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Contrasting myelin damage through the generation of new myelinating oligodendrocytes represents a promising approach to promote functional recovery after stroke. Here, we asked whether activation of microglia and monocyte-derived macrophages affects the regenerative process sustained by G protein-coupled receptor 17 (GPR17)-expressing oligodendrocyte precursor cells (OPCs), a subpopulation of OPCs specifically reacting to ischemic injury. GPR17-iCreER T2 :CAG-eGFP reporter mice were employed to trace the fate of GPR17-expressing OPCs, labeled by the green fluorescent protein (GFP), after permanent middle cerebral artery occlusion. By microglia/macrophages pharmacological depletion studies, we show that innate immune cells favor GFP + OPC reaction and limit myelin damage early after injury, whereas they lose their pro-resolving capacity and acquire a dystrophic "senescent-like" phenotype at later stages. Intracerebral infusion of regenerative microglia-derived extracellular vesicles (EVs) restores protective microglia/macrophages functions, limiting their senescence during the post-stroke phase, and enhances the maturation of GFP + OPCs at lesion borders, resulting in ameliorated neurological functionality. In vitro experiments show that EV-carried transmembrane tumor necrosis factor (tmTNF) mediates the pro-differentiating effects on OPCs, with future implications for regenerative therapies., (Copyright © 2020 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.)

Spinal cord injury (SCI) results in loss of neurons, oligodendrocytes and myelin sheaths, all of which are not efficiently restored. The scarcity of oligodendrocytes in the lesion site impairs re-myelination of spared fibres, which leaves axons denuded, impedes signal transduction and contributes to permanent functional deficits. In contrast to mammals, zebrafish can functionally regenerate the spinal cord. Yet, little is known about oligodendroglial lineage biology and re-myelination capacity after SCI in a regeneration-permissive context. Here, we report that, in adult zebrafish, SCI results in axonal, oligodendrocyte and myelin sheath loss. We find that OPCs, the oligodendrocyte progenitor cells, survive the injury, enter a reactive state, proliferate and differentiate into oligodendrocytes. Concomitantly, the oligodendrocyte population is re-established to pre-injury levels within 2 weeks. Transcriptional profiling revealed that reactive OPCs upregulate the expression of several myelination-related genes. Interestingly, global reduction of axonal tracts and partial re-myelination, relative to pre-injury levels, persist at later stages of regeneration, yet are sufficient for functional recovery. Taken together, these findings imply that, in the zebrafish spinal cord, OPCs replace lost oligodendrocytes and, thus, re-establish myelination during regeneration., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2020. Published by The Company of Biologists Ltd.)

Among the numerous candidates for cell therapy of the central nervous system (CNS), olfactory progenitors (OPs) represent an interesting alternative because they are free of ethical concerns, are easy to collect, and allow autologous transplantation. In the present study, we focused on the optimization of neuron production and maturation. It is known that plated OPs respond to various trophic factors, and we also showed that the use of Nerve Growth Factor (NGF) allowed switching from a 60/40 neuron/glia ratio to an 80/20 one. Nevertheless, in order to focus on the integration of OPs in mature neural circuits, we cocultured OPs in primary cultures obtained from the cortex and hippocampus of newborn mice. When dissociated OPs were plated, they differentiated into both glial and neuronal phenotypes, but we obtained a 1.5-fold higher viability in cortex/OP cocultures than in hippocampus/OP ones. The fate of OPs in cocultures was characterized with different markers such as BrdU, Map-2, and Synapsin, indicating a healthy integration. These results suggest that the integration of transplanted OPs might by affected by trophic factors and the environmental conditions/cell phenotypes of the host tissue. Thus, a model of coculture could provide useful information on key cell events for the use of progenitors in cell therapy.

Pelizaeus-Merzbacher disease (PMD) is an X-linked leukodystrophy caused by mutations in Proteolipid Protein 1 (PLP1), encoding a major myelin protein, resulting in profound developmental delay and early lethality. Previous work showed involvement of unfolded protein response (UPR) and endoplasmic reticulum (ER) stress pathways, but poor PLP1 genotype-phenotype associations suggest additional pathogenetic mechanisms. Using induced pluripotent stem cell (iPSC) and gene-correction, we show that patient-derived oligodendrocytes can develop to the pre-myelinating stage, but subsequently undergo cell death. Mutant oligodendrocytes demonstrated key hallmarks of ferroptosis including lipid peroxidation, abnormal iron metabolism, and hypersensitivity to free iron. Iron chelation rescued mutant oligodendrocyte apoptosis, survival, and differentiationin vitro, and post-transplantation in vivo. Finally, systemic treatment of Plp1 mutant Jimpy mice with deferiprone, a small molecule iron chelator, reduced oligodendrocyte apoptosis and enabled myelin formation. Thus, oligodendrocyte iron-induced cell death and myelination is rescued by iron chelation in PMD pre-clinical models., (Copyright © 2019. Published by Elsevier Inc.)

Intracerebral hemorrhage (ICH) is a cerebrovascular disorder with high mortality and disability rates. Although a lot of effort has been put in ICH, there is still no effective treatment for this devastating disease. Recent studies suggest that oligodendrocytes play an important role in brain repair after ICH and thus may be targeted for the therapies of ICH. Here in this review, we first introduce the origin, migration, proliferation, differentiation, and myelination of oligodendrocytes under physiological condition. Second, recent findings on how ICH affects oligodendrocyte biology and function are reviewed. Third, potential crosstalk between oligodendrocytes and other cells in the brain is also summarized. Last, we discuss the therapeutic potential of oligodendrocyte-based treatments in ICH. Our goal is to provide a comprehensive review on the biology and function of oligodendrocytes under both physiological and ICH conditions., (© 2019 The Authors. CNS Neuroscience & Therapeutics Published by John Wiley & Sons Ltd.)

