Global gene and cell replacement strategies via stem cells

Prospect of Stem Cells as Promising Therapy for Brachial Plexus Injury: A Systematic Review

Background

Brachial plexus injury is an advanced and devastating neurological injury, for which both nerve surgery and tendon transfers sometimes remain insufficient in restoring normal movement. Stem cell therapy may be applicable to rescue the injured motor neurons from degeneration which potentially improves muscle strength.

Study Design

Systematic Review; Level of evidence V.

Data Sources

A systematic literature search was conducted on PubMed (MEDLINE), EMBASE, the Cochrane Library, and Scopus using the terms ("stem cell") AND ("brachial plexus") as search keywords.

Methods

The process of study selection was summarized by PRISMA flow diagram. The study included in vivo and in vitro studies with English language, humans or animals with some brachial plexus injuries, interventions, some applications of stem cells to the groups of study, with functional, biomechanical, or safety outcomes.

Results

In total, there were 199 studies identified from the literature sources where 75 articles were qualified for forward evaluation following selecting the titles and abstracts. Ten studies were finally included in this systematic review after full-text assessment. Stem cells can produce neurotrophic factors in vitro and in vivo in rats, and their level was increased after injury. Electrophysiological measurement showed that the intervention group had distinctly higher CMAP amplitude and evidently shorter CMAP latency than the model group. Application of bone marrow stem cells (BMSCs) showed an elevation in the numbers of axons and density of myelinated fibers, the density of nerve fibers, the diameter of regenerating axons, and a decrease in axonal degeneration. A study in humans indicated an improvement of the movements in a patient with traumatic total BPI after injection of Ad-MSC. It is associated with increased muscle mass and sensory recovery and also suggested that mononuclear cell injection enhances muscle regeneration and reinnervation in the partly denervated muscle of brachial plexus injury. Various muscle groups had obtained strength together with restoration, the muscle strength attained after the previous transplantation were preserved. The results of this review support stem cell treatment in brachial plexus injury.

Conclusion

This review provides evidence of the positive effects of stem cell treatment in brachial plexus injury.

Delayed Maturation of Oligodendrocyte Progenitors by Microgravity: Implications for Multiple Sclerosis and Space Flight

In previous studies, we examined the effects of space microgravity on human neural stem cells. To date, there are no studies on a different type of cell that is critical for myelination and electrical signals transmission, oligodendrocyte progenitors (OLPs). The purpose of the present study was to examine the behavior of space-flown OLPs (SPC-OLPs) as they were adapting to Earth's gravity. We found that SPC-OLPs survived, and most of them proliferated normally. Nonetheless, some of them displayed incomplete cytokinesis. Both morphological and ontogenetic analyses showed that they remained healthy and expressed the immature OLP markers Sox2, PDGFR-α, and transferrin (Tf) after space flight, which confirmed that SPC-OLPs displayed a more immature phenotype than their ground control (GC) counterparts. In contrast, GC OLPs expressed markers that usually appear later (GPDH, O4, and ferritin), indicating a delay in SPC-OLPs' development. These cells remained immature even after treatment with culture media designed to support oligodendrocyte (OL) maturation. The most remarkable and surprising finding was that the iron carrier glycoprotein Tf, previously described as an early marker for OLPs, was expressed ectopically in the nucleus of all SPC-OLPs. In contrast, their GC counterparts expressed it exclusively in the cytoplasm, as previously described. In addition, analysis of the secretome demonstrated that SPC-OLPs contained 3.5 times more Tf than that of GC cells, indicating that Tf is gravitationally regulated, opening two main fields of study to understand the upregulation of the Tf gene and secretion of the protein that keep OLPs at a progenitor stage rather than moving forward to more mature phenotypes. Alternatively, because Tf is an autocrine and paracrine factor in the central nervous system (CNS), in the absence of neurons, it accumulated in the secretome collected after space flight. We conclude that microgravity is becoming a novel platform to study why in some myelin disorders OLPs are present but do not mature.

Metabolic Labeling of Live Stem Cell for In Vitro Imaging and In Vivo Tracking

Stem cell therapy offers promising solutions to diseases and injuries that traditional medicines and therapies can't effectively cure. To get and explain their full therapeutic potentials, the survival, viability, integration, homing, and differentiation of stem cells after transplant must be clearly understood. To meet these urgent needs, noninvasive stem cell imaging and tracking technologies have been developed. Metabolic labeling technique is one of the most powerful tools for live cell imaging and tracking. In addition, it has many advantages for in vivo live cell imaging and tracking such as low background, correlation of survival, and very toxic and nontoxic by-products. Herein, we described the fundamental information and process of metabolic labeling techniques and suggested optimal condition for in vitro and in vivo imaging and tracking of human umbilical cord blood-derived endothelial progenitor cells (hUCB-EPCs). Based on this study, metabolic labeling techniques can be helpful for understanding the safety and effectiveness of stem cell-based therapy and determining the utility of stem cells in downstream experiments.

Advanced nanotherapies to promote neuroregeneration in the injured newborn brain

Neonatal brain injury affects thousands of babies each year and may lead to long-term and permanent physical and neurological problems. Currently, therapeutic hypothermia is standard clinical care for term newborns with moderate to severe neonatal encephalopathy. Nevertheless, it is not completely protective, and additional strategies to restore and promote regeneration are urgently needed. One way to ensure recovery following injury to the immature brain is to augment endogenous regenerative pathways. However, novel strategies such as stem cell therapy, gene therapies and nanotechnology have not been adequately explored in this unique age group. In this perspective review, we describe current efforts that promote neuroprotection and potential targets that are unique to the developing brain, which can be leveraged to facilitate neuroregeneration.

Lentivirus-mediated microRNA-26a-modified neural stem cells improve brain injury in rats with cerebral palsy

This study is launched to investigate the effect of lentivirus-mediated microRNA-26a (miR-26a)-modified neural stem cells (NSCs) in brain injury in rats with cerebral palsy (CP). The successfully constructed miR-26a lentivirus expression vector and empty vector virus were used to modify NSCs. The model of CP with ischemia and anoxia was established in rats. NSCs and miR-26a-NSCs were stereoscopically injected into the cerebral cortex of the modeled rats, respectively. The survival and migration of NSCs infected with recombinant lentivirus expressing green fluorescence in vivo was observed under a light microscope. The neurobehavioral functions, morphology, and ultrastructure of cerebral cortex and hippocampus, apoptosis of brain cells, expression of apoptosis-related protein caspase-3 and Bax, together with the expression of the glial fibrillary acidic protein (GFAP) in cerebral cortex and hippocampus were determined. Expression of miR-26a in NSCs infected with plVTHM-miR-26a increased significantly. After NSCs transplantation, the neurobehavioral status of CP rats was improved, the degree of brain pathological injury was alleviated, the apoptotic index of cells in cerebral cortex and hippocampus and the expression of the apoptotic protein (caspase-3 and Bax) were decreased, the expression of GFAP were significantly decreased. After miR-26a-NSCs transplantation, these aforementioned results further improved or decreased. Our study suggests that miR-26a-modified NSCs mediated by lentivirus can improve brain injury, inhibit apoptosis of brain cells and activation of astrocytes in CP rats.

