Neuroprotective effect of grafting GDNF gene-modified neural stem cells on cerebral ischemia in rats

Emerging strategies for nerve repair and regeneration in ischemic stroke: neural stem cell therapy

Ischemic stroke is a major cause of mortality and disability worldwide, with limited treatment options available in clinical practice. The emergence of stem cell therapy has provided new hope to the field of stroke treatment via the restoration of brain neuron function. Exogenous neural stem cells are beneficial not only in cell replacement but also through the bystander effect. Neural stem cells regulate multiple physiological responses, including nerve repair, endogenous regeneration, immune function, and blood-brain barrier permeability, through the secretion of bioactive substances, including extracellular vesicles/exosomes. However, due to the complex microenvironment of ischemic cerebrovascular events and the low survival rate of neural stem cells following transplantation, limitations in the treatment effect remain unresolved. In this paper, we provide a detailed summary of the potential mechanisms of neural stem cell therapy for the treatment of ischemic stroke, review current neural stem cell therapeutic strategies and clinical trial results, and summarize the latest advancements in neural stem cell engineering to improve the survival rate of neural stem cells. We hope that this review could help provide insight into the therapeutic potential of neural stem cells and guide future scientific endeavors on neural stem cells.

[The secretome of mesenchymal stromal cells as a new hope in the treatment of acute brain tissue injuries]

Ischemic and hemorrhagic strokes, traumatic brain injury, bacterial and viral encephalitis, toxic and metabolic encephalopathies are very different pathologies. But, they have much more in common than it might seem at first glance. In this review, the authors propose to consider these brain pathologies from the point of view of the unity of their pathogenetic mechanisms and approaches to therapy. Particular attention is paid to promising therapeutic approaches, such as therapy using cells and their secretion products: an analysis of the accumulated experimental data, the advantages and limitations of these approaches in the treatment of brain damage was carried out. The review may be of interest both to specialists in the field of neurology, neurosurgery and neurorehabilitation, and to readers who want to learn more about the progress of regenerative biomedicine in the treatment of brain pathologies.

Targeting Neurogenesis in Seeking Novel Treatments for Ischemic Stroke

The interruption of cerebral blood flow leads to ischemic cell death and results in ischemic stroke. Although ischemic stroke is one of the most important causes of long-term disability and mortality, limited treatments are available for functional recovery. Therefore, extensive research has been conducted to identify novel treatments. Neurogenesis is regarded as a fundamental mechanism of neural plasticity. Therefore, therapeutic strategies targeting neurogenesis are thought to be promising. Basic research has found that therapeutic intervention including cell therapy, rehabilitation, and pharmacotherapy increased neurogenesis and was accompanied by functional recovery after ischemic stroke. In this review, we consolidated the current knowledge of the relationship between neurogenesis and treatment for ischemic stroke. It revealed that many treatments for ischemic stroke, including clinical and preclinical ones, have enhanced brain repair and functional recovery post-stroke along with neurogenesis. However, the intricate mechanisms of neurogenesis and its impact on stroke recovery remain areas of extensive research, with numerous factors and pathways involved. Understanding neurogenesis will lead to more effective stroke treatments, benefiting not only stroke patients but also those with other neurological disorders. Further research is essential to bridge the gap between preclinical discoveries and clinical implementation.

Genetically engineered neural stem cells (NSCs) therapy for neurological diseases; state-of-the-art

Neural stem cells (NSCs) are multipotent stem cells with remarkable self-renewal potential and also unique competencies to differentiate into neurons, astrocytes, and oligodendrocytes (ODCs) and improve the cellular microenvironment. In addition, NSCs secret diversity of mediators, including neurotrophic factors (e.g., BDNF, NGF, GDNF, CNTF, and NT-3), pro-angiogenic mediators (e.g., FGF-2 and VEGF), and anti-inflammatory biomolecules. Thereby, NSCs transplantation has become a reasonable and effective treatment for various neurodegenerative disorders by their capacity to induce neurogenesis and vasculogenesis and dampen neuroinflammation and oxidative stress. Nonetheless, various drawbacks such as lower migration and survival and less differential capacity to a particular cell lineage concerning the disease pathogenesis hinder their application. Thus, genetic engineering of NSCs before transplantation is recently regarded as an innovative strategy to bypass these hurdles. Indeed, genetically modified NSCs could bring about more favored therapeutic influences post-transplantation in vivo, making them an excellent option for neurological disease therapy. This review for the first time offers a comprehensive review of the therapeutic capability of genetically modified NSCs rather than naïve NSCs in neurological disease beyond brain tumors and sheds light on the recent progress and prospect in this context.

From Hair to the Brain: The Short-Term Therapeutic Potential of Human Hair Follicle-Derived Stem Cells and Their Conditioned Medium in a Rat Model of Stroke

The short-term therapeutic impacts of stem cells and their derivatives were frequently reported in preclinical investigations of ischemic stroke (IS); however, several drawbacks including accessibility, abundancy, and ethical concerns limited their clinical application. We describe here for the first time the therapeutic potential of human hair follicle-derived stem cells (hHFSCs) and their conditioned medium (CM) in a rat model of IS. Furthermore, we hypothesized that a combination of cell therapy with repeated CM administration might enhance the restorative efficiency of this approach compared to each treatment alone. Middle cerebral artery occlusion was performed for 30 min to induce IS. Immediately after reperfusion, hHFSCs were transplanted through the intra-arterial route and/or hHFSC-CM administered intranasally. The neurological outcomes, short-term spatial working memory, and infarct size were evaluated. Furthermore, relative expression of seven target genes in three categories of neuronal markers, synaptic markers, and angiogenic markers was assessed. The hHFSCs and hHFSC-CM treatments improved neurological impairments and reduced infarct size in the IS rats. Moreover, molecular data elucidated that IS was accompanied by attenuation in the expression of neuronal and synaptic markers in the evaluated brain regions and the interventions rescued these expression changes. Although there was no considerable difference between hHFSCs and hHFSC-CM treatments in the improvement of neurological function and decrement of infarct size, combination therapy was more effective to reduce infarction and elevation of target gene expression especially in the hippocampus. These findings highlight the curative potential of hHFSCs and their CM in a rat model of IS.

Hippocampal region-specific endogenous neuroprotection as an approach in the search for new neuroprotective strategies in ischemic stroke. Fiction or fact?