Sox2 transcription factor has been frequently used for reprograming starting cells to neural progenitor/stem cells. In vivo administration of Sox2 in the adult mouse brain reprogrammed the transduced astrocytes to neurons. In searching for adequate cell source for repairing the myelin insults, here, we studied the possible conversion of astrocytes to oligodendrocyte lineage cells by Sox2, while an extensive demyelination exists in animal brain. Lentiviral particles expressing Sox2-GFP were injected into the corpora callosa of animals fed with cuprizone diet for 12 weeks. Transduced cells were mainly astrocytes that changed their fate to oligodendrocyte lineage cells by time. For further conformation astrocytes received the vector in culture and then transplanted to the animal brains. Tracing the fate of transplanted cells showed their conversion to oligodendrocyte lineage cells. In vitro transduced cell were also maintained in the oligodendrocyte progenitor cell (OPC) induction medium. Produced OPC-like cells were positive for specific markers. This study provides a new strategy for endogenous production of myelinating cells. After optimizing the experimental conditions for safety and feasibility, this approach may contribute into future cell based therapies in patients with white matter insults as like as those with multiple sclerosis., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A recent clinical trial proves that autologous olfactory mucosal cell (OMC) transplantation improves locomotion in dogs with naturally occurring spinal injuries comparable to human lesions. However, not all dogs respond to the treatment, likely due to the transplantation procedures involving injections of cell suspensions that are associated with cell death, uneven cell distribution, and cell washout. Encapsulating cells in protective hydrogel matrices offers a tissue engineering solution to safely achieve 3D growth of viable transplant cells for implantation into injury sites, to improve regenerative outcomes. It is shown for the first time that canine OMCs (cOMCs) can be propagated with high viability in 3D collagen matrices. Further, a method to incorporate cOMCs pre-labeled with clinical-grade iron oxide nanoparticles into the constructs is described. Intraconstruct labeled cells are visualized using magnetic resonance imaging, offering substantial promise for in vivo tracking of cOMCs delivered in protective matrices., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Treatment of chronic spinal cord injury (SCI) is challenging due to cell loss, cyst formation, and the glial scar. Previously, we reported on the therapeutic potential of a neural progenitor cell (NPC) and chondroitinase ABC (ChABC) combinatorial therapy for chronic SCI. However, the source of NPCs and delivery system required for ChABC remained barriers to clinical application. Here, we investigated directly reprogrammed human NPCs biased toward an oligodendrogenic fate (oNPCs) in combination with sustained delivery of ChABC using an innovative affinity release strategy in a crosslinked methylcellulose biomaterial for the treatment of chronic SCI in an immunodeficient rat model. This combinatorial therapy increased long-term survival of oNPCs around the lesion epicenter, facilitated greater oligodendrocyte differentiation, remyelination of the spared axons by engrafted oNPCs, enhanced synaptic connectivity with anterior horn cells and neurobehavioral recovery. This combinatorial therapy is a promising strategy to regenerate the chronically injured spinal cord., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)

Scarce access to primary samples and lack of efficient protocols to generate oligodendrocytes (OLs) from human pluripotent stem cells (hPSCs) are hampering our understanding of OL biology and the development of novel therapies. Here, we demonstrate that overexpression of the transcription factor SOX10 is sufficient to generate surface antigen O4-positive (O4 + ) and myelin basic protein-positive OLs from hPSCs in only 22 days, including from patients with multiple sclerosis or amyotrophic lateral sclerosis. The SOX10-induced O4 + population resembles primary human OLs at the transcriptome level and can myelinate neurons in vivo. Using in vitro OL-neuron co-cultures, myelination of neurons by OLs can also be demonstrated, which can be adapted to a high-throughput screening format to test the response of pro-myelinating drugs. In conclusion, we provide an approach to generate OLs in a very rapid and efficient manner, which can be used for disease modeling, drug discovery efforts, and potentially for therapeutic OL transplantation., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

It has been reported that oligodendrocyte precursor cells (OPCs) may be used to treat contusive spinal cord injury (SCC), and may alter microRNA (miRNA/miR) expression following SCC in rats. However, the association between miRNA expression and the treatment of rats with SCC with OPC transplantation remain unclear. The present study transplanted OPCs into the spinal cord of rats with SCC and subsequently used the Basso, Beattie and Bresnahan (BBB) score to assess the functional recovery and pain scores. An miRNA assay was performed to detect differentially expressed miRNAs in the spinal cord of SCC rats transplanted with OPCs, compared with SCC rats transplanted with medium. Quantitative polymerase chain reaction was used to verify significantly altered miRNA expression levels. The results demonstrated that OPC transplantation was able to improve motor recovery and relieve mechanical allodynia in rats with SCC. In addition, through a miRNA assay, 45 differentially expressed miRNAs (40 upregulated miRNAs and 5 downregulated miRNAs) were detected in the spinal cord of rats in the OPC group compared with in the Medium group. Differentially expressed miRNAs were identified according to the following criteria: Fold change >2 and P<0.05. Furthermore, quantitative polymerase chain reaction was used to verify the most highly upregulated (miR‑375‑3p and miR‑1‑3p) and downregulated (miR‑363‑3p, miR‑449a‑5p and miR‑3074) spinal cord miRNAs that were identified in the miRNA assay. In addition, a bioinformatics analysis of these miRNAs indicated that miR‑375 and miR‑1 may act primarily to inhibit cell proliferation and apoptosis via transcriptional and translational regulation, whereas miR‑363, miR‑449a and miR‑3074 may act primarily to inhibit cell proliferation and neuronal differentiation through transcriptional regulation. These results suggested that OPC transplantation may promote functional recovery of rats with SCC, which may be associated with the expression of various miRNAs in the spinal cord, including miR‑375‑3p, miR‑1‑3p, miR‑363‑3p, miR‑449a‑5p and miR‑3074.

Cervical spinal cord injury (SCI) remains an important research focus for regenerative medicine given the potential for severe functional deficits and the current lack of treatment options to augment neurological recovery. We recently reported the preclinical safety data of a human embryonic cell-derived oligodendrocyte progenitor cell (OPC) therapy that supported initiation of a phase I clinical trial for patients with sensorimotor complete thoracic SCI. To support the clinical use of this OPC therapy for cervical injuries, we conducted preclinical efficacy and safety testing of the OPCs in a nude rat model of cervical SCI. Using the automated TreadScan system to track motor behavioral recovery, we found that OPCs significantly improved locomotor performance when administered directly into the cervical spinal cord 1 week after injury, and that this functional improvement was associated with reduced parenchymal cavitation and increased sparing of myelinated axons within the injury site. Based on large scale biodistribution and toxicology studies, we show that OPC migration is limited to the spinal cord and brainstem and did not cause any adverse clinical observations, toxicities, allodynia, or tumors. In combination with previously published efficacy and safety data, the results presented here supported initiation of a phase I/IIa clinical trial in the U.S. for patients with sensorimotor complete cervical SCI. Stem Cells Translational Medicine 2017;6:1917-1929., (© 2017 The Authors Stem Cells Translational Medicine published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.)

