Proteomic identification of differentially expressed genes in mouse neural stem cells and neurons differentiated from embryonic stem cells in vitro

Embryonic stem (ES) cells are pluripotent stem cells and give rise to a variety of differentiated cell types including neurons. To study a molecular basis for differentiation from ES cells to neural cells, we searched for proteins involved in mouse neurogenesis from ES cells to neural stem (NS) cells and neurons by two-dimensional gel electrophoresis (2-DE) and peptide mass fingerprinting, using highly homogeneous cells differentiated from ES cells in vitro. We newly identified seven proteins with increased expression and one protein with decreased expression from ES cells to NS cells, and eight proteins with decreased expression from NS cells to neurons. Western blot analysis confirmed that a tumor-specific transplantation antigen, HS90B, decreased, and an extracellular matrix and membrane glycoprotein (such as laminin)-binding protein, galectin 1 (LEG1), increased in NS cells, and LEG1 and a cell adhesion receptor, laminin receptor (RSSA), decreased in neurons. The results of RT-PCR showed that mRNA of LEG1 was also up-regulated in NS cells and down-regulated in neurons, implying an important role of LEG1 in regulating the differentiation. The differentially expressed proteins identified here provide insight into the molecular basis of neurogenesis from ES cells to NS cells and neurons.     

CMV promotor activity during ES cell differentiation: potential insight into embryonic stem cell differentiation

The activity of the P(CMV IE) promoter was studied during the differentiation of ES cells into neurons. In order to do this, stable embryonic stem (ES) cell lines that express enhanced green fluorescent protein (EGFP) under the control of P(CMV IE) were created and these ES cells were differentiated by aggregation of cells in the presence of retinoic acid (RA). Based on our observations that the activity of P(CMV IE) was highest in undifferentiated cells, and that cell-cell interaction and addition of RA that lead to enhanced cell proliferation also increased expression from P(CMV IE), we hypothesized that the activity of P(CMV IE) was positively regulated in cycling cells. However, when analysis was done at the single cell level it was found that BrdU label and EGFP expression were not correlated. EGFP expression was found to be down-regulated in many cells that were BrdU positive and conversely there were significant numbers of BrdU negative cells that were EGFP positive. Further, P(CMV IE) activity was not observed in cells that were nestin positive or in differentiated neurons, but P(CMV IE) was active in cells with a fibroblast-like morphology. Finally, several proteins present in undifferentiated ES cells were found to bind to regulatory regions of P(CMV IE). These were absent when cells were aggregated in the presence of RA. The above results have implications for expression of transgenes in ES cells as well as providing new insight into the mechanism of lineage restriction.     

Developmental potential of defined neural progenitors derived from mouse embryonic stem cells

The developmental potential of a uniform population of neural progenitors was tested by implanting them into chick embryos. These cells were generated from retinoic acid-treated mouse embryonic stem (ES) cells, and were used to replace a segment of the neural tube. At the time of implantation, the progenitors expressed markers defining them as Pax6-positive radial glial (RG) cells, which have recently been shown to generate most pyramidal neurons in the developing cerebral cortex. Six days after implantation, the progenitors generated large numbers of neurons in the spinal cord, and differentiated into interneurons and motoneurons at appropriate locations. They also colonized the host dorsal root ganglia (DRG) and differentiated into neurons, but, unlike stem cell-derived motoneurons, they failed to elongate axons out of the DRG. In addition, they neither expressed the DRG marker Brn3a nor the Trk neurotrophin receptors. Control experiments with untreated ES cells indicated that when colonizing the DRG, these cells did elongate axons and expressed Brn3a, as well as Trk receptors. Our results thus indicate that ES cell-derived progenitors with RG characteristics generate neurons in the spinal cord and the DRG. They are able to respond appropriately to local cues in the spinal cord, but not in the DRG, indicating that they are restricted in their developmental potential.     

