Directed neuronal differentiation of human embryonic stem cells

Automated human induced pluripotent stem cell culture and sample preparation for 3D live-cell microscopy

To produce abundant cell culture samples to generate large, standardized image datasets of human induced pluripotent stem (hiPS) cells, we developed an automated workflow on a Hamilton STAR liquid handler system. This was developed specifically for culturing hiPS cell lines expressing fluorescently tagged proteins, which we have used to study the principles by which cells establish and maintain robust dynamic localization of cellular structures. This protocol includes all details for the maintenance, passage and seeding of cells, as well as Matrigel coating of 6-well plastic plates and 96-well optical-grade, glass plates. We also developed an automated image-based hiPS cell colony segmentation and feature extraction pipeline to streamline the process of predicting cell count and selecting wells with consistent morphology for high-resolution three-dimensional (3D) microscopy. The imaging samples produced with this protocol have been used to study the integrated intracellular organization and cell-to-cell variability of hiPS cells to train and develop deep learning-based label-free predictions from transmitted-light microscopy images and to develop deep learning-based generative models of single-cell organization. This protocol requires some experience with robotic equipment. However, we provide details and source code to facilitate implementation by biologists less experienced with robotics. The protocol is completed in less than 10 h with minimal human interaction. Overall, automation of our cell culture procedures increased our imaging samples' standardization, reproducibility, scalability and consistency. It also reduced the need for stringent culturist training and eliminated culturist-to-culturist variability, both of which were previous pain points of our original manual pipeline workflow.

Challenges involved in cell therapy for Parkinson's disease using human pluripotent stem cells

Neurons derived from human pluripotent stem cells (hPSCs) provide a valuable tool for studying human neural development and neurodegenerative diseases. The investigation of hPSC-based cell therapy, involving the differentiation of hPSCs into target cells and their transplantation into affected regions, is of particular interest. One neurodegenerative disease that is being extensively studied for hPSC-based cell therapy is Parkinson's disease (PD), the second most common among humans. Various research groups are focused on differentiating hPSCs into ventral midbrain dopaminergic (vmDA) progenitors, which have the potential to further differentiate into neurons closely resembling DA neurons found in the substantia nigra pars compacta (SNpc) after transplantation, providing a promising treatment option for PD. In vivo experiments, where hPSC-derived vmDA progenitor cells were transplanted into the striatum or SNpc of animal PD models, the transplanted cells demonstrated stable engraftment and resulted in behavioral recovery in the transplanted animals. Several differentiation protocols have been developed for this specific cell therapy. However, the lack of a reliable live-cell lineage identification method presents a significant obstacle in confirming the precise lineage of the differentiated cells intended for transplantation, as well as identifying potential contamination by non-vmDA progenitors. This deficiency increases the risk of adverse effects such as dyskinesias and tumorigenicity, highlighting the importance of addressing this issue before proceeding with transplantation. Ensuring the differentiation of hPSCs into the target cell lineage is a crucial step to guarantee precise therapeutic effects in cell therapy. To underscore the significance of lineage identification, this review focuses on the differentiation protocols of hPSC-derived vmDA progenitors developed by various research groups for PD treatment. Moreover, in vivo experimental results following transplantation were carefully analyzed. The encouraging outcomes from these experiments demonstrate the potential efficacy and safety of hPSC-derived vmDA progenitors for PD cell therapy. Additionally, the results of clinical trials involving the use of hPSC-derived vmDA progenitors for PD treatment were briefly reviewed, shedding light on the progress and challenges faced in translating this promising therapy into clinical practice.

Isolation and Purification of Self-Renewable Human Neural Stem Cells from iPSCs for Cell Therapy in Experimental Model of Ischemic Stroke

Neural stem cell therapy has been galvanized by the discovery of pluripotent stem cells. The possibility to generate specialized central nervous system-specific differentiated cells using human somatic cells engineered to become induced pluripotent stem cells (iPSCs) was a game changer. This technology has broad applications in the field of regenerative medicine, in vitro disease modeling, targeted drug discovery, and precision medicine. Currently, iPSCs are one of the most promising cell sources amenable for commercialization and off-the-shelf neural stem cell therapy products. iPSCs exhibit a strong self-renewable ability that supports the development of a virtually unlimited source of neural cells for structural repair in neurological disorders. However, along with this strong proliferative capacity of iPSCs comes the tumorigenic potential of these cells after transplantation. Thus, the isolation and purification of a homogeneous population of human neural stem cells (hNSCs) are of paramount importance to ensure consistency in the composition of the cellular product and to avoid tumor formation in the host brain. This chapter describes the isolation, neuralization, and long-term perpetuation of hNSCs derived from iPSCs through the use of specific growth medium and the preparation of hNSCs for transplantation in an experimental model of stroke. Additionally, we will describe methods to analyze the ischemic stroke and size of grafts using magnetic resonance imaging and OsiriX software and neuroanatomical tracing procedures to study axonal remodeling after ischemic stroke and cell transplantation.

Differentiation of Human Pluripotent Stem Cells Into Specific Neural Lineages

Human pluripotent stem cells (hPSCs) are sources of several somatic cell types for human developmental studies, in vitro disease modeling, and cell transplantation therapy. Improving strategies of derivation of high-purity specific neural and glial lineages from hPSCs is critical for application to the study and therapy of the nervous system. Here, we will focus on the principles behind establishment of neuron and glia differentiation methods according to developmental studies. We will also highlight the limitations and challenges associated with the differentiation of several “difficult” neural lineages and delay in neuronal maturation and functional integration. To overcome these challenges, we will introduce strategies and novel technologies aimed at improving the differentiation of various neural lineages to expand the application potential of hPSCs to the study of the nervous system.

