Efficacy of Multilayered Hepatocyte Sheet Transplantation for Radiation-Induced Liver Damage and Partial Hepatectomy in a Rat Model

A Novel Approach to Orthotopic Hepatocyte Transplantation Engineered With Liver Hydrogel for Fibrotic Livers, Enhancing Cell-Cell Interaction and Angiogenesis

Hepatocyte transplantation (HCT) is a potential bridging therapy or an alternative to liver transplantation. Conventionally, single-cell hepatocytes are injected via the portal vein. This strategy, however, has yet to overcome poor cell engraftment and function. Therefore, we developed an orthotopic HCT method using a liver-derived extracellular matrix (L-ECM) gel. PXB cells (flesh mature human hepatocytes) were dispersed into the hydrogel solution in vitro, and the gel solution was immediately gelated in 37°C incubators to investigate the affinity between mature human hepatocyte and the L-ECM gel. During the 3-day cultivation in hepatocyte medium, PXB cells formed cell aggregates via cell-cell interactions. Quantitative analysis revealed human albumin production in culture supernatants. For the in vivo assay, PXB cells were encapsulated in the L-ECM gel and transplanted between the liver lobes of normal rats. Pathologically, the L-ECM gel was localized at the transplant site and retained PXB cells. Cell survival and hepatic function marker expression were verified in another rat model wherein thioacetamide was administered to induce liver fibrosis. Moreover, cell-cell interactions and angiogenesis were enhanced in the L-ECM gel compared with that in the collagen gel. Our results indicate that L-ECM gels can help engraft transplanted hepatocytes and express hepatic function as a scaffold for cell transplantation.

Reproducible Preparation of Primary Rat Hepatocyte Sheets Using a Thermoresponsive Culture Dish

Hepatocyte transplantation has been utilized as a therapy for congenital metabolic liver diseases such as hemophilia and for liver function support in acute liver failure. Hepatocyte sheet technology using a thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-grafted dish is expected to provide an efficient cell transplantation method because the resulting hepatocyte sheet possesses extracellular matrix (ECM) on the basal surface, which enhances attachment to the target sites. However, the cultured hepatocytes consume large amounts of oxygen, leading to the loss of a few hepatocytes within the confluent culture sheet owing to a lack of oxygen. To circumvent this problem, this work demonstrates the shortening of diffusion distance, that is, the medium depth, to accelerate oxygen supply from the gas phase/medium interface to the cultured hepatocytes, allowing them to form a monolayer hepatocyte sheet. Incubation of hepatocytes with medium at a depth of 1.3 mm facilitates confluent culture of hepatocytes for 72 h, whereas viable hepatocytes decreased at 2.6 mm depth. Hepatocyte sheets are formed on a 0.5 μg/cm2 fibronectin-physisorbed PIPAAm-grafted dish during 72 h incubation at 37°C. Detachment of the cultured hepatocyte sheet from the PIPAAm-grafted dish where the surface becomes hydrophilic at 20°C is accomplished by scraping the periphery of the sheet using a cell scraper. Furthermore, the apical side of the hepatocyte sheet can be physically grabbed using a gelatin-coated membrane, and the sheet with ECM on the basal surface can be readily transferred to the target site after melting the coated gelatin at 37°C. Both methods are beneficial for creating tissue models by layering with another type of cell sheets, and for quick transplantation, such as into the subcutaneous space and orthotopic transplantation on the surface of the liver.

The preclinical and clinical progress of cell sheet engineering in regenerative medicine

Cell therapy is an accessible method for curing damaged organs or tissues. Yet, this approach is limited by the delivery efficiency of cell suspension injection. Over recent years, biological scaffolds have emerged as carriers of delivering therapeutic cells to the target sites. Although they can be regarded as revolutionary research output and promote the development of tissue engineering, the defect of biological scaffolds in repairing cell-dense tissues is apparent. Cell sheet engineering (CSE) is a novel technique that supports enzyme-free cell detachment in the shape of a sheet-like structure. Compared with the traditional method of enzymatic digestion, products harvested by this technique retain extracellular matrix (ECM) secreted by cells as well as cell-matrix and intercellular junctions established during in vitro culture. Herein, we discussed the current status and recent progress of CSE in basic research and clinical application by reviewing relevant articles that have been published, hoping to provide a reference for the development of CSE in the field of stem cells and regenerative medicine.