HIV Non-Nucleoside Reverse Transcriptase Inhibitor Efavirenz Reduces Neural Stem Cell Proliferation in Vitro and in Vivo

The prevalence of HIV-associated neurocognitive disorders (HAND) remains high despite combination antiretroviral therapy (cART). There is evidence that neural stem cells (NSCs) can migrate to sites of brain injury such as those caused by inflammation and oxidative stress, which are pathological features of HAND. Thus, reductions in NSCs may contribute to HAND pathogenesis. Since the HIV non-nucleoside reverse transcriptase inhibitor efavirenz (EFV) has previously been associated with cognitive deficits and promotion of oxidative stress pathways, we examined its effect on NSCs in vitro as well as in C57BL/6J mice. Here we report that EFV induced a decrease in NSC proliferation in vitro as indicated by MTT assay, as well as BrdU and nestin immunocytochemistry. In addition, EFV decreased intracellular NSC adenosine triphosphate (ATP) stores and NSC mitochondrial membrane potential (MMP). Further, we found that EFV promoted increased lactate dehydrogenase (LDH) release, activation of p38 mitogen-activated protein kinase (MAPK), and increased Bax expression in cultured NSCs. Moreover, EFV reduced the quantity of proliferating NSCs in the subventricular zone (SVZ) of C57BL/6J mice as suggested by BrdU, and increased apoptosis as measured by active caspase-3 immunohistochemistry. If these in vitro and in vivo models translate to the clinical syndrome, then a pharmacological or cell-based therapy aimed at opposing EFV-mediated reductions in NSC proliferation may be beneficial to prevent or treat HAND in patients receiving EFV.

Combined Medication of Antiretroviral Drugs Tenofovir Disoproxil Fumarate, Emtricitabine, and Raltegravir Reduces Neural Progenitor Cell Proliferation In Vivo and In Vitro

The application of combination antiretroviral therapy has greatly reduced the death rate from AIDS. However, up to 50% of patients on combination antiretroviral therapy develop HIV-associated neurocognitive disorders (HAND), which is associated with residual neuroinflammation and oxidative injury in the brain. Neural stem cells (NSCs) and progenitors play a vital role in repairing neuronal injuries. Therefore, we hypothesize that combination antiretroviral therapy may adversely affect NSCs/progenitors, contributing to the increasing prevalence of HAND. Here, we show that combined medication of three antiretroviral drugs tenofovir disoproxil fumarate (TDF), emtricitabine (FTC), and raltegravir (RAL) affects NSC homeostasis and progenitor proliferation in the mouse dentate gyrus (DG). Our results also show that TDF/FTC/RAL treatment prohibits proliferation and induces apoptosis of cultured mouse neural progenitor cells (NPCs), resulting in a reduction in the viability of NPCs. Moreover, we find that TDF, among the three drugs used in this combination antiretroviral treatment, accounts for most of the effects on neural progenitors. Together, our results offer a mechanistic explanation for the prevalence of HAND in AIDS patients treated with combination antiretroviral therapy.

ProBDNF inhibits proliferation, migration and differentiation of mouse neural stem cells

ProBDNF, a precursor of brain-derived neurotrophic factor (BDNF), is an important regulator of neurodegeneration, hippocampal long-term depression, and synaptic plasticity. ProBDNF and its receptors pan-neurotrophin receptor p75 (p75NTR), vps10p domain-containing receptor Sortilin and tropomyosin receptor kinase B (TrkB) are expressed in neuronal and glial cells. The role of proBDNF in regulation of neurogenesis is not fully defined. This study aims to uncover the function of proBDNF in regulating the differentiation, migration and proliferation of mouse neural stem cells (NSCs) in vitro. We have found that proBDNF and its receptors are constitutively expressed in NSCs when assessed by immunocytochemistry and western blotting. MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay showed that exogenous proBDNF treatment reduced mouse NSCs viability by 38% at 10ng/mL. The migration of NSCs was also reduced by exogenous proBDNF treatment in a concentration-dependent manner (by 90% at 10ng/mL) but increased by anti-proBDNF antibody treatment (by 50%). BrdU (5-Bromo-2'-Deoxyuridine) incorporation was performed for detection of newborn cells. We have found that proBDNF significantly inhibited proliferation of NSCs and reduced the number of differentiated neurons, oligodendrocytes and astrocytes, while anti-proBDNF antibody treatment promoted proliferation and differentiation of NSCs. In conclusion, proBDNF may oppose the functions of mature BDNF by inhibiting the proliferation, differentiation and migration of NSCs during development. Conversely, anti-proBDNF antibody treatment promoted proliferation and differentiation of NSCs.

The effect of magnetic nanoparticles on neuronal differentiation of induced pluripotent stem cell-derived neural precursors

Introduction

Magnetic resonance (MR) imaging is suitable for noninvasive long-term tracking. We labeled human induced pluripotent stem cell-derived neural precursors (iPSC-NPs) with two types of iron-based nanoparticles, silica-coated cobalt zinc ferrite nanoparticles (CZF) and poly-l-lysine-coated iron oxide superparamagnetic nanoparticles (PLL-coated γ-Fe₂O₃) and studied their effect on proliferation and neuronal differentiation.

Materials and methods

We investigated the effect of these two contrast agents on neural precursor cell proliferation and differentiation capability. We further defined the intracellular localization and labeling efficiency and analyzed labeled cells by MR.

Results

Cell proliferation was not affected by PLL-coated γ-Fe₂O₃ but was slowed down in cells labeled with CZF. Labeling efficiency, iron content and relaxation rates measured by MR were lower in cells labeled with CZF when compared to PLL-coated γ-Fe₂O₃. Cytoplasmic localization of both types of nanoparticles was confirmed by transmission electron microscopy. Flow cytometry and immunocytochemical analysis of specific markers expressed during neuronal differentiation did not show any significant differences between unlabeled cells or cells labeled with both magnetic nanoparticles.