In vivo surveillance and elimination of teratoma-forming human embryonic stem cells with monoclonal antibody 2448 targeting annexin A2

This study describes the use of a previously reported chimerised monoclonal antibody (mAb), ch2448, to kill human embryonic stem cells (hESCs) in vivo and prevent or delay the formation of teratomas. ch2448 was raised against hESCs and was previously shown to effectively kill ovarian and breast cancer cells in vitro and in vivo. The antigen target was subsequently found to be Annexin A2, an oncofetal antigen expressed on both embryonic cells and cancer cells. Against cancer cells, ch2448 binds and kills via antibody‐dependent cell‐mediated cytotoxicity (ADCC) and/or antibody‐drug conjugate (ADC) routes. Here, we investigate if the use of ch2448 can be extended to hESC. ch2448 was found to bind specifically to undifferentiated hESC but not differentiated progenitors. Similar to previous study using cancer cells, ch2448 kills hESC in vivo either indirectly by eliciting ADCC or directly as an ADC. The treatment with ch2448 post‐transplantation eliminated the in vivo circulating undifferentiated cells and prevented or delayed the formation of teratomas. This surveillance role of ch2448 adds an additional layer of safeguard to enhance the safety and efficacious use of pluripotent stem cell‐derived products in regenerative medicine. Thereby, translating the use of ch2448 in the treatment of cancers to a proof of concept study in hESC (or pluripotent stem cell [PSC]), we show that mAbs can also be used to eliminate teratoma forming cells in vivo during PSC‐derived cell therapies. We propose to use this strategy to complement existing methods to eliminate teratoma‐forming cells in vitro. Residual undifferentiated cells may escape in vitro removal methods and be introduced into patients together with the differentiated cells.

Plasmonic nano surface for neuronal differentiation and manipulation

Neurodegenerative diseases and traumatic brain injuries can destroy neurons, resulting in sensory and motor function loss. Transplantation of differentiated neurons from stem cells could help restore such lost functions. Plasmonic gold nanorods (AuNR) were integrated in growth surfaces to stimulate and modulate neural cells in order to tune cell physiology. An AuNR nanocomposite system was fabricated, characterized, and then utilized to study the differentiation of embryonic rat neural stem cells (NSCs). Results demonstrated that this plasmonic surface 1) accelerated differentiation, yielding almost twice as many differentiated neural cells as a traditional NSC culture surface coated with poly-D-lysine and laminin for the same time period; and 2) promoted differentiation of NSCs into neurons and astrocytes in a 2:1 ratio, as evidenced by the expression of relevant marker proteins. These results indicate that the design and properties of this AuNR plasmonic surface would be advantageous for tissue engineering to address neural degeneration.

Fn14 Participates in Neuropathic Pain Through NF-κB Pathway in Primary Sensory Neurons

Fibroblast growth factor-inducible-14 (Fn14), a receptor for tumor necrosis-like weak inducer of apoptosis, is expressed in the neurons of dorsal root ganglion (DRG). Its mRNA is increased in the injured DRG following peripheral nerve injury. Whether this increase contributes to neuropathic pain is unknown. We reported here that peripheral nerve injury caused by spinal nerve ligation (SNL) increased the expression of Fn14 at both protein and mRNA levels in the injured DRG. Blocking this increase attenuated the development of SNL-induced mechanical, thermal, and cold pain hypersensitivities. Conversely, mimicking this increase produced the increases in the levels of phosphorylated extracellular signal-regulated kinase ½ and glial fibrillary acidic protein in ipsilateral dorsal horn and the enhanced responses to mechanical, thermal, and cold stimuli in the absence of SNL. Mechanistically, the increased Fn14 activated the NF-κB pathway through promoting the translocation of p65 into the nucleus of the injured DRG neurons. Our findings suggest that Fn14 may be a potential target for the therapeutic treatment of peripheral neuropathic pain.

Analysis of Promyelocytic Leukemia in Human Embryonic Carcinoma Stem Cells During Retinoic Acid-Induced Neural Differentiation

BACKGROUND

Promyelocytic leukemia protein (PML) is a tumor suppressor protein that is involved in myeloid cell differentiation in response to retinoic acid (RA). In addition, RA acts as a natural morphogen in neural development.

OBJECTIVES

This study aimed to examine PML gene expression in different stages of in vitro neural differentiation of NT2 cells, and to investigate the possible role of PML in pluripotency and/or neural development.

MATERIALS AND METHODS

RA was used as a neural inducer for in vitro neural differentiation of NT2 cells. During this process PML mRNA and protein levels were assessed by quantitative real time RT-PCR (QRT-PCR) and Immunoblotting, respectively. Furthermore bisulfite sequencing PCR (BSP) was used to assess PML promoter methylation in NT2 cells and NT2 derived neuronal precursor cells (NT2.NPCs).

RESULTS

QRT-PCR results showed that, PML had maximum expression with significant differences in NT2 derived neuronal precursor cells relative to NT2 cells and NT2 derived neural cells (NT2.NCs). Numerous isoforms of PML with different intensities appeared in immunoblots of pluripotent NT2 cells, NT2.NPCs, and NT2.NCs. Furthermore, the methylation of the PML promoter in NT2.NCs was 2.6 percent lower than NT2 cell.

CONCLUSIONS

The observed differences in PML expression in different cellular stages possibly could be attributed to the fact that PML in each developmental state might be involved in different cell signaling machinery and different functions. The appearance of different PML isoforms with more intensity in neural progenitor cells; may suggest apossible role for this protein in neural development.

An integrative approach predicted co-expression sub-networks regulating properties of stem cells and differentiation

The differentiation of human Embryonic Stem Cells (hESCs) is accompanied by the formation of different intermediary cells, gradually losing its stemness and acquiring differentiation. The precise mechanisms underlying hESCs integrity and its differentiation into fibroblast (Fib) are still elusive. Here, we aimed to assess important genes and co-expression sub-networks responsible for stemness, early differentiation of hESCs into embryoid bodies (EBs) and its lineage specification into Fibs. To achieve this, we compared transcriptional profiles of hESCs-EBs and EBs-Fibs and obtained differentially expressed genes (DEGs) exclusive to hESCs-EBs (early differentiation), EBs-Fibs (late differentiation) and common DEGs in hESCs-EBs and EBs-Fibs. Then, we performed gene set enrichment analysis (GSEA) followed by overrepresentation study and identified key genes for each gene category. The regulations of these genes were studied by integrating ChIP-Seq data of core transcription factors (TFs) and histone methylation marks in hESCs. Finally, we identified co-expression sub-networks from key genes of each gene category using k-clique sub-network extraction method. Our study predicted seven genes edicting core stemness properties forming a co-expression network. From the pathway analysis of sub-networks of hESCs-EBs, we hypothesize that FGF2 is contributing to pluripotent transcription network of hESCs in association with DNMT3B and JARID2 thereby facilitating cell proliferation. On the contrary, FGF2 is found to promote cell migration in Fibs along with DDR2, CAV1, DAB2, and PARVA. Moreover, our study identified three k-clique sub-networks regulating TGF-β signaling pathway thereby promoting EBs to Fibs differentiation by: (i) modulating extracellular matrix involving ITGB1, TGFB1I1 and GBP1, (ii) regulating cell cycle remodeling involving CDKN1A, JUNB and DUSP1 and (iii) helping in epithelial to mesenchymal transition (EMT) involving THBS1, INHBA and LOX. This study put forward the unexplored genes and co-expression sub-networks regulating stemness and different stages of differentiation of hESCs which will undoubtedly add to the comprehensive understanding of hESCs biology.

