Embryonic stem cells as a source of models for drug discovery

Current Applications of Human Pluripotent Stem Cells in Neuroscience Research and Cell Transplantation Therapy for Neurological Disorders

Many neurological diseases involving tissue damage cannot be treated with drug-based approaches, and the inaccessibility of human brain samples further hampers the study of these diseases. Human pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), provide an excellent model for studying neural development and function. PSCs can be differentiated into various neural cell types, providing a renewal source of functional human brain cells. Therefore, PSC-derived neural cells are increasingly used for multiple applications, including neurodevelopmental and neurotoxicological studies, neurological disease modeling, drug screening, and regenerative medicine. In addition, the neural cells generated from patient iPSCs can be used to study patient-specific disease signatures and progression. With the recent advances in genome editing technologies, it is possible to remove the disease-related mutations in the patient iPSCs to generate corrected iPSCs. The corrected iPSCs can differentiate into neural cells with normal physiological functions, which can be used for autologous transplantation. This review highlights the current progress in using PSCs to understand the fundamental principles of human neurodevelopment and dissect the molecular mechanisms of neurological diseases. This knowledge can be applied to develop better drugs and explore cell therapy options. We also discuss the basic requirements for developing cell transplantation therapies for neurological disorders and the current status of the ongoing clinical trials.

A simple guideline for designing droplet microfluidic chips to achieve an improved single (bio)particle encapsulation rate using a stratified flow-assisted particle ordering method

Encapsulation of a single (bio)particle into individual droplets (referred to as single encapsulation) presents tremendous potential for precise biological and chemical reactions at the single (bio)particle level. Previously demonstrated successful strategies often rely on the use of high flow rates, gel, or viscoelastic materials for initial cell ordering prior to encapsulation into droplets, which could potentially challenge the system's operation. We propose to enhance the single encapsulation rate by using a stratified flow structure to focus and pre-order the (bio)particles before encapsulation. The stratified flow structure is formed using two simple aqueous Newtonian fluids with a viscosity contrast, which together serve as the dispersed phase. The single encapsulation rate is influenced by many parameters, including fluid viscosity contrast, geometric conditions, flow conditions and flow rate ratios, and dimensionless numbers such as the capillary number. This study focuses on investigating the influences of these parameters on the focused stream of the stratified flow, which is key for single encapsulation. The results allow the proposal of a simple guideline that can be adopted to design droplet microfluidic chips with an improved single encapsulation rate demanded by a wide range of applications. The guideline was validated by performing the single encapsulation of mouse embryonic stem cells suspended in a gelatin-methacryloyl solution in individual droplets of phosphate buffer saline, achieving a single encapsulation efficiency of up to 70%.

Regulatory role of apelin receptor signaling in migration and differentiation of mouse embryonic stem cell-derived mesoderm cells and mesenchymal stem/stromal cells

Mesoderm-derived cells, including bone, muscle, and mesenchymal stem/stromal cells (MSCs), constitute various parts of vertebrate body. Cell therapy with mesoderm specification in vitro may be a promising treatment for diseases affecting organs of mesodermal origin. Repair and regeneration of damaged organs with in vitro generation of mesoderm-derived tissues and MSCs hold a great potential for regenerative therapy. Therefore, understanding the signaling pathways involving mesoderm and mesoderm-derived cellular differentiation is important. Previous findings indicated the importance of Apelin receptor (Aplnr) signaling, during embryonic development, in gastrulation, cell migration, and differentiation. Nevertheless, regulatory role of Aplnr pathway in differentiation of mesoderm and mesoderm-derived MSCs remains unclear. In the current study, we tried to elucidate the role of Aplnr signaling during mesoderm cell migration and differentiation from mouse embryonic stem cells (mESCs). By activating and suppressing Aplnr signaling pathway via peptide, small molecule, and genetic modifications including siRNA- and shRNA-mediated knockdown and CRISPR-Cas9-mediated knockout (KO), we revealed that Aplnr signaling not only induces migration of cells during germ layer formation but also enhances mesoderm differentiation through FGF/MAPK pathway. Antibody array and LC/MS protein profiling data demonstrated that Apelin-13 treatment enhanced cell cycle, EGFR, FGF, Wnt, and Integrin signaling pathway proteins. Furthermore, Aplelin-13 treatment improved MSC characteristics, with mesenchymal phenotype and high expression of MSC markers, and silencing Aplnr signaling components resulted in significantly reduced expression of MSC markers. Also, Aplnr signaling activity enhanced proliferation and survival of the cells during MSC derivation from mesoderm.

The potential of plant extracts in cell therapy

Cell therapy is the frontier technology of biotechnology innovation and the most promising method for the treatment of refractory diseases such as tumours. However, cell therapy has disadvantages, such as toxicity and poor therapeutic effects. Plant extracts are natural, widely available, and contain active small molecule ingredients that are widely used in the treatment of various diseases. By studying the effect of plant extracts on cell therapy, active plant extracts that have positive significance in cell therapy can be discovered, and certain contributions to solving the current problems of attenuation and adjuvant therapy in cell therapy can be made. Therefore, this article reviews the currently reported effects of plant extracts in stem cell therapy and immune cell therapy, especially the effects of plant extracts on the proliferation and differentiation of mesenchymal stem cells and nerve stem cells and the potential role of plant extracts in chimeric antigen receptor T-cell immunotherapy (CAR-T) and T-cell receptor modified T-cell immunotherapy (TCR-T), in the hope of encouraging further research and clinical application of plant extracts in cell therapy.