Background: Demyelination is a common lesion in spinal cord injury, cell therapy is one of the approaches for replacing the lost oligodendrocytes. In this study, bone marrow stromal cells (BMSCs) have been transdifferentiated into oligodendrocyte-like cells (OLCs) and used in cytotherapy of contused spinal cords in rats., Methods: The BMSCs were collected from the rat long bones, and cultured and characterized by different markers, then they were preinduced with dimethyl sulfoxide followed by retinoic acid, and then the preinduced cells were induced with combination of basic fibroblast growth factor, platelet-derived growth factor and heregulin, followed by triiodothyronine. The OLCs were transplanted in the contused spinal cords of the rats, combined with undifferentiated BMSCs. Specific markers were used in order to characterize the cells by immunohistochemistry and real-time polymerase chain reaction. The BMSCs showed typical immnuoreactivity to the markers, and the OLCs were immunostained with specific markers., Results: There was an improvement in the Basso, Beattie and Bresnahan score with reduction in the cavitation in the contused rats treated with OLCs combined with BMSCs. The transplanted cells were detected in the contused spinal cord., Conclusions: The combination of the transdifferentiated BMSCs into OLCs with the undifferentiated BMSCs improved the contused spinal cord.

Pelizaeus-Merzbacher disease (PMD) results from an X-linked misexpression of proteolipid protein 1 (PLP1). This leukodystrophy causes severe hypomyelination with progressive inflammation, leading to neurological dysfunctions and shortened life expectancy. While no cure exists for PMD, experimental cell-based therapy in the dysmyelinated shiverer model suggested that human oligodendrocyte progenitor cells (hOPCs) or human neural precursor cells (hNPCs) are promising candidates to treat myelinopathies. However, the fate and restorative advantages of human NPCs/OPCs in a relevant model of PMD has not yet been addressed. Using a model of Plp1 overexpression, resulting in demyelination with progressive inflammation, we compared side-by-side the therapeutic benefits of intracerebrally grafted hNPCs and hOPCs. Our findings reveal equal integration of the donor cells within presumptive white matter tracks. While the onset of exogenous remyelination was earlier in hOPCs-grafted mice than in hNPC-grafted mice, extended lifespan occurred only in hNPCs-grafted animals. This improved survival was correlated with reduced neuroinflammation (microglial and astrocytosis loads) and microglia polarization toward M2-like phenotype followed by remyelination. Thus modulation of neuroinflammation combined with myelin restoration is crucial to prevent PMD pathology progression and ensure successful rescue of PMD mice. These findings should help to design novel therapeutic strategies combining immunomodulation and stem/progenitor cell-based therapy for disorders associating hypomyelination with inflammation as observed in PMD., (© 2015 AlphaMed Press.)

Transplantation of pluripotent stem cells and their differentiated progeny has the potential to preserve or regenerate functional pathways and improve function after central nervous system injury. However, their utility has been hampered by poor survival and the potential to form tumors. Peptide-modified biomaterials influence cell adhesion, survival and differentiation in vitro, but their effectiveness in vivo remains uncertain. We synthesized a peptide-modified, minimally invasive, injectable hydrogel comprised of hyaluronan and methylcellulose to enhance the survival and differentiation of human induced pluripotent stem cell-derived oligodendrocyte progenitor cells. Cells were transplanted subacutely after a moderate clip compression rat spinal cord injury. The hydrogel, modified with the RGD peptide and platelet-derived growth factor (PDGF-A), promoted early survival and integration of grafted cells. However, prolific teratoma formation was evident when cells were transplanted in media at longer survival times, indicating that either this cell line or the way in which it was cultured is unsuitable for human use. Interestingly, teratoma formation was attenuated when cells were transplanted in the hydrogel, where most cells differentiated to a glial phenotype. Thus, this hydrogel promoted cell survival and integration, and attenuated teratoma formation by promoting cell differentiation., (Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.)

There are an important number of neurological diseases where not neurons but glia are the responsible cells for the degeneration of the nervous system. In the last years, determinant roles for oligodendrocytes (OLs) have been demonstrated not only in myelin generation and maintenance but also for metabolic support of neurons. Oligodendroglial defects lead to brain degeneration in several diseases, supporting the idea that not only endogenous regeneration but also administration of exogenous OL precursors will lead to overcome functional deficits. In this review, we discuss many diseases where OLs play a crucial role, and focus on the different sources and methods to obtain oligodendroglial cells that could be used in cell therapy for myelin-related and oligodendrocyte-deficient diseases.

Aim: To characterize the preclinical safety profile of a human embryonic stem cell-derived oligodendrocyte progenitor cell therapy product (AST-OPC1) in support of its use as a treatment for spinal cord injury (SCI)., Materials & Methods: The phenotype and functional capacity of AST-OPC1 was characterized in vitro and in vivo. Safety and toxicology of AST-OPC1 administration was assessed in rodent models of thoracic SCI., Results: These results identify AST-OPC1 as an early-stage oligodendrocyte progenitor population capable of promoting neurite outgrowth in vitro and myelination in vivo. AST-OPC1 administration did not cause any adverse clinical observations, toxicities, allodynia or tumors., Conclusion: These results supported initiation of a Phase I clinical trial in patients with sensorimotor complete thoracic SCI.

Induced neural stem cells (iNSCs) can be directly transdifferentiated from somatic cells. One potential clinical application of the iNSCs is for nerve regeneration. However, it is unknown whether iNSCs function in disease models. We produced transdifferentiated iNSCs by conditional overexpressing Oct4, Sox2, Klf4, c-Mycin mouse embryonic fibroblasts. They expanded readily in vitro and expressed NSC mRNA profile and protein markers. These iNSCs differentiated into mature astrocytes, neurons and oligodendrocytes in vitro. Importantly, they reduced lesion size, promoted the recovery of motor and sensory function as well as metabolism status in middle cerebral artery stroke rats. These iNSCs secreted nerve growth factors, which was associated with observed protection of neurons from apoptosis. Furthermore, iNSCs migrated to and passed through the lesion in the cerebral cortex, where Tuj1+ neurons were detected. These findings have revealed the function of transdifferentiated iNSCs in vivo, and thus provide experimental evidence to support the development of personalized regenerative therapy for CNS diseases by using genetically engineered autologous somatic cells.

The inability of the mammalian central nervous system (CNS) to undergo spontaneous regeneration has long been regarded as a central tenet of neurobiology. However, although this is largely true of the neuronal elements of the adult mammalian CNS, save for discrete populations of granular neurons, the same is not true of its glial elements. In particular, the loss of oligodendrocytes, which results in demyelination, triggers a spontaneous and often highly efficient regenerative response, remyelination, in which new oligodendrocytes are generated and myelin sheaths are restored to denuded axons. Yet, remyelination in humans is not without limitation, and a variety of demyelinating conditions are associated with sustained and disabling myelin loss. In this review, we will review the biology of remyelination, including the cells and signals involved; describe when remyelination occurs and when and why it fails and the consequences of its failure; and discuss approaches for therapeutically enhancing remyelination in demyelinating diseases of both children and adults, both by stimulating endogenous oligodendrocyte progenitor cells and by transplanting these cells into demyelinated brain., (Copyright © 2015 Cold Spring Harbor Laboratory Press; all rights reserved.)

