Dopaminergic differentiation of human embryonic stem cells

Electrochemical Detection of Dopamine Release from Living Neurons Using Graphene Oxide-Incorporated Polypyrrole/Gold Nanocluster Hybrid Nanopattern Arrays

Stem-cell-based therapeutics have shown immense potential in treating various diseases that are currently incurable. In particular, partial recovery of Parkinson's disease, which occurs due to massive loss or abnormal functionality of dopaminergic (DAnergic) neurons, through the engraftment of stem-cell-derived neurons ex vivo is reported. However, precise assessment of the functionality and maturity of DAnergic neurons is still challenging for their enhanced clinical efficacy. Here, a novel conductive cell cultivation platform, a graphene oxide (GO)-incorporated metallic polymer nanopillar array (GOMPON), that can electrochemically detect dopamine (DA) exocytosis from living DAnergic neurons, is reported. In the cell-free configuration, the linear range is 0.5-100 µm, with a limit of detection of 33.4 nm. Owing to its excellent biocompatibility, a model DAnergic neuron (SH-SY5Y cell) can be cultivated and differentiated on the platform while their DA release can be quantitatively measured in a real-time and nondestructive manner. Finally, it is showed that the functionality of the DAnergic neurons derived from stem cells can be precisely assessed via electrochemical detection of their DA exocytosis. The developed GOMPON is highly promising for a wide range of applications, including real-time monitoring of stem cell differentiation into neuronal lineages, evaluating differentiation protocols, and finding practical stem cell therapies.

Crater-like nanoelectrode arrays for electrochemical detection of dopamine release from neuronal cells

Stem cell therapy has shown great potential in treating various incurable diseases using conventional chemotherapy. Parkinson's disease (PD)-a neurodegenerative disease-has been reported to be caused by quantitative loss or abnormal functionality of dopaminergic neurons (DAnergic neurons). To date, stem cell therapies have shown some potential in treating PD throughex vivoengraftment of stem-cell-derived neurons. However, accurately identifying the differentiation and non-invasively evaluating the functionality and maturity of DAnergic neurons are formidable challenges in stem cell therapies. These strategies are important in enhancing the efficacy of stem cell therapies. In this study, we report a novel cell cultivation platform, that is, a nanocrater-like electrochemical nanoelectrode array (NCENA) for monitoring dopamine (DA) release from neurons to detect exocytotic DA release from DAnergic neurons. In particular, the developed NCENA has a nanostructure in which three-dimensional porous gold nanopillars are uniformly arranged on conductive electrodes. The developed NCENA exhibited great DA sensing capabilities with a linear range of 0.39-150μM and a limit of detection of 1.16μM. Furthermore, the nanotopographical cues provided by the NCENA are suitable for cell cultivation with enhanced cellular adhesion. Finally, we successfully analysed the functionality and maturity of differentiated neurons on the NCENA through its excellent sensing ability for exocytotic DA.

Potential of the Coordinated Actions of Multiple Protein-Based Micromachines for Medical Applications

Untethered mobile micromachines hold great promise in the development of effective and minimally invasive therapies. Although diverse medical micromachines for specific applications have been developed over the past few decades, the coordinated action of multiple machines with different functions remains largely unexplored. In this study, we created three types of biocompatible micromachines using proteins and demonstrated the potential of their coordinated action for medical applications. As a proof of concept, we demonstrated neural replacement therapy, in which neuroblastomas were killed by using an anticancer prodrug and the first machine that contains enzymes, enabling the conversion of the prodrug into a cytotoxic drug. Subsequently, a second machine composed of extracellular matrix was placed on the dead cancer cells to provide a suitable environment for cell adhesion, on which embryonic stem (ES) cells and stromal cells that promote neural differentiation of stem cells were attached by using third machines capable of delivering cells to target positions with desired patterns. As a result, neuroblastomas were replaced with novel healthy neurons derived from ES cells by teaming multiple protein-based machines. We believe that this work highlights the potential of heterogeneous machine groups for medical treatment and the utility of highly biocompatible and functional micromachines made from proteins, representing an important step forward in building more sophisticated micromachine-based therapies.

Biomaterial Strategies for Restorative Therapies in Parkinson's Disease

Parkinson's disease (PD) is a progressive neurological disorder, in which dopaminergic midbrain neurons degenerate, leading to dopamine depletion that is associated with neuronal death. In this Review, we initially describe the pathogenesis of PD and established therapies that unfortunately only delay progression of the disease. With a rapidly escalating incidence in PD, there is an urgent need to develop new therapies that not only halt progression but even reverse degeneration. Biomaterials are playing critical roles in these new therapies which include controlled and site-specific delivery of neurotrophins, increased engraftment of implanted neural stem cells, and redirection of endogenous stem cell populations away from their niche to encourage reparative mechanisms. This Review will therefore cover important design features of biomaterials used in regenerative medicine and tissue engineering strategies targeted at PD.

Development and evaluation of hyaluronan nanocomposite conduits for neural tissue regeneration

Hyaluronan-based hydrogels are among the most promising neural tissue engineering materials because of their biocompatibility and the immunomodulation capabilities of their degradation byproducts. Despite these features, the problems related to their handling and mechanical properties have not yet been solved. In the present work it is proposed to address these drawbacks through the development of nanohybrid materials in which different nanometric phases (carbon nanotubes, mesoporous silica nanoparticles) are embedded in a crosslinked hyaluronan matrix. These nanohybrid matrices were next processed in the shape of cylindrical conduits aimed at promoting and improving neural stem cell differentiation and regeneration in neural tracts. These constructs could be of use specifically for peripheral nerve regeneration. Results of the study show that the inclusion of the different phases improved physico-chemical features of the gel such as its relative electrical permittivity, water intake and elastic modulus, giving hints on how the nanometric phase interacts with hyaluronan in the composite as well as for their potential in combined therapeutic approaches. Regarding the in vitro biological behavior of the hybrid tubular scaffolds, an improved early cell adhesion and survival of Schwann cells in their lumen was found, as compared to conduits made of pure hyaluronan gels. Furthermore, the differentiation and survival of neural precursors was not compromised, despite alleged safety concerns.

