Homologous Transplantation of Neural Stem Cells to the Injured Spinal Cord of Mice

Advances of Schwann cells in peripheral nerve regeneration: From mechanism to cell therapy

Peripheral nerve injuries (PNIs) frequently occur due to various factors, including mechanical trauma such as accidents or tool-related incidents, as well as complications arising from diseases like tumor resection. These injuries frequently result in persistent numbness, impaired motor and sensory functions, neuropathic pain, or even paralysis, which can impose a significant financial burden on patients due to outcomes that often fall short of expectations. The most frequently employed clinical treatment for PNIs involves either direct sutures of the severed ends or bridging the proximal and distal stumps using autologous nerve grafts. However, autologous nerve transplantation may result in sensory and motor functional loss at the donor site, as well as neuroma formation and scarring. Transplantation of Schwann cells/Schwann cell-like cells has emerged as a promising cellular therapy to reconstruct the microenvironment and facilitate peripheral nerve regeneration. In this review, we summarize the role of Schwann cells and recent advances in Schwann cell therapy in peripheral nerve regeneration. We summarize current techniques used in cell therapy, including cell injection, 3D-printed scaffolds for cell delivery, cell encapsulation techniques, as well as the cell types employed in experiments, experimental models, and research findings. At the end of the paper, we summarize the challenges and advantages of various cells (including ESCs, iPSCs, and BMSCs) in clinical cell therapy. Our goal is to provide the theoretical and experimental basis for future treatments targeting peripheral nerves, highlighting the potential of cell therapy and tissue engineering as invaluable resources for promoting nerve regeneration.

Biomaterial-Based Schwann Cell Transplantation and Schwann Cell-Derived Biomaterials for Nerve Regeneration

Schwann cells (SCs) dominate the regenerative behaviors after peripheral nerve injury by supporting axonal regrowth and remyelination. Previous reports also demonstrated that the existence of SCs is beneficial for nerve regeneration after traumatic injuries in central nervous system. Therefore, the transplantation of SCs/SC-like cells serves as a feasible cell therapy to reconstruct the microenvironment and promote nerve functional recovery for both peripheral and central nerve injury repair. However, direct cell transplantation often leads to low efficacy, due to injection induced cell damage and rapid loss in the circulatory system. In recent years, biomaterials have received great attention as functional carriers for effective cell transplantation. To better mimic the extracellular matrix (ECM), many biodegradable materials have been engineered with compositional and/or topological cues to maintain the biological properties of the SCs/SCs-like cells. In addition, ECM components or factors secreted by SCs also actively contribute to nerve regeneration. Such cell-free transplantation approaches may provide great promise in clinical translation. In this review, we first present the current bio-scaffolds engineered for SC transplantation and their achievement in animal models and clinical applications. To this end, we focus on the physical and biological properties of different biomaterials and highlight how these properties affect the biological behaviors of the SCs/SC-like cells. Second, the SC-derived biomaterials are also reviewed and discussed. Finally, the relationship between SCs and functional biomaterials is summarized, and the trends of their future development are predicted toward clinical applications.

Adult Neural Progenitor Cells Transplanted into Spinal Cord Injury Differentiate into Oligodendrocytes, Enhance Myelination, and Contribute to Recovery

Long-term survival and integration of neural progenitor cells (NPCs) transplanted following spinal cord injury (SCI) have been observed. However, questions concerning the differentiation choice, the mechanism of action, and the contribution of NPCs to functional recovery remains unanswered. Therefore, we investigated the differentiation of NPCs, global transcriptomal changes in transplanted NPCs, the effect of NPCs on neuroinflammation, and the causality between NPC transplantation and functional recovery. We found that NPCs transplanted following SCI differentiate mainly into oligodendrocytes and enhance myelination, upregulate genes related to synaptic signaling and mitochondrial activity, and downregulate genes related to cytokine production and immune system response. NPCs suppress the expression of pro-inflammatory cytokines/chemokines; moreover, NPC ablation confirm that NPCs were responsible for enhanced recovery in hindlimb locomotor function. Understanding the reaction of transplanted NPCs is important for exploiting their full potential. Existence of causality implies that NPCs are useful in the treatment of SCI.

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NPCs differentiate mainly into oligodendrocytes and enhance myelination

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NPCs suppress expression of pro-inflammatory cytokines/chemokines

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Causality exists between transplantation of NPCs and functional recovery

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NPCs upregulate genes related to synaptic signaling, oligodendrocytes/myelination

Effect of hyperbaric oxygen therapy on HMGB1/NF-κB expression and prognosis of acute spinal cord injury: A randomized clinical trial

Although there are reports of the beneficial effects of hyperbaric oxygen (HBO) therapy in experimental settings, there are few clinical trials of HBO therapy for acute spinal cord injury (SCI). We investigated the effect of HBO in acute SCI by measuring plasma high mobility group box 1 (HMGB1) and nuclear factor kappa-B (NF-κB) levels, and by monitoring changes in electromyogram F-persistence (the percentage of discernible F-waves) and F-chronodispersion (the difference between minimal and maximal latency). We enrolled 79 acute SCI patients and randomly divided them into control (conventional treatment) and the treatment (conventional treatment plus HBO therapy) groups. Plasma was collected before treatment and after treatment on 1st, 3rd, 7th, 10th and 30th day for the measurement of HMGB1 and NF-κB. Electromyogram F-waves were detected before therapy and after therapy on the 10th and 30th days. Clinical profiles and neurological outcomes were evaluated using American Spinal Injury Association (ASIA) and Frankel Grade scores. Compared to the control group, HBO therapy down-regulated HMGB1 and NF-κB expression in patients with acute SCI on days 3, 7, 10 and 30 (p < 0.05). F-wave chronodispersion decreased at days 10 and 30 (p < 0.01) following HBO. ASIA and Frankel Grade motor/pain scores in the treatment group were significantly improved on day 30 (p < 0.01). There was a positive correlation between plasma NF-κB at day 7 and F-wave dispersion at day 30 (r = 0.76, p = 0.00). In summary, HBO therapy regulated the inflammatory reaction in secondary SCI by decreasing plasma HMGB1/NF-κB levels and reducing the dispersion of electromyogram F-waves of the lower limbs, thereby promoting neurological function recovery.

Repeated injections of human umbilical cord blood-derived mesenchymal stem cells significantly promotes functional recovery in rabbits with spinal cord injury of two noncontinuous segments

Background

Spinal cord injuries (SCIs) are sustained by an increasing number of patients each year worldwide. The treatment of SCIs has long been a hard nut to crack for doctors around the world. Mesenchymal stem cells (MSCs) have shown benefits for the repair of SCI and recovery of function. Our present study aims to investigate the effects of intravenously infused human umbilical cord blood-derived MSCs (hUCB-MSCs) on functional recovery after subacute spinal cord compression injury of two noncontinuous segments. In addition, we compared the effects of single infusion and repeated intravenous (i.v.) injections on the recovery of spinal cord function.

Methods

A total of 43 adult rabbits were randomly divided into four groups: control, single injection (SI), repeated injection at a 3-day (3RI) or repeated injection at a 7-day interval (7RI) groups. Non-immunosuppressed rabbits in the transplantation groups were infused with either a single complete dose or three divided doses of 2 × 10⁶ hUCB-MSCs (3-day or 7-day intervals) on the first day post decompression. Behavioural scores and somatosensory evoked potentials (SEPs) were used to evaluate hindlimb functional recovery. The survival and differentiation of the transplanted human cells and the activation of the host glial and inflammatory reaction in the injured spinal cord were studied by immunohistochemical staining.

Results

Our results showed that hUCB-MSCs survived, proliferated, and primarily differentiated into oligodendrocytes in the injured area. Treatment with hUCB-MSCs reduced the extent of astrocytic activation, increased axonal preservation, potentially promoted axonal regeneration, decreased the number of Iba-1+ and TUNEL+ cells, increased the amplitude and decreased the onset latency of SEPs and significantly promoted functional improvement. However, these effects were more pronounced in the 3RI group compared with the SI and 7RI groups.

Conclusions

Our results suggest that treatment with i.v. injected hUCB-MSCs after subacute spinal cord compression injury of two noncontinuous segments can promote functional recovery through the differentiation of hUCB-MSCs into specific cell types and the enhancement of anti-inflammatory, anti-astrogliosis, anti-apoptotic and axonal preservation effects. Furthermore, the recovery was more pronounced in the rabbits repeatedly injected with cells at 3-day intervals. The results of this study may provide a novel and useful treatment strategy for the transplantation treatment of SCI.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0879-0) contains supplementary material, which is available to authorized users.

Hyperbaric oxygen ameliorated the lesion scope and nerve function in acute spinal cord injury patients: A retrospective study

OBJECTIVE

This is a retrospective study to assess the therapeutic effect of hyperbaric oxygen (HBO) in early treatment of acute spinal cord injury (SCI) using magnetic resonance imaging (MRI) and electrophysiology in diagnosing.

METHODS

Forty acute SCI patients from Sun Yat-Sen Memorial Hospital who were assigned into HBO treatment were included during August 2013 to October 2014.The patients with adverse reactions or contraindications for HBO were assigned as controls. Both of two groups (HBO and Control) received medicine treatment with Urbason, GM-1 and mecobalamine after surgery. ASIA and the Frankel scores were used to evaluate the therapeutic effect of HBO at the 15th and 30th day after HBO treatment by using MRI and electrophysiology features.

RESULTS

Significant therapeutic effect of HBO treatment on acute SCI patients was observed compared with the control group (P<0.05). Comparison for ASIA and Frankel scores showed that motor and neurological functions were significantly improved in HBO group at day 15 and day 30 post treatment. MRI images showed that the grade III injury in HBO group was significant lower than the control group. In comparison with the control, the peak of somatosensory evoked potential (SEP) and motor evoked potential (MEP) amplitude increased, the latency was shortened, and the conduction velocity of sensory nerve (SCV) and motor nerve (MCV) was significantly increased in the HBO group (P<0.05).

CONCLUSIONS

HBO treatment has a great efficacy in acute SCI patients. HBO therapy at early stage of acute SCI is beneficiary to the recovery.

Nerve growth factor delivery by ultrasound-mediated nanobubble destruction as a treatment for acute spinal cord injury in rats

Background

Spinal cord injuries (SCIs) can cause severe disability or death. Treatment options include surgical intervention, drug therapy, and stem cell transplantation. However, the efficacy of these methods for functional recovery remains unsatisfactory.

Purpose

This study was conducted to explore the effect of ultrasound (US)-mediated destruction of poly(lactic-co-glycolic acid) (PLGA) nanobubbles (NBs) expressing nerve growth factor (NGF) (NGF/PLGA NBs) on nerve regeneration in rats following SCI.

Materials and methods

Adult male Sprague Dawley rats were randomly divided into four treatment groups after Allen hit models of SCI were established. The groups were normal saline (NS) group, NGF and NBs group, NGF and US group, and NGF/PLGA NBs and US group. Histological changes after SCI were observed by hematoxylin and eosin staining. Neuron viability was determined by Nissl staining. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining was used to examine cell apoptosis. NGF gene and protein expressions were detected by quantitative reverse transcription polymerase chain reaction and Western blotting. Green fluorescent protein expression in the spinal cord was examined using an inverted fluorescence microscope. The recovery of neural function was determined using the Basso, Beattie, and Bresnahan test.

Results

NGF therapy using US-mediated NGF/PLGA NBs destruction significantly increased NGF expression, attenuated histological injury, decreased neuron loss, inhibited neuronal apoptosis in injured spinal cords, and increased BBB scores in rats with SCI.

Conclusion

US-mediated NGF/PLGA NBs destruction effectively transfects the NGF gene into target tissues and has a significant effect on the injured spinal cord. The combination of US irradiation and gene therapy through NGF/PLGA NBs holds great promise for the future of nanomedicine and the development of noninvasive treatment options for SCI and other diseases.

Stem cell transplantation for spinal cord injury repair

Stem cells, especially neural stem cells (NSCs), are a very attractive cell source for potential reconstruction of injured spinal cord though either neuroprotection, neural regeneration, remyelination, replacement of lost neural cells, or reconnection of disrupted axons. The later have great potential since recent studies demonstrate long-distance growth and connectivity of axons derived from transplanted NSCs after spinal cord injury (SCI). In addition, transplanted NSCs constitute a permissive environment for host axonal regeneration and serve as new targets for host axonal connection. This reciprocal connection between grafted neurons and host neurons constitutes a neuronal relay formation that could restore functional connectivity after SCI.

CD44 fucosylation on mesenchymal stem cell enhances homing and macrophage polarization in ischemic kidney injury

The lack of homing ability possibly reduces the healing potential of bone-marrow-derived mesenchymal stem cells (MSCs). Therefore, transforming native CD44 on MSCs into a hematopoietic cell E-/L-selectin ligand (HCELL) that possesses potent E-selectin affinity might enhance the homing and regenerative abilities of MSCs. Through fucosyltransferase VI (FTVI) transfection, MSCs were fucosylated on N-glycans of CD44 to become HCELL positive, thus interacting with E-selectin on injured endothelial cells. HCELL expression facilitated MSC homing in kidneys within 24h after injury and reduced lung stasis. An in vitro adhesion assay revealed that transfection enhanced the association between MSCs and hypoxic endothelial cells. In mice treated with HCELL-positive MSCs, the injured kidneys exhibited clusters of homing MSCs, whereas MSCs were rarely observed in mouse kidneys treated with HCELL-negative MSCs. Most MSCs were initially localized at the renal capsule, and some MSCs later migrated inward between tubules. Most homing MSCs were in close contact with inflammatory cells without tubular transdifferentiation. Furthermore, HCELL-positive MSCs substantially alleviated renal injury, partly by enhancing the polarization of infiltrating macrophages. In conclusion, engineering the glycan of CD44 on MSCs through FTVI transfection might enhance renotropism and the regenerating ability of MSCs in ischemic kidney injury.

Neural stem/progenitor cell transplantation for spinal cord injury treatment; A systematic review and meta-analysis

Despite the vast improvements of cell therapy in spinal cord injury treatment, no optimum protocol has been developed for application of neural stem/progenitor cells. In this regard, the present meta-analysis showed that the efficacy of the neural stem/progenitor cell (NSPC) transplantation depends mainly on injury model, intervention phase, transplanted cell count, immunosuppressive use, and probably stem cell source. Improved functional recovery post NSPC transplantation was found to be higher in transection and contusion models. Moreover, NSPC transplantation in acute phase of spinal injury was found to have better functional recovery. Higher doses (>3×10(6)cell/kg) were also shown to be optimum for transplantation, but immunosuppressive agent administration negatively affected the motor function recovery. Scaffold use in NSPC transplantation could also effectively raise functional recovery.

Therapeutic potential of human olfactory bulb neural stem cells for spinal cord injury in rats

STUDY DESIGN

Adult human olfactory bulb neural stem cells (OBNSCs) were isolated from human patients undergoing craniotomy for tumor resection. They were genetically engineered to overexpresses green fluorescent protein (GFP) to help trace them following engraftment. Spinal cord injury (SCI) was induced in rats using standard laminectomy protocol, and GFP-OBNSC were engrafted into rat model of SCI at day 7 post injury. Three rat groups were used: (i) Control group, (ii) Sham group (injected with cerebrospinal fluid) and treated group (engrafted with OBNSCs). Tissues from different groups were collected weekly up to 2 months. The collected tissues were fixed in 4% paraformaldehyde, processed for paraffin sectioning, immunohistochemically stained for different neuronal and glial markers and examined with bright-field fluorescent microscopy. Restoration of sensory motor functions we assessed on a weekly bases using the BBB score.

OBJECTIVES

To assess the therapeutic potential of OBNSCs-GFP and their ability to survive, proliferate, differentiate and to restore lost sensory motor functions following their engraftment in spinal cord injury (SCI).

METHODS

GFP-OBNSC were engrafted into a rat model of SCI at day 7 post injury and were followed-up to 8 weeks using behavioral and histochemical methods.

RESULTS

All transplanted animals exhibited successful engraftment. The survival rate was about 30% of initially transplanted cells. Twenty-seven percent of the engrafted cells differentiated along the NG2 and O4-positive oligodendrocyte lineage, 16% into MAP2 and β-tubulin-positive neurons, and 56% into GFAP-positive astrocytes.

CONCLUSION

GFP-OBNSCs had survived for >8 weeks after engraftment and were differentiated into neurons, astrocytes and oligodendrocytes, The engrafted cells were distributed throughout gray and white matter of the cord with no evidence of abnormal morphology or any mass formation indicative of tumorigenesis. However, the engrafted cells failed to restore lost sensory and motor functions as evident from behavioral analysis using the BBB score test.

α-Linolenic Acid, A Nutraceutical with Pleiotropic Properties That Targets Endogenous Neuroprotective Pathways to Protect against Organophosphate Nerve Agent-Induced Neuropathology

α-Linolenic acid (ALA) is a nutraceutical found in vegetable products such as flax and walnuts. The pleiotropic properties of ALA target endogenous neuroprotective and neurorestorative pathways in brain and involve the transcription factor nuclear factor kappa B (NF-κB), brain-derived neurotrophic factor (BDNF), a major neuroprotective protein in brain, and downstream signaling pathways likely mediated via activation of TrkB, the cognate receptor of BDNF. In this review, we discuss possible mechanisms of ALA efficacy against the highly toxic OP nerve agent soman. Organophosphate (OP) nerve agents are highly toxic chemical warfare agents and a threat to military and civilian populations. Once considered only for battlefield use, these agents are now used by terrorists to inflict mass casualties. OP nerve agents inhibit the critical enzyme acetylcholinesterase (AChE) that rapidly leads to a cholinergic crisis involving multiple organs. Status epilepticus results from the excessive accumulation of synaptic acetylcholine which in turn leads to the overactivation of muscarinic receptors; prolonged seizures cause the neuropathology and long-term consequences in survivors. Current countermeasures mitigate symptoms and signs as well as reduce brain damage, but must be given within minutes after exposure to OP nerve agents supporting interest in newer and more effective therapies. The pleiotropic properties of ALA result in a coordinated molecular and cellular program to restore neuronal networks and improve cognitive function in soman-exposed animals. Collectively, ALA should be brought to the clinic to treat the long-term consequences of nerve agents in survivors. ALA may be an effective therapy for other acute and chronic neurodegenerative disorders.

Propofol promotes spinal cord injury repair by bone marrow mesenchymal stem cell transplantation

Propofol is a neuroprotective anesthetic. Whether propofol can promote spinal cord injury repair by bone marrow mesenchymal stem cells remains poorly understood. We used rats to investigate spinal cord injury repair using bone marrow mesenchymal stem cell transplantation combined with propofol administration via the tail vein. Rat spinal cord injury was clearly alleviated; a large number of newborn non-myelinated and myelinated nerve fibers appeared in the spinal cord, the numbers of CM-Dil-labeled bone marrow mesenchymal stem cells and fluorogold-labeled nerve fibers were increased and hindlimb motor function of spinal cord-injured rats was markedly improved. These improvements were more prominent in rats subjected to bone marrow mesenchymal cell transplantation combined with propofol administration than in rats receiving monotherapy. These results indicate that propofol can enhance the therapeutic effects of bone marrow mesenchymal stem cell transplantation on spinal cord injury in rats.

Hyperbaric oxygen therapy combined with Schwann cell transplantation promotes spinal cord injury recovery

Schwann cell transplantation and hyperbaric oxygen therapy each promote recovery from spinal cord injury, but it remains unclear whether their combination improves therapeutic results more than monotherapy. To investigate this, we used Schwann cell transplantation via the tail vein, hyperbaric oxygen therapy, or their combination, in rat models of spinal cord contusion injury. The combined treatment was more effective in improving hindlimb motor function than either treatment alone; injured spinal tissue showed a greater number of neurite-like structures in the injured spinal tissue, somatosensory and motor evoked potential latencies were notably shorter, and their amplitudes greater, after combination therapy than after monotherapy. These findings indicate that Schwann cell transplantation combined with hyperbaric oxygen therapy is more effective than either treatment alone in promoting the recovery of spinal cord in rats after injury.

Olfactory ensheathing cells promote differentiation of neural stem cells and robust neurite extension

AIMS

The goal of this study was to gain insight into the signaling between olfactory ensheathing cells (OECs) and neural stem cells (NSCs). We sought to understand the impact of OECs on NSC differentiation and neurite extension and to begin to elucidate the factors involved in these interactions to provide new targets for therapeutic interventions.

MATERIALS AND METHODS

We utilized lines of OECs that have been extremely well characterized in vitro and in vivo along with well studied NSCs in gels to determine the impact of the coculture in three dimensions. To further elucidate the signaling, we used conditioned media from the OECs as well as fractioned components on NSCs to determine the molecular weight range of the soluble factors that was most responsible for the NSC behavior.

RESULTS

We found that the coculture of NSCs and OECs led to robust NSC differentiation and extremely long neural processes not usually seen with NSCs in three dimensional gels in vitro. Through culture of NSCs with fractioned OEC media, we determined that molecules larger than 30 kDa have the greatest impact on the NSC behavior.

CONCLUSIONS

Overall, our findings suggest that cocultures of NSCs and OECs may be a novel combination therapy for neural injuries including spinal cord injury (SCI). Furthermore, we have identified a class of molecules which plays a substantial role in the behavior that provides new targets for investigating pharmacological therapies.

Alpha-linolenic acid: an omega-3 fatty acid with neuroprotective properties-ready for use in the stroke clinic?

Alpha-linolenic acid (ALA) is plant-based essential omega-3 polyunsaturated fatty acids that must be obtained through the diet. This could explain in part why the severe deficiency in omega-3 intake pointed by numerous epidemiologic studies may increase the brain's vulnerability representing an important risk factor in the development and/or deterioration of certain cardio- and neuropathologies. The roles of ALA in neurological disorders remain unclear, especially in stroke that is a leading cause of death. We and others have identified ALA as a potential nutraceutical to protect the brain from stroke, characterized by its pleiotropic effects in neuroprotection, vasodilation of brain arteries, and neuroplasticity. This review highlights how chronic administration of ALA protects against rodent models of hypoxic-ischemic injury and exerts an anti-depressant-like activity, effects that likely involve multiple mechanisms in brain, and may be applied in stroke prevention. One major effect may be through an increase in mature brain-derived neurotrophic factor (BDNF), a widely expressed protein in brain that plays critical roles in neuronal maintenance, and learning and memory. Understanding the precise roles of ALA in neurological disorders will provide the underpinnings for the development of new therapies for patients and families who could be devastated by these disorders.

Hyperbaric oxygen therapy improves local microenvironment after spinal cord injury

Clinical studies have shown that hyperbaric oxygen therapy improves motor function in patients with spinal cord injury. In the present study, we explored the mechanisms associated with the recovery of neurological function after hyperbaric oxygen therapy in a rat model of spinal cord injury. We established an acute spinal cord injury model using a modification of the free-falling object method, and treated the animals with oxygen at 0.2 MPa for 45 minutes, 4 hours after injury. The treatment was administered four times per day, for 3 days. Compared with model rats that did not receive the treatment, rats exposed to hyperbaric oxygen had fewer apoptotic cells in spinal cord tissue, lower expression levels of aquaporin 4/9 mRNA and protein, and more NF-200 positive nerve fibers. Furthermore, they had smaller spinal cord cavities, rapid recovery of somatosensory and motor evoked potentials, and notably better recovery of hindlimb motor function than model rats. Our findings indicate that hyperbaric oxygen therapy reduces apoptosis, downregulates aquaporin 4/9 mRNA and protein expression in injured spinal cord tissue, improves the local microenvironment for nerve regeneration, and protects and repairs the spinal cord after injury.

Mild hypothermia combined with a scaffold of NgR-silenced neural stem cells/Schwann cells to treat spinal cord injury

Because the inhibition of Nogo proteins can promote neurite growth and nerve cell differentiation, a cell-scaffold complex seeded with Nogo receptor (NgR)-silenced neural stem cells and Schwann cells may be able to improve the microenvironment for spinal cord injury repair. Previous studies have found that mild hypothermia helps to attenuate secondary damage in the spinal cord and exerts a neuroprotective effect. Here, we constructed a cell-scaffold complex consisting of a poly(D,L-lactide-co-glycolic acid) (PLGA) scaffold seeded with NgR-silenced neural stem cells and Schwann cells, and determined the effects of mild hypothermia combined with the cell-scaffold complexes on the spinal cord hemi-transection injury in the T₉ segment in rats. Compared with the PLGA group and the NgR-silencing cells + PLGA group, hindlimb motor function and nerve electrophysiological function were clearly improved, pathological changes in the injured spinal cord were attenuated, and the number of surviving cells and nerve fibers were increased in the group treated with the NgR-silenced cell scaffold + mild hypothermia at 34°C for 6 hours. Furthermore, fewer pathological changes to the injured spinal cord and more surviving cells and nerve fibers were found after mild hypothermia therapy than in injuries not treated with mild hypothermia. These experimental results indicate that mild hypothermia combined with NgR gene-silenced cells in a PLGA scaffold may be an effective therapy for treating spinal cord injury.

Magnetic manipulation of bacterial magnetic nanoparticle-loaded neurospheres

Specific targeting of cells to sites of tissue damage and delivery of high numbers of transplanted cells to lesion tissue in vivo are critical parameters for the success of cell-based therapies. Here, we report a promising in vitro model system for studying the homing of transplanted cells, which may eventually be applicable for targeted regeneration of damaged neurons in spinal cord injury. In this model system, neurospheres derived from human neuroblastoma SH-SY5Y cells labeled with bacterial magnetic nanoparticles were guided by a magnetic field and successfully accumulated near the focus site of the magnetic field. Our results demonstrate the effectiveness of using an in vitro model for testing bacterial magnetic nanoparticles to develop successful stem cell targeting strategies during fluid flow, which may ultimately be translated into in vivo targeted delivery of cells through circulation in various tissue-repair models.

Neural stem cell transplantation in a double-layer collagen membrane with unequal pore sizes for spinal cord injury repair

A novel double-layer collagen membrane with unequal pore sizes in each layer was designed and tested in this study. The inner, loose layer has about 100-μm-diameter pores, while the outer, compact layer has about 10-μm-diameter pores. In a rat model of incomplete spinal cord injury, a large number of neural stem cells were seeded into the loose layer, which was then adhered to the injured side, and the compact layer was placed against the lateral side. The results showed that the transplantation of neural stem cells in a double-layer collagen membrane with unequal pore sizes promoted the differentiation of neural stem cells, attenuated the pathological lesion, and significantly improved the motor function of the rats with incomplete spinal cord injuries. These experimental findings suggest that the transplantation of neural stem cells in a double-layer collagen membrane with unequal pore sizes is an effective therapeutic strategy to repair an injured spinal cord.

Transplantation of Nogo-66 receptor gene-silenced cells in a poly(D,L-lactic-co-glycolic acid) scaffold for the treatment of spinal cord injury

Inhibition of neurite growth, which is in large part mediated by the Nogo-66 receptor, affects neural regeneration following bone marrow mesenchymal stem cell transplantation. The tissue engineering scaffold poly(D,L-lactide-co-glycolic acid) has good histocompatibility and can promote the growth of regenerating nerve fibers. The present study used small interfering RNA to silence Nogo-66 receptor gene expression in bone marrow mesenchymal stem cells and Schwann cells, which were subsequently transplanted with poly(D,L-lactide-co-glycolic acid) into the spinal cord lesion regions in rats. Simultaneously, rats treated with scaffold only were taken as the control group. Hematoxylin-eosin staining and immunohistochemistry revealed that at 4 weeks after transplantation, rats had good motor function of the hind limb after treatment with Nogo-66 receptor gene-silenced cells plus the poly(D,L-lactide-co-glycolic acid) scaffold compared with rats treated with scaffold only, and the number of bone marrow mesenchymal stem cells and neuron-like cells was also increased. At 8 weeks after transplantation, horseradish peroxidase tracing and transmission electron microscopy showed a large number of unmyelinated and myelinated nerve fibers, as well as intact regenerating axonal myelin sheath following spinal cord hemisection injury. These experimental findings indicate that transplantation of Nogo-66 receptor gene-silenced bone marrow mesenchymal stem cells and Schwann cells plus a poly(D,L-lactide-co-glycolic acid) scaffold can significantly enhance axonal regeneration of spinal cord neurons and improve motor function of the extremities in rats following spinal cord injury.

Influence of local environment on the differentiation of neural stem cells engrafted onto the injured spinal cord

OBJECTIVES

In vitro, neural stem cells (NSCs) proliferate as undifferentiated spheroids and differentiate into neurons, astrocytes and oligodendrocytes. These features make NSCs suitable for spinal cord (SC) reconstruction. However, in vivo experiments have demonstrated that in the injured SC transplanted NSCs either remain undifferentiated or differentiate into the astrocytic phenotype. The microenvironment of the injured SC is believed to play a crucial role in driving the differentiation of the engrafted NSCs. Here, we tested the hypothesis that inflammatory cytokines (ICs) may be involved in the restricted differentiation of NSCs after grafting onto the injured SC.

METHODS

As the first step, we used immunohistochemistry to analyse the expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta and interferon (IFN)-gamma in the normal SC of mice and following traumatic injury. Then, we investigated whether a combination of TNF-alpha, IL-1beta and IFN-gamma may affect the phenotype of murine NSCs in vitro.

RESULTS

We found that TNF-alpha, IL-1beta and IFN-gamma, which are absent in the normal SC, are all expressed in the injured SC and the expression of these cytokines follows a timely tuned fashion with IFN-gamma being detectable as long as 4 weeks after injury. In culture, exposure of proliferating NSCs to a combination of TNF-alpha, IL-1beta and IFN-gamma was per se sufficient to induce the astrocytic differentiation of these cells even in the absence of serum.

CONCLUSIONS

In the traumatically injured SC, differentiation of engrafted NSCs is restricted towards the astrocytic lineage because of the inflammatory environment. ICs are likely to play a major role in differentiation of NSCs in the in vivo conditions.

Locomotor recovery after spinal cord hemisection/contusion injures in bonnet monkeys: footprint testing--a minireview

Spinal cord injuries usually produce loss or impairment of sensory, motor and reflex function below the level of damage. In the absence of functional regeneration or manipulations that promote regeneration, spontaneous improvements in motor functions occur due to the activation of multiple compensatory mechanisms in animals and humans following the partial spinal cord injury. Many studies were performed on quantitative evaluation of locomotor recovery after induced spinal cord injury in animals using behavioral tests and scoring techniques. Although few studies on rodents have led to clinical trials, it would appear imperative to use nonhuman primates such as macaque monkeys in order to relate the research outcomes to recovery of functions in humans. In this review, we will discuss some of our research evidences concerning the degree of spontaneous recovery in bipedal locomotor functions of bonnet monkeys that underwent spinal cord hemisection/contusion lesions. To our knowledge, this is the first report to discuss on the extent of spontaneous recovery in bipedal locomotion of macaque monkeys through the application of footprint analyzing technique. In addition, the results obtained were compared with the published data on recovery of quadrupedal locomotion of spinally injured rodents. We propose that the mechanisms underlying spontaneous recovery of functions in spinal cord lesioned monkeys may be correlated to the mature function of spinal pattern generator for locomotion under the impact of residual descending and afferent connections. Moreover, based on analysis of motor functions observed in locomotion in these subjected monkeys, we understand that spinal automatism and development of responses by afferent stimuli from outside the cord could possibly contribute to recovery of paralyzed hindlimbs. This report also emphasizes the functional contribution of progressive strengthening of undamaged nerve fibers through a collateral sprouts/synaptic plasticity formed in partially lesioned cord of monkeys.

Combined Transplantation of Human Neuronal and Mesenchymal Stem Cells following Spinal Cord Injury

Transplantation of human fetal neural stem cells (hNSCs) previously demonstrated significant functional recovery after spinal cord contusion in rats. Other studies indicated that human mesenchymal stem cells (hMSCs) can home to areas of damage and cross the blood-brain barrier. The purpose of this article is to determine if combined administration of mesenchymal stem cells and neuronal stem cells improves functional outcomes in rats. The study design was a randomized controlled animal trial. Female adult Long-Evans hooded rats underwent laminectomy at T10 level. Moderate spinal cord contusion at T10 level was induced by the MASCIS Impactor. Four groups were identified. The MSC + NSC group received hMSCs intravenously (IV) immediately after spinal cord injury (acute) and returned 1 week later (subacute) for injection of hNSC directly at site of injury. The MSC-only group received hMSC IV acutely and cell media subacutely. The NSC-only group received cell media IV acutely and hNSC subacutely. The control group received cell media IV acutely and subacutely. Subjects were assessed for 6 weeks using Basso, Beattie, Bresnahan Locomotor Rating Score. Twenty-four subjects were utilized, six subjects in each group. Statistically significant functional improvement was seen in the MSC + NSC group and the NSC-only group versus controls (p = 0.027, 0.042, respectively). The MSC-only group did not demonstrate a significant improvement over control (p = 0.145). Comparing the MSC + NSC group and the NSC-only group, there was no significant difference (p = 0.357). Subacute transplantation of hNSCs into contused spinal cord of rats led to significant functional recovery when injected either with or without acute IV administration of hMSCs. Neither hMSCs nor addition of hMSC to hNSC resulted in significant improvement.

Concise review: the potential of stromal cell-derived factor 1 and its receptors to promote stem cell functions in spinal cord repair

Transplanted stem cells provide beneficial effects on regeneration/recovery after spinal cord injury (SCI) by the release of growth-promoting factors, increased tissue preservation, and provision of a permissive environment for axon regeneration. A rise in chemokine stromal cell-derived factor 1 (SDF-1/CXCL12) expression levels in central nervous system (CNS) injury sites has been shown to play a central role in recruiting transplanted stem cells. Although technically more challenging, it has been shown that after SCI few endogenous stem cells are recruited via SDF-1/CXCR4 signaling. Evidence is accumulating that increasing SDF-1 levels at the injury site (e.g., by exogenous application or transfection methods) further enhances stem cell recruitment. Moreover, SDF-1 might, in addition to migration, also influence survival, proliferation, differentiation, and cytokine secretion of stem cells. Here, we discuss the experimental data available on the role of SDF-1 in stem and progenitor cell biology following CNS injury and suggest strategies for how manipulation of the SDF-1 system could facilitate stem cell-based therapeutic approaches in SCI. In addition, we discuss challenges such as how to circumvent off-target effects in order to facilitate the transfer of SDF-1 to the clinic.

Estradiol promotes neural stem cell differentiation into endothelial lineage and angiogenesis in injured peripheral nerve

Neural stem cells (NSCs) differentiate into endothelial cells (ECs) and neuronal cells. Estradiol (E2) is known to exhibit proangiogenic effects on ischemic tissues via EC activation. Therefore, we hypothesized that E2 can promote the therapeutic potential of NSC transplantation for injured nerve repair via the differentiation of NSCs into ECs during neovascularization. NSCs isolated from newborn mouse brains were transplanted into injured sciatic nerves with (NSC/E2 group) or without E2-conjugated gelatin hydrogel (E2 group). The NSC/E2 group exhibited the greatest recovery in motor nerve conduction velocity, voltage amplitude, and exercise tolerance. Histological analyses revealed increased intraneural vascularity and blood perfusion as well as striking NSC recruitment to the neovasculature in the injured nerves in the NSC/E2 group. In vitro, E2 enhanced the NSC migration and proliferation inhibiting apoptosis. Fluorescence-activated cell sorting analysis also revealed that E2 significantly increased the percentage of CD31 in NSCs, and the effect of E2 was completely neutralized by the estrogen receptor antagonist ICI. The combination of E2 administration and NSC transplantation cooperatively improved the functional recovery of injured peripheral nerves, at least in part, via E2-associated NSC differentiation into ECs. These findings provide a novel mechanistic insight into both NSC biology and the biological effects of endogenous E2.

Current challenges for the advancement of neural stem cell biology and transplantation research

Transplantation of neural stem cells (NSC) is hoped to become a promising primary or secondary therapy for the treatment of various neurodegenerative disorders of the central nervous system (CNS), as demonstrated by multiple pre-clinical animal studies in which functional recovery has already been demonstrated. However, for NSC therapy to be successful, the first challenge will be to define a transplantable cell population. In the first part of this review, we will briefly discuss the main features of ex vivo culture and characterisation of NSC. Next, NSC grafting itself may not only result in the regeneration of lost tissue, but more importantly has the potential to improve functional outcome through many bystander mechanisms. In the second part of this review, we will briefly discuss several pre-clinical studies that contributed to a better understanding of the therapeutic potential of NSC grafts in vivo. However, while many pre-clinical animal studies mainly report on the clinical benefit of NSC grafting, little is known about the actual in vivo fate of grafted NSC. Therefore, the third part of this review will focus on non-invasive imaging techniques for monitoring cellular grafts in the brain under in vivo conditions. Finally, as NSC transplantation research has evolved during the past decade, it has become clear that the host micro-environment itself, either in healthy or injured condition, is an important player in defining success of NSC grafting. The final part of this review will focus on the host environmental influence on survival, migration and differentiation of grafted NSC.

Cell transplantation: stem cells and precursor cells

Stem cells have been used to approach four different therapeutic repair strategies in spinal cord injury (SCI): (1) replacement of lost neurons, (2) replacement of oligodendrocytes to promote remyelination of demyelinated and/or regenerated axons, (3) providing a permissive substrate for axonal regeneration to overcome the intrinsic inhibition of surface molecules, and (4) engendering host repair. The first two strategies involve cell-specific differentiation of engrafted neural cells and the latter two may involve grafted neural or non-neural cells. The preclinical data for all of these approaches is at times contradictory and there is no consensus as to what type of stem cell is optimal to facilitate repair in specific injuries. Remyelination has been the most successful stem cell replacement strategy. Partial lineage restriction and pharmacological and/or genetic manipulation to express additional trophic support or restrict responses to host signals appears necessary for optimal neuronal and oligodendrocytic differentiation. However, these modifications will make their clinical application exceedingly difficult. Effects of grafted stem cells on abrogating host immune responses and engendering intrinsic repair is also a mechanism through which stem cells are likely therapeutically beneficial. While clinical trials with stem cell grafting into the injured spinal cord are ongoing, preclinical studies have yet to define mechanisms of action that can be definitively translated to those clinical approaches.

MK801 attenuates secondary injury in a mouse experimental compression model of spinal cord trauma

BACKGROUND

Glutamergic excitotoxicity has been shown to play a deleterious role in the pathophysiology of spinal cord injury (SCI). The aim of this study was to investigate the neuroprotective effect of dizocilpine maleate, MK801 (2 mg/Kg, 30 min and 6 hours after injury) in a mice model of SCI. The spinal cord trauma was induced by the application of vascular clips to the dura via a four-level T5-T8 laminectomy.

RESULTS

Spinal cord injury in mice resulted in severe trauma characterized by edema, neutrophil infiltration and apoptosis. In this study we clearly demonstrated that administration of MK801 attenuated all inflammatory parameters. In fact 24 hours after injury, the degree of spinal cord inflammation and tissue injury (evaluated as histological score), infiltration of neutrophils, NF-κB activation, iNOS, cytokines levels (TNF-α and IL-1β), neurotrophin expression were markedly reduced by MK801 treatment. Moreover, in a separate set of experiments, we have demonstrated that MK801 treatment significantly improved the recovery of locomotory function.

CONCLUSIONS

Blockade of NMDA by MK801 lends support to the potential importance of NMDA antagonists as therapeutic agents in the treatment of acute spinal cord injury.

Feasibility of combination allogeneic stem cell therapy for spinal cord injury: a case report

Cellular therapy for spinal cord injury (SCI) is overviewed focusing on bone marrow mononuclear cells, olfactory ensheathing cells, and mesenchymal stem cells. A case is made for the possibility of combining cell types, as well as for allogeneic use. We report the case of 29 year old male who suffered a crush fracture of the L1 vertebral body, lacking lower sensorimotor function, being a score A on the ASIA scale. Stem cell therapy comprised of intrathecal administration of allogeneic umbilical cord blood ex-vivo expanded CD34 and umbilical cord matrix MSC was performed 5 months, 8 months, and 14 months after injury. Cell administration was well tolerated with no adverse effects observed. Neuropathic pain subsided from intermittent 10/10 to once a week 3/10 VAS. Recovery of muscle, bowel and sexual function was noted, along with a decrease in ASIA score to "D". This case supports further investigation into allogeneic-based stem cell therapies for SCI.

Preclinical safety validation of a stabilized viral vector direct injection approach to the cervical spinal cord

The current lack of a validated intraspinal delivery approach precludes translation of promising cell or viral-based therapeutics for treatment of varied spinal cord afflictions. We have developed a stabilized cervical microinjection platform with the intent of precise delivery to intraspinal sites of interest. Nine 30-40 kg female swine underwent coordinate-based microinjection AAV2-GFP at three injected volumes (10, 25, and 50 microL (n= 3/group)) and matched infusion rates (1.0, 2.5, and 5.0 microL/min) over a period (t= 10 minutes). Preliminary validation is provided by behavioral and targeting data demonstrating safe delivery of a viral vector carrying a fluorescent reporter gene to the cervical spinal cord ventral horn.

Human neural stem cells differentiate and promote locomotor recovery in an early chronic spinal cord injury NOD-scid mouse model

Background

Traumatic spinal cord injury (SCI) results in partial or complete paralysis and is characterized by a loss of neurons and oligodendrocytes, axonal injury, and demyelination/dysmyelination of spared axons. Approximately 1,250,000 individuals have chronic SCI in the U.S.; therefore treatment in the chronic stages is highly clinically relevant. Human neural stem cells (hCNS-SCns) were prospectively isolated based on fluorescence-activated cell sorting for a CD133⁺ and CD24^−/lo population from fetal brain, grown as neurospheres, and lineage restricted to generate neurons, oligodendrocytes and astrocytes. hCNS-SCns have recently been transplanted sub-acutely following spinal cord injury and found to promote improved locomotor recovery. We tested the ability of hCNS-SCns transplanted 30 days post SCI to survive, differentiate, migrate, and promote improved locomotor recovery.

Methods and Findings

hCNS-SCns were transplanted into immunodeficient NOD-scid mice 30 days post spinal cord contusion injury. hCNS-SCns transplanted mice demonstrated significantly improved locomotor recovery compared to vehicle controls using open field locomotor testing and CatWalk gait analysis. Transplanted hCNS-SCns exhibited long-term engraftment, migration, limited proliferation, and differentiation predominantly to oligodendrocytes and neurons. Astrocytic differentiation was rare and mice did not exhibit mechanical allodynia. Furthermore, differentiated hCNS-SCns integrated with the host as demonstrated by co-localization of human cytoplasm with discrete staining for the paranodal marker contactin-associated protein.

Conclusions

The results suggest that hCNS-SCns are capable of surviving, differentiating, and promoting improved locomotor recovery when transplanted into an early chronic injury microenvironment. These data suggest that hCNS-SCns transplantation has efficacy in an early chronic SCI setting and thus expands the “window of opportunity” for intervention.

Biomaterials for neural-tissue engineering — Chitosan supports the survival, migration, and differentiation of adult-derived neural stem and progenitor cells

Neural precursor cells (NPCs or stem and progenitor cells) are promising in transplantation strategies to treat an injury to the central nervous system, such as a spinal cord injury (SCI), because of their ability to differentiate into neurons and glia. Transplantation studies to date have met with limited success for a number of reasons, including poor cell survival. One way to encourage cell survival in injured tissue is to provide the cells with a scaffold to enhance their survival, their integration, and potentially their differentiation into appropriate cell types. Towards this end, four amine-functionalized hydrogels were screened in vitro for adult murine NPC viability, migration, and differentiation: chitosan, poly(oligoethylene oxide dimethacrylate-co-2-amino ethyl methacrylate), blends of poly(oligoethylene oxide dimethacrylate-co-2-amino ethyl methacrylate), and poly(vinyl alcohol), and poly(glycerol dimethacrylate-co-2-amino ethyl methacrylate). The greatest cell viability was found on chitosan at all times examined, Chitosan had the greatest surface amine content and the lowest equilibrium water content, which likely contributed to the greater NPC viability observed over three weeks in culture. Only chitosan supported survival of multipotent stem cells and the differentiation of the progenitors into neurons, astrocytes, and oligodendrocytes. Plating intact NPC colonies revealed greater cell migration on chitosan relative to the other hydrogels. Importantly, long term cultures on chitosan showed no significant difference in total cell counts over time, suggesting no net cell growth. Together, these findings reveal chitosan as a promising material for the delivery of adult NPC cell-based therapies.

Subchronic alpha-linolenic acid treatment enhances brain plasticity and exerts an antidepressant effect: a versatile potential therapy for stroke

Omega-3 polyunsaturated fatty acids are known to have therapeutic potential in several neurological and psychiatric disorders. However, the molecular mechanisms of action underlying these effects are not well elucidated. We previously showed that alpha-linolenic acid (ALA) reduced ischemic brain damage after a single treatment. To follow-up this finding, we investigated whether subchronic ALA treatment promoted neuronal plasticity. Three sequential injections with a neuroprotective dose of ALA increased neurogenesis and expression of key proteins involved in synaptic functions, namely, synaptophysin-1, VAMP-2, and SNAP-25, as well as proteins supporting glutamatergic neurotransmission, namely, V-GLUT1 and V-GLUT2. These effects were correlated with an increase in brain-derived neurotrophic factor (BDNF) protein levels, both in vitro using neural stem cells and hippocampal cultures and in vivo, after subchronic ALA treatment. Given that BDNF has antidepressant activity, this led us to test whether subchronic ALA treatment could produce antidepressant-like behavior. ALA-treated mice had significantly reduced measures of depressive-like behavior compared with vehicle-treated animals, suggesting another aspect of ALA treatment that could stimulate functional stroke recovery by potentially combining acute neuroprotection with long-term repair/compensatory plasticity. Indeed, three sequential injections of ALA enhanced protection, either as a pretreatment, wherein it reduced post-ischemic infarct volume 24 h after a 1-hour occlusion of the middle cerebral artery or as post-treatment therapy, wherein it augmented animal survival rates by threefold 10 days after ischemia.

Downregulation of thymosin beta4 in neural progenitor grafts promotes spinal cord regeneration

Thymosin beta4 (Tbeta4) is an actin-binding peptide whose expression in developing brain correlates with migration and neurite extension of neurons. Here, we studied the effects of the downregulation of Tbeta4 expression on growth and differentiation of murine neural progenitor cells (NPCs), using an antisense lentiviral vector. In differentiation-promoting medium, we found twice the number of neurons derived from the Tbeta4-antisense-transduced NPCs, which showed enhanced neurite outgrowth accompanied by increased expression of the adhesion complex N-cadherin-beta-catenin and increased ERK activation. Importantly, when the Tbeta4-antisense-transduced NPCs were transplanted in vivo into a mouse model of spinal cord injury, they promoted a significantly greater functional recovery. Locomotory recovery correlated with increased expression of the regeneration-promoting cell adhesion molecule L1 by the grafted Tbeta4-antisense-transduced NPCs. This resulted in an increased number of regenerating axons and in sprouting of serotonergic fibers surrounding and contacting the Tbeta4-antisense-transduced NPCs grafted into the lesion site. In conclusion, our data identify a new role for Tbeta4 in neuronal differentiation of NPCs by regulating fate determination and process outgrowth. Moreover, NPCs with reduced Tbeta4 levels generate an L1-enriched environment in the lesioned spinal cord that favors growth and sprouting of spared host axons and enhances the endogenous tissue-repair processes.

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.

Cell therapy for CNS trauma

Cell therapy plays an important role in multidisciplinary management of the two major forms of central nervous system (CNS) injury, traumatic brain injury and spinal cord injury, which are caused by external physical trauma. Cell therapy for CNS disorders involves the use of cells of neural or non-neural origin to replace, repair, or enhance the function of the damaged nervous system and is usually achieved by transplantation of the cells, which are isolated and may be modified, e.g., by genetic engineering, when it may be referred to as gene therapy. Because the adult brain cells have a limited capacity to migrate to and regenerate at sites of injury, the use of embryonic stem cells that can be differentiated into various cell types as well as the use of neural stem cells has been explored. Preclinical studies and clinical trials are reviewed. Advantages as well as limitations are discussed. Cell therapy is promising for the treatment of CNS injury because it targets multiple mechanisms in a sustained manner. It can provide repair and regeneration of damaged tissues as well as prolonged release of neuroprotective and other therapeutic substances.

Tumorigenic potential of olfactory bulb-derived human adult neural stem cells associates with activation of TERT and NOTCH1

Background

Multipotent neural stem cells (NSCs) have been isolated from neurogenic regions of the adult brain. Reportedly, these cells can be expanded in vitro under prolonged mitogen stimulation without propensity to transform. However, the constitutive activation of the cellular machinery required to bypass apoptosis and senescence places these cells at risk for malignant transformation.

Methodology/Principal Findings

Using serum-free medium supplemented with epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), we established clonally derived NS/progenitor cell (NS/PC) cultures from the olfactory bulb (OB) of five adult patients. The NS/PC cultures obtained from one OB specimen lost growth factor dependence and neuronal differentiation at early passage. These cells developed glioblastoma tumors upon xenografting in immunosuppressed mice. The remaining NS/PC cultures were propagated either as floating neurospheres or as adherent monolayers with mainteinance of growth factor dependence and multipotentiality at late passage. These cells were engrafted onto the CNS of immunosuppressed rodents. Overall, the grafted NS/PCs homed in the host parenchyma showing ramified morphology and neuronal marker expression. However, a group of animals transplanted with NS/PCs obtained from an adherent culture developed fast growing tumors histologically resembling neuroesthesioblastoma. Cytogenetic and molecular analyses showed that the NS/PC undergo chromosomal changes with repeated in vitro passages under mitogen stimulation, and that up-regulation of hTERT and NOTCH1 associates with in vivo tumorigenicity.

Conclusions/Significance

Using culturing techniques described in current literature, NS/PCs arise from the OB of adult patients which in vivo either integrate in the CNS parenchyma showing neuron-like features or initiate tumor formation. Extensive xenografting studies on each human derived NS cell line appear mandatory before any use of these cells in the clinical setting.

Gene expression profiling of human neural progenitor cells following the serum-induced astrocyte differentiation

Neural stem cells (NSC) with self-renewal and multipotent properties could provide an ideal cell source for transplantation to treat spinal cord injury, stroke, and neurodegenerative diseases. However, the majority of transplanted NSC and neural progenitor cells (NPC) differentiate into astrocytes in vivo under pathological environments in the central nervous system, which potentially cause reactive gliosis. Because the serum is a potent inducer of astrocyte differentiation of rodent NPC in culture, we studied the effect of the serum on gene expression profile of cultured human NPC to identify the gene signature of astrocyte differentiation of human NPC. Human NPC spheres maintained in the serum-free culture medium were exposed to 10% fetal bovine serum (FBS) for 72 h, and processed for analyzing on a Whole Human Genome Microarray of 41,000 genes, and the microarray data were validated by real-time RT-PCR. The serum elevated the levels of expression of 45 genes, including ID1, ID2, ID3, CTGF, TGFA, METRN, GFAP, CRYAB and CSPG3, whereas it reduced the expression of 23 genes, such as DLL1, DLL3, PDGFRA, SOX4, CSPG4, GAS1 and HES5. Thus, the serum-induced astrocyte differentiation of human NPC is characterized by a counteraction of ID family genes on Delta family genes. Coimmunoprecipitation analysis identified ID1 as a direct binding partner of a proneural basic helix-loop-helix (bHLH) transcription factor MASH1. Luciferase assay indicated that activation of the DLL1 promoter by MASH1 was counteracted by ID1. Bone morphogenetic protein 4 (BMP4) elevated the levels of ID1 and GFAP expression in NPC under the serum-free culture conditions. Because the serum contains BMP4, these results suggest that the serum factor(s), most probably BMP4, induces astrocyte differentiation by upregulating the expression of ID family genes that repress the proneural bHLH protein-mediated Delta expression in human NPC.

Engineering angiogenesis following spinal cord injury: a coculture of neural progenitor and endothelial cells in a degradable polymer implant leads to an increase in vessel density and formation of the blood-spinal cord barrier

Angiogenesis precedes recovery following spinal cord injury and its extent correlates with neural regeneration, suggesting that angiogenesis may play a role in repair. An important precondition for studying the role of angiogenesis is the ability to induce it in a controlled manner. Previously, we showed that a coculture of endothelial cells (ECs) and neural progenitor cells (NPCs) promoted the formation of stable tubes in vitro and stable, functional vascular networks in vivo in a subcutaneous model. We sought to test whether a similar coculture would lead to the formation of stable functional vessels in the spinal cord following injury. We created microvascular networks in a biodegradable two-component implant system and tested the ability of the coculture or controls (lesion control, implant alone, implant + ECs or implant + NPCs) to promote angiogenesis in a rat hemisection model of spinal cord injury. The coculture implant led to a fourfold increase in functional vessels compared with the lesion control, implant alone or implant + NPCs groups and a twofold increase in functional vessels over the implant + ECs group. Furthermore, half of the vessels in the coculture implant exhibited positive staining for the endothelial barrier antigen, a marker for the formation of the blood-spinal cord barrier. No other groups have shown positive staining for the blood-spinal cord barrier in the injury epicenter. This work provides a novel method to induce angiogenesis following spinal cord injury and a foundation for studying its role in repair.

Stem and progenitor cell therapies: recent progress for spinal cord injury repair

Mechanical trauma to the spinal cord is often accompanied by irreversible tissue damage, limited endogenous repair and permanent loss of motor, sensory and autonomic function. The implantation of exogenous cells or the stimulation of endogenous cells, to repopulate and replace or to provide a conducive environment for repair, offers a promising therapeutic direction for overcoming the multitude of obstacles facing successful recovery from spinal cord injury. Although relatively new to the scene of cell based therapies for reparative medicine, stem cells and their progenitors have been labeled as the 'cell of the future' for revolutionizing the treatment of CNS injury and neurodegenerative disorders. The following review examines the different types of stem cells and their progenitors, their utility in experimental models of spinal cord injury and explores the outstanding issues that still need to be addressed before they move towards clinical implementation.

Nerve repair using acidic fibroblast growth factor in human cervical spinal cord injury: a preliminary Phase I clinical study

Object

The aim of this study was to assess functional outcomes of nerve repair using acidic fibroblast growth factor (FGF) in patients with cervical spinal cord injury (SCI).

Methods

Nine patients who had cervical SCI for longer than 5 months were included in pre- and postoperative assessments of their neurological function. The assessments included evaluating activities of daily living, associated functional ability, and degree of spasticity, motor power, sensation, and pain perception. After the first set of assessments, the authors repaired the injured segment of the spinal cord using a total laminectomy followed by the application of fibrin glue containing acidic FGF. Clinical evaluations were conducted 1, 2, 3, 4, 5, and 6 months after the surgery. Preoperative versus postoperative differences in injury severity and grading of key muscle power and sensory points were calculated using the Wilcoxon signed-rank test.

Results

The preoperative degree of injury severity, as measured using the American Spinal Injury Association (ASIA) scoring system, showed that preoperative motor (52.4 ± 25.9 vs 68.6 ± 21.5), pinprick (61.0 ± 34.9 vs 71.6 ± 31.0), and light touch scores (57.3 ± 33.9 vs 71.9 ± 30.2) were significantly lower than the respective postoperative scores measured 6 months after surgery (p = 0.005, 0.012, and 0.008, respectively).

Conclusions

Based on the significant difference in ASIA motor and sensory scale scores between the preoperative status and the 6-month postoperative follow-up, this novel nerve repair strategy of using acidic FGF may have a role in the repair of human cervical SCI. Modest nerve regeneration occurred in all 9 patients after this procedure without any observed adverse effects. This repair strategy thus deserves further investigation, clinical consideration, and refinement.

Primitive Stem Cells Residing in the Skeletal Muscle of Adult Pigs are Mobilized into the Peripheral Blood after Trauma

This study was designed to determine if trauma causes the release of adult-derived blastomere-like stem cells (BLSCs) from skeletal muscle into the circulating blood of adult pigs. Experimental procedures followed the guidelines of Fort Valley State University's Institutional Animal Care and Utilization Committee. Pigs were traumatized by splenectomy followed by pancreatectomy. Blood samples and skeletal muscle biopsies were taken before and after trauma. Adult-derived BLSCs were isolated from skeletal muscle and blood samples following established procedures. Nontraumatized skeletal muscle contained approximately 277 million BLSCs per gram of muscle. After trauma, skeletal muscle contained approximately 2 million BLSCs per gram of muscle. Blood taken before trauma contained approximately 22 million BLSCs per milliliter, whereas approximately 512 million BLSCs per milliliter were present within the blood after trauma. Blood values were statistically significant with a P < 0.05. This report is the first demonstration that trauma causes the release of adult-derived BLSCs from skeletal muscle into blood. Further studies are required to elucidate the roles that adult-derived BLSCs play in the response to injury and in the healing process. Surgeons must take a role in this evolving field.

Use of stem cells for the treatment of multiple sclerosis

The reported evidence of neurodegeneration in multiple sclerosis (MS) may explain the lack of efficacy of the currently used immunomodulating modalities and the irreversible axonal damage, which results in accumulating disability. To date, efforts for neuroprotective treatments have not been successful in clinical studies in other CNS diseases. Therefore, for MS, the use of stem cells may provide a logical solution, since these cells can migrate locally into the areas of white-matter lesions (plaques) and have the potential to support local neurogenesis and rebuilding of the affected myelin. This is achieved both by support of the resident CNS stem cell repertoire and by differentiation of the transplanted cells into neurons and myelin-producing cells (oligodendrocytes). Stem cells were also shown to possess immunomodulating properties, inducing systemic and local suppression of the myelin-targeting autoimmune lymphocytes. Several types of stem cells (embryonic and adult) have been described and extensively studied in animal models of CNS diseases and the various models of MS (experimental autoimmune encephalomyelitis [EAE]). In this review, we summarize the experience with the use of different types of stem cells in CNS disease models, focusing on the models of EAE and describe the advantages and disadvantages of each stem cell type for future clinical applications in MS.

Transplantation of rat neural stem cells reduces stereotypic behaviors in rats after intrastriatal microinfusion of Tourette syndrome sera

Tourette syndrome (TS) is a heterogenous neuropsychiatric disorder. In most cases, tics are self-limited or can be treated by behavioral or pharmacological therapy. However, for some individuals, tics can cause lifelong impairment and life-threatening symptoms, which are intractable to traditional treatment. Neural stem cell (NSC) is a potential tool to treat certain neurological diseases. In this study, we proposed to use neural stem cell transplantation as a novel therapy to treat TS and discussed its efficacy. Wistar rats were microinfused with TS sera into the striatum followed by the transplantation of NSCs or vehicle at the infusion site. The sera of the TS patients were identified to have enriched antineural antibodies. Prior to grafting, rat embryonic NSCs were co-cultured with 5-bromodeoxyuridine (Brdu) for 24 h. Stereotypic behaviors were counted at 1, 7, 14 and 21 days after transplantation of NSCs. Morphological analyses revealed that NSCs survived and differentiated into neurons and astrocytes in the striatum 3 weeks after grafting. To sum it up, rat embryonic neural stem cell grafts survived and differentiated in the striatum of TS rat may help relieve stereotypic behaviors of the host. Our results suggest that transplantation of NSCs intrastriatum may have therapeutic potential for TS.

Neurosphere-derived cells exert a neuroprotective action by changing the ischemic microenvironment

Background

Neurosphere-derived cells (NC), containing neural stem cells, various progenitors and more differentiated cells, were obtained from newborn C57/BL6 mice and infused in a murine model of focal ischemia with reperfusion to investigate if: 1) they decreased ischemic injury and restored brain function; 2) they induced changes in the environment in which they are infused; 3) changes in brain environment consequent to transient ischemia were relevant for NC action.

Methodology/Principal Findings

NC were infused intracerebroventricularly 4 h or 7 d after 30 min middle cerebral artery occlusion. In ischemic mice receiving cells at 4 h, impairment of open field performance was significantly improved and neuronal loss significantly reduced 7–14 d after ischemia compared to controls and to ischemic mice receiving cells at 7 d. Infusion of murine foetal fibroblast in the same experimental conditions was not effective. Assessment of infused cell distribution revealed that they migrated from the ventricle to the parenchyma, progressively decreased in number but they were observable up to 14 d. In mice receiving NC at 7 d and in sham-operated mice, few cells could be observed only at 24 h, indicating that the survival of these cells in brain tissue relates to the ischemic environment. The mRNA expression of trophic factors such as Insulin Growth Factor-1, Vascular Endothelial Growth Factor-A, Transforming Growth Factor-β1, Brain Derived Neurotrophic Factor and Stromal Derived Factor−1α, as well as microglia/macrophage activation, increased 24 h after NC infusion in ischemic mice treated at 4 h compared to sham-operated and to mice receiving cells at 7 d.

Conclusions/Significance

NC reduce functional impairment and neuronal damage after ischemia/reperfusion injury. Several lines of evidence indicate that the reciprocal interaction between NC and the ischemic environment is crucial for NC protective actions. Based on these results we propose that a bystander control of the ischemic environment may be the mechanism used by NC to rapidly restore acutely injured brain function.

Altered nestin expression in the cerebrum with periventricular leukomalacia

Nestin is a cytoskeletal protein expressed by neural stem cells, and by immature neurons and glial cells. In an effort to explore the potential of the infant brain for repair and plasticity, we immunohistochemically studied nestin expression in the human cerebral cortex of control subjects and of patients with periventricular leukomalacia. During normal development, nestin immunoreactivity of the cortical gray and white matter was detectable throughout the fetal period, and disappeared around birth. In brain with periventricular leukomalacia, nestin expression was altered in a time- and space-dependent manner. In the cortical gray matter, neuronal immunoreactivity was often reduced in the subacute stage, but was increased in chronic and remote stages. In the white matter near a lesion of periventricular leukomalacia, glial immunoreactivity was increased in all stages. In many cases, neurons and axons far from a lesion also showed an altered expression of nestin. These findings indicate that in brain with periventricular leukomalacia, neurons and glial cells may recapitulate nestin expression in response to ischemic brain injury, suggesting functional relevance in repair and plasticity.