Proliferation and differentiation of human embryonic germ cell derivatives in bioactive polymeric fibrous scaffold

Experimental Models to Study the Functions of the Blood-Brain Barrier

The purpose of this paper was to discuss the achievements of in vitro modeling in terms of the blood-brain barrier [BBB] and to create a clear overview of this research area, which is useful in research planning. The text was divided into three main parts. The first part describes the BBB as a functional structure, its constitution, cellular and noncellular components, mechanisms of functioning and importance for the central nervous system, in terms of both protection and nourishment. The second part is an overview of parameters important in terms of establishing and maintaining a barrier phenotype that allows for formulating criteria of evaluation of the BBB in vitro models. The third and last part discusses certain techniques for developing the BBB in vitro models. It describes subsequent research approaches and models, as they underwent change alongside technological advancement. On the one hand, we discuss possibilities and limitations of different research approaches: primary cultures vs. cell lines and monocultures vs. multicultures. On the other hand, we review advantages and disadvantages of specific models, such as models-on-a-chip, 3D models or microfluidic models. We not only attempt to state the usefulness of specific models in different kinds of research on the BBB but also emphasize the significance of this area of research for advancement of neuroscience and the pharmaceutical industry.

Small Molecule Differentiate PDX1-Expressing Cells Derived from Human Endometrial Stem Cells on PAN Electrospun Nanofibrous Scaffold: Applications for the Treatment of Diabetes in Rat

In this study, we designed an engineered tissue and transplanted it to an animal model, trying to take an effective step toward meeting the needs of diabetic patients. Here, human endometrial cells were differentiated into PDX1-expressing cells using a small molecule of Y-27632 on polyacrylonitrile (PAN) electrospun scaffolds and transplanted into diabetic rats. PAN nanofibers were made by electrospinning. RT-PCR and immunocytochemical analysis were performed to express pancreatic precursor (PP) genes. The differentiated cells were then transplanted into the abdominal cavity of diabetic rats with Streptozotocin. In another group of rats, differentiated cells were injected through the tail. Blood glucose was measured 7, 14, and 28 days after transplantation, and rat weight was also measured. The results showed that the expression of PP markers including Sox-17, Ngn3, Pdx1, and NKx2.2 genes was significantly increased in differentiated cells compared to the control group. In diabetic rats receiving differentiated cells, both transplanted and injected, glucose concentration as well as body weight improved compared to the control group. Rats receiving transplants in the peritoneum had a lower blood glucose concentration than those in the cell receiving group by injection, and the cell receiving group in the form of injections was more effective in increasing the body weight of rats than in the other groups. According to the results of the study, the transplantation of PP from endometrium using PAN scaffolding at the site of peritoneum could be recommended for the treatment of diabetes, although further studies are needed to provide a complete cure.

Improved Survival and Hematopoietic Differentiation of Murine Embryonic Stem Cells on Electrospun Polycaprolactone Nanofiber

OBJECTIVE

Three-dimensional (3D) biomimetic nanofiber scaffolds have widespread ap- plications in biomedical tissue engineering. They provide a suitable environment for cel- lular adhesion, survival, proliferation and differentiation, guide new tissue formation and development, and are one of the outstanding goals of tissue engineering. Electrospinning has recently emerged as a leading technique for producing biomimetic scaffolds with mi- cro to nanoscale topography and a high porosity similar to the natural extracellular matrix (ECM). These scaffolds are comprised of synthetic and natural polymers for tissue engi- neering applications. Several kinds of cells such as human embryonic stem cells (hESCs) and mouse ESCs (mESCs) have been cultured and differentiated on nanofiber scaffolds. mESCs can be induced to differentiate into a particular cell lineage when cultured as em- bryoid bodies (EBs) on nano-sized scaffolds.

