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

Behavioral and histopathological assessment of adult ischemic rat brains after intracerebral transplantation of NSI-566RSC cell lines

Stroke is a major cause of death and disability, with very limited treatment option. Cell-based therapies have emerged as potential treatments for stroke. Indeed, studies have shown that transplantation of neural stem cells (NSCs) exerts functional benefits in stroke models. However, graft survival and integration with the host remain pressing concerns with cell-based treatments. The current study set out to investigate those very issues using a human NSC line, NSI-566RSC, in a rat model of ischemic stroke induced by transient occlusion of the middle cerebral artery. Seven days after stroke surgery, those animals that showed significant motor and neurological impairments were randomly assigned to receive NSI-566RSC intracerebral transplants at two sites within the striatum at three different doses: group A (0 cells/µl), group B (5,000 cells/µl), group C (10,000 cells/µl), and group D (20,000 cells/µl). Weekly behavioral tests, starting at seven days and continued up to 8 weeks after transplantation, revealed dose-dependent recovery from both motor and neurological deficits in transplanted stroke animals. Eight weeks after cell transplantation, immunohistochemical investigations via hematoxylin and eosin staining revealed infarct size was similar across all groups. To identify the cell graft, and estimate volume, immunohistochemistry was performed using two human-specific antibodies: one to detect all human nuclei (HuNu), and another to detect human neuron-specific enolase (hNSE). Surviving cell grafts were confirmed in 10/10 animals of group B, 9/10 group C, and 9/10 in group D. hNSE and HuNu staining revealed similar graft volume estimates in transplanted stroke animals. hNSE-immunoreactive fibers were also present within the corpus callosum, coursing in parallel with host tracts, suggesting a propensity to follow established neuroanatomical features. Despite absence of reduction in infarct volume, NSI-566RSC transplantation produced behavioral improvements possibly via robust engraftment and neuronal differentiation, supporting the use of this NSC line for stroke therapy.

Intraspinal neural stem cell transplantation in amyotrophic lateral sclerosis: phase 1 trial outcomes

Objective

The US Food and Drug Administration–approved trial, “A Phase 1, Open-Label, First-in-Human, Feasibility and Safety Study of Human Spinal Cord-Derived Neural Stem Cell Transplantation for the Treatment of Amyotrophic Lateral Sclerosis, Protocol Number: NS2008-1,” is complete. Our overall objective was to assess the safety and feasibility of stem cell transplantation into lumbar and/or cervical spinal cord regions in amyotrophic lateral sclerosis (ALS) subjects.

Methods

Preliminary results have been reported on the initial trial cohort of 12 ALS subjects. Here, we describe the safety and functional outcome monitoring results for the final trial cohort, consisting of 6 ALS subjects receiving 5 unilateral cervical intraspinal neural stem cell injections. Three of these subjects previously received 10 total bilateral lumbar injections as part of the earlier trial cohort. All injections utilized a novel spinal-mounted stabilization and injection device to deliver 100,000 neural stem cells per injection, for a dosing range up to 1.5 million cells. Subject assessments included detailed pre- and postsurgical neurological outcome measures.

Results

The cervical injection procedure was well tolerated and disease progression did not accelerate in any subject, verifying the safety and feasibility of cervical and dual-targeting approaches. Analyses on outcome data revealed preliminary insight into potential windows of stem cell biological activity and identified clinical assessment measures that closely correlate with ALS Functional Rating Scale-Revised scores, a standard assessment for ALS clinical trials.

Interpretation

This is the first report of cervical and dual-targeted intraspinal transplantation of neural stem cells in ALS subjects. This approach is feasible and well-tolerated, supporting future trial phases examining therapeutic dosing and efficacy.

Glycan-dependent binding of galectin-1 to neuropilin-1 promotes axonal regeneration after spinal cord injury

Following spinal cord injury (SCI), semaphorin 3A (Sema3A) prevents axonal regeneration through binding to the neuropilin-1 (NRP-1)/PlexinA4 receptor complex. Here, we show that galectin-1 (Gal-1), an endogenous glycan-binding protein, selectively bound to the NRP-1/PlexinA4 receptor complex in injured neurons through a glycan-dependent mechanism, interrupts the Sema3A pathway and contributes to axonal regeneration and locomotor recovery after SCI. Although both Gal-1 and its monomeric variant contribute to de-activation of microglia, only high concentrations of wild-type Gal-1 (which co-exists in a monomer-dimer equilibrium) bind to the NRP-1/PlexinA4 receptor complex and promote axonal regeneration. Our results show that Gal-1, mainly in its dimeric form, promotes functional recovery of spinal lesions by interfering with inhibitory signals triggered by Sema3A binding to NRP-1/PlexinA4 complex, supporting the use of this lectin for the treatment of SCI patients.

Transplantation of mesenchymal stem cells in ALS

Amyotrophic lateral sclerosis (ALS) is a devastating incurable, neurodegenerative disease that targets motor neurons (MNs) in the primary motor cortex, brainstem, and spinal cord, leading to muscle atrophy, paralysis, and death due to respiratory failure within 2-5 years. Currently, there is no cure for ALS. The development of a therapy that can support or restore MN function and attenuate toxicity in the spinal cord provides the most comprehensive approach for treating ALS. Mesenchymal stem cells might be suitable for cell therapy in ALS because of their immunomodulatory and protective properties. In this review, the authors discuss the major challenges to the translation of in vitro and animal studies of MSCs therapy in the clinical setting.

Stem cell therapy in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of upper and lower motor neurons, characterized by progressive muscular atrophy and weakness which culminates in death within 2-5 years. Despite various hypotheses about the responsible mechanisms, the etiology of ALS remains incompletely understood. However, it has been recently postulated that stem cell therapy could potentially target several mechanisms responsible for the etiology of ALS and other nervous system disorders, and could be regarded as one of the most promising therapeutic strategies for ALS treatment. We present a brief review of different methods of stem cell therapy in ALS patients and discuss the results with different cell types and routes of administration.