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.

Neural Stem Cells (NSCs) and Proteomics

Neural stem cells (NSCs) can self-renew and give rise to the major cell types of the CNS. Studies of NSCs include the investigation of primary, CNS-derived cells as well as animal and human embryonic stem cell (ESC)-derived and induced pluripotent stem cell (iPSC)-derived sources. NSCs provide a means with which to study normal neural development, neurodegeneration, and neurological disease and are clinically relevant sources for cellular repair to the damaged and diseased CNS. Proteomics studies of NSCs have the potential to delineate molecules and pathways critical for NSC biology and the means by which NSCs can participate in neural repair. In this review, we provide a background to NSC biology, including the means to obtain them and the caveats to these processes. We then focus on advances in the proteomic interrogation of NSCs. This includes the analysis of posttranslational modifications (PTMs); approaches to analyzing different proteomic compartments, such the secretome; as well as approaches to analyzing temporal differences in the proteome to elucidate mechanisms of differentiation. We also discuss some of the methods that will undoubtedly be useful in the investigation of NSCs but which have not yet been applied to the field. While many proteomics studies of NSCs have largely catalogued the proteome or posttranslational modifications of specific cellular states, without delving into specific functions, some have led to understandings of functional processes or identified markers that could not have been identified via other means. Many challenges remain in the field, including the precise identification and standardization of NSCs used for proteomic analyses, as well as how to translate fundamental proteomics studies to functional biology. The next level of investigation will require interdisciplinary approaches, combining the skills of those interested in the biochemistry of proteomics with those interested in modulating NSC function.

Dynamic changes in replication timing and gene expression during lineage specification of human pluripotent stem cells

Duplication of the genome in mammalian cells occurs in a defined temporal order referred to as its replication-timing (RT) program. RT changes dynamically during development, regulated in units of 400-800 kb referred to as replication domains (RDs). Changes in RT are generally coordinated with transcriptional competence and changes in subnuclear position. We generated genome-wide RT profiles for 26 distinct human cell types, including embryonic stem cell (hESC)-derived, primary cells and established cell lines representing intermediate stages of endoderm, mesoderm, ectoderm, and neural crest (NC) development. We identified clusters of RDs that replicate at unique times in each stage (RT signatures) and confirmed global consolidation of the genome into larger synchronously replicating segments during differentiation. Surprisingly, transcriptome data revealed that the well-accepted correlation between early replication and transcriptional activity was restricted to RT-constitutive genes, whereas two-thirds of the genes that switched RT during differentiation were strongly expressed when late replicating in one or more cell types. Closer inspection revealed that transcription of this class of genes was frequently restricted to the lineage in which the RT switch occurred, but was induced prior to a late-to-early RT switch and/or down-regulated after an early-to-late RT switch. Analysis of transcriptional regulatory networks showed that this class of genes contains strong regulators of genes that were only expressed when early replicating. These results provide intriguing new insight into the complex relationship between transcription and RT regulation during human development.

Autologous iPSC-derived dopamine neuron transplantation in a nonhuman primate Parkinson's disease model

Autologous dopamine (DA) neurons are a new cell source for replacement therapy of Parkinson's disease (PD). In this study, we tested the safety and efficacy of autologous induced pluripotent stem cell (iPSC)-derived DA cells for treatment of a cynomolgus monkey PD model. Monkey bone marrow mesenchymal cells were isolated and induced to iPSCs, followed by differentiation into DA cells using a method with high efficiency. Autologous DA cells were introduced into the brain of a cynomolgus monkey PD model without immunosuppression; three PD monkeys that had received no grafts served as controls. The PD monkey that had received autologous grafts experienced behavioral improvement compared with that of controls. Histological analysis revealed no overgrowth of grafts and a significant number of surviving A9 region-specific graft-derived DA neurons. The study provided a proof-of-principle to employ iPSC-derived autologous DA cells for PD treatment using a nonhuman primate PD model.

MicroRNAs: New Players in Anesthetic-Induced Developmental Neurotoxicity

Growing evidence demonstrates that prolonged exposure to general anesthetics during brain development induces widespread neuronal cell death followed by long-term memory and learning disabilities in animal models. These studies have raised serious concerns about the safety of anesthetic use in pregnant women and young children. However, the underlying mechanisms of anesthetic-induced neurotoxicity are complex and are not well understood. MicroRNAs are endogenous, small, non-coding RNAs that have been implicated to play important roles in many different disease processes by negatively regulating target gene expression. A possible role for microRNAs in anesthetic-induced developmental neurotoxicity has recently been identified, suggesting that microRNA-based signaling might be a novel target for preventing the neurotoxicity. Here we provide an overview of anesthetic-induced developmental neurotoxicity and focus on the role of microRNAs in the neurotoxicity observed in both human stem cell-derived neuron and animal models. Aberrant expression of some microRNAs has been shown to be involved in anesthetic-induced developmental neurotoxicity, revealing the potential of microRNAs as therapeutic or preventive targets against the toxicity.

Distinct gene expression responses of two anticonvulsant drugs in a novel human embryonic stem cell based neural differentiation assay protocol

Hazard assessment of chemicals and pharmaceuticals is increasingly gaining from knowledge about molecular mechanisms of toxic action acquired in dedicated in vitro assays. We have developed an efficient human embryonic stem cell neural differentiation test (hESTn) that allows the study of the molecular interaction of compounds with the neural differentiation process. Within the 11-day differentiation protocol of the assay, embryonic stem cells lost their pluripotency, evidenced by the reduced expression of stem cell markers Pou5F1 and Nanog. Moreover, stem cells differentiated into neural cells, with morphologically visible neural structures together with increased expression of neural differentiation-related genes such as βIII-tubulin, Map2, Neurogin1, Mapt and Reelin. Valproic acid (VPA) and carbamazepine (CBZ) exposure during hESTn differentiation led to concentration-dependent reduced expression of βIII-tubulin, Neurogin1 and Reelin. In parallel VPA caused an increased gene expression of Map2 and Mapt which is possibly related to the neural protective effect of VPA. These findings illustrate the added value of gene expression analysis for detecting compound specific effects in hESTn. Our findings were in line with and could explain effects observed in animal studies. This study demonstrates the potential of this assay protocol for mechanistic analysis of specific compound-induced inhibition of human neural cell differentiation.

