Spheroid formation and differentiation into hepatocyte-like cells of rat mesenchymal stem cell induced by co-culture with liver cells

Stem Cell-Based Strategies: The Future Direction of Bioartificial Liver Development

Acute liver failure (ALF) results from severe liver damage or end-stage liver disease. It is extremely fatal and causes serious health and economic burdens worldwide. Once ALF occurs, liver transplantation (LT) is the only definitive and recommended treatment; however, LT is limited by the scarcity of liver grafts. Consequently, the clinical use of bioartificial liver (BAL) has been proposed as a treatment strategy for ALF. Human primary hepatocytes are an ideal cell source for these methods. However, their high demand and superior viability prevent their widespread use. Hence, finding alternatives that meet the seed cell quality and quantity requirements is imperative. Stem cells with self-renewing, immunogenic, and differentiative capacities are potential cell sources. MSCs and its secretomes encompass a spectrum of beneficial properties, such as anti-inflammatory, immunomodulatory, anti-ROS (reactive oxygen species), anti-apoptotic, pro-metabolomic, anti-fibrogenesis, and pro-regenerative attributes. This review focused on the recent status and future directions of stem cell-based strategies in BAL for ALF. Additionally, we discussed the opportunities and challenges associated with promoting such strategies for clinical applications.

The Efficiency of Stem Cells (SCs) Differentiation into Functional Hepatocytes for Treating Liver Disorders: A Systematic Review

Stem cells provided new opportunity to treat various diseases, including liver disorders. Stem cells are unspecialized cells, stimulating influential research interest be indebted to their multipotent self-renewal capacity and differentiation characteristics into several specialized cell types. Many factors contribute to their differentiation into different cell types such as insulin producing cells, osteoblast, and hepatocytes. Accordingly, wide range methods and materials have been used to transform stem cells into hepatocytes, but effectiveness of differentiation is different and depends on several factors such as cell-to-cell adhesion, cell-to-cell contact, and cell biological change. Search was done in PubMed, Scopus, and WOS to evaluate results of studies about stem cells differentiation for higher efficacy. Among more than 28000 papers, 51 studies were considered eligible for more evaluations. Results indicated that most studies were performed on mesenchymal stem cells compared with other types. Acute liver failure was the most investigated liver disorder, and tissue engineering was the most investigated differentiation methods. Also, functional parameters were the most evaluated parameters in assessing differentiation efficacy. We summarize recent advances in increasing efficiency of stem cells differentiation using varied materials, since promising results of this review, further studies are needed to assess efficiency and safety of these cells transplantation in some liver disease treatment.

Therapeutic Efficiency of Nasal Mucosa-Derived Ectodermal Mesenchymal Stem Cells in Rats with Acute Hepatic Failure

Background

Liver transplantation is limited by the insufficiency of liver organ donors when treating end-stage liver disease or acute liver failure (ALF). Ectodermal mesenchymal stem cells (EMSCs) derived from nasal mucosa have emerged as an alternative cell-based therapy. However, the role of EMSCs in acute liver failure remains unclear.

Methods

EMSCs were obtained from the nasal mucosa tissue of rats. First, EMSCs were seeded on the gelatin-chitosan scaffolds, and the biocompatibility was evaluated. Next, the protective effects of EMSCs were investigated in carbon tetrachloride- (CCl₄-) induced ALF rats. Finally, we applied an indirect coculture system to analyze the paracrine effects of EMSCs on damaged hepatocytes. A three-step nontransgenic technique was performed to transform EMSCs into hepatocyte-like cells (HLCs) in vitro.

Results

EMSCs exhibited a similar phenotype to other mesenchymal stem cells along with self-renewal and multilineage differentiation capabilities. EMSC-seeded gelatin-chitosan scaffolds can increase survival rates and ameliorate liver function and pathology of ALF rat models. Moreover, transplanted EMSCs can secrete paracrine factors to promote hepatocyte regeneration, targeted migration, and transdifferentiate into HLCs in response to the liver's microenvironment, which will then repair or replace the damaged hepatocytes. Similar to mature hepatocytes, HLCs generated from EMSCs possess functions of expressing specific hepatic markers, storing glycogen, and producing urea.

Conclusions

These results confirmed the feasibility of EMSCs in acute hepatic failure treatment. To our knowledge, this is the first time that EMSCs are used in the therapy of liver diseases. EMSCs are expected to be a novel and promising cell source in liver tissue engineering.

The Effect of Oral Mucosal Mesenchymal Stem Cells on Pathological and Long-Term Outcomes in Experimental Traumatic Brain Injury

Background

Neuroprotective effects of stem cells have been shown in some neurologic diseases. In this study, the effect of oral mucosal mesenchymal stem cells (OMSCs) on traumatic brain injury (TBI) was evaluated in long term.

Materials and Methods

TBI was induced by Marmarou's method. The number of 2 × 10⁶ OMSCs was intravenously injected 1 and 24 h after the injury. Brain edema and pathological outcome were assessed at 24 h and 21 days after the injury. Besides, long-term neurological, motor, and cognitive outcomes were evaluated at days 3, 7, 14, and 21 after the injury.

Results

OMSCs administration could significantly inhibit microglia proliferation, and reduce brain edema and neuronal damage, at 24 h and 21 days after the injury. Neurological function improvement was observed in the times evaluated in OMSCs group. Cognitive and motor function dysfunction and anxiety-like behavior were prevented especially at 14 and 21 days after the injury in the treatment group.

Conclusion

According to the results of this study, OMSCs administration after TBI reduced brain edema and neuronal damage, improved neurologic outcome, and prevented memory and motor impairments and anxiety-like behavior in long term.

From hair to liver: emerging application of hair follicle mesenchymal stem cell transplantation reverses liver cirrhosis by blocking the TGF-β/Smad signaling pathway to inhibit pathological HSC activation

Liver cirrhosis (LC) involves multiple systems throughout the body, and patients with LC often die of multiple organ failure. However, few drugs are useful to treat LC. Hair follicle mesenchymal stem cells (HF-MSCs) are derived from the dermal papilla and the bulge area of hair follicles and are pluripotent stem cells in the mesoderm with broad prospects in regenerative medicine. As an emerging seed cell type widely used in skin wound healing and plastic surgery, HF-MSCs show considerable prospects in the treatment of LC due to their proliferation and multidirectional differentiation capabilities. We established an LC model in C57BL/6J mice by administering carbon tetrachloride (CCl₄) and injected HF-MSCs through the tail vein to explore the therapeutic effects and potential mechanisms of HF-MSCs on LC. Here, we found that HF-MSCs improved liver function and ameliorated the liver pathology of LC. Notably, PKH67-labeled HF-MSCs were detected in the injured liver and expressed the hepatocyte-specific markers cytokeratin 18 (CK18) and albumin (ALB). In addition, in contrast to that in the LC group, the α-SMA expression showed a decreasing trend in the treatment group in vitro and in vivo, indicating that the pathological activation of hepatic stellate cells (HSCs) was inhibited by HF-MSC treatment. Moreover, the levels of transforming growth factor β (TGF-β1) and p-Smad3, a signaling molecule downstream of TGF-β1, were increased in mice with LC, while HF-MSC treatment reversed these changes in vivo and in vitro. Based on these findings, HF-MSCs may reverse LC by blocking the TGF-β/Smad pathway and inhibiting the pathological activation of HSCs, which may provide evidence for the application of HF-MSCs to treat LC.