A simplified method to generate serotonergic neurons from mouse embryonic stem and induced pluripotent stem cells

We have developed a new simple method to induce serotonergic neurons from embryonic stem (ES) and induced pluripotent stem cells. When ES or induced pluripotent stem cells were cultured on a thick gel layer of Matrigel, most colonies extended TuJ1-positive neurites. We found that noggin, a known antagonist of bone morphogenic protein, induces ES cells to express genes involved in serotonergic differentiation, such as Nkx2.2, Pet-1, Sonic hedgehog, tryptophan hydroxylase 2, and serotonin transporter, as well as increases high potassium-induced release of serotonin. To concentrate serotonergic neurons, ES cells carrying Pet-1-enhancer-driven enhanced green fluorescent protein were differentiated and sorted into about 80% pure cultures of serotonergic neurons. Whole cell voltage-clamp recordings showed a voltage-dependent current in dissociated neurons. This simplified method provides an alternative option for serotonergic differentiation of pluripotent stem cells and will likely contribute a deeper understanding regarding the nature of serotonergic neurons and open new therapeutic perspectives for the treatment of psychiatric disorders.     

Differentiation patterns of mouse embryonic stem cells and induced pluripotent stem cells into neurons

Mouse embryonic stem (ES) cells and induced pluripotent stem (iPS) cells have the ability to differentiate in vitro into various cell lineages including neurons. The differentiation of these cells into neurons has potential applications in regenerative medicine. Previously, we reported that a chick dorsal root ganglion (DRG)-conditioned medium (CM) promoted the differentiation of mouse ES and iPS cells into neurons. Here, we used real-time PCR to investigate the differentiation patterns of ES and iPS cells into neurons when DRG-CM was added. DRG-CM promoted the expression levels of βIII-tubulin gene (a marker of postmitotic neurons) in ES and iPS cells. ES cells differentiated into neurons faster than iPS cells, and the maximum peaks of gene expression involved in motor, sensory, and dopaminergic neurons were different. Rho kinase (ROCK) inhibitors could be very valuable at numerous stages in the production and use of stem cells in basic research and eventual cell-based therapies. Thus, we investigated whether the addition of a ROCK inhibitor Y-27632 and DRG-CM on the basis of the differentiation patterns promotes the neuronal differentiation of ES cells. When the ROCK inhibitor was added to the culture medium at the initial stages of cultivation, it stimulated the neuronal differentiation of ES cells more strongly than that stimulated by DRG-CM. Moreover, the combination of the ROCK inhibitor and DRG-CM promoted the neuronal differentiation of ES cells when the ROCK inhibitor was added to the culture medium at day 3. The ROCK inhibitor may be useful for promoting neuronal differentiation of ES cells.     

小鼠胚胎干细胞分化扩增期连续低密度传代对原始细胞中Oct-4阳性细胞比例及神经分化能力的影响

目的：探讨在分化扩增期采用连续低密度传代的方法是否能降低小鼠胚胎干细胞向神经细胞分化的前体细胞中Oct-4阳性细胞的比例,以及对神经分化能力的影响。方法：采用“五步法”将小鼠胚胎干细胞向神经元分化,进入扩增期后采用连续低密度传代的方法连续传10代。然后应用细胞免疫组化鉴定Oct-4阳性细胞、神经元与胶质细胞、流式细胞仪检测Oct-4阳性细胞比例、凋亡试剂盒测定细胞凋亡。结果：流式细胞仪检测出扩增期连续低密度传代得到的前体细胞中Oct-4阳性细胞的比例由16.17±4.8％降至4.33±1.63％,扩增期低密度传代细胞和正常高密度传代细胞的细胞凋亡率鉴定分别为15.16±3.64% 和11.88±2.63%,步骤5诱导分化后的细胞GFAP和Tuj-1免疫组化染色呈阴性。结论：低密度传代培养可以减少分化后Oct-4阳性细胞的比例,且该比例下降不是由Oct-4阳性细胞的凋亡引起的。同时可能是因为低密度传代培养和高密度相比引起了细胞的质变、或者改变了前体细胞向神经元分化的某种微环境,导致了前体细胞不能分化为神经细胞。提示高密度培养在前体细胞向神经元分化过程中具有重要作用,高密度和低密度培养的比较,提供了研究ES细胞向神经元分化机制的新平台和研究方向。     