Recent Advances in Cell Sheet Engineering: From Fabrication to Clinical Translation

Cell sheet engineering, a scaffold-free tissue fabrication technique, has proven to be an important breakthrough technology in regenerative medicine. Over the past two decades, the field has developed rapidly in terms of investigating fabrication techniques and multipurpose applications in regenerative medicine and biological research. This review highlights the most important achievements in cell sheet engineering to date. We first discuss cell sheet harvesting systems, which have been introduced in temperature-responsive surfaces and other systems to overcome the limitations of conventional cell harvesting methods. In addition, we describe several techniques of cell sheet transfer for preclinical (in vitro and in vivo) and clinical trials. This review also covers cell sheet cryopreservation, which allows short- and long-term storage of cells. Subsequently, we discuss the cell sheet properties of angiogenic cytokines and vasculogenesis. Finally, we discuss updates to various applications, from biological research to clinical translation. We believe that the present review, which shows and compares fundamental technologies and recent advances in cell engineering, can potentially be helpful for new and experienced researchers to promote the further development of tissue engineering in different applications.

Preclinical models of acute liver failure: a comprehensive review

Acute liver failure is marked by the rapid deterioration of liver function in a previously well patient over period of days to weeks. Though relatively rare, it is associated with high morbidity and mortality. This makes it a challenging disease to study clinically, necessitating reliance on preclinical models as means to explore pathophysiology and novel therapies. Preclinical models of acute liver failure are artificial by nature, and generally fall into one of three categories: surgical, pharmacologic or immunogenic. This article reviews preclinical models of acute liver failure and considers their relevance in modeling clinical disease.

Liver bioengineering: Recent trends/advances in decellularization and cell sheet technologies towards translation into the clinic

Development of novel technologies provides the best tissue constructs engineering and maximizes their therapeutic effects in regenerative therapy, especially for liver dysfunctions. Among the currently investigated approaches of tissue engineering, scaffold-based and scaffold-free tissues are widely suggested for liver regeneration. Analogs of liver acellular extracellular matrix (ECM) are utilized in native scaffolds to increase the self-repair and healing ability of organs. Native ECM analog could improve liver repairing through providing the supportive framework for cells and signaling molecules, exerting normal biomechanical, biochemical, and physiological signal complexes. Recently, innovative cell sheet technology is introduced as an alternative for conventional tissue engineering with the advantage of fewer scaffold restrictions and cell culture on a Thermo-Responsive Polymer Surface. These sheets release the layered cells through a temperature-controlled procedure without enzymatic digestion, while preserving the cell-ECM contacts and adhesive molecules on cell-cell junctions. In addition, several novelties have been introduced into the cell sheet and decellularization technologies to aid cell growth, instruct differentiation/angiogenesis, and promote cell migration. In this review, recent trends, advancements, and issues linked to translation into clinical practice are dissected and compared regarding the decellularization and cell sheet technologies for liver tissue engineering.

Chemical conversion of aged hepatocytes into bipotent liver progenitor cells

AIM

In the aging society, understanding the influence of hepatocyte age on hepatocyte donation may inform efforts to expand alternative cell sources to mitigate liver donor shortage. A combination of the molecules Y27632, A-83-01, and CHIR99021 has been used to reprogram rodent young hepatocytes into chemically induced liver progenitor (CLiP) cells; however, whether it could also reprogram aged hepatocytes has not yet been elucidated.

METHODS

Primary hepatocytes were isolated from aged and young donor rats, respectively. Hepatic histological changes were evaluated. Differences in gene expression in hepatocytes were identified. The in vitro reprogramming plasticity of hepatocytes as evidenced by CLiP conversion and the hepatocyte and cholangiocyte maturation capacity of reprogrammed CLIPs were analyzed. The effect of hepatocyte growth factor (HGF) on cell propagation was also investigated.

RESULTS

The histological findings revealed ongoing liver damage with inflammation, fibrosis, senescence, and ductular reaction in aged livers. Microarray analysis showed altered gene expression profiles in hepatocytes from aged donors, especially with regard to metabolic pathways. Aged hepatocytes could be converted into CLiPs (Aged-CLiPs) expressing progenitor cell markers, but with a relatively low proliferative rate compared with young hepatocytes. Aged-CLiPs possessed both hepatocyte and cholangiocyte maturation capacity. HGF facilitated CLiP conversion in aged hepatocytes, which was partly related to the activation of Erk1 and Akt1 signaling.