Amyotrophic Lateral Sclerosis: An update for 2013 Clinical Features, Pathophysiology, Management and Therapeutic Trials

Amyotrophic lateral sclerosis (ALS), first described by Jean-Martin Charcot in the 1870s, is an age-related disorder that leads to degeneration of motor neurons. The disease begins focally in the central nervous system and then spreads relentlessly. The clinical diagnosis, defined by progressive signs and symptoms of upper and lower motor neuron dysfunction, is confirmed by electromyography. Additional testing excludes other conditions. The disease is heterogeneous, but most patients die of respiratory muscle weakness less than 3 years from symptom-onset. Like other age-related neurodegenerative diseases, ALS has genetic and environmental triggers. Of the five to 10% of cases that are inherited, mutations have been discovered for a high proportion. In addition to genetic factors, age, tobacco use, and athleticism may contribute to sporadic ALS, but important etiologies are unidentified for most patients. Complex pathophysiological processes, including mitochondrial dysfunction, aggregation of misfolded protein, oxidative stress, excitotoxicity, inflammation and apoptosis, involve both motor neurons and surrounding glial cells. There is clinical and pathological overlap with other neurodegenerative diseases, particularly frontotemporal dementia. The mechanisms leading to disease propagation in the brain are a current focus of research. To date, one medication, riluzole, licensed in 1996, has been proved to prolong survival in ALS. Numerous clinical trials have so far been unable to identify another neuroprotective agent. Researchers now aim to slow disease progression by targeting known pathophysiological pathways or genetic defects. Current approaches are directed at muscle proteins such as Nogo, energetic balance, cell replacement, and abnormal gene products resulting from mutations. Until better understanding of the causes and mechanisms underlying progression lead to more robust neuroprotective agents, symptomatic therapies can extend life and improve quality of life. Palliative care programs such as hospice give emotional and physical support to patients and families throughout much of the disease course.

Neural stem cells grafts decrease neural apoptosis associated with caspase-7 downregulation and BDNF upregulation in rats following spinal cord hemisection

Transplantation of neural stem cells (NSCs) into lesioned spinal cord demonstrated a beneficial effect for neural repair, the underlying mechanism, however, remains to be elusive. Here, we showed that NSCs, possessing the capacity to differentiate toward into neurons and astrocytes, exhibit a neuroprotective effect by anti-apoptosis mechanism in spinal cord hemi-transected rats despite it did not improve behavior. Intravenous NSCs injection substantially upregulated the level of BDNF mRNA but not its receptor TrkB in hemisected spinal cord, while caspase-7, a downstream apoptosis gene of caspase-3, has been largely down-regulated. TUNEL staining showed that the number of apoptosis cells in injured spinal cord decreased significantly, compared with seen in rats with no NSCs administration. The present finding therefore provided crucial evidence to explain neuroprotective effect of NSCs grafts in hemisected spinal cord, which is associated with BDNF upregulation and caspase-7 downregulation.

Stem cells as promising therapeutic options for neurological disorders

Due to the limitations of pharmacological and other current therapeutic strategies, stem cell therapies have emerged as promising options for treating many incurable neurologic diseases. A variety of stem cells including pluripotent stem cells (i.e., embryonic stem cells and induced pluripotent stem cells) and multipotent adult stem cells (i.e., fetal brain tissue, neural stem cells, and mesenchymal stem cells from various sources) have been explored as therapeutic options for treating many neurologic diseases, and it is becoming obvious that each type of stem cell has pros and cons as a source for cell therapy. Wise selection of stem cells with regard to the nature and status of neurologic dysfunctions is required to achieve optimal therapeutic efficacy. To this aim, the stem cell-mediated therapeutic efforts on four major neurological diseases, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and stroke, will be introduced, and current problems and future directions will be discussed.

Transplantation of human fetal-derived neural stem cells improves cognitive function following cranial irradiation

Treatment of central nervous system (CNS) malignancies typically involves radiotherapy to forestall tumor growth and recurrence following surgical resection. Despite the many benefits of cranial radiotherapy, survivors often suffer from a wide range of debilitating and progressive cognitive deficits. Thus, while patients afflicted with primary and secondary malignancies of the CNS now experience longer local regional control and progression-free survival, there remains no clinical recourse for the unintended neurocognitive sequelae associated with their cancer treatments. Multiple mechanisms contribute to disrupted cognition following irradiation, including the depletion of radiosensitive populations of stem and progenitor cells in the hippocampus. We have explored the potential of using intrahippocampal transplantation of human stem cells to ameliorate radiation-induced cognitive dysfunction. Past studies demonstrated the capability of cranially transplanted human embryonic (hESCs) and neural (hNSCs) stem cells to functionally restore cognition in rats 1 and 4 months after cranial irradiation. The present study employed an FDA-approved fetal-derived hNSC line capable of large scale-up under good manufacturing practice (GMP). Animals receiving cranial transplantation of these cells 1 month following irradiation showed improved hippocampal spatial memory and contextual fear conditioning performance compared to irradiated, sham surgery controls. Significant newly born (doublecortin positive) neurons and a smaller fraction of glial subtypes were observed within and nearby the transplantation core. Engrafted cells migrated and differentiated into neuronal and glial subtypes throughout the CA1 and CA3 subfields of the host hippocampus. These studies expand our prior findings to demonstrate that transplantation of fetal-derived hNSCs improves cognitive deficits in irradiated animals, as assessed by two separate cognitive tasks.

New therapy options for amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease leading almost irrevocably to paralysis and death within 5 years after the first symptoms. Since the approval of riluzole, all other therapeutic trials have been negative, including many that followed hopeful preclinical and early clinical data. New approaches are needed to uncover effective treatments for this still-devastating disease.

AREAS COVERED

The review summarizes the current approaches to clinical drug development in ALS. It focuses on several new trials listed on PubMed Central or the National Institutes of Health online trial registry. New targets for therapeutic intervention in ALS include skeletal muscle, energetic metabolism and cell replacement. Two different approaches are directed at muscle: interventions that influence proteins near the neuromuscular junction such as Nogo-A; in contrast to drugs pointed toward disease physiology, therapies that directly increase strength. Other trials are evaluating nutritional interventions. Current cell therapy strategies utilize various types of stem cells to study disease pathophysiology, support neurons or surrounding cells through gene therapy or release of neurotrophic factors, or directly replace cells. The review includes a section on known genetic influences in ALS and future directions for the field.

EXPERT OPINION

These new interventions have important implications for the direction of ALS research. Investigators are focusing less on physiological mechanisms inside the neuron, a process that has proved unfruitful for nearly two decades, and more on concepts that have not been examined previously. These studies will surely add to the overall understanding of ALS. Future research will test ways to reduce gene expression in those with known mutations, as well as means to reduce the spread of aggregated protein.