Differentiation of rhesus embryonic stem cells to neural progenitors and neurons

Embryonic stem (ES) cells are pluripotent cells capable of differentiating into cell lineages derived from all primary germ layers including neural cells. In this study we describe an efficient method for differentiating rhesus monkey ES cells to neural lineages and the subsequent isolation of an enriched population of Nestin and Musashi positive neural progenitor (NP) cells. Upon differentiation, these cells exhibit electrophysiological characteristics resembling cultured primary neurons. Embryoid bodies (EBs) were formed in ES growth medium supplemented with 50% MEDII. After 7 days in suspension culture, EBs were transferred to adherent culture and either differentiated in serum containing medium or expanded in serum free medium. Immunocytochemistry on differentiating cells derived from EBs revealed large networks of MAP-2 and NF200 positive neurons. DAPI staining showed that the center of the MEDII-treated EBs was filled with rosettes. NPs isolated from adherent EB cultures expanded in serum free medium were passaged and maintained in an undifferentiated state by culture in serum free N2 with 50% MEDII and bFGF. Differentiating neurons derived from NPs fired action potentials in response to depolarizing current injection and expressed functional ionotropic receptors for the neurotransmitters glutamate and gamma-aminobutyric acid (GABA). NPs derived in this way could serve as models for cellular replacement therapy in primate models of neurodegenerative disease, a source of neural cells for toxicity and drug testing, and as a model of the developing primate nervous system.     

Region-specific generation of functional neurons from naive embryonic stem cells in adult brain

Embryonic stem (ES) cells are multipotent progenitors with unlimited developmental potential, and in vitro differentiated ES cell-derived neuronal progenitors can develop into functional neurons when transplanted in the central nervous system. As the capacity of naive primary ES cells to integrate in the adult brain and the role of host neural tissue therein are yet largely unknown, we grafted low densities of undifferentiated mouse ES (mES) cells in adult mouse brain regions associated with neurodegenerative disorders; and we demonstrate that ES cell-derived neurons undergo gradual integration in recipient tissue and acquire morphological and electrophysiological properties indistinguishable from those of host neurons. Only some brain areas permitted survival of mES-derived neural progenitors and formed instructive environments for neuronal differentiation and functional integration of naive mES cells. Hence, region-specific presence of microenvironmental cues and their pivotal involvement in controlling ES cell integration in adult brain stress the importance of recipient tissue characteristics in formulating cell replacement strategies for neurodegenerative disorders.     

In vitro differentiation of transplantable neural precursors from human embryonic stem cells.

The remarkable developmental potential and replicative capacity of human embryonic stem (ES) cells promise an almost unlimited supply of specific cell types for transplantation therapies. Here we describe the in vitro differentiation, enrichment, and transplantation of neural precursor cells from human ES cells. Upon aggregation to embryoid bodies, differentiating ES cells formed large numbers of neural tube-like structures in the presence of fibroblast growth factor 2 (FGF-2). Neural precursors within these formations were isolated by selective enzymatic digestion and further purified on the basis of differential adhesion. Following withdrawal of FGF-2, they differentiated into neurons, astrocytes, and oligodendrocytes. After transplantation into the neonatal mouse brain, human ES cell-derived neural precursors were incorporated into a variety of brain regions, where they differentiated into both neurons and astrocytes. No teratoma formation was observed in the transplant recipients. These results depict human ES cells as a source of transplantable neural precursors for possible nervous system repair.     

Oligoprogenitor Cells Derived from Spermatogonia Stem Cells Improve Remyelination in Demyelination Model

Embryonic stem (ES) like cells-derived testis represents a possible alternative to replace of neurons and glia. Here, we differentiated spermatogonia cells to oligoprogenitor (OP) like cells and transplanted them to demyelination model and assess their recovery potential in a demyelinated corpus callosum model in rats. ES like cells were differentiated to OP like cells using appropriate inducers and were transplanted in situ to demyelinated corpus callosum. Cell integration as well as demyelination extension and myelination intensity changes were evaluated using histologic studies and immunocytochemistry after 2 and 4 weeks post transplantation. Investigation of Nestin, NF68, Olig2, and NG2 by immunocytochemical technique indicated the differentiation of ES like cells to neuroprogenitor and oligodendrocyte like cells in each induction stage. Histologic findings showed a significant decrease in demyelination extension and a significant increase in remyelination intensity in cell transplanted groups. Also on the base of PLP expression, differentiation of transplanted cells was confirmed to myelinogenic cells using immunocytochemistry technique. We conclude that ES like cells derived from spermatogonia cells can be differentiated to OP like cells that can form myelin after transplantation into the demyelination model in rat, this represents recovery potential of spermatogonia cells which opens new window for cell therapeutic approaches using spermatogonial stem cells.     