Ischemic stroke is the leading cause of death and long-term disability worldwide, and, while considerable progress has been made in understanding its pathophysiology, the lack of effective treatments remains a major concern. In that context, receiving more and more consideration as a promising therapeutic method is the activation of natural adaptive mechanisms (endogenous neuroprotection) - an approach that seeks to enhance and/or stimulate the endogenous processes of plasticity and protection of the neuronal system that trigger the brain's intrinsic capacity for self-defence. Ischemic preconditioning is a classic example of endogenous neuroprotection, being the process by which one or more brief, non-damaging episodes of ischemia-reperfusion (I/R) induce tissue resistance to subsequent prolonged, damaging ischemia. Another less-known example is resistance to an I/R episode mounted by the hippocampal region consisting of CA2, CA3, CA4 and the dentate gyrus (here abbreviated to CA2-4, DG). This can be contrasted with the ischemia-vulnerable CA1 region. There is not yet a good understanding of these different sensitivities of the hippocampal regions, and hence of the endogenous neuroprotection characteristic of CA2-4, DG. However, this region is widely reported to have properties distinct from CA1, and capable of generating resistance to an I/R episode. These include activation of neurotrophic and neuroprotective factors, greater activation of anti-excitotoxic and anti-oxidant mechanisms, increased plasticity potential, a greater energy reserve and improved mitochondrial function. This review seeks to summarize properties of CA2-4, DG in the context of endogenous neuroprotection, and then to assess the potential utility of these properties to therapeutic approaches. In so doing, it appears to represent the first such addressing of the issue of ischemia resistance attributable to CA2-4, DG.

l-Borneol and d-Borneol promote transdifferentiation of astrocytes into neurons in rats by regulating Wnt/Notch pathway to exert neuroprotective effect during recovery from cerebral ischaemia

BACKGROUND

The Chinese medicines Borneolum and l-Borneolum have neuroprotective effects on acute cerebral ischaemia-reperfusion (IR) in rats. Research on their effects during recovery from cerebral IR is lacking. Cerebral ischaemia can activate astrocytes for conversion into neurons. Neurogenesis cannot be achieved without nutritional support from an improved brain microenvironment through the blood circulation.

PURPOSE

The purpose of this study was to determine whether Borneolum and l-Borneolum can promote transdifferentiation of astrocytes into neurons by regulating the Wnt/Notch pathway to exert neuroprotective effects during recovery from cerebral ischaemia.

STUDY DESIGN AND METHODS

A suture crossing the external carotid artery to occlude the middle cerebral artery was used to prepare a model of cerebral IR (Longa et al., 1989). The Longa neurological function score, modified neurological severity score, tape removal test and grid misstep experiment were used to evaluate motor nerve function. Triphenyltetrazolium chloride was used to determine the extent of cerebral infarction. Left/right hemisphere contrast was used to measure brain atrophy. Astrocytes labelled with adeno-associated virus were used to track their fate after transdifferentiation. Laser speckle contrast imaging was used to observe the effects of l-Borneolum and Borneolum on cerebral blood flow. Immunofluorescence and western blotting were used to investigate their mechanisms.

RESULTS

l-Borneolum and Borneolum significantly improved neurological function and limb movement in rats with cerebral ischaemia during recovery and increased cerebral blood flow. l-Borneolum improved forelimb motor coordination more effectively than Borneolum and promoted transdifferentiation of astrocytes to GABAergic neurons in the striatal region. The expression of Wnt3a and Notch-1 was downregulated. The expression of vascular endothelial growth factor was not significantly changed. Borneolum improved forelimb sensitivity and alleviated cerebral infarction and brain atrophy more effectively than l-Borneolum, which promoted transdifferentiation of astrocytes into neurons and nestin expression and neurogenesis in the striatal zone. The expression of glycogen synthase kinase-3β and β-catenin was upregulated. l-Borneolum and Borneolum had no significant neuroprotective effect on the cortex and hippocampus.

CONCLUSIONS

l-Borneolum and Borneolum exerted neuroprotective effects on cerebral ischaemia during recovery by promoting neurogenesis and blood circulation in the striatal and subventricular zones. Their mechanisms may be related to the Wnt3a and Notch-1 pathways.

Stem-Cell-Based Therapy: The Celestial Weapon against Neurological Disorders

Stem cells are a versatile source for cell therapy. Their use is particularly significant for the treatment of neurological disorders for which no definitive conventional medical treatment is available. Neurological disorders are of diverse etiology and pathogenesis. Alzheimer's disease (AD) is caused by abnormal protein deposits, leading to progressive dementia. Parkinson's disease (PD) is due to the specific degeneration of the dopaminergic neurons causing motor and sensory impairment. Huntington's disease (HD) includes a transmittable gene mutation, and any treatment should involve gene modulation of the transplanted cells. Multiple sclerosis (MS) is an autoimmune disorder affecting multiple neurons sporadically but induces progressive neuronal dysfunction. Amyotrophic lateral sclerosis (ALS) impacts upper and lower motor neurons, leading to progressive muscle degeneration. This shows the need to try to tailor different types of cells to repair the specific defect characteristic of each disease. In recent years, several types of stem cells were used in different animal models, including transgenic animals of various neurologic disorders. Based on some of the successful animal studies, some clinical trials were designed and approved. Some studies were successful, others were terminated and, still, a few are ongoing. In this manuscript, we aim to review the current information on both the experimental and clinical trials of stem cell therapy in neurological disorders of various disease mechanisms. The different types of cells used, their mode of transplantation and the molecular and physiologic effects are discussed. Recommendations for future use and hopes are highlighted.

The Beneficial Potential of Genetically Modified Stem Cells in the Treatment of Stroke: a Review

The last two decades have witnessed a surge in investigations proposing stem cells as a promising strategy to treat stroke. Since growth factor release is considered as one of the most important aspects of cell-based therapy, stem cells over-expressing growth factors are hypothesized to yield higher levels of therapeutic efficiency. In pre-clinical studies of the last 15 years that were investigating the efficiency of stem cell therapy for stroke, a variety of stem cell types were genetically modified to over-express various factors. In this review we summarize the current knowledge on the therapeutic efficiency of stem cell-derived growth factors, encompassing techniques employed and time points to evaluate. In addition, we discuss several types of stem cells, including the recently developed model of epidermal neural crest stem cells, and genetically modified stem cells over-expressing specific factors, which could elevate the restorative potential of naive stem cells. The restorative potential is based on enhanced survival/differentiation potential of transplanted cells, apoptosis inhibition, infarct volume reduction, neovascularization or functional improvement. Since the majority of studies have focused on the short-term curative effects of genetically engineered stem cells, we emphasize the need to address their long-term impact.

Gene Therapy Approach with an Emphasis on Growth Factors: Theoretical and Clinical Outcomes in Neurodegenerative Diseases

The etiology of many neurological diseases affecting the central nervous system (CNS) is unknown and still needs more effective and specific therapeutic approaches. Gene therapy has a promising future in treating neurodegenerative disorders by correcting the genetic defects or by therapeutic protein delivery and is now an attraction for neurologists to treat brain disorders, like Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, spinal muscular atrophy, spinocerebellar ataxia, epilepsy, Huntington's disease, stroke, and spinal cord injury. Gene therapy allows the transgene induction, with a unique expression in cells' substrate. This article mainly focuses on the delivering modes of genetic materials in the CNS, which includes viral and non-viral vectors and their application in gene therapy. Despite the many clinical trials conducted so far, data have shown disappointing outcomes. The efforts done to improve outcomes, efficacy, and safety in the identification of targets in various neurological disorders are also discussed here. Adapting gene therapy as a new therapeutic approach for treating neurological disorders seems to be promising, with early detection and delivery of therapy before the neuron is lost, helping a lot the development of new therapeutic options to translate to the clinic.