Host induction by transplanted neural stem cells in the spinal cord: further evidence for an adult spinal cord neurogenic niche

AIM

To explore the hypothesis that grafts of exogenous stem cells in the spinal cord of athymic rats or rats with transgenic motor neuron disease can induce endogenous stem cells and initiate intrinsic repair mechanisms that can be exploited in amyotrophic lateral sclerosis therapeutics.

MATERIALS & METHODS

Human neural stem cells (NSCs) were transplanted into the lower lumbar spinal cord of healthy rats or rats with transgenic motor neuron disease to explore whether signals related to stem cells can initiate intrinsic repair mechanisms in normal and amyotrophic lateral sclerosis subjects. Patterns of migration and differentiation of NSCs in the gray and white matter, with emphasis on the central canal region and ependymal cell-driven neurogenesis, were analyzed.

RESULTS

Findings suggest that there is extensive cross-signaling between transplanted NSCs and a putative neurogenic niche in the ependyma of the lower lumbar cord. The formation of a neuronal cord from NSC-derived cells next to ependyma suggests that this structure may serve a mediating or auxiliary role for ependymal induction.

CONCLUSION

These findings raise the possibility that NSCs may stimulate endogenous neurogenesis and initiate intrinsic repair mechanisms in the lower spinal cord.

Performance and mechanism of neuroleukin in the growth and survival of sertoli cell-induced neurons in a coculture system

Sertoli cells (SCs), which are recognized as the "nurse cells" of the testis due to their important biofunctions, have been used in cotransplantation with neurons in cell therapy. However, it is not clear whether SCs influence neuronal communication and survival. In this study, we showed that approximately 60% of cortical neural stem cells (NSCs) cocultured with SCs differentiated into mature neurons. In addition, the neurite outgrowth and neuronal survival rates were significantly enhanced in the coculture system compared with differentiated neurons induced by a differentiation medium. The neuroleukin (NLK) secretion of SCs was also identified at the RNA and protein level, and the roles of NLK in neuromorphology and physiological regulation were systematically investigated for the first time. These results not only highlight the significance of paracrine regulation of NSCs by SCs but also confirm the role NLK plays in the differentiation and survival of NSCs. Finally, we proposed a possible hypothesis for the mechanism of NLK in the growth and survival of SC-induced neurons based on Western blotting results, which is that NLK secreted by SCs activates the Ras/Raf/MEK/Erk, Jak/Stat, and PI3K/Akt pathways, but not the NF-κB pathway, in neurons resulting in their growth and survival.

Intraspinal stem cell transplantation in amyotrophic lateral sclerosis: a phase I safety trial, technical note, and lumbar safety outcomes

BACKGROUND

No United States-based clinical trials have attempted delivery of biological therapies directly to the spinal cord for treatment of amyotrophic lateral sclerosis (ALS) because of the lack of a meaningful US Food and Drug Administration-authorized cell candidate and a validated delivery approach.

OBJECTIVE

To assess safety of delivery of a neural stem cell-based treatment into the upper lumbar segments of the ALS spinal cord in the first US Food and Drug Administration-authorized phase I trial.

METHODS

Each microinjection series comprised 5 injections (10 μL/injection) separated by 4 mm. Each injection deposited 100,000 neural stem cells derived from a fetal spinal cord. Twelve patients were treated with either unilateral or bilateral injections. Group A, nonambulatory patients, underwent unilateral (n = 3) or bilateral (n = 3) lumbar microinjections. Groups B and C were ambulatory (n = 3 each) and, respectively, received unilateral or bilateral injections. Patients are followed clinically and radiologically to assess potential toxicity of the procedure.

RESULTS

Twelve patients have received a transplant. There was one instance of transient intraoperative somatosensory-evoked potentials depression. In the immediate postoperative period, there was 1 episode of urinary retention requiring Foley catheter reinsertion. By discharge, none had a documented motor function decrement. Two patients required readmission and reoperation for cerebrospinal fluid leak or suprafascial wound dehiscence (n = 1 each). Two deaths occurred at 8 and 13 months postsurgery; neither was related to the surgical transplant.

CONCLUSION

Our experience in 12 patients supports the procedural safety of unilateral and bilateral intraspinal lumbar microinjection. Completion of this phase I safety trial is planned by proceeding to cervical and combined cervical + lumbar microinjections in ALS patients.

Lumbar intraspinal injection of neural stem cells in patients with amyotrophic lateral sclerosis: results of a phase I trial in 12 patients

Advances in stem cell biology have generated intense interest in the prospect of transplanting stem cells into the nervous system for the treatment of neurodegenerative diseases. Here, we report the results of an ongoing phase I trial of intraspinal injections of fetal-derived neural stems cells in patients with amyotrophic lateral sclerosis (ALS). This is a first-in-human clinical trial with the goal of assessing the safety and tolerability of the surgical procedure, the introduction of stem cells into the spinal cord, and the use of immunosuppressant drugs in this patient population. Twelve patients received either five unilateral or five bilateral (10 total) injections into the lumbar spinal cord at a dose of 100,000 cells per injection. All patients tolerated the treatment without any long-term complications related to either the surgical procedure or the implantation of stem cells. Clinical assessments ranging from 6 to 18 months after transplantation demonstrated no evidence of acceleration of disease progression due to the intervention. One patient has shown improvement in his clinical status, although these data must be interpreted with caution since this trial was neither designed nor powered to measure treatment efficacy. These results allow us to report success in achieving the phase I goal of demonstrating safety of this therapeutic approach. Based on these positive results, we can now advance this trial by testing intraspinal injections into the cervical spinal cord, with the goal of protecting motor neuron pools affecting respiratory function, which may prolong life for patients with ALS.