Dynamic gelatin-based hydrogels promote the proliferation and self-renewal of embryonic stem cells in long-term 3D culture

Long-term maintenance of embryonic stem cells (ESCs) in the undifferentiated state is still challenging. Compared with traditional 2D culture methods, 3D culture in biomaterials such as hydrogels is expected to better support the long-term self-renewal of ESCs by emulating the biophysical and biochemical properties of the extracellular matrix (ECM). Although prior studies showed that soft and degradable hydrogels favor the 3D growth of ESCs, few studies have examined the impact of the structural dynamics of the hydrogel matrix on ESC behaviors. Herein, we report a gelatin-based structurally dynamic hydrogel (GelCD hydrogel) that emulates the intrinsic structural dynamics of the ECM. Compared with covalently crosslinked gelatin hydrogels (GelMA hydrogels) with similar stiffness and biodegradability, GelCD hydrogels significantly promote the clonal expansion and viability of encapsulated mouse ESCs (mESCs) independent of MMP-mediated hydrogel degradation. Furthermore, GelCD hydrogels better maintain the pluripotency of encapsulated mESCs than do traditional 2D culture methods that use MEF feeder cells or medium supplementation with GSK3β and MEK 1/2 inhibitors (2i). When cultured in GelCD hydrogels for an extended period (over 2 months) with cell passaging every 7 days, mESCs preserve their normal morphology and maintain their pluripotency and full differentiation capability. Our findings highlight the critical role of the structural dynamics of the hydrogel matrix in accommodating the volume expansion that occurs during clonal ESC growth, and we believe that our dynamic hydrogels represent a valuable tool to support the long-term 3D culture of ESCs.

Application of Induced Pluripotent Stem Cell-Derived Models for Investigating microRNA Regulation in Developmental Processes

Advances in induced pluripotent stem cell (iPSC) techniques have opened up new perspectives in research on developmental biology. Compared with other sources of human cellular models, iPSCs present a great advantage in hosting the unique genotype background of donors without ethical concerns. A wide spectrum of cellular and organoid models can be generated from iPSCs under appropriate in vitro conditions. The pluripotency of iPSCs is orchestrated by external signalling and regulated at the epigenetic, transcriptional and posttranscriptional levels. Recent decades have witnessed the progress of studying tissue-specific expressions and functions of microRNAs (miRNAs) using iPSC-derived models. MiRNAs are a class of short non-coding RNAs with regulatory functions in various biological processes during development, including cell migration, proliferation and apoptosis. MiRNAs are key modulators of gene expression and promising candidates for biomarker in development; hence, research on the regulation of human development by miRNAs is expanding. In this review, we summarize the current progress in the application of iPSC-derived models to studies of the regulatory roles of miRNAs in developmental processes.

Advances in microfluidic 3D cell culture for preclinical drug development

Drug development is often a very long, costly, and risky process due to the lack of reliability in the preclinical studies. Traditional current preclinical models, mostly based on 2D cell culture and animal testing, are not full representatives of the complex in vivo microenvironments and often fail. In order to reduce the enormous costs, both financial and general well-being, a more predictive preclinical model is needed. In this chapter, we review recent advances in microfluidic 3D cell culture showing how its development has allowed the introduction of in vitro microphysiological systems, laying the foundation for organ-on-a-chip technology. These findings provide the basis for numerous preclinical drug discovery assays, which raise the possibility of using micro-engineered systems as emerging alternatives to traditional models, based on 2D cell culture and animals.

Compartmentalized microfluidic chambers enable long-term maintenance and communication between human pluripotent stem cell-derived forebrain and midbrain neurons

Compartmentalized microfluidic devices are becoming increasingly popular and have proven to be valuable tools to probe neurobiological functions that are inherently difficult to study using traditional approaches. The ability of microfluidic devices to compartmentalize neurons offers considerable promise for disease modeling and drug discovery. Rodent cortical neurons/neural progenitors are commonly used in such studies but, while these cells mature rapidly, they do not possess the same receptors, ion channels and transport proteins found in human cortical neurons. Human pluripotent stem cell derived neurons offer a human phenotype, but their slow maturation offsets this phenotypic advantage, particularly over long-term culture where overgrowth and subsequent death of neurons may be a problem. In this work, we integrate the use of Matrigel as a 3D cell culture scaffold that enables high cell seeding density over a small fraction of the culture surface. This approach, in an open chamber microfluidic system, enables culture over a five-month period without the use of growth inhibitors. Matrigel was also uniquely utilized to hinder agonist diffusion across microchannels. We demonstrate the development of neuron-to-neuron communication networks by showing that electrical stimulation or the unilateral addition of agonists to one chamber resulted in activation of neurons in the adjacent chamber. Lastly, using a delayed neuron seeding strategy, we show that we can foster essentially one-way communication between separate populations of human forebrain and midbrain dopaminergic neuron containing cultures.

Novel cell sources for bone regeneration

A plethora of both acute and chronic conditions, including traumatic, degenerative, malignant, or congenital disorders, commonly induce bone disorders often associated with severe persisting pain and limited mobility. Over 1 million surgical procedures involving bone excision, bone grafting, and fracture repair are performed each year in the U.S. alone, resulting in immense levels of public health challenges and corresponding financial burdens. Unfortunately, the innate self-healing capacity of bone is often inadequate for larger defects over a critical size. Moreover, as direct transplantation of committed osteoblasts is hindered by deficient cell availability, limited cell spreading, and poor survivability, an urgent need for novel cell sources for bone regeneration is concurrent. Thanks to the development in stem cell biology and cell reprogramming technology, many multipotent and pluripotent cells that manifest promising osteogenic potential are considered the regenerative remedy for bone defects. Considering these cells' investigation is still in its relative infancy, each of them offers their own particular challenges that must be conquered before the large-scale clinical application.

Co-administration of TiO2-nanowired dl-3-n-butylphthalide (dl-NBP) and mesenchymal stem cells enhanced neuroprotection in Parkinson's disease exacerbated by concussive head injury

dl-3-n-butylphthalide (dl-NBP) is a powerful antioxidant compound with profound neuroprotective effects in stroke and brain injury. However, its role in Parkinson's disease (PD) is not well known. Traumatic brain injury (TBI) is one of the key factors in precipitating PD like symptoms in civilians and particularly in military personnel. Thus, it would be interesting to explore the possible neuroprotective effects of NBP in PD following concussive head injury (CHI). In this chapter effect of nanowired delivery of NBP together with mesenchymal stem cells (MSCs) in PD with CHI is discussed based on our own investigations. It appears that CHI exacerbates PD pathophysiology in terms of p-tau, α-synuclein (ASNC) levels in the cerebrospinal fluid (CSF) and the loss of TH immunoreactivity in substantia niagra pars compacta (SNpc) and striatum (STr) along with dopamine (DA), dopamine decarboxylase (DOPAC). And homovanillic acid (HVA). Our observations are the first to show that a combination of NBP with MSCs when delivered using nanowired technology induces superior neuroprotective effects in PD brain pathology exacerbated by CHI, not reported earlier.