Biotechnology-based therapeutics for management of cerebral stroke

Cerebral stroke, commonly caused due to hindrance in blood flow, is broadly classified into two categories-ischemic and haemorrhagic strokes. The onset of stroke triggers multiple mechanisms causing inflammation, generation of free radicals and protein damage leading to apoptosis of neuronal cells. The current therapies available for cerebral strokes involve use of complex surgical treatments and tissue plasminogen activator which increases the risk of internal bleeding, brain edema and cerebral damage, thereby restricting their use in clinical setting. The alarming need to develop safe, effective, target specific systems which, promote neuronal growth and reduce cerebral inflammation can be accomplished with use of biotechnological approaches. The article gives an insight to biotechnology-based advancements for tissue plasminogen activators, cell penetrating peptides, growth factors, ribonucleic acid systems and monoclonal antibodies for cerebral stroke. We also emphasis on challenges and future perspective of biotechnology-based therapeutics for better management of stroke.

The Role of Stem Cells in the Therapy of Stroke

Background: Stroke is a major challenge in neurology due to its multifactorial genesis and irreversible consequences. Processes of endogenous post-stroke neurogenesis, although insufficient, may indicate possible direction of future therapy. Multiple research considers stem-cell-based approaches in order to maximize neuroregeneration and minimize post-stroke deficits.

Objective: Aim of this study is to review current literature considering post-stroke stem-cell-based therapy and possibilities of inducing neuroregeneration after brain vascular damage.

Methods: Papers included in this article were obtained from PubMed and MEDLINE databases. The following medical subject headings (MeSH) were used: “stem cell therapy”, “post-stroke neurogenesis”, “stem-cells stroke”, “stroke neurogenesis”, “stroke stem cells”, “stroke”, “cell therapy”, “neuroregeneration”, “neurogenesis”, “stem-cell human”, “cell therapy in human”. Ultimate inclusion was made after manual review of the obtained reference list.

Results: Attempts of stimulating neuroregeneration after stroke found in current literature include supporting endogenous neurogenesis, different routes of exogenous stem cells supplying and extracellular vesicles used as a method of particle transport.

Conclusion: Although further research in this field is required, post stroke brain recovery supported by exogenous stem cells seems to be promising future therapy revolutionizing modern neurology.

Viral and Prion Infections Associated with Central Nervous System Syndromes in Brazil

Virus-induced infections of the central nervous system (CNS) are among the most serious problems in public health and can be associated with high rates of morbidity and mortality, mainly in low- and middle-income countries, where these manifestations have been neglected. Typically, herpes simplex virus 1 and 2, varicella-zoster, and enterovirus are responsible for a high number of cases in immunocompetent hosts, whereas other herpesviruses (for example, cytomegalovirus) are the most common in immunocompromised individuals. Arboviruses have also been associated with outbreaks with a high burden of neurological disorders, such as the Zika virus epidemic in Brazil. There is a current lack of understanding in Brazil about the most common viruses involved in CNS infections. In this review, we briefly summarize the most recent studies and findings associated with the CNS, in addition to epidemiological data that provide extensive information on the circulation and diversity of the most common neuro-invasive viruses in Brazil. We also highlight important aspects of the prion-associated diseases. This review provides readers with better knowledge of virus-associated CNS infections. A deeper understanding of these infections will support the improvement of the current surveillance strategies to allow the timely monitoring of the emergence/re-emergence of neurotropic viruses.

Cell Therapy for Stroke: A Mechanistic Analysis

Cell therapy has been widely recognized as a promising strategy to enhance recovery in stroke survivors. However, despite an abundance of encouraging preclinical data, successful clinical translation remains elusive. As the field continues to advance, it is important to reexamine prior clinical trials in the context of their intended mechanisms, as this can inform future preclinical and translational efforts. In the present work, we review the major clinical trials of cell therapy for stroke and highlight a mechanistic shift between the earliest studies, which aimed to replace dead and damaged neurons, and later ones that focused on exploiting the various neuromodulatory effects afforded by stem cells. We discuss why both mechanisms are worth pursuing and emphasize the means through which cell replacement can still be achieved.

Neural Stem Cell-Laden Self-Healing Polysaccharide Hydrogel Transplantation Promotes Neurogenesis and Functional Recovery after Cerebral Ischemia in Rats

Exploring a strategy to effectively repair cerebral ischemic injury is a critical requirement for neuroregeneration. Herein, we transplanted a neural stem cell (NSC)-laden self-healing and injectable hydrogel into the brains of ischemic rats and evaluated its therapeutic effects. We observed an improvement in neurological functions in rats transplanted with the NSC-laden hydrogel. This strategy is sufficiently efficient to support neuroregeneration evidenced by NSC proliferation, differentiation, and athletic movement recovery of rats. This therapeutic effect relates to the inhibition of the astrocyte reaction and the increased expression of vascular endothelial growth factor. This work provides a novel approach to repair cerebral ischemic injury.

Stem Cell-Based Therapy for Experimental Ischemic Stroke: A Preclinical Systematic Review

Stem cell transplantation offers promise in the treatment of ischemic stroke. Here we utilized systematic review, meta-analysis, and meta-regression to study the biological effect of stem cell treatments in animal models of ischemic stroke. A total of 98 eligible publications were included by searching PubMed, EMBASE, and Web of Science from inception to August 1, 2020. There are about 141 comparisons, involving 5,200 animals, that examined the effect of stem cell transplantation on neurological function and infarct volume as primary outcome measures in animal models for stroke. Stem cell-based therapy can improve both neurological function (effect size, −3.37; 95% confidence interval, −3.83 to −2.90) and infarct volume (effect size, −11.37; 95% confidence interval, −12.89 to −9.85) compared with controls. These results suggest that stem cell therapy could improve neurological function deficits and infarct volume, exerting potential neuroprotective effect for experimental ischemic stroke, but further clinical studies are still needed.

Effects of primary microglia and astrocytes on neural stem cells in in vitro and in vivo models of ischemic stroke

Transplantation of neural stem cells (NSCs) can protect neurons in animal stroke models; however, their low rates of survival and neuronal differentiation limit their clinical application. Glial niches, an important location of neural stem cells, regulate survival, proliferation and differentiation of neural stem cells. However, the effects of activated glial cells on neural stem cells remain unclear. In the present study, we explored the effects of activated astrocytes and microglia on neural stem cells in vitro stroke models. We also investigated the effects of combined transplantation of neural stem cells and glial cells after stroke in rats. In a Transwell co-culture system, primary cultured astrocytes, microglia or mixed glial cells were exposed to glutamate or H₂O₂ and then seeded in the upper inserts, while primary neural stem cells were seeded in the lower uncoated wells and cultured for 7 days. Our results showed that microglia were conducive to neurosphere formation and had no effects on apoptosis within neurospheres, while astrocytes and mixed glial cells were conducive to neurosphere differentiation and reduced apoptosis within neurospheres, regardless of their pretreatment. In contrast, microglia and astrocytes induced neuronal differentiation of neural stem cells in differentiation medium, regardless of their pretreatment, with an exception of astrocytes pretreated with H₂O₂. Rat models of ischemic stroke were established by occlusion of the middle cerebral artery. Three days later, 5 × 10⁵ neural stem cells with microglia or astrocytes were injected into the right lateral ventricle. Neural stem cell/astrocyte-treated rats displayed better improvement of neurological deficits than neural stem cell only-treated rats at 4 days after cell transplantation. Moreover, neural stem cell/microglia-, and neural stem cell/astrocyte-treated rats showed a significant decrease in ischemic volume compared with neural stem cell-treated rats. These findings indicate that microglia and astrocytes exert different effects on neural stem cells, and that co-transplantation of neural stem cells and astrocytes is more conducive to the recovery of neurological impairment in rats with ischemic stroke. The study was approved by the Animal Ethics Committee of Tongji University School of Medicine, China (approval No. 2010-TJAA08220401) in 2010.

