine-induced MSC apoptosis by down-regulating the Caspase-3- and 8- associated proapoptotic cascades, leading to higher amounts of ectopic bone regeneration. Additionally, dental-derived MSCs encapsulated in hydrogel with higher elasticity exhibited lower expression levels of NF-kB p65 and Cox-2 in vivo. Taken together, our findings demonstrate that the mechanical characteristics and microarchitecture of the microenvironment encapsulating MSCs, in addition to presence of T-lymphocytes and their pro-inflammatory cytokines, affect the fate of encapsulated dental-derived MSCs.

STATEMENT OF SIGNIFICANCE

In this study, we demonstrate that alginate hydrogel regulates the viability and the fate of the encapsulated dental-derived MSCs through modulation of NF-kB pathway. Alginate hydrogels with smaller pores and higher elasticity prevent pro-inflammatory cytokine-induced MSC apoptosis by down-regulating the Caspase-3- and 8- associated proapoptotic cascade, leading to higher amounts of ectopic bone regeneration. MSCs encapsulated in hydrogel with higher elasticity exhibited lower expression levels of NF-kB p65 and Cox-2 in vivo. These findings confirm that the fate of encapsulated MSCs are affected by the stiffness and microarchitecture of the encapsulating hydrogel biomaterial, as well as presence of T-lymphocytes/pro-inflammatory cytokines providing evidence concerning material science, stem cell biology, the molecular mechanism of dental-derived MSC-associated therapies, and the potential clinical therapeutic impact of MSCs.

Effects of gelling bath on the physical properties of alginate gel beads and the biological characteristics of entrapped HepG2 cells

Optimizing alginate gel beads is necessary to support the survival, proliferation, and function of entrapped hepatocytes. In this study, gelling bath was modified by decreasing calcium ion concentration and increasing sodium ion concentration. Alginate gel beads (using 36% G sodium alginate) prepared in the modified gelling bath had more homogeneous structure and better mass transfer properties compared with the traditional gelling bath that contains only calcium ions. Moreover, alginate gel beads generated in the modified gelling bath could significantly promote the HepG2 cell proliferation and the growth of cell spheroids, and maintain the albumin secretion ability similar to alginate gel beads prepared in the traditional gelling bath with only calcium ions. The mass transfer properties and cell proliferation were similar in ALG beads with different M/G ratio (36% G and 55% G) generated in the modified gelling bath, whereas they were significantly increased compared with alginate gel beads (55% G) in traditional gelling bath. These results indicated that adjusting the gelling bath was a simple and convenient method to enhance the mass transfer properties of alginate gel beads for 3D hepatocyte culture, which might provide more hepatocytes for the bioartificial liver support system.

Optimizing the fluidized bed bioreactor as an external bioartificial liver

BACKGROUND

Our team previously designed and validated a new bioartificial liver (BAL) called Suppliver based on a Prismaflex™ device, including fluidized bed bioreactors hosting alginate-encapsulated hepatocytes. To ensure correct fluidization within the bioreactor, the beads need to become heavier with the addition of inert glass microspheres.

METHODS

In this study, we assessed the impact of this additional component on the bead production process, bed fluidization, mass transfer and the mechanical properties of the beads, as well as cell viability and basic metabolic function.

RESULTS

A concentration of 20 mg (1% v/v) of microspheres for 15-20 million cells per milliliter of alginate solution appears to be the best configuration. The filling ratio for the beads in the bioreactors can reach 60%. Four 250-mL bioreactors represent approximately 15% of the hepatocytes in a liver, which is a reasonable target for extracorporeal liver supply.

CONCLUSIONS

Increasing bead density clearly maintained the performances of the fluidized bed with plasma of different compositions, without any risk of release out of the bioreactor. A 1% (v/v)-concentration of microspheres in alginate solution did not result in any alteration of the mechanical or biological behavior. This concentration can thus be applied to the production of large-scale encapsulated biomass for further use of the Suppliver setup in human scale preclinical studies.