Introduction: Globoid cell leukodystrophy (GLD) is a severe disorder of the central and peripheral nervous system caused by the absence of galactocerebrosidase (GALC) activity. Cell-based therapies are highly promising strategies for GLD. In this study, G-Olig2 mouse embryonic stem cells (ESCs) were induced into oligodendrocyte progenitor cells (OPCs) and were implanted into the brains of twitcher mice, an animal model of GLD, to explore the therapeutic potential of the cells., Methods: The G-Olig2 ESCs were induced into OPCs by using cytokines and a multi-step differentiation procedure. Oligodendrocyte markers were detected by reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemistry. The toxicity of psychosine to OPCs was determined by a cell proliferation assay kit. The GALC level of OPCs was also examined. OPCs were labeled with Dir and transplanted into the brains of twitcher mice. The transplanted cells were detected by in-Vivo Multispectral Imaging System and real-time PCR. The physiological effects of twitcher mice were assessed., Results: Oligodendrocyte markers were expressed in OPCs, and 76%±5.76% of the OPCs were enhanced green fluorescent protein (eGFP)-positive, eGFP was driven by the Olig2 promoter. The effect of psychosine on cell viability indicated that OPCs were more resistant to psychosine toxicity. The GALC level of OPCs was 10.0±1.23 nmol/hour per mg protein, which was significantly higher than other cells. Dir-labeled OPCs were injected into the forebrain of post-natal day 10 twitcher mice. The transplanted OPCs were myelin basic protein (MBP)-positive and remained along the injection tract as observed by fluorescent microscopy. The level of the Dir fluorescent signal and eGFP mRNA significantly decreased at days 10 and 20 after injection, as indicated by in-Vivo Multispectral Imaging System and real-time PCR. Because of poor cell survival and limited migration ability, there was no significant improvement in brain GALC activity, MBP level, life span, body weight, and behavioral deficits of twitcher mice., Conclusions: ESC-derived OPC transplantation was not sufficient to reverse the clinical course of GLD in twitcher mice.

Therapeutic repair of myelin disorders may be limited by the relatively slow rate of human oligodendrocyte differentiation. To identify appropriate pharmacological targets with which to accelerate differentiation of human oligodendrocyte progenitors (hOPCs) directly, we used CD140a/O4-based FACS of human forebrain and microarray to hOPC-specific receptors. Among these, we identified CHRM3, a M3R muscarinic acetylcholine receptor, as being restricted to oligodendrocyte-biased CD140a(+)O4(+) cells. Muscarinic agonist treatment of hOPCs resulted in a specific and dose-dependent blockade of oligodendrocyte commitment. Conversely, when hOPCs were cocultured with human neurons, M3R antagonist treatment stimulated oligodendrocytic differentiation. Systemic treatment with solifenacin, an FDA-approved muscarinic receptor antagonist, increased oligodendrocyte differentiation of transplanted hOPCs in hypomyelinated shiverer/rag2 brain. Importantly, solifenacin treatment of engrafted animals reduced auditory brainstem response interpeak latency, indicative of increased conduction velocity and thereby enhanced functional repair. Therefore, solifenacin and other selective muscarinic antagonists represent new adjunct approaches to accelerate repair by engrafted human progenitors., (Copyright © 2015 the authors 0270-6474/15/353676-13$15.00/0.)

Radiation therapy to the brain is a powerful tool in the management of many cancers, but it is associated with significant and irreversible long-term side effects, including cognitive decline and impairment of motor coordination. Depletion of oligodendrocyte progenitors and demyelination are major pathological features that are particularly pronounced in younger individuals and severely limit therapeutic options. Here we tested whether human ESC-derived oligodendrocytes can functionally remyelinate the irradiated brain using a rat model. We demonstrate the efficient derivation and prospective isolation of human oligodendrocyte progenitors, which, upon transplantation, migrate throughout the major white matter tracts resulting in both structural and functional repair. Behavioral testing showed complete recovery of cognitive function while additional recovery from motor deficits required concomitant transplantation into the cerebellum. The ability to repair radiation-induced damage to the brain could dramatically improve the outlook for cancer survivors and enable more effective use of radiation therapies, especially in children., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Multiple sclerosis (MS) is a chronic demyelinating disease of unknown etiology that affects the CNS. While current therapies are primarily directed against the immune system, the new challenge is to address progressive MS with remyelinating and neuroprotective strategies. Here, we develop a highly reproducible protocol to efficiently derive oligodendrocyte progenitor cells (OPCs) and mature oligodendrocytes from induced pluripotent stem cells (iPSCs). Key elements of our protocol include adherent cultures, dual SMAD inhibition, and addition of retinoids from the beginning of differentiation, which lead to increased yields of OLIG2 progenitors and high numbers of OPCs within 75 days. Furthermore, we show the generation of viral and integration-free iPSCs from primary progressive MS (PPMS) patients and their efficient differentiation to oligodendrocytes. PPMS OPCs are functional, as demonstrated by in vivo myelination in the shiverer mouse. These results provide encouraging advances toward the development of autologous cell therapies using iPSCs., (Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.)

Pelizaeus-Merzbacher disease (PMD) is a form of X-linked leukodystrophy caused by mutations in the proteolipid protein 1 (PLP1) gene. Although PLP1 proteins with missense mutations have been shown to accumulate in the rough endoplasmic reticulum (ER) in disease model animals and cell lines transfected with mutant PLP1 genes, the exact pathogenetic mechanism of PMD has not previously been clarified. In this study, we established induced pluripotent stem cells (iPSCs) from two PMD patients carrying missense mutation and differentiated them into oligodendrocytes in vitro. In the PMD iPSC-derived oligodendrocytes, mislocalization of mutant PLP1 proteins to the ER and an association between increased susceptibility to ER stress and increased numbers of apoptotic oligodendrocytes were observed. Moreover, electron microscopic analysis demonstrated drastically reduced myelin formation accompanied by abnormal ER morphology. Thus, this study demonstrates the involvement of ER stress in pathogenic dysmyelination in the oligodendrocytes of PMD patients with the PLP1 missense mutation.

Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system (CNS). A potential new therapeutic approach for MS is cell transplantation which may promote remyelination. We transplanted human Wharton's jelly stem cell-derived oligodendrocyte progenitor cells (hWJ-MSC-derived OPCs) into the brain ventricles of mice induced with experimental autoimmune encephalomyelitis (EAE), the animal model of MS. We studied the effect of the transplanted OPCs on the functional and pathological manifestations of the disease. Transplanted hWJ-MSC-derived OPCs significantly reduced the clinical signs of EAE. Histological examinations showed that remyelination was significantly increased after transplantation. These results suggest that hWJ-MSC-derived OPCs promote the regeneration of myelin sheaths in the brain.

Halting the first clinical trial on the use of embryonic stem cell derivatives for spinal cord injury resulted in disappointment and created concerns about the future use of pluripotent stem cell-based therapy in the treatment of human diseases. This article presents reflections and concerns related to the halted embryonic stem cell-based clinical trial and discusses some important and controversial issues for achieving safe and successful cell therapy. This manuscript highlights two important points for successful translation of pluripotent stem cell-based therapy in clinics: (i) reproducible xeno-free growth and differentiation of pluripotent stem cells in good manufacturing practice conditions as the prerequisites to ensure a defined and controlled cell source and (ii) extensive studies in small and large animal models and comprehensive basic studies to determine any adverse or toxic effects of transplanted cells, especially teratoma formation, in addition to improving surgical procedure and cell delivery system.

Olfactory ensheathing cells (OECs) and Schwann cells (SCs) share many characteristics, including the ability to promote neuronal repair when transplanted directly into spinal cord lesions, but poor survival and migration when transplanted into intact adult spinal cord. Interestingly, transplanted OECs, but not SCs, migrate extensively within the X-irradiated (40 Gy) adult rat spinal cord, suggesting distinct responses to environmental cues [Lankford et al., (2008) GLIA 56:1664-1678]. In this study, GFP-expressing OECs and SCs were transplanted into juvenile rat brains (hippocampus) subjected to a moderate radiation dose (16 Gy). As in the adult spinal cord, OECs, but not SCs, migrated extensively within the irradiated juvenile rat brain. Unbiased stereology revealed that the number of OECs observed within irradiated rat brains three weeks after transplantation was as much as 20 times greater than the number of cells transplanted, and the cells distributed extensively within the brain. In conjunction with the OEC dispersion, the number of activated microglia in OEC-transplanted irradiated brains was reduced. Unlike in the intact adult spinal cord, both OECs and SCs showed some, but limited, migration within nonirradiated rat brains, suggesting that the developing brain may be a more permissive environment for cell migration than the adult CNS. These results show that OECs display unique migratory, proliferative, and microglia interaction properties as compared with SCs when transplanted into the moderately X-irradiated brain., (Copyright © 2013 Wiley Periodicals, Inc.)

The spinal cord injury (SCI) microenvironment undergoes dynamic changes over time, which could potentially affect survival or differentiation of cells in early versus delayed transplantation study designs. Accordingly, assessment of safety parameters, including cell survival, migration, fate, sensory fiber sprouting, and behavioral measures of pain sensitivity in animals receiving transplants during the chronic postinjury period is required for establishing a potential therapeutic window. The goal of the study was assessment of safety parameters for delayed transplantation of human central nervous system-derived neural stem cells (hCNS-SCns) by comparing hCNS-SCns transplantation in the subacute period, 9 days postinjury (DPI), versus the chronic period, 60 DPI, in contusion-injured athymic nude rats. Although the number of surviving human cells after chronic transplantation was lower, no changes in cell migration were detected between the 9 and 60 DPI cohorts; however, the data suggest chronic transplantation may have enhanced the generation of mature oligodendrocytes. The timing of transplantation did not induce changes in allodynia or hyperalgesia measures. Together, these data support the safety of hCNS-SCns transplantation in the chronic period post-SCI.

The endoplasmic reticulum (ER) stress response (ERSR) is activated to maintain protein homeostasis or induce apoptosis in the ER in response to distinct cellular insults including hypoxia, inflammation, and oxidative damage. Recently, we showed ERSR activation in a mouse model of a contusive spinal cord injury (SCI) and an improved hindlimb locomotor function following SCI when the pro-apoptotic arm of ERSR was genetically inhibited. The objective of the current study was to explore if the pharmacological enhancement of the homeostatic arm of the ERSR pathway can improve the functional outcome after SCI. Salubrinal enhances the homeostatic arm of the ERSR by increasing phosphorylation of eIF2α. Salubrinal significantly enhanced the levels of phosphorylated eIF2α protein and modulated the downstream ERSR effectors assessed at the lesion epicenter 6h post-SCI. Hindlimb locomotion showed significant improvement in animals treated with salubrinal. Treadmill-based-gait assessment showed a significant increase in maximum speed of coordinated walking and a decrease in rear stance time and stride length in salubrinal-treated animals. This improved functional recovery corresponded with increased white matter sparing and decreased oligodendrocyte apoptosis. In addition, salubrinal protected cultured mouse oligodendrocyte progenitor cells against the ER stress-inducing toxin tunicamycin. These data suggest that boosting the homeostatic arm of the ERSR reduces oligodendrocyte loss after traumatic SCI and support the contention that pharmacological targeting of the ERSR after CNS trauma is a therapeutically viable approach., (Copyright © 2013 Elsevier Inc. All rights reserved.)

To examine the role of gray and white matter niches for oligodendrocyte differentiation, we used homo- and heterotopic transplantations into the adult mouse cerebral cortex. White matter-derived cells differentiated into mature oligodendrocytes in both niches with equal efficiency, whereas gray matter-derived cells did not. Thus, white matter promotes oligodendrocyte differentiation, and cells from this niche differentiate more easily, even in the less supportive gray matter environment.

Stem cell repair shows substantial translational potential for neurological injury, but the mechanisms of action remain unclear. This study aimed to investigate whether transplanted stem cells could induce comprehensive functional remyelination. Subventricular zone (SVZ)-derived adult neural precursor cells (aNPCs) were injected bilaterally into major cerebral white matter tracts of myelin-deficient shiverer mice on postnatal day (P) 0, P7, and P21. Tripotential NPCs, when transplanted in vivo, integrated anatomically and functionally into local white matter and preferentially became Olig2+, Myelin Associated Glycoprotein-positive, Myelin Basic Protein-positive oligodendrocytes, rather than Glial Fibrillary Acidic Protein-positive astrocytes or Neurofiliment 200-positive neurons. Processes interacted with axons and transmission electron microscopy showed multilamellar axonal ensheathment. Nodal architecture was restored and by quantifying these anatomical parameters a computer model was generated that accurately predicted action potential velocity, determined by ex vivo slice recordings. Although there was no obvious phenotypic improvement in transplanted shi/shis, myelinated axons exhibited faster conduction, lower activation threshold, less refractoriness, and improved response to high-frequency stimulation than dysmyelinated counterparts. Furthermore, they showed improved resilience to ischemic insult, a promising finding in the context of perinatal brain injury. This study describes, for the first time mechanistically, the functional characteristics and anatomical integration of nonimmortalized donor SVZ-derived murine aNPCs in the dysmyelinated brain at key developmental time points.