Conclusion

Our results show that cells labeled with PLL-coated γ-Fe₂O₃ are suitable for MR detection, did not affect the differentiation potential of iPSC-NPs and are suitable for in vivo cell therapies in experimental models of central nervous system disorders.

Efficacy of Two Delivery Routes for Transplanting Human Neural Progenitor Cells (NPCs) Into the Spastic Han-Wistar Rat, a Model of Ataxia

An emerging avenue for recalcitrant neurodegenerative disease treatment is neural progenitor cell (NPC) transplantation. In this study, we investigated the effectiveness of two different delivery routes of human-derived NPC inoculation: injection into the common carotid artery or unilateral stereotactic implantation into the degenerating cerebellum and hippocampus of spastic Han-Wistar (sHW) rats, a model of ataxia. At 30 days of age, sHW mutants were implanted with osmotic pumps preloaded with cyclosporine. Ten days after pump implantation, the animals were given either 3,000,000 live human-derived NPCs (hNPCs; n = 12) or 3,000,000 dead NPCs (dNPCs; n = 12) injected into the common carotid artery, or were given two unilateral implantations of 500,000 hNPCs into the cerebellum and 500,000 hNPCs into the hippocampus of each sHW rat (n = 12) or 500,000 dNPCs by unilateral implantation into the cerebellum and hippocampus (n = 12). We also compared treated sHW rats to untreated sHW rats: normal rats (n = 12) and sibling sHW rats (n = 12). Motor activity and animal weights were monitored every 5 days to ascertain effectiveness of the two types of delivery methods compared to the untreated mutant and normal animals. Mutant rats with hNPC implantations, but not dNPC or carotid artery injections, showed significant deceleration of motor deterioration (p < 0.05). These mutants with hNPC implantations also retained weight longer than dNPC mutants did (p < 0.05). At the end of the experiment, animals were sacrificed for histological evaluation. Using fluorescent markers (Qtracker) incorporated into the hNPC prior to implantation and human nuclear immunostaining, we observed few hNPCs in the brains of carotid artery-injected mutants. However, significant numbers of surviving hNPCs were seen using these techniques in mutant cerebellums and hippocampi implanted with hNPC. Our results show that direct implantation of hNPCs reduced ataxic symptoms in the sHW rat, demonstrating that stereotactic route of stem cell delivery correlates to improved clinical outcomes.

Neurotrophin Signaling and Stem Cells-Implications for Neurodegenerative Diseases and Stem Cell Therapy

Neurotrophins (NTs) are members of a neuronal growth factor protein family whose action is mediated by the tropomyosin receptor kinase (TRK) receptor family receptors and the p75 NT receptor (p75NTR), a member of the tumor necrosis factor (TNF) receptor family. Although NTs were first discovered in neurons, recent studies have suggested that NTs and their receptors are expressed in various types of stem cells mediating pivotal signaling events in stem cell biology. The concept of stem cell therapy has already attracted much attention as a potential strategy for the treatment of neurodegenerative diseases (NDs). Strikingly, NTs, proNTs, and their receptors are gaining interest as key regulators of stem cells differentiation, survival, self-renewal, plasticity, and migration. In this review, we elaborate the recent progress in understanding of NTs and their action on various stem cells. First, we provide current knowledge of NTs, proNTs, and their receptor isoforms and signaling pathways. Subsequently, we describe recent advances in the understanding of NT activities in various stem cells and their role in NDs, particularly Alzheimer's disease (AD) and Parkinson's disease (PD). Finally, we compile the implications of NTs and stem cells from a clinical perspective and discuss the challenges with regard to transplantation therapy for treatment of AD and PD.

Efficient Generation of Viral and Integration-Free Human Induced Pluripotent Stem Cell-Derived Oligodendrocytes

Here we document three highly reproducible protocols: (1) a culture system for the derivation of human oligodendrocytes (OLs) from human induced pluripotent stem cells (hiPS) and their further maturation-our protocol generates viral- and integration-free OLs that efficiently commit and move forward in the OL lineage, recapitulating all the steps known to occur during in vivo development; (2) a method for the isolation, propagation and maintenance of neural stem cells (NSCs); and (3) a protocol for the production, isolation, and maintenance of OLs from perinatal rodent and human brain-derived NSCs. Our unique culture systems rely on a series of chemically defined media, specifically designed and carefully characterized for each developmental stage of OL as they advance from OL progenitors to mature, myelinating cells. We are confident that these protocols bring our field a step closer to efficient autologous cell replacement therapies and disease modeling. © 2016 by John Wiley & Sons, Inc.

Transplantation of vascular endothelial growth factor-modified neural stem/progenitor cells promotes the recovery of neurological function following hypoxic-ischemic brain damage

Neural stem/progenitor cell (NSC) transplantation has been shown to effectively improve neurological function in rats with hypoxic-ischemic brain damage. Vascular endothelial growth factor (VEGF) is a signaling protein that stimulates angiogenesis and improves neural regeneration. We hypothesized that transplantation of VEGF-transfected NSCs would alleviate hypoxic-ischemic brain damage in neonatal rats. We produced and transfected a recombinant lentiviral vector containing the VEGF₁₆₅ gene into cultured NSCs. The transfected NSCs were transplanted into the left sensorimotor cortex of rats 3 days after hypoxic-ischemic brain damage. Compared with the NSCs group, VEGF mRNA and protein expression levels were increased in the transgene NSCs group, and learning and memory abilities were significantly improved at 30 days. Furthermore, histopathological changes were alleviated in these animals. Our findings indicate that transplantation of VEGF-transfected NSCs may facilitate the recovery of neurological function, and that its therapeutic effectiveness is better than that of unmodified NSCs.

Targeting breast to brain metastatic tumours with death receptor ligand expressing therapeutic stem cells

Characterizing clinically relevant brain metastasis models and assessing the therapeutic efficacy in such models are fundamental for the development of novel therapies for metastatic brain cancers. In this study, we have developed an in vivo imageable breast-to-brain metastasis mouse model. Using real time in vivo imaging and subsequent composite fluorescence imaging, we show a widespread distribution of micro- and macro-metastasis in different stages of metastatic progression. We also show extravasation of tumour cells and the close association of tumour cells with blood vessels in the brain thus mimicking the multi-foci metastases observed in the clinics. Next, we explored the ability of engineered adult stem cells to track metastatic deposits in this model and show that engineered stem cells either implanted or injected via circulation efficiently home to metastatic tumour deposits in the brain. Based on the recent findings that metastatic tumour cells adopt unique mechanisms of evading apoptosis to successfully colonize in the brain, we reasoned that TNF receptor superfamily member 10A/10B apoptosis-inducing ligand (TRAIL) based pro-apoptotic therapies that induce death receptor signalling within the metastatic tumour cells might be a favourable therapeutic approach. We engineered stem cells to express a tumour selective, potent and secretable variant of a TRAIL, S-TRAIL, and show that these cells significantly suppressed metastatic tumour growth and prolonged the survival of mice bearing metastatic breast tumours. Furthermore, the incorporation of pro-drug converting enzyme, herpes simplex virus thymidine kinase, into therapeutic S-TRAIL secreting stem cells allowed their eradication post-tumour treatment. These studies are the first of their kind that provide insight into targeting brain metastasis with stem-cell mediated delivery of pro-apoptotic ligands and have important clinical implications.