CONCLUSIONS

Aged rat hepatocytes have retained reprogramming plasticity as evidenced by CLiP conversion in culture. HGF promoted proliferation and CLiP conversion in aged hepatocytes. Hepatocytes from aged donors may be used as an alternative cell source to mitigate donor shortage.

Regenerative medicine for the hepatobiliary system: A review

Liver transplantation, the only proven treatment for end-stage liver disease and acute liver failure, is hampered by the scarcity of donors. Regenerative medicine provides an alternative therapeutic approach. Tremendous efforts dedicated to liver regenerative medicine include the delivery of transplantable cells, microtissues, and bioengineered whole livers via tissue engineering and the maintenance of partial liver function via extracorporeal support. This brief review summarizes the current status of regenerative medicine for the hepatobiliary system. For liver regenerative medicine, the focus is on strategies for expansion of transplantable hepatocytes, generation of hepatocyte-like cells, and therapeutic potential of engineered tissues in liver disease models. For biliary regenerative medicine, the discussion concentrates on the methods for generation of cholangiocyte-like cells and strategies in the treatment of biliary disease. Significant advances have been made in large-scale and long-term expansion of liver cells. The development of tissue engineering and stem cell induction technology holds great promise for the future treatment of hepatobiliary diseases. The application of regenerative medicine in liver still lacks extensive animal experiments. Therefore, a large number of preclinical studies are necessary to provide sufficient evidence for their therapeutic effectiveness. Much remains to be done for the treatment of hepatobiliary diseases with regenerative medicine.

Cell Sheets Restore Secretory Function in Wounded Mouse Submandibular Glands

Thermoresponsive cell culture plates release cells as confluent living sheets in response to small changes in temperature, with recovered cell sheets retaining functional extracellular matrix proteins and tight junctions, both of which indicate formation of intact and functional tissue. Our recent studies demonstrated that cell sheets are highly effective in promoting mouse submandibular gland (SMG) cell differentiation and recovering tissue integrity. However, these studies were performed only at early time points and extension of the observation period is needed to investigate duration of the cell sheets. Thus, the goal of this study was to demonstrate that treatment of wounded mouse SMG with cell sheets is capable of increasing salivary epithelial integrity over extended time periods. The results indicate that cell sheets promote tissue organization as early as eight days after transplantation and that these effects endure through Day 20. Furthermore, cell sheet transplantation in wounded SMG induces a significant time-dependent enhancement of cell polarization, differentiation and ion transporter expression. Finally, this treatment restored saliva quantity to pre-wounding levels at both eight and twenty days post-surgery and significantly improved saliva quality at twenty days post-surgery. These data indicate that cell sheets engineered with thermoresponsive cell culture plates are useful for salivary gland regeneration and provide evidence for the long-term stability of cell sheets, thereby offering a potential new therapeutic strategy for treating hyposalivation.

Decellularized human corneal stromal cell sheet as a novel matrix for ocular surface reconstruction

The shortage of donor corneas as well as the limitations of tissue substitutes leads to the necessity to develop alternative materials for ocular surface reconstruction. Corneal surface substitutes must fulfill specific requirements such as high transparency, low immunogenicity, and mechanical stability combined with elasticity. This in vitro study evaluates a decellularized matrix secreted from human corneal fibroblasts (HCF) as an alternative material for ocular surface reconstruction. HCF from human donors were cultivated with the supplementation of vitamin C to form a stable and thick matrix. Furthermore, due to enhanced cultivation time, a three-dimensional like multilayered construct which partly mimics the complex structure of the corneal stroma could be generated. The formed human cell-based matrices (so-called cell sheets [CS]) were subsequently decellularized. The complete cell removal, collagen content, ultrastructure, and cell toxicity of the decellularized CS (DCS) as well as biomechanical properties were analyzed. Surgical feasibility was tested on enucleated porcine eyes. After decellularization and sterilization, a transparent, thick, cell free, and sterile tissue substitute resulted, which allowed expansion of limbal epithelial stem cells with no signs of cytotoxicity, and good surgical feasibility. DCS seem to be a promising new corneal tissue substitute derived from human cells without the limitation of donor material; however, future in vivo studies are necessary to further elucidate its potential for ocular surface reconstruction.