Remyelination of chronically demyelinated axons in multiple sclerosis (MS) requires the recruitment of endogenous cells or their replacement by transplanted, exogenous oligodendrocyte progenitor cells (OPCs). We have previously shown that an OPC line, CG4, preferentially migrates after transplantation toward focal areas of inflammatory demyelination and axon loss created by injection of zymosan in the rat spinal cord. Here we show that many transplanted CG4 cells had already migrated into the inflammatory lesion after 1 day. We demonstrate that a large number of CG4 cells that had migrated, expressed the adhesion protein, CD44, and that CD44's main ligand, hyaluronic acid (HA) was robustly expressed in the inflammatory lesion. In an in vitro migration assay, migration declined significantly following blocking of CD44 expression on CG4 cells. Likewise, migration of CG4 cells toward a zymosan lesion in vivo was inhibited when transplanted cells were exposed to a CD44 blocking antibody prior to transplantation. These findings suggest that CD44 is a key molecule in the migration of OPCs toward the focal inflammatory demyelinated lesion induced by zymosan, and may be an important in OPC repair in MS., (Copyright © 2012 Wiley Periodicals, Inc.)

Remyelination has to occur to fully regenerate injured spinal cords or brain tissues. A growing body of evidence has suggested that exogenous cell transplantation is one promising strategy to promote remyelination. However, direct injection of neural stem cells or oligodendrocyte progenitor cells (OPCs) to the lesion site may not be an optimal therapeutic strategy due to poor viability and functionality of transplanted cells resulted from the local hostile tissue environment. The overall objective of this study was to engineer an injectable biocompatible hydrogel system as a supportive niche to provide a regeneration permissive microenvironment for transplanted OPCs to survive, functionally differentiate, and remyelinate central nervous system (CNS) lesions. A highly biocompatible hydrogel, based on thiol-functionalized hyaluronic acid and thiol-functionalized gelatin, which can be crosslinked by poly-(ethylene glycol) diacrylate (PEGDA), was used. These hydrogels were optimized first regarding cell adhesive properties and mechanical properties to best support the growth properties of OPCs in culture. Transplanted OPCs with the hydrogels optimized in vitro exhibited enhanced survival and oligodendrogenic differentiation and were able to remyelinate demyelinated axons inside ethidium bromide (EB) demyelination lesion in adult spinal cord. This study provides a new possible therapeutic approach to treat CNS injuries in which cell therapies may be essential.

In demyelinating disorders such as Multiple Sclerosis (MS), targets of injury are myelin and oligodendrocytes, leading to severe neurological dysfunction. Regenerative therapies aimed at promoting oligodendrocyte maturation and remyelination are promising strategies for treatment in demyelinating disorders. Endogenous precursor cells or exogenous transplanted cells are potential sources for remyelinating oligodendrocytes in the central nervous system (CNS). Several signalling pathways have been implicated in regulating the capacity of these cell populations for myelin repair. Here, we review neural precursor cells and oligodendrocyte progenitor cells as potential sources for remyelinating oligodendrocytes and evidence for the functional role of key signalling pathways in inhibiting regeneration from these precursor cell populations.

Chronic neuropathic pain is a common and debilitating consequence of spinal cord injury (SCI). In a rat contusion injury model, we observed that chronic neuropathic pain is present on day 7 after SCI and persists for the entire 56-day observation period. However, currently available pain therapies are inadequate for SCI-induced neuropathic pain. In this study, we show that spinal transplantation of mouse embryonic stem cell-derived oligodendrocyte progenitor cells (OPCs) enhances remyelination in the injured spinal cord and reduces SCI-induced chronic neuropathic pain. Moreover, we found that SCI reduces the protein level of neuregulin-1 and ErbB4 in the injured spinal cord and that OPC transplantation enhances the spinal expression of both proteins after SCI. Finally, intrathecal injection of neuregulin-1 small interfering RNA, but not the control nontarget RNA, diminishes OPC transplantation-produced remyelination and reverses the antinociceptive effect of OPC transplantation. Our findings suggest that the transplantation of embryonic stem cell-derived OPCs is an appropriate therapeutic intervention for treatment of SCI-induced chronic neuropathic pain, and that neuregulin-1/ErbB signaling plays an important role in central remyelination under pathological conditions and contributes to the alleviation of such pain., (Copyright © 2012 AlphaMed Press.)

Demyelination contributes to the functional impairment of irradiation injured spinal cord. One potential therapeutic strategy involves replacing the myelin-forming cells. Here, we asked whether transplantation of Olig2(+)-GFP(+)-oligodendrocyte precursor cells (OPCs), which are derived from Olig2-GFP-mouse embryonic stem cells (mESCs), could enhance remyelination and functional recovery after spinal cord irradiation injury. We differentiated Olig2-GFP-mESCs into purified Olig2(+)-GFP(+)-OPCs and transplanted them into the rats' cervical 4-5 dorsal spinal cord level at 4 months after irradiation injury. Eight weeks after transplantation, the Olig2(+)-GFP(+)-OPCs survived and integrated into the injured spinal cord. Immunofluorescence analysis showed that the grafted Olig2(+)-GFP(+)-OPCs primarily differentiated into adenomatous polyposis coli (APC(+)) oligodendrocytes (54.6±10.5%). The staining with luxol fast blue, hematoxylin & eosin (LFB/H&E) and electron microscopy demonstrated that the engrafted Olig2(+)-GFP(+)-OPCs attenuated the demyelination resulted from the irradiation. More importantly, the recovery of forelimb locomotor function was enhanced in animals receiving grafts of Olig2(+)-GFP(+)-OPCs. We concluded that OPC transplantation is a feasible therapy to repair the irradiated lesions in the central nervous system (CNS).

The diseases of myelin are among the most prevalent and disabling conditions in neurology. These diseases include both the vascular and inflammatory demyelinating disorders of adulthood, as well as the childhood leukodystrophies and cerebral palsy. These fundamentally glial disorders may be amenable to treatment by glial progenitor cells (GPCs), which give rise to astroglia and myelin-producing oligodendrocytes. Given the development of new methods for generating and isolating human GPCs, the myelin disorders may now be compelling targets for cell-based therapy. In addition, the efficient engraftment and expansion of human GPCs in murine hosts has led to the development of human glial chimeric mouse brains, which provides new opportunities for studying the species-specific roles of human glia in cognition, as well as in disease pathogenesis.