Human olfactory bulb neural stem cells expressing hNGF restore cognitive deficit in Alzheimer's disease rat model

In this study, we aim to demonstrate the fate of allogenic adult human olfactory bulb neural stem/progenitor cells (OBNSC/NPCs) transplanted into the rat hippocampus treated with ibotenic acid (IBO), a neurotoxicant specific to hippocampal cholinergic neurons that are lost in Alzheimer's disease. We assessed their possible ability to survive, integrate, proliferate, and differentiate into different neuronal and glial elements: we also evaluate their possible therapeutic potential, and the mechanism(s) relevant to neuroprotection following their engraftment into the CNS milieu. OBNSC/NPCs were isolated from adult human olfactory bulb patients, genetically engineered to express GFP and human nerve growth factor (hNGF) by lentivirus-mediated infection, and stereotaxically transplanted into the hippocampus of IBO-treated animals and controls. Stereological analysis of engrafted OBNSCs eight weeks post transplantation revealed a 1.89 fold increase with respect to the initial cell population, indicating a marked ability for survival and proliferation. In addition, 54.71 ± 11.38%, 30.18 ± 6.00%, and 15.09 ± 5.38% of engrafted OBNSCs were identified by morphological criteria suggestive of mature neurons, oligodendrocytes and astrocytes respectively. Taken together, this work demonstrated that human OBNSCs expressing NGF ameliorate the cognitive deficiencies associated with IBO-induced lesions in AD model rats, and the improvement can probably be attributed primarily to neuronal and glial cell replacement as well as the trophic influence exerted by the secreted NGF.

Response of the sensorimotor cortex of cerebral palsy rats receiving transplantation of vascular endothelial growth factor 165-transfected neural stem cells

Neural stem cells are characterized by the ability to differentiate and stably express exogenous ge-nes. Vascular endothelial growth factor plays a role in protecting local blood vessels and neurons of newborn rats with hypoxic-ischemic encephalopathy. Transplantation of vascular endothelial growth factor-transfected neural stem cells may be neuroprotective in rats with cerebral palsy. In this study, 7-day-old Sprague-Dawley rats were divided into five groups: (1) sham operation (control), (2) cerebral palsy model alone or with (3) phosphate-buffered saline, (4) vascular endothelial growth factor 165 + neural stem cells, or (5) neural stem cells alone. The cerebral palsy model was established by ligating the left common carotid artery followed by exposure to hypoxia. Phosphate-buffered saline, vascular endothelial growth factor + neural stem cells, and neural stem cells alone were administered into the sensorimotor cortex using the stereotaxic instrument and microsyringe. After transplantation, the radial-arm water maze test and holding test were performed. Immunohistochemistry for vascular endothelial growth factor and histology using hematoxylin-eosin were performed on cerebral cortex. Results revealed that the number of vascular endothelial growth factor-positive cells in cerebral palsy rats transplanted with vascular endothelial growth factor-transfected neural stem cells was increased, the time for finding water and the finding repetitions were reduced, the holding time was prolonged, and the degree of cell degeneration or necrosis was reduced. These findings indicate that the transplantation of vascular endothelial growth factor-transfected neural stem cells alleviates brain damage and cognitive deficits, and is neuroprotective in neonatal rats with hypoxia ischemic-mediated cerebral palsy.

Primate adult brain cell autotransplantation produces behavioral and biological recovery in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonian St. Kitts monkeys

The potential for "replacement cells" to restore function in Parkinson's disease has been widely reported over the past 3 decades, rejuvenating the central nervous system rather than just relieving symptoms. Most such experiments have used fetal or embryonic sources that may induce immunological rejection and generate ethical concerns. Autologous sources, in which the cells to be implanted are derived from recipients' own cells after reprogramming to stem cells, direct genetic modifications, or epigenetic modifications in culture, could eliminate many of these problems. In a previous study on autologous brain cell transplantation, we demonstrated that adult monkey brain cells, obtained from cortical biopsies and kept in culture for 7 weeks, exhibited potential as a method of brain repair after low doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) caused dopaminergic cell death. The present study exposed monkeys to higher MPTP doses to produce significant parkinsonism and behavioral impairments. Cerebral cortical cells were biopsied from the animals, held in culture for 7 weeks to create an autologous neural cell "ecosystem" and reimplanted bilaterally into the striatum of the same six donor monkeys. These cells expressed neuroectodermal and progenitor markers such as nestin, doublecortin, GFAP, neurofilament, and vimentin. Five to six months after reimplantation, histological analysis with the dye PKH67 and unbiased stereology showed that reimplanted cells survived, migrated bilaterally throughout the striatum, and seemed to exert a neurorestorative effect. More tyrosine hydroxylase-immunoreactive neurons and significant behavioral improvement followed reimplantation of cultured autologous neural cells as a result of unknown trophic factors released by the grafts.

Encapsulated stem cells for cancer therapy

Stem cells have inherent tumor‑trophic migratory properties and can serve as vehicles for delivering effective, targeted therapy to isolated tumors and metastatic disease, making them promising anti‑cancer agents. Encapsulation of therapeutically engineered stem cells in hydrogels has been utilized to provide a physical barrier to protect the cells from hostile extrinsic factors and significantly improve the therapeutic efficacy of transplanted stem cells in different models of cancer. This review aims to discuss the potential of different stem cell types for cancer therapy, various engineered stem cell based therapies for cancer, stem cell encapsulation process and provide an in depth overview of current applications of therapeutic stem cell encapsulation in the highly malignant brain tumor, glioblastoma multiforme (GBM), as well as the prospects for their clinical translation.