Advanced Biomaterials and Processing Methods for Liver Regeneration: State-of-the-Art and Future Trends

Liver diseases contribute markedly to the global burden of mortality and disease. The limited organ disposal for orthotopic liver transplantation results in a continuing need for alternative strategies. Over the past years, important progress has been made in the field of tissue engineering (TE). Many of the early trials to improve the development of an engineered tissue construct are based on seeding cells onto biomaterial scaffolds. Nowadays, several TE approaches have been developed and are applied to one vital organ: the liver. Essential elements must be considered in liver TE-cells and culturing systems, bioactive agents or growth factors (GF), and biomaterials and processing methods. The potential of hepatocytes, mesenchymal stem cells, and others as cell sources is demonstrated. They need engineered biomaterial-based scaffolds with perfect biocompatibility and bioactivity to support cell proliferation and hepatic differentiation as well as allowing extracellular matrix deposition and vascularization. Moreover, they require a microenvironment provided using conventional or advanced processing technologies in order to supply oxygen, nutrients, and GF. Herein the biomaterials and the conventional and advanced processing technologies, including cell-sheets process, 3D bioprinting, and microfluidic systems, as well as the future trends in these major fields are discussed.

Generation of Transplantable Three-Dimensional Hepatic-Patch to Improve the Functionality of Hepatic Cells In Vitro and In Vivo

Cell therapy and tissue engineering (TE) are considered alternative therapeutic approaches to organ transplantation. Since cell therapy approaches achieved little success for liver failure treatment, liver TE is considered a more promising alternative. In this study, we produced a liver tissue equivalent (called "liver-derived extracellular matrix scaffold [LEMS]-Patch") by co-culture of human bone marrow stromal cells, human umbilical vein endothelial cells, and a hepatoma cell line, Huh7, within an artificial three-dimensional liver-extracellular matrix scaffold. The results showed significant increase in the liver-specific gene expression and hepatic functions, in terms of albumin (ALB) and fibrinogen secretion, urea production, and cytochrome inducibility in the LEMS-Patch compared to controls. In addition, transplanted LEMS-Patch was successfully incorporated into the recipient liver of acute liver failure mice and produced human ALB. Consequently, our data demonstrated that the generated LEMS-Patch could be used as a good platform for functional improvement of hepatic cells in vitro and in vivo.

Using cell sheets to regenerate mouse submandibular glands

Temperature-responsive polymer grafted tissue culture dishes release cells as confluent living sheets in response to small changes in temperature, with recovered cell sheets retaining cell-cell communications, functional extracellular matrices and tissue-like behaviors. These features promote tissue regeneration and improve transplantation efficacy in various tissues including cartilage, heart, kidney, liver, endometrium, cornea, middle ear, periodontium, and esophageal living sheet transplants. However, the functional effects of cell sheets for salivary gland regeneration to treat hyposalivation have not yet been studied. Thus, the present study aims to both establish the viability of thermoresponsive cell sheets for use in salivary glands and then explore the delivery option (i.e., single vs. multiple layers) that would result in the most complete tissue growth in terms of cell differentiation and recovered tissue integrity. Results indicate that single cell sheets form polarized structures that maintain cell-cell junctions and secretory granules in vitro while layering of two-single cell sheets forms a glandular-like pattern in vitro. Moreover, double layer cell sheets enhance tissue formation, cell differentiation and saliva secretion in vivo. In contrast, single cell sheets demonstrated only modest gains relative to the robust growth seen with the double layer variety. Together, these data verify the utility of thermoresponsive cell sheets for use in salivary glands and indicates the double layer form to provide the best option in terms of cell differentiation and recovered tissue integrity, thereby offering a potential new therapeutic strategy for treating hyposalivation.

In vitro and in vivo fabrication of stable human hepatocyte tissue in combination with normal fibroblasts derived from donors of various ages

In order to establish a minimally invasive and safe liver regenerative technology, a technique for fabricating liver tissue possessing a vascular network was developed by subcutaneously transplanting a cell sheet composed of primary human hepatocytes and normal fibroblasts. However, differences in fibroblast characteristics owing to donor age may threaten the stability of liver tissue regenerated via this technology. Herein we describe the influence of fibroblasts from multiple donors on the fabrication of engineered human hepatocyte tissues invitro and in vivo. Primary human hepatocytes were cultured with seven strains of fibroblasts derived from the skins of donors of various ages, ranging from a fetus (12 weeks) to the elderly (69 years). Engineered hepatocyte sheets were successfully harvested for all strains. At 2 weeks after the subcutaneous transplantation of the hepatocyte sheets into mice, the highest human albumin (hALB) serum concentration was noted in the mouse containing fibroblasts from a 12 year old (TIG-118). Since the platelet-derived growth factor subunit B (PDGFB) gene expression of TIG-118 cells was significantly higher than that in the other cells, PDGFB may be considered to play an important role in the initial subcutaneous engraftment of primary human hepatocytes. Even though hALB concentration exhibited a parabolic tendency with age, there was no statistically significant difference noted within 6-8 weeks after transplantation. The present study demonstrates that this technology can produce consistent and stable hepatocyte sheets that exhibit long-term survival and liver-specific functionality in vivo regardless of the fibroblast donor age.