Neuronal differentiation of cryopreserved neural progenitor cells derived from mouse embryonic stem cells

Embryonic stem cells (ES cells) are developmentally pluripotent cells isolated from pre-implantation mammalian embryos. In cell culture ES cells can be easily differentiated to generate cultures of neural progenitors. We present a simple method for the cryopreservation of these ES-derived neural progenitors. Cryopreserved neural progenitor stocks can be thawed, expanded with FGF2, and differentiated into functional neurons. This method will facilitate studies using ES-derived neural progenitor cells as a cell culture model system for neural development and differentiation. It will also aid studies designed to test the ability of these progenitor cells to functionally engraft and repair damaged neural tissue.     

ES cell-derived neuroepithelial cell cultures

ES cells have the potential to differentiate into cells from all germ layers, which makes them an attractive tool for the development of new therapies. In general, the differentiation of ES cells follows the concept to first generate immature progenitor cells, which then can be propagated and differentiated into mature cellular phenotypes. This also applies for ES cell-derived neurogenesis, in which the development of neural cells follows two major steps: First, the derivation and expansion of immature neuroepithelial precursors and second, their differentiation into mature neural cells. A common method to produce neural progenitors from ES cells is based on embryoid body (EB) formation, which reveals the differentiation of cells from all germ layers including neuroectoderm. An alternative and more efficient method to induce neuroepithelial cell development uses stromal cell-derived inducing activity (SDIA), which can be achieved by co-culturing ES cells with skull bone marrow-derived stromal cells. Both, EB formation and SDIA, reveal the development of rosette-like structures, which are thought to resemble neural tube- and/or neural crest-like progenitors. The neural precursors can be isolated, expanded and further differentiated into specific neurons and glia cells using defined culture conditions. Here, we describe the generation and isolation of such rosettes in co-culture experiments with the stromal cell line MS5 (2-5).     

Detection of Calcium Transients in Embryonic Stem Cells and Their Differentiated Progeny

A central issue in stem cell biology is the determination of function and activity of differentiated stem cells, features that define the true phenotype of mature cell types. Commonly, physiological mechanisms are used to determine the functionality of mature cell types, including those of the nervous system. Calcium imaging provides an indirect method of determining the physiological activities of a mature cell. Camgaroos are variants of yellow fluorescent protein that act as intracellular calcium sensors in transfected cells. We expressed one version of the camgaroos, Camgaroo-2, in mouse embryonic stem (ES) cells under the control of the CAG promoter system. Under the control of this promoter, Camgaroo-2 fluorescence was ubiquitously expressed in all cell types derived from the ES cells that were tested. In response to pharmacological stimulation, the fluorescence levels in transfected cells correlated with cellular depolarization and hyperpolarization. These changes were observed in both undifferentiated ES cells as well as ES cells that had been neurally induced, including putative neurons that were differentiated from transfected ES cells. The results presented here indicate that Camgaroo-2 may be used like traditional fluorescent proteins to track cells as well as to study the functionality of stem cells and their progeny.     

Differentiation of mouse induced pluripotent stem cells into neurons using conditioned medium of dorsal root ganglia

Mouse induced pluripotent stem (iPS) cells are known to have the ability to differentiate into various cell lineages including neurons in vitro. We have reported that chick dorsal root ganglion (DRG)-conditioned medium (CM) promoted the differentiation of mouse embryonic stem (ES) cells into motor neurons. We investigated the formation of undifferentiated iPS cell colonies and the differentiation of iPS cells into neurons using DRG-CM. When iPS cells were cultured in DMEM containing leukemia inhibitory factor (LIF), the iPS cells appeared to be maintained in an undifferentiated state for 19 passages. The number of iPS cell colonies (200 μm in diameter) was maximal at six days of cultivation and the colonies were maintained in an undifferentiated state, but the iPS cell colonies at ten days of cultivation had hollows inside the colonies and were differentiated. By contrast, the number of ES cell colonies (200 μm in diameter) was maximal at ten days of cultivation. The iPS cells were able to proliferate and differentiate easily into various cell lineages, compared to ES cells. When iPS cell colonies were cultured in a manner similar to ES cells with DMEM/F-12K medium supplemented with DRG-CM, the iPS cells mainly differentiated into motor and sensory neurons. These results suggested that the differentiation properties of iPS cells differ from those of ES cells.     