Neurotrophin-induced migration and neuronal differentiation of multipotent astrocytic stem cells in vitro

Hypoxic ischemic encephalopathy (HIE) affects 2-3 per 1000 full-term neonates. Up to 75% of newborns with severe HIE die or have severe neurological handicaps. Stem cell therapy offers the potential to replace HIE-damaged cells and enhances the autoregeneration process. Our laboratory implanted Multipotent Astrocytic Stem Cells (MASCs) into a neonatal rat model of hypoxia-ischemia (HI) and demonstrated that MASCs move to areas of injury in the cortex and hippocampus. However, only a small proportion of the implanted MASCs differentiated into neurons. MASCs injected into control pups did not move into the cortex or differentiate into neurons. We do not know the mechanism by which the MASCs moved from the site of injection to the injured cortex. We found neurotrophins present after the hypoxic-ischemic milieu and hypothesized that neurotrophins could enhance the migration and differentiation of MASCs. Using a Boyden chamber device, we demonstrated that neurotrophins potentiate the in vitro migration of stem cells. NGF, GDNF, BDNF and NT-3 increased stem cell migration when compared to a chemokinesis control. Also, MASCs had increased differentiation toward neuronal phenotypes when these neurotrophins were added to MASC culture tissue. Due to this finding, we believed neurotrophins could guide migration and differentiation of stem cell transplants after brain injury.

Gene expression profile of adult human olfactory bulb and embryonic neural stem cell suggests distinct signaling pathways and epigenetic control

Global gene expression profiling was performed using RNA from human embryonic neural stem cells (hENSC), and adult human olfactory bulb-derived neural stem cells (OBNSCs), to define a gene expression pattern and signaling pathways that are specific for each cell lineage. We have demonstrated large differences in the gene expression profile of human embryonic NSC, and adult human OBNSCs, but less variability between parallel cultures. Transcripts of genes involved in neural tube development and patterning (ALDH1A2, FOXA2), progenitor marker genes (LMX1a, ALDH1A1, SOX10), proliferation of neural progenitors (WNT1 and WNT3a), neuroplastin (NPTN), POU3F1 (OCT6), neuroligin (NLGN4X), MEIS2, and NPAS1 were up-regulated in both cell populations. By Gene Ontology, 325 out of 3875 investigated gene sets were scientifically different. 41 out of the 307 investigated Cellular Component (CC) categories, 45 out of the 620 investigated Molecular Function (MF) categories, and 239 out of the 2948 investigated Biological Process (BP) categories were significant. KEGG Pathway Class Comparison had revealed that 75 out of 171 investigated gene sets passed the 0.005 significance threshold. Levels of gene expression were explored in three signaling pathways, Notch, Wnt, and mTOR that are known to be involved in NS cell fates determination. The transcriptional signature also deciphers the role of genes involved in epigenetic modifications. SWI/SNF DNA chromatin remodeling complex family, including SMARCC1 and SMARCE1, were found specifically up-regulated in our OBNSC but not in hENSC. Differences in gene expression profile of transcripts controlling epigenetic modifications, and signaling pathways might indicate differences in the therapeutic potential of our examined two cell populations in relation to in cell survival, proliferation, migration, and differentiation following engraftments in different CNS insults.

Plasma membrane-associated glycohydrolases along differentiation of murine neural stem cells

The activities of plasma membrane associated sialidase Neu3, total β-glucosidase, CBE-sensitive β-glucosidase, non-lysosomal β-glucosyl ceramidase GBA2, β-galactosidase, β-hexosaminidase and sphingomyelinase were determined at three different stages of differentiation of murine neural stem cell cultures, corresponding to precursors, commited progenitors, and differentiated cells. Cell immunostaining for specific markers of the differentiation process, performed after 7 days in culture in presence of differentiating agents, clearly showed the presence of oligodendrocytes, astrocytes and neurons. Glial cells were the most abundant. Sialidase Neu3 after a decrease from progenitors to precursors, showed an increase parallel to the differentiation process. All the other glycosidases increased their activity along differentiation. The activity of CBE-sensitive β-glucosidase and GBA2 were very similar at the precursor stage, but CBE-sensitive β-glucosidase increased 7 times while GBA2 only two in the differentiated cells. In addition, we analysed also sphingomyelinase as enzyme specifically associated to sphingolipids. The activity of this enzyme increased from precursors to differentiated cells.

Neuroprotection of VEGF-expression neural stem cells in neonatal cerebral palsy rats

Cerebral palsy (CP) is a very common neural system development disorder that can cause physical disability in human. Here, we studied the neuroprotective effect of vascular endothelial growth factor (VEGF)-transfected neural stem cells (NSCs) in newborn rats with cerebral palsy (CP). Seven-day-old Sprague-Dawley rats were randomly divided into four groups: sham operation (control group), PBS transplantation (PBS group), VEGF+NSCs transplantation (transgene NSCs group) and NSCs transplantation groups (NSCs group). PBS, Transgene NSCs and NSCs groups respectively received stereotactic injections of PBS, lentiviral vector (pGC-FU-VEGF) infected NSCs or a NSCs suspension in the left sensory-motor cortex 3 days after CP model was established. The NSCs activity, their impacts on neural cell growth and apoptosis, brain development and animal behaviors were examined on the animals up to age 35-days. As expected, unilateral carotid artery occlusion plus hypoxia (cerebral palsy model) resulted in severe neural developmental disorders, including slowed growth, increased in cortical neuron apoptosis, decreased cerebral cortex micro-vessel density and retarded behavior developments. Transplantation of NSCs not only resulted in increases in VEGF protein expression in rat brains, but also largely prevented the behavioral defects and brain tissue pathology that resulted from cerebral palsy procedure, with animals received VEGF transfected NSCs always being marginally better than these received un-transfected cells. In conclusion, NSCs transplantation can partially prevent/slow down the brain damages that are associated with CP in the newborn rats, suggesting a new possible strategy for CP treatment.

Neural stem cell gene therapy ameliorates pathology and function in a mouse model of globoid cell leukodystrophy

Murine neural stem cells (mNSCs), either naive or genetically modified to express supranormal levels of β-galactocerebrosidase (GALC), were transplanted into the brain of Twitcher mice, a murine model of globoid cell leukodystrophy, a severe sphingolipidosis. Cells engrafted long-term into the host cytoarchitecture, producing functional GALC. Levels of enzyme activity in brain and spinal cord tissues were enhanced when GALC-overexpressing NSC were used. Enzymatic correction correlated with reduced tissue storage, decreased activation of astroglia and microglia, delayed onset of symptoms, and longer lifespan. Mechanisms underlying the therapeutic effect of mNSC included widespread enzyme distribution, cross-correction of host cells, anti-inflammatory activity, and neuroprotection. Similar cell engraftment and metabolic correction were reproduced using human NSC. Thus, NSC gene therapy rapidly reconstitutes sustained and long-lasting enzyme activity in central nervous system tissues. Combining this approach with treatments targeting the systemic disease associated with leukodystrophies may provide significant therapeutic benefit. Stem Cells 2011;29:1559–1571

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.

