Electrospun polystyrene scaffolds as a synthetic substrate for xeno-free expansion and differentiation of human induced pluripotent stem cells

Nonwoven fiber meshes for oxygen sensing

Accurate oxygen sensing and cost-effective fabrication are crucial for the adoption of wearable devices inside and outside the clinical setting. Here we introduce a simple strategy to create nonwoven polymeric fibrous mats for a notable contribution towards addressing this need. Although morphological manipulation of polymers for cell culture proliferation is commonplace, especially in the field of regenerative medicine, non-woven structures have not been used for oxygen sensing. We used an airbrush spraying, i.e. solution blowing, to obtain nonwoven fiber meshes embedded with a phosphorescent dye. The fibers serve as a polymer host for the phosphorescent dye and are shown to be non-cytotoxic. Different composite fibrous meshes were prepared and favorable mechanical and oxygen-sensing properties were demonstrated. A Young's modulus of 9.8 MPa was achieved and the maximum oxygen sensitivity improved by a factor of ∼2.9 compared to simple drop cast film. The fibers were also coated with silicone rubbers to produce mechanically robust sensing films. This reduced the sensing performance but improved flexibility and mechanical properties. Lastly, we are able to capture oxygen concentration maps via colorimetry using a smartphone camera, which should offer unique advantages in wider usage. Overall, the introduced composite fiber meshes show a potential to significantly improve cell cultures and healthcare monitoring via absolute oxygen sensing.

Biomaterials based on hyaluronic acid, collagen and peptides for three-dimensional cell culture and their application in stem cell differentiation

In recent decades, three-dimensional (3D) cell culture technologies have been developed rapidly in the field of tissue engineering and regeneration, and have shown unique advantages and great prospects in the differentiation of stem cells. Herein, the article reviews the progress and advantages of 3D cell culture technologies in the field of stem cell differentiation. Firstly, 3D cell culture technologies are divided into two main categories: scaffoldless and scaffolds. Secondly, the effects of hydrogels scaffolds and porous scaffolds on stem cell differentiation in the scaffold category were mainly reviewed. Among them, hydrogels scaffolds are divided into natural hydrogels and synthetic hydrogels. Natural materials include polysaccharides, proteins, and their derivatives, focusing on hyaluronic acid, collagen and polypeptides. Synthetic materials mainly include polyethylene glycol (PEG), polyacrylic acid (PAA), polyvinyl alcohol (PVA), etc. In addition, since the preparation techniques have a large impact on the properties of porous scaffolds, several techniques for preparing porous scaffolds based on different macromolecular materials are reviewed. Finally, the future prospects and challenges of 3D cell culture in the field of stem cell differentiation are reviewed. This review will provide a useful guideline for the selection of materials and techniques for 3D cell culture in stem cell differentiation.

A functional neuron maturation device provides convenient application on microelectrode array for neural network measurement

BACKGROUND

Microelectrode array (MEA) systems are valuable for in vitro assessment of neurotoxicity and drug efficiency. However, several difficulties such as protracted functional maturation and high experimental costs hinder the use of MEA analysis requiring human induced pluripotent stem cells (hiPSCs). Neural network functional parameters are also needed for in vitro to in vivo extrapolation.

METHODS

In the present study, we produced a cost effective nanofiber culture platform, the SCAD device, for long-term culture of hiPSC-derived neurons and primary peripheral neurons. The notable advantage of SCAD device is convenient application on multiple MEA systems for neuron functional analysis.

RESULTS

We showed that the SCAD device could promote functional maturation of cultured hiPSC-derived neurons, and neurons responded appropriately to convulsant agents. Furthermore, we successfully analyzed parameters for in vitro to in vivo extrapolation, i.e., low-frequency components and synaptic propagation velocity of the signal, potentially reflecting neural network functions from neurons cultured on SCAD device. Finally, we measured the axonal conduction velocity of peripheral neurons.

CONCLUSIONS

Neurons cultured on SCAD devices might constitute a reliable in vitro platform to investigate neuron functions, drug efficacy and toxicity, and neuropathological mechanisms by MEA.