The Effect of Allograft Transplantation of Sertoli Cell on Expression of NF-кB, Bax Proteins, and Ischemic Tolerance in Rats with Focal Cerebral Ischemia

One of the newest methods to reduce cerebral ischemia damages is cell therapy. The aim of this study is to evaluate the effect of Sertoli cell transplantation on ischemia-induced injuries in animal models of stroke. Rats were divided into four groups: transplant+ischemia, ischemia, sham, and control. Sertoli cells were separated from the other testis of rats and cultured. Unilateral Sertoli cell transplantation was performed in the right striatum by using stereotaxic surgery. For induction of brain ischemia, middle cerebral artery occlusion surgery was used 14 days after transplantation. By using western blotting method, expression of nuclear factor kappa (NF-кB) and Bax were evaluated. In this study, a remarkable decrease in neurological deficits, infection, blood-brain barrier permeability, and brain edema was observed in the cell transplant recipient group in comparison with the ischemia group. Probably, a reduction in inflammation (NF-кB factor) and apoptosis (Bax) following injection of Sertoli cells result in amelioration of ischemic damages induced by MCAO surgery.

Neural Stem Cell Transplantation for Neurodegenerative Diseases

Neurodegenerative diseases are disabling and fatal neurological disorders that currently lack effective treatment. Neural stem cell (NSC) transplantation has been studied as a potential therapeutic approach and appears to exert a beneficial effect against neurodegeneration via different mechanisms, such as the production of neurotrophic factors, decreased neuroinflammation, enhanced neuronal plasticity and cell replacement. Thus, NSC transplantation may represent an effective therapeutic strategy. To exploit NSCs' potential, some of their essential biological characteristics must be thoroughly investigated, including the specific markers for NSC subpopulations, to allow profiling and selection. Another key feature is their secretome, which is responsible for the regulation of intercellular communication, neuroprotection, and immunomodulation. In addition, NSCs must properly migrate into the central nervous system (CNS) and integrate into host neuronal circuits, enhancing neuroplasticity. Understanding and modulating these aspects can allow us to further exploit the therapeutic potential of NSCs. Recent progress in gene editing and cellular engineering techniques has opened up the possibility of modifying NSCs to express select candidate molecules to further enhance their therapeutic effects. This review summarizes current knowledge regarding these aspects, promoting the development of stem cell therapies that could be applied safely and effectively in clinical settings.

Using Dental Pulp Stem Cells for Stroke Therapy

Stroke is a leading cause of permanent disability world-wide, but aside from rehabilitation, there is currently no clinically-proven pharmaceutical or biological agent to improve neurological disability. Cell-based therapies using stem cells, such as dental pulp stem cells, are a promising alternative for treatment of neurological diseases, including stroke. The ischaemic environment in stroke affects multiple cell populations, thus stem cells, which act through cellular and molecular mechanisms, are promising candidates. The most common stem cell population studied in the neurological setting has been mesenchymal stem cells due to their accessibility. However, it is believed that neural stem cells, the resident stem cell of the adult brain, would be most appropriate for brain repair. Using reprogramming strategies, alternative sources of neural stem and progenitor cells have been explored. We postulate that a cell of closer origin to the neural lineage would be a promising candidate for reprogramming and modification towards a neural stem or progenitor cell. One such candidate population is dental pulp stem cells, which reside in the root canal of teeth. This review will focus on the neural potential of dental pulp stem cells and their investigations in the stroke setting to date, and include an overview on the use of different sources of neural stem cells in preclinical studies and clinical trials of stroke.

Protective effects of mesenchymal stem cells overexpressing extracellular regulating kinase 1/2 against stroke in rats

OBJECTIVE

Although transplantation of bone marrow-derived mesenchymal stem cells (MSCs) has shown beneficial effects on stroke, lower survival of MSCs limits effects. Extracellular regulating kinase 1/2 signaling (ERK1/2) is crucial for cell survival, differentiation, and proliferation. This study was designed to explore whether MSCs modified by over-expressing ERK1/2 may reinforce beneficial effects on stroke in rats.

METHODS

rat MSCs transfected with ERK1/2 and empty lentivirus to generate MSCs overexpressing ERK1/2 (ERK/MSCs) and MSCs (as a control), respectively. In vitro, ERK/MSCs were plated and exposed to glutamate-induced condition, and viability of ERK/MSCs was measured. Furthermore, neural induction of ERK/MSCs was investigated in vitro. Cerebral ischemic rats were induced by occluding middle cerebral artery, and then were stereotaxically injected into ipsilateral right lateral ventricle with ERK/MSCs or MSCs 3 days after stroke and survived for 7 or 14 days after injection.

RESULTS

ERK/MSCs showed better viability in physiological and glutamate-induced neurotoxic conditions compared to MSCs. After neural induction, more neurons were be differentiated from ERK/MSCs than from MSCs. After transplantation, more numbers of grafted cells and improved functional recovery were observed in ERK/MSCs-treated rats compared with MSCs-treated rats. Compared with MSCs treatment, ERK/MSCs treatment significantly increased proliferation of neural stem cells in the subventricle zone (SVZ) and the MAP2/nestin double-labeled cells adjacent to the SVZ, enhanced the numbers of reactive astrocytes while suppressed microglial activation. Besides, TNF-α level was elevated in ERK/MSCs-treated rats.

CONCLUSION

ERK/MSCs transplantation showed better functional recovery after stroke in rats, likely in part through enhancing survival of MSCs and possibly by modulating the proliferation, neuronal de-differentiation and neuroinflammation.

Neural Stem Cells Transfected with Reactive Oxygen Species-Responsive Polyplexes for Effective Treatment of Ischemic Stroke

Neural stem cells (NSCs), capable of ischemia-homing, regeneration, and differentiation, exert strong therapeutic potentials in treating ischemic stroke, but the curative effect is limited in the harsh microenvironment of ischemic regions rich in reactive oxygen species (ROS). Gene transfection to make NSCs overexpress brain-derived neurotrophic factor (BDNF) can enhance their therapeutic efficacy; however, viral vectors must be used because current nonviral vectors are unable to efficiently transfect NSCs. The first polymeric vector, ROS-responsive charge-reversal poly[(2-acryloyl)ethyl(p-boronic acid benzyl)diethylammonium bromide] (B-PDEA), is shown here, that mediates efficient gene transfection of NSCs and greatly enhances their therapeutics in ischemic stroke treatment. The cationic B-PDEA/DNA polyplexes can effectively transfect NSCs; in the cytosol, the B-PDEA is oxidized by intracellular ROS into negatively charged polyacrylic acid, quickly releasing the BDNF plasmids for efficient transcription and secreting a high level of BDNF. After i.v. injection in ischemic stroke mice, the transfected NSCs (BDNF-NSCs) can home to ischemic regions as efficiently as the pristine NSCs but more efficiently produce BDNF, leading to significantly augmented BDNF levels, which in turn enhances the mouse survival rate to 60%, from 0% (nontreated mice) or ≈20% (NSC-treated mice), and enables more rapid and superior functional reconstruction.