Targeted epigenetic modulation using a DNA-based histone deacetylase inhibitor enhances cardiomyogenesis in mouse embryonic stem cells

The epigenome has an essential role in orchestrating transcriptional activation and modulating key developmental processes. Previously, we developed a library of pyrrole-imidazole polyamides (PIPs) conjugated with suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor, for the purpose of sequence-specific modification of epigenetics. Based on the gene expression profile of SAHA-PIPs and screening studies using the α-myosin heavy chain promoter-driven reporter and SAHA-PIP library, we identified that SAHA-PIP G activates cardiac-related genes. Studies in mouse ES cells showed that SAHA-PIP G could enhance the generation of spontaneous beating cells, which is consistent with upregulation of several cardiac-related genes. Moreover, ChIP-seq results confirmed that the upregulation of cardiac-related genes is highly correlated with epigenetic activation, relevant to the sequence-specific binding of SAHA-PIP G. This proof-of-concept study demonstrating the applicability of SAHA-PIP not only improves our understanding of epigenetic alterations involved in cardiomyogenesis but also provides a novel chemical-based strategy for stem cell differentiation.

An automated and high-throughput-screening compatible pluripotent stem cell-based test platform for developmental and reproductive toxicity assessment of small molecule compounds

The embryonic stem cell test (EST) represents the only validated and accepted in vitro system for the detection and classification of compounds according to their developmental and reproductive teratogenic potency. The widespread implementation of the EST, however, in particular for routine application in pharmaceutical development, has not been achieved so far. Several drawbacks still limit the high-throughput screening of potential drug candidates in this format: The long assay period, the use of non-homogeneous viability assays, the low throughput analysis of marker protein expression and the compatibility of the assay procedures to automation. We have therefore introduced several advancements into the EST workflow: A reduction of the assay period, an introduction of homogeneous viability assays, and a straightforward analysis of marker proteins by flow cytometry and high content imaging to assess the impact of small molecules on differentiation capacity. Most importantly, essential parts of the assay procedure have been adapted to lab automation in 96-well format, thus enabling the interrogation of several compounds in parallel. In addition, extensive investigations were performed to explore the predictive capacity of this next-generation EST, by testing a set of well-known embryotoxicants that encompasses the full range of chemical-inherent embryotoxic potencies possible. Due to these significant improvements, the augmented workflow provides a basis for a sensitive, more rapid, and reproducible high throughput screening compatible platform to predict in vivo developmental toxicity from in vitro data which paves the road towards application in an industrial setting.

Graphical abstract

Evaluation of in vitro models of stem cell-derived cardiomyocytes to screen for potential cardiotoxicity of chemicals

Cardiotoxicity is an important toxicological endpoint for chemical and drug safety assessment. The present study aims to evaluate two stemcell-based in vitro models for cardiotoxicity screening of chemicals. Eleven model compounds were used to evaluate responses of mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) using beating arrest as a readout and the analysis of electrophysiological parameters measured with a multi-electrode array (MEA) platform of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Results revealed that the hiPSC-CM MEA assay responded to all compounds. The mESC-CM beating arrest assay was not responsive to potassium channel blockers and showed a lower sensitivity to sodium channel blockers and Na⁺/K⁺ ATPase inhibitors compared to the hiPSC-CM MEA assay. Calcium channel blockers and a β-adrenergic receptor agonist showed comparable potencies in both models. The in vitro response concentrations from hiPSC-CMs were highly concordant with human effective serum concentrations of potassium and sodium channel blockers. It is concluded that both in vitro models enable the cardiotoxicity screening with different applicability domains. The mESC-CM beating arrest assay may be used as a first step in a tiered approach while the hiPSC-CM MEA assay may be the best starting point for quantitative in vitro to in vivo extrapolations.

Profiling embryonic stem cell differentiation by MALDI TOF mass spectrometry: development of a reproducible and robust sample preparation workflow

MALDI TOF mass spectrometry (MS) is widely used to characterise and biotype bacterial samples, but a complementary method for profiling of mammalian cells is still underdeveloped. Current approaches vary dramatically in their sample preparation methods and are not suitable for high-throughput studies. In this work, we present a universal workflow for mammalian cell MALDI TOF MS analysis and apply it to distinguish ground-state naïve and differentiating mouse embryonic stem cells (mESCs), which can be used as a model for drug discovery. We employed a systematic approach testing many parameters to evaluate how efficiently and reproducibly each method extracted unique mass features from four different human cell lines. These data enabled us to develop a unique mammalian cell MALDI TOF workflow involving a freeze-thaw cycle, methanol fixing and a CHCA matrix to generate spectra that robustly phenotype different cell lines and are highly reproducible in peak identification across replicate spectra. We applied our optimised workflow to distinguish naïve and differentiating populations using multivariate analysis and reproducibly identify unique features. We were also able to demonstrate the compatibility of our optimised method for current automated liquid handling technologies. Consequently, our MALDI TOF MS profiling method enables identification of unique features and robust phenotyping of mESC differentiation in under 1 hour from culture to analysis, which is significantly faster and cheaper when compared with conventional methods such as qPCR. This method has the potential to be automated and can in the future be applied to profile other cell types and expanded towards cellular MALDI TOF MS screening assays.

Naturally-Derived Biomaterials for Tissue Engineering Applications

Naturally-derived biomaterials have been used for decades in multiple regenerative medicine applications. From the simplest cell microcarriers made of collagen or alginate, to highly complex decellularized whole-organ scaffolds, these biomaterials represent a class of substances that is usually first in choice at the time of electing a functional and useful biomaterial. Hence, in this chapter we describe the several naturally-derived biomaterials used in tissue engineering applications and their classification, based on composition. We will also describe some of the present uses of the generated tissues like drug discovery, developmental biology, bioprinting and transplantation.