MATERIALS AND METHODS

We cultured mESCs (2500 cells/100 µl) in 96-well plates with knockout Dulbecco's modified eagle medium (DMEM-KO) and Roswell Park Memorial Institute-1640 (RPMI-1640), both supplemented with 20% ESC grade fetal bovine serum (FBS) and essential factors in the presence of leukemia inhibitory factor (LIF). mESCs were seeded at a density of 2500 cells/100 µl onto electrospun polycaprolactone (PCL) nanofibers in 96-well plates. The control group comprised mESCs grown on tissue cul- ture plates (TCP) at a density of 2500 cells/100 µl. Differentiation of mESCs into mouse hematopoietic stem cells (mHSCs) was performed by stem cell factor (SCF), interleukin-3 (IL-3), IL-6 and Fms-related tyrosine kinase ligand (Flt3-L) cytokines for both the PCL and TCP groups. We performed an experimental study of mESCs differentiation.

RESULTS

PCL was compared to conventional TCP for survival and differentiation of mESCs to mHSCs. There were significantly more mESCs in the PCL group. Flowcyto- metric analysis revealed differences in hematopoietic differentiation between the PCL and TCP culture systems. There were more CD34+(Sca1+) and CD133+cells subpopulations in the PCL group compared to the conventional TCP culture system.

CONCLUSION

The nanofiber scaffold, as an effective surface, improves survival and differentiation of mESCs into mHSCs compared to gelatin coated TCP. More studies are necessary to understand how the topographical features of electrospun fibers af- fect cell growth and behavior. This can be achieved by designing biomimetic scaffolds for tissue engineering.

One-stop microfiber spinning and fabrication of a fibrous cell-encapsulated scaffold on a single microfluidic platform

This paper provides a method for microscale fiber spinning and the in situ construction of a 3D fibrous scaffold on a single microfluidic platform. This platform was also used to fabricate a variety of fibrous scaffolds with diverse compositions without the use of complicated devices. We explored the potential utility of the fibrous scaffolds for tissue engineering applications by constructing a fibrous scaffold encapsulating primary hepatocytes. The cells in scaffold were cultured over seven days and maintained higher viability comparing with 3D alginate non-fibrous block. The main advantage of this platform is that the fibrous structure used to form a scaffold can be generated without damaging the mechanically weak alginate fibers or encapsulated cells because all procedures are performed in a single platform without the intervention of the operator. In addition, the proposed fibrous scaffold permitted high diffusion capability of molecules, which enabled better viability of encapsulated cells than non-fibrous scaffold even in massive cell culture.

Progress of electrospun fibers as nerve conduits for neural tissue repair

Nerve tissue regeneration approaches have gained much attention in recent years, and nerve conduits (NCs), which facilitate nerve tissue regeneration, have become an attractive alternative to nerve autologous graft. Several methods are proposed to fabricate NCs, including electrospinning, which is a widely used approach for NCs and other tissue scaffolds, and has advantages such as the ability to control the thickness, diameter and porosity of fibers, as well as its simple experimental set up. This article gives an overview of electrospun fibers for nerve conduits utilized in peripheral and central nerve regeneration. Natural and synthetic materials with different mechanical strength, degradation rates and biocompatibility are proposed. Several bioactive proteins that can help the process of nerve regeneration are introduced. Finally, some approaches to control the morphology of electrospun fibers and to deliver bioactive proteins are discussed in detail.

In vitro cerebrovascular modeling in the 21st century: current and prospective technologies

The blood-brain barrier (BBB) maintains the brain homeostasis and dynamically responds to events associated with systemic and/or rheological impairments (e.g., inflammation, ischemia) including the exposure to harmful xenobiotics. Thus, understanding the BBB physiology is crucial for the resolution of major central nervous system CNS) disorders challenging both health care providers and the pharmaceutical industry. These challenges include drug delivery to the brain, neurological disorders, toxicological studies, and biodefense. Studies aimed at advancing our understanding of CNS diseases and promoting the development of more effective therapeutics are primarily performed in laboratory animals. However, there are major hindering factors inherent to in vivo studies such as cost, limited throughput and translational significance to humans. These factors promoted the development of alternative in vitro strategies for studying the physiology and pathophysiology of the BBB in relation to brain disorders as well as screening tools to aid in the development of novel CNS drugs. Herein, we provide a detailed review including pros and cons of current and prospective technologies for modelling the BBB in vitro including ex situ, cell based and computational (in silico) models. A special section is dedicated to microfluidic systems including micro-BBB, BBB-on-a-chip, Neurovascular Unit-on-a-Chip and Synthetic Microvasculature Blood-brain Barrier.