Cell-based therapy against prion diseases

Despite multiple efforts to find treatments, prion diseases are still incurable. The currently available therapeutic strategies are mostly based on compounds to inhibit pathological PrP (PrPSc) accumulation, and cellular PrP (PrP^C) conversion into PrP^Sc. However, they cannot reverse the pathological changes already present in the brain. Cell-based therapeutic strategies could promote the repair of the pre-existing brain damage. The few available data come mostly from preclinical studies using neural stem cells, bone marrow-derived microglia and mesenchymal stem cells, as cell sources. Moreover, the benefits of cell-based therapeutic strategies could be linked not only to the replacement of damaged cells, but also to the secretion of trophic factors by the grafted cells that might modulate inflammation, cell death, or endogenous neurogenesis.

Preconditioning and Cellular Engineering to Increase the Survival of Transplanted Neural Stem Cells for Motor Neuron Disease Therapy

Despite the extensive research effort that has been made in the field, motor neuron diseases, namely, amyotrophic lateral sclerosis and spinal muscular atrophies, still represent an overwhelming cause of morbidity and mortality worldwide. Exogenous neural stem cell-based transplantation approaches have been investigated as multifaceted strategies to both protect and repair upper and lower motor neurons from degeneration and inflammation. Transplanted neural stem cells (NSCs) exert their beneficial effects not only through the replacement of damaged cells but also via bystander immunomodulatory and neurotrophic actions. Notwithstanding these promising findings, the clinical translatability of such techniques is jeopardized by the limited engraftment success and survival of transplanted cells within the hostile disease microenvironment. To overcome this obstacle, different methods to enhance graft survival, stability, and therapeutic potential have been developed, including environmental stress preconditioning, biopolymers scaffolds, and genetic engineering. In this review, we discuss current engineering techniques aimed at the exploitation of the migratory, proliferative, and secretive capacity of NSCs and their relevance for the therapeutic arsenal against motor neuron disorders and other neurological disorders.

Poly-l-lysine-coated superparamagnetic nanoparticles: a novel method for the transfection of pro-BDNF into neural stem cells

Poly-l-lysine-coated superparamagnetic iron oxide nanoparticles (SPIONs-PLL) were prepared and used as a novel-carrier for the transfer of brain-derived neurotrophic factor (BDNF) into neural stem cells (NSCs) under the beneficial influence of an external magnetic field. Pro-BDNF, a gene from human brain cDNA libraries, was obtained by polymerase chain reaction and constructed in a mammalian expression vector (PSecTag2/HygroB). The nanoparticles (NPs) were examined using Fourier transform infrared spectroscopy, zeta potential, and Transmission electron microscopy. From the results, the levels of BDNF among the transfected and untransfected cells were 30.326 ± 5.9 and 5.85 ± 3.11 pg/mL, respectively, as detected by an ELISA method. Moreover, the enhanced green fluorescent protein vector was used to evaluate the gene expression efficiency for SPIONs-PLL as a non-viral carrier in NSCs. This was performed under the influence of a magnetic field and the transfection reagents (such as Lipofectamine 2000), which served as a positive control. The histological analysis revealed that the concentration of intracellular NPs was significantly higher than intercellular NPs. These results suggest that SPIONs-PLL can serve as a novel alternative for the transfection of BDNF-NSCs and could be used in gene therapy.

Pharmacological approaches promoting stem cell-based therapy following ischemic stroke insults

Stroke can lead to long-term neurological deficits. Adult neurogenesis, the continuous generation of newborn neurons in distinct regions of the brain throughout life, has been considered as one of the appoaches to restore the neurological function following ischemic stroke. However, ischemia-induced spontaneous neurogenesis is not suffcient, thus cell-based therapy, including infusing exogenous stem cells or stimulating endogenous stem cells to help repair of injured brain, has been studied in numerous animal experiments and some pilot clinical trials. While the effects of cell-based therapy on neurological function during recovery remains unproven in randomized controlled trials, pharmacological agents have been administrated to assist the cell-based therapy. In this review, we summarized the limitations of ischemia-induced neurogenesis and stem-cell transplantation, as well as the potential proneuroregenerative effects of drugs that may enhance efficacy of cell-based therapies. Specifically, we discussed drugs that enhance proliferation, migration, differentiation, survival and function connectivity of newborn neurons, which may restore neurobehavioral function and improve outcomes in stroke patients.

Promoting neuroregeneration after perinatal arterial ischemic stroke: neurotrophic factors and mesenchymal stem cells

Newborns suffering from perinatal arterial ischemic stroke (PAIS) are at risk of neurodevelopmental problems. Current treatment options for PAIS are limited and mainly focus on supportive care, as presentation of PAIS is beyond the time window of current treatment strategies. Therefore, recent focus has shifted to interventions that stimulate regeneration of damaged brain tissue. From animal models, it is known that the brain increases its neurogenic capability after ischemic injury, by promoting neural cell proliferation and differentiation. However, neurogenesis is not maintained at the long term, which consequently impedes full repair leading to adverse consequences later in life. Boosting neuroregeneration of the newborn brain using treatment with neurotrophic factors and/or mesenchymal stem cells (MSCs) may be promising novel therapeutic strategies to improve neurological prospects and quality of life of infants with PAIS. This review focuses on effectiveness of neurotrophic growth factors, including erythropoietin, brain-derived neurotrophic factor, vascular endothelial growth factor, glial-derived neurotrophic factor, and MSC therapy, in both experimental neonatal stroke studies and first clinical trials for neonatal ischemic brain injury.

Neural stem cell transplantation in ischemic stroke: A role for preconditioning and cellular engineering

Ischemic stroke continues to be a leading cause of morbidity and mortality throughout the world. To protect and/or repair the ischemic brain, a multitiered approach may be centered on neural stem cell (NSC) transplantation. Transplanted NSCs exert beneficial effects not only via structural replacement, but also via immunomodulatory and/or neurotrophic actions. Unfortunately, the clinical translation of such promising therapies remains elusive, in part due to their limited persistence/survivability within the hostile ischemic microenvironment. Herein, we discuss current approaches for the development of NSCs more amenable to survival within the ischemic brain as a tool for future cellular therapies in stroke.

Ex vivo gene therapy for the treatment of neurological disorders

Ex vivo gene therapy involves the genetic modification of cells outside of the body to produce therapeutic factors and their subsequent transplantation back into patients. Various cell types can be genetically engineered. However, with the explosion in stem cell technologies, neural stem/progenitor cells and mesenchymal stem cells are most often used. The synergy between the effect of the new cell and the additional engineered properties can often provide significant benefits to neurodegenerative changes in the brain. In this review, we cover both preclinical animal studies and clinical human trials that have used ex vivo gene therapy to treat neurological disorders with a focus on Parkinson's disease, Huntington's disease, Alzheimer's disease, ALS, and stroke. We highlight some of the major advances in this field including new autologous sources of pluripotent stem cells, safer ways to introduce therapeutic transgenes, and various methods of gene regulation. We also address some of the remaining hurdles including tunable gene regulation, in vivo cell tracking, and rigorous experimental design. Overall, given the current outcomes from researchers and clinical trials, along with exciting new developments in ex vivo gene and cell therapy, we anticipate that successful treatments for neurological diseases will arise in the near future.