Embryonic stem cell-derived neural progenitors as non-tumorigenic source for dopaminergic neurons

AIM:To find a safe source for dopaminergic neurons,we generated neural progenitor cell lines from human embryonic stem cells.METHODS:The human embryonic stem(hES)cell line H9 was used to generate human neural progenitor(HNP)cell lines.The resulting HNP cell lines were differentiated into dopaminergic neurons and analyzed by quantitative real-time polymerase chain reaction and immunofluorescence for the expression of neuronal differentiation markers,including beta-III tubulin(TUJ1)and tyrosine hydroxylase(TH).To assess the risk of teratoma or other tumor formation,HNP cell lines and mouse neuronal progenitor(MNP)cell lines were injected subcutaneously into immunodeficient SCID/beige mice.RESULTS:We developed a fairly simple and fast protocol to obtain HNP cell lines from hES cells.These cell lines,which can be stored in liquid nitrogen for several years,have the potential to differentiate in vitro into dopaminergic neurons.Following day 30 of differentiation culture,the majority of the cells analyzed expressed the neuronal marker TUJ1 and a high proportion of these cells were positive for TH,indicating differentiation into dopaminergic neurons.In contrast to H9 ES cells,the HNP cell lines did not form tumors in immunodeficient SCID/beige mice within 6 mo after subcutaneous injection.Similarly,no tumors developed after injection of MNP cells.Notably,mouse ES cells or neuronal cells directly differentiated from mouse ES cells formed teratomas in more than 90%of the recipients.CONCLUSION:Our findings indicate that neural progenitor cell lines can differentiate into dopaminergic neurons and bear no risk of generating teratomas or other tumors in immunodeficient mice.     

Embryonic stem cells as a model for studying regulation of cellular differentiation

Mouse embryonic stem (ES) cells can be differentiated in vitro into near homogeneous populations of both neurons and skeletal muscle as well as other cell types. We previously showed that treatment of pluripotent ES cells with retinoic acid (RA) induced differentiation into highly enriched populations of gamma-aminobutyric acid (GABA) expressing neurons. The reasons for generation of only GABA neurons as opposed to other neuronal cell types were not known. We have extended our previous work and now show that with RA induction of ES cells we not only obtain GABA neurons, but also dopaminergic neurons. Critical for the production of dopaminergic neurons after RA induction was the post-induction plating conditions used. No dopaminergic neurons were detected if cells were plated in serum-free media optimized for neuronal survival. However, significant numbers of dopamine neurons could be detected when cells were plated in media containing fetal calf serum. These observations support the conclusion that RA acts as a general neural inducing agent and that conditions post-induction either selectively support survival of a particular class of neuronal cells or that the conditions post-induction actually further instruct cells to differentiate into different types of neurons.     

Neural progenitors from human embryonic stem cells.

The derivation of neural progenitor cells from human embryonic stem (ES) cells is of value both in the study of early human neurogenesis and in the creation of an unlimited source of donor cells for neural transplantation therapy. Here we report the generation of enriched and expandable preparations of proliferating neural progenitors from human ES cells. The neural progenitors could differentiate in vitro into the three neural lineages--astrocytes, oligodendrocytes, and mature neurons. When human neural progenitors were transplanted into the ventricles of newborn mouse brains, they incorporated in large numbers into the host brain parenchyma, demonstrated widespread distribution, and differentiated into progeny of the three neural lineages. The transplanted cells migrated along established brain migratory tracks in the host brain and differentiated in a region-specific manner, indicating that they could respond to local cues and participate in the processes of host brain development. Our observations set the stage for future developments that may allow the use of human ES cells for the treatment of neurological disorders.     

Naive-like Conversion Overcomes the Limited Differentiation Capacity of Induced Pluripotent Stem Cells

Although induced pluripotent stem (iPS) cells are indistinguishable from ES cells in their expression of pluripotent markers, their differentiation into targeted cells is often limited. Here, we examined whether the limited capacity of iPS cells to differentiate into neural lineage cells could be mitigated by improving their base-line level of pluripotency, i.e. by converting them into the so-called “naive” state. In this study, we used rabbit iPS and ES cells because of the easy availability of both cell types and their typical primed state characters. Repeated passages of the iPS cells permitted their differentiation into early neural cell types (neural stem cells, neurons, and glial astrocytes) with efficiencies similar to ES cells. However, unlike ES cells, their ability to differentiate later into neural cells (oligodendrocytes) was severely compromised. In contrast, after these iPS cells had been converted to a naive-like state, they readily differentiated into mature oligodendrocytes developing characteristic ramified branches, which could not be attained even with ES cells. These results suggest that the naive-like conversion of iPS cells might endow them with a higher differentiation capacity.