Functional Pathway Identification With CRISPR/Cas9 Genome-wide Gene Disruption in Human Dopaminergic Neuronal Cells Following Chronic Treatment With Dieldrin

Organochlorine pesticides, once widely used, are extremely persistent and bio-accumulative in the environment. Epidemiological studies have implicated that environmental exposure to organochlorine pesticides including dieldrin is a risk factor for the development of Parkinson's disease. However, the pertinent mechanisms of action remain poorly understood. In this study, we carried out a genome-wide (Brunello library, 19 114 genes, 76 411 sgRNAs) CRISPR/Cas9 screen in human dopaminergic SH-SY5Y neuronal cells exposed to a chronic treatment (30 days) with dieldrin to identify cellular pathways that are functionally related to the chronic cellular toxicity. Our results indicate that dieldrin toxicity was enhanced by gene disruption of specific components of the ubiquitin proteasome system as well as, surprisingly, the protein degradation pathways previously implicated in inherited forms of Parkinson's disease, centered on Parkin. In addition, disruption of regulatory components of the mTOR pathway which integrates cellular responses to both intra- and extracellular signals and is a central regulator for cell metabolism, growth, proliferation, and survival, led to increased sensitivity to dieldrin-induced cellular toxicity. This study is one of the first to apply a genome-wide CRISPR/Cas9-based functional gene disruption screening approach in an adherent neuronal cell line to globally decipher cellular mechanisms that contribute to environmental toxicant-induced neurotoxicity and provides novel insight into the dopaminergic neurotoxicity associated with chronic exposure to dieldrin.

On the Road from Phenotypic Plasticity to Stem Cell Therapy

In 1981, I published a paper in the first issue of The Journal of Neuroscience with my postdoctoral mentor, Richard Bunge. At that time, the long-standing belief that each neuron expressed only one neurotransmitter, known as Dale's Principle (Dale, 1935), was being hotly debated following a report by French embryologist Nicole Le Douarin showing that neural crest cells destined for one transmitter phenotype could express characteristics of another if transplanted to alternate sites in the developing embryo (Le Douarin, 1980). In the Bunge laboratory, we were able to more directly test the question of phenotypic plasticity in the controlled environment of the tissue culture dish. Thus, in our paper, we grew autonomic catecholaminergic neurons in culture under conditions which promoted the acquisition of cholinergic traits and showed that cells did not abandon their inherited phenotype to adopt a new one but instead were capable of dual transmitter expression. In this Progressions article, I detail the path that led to these findings and how this study impacted the direction I followed for the next 40 years. This is my journey from phenotypic plasticity to the promise of a stem cell therapy.

SOX1 Is a Backup Gene for Brain Neurons and Glioma Stem Cell Protection and Proliferation

Failed neuroprotection leads to the initiation of several diseases. SOX1 plays many roles in embryogenesis, oncogenesis, and male sex determination, and can promote glioma stem cell proliferation, invasion, and migration due to its high expression in glioblastoma cells. The functional versatility of the SOX1 gene in malignancy, epilepsy, and Parkinson's disease, as well as its adverse effects on dopaminergic neurons, makes it an interesting research focus. Hence, we collate the most important discoveries relating to the neuroprotective effects of SOX1 in brain cancer and propose hypothesis worthy of SOX1's role in the survival of senescent neuronal cells, its roles in fibroblast cell proliferation, and cell fat for neuroprotection, and the discharge of electrical impulses for homeostasis. Increase in electrical impulses transmitted by senescent cells affects the synthesis of neurotransmitters, which will modify the brain cell metabolism and microenvironment.

In Situ Detection of Neurotransmitters from Stem Cell-Derived Neural Interface at the Single-Cell Level via Graphene-Hybrid SERS Nanobiosensing

In situ quantitative measurements of neurotransmitter activities can provide useful insights into the underlying mechanisms of stem cell differentiation, the formation of neuronal networks, and neurodegenerative diseases. Currently, neurotransmitter detection methods suffer from poor spatial resolution, nonspecific detection, and a lack of in situ analysis. To address this challenge, herein, we first developed a graphene oxide (GO)-hybrid nanosurface-enhanced Raman scattering (SERS) array to detect dopamine (DA) in a selective and sensitive manner. Using the GO-hybrid nano-SERS array, we successfully measured a wide range of DA concentrations (10^-4 to 10^-9 M) rapidly and reliably. Moreover, the measurement of DA from differentiating neural stem cells applies to the characterization of neuronal differentiation. Given the challenges of in situ detection of neurotransmitters at the single-cell level, our developed SERS-based detection method can represent a unique tool for investigating single-cell signaling pathways associated with DA, or other neurotransmitters, and their roles in neurological processes.

Ddx56 maintains proliferation of mouse embryonic stem cells via ribosome assembly and interaction with the Oct4/Sox2 complex

Background

Embryonic stem cells (ESCs) are important source of clinical stem cells for therapy, so dissecting the functional gene regulatory network involved in their self-renewal and proliferation is an urgent task. We previously reported that Ddx56 interacts with the core transcriptional factor Oct4 by mass spectrometry analysis in ESCs. However, the exact function of Ddx56 in ESCs remains unclear.

Methods

We investigated the role of Ddx56 in mouse ESCs (mESCs) through both gain- and loss-of-function strategies. The effect of Ddx56 on mESCs was determined based on morphological changes, involvement in the network of pluripotency markers (Nanog, Oct4, Sox2), and altered lineage marker expression. In addition, the role of Ddx56 in mESCs was evaluated by polysome fractionation, qRT-PCR, and co-immunoprecipitation (co-IP). Finally, RNA sequencing was applied to explore potential network regulation by Ddx56 in mESCs.

Result

We found that Ddx56 participated in ribosome assembly, as knockout or RNAi knockdown of Ddx56 led to ribosome dysfunction and cell lethality. Surprisingly, exogenous expression of C-terminal domain truncated Ddx56 (Ddx56 ΔC-ter) did not affect ribosome assembly, but decreased mESC proliferation by downregulation of proliferation-related genes and cell cycle changing. In terms of mechanism, Ddx56 interacted with the Oct4 and Sox2 complex by binding to Sox2, whereas Ddx56 ΔC-ter showed weaker interaction with Sox2 and led to retardation of mESC proliferation.

Conclusions

Ddx56 maintains ESC proliferation by conventional regulation of ribosome assembly and interaction with the Oct4 and Sox2 complex.

Development and Differentiation of Midbrain Dopaminergic Neuron: From Bench to Bedside

Parkinson’s Disease (PD) is a neurodegenerative disorder affecting the motor system. It is primarily due to substantial loss of midbrain dopamine (mDA) neurons in the substantia nigra pars compacta and to decreased innervation to the striatum. Although existing drug therapy available can relieve the symptoms in early-stage PD patients, it cannot reverse the pathogenic progression of PD. Thus, regenerating functional mDA neurons in PD patients may be a cure to the disease. The proof-of-principle clinical trials showed that human fetal graft-derived mDA neurons could restore the release of dopamine neurotransmitters, could reinnervate the striatum, and could alleviate clinical symptoms in PD patients. The invention of human-induced pluripotent stem cells (hiPSCs), autologous source of neural progenitors with less ethical consideration, and risk of graft rejection can now be generated in vitro. This advancement also prompts extensive research to decipher important developmental signaling in differentiation, which is key to successful in vitro production of functional mDA neurons and the enabler of mass manufacturing of the cells required for clinical applications. In this review, we summarize the biology and signaling involved in the development of mDA neurons and the current progress and methodology in driving efficient mDA neuron differentiation from pluripotent stem cells.