Olfactory ensheathing cell neurorestorotherapy for amyotrophic lateral sclerosis patients: benefits from multiple transplantations

Our previous series of studies have proven that olfactory ensheathing cell (OEC) transplantation appears to be able to slow the rate of clinical progression after OEC transplantation in the first 4 months and cell intracranial (key points for neural network restoration, KPNNR) and/or intraspinal (impaired segments) implants provide benefit for patients (including both the bulbar onset and limb onset subtypes) with amyotrophic lateral sclerosis (ALS). Here we report the results of cell therapy in patients with ALS on the basis of long-term observation following multiple transplants. From March of 2003 to January of 2010, 507 ALS patients received our cellular treatment. Among them, 42 patients underwent further OEC therapy by the route of KPNNR for two or more times (two times in 35 patients, three times in 5 patients, four times in 1 patient, and five times in 1 patient). The time intervals are 13.1 (6-60) months between the first therapy and the second one, 15.2 (8-24) months between the second therapy and the third one, 16 (6-26) months between the third therapy and the fourth one, and 9 months between the fourth therapy and the fifth time. All of the patients exhibited partial neurological functional recovery after each cell-based administration. Firstly, the scores of the ALS Functional Rating Scale (ALS-FRS) and ALS Norris Scale increased by 2.6 + 2.4 (0-8) and 4.9 + 5.2 (0-20) after the first treatment, 1.1 + 1.3 (0-5) and 2.3 + 2.9 (0-13) after the second treatment, 1.1 + 1.5 (0-4), and 3.4 + 6.9 (0-19) after the third treatment, 0.0 + 0.0 (0-0), and 2.5 + 3.5 (0-5) after the fourth treatment, and 1 point after the fifth cellular therapy, which were evaluated by independent neurologists. Secondly, the majority of patients have achieved improvement in electromyogram (EMG) assessments after the first, second, third, and fourth cell transplantation. After the first treatment, among the 42 patients, 36 (85.7%) patients' EMG test results improved, the remaining 6 (14.3%) patients' EMG results showed no remarkable change. After the second treatment, of the 42 patients, 30 (71.4%) patients' EMG results improved, 11 (26.2%) patients showed no remarkable change, and 1 (2.4%) patient became worse. After the third treatment, out of the 7 patients, 4 (57.1%) patients improved, while the remaining 3 (42.9%) patients showed no change. Thirdly, the patients have partially recovered their breathing ability as demonstrated by pulmonary functional tests. After the first treatment, 20 (47.6%) patients' pulmonary function ameliorated. After the second treatment, 18 (42.9%) patients' pulmonary function improved. After the third treatment, 2 (28.6%) patients recovered some pulmonary function. After the fourth and fifth treatment, patients' pulmonary function did not reveal significant change. The results show that multiple doses of cellular therapy definitely serve as a positive role in the treatment of ALS. This repeated and periodic cell-based therapy is strongly recommended for the patients, for better controlling this progressive deterioration disorder.

Human neural stem cell replacement therapy for amyotrophic lateral sclerosis by spinal transplantation

Background

Mutation in the ubiquitously expressed cytoplasmic superoxide dismutase (SOD1) causes an inherited form of Amyotrophic Lateral Sclerosis (ALS). Mutant synthesis in motor neurons drives disease onset and early disease progression. Previous experimental studies have shown that spinal grafting of human fetal spinal neural stem cells (hNSCs) into the lumbar spinal cord of SOD1^G93A rats leads to a moderate therapeutical effect as evidenced by local α-motoneuron sparing and extension of lifespan. The aim of the present study was to analyze the degree of therapeutical effect of hNSCs once grafted into the lumbar spinal ventral horn in presymptomatic immunosuppressed SOD1^G93A rats and to assess the presence and functional integrity of the descending motor system in symptomatic SOD1^G93A animals.

Methods/Principal Findings

Presymptomatic SOD1^G93A rats (60–65 days old) received spinal lumbar injections of hNSCs. After cell grafting, disease onset, disease progression and lifespan were analyzed. In separate symptomatic SOD1^G93A rats, the presence and functional conductivity of descending motor tracts (corticospinal and rubrospinal) was analyzed by spinal surface recording electrodes after electrical stimulation of the motor cortex. Silver impregnation of lumbar spinal cord sections and descending motor axon counting in plastic spinal cord sections were used to validate morphologically the integrity of descending motor tracts. Grafting of hNSCs into the lumbar spinal cord of SOD1^G93A rats protected α-motoneurons in the vicinity of grafted cells, provided transient functional improvement, but offered no protection to α-motoneuron pools distant from grafted lumbar segments. Analysis of motor-evoked potentials recorded from the thoracic spinal cord of symptomatic SOD1^G93A rats showed a near complete loss of descending motor tract conduction, corresponding to a significant (50–65%) loss of large caliber descending motor axons.

Conclusions/Significance

These data demonstrate that in order to achieve a more clinically-adequate treatment, cell-replacement/gene therapy strategies will likely require both spinal and supraspinal targets.

Translating cellular therapies from bench to bedside for amyotrophic lateral sclerosis

The last decade has witnessed an increasing number of biologic (e.g., cell- or viral vector-based) therapeutics supported by preclinical efficacy data for the treatment of afflictions to the CNS. While some international investigators have undertaken preliminary clinical safety studies, published literature indicate varying degrees of rigor with respect to study design and technical approach. To our knowledge, ours is the first group to have systematically generated preclinical validation data for a delivery approach and translated this into a Phase I trial attempting to covalidate the safety of a direct, targeted delivery approach, as well as a cell-based therapeutic. This article discusses the rationale for cell-based therapy in amyotrophic lateral sclerosis and several of the unique considerations encountered during this process.

Stem cell therapy for the spinal cord

Injury and disease of the spinal cord are generally met with a poor prognosis. This poor prognosis is due not only to the characteristics of the diseases but also to our poor ability to deliver therapeutics to the spinal cord. The spinal cord is extremely sensitive to direct manipulation, and delivery of therapeutics has proven a challenge for both scientists and physicians. Recent advances in stem cell technologies have opened up a new avenue for the treatment of spinal cord disease and injury. Stem cells have proven beneficial in rodent models of spinal cord disease and injury. In these animal models, stem cells have been shown to produce their effect by the dual action of cell replacement and the trophic support of the factors secreted by these cells. In this review we look at the main clinical trials involving stem cell transplant into the spinal cord, focusing on motor neuron diseases and spinal cord injury. We will also discuss the major hurdles in optimizing stem cell delivery methods into the spinal cord. We shall examine current techniques such as functional magnetic resonance imaging guidance and cell labeling and will look at the current research striving to improve these techniques. With all caveats and future research taken into account, this is a very exciting time for stem cell transplant into the spinal cord. We are only beginning to realize the huge potential of stem cells in a central nervous system setting to provide cell replacement and trophic support. Many more trials will need to be undertaken before we can fully exploit the attributes of stem cells.

What do we know about the neurogenic potential of different stem cell types?

Cell therapies, based on transplantation of immature cells, are being considered as a promising tool in the treatment of neurological disorders. Many efforts are being concentrated on the development of safe and effective stem cell lines. Nevertheless, the neurogenic potential of some cell lines, i.e., the ability to generate mature neurons either in vitro or in vivo, is largely unknown. Recent evidence indicate that this potential might be distinct among different cell lines, therefore limiting their broad use as replacement cells in the central nervous system. Here, we have reviewed the latest advancements regarding the electrophysiological maturation of stem cells, focusing our attention on fetal-derived-, embryonic-, and induced pluripotent stem cells. In summary, a large body of evidence supports the biological safety, high neurogenic potential, and in some diseases probable clinical efficiency related to fetal-derived cells. By contrast, reliable data regarding embryonic and induced pluripotent stem cells are still missing.