Neuroprotection Induced by Transplanted CDK5 Knockdown Astrocytes in Global Cerebral Ischemic Rats

Cerebral ischemia is a cerebrovascular episode that generates a high incidence of death and physical and mental disabilities worldwide. Excitotoxicity, release of free radicals, and exacerbated immune response cause serious complications in motor and cognitive areas during both short and long time frames post-ischemia. CDK5 is a kinase that is widely involved in the functions of neurons and astrocytes, and its over-activation is implicated in neurodegenerative processes. In this study, we evaluated the brain parenchymal response to the transplantation of CDK5-knockdown astrocytes into the somatosensory cortex after ischemia in rats. Male Wistar rats were subjected to the two-vessel occlusion (2VO) model of global cerebral ischemia and immediately transplanted with shCDK5miR- or shSCRmiR-transduced astrocytes or with untransduced astrocytes (Control). Our findings showed that animals transplanted with shCDK5miR astrocytes recovered motor and neurological performance better than with those transplanted with WT or shSCRmiR astrocytes. Cell transplantation produced an overall prevention of neuronal loss, and CDK5-knockdown astrocytes significantly increased the immunoreactivity (IR) of endogenous GFAP in branches surrounding blood vessels, accompanied by the upregulation of PECAM-1 IR in the walls of vessels in the motor and somatosensory regions and by an increase in Ki67 IR in the subventricular zone (SVZ), partially associated with the production of BDNF. Together, our data suggest that transplantation of shCDK5miR astrocytes protects the neurovascular unit in ischemic rats, allowing the motor and neurological function recovery.

Meta-Analysis and Systematic Review of Neural Stem Cells therapy for experimental ischemia stroke in preclinical studies

To evaluate the preclinical studies using NSCs transplantation therapy for experimental ischemic stroke, and determine the effect size of NSCs therapy and the correlations between different clinical measures. We firstly searched literatures to identify studies of NSCs therapy in animal cerebral ischemia models, and then calculated the quality score of studies, assessed the effect size of NSCs therapy relative to behavioral and histologic endpoints by meta-analysis. A total of 37 studies and 54 independent treated interventions were used for systematic review and meta-analysis. The median quality score was 5 of 10. 36 studies (53 intervention arms) reported functional outcome, 22 studies (34 intervention arms) reported structural outcome. After adjusted by subgroup and sensitivity analysis, the mean effect sizes were improved by 1.35 for mNSS, 1.84 for rotarod test, 0.61 for cylinder test, and 0.84 for infarct volume. Furthermore, effect size had a certain interaction with clinical variables, for example early NSCs therapy etc. In this preclinical studies, we demonstrated that transplanted NSCs significantly improved outcomes (both functional and structural outcome) in ischemic stroke. It is suggested that future preclinical animal model studies of stroke should improve study quality validity and reduce potentially confounded publication bias.

Sensitive Tumorigenic Potential Evaluation of Adult Human Multipotent Neural Cells Immortalized by hTERT Gene Transduction

Stem cells and therapeutic genes are emerging as a new therapeutic approach to treat various neurodegenerative diseases with few effective treatment options. However, potential formation of tumors by stem cells has hampered their clinical application. Moreover, adequate preclinical platforms to precisely test tumorigenic potential of stem cells are controversial. In this study, we compared the sensitivity of various animal models for in vivo stem cell tumorigenicity testing to identify the most sensitive platform. Then, tumorigenic potential of adult human multipotent neural cells (ahMNCs) immortalized by the human telomerase reverse transcriptase (hTERT) gene was examined as a stem cell model with therapeutic genes. When human glioblastoma (GBM) cells were injected into adult (4-6-week-old) Balb/c-nu, adult NOD/SCID, adult NOG, or neonate (1-2-week-old) NOG mice, the neonate NOG mice showed significantly faster tumorigenesis than that of the other groups regardless of intracranial or subcutaneous injection route. Two kinds of ahMNCs (682TL and 779TL) were primary cultured from surgical samples of patients with temporal lobe epilepsy. Although the ahMNCs were immortalized by lentiviral hTERT gene delivery (hTERT-682TL and hTERT-779TL), they did not form any detectable masses, even in the most sensitive neonate NOG mouse platform. Moreover, the hTERT-ahMNCs had no gross chromosomal abnormalities on a karyotype analysis. Taken together, our data suggest that neonate NOG mice could be a sensitive animal platform to test tumorigenic potential of stem cell therapeutics and that ahMNCs could be a genetically stable stem cell source with little tumorigenic activity to develop regenerative treatments for neurodegenerative diseases.

GDNF Enhances Therapeutic Efficiency of Neural Stem Cells-Based Therapy in Chronic Experimental Allergic Encephalomyelitis in Rat

Multiple sclerosis (MS) is an autoimmune disease in the CNS. The current immunomodulating drugs for MS do not effectively prevent the progressive neurological decline. Neural stem cells (NSCs) transplantation has been proven to promote repair and functional recovery of experimental allergic encephalomyelitis (EAE) animal model for MS, and glial cell line-derived neurotrophic factor (GDNF) has also been found to have capability of promoting axonal regeneration and remyelination of regenerating axons. In the present study, to assess whether GDNF would enhance therapeutic effect of NSCs for EAE, GDNF gene-modified NSCs (GDNF/NSCs) and native NSCs were transplanted into each lateral ventricle of rats at 10 days and rats were sacrificed at 60 days after EAE immunization. We found that NSCs significantly reduced the clinical signs, and GDNF gene-modification further promoted functional recovery. GDNF/NSCs more profoundly suppressed brain inflammation and improved density of myelin compared with NSCs. The survival of GDNF/NSCs was significantly higher than that of transplanted NSCs. Transplanted GDNF/NSCs, in contrast to NSCs, differentiated into more neurons and oligodendrocytes. Moreover, the mRNA expression of oligodendrocyte lineage cells in rats with GDNF/NSCs was significantly increased compared to rats with NSCs. These results suggest that GDNF enhances therapeutic efficiency of NSCs-based therapy for EAE.

Neurogenesis in Stroke Recovery

Stroke, resulting from limited blood flow to the brain, is one of the most important causes of morbidity and mortality worldwide. Stroke is classified as ischemic, due to lack of blood flow, or hemorrhagic, due to bleeding. Because 87 % of strokes are classified as ischemic, this type will be the predominant focus of this review. Except for thrombolytic therapy, there is no established treatment to reduce the neurological deficits caused by ischemic stroke. Therefore, it is necessary to develop new therapeutic strategies designed to improve neurological functions after ischemic stroke. Recently, therapies to enhance neurogenesis after ischemic stroke have been investigated. However, these approaches have not led to successful clinical outcomes. This review addresses the pathophysiology of stroke, neurogenesis after stroke, and how to stimulate these processes based on the current literature. Finally, ongoing clinical trials to improve neurological functions after stroke by enhancing neurogenesis are discussed in this review.