Disruption of mitochondrial membrane potential coupled with alterations in cardiac biomarker expression as early cardiotoxic signatures in human ES cell-derived cardiac cells

Cardiotoxicity is one of the most significant reasons of attrition in drug development. The present study assessed the sensitivity of various endpoints for early monitoring of drug-induced cardiotoxicity using human embryonic stem cell-derived cardiac cells, including precursors as well as mature cardiomyocytes, by correlating changes in cardiac biomarker expression. Directed differentiation was induced and cardiac progenitor cell (CPC) population were treated with cardiotoxic drugs, namely, doxorubicin (Dox) and paclitaxel (Pac), and with noncardiotoxic drug, namely penicillin G. To assess cardiac-specific toxicity, the changes in the expression of key markers of cardiac lineage, such as Nkx2.5, Tbx5, α-myosin heavy chain α-MHC, and cardiac troponin T, were studied using quantitative real-time polymerase chain reaction (qRT-PCR) and flow cytometry (FC). The half-maximal inhibition in the expression of these cardiac markers was analyzed from the dose-response curves. We also assessed the half-maximal inhibition (IC₅₀) in cardiac cells using propidium iodide dye (IC₅₀ PI) and by measuring disruption in the mitochondrial membrane potential (IC₅₀ MMP). We observed that the most sensitive marker was α-MHC in the case of both Dox and Pac, and the order of sensitivity of the various prediction assays was MMP > protein expression by FC > gene expression by qRT-PCR > cell viability by PI staining. The results could enrich the screening of drug-induced cardiotoxicity in vitro and propose disruption in MMP along with downregulation of α-MHC protein as a potential biomarker of predicting cardiotoxicity earlier during drug safety evaluation.

Transition of inner cell mass to embryonic stem cells: mechanisms, facts, and hypotheses

Embryonic stem cells (ESCs) are immortal stem cells that own multi-lineage differentiation potential. ESCs are commonly derived from the inner cell mass (ICM) of pre-implantation embryos. Due to their tremendous developmental capacity and unlimited self-renewal, ESCs have diverse biomedical applications. Different culture media have been developed to procure and maintain ESCs in a state of naïve pluripotency, and to preserve a stable genome and epigenome during serial passaging. Chromatin modifications such as DNA methylation and histone modifications along with microRNA activity and different signaling pathways dynamically contribute to the regulation of the ESC gene regulatory network (GRN). Such modifications undergo remarkable changes in different ESC media and determine the quality and developmental potential of ESCs. In this review, we discuss the current approaches for derivation and maintenance of ESCs, and examine how differences in culture media impact on the characteristics of pluripotency via modulation of GRN during the course of ICM outgrowth into ESCs. We also summarize the current hypotheses concerning the origin of ESCs and provide a perspective about the relationship of these cells to their in vivo counterparts (early embryonic cells around the time of implantation). Finally, we discuss generation of ESCs from human embryos and domesticated animals, and offer suggestions to further advance this fascinating field.

Acoustic Tweezing Cytometry Induces Rapid Initiation of Human Embryonic Stem Cell Differentiation

Mechanical forces play critical roles in influencing human embryonic stem cell (hESC) fate. However, it remains largely uncharacterized how local mechanical forces influence hESC behavior in vitro. Here, we used an ultrasound (US) technique, acoustic tweezing cytometry (ATC), to apply targeted cyclic subcellular forces to hESCs via integrin-bound microbubbles (MBs). We found that ATC-mediated cyclic forces applied for 30 min to hESCs near the edge of a colony induced immediate global responses throughout the colony, suggesting the importance of cell-cell connection in the mechanoresponsiveness of hESCs to ATC-applied forces. ATC application generated increased contractile force, enhanced calcium activity, as well as decreased expression of pluripotency transcription factors Oct4 and Nanog, leading to rapid initiation of hESC differentiation and characteristic epithelial-mesenchymal transition (EMT) events that depend on focal adhesion kinase (FAK) activation and cytoskeleton (CSK) tension. These results reveal a unique, rapid mechanoresponsiveness and community behavior of hESCs to integrin-targeted cyclic forces.

Probing flecainide block of INa using human pluripotent stem cell-derived ventricular cardiomyocytes adapted to automated patch-clamping and 2D monolayers

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) are emerging tools for applications such as drug discovery and screening for pro-arrhythmogenicity and cardiotoxicity as leading causes for drug attrition. Understanding the electrophysiology (EP) of hPSC-CMs is essential but conventional manual patch-clamping is highly laborious and low-throughput. Here we adapted hPSC-CMs derived from two human embryonic stem cell (hESC) lines, HES2 and H7, for a 16-channel automated planar-recording approach for single-cell EP characterization. Automated current- and voltage-clamping, with an overall success rate of 55.0 ± 11.3%, indicated that 90% of hPSC-CMs displayed ventricular-like action potential (AP) and the ventricular cardiomyocytes (VCMs) derived from the two hESC lines expressed similar levels of I_Na, I_CaL, I_kr and I_f and similarly lacked I_to and I_K1. These well-characterized hPSC-VCMs could also be readily adapted for automated assays of pro-arrhythmic drug screening. As an example, we showed that flecainide (FLE) induced I_Na blockade, leftward steady-state inactivation shift, slowed recovery from inactivation in our hPSC-VCMs. Since single-cell EP assay is insufficient to predict drug-induced reentrant arrhythmias, hPSC-VCMs were further reassembled into 2D human ventricular cardiac monolayers (hvCMLs) for multi-cellular electrophysiological assessments. Indeed, FLE significantly slowed the conduction velocity while causing AP prolongation. Our RNA-seq data suggested that cell-cell interaction enhanced the maturity of hPSC-VCMs. Taken collectively, a combinatorial approach using single-cell EP and hvCMLs is needed to comprehensively assess drug-induced arrhythmogenicity.

Suspended graphene oxide nanosheets maintain the self-renewal of mouse embryonic stem cells via down-regulating the expression of Vinculin

Graphene oxide (GO), with good hydrophilicity and biocompatibility, is widely explored as a carrier for various factors in the field of stem cell differentiation. However, its function of sustaining the stemness of mouse embryonic stem cells (mESCs) and the underlying mechanisms of this process remains undiscovered. Herein, we explored the biofunction of GO on mESCs and revealed the involved signaling pathways and key gene. The alkaline phosphatase activity detection, pluripotency genes quantification and the teratomas formation in vivo confirmed that GO nanosheets could sustain the self-renewal ability of mESCs instead of influencing its pluripotency. The underlying signaling pathways were uncovered by RNA-seq that integrin signaling pathway was involved in the biofunction of GO on mESCs and Vinculin turned to be a key gene for the effect of GO. Further experiments confirmed that the downregulation of Vinculin influenced the fate of mESCs through decreasing the expression of MEK1. Altogether, the study demonstrated for the first time that GOs hold the potential in sustaining the self-renewal of mESCs and clarified the mechanism of this function, which make it play a new role in stem cell research and regenerative medicine.

miR-302b-3p Promotes Self-Renewal Properties in Leukemia Inhibitory Factor-Withdrawn Embryonic Stem Cells

OBJECTIVES

Embryonic stem cells (ESCs) are regulated by a gene regulatory circuitry composed of transcription factors, signaling pathways, metabolic mediators, and non-coding RNAs (ncRNAs). MicroRNAs (miRNAs) are short ncRNAs which play crucial roles in ESCs. Here, we explored the impact of miR-302b-3p on ESC self-renewal in the absence of leukemia inhibitory factor (LIF).