Placenta mesenchymal stem cells differentiation toward neuronal-like cells on nanofibrous scaffold

Introduction: Transplantation of stem cells with a nanofibrous scaffold is a promising approach for spinal cord injury therapy. The aim of this work was to differentiate neural-like cells from placenta-derived mesenchymal stem cells (PDMSCs) using suitable induction reagents in three (3D) and two dimensional (2D) culture systems. Methods: After isolation and characterization of PDMSCs, the cells were cultivated on poly-L-lactide acid (PLLA)/poly caprolactone (PCL) nanofibrous scaffold and treated with a neuronal medium for 7 days. Electron microscopy, qPCR, and immunostaining were used to examine the differentiation of PDMSCs (on scaffold and tissue culture polystyrene [TCPS]) and the expression rate of neuronal markers (beta-tubulin, nestin, GFAP, and MAP-2). Results: qPCR analysis showed that beta-tubulin (1.672 fold; P ≤ 0.0001), nestin (11.145 fold; P ≤ 0.0001), and GFAP (80.171; P ≤ 0.0001) gene expressions were higher on scaffolds compared with TCPS. Immunofluorescence analysis showed that nestin and beta-tubulin proteins were recognized in the PDMSCs differentiated on TCPS and scaffold after 7 days in the neuroinductive differentiation medium. Conclusion: Taken together, these results delegated that PDMSCs differentiated on PLLA/PCL scaffolds are more likely to differentiate towards diversity lineages of neural cells. It proposed that PDMSCs have cell subpopulations that have the capability to be differentiated into neurogenic cells.

Patient-specific pluripotent stem cell-based Parkinson's disease models showing endogenous alpha-synuclein aggregation

After the first research declaring the generation of human induced pluripotent stem cells (hiPSCs) in 2007, several attempts have been made to model neurodegenerative disease in vitro during the past decade. Parkinson’s disease (PD) is the second most common neurodegenerative disorder, which is mainly characterized by motor dysfunction. The formation of unique and filamentous inclusion bodies called Lewy bodies (LBs) is the hallmark of both PD and dementia with LBs. The key pathology in PD is generally considered to be the alpha-synuclein (α-syn) accumulation, although it is still controversial whether this protein aggregation is a cause or consequence of neurodegeneration. In the present work, the recently published researches which recapitulated the α-syn aggregation phenomena in sporadic and familial PD hiPSC models were reviewed. Furthermore, the advantages and potentials of using patient-derived PD hiPSC with focus on α-syn aggregation have been discussed.

Stem Cell Therapy for Parkinson's Disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases caused by specific degeneration and loss of dopamine neurons in substantia nigra of the midbrain. PD is clinically characterized by motor dysfunctions and non-motor symptoms. Even though the dopamine replacement can improve the motor symptoms of PD, it cannot stop the neural degeneration and disease progression. Electrical deep brain stimulation (DBS) to the specific brain areas can improve the symptoms, but it eventually loses the effectiveness. Stem cell transplantation provides an exciting potential for the treatment of PD. Current available cell sources include neural stem cells (NSCs) from fetal brain tissues, human embryonic stem cells (hESCs) isolated from blastocyst, and induced pluripotent stem cells (iPSCs) reprogrammed from the somatic cells such as the fibroblasts and blood cells. Here, we summarize the research advance in experimental and clinical studies to transplant these cells into animal models and clinical patients, and specifically highlight the studies to use hESCs /iPSCs-derived dopaminergic precursor cells and dopamine neurons for the treatment of PD, at last propose future challenges for developing clinical-grade dopaminergic cells for treating the PD.

Enhanced survival of human-induced pluripotent stem cell transplant in parkinsonian rat brain by locally applied cyclosporine

A major limitation with cell transplantation in patients is the unimpressive number of cells survived. The death of grafted cells involves apoptosis and immunorejection. In this review, we encapsulate the recent preclinical development that improves the survival of grafted cells and mitigates the immunorejection of human-induced pluripotent stem cells (iPSCs) through co-grating nanoparticles-containing cyclosporine A (NanoCsA) in hemiparkinsonian rats. The study supported the notion that NanoCsA allows for long-lasting CsA discharge and limits immunorejection of human iPSC xenograft in a 6-hydroxydopamine Parkinson's disease rat model.

NanoCsA improves the survival of human iPSC transplant in hemiparkinsonian rats

Increasing evidence has supported that transplantation of human stem cells induces neuroprotective and reparative effects in animal models of Parkinson's disease (PD). However, without systemic immunosuppressive therapy, most of these grafted cells are rejected by the hosts. Long term and systemic injection of cyclosporine-A (CsA) is required to maintain the survival of grafted cells. The purpose this study is to examine a new treatment strategy to suppress the immunorejection by locally co-grafting of polylactic/glycolic acid nanoparticles containing CsA (NanoCsA) with differentiated human induced pluripotent stem cells (iPSCs). In the in vitro media, NanoCsA provided sustained release of CsA for >6 weeks. The differentiated human iPSCs were co-grafted with NanoCsA or NanoVeh (nanoparticle without CsA) to the striatum of unilaterally 6-hydroxydopamine -lesioned rats. NanoCsA/iPSCs co-graft significantly improved locomotor activity compared to NanoVeh/iPSCs co-grafts or iPSC grafts + sytemic CsA at 1 month after transplantation. Brain tissues were collected for measurements of tyrosine hydroxylase (TH) and human marker Stem121 immunoreactivity. Cografting with NanoCsA/iPSCs, compared to NanoVeh/iPSCs, significantly increased TH and Stem121 immunoreactivity as well as tumor formation in the lesioned striatum. Taken together, our study supports that NanoCsA provides long-lasting CsA release and reduces immunorejection of human iPSCs xenograft in a 6-hydroxydopamine rat model of PD.

Differentiation of Neural Stem Cells Derived from Induced Pluripotent Stem Cells into Dopaminergic Neurons

Dopaminergic (DA) neurons are involved in many critical functions within the central nervous system (CNS), and dopamine neurotransmission impairment underlies a wide range of disorders from motor control deficiencies, such as Parkinson's disease (PD), to psychiatric disorders, such as alcoholism, drug addictions, bipolar disorders, schizophrenia and depression. Neural stem cell-based technology has potential to play an important role in developing efficacious biological and small molecule therapeutic products for disorders with dopamine dysregulation. Various methods of differentiating DA neurons from pluripotent stem cells have been reported. In this chapter, we describe a simple technique using dopamine-inducing factors (DIFs) to differentiate neural stem cells (NSCs), isolated from induced pluripotent stem cells (iPSCs) into DA neurons.