Therapy development for spinal muscular atrophy in SMN independent targets

Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder, leading to progressive muscle weakness, atrophy, and sometimes premature death. SMA is caused by mutation or deletion of the survival motor neuron-1 (SMN1) gene. An effective treatment does not presently exist. Since the severity of the SMA phenotype is inversely correlated with expression levels of SMN, the SMN-encoded protein, SMN is the most important therapeutic target for development of an effective treatment for SMA. In recent years, numerous SMN independent targets and therapeutic strategies have been demonstrated to have potential roles in SMA treatment. For example, some neurotrophic, antiapoptotic, and myotrophic factors are able to promote survival of motor neurons or improve muscle strength shown in SMA mouse models or clinical trials. Plastin-3, cpg15, and a Rho-kinase inhibitor regulate axonal dynamics and might reduce the influences of SMN depletion in disarrangement of neuromuscular junction. Stem cell transplantation in SMA model mice resulted in improvement of motor behaviors and extension of survival, likely from trophic support. Although most therapies are still under investigation, these nonclassical treatments might provide an adjunctive method for future SMA therapy.

Functional recovery after spinal cord injury in dogs treated with a combination of Matrigel and neural-induced adipose-derived mesenchymal Stem cells

BACKGROUND AIMS

Previous studies have reported that scaffold or cell-based transplantation may improve functional recovery following spinal cord injury (SCI), but these results were based on neuronal regeneration and cell replacement. In this study, we investigated whether a combination of Matrigel and neural-induced mesenchymal stem cells (NMSC) improved hindlimb function in dogs with SCI, and what mechanisms were involved.

METHODS

We pre-differentiated canine adipose-derived mesenchymal stem cells into NMSC. A total of 12 dogs subjected to SCI procedures were assigned to one of the following three transplantation treatment groups: phosphate-buffered saline (PBS); Matrigel; or Matrigel seeded with NMSC. Treatment occurred 1 week after SCI. Basso, Beattie and Bresnahan (B.B.B.) and Tarlov scores, histopathology, immunofluorescence staining and Western blot analysis were used to evaluate the treatment effects.

RESULTS

Compared with dogs administered PBS or Matrigel alone, dogs treated with Matrigel + NMSC showed significantly better functional recovery 8 weeks after transplantation. Histology and immunochemical analysis revealed that the combination of Matrigel + NMSC reduced fibrosis from secondary injury processes and improved neuronal regeneration more than the other treatments. In addition, the combination of Matrigel + NMSC decreased the expression of inflammation and/or astrogliosis markers. Increased expressions of intracellular molecules related to neuronal extension, neuronal markers and neurotrophic factors were also found in the Matrigel + NMSC group. However, the expression of nestin as a neural stem cell marker was increased with Matrigel alone.

CONCLUSIONS

The combination of Matrigel + NMSC produced beneficial effects in dogs with regard to functional recovery following SCI through enhancement of anti-inflammation, anti-astrogliosis, neuronal extension and neuronal regeneration effects.

Current and prospective disease-modifying therapies for amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a devastating illness of unclear etiology affecting motor neurons. It causes unremitting muscle paralysis, atrophy and death usually within 3 - 5 years from diagnosis. The human and economic costs for those affected are sobering. To date, tremendous efforts have failed to find a cure.

AREAS COVERED

An extensive literature search was undertaken using Medline and the Cochrane Systematic Review and Clinical Trial databases. Riluzole and investigational ALS drugs are discussed. Riluzole is the only approved disease-modifying therapy despite its modest effect on survival. Recent research has produced promising agents aimed at better disease control if not a cure. This review discusses agents targeting neuronal glutamate excitotoxicity, protein misfolding and accumulation, autophagy, apoptosis, mitochondrial dysfunction, free radical oxidative injury, immunomodulation, mutant mRNA counteraction, muscle physiology, neurotrophic factors and stem cell applications. The challenges in ALS drug development are highlighted.

EXPERT OPINION

Riluzole should be used for patients with definite, probable, suspected or possible ALS by World Federation of Neurology diagnostic criteria. Systematic monitoring for hepatic dysfunction, neutropenia and other serious adverse effects should be done routinely as outlined. All ALS patients should consider genetic screening and enrollment in ALS trials guided by the data reviewed.

Intraspinal transplantation of neurogenin-expressing stem cells generates spinal cord neural progenitors

Embryonic stem (ES) cells and their derivatives are an important resource for developing novel cellular therapies for disease. Controlling proliferation and lineage selection, however, are essential to circumvent the possibility of tumor formation and facilitate the safe translation of ES-based therapies to man. Expression of appropriate transcription factors is one approach to direct the differentiation of ES cells towards a specific lineage and stop proliferation. Neural differentiation can be initiated in ES cells by expression of Neurogenin1 (Ngn1). In this study we investigate the effects of controlled Ngn1 expression on mouse ES (mES) cell differentiation in vitro and following grafting into the rat spinal cord. In vitro, Ngn1 expression in mES cells leads to rapid and specific neural differentiation, and a concurrent decrease in proliferation. Similarly transplantation of Ngn1-expressing mES cells into the spinal cord lead to in situ differentiation and spinal precursor formation. These data demonstrate that Ngn1 expression in mES cells is sufficient to promote neural differentiation and inhibit proliferation, thus establishing an approach to safely graft ES cells into the spinal cord.

Translational stem cell therapy for amyotrophic lateral sclerosis

Effective treatments are urgently needed for amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease characterized by the loss of motor neurons. In 2009, the FDA approved the first phase I safety trial of direct intraspinal transplantation of neural stem cells into patients with ALS, which is currently in progress. Stem cell technologies represent a promising approach for treating ALS, but several issues must be addressed when translating promising experimental ALS therapies to patients. This article highlights the key research that supports the use of stem cells as a therapy for ALS, and discusses the rationale behind and approach to the phase I trial. Completion of the trial could pave the way for continued advances in stem cell therapy for ALS and other neurodegenerative diseases.