A tryptophan derivative, ITE, enhances liver cell metabolic functions in vitro

Cell encapsulation provides a three-dimensional support by incorporating isolated cells into microcapsules with the goal of simultaneously maintaining cell survival and function, as well as providing active transport for a bioreactor in vitro similarly to that observed in vivo. However, the biotransformation and metabolic functions of the encapsulated cells are not satisfactory for clinical applications. For this purpose, in this study, hepatoma-derived Huh7 cells/C3A cells were treated with 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE), an endogenous non-toxic ligand for aryl hydrocarbon receptor, in monolayer cultures and on microspheres. The mRNA and protein levels, as well as the metabolic activities of drug metabolizing enzymes, albumin secretion and urea synthesis were determined. When the Huh7 and C3A cells cultured in a monolayer on two-dimensional surfaces, ITE enhanced the protein levels and the metabolic activities of the major cytochrome P450 (CYP450) enzymes, CYP1A1, CYP1A2, CYP3A4 and CYP1B1, and slightly increased albumin secretion and urea synthesis. Moreover, when cultured on microspheres, ITE also substantially increased the protein levels and metabolic activities of CYP1A1, CYP1A2, CYP3A4 and CYP1B1 in both liver cell lines. On the whole, our findings indicate that ITE enhances the enzymatic activities of major CYP450 enzymes and the metabolic functions of liver cells cultured in monolayer or on microspheres, indicating that it may be utilized to improve the functions of hepatocytes. Thus, it may be used in the future for the treatment of liver diseases.

Microstructural, mechanical, and histological evaluation of modified alginate-based scaffolds

Scaffolds are three-dimensional structures used for tissue regeneration being the base in tissue engineering. These scaffolds are obtained from natural and/or synthetic polymers and they should satisfy some specific requirements such as biocompatibility, suitable mechanical, and microstructural properties to favor cellular adhesion and neovascularization. This work shows a preclinic study about the production of low and medium molecular weight alginate through the use of calcium salts (calcium glutamate). The results showed prove that better structures, distribution, and pore sizes as well as better mechanical properties correspond to medium molecular weight alginate and higher calcium salts concentration. This type of scaffold, after muscular cells cultivation, has been proved as an excellent material for muscle growth. The histopathological analysis shows a low inflammatory response, without a foreign body reaction, suitable neovascularization and good fibroblasts incorporation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 3107-3114, 2016.

Selecting Cells for Bioartificial Liver Devices and the Importance of a 3D Culture Environment: A Functional Comparison between the HepaRG and C3A Cell Lines

Recently, the first clinical trials on Bioartificial Livers (BALs) loaded with a proliferative human hepatocyte cell source have started. There are two cell lines that are currently in an advanced state of BAL development; HepaRG and HepG2/C3A. In this study we aimed to compare both cell lines on applicability in BALs and to identify possible strategies for further improvement. We tested both cell lines in monolayer- and BAL cultures on growth characteristics, hepatic differentiation, nitrogen-, carbohydrate-, amino acid- and xenobiotic metabolism. Interestingly, both cell lines adapted the hepatocyte phenotype more closely when cultured in BALs; e.g. monolayer cultures produced lactate, while BAL cultures showed diminished lactate production (C3A) or conversion to elimination (HepaRG), and urea cycle activity increased upon BAL culturing in both cell lines. HepaRG-BALs outperformed C3A-BALs on xenobiotic metabolism, ammonia elimination and lactate elimination, while protein synthesis was comparable. In BAL cultures of both cell lines ammonia elimination correlated positively with glutamine production and glutamate consumption, suggesting ammonia elimination was mainly driven by the balance between glutaminase and glutamine synthetase activity. Both cell lines lacked significant urea cycle activity and both required multiple culture weeks before reaching optimal differentiation in BALs. In conclusion, culturing in BALs enhanced hepatic functionality of both cell lines and from these, the HepaRG cells are the most promising proliferative cell source for BAL application.

Biomedical-grade, high mannuronic acid content (BioMVM) alginate enhances the proteoglycan production of primary human meniscal fibrochondrocytes in a 3-D microenvironment