Standardized generation and differentiation of neural precursor cells from human pluripotent stem cells

Precise, robust and scalable directed differentiation of pluripotent stem cells is an important goal with respect to disease modeling or future therapies. Using the AggreWell™400 system we have standardized the differentiation of human embryonic and induced pluripotent stem cells to a neuronal fate using defined conditions. This allows reproducibility in replicate experiments and facilitates the direct comparison of cell lines. Since the starting point for EB formation is a single cell suspension, this protocol is suitable for standard and novel methods of pluripotent stem cell culture. Moreover, an intermediate population of neural precursor cells, which are routinely >95% NCAM(pos) and Tra-1-60(neg) by FACS analysis, may be expanded and frozen prior to differentiation allowing a convenient starting point for downstream experiments.

Vector-free and transgene-free human iPS cells differentiate into functional neurons and enhance functional recovery after ischemic stroke in mice

Stroke is a leading cause of human death and disability in the adult population in the United States and around the world. While stroke treatment is limited, stem cell transplantation has emerged as a promising regenerative therapy to replace or repair damaged tissues and enhance functional recovery after stroke. Recently, the creation of induced pluripotent stem (iPS) cells through reprogramming of somatic cells has revolutionized cell therapy by providing an unlimited source of autologous cells for transplantation. In addition, the creation of vector-free and transgene-free human iPS (hiPS) cells provides a new generation of stem cells with a reduced risk of tumor formation that was associated with the random integration of viral vectors seen with previous techniques. However, the potential use of these cells in the treatment of ischemic stroke has not been explored. In the present investigation, we examined the neuronal differentiation of vector-free and transgene-free hiPS cells and the transplantation of hiPS cell-derived neural progenitor cells (hiPS-NPCs) in an ischemic stroke model in mice. Vector-free hiPS cells were maintained in feeder-free and serum-free conditions and differentiated into functional neurons in vitro using a newly developed differentiation protocol. Twenty eight days after transplantation in stroke mice, hiPS-NPCs showed mature neuronal markers in vivo. No tumor formation was seen up to 12 months after transplantation. Transplantation of hiPS-NPCs restored neurovascular coupling, increased trophic support and promoted behavioral recovery after stroke. These data suggest that using vector-free and transgene-free hiPS cells in stem cell therapy are safe and efficacious in enhancing recovery after focal ischemic stroke in mice.

Isolation and purification of self-renewable human neural stem cells for cell therapy in experimental model of ischemic stroke

Human embryonic stem cells (hESCs) are pluripotent with a strong self-renewable ability making them a virtually unlimited source of neural cells for structural repair in neurological disorders. Currently, hESCs are one of the most promising cell sources amenable for commercialization of off-shelf cell therapy products. However, along with this strong proliferative capacity of hESCs comes the tumorigenic potential of these cells after transplantation. Thus, the isolation and purification of a homogeneous, population of neural stem cells (hNSCs) are of paramount importance to avoid tumor formation in the host brain. This chapter describes the isolation, neuralization, and long-term perpetuation of hNSCs derived from hESCs through use of specific mitogenic growth factors and the preparation of hNSCs for transplantation in an experimental model of stroke. Additionally, we describe methods to analyze the stroke and size of grafts using magnetic resonance imaging and Osirix software, and neuroanatomical tracing procedures to study axonal remodeling after stroke and cell transplantation.

Challenges for stem cells to functionally repair the damaged auditory nerve

INTRODUCTION

In the auditory system, a specialized subset of sensory neurons are responsible for correctly relaying precise pitch and temporal cues to the brain. In individuals with severe-to-profound sensorineural hearing impairment these sensory auditory neurons can be directly stimulated by a cochlear implant, which restores sound input to the brainstem after the loss of hair cells. This neural prosthesis therefore depends on a residual population of functional neurons in order to function effectively.

AREAS COVERED

In severe cases of sensorineural hearing loss where the numbers of auditory neurons are significantly depleted, the benefits derived from a cochlear implant may be minimal. One way in which to restore function to the auditory nerve is to replace these lost neurons using differentiated stem cells, thus re-establishing the neural circuit required for cochlear implant function. Such a therapy relies on producing an appropriate population of electrophysiologically functional neurons from stem cells, and on these cells integrating and reconnecting in an appropriate manner in the deaf cochlea.

EXPERT OPINION

Here we review progress in the field to date, including some of the key functional features that stem cell-derived neurons would need to possess and how these might be enhanced using electrical stimulation from a cochlear implant.

FGF inhibition directs BMP4-mediated differentiation of human embryonic stem cells to syncytiotrophoblast

Bone morphogenetic protein (BMP) signaling is known to support differentiation of human embryonic stem cells (hESCs) into mesoderm and extraembryonic lineages, whereas other signaling pathways can largely influence this lineage specification. Here, we set out to reinvestigate the influence of ACTIVIN/NODAL and fibroblast growth factor (FGF) pathways on the lineage choices made by hESCs during BMP4-driven differentiation. We show that BMP activation, coupled with inhibition of both ACTIVIN/NODAL and FGF signaling, induces differentiation of hESCs, specifically to βhCG hormone-secreting multinucleated syncytiotrophoblast and does not support induction of embryonic and extraembryonic lineages, extravillous trophoblast, and primitive endoderm. It has been previously reported that FGF2 can switch BMP4-induced hESC differentiation outcome to mesendoderm. Here, we show that FGF inhibition alone, or in combination with either ACTIVIN/NODAL inhibition or BMP activation, supports hESC differentiation to hCG-secreting syncytiotrophoblast. We show that the inhibition of the FGF pathway acts as a key in directing BMP4-mediated hESC differentiation to syncytiotrophoblast.