MATERIALS AND METHODS

In this experimental study, ESCs were cultured in the presence of 15% fetal bovine serum (FBS) and induced to differentiate by LIF removal. miR-302b-3p overexpression was performed by transient transfection of mature miRNA mimics. Cell cycle profiling was done using propidium iodide (PI) staining followed by flow cytometry. miRNA expression was quantified using a miR-302b-3p-specific TaqMan assay. Data were analyzed using t test, and a P<0.05 was considered statistically significant.

RESULTS

We observed that miR-302b-3p promoted the viability of both wild-type and LIF-withdrawn ESCs. It also increased ESC clonogenicity and alkaline phosphatase (AP) activity. The defective cell cycling of LIF-deprived ESCs was completely rescued by miR-302b-3p delivery. Moreover, miR-302b-3p inhibited the increased cell death rate induced by LIF removal.

CONCLUSIONS

miR-302b-3p, as a pluripotency-associated miRNA, promotes diverse features of ESC self-renewal in the absence of extrinsic LIF signals.

Ascorbic acid-mediated enhanced cardiomyocyte differentiation of mouse ES-cells involves interplay of DNA methylation and multiple-signals

Embryonic stem cells (ES-cells) provide a good model system to study lineage-specific differentiation. Though, the differentiation of ES-cells to cardiomyocytes is documented, a clear understanding of the molecular mechanism of differentiation and improved functional-differentiation efficiency are yet to be achieved. In this regard, ascorbic acid (Aa) is shown to be one of the effective cardiac inducers in ES-cells. But, its mechanism is poorly understood. We therefore, investigated the mechanism of Aa-mediated cardiomyocyte differentiation of ES-cells. Here, we describe the potential involvement of epigenetic (DNA methylation) as well as integrin- and Erk- signaling systems during cardiomyocyte differentiation. Transgenic GS-2 ES-cells and wild-type D3 ES-cells were differentiated to cardiomyocytes, in the presence or absence of Aa and with or without inhibitors of Erk-, collagen- and integrin- pathways. At specific time points, differentiated states of ES-cells were scored by gene expression analyses and the proportion of functional cTnI⁺ cardiomyocytes. DNA methylation changes of Isl-1, BMP-2, GATA-4 and α-MHC in cardiogenic cells, following stimulation with Aa, were analyzed by using methylation specific PCR (MSP). We observed that Aa, when applied in initial phase of ES-cell differentiation, consistently enhanced cardiac differentiation (99%) over that observed during spontaneous differentiation (70%). This was associated with enhanced expressions of cardiogenesis-associated genes. A two-fold increase in cTnI⁺ cells was observed, with appropriate myofibril arrangement. The observed effect of Aa was due to enhanced collagen and integrin signaling, coupled with a high p-ERK1/2 expression, downstream. Besides, the involvement of DNA methylation in regulating the expression of cardiac genes i.e., Isl-1 and α-MHC was also observed. Overall, this study, for the first time, demonstrates that Aa-mediated cardiac enhancement is brought about, mechanistically, through the interplay of epigenetic changes in DNA methylation of cardiac genes (Isl-1 and α-MHC) and integrin signaling system.

Nano-on-micro fibrous extracellular matrices for scalable expansion of human ES/iPS cells

Human pluripotent stem cells (hPSCs) hold great potential for industrial and clinical applications. Clinical-grade scaffolds and high-quality hPSCs are required for cell expansion as well as easy handling and manipulation of the products. Current hPSC culture methods do not fulfill these requirements because of a lack of proper extracellular matrices (ECMs) and cell culture wares. We developed a layered nano-on-micro fibrous cellular matrix mimicking ECM, named "fiber-on-fiber (FF)" matrix, which enables easy handling and manipulation of cultured cells. While non-woven sheets of cellulose and polyglycolic acid were used as a microfiber layer facilitating mechanical stability, electrospun gelatin nanofibers were crosslinked on the microfiber layer, generating a mesh structure with connected nanofibers facilitating cell adhesion and growth. Our results showed that the FF matrix supports effective hPSC culture with maintenance of their pluripotency and normal chromosomes over two months, as well as effective scaled-up expansion, with fold increases of 54.1 ± 15.6 and 40.4 ± 8.4 in cell number per week for H1 human embryonic stem cells and 253G1 human induced pluripotent stem cells, respectively. This simple approach to mimick the ECM may have important implications after further optimization to generate lineage-specific products.

Efficient generation of hPSC-derived midbrain dopaminergic neurons in a fully defined, scalable, 3D biomaterial platform

Pluripotent stem cells (PSCs) have major potential as an unlimited source of functional cells for many biomedical applications; however, the development of cell manufacturing systems to enable this promise faces many challenges. For example, there have been major recent advances in the generation of midbrain dopaminergic (mDA) neurons from stem cells for Parkinson's Disease (PD) therapy; however, production of these cells typically involves undefined components and difficult to scale 2D culture formats. Here, we used a fully defined, 3D, thermoresponsive biomaterial platform to rapidly generate large numbers of action-potential firing mDA neurons after 25 days of differentiation (~40% tyrosine hydroxylase (TH) positive, maturing into 25% cells exhibiting mDA neuron-like spiking behavior). Importantly, mDA neurons generated in 3D exhibited a 30-fold increase in viability upon implantation into rat striatum compared to neurons generated on 2D, consistent with the elevated expression of survival markers FOXA2 and EN1 in 3D. A defined, scalable, and resource-efficient cell culture platform can thus rapidly generate high quality differentiated cells, both neurons and potentially other cell types, with strong potential to accelerate both basic and translational research.