Reversal of established liver fibrosis by IC-2-engineered mesenchymal stem cell sheets

Chronic hepatitis viral infection, alcoholic intoxication, and obesity cause liver fibrosis, which progresses to decompensated liver cirrhosis, a disease for which medical demands cannot be met. Since there are currently no approved anti-fibrotic therapies for established liver fibrosis, the development of novel modalities is required to improve patient prognosis. In this study, we clarified the anti-fibrotic effects of cell sheets produced from human bone marrow-derived mesenchymal stem cells (MSCs) incubated on a temperature-sensitive culture dish with the chemical compound IC-2. Orthotopic transplantation of IC-2-engineered MSC sheets (IC-2 sheets) remarkably reduced liver fibrosis induced by chronic CCl4 administration. Further, the marked production of fibrolytic enzymes such as matrix metalloproteinase (MMP)-1 and MMP-14, as well as thioredoxin, which suppresses hepatic stellate cell activation, was observed in IC-2 sheets. Moreover, the anti-fibrotic effect of IC-2 sheets was much better than that of MSC sheets. Finally, knockdown experiments revealed that MMP-14 was primarily responsible for the reduction of liver fibrosis. Here, we show that IC-2 sheets could be a promising therapeutic option for established liver fibrosis.

Cell encapsulation: Overcoming barriers in cell transplantation in diabetes and beyond

Cell-based therapy is emerging as a promising strategy for treating a wide range of human diseases, such as diabetes, blood disorders, acute liver failure, spinal cord injury, and several types of cancer. Pancreatic islets, blood cells, hepatocytes, and stem cells are among the many cell types currently used for this strategy. The encapsulation of these "therapeutic" cells is under intense investigation to not only prevent immune rejection but also provide a controlled and supportive environment so they can function effectively. Some of the advanced encapsulation systems provide active agents to the cells and enable a complete retrieval of the graft in the case of an adverse body reaction. Here, we review various encapsulation strategies developed in academic and industrial settings, including the state-of-the-art technologies in advanced preclinical phases as well as those undergoing clinical trials, and assess their advantages and challenges. We also emphasize the importance of stimulus-responsive encapsulated cell systems that provide a "smart and live" therapeutic delivery to overcome barriers in cell transplantation as well as their use in patients.

Hepatic cell sheets engineered from human mesenchymal stem cells with a single small molecule compound IC-2 ameliorate acute liver injury in mice

INTRODUCTION

We previously reported that transplantation of hepatic cell sheets from human bone marrow-derived mesenchymal stem cells (BM-MSCs) with hexachlorophene, a Wnt/β-catenin signaling inhibitor, ameliorated acute liver injury. In a further previous report, we identified IC-2, a newly synthesized derivative of the Wnt/β-catenin signaling inhibitor ICG-001, as a potent inducer of hepatic differentiation of BM-MSCs.

METHODS

We manufactured hepatic cell sheets by engineering from human BM-MSCs using the single small molecule IC-2. The therapeutic potential of IC-2-induced hepatic cell sheets was assessed by transplantation of IC-2- and hexachlorophene-treated hepatic cell sheets using a mouse model of acute liver injury.

RESULTS

Significant improvement of liver injury was elicited by the IC-2-treated hepatic cell sheets. The expression of complement C3 was enhanced by IC-2, followed by prominent hepatocyte proliferation stimulated through the activation of NF-κB and its downstream molecule STAT-3. Indeed, IC-2 also enhanced the expression of amphiregulin, resulting in the activation of the EGFR pathway and further stimulation of hepatocyte proliferation. As another important therapeutic mechanism, we revealed prominent reduction of oxidative stress mediated through upregulation of the thioredoxin (TRX) system by IC-2-treated hepatic cell sheets. The effects mediated by IC-2-treated sheets were superior compared with those mediated by hexachlorophene-treated sheets.