Dopaminergic neurons from midbrain-specified human embryonic stem cell-derived neural stem cells engrafted in a monkey model of Parkinson's disease

The use of human embryonic stem cells (hESCs) to repair diseased or injured brain is promising technology with significant humanitarian, societal and economic impact. Parkinson’s disease (PD) is a neurological disorder characterized by the loss of midbrain dopaminergic (DA) neurons. The generation of this cell type will fulfill a currently unmet therapeutic need. We report on the isolation and perpetuation of a midbrain-specified self-renewable human neural stem cell line (hNSCs) from hESCs. These hNSCs grew as a monolayer and uniformly expressed the neural precursor markers nestin, vimentin and a radial glial phenotype. We describe a process to direct the differentiation of these hNSCs towards the DA lineage. Glial conditioned media acted synergistically with fibroblastic growth factor and leukemia inhibitory factor to induce the expression of the DA marker, tyrosine hydroxylase (TH), in the hNSC progeny. The glial-derived neurotrophic factor did not fully mimic the effects of conditioned media. The hNSCs expressed the midbrain-specific transcription factors Nurr1 and Pitx3. The inductive effects did not modify the level of the glutamic acid decarboxylase (GAD) transcript, a marker for GABAergic neurons, while the TH transcript increased 10-fold. Immunocytochemical analysis demonstrated that the TH-expressing cells did not co-localize with GAD. The transplantation of these DA-induced hNSCs into the non-human primate MPTP model of PD demonstrated that the cells maintain their DA-induced phenotype, extend neurite outgrowths and express synaptic markers.

It's a lipid's world: bioactive lipid metabolism and signaling in neural stem cell differentiation

Lipids are often considered membrane components whose function is to embed proteins into cell membranes. In the last two decades, studies on brain lipids have unequivocally demonstrated that many lipids have critical cell signaling functions; they are called "bioactive lipids". Pioneering work in Dr. Robert Ledeen's laboratory has shown that two bioactive brain sphingolipids, sphingomyelin and the ganglioside GM1 are major signaling lipids in the nuclear envelope. In addition to derivatives of the sphingolipid ceramide, the bioactive lipids discussed here belong to the classes of terpenoids and steroids, eicosanoids, and lysophospholipids. These lipids act mainly through two mechanisms: (1) direct interaction between the bioactive lipid and a specific protein binding partner such as a lipid receptor, protein kinase or phosphatase, ion exchanger, or other cell signaling protein; and (2) formation of lipid microdomains or rafts that regulate the activity of a group of raft-associated cell signaling proteins. In recent years, a third mechanism has emerged, which invokes lipid second messengers as a regulator for the energy and redox balance of differentiating neural stem cells (NSCs). Interestingly, developmental niches such as the stem cell niche for adult NSC differentiation may also be metabolic compartments that respond to a distinct combination of bioactive lipids. The biological function of these lipids as regulators of NSC differentiation will be reviewed and their application in stem cell therapy discussed.

DA neurons derived from hES cells that express HLA-G1 are capable of immunosuppression

Human embryonic stem (hES) cells have the capacity for self-renewal and exhibit multipotentiality. hES cells have promise for serving as an unlimited source of ideal seed cells for cell transplantation. However, the rejection that occurs between the transplant recipient and the transplanted cell poses a major challenge for therapeutic transplantation. This study was designed to devise methods to enhance immune tolerance in cell therapy. We established an hES cell line that could stably express human leukocyte antigen-G1 (HLA-G1). The established HLA-G1-H1 hES cells still retained all the characteristics of normal human embryonic stem cells. By using the SDIA method, we induced dopaminergic (DA) neurons by coculturing HLA-G1-H1 hES cells with the mouse stromal cell line PA6. Tyrosine hydroxylase (TH)+neurons were detected on the 10th day of differentiation, and 70% of the HLA-G1-H1 hES cells were TH+mature DA neurons because the differentiation time was only 3 weeks. Cells that had been differentiating for different periods of time still expressed HLA-G1, and these differentiated DA neurons released dopamine and other catecholamines in response to K+ depolarization as measured by HPLC. After careful study, we found that HLA-G1-H1 hES cells are capable of inhibiting the proliferation of mixed T-lymphocytes. DA neurons derived from HLA-G1-H1 hES attenuated the release of proinflammatory cytokines IL-1β and IFN-γ from lipopolysaccharide (LPS)-stimulated BV2 microglia. The efficiency of inhibition was significant and dose-dependent. This method might be used to treat Parkinson's patients via cell transplantation.

Cell transplantation and gene therapy in Parkinson's disease

Parkinson's disease is a progressive neurodegenerative disorder affecting, in part, dopaminergic motor neurons of the ventral midbrain and their terminal projections that course to the striatum. Symptomatic strategies focused on dopamine replacement have proven effective at remediating some motor symptoms during the course of disease but ultimately fail to deliver long-term disease modification and lose effectiveness due to the emergence of side effects. Several strategies have been experimentally tested as alternatives for Parkinson's disease, including direct cell replacement and gene transfer through viral vectors. Cellular transplantation of dopamine-secreting cells was hypothesized as a substitute for pharmacotherapy to directly provide dopamine, whereas gene therapy has primarily focused on restoration of dopamine synthesis or neuroprotection and restoration of spared host dopaminergic circuitry through trophic factors as a means to enhance sustained controlled dopamine transmission. This seems now to have been verified in numerous studies in rodents and nonhuman primates, which have shown that grafts of fetal dopamine neurons or gene transfer through viral vector delivery can lead to improvements in biochemical and behavioral indices of dopamine deficiency. However, in clinical studies, the improvements in parkinsonism have been rather modest and variable and have been plagued by graft-induced dyskinesias. New developments in stem-cell transplantation and induced patient-derived cells have opened the doors for the advancement of cell-based therapeutics. In addition, viral-vector-derived therapies have been developed preclinically with excellent safety and efficacy profiles, showing promise in clinical trials thus far. Further progress and optimization of these therapies will be necessary to ensure safety and efficacy before widespread clinical use is deemed appropriate.