Derivation of human embryonic stem cells (hESC)

Stem cells are characterized by their absolute or relative lack of specialization their ability for self-renewal, as well as their ability to generate differentiated progeny through cellular lineages with one or more branches. The increased availability of embryonic tissue and greatly improved derivation methods have led to a large increase in the number of hESC lines.

Nerve growth factor-immobilized electrically conducting fibrous scaffolds for potential use in neural engineering applications

Engineered scaffolds simultaneously exhibiting multiple cues are highly desirable for neural tissue regeneration. To this end, we developed a neural tissue engineering scaffold that displays submicrometer-scale features, electrical conductivity, and neurotrophic activity. Specifically, electrospun poly(lactic acid-co-glycolic acid) (PLGA) nanofibers were layered with a nanometer thick coating of electrically conducting polypyrrole (PPy) presenting carboxylic groups. Then, nerve growth factor (NGF) was chemically immobilized onto the surface of the fibers. These NGF-immobilized PPy-coated PLGA (NGF-PPyPLGA) fibers supported PC12 neurite formation ( 28.0±3.0% of the cells) and neurite outgrowth (14.2 μm median length), which were comparable to that observed with NGF (50 ng/mL) in culture medium ( 29.0±1.3%, 14.4 μm). Electrical stimulation of PC12 cells on NGF-immobilized PPyPLGA fiber scaffolds was found to further improve neurite development and neurite length by 18% and 17%, respectively, compared to unstimulated cells on the NGF-immobilized fibers. Hence, submicrometer-scale fibrous scaffolds that incorporate neurotrophic and electroconducting activities may serve as promising neural tissue engineering scaffolds such as nerve guidance conduits.

The promotion of stemness and pluripotency following feeder-free culture of embryonic stem cells on collagen-grafted 3-dimensional nanofibrous scaffold

The components of extracellular matrix (ECM) may substitute for feeder layers that promote the self-renewal pathways in embryonic stem cells. Surface modification of electrospun nanofibrous scaffolds have been studied to closely resemble natural ECMs and support in vitro and in vivo proliferation, pluripotency and differentiation of stem cells. In this study, we analyzed the maintenance of stemness and pluripotency of the mouse embryonic stem cell (mESC) following feeder-free culture on collagen-grafted polyethersulfone (PES-COL) electrospun nanofibrous scaffold. Our results showed that, the mESCs cultured for seven passages on PES-COL scaffolds had a typical undifferentiated morphology, enhanced proliferation, stable diploid normal karyotype, and continued expression of stemness and pluripotency-associated markers, Oct-4, Nanog, SSEA-1, and Alkaline phosphatase (ALP) in comparison with PES scaffolds and gelatin-coated plate. Moreover, these cells retained their in vitro and in vivo pluripotency. Our results indicated the enhanced infiltration and teratoma formation of mESCs in PES-COL. Collagen-grafted polyethersulfone nanofibrous scaffold has potential for feeder-free culture of pluripotent stem cells because of its 3-dimensional structure and bioactivity which enhance pluripotency, proliferation, differentiation, and infiltration of embryonic stem cells.