Myelin-specific CD8(+) T cells are thought to contribute to the pathogenesis of multiple sclerosis. Here we modeled this contribution in mice with CD8(+) T cells recognizing ovalbumin (OVA) expressed in oligodendrocytes (ODCs). Surprisingly, even very high numbers of activated OVA-reactive CD8(+) T cells failed to induce disease and were cleared from the immune system after antigen encounter in the central nervous system (CNS). Peripheral infection with OVA-expressing Listeria (Lm-OVA) enabled CD8(+) T cells to enter the CNS, leading to the deletion of OVA-specific clones after OVA recognition on ODCs. In contrast, intracerebral infection allowed OVA-reactive CD8(+) T cells to cause demyelinating disease. Thus, in response to infection, CD8(+) T cells also patrol the CNS. If the CNS itself is infected, they destroy ODCs upon cognate antigen recognition in pursuit of pathogen eradication. In the sterile brain, however, antigen recognition on ODCs results in their deletion, thereby maintaining tolerance., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Loss of oligodendrocytes and demyelination further impair neural function after spinal cord injury (SCI). Replacement of lost oligodendrocytes and improvement of myelination have a therapeutic significance in treatment of SCI. Here, we transplanted oligodendrocyte precursor cells (OPCs) to improve myelination in a rat model of contusive SCI. The labelled OPCs were transplanted to injured cord 7 days after injury. As a result, the implanted cells still survived in vivo 8 weeks after transplantation. They proliferated, integrated and differentiated in the injured cord. In the OPCs-treated rats, enhanced myelination in the lesioned area was observed and substantial improvement of motor function and nerve conduction was also recorded. Thus, this study provides strong evidence to support that transplantation of OPCs could improve myelination of injured cord and enhance functional recovery after contusive SCI., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Background: Transplantations of human stem cell derivatives have been widely investigated in rodent models for the potential restoration of function of neural pathways after spinal cord injury (SCI). Studies have already demonstrated cells survival following transplantation in SCI. We sought to evaluate survival and potential therapeutic effects of transplanted human embryonic stem (hES) cell-derived oligodendrocyte progenitor cells (OPCs) in a contusive injury in rats. Bioluminescence imaging was utilized to verify survivability of cells up to 4 weeks, and somatosensory evoked potential (SSEPs) were recorded at the cortex to monitor function of sensory pathways throughout the 6-week recovery period., Principal Findings: hES cells were transduced with the firefly luciferase gene and differentiated into OPCs. OPCs were transplanted into the lesion epicenter of rat spinal cords 2 hours after inducing a moderate contusive SCI. The hES-treatment group showed improved SSEPs, including increased amplitude and decreased latencies, compared to the control group. The bioluminescence of transplanted OPCs decreased by 97% in the injured spinal cord compared to only 80% when injected into an uninjured spinal cord. Bioluminescence increased in both experimental groups such that by week 3, no statistical difference was detected, signifying that the cells survived and proliferated independent of injury. Post-mortem histology of the spinal cords showed integration of human cells expressing mature oligodendrocyte markers and myelin basic protein without the expression of markers for astrocytes (GFAP) or pluripotent cells (OCT4)., Conclusions: hES-derived OPCs transplanted 2 hours after contusive SCI survive and differentiate into OLs that produce MBP. Treated rats demonstrated functional improvements in SSEP amplitudes and latencies compared to controls as early as 1 week post-injury. Finally, the hostile injury microenvironment at 2 hours post-injury initially caused increased cell death but did not affect the long-term cell proliferation or survival, indicating that cells can be transplanted sooner than conventionally accepted.

In multiple sclerosis (MS), a chronic inflammatory relapsing demyelinating disease, failure to control or repair damage leads to progressive neurological dysfunction and neurodegeneration. Implantation of neural stem cells (NSCs) has been shown to promote repair and functional recovery in the acute experimental autoimmune encephalomyelitis (EAE) animal model for MS; the major therapeutic mechanism of these NSCs appeared to be immune regulation. In the present study, we examined the efficacy of intraventricularly injected NSCs in chronic relapsing experimental autoimmune encephalomyelitis (CREAE), the animal disease model that is widely accepted to mimic most closely recurrent inflammatory demyelination lesions as observed in relapsing-remitting MS. In addition, we assessed whether priming these NSCs to become oligodendrocyte precursor cells (OPCs) by transient overexpression of Olig2 would further promote functional recovery, for example, by contributing to actual remyelination. Upon injection at the onset of the acute phase or the relapse phase of CREAE, NSCs as well as Olig2-NSCs directly migrated toward active lesions in the spinal cord as visualized by in vivo bioluminescence and biofluorescence imaging, and once in the spinal cord, the majority of Olig2-NSCs, in contrast to NSCs, differentiated into OPCs. The survival of Olig2-NSCs was significantly higher than that of injected control NSCs, which remained undifferentiated. Nevertheless, both Olig2-NSCs and NSC significantly reduced the clinical signs of acute and relapsing disease and, in case of Olig2-NSCs, even completely abrogated relapsing disease when administered early after onset of acute disease. We provide the first evidence that NSCs and in particular NSC-derived OPCs (Olig2-NSCs) ameliorate established chronic relapsing EAE in mice. Our experimental data in established neurological disease in mice indicate that such therapy may be effective in relapsing-remitting MS preventing chronic progressive disease.

Understanding the basic mechanisms that control CNS remyelination is of direct clinical relevance. Suitable model systems include the analysis of naturally occurring and genetically generated mouse mutants and the transplantation of oligodendrocyte precursor cells (OPCs) following experimental demyelination. However, aforementioned studies were exclusively carried out in rats and little is known about the in vivo behavior of transplanted murine OPCs. Therefore in the present study, we (i) established a model of ethidium bromide-induced demyelination of the caudal cerebellar peduncle (CCP) in the adult mouse and (ii) studied the distribution and marker expression of the murine OPC line BO-1 expressing the enhanced green fluorescent protein (eGFP) 10 and 17 days after stereotaxic implantation. Injection of ethidium bromide (0.025%) in the CCP resulted in a severe loss of myelin, marked astrogliosis, and mild to moderate axonal alterations. Transplanted cells formed an invasive and liquorogenic metastasizing tumor, classified as murine giant cell glioblastoma. Transplanted BO-1 cells displayed substantially reduced CNPase expression as compared to their in vitro phenotype, low levels of MBP and GFAP, prominent upregulation of NG2, PDGFRα, nuclear p53, and an unaltered expression of signal transducer and activator of transcription (STAT)-3. Summarized environmental signaling in the brain stem was not sufficient to trigger oligodendrocytic differentiation of BO-1 cells and seemed to block CNPase expression. Moreover, the lack of the remyelinating capacity was associated with tumor formation indicating that BO-1 cells may serve as a versatile experimental model to study tumorigenesis of glial tumors.