Directed neural differentiation of duck embryonic germ cells

Although the avian primordial germ cells (PGCs) have been used to produce transgenic birds, their characteristics largely remain unknown. The isolation, culture, biological characterization, and directed neural differentiation of duck EG cells were assayed in this study. The Results showed that the EG cells were got by isolating embryonic gonad and surrounding tissue from 7-day-old duck embryo. The PGCs co-cultured with their gonadal somatic cells were well grown. After passaging, the EG cells were incubated in medium with cytokines and Mitomycin C on inactivated duck embryonic fibroblasts (DEFs) feeder layers. After several passages, alkaline phosphatase (ALP) and periodic acid-Schiff (PAS) resulted positive, cellular markers detection positive for SSEA-1, SSEA-4, TRA-1-60, and TRA-1-81. Karyotype analysis showed the EG cells kept diploid condition and the hereditary feature was stable in accordance with varietal characteristics of duck. These cells grew continuously for 11 passages on DEFs. Under induction of medium with BME, RA, and IBMX, the EG cells lost undifferentiated state, large amount of neural cells appeared with the formation of neural cells networks. Special Nissl body was found by toluidine blue stain after induced for 7 days. Immunofluorescence staining results indicated that differentiated EG cells expressed Nestin, NSE, and GFAP positive. The expression of Nestin, NSE, and GFAP mRNA were positive by RT-PCR. The results revealed that RA can obviously promote the directed differentiation of duck EG cells into neural lineage. The duck EG cells will be useful for the production of transgenic birds, for cell replacement therapy and for studies of germ cell differentiation.

Using human pluripotent stem cells to untangle neurodegenerative disease mechanisms

Human pluripotent stem cells, including embryonic (hES) and induced pluripotent stem cells (hiPS), retain the ability to self-renew indefinitely, while maintaining the capacity to differentiate into all cell types of the nervous system. While human pluripotent cell-based therapies are unlikely to arise soon, these cells can currently be used as an inexhaustible source of committed neurons to perform high-throughput screening and safety testing of new candidate drugs. Here, we describe critically the available methods and molecular factors that are used to direct the differentiation of hES or hiPS into specific neurons. In addition, we discuss how the availability of patient-specific hiPS offers a unique opportunity to model inheritable neurodegenerative diseases and untangle their pathological mechanisms, or to validate drugs that would prevent the onset or the progression of these neurological disorders.

Similarly derived and cultured hESC lines show variation in their developmental potential towards neuronal cells in long-term culture

BACKGROUND

Human embryonic stem cells (hESCs) can differentiate into any human cell type, including CNS cells, and thus have high potential in regenerative medicine. Several protocols exist for neuronal differentiation of hESCs, which do not necessarily work for all hESC lines.

MATERIALS & METHODS

We tested the differentiation capacity of four similarly derived and cultured hESC lines (HS181, HS360, HS362 and HS401) in suspension culture in relatively simple neural differentiation medium for up to 20 weeks.

RESULTS

All the hESC lines differentiated into neuronal cells, but in a line-dependent manner. Using our method, the HS181- and HS360-derived neurospheres differentiated in vitro into pure neuronal cell populations within 6 weeks, whereas HS362 and HS401 reached their peak of differentiation in 12 weeks, but never produced pure neuronal cell populations using the present method. The withdrawal of FGF from suspension culture increased the in vitro differentiation potential. The hESC-derived neurospheres formed functional neuronal networks when replated on a microelectrode array and responded as expected to pharmacologic modulation.

CONCLUSION

Simple neurosphere culture is a suitable method for producing hESC-derived neuronal cells that can form functional neuronal networks from a number of hESC lines. The variation in the differentiation potential of hESC lines into neuronal cells must be carefully considered by those comparing various differentiation methods and designing transplantation therapies for neuronal disorders.

Differential bone-forming capacity of osteogenic cells from either embryonic stem cells or bone marrow-derived mesenchymal stem cells

For more than a decade, human mesenchymal stem cells (hMSCs) have been used in bone tissue-engineering research. More recently some of the focus in this field has shifted towards the use of embryonic stem cells. While it is well known that hMSCs are able to form bone when implanted subcutaneously in immune-deficient mice, the osteogenic potential of embryonic stem cells has been mainly assessed in vitro. Therefore, we performed a series of studies to compare the in vitro and in vivo osteogenic capacities of human and mouse embryonic stem cells to those of hMSCs. Embryonic and mesenchymal stem cells showed all characteristic signs of osteogenic differentiation in vitro when cultured in osteogenic medium, including the deposition of a mineralized matrix and expression of genes involved in osteogenic differentiation. As such, based on the in vitro results, osteogenic ES cells could not be discriminated from osteogenic hMSCs. Nevertheless, although osteogenic hMSCs formed bone upon implantation, osteogenic cells derived from both human and mouse embryonic stem cells did not form functional bone, indicated by absence of osteocytes, bone marrow and lamellar bone. Although embryonic stem cells show all signs of osteogenic differentiation in vitro, it appears that, in contrast to mesenchymal stem cells, they do not possess the ability to form bone in vivo when a similar culture method and osteogenic differentiation protocol was applied.

Stem cell-based models and therapies for neurodegenerative diseases

Multiple neurodegenerative disorders typically result from irrevocable damage and improper functioning of specialized neuronal cells or populations of neuronal cells. These disorders have the potential to contribute to an already overburdened health care system unless the progression of neurodegeneration can be altered. Progress in understanding neurodegenerative cell biology has been hampered by a lack of predictive and, some would claim, relevant cellular models. Additionally, the research needed to develop new drugs and determine methods for repair or replacement of damaged neurons is severely hampered by the lack of an adequate in vitro human neuron cell-based model. In this context, pluripotent stem cells and neural progenitors and their properties including unlimited proliferation, plasticity to generate other cell types, and a readily available source of cells--pose an excellent alternative to ex vivo primary cultures or established immortalized cell lines in contributing to our understanding of neurodegenerative cell biology and our ability to analyze the therapeutic or cytotoxic effects of chemicals, drugs, and xenobiotics. Many questions that define the underlying "genesis" of the neuronal death in these disorders also remain unanswered, with evidence suggesting a key role for mitochondrial dysfunction. The assessment of stem cells, neural progenitors, and engineered adult cells can provide useful insights into neuronal development and neurodegenerative processes. Finally, the potential for a combination of cell- and gene-based therapeutics for neurodegenerative disorders is also discussed.