Alginates are important hydrogels for meniscus tissue engineering as they support the meniscal fibrochondrocyte phenotype and proteoglycan production, the extracellular matrix (ECM) component chiefly responsible for its viscoelastic properties. Here, we systematically evaluated four biomedical- and two nonbiomedical-grade alginates for their capacity to provide the best three-dimensional (3-D) microenvironment and to support proteoglycan synthesis of encapsulated human meniscal fibrochondrocytes in vitro. Biomedical-grade, high mannuronic acid alginate spheres (BioLVM, BioMVM) were the most uniform in size, indicating an effect of the purity of alginate on the shape of the spheres. Interestingly, the purity of alginates did not affect cell viability. Of note, only fibrochondrocytes encapsulated in BioMVM alginate produced and retained significant amounts of proteoglycans. Following transplantation in an explant culture model, the alginate spheres containing fibrochondrocytes remained in close proximity with the meniscal tissue adjacent to the defect. The results reveal a promising role of BioMVM alginate to enhance the proteoglycan production of primary human meniscal fibrochondrocytes in a 3-D hydrogel microenvironment. These findings have significant implications for cell-based translational studies aiming at restoring lost meniscal tissue in regions containing high amounts of proteoglycans.

A New Fluidized Bed Bioreactor Based on Diversion-Type Microcapsule Suspension for Bioartificial Liver Systems

A fluidized bed bioreactor containing encapsulated hepatocytes may be a valuable alternative to a hollow fiber bioreactor for achieving the improved mass transfer and scale-up potential necessary for clinical use. However, a conventional fluidized bed bioreactor (FBB) operating under high perfusion velocity is incapable of providing the desired performance due to the resulting damage to cell-containing microcapsules and large void volume. In this study, we developed a novel diversion-type microcapsule-suspension fluidized bed bioreactor (DMFBB). The void volume in the bioreactor and stability of alginate/chitosan microcapsules were investigated under different flow rates. Cell viability, synthesis and metabolism functions, and expression of metabolizing enzymes at transcriptional levels in an encapsulated hepatocyte line (C3A cells) were determined. The void volume was significantly less in the novel bioreactor than in the conventional FBB. In addition, the microcapsules were less damaged in the DMFBB during the fluidization process as reflected by the results for microcapsule retention rates, swelling, and breakage. Encapsulated C3A cells exhibited greater viability and CYP1A2 and CYP3A4 activity in the DMFBB than in the FBB, although the increases in albumin and urea synthesis were less prominent. The transcription levels of several CYP450-related genes and an albumin-related gene were dramatically greater in cells in the DMFBB than in those in the FBB. Taken together, our results suggest that the DMFBB is a promising alternative for the design of a bioartificial liver system based on a fluidized bed bioreactor with encapsulated hepatocytes for treating patients with acute hepatic failure or other severe liver diseases.

Gingival Mesenchymal Stem Cell (GMSC) Delivery System Based on RGD-Coupled Alginate Hydrogel with Antimicrobial Properties: A Novel Treatment Modality for Peri-Implantitis

PURPOSE

Peri-implantitis is one of the most common inflammatory complications in dental implantology. Similar to periodontitis, in peri-implantitis, destructive inflammatory changes take place in the tissues surrounding a dental implant. Bacterial flora at the failing implant sites resemble the pathogens in periodontal disease and consist of Gram-negative anaerobic bacteria including Aggregatibacter actinomycetemcomitans (Aa). Here we demonstrate the effectiveness of a silver lactate (SL)-containing RGD-coupled alginate hydrogel scaffold as a promising stem cell delivery vehicle with antimicrobial properties.

MATERIALS AND METHODS

Gingival mesenchymal stem cells (GMSCs) or human bone marrow mesenchymal stem cells (hBMMSCs) were encapsulated in SL-loaded alginate hydrogel microspheres. Stem cell viability, proliferation, and osteo-differentiation capacity were analyzed.

RESULTS

Our results showed that SL exhibited antimicrobial properties against Aa in a dose-dependent manner, with 0.50 mg/ml showing the greatest antimicrobial properties while still maintaining cell viability. At this concentration, SL-containing alginate hydrogel was able to inhibit Aa growth on the surface of Ti discs and significantly reduce the bacterial load in Aa suspensions. Silver ions were effectively released from the SL-loaded alginate microspheres for up to 2 weeks. Osteogenic differentiation of GMSCs and hBMMSCs encapsulated in the SL-loaded alginate microspheres were confirmed by the intense mineral matrix deposition and high expression of osteogenesis-related genes.

CONCLUSION

Taken together, our findings confirm that GMSCs encapsulated in RGD-modified alginate hydrogel containing SL show promise for bone tissue engineering with antimicrobial properties against Aa bacteria in vitro.