Influence of acellular natural lung matrix on murine embryonic stem cell differentiation and tissue formation

We report here the first attempt to produce and use whole acellular (AC) lung as a matrix to support development of engineered lung tissue from murine embryonic stem cells (mESCs). We compared the influence of AC lung, Gelfoam, Matrigel, and a collagen I hydrogel matrix on the mESC attachment, differentiation, and subsequent formation of complex tissue. We found that AC lung allowed for better retention of cells with more differentiation of mESCs into epithelial and endothelial lineages. In constructs produced on whole AC lung, we saw indications of organization of differentiating ESC into three-dimensional structures reminiscent of complex tissues. We also saw expression of thyroid transcription factor-1, an immature lung epithelial cell marker; pro-surfactant protein C, a type II pneumocyte marker; PECAM-1/CD31, an endothelial cell marker; cytokeratin 18; alpha-actin, a smooth muscle marker; CD140a or platelet-derived growth factor receptor-alpha; and Clara cell protein 10. There was also evidence of site-specific differentiation in the trachea with the formation of sheets of cytokeratin-positive cells and Clara cell protein 10-expressing Clara cells. Our findings support the utility of AC lung as a matrix for engineering lung tissue and highlight the critical role played by matrix or scaffold-associated cues in guiding ESC differentiation toward lung-specific lineages.

Ciliary neurotrophic factor-coated polylactic-polyglycolic acid chitosan nerve conduit promotes peripheral nerve regeneration in canine tibial nerve defect repair

A variety of nerve conduits incorporated with chemical and biological factors have been developed to further stimulate nerve regeneration. Although most of the nerve guides in studies are basically limited to bridge a short gap of nerve defect in rat models, it is vital to evaluate effects of conduits on nerve regeneration over distance greater than 20 mm, or more clinically relevant nerve gap lengths in higher mammals. In this study, a poly(lactide-co-glycolide) (PLGA) nerve conduit, treated with pulsed plasma and coated with ciliary neurotrophic factor (CNTF) as well as chitosan, was used to repair 25-mm-long canine tibial nerve defects in eighteen cross-bred dogs. The canines were randomly divided into three groups (n = 6), a 25-mm segment of the tibial nerve was removed and replaced by a PLGA/chitosan-CNTF nerve conduit, PLGA/chitosan conduit and autologous nerve grafts were performed as the control. The results were evaluated by general observation, electromyogram testing, S-100 histological immunostaining, and image analysis at 3 months after operation. The histological results demonstrated that the PLGA/chitosan-CNTF conduits and PLGA/chitosan conduits were capable of leading the damaged axons through the lesioned area. Through the comparison of the three groups, the results in PLGA/chitosan-CNTF conduits group were better than that of PLGA/chitosan conduits group, while they were similar to autologous nerve grafts group. Therefore, CNTF-coated PLGA/chitosan nerve conduits could be an alternative artificial nerve conduit for nerve regeneration.

Human embryonic stem cells: derivation, culture, and differentiation: a review

The greatest therapeutic promise of human embryonic stem cells (hESC) is to generate specialized cells to replace damaged tissue in patients suffering from various degenerative diseases. However, the signaling mechanisms involved in lineage restriction of ESC to adopt various cellular phenotypes are still under investigation. Furthermore, for progression of hESC-based therapies towards clinical applications, appropriate culture conditions must be developed to generate genetically stable homogenous populations of cells, to hinder possible adverse effects following transplantation. Other critical challenges that must be addressed for successful cell implantation include problems related to survival and functional efficacy of the grafted cells. This review initially describes the derivation of hESC and focuses on recent advances in generation, characterization, and maintenance of these cells. We also give an overview of original and emerging differentiation strategies used to convert hESC to different cell types. Finally, we will discuss transplantation studies of hESC-derived cells with respect to safety and functional recovery.