CONCLUSION

The single compound IC-2 induced hepatic cell sheets that possess potent regeneration capacity and ameliorate acute liver injury.

Liver cell therapy: is this the end of the beginning?

The prevalence of liver diseases is increasing globally. Orthotopic liver transplantation is widely used to treat liver disease upon organ failure. The complexity of this procedure and finite numbers of healthy organ donors have prompted research into alternative therapeutic options to treat liver disease. This includes the transplantation of liver cells to promote regeneration. While successful, the routine supply of good quality human liver cells is limited. Therefore, renewable and scalable sources of these cells are sought. Liver progenitor and pluripotent stem cells offer potential cell sources that could be used clinically. This review discusses recent approaches in liver cell transplantation and requirements to improve the process, with the ultimate goal being efficient organ regeneration. We also discuss the potential off-target effects of cell-based therapies, and the advantages and drawbacks of current pre-clinical animal models used to study organ senescence, repopulation and regeneration.

Hepatocyte Transplantation: Cell Sheet Technology for Liver Cell Transplantation

Purpose of Review

We will review the recent developments of cell sheet technology as a feasible tissue engineering approach. Specifically, we will focus on the technological advancement for engineering functional liver tissue using cell sheet technology, and the associated therapeutic effect of cell sheets for liver diseases, highlighting hemophilia.

Recent Findings

Cell-based therapies using hepatocytes have recently been explored as a new therapeutic modality for patients with many forms of liver disease. We have developed a cell sheet technology, which allows cells to be harvested in a monolithic layer format. We have succeeded in fabricating functional liver tissues in mice by stacking the cell sheets composed of primary hepatocytes. As a curative measure for hemophilia, we have also succeeded in treating hemophilia mice by transplanting of cells sheets composed of genetically modified autologous cells.

Summary

Tissue engineering using cell sheet technology provides the opportunity to create new therapeutic options for patients with various types of liver diseases.

In vivo construction of liver tissue by implantation of a hepatic non-parenchymal/adipose-derived stem cell sheet

Subcutaneous hepatocyte sheet implantation is an attractive therapeutic option for various liver diseases. However, this technique is limited by the availability of hepatocytes. Thus, the use of hepatic non-parenchymal cells (NPCs) containing small hepatocytes, which have the ability to proliferate more rapidly than mature hepatocytes, for transplantation has been suggested. The aim of our study was to construct liver tissue subcutaneously in rats by implanting NPC sheets co-cultivated with adipose-derived stem cells (ADSCs), which produce certain angiogenic factors. We crafted NPC-ADSC sheets on temperature-responsive culture dishes. NPCs formed functioning bile canaliculi and stored glycogen. In addition, their ability to produce albumin was not inferior to that of hepatocytes. Albumin production increased over time when co-cultivated with ADSCs. We then implanted the co-cultivated cell sheets subcutaneously. The co-cultivated sheets retained glycogen, formed bile canaliculi, showed signs of vascularization and survived subcutaneously without pre-vascularization. These results suggest that NPCs can be a viable option in cell therapy for liver diseases. This technique using co-cultivated cell sheets may be useful in the field of regenerative medicine. Copyright © 2017 John Wiley & Sons, Ltd.

Metabolic Oscillations in Co-Cultures of Hepatocytes and Mesenchymal Stem Cells: Effects of Seeding Arrangement and Culture Mixing

In vitro assembly of functional liver tissue is a prerequisite for the transplantation of tissue-engineered livers. There is an increasing demand for in vitro models that replicate complex events occurring in the liver. However, tissue engineering of implantable liver systems is currently limited by the difficulty of assembling three dimensional hepatocyte cultures of a useful size, while maintaining full cell viability. Recent reports have demonstrated that bone marrow mesenchymal stem cells (BM-MSCs) can provide a number of cues promoting hepatocyte growth and development. In this study, the effects of BM-MSCs co-culture on hepatocyte metabolism were evaluated as a function of scaffold seeding arrangement. BM-MSCs were co-cultured with hepatocytes in porous chitosan-heparin scaffolds using several seeding arrangements. The seeded scaffolds were subjected to orbital shaking to enhance mass transfer. BM-MSC-hepatocyte co-cultures exhibited higher rates of hepatocyte-specific functions, compared to hepatocyte-only cultures, regardless of the seeding arrangement. Cells formed smaller-compact spheroids in the heterotypic systems compared to mono-cultures of hepatocytes only. The spheroids exhibited reduction in size with time in all conditions except for the condition where BM-MSCs were seeded one day after seeding hepatocytes. In this condition, spheroids increased in size due to BM-MSC proliferation. Spheroid size reduction was hypothesized to be the result of cyclic shear stresses generated by the orbital shaking. Furthermore, results suggested that BM-MSC seeding onto preformed hepatocyte spheroids provide a degree of shear-protection and trophic stimuli. Overall, the results indicate that co-culturing hepatocytes with BM-MSCs enhanced their metabolic functions for the first week of culture. J. Cell. Biochem. 118: 3003-3015, 2017. © 2017 Wiley Periodicals, Inc.