3D Cell Culture Systems: Tumor Application, Advantages, and Disadvantages

The traditional two-dimensional (2D) in vitro cell culture system (on a flat support) has long been used in cancer research. However, this system cannot be fully translated into clinical trials to ideally represent physiological conditions. This culture cannot mimic the natural tumor microenvironment due to the lack of cellular communication (cell-cell) and interaction (cell-cell and cell-matrix). To overcome these limitations, three-dimensional (3D) culture systems are increasingly developed in research and have become essential for tumor research, tissue engineering, and basic biology research. 3D culture has received much attention in the field of biomedicine due to its ability to mimic tissue structure and function. The 3D matrix presents a highly dynamic framework where its components are deposited, degraded, or modified to delineate functions and provide a platform where cells attach to perform their specific functions, including adhesion, proliferation, communication, and apoptosis. So far, various types of models belong to this culture: either the culture based on natural or synthetic adherent matrices used to design 3D scaffolds as biomaterials to form a 3D matrix or based on non-adherent and/or matrix-free matrices to form the spheroids. In this review, we first summarize a comparison between 2D and 3D cultures. Then, we focus on the different components of the natural extracellular matrix that can be used as supports in 3D culture. Then we detail different types of natural supports such as matrigel, hydrogels, hard supports, and different synthetic strategies of 3D matrices such as lyophilization, electrospiding, stereolithography, microfluid by citing the advantages and disadvantages of each of them. Finally, we summarize the different methods of generating normal and tumor spheroids, citing their respective advantages and disadvantages in order to obtain an ideal 3D model (matrix) that retains the following characteristics: better biocompatibility, good mechanical properties corresponding to the tumor tissue, degradability, controllable microstructure and chemical components like the tumor tissue, favorable nutrient exchange and easy separation of the cells from the matrix.

3D bioprinted tissue-specific spheroidal multicellular microarchitectures for advanced cell therapy

Intercellular interaction is the most crucial factor in promoting cell viability and functionality in an engineered tissue system. Of the various shapes available for cell-laden constructs, spheroidal multicellular microarchitectures (SMMs) have been introduced as building blocks and injectable cell carriers with substantial cell-cell and cell-extracellular matrix (ECM) interactions. Here, we developed a precise and expeditious SMM printing method that can create a tissue-specific microenvironment and thus be potentially useful for cell therapy. This printing strategy is designed to manufacture SMMs fabricated with optimal bioink blended with decellularized ECM and alginate to enhance the functional performance of the encapsulated cells. Experimental results showed that the proposed method allowed for size controllability and mass production of SMMs with high cell viability. Moreover, SMMs co-cultured with endothelial cells promoted lineage-specific maturation and increased functionality compared to monocultured SMMs. Overall, it was concluded that SMMs have the potential for use in cell therapy due to their high cell retention and proliferation rate compared to single-cell injection, particularly for efficient tissue regeneration after myocardial infarction. This study suggests that utilizing microextrusion-based 3D bioprinting technology to encapsulate cells in cell-niche-standardized SMMs can expand the range of possible applications.

Changes in characteristics of periodontal ligament stem cells in spheroid culture

OBJECTIVES

The periodontal ligament (PDL) has important roles in maintaining homeostasis, wound healing, and regeneration of periodontal tissues by supplying stem/progenitor cells. Periodontal ligament stem cells (PDLSCs) have mesenchymal stem cell (MSC)-like characteristics and can be isolated from periodontal tissues. The aim of this study was to examine the effect of three-dimensional spheroid culture on the characteristics of PDLSCs.

MATERIAL AND METHODS

Periodontal ligament stem cells were isolated and cultured from healthy teeth, and PDLSC spheroids were formed by pellet culture in polypropylene tubes. The proliferation of PDLSCs in spheroids and conventional two-dimensional (2D) cultures were examined by immunostaining for Ki67. Cell death and cell size were analyzed using flow cytometry. Gene expression changes were investigated by quantitative real time PCR.

RESULTS

Periodontal ligament stem cells spontaneously formed spheroid masses in pellet culture. The size of PDLSC spheroids was inversely proportional to the culture period. Fewer Ki67-positive cells were detected in PDLSC spheroids compared to those in 2D culture. Flow cytometry revealed an increase in dead cells and a decrease in cell size in PDLSC spheroids. The expression levels of genes related to anti-inflammation (TSG6, COX2, MnSOD) and angiogenesis (VEGF, bFGF, HGF) were drastically increased by spheroid culture compared to 2D culture. TSG6 gene expression was inhibited in PDLSC spheroids in the presence of the apoptosis signal inhibitor, Z-VAD-FMK. Additionally, PDLSC spheroid transplantation into rat periodontal defects did not induce the regeneration of periodontal tissues.

CONCLUSIONS

We found that spheroid culture of PDLSCs affected several characteristics of PDLSCs, including the expression of genes related to anti-inflammation and angiogenesis; apoptosis signaling may be involved in these changes. Our results revealed the characteristics of PDLSCs in spheroid culture and have provided new information to the field of stem cell research.

Historical Perspectives and Advances in Mesenchymal Stem Cell Research for the Treatment of Liver Diseases

Liver transplantation is the only effective therapy for patients with decompensated cirrhosis and fulminant liver failure. However, due to a shortage of donor livers and complications associated with immune suppression, there is an urgent need for new therapeutic strategies for patients with end-stage liver diseases. Given their unique function in self-renewal and differentiation potential, stem cells might be used to regenerate damaged liver tissue. Recent studies have shown that stem cell-based therapies can improve liver function in a mouse model of hepatic failure. Moreover, acellular liver scaffolds seeded with hepatocytes produced functional bioengineered livers for organ transplantation in preclinical studies. The therapeutic potential of stem cells or their differentiated progenies will depend on their capacity to differentiate into mature and functional cell types after transplantation. It will also be important to devise methods to overcome their genomic instability, immune reactivity, and tumorigenic potential. We review directions and advances in the use of mesenchymal stem cells and their derived hepatocytes for liver regeneration. We also discuss the potential applications of hepatocytes derived from human pluripotent stem cells and challenges to using these cells in treating end-stage liver disease.