Three-dimensional differentiation of embryonic stem cells into islet-like insulin-producing clusters

The production of mature pancreatic cells that function similarly to primary islets is the premise of cell therapy for diabetes. Here, we describe a novel approach to generating more mature insulin-producing cells from embryonic stem (ES) cells. A three-dimensional (3D) ES cell pancreatic differentiation system was developed and used to direct the ES cell differentiation into glucose-responsive, insulin-secreting cells. Using mouse ES cells as a model, we demonstrate that more mature insulin-producing cells can be generated from ES cells in 3D cultures. The 3D differentiated pancreatic endocrine cells can assemble into an islet-like tissue structure that displays greater similarities in phenotype and gene expression profile to adult mouse pancreatic islets, that is, with beta cells in the core and non-beta cells forming the mantel, leading to a significant improvement of the maturity of the insulin-producing cells. Our findings show that nearly 50-60% of the cells in 3D formed cell clusters express insulin. More importantly, those cells exhibit a high level of glucose-responsive insulin and C-peptide syntheses and release. A high level of expression of glucose transporter-2 was also detected in these cells. Compared to two-dimensional ES cell-derived insulin-producing cells, the insulin release from 3D ES cell-derived insulin-producing cells showed a nearly fivefold (p<0.05) increase when exposed to a high glucose (27.7 mM) medium. This 3D culture model provides an excellent system to study pancreatic endocrine morphogenesis and tissue organization. This study also demonstrates the feasibility of producing clinically relevant beta cells from ES cells in a 3D environment.

Hydrogels as extracellular matrix mimics for 3D cell culture

Methods for culturing mammalian cells ex vivo are increasingly needed to study cell and tissue physiology and to grow replacement tissue for regenerative medicine. Two-dimensional culture has been the paradigm for typical in vitro cell culture; however, it has been demonstrated that cells behave more natively when cultured in three-dimensional environments. Permissive, synthetic hydrogels and promoting, natural hydrogels have become popular as three-dimensional cell culture platforms; yet, both of these systems possess limitations. In this perspective, we discuss the use of both synthetic and natural hydrogels as scaffolds for three-dimensional cell culture as well as synthetic hydrogels that incorporate sophisticated biochemical and mechanical cues as mimics of the native extracellular matrix. Ultimately, advances in synthetic-biologic hydrogel hybrids are needed to provide robust platforms for investigating cell physiology and fabricating tissue outside of the organism.

Collagen-based fibrous scaffold for spatial organization of encapsulated and seeded human mesenchymal stem cells

Living tissues consist of groups of cells organized in a controlled manner to perform a specific function. Spatial distribution of cells within a three-dimensional matrix is critical for the success of any tissue-engineering construct. Fibers endowed with cell-encapsulation capability would facilitate the achievement of this objective. Here we report the synthesis of a cell-encapsulated fibrous scaffold by interfacial polyelectrolyte complexation (IPC) of methylated collagen and a synthetic terpolymer. The collagen component was well distributed in the fiber, which had a mean ultimate tensile strength of 244.6+/-43.0 MPa. Cultured in proliferating medium, human mesenchymal stem cells (hMSCs) encapsulated in the fibers showed higher proliferation rate than those seeded on the scaffold. Gene expression analysis revealed the maintenance of multipotency for both encapsulated and seeded samples up to 7 days as evidenced by Sox 9, CBFA-1, AFP, PPARgamma2, nestin, GFAP, collagen I, osteopontin and osteonectin genes. Beyond that, seeded hMSCs started to express neuronal-specific genes such as aggrecan and MAP2. The study demonstrates the appeal of IPC for scaffold design in general and the promise of collagen-based hybrid fibers for tissue engineering in particular. It lays the foundation for building fibrous scaffold that permits 3D spatial cellular organization and multi-cellular tissue development.