Design of chemically defined synthetic substrate surfaces for the in vitro maintenance of human pluripotent stem cells: A review

Human pluripotent stem cells (hPSCs) have the potential of long-term self-renewal and differentiation into nearly all cell types in vitro. Prior to the downstream applications, the design of chemically defined synthetic substrates for the large-scale proliferation of quality-controlled hPSCs is critical. Although great achievements have been made, Matrigel and recombinant proteins are still widely used in the fundamental research and clinical applications. Therefore, much effort is still needed to improve the performance of synthetic substrates in the culture of hPSCs, realizing their commercial applications. In this review, we summarized the design of reported synthetic substrates and especially their limitations in terms of cell culture. Moreover, much attention was paid to the development of promising peptide displaying surfaces. Besides, the biophysical regulation of synthetic substrate surfaces as well as the three-dimensional culture systems were described.

Unraveling molecular mechanism underlying biomaterial and stem cells interaction during cell fate commitment using high throughput data analysis

Stem cell differentiation towards various somatic cells and body organs has proven to be an effective technique in the understanding and progression of regenerative medicine. Despite the advances made, concerns regarding the low efficiency of differentiation and the remaining differences between stem cell products and their in vivo counterparts must be addressed. Biomaterials that mimic endogenous growth conditions represent one recent method used to improve the quality and efficiency of stem cell differentiation, though the mechanisms of this improvement remain to be completely understood. The effectiveness of various biomaterials can be analyzed through a multidisciplinary approach involving bioinformatics and systems biology tools. Here, we aim to use bioinformatics to accomplish two aims: 1) determine the effect of different biomaterials on stem cell growth and differentiation, and 2) understand the effect of cell of origin on the differentiation potential of multipotent stem cells. First, we demonstrate that the dimensionality (2D versus 3D) and the degradability of biomaterials affects the way that the cells are able to grow and differentiate at the transcriptional level. Additionally, according to transcriptional state of the cells, the particular cell of origin is an important factor in determining the response of stem cells to same biomaterial. Our data demonstrates the ability of bioinformatics to understand novel molecular mechanisms and context by which stem cells are most efficiently able to differentiate. These results and strategies can be used to suggest proper combinations of biomaterials and stem cells to achieve high differentiation efficiency and functionality of desired cell types.

Micro-scaffolds as synthetic cell niches: recent advances and challenges

Micro-fabrication and nano-fabrication provide useful approaches to address fundamental biological questions by mimicking the physiological microenvironment in which cells carry out their functions. In particular, 2D patterns and 3D scaffolds obtained via lithography, direct laser writing, and other techniques allow for shaping hydrogels, synthetic polymers and biologically derived materials to create structures for (single) cell culture. Applications of micro-scaffolds mimicking cell niches include stem cell self-renewal, differentiation, and lineage specification. This review moves from technological aspects of scaffold microfabrication for cell biological applications to a broad overview of advances in (stem) cell research: achievements for embryonic, induced pluripotent, mesenchymal, and neural stem cells are treated in detail, while a particular section is dedicated to micro-scaffolds used to study single cells in basic cell biology.

From cells-on-a-chip to organs-on-a-chip: scaffolding materials for 3D cell culture in microfluidics

It is an emerging research area to integrate scaffolding materials in microfluidic devices for 3D cell culture (organs-on-a-chip). The technology of organs-on-a-chip holds the potential to obviate the gaps between pre-clinical and clinical studies. As accumulating evidence shows the importance of extracellular matrix in in vitro cell culture, significant efforts have been made to integrate 3D ECM/scaffolding materials in microfluidics. There are two families of materials that are commonly used for this purpose: hydrogels and electrospun fibers. In this review, we briefly discuss the properties of the materials, and focus on the various technologies to obtain the materials (e.g. extraction of collagen from animal tissues) and to include the materials in microfluidic devices. Challenges and potential solutions of the current materials and technologies were also thoroughly discussed. At the end, we provide a perspective on future efforts to make these technologies more translational to broadly benefit pharmaceutical and pathophysiological research.