Transplantation of Neural Stem Cells Cotreated with Thyroid Hormone and GDNF Gene Induces Neuroprotection in Rats of Chronic Experimental Allergic Encephalomyelitis

The present study investigates whether transplantation of NSCs treated with T3 alone (T3/NSCs), or in conjunction with GDNF gene (GDNF-T3/NSCs), provides a better therapeutic effect than NSCs for chronic EAE. EAE rats were, respectively, injected with NSCs, T3/NSCs, GDNF-T3/NSCs, and saline at 10 days and sacrificed at 60 days after EAE immunization. The three cell grafted groups showed a significant reduction in clinical scores, inflammatory infiltration, and demyelination compared with the saline-injected group, and among the cell grafted groups, the reduction in GDNF-T3/NSCs group was the most notable, followed by T3/NSCs group. Grafted T3/NSCs and GDNF-T3/NSCs acquired more MAP2, GalC, and less GFAP in brain compared with grafted NSCs, and grafted GDNF-T3/NSCs acquired most MAP2 and least GalC among the cell grafted groups. Furthermore, T3/NSCs and GDNF-T3/NSCs grafting increased the expression of mRNA for PDGFαR, GalC, and MBP in lesion areas of brain compared with NSCs grafting, and the expression of mRNA for GalC and MBP in GDNF-T3/NSCs group was higher than that in T3/NSCs group. In conclusion, T3/NSCs grafting, especially GDNF-T3/NSCs grafting, provides a better neuroprotective effect for EAE than NSCs transplantation.

[The influence of the immunity activation and suppression on the outcome of brain ischemia]

AIM

To explore the influence of the immunity activation and suppression on the outcome of brain ischemia in experimental animals.

MATERIAL AND METHODS

Brain ischemia has been modulated by irreversible staged bilateral common carotid arteries occlusion. Suppression of the immune system has been conducted by administration of cyclosporin A (5 mg/kg, per os). Activation of the immune system has been conducted by administration of lipopolysaccharide (10 mkg/kg, i.p.).

RESULTS

Authors have established that in animals with immunosuppression there is an increase in the concentration of the neuron specific proteins in blood serum (NSE and MBP), mortality (by 20%) and severity of neurological deficit (by 33%). Rats with immunosuppression have reduced general locomotor activity (by 44%), exploratory behavior in the Open Field Test (by 43%) and decrease in the motor activity in the Rotarod Test (by 19%) compared to the group of rats with brain ischemia and intact immune systems. During the immunity activation after brain ischemia injury, the decrease in NSE and MBP levels, mortality (by 15%) and severity of neurological deficit (by 13%) as well as higher concentrations of neurotrophins BDNF and NGF and higher general locomotor activity of animals (by 34%) and physical endurance (by 55%) in the Open Field and Rotarod Tests, respectively, were observed.

CONCLUSION

Immunosupression negatively affected the outcome of brain ischemia.

Isolation of Human Neural Stem Cells from the Amniotic Fluid with Diagnosed Neural Tube Defects

Human neural stem cells (NSCs) are particularly valuable for the study of neurogenesis process and have a therapeutic potential in treating neurodegenerative disorders. However, current progress in the use of human NSCs is limited due to the available NSC sources and the complicated isolation and culture techniques. In this study, we describe an efficient method to isolate and propagate human NSCs from the amniotic fluid with diagnosed neural tube defects (NTDs), specifically, anencephaly. These amniotic fluid-derived NSCs (AF-NSCs) formed neurospheres and underwent long-term expansion in vitro. In addition, these cells showed normal karyotypes and telomerase activity and expressed NSC-specific markers, including Nestin, Sox2, Musashi-1, and the ATP-binding cassette G2 (ABCG2). AF-NSCs displayed typical morphological patterns and expressed specific markers that were consistent with neurons, astrocytes, oligodendrocytes, and dopaminergic neurons after proper induction conditions. Furthermore, grafted AF-NSCs improved the physiological functions in a rat stroke model. The ability to isolate and bank human NSCs from this novel source provides a unique opportunity for translational studies of neurological disorders.

Neuroprotective effects of oligodendrocyte progenitor cell transplantation in premature rat brain following hypoxic-ischemic injury

Periventricular leukomalacia (PVL) is a common ischemic brain injury in premature infants for which there is no effective treatment. The objective of this study was to determine whether transplanted mouse oligodendrocyte progenitor cells (OPCs) have neuroprotective effects in a rat model of PVL. Hypoxia-ischemia (HI) was induced in 3-day-old rat pups by left carotid artery ligation, followed by exposure to 6% oxygen for 2.5 h. Animals were assigned to OPC transplantation or sham control groups and injected with OPCs or PBS, respectively, and sacrificed up to 6 weeks later for immunohistochemical analysis to investigate the survival and differentiation of transplanted OPCs. Apoptosis was evaluated by double immunolabeling of brain sections for caspase-3 and neuronal nuclei (NeuN), while proliferation was assessed using a combination of anti-Nestin and -bromodeoxyuridine antibodies. The expression of brain-derived neurotrophic factor (BDNF) and Bcl-2 was examined 7 days after OPC transplantation. The Morris water maze was used to test spatial learning and memory. The results showed that transplanted OPCs survived and formed a myelin sheath, and stimulated BDNF and Bcl-2 expression and the proliferation of neural stem cells (NSC), while inhibiting HI-induced neuronal apoptosis relative to control animals. Moreover, deficits in spatial learning and memory resulting from HI were improved by OPC transplantation. These results demonstrate an important neuroprotective role for OPCs that can potentially be exploited in cell-based therapeutic approaches to minimize HI-induced brain injury.

Neuroprotective effects of GDNF-expressing human amniotic fluid cells

Brain injury continues to be one of the leading causes of disability worldwide. Despite decades of research, there is currently no pharmacologically effective treatment for preventing neuronal loss and repairing the brain. As a result, novel therapeutic approaches, such as cell-based therapies, are being actively pursued to repair tissue damage and restore neurological function after injury. In this study, we examined the neuroprotective potential of amniotic fluid (AF) single cell clones, engineered to secrete glial cell derived neurotrophic factor (AF-GDNF), both in vitro and in a surgically induced model of brain injury. Our results show that pre-treatment with GDNF significantly increases cell survival in cultures of AF cells or cortical neurons exposed to hydrogen peroxide. Since improving the efficacy of cell transplantation depends on enhanced graft cell survival, we investigated whether AF-GDNF cells seeded on polyglycolic acid (PGA) scaffolds could enhance graft survival following implantation into the lesion cavity. Encouragingly, the AF-GDNF cells survived longer than control AF cells in serum-free conditions and continued to secrete GDNF both in vitro and following implantation into the injured motor cortex. AF-GDNF implantation in the acute period following injury was sufficient to activate the MAPK/ERK signaling pathway in host neural cells in the peri-lesion area, potentially boosting endogenous neuroprotective pathways. These results were complemented with promising trends in beam walk tasks in AF-GDNF/PGA animals during the 7 day timeframe. Further investigation is required to determine whether significant behavioural improvement can be achieved at a longer timeframe.