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. Exogenous cell replacement in MS lesions has been proposed as a means of achieving remyelination when endogenous remyelination has failed. However, the ability of exogenous cells to remyelinate axons in the presence of inflammation remains uncertain. We have explored the remyelinating capacity of an oligodendrocyte progenitor cell line CG-4 transduced with the GFP gene and transplanted adjacent to a zymosan-induced focal demyelination model in the rat spinal cord. The resulting zymosan-induced lesions were characterized by persistent macrophage/microglia activation, focal demyelination, degeneration of axons, and reactive astrogliosis. GFP(+) CG-4 cells were found to migrate preferentially toward the inflammatory lesion and survive inside the lesion. A proportion of GFP(+) CG-4 cells differentiated into mature oligodendrocytes and remyelinated axons within the lesion. These findings suggest that grafted oligodendrocyte progenitors may migrate toward areas of inflammation in the adult rat spinal cord, where they can survive and differentiate into myelinating oligodendrocytes., (Copyright © 2011 Wiley-Liss, Inc.)

Enhancing the ability of either endogenous or transplanted oligodendrocyte progenitors (OPs) to engage in myelination may constitute a novel therapeutic approach to demyelinating diseases of the brain. It is known that in adults neural progenitors situated in the subventricular zone of the lateral ventricle (SVZ) are capable of generating OPs which can migrate into white matter tracts such as the corpus callosum (CC). We observed that progenitor cells in the SVZ of adult mice expressed CXCR4 chemokine receptors and that the chemokine SDF-1/CXCL12 was expressed in the CC. We therefore investigated the role of chemokine signaling in regulating the migration of OPs into the CC following their transplantation into the lateral ventricle. We established OP cell cultures from Olig2-EGFP mouse brains. These cells expressed a variety of chemokine receptors, including CXCR4 receptors. Olig2-EGFP OPs differentiated into CNPase-expressing oligodendrocytes in culture. To study the migratory capacity of Olig2-EGFP OPs in vivo, we transplanted them into the lateral ventricles of mice. Donor cells migrated into the CC and differentiated into mature oligodendrocytes. This migration was enhanced in animals with Experimental Autoimmune Encephalomyelitis (EAE). Inhibition of CXCR4 receptor expression in OPs using shRNA inhibited the migration of transplanted OPs into the white matter suggesting that their directed migration is regulated by CXCR4 signaling. These findings indicate that CXCR4 mediated signaling is important in guiding the migration of transplanted OPs in the context of inflammatory demyelinating brain disease., (Published by Elsevier Inc.)

Experimental animals with myelin disorders can be treated by transplanting oligodendrocyte progenitor cells (OPCs) into the affected brain or spinal cord. OPCs have been isolated by their expression of gangliosides recognized by mAb A2B5, but this marker also identifies lineage-restricted astrocytes and immature neurons. To establish a more efficient means of isolating myelinogenic OPCs, we sorted fetal human forebrain cells for CD140a, an epitope of platelet derived growth factor receptor (PDGFR)α, which is differentially expressed by OPCs. CD140a(+) cells were isolated as mitotic bipotential progenitors that initially expressed neither mature neuronal nor astrocytic phenotypic markers, yet could be instructed to either oligodendrocyte or astrocyte fate in vitro. Transplanted CD140a(+) cells were highly migratory and robustly myelinated the hypomyelinated shiverer mouse brain more rapidly and efficiently than did A2B5(+)cells. Microarray analysis of CD140a(+) cells revealed overexpression of the oligodendroglial marker CD9, suggesting that CD9(+)/CD140a(+) cells may constitute an even more highly enriched population of myelinogenic progenitor cells.

Background: Spinal cord injury is a serious and debilitating condition, affecting millions of people worldwide. Long seen as a permanent injury, recent advances in stem cell research have brought closer the possibility of repairing the spinal cord. One such approach involves injecting oligodendrocyte progenitor cells, derived from human embryonic stem cells, into the injured spinal cord in the hope that they will initiate repair. A phase I clinical trial of this therapy was started in mid 2010 and is currently underway., Discussion: The theory underlying this approach is that these myelinating progenitors will phenotypically replace myelin lost during injury whilst helping to promote a repair environment in the lesion. However, the importance of demyelination in the pathogenesis of human spinal cord injury is a contentious issue and a body of literature suggests that it is only a minor factor in the overall injury process., Summary: This review examines the validity of the theory underpinning the on-going clinical trial as well as analysing published data from animal models and finally discussing issues surrounding safety and purity in order to assess the potential of this approach to successfully treat acute human spinal cord injury.

This study has tested the feasibility of using physical delivery methods, employing static and oscillating field "magnetofection" techniques, to enhance magnetic nanoparticle-mediated gene transfer to rat oligodendrocyte precursor cells derived for transplantation therapies. These cells are a major transplant population to mediate repair of damage as occurs in spinal cord injury and neurological diseases such as multiple sclerosis. We show for the first time that magnetic nanoparticles mediate effective transfer of reporter and therapeutic genes to oligodendrocyte precursors; transfection efficacy was significantly enhanced by applied static or oscillating magnetic fields, the latter using an oscillating array employing high-gradient NdFeB magnets. The effects of oscillating fields were frequency-dependent, with 4 Hz yielding optimal results. Transfection efficacies obtained using magnetofection methods were highly competitive with or better than current widely used nonviral transfection methods (e.g., electroporation and lipofection) with the additional critical advantage of high cell viability. No adverse effects were found on the cells' ability to divide or give rise to their daughter cells, the oligodendrocytes-key properties that underpin their regeneration-promoting effects. The transplantation potential of transfected cells was tested in three-dimensional tissue engineering models utilizing brain slices as the host tissue; modified transplanted cells were found to migrate, divide, give rise to daughter cells, and integrate within host tissue, further evidencing the safety of the protocols used. Our findings strongly support the concept that magnetic nanoparticle vectors in conjunction with state-of-the-art magnetofection strategies provide a technically simple and effective alternative to current methods for gene transfer to oligodendrocyte precursor cells., (© 2011 American Chemical Society)