Application of Multiplex PCR for Characterization of Human Embryonic Stem Cells (hESCs) and Its Differentiated Progenies

Techniques to evaluate gene expression profiling, including real-time quantitative PCR, TaqMan® low-density arrays, and sufficiently sensitive cDNA microarrays, are efficient methods for monitoring human embryonic stem cell (hESC) cultures. However, most of these high-throughput tests have a limited use due to high cost, extended turnaround time, and the involvement of highly specialized technical expertise. Hence, there is a paucity of rapid, cost-effective, robust, yet sensitive methods for routine screening of hESCs. A critical requirement in hESC cultures is to maintain a uniform undifferentiated state and to determine their differentiation capacity by showing the expression of gene markers representing all germ layers, including ecto-, meso-, and endoderm. To quantify the modulation of gene expression in hESCs during their propagation, expansion, and differentiation via embryoid body (EB) formation, the authors developed a simple, rapid, inexpensive, and definitive multimarker, semiquantitative multiplex RT-PCR (mxPCR) platform technology. Among the 15 gene primers tested, 4 were pluripotent markers comprising set 1, and 3 lineage-specific markers from each ecto-, meso-, and endoderm layers were combined as sets 2 to 4, respectively. The authors found that these 4 sets were not only effective in determining the relative differentiation in hESCs, but were easily reproducible. In this study, they used the HUES-7 cell line to standardize the technique, which was subsequently validated with HUES-9, NTERA-2, and mouse embryonic fibroblast cells. This single-reaction mxPCR assay was flexible and, by selecting appropriate reporter genes, can be designed for characterization of different hESC lines during routine maintenance and directed differentiation.

Cell-based therapeutic approaches for Parkinson's disease: progress and perspectives

Motor dysfunctions in Parkinson's disease are believed to be primarily due to the degeneration of dopaminergic neurons located in the substantia nigra pars compacta. Because a single-type cell population is depleted, Parkinson's disease is considered a primary target for cell replacement-based therapeutic strategies. Extensive studies have confirmed transplantation of donor neurons could be beneficial, yet identifying an alternative cell source is clearly essential. Human embryonic stem cells (hESCs) have been proposed as a renewable source of dopaminergic neurons for transplantation in Parkinson's disease; other potential sources could include neural stem cells (hNSCs) and adult mesenchymal stem cells (hMSCs). However, numerous difficulties avert practical application of stem cell-based therapeutic approaches for the treatment of Parkinson's disease. Among the latter, ethical, safety (including xeno- and tumor formation-associated risks) and technical issues stand out. This review aims to provide a balanced and updated outlook on various issues associated with stem cells in regard to their potential in the treatment of Parkinson's disease. Essential features of the individual stem cell subtypes, principles of available differentiation protocols, transplantation, and safety issues are discussed extensively.

Long-term, stable differentiation of human embryonic stem cell-derived neural precursors grafted into the adult mammalian neostriatum

Stem cell grafts have been advocated as experimental treatments for neurological diseases by virtue of their ability to offer trophic support for injured neurons and, theoretically, to replace dead neurons. Human embryonic stem cells (HESCs) are a rich source of neural precursors (NPs) for grafting, but have been questioned for their tendency to form tumors. Here we studied the ability of HESC-derived NP grafts optimized for cell number and differentiation stage prior to transplantation, to survive and stably differentiate and integrate in the basal forebrain (neostriatum) of young adult nude rats over long periods of time (6 months). NPs were derived from adherent monolayer cultures of HESCs exposed to noggin. After transplantation, NPs showed a drastic reduction in mitotic activity and an avid differentiation into neurons that projected via major white matter tracts to a variety of forebrain targets. A third of NP-derived neurons expressed the basal forebrain-neostriatal marker dopamine-regulated and cyclic AMP-regulated phosphoprotein. Graft-derived neurons formed mature synapses with host postsynaptic structures, including dendrite shafts and spines. NPs inoculated in white matter tracts showed a tendency toward glial (primarily astrocytic) differentiation, whereas NPs inoculated in the ventricular epithelium persisted as nestin(+) precursors. Our findings demonstrate the long-term ability of noggin-derived human NPs to structurally integrate tumor-free into the mature mammalian forebrain, while maintaining some cell fate plasticity that is strongly influenced by particular central nervous system (CNS) niches.

Long-term culture and differentiation of CNS precursors derived from anterior human neural rosettes following exposure to ventralizing factors

In this study we demonstrated that neural rosettes derived from human ES cells can give rise either to neural crest precursors, following expansion in presence of bFGF and EGF, or to dopaminergic precursors after exposure to ventralizing factors Shh and FGF8. Both regionalised precursors are capable of extensive proliferation and differentiation towards the corresponding terminally differentiated cell types. In particular, peripheral neurons, cartilage, bone, smooth muscle cells and also pigmented cells were obtained from neural crest precursors while tyrosine hydroxylase and Nurr1 positive dopaminergic neurons were derived from FGF8 and Shh primed rosette cells. Gene expression and immunocytochemistry analyses confirmed the expression of dorsal and neural crest genes such as Sox10, Slug, p75, FoxD3, Pax7 in neural precursors from bFGF-EGF exposed rosettes. By contrast, priming of rosettes with FGF8 and Shh induced the expression of dopaminergic markers Engrailed1, Pax2, Pitx3, floor plate marker FoxA2 and radial glia markers Blbp and Glast, the latter in agreement with the origin of dopaminergic precursors from floor plate radial glia. Moreover, in vivo transplant of proliferating Shh/FGF8 primed precursors in parkinsonian rats demonstrated engraftment and terminal dopaminergic differentiation. In conclusion, we demonstrated the derivation of long-term self-renewing precursors of selected regional identity as potential cell reservoirs for cell therapy applications, such as CNS degenerative diseases, or for the development of toxicological tests.

Epithelial-mesenchymal transition in rhesus monkey embryonic stem cell colonies: the role of culturing conditions

Colonies of rhesus monkey embryonic stem cells (rhESC; cell line R366.4) have been described before to show a spatially ordered process of epithelial-mesenchymal transition in vitro. In the present investigations, we have studied variables of culturing conditions which influence the reproducibility of the formation of crater-like ingression centers in the colonies. Critical parameters are found to be age and density of mouse embryonic fibroblast (MEF) feeder cell layers, the mode of mitotic inactivation of the MEFs (mitomycin C, or irradiation), and the mode of rhESC isolation during subculturing (enzymatic/mechanical cell cluster isolation; type of enzyme). The described culturing system appears to offer a reproducible in vitro model potentially useful for studies on cellular processes involved in gastrulation in the primate.