Development of a Microscale Red Blood Cell-Shaped Pectin-Oligochitosan Hydrogel System Using an Electrospray-Vibration Method: Preparation and Characterization

Purpose

To develop and characterize a microscale pectin-oligochitosan hydrogel microcapsule system that could be applied in such biological fields as drug delivery, cell immobilization/encapsulation, and tissue engineering.

Methods

Microscale pectin-oligochitosan hydrogel microcapsules were prepared by using the vibration/electrostatic spray method. The morphology and chemistry of the hydrogel microcapsules were characterized by using scanning electron microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), respectively. The designed hydrogel microcapsule system was then used to study the responsiveness of the microcapsules to different simulated human body fluids as well as cell encapsulation.

Results

The designed hydrogel microcapsule system exhibited a large surface area-to-volume ratio (red blood cell-shaped) and great pH/enzymatic responsiveness. In addition, this system showed the potential for controlled drug delivery and three-dimensional cell culture.

Conclusion

This system showed a significant potential not only for bioactive-agent delivery, especially to the lower gastrointestinal (GI) tract, but also as a three-dimensional niche for cell culture. In particular, the hydrogel microcapsule system could be used to create artificial red-blood-cells as well as blood substitutes.

Enhanced Viability of Endothelial Colony Forming Cells in Fibrin Microbeads for Sensor Vascularization

Enhanced vascularization at sensor interfaces can improve long-term function. Fibrin, a natural polymer, has shown promise as a biomaterial for sensor coating due to its ability to sustain endothelial cell growth and promote local vascularization. However, the culture of cells, particularly endothelial cells (EC), within 3D scaffolds for more than a few days is challenging due to rapid loss of EC viability. In this manuscript, a robust method for developing fibrin microbead scaffolds for long-term culture of encapsulated ECs is described. Fibrin microbeads are formed using sodium alginate as a structural template. The size, swelling and structural properties of the microbeads were varied with needle gauge and composition and concentration of the pre-gel solution. Endothelial colony-forming cells (ECFCs) were suspended in the fibrin beads and cultured within a perfusion bioreactor system. The perfusion bioreactor enhanced ECFCs viability and genome stability in fibrin beads relative to static culture. Perfusion bioreactors enable 3D culture of ECs within fibrin beads for potential application as a sensor coating.

Three-dimensional systems for in vitro follicular culture: overview of alginate-based matrices

The in vitro culture of ovarian follicles has provided critical insight into the biology of the follicle and its enclosed oocyte and the physical interaction and communication between the theca and granulosa cells and the oocyte that is necessary to produce meiotically competent oocytes. Various two-dimensional (2D) and three-dimensional (3D) culture systems have been developed to evaluate the effect of growth factors, hormones, extracellular matrix components and culture conditions on follicle development and oocyte growth and maturation. Among these culture systems, 3D systems make it possible to maintain follicle structure and support communication between the various cell compartments within the follicle. In this review article, we will discuss the three main approaches to ovarian follicle culture: 2D attachment systems, 3D floating systems and 3D encapsulated systems. We will specifically emphasise the development of and advances in alginate-based encapsulated systems for in vitro follicle culture.

Bone regeneration potential of stem cells derived from periodontal ligament or gingival tissue sources encapsulated in RGD-modified alginate scaffold

Mesenchymal stem cells (MSCs) provide an advantageous alternative therapeutic option for bone regeneration in comparison to current treatment modalities. However, delivering MSCs to the defect site while maintaining a high MSC survival rate is still a critical challenge in MSC-mediated bone regeneration. Here, we tested the bone regeneration capacity of periodontal ligament stem cells (PDLSCs) and gingival mesenchymal stem cells (GMSCs) encapsulated in a novel RGD- (arginine-glycine-aspartic acid tripeptide) coupled alginate microencapsulation system in vitro and in vivo. Five-millimeter-diameter critical-size calvarial defects were created in immunocompromised mice and PDLSCs and GMSCs encapsulated in RGD-modified alginate microspheres were transplanted into the defect sites. New bone formation was assessed using microcomputed tomography and histological analyses 8 weeks after transplantation. Results confirmed that our microencapsulation system significantly enhanced MSC viability and osteogenic differentiation in vitro compared with non-RGD-containing alginate hydrogel microspheres with larger diameters. Results confirmed that PDLSCs were able to repair the calvarial defects by promoting the formation of mineralized tissue, while GMSCs showed significantly lower osteogenic differentiation capability. Further, results revealed that RGD-coupled alginate scaffold facilitated the differentiation of oral MSCs toward an osteoblast lineage in vitro and in vivo, as assessed by expression of osteogenic markers Runx2, ALP, and osteocalcin. In conclusion, these results for the first time demonstrated that MSCs derived from orofacial tissue encapsulated in RGD-modified alginate scaffold show promise for craniofacial bone regeneration. This treatment modality has many potential dental and orthopedic applications.