Cell reprogramming approaches in gene- and cell-based therapies for Parkinson's disease

Degeneration of dopamine (DA) neurons in the substantia nigra pars compacta is the pathological hallmark of Parkinson's disease (PD). In PD multiple pathogenic mechanisms initiate and drive this neurodegenerative process, making the development of effective treatments challenging. To date, PD patients are primarily treated with dopaminergic drugs able to temporarily enhance DA levels, therefore relieving motor symptoms. However, the drawbacks of these therapies including the inability to alter disease progression are constantly supporting the search for alternative treatment approaches. Over the past years efforts have been put into the development of new therapeutic strategies based on the delivery of therapeutic genes using viral vectors or transplantation of DA neurons for cell-based DA replacement. Here, past achievements and recent advances in gene- and cell-based therapies for PD are outlined. We discuss how current gene and cell therapy strategies hold great promise for the treatment of PD and how the use of stem cells and recent developments in cellular reprogramming could contribute to open a new avenue in PD therapy.

Laterally confined growth of cells induces nuclear reprogramming in the absence of exogenous biochemical factors

In this study, we demonstrate a platform for reprogramming somatic cells with high efficiency in the absence of exogenous reprogramming factors. Sustained laterally confined growth of cells on micropatterned substrates results in sequential changes to the nucleus and chromatin with each cell division, leading to the progressive erasure of lineage specific characteristics and incorporation of pluripotency. After 10 days of confined growth, the cells exhibit stemness and have multilineage differentiation potential. Our observation highlights a previously unknown role of mechanical constraints in nuclear reprogramming. Our method provides a unique approach to greatly improve stem cell technologies for developing patient specific disease models and regenerative medicine.

Cells in tissues undergo transdifferentiation programs when stimulated by specific mechanical and biochemical signals. While seminal studies have demonstrated that exogenous biochemical factors can reprogram somatic cells into pluripotent stem cells, the critical roles played by mechanical signals in such reprogramming process have not been well documented. In this paper, we show that laterally confined growth of fibroblasts on micropatterned substrates induces nuclear reprogramming with high efficiency in the absence of any exogenous reprogramming factors. We provide compelling evidence on the induction of stem cell-like properties using alkaline phosphatase assays and expression of pluripotent markers. Early onset of reprogramming was accompanied with enhanced nuclear dynamics and changes in chromosome intermingling degrees, potentially facilitating rewiring of the genome. Time-lapse analysis of promoter occupancy by immunoprecipitation of H3K9Ac chromatin fragments revealed that epithelial, proliferative, and reprogramming gene promoters were progressively acetylated, while mesenchymal promoters were deacetylated by 10 days. Consistently, RNA sequencing analysis showed a systematic progression from mesenchymal to stem cell transcriptome, highlighting pathways involving mechanisms underlying nuclear reprogramming. We then demonstrated that these mechanically reprogrammed cells could be maintained as stem cells and can be redifferentiated into multiple lineages with high efficiency. Importantly, we also demonstrate the induction of cancer stemness properties in MCF7 cells grown in such laterally confined conditions. Collectively, our results highlight an important generic property of somatic cells that, when grown in laterally confined conditions, acquire stemness. Such mechanical reprogramming of somatic cells demonstrated here has important implications in tissue regeneration and disease models.

Pluripotent stem cell-based therapy for Parkinson's disease: Current status and future prospects

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, which affects about 0.3% of the general population. As the population in the developed world ages, this creates an escalating burden on society both in economic terms and in quality of life for these patients and for the families that support them. Although currently available pharmacological or surgical treatments may significantly improve the quality of life of many patients with PD, these are symptomatic treatments that do not slow or stop the progressive course of the disease. Because motor impairments in PD largely result from loss of midbrain dopamine neurons in the substantia nigra pars compacta, PD has long been considered to be one of the most promising target diseases for cell-based therapy. Indeed, numerous clinical and preclinical studies using fetal cell transplantation have provided proof of concept that cell replacement therapy may be a viable therapeutic approach for PD. However, the use of human fetal cells as a standardized therapeutic regimen has been fraught with fundamental ethical, practical, and clinical issues, prompting scientists to explore alternative cell sources. Based on groundbreaking establishments of human embryonic stem cells and induced pluripotent stem cells, these human pluripotent stem cells have been the subject of extensive research, leading to tremendous advancement in our understanding of these novel classes of stem cells and promising great potential for regenerative medicine. In this review, we discuss the prospects and challenges of human pluripotent stem cell-based cell therapy for PD.

Understanding Parkinson's Disease through the Use of Cell Reprogramming

Recent progress in the field of somatic cell reprogramming offers exciting new possibilities for the study and treatment of Parkinson's disease (PD). Reprogramming technology offers the ability to untangle the diverse contributing risk factors for PD, such as ageing, genetics and environmental toxins. In order to gain novel insights into such a complex disease, cell-based models of PD should represent, as closely as possible, aged human dopaminergic neurons of the substantia nigra. However, the generation of high yields of functionally mature, authentic ventral midbrain dopamine (vmDA) neurons has not been easy to achieve. Furthermore, ensuring cells represent aged rather than embryonic neurons has presented a significant challenge. To date, induced pluripotent stem (iPS) cells have received much attention for modelling PD. Nonetheless, direct reprogramming strategies (either to a neuronal or neural stem/progenitor fate) represent a valid alternative that are yet to be extensively explored. Direct reprogramming is faster and more efficient than iPS cell reprogramming, and appears to conserve age-related markers. At present, however, protocols aiming to derive authentic, mature vmDA neurons by direct reprogramming of adult human somatic cells are sorely lacking. This review will discuss the strategies that have been employed to generate vmDA neurons and their potential for the study and treatment of PD.

Transplantation in the nonhuman primate MPTP model of Parkinson's disease: update and perspectives

In order to calibrate stem cell exploitation for cellular therapy in neurodegenerative diseases, fundamental and preclinical research in NHP (nonhuman primate) models is crucial. Indeed, it is consensually recognized that it is not possible to directly extrapolate results obtained in rodent models to human patients. A large diversity of neurological pathologies should benefit from cellular therapy based on neural differentiation of stem cells. In the context of this special issue of Primate Biology on NHP stem cells, we describe past and recent advances on cell replacement in the NHP model of Parkinson's disease (PD). From the different grafting procedures to the various cell types transplanted, we review here diverse approaches for cell-replacement therapy and their related therapeutic potential on behavior and function in the NHP model of PD.

Cell-Engineered Nanovesicle as a Surrogate Inducer of Contact-Dependent Stimuli

Heterotypic interactions between cells are crucial in various biological phenomena. Particularly, stimuli that regulate embryonic stem cell (ESC) fate are often provided from neighboring cells. However, except for feeder cultures, no practical methods are identified that can provide ESCs with contact-dependent cell stimuli. To induce contact-dependent cell stimuli in the absence of living cells, a novel method that utilizes cell-engineered nanovesicles (CNVs) that are made by extruding living cells through microporous membranes is described. Protein compositions of CNVs are similar to their originating cells, as well as freely diffusible and precisely scalable. Treatment of CNVs produced from three different stromal cells successfully induces the same effect as feeder cultures. The results suggest that the effects of CNVs are mainly mediated by membrane-associated components. The use of CNVs might constitute a novel and efficient tool for ESC research.