Neural stem cells: properties and therapeutic potentials for hypoxic-ischemic brain injury in newborn infants

Neural stem cells (NSCs) are defined by their ability to self-renew, to differentiate into cells of all glial and neuronal lineages throughout the neuraxis, and to populate developing or degenerating central nervous system (CNS) regions. The recognition that NSCs propagated in culture could be reimplanted into the mammalian brain, where they might integrate appropriately throughout the mammalian CNS and stably express foreign genes, has unveiled a new role for neural transplantation and gene therapy and a possible strategy for addressing the CNS manifestations of diseases that hitherto had been refractory to intervention. An intriguing phenomenon with possible therapeutic potentials has begun to emerge from our observations of the behavior of NSCs in animal models of neonatal hypoxic-ischemic (HI) brain injury. During phases of active neurodegeneration, factors seem to be transiently elaborated to which NSCs may respond by migrating to degenerating regions and differentiating specifically towards replacement of dying neural cells. NSCs may attempt to repopulate and reconstitute ablated regions. These 'repair mechanisms' may actually reflect the reexpression of basic developmental principles that may be harnessed for therapeutic ends. In addition, NSCs may serve as vehicles for gene delivery and appear capable of simultaneous neural cell replacement and gene therapy (e.g. with factors that might enhance neuronal differentiation, neurites outgrowth, proper connectivity, and/or neuroprotection). When combined with certain synthetic biomaterials, NSCs may be even more effective in 'engineering' the damaged CNS towards reconstitution. We have also cultured human NSCs or progenitors as neurospheres which were derived from fetal cadavers at 13 weeks of gestation, and transplanted them into HI-injured immature brains to investigate their therapeutic potentials in this type of model.

Optimal time point for neuronal generation of transplanted neural progenitor cells in injured spinal cord following root avulsion

Root avulsion of the brachial plexus results in a progressive and pronounced loss of motoneurons. Cell replacement strategies have therapeutic potential in the treatment of motoneuron degenerative neurological disorders. Here, we transplanted spinal cord-derived neural progenitor cells (NPCs) into the cervical ventral horn of adult rats immediately, 2 weeks, or 6 weeks after root avulsion to determine an optimal time scale for the survival and differentiation of grafted cells. We showed that grafted NPCs survived robustly at all three time points and there was no statistical difference in survival rate. Interestingly, however, transplantation at 2 weeks postavulsion significantly increased the neuronal differentiation of transplanted NPCs compared to transplantation immediately or at 6 weeks postavulsion. Moreover, only NPCs transplanted at 2 weeks postavulsion were able to differentiate into choline acetyltransferase (ChAT)-positive neurons. Specific ELISAs and quantitative reverse transcriptase polymerase chain reaction (RT-PCR) demonstrated that expression levels of BDNF and GDNF were significantly upregulated in the ventral cord at 2 weeks postavulsion compared to immediately or at 6 weeks postavulsion. Our study suggests that the cervical ventral horn at 2 weeks postavulsion both supports neuronal differentiation and induces region-specific neuronal generation possibly because of its higher expression of BDNF and GDNF.

Culture and manipulation of neural stem cells

Despite advances in the treatment of cancer, the prognosis of patient diagnosed with metastatis cancer to the brain remains poor. The role of neural stem cells as a viable tool in the treatment of metastatic cancer to the brain alone or in conjuction with current therapeutic modalities is promising. Both murine and human neural stem cells (NSCs) have been shown to migrate through the central nervous system (CNS) and infiltrate tumors and other pathological disease states of the brain. Genetic modification of NSCs to produce cytotoxic or immunomodulatory agents in the vicinity of a primary tumor and/or satellite lesion or has proven instrumental to the reduction of tumor bulk in murine models. Although the use of stem cells proves to be a volatile social topic, scientists have discovered that NSCs are present in the adult brain and continue to propagate and differentiate. These cells may be isolated and cultured to produce clonal NSC lines that are capable of self renewal and differentiation when introduced into the CNS. In this chapter, we describe protocols currently used in ourlab for the successful maintenance of NSCs in vitro advancing the role of neural stem cells in the treatment of brain tumors.

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.

Culture system for rodent and human oligodendrocyte specification, lineage progression, and maturation

Here we document protocols for the production, isolation, and maintenance of the oligodendrocyte phenotype from rodent and human neural stem cells. Our unique method relies on a series of chemically defined media, specifically designed and carefully characterized for each developmental stage of oligodendrocytes as they advance from oligodendrocyte progenitors to mature, myelinating oligodendrocytes.

Bone marrow mononuclear cells have neurovascular tropism and improve diabetic neuropathy

Bone marrow-derived mononuclear cells (BMNCs) have been shown to effectively treat ischemic cardiovascular diseases. Because diabetic neuropathy (DN) is causally associated with impaired angiogenesis and deficiency of angiogenic and neurotrophic factors in the nerves, we investigated whether DN can be ameliorated by local injection of BMNCs. Severe peripheral neuropathy, characterized by a significant decrease in the motor and sensory nerve conduction velocities (NCVs), developed 12 weeks after the induction of diabetes with streptozotocin in rats. The injection of BMNCs restored motor and sensory NCVs to normal levels and significantly improved vascular density and blood flow in diabetic nerves over 4 weeks. Fluorescent microscopic observation revealed that DiI-labeled BMNCs preferentially engrafted in sciatic nerves. Whole-mount fluorescent imaging and confocal microscopic evaluation demonstrated that many of the BMNCs localized following the course of the vasa nervorum in close proximity to blood vessels without incorporation into vasa nervorum as endothelial cells at a detectable level. Real-time reverse transcription-polymerase chain reaction analysis showed that the levels of angiogenic and neurotrophic factors were significantly increased in the nerves by BMNC injection. Local transplantation of BMNCs improved experimental DN by augmenting angiogenesis and increasing angiogenic and neurotrophic factors in peripheral nerves. These findings suggest that BMNC transplantation may represent a novel therapeutic option for treating DN.