Transfection of the glial cell line-derived neurotrophic factor gene promotes neuronal differentiation

Glial cell line-derived neurotrophic factor recombinant adenovirus vector-transfected bone marrow mesenchymal stem cells were induced to differentiate into neuron-like cells using inductive medium containing retinoic acid and epidermal growth factor. Cell viability, microtubule-associated protein 2-positive cell ratio, and the expression levels of glial cell line-derived neurotrophic factor, nerve growth factor and growth-associated protein-43 protein in the supernatant were significantly higher in glial cell line-derived neurotrophic factor/bone marrow mesenchymal stem cells compared with empty virus plasmid-transfected bone marrow mesenchymal stem cells. Furthermore, microtubule-associated protein 2, glial cell line-derived neurotrophic factor, nerve growth factor and growth-associated protein-43 mRNA levels in cell pellets were statistically higher in glial cell line-derived neurotrophic factor/bone marrow mesenchymal stem cells compared with empty virus plasmid-transfected bone marrow mesenchymal stem cells. These results suggest that glial cell line-derived neurotrophic factor/bone marrow mesenchymal stem cells have a higher rate of induction into neuron-like cells, and this enhanced differentiation into neuron-like cells may be associated with up-regulated expression of glial cell line-derived neurotrophic factor, nerve growth factor and growth-associated protein-43.

Stem cell therapies for the treatment of radiation-induced normal tissue side effects

SIGNIFICANCE

Targeted irradiation is an effective cancer therapy but damage inflicted to normal tissues surrounding the tumor may cause severe complications. While certain pharmacologic strategies can temper the adverse effects of irradiation, stem cell therapies provide unique opportunities for restoring functionality to the irradiated tissue bed.

RECENT ADVANCES

Preclinical studies presented in this review provide encouraging proof of concept regarding the therapeutic potential of stem cells for treating the adverse side effects associated with radiotherapy in different organs. Early-stage clinical data for radiation-induced lung, bone, and skin complications are promising and highlight the importance of selecting the appropriate stem cell type to stimulate tissue regeneration.

CRITICAL ISSUES

While therapeutic efficacy has been demonstrated in a variety of animal models and human trials, a range of additional concerns regarding stem cell transplantation for ameliorating radiation-induced normal tissue sequelae remain. Safety issues regarding teratoma formation, disease progression, and genomic stability along with technical issues impacting disease targeting, immunorejection, and clinical scale-up are factors bearing on the eventual translation of stem cell therapies into routine clinical practice.

FUTURE DIRECTIONS

Follow-up studies will need to identify the best possible stem cell types for the treatment of early and late radiation-induced normal tissue injury. Additional work should seek to optimize cellular dosing regimes, identify the best routes of administration, elucidate optimal transplantation windows for introducing cells into more receptive host tissues, and improve immune tolerance for longer-term engrafted cell survival into the irradiated microenvironment.

L-serine treatment may improve neurorestoration of rats after permanent focal cerebral ischemia potentially through improvement of neurorepair

The present study was conducted to clarify whether treatment with L-serine can improve the brain repair and neurorestoration of rats after permanent middle cerebral artery occlusion (pMCAO). After pMCAO, the neurological functions, brain lesion volume, and cortical injury were determined. GDNF, NGF, NCAM L1, tenascin-C, and Nogo-A levels were measured. Proliferation and differentiation of the neural stem cells (NSCs) and proliferation of the microvessels in the ischemic boundary zone of the cortex were evaluated. Treatment with L-serine (168 mg/kg body weight, i.p.) began 3 h after pMCAO and was repeated every 12 h for 7 days or until the end of the experiment. L-Serine treatment: 1) reduced the lesion volume and neuronal loss; 2) improved the recovery of neurological functions; 3) elevated the expression of nerve growth-related factors; and 4) facilitated the proliferation of endogenous NSCs and microvessels activated after pMCAO and increased the number of new-born neurons. 5) D-cycloserine, an inhibitor of serine hydroxymethyltransferase, blunted the effects of L-serine on NSC proliferation, differentiation, microvascular proliferation. In conclusions, L-serine treatment in pMCAO rats can reduce brain injury and facilitate neurorestoration which is partly associated with the improvement of proliferation of NSCs and microvessels, reconstruction of neurovascular units and resultant neurorepair. The effects of L-serine on endogenous NSC proliferation and microvascular proliferation are partly mediated by the action of L-serine as a substrate for the production of one-carbon groups used for purine and pyrimidine synthesis and modulation of the expression of some nerve growth-related factors.

Stem cell-based therapies for ischemic stroke

In recent years, stem cell-based approaches have attracted more attention from scientists and clinicians due to their possible therapeutical effect on stroke. Animal studies have demonstrated that the beneficial effects of stem cells including embryonic stem cells (ESCs), inducible pluripotent stem cells (iPSCs), neural stem cells (NSCs), and mesenchymal stem cell (MSCs) might be due to cell replacement, neuroprotection, endogenous neurogenesis, angiogenesis, and modulation on inflammation and immune response. Although several clinical studies have shown the high efficiency and safety of stem cell in stroke management, mainly MSCs, some issues regarding to cell homing, survival, tracking, safety, and optimal cell transplantation protocol, such as cell dose and time window, should be addressed. Undoubtably, stem cell-based gene therapy represents a novel potential therapeutic strategy for stroke in future.

Cell based therapies for ischemic stroke: from basic science to bedside

Cell therapy is emerging as a viable therapy to restore neurological function after stroke. Many types of stem/progenitor cells from different sources have been explored for their feasibility and efficacy for the treatment of stroke. Transplanted cells not only have the potential to replace the lost circuitry, but also produce growth and trophic factors, or stimulate the release of such factors from host brain cells, thereby enhancing endogenous brain repair processes. Although stem/progenitor cells have shown a promising role in ischemic stroke in experimental studies as well as initial clinical pilot studies, cellular therapy is still at an early stage in humans. Many critical issues need to be addressed including the therapeutic time window, cell type selection, delivery route, and in vivo monitoring of their migration pattern. This review attempts to provide a comprehensive synopsis of preclinical evidence and clinical experience of various donor cell types, their restorative mechanisms, delivery routes, imaging strategies, future prospects and challenges for translating cell therapies as a neurorestorative regimen in clinical applications.

Electroacupuncture enhances hippocampal NSCs proliferation in cerebral ischemia-reperfusion injured rats via activation of notch signaling pathway

The purpose of this study was to investigate the mechanisms by which electroacupuncture (EA) enhances hippocampal neural stem cells (NSCs) proliferation in cerebral ischemia-reperfusion (I/R) injured rats. A total of 72 male adult Sprague-Dawley rats were randomly divided into the sham operation control group (SC), the ischemia control group (IC) and the EA group. Middle cerebral artery occlusion (MCAO) was performed to establish the focal cerebral I/R injury model. Proliferation of hippocampal NSCs in cerebral I/R injured rats was determined by the Nestin immunohistochemical staining. Activation of the notch signaling pathway was detected by Western blotting and reverse transcription polymerase chain reaction analysis. The serum level of neurotrophic factors, e.g., the brain-derived neurotrophic factor (BDNF) and the Glial cell line-derived neurotrophic factor (GDNF), was measured using enzyme-linked immunosorbent assay (ELISA). The results showed that EA at Quchi (LI11) and Zusanli (ST36) acupoints significantly alleviated neurological deficits, reduced infarct volumes and promoted the proliferation of hippocampal NSCs in cerebral I/R injured rats. The crucial signaling molecules in the notch signaling pathway were activated and the secretion of BDNF and GDNF was increased upon EA. The protein and mRNA levels of Cyclin D1, Cdk4 and p-Rb were increased, while p21 and p27 transcripts were suppressed by notch signaling. These results suggest that the up-regulