Neural stem cells display an inherent mechanism for rescuing dysfunctional neurons

Recent progress in cell therapy for basal ganglia disorders with emphasis on menstrual blood transplantation in stroke

Cerebrovascular diseases are the third leading cause of death and the primary cause of long-term disability in the United States. The only approved therapy for stroke is tPA, strongly limited by the short therapeutic window and hemorrhagic complications, therefore excluding most patients from its benefits. Parkinson's and Huntington's disease are the other two most studied basal ganglia diseases and, as stroke, have very limited treatment options. Inflammation is a key feature in central nervous system disorders and it plays a dual role, either improving injury in early phases or impairing neural survival at later stages. Stem cells can be opportunely used to modulate inflammation, abrogate cell death and, therefore, preserve neural function. We here discuss the role of stem cells as restorative treatments for basal ganglia disorders, including Parkinson's disease, Huntington's disease and stroke, with special emphasis to the recently investigated menstrual blood stem cells. We highlight the availability, proliferative capacity, pluripotentiality and angiogenic features of these cells and explore their present and future experimental and clinical applications.

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.

In vivo stem cell tracking in neurodegenerative therapies

INTRODUCTION

Cell transplants to replace cells lost due to injury or degenerative diseases, for which there are currently no cures, are being pursued in a wide range of experimental models. Thus, the application of stem cell-based therapies to treat neurodegenerative and traumatic injuries is now a clinical reality. However, the monitoring of cellular grafts, non-invasively, is an important aspect of the ongoing efficacy and safety assessment of cell-based therapies. Hence, there is a need for non-invasive imaging techniques to ensure that transplants are not only administered to the relevant site, but also allow the monitoring of inappropriate cellular migration to improve our understanding of stem cell migration in the context of the whole organism.

AREAS COVERED

This review provides an up to date overview of molecular imaging approaches that have been used for visualizing and tracking transplanted stem cells, in vivo.

EXPERT OPINION

It's important to emphasize that the application of molecular imaging to interrogate transplanted cells may require one or even two imaging modalities to provide a reasonable assessment of transplanted cells in specific organs.

Manual vs automated delivery of cells for transplantation: accuracy, reproducibility, and impact on viability

BACKGROUND

Cellular transplantation holds promise for the management of a variety of neurological disorders. However, there is great variability in cell type, preparation methods, and implantation technique, which are crucial to clinical outcomes.

OBJECTIVE

We compared manual injection with automated injection using a prototype device to determine the possible value of a mechanized delivery system.

METHODS

Neural progenitor cells and bone marrow stromal cells were injected using manual or automated methods. Consistency of injection volumes and cell number and viability were evaluated immediately or 1 day after injection.

RESULTS

When cells were delivered as a series of 3 manual injections from the same syringe, the variation in fluid volume was greater than for single manual injections. Automated delivery of a series of 3 injections resulted in a lower variability in the amount of delivery than manual injection for both cell lines (1.2%-2.6% coefficient of variability for automated delivery vs 4.3%-24.0% for manual delivery). The amount delivered from injection 1 to injection 3 increased significantly with manual injections, whereas the amount injected did not vary over the 3 injections for the automated unit. Cell viability 1 day after injection was typically 30% to 40% of the value immediately after injection for the bone marrow stromal cells and 30% to 70% for the neural progenitor cells. There were no significant differences in viability attributed to the method of injection.

CONCLUSION

The automated delivery device led to enhanced consistency of volumetric cell delivery but did not improve cell viability in the methods tested. Automated techniques could be useful in standardizing reproducible procedures for cell transplantation and improve both preclinical and clinical research.

Glial cell line-derived neurotrophic factor-secreting genetically modified human bone marrow-derived mesenchymal stem cells promote recovery in a rat model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive degeneration of nigrostriatal dopaminergic (DA) neurons. The therapeutic potential of glial cell line-derived neurotrophic factor (GDNF), the most potent neurotrophic factor for DA neurons, has been demonstrated in many experimental models of PD. However, chronic delivery of GDNF to DA neurons in the brain remains an unmet challenge. Here, we report the effects of GDNF-releasing Notch-induced human bone marrow-derived mesenchymal stem cells (MSC) grafted into striatum of the 6-hydroxydopamine (6-OHDA) progressively lesioned rat model of PD. Human MSC, obtained from bone marrow aspirates of young, healthy adult volunteers, were transiently transfected with the intracellular domain of the Notch1 gene (NICD) to generate SB623 cells. SB623 cells expressing GDNF and/or humanized Renilla green fluorescent protein (hrGFP) following lentiviral transduction or nontransduced cells were stereotaxically placed into rat striatum 1 week after a unilateral partial 6-OHDA striatal lesion. At 4 weeks, rats that had received GDNF-transduced SB623 cells had significantly decreased amphetamine-induced rotation compared with control rats, although this effect was not observed in rats that received GFP-transduced or nontransduced SB623 cells. At 5 weeks, rejuvenated tyrosine hydroxylase-immunoreactive (TH-IR) fibers that appeared to be host DA axons were observed in and around grafts. This effect was more prominent in rats that received GDNF-secreting cells and was not observed in controls. These observations suggest that human bone-marrow derived MSC, genetically modified to secrete GDNF, hold potential as an allogeneic or autologous stem cell therapy for PD.

Administration of granulocyte colony-stimulating factor ameliorates radiation-induced hepatic fibrosis in mice

On the basis of the recent report that granulocyte colony-stimulating factor (G-CSF) treatment significantly improves survival and liver histology among chemically injured mice, we investigated whether G-CSF administration could contribute to faster recovery and promote tissue repair after local liver irradiation. Bone marrow chimeric female C57BL/6 mice were treated with G-CSF at days 7, 14, and 21 after local liver irradiation. We assessed the fibrosis index and the origin of proliferating cells reconstituting the liver at 2 or 5 weeks after radiation challenge. At day 35 after local irradiation, we observed G-CSF treatment to significantly reduce radiation-induced liver damage and collagen deposition. In addition, hepatic hydroxyproline levels and serum fibrosis markers in mice receiving G-CSF administration after radiation challenge were significantly lower compared with those of control mice. More importantly, histological examination suggested that recovery from hepatic damage was much better among the G-CSF-treated mice. Immunofluorescence and fluorescence in situ hybridization analyses revealed that donor cells engrafted into the host liver displayed epithelium-like morphology and expressed albumin, albeit at low frequency. These results suggested that G-CSF treatment initiated endogenous hepatic tissue regeneration in response to radiation injury and ameliorated its fibrogenic effects.

Graft and host interactions following transplantation of neural stem cells to organotypic striatal cultures

AIMS

To investigate neural stem cell (NSC) interactions with striatal tissue following engraftment and the effects of growth factors.

MATERIALS & METHODS

Organotypic striatal slice cultures established from neonatal rats were used as an ex vivo model system. Survival, integration and differentiation of grafted NSCs from the previously generated C17.2 clone and host tissue response were investigated weekly for 28 days in vitro. To direct grafted cells towards a neuronal lineage, the role of growth factor supplementation and serum-free culturing conditions was studied using neural stem cells overexpressing neurotrophin-3 and Neurobasal/B27 culture medium.

RESULTS

Following engraftment, NSCs gradually integrated morphologically and formed a part of the host 3D cytoarchitecture. Compared with nongrafted cultures, NSC engraftment increased the overall survival of the organotypic cultures by 39%, and reduced the host cell necrosis by more than 80% (from 2.1 ± 0.5% to 0.3 ± 0.1%), the host cell apoptosis by more than 60% (from 1.4 ± 0.4% to 0.5 ± 0.1%) and the reactions to mechanical trauma by 30% (estimated by nestin and glial fibrillary acidic protein immunohistochemistry) 7 days after engraftment. Elevated neurotrophin-3 production in NSCs and serum-free culturing conditions directed grafted NSCs towards a neuronal lineage as indicated by increased Tuj1 and Map2ab expression. However, this did not alter the survival of organotypic cultures.

CONCLUSIONS

NSC engraftment was associated with rescue of imperiled host cells and reduction of host cell gliosis. These NSC effects were not related to the addition of growth factors, suggesting that other factors are involved in the supportive effects of the host following NSC engraftment.

Stem cells and stroke: opportunities, challenges and strategies

INTRODUCTION

Stroke remains the leading cause of disability in the Western world. Despite decades of work, no clinically effective therapies exist to facilitate recovery from stroke. Stem cells may have the potential to minimize injury and promote recovery after stroke.

AREAS COVERED

Transplanted stem cells have been shown in animal models to migrate to the injured region, secrete neurotrophic compounds, promote revascularization, enhance plasticity and regulate the inflammatory response, thereby minimizing injury. Endogenous neural stem cells also have a remarkable propensity to respond to injury. Under select conditions, subventricular zone progenitors may be mobilized to replace lost neurons. In response to focal infarcts, neuroblasts play important trophic roles to minimize neural injury. Importantly, these endogenous repair mechanisms may be experimentally augmented, leading to robust improvements in function. Ongoing clinical studies are now assessing the safety and feasibility of cell-based therapies for stroke.

EXPERT OPINION

We outline the unique challenges and potential pitfalls in the clinical translation of stem cell research for stroke. We then detail what we believe to be the specific basic science and clinical strategies needed to overcome these challenges, fill remaining gaps in knowledge and facilitate development of clinically viable stem cell-based therapies for stroke.

Attenuation of mouse melanoma by A/C magnetic field after delivery of bi-magnetic nanoparticles by neural progenitor cells

Localized magnetic hyperthermia as a treatment modality for cancer has generated renewed interest, particularly if it can be targeted to the tumor site. We examined whether tumor-tropic neural progenitor cells (NPCs) could be utilized as cell delivery vehicles for achieving preferential accumulation of core/shell iron/iron oxide magnetic nanoparticles (MNPs) within a mouse model of melanoma. We developed aminosiloxane-porphyrin functionalized MNPs, evaluated cell viability and loading efficiency, and transplanted neural progenitor cells loaded with this cargo into mice with melanoma. NPCs were efficiently loaded with core/shell Fe/Fe(3)O(4) MNPs with minimal cytotoxicity; the MNPs accumulated as aggregates in the cytosol. The NPCs loaded with MNPs could travel to subcutaneous melanomas, and after A/C (alternating current) magnetic field (AMF) exposure, the targeted delivery of MNPs by the cells resulted in a measurable regression of the tumors. The tumor attenuation was significant (p < 0.05) a short time (24 h) after the last of three AMF exposures.

The RhoGAP domain-containing protein, Porf-2, inhibits proliferation and enhances apoptosis in neural stem cells

Neural stem cells (NSCs) are essential to developing and mature CNS. They shape the structural and functional layouts of the brain in developing CNS and continue to proliferate, generating new neurons in several adult brain regions. Preoptic regulatory factor-2 (Porf-2), a RhoGAP domain-containing protein expressed in CNS, has a role in gender-related brain development and function. Porf-2 expression was knocked down in C17.2, a mouse cerebellar multipotent cell line. This increased proliferation and decreased drug-induced apoptosis without affecting cell type distribution following differentiation induction. It lowered levels of cyclin kinase inhibitor p21, affected G1 to S phase cell cycle transition; partially blocked the elevation in p53 transcriptional activity, p21 and Bcl-2-associated X protein (Bax) levels caused by bleomycin, but had no influence on enhancement of Bax in response to staurosporine. Thus Porf-2 may inhibit NSC proliferation by enhancing p21 protein levels followed by G1 phase arrest; it plays pro-apoptotic roles in response to drug treatment through both p53 transcription-dependent and independent pathways. This is consistent with categorization of Porf-2 as a functional RhoGAP in CNS.

Human embryonic stem cells: derivation, culture, and differentiation: a review

The greatest therapeutic promise of human embryonic stem cells (hESC) is to generate specialized cells to replace damaged tissue in patients suffering from various degenerative diseases. However, the signaling mechanisms involved in lineage restriction of ESC to adopt various cellular phenotypes are still under investigation. Furthermore, for progression of hESC-based therapies towards clinical applications, appropriate culture conditions must be developed to generate genetically stable homogenous populations of cells, to hinder possible adverse effects following transplantation. Other critical challenges that must be addressed for successful cell implantation include problems related to survival and functional efficacy of the grafted cells. This review initially describes the derivation of hESC and focuses on recent advances in generation, characterization, and maintenance of these cells. We also give an overview of original and emerging differentiation strategies used to convert hESC to different cell types. Finally, we will discuss transplantation studies of hESC-derived cells with respect to safety and functional recovery.

Cellular transplantation for the nervous system: impact of time after preparation on cell viability and survival

OBJECT

Cell transplantation has shown promise for the treatment of various neurological disorders, but the factors that influence cell survival and integration following transplantation are poorly understood. In fact, little is known regarding how simple but potentially critical variables, including the method of cellular preparation and administration, might affect transplant success. The goal of the present study was to determine the impact of time between tissue preparation and implantation on cellular viability. Time can vary with cell preparation, delivery to the operating room, and surgical technique. This study was also designed to evaluate the sensitivity of various methods of assessing implant viability.

METHODS

Cell lines of neural progenitor cells and bone marrow stromal cells were generated from healthy adult mice. On the day of experimentation, the cells were collected, suspended in a balanced salt solution, and sequentially assessed for viability for up to 3.5 hours based on their appearance under phase-contrast microscopy, their ability to retain a fluorescent dye, and their attachment to a cultivation surface for 24 hours.

RESULTS

When viability was measured based on the ability of cells to retain a fluorescent dye, there was a decrease in viability of 10-15% each hour. Based on the ability of the cells to attach to a culture surface and grow for 24 hours, viability decreased more rapidly at approximately 20% per hour. In addition, only about one-third of the cells judged viable based on phase-contrast microscopy or acute dye retention were found to be viable based on plating, and only 10% of the cells initially judged as viable were still capable of survival after 3 hours in suspension.

CONCLUSIONS

The authors' results indicate that that there can be significant losses in viability between preparation and implantation and that more sophisticated methods of evaluation, such as the ability of cells to attach to a substrate and grow, may be required to detect decreases in viability. The time between preparation and implantation will be an important factor in clinical trial design.

Rat neurosphere cells protect axotomized rat retinal ganglion cells and facilitate their regeneration

We investigated the ability of a population of rat neural stem and precursor cells derived from rat embryonic spinal cord to protect injured neurons in the rat central nervous system (CNS). The neonatal rat optic pathway was used as a model of CNS injury, whereby retinal ganglion cells (RGCs) were axotomized by lesion of the lateral geniculate nucleus one day after birth. Neural stem and precursor cells derived from expanded neurospheres (NS) were transplanted into the lesion site at the time of injury. Application of Fast Blue tracer dye to the lesion site demonstrated that significant numbers of RGCs survived at 4 and 8 weeks in animals that received a transplant, with an average of 28% survival, though in some individual cases survival was greater than 50%. No RGCs survived in animals that received a lesion alone. Furthermore, labeled RGCs were also observed when Fast Blue was applied to the superior colliculus (SC) at 4 weeks, suggesting that neurosphere cells also facilitated RGC to regenerate to their normal target. Transplanted cells did not migrate or express neural markers after transplantation, and secreted several neurotrophic factors in vitro. We conclude that NS cells can protect injured CNS neurons and promote their regeneration. These effects are not attributable to cell replacement, and may be mediated via secretion of neurotrophic factors. Thus, neuroprotection by stem cell populations may be a more viable approach for treatment of CNS disorders than cell replacement therapy.

Seeding neural progenitor cells on silicon-based neural probes

Object

Chronically implanted neural electrode arrays have the potential to be used as neural prostheses in patients with various neurological disorders. While these electrodes perform well in acute recordings, they often fail to function reliably in clinically relevant chronic settings because of glial encapsulation and the loss of neurons. Surface modification of these implants may provide a means of improving their biocompatibility and integration within host brain tissue. The authors proposed a method of improving the brain-implant interface by seeding the implant's surface with a layer of neural progenitor cells (NPCs) derived from adult murine subependyma. Neural progenitor cells may reduce the foreign body reaction by presenting a tissue-friendly surface and repair implant-induced injury and inflammation by releasing neurotrophic factors. In this study, the authors evaluated the growth and differentiation of NPCs on laminin-immobilized probe surfaces and explored the potential impact on transplant survival of these cells.

Methods

Laminin protein was successfully immobilized on the silicon surface via covalent binding using silane chemistry. The growth, adhesion, and differentiation of NPCs expressing green fluorescent protein (GFP) on laminin-modified silicon surfaces were characterized in vitro by using immunocytochemical techniques. Shear forces were applied to NPC cultures in growth medium to evaluate their shearing properties. In addition, neural probes seeded with GFP-labeled NPCs cultured in growth medium for 14 days were implanted in murine cortex. The authors assessed the adhesion properties of these cells during implantation conditions. Moreover, the tissue response around NPC-seeded implants was observed after 1 and 7 days postimplantation.

Results

Significantly improved NPC attachment and growth was found on the laminin-immobilized surface compared with an unmodified control before and after shear force application. The NPCs grown on the laminin-immobilized surface showed differentiation potential similar to those grown on polylysine-treated well plates, as previously reported. Viable (still expressing GFP) NPCs were found on and in proximity to the neural implant after 1 and 7 days postimplantation. Preliminary examinations indicated that the probe's NPC coating might reduce the glial response at these 2 different time points.

Conclusions

The authors' findings suggest that NPCs can differentiate and strongly adhere to laminin-immobilized surfaces, providing a stable matrix for these cells to be implanted in brain tissue on the neural probe's surface. In addition, NPCs were found to improve the astrocytic reaction around the implant site. Further in vivo work revealing the mechanisms of this effect could lead to improvement of biocompatibility and chronic recording performance of neural probes.

Cell-mediated neuroprotection in a mouse model of human tauopathy

Tau protein in a hyperphosphorylated state makes up the intracellular inclusions of several neurodegenerative diseases, including Alzheimer's disease and cases of frontotemporal dementia. Mutations in Tau cause familial forms of frontotemporal dementia, establishing that dysfunction of tau protein is sufficient to cause neurodegeneration and dementia. Transgenic mice expressing human mutant tau in neurons exhibit the essential features of tauopathies, including neurodegeneration and abundant filaments composed of hyperphosphorylated tau. Here we show that a previously described mouse line transgenic for human P301S tau exhibits an age-related, layer-specific loss of superficial cortical neurons, similar to what has been observed in human frontotemporal dementias. We also show that focal neural precursor cell implantation, resulting in glial cell differentiation, leads to the sustained rescue of cortical neurons. Together with evidence indicating that astrocyte transplantation may be neuroprotective, our findings suggest a beneficial role for glial cell-based repair in neurodegenerative diseases.

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.

The regulation of the CNS innate immune response is vital for the restoration of tissue homeostasis (repair) after acute brain injury: a brief review

Neurons and glia respond to acute injury by participating in the CNS innate immune response. This involves the recognition and clearance of "not self " pathogens and "altered self " apoptotic cells. Phagocytic receptors (CD14, CD36, TLR-4) clear "not self" pathogens; neurons and glia express "death signals" to initiate apoptosis in T cells.The complement opsonins C1q, C3, and iC3b facilitate the clearance of apoptotic cells by interacting with CR3 and CR4 receptors. Apoptotic cells are also cleared by the scavenger receptors CD14, Prs-R, TREM expressed by glia. Serpins also expressed by glia counter the neurotoxic effects of thrombin and other systemic proteins that gain entry to the CNS following injury. Complement pathway and T cell activation are both regulated by complement regulatory proteins expressed by glia and neurons. CD200 and CD47 are NIRegs expressed by neurons as "don't eat me" signals and they inhibit microglial activity preventing host cell attack. Neural stem cells regulate T cell activation, increase the Treg population, and suppress proinflammatory cytokine expression. Stem cells also interact with the chemoattractants C3a, C5a, SDF-1, and thrombin to promote stem cell migration into damaged tissue to support tissue homeostasis.

Differentiation and behavior of human neural progenitors on micropatterned substrates and in the developing retina

In this study we investigated the differentiation of human neural progenitor cells (hNPCs) in vitro to evaluate their differentiation potential and in vivo to explore their viability and behavior following transplantation. Progenitors were maintained as neurospheres in media containing basic fibroblast growth factor and epidermal growth factor. Micropatterned polystyrene substrates were fabricated and coated with ECL (entactin, collagen, and laminin) to provide physical and chemical guidance during the differentiation of the hNPCs. The hNPCs growing on the micropatterned substrates showed no differences in proliferation or differentiation potential compared with those hNPCs growing on the nonpatterned substrates. However, hNPCs cultured on the micropatterned substrates were aligned in the direction of the micropattern compared with those cells growing on the nonpatterned substrates. Furthermore, hNPC migration was directed in alignment with the micropatterned substrates. Transplantation of the hNPCs into the developing retina was used to evaluate their behavior in vivo. Cells displayed extensive survival, differentiation, and morphological integration following xenotransplant into the retina, even in the absence of immunosuppression. Taken together, our results show that these multipotent hNPCs are a neurogenic progenitor population that can be maintained in culture for extended periods. Although the micropatterned substrates have no major effect on the proliferation or differentiation of the hNPCs, they clearly promoted alignment and directed neurite outgrowth along the pattern as well as directing migration of the cells. These approaches may provide important strategies to guide the growth and differentiation of NPCs in vitro and in vivo.

Intranigral transplantation of epigenetically induced BDNF-secreting human mesenchymal stem cells: implications for cell-based therapies in Parkinson's disease

It is thought that the ability of human mesenchymal stem cells (hMSC) to deliver neurotrophic factors might be potentially useful for the treatment of neurodegenerative disorders. The aim of the present study was to characterize signals and/or molecules that regulate brain-derived neurotrophic factor (BDNF) protein expression/delivery in hMSC cultures and evaluate the effect of epigenetically generated BDNF-secreting hMSC on the intact and lesioned substantia nigra (SN). We tested 4 different culture media and found that the presence of fetal bovine serum (FBS) decreased the expression of BDNF, whereas exogenous addition of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) to serum-free medium was required to induce BDNF release (125 ± 12 pg/day/10⁶ cells). These cells were called hM(N)SC. Although the induction medium inhibited the expression of alpha smooth muscle actin (ASMA), an hMSC marker, and increased the nestin-positive subpopulation of hMSC cultures, the ability to express BDNF was restricted to the nestin-negative subpopulation. One week after transplantation into the SN, the human cells integrated into the surrounding tissue, and some showed a dopaminergic phenotype. We also observed the activation of Trk receptors for neurotrophic factors around the implant site, including the BDNF receptor TrkB. When we transplanted these cells into the unilateral lesioned SN induced by striatal injection of 6-hydroxydopamine (6-OHDA), a significant hypertrophy of nigral tyrosine hydroxylase (TH)(+) cells, an increase of striatal TH-staining and stabilization of amphetamine-induced motor symptoms were observed. Therefore, hMSC cultures exposed to the described induction medium might be highly useful as a vehicle for neurotrophic delivery to the brain and specifically are strong candidates for future therapeutic application in Parkinson's disease.

Genetically engineered mesenchymal stem cells reduce behavioral deficits in the YAC 128 mouse model of Huntington's disease

The purpose of this study was to evaluate the therapeutic effects of the transplantation of bone-marrow mesenchymal stem cells (MSCs), genetically engineered to over-express brain-derived neurotrophic factor (BDNF) or nerve growth factor (NGF) on motor deficits and neurodegeneration in YAC 128 transgenic mice. MSCs, harvested from mouse femurs, were genetically engineered to over-express BDNF and/or NGF and these cells, or the vehicle solution, were injected into the striata of four-month old YAC 128 transgenic and wild-type mice. Assessments of motor ability on the rotarod and the severity of clasping were made one day prior to transplantation and once monthly, thereafter, to determine the effects of the transplanted cells on motor function. The mice were sacrificed at 13-months of age for immunohistological examination. All YAC 128 mice receiving transplants had reduced clasping, relative to vehicle-treated YAC 128 mice, while YAC 128 mice that were transplanted with MSCs which were genetically engineered to over-express BDNF, had the longest latencies on the rotarod and the least amount of neuronal loss within the striatum of the YAC 128 mice. These results indicate that intrastriatal transplantation of MSCs that over-express BDNF may create an environment within the striatum that slows neurodegenerative processes and provides behavioral sparing in the YAC 128 mouse model of HD. Further research on the long-term safety and efficacy of this approach is needed before its potential clinical utility can be comprehensively assessed.

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.

Survival, differentiation, and reversal of heroin neurobehavioral teratogenicity in mice by transplanted neural stem cells derived from embryonic stem cells

Cell therapies in animal models of neurobehavioral defects are normally derived from neural stem cells (NSC) of the developing cortex. However, the clinical feasibility of NSC therapies would be greatly improved by deriving transplanted cells and from a tissue culture source that is self-renewing, containing cells that potentially differentiate into the desired neuronal phenotypes. These cultures can be engineered to contain the appropriate factors to support their therapeutic action and likely evoke lesser immune reactions. In the current study, we employed our model of mice neurobehaviorally impaired via prenatal exposure to heroin, to test the therapeutic efficacy of NSC derived from murine embryonic stem cells culture (ESC). The culture contained elongated bipolar cells, 90% of which are positive for nestin, the intermediate filament protein found in neural precursors. After removal of growth factors, the NSC differentiated into neurons (34.0% +/- 3.8% NF-160 positive), including cholinergic cells (ChAT positive), oligodendrocytes (29.9% +/- 4.2% O(4)), and astrocytes (36.1% +/- 4.7% GFAP positive). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis confirmed the immunocytochemical findings. Mice made deficient in Morris maze behavior by prenatal heroin exposure (10 mg/kg heroin s.c. on gestational days 9-18) were transplanted into the hippocampus region on postnatal day 35 with the ES culture-derived NSC (ES-NSC) labeled with dialkylcarbocyanine (Dil) cell tracker. Dil+ and NF160+ cells were detected in the hippocampal region (50% +/- 8% survival). The transplantation completely restored maze performance to normal; e.g., on day 3, transplantation improved the behavior from the deficient level of 11.9-sec latency to the control of 5.6-sec latency (44.5% improvement).

Transplantation of human neural precursor cells in Matrigel scaffolding improves outcome from focal cerebral ischemia after delayed postischemic treatment in rats

Transplantation of neural cells is a potential approach for stroke treatment, but disruption of tissue architecture may limit transplant efficacy. One strategy for enhancing the ability of transplants to restore brain structure and function is to administer cells together with biomaterial scaffolding. We electrocoagulated the distal middle cerebral artery in adult rats and, 3 weeks later, injected one of the following into the infarct cavity: artificial cerebrospinal fluid, Matrigel scaffolding, human embryonic stem cell-derived neuronal precursor cells, scaffolding plus cells, or cells cultured in and administered together with scaffolding. Five weeks after transplantation, the latter two groups showed approximately 50% and approximately 60% reductions, respectively, in infarct cavity volume. Rats given cells cultured in and administered together with scaffolding also showed (1) survival and neuronal differentiation of transplanted cells shown by immunostaining for neuronal marker proteins and cleaved caspase-3, and by patch-clamp recording, 8 weeks after transplantation and (2) improved outcome on tests of sensorimotor and cognitive functions, 4 to 9 weeks after transplantation. These results indicate that transplantation of human neural cells together with biomaterial scaffolding has the potential to improve the outcome from stroke, even when treatment is delayed for several weeks after the ischemic event.

Neurotoxicity screening in a multipotent neural stem cell line established from the mouse brain

Neural stem cells (NSCs) have mainly been applied to neurodegeneration in some medically intractable neurologic diseases. In this study, we established a novel NSC line and investigated the cytotoxic responses of NSCs to exogenous neurotoxicants, glutamates and reactive oxygen species (ROS). A multipotent NSC line, B2A1 cells, was established from long-term primary cultures of oligodendrocyte-enriched cells from an adult BALB/c mouse brain. B2A1 cells could be differentiated into neuronal, astrocytic and oligodendroglial lineages. The cells also expressed genotypic mRNA messages for both neural progenitor cells and differentiated neuronoglial cells. B2A1 cells treated with hydrogen peroxide and L-buthionine-(S,R)-sulfoximine underwent 30-40% cell death, while B2A1 cells treated with glutamate and kainate showed 25-35% cell death. Cytopathologic changes consisting of swollen cell bodies, loss of cytoplasmic processes, and nuclear chromatin disintegration, developed after exposure to both ROS and excitotoxic chemicals. These results suggest that B2A1 cells may be useful in the study of NSC biology and may constitute an effective neurotoxicity screening system for ROS and excitotoxic chemicals.

Alginate composition effects on a neural stem cell-seeded scaffold

The purpose of this study was to evaluate the effects of alginate composition on the neurotrophic factor release, viability, and proliferation of encapsulated neural stem cells (NSCs), as well as on the mechanical stability of the scaffold itself. Four compositions were tested: a high guluronic acid (68%) and a high mannuronic acid (54%) content alginate, with or without a poly-L-lysine (PLL) coating layer. Enzyme-linked immunosorbent assay was used to quantify the release of brain-derived neurotrophic factor, glial-derived neurotrophic factor, and nerve growth factor from the encapsulated cells. All three factors were detected from encapsulated cells only when a high L-guluronic acid alginate without PLL was used. Additionally, capsules with this composition remained intact more frequently when exposed to solutions of low osmolarity, potentially indicating superior mechanical stability. Alginate beads with a PLL-coated, high D-mannuronic acid composition were the most prone to breakage in the osmotic pressure test, and were too fragile for histology and proliferation assays after 1 week in vitro. NSCs survived and proliferated in the three remaining alginate compositions similarly over the 21-day study course irrespective of scaffold condition. NSC-seeded alginate beads with a high L-guluronic acid, non-PLL-coated composition may be useful in the repair of injured nervous tissue, where the mechanism is the secretion of neuroprotective factors. We verify the neuroprotective effects of medium conditioned by NSC-seeded alginate beads on the serum withdrawal-mediated death of PC-12 cells here.

Embryonic stem cell-derived L1 overexpressing neural aggregates enhance recovery in Parkinsonian mice

Parkinson's disease is the second most common neurodegenerative disease, after Alzheimer's disease, and the most common movement disorder. Drug treatment and deep brain stimulation can ameliorate symptoms, but the progressive degeneration of dopaminergic neurons in the substantia nigra eventually leads to severe motor dysfunction. The transplantation of stem cells has emerged as a promising approach to replace lost neurons in order to restore dopamine levels in the striatum and reactivate functional circuits. We have generated substrate-adherent embryonic stem cell-derived neural aggregates overexpressing the neural cell adhesion molecule L1, because it has shown beneficial functions after central nervous system injury. L1 enhances neurite outgrowth and neuronal migration, differentiation and survival as well as myelination. In a previous study, L1 was shown to enhance functional recovery in a mouse model of Huntington's disease. In another study, a new differentiation protocol for murine embryonic stem cells was established allowing the transplantation of stem cell-derived neural aggregates consisting of differentiated neurons and radial glial cells into the lesioned brain. In the present study, this embryonic stem cell line was engineered to overexpress L1 constitutively at all stages of differentiation and used to generate stem cell-derived neural aggregates. These were monitored in their effects on stem cell survival and differentiation, rescue of endogenous dopaminergic neurons and ability to influence functional recovery after transplantation in an animal model of Parkinson's disease. Female C57BL/6J mice (2 months old) were treated with the mitochondrial toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine intraperitoneally to deplete dopaminergic neurons selectively, followed by unilateral transplantation of stem cell-derived neural aggregates into the striatum. Mice grafted with L1 overexpressing stem cell-derived neural aggregates showed better functional recovery when compared to mice transplanted with wild-type stem cell-derived neural aggregates and vehicle-injected mice. Morphological analysis revealed increased numbers and migration of surviving transplanted cells, as well as increased numbers of dopaminergic neurons, leading to enhanced levels of dopamine in the striatum ipsilateral to the grafted side in L1 overexpressing stem cell-derived neural aggregates, when compared to wild-type stem cell-derived neural aggregates. The striatal levels of gamma-aminobutyric acid were not affected by L1 overexpressing stem cell-derived neural aggregates. Furthermore, L1 overexpressing, but not wild-type stem cell-derived neural aggregates, enhanced survival of endogenous host dopaminergic neurons after transplantation adjacent to the substantia nigra pars compacta. Thus, L1 overexpressing stem cell-derived neural aggregates enhance survival and migration of transplanted cells, differentiation into dopaminergic neurons, survival of endogenous dopaminergic neurons, and functional recovery after syngeneic transplantation in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson's disease.

Slowed progression in models of Huntington disease by adipose stem cell transplantation

OBJECTIVE

Adipose-derived stem cells (ASCs) are readily accessible and secrete multiple growth factors. Here, we show that ASC transplantation rescues the striatal pathology of Huntington disease (HD) models.

METHODS

ASCs were isolated from human subcutaneous adipose tissue. In a quinolinic acid (QA)-induced rat model of striatal degeneration, human ASCs (1 million cells) were transplanted into the ipsilateral striatal border immediately after the QA injection. In 60-day-old R6/2 mice transgenic for HD, ASCs (0.5 million cells) were transplanted into each bilateral striata. In in vitro experiments, we treated mutant huntingtin gene-transfected cerebral neurons with ASC-conditioned media.

RESULTS

In the QA model, human ASCs reduced apomorphine-induced rotation behavior, lesion volume, and striatal apoptosis. In R6/2 transgenic mice, transplantation of ASCs improved Rota-Rod performance and limb clasping, increased survival, attenuated the loss of striatal neurons, and reduced the huntingtin aggregates. ASC-transplanted R6/2 mice expressed elevated levels of peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) and reactive oxygen defense enzymes and showed activation of the Akt/cAMP-response element-binding proteins. ASC-conditioned media decreased the level of N-terminal fragments of mutant huntingtin and associated apoptosis, and increased PGC-1alpha expression.

INTERPRETATION

Collectively, ASC transplantation slowed striatal degeneration and behavioral deterioration of HD models, possibly via secreted factors.

Japanese encephalitis virus induce immuno-competency in neural stem/progenitor cells

Background

The low immunogenicity of neural stem/progenitor cells (NSPCs) coupled with negligible expression of MHC antigens has popularized their use in transplantation medicine. However, in an inflammatory environment, the NSPCs express costimulatory molecules and MHC antigens, and also exhibit certain immunomodulatory functions. Since NSPCs are the cellular targets in a number of virus infections both during postnatal and adult stages, we wanted to investigate the immunological properties of these stem cells in response to viral pathogen.

Methodology/Principal Findings

We utilized both in vivo mouse model and in vitro neurosphere model of Japanese encephalitis virus (JEV) infection for the study. The NSPCs residing in the subventricular zone of the infected brains showed prominent expression of MHC-I and costimulatory molecules CD40, CD80, and CD86. Using Flow cytometry and fluorescence microscopy, we observed increased surface expression of co-stimulatory molecule and MHC class I antigen in NSPCs upon progressive JEV infection in vitro. Moreover, significant production of pro-inflammatory cyto/chemokines was detected in JEV infected NSPCs by Cytokine Bead Array analysis. Interestingly, NSPCs were capable of providing functional costimulation to allogenic T cells and JEV infection resulted in increased proliferation of allogenic T cells, as detected by Mixed Lymphocyte reaction and CFSE experiments. We also report IL-2 production by NSPCs upon JEV infection, which possibly provides mitogenic signals to T cells and trigger their proliferation.

Conclusion/Significance

The in vivo and in vitro findings clearly indicate the development of immunogenicity in NSPCs following progressive JEV infection, in our case, JEV infection. Following a neurotropic virus infection, NSPCs possibly behave as immunogenic cells and contribute to both the innate and adaptive immune axes. The newly discovered immunological properties of NSPCs may have implications in assigning a new role of these cells as non-professional antigen presenting cells in the central nervous system.

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.

A synergistic approach for neural repair: cell transplantation and induction of endogenous precursor cell activity

Stem cell research offers enormous potential for treating many diseases of the nervous system. At present, therapeutic strategies in stem cell research segregate into two approaches: cell transplantation or endogenous cell stimulation. Realistically, future cell therapies will most likely involve a combination of these two approaches, a theme of our current research. Here, we propose that there exists a 'synergy' between exogenous (transplanted) and endogenous stem cell actions that can be utilized to achieve therapeutic ends. Elucidating mechanisms underlying this exogenous-endogenous stem cell synergism may lead to the development of optimal cell therapies for neural disorders.

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.

Neural stem cell transplantation benefits a monogenic neurometabolic disorder during the symptomatic phase of disease

Although we and others have demonstrated that neural stem cells (NSCs) may impact such neurogenetic conditions as lysosomal storage diseases when transplanted at birth, it has remained unclear whether such interventions can impact well-established mid-stage disease, a situation often encountered clinically. Here we report that when NSCs were injected intracranially into the brain of adult symptomatic Sandhoff (Hexb(-/-)) mice, cells migrated far from the injection site and integrated into the host cytoarchitecture, restoring beta-hexosaminidase enzyme activity and promoting neuropathologic and behavioral improvement. Mouse lifespan increased, neurological function improved, and disease progression was slowed. These clinical benefits correlated with neuropathological correction at the cellular and molecular levels, reflecting the multiple potential beneficial actions of stem cells, including enzyme cross-correction, cell replacement, tropic support, and direct anti-inflammatory action. Pathotropism (i.e., migration and homing of NSCs to pathological sites) could be imaged in real time by magnetic resonance imaging. Differentially expressed chemokines might play a role in directing the migration of transplanted stem cells to sites of pathology. Significantly, the therapeutic impact of NSCs implanted in even a single location was surprisingly widespread due to both cell migration and enzyme diffusion. Because many of the beneficial actions of NSCs observed in newborn brains were recapitulated in adult brains to the benefit of Sandhoff recipients, NSC-based interventions may also be useful in symptomatic subjects with established disease.

Applications of neural and mesenchymal stem cells in the treatment of gliomas

In addition to stem cells providing a better understanding about the biology and origins of gliomas, new therapeutic approaches have been developed based on the use of stem cells as delivery vehicles. The unique ability of stem cells to track down tumor cells makes them a very appealing therapeutic modality. This review introduces neural and mesenchymal stem cells, discusses the advances that have been made in the utilization of these stem cells as therapies and in diagnostic imaging (to track the advancement of the stem cells towards the tumor cells), and concludes by addressing various challenges and concerns regarding these therapies.

Transplantation of subventricular zone neural precursors induces an endogenous precursor cell response in a rat model of Parkinson's disease

Realistically, future stem cell therapies for neurological conditions including Parkinson's disease (PD) will most probably entail combination treatment strategies, involving both the stimulation of endogenous cells and transplantation. Therefore, this study investigates these two modes of neural precursor cell (NPC) therapy in concert in order to determine their interrelationships in a rat PD model. Human placental alkaline phosphatase (hPAP)-labeled NPCs were transplanted unilaterally into host rats which were subsequently infused ipsilaterally with 6-hydroxydopamine (6-OHDA). The reaction of host NPCs to the transplantation and 6-OHDA was tracked by bromodeoxyuridine (BrdU) labeling. Two weeks after transplantation, in animals transplanted with NPCs we found evidence of elevated host subventricular zone NPC proliferation, neurogenesis, and migration to the graft site. In these animals, we also observed a significant preservation of striatal tyrosine hydroxylase (TH) expression and substantia nigra TH cell number. We have seen no evidence that neuroprotection is a product of dopamine neuron replacement by NPC-derived cells. Rather, the NPCs expressed glial cell line-derived neurotrophic factor (GDNF), sonic hedgehog (Shh), and stromal cell-derived factor 1 alpha (SDF1alpha), providing a molecular basis for the observed neuroprotection and endogenous NPC response to transplantation. In summary, our data suggests plausible synergy between exogenous and endogenous NPC actions, and that NPC implantation before the 6-OHDA insult can create a host microenvironment conducive to stimulation of endogenous NPCs and protection of mature nigral neurons.

Stem cells for ischemic brain injury: a critical review

No effective therapy is currently available to promote recovery following ischemic stroke. Stem cells have been proposed as a potential source of new cells to replace those lost due to central nervous system injury, as well as a source of trophic molecules to minimize damage and promote recovery. We undertook a detailed review of data from recent basic science and preclinical studies to investigate the potential application of endogenous and exogenous stem cell therapies for treatment of cerebral ischemia. To date, spontaneous endogenous neurogenesis has been observed in response to ischemic injury, and can be enhanced via infusion of appropriate cytokines. Exogenous stem cells from multiple sources can generate neural cells that survive and form synaptic connections after transplantation in the stroke-injured brain. Stem cells from multiple sources cells also exhibit neuroprotective properties that may ameliorate stroke deficits. In many cases, functional benefits observed are likely independent of neural differentiation, although the exact mechanisms remain poorly understood. Future studies of neuroregeneration will require the demonstration of function in endogenously born neurons following focal ischemia. Further, methods are currently lacking to demonstrate definitively the therapeutic effect of newly introduced neural cells. Increased plasticity following stroke may facilitate the functional integration of new neurons, but the loss of appropriate guidance cues and supporting architecture in the infarct cavity will likely impede the restoration of lost circuitry. Thus careful investigation of the mechanisms underlying trophic benefits will be essential. Evidence to date suggests that continued development of stem cell therapies may ultimately lead to viable treatment options for ischemic brain injury.

The neural stem cell line CTX0E03 promotes behavioral recovery and endogenous neurogenesis after experimental stroke in a dose-dependent fashion

BACKGROUND

This study investigated behavioral recovery in rats following implanting increasing doses of CTX0E03 cells into the putamen ipsilateral to the stroke damage. Postmortem histological analysis investigated possible mechanisms of behavioral recovery.

METHODS

. At 4 weeks after middle cerebral artery occlusion (MCAO), rats were treated with 4500, 45,000, or 450,000 CTX0E03 cells or vehicle implanted into the putamen with testing on a battery of tasks preocclusion and postocclusion. Histological examination of brains included assessment of lesion volumes, implant cell survival and differentiation, changes to host brain matrix, angiogenesis, and neurogenesis using immunohistochemical methods.

RESULTS

. Statistically significant dose-related recovery in sensorimotor function deficits (bilateral asymmetry test [BAT; P < .0002] in the mid- and high-dose groups and rotameter test after amphetamine exposure [P < .05] in the high-dose group) was found in the CTX0E03 cell implanted groups compared to the vehicle group. In-life functional improvements correlated with cell dose, though did not correlate with survival of CTX0E03 cells measured at postmortem. Surviving CTX0E03 cells differentiated into oligodendroglial and endothelial phenotypes. MCAO-induced reduction of neurogenesis in the subventricular zone (SVZ) was partially restored to that observed in sham operated controls. No adverse CTX0E03 cell-related effects were observed during in-life observations or on tissue histology.

CONCLUSIONS

. This study found that the implantation of CTX0E03 human neural stem cells in rats after MCAO stroke promoted significant behavioral recovery depending on cell dose. The authors propose a paracrine trophic mechanism, which is triggered early after CTX0E03 cell implantation, and which in turn targets restoration of neurogenesis in the SVZ of MCAO rats.

Adult stem cell therapies for neurological disorders: benefits beyond neuronal replacement?

The modest capacity of endogenous repair processes in the central nervous system (CNS) justifies the broad interest in the development of effective stem cell based therapies for neurodegenerative disorders and other acute or chronic lesions. Motivated by the ambitious expectation to achieve functional neuronal replacement, several studies have already evidenced a potential benefit of stem cell grafts in animal models of human disorders. Nevertheless, growing evidence suggests that the effects orchestrated by stem cells, in most experimental cases, are not necessarily associated with the generation of new neurons. This hypothesis correlates with the versatile properties of adult and embryonic stem cells. When introduced into the lesioned CNS, nondifferentiated stem cells can have a positive influence through intrinsic neuroprotective capacities related to the production of neurotrophic factors, stimulation of endogenous neurogenesis, and modulation of neuroinflammation. Stem cells are also endowed with a multipotent differentiation profile, suggesting that a positive outcome could result from the replacement of nonneuronal cell types, in particular astrocytes and oligodendrocytes. Focusing on adult stem cells, this Review aims at summarizing experimental observations supporting the concept that, in cell-based therapies, stem cells operate not through a unidirectional mechanism (e.g., generating neurons) but rather as cellular mediators of a multitude of biological activities that could provide a favorable outcome for diverse nervous disorders.

In vivo multimodal imaging of stem cell transplantation in a rodent model of Parkinson's disease

Stem cell therapy in the nervous system aims to replace the lost neurons and provide functional recovery. However, it is imperative that we understand the in vivo behaviour of these cells post-implantation. We report visualisation of iron oxide labelled bone marrow-derived stem cells (BMSCs) implanted into the striatum of hemi-parkinsonian rats by magnetic resonance imaging (MRI). Functional efficacy of the donor cells was monitored in vivo using the positron emission tomography (PET) radioligand [11C]raclopride. The cells were visible for 28 days by in vivo MRI. BMSCs provided functional recovery demonstrated by a decreased binding of [11C]raclopride. Although, histology confirmed the persistence of donor cells, no tyrosine hydroxylase positive cells were present. This suggests that BMSCs may have a limited paracrine effect and influence functional recovery. We demonstrate, using multimodal imaging, that we can not only track BMSCs but also establish their effects in a pre-clinical model of Parkinson's disease.

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 umbilical cord blood-derived mesenchymal stem cells do not differentiate into neural cell types or integrate into the retina after intravitreal grafting in neonatal rats

This study investigated the ability of mesenchymal stem cells (MSCs) derived from full-term human umbilical cord blood to survive, integrate and differentiate after intravitreal grafting to the degenerating neonatal rat retina following intracranial optic tract lesion. MSCs survived for 1 week in the absence of immunosuppression. When host animals were treated with cyclosporin A and dexamethasone to suppress inflammatory and immune responses, donor cells survived for at least 3 weeks, and were able to spread and cover the entire vitreal surface of the host retina. However, MSCs did not significantly integrate into or migrate through the retina. They also maintained their human antigenicity, and no indication of neural differentiation was observed in retinas where retinal ganglion cells either underwent severe degeneration or were lost. These results have provided the first in vivo evidence that MSCs derived from human umbilical cord blood can survive for a significant period of time when the host rat response is suppressed even for a short period. These results, together with the observation of a lack of neuronal differentiation and integration of MSCs after intravitreal grafting, has raised an important question as to the potential use of MSCs for neural repair through the replacement of lost neurons in the mammalian retina and central nervous system.