Neural progenitor cells enhance the survival and axonal regeneration of injured motoneurons after transplantation into the avulsed ventral horn of adult rats

In the present study, we transplanted E13.5 spinal cord-derived neural progenitor cells (NPCs) into the acutely avulsed ventral horn of adult rats. The results showed that NPCs survived and integrated nicely within the host ventral horn at 6 weeks post-grafting. Although the majority of grafted NPCs differentiated into astrocytes and only a small proportion into neuronal cells, interestingly, grafted NPCs in the avulsed ventral horn significantly enhanced the survival of injured motoneurons and promoted their regeneration into a peripheral nerve (PN) graft, as revealed by retrograde FluoroGold (FG) labeling. Specific ELISAs, Western blotting, and quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR) demonstrated that NPCs produced nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and glial cell line-derived neutrophilic factor (GDNF), both in vitro and after transplantation in vivo. These results indicate that NPCs have beneficial effects on the survival and axonal regeneration of avulsion-injured motoneurons after transplantation. Such beneficial effects are possibly due to their inherent ability to secrete various trophic factors after transplantation in vivo.

The identification of proteoglycan, collagen and neuron in precursor cells from human fetal spinal cord

After spinal cord injury (SCI), a loss of myelinating oligodendrocytes and neurons occurs. The functional recovery of injured spinal cords is the principal objective of SCI repair. Cell transplantation may prove beneficial to help replace lost myelin and spinal cord circuitry. In this study, we demonstrated that neural precursor cells (hNPCs) from human fetal spinal cord express three types of proteoglycan proteins-chondroitin sulfate, keratan sulfate, and cartilage proteoglycan (an extracellular matrix detected in normal spinal cord), and non-proteoglycan matrix collagen. Both proteoglycan and collagen evidenced profound immunoreactivity in double-stained cell clusters. In addition, whether or not hNPCs were capable of differentiating into a variety of cells, including GABAergic and cholinergic neurons, were assessed. The differentiated cells of eight passages grown on a monolayer expressed the human nuclear protein (HNu), the progenitor marker nestin, GAD, ChAT, TJU, and MAP-2. These results indicate that hNPCs may prove to be candidate cells for therapeutic SCI strategies.

Long-term multilayer adherent network (MAN) expansion, maintenance, and characterization, chemical and genetic manipulation, and transplantation of human fetal forebrain neural stem cells

Human neural stem/precursor cells (hNSC/hNPC) have been targeted for application in a variety of research models and as prospective candidates for cell-based therapeutic modalities in central nervous system (CNS) disorders. To this end, the successful derivation, expansion, and sustained maintenance of undifferentiated hNSC/hNPC in vitro, as artificial expandable neurogenic micro-niches, promises a diversity of applications as well as future potential for a variety of experimental paradigms modeling early human neurogenesis, neuronal migration, and neurogenetic disorders, and could also serve as a platform for small-molecule drug screening in the CNS. Furthermore, hNPC transplants provide an alternative substrate for cellular regeneration and restoration of damaged tissue in neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. Human somatic neural stem/progenitor cells (NSC/NPC) have been derived from a variety of cadaveric sources and proven engraftable in a cytoarchitecturally appropriate manner into the developing and adult rodent and monkey brain while maintaining both functional and migratory capabilities in pathological models of disease. In the following unit, we describe a new procedure that we have successfully employed to maintain operationally defined human somatic NSC/NPC from developing fetal, pre-term post-natal, and adult cadaveric forebrain. Specifically, we outline the detailed methodology for in vitro expansion, long-term maintenance, manipulation, and transplantation of these multipotent precursors.

Human neural stem cell grafts in the spinal cord of SOD1 transgenic rats: differentiation and structural integration into the segmental motor circuitry

Cell replacement strategies for degenerative and traumatic diseases of the nervous system depend on the functional integration of grafted cells into host neural circuitry, a condition necessary for the propagation of physiological signals and, perhaps, targeting of trophic support to injured neurons. We have recently shown that human neural stem cell (NSC) grafts ameliorate motor neuron disease in SOD1 transgenic rodents. Here we study structural aspects of integration of neuronally differentiated human NSCs in the motor circuitry of SOD1 G93A rats. Human NSCs were grafted into the lumbar protuberance of 8-week-old SOD1 G93A rats; the results were compared to those on control Sprague-Dawley rats. Using pre-embedding immuno-electron microscopy, we found human synaptophysin (+) terminals contacting the perikarya and proximal dendrites of host alpha motor neurons. Synaptophysin (+) terminals had well-formed synaptic vesicles and were associated with membrane specializations primarily in the form of symmetrical synapses. To analyze the anatomy of motor circuits engaging differentiated NSCs, we injected the retrograde transneuronal tracer Bartha-pseudorabies virus (PRV) or the retrograde marker cholera toxin B (CTB) into the gastrocnemius muscle/sciatic nerve of SOD1 rats before disease onset and also into control rats. With this tracing, NSC-derived neurons were labeled with PRV but not CTB, a pattern suggesting that PRV entered NSC-derived neurons via transneuronal transfer from host motor neurons but not via direct transport from the host musculature. Our results indicate an advanced degree of structural integration, via functional synapses, of differentiated human NSCs into the segmental motor circuitry of SOD1-G93A rats.

Primate adult brain cell autotransplantation, a pilot study in asymptomatic MPTP-treated monkeys

Autologous brain cell transplantation might be useful for repairing lesions and restoring function of the central nervous system. We have demonstrated that adult monkey brain cells, obtained from cortical biopsy and kept in culture for a few weeks, exhibit neural progenitor characteristics that make them useful for brain repair. Following MPTP treatment, primates were dopamine depleted but asymptomatic. Autologous cultured cells were reimplanted into the right caudate nucleus of the donor monkey. Four months after reimplantation, histological analysis by stereology and TH immunolabeling showed that the reimplanted cells successfully survived, bilaterally migrated in the whole striatum, and seemed to have a neuroprotection effect over time. These results may add a new strategy to the field of brain neuroprotection or regeneration and could possibly lead to future clinical applications.

Vascular endothelial growth factor-stimulated cerebral microvascular endothelial cells mediate the recruitment of neural stem cells to the neurovascular niche

Endogenous and transplanted neural stem cells (NSC) are highly migratory and display a unique tropism for areas of neuro-pathology. However, signals controlling NSC motility in health and disease are still ill-defined. NSC appear to be intimately associated with the cerebral vasculature and angiogenesis is a hallmark of many neurological disorders. This has led us to investigate the influence of quiescent and angiogenically active human endothelial cells on human NSC migration. In vivo we observed frequent perivascular accumulation of human NSC in the proximity of cerebral microvessels upon induction of angiogenesis by cerebral infusion of vascular endothelial growth factor (VEGF) into the murine brain. We analyzed the in vitro effects of conditioned media from human endothelial cells before and after angiogenic stimulation with VEGF on the migration of human NSC in vitro. Non-stimulated endothelial cells induced a moderate chemotactic migration that was significantly enhanced after angiogenic activation by VEGF. In order to identify cytokines that may function as stimulators of NSC chemotaxis, we screened endothelial cell-conditioned media for the expression of 120 different cytokines. We identified PDGF-BB, RANTES, I-TAC, NAP-2, GROalpha, Ang-2, and M-CSF as endothelial cell-released chemoattractants for human NSC in vitro. VEGF-stimulated cerebral microvascular endothelial cells secreted higher levels of Ang-2 and GROalpha, which in part were responsible for the enhanced chemoattraction of NSC. Our findings support the hypothesis that the angiogenically active microvasculature modulates the local guidance of NSC through endothelial cell-derived chemoattractants.