Derivation of Functional Dopamine Neurons from Embryonic Stem Cells

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the selective degeneration of dopaminergic (DA) neurons in the substantia nigra of the midbrain. Pharmacological treatment of PD has been a prevailing strategy. However, it has some limitations because its effectiveness gradually decreases and side effects develop. As an alternative, cell transplantation therapy has been tried. Although transplantation of fetal ventral mesencephalic cells looks promising for the treatment of PD in some cases, ethical and technical problems in obtaining large numbers of human fetal brain tissues also lead to difficulty in its clinical application. Our recent studies showed that a high yield of DA neurons could be derived from embryonic stem (ES) cells and they efficiently induced behavioral recovery in a PD animal model. Here we summarize methods for generation of functional DA neurons from ES cells for application to PD models.

A Knockin Reporter Allows Purification and Characterization of mDA Neurons from Heterogeneous Populations

Generation of midbrain dopaminergic (mDA) neurons from human pluripotent stem cells provides a platform for inquiry into basic and translational studies of Parkinson's disease (PD). However, heterogeneity in differentiation in vitro makes it difficult to identify mDA neurons in culture or in vivo following transplantation. Here, we report the generation of a human embryonic stem cell (hESC) line with a tyrosine hydroxylase (TH)-RFP (red fluorescent protein) reporter. We validated that RFP faithfully mimicked TH expression during differentiation. Use of this TH-RFP reporter cell line enabled purification of mDA-like neurons from heterogeneous cultures with subsequent characterization of neuron transcriptional and epigenetic programs (global binding profiles of H3K27ac, H3K4me1, and 5-hydroxymethylcytosine [5hmC]) at four different stages of development. We anticipate that the tools and data described here will contribute to the development of mDA neurons for applications in disease modeling and/or drug screening and cell replacement therapies for PD.

Generation of Cholinergic and Dopaminergic Interneurons from Human Pluripotent Stem Cells as a Relevant Tool for In Vitro Modeling of Neurological Disorders Pathology and Therapy

The cellular and molecular bases of neurological diseases have been studied for decades; however, the underlying mechanisms are not yet fully elucidated. Compared with other disorders, diseases of the nervous system have been very difficult to study mainly due to the inaccessibility of the human brain and live neurons in vivo or in vitro and difficulties in examination of human postmortem brain tissue. Despite the availability of various genetically engineered animal models, these systems are still not adequate enough due to species variation and differences in genetic background. Human induced pluripotent stem cells (hiPSCs) reprogrammed from patient somatic cells possess the potential to differentiate into any cell type, including neural progenitor cells and postmitotic neurons; thus, they open a new area to in vitro modeling of neurological diseases and their potential treatment. Currently, many protocols for generation of various neuronal subtypes are being developed; however, most of them still require further optimization. Here, we highlight accomplishments made in the generation of dopaminergic and cholinergic neurons, the two subtypes most affected in Alzheimer's and Parkinson's diseases and indirectly affected in Huntington's disease. Furthermore, we discuss the potential role of hiPSC-derived neurons in the modeling and treatment of neurological diseases related to dopaminergic and cholinergic system dysfunction.

Efficient induction of neural precursor cells from fibroblasts using stromal cell-derived inducing activity

The direct lineage conversion of fibroblasts into neuronal or neural precursor cells (NPCs) has become a hot issue in recent years as an attractive approach in the field of stem cell regenerative medicine. In this study, we adopted the stromal feeder co-culture method during the early conversion period to enhance conversion efficiency. Stromal cells are often used in directed differentiation of dopaminergic (DA) neurons from pluripotent stem cells. We co-cultured rat embryonic fibroblasts (REFs) on γ-irradiated sonic hedgehog-overexpressing MS5 stromal (MS5-SHH) cells after transduction with Brn2, Ascl1, Myt1L, and BclxL-GFP (BAMX^GFP) transcription factors to REFs. One week after co-culture, transduced cells (GFP+ cells) that proliferated on MS5-SHH cells were separated from MS5-SHH cells through a 40 µm cell strainer. Subsequently, the converted cells (GFP+ cells) were expanded on fibronectin-coated culture plates in NPC expansion medium. The induced NPCs (iNPCs) expressed NPC potential (NESTIN+/SOX2+) earlier than seen with non-co-culture methods and were efficiently differentiated into DA neurons by overexpression of Nurr1 and Foxa2 genes, which are specific transcription factors for midbrain DA neuron development. These observations indicated that direct conversion to NPCs using an MS5 stromal cells co-culture method is a suitable technique for efficient generation of iNPC/DA neurons from fibroblasts.

Brain repair and reprogramming: the route to clinical translation

The adult brain has a very limited capacity for generation of new neurons, and neurogenesis only takes place in restricted regions. Some evidence for neurogenesis after injury has been reported, but few, if any, neurons are replaced after brain injury or degeneration, and the permanent loss of neurons leads to long-term disability and loss of brain function. For decades, researchers have been developing cell transplantation using exogenous cell sources for brain repair, and this method has now been shown to successfully restore lost function in experimental and clinical trials. Here, we review the development of cell-replacement strategies for brain repair in Parkinson's disease using the example of human foetal brain cells being successfully translated from preclinical findings to clinical trials. These trials demonstrate that cell-replacement therapy is a viable option for patients with Parkinson's disease, but more importantly also show how the limited availability of foetal cells calls for development of novel cell sources and methods for generating new neurons for brain repair. We focus on new stem cell sources that are on the threshold of clinical application for brain repair and discuss emerging cellular reprogramming technologies. Reviewing the current status of direct neural conversion, both in vitro and in vivo, where somatic cells are directly reprogrammed into functional neurons without passing through a stem cell intermediate, we conclude that both methods result in the successful replacement of new neurons that mature and integrate into the host brain. Thus, this new field shows great promise for future brain repair, although much work is still needed in preclinical animal models before it can be seriously considered for clinical applications.

PA6 Stromal Cell Co-Culture Enhances SH-SY5Y and VSC4.1 Neuroblastoma Differentiation to Mature Phenotypes

Neuroblastoma cell lines such as SH-SY5Y have been used for modelling neurodegenerative diseases and for studying basic mechanisms in neuroscience. Since neuroblastoma cells proliferate and generally do not express markers of mature or functional neurons, we exploited a co-culture system with the stromal cell line PA6 to better induce differentiation to a more physiologically relevant status. We found that co-culture of the neuroblastoma cell lines in the presence of neural inducers such retinoic acid was able to generate a high proportion of quiescent neurons with very long neurites expressing differentiation markers. The co-culture system additionally cuts short the time taken to produce a more mature phenotype. We also show the application of this system to study proteins implicated in motor neuron disease.

A new technique for modeling neuronal connectivity using human pluripotent stem cells

Purpose: We describe a technique for independently differentiating neocortical and mesencephalic dopaminergic (mDA) neurons from a single human pluripotent stem cell (hPSC) line, and subsequently allowing the two cell types to interact and form connections.

Methods: Dopaminergic and neocortical progenitors were differentiated in separate vessels, then separately seeded into the inner and outer compartments of specialized cell culture vessels designed for in vitro studies of wound healing. Cells were further differentiated using dopamine-specific and neocortex-specific trophic factors, respectively. The barrier was then removed, and differentiation was continued for three weeks in the presence of BDNF.

Results: After three weeks of differentiation, neocortical and mDA cell bodies largely remained in the areas into which they had been seeded, and the gap between the mDA and neocortical neuron populations could still be discerned. Abundant tyrosine hydroxylase (TH)-positive projections had extended from the area of the inner chamber to the outer chamber neocortical area.

Conclusions: We have developed a hPSC-based system for producing connections between neurons from two brain regions, neocortex and midbrain. Future experiments could employ modifications of this method to examine connections between any two brain regions or neuronal subtypes that can be produced from hPSCs in vitro.

In Vitro Models for Neurogenesis

The process of generating new neurons of different phenotype and function from undifferentiated stem and progenitor cells starts at very early stages of development and continues in discrete regions of the mammalian nervous system throughout life. Understanding mechanisms underlying neuronal cell development, biology, function, and interaction with other cells, especially in the neurogenic niche of fully developed adults, is important in defining and developing new therapeutic regimes in regenerative neuroscience. Studying these complex and dynamic processes in vivo is challenging because of the complexity of the nervous system and the presence of many known and unknown confounding variables. However, the challenges could be overcome with simple and robust in vitro models that more or less recapitulate the in vivo events. In this work, we will present an overview of present available in vitro cell-based models of neurogenesis.

A Compendium of Preparation and Application of Stem Cells in Parkinson's Disease: Current Status and Future Prospects

Parkinson's Disease (PD) is a progressively neurodegenerative disorder, implicitly characterized by a stepwise loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and explicitly marked by bradykinesia, rigidity, resting tremor and postural instability. Currently, therapeutic approaches available are mainly palliative strategies, including L-3,4-dihydroxy-phenylalanine (L-DOPA) replacement therapy, DA receptor agonist and deep brain stimulation (DBS) procedures. As the disease proceeds, however, the pharmacotherapeutic efficacy is inevitably worn off, worse still, implicated by side effects of motor response oscillations as well as L-DOPA induced dyskinesia (LID). Therefore, the frustrating status above has propeled the shift to cell replacement therapy (CRT), a promising restorative therapy intending to secure a long-lasting relief of patients' symptoms. By far, stem cell lines of multifarious origins have been established, which can be further categorized into embryonic stem cells (ESCs), neural stem cells (NSCs), induced neural stem cells (iNSCs), mesenchymal stem cells (MSCs), and induced pluripotent stem cells (iPSCs). In this review, we intend to present a compendium of preparation and application of multifarious stem cells, especially in relation to PD research and therapy. In addition, the current status, potential challenges and future prospects for practical CRT in PD patients will be elaborated as well.

Derivation, Characterization, and Neural Differentiation of Integration-Free Induced Pluripotent Stem Cell Lines from Parkinson's Disease Patients Carrying SNCA, LRRK2, PARK2, and GBA Mutations

We report generation of induced pluripotent stem cell (iPSC) lines from ten Parkinson’s disease (PD) patients carrying SNCA, PARK2, LRRK2, and GBA mutations, and one age-matched control. After validation of pluripotency, long-term genome stability, and integration-free reprogramming, eight of these lines (one of each SNCA, LRRK2 and GBA, four PARK2 lines, and the control) were differentiated into neural stem cells (NSC) and subsequently to dopaminergic cultures. We did not observe significant differences in the timeline of neural induction and NSC derivation between the patient and control line, nor amongst the patient lines, although we report considerable variability in the efficiency of dopaminergic differentiation among patient lines. We performed whole genome expression analyses of the lines at each stage of differentiation (fibroblast, iPSC, NSC, and dopaminergic culture) in an attempt to identify alterations by large-scale evaluation. While gene expression profiling clearly distinguished cells at different stages of differentiation, no mutation-specific clustering or difference was observed, though consistent changes in patient lines were detected in genes associated mitochondrial biology. We further examined gene expression in a stress model (MPTP-induced dopaminergic neuronal death) using two clones from the SNCA triplication line, and detected changes in genes associated with mitophagy. Our data suggested that even a well-characterized line of a monogenic disease may not be sufficient to determine the cause or mechanism of the disease, and highlights the need to use more focused strategies for large-scale data analysis.

The Human Model: Changing Focus on Autism Research

The lack of live human brain cells for research has slowed progress toward understanding the mechanisms underlying autism spectrum disorders. A human model using reprogrammed patient somatic cells offers an attractive alternative, as it captures a patient's genome in relevant cell types. Despite the current limitations, the disease-in-a-dish approach allows for progressive time course analyses of target cells, offering a unique opportunity to investigate the cellular and molecular alterations before symptomatic onset. Understanding the current drawbacks of this model is essential for the correct data interpretation and extrapolation of conclusions applicable to the human brain. Innovative strategies for collecting biological material and clinical information from large patient cohorts are important for increasing the statistical power that will allow for the extraction of information from the noise resulting from the variability introduced by reprogramming and differentiation methods. Working with large patient cohorts is also important for understanding how brain cells derived from diverse human genetic backgrounds respond to specific drugs, creating the possibility of personalized medicine for autism spectrum disorders.

Gene Expression Studies on Human Trisomy 21 iPSCs and Neurons: Towards Mechanisms Underlying Down's Syndrome and Early Alzheimer's Disease-Like Pathologies

The cause of Alzheimer disease (AD) is not well understood and there is no cure. Our ability to understand the early events in the course of AD is severely limited by the difficulty of identifying individuals who are in the early, preclinical stage of this disease. Most individuals with Down's syndrome (DS, trisomy 21) will predictably develop AD and that they will do so at a young age makes them an ideal population in which to study the early stages of AD. Several recent studies have exploited induced pluripotent stem cells (iPSCs) generated from individuals with familial AD, spontaneous AD and DS to attempt to identify early events and discover novel biomarkers of disease progression in AD. Here, we summarize the progress and limitations of these iPSC studies with a focus on iPSC-derived neurons. Further, we outline the methodology and results for comparing gene expression between AD and DS iPSC-derived neurons. We highlight differences and commonalities in these data that may implicate underlying genes and pathways that are causative for AD.