The effect of controlled growth factor delivery on embryonic stem cell differentiation inside fibrin scaffolds

The goal of this project was to develop 3-D biomaterial scaffolds that present cues to direct the differentiation of embryonic stem (ES) cell-derived neural progenitor cells, seeded inside the scaffolds, into mature neural phenotypes, specifically neurons and oligodendrocytes. Release studies were performed to determine the appropriate conditions for retention of neurotrophin-3 (NT-3), sonic hedgehog, and platelet-derived growth factor (PDGF) by an affinity-based delivery system incorporated into fibrin scaffolds. Embryoid bodies containing neural progenitors were formed from mouse ES cells, using a 4-/4+ retinoic acid treatment protocol, and then seeded inside fibrin scaffolds containing the drug delivery system. This delivery system was used to deliver various growth factor doses and combinations to the cells seeded inside the scaffolds. Controlled delivery of NT-3 and PDGF simultaneously increased the fraction of neural progenitors, neurons, and oligodendrocytes while decreasing the fraction of astrocytes obtained compared to control cultures seeded inside unmodified fibrin scaffolds with no growth factors present in the medium. These results demonstrate that such a strategy can be used to generate an engineered tissue for the potential treatment of spinal cord injury and could be extended to the study of differentiation in other tissues.

Designing synthetic materials to control stem cell phenotype

The micro-environment in which stem cells reside regulates their fate, and synthetic materials have recently been designed to emulate these regulatory processes for various medical applications. Ligands inspired by the natural extracellular matrix, cell-cell contacts, and growth factors have been incorporated into synthetic materials with precisely engineered density and presentation. Furthermore, material architecture and mechanical properties are material design parameters that provide a context for receptor-ligand interactions and thereby contribute to fate determination of uncommitted stem cells. Although significant progress has been made in biomaterials development for cellular control, the design of more sophisticated and robust synthetic materials can address future challenges in achieving spatiotemporal control of cellular phenotype and in implementing histocompatible clinical therapies.

The effects of soluble growth factors on embryonic stem cell differentiation inside of fibrin scaffolds

The goal of this research was to determine the effects of different growth factors on the survival and differentiation of murine embryonic stem cell-derived neural progenitor cells (ESNPCs) seeded inside of fibrin scaffolds. Embryoid bodies were cultured for 8 days in suspension, retinoic acid was applied for the final 4 days to induce ESNPC formation, and then the EBs were seeded inside of three-dimensional fibrin scaffolds. Scaffolds were cultured in the presence of media containing different doses of the following growth factors: neurotrophin-3 (NT-3), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF)-AA, ciliary neurotrophic factor, and sonic hedgehog (Shh). The cell phenotypes were characterized using fluorescence-activated cell sorting and immunohistochemistry after 14 days of culture. Cell viability was also assessed at this time point. Shh (10 ng/ml) and NT-3 (25 ng/ml) produced the largest fractions of neurons and oligodendrocytes, whereas PDGF (2 and 10 ng/ml) and bFGF (10 ng/ml) produced an increase in cell viability after 14 days of culture. Combinations of growth factors were tested based on the results of the individual growth factor studies to determine their effect on cell differentiation. The incorporation of ESNPCs and growth factors into fibrin scaffolds may serve as potential treatment for spinal cord injury.

Approaches to neural tissue engineering using scaffolds for drug delivery

This review seeks to give an overview of the current approaches to drug delivery from scaffolds for neural tissue engineering applications. The challenges presented by attempting to replicate the three types of nervous tissue (brain, spinal cord, and peripheral nerve) are summarized. Potential scaffold materials (both synthetic and natural) and target drugs are discussed with the benefits and drawbacks given. Finally, common methods of drug delivery, including degradable/diffusion-based delivery systems, affinity-based delivery systems, immobilized drug delivery systems, and electrically controlled drug delivery systems, are examined and critiqued. Based on the current body of work, suggestions for future directions of research in the field of neural tissue engineering are presented.

Biomaterials approach to expand and direct differentiation of stem cells

Stem cells play increasingly prominent roles in tissue engineering and regenerative medicine. Pluripotent embryonic stem (ES) cells theoretically allow every cell type in the body to be regenerated. Adult stem cells have also been identified and isolated from every major tissue and organ, some possessing apparent pluripotency comparable to that of ES cells. However, a major limitation in the translation of stem cell technologies to clinical applications is the supply of cells. Advances in biomaterials engineering and scaffold fabrication enable the development of ex vivo cell expansion systems to address this limitation. Progress in biomaterial design has also allowed directed differentiation of stem cells into specific lineages. In addition to delivering biochemical cues, various technologies have been developed to introduce micro- and nano-scale features onto culture surfaces to enable the study of stem cell responses to topographical cues. Knowledge gained from these studies portends the alteration of stem cell fate in the absence of biological factors, which would be valuable in the engineering of complex organs comprising multiple cell types. Biomaterials may also play an immunoprotective role by minimizing host immunoreactivity toward transplanted cells or engineered grafts.