Human mesenchymal stem cell culture for neural transplantation

Mesenchymal stem cells (MSCs) have the potential to play a role in autologous repair of central nervous system injury or disease, circumventing both the complications associated with immune rejection of allogenic cells, and many of the ethical concerns associated with embryonic stem cell use. Human bone marrow-derived MSCs can be extracted relatively simply from the marrow of adult patients and maintained and expanded in culture. More importantly, it has been previously demonstrated that MSCs have the capacity to differentiate into neurons and glia in vitro when grown under appropriate conditions. Multipotent MSCs have also been successfully used in transplantation studies in animal models of disease as diverse as demyelination, stroke, trauma and Parkinson's disease. MSCs therefore provide an attractive and practical source of stem cells for reparative therapy in patients, and in this paper we describe methods for the reproducible culture and neural differentiation of human MSCs generated from patient marrow.

Important precautions when deriving patient-specific neural elements from pluripotent cells

Multipotent human neural stem cells (hNSC) have traditionally been isolated directly from the central nervous system (CNS). To date, as a therapeutic tool in the treatment of neurologic disorders, the most promising results have been obtained using hNSC isolated directly from the human fetal neuroectoderm. The propagation ability of such tissue-derived hNSC is often limited, however, making it difficult to establish a large-scale culture. Following engraftment, these hNSC often show low efficiency in generating the desired neuronal cells necessary for reconstruction of the damaged host milieu and, as a result, have failed to give satisfactory results in clinical trials so far. Alternatively, human embryonic stem cells (hESC) offer a pluripotent reservoir for in vitro derivation of a rich spectrum of well-characterized neural-lineage committed stem/progenitor/precursor cells that can, theoretically, be picked at precisely their safest and most efficacious state of plasticity to meet a given clinical challenge. However, the need for 'foreign' biologic additives and multilineage differentiation inclination may make direct use of such cell-derived hNSC in patients problematic. The hNSC, when derived from pluripotent cells under protocols presently employed in the field, tend to display not only a low efficiency in neuronal differentiation, but also an inclination for phenotypic heterogeneity and instability and, hence, increased risk of tumorigenesis following engraftment. For hNSC derived in vitro to be used safely in therapeutic paradigms, it requires conversion of human pluripotent cells uniformly to cells that are restricted to the neural lineage in need of repair. Developing strategies for direct induction of human pluripotent cells exclusively into neural-committed progenies at a broad range of developmental stages will allow a large supply of optimal therapeutic hNSC tailor-made for safe and effective treatment of particular neurologic diseases and injuries in patients.

Proteomics of neural stem cells

The isolation of neural stem cells from fetal and adult mammalian CNS and the demonstration of functional neurogenesis in adult CNS have offered perspectives for treatment of many devastating hereditary and acquired neurological diseases. Due to this enormous potential, neural stem cells are a subject of extensive molecular profiling studies with a search for new markers and regulatory pathways governing their self-renewal as opposed to differentiation. Several in-depth proteomic studies have been conducted on primary or immortalized cultures of neural stem cells and neural progenitor cells, and yet more remains to be done. Additionally, neurons and glial cells have been obtained from embryonic stem cells and mesenchymal stem cells, and proteins associated with the differentiation process have been characterized to a certain degree with a view to further investigations. This review summarizes recent findings relevant to the proteomics of neural stem cells and discusses major proteins significantly regulated during neural stem cell differentiation with a view to their future use in cell-based regenerative and reparative therapy.

Fetal striatum- and ventral mesencephalon-derived expanded neurospheres rescue dopaminergic neurons in vitro and the nigro-striatal system in vivo

The pathogenesis of Parkinson's disease (PD) involves ongoing apoptotic loss of dopaminergic neurons in the substantia nigra pars compacta. Local delivery of the trophic factors can rescue dopaminergic neurons and halt the progression of PD. In this study we show that fetal E11 striatum-derived neurospheres and E14.5 ventral mesencephalon (VM) -derived neurospheres (NS E11 and NSvm, respectively) are a source of factors that rescue dopaminergic neurons. First, long-term expanded NS E11 and NSvm rescued primary dopaminergic neurons from serum-deprivation induced apoptosis and promoted survival of dopaminergic neurons for 14 days in vitro and this effect was due to soluble contact-independent factor/s. Second, green fluorescent protein-expressing NS E11 and NSvm grafted into the midbrain of mice with unilateral 6-hydroxydopamine-induced Parkinsonism resulted in partial rescue of the nigro-striatal system and improvement of the hypo-dopaminergic behavioral deficit. Reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that intact NS E11 and NSvm expressed fibroblast growth factor-2, brain-derived neurotrophic factor (BDNF), pleiotrophin, neurotrophin-3, but not glial cell line-derived neurotrophic factor (GDNF). GDNF expression was also undetectable in vivo in grafted NS E11 and NSvm suggesting that NS-derived factor/s other than GDNF mediated the rescue of nigral dopaminergic neurons. Identification of NS-derived soluble factor(s) may lead to development of novel neuroprotective therapies for PD. An unexpected observation of the present study was the detection of the ectopic host-derived tyrosine hydroxylase (TH) -expressing cells in sham-grafted mice and NS E11- and NSvm -grafted mice. We speculate that injury-derived signals (such as inflammatory cytokines that are commonly released during transplantation) induce TH expression in susceptible cells.

Cellular therapy for childhood neurodegenerative disease. Part I: rationale and preclinical studies

✓ Successful cellular replacement in the diseased human central nervous system (CNS) faces numerous hurdles. In this first installment of a 2-part review, the authors report on the preclinical challenges involved in preparing for a major Phase I trial investigating the safety of human neural stem cell transplantation in a lysosomal storage disorder. Specifically, they discuss choice of the ideal disease for treatment, best donor cell type and source for implantation, the in vitro and in vivo methods used to estimate safety and efficacy, the challenges to noninvasive tracking of cells after transplantation, and the unique issues related to the immunology of CNS cellular transplantation.