Human hepatocytes loaded in 3D bioprinting generate mini-liver

BACKGROUND

Because of an increasing discrepancy between the number of potential liver graft recipients and the number of organs available, scientists are trying to create artificial liver to mimic normal liver function and therefore, to support the patient's liver when in dysfunction. 3D printing technique meets this purpose. The present study was to test the feasibility of 3D hydrogel scaffolds for liver engineering.

METHODS

We fabricated 3D hydrogel scaffolds with a bioprinter. The biocompatibility of 3D hydrogel scaffolds was tested. Sixty nude mice were randomly divided into four groups, with 15 mice in each group: control, hydrogel, hydrogel with L02 (cell line HL-7702), and hydrogel with hepatocyte growth factor (HGF). Cells were cultured and deposited in scaffolds which were subsequently engrafted into livers after partial hepatectomy and radiation-induced liver damage (RILD). The engrafted tissues were examined after two weeks. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, total bilirubin, CYP1A2, CYP2C9, glutathione S-transferase (a-GST), and UDP-glucuronosyl transferase (UGT-2) were compared among the groups. Hematoxylin-eosin (HE) staining and immunohistochemistry of cKit and cytokeratin 18 (CK18) of engrafted tissues were evaluated. The survival time of the mice was also compared among the four groups.

RESULTS

3D hydrogel scaffolds did not impact the viability of cells. The levels of ALT, AST, albumin, total bilirubin, CYP1A2, CYP2C9, a-GST and UGT-2 were significantly improved in mice engrafted with 3D scaffold loaded with L02 compared with those in control and scaffold only (P<0.05). HE staining showed clear liver tissue and immunohistochemistry of cKit and CK18 were positive in the engrafted tissue. Mice treated with 3D scaffold+L02 cells had longer survival time compared with those in control and scaffold only (P<0.05).

CONCLUSION

3D scaffold has the potential of recreating liver tissue and partial liver functions and can be used in the reconstruction of liver tissues.

Fabrication of Inverted Colloidal Crystal Poly(ethylene glycol) Scaffold: A Three-dimensional Cell Culture Platform for Liver Tissue Engineering

The ability to maintain hepatocyte function in vitro, for the purpose of testing xenobiotics' cytotoxicity, studying virus infection and developing drugs targeted at the liver, requires a platform in which cells receive proper biochemical and mechanical cues. Recent liver tissue engineering systems have employed three-dimensional (3D) scaffolds composed of synthetic or natural hydrogels, given their high water retention and their ability to provide the mechanical stimuli needed by the cells. There has been growing interest in the inverted colloidal crystal (ICC) scaffold, a recent development, which allows high spatial organization, homotypic and heterotypic cell interaction, as well as cell-extracellular matrix (ECM) interaction. Herein, we describe a protocol to fabricate the ICC scaffold using poly (ethylene glycol) diacrylate (PEGDA) and the particle leaching method. Briefly, a lattice is made from microsphere particles, after which a pre-polymer solution is added, properly polymerized, and the particles are then removed, or leached, using an organic solvent (e.g., tetrahydrofuran). The dissolution of the lattice results in a highly porous scaffold with controlled pore sizes and interconnectivities that allow media to reach cells more easily. This unique structure allows high surface area for the cells to adhere to as well as easy communication between pores, and the ability to coat the PEGDA ICC scaffold with proteins also shows a marked effect on cell performance. We analyze the morphology of the scaffold as well as the hepatocarcinoma cell (Huh-7.5) behavior in terms of viability and function to explore the effect of ICC structure and ECM coatings. Overall, this paper provides a detailed protocol of an emerging scaffold that has wide applications in tissue engineering, especially liver tissue engineering.