Conditioned Medium From Azurin-Expressing Human Mesenchymal Stromal Cells Demonstrates Antitumor Activity Against Breast and Lung Cancer Cell Lines

Recently, cell-based therapies have been explored as a strategy to enhance the specificity of anticancer therapeutic agents. In this perspective, human mesenchymal stromal cells (MSC) hold a promising future as cell delivery systems for anticancer proteins due to their unique biological features. In this study, we engineered human MSC to secrete a human codon-optimized version of azurin (hazu), a bacterial protein that has demonstrated anticancer activity toward different cancer models both in vitro and in vivo. To this end, microporation was used to deliver plasmid DNA encoding azurin into MSC derived from bone marrow (BM) and umbilical cord matrix (UCM), leading to expression and secretion of hazu to the conditioned medium (CM). Engineered hazu-MSC were shown to preserve tumor tropism toward breast (MCF-7) and lung (A549) cancer cell lines, comparable to non-modified MSC. Azurin was detected in the CM of transfected MSC and, upon treatment with hazu-MSC-CM, we observed a decrease in cancer cell proliferation, migration, and invasion, and an increase in cell death for both cancer cell lines. Moreover, expression of azurin caused no changes in MSC expression profile of cytokines relevant in the context of cancer progression, thus suggesting that the antitumoral effects induced by hazu-MSC secretome might be due to the presence of azurin independently. In conclusion, data shown herein indicate that MSC-produced azurin in a CM configuration elicits an anticancer effect.

Synthetic alternatives to Matrigel

Matrigel, a basement-membrane matrix extracted from Engelbreth-Holm-Swarm mouse sarcomas, has been used for more than four decades for a myriad of cell culture applications. However, Matrigel is limited in its applicability to cellular biology, therapeutic cell manufacturing and drug discovery owing to its complex, ill-defined and variable composition. Variations in the mechanical and biochemical properties within a single batch of Matrigel - and between batches - have led to uncertainty in cell culture experiments and a lack of reproducibility. Moreover, Matrigel is not conducive to physical or biochemical manipulation, making it difficult to fine-tune the matrix to promote intended cell behaviours and achieve specific biological outcomes. Recent advances in synthetic scaffolds have led to the development of xenogenic-free, chemically defined, highly tunable and reproducible alternatives. In this Review, we assess the applications of Matrigel in cell culture, regenerative medicine and organoid assembly, detailing the limitations of Matrigel and highlighting synthetic scaffold alternatives that have shown equivalent or superior results. Additionally, we discuss the hurdles that are limiting a full transition from Matrigel to synthetic scaffolds and provide a brief perspective on the future directions of synthetic scaffolds for cell culture applications.

Biomaterial-assisted scalable cell production for cell therapy

Cell therapy, the treatment of diseases using living cells, offers a promising clinical approach to treating refractory diseases. The global market for cell therapy is growing rapidly, and there is an increasing demand for automated methods that can produce large quantities of high quality therapeutic cells. Biomaterials can be used during cell production to establish a biomimetic microenvironment that promotes cell adhesion and proliferation while maintaining target cell genotype and phenotype. Here we review recent progress and emerging techniques in biomaterial-assisted cell production. The increasing use of auxiliary biomaterials and automated production methods provides an opportunity to improve quality control and increase production efficiency using standardized GMP-compliant procedures.

Differentiation of retinal ganglion cells from induced pluripotent stem cells: a review

Glaucoma is a common optic neuropathy that is characterized by the progressive degeneration of axons and the loss of retinal ganglion cells (RGCs). Glaucoma is one of the leading causes of irreversible blindness worldwide. Current glaucoma treatments only slow the progression of RGCs loss. Induced pluripotent stem cells (iPSCs) are capable of differentiating into all three germ layer cell lineages. iPSCs can be patient-specific, making iPSC-derived RGCs a promising candidate for cell replacement. In this review, we focus on discussing the detailed approaches used to differentiate iPSCs into RGCs.

Application of Human-Induced Pluripotent Stem Cells (hiPSCs) to Study Synaptopathy of Neurodevelopmental Disorders

Synapses are the basic structural and functional units for information processing and storage in the brain. Their diverse properties and functions ultimately underlie the complexity of human behavior. Proper development and maintenance of synapses are essential for normal functioning of the nervous system. Disruption in synaptogenesis and the consequent alteration in synaptic function have been strongly implicated to cause neurodevelopmental disorders such as autism spectrum disorders (ASDs) and schizophrenia (SCZ). The introduction of human-induced pluripotent stem cells (hiPSCs) provides a new path to elucidate disease mechanisms and potential therapies. In this review, we will discuss the advantages and limitations of using hiPSC-derived neurons to study synaptic disorders. Many mutations in genes encoding for proteins that regulate synaptogenesis have been identified in patients with ASDs and SCZ. We use Methyl-CpG binding protein 2 (MECP2), SH3 and multiple ankyrin repeat domains 3 (SHANK3) and Disrupted in schizophrenia 1 (DISC1) as examples to illustrate the promise of using hiPSCs as cellular models to elucidate the mechanisms underlying disease-related synaptopathy.

The Evolution of Polystyrene as a Cell Culture Material

Polystyrene (PS) has brought in vitro cell culture from its humble beginnings to the modern era, propelling dozens of research fields along the way. This review discusses the development of the material, fabrication, and treatment approaches to create the culture material. However, native PS surfaces poorly facilitate cell adhesion and growth in vitro. To overcome this, liquid surface deposition, energetic plasma activation, and emerging functionalization methods transform the surface chemistry. This review seeks to highlight the many potential applications of the first widely accepted polymer growth surface. Although the majority of in vitro research occurs on two-dimensional surfaces, the importance of three-dimensional (3D) culture models cannot be overlooked. The methods to transition PS to specialized 3D culture surfaces are also reviewed. Specifically, casting, electrospinning, 3D printing, and microcarrier approaches to shift PS to a 3D culture surface are highlighted. The breadth of applications of the material makes it impossible to highlight every use, but the aim remains to demonstrate the versatility and potential as both a general and custom cell culture surface. The review concludes with emerging scaffolding approaches and, based on the findings, presents our insights on the future steps for PS as a tissue culture platform.

Enhanced Differentiation of Human Preosteoblasts on Electrospun Blend Fiber Mats of Polydioxanone and Anionic Sulfated Polysaccharides

The viability and differentiation of SaOS-2 preosteoblasts on fiber mats of blends comprising of the biodegradable poly(ester-ether) polydioxanone (PDX) and the sulfate-containing anionic polysaccharides kappa-carrageenan (KCG) and fucoidan (FUC) were investigated for a range of different blend compositions. The detailed analysis of the blend nanofiber properties revealed a different degree of miscibility of PDX and the polysaccharide leading to a different enrichment at the surface of the blend nanofibers, which were observed to be stable in phosphate buffer solution (PBS) for up to 5 weeks. The fibrous mats of PDX/FUC led to the highest osteogenic differentiation with very good cell viability. The electrospun blend fibers also supported human-induced pluripotent stem (iPS) cells and iPS cell-derived embryoid bodies with high cell viability, which underlines the potential of these novel blend fiber systems for optimized performance in bone tissue engineering applications.

Advances and challenges in stem cell culture

Stem cells (SCs) hold great promise for cell therapy, tissue engineering, and regenerative medicine as well as pharmaceutical and biotechnological applications. They have the capacity to self-renew and the ability to differentiate into specialized cell types depending upon their source of isolation. However, use of SCs for clinical applications requires a high quality and quantity of cells. This necessitates large-scale expansion of SCs followed by efficient and homogeneous differentiation into functional derivatives. Traditional methods for maintenance and expansion of cells rely on two-dimensional (2-D) culturing techniques using plastic culture plates and xenogenic media. These methods provide limited expansion and cells tend to lose clonal and differentiation capacity upon long-term passaging. Recently, new approaches for the expansion of SCs have emphasized three-dimensional (3-D) cell growth to mimic the in vivo environment. This review provides a comprehensive compendium of recent advancements in culturing SCs using 2-D and 3-D techniques involving spheroids, biomaterials, and bioreactors. In addition, potential challenges to achieve billion-fold expansion of cells are discussed.

Human embryonic stem cell dispersion in electrospun PCL fiber scaffolds by coating with laminin-521 and E-cadherin-Fc

Advances in human pluripotent cell cultivation and differentiation protocols have led to production of stem cell-derived progenitors as a promising cell source for replacement therapy. Three-dimensional (3-D) culture is a better mimic of the natural niche for stem cells and is widely used for disease modeling. Here, we describe a nonaggregate culture system of human embryonic stem cells inside electrospun polycaprolactone (PCL) fiber scaffolds combined with defined extracellular proteins naturally occurring in the stem cell niche. PCL fiber scaffolds coated with recombinant human laminin-521 readily supported initial stem cell attachment and growth from a single-cell suspension. The combination of recombinant E-cadherin-Fc and laminin-521 further improved cell dispersion rendering a uniform cell population. Finally, we showed that the cells cultured in E-cadherin-Fc- and laminin-521-coated PCL scaffolds could differentiate into all three germ layers. Importantly, we provided a chemically defined 3-D system in which pluripotent stem cells grown and differentiated avoiding the formation of cell aggregates. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1226-1236, 2018.