Treatment with normal prion protein delays differentiation and helps to maintain high proliferation activity in human embryonic stem cells

The normal cellular form of prion protein (PrP(C)) has been shown to exhibit a diverse range of biological activities. Several recent studies highlighted potential involvement of PrP(C) in embryogenesis or in regulating stem cell self-renewal and proliferation. In the current study, we employed human embryonic stem cells (hESCs) for assessing the potential role of prion protein in early human development. Here, we showed that treatment of hESCs with full-length recombinant PrP folded into an alpha-helical conformation similar to that of PrP(C) delayed the spontaneous differentiation of hESCs and helped to maintain their high proliferation activity during spontaneous differentiation. Considering that administration of alpha-rPrP was also found to down-regulate the expression of endogenous PrP(C), the effects of alpha-rPrP were likely to be indirect, i.e. executed by endogenous PrP(C). Together with previous observations, these work support the hypothesis that PrP(C) is involved in regulating self-renewal/differentiation status of stem cells including hESCs.

mAb 84, a cytotoxic antibody that kills undifferentiated human embryonic stem cells via oncosis

The monoclonal antibody mAb 84, which binds to podocalyxin-like protein-1 (PODXL) on human embryonic stem cells (hESCs), was previously reported to bind and kill undifferentiated cells in in vitro and in vivo assays. In this study, we investigate the mechanism responsible for mAb 84-induced hESCs cytotoxicity. Apoptosis was likely not the cause of mAb 84-mediated cell death because no elevation of caspase activities or increased DNA fragmentation was observed in hESCs following incubation with mAb 84. Instead, it was preceded by cell aggregation and damage to cell membranes, resulting in the uptake of propidium iodide, and the leakage of intracellular sodium ions. Furthermore, examination of the cell surface by scanning electron microscopy revealed the presence of pores on the cell surface of mAb 84-treated cells, which was absent from the isotype control. This mechanism of cell death resembles that described for oncosis, a form of cell death resulting from membrane damage. Additional data suggest that the binding of mAb 84 to hESCs initiates a sequence of events prior to membrane damage, consistent with oncosis. Degradation of actin-associated proteins, namely, alpha-actinin, paxillin, and talin, was observed. The perturbation of these actin-associated proteins consequently permits the aggregation of PODXL, thus leading to the formation of pores. To our knowledge, this is the first report of oncotic cell death with hESCs as a model.

Embryonic stem cell biology: insights from molecular imaging

Embryonic stem (ES) cells have therapeutic potential in disorders of cellular loss such as myocardial infarction, type I diabetes and neurodegenerative disorders. ES cell biology in living subjects was largely poorly understood until incorporation of molecular imaging into the field. Reporter gene imaging works by integrating a reporter gene into ES cells and using a reporter probe to induce a signal detectable by normal imaging modalities. Reporter gene imaging allows for longitudinal tracking of ES cells within the same host for a prolonged period of time. This has advantages over postmortem immunohistochemistry and traditional imaging modalities. The advantages include expression of reporter gene is limited to viable cells, expression is conserved between generations of dividing cells, and expression can be linked to a specific population of cells. These advantages were especially useful in studying a dynamic cell population such as ES cells and proved useful in elucidating the biology of ES cells. Reporter gene imaging identified poor integration of differentiated ES cells transplanted into host tissue as well as delayed donor cell death as reasons for poor long-term survival in vivo. This imaging technology also confirmed that ES cells indeed have immunogenic properties that factor into cell survival and differentiation. Finally, reporter gene imaging improved our understanding of the neoplastic risk of undifferentiated ES cells in forming teratomas. Despite such advances, much remains to be understood about ES cell biology to translate this technology to the bedside, and reporter gene imaging will certainly play a key role in formulating this understanding.

nAChRs mediate human embryonic stem cell-derived endothelial cells: proliferation, apoptosis, and angiogenesis

BACKGROUND

Many patients with ischemic heart disease have cardiovascular risk factors such as cigarette smoking. We tested the effect of nicotine (a key component of cigarette smoking) on the therapeutic effects of human embryonic stem cell-derived endothelial cells (hESC-ECs).

METHODS AND RESULTS

To induce endothelial cell differentiation, undifferentiated hESCs (H9 line) underwent 4-day floating EB formation and 8-day outgrowth differentiation in EGM-2 media. After 12 days, CD31(+) cells (13.7+/-2.5%) were sorted by FACScan and maintained in EGM-2 media for further differentiation. After isolation, these hESC-ECs expressed endothelial specific markers such as vWF (96.3+/-1.4%), CD31 (97.2+/-2.5%), and VE-cadherin (93.7+/-2.8%), form vascular-like channels, and incorporated DiI-labeled acetylated low-density lipoprotein (DiI-Ac-LDL). Afterward, 5x10(6) hESC-ECs treated for 24 hours with nicotine (10(-8) M) or PBS (as control) were injected into the hearts of mice undergoing LAD ligation followed by administration for two weeks of vehicle or nicotine (100 microg/ml) in the drinking water. Surprisingly, bioluminescence imaging (BLI) showed significant improvement in the survival of transplanted hESC-ECs in the nicotine treated group at 6 weeks. Postmortem analysis confirmed increased presence of small capillaries in the infarcted zones. Finally, in vitro mechanistic analysis suggests activation of the MAPK and Akt pathways following activation of nicotinic acetylcholine receptors (nAChRs).

CONCLUSIONS

This study shows for the first time that short-term systemic administrations of low dose nicotine can improve the survival of transplanted hESC-ECs, and enhance their angiogenic effects in vivo. Furthermore, activation of nAChRs has anti-apoptotic, angiogenic, and proliferative effects through MAPK and Akt signaling pathways.

A method for rapid derivation and propagation of neural progenitors from human embryonic stem cells

Neuronal loss is a common feature of many neurological disorders, including stroke, Parkinson's disease, Alzheimer's disease and traumatic brain injury. Human embryonic stem cell (hESC)-derived neural progenitors (NPs) may provide new ways of treatment for several diseases and injuries in the brain, as well as enhance our understanding of early human development. Here we report a method for rapid generation of proliferating NPs from feeder free cultures of undifferentiated hESCs. In this rapid and simple protocol, NPs are derived by seeding undifferentiated hESC on adherent surfaces of laminin or gelatine with normal hESC culturing medium and with the addition of basic fibroblast growth factor. After the first passage, adherent monolayer progenitors are derived that express early neuroectodermal and progenitor markers, such as Nestin, Sox1, Sox2, Sox3, Internexin, Musashi-1, NCAM, and Pax6. This novel protocol renders hESCs suitable for large scale progenitor production and long-term propagation, and the progenitors have the capacity to differentiate in vitro into all three neural lineages (neurons, astrocytes and oligodendrocytes). This method allows rapid, cost-efficient production of expandable progenitors that may be a source of cells for the restoration of cellular and functional loss after neurodegeneration and/or provide a useful source of progenitor cells for studying early brain development.