Microvalve-based bioprinting – process, bio-inks and applications

DOD microvalve-based bioprinting system provides a highly advanced manufacturing platform that facilitates precise control over the cellular and biomaterial deposition in a highly reproducible and reliable manner. This article highlights promising directions to transform microvalve-based bioprinting into an enabling technology that will potentially drive significant advances in the field of TERM.

Human Induced Pluripotent Stem Cells as a Platform for Personalized and Precision Cardiovascular Medicine

Human induced pluripotent stem cells (hiPSCs) have revolutionized the field of human disease modeling, with an enormous potential to serve as paradigm shifting platforms for preclinical trials, personalized clinical diagnosis, and drug treatment. In this review, we describe how hiPSCs could transition cardiac healthcare away from simple disease diagnosis to prediction and prevention, bridging the gap between basic and clinical research to bring the best science to every patient.

Pluripotent stem cells: An in vitro model for nanotoxicity assessments

The advent of technology has led to an established range of engineered nanoparticles that are used in diverse applications, such as cell-cell interactions, cell-material interactions, medical therapies and the target modulation of cellular processes. The exponential increase in the utilization of nanomaterials and the growing number of associated criticisms has highlighted the potential risks of nanomaterials to human health and the ecosystem. The existing in vivo and in vitro platforms show limitations, with fluctuations being observed in the results of toxicity assessments. Pluripotent stem cells (PSCs) are viable source of cells that are capable of developing into specialized cells of the human body. PSCs can be efficiently used to screen new biomaterials/drugs and are potential candidates for studying impairments of biophysical morphology at both the cellular and tissue levels during interactions with nanomaterials and for diagnosing toxicity. Three-dimensional in vitro models obtained using PSC-derived cells would provide a realistic, patient-specific platform for toxicity assessments and in drug screening applications. The current review focuses on PSCs as an alternative in vitro platform for assessing the hazardous effects of nanomaterials on health systems and highlights the importance of PSC-derived in vitro platforms. Copyright © 2016 John Wiley & Sons, Ltd.

Coupling switch of P2Y-IP3 receptors mediates differential Ca(2+) signaling in human embryonic stem cells and derived cardiovascular progenitor cells

Purinergic signaling mediated by P2 receptors (P2Rs) plays important roles in embryonic and stem cell development. However, how it mediates Ca(2+) signals in human embryonic stem cells (hESCs) and derived cardiovascular progenitor cells (CVPCs) remains unclear. Here, we aimed to determine the role of P2Rs in mediating Ca(2+) mobilizations of these cells. hESCs were induced to differentiate into CVPCs by our recently established methods. Gene expression of P2Rs and inositol 1,4,5-trisphosphate receptors (IP3Rs) was analyzed by quantitative/RT-PCR. IP3R3 knockdown (KD) or IP3R2 knockout (KO) hESCs were established by shRNA- or TALEN-mediated gene manipulations, respectively. Confocal imaging revealed that Ca(2+) responses in CVPCs to ATP and UTP were more sensitive and stronger than those in hESCs. Consistently, the gene expression levels of most P2YRs except P2Y1 were increased in CVPCs. Suramin or PPADS blocked ATP-induced Ca(2+) transients in hESCs but only partially inhibited those in CVPCs. Moreover, the P2Y1 receptor-specific antagonist MRS2279 abolished most ATP-induced Ca(2+) signals in hESCs but not in CVPCs. P2Y1 receptor-specific agonist MRS2365 induced Ca(2+) transients only in hESCs but not in CVPCs. Furthermore, IP3R2KO but not IP3R3KD decreased the proportion of hESCs responding to MRS2365. In contrast, both IP3R2 and IP3R3 contributed to UTP-induced Ca(2+) responses while ATP-induced Ca(2+) responses were more dependent on IP3R2 in the CVPCs. In conclusion, a predominant role of P2Y1 receptors in hESCs and a transition of P2Y-IP3R coupling in derived CVPCs are responsible for the differential Ca(2+) mobilization between these cells.

Generation of Integration-Free Patient Specific iPS Cells Using Episomal Plasmids Under Feeder Free Conditions

Reprogramming somatic cells into a pluripotent state involves the overexpression of transcription factors leading to a series of changes that end in the formation of induced pluripotent stem cells (iPSCs). These iPSCs have a wide range of potential uses from drug testing and in vitro disease modelling to personalized cell therapies for patients. While viral methods for reprogramming factor delivery have been traditionally preferred due to their high efficiency, it is now possible to generate iPSCs using nonviral methods at similar efficiencies. We developed a robust reprogramming strategy that combines episomal plasmids and the use of commercially available animal free reagents that can be easily adapted for the GMP manufacture of clinical grade cells.

Cardiotoxicity screening: a review of rapid-throughput in vitro approaches

Cardiac toxicity represents one of the leading causes of drug failure along different stages of drug development. Multiple very successful pharmaceuticals had to be pulled from the market or labeled with strict usage warnings due to adverse cardiac effects. In order to protect clinical trial participants and patients, the International Conference on Harmonization published guidelines to recommend that all new drugs to be tested preclinically for hERG (Kv11.1) channel sensitivity before submitting for regulatory reviews. However, extensive studies have demonstrated that measurement of hERG activity has limitations due to the multiple molecular targets of drug compound through which it may mitigate or abolish a potential arrhythmia, and therefore, a model measuring multiple ion channel effects is likely to be more predictive. Several phenotypic rapid-throughput methods have been developed to predict the potential cardiac toxic compounds in the early stages of drug development using embryonic stem cells- or human induced pluripotent stem cell-derived cardiomyocytes. These rapid-throughput methods include microelectrode array-based field potential assay, impedance-based or Ca(2+) dynamics-based cardiomyocytes contractility assays. This review aims to discuss advantages and limitations of these phenotypic assays for cardiac toxicity assessment.