Liver tissue engineering and cell sources: issues and challenges

Liver diseases are of major concern as they now account for millions of deaths annually. As a result of the increased incidence of liver disease, many patients die on the transplant waiting list, before a donor organ becomes available. To meet the huge demand for donor liver, alternative approaches using liver tissue engineering principles are being actively pursued. Even though adult hepatocytes, the primary cells of the liver are most preferred for tissue engineering of liver, their limited availability, isolation from diseased organs, lack of in vitro propagation and deterioration of function acts as a major drawback to their use. Various approaches have been taken to prevent the functional deterioration of hepatocytes including the provision of an adequate extracellular matrix and co-culture with non-parenchymal cells of liver. Great progress has also been made to differentiate human stem cells to hepatocytes and to use them for liver tissue engineering applications. This review provides an overview of recent challenges, issues and cell sources with regard to liver tissue engineering.

Impact of alginate composition: from bead mechanical properties to encapsulated HepG2/C3A cell activities for in vivo implantation

Recently, interest has focused on hepatocytes' implantation to provide end stage liver failure patients with a temporary support until spontaneous recovery or a suitable donor becomes available. To avoid cell damage and use of an immunosuppressive treatment, hepatic cells could be implanted after encapsulation in a porous biomaterial of bead or capsule shape. The aim of this study was to compare the production and the physical properties of the beads, together with some hepatic cell functions, resulting from the use of different material combinations for cell microencapsulation: alginate alone or combined with type I collagen with or without poly-L-lysine and alginate coatings. Collagen and poly-L-lysine increased the bead mechanical resistance but lowered the mass transfer kinetics of vitamin B12. Proliferation of encapsulated HepG2/C3A cells was shown to be improved in alginate-collagen beads. Finally, when the beads were subcutaneously implanted in mice, the inflammatory response was reduced in the case of alginate mixed with collagen. This in vitro and in vivo study clearly outlines, based on a systematic comparison, the necessity of compromising between material physical properties (mechanical stability and porosity) and cell behavior (viability, proliferation, functionalities) to define optima hepatic cell microencapsulation conditions before implantation.

Advances in cell sources of hepatocytes for bioartificial liver

BACKGROUND

Orthotopic liver transplantation (OLT) is the most effective therapy for liver failure. However, OLT is severely limited by the shortage of liver donors. Bioartificial liver (BAL) shows great potential as an alternative therapy for liver failure. In recent years, progress has been made in BAL regarding genetically engineered cell lines, immortalized human hepatocytes, methods for preserving the phenotype of primary human hepatocytes, and other functional hepatocytes derived from stem cells.

DATA SOURCES

A systematic search of PubMed and ISI Web of Science was performed to identify relevant studies in English language literature using the key words such as liver failure, bioartificial liver, hepatocyte, stem cells, differentiation, and immortalization. More than 200 articles related to the cell sources of hepatocyte in BAL were systematically reviewed.

RESULTS

Methods for preserving the phenotype of primary human hepatocytes have been successfully developed. Many genetically engineered cell lines and immortalized human hepatocytes have also been established. Among these cell lines, the incorporation of BAL with GS-HepG2 cells or alginate-encapsulated HepG2 cells could prolong the survival time and improve pathophysiological parameters in an animal model of liver failure. The cBAL111 cells were evaluated using the AMC-BAL bioreactor, which could eliminate ammonia and lidocaine, and produce albumin. Importantly, BAL loading with HepLi-4 cells could significantly improve the blood biochemical parameters, and prolong the survival time in pigs with liver failure. Other functional hepatocytes differentiated from stem cells, such as human liver progenitor cells, have been successfully achieved.

CONCLUSIONS

Aside from genetically modified liver cell lines and immortalized human hepatocytes, other functional hepatocytes derived from stem cells show great potential as cell sources for BAL. BAL with safe and effective liver cells may be achieved for clinical liver failure in the near future.