Optimization of fibrin scaffolds for differentiation of murine embryonic stem cells into neural lineage cells

The objective of this research was to determine the appropriate cell culture conditions for embryonic stem (ES) cell proliferation and differentiation in fibrin scaffolds by examining cell seeding density, location, and the optimal concentrations of fibrinogen, thrombin, and aprotinin (protease inhibitor). Mouse ES cells were induced to become neural progenitors by adding retinoic acid for 4 days to embryoid body (EB) cultures. For dissociated EBs, the optimal cell seeding density and location was determined to be 250,000 cells/cm(2) seeded on top of fibrin scaffolds. For intact EBs, three-dimensional (3D) cultures with one EB per 400 microL fibrin scaffold resulted in greater cell proliferation and differentiation than two-dimensional (2D) cultures. Optimal concentrations for scaffold polymerization were 10mg/mL of fibrinogen and 2 NIH units/mL of thrombin. The optimal aprotinin concentration was determined to be 50 microg/mL for dissociated EBs (2D) and 5 microg/mL for intact EBs in 3D fibrin scaffolds. Additionally, after 14 days in 3D culture EBs differentiated into neurons and astrocytes as indicated by immunohistochemisty. These conditions provide an optimal fibrin scaffold for evaluating ES cell differentiation and proliferation in culture, and for use as a platform for neural tissue engineering applications, such as the treatment for spinal cord injury.

Enhanced extracellular matrix production and differentiation of human embryonic germ cell derivatives in biodegradable poly(epsilon-caprolactone-co-ethyl ethylene phosphate) scaffold

Extracellular environment regulates cell behavior and also influences the differentiation of stem cells. Two cell lines of pluriopotent human embryonic germ cell derivatives (EBD cells) were cultured on a biodegradable poly(epsilon-caprolactone-co-ethyl ethylene phosphate) (PCLEEP) and non-degradable cellulose acetate scaffold. Their cell behaviors including proliferation, differentiation, cell distribution and extracellular matrix production were studied for 4 weeks and 10 months. The proliferation of the EBD cells was enhanced in both of the three-dimensional scaffolds in the first 5 weeks of culture, regardless of the material difference, compared to monolayer culture. While the gene expression profile remained multilineage for the EBD cells cultured in the cellulose acetate fibrous scaffold, much of the neuronal lineage markers were down-regulated in EBD cells cultured in the PCLEEP scaffold. On the other hand, extracellular matrix production was significantly enhanced in the PCLEEP scaffold. The study showed that the polymer substrate could influence the differentiation and growth of pluripotent stem cells in the absence of exogenous biochemical signals.

Toward xeno-free culture of human embryonic stem cells

The culture of human embryonic stem cells (hESCs) is limited, both technically and with respect to clinical potential, by the use of mouse embryonic fibroblasts (MEFs) as a feeder layer. The concern over xenogeneic contaminants from the mouse feeder cells may restrict transplantation to humans and the variability in MEFs from batch-to-batch and laboratory-to-laboratory may contribute to some of the variability in experimental results. Finally, use of any feeder layer increases the work load and subsequently limits the large-scale culture of human ES cells. Thus, the development of feeder-free cultures will allow more reproducible culture conditions, facilitate scale-up and potentiate the clinical use of cells differentiated from hESC cultures. In this review, we describe various methods tested to culture cells in the absence of MEF feeder layers and other advances in eliminating xenogeneic products from the culture system.