In vitro and in vivo study of the application of volvox spheres to co-culture vehicles in liver tissue engineering

Volvox sphere is a biomimetic concept of a natural Volvox, wherein a large outer sphere contains smaller inner spheres, which can encapsulate cells and provide a double-layer three-dimensional environment for culturing cells. This study simultaneously encapsulated rat mesenchymal stem cells (MSCs) and AML12 hepatocytes in volvox spheres and extensively evaluated the effects of various culturing modes on cell functions and fates. The results showed that compared with a static flask culture, MSCs encapsulated in volvox spheres differentiated into hepatocyte-like cells with a 2-fold increase in albumin (ALB) expression and a 2.5-fold increase in cytokeratin 18 expression in a dynamic bioreactor. Moreover, the restorative effects of volvox spheres encapsulating cells on retrorsine-exposed CCl₄-induced liver injuries in rats were evaluated. The data presented significant reductions in AST and ALT levels after the implantation of volvox spheres encapsulating both MSCs and AML12 hepatocytes in vivo. In contrast to the negative control group, histopathological analysis demonstrated liver repair and formation of the new liver tissue in groups implanted with volvox spheres containing cells. These results demonstrate that liver cells implanted with volvox spheres encapsulating both MSCs and AML12 hepatocytes promote liver repair and liver tissue regeneration in liver failure caused by necrotizing agents such as retrorsine and CCl₄. Hence, volvox spheres encapsulating MSCs and liver cells can be a promising and clinically effective therapy for liver injury.

STATEMENT OF SIGNIFICANCE

In this study, we used a volvox sphere, which is a unique design that mimics the natural Volvox, that consists of a large outer sphere that contains smaller inner spheres, which provide a three-dimensional environment to culture cells. The purpose of this study is to co-culture mesenchymal stem cells (MSCs) and AML12 liver cells in volvox spheres and evaluate two different culture methods, dynamic bioreactor and static culture flask,on the cultured cells. In addition, we aimed to evaluate the restorative effects of volvox spheres encapsulating MSCs and/or AML12 liver cells on rats with retrorsine-exposed CCl₄-induced liver injuries. The results showed that MSCs encapsulated in volvox spheres differentiated into hepatocyte-like cells with a 2-fold increase in albumin expression and a 2.5-fold increase in cytokeratin 18 expression ina dynamic bioreactor. Moreover, the data presented significant reductions in AST and ALT levels after the implantation of volvox spheres encapsulating both MSCs and AML12 hepatocytes in vivo. In contrast to the negative control group, histopathological analysis demonstrated liver repair and formation of new liver tissue in groups implanted with volvox spheres containing cells. These results demonstrate that liver cells implanted with volvox spheres encapsulating both MSCs and AML12 hepatocytes promote liver repair and liver tissue regeneration in liver failure caused by necrotizing agents such as retrorsine and CCl₄. Hence, volvox spheres encapsulating MSCs and liver cells can be a promising and clinically effective therapy for liver injury.

Differentiation Potential of Breast Milk-Derived Mesenchymal Stem Cells into Hepatocyte-Like Cells

Human breast milk stem cells (hBSCs) contain a population of cells with the ability to differentiate into various cell lineages for cell therapy applications. The current study examined the differentiation potential of hBSCs into hepatocytes-like cells. The cells were isolated from the breast milk and were treated with hepatogenic medium containing hepatocyte growth factor, insulin-like growth factor and dexamethasone for 7 days subsequently; Oncostatin M was added to the culture media. RT-PCR and immunocytochemistry were performed to detect the hepatogenic markers. The glycogen storage and the ability of the cells to absorb and release indocynanin green were also tested. The data showed that most of the differentiated cells formed cell aggregates after the 30th day, with more cells accumulated to form spheroids. RT-PCR revealed the expression of the hepatic nuclear factor, albumin, cytokeratin 18 and 19, cytochrome P2B6, glucose-6-phospahtase and claudin. The functional assays also showed glycogen storage and omission of indicynine green. Our study demonstrated hBSCs are novel population that can differentiate into hepatocyte-like cells.

Advances in multicellular spheroids formation

Three-dimensional multicellular spheroids (MCSs) have a complex architectural structure, dynamic cell-cell/cell-matrix interactions and bio-mimicking in vivo microenvironment. As a fundamental building block for tissue reconstruction, MCSs have emerged as a powerful tool to narrow down the gap between the in vitro and in vivo model. In this review paper, we discussed the structure and biology of MCSs and detailed fabricating methods. Among these methods, the approach in microfluidics with hydrogel support for MCS formation is promising because it allows essential cell-cell/cell-matrix interactions in a confined space.

Biomaterials and Culture Technologies for Regenerative Therapy of Liver Tissue

Regenerative approach has emerged to substitute the current extracorporeal technologies for the treatment of diseased and damaged liver tissue. This is based on the use of biomaterials that modulate the responses of hepatic cells through the unique matrix properties tuned to recapitulate regenerative functions. Cells in liver preserve their phenotype or differentiate through the interactions with extracellular matrix molecules. Therefore, the intrinsic properties of the engineered biomaterials, such as stiffness and surface topography, need to be tailored to induce appropriate cellular functions. The matrix physical stimuli can be combined with biochemical cues, such as immobilized functional groups or the delivered actions of signaling molecules. Furthermore, the external modulation of cells, through cocultures with nonparenchymal cells (e.g., endothelial cells) that can signal bioactive molecules, is another promising avenue to regenerate liver tissue. This review disseminates the recent approaches of regenerating liver tissue, with a focus on the development of biomaterials and the related culture technologies.