Neuronal developmental gene and miRNA signatures induced by histone deacetylase inhibitors in human embryonic stem cells

Human embryonic stem cells (hESCs) may be applied to develop human-relevant sensitive in vitro test systems for monitoring developmental toxicants. The aim of this study was to identify potential developmental toxicity mechanisms of the histone deacetylase inhibitors (HDAC) valproic acid (VPA), suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA) relevant to the in vivo condition using a hESC model in combination with specific differentiation protocols and genome-wide gene expression and microRNA profiling. Analysis of the gene expression data showed that VPA repressed neural tube and dorsal forebrain (OTX2, ISL1, EMX2 and SOX10)-related transcripts. In addition, VPA upregulates axonogenesis and ventral forebrain-associated genes, such as SLIT1, SEMA3A, DLX2/4 and GAD2. HDACi-induced expression of miR-378 and knockdown of miR-378 increases the expression of OTX2 and EMX2, which supports our hypothesis that HDACi targets forebrain markers through miR-378. In conclusion, multilineage differentiation in vitro test system is very sensitive for monitoring molecular activities relevant to in vivo neuronal developmental toxicity. Moreover, miR-378 seems to repress the expression of the OTX2 and EMX2 and therefore could be a regulator of the development of neural tube and dorsal forebrain neurons.

A new system for profiling drug-induced calcium signal perturbation in human embryonic stem cell-derived cardiomyocytes

The emergence of human stem cell–derived cardiomyocyte (hSCCM)–based assays in the cardiovascular (CV) drug discovery sphere requires the development of improved systems for interrogating the rich information that these cell models have the potential to yield. We developed a new analytical framework termed SALVO (synchronization, amplitude, length, and variability of oscillation) to profile the amplitude and temporal patterning of intra- and intercellular calcium signals in hSCCM. SALVO quantified drug-induced perturbations in the calcium signaling “fingerprint” in spontaneously contractile hSCCM. Multiparametric SALVO outputs were integrated into a single index of in vitro cytotoxicity that confirmed the rank order of perturbation as astemizole > thioridazine > cisapride > flecainide > valdecoxib > sotalol > nadolol ≈ control. This rank order of drug-induced Ca²⁺ signal disruption is in close agreement with the known arrhythmogenic liabilities of these compounds in humans. Validation of the system using a second set of compounds and hierarchical cluster analysis demonstrated the utility of SALVO to discriminate drugs based on their mechanisms of action. We discuss the utility of this new mechanistically agnostic system for the evaluation of in vitro drug cytotoxicity in hSCCM syncytia and the potential placement of SALVO in the early stage drug screening framework.

Databases and collaboration require standards for human stem cell research

Stem cell research is at an important juncture: despite significant potential for human health and several countries with key initiatives to expedite commercialization, there are gaps in capturing and exploiting the results of past and current research. Here, we propose a concerted plan that could be taken to foster a more collaborative approach and ensure that all research efforts can be leveraged across the community. The creation of a definitive centralized database repository, or at least harmonized data repositories, for stem cell groups in academia and industry, enabling secure selective sharing of data when needed, could provide the core structure that is sought globally and protect intellectual property. The development of minimum information about stem cell experiments (MIASCE) could be key to this development.

Skeletal muscle tissue engineering: methods to form skeletal myotubes and their applications

Skeletal muscle tissue engineering (SMTE) aims to repair or regenerate defective skeletal muscle tissue lost by traumatic injury, tumor ablation, or muscular disease. However, two decades after the introduction of SMTE, the engineering of functional skeletal muscle in the laboratory still remains a great challenge, and numerous techniques for growing functional muscle tissues are constantly being developed. This article reviews the recent findings regarding the methodology and various technical aspects of SMTE, including cell alignment and differentiation. We describe the structure and organization of muscle and discuss the methods for myoblast alignment cultured in vitro. To better understand muscle formation and to enhance the engineering of skeletal muscle, we also address the molecular basics of myogenesis and discuss different methods to induce myoblast differentiation into myotubes. We then provide an overview of different coculture systems involving skeletal muscle cells, and highlight major applications of engineered skeletal muscle tissues. Finally, potential challenges and future research directions for SMTE are outlined.

Phenotypic assays for β-amyloid in mouse embryonic stem cell-derived neurons

Given the complex nature of Alzheimer's disease (AD), a cell-based model that recapitulates the physiological properties of the target neuronal population would be extremely valuable for discovering improved drug candidates and chemical probes to uncover disease mechanisms. We established phenotypic neuronal assays for the biogenesis and synaptic action of amyloid β peptide (Aβ) based on embryonic stem cell-derived neurons (ESNs). ESNs enriched with pyramidal neurons were robust, scalable, and amenable to a small-molecule screening assay, overcoming the apparent limitations of neuronal models derived from human pluripotent cells. Small-molecule screening of clinical compounds identified four compounds capable of reducing Aβ levels in ESNs derived from the Tg2576 mouse model of AD. Our approach is therefore highly suitable for phenotypic screening in AD drug discovery and has the potential to identify therapeutic candidates with improved efficacy and safety potential.

Development of a dynamic stem cell culture platform for mesenchymal stem cell adhesion and evaluation

The importance of providing a physiologically relevant environment for cell culture is well recognized. The combination of proper environmental cues which are provided in vivo by the bloodstream and extracellular matrix must be reproduced to properly examine cell response in vitro, and cannot be recapitulated using traditional culture on polystyrene. Here, we have developed a device, the dynamic stem cell culture platform (DSCCP), consisting of a biomimetic scaffold cultured within the dynamic environment of a perfusion bioreactor. By varying scaffold parameters including stiffness and protein inclusion at the material surface, we found that human mesenchymal stem cells (hMSCs) were able to adhere to modified substrates, while still maintaining multipotency. Culture in a perfusion bioreactor showed cell survival and proliferation, particularly on modified substrates. The DSCCP represents a complete platform for cell adhesion and subsequent evaluation, including the response of a cell population to drug treatment.

Full factorial screening of human embryonic stem cell maintenance with multiplexed microbioreactor arrays

Use of human pluripotent stem cells (hPSCs) in regenerative medicine applications relies on control of cell fate decisions by exogenous factors. This control can be hindered by the use of undefined culture components, poorly understood autocrine/paracrine effects, spatiotemporal variations in microenvironmental composition inherent to static culture formats, and signal cross-talk between multiple factors. We recently described microbioreactor arrays that provide a full factorial spectrum of exogenous factors, and allow gradual accumulation of paracrine factors through serial culture chambers. We combined these with defined biochemical conditions, and in situ reporter gene- and immunofluorescence-based readouts to create an hPSC screening platform with enhanced data throughput and microenvironmental control. HES3-EOS-C(3+)-EiP reporter hESCs were screened against FGF-2, TGF-β1, and retinoic acid in a modified mTeSR-1 medium background. Differential pluripotency marker expression reflected mTeSR-1's maintenance capacity, and differentiation in response to removal of maintenance factors or addition of retinoic acid. Interestingly, pluripotency marker expression was downregulated progressively through serial chambers. Since downstream chambers are exposed to greater levels of paracrine factors under continuous flow, this effect is thought to result from secreted factors that negatively influence pluripotency. The microbioreactor array platform decodes factor interplay, and has a broad application in deciphering microenvironmental control of cell fate.