Stem cell technology for neurodegenerative diseases

Over the past 20 years, stem cell technologies have become an increasingly attractive option to investigate and treat neurodegenerative diseases. In the current review, we discuss the process of extending basic stem cell research into translational therapies for patients suffering from neurodegenerative diseases. We begin with a discussion of the burden of these diseases on society, emphasizing the need for increased attention toward advancing stem cell therapies. We then explain the various types of stem cells utilized in neurodegenerative disease research, and outline important issues to consider in the transition of stem cell therapy from bench to bedside. Finally, we detail the current progress regarding the applications of stem cell therapies to specific neurodegenerative diseases, focusing on Parkinson disease, Huntington disease, Alzheimer disease, amyotrophic lateral sclerosis, and spinal muscular atrophy. With a greater understanding of the capacity of stem cell technologies, there is growing public hope that stem cell therapies will continue to progress into realistic and efficacious treatments for neurodegenerative diseases.

Achieving stable human stem cell engraftment and survival in the CNS: is the future of regenerative medicine immunodeficient?

There is potential for a variety of stem cell populations to mediate repair in the diseased or injured CNS; in some cases, this theoretical possibility has already transitioned to clinical safety testing. However, careful consideration of preclinical animal models is essential to provide an appropriate assessment of stem cell safety and efficacy, as well as the basic biological mechanisms of stem cell action. This article examines the lessons learned from early tissue, organ and hematopoietic grafting, the early assumptions of the stem cell and CNS fields with regard to immunoprivilege, and the history of success in stem cell transplantation into the CNS. Finally, we discuss strategies in the selection of animal models to maximize the predictive validity of preclinical safety and efficacy studies.

Stem cell transplantation for motor neuron disease: current approaches and future perspectives

Motor neuron degeneration leading to muscle atrophy and death is a pathological hallmark of disorders, such as amyotrophic lateral sclerosis or spinal muscular atrophy. No effective treatment is available for these devastating diseases. At present, cell-based therapies targeting motor neuron replacement, support, or as a vehicle for the delivery of neuroprotective molecules are being investigated. Although many challenges and questions remain, the beneficial effects observed following transplantation therapy in animal models of motor neuron disease has sparked hope and a number of clinical trials. Here, we provide a comprehensive review of cell-based therapeutics for motor neuron disorders, with a particular emphasis on amyotrophic lateral sclerosis.

Stem cell technology for the study and treatment of motor neuron diseases

Amyotrophic lateral sclerosis and spinal muscular atrophy are devastating neurodegenerative diseases that lead to the specific loss of motor neurons. Recently, stem cell technologies have been developed for the investigation and treatment of both diseases. Here we discuss the different stem cells currently being studied for mechanistic discovery and therapeutic development, including embryonic, adult and induced pluripotent stem cells. We also present supporting evidence for the utilization of stem cell technology in the treatment of amyotrophic lateral sclerosis and spinal muscular atrophy, and describe key issues that must be considered for the transition of stem cell therapies for motor neuron diseases from bench to bedside. Finally, we discuss the first-in-human Phase I trial currently underway examining the safety and feasibility of intraspinal stem cell injections in amyotrophic lateral sclerosis patients as a foundation for translating stem cell therapies for various neurological diseases.

Emerging targets and treatments in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease that is currently untreatable. Many compounds have been tested in laboratory-based models and in patients with ALS, but so far only one drug, riluzole, has shown efficacy, yet it only slightly slows disease progression. Several new insights into the causes of motor neuron death have led to the identification of some important novel targets for intervention. At no time have studies involved such a wide range of innovations and such advanced technologies. Many promising studies are underway to test potential targets that will hopefully translate into meaningful therapeutics for patients with ALS.

Projections from the rat pedunculopontine and laterodorsal tegmental nuclei to the anterior thalamus and ventral tegmental area arise from largely separate populations of neurons

Cholinergic and non-cholinergic neurons in the brainstem pedunculopontine (PPT) and laterodorsal tegmental (LDT) nuclei innervate diverse forebrain structures. The cholinergic neurons within these regions send heavy projections to thalamic nuclei and provide modulatory input as well to midbrain dopamine cells in the ventral tegmental area (VTA). Cholinergic PPT/LDT neurons are known to send collateralized projections to thalamic and non-thalamic targets, and previous studies have shown that many of the afferents to the VTA arise from neurons that also project to midline and intralaminar thalamic nuclei. However, whether cholinergic projections to the VTA and anterior thalamus (AT) are similarly collateralized is unknown. Ultrastructural work from our laboratory has demonstrated that cholinergic axon varicosities in these regions differ both morphologically and with respect to the expression and localization of the high-affinity choline transporter. We therefore hypothesized that the cholinergic innervation to these regions is provided by separate sets of PPT/LDT neurons. Dual retrograde tract-tracing from the AT and VTA indicated that only a small percentage of the total afferent population to either region showed evidence of providing collateralized input to the other target. Cholinergic and non-cholinergic cells displayed a similarly low percentage of collateralization. These results are contrasted to a control case in which retrograde labeling from the midline paratenial thalamic nucleus and the VTA resulted in higher percentages of cholinergic and non-cholinergic dual-tracer labeled cells. Our results indicate that functionally distinct limbic target regions receive primarily segregated signaling from PPT/LDT neurons.

Research advances in amyotrophic lateral sclerosis, 2009 to 2010

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of upper and lower motor neurons that causes progressive weakness and death. The breadth of research in ALS continues to grow with exciting new discoveries in disease pathogenesis and potential future therapeutics. There is a growing list of identified mutations in familial ALS, including those in genes encoding TDP-43 and FUS/TLS, which are expanding our understanding of the role of RNA modulation in ALS pathogenesis. There is a greater appreciation for the role of glial cells in motor neuron disease. Mitochondrial dysfunction is also being shown to be critical for motor neuron degeneration. In addition to pharmacotherapy, there are promising early developments with therapeutic implications in the areas of RNA interference, stem cell therapies, viral vector-mediated gene therapy, and immunotherapy. With greater understanding of ALS pathogenesis and exciting new therapeutic technologies, there is hope for future progress in treating this disease.

Dual transplantation of human neural stem cells into cervical and lumbar cord ameliorates motor neuron disease in SOD1 transgenic rats

Stem cells provide novel sources of cell therapies for motor neuron disease that have recently entered clinical trials. In the present study, we transplanted human neural stem cells (NSCs) into the ventral horn of both the lumbar (L4-L5) and cervical (C4-C5) protuberance of SOD1 G93A rats, in an effort to test the feasibility and general efficacy of a dual grafting paradigm addressing several muscle groups in the front limbs, hind limbs and the respiratory apparatus. Transplantation was done prior to the onset of motor neuron disease. Compared with animals that had received dead NSC grafts (serving as controls), rats with live NSCs grafted at the two spinal levels lived 17 days longer. Disease onset in dually grafted animals was delayed by 10 days compared to control animals. Disease duration in NSC-grafted animals was longer by 7 days compared to controls. Our results support the potential of NSC grafts at multiple levels of spinal cord as future cellular therapy for motor neuron disease.

Cervical multilevel intraspinal stem cell therapy: assessment of surgical risks in Gottingen minipigs

STUDY DESIGN

Assessment of long-term surgical risks from multiple intraspinal cell injections.

OBJECTIVE

To prove that multilevel-targeted cell injection to the spinal cord can be a feasible and safe procedure.

SUMMARY OF BACKGROUND DATA

Neural cell transplantation has been proposed as a treatment for a variety of neurologic disorders, including degenerative, ischemic, autoimmune, and traumatic etiologies. Among these diseases, the lack of effective treatment for amyotrophic lateral sclerosis has prompted the search for cell-based neuroprotection or motor neuron-replacement therapies.

METHODS

Fifteen female minipigs, divided into 3 experimental groups, underwent either 5 or 10 unilateral injections of neural stem cells or 10 vehicle injections into the C3-C5 segments of the spinal cord, using a device and technique developed for safe and accurate injection into the human spinal cord. All animals received intravenous Tacrolimus (0.025 mg/kg) BID during the course of the study. Sensory and motor functions as well as general morbidity were assessed for 28 days. Full necropsy was performed and spinal cords were analyzed for graft survival. This study was performed under Good Laboratory Practice conditions.

RESULTS

Neither mortality nor permanent surgical complications were observed within the 28-day study period. All animals returned to preoperative baseline showing full motor function recovery. Graft survival was demonstrated by immunohistochemistry.

CONCLUSION

Clinically acceptable neural progenitor survival, distribution, and density were achieved using the number of injections and surgical techniques specifically developed for this purpose.

Nanofiber matrices promote the neuronal differentiation of human embryonic stem cell-derived neural precursors in vitro

The potential of human embryonic stem (ES) cells as experimental therapies for neuronal replacement has recently received considerable attention. In view of the organization of the mature nervous system into distinct neural circuits, key challenges of such therapies are the directed differentiation of human ES cell-derived neural precursors (NPs) into specific neuronal types and the directional growth of axons along specified trajectories. In the present study, we cultured human NPs derived from the NIH-approved ES line BGO1 on polycaprolactone fiber matrices of different diameter (i.e., nanofibers and microfibers) and orientation (i.e., aligned and random); fibers were coated with poly-L-ornithine/laminin to mimic the extracellular matrix and support the adhesion, viability, and differentiation of NPs. On aligned fibrous meshes, human NPs adopt polarized cell morphology with processes extending along the axis of the fiber, whereas NPs on plain tissue culture surfaces or random fiber substrates form nonpolarized neurite networks. Under differentiation conditions, human NPs cultured on aligned fibrous substrates show a higher rate of neuronal differentiation than other matrices; 62% and 86% of NPs become TUJ1 (+) early neurons on aligned micro- and nanofibers, respectively, whereas only 32% and 27% of NPs acquire the same fate on random micro- and nanofibers. Metabolic cell activity/viability studies reveal that fiber alignment and diameter also have an effect on NP viability, but only in the presence of mitogens. Our findings demonstrate that fibrous substrates serve as an artificial extracellular matrix and provide a microenviroment that influences key aspects of the neuronal differentiation of ES-derived NPs.

The promise and the reality of stem-cell therapies for neurodegenerative diseases

Jonathan D. Glass, M.D., is leading a clinical trial testing the safety of using adult stem cells to treat patients with amyotrophic lateral sclerosis (ALS), a neurodegenerative disease that remains untreatable. This trial, along with others like it, is just the beginning of a time-intensive process necessary to determine whether stem-cell treatments are safe and effective, meaning that the benefits-if there prove to be any-outweigh the risks. But even as FDA-approved trials are underway, some people with neurodegenerative disorders are turning to dangerous, unapproved stem-cell treatments out of desperation. Dr. Glass warns that researchers must strictly adhere to the scientific process in order to convert the hope of stem-cell treatments into reality.

Amyotrophic lateral sclerosis: applications of stem cells - an update

Neurodegenerative diseases are a growing public health challenge, and amyotrophic lateral sclerosis (ALS) remains a fatal incurable disease. The advent of stem cell therapy has opened new horizons for both researchers and ALS patients, desperately looking for a treatment. ALS must be considered a systemic disease affecting many cell phenotypes besides motor neurons, even outside the central nervous system. Cell replacement therapy needs to address the specific neurobiological issues of ALS to safely and efficiently reach clinical settings. Moreover, the enormous potential of induced pluripotent cells directly derived from patients for modeling and understanding the pathological mechanisms, in correlation with the discoveries of new genes and animal models, provides new opportunities that need to be integrated with previously described transplantation strategies. Finally, a careful evaluation of preclinical data in conjunction with wary patient choice in clinical trials needs to be established in order to generate meaningful results.

The pleotrophic effects of insulin-like growth factor-I on human spinal cord neural progenitor cells

Most stem cell therapies involve direct, intraparachymal placement of neural progenitor cells. These cells provide physical support to the endogenous neuronal population and may be engineered to provide in situ growth factor support. Insulin-like growth factor-I (IGF-I) has potent neurotrophic and neuroprotective properties and is expressed by human neural stem cells (hNSCs). IGF-I is implicated in multiple aspects of cell behavior, including proliferation, differentiation, and survival. Enhancing hNSC function through IGF-I overexpression may increase the benefits of stem cell therapy. As a first step to that goal, we examined the direct effects of IGF-I on hNSC behavior in vitro. We demonstrate that IGF-I treatment enhances both the number and length of hNSC neurites. This is correlated with a decrease in proliferation, suggesting that IGF-I promotes neurite outgrowth but not proliferation. While IGF-I activates both AKT and MAPK signaling in hNSCs, we demonstrate that IGF-I-mediated neurite outgrowth is dependent only on AKT signaling. Finally, we demonstrate that IGF-I is neuroprotective after glutamate exposure in a model of excitotoxic cell death.

Recent advances in amyotrophic lateral sclerosis research: perspectives for personalized clinical application

Treatment of amyotrophic lateral sclerosis (ALS) has been fueled, in part, by frustration over the shortcomings of the symptomatic drugs available, since these do not impede the progression of this disease. Currently, over 150 different potential therapeutic agents or strategies have been tested in preclinical models of ALS. Unfortunately, therapeutic modifiers of murine ALS have failed to be successfully translated into strategies for patients, probably because of differences in pharmacokinetics of the therapeutic agents, route of delivery, inefficiency of the agents to affect the distinct pathologies of the disease or inherent limitations of the available animal models. Given the multiplicity of the pathological mechanisms implicated in ALS, new therapies should consider the simultaneous manipulation of multiple targets. Additionally, a better management of ALS therapy should include understanding the interactions between potential risk factors, biomarkers and heterogeneous clinical features of the patients, aiming to manage their adverse events or personalize the safety profile of these agents. This review will discuss novel pharmacological approaches concerning adjusted therapy for ALS patients: iron-binding brain permeable multimodal compounds, genetic manipulation and cell-based treatment.

Pluripotent stem cells in neurodegenerative and neurodevelopmental diseases

Most of our current knowledge about cellular phenotypes in neurodevelopmental and neurodegenerative diseases in humans was gathered from studies in postmortem brain tissues. These samples often represent the end-stage of the disease and therefore are not always a fair representation of how the disease developed. Moreover, under these circumstances, the pathology observed could be a secondary effect rather than the authentic disease cellular phenotype. Likewise, the rodent models available do not always recapitulate the pathology from human diseases. In this review, we will examine recent literature on the use of induced pluripotent stem cells to model neurodegenerative and neurodevelopmental diseases. We highlight the characteristics of diseases like spinal muscular atrophy and familial dysautonomia that allowed partial modeling of the disease phenotype. We review human stem cell literature on common neurodegenerative late-onset diseases such as Parkinson's disease and amyotrophic lateral sclerosis where patients' cells have been successfully reprogrammed but a disease phenotype has not yet been described. So far, the technique is of great interest for early onset monogenetic neurodevelopmental diseases. We speculate about potential further experimental requirements and settings for reprogrammed neurons for in vitro disease modeling and drug discovery.

Personalizing Stem Cell Research and Therapy: The Arduous Road Ahead or Missed Opportunity?

The euphoria of stem cell therapy has diminished, allowing scientists, clinicians and the general public to seriously re-examine how and what types of stem cells would effectively repair damaged tissue, prevent further tissue damage and/or replace lost cells. Importantly, there is a growing recognition that there are substantial person-to-person differences in the outcome of stem cell therapy. Even though the small molecule pharmaceuticals have long remained a primary focus of the personalized medicine research, individualized or targeted use of stem cells to suit a particular individual could help forecast potential failures of the therapy or identify, early on, the individuals who might benefit from stem cell interventions. This would however demand collaboration among several specialties such as pharmacology, immunology, genomics and transplantation medicine. Such transdisciplinary work could also inform how best to achieve efficient and predictable stem cell migration to sites of tissue damage, thereby facilitating tissue repair. This paper discusses the possibility of polarizing immune responses to rationalize and individualize therapy with stem cell interventions, since generalized "one-size-fits-all" therapy is difficult to achieve in the face of the diverse complexities posed by stem cell biology. We also present the challenges to stem cell delivery in the context of the host related factors. Although we focus on the mesenchymal stem cells in this paper, the overarching rationale can be extrapolated to other types of stem cells as well. Hence, the broader purpose of this paper is to initiate a dialogue within the personalized medicine community by expanding the scope of inquiry in the field from pharmaceuticals to stem cells and related cell-based health interventions.

Recent advancements in stem cell and gene therapies for neurological disorders and intractable epilepsy

The potential applications of stem cell therapies for treating neurological disorders are enormous. Many laboratories are focusing on stem cell treatments for CNS diseases, including spinal cord injury, Amyotrophic lateral sclerosis, Parkinson's disease, Huntington's disease, multiple sclerosis, stroke, traumatic brain injury, and epilepsy. Among the many stem cell types under testing for neurological treatments, the most common are fetal and adult brain stem cells, embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells. An expanding toolbox of molecular probes is now available to allow analyses of neural stem cell fates prior to and after transplantation. Concomitantly, protocols are being developed to direct the fates of stem cell-derived neural progenitors, and also to screen stem cells for tumorigenicity and aneuploidy. The rapid progress in the field suggests that novel stem cell and gene therapies for neurological disorders are in the pipeline.

Stem cells and spinal cord regeneration

Cell-based transplantation strategies are inherently combination therapies, as they may mediate spinal cord repair via trophic or phenotypic mechanisms. The growth factor expression profile and phenotype of transplanted cells are determined by the transplant population as well as by the site into which they are transplanted. Identifying the key pathways involved in transplant survival and differentiation, as well as neuroprotection and regeneration of endogenous tissue, will enable manipulation of both the transplanted cells and the microenvironment to improve transplant efficiency. High purity populations derived from stem cells will serve to better delineate lineage-specific mechanisms of repair, while providing both neurotrophic and phenotypic benefits to the injured spinal cord.

Stem cells in human neurodegenerative disorders--time for clinical translation?

Stem cell-based approaches have received much hype as potential treatments for neurodegenerative disorders. Indeed, transplantation of stem cells or their derivatives in animal models of neurodegenerative diseases can improve function by replacing the lost neurons and glial cells and by mediating remyelination, trophic actions, and modulation of inflammation. Endogenous neural stem cells are also potential therapeutic targets because they produce neurons and glial cells in response to injury and could be affected by the degenerative process. As we discuss here, however, significant hurdles remain before these findings can be responsibly translated to novel therapies. In particular, we need to better understand the mechanisms of action of stem cells after transplantation and learn how to control stem cell proliferation, survival, migration, and differentiation in the pathological environment.

Advances in stem cell research for Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disorder characterized primarily by motor neuron loss in the motor cortex and spinal cord leading to progressive disability and death. Despite the relative selectivity of motor neuron loss, recent studies have implicated other cell types including astrocytes and microglia as contributors to this cell death. This understanding has resulted in stem-cell-replacement strategies of these cell types, which may result in neuroprotection. In addition to cell-replacement strategies, the development of induced pluripotent stem cell (iPSC) technologies has resulted in the establishment of motor neuron cell lines from patients with ALS. The use of iPSCs from ALS patients will allow for potential autologous cell transplantation, drug discovery, and an increased understanding of ALS pathobiology.