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

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

Dual-crosslinked hydrogel microwell system for formation and culture of multicellular human adipose tissue-derived stem cell spheroids

Three-dimensional (3D) multicellular spheroids of human adipose tissue-derived stem cells (hASCs) are an attractive system for basic science studies and tissue engineering applications, as they can resemble cellular condensations present in developmental and healing processes. The purpose of this study was to engineer a hydrogel-based microwell platform by capitalizing on the differential swelling behavior of micropatterned dual-crosslinked oxidized, methacrylated alginate (OMA)/multi-arm polyethylene glycol (PEG) hydrogels for rapid formation of uniform multicellular hASC spheroids with controllable size and evaluation of the capacity of the system to be used to drive osteogenic differentiation of the spheroids. By changing the micropattern size, the size of the hydrogel microwells was easily controllable. Microwell-seeded hASCs generated spheroids of relatively uniform size and high cell viability. hASC spheroids exhibited rapid mineralization in osteogenic media, which was faster than that of conventional two-dimensionally cultured hASCs. This new hydrogel microwell system has great potential for controlled multicellular spheroid formation and defined signal presentation from the hydrogel material to the cell aggregates to regulate tissue formation.

Optimization of mesenchymal stem cells (MSCs) delivery dose and route in mice with acute liver injury by bioluminescence imaging

PURPOSE

Both experimental and initial clinical studies have shown the therapeutic potential of mesenchymal stem cells (MSCs) in liver disease. Noninvasive tracking of MSCs could facilitate its clinical translation. The purpose of this study was to optimize MSCs delivery dose and route in mice with acute liver injury using bioluminescence imaging (BLI) to track the cells.

PROCEDURES

MSCs were labeled with the Luc2-mKate2 dual-fusion reporter gene (MSCs-R). The fate of MSCs-R was tracked through in vivo BLI after administration of different doses or delivery through different routes.

RESULTS

When delivered via the superior mesenteric vein (SMV), the high-dose (1.0 × 10(6) and 5.0 × 10(5)) group mice demonstrated high liver BLI signal but also had lethal portal vein embolization (PVE). By contrast, no PVE and its related death occurred in the low-dose (2.5 × 10(5)) group mice. Thus, 2.5 × 10(5) is the optimal delivery dose. Three delivery routes, i.e., inferior vena cava (IVC), SMV, and intrahepatic (IH) injection, were also systematically compared. After IVC infusion, MSCs-R were quickly trapped inside the lungs, and no detectable homing to the liver and other organs was observed. By IH injection, lung entrapment was bypassed, but MSCs-R distribution was only localized in the injection region of the liver. By contrast, after SMV infusion, MSCs-R were dispersedly distributed and stayed as long as 7-day posttransplantation in the liver. The in vivo imaging results were further validated by ex vivo imaging, digital subtraction angiography (DSA), and tissue analysis. Therefore, SMV is the optimal MSCs delivery route for liver disease.

CONCLUSIONS

Collectively, BLI, which could dynamically and quantitatively track cellular location and survival, is useful in determining MSCs transplantation parameters.

Unique characteristics of human mesenchymal stromal/progenitor cells pre-activated in 3-dimensional cultures under different conditions

BACKGROUND AIMS

Human mesenchymal stromal cells (MSCs) are being used in clinical trials, but the best protocol to prepare the cells for administration to patients remains unclear. We previously demonstrated that MSCs could be pre-activated to express therapeutic factors by culturing the cells in 3 dimensions (3D). We compared the activation of MSCs in 3D in fetal bovine serum containing medium and in multiple xeno-free media formulations.

METHODS

MSC aggregation and sphere formation was studied with the use of hanging drop cultures with medium containing fetal bovine serum or with various commercially available stem cell media with or without human serum albumin (HSA). Activation of MSCs was studied with the use of gene expression and protein secretion measurements and with functional studies with the use of macrophages and cancer cells.

RESULTS

MSCs did not condense into tight spheroids and express a full complement of therapeutic genes in α-minimum essential medium or several commercial stem-cell media. However, we identified a chemically defined xeno-free media, which, when supplemented with HSA from blood or recombinant HSA, resulted in compact spheres with high cell viability, together with high expression of anti-inflammatory (prostaglandin E2, TSG-6 TNF-alpha induced gene/protein 6) and anti-cancer molecules (TRAIL TNF-related apoptosis-inducing ligand, interleukin-24). Furthermore, spheres cultured in this medium showed potent anti-inflammatory effects in a lipopolysaccharide-stimulated macrophage system and suppressed the growth of prostate cancer cells by promoting cell-cycle arrest and cell death.

CONCLUSIONS

We demonstrated that cell activation in 3D depends critically on the culture medium. The conditions developed in the present study for 3D culture of MSCs should be useful in further research on MSCs and their potential therapeutic applications.

Critical analysis of 3-D organoid in vitro cell culture models for high-throughput drug candidate toxicity assessments

Drug failure due to toxicity indicators remains among the primary reasons for staggering drug attrition rates during clinical studies and post-marketing surveillance. Broader validation and use of next-generation 3-D improved cell culture models are expected to improve predictive power and effectiveness of drug toxicological predictions. However, after decades of promising research significant gaps remain in our collective ability to extract quality human toxicity information from in vitro data using 3-D cell and tissue models. Issues, challenges and future directions for the field to improve drug assay predictive power and reliability of 3-D models are reviewed.

Preparation of anti-inflammatory mesenchymal stem/precursor cells (MSCs) through sphere formation using hanging-drop culture technique

Herein, we describe a protocol for preparation of pre-activated anti-inflammatory human mesenchymal stem/precursor cells (MSCs) in 3-D culture without addition of exogenous chemicals or gene-transfer approaches. MSCs are an easily procurable source of multipotent adult stem cells with therapeutic potential largely attributed to their paracrine regulation of inflammation and immunity. However, the culture conditions to prepare the ideal MSCs for cell therapy remain elusive. Furthermore, the reported lag time for activation in experimental models has prompted investigations on pre-activating the cells prior to their administration. In this protocol, standard 2-D culture-expanded MSCs are activated by aggregation into 3-D spheres using hanging-drop cultures. MSC activation is evaluated by real-time PCR and/or ELISA for anti-inflammatory factors (TSG-6, STC-1, PGE2), and by a functional assay using lipopolysaccharide-stimulated macrophage cultures. Further, we elucidate methods to prepare MSC-sphere conditioned medium, intact spheres, and suspension of single cells from spheres for experimental and clinical applications.

Role of BMSCs in liver regeneration and metastasis after hepatectomy

Hepatocellular carcinoma (HCC), which develops from liver cirrhosis, is highly prevalent worldwide and is a malignancy that leads to liver failure and systemic metastasis. While surgery is the preferred treatment for HCC, intervention and liver transplantation are also treatment options for end-stage liver disease. However, the success of partial hepatectomy and intervention is hindered by the decompensation of liver function. Conversely, liver transplantation is difficult to carry out due to its high cost and the lack of donor organs. Fortunately, research into bone-marrow stromal cells (BMSCs) has opened a new door in this field. BMSCs are a type of stem cell with powerful proliferative and differential potential that represent an attractive tool for the establishment of successful stem cell-based therapy for liver diseases. A number of different stromal cells contribute to the therapeutic effects exerted by BMSCs because BMSCs can differentiate into functional hepatic cells and can produce a series of growth factors and cytokines capable of suppressing inflammatory responses, reducing hepatocyte apoptosis, reversing liver fibrosis and enhancing hepatocyte functionality. Additionally, it has been shown that BMSCs can increase the apoptosis rate of cancer cells and inhibit tumor metastasis in some microenvironments. This review focuses on BMSCs and their possible applications in liver regeneration and metastasis after hepatectomy.

Dynamic compaction of human mesenchymal stem/precursor cells into spheres self-activates caspase-dependent IL1 signaling to enhance secretion of modulators of inflammation and immunity (PGE2, TSG6, and STC1)

Human mesenchymal stem/precursor cells (MSC) are similar to some other stem/progenitor cells in that they compact into spheres when cultured in hanging drops or on nonadherent surfaces. Assembly of MSC into spheres alters many of their properties, including enhanced secretion of factors that mediate inflammatory and immune responses. Here we demonstrated that MSC spontaneously aggregated into sphere-like structures after injection into a subcutaneous air pouch or the peritoneum of mice. The structures were similar to MSC spheres formed in cultures demonstrated by the increased expression of genes for inflammation-modulating factors TSG6, STC1, and COX2, a key enzyme in production of PGE2. To identify the signaling pathways involved, hanging drop cultures were used to follow the time-dependent changes in the cells as they compacted into spheres. Among the genes upregulated were genes for the stress-activated signaling pathway for IL1α/β, and the contact-dependent signaling pathway for Notch. An inhibitor of caspases reduced the upregulation of IL1A/B expression, and inhibitors of IL1 signaling decreased production of PGE2, TSG6, and STC1. Also, inhibition of IL1A/B expression and secretion of PGE2 negated the anti-inflammatory effects of MSC spheres on stimulated macrophages. Experiments with γ-secretase inhibitors suggested that Notch signaling was also required for production of PGE2 but not TSG6 or STC1. The results indicated that assembly of MSC into spheres triggers caspase-dependent IL1 signaling and the secretion of modulators of inflammation and immunity. Similar aggregation in vivo may account for some of the effects observed with administration of the cells in animal models.

Droplet-based microfluidic system to form and separate multicellular spheroids using magnetic nanoparticles

The importance of creating a three-dimensional (3-D) multicellular spheroid has recently been gaining attention due to the limitations of monolayer cell culture to precisely mimic in vivo structure and cellular interactions. Due to this emerging interest, researchers have utilized new tools, such as microfluidic devices, that allow high-throughput and precise size control to produce multicellular spheroids. We have developed a droplet-based microfluidic system that can encapsulate both cells and magnetic nanoparticles within alginate beads to mimic the function of a multicellular tumor spheroid. Cells were entrapped within the alginate beads along with magnetic nanoparticles, and the beads of a relatively uniform size (diameters of 85% of the beads were 170-190 μm) were formed in the oil phase. These beads were passed through parallel streamlines of oil and culture medium, where the beads were magnetically transferred into the medium phase from the oil phase using an external magnetic force. This microfluidic chip eliminates additional steps for collecting the spheroids from the oil phase and transferring them to culture medium. Ultimately, the overall spheroid formation process can be achieved on a single microchip.

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

BACKGROUNDS/AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Human mesenchymal stem/stromal cells cultured as spheroids are self-activated to produce prostaglandin E2 that directs stimulated macrophages into an anti-inflammatory phenotype

Culturing cells in three dimension (3D) provides an insight into their characteristics in vivo. We previously reported that human mesenchymal stem/stromal cells (hMSCs) cultured as 3D spheroids acquire enhanced anti-inflammatory properties. Here, we explored the effects of hMSC spheroids on macrophages that are critical cells in the regulation of inflammation. Conditioned medium (CM) from hMSC spheroids inhibited lipopolysaccharide-stimulated macrophages from secreting proinflammatory cytokines TNFα, CXCL2, IL6, IL12p40, and IL23. CM also increased the secretion of anti-inflammatory cytokines IL10 and IL1ra by the stimulated macrophages, and augmented expression of CD206, a marker of alternatively activated M2 macrophages. The principal anti-inflammatory activity in CM had a small molecular weight, and microarray data suggested that it was prostaglandin E2 (PGE2). This was confirmed by the observations that PGE2 levels were markedly elevated in hMSC spheroid-CM, and that the anti-inflammatory activity was abolished by an inhibitor of cyclooxygenase-2 (COX-2), a silencing RNA for COX-2, and an antibody to PGE2. The anti-inflammatory effects of the PGE2 on stimulated macrophages were mediated by the EP4 receptor. Spheroids formed by human adult dermal fibroblasts produced low levels of PGE2 and displayed negligible anti-inflammatory effects on stimulated macrophages, suggesting the features as unique to hMSCs. Moreover, production of PGE2 by hMSC spheroids was dependent on the activity of caspases and NFκB activation in the hMSCs. The results indicated that hMSCs in 3D-spheroid cultures are self-activated, in part by intracellular stress responses, to produce PGE2 that can change stimulated macrophages from a primarily proinflammatory M1 phenotype to a more anti-inflammatory M2 phenotype.

Stellate cells from rat pancreas are stem cells and can contribute to liver regeneration

The identity of pancreatic stem/progenitor cells is still under discussion. They were suggested to derive from the pancreatic ductal epithelium and/or islets. Here we report that rat pancreatic stellate cells (PSC), which are thought to contribute to pancreatic fibrosis, have stem cell characteristics. PSC reside in islets and between acini and display a gene expression pattern similar to umbilical cord blood stem cells and mesenchymal stem cells. Cytokine treatment of isolated PSC induced the expression of typical hepatocyte markers. The PSC-derived hepatocyte-like cells expressed endodermal proteins such as bile salt export pump along with the mesodermal protein vimentin. The transplantation of culture-activated PSC from enhanced green fluorescent protein-expressing rats into wild type rats after partial hepatectomy in the presence of 2-acetylaminofluorene revealed that PSC were able to reconstitute large areas of the host liver through differentiation into hepatocytes and cholangiocytes. This developmental fate of transplanted PSC was confirmed by fluorescence in situ hybridization of chromosome Y after gender-mismatched transplantation of male PSC into female rats. Transplanted PSC displayed long-lasting survival, whereas muscle fibroblasts were unable to integrate into the host liver. The differentiation potential of PSC was further verified by the transplantation of clonally expanded PSC. PSC clones maintained the expression of stellate cell and stem cell markers and preserved their differentiation potential, which indicated self-renewal potential of PSC. These findings demonstrate that PSC have stem cell characteristics and can contribute to the regeneration of injured organs through differentiation across tissue boundaries.

Functional 3D human primary hepatocyte spheroids made by co-culturing hepatocytes from partial hepatectomy specimens and human adipose-derived stem cells

We have generated human hepatocyte spheroids with uniform size and shape by co-culturing 1∶1 mixtures of primary human hepatocytes (hHeps) from partial hepatectomy specimens and human adipose-derived stem cells (hADSCs) in concave microwells. The hADSCs in spheroids could compensate for the low viability and improve the functional maintenance of hHeps. Co-cultured spheroids aggregated and formed compact spheroidal shapes more rapidly, and with a significantly higher viability than mono-cultured spheroids. The liver-specific functions of co-cultured spheroids were greater, although they contained half the number of hepatocytes as mono-cultured spheroids. Albumin secretion by co-cultured spheroids was 10% higher on day 7, whereas urea secretion was similar, compared with mono-cultured spheroids. A quantitative cytochrome P450 assay showed that the enzymatic activity of co-cultured spheroids cultured for 9 days was 28% higher than that of mono-cultured spheroids. These effects may be due to the transdifferentiation potential and paracrine healing effects of hADSCs on hHeps. These co-cultured spheroids may be useful for creating artificial three-dimensional hepatic tissue constructs and for cell therapy with limited numbers of human hepatocytes.

Several important in vitro improvements in the amplification, differentiation and tracing of fetal liver stem/progenitor cells

Objective

We previously isolated fetal liver stem/progenitor cells (FLSPCs), but there is an urgent need to properly amplify FLSPCs, effectively induce FLSPCs differentiation, and steadily trace FLSPCs for in vivo therapeutic investigation.

Methods

FLSPCs were maintained in vitro as adherent culture or soft agar culture for large-scale amplification. To direct the differentiation of FLSPCs into hepatocytes, FLSPCs were randomly divided into four groups: control, 1% DMSO-treated, 20 ng/ml HGF-treated and 1% DMSO+20 ng/ml HGF-treated. To trace FLSPCs, the GFP gene was introduced into FLSPCs by liposome-mediated transfection.

Results

For amplifying FLSPCs, the soft agar culture were more suitable than the adherent culture, because the soft agar culture obtained more homogeneous cells. These cells were with high nuclear:cytoplasmic ratio, few cell organelles, high expression of CD90.1 and CD49f, and strong alkaline phosphatase staining. For inducing FLSPCs differentiation, treatment with HGF+DMSO was most effective (P<0.05), which was strongly supported by the typical morphological change and the significant decrease of OV-6 positive cells (P<0.01). In addition, the time of indocyanine green elimination, the percentage of glycogen synthetic cells, and the expressions of ALB, G-6-P, CK-8, CK-18 and CYP450-3A1 in HGF+DMSO-treated group were higher than in any other group. For tracing FLSPCs, after the selection of stable FLSPC transfectants, GFP expression continued over successive generations.

Conclusions

FLSPCs can properly self-renew in soft agar culture and effectively differentiate into hepatocyte-like cells by HGF+DMSO induction, and they can be reliably traced by GFP expression.

Hepatocyte differentiation of mesenchymal stem cells

BACKGROUND

Liver cell transplantation and bioartificial liver may provide metabolic support of liver function temporary and are prospective treatments for patients with liver failure. Mesenchymal stem cells (MSCs) are expected to be an ideal cell source for transplantation or liver tissue engineering, however the hepatic differentiation of MSCs is still insufficient for clinical application.

DATA SOURCES

A PubMed search on "mesenchymal stem cells", "liver cell" and "hepatocyte differentiation" was performed on the topic, and the relevant articles published in the past ten years were reviewed.

RESULTS

Hepatocyte-like cells differentiated from MSCs are a promising cell source for liver regeneration or tissue engineering. Although it is still a matter of debate as to whether MSC-derived hepatocytes may efficiently repopulate a host liver to provide adequate functional substitution, the majority of animal studies support that MSCs can become key players in liver-directed regenerative medicine. However the clinical application of human stem cells in the treatment of liver diseases is still in its infancy.

CONCLUSIONS

Future studies are required to improve the efficacy and consistency of hepatic differentiation from MSCs. It is necessary to better understand the mechanism to achieve transdifferentiation with high efficiency. More clinical trials are warranted to prove their efficacy in the management of patients with liver failure.

Advances in the formation, use and understanding of multi-cellular spheroids

INTRODUCTION

Developing in vitro models for studying cell biology and cell physiology is of great importance to the fields of biotechnology, cancer research, drug discovery, toxicity testing, as well as the emerging fields of tissue engineering and regenerative medicine. Traditional two-dimensional (2D) methods of mammalian cell culture have several limitations and it is increasingly recognized that cells grown in a three-dimensional (3D) environment more closely represent normal cellular function due to the increased cell-to-cell interactions, and by mimicking the in vivo architecture of natural organs and tissues.

AREAS COVERED

In this review, we discuss the methods to form 3D multi-cellular spheroids, the advantages and limitations of these methods, and assays used to characterize the function of spheroids. The use of spheroids has led to many advances in basic cell sciences, including understanding cancer cell interactions, creating models for drug discovery and cancer metastasis, and they are being investigated as basic units for engineering tissue constructs. As so, this review will focus on contributions made to each of these fields using spheroid models.

EXPERT OPINION

Multi-cellular spheroids are rich in biological content and mimic better the in vivo environment than 2D cell culture. New technologies to form and analyze spheroids are rapidly increasing their adoption and expanding their applications.

Spherical bullet formation via E-cadherin promotes therapeutic potency of mesenchymal stem cells derived from human umbilical cord blood for myocardial infarction

The beneficial effects of stem cells in clinical applications to date have been modest, and studies have reported that poor engraftment might be an important reason. As a strategy to overcome such a hurdle, we developed the spheroid three dimensional (3D) bullet as a delivery method for human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) through the maintenance of cell-cell interactions without additional xenofactors, cytokines, or matrix. We made spheroid 3D-bullets from hUCB-MSCs at 24 hours' anchorage-deprived suspension culture. To investigate the in vivo therapeutic efficacy of 3D-bullets, we used rat myocardial infarction (MI) model. Transplantation of 3D-bullet was better than that of single cells from monolayer culture or from 3D-bullet in improving left ventricular (LV) contractility [LV ejection fraction (LVEF) or LV fractional shortening (LVFS)] and preventing pathologic LV dilatation [LV end-systolic diameter (LVESD) or LV end-diastolic diameter (LVEDD)] at 8 weeks. In the mechanism study of 3D-bullet formation, we found that calcium-dependent cell-cell interaction was essential and that E-cadherin is a key inducer mediating hUCB-MSC 3D-bullet formation among several calcium-dependent adhesion molecules which were nominated as candidates after cDNA array analysis. In more specific experiments with E-cadherin overexpression using adenoviral vector or with E-cadherin neutralization using blocking antibody, we found that E-cadherin regulates vascular endothelial growth factor (VEGF) secretion via extracellular signal-regulated kinase (ERK)/v-akt murine thymoma viral oncogene homolog1 (AKT) pathways. During formation of spheroid 3D-bullets, activation of E-cadherin in association with cell-cell interaction turns on ERK/AKT signaling pathway that are essential to proliferative and paracrine activity of MSCs leading to the enhanced therapeutic efficacy.

Transplantation of human umbilical cord blood mesenchymal stem cells improves survival rates in a rat model of acute hepatic necrosis

INTRODUCTION

Stem cell-based therapies are emerging as important and promising methods in the treatment of end-stage liver disease. This study is aimed to evaluate the effects of human umbilical cord blood mesenchymal stem cell (HUCBMSC) transplantation in acute hepatic necrosis (AHN).

METHODS

Green fluorescent protein (GFP)-labeled HUCBMSCs were injected into the liver of rats in which AHN was induced by carbon tetrachloride, and the migration of these cells in liver slices was evaluated from 48 hours to 4 weeks post-transplantation. The transdifferentiation status of the HUCBMSCs was evaluated using immunohistochemistry and real-time reverse transcription-polymerase chain reaction, and survival rates were statistically analyzed.

RESULTS

Dispersed GFP fluorescence was observed along the portal area 48 hours after transplantation. One week post-transplantation, GFP-positive cells were found in necrotic liver areas, and GFP-positive cells persisted after 4 weeks. Immunohistochemistry and real-time polymerase chain reaction analysis showed that transplanted HUCBMSCs expressed several human liver tissue-specific markers in rats with AHN. Statistical analysis revealed that rats with AHN that were transplanted with HUCBMSCs had significantly lower death rates after 48 hours than those receiving no HUCBMSCs.

CONCLUSION

HUCBMSC transplantation can significantly improve the survival of rats with AHN. The underlying mechanisms involved may include the transdifferentiation of HUCBMSCs into hepatocyte-like cells and targeted migration of these cells to liver lesion sites.

Human multipotent stromal cells attenuate lipopolysaccharide-induced acute lung injury in mice via secretion of tumor necrosis factor-α-induced protein 6

INTRODUCTION

Multipotent stromal cells (MSCs) are currently in clinical trials for a number of inflammatory diseases. Recent studies have demonstrated the ability of MSCs to attenuate inflammation in rodent models of acute lung injury (ALI) suggesting that MSCs may also be beneficial in treating ALI.

METHODS

To better understand how human MSCs (hMSCs) may act in ALI, the lungs of immunocompetent mice were exposed to lipopolysaccharide (LPS) and four hours later bone marrow derived hMSCs were delivered by oropharyngeal aspiration (OA). The effect of hMSCs on lung injury was assessed by measuring the lung wet/dry weight ratio and total protein in bronchoalveolar lavage (BAL) fluid 24 or 48 h after LPS. BAL fluid was also analyzed for the presence of inflammatory cells and cytokine expression by multiplex immunoassay. Microarray analysis of total RNA isolated from treated and untreated lungs was performed to elucidate the mechanism(s) involved in hMSC modulation of lung inflammation.

RESULTS

Administration of hMSCs significantly reduced the expression of pro-inflammatory cytokines, neutrophil counts and total protein in bronchoalveolar lavage. There was a concomitant reduction in pulmonary edema. The anti-inflammatory effects of hMSCs were not dependent on localization to the lung, as intraperitoneal administration of hMSCs also attenuated LPS-induced inflammation in the lung. Microarray analysis revealed significant induction of tumor necrosis factor (TNF)-α-induced protein 6 (TNFAIP6/TSG-6) expression by hMSCs 12 h after OA delivery to LPS-exposed lungs. Knockdown of TSG-6 expression in hMSCs by RNA interference abrogated most of their anti-inflammatory effects. In addition, intra-pulmonary delivery of recombinant human TSG-6 reduced LPS-induced inflammation in the lung.

CONCLUSIONS

These results show that hMSCs recapitulate the observed beneficial effects of rodent MSCs in animal models of ALI and suggest that the anti-inflammatory properties of hMSCs in the lung are explained, at least in part, by activation of hMSCs to secrete TSG-6.

Scalable robotic biofabrication of tissue spheroids

Development of methods for scalable biofabrication of uniformly sized tissue spheroids is essential for tissue spheroid-based bioprinting of large size tissue and organ constructs. The most recent scalable technique for tissue spheroid fabrication employs a micromolded recessed template prepared in a non-adhesive hydrogel, wherein the cells loaded into the template self-assemble into tissue spheroids due to gravitational force. In this study, we present an improved version of this technique. A new mold was designed to enable generation of 61 microrecessions in each well of a 96-well plate. The microrecessions were seeded with cells using an EpMotion 5070 automated pipetting machine. After 48 h of incubation, tissue spheroids formed at the bottom of each microrecession. To assess the quality of constructs generated using this technology, 600 tissue spheroids made by this method were compared with 600 spheroids generated by the conventional hanging drop method. These analyses showed that tissue spheroids fabricated by the micromolded method are more uniform in diameter. Thus, use of micromolded recessions in a non-adhesive hydrogel, combined with automated cell seeding, is a reliable method for scalable robotic fabrication of uniform-sized tissue spheroids.

Properties of hepatocyte-like cell clusters from human adipose tissue-derived mesenchymal stem cells

There are only a few reports that describe the hepatocytic differentiation potential of human adipose tissue-derived mesenchymal stem cells (hADMSCs) and no reports that describe the in vivo functions of hepatocyte-like cells differentiated from somatic stem cells including hADMSCs. In this study, we established a new method for generation of functional hepatocyte-like cell clusters using floating culture method and induced functional hepatocyte-like cell clusters, which functioned effectively not only in vitro but also in vivo. The generated hepatocyte-like cell clusters were characterized by gene expression analysis, functional assays, and transplantation into non-obese diabetic severe combined immunodeficiency (NOD-SCID) mouse with chronic liver injury. The generated hepatocyte-like cell clusters expressed various genes normally found on mature hepatocytes. The cell clusters exhibited functional characteristics of hepatocytes: they expressed albumin, secreted urea, had cytochrome P450 activity, could take up low-density lipoprotein, and stored glycogen. Transplantation of these cell clusters into NOD-SCID mouse with chronic liver injury resulted in a significant improvement of serum albumin and total bilirubin levels. In summary, we established a new protocol for efficient induction of hADMSCs into functional hepatocyte-like cell clusters.

Aggregation of human mesenchymal stromal cells (MSCs) into 3D spheroids enhances their antiinflammatory properties

Previous reports suggested that culture as 3D aggregates or as spheroids can increase the therapeutic potential of the adult stem/progenitor cells referred to as mesenchymal stem cells or multipotent mesenchymal stromal cells (MSCs). Here we used a hanging drop protocol to prepare human MSCs (hMSCs) as spheroids that maximally expressed TNFalpha stimulated gene/protein 6 (TSG-6), the antiinflammatory protein that was expressed at high levels by hMSCs trapped in the lung after i.v. infusion and that largely explained the beneficial effects of hMSCs in mice with myocardial infarcts. The properties of spheroid hMSCs were found to depend critically on the culture conditions. Under optimal conditions for expression of TSG-6, the hMSCs also expressed high levels of stanniocalcin-1, a protein with both antiinflammatory and antiapoptotic properties. In addition, they expressed high levels of three anticancer proteins: IL-24, TNFalpha-related apoptosis inducing ligand, and CD82. The spheroid hMSCs were more effective than hMSCs from adherent monolayer cultures in suppressing inflammatory responses in a coculture system with LPS-activated macrophages and in a mouse model for peritonitis. In addition, the spheroid hMSCs were about one-fourth the volume of hMSCs from adherent cultures. Apparently as a result, larger numbers of the cells trafficked through the lung after i.v. infusion and were recovered in spleen, liver, kidney, and heart. The data suggest that spheroid hMSCs may be more effective than hMSCs from adherent cultures in therapies for diseases characterized by sterile tissue injury and unresolved inflammation and for some cancers that are sensitive to antiinflammatory agents.

Hepatospheres: Three dimensional cell cultures resemble physiological conditions of the liver

Studying physiological and pathophysiological mechanisms in the liver on a molecular basis is a challenging task. During two dimensional (2D) culture conditions hepatocytes dedifferentiate rapidly by losing metabolic functions and structural integrity. Hence, inappropriate 2D hepatocellular models hamper studies on the xenobiotic metabolism of the liver which strongly influences drug potency. Also, the lack of effective therapies against hepatocellular carcinoma shows the urgent need for robust models to investigate liver functions in a defined hepatic microenvironment. Here, we summarize and discuss three-dimensional cultures of hepatocytes, herein referred to as hepatospheres, which provide versatile tools to investigate hepatic metabolism, stemness and cancer development.

Serum from radiofrequency-injured livers induces differentiation of bone marrow stem cells into hepatocyte-like cells

BACKGROUND

Roles that bone marrow stem cells (BMSCs) play in liver repair after liver injury and the cell therapy for liver diseases are widely accepted. However, the availability of hepatocyte-like cells from BMSCs and possible animal diseases association with culturing in fetal calf serum (FCS) are the major limitations of clinical therapy. Therefore, this study was designed to search for a new cell source for the treatment of liver injuries through investigating whether serum from radiofrequency ablation-injured rabbit livers can induce the differentiation of BMSCs into hepatocyte-like cells.

METHODS

Serum was collected from rabbits 36 h after radiofrequency ablation (RFA) treatment of the liver. BMSCs were isolated from rabbit bone marrow and were cultured in the collected serum. Cellular morphology and cell cycle were observed. Hepatocyte markers of the differentiated cells were detected by immunohistochemistry.

RESULTS

After induction for 7 d, spindle-shaped BMSCs turned into round cells that resembled the morphology of hepatocyte-like cells. Flow cytometry showed that the percentage of cells in the S/G2/M phase was higher in the RFA group than that in the FCS group and HGF groups. This result suggests that BMSC can transform into mature cells from stem cell phase. Albumin and CK18 were considered as typical marker of hepatocytes. Following induction for 14 d, the differentiated cells expressed immunofluorescence of FITC-labeled albumin and TRITC-labeled CK18.

CONCLUSION

BMSCs treated with serum collected from radiofrequency ablation-injured livers can differentiate into hepatocyte-like cells providing a cell source to cell therapy.

Recent advances in three-dimensional multicellular spheroid culture for biomedical research

Many types of mammalian cells can aggregate and differentiate into 3-D multicellular spheroids when cultured in suspension or a nonadhesive environment. Compared to conventional monolayer cultures, multicellular spheroids resemble real tissues better in terms of structural and functional properties. Multicellular spheroids formed by transformed cells are widely used as avascular tumor models for metastasis and invasion research and for therapeutic screening. Many primary or progenitor cells on the other hand, show significantly enhanced viability and functional performance when grown as spheroids. Multicellular spheroids in this aspect are ideal building units for tissue reconstruction. Here we review the current understanding of multicellular spheroid formation mechanisms, their biomedical applications, and recent advances in spheroid culture, manipulation, and analysis techniques.

The mixed coculture effect of primary rat hepatocytes and bone marrow cells is caused by soluble factors derived from bone marrow cells

Heterospheroids consisting of hepatocytes and bone marrow cells (BMCs) are formed by the mixed coculture of these cells and enhance the expression and maintenance of the liver-specific functions of hepatocytes. Not only the soluble factors derived from these cells, but also functional organoid (heterospheroid) formation, are considered to underlie this coculture effect. Therefore, in the present study, we aimed to clarify the mechanism of this co-culture effect. We performed hepatocyte monoculture with conditioned media prepared from hepatocyte cultures, BMC cultures and a coculture of hepatocytes and BMCs. When using any type of conditioned medium, no hepatocyte spheroids formed, and the hepatocytes formed a monolayer. In addition, an effect for these conditioned media was shown in terms of the albumin production and ammonia metabolism activities of the hepatocytes; conditioned medium from BMCs showed the strongest effect. The monocultured hepatocytes in the conditioned medium derived from BMCs showed equivalent albumin production and ammonia metabolism activities to the cocultured spheroids of hepatocytes and BMCs. Therefore, it was determined that the effect of the coculture of hepatocytes and BMCs was caused by soluble factors derived from BMCs.