Derivation of Human Embryonic Stem Cell Lines from Vitrified Human Blastocysts

Human embryonic stem cells are pluripotent cells typically derived from blastulating embryos that have become excess to clinical needs in assisted reproduction programs. They provide cellular models for embryonic development and disease, and are thought to be useful for future cell replacement therapies and regenerative medicine. Here we describe methods to derive human embryonic stem cell lines. This includes blastocyst cryopreservation using a highly efficient vitrification protocol, the production and use of fibroblast feeder cells, embryo plating and passaging of resulting cellular outgrowths, and cryopreservation of putative stem cells lines.

New iPSC for old long QT syndrome modeling: putting the evidence into perspective

Induced pluripotent stem cells (iPS cells or iPSCs) are typically derived by transfection of certain stem cell-associated genes into non-pluripotent cells, such as adult fibroblasts (typically adult somatic cells). Various diseases can be modeled through iPSC technology. The important implication of iPSCs to offer an unprecedented opportunity to recapitulate pathologic human tissue formation in vitro has generated great excitement and interest in the whole biomedical research community. Long QT syndrome (LQTS), an inherited heart disease, is characterized by prolonged QT interval on a surface electrocardiogram. LQTS presents with life-threatening cardiac arrhythmias, which can lead to fainting, syncope, and sudden death. The iPSC-derived cardiomyocytes from LQTS patients offer a potentially unlimited source of materials for biomedical study. They can be used to recapitulate complex physiological phenotypes, probe toxicological testing and drug screening, clarify the novel mechanistic insights and may also rectify gene defects at the cellular and molecular level. Despite the emerging challenges, iPSC technology has been increasingly recognized as a valuable and growing toolkit for modeling LQTS over other various models of human diseases.

Targeting human embryonic stem cells with quantum dot-conjugated phages

Targeting embryonic stem cells (ESCs) is important for ESC labeling, drug delivery and cell fate control. In this study, we identified twenty-two phage clones that bind specifically to the hESC cell line X-01, which was derived from human blastocysts of Chinese origin. One phage (H178), which displays the sequence VGGEAWSSPTDL, showed higher binding affinity to hESCs than to a monkey ES cell line (RS366.4) and two mouse ES cell lines (R1 and E14). Using quantum dots (QDs) conjugated to the H178 phage, we demonstrate that the phage can specifically bind to hESCs in vitro. Our results suggest a possible interaction between the selected peptide and the stem cell extracellular matrix (ECM). The selection method described here allows rapid and efficient screening of unique phage clones and targeting cells. The phages displaying peptides identified by this study have potential applications for cargo delivery and receptor studies.

Pluripotent stem cell-derived dopaminergic neurons as models of neurodegeneration

Researchers utilize a number of models of Parkinson’s disease ranging in complexity from immortalized cell lines to nonhuman primates. These models are used to investigate everything from the mechanisms underlying neurodegeneration, to drugs that may improve patient outcomes. Each model system has advantages and disadvantages, depending on their application. In this review, the authors assess the potential value of embryonic stem and induced-pluripotent stem cells as additions to the crowded Parkinson’s disease in vitro model landscape.

Automated selection and harvesting of pluripotent stem cell colonies

The ability of pluripotent stem cells to differentiate into specialized cells of all three germ layers, their capability to self-renew, and their amenability to genetic modification provide fascinating prospects for the generation of cell lines for biomedical applications. Therefore, stem cells must increasingly suffice in terms of industrial standards, and automation of critical or time-consuming steps becomes a fundamental prerequisite for their routine application. Cumbersome manual picking of individual stem cell colonies still represents the most frequently used method for passaging or derivation of clonal stem cell lines. Here, we explore an automated harvesting system (CellCelector™) for detection, isolation, and propagation of human embryonic stem cells (hESCs) and murine induced pluripotent stem cells (iPSCs). Automatically transferred hESC colonies maintained their specific biological characteristics even after repeated passaging. We also selected and harvested primary iPSCs derived from mouse embryonic fibroblasts expressing the green fluorescent protein (GFP) under the control of the Oct4 promotor using either morphological criteria or GFP fluorescence. About 80% of the selected and harvested primary iPSC colonies gave rise to homogenously GFP-expressing iPSC lines. To validate the iPSC lines, we analyzed the expression of pluripotency-associated markers and multi-germ layer differentiation potential in vitro. Our data indicate that the CellCelector™ technology enables efficient identification and isolation of pluripotent stem cell colonies at the phase contrast or fluorescence level.

Functional screening assays with neurons generated from pluripotent stem cell-derived neural stem cells

Rapid and effective drug discovery for neurodegenerative disease is currently impeded by an inability to source primary neural cells for high-throughput and phenotypic screens. This limitation can be addressed through the use of pluripotent stem cells (PSCs), which can be derived from patient-specific samples and differentiated to neural cells for use in identifying novel compounds for the treatment of neurodegenerative diseases. We have developed an efficient protocol to culture pure populations of neurons, as confirmed by gene expression analysis, in the 96-well format necessary for screens. These differentiated neurons were subjected to viability assays to illustrate their potential in future high-throughput screens. We have also shown that organelles such as nuclei and mitochondria could be live-labeled and visualized through fluorescence, suggesting that we should be able to monitor subcellular phenotypic changes. Neurons derived from a green fluorescent protein-expressing reporter line of PSCs were live-imaged to assess markers of neuronal maturation such as neurite length and co-cultured with astrocytes to demonstrate further maturation. These studies confirm that PSC-derived neurons can be used effectively in viability and functional assays and pave the way for high-throughput screens on neurons derived from patients with neurodegenerative disorders.