Human induced pluripotent stem cells in Parkinson's disease: A novel cell source of cell therapy and disease modeling

Human induced pluripotent stem cells (hiPSCs) and human embryonic stem cells (hESCs) are two novel cell sources for studying neurodegenerative diseases. Dopaminergic neurons derived from hiPSCs/hESCs have been implicated to be very useful in Parkinson's disease (PD) research, including cell replacement therapy, disease modeling and drug screening. Recently, great efforts have been made to improve the application of hiPSCs/hESCs in PD research. Considerable advances have been made in recent years, including advanced reprogramming strategies without the use of viruses or using fewer transcriptional factors, optimized methods for generating highly homogeneous neural progenitors with a larger proportion of mature dopaminergic neurons and better survival and integration after transplantation. Here we outline the progress that has been made in these aspects in recent years, particularly during the last year, and also discuss existing issues that need to be addressed.

Noggin Over-Expressing Mouse Embryonic Fibroblasts and MS5 Stromal Cells Enhance Directed Differentiation of Dopaminergic Neurons from Human Embryonic Stem Cells

Directed methods for differentiating human embryonic stem cells (hESCs) into dopaminergic (DA) precursor cells using stromal cells co-culture systems are already well established. However, not all of the hESCs differentiate into DA precursors using these methods. HSF6, H1, H7, and H9 cells differentiate well into DA precursors, but CHA13 and CHA15 cells hardly differentiate. To overcome this problem, we modified the differentiation system to include a co-culturing step that exposes the cells to noggin early in the differentiation process. This was done using γ-irradiated noggin-overexpressing CF1-mouse embryonic fibroblasts (MEF-noggin) and MS5 stromal cells (MS5-noggin and MS5-sonic hedgehog). After directed differentiation, RT-PCR analyses revealed that engrailed-1 (En-1), Lmx1b, and Nurr1, which are midbrain DA markers, were expressed regardless of differentiation stage. Moreover, tyrosine hydroxylase (Th) and an A9 midbrain-specific DA marker (Girk2) were expressed during differentiation, whereas levels of Oct3/4, an undifferentiated marker, decreased. Immunocytochemical analyses revealed that protein levels of the neuronal markers TH and TuJ1 increased during the final differentiation stage. These results demonstrate that early noggin exposure may play a specific role in the directed differentiation of DA cells from human embryonic stem cells.

Development of stem cell-based therapy for Parkinson's disease

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders of aging, characterized by the degeneration of dopamine neurons (DA neurons) in the substantial nigra, leading to the advent of both motor symptoms and non-motor symptoms. Current treatments include electrical stimulation of the affected brain areas and dopamine replacement therapy. Even though both categories are effective in treating PD patients, the disease progression cannot be stopped. The research advance into cell therapies provides exciting potential for the treatment of PD. Current cell sources include neural stem cells (NSCs) from fetal brain tissues, human embryonic stem cells (hESCs), induced pluripotent stem cells (iPSCs) and directly induced dopamine neurons (iDA neurons). Here, we evaluate the research progress in different cell sources with a focus on using iPSCs as a valuable source and propose key challenges for developing cells suitable for large-scale clinical applications in the treatment of PD.

Cell-based therapies for Parkinson disease—past insights and future potential

Parkinson disease (PD) is characterized by loss of the A9 nigral neurons that provide dopaminergic innervation to the striatum. This discovery led to the successful instigation of dopaminergic drug treatments in the 1960s, although these drugs were soon recognized to lose some of their efficacy and generate their own adverse effects over time. Despite the fact that PD is now known to have extensive non-nigral pathology with a wide range of clinical features, dopaminergic drug therapies are still the mainstay of therapy, and work well for many years. Given the success of pharmacological dopamine replacement, pursuit of cell-based dopamine replacement strategies seemed to be the next logical step, and studies were initiated over 30 years ago to explore the possibility of dopaminergic cell transplantation. In this Review, we outline the history of this therapeutic approach to PD and highlight the lessons that we have learned en route. We discuss how the best clinical outcomes have been obtained with fetal ventral mesencephalic allografts, while acknowledging inconsistencies in the results owing to problems in trial design, patient selection, tissue preparation, and immunotherapy used post-grafting. We conclude by discussing the challenges of bringing the new generation of stem cell-derived dopamine cells to the clinic.

Cell reprogramming and neuronal differentiation applied to neurodegenerative diseases: Focus on Parkinson's disease

Adult cells from patients can be reprogrammed to induced pluripotent stem cells (iPSCs) which successively can be used to obtain specific cells such as neurons. This remarkable breakthrough represents a new way of studying diseases and brought new therapeutic perspectives in the field of regenerative medicine. This is particular true in the neurology field, where few techniques are amenable to study the affected tissue of the patient during illness progression, in addition to the lack of neuroprotective therapies for many diseases. In this review we discuss the advantages and unresolved issues of cell reprogramming and neuronal differentiation. We reviewed evidence using iPSCs-derived neurons from neurological patients. Focusing on data obtained from Parkinson's disease (PD) patients, we show that iPSC-derived neurons possess morphological and functional characteristics of this disease and build a case for the use of this technology to study PD and other neuropathologies while disease is in progress. These data show the enormous impact that this new technology starts to have on different purposes such as the study and design of future therapies of neurological disease, especially PD.

How to make a midbrain dopaminergic neuron

Midbrain dopaminergic (mDA) neuron development has been an intense area of research during recent years. This is due in part to a growing interest in regenerative medicine and the hope that treatment for diseases affecting mDA neurons, such as Parkinson's disease (PD), might be facilitated by a better understanding of how these neurons are specified, differentiated and maintained in vivo. This knowledge might help to instruct efforts to generate mDA neurons in vitro, which holds promise not only for cell replacement therapy, but also for disease modeling and drug discovery. In this Primer, we will focus on recent developments in understanding the molecular mechanisms that regulate the development of mDA neurons in vivo, and how they have been used to generate human mDA neurons in vitro from pluripotent stem cells or from somatic cells via direct reprogramming. Current challenges and future avenues in the development of a regenerative medicine for PD will be identified and discussed.

The potential of alternate sources of cells for neural grafting in Parkinson's and Huntington's disease

Cell-based therapies for Parkinson's and Huntington's disease have provided mixed clinical outcomes and one of the reasons underlying this is the use of primary fetal tissue as the source of grafted cells. An alternate source of cells, such as stem cells, could overcome many of the issues associated with primary fetal tissue and would help bring forward cell replacement therapy as a reliable and effective treatment for these two neurodegenerative disorders. This review will discuss which stem cells are likely to go to clinic in the next generation of cells, based on trials for Parkinson's and Huntington's disease.

Interventional magnetic resonance imaging-guided cell transplantation into the brain with radially branched deployment

Intracerebral cell transplantation is being pursued as a treatment for many neurological diseases, and effective cell delivery is critical for clinical success. To facilitate intracerebral cell transplantation at the scale and complexity of the human brain, we developed a platform technology that enables radially branched deployment (RBD) of cells to multiple target locations at variable radial distances and depths along the initial brain penetration tract with real-time interventional magnetic resonance image (iMRI) guidance. iMRI-guided RBD functioned as an "add-on" to standard neurosurgical and imaging workflows, and procedures were performed in a commonly available clinical MRI scanner. Multiple deposits of super paramagnetic iron oxide beads were safely delivered to the striatum of live swine, and distribution to the entire putamen was achieved via a single cannula insertion in human cadaveric heads. Human embryonic stem cell-derived dopaminergic neurons were biocompatible with the iMRI-guided RBD platform and successfully delivered with iMRI guidance into the swine striatum. Thus, iMRI-guided RBD overcomes some of the technical limitations inherent to the use of straight cannulas and standard stereotactic targeting. This platform technology could have a major impact on the clinical translation of a wide range of cell therapeutics for the treatment of many neurological diseases.

Dopamine release from transplanted neural stem cells in Parkinsonian rat striatum in vivo

Embryonic stem cell-based therapies exhibit great potential for the treatment of Parkinson's disease (PD) because they can significantly rescue PD-like behaviors. However, whether the transplanted cells themselves release dopamine in vivo remains elusive. We and others have recently induced human embryonic stem cells into primitive neural stem cells (pNSCs) that are self-renewable for massive/transplantable production and can efficiently differentiate into dopamine-like neurons (pNSC-DAn) in culture. Here, we showed that after the striatal transplantation of pNSC-DAn, (i) pNSC-DAn retained tyrosine hydroxylase expression and reduced PD-like asymmetric rotation; (ii) depolarization-evoked dopamine release and reuptake were significantly rescued in the striatum both in vitro (brain slices) and in vivo, as determined jointly by microdialysis-based HPLC and electrochemical carbon fiber electrodes; and (iii) the rescued dopamine was released directly from the grafted pNSC-DAn (and not from injured original cells). Thus, pNSC-DAn grafts release and reuptake dopamine in the striatum in vivo and alleviate PD symptoms in rats, providing proof-of-concept for human clinical translation.

Directed dopaminergic neuron differentiation from human pluripotent stem cells

Dopaminergic (DA) neurons in the substantia nigra pars compacta (also known as A9 DA neurons) are the specific cell type that is lost in Parkinson's disease (PD). There is great interest in deriving A9 DA neurons from human pluripotent stem cells (hPSCs) for regenerative cell replacement therapy for PD. During neural development, A9 DA neurons originate from the floor plate (FP) precursors located at the ventral midline of the central nervous system. Here, we optimized the culture conditions for the stepwise differentiation of hPSCs to A9 DA neurons, which mimics embryonic DA neuron development. In our protocol, we first describe the efficient generation of FP precursor cells from hPSCs using a small molecule method, and then convert the FP cells to A9 DA neurons, which could be maintained in vitro for several months. This efficient, repeatable and controllable protocol works well in human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) from normal persons and PD patients, in which one could derive A9 DA neurons to perform in vitro disease modeling and drug screening and in vivo cell transplantation therapy for PD.

Survival and engraftment of dopaminergic neurons manufactured by a Good Manufacturing Practice-compatible process

BACKGROUND AIMS

We have previously reported a Good Manufacturing Practice (GMP)-compatible process for generating authentic dopaminergic neurons in defined media from human pluripotent stem cells and determined the time point at which dopaminergic precursors/neurons (day 14 after neuronal stem cell [NSC] stage) can be frozen, shipped and thawed without compromising their viability and ability to mature in vitro. One important issue we wished to address is whether dopaminergic precursors/neurons manufactured by our GMP-compatible process can be cryopreserved and engrafted in animal Parkinson disease (PD) models.

METHODS

In this study, we evaluated the efficacy of freshly prepared and cryopreserved dopaminergic neurons in the 6-hydroxydopamine-lesioned rat PD model.

RESULTS

We showed functional recovery up to 6 months post-transplantation in rats transplanted with our cells, whether freshly prepared or cryopreserved. In contrast, no motor improvement was observed in two control groups receiving either medium or cells at a slightly earlier stage (day 10 after NSC stage). Histologic analysis at the end point of the study (6 months post-transplantation) showed robust long-term survival of donor-derived tyrosine hydroxylase (TH)(+) dopaminergic neurons in rats transplanted with day 14 dopaminergic neurons. Moreover, TH(+) fibers emanated from the graft core into the surrounding host striatum. Consistent with the behavioral analysis, no or few TH(+) neurons were detected in animals receiving day 10 cells, although human cells were present in the graft. Importantly, no tumors were detected in any grafted rats, but long-term tumorigenic studies will need to determine the safety of our products.

CONCLUSIONS

Dopaminergic neurons manufactured by a GMP-compatible process from human ESC survived and engrafted efficiently in the 6-OHDA PD rat model.

Self-renewal and cell lineage differentiation strategies in human embryonic stem cells and induced pluripotent stem cells

INTRODUCTION

Since the initial discoveries of human embryonic and induced pluripotent stem cells, many strategies have been developed to utilize the potential of these cells for translational research and disease modeling. The success of these aims and the development of future applications in this area will depend on the ability to generate high-quality and large numbers of differentiated cell types that genetically, epigenetically, and functionally mimic the cells found in the body.

AREAS COVERED

In this review, we highlight the current strategies used to maintain stem cell pluripotency (a measure of stem cell quality), as well as provide an overview of the various differentiation strategies being used to generate cells from all three germ lineages. We also discuss the particular considerations that must be addressed when utilizing these cells for translational therapy, and provide an example of a cell type currently used in clinical trials.

EXPERT OPINION

The major challenge in regenerative medicine and disease modeling will be in generating functional cells of sufficient quality that are physiologically and epigenetically similar to the diverse cells that they are modeled after. By meeting these criteria, these differentiated products can be successfully used in disease modeling, drug/toxicology screens, and cellular replacement therapy.

Non-coding RNAs in pluripotency and neural differentiation of human pluripotent stem cells

Several studies have demonstrated the important role of non-coding RNAs as regulators of posttranscriptional processes, including stem cells self-renewal and neural differentiation. Human embryonic stem cells (hESCs) and induced pluripotent stem cells (ihPSCs) show enormous potential in regenerative medicine due to their capacity to differentiate to virtually any type of cells of human body. Deciphering the role of non-coding RNAs in pluripotency, self-renewal and neural differentiation will reveal new molecular mechanisms involved in induction and maintenances of pluripotent state as well as triggering these cells toward clinically relevant cells for transplantation. In this brief review we will summarize recently published studies which reveal the role of non-coding RNAs in pluripotency and neural differentiation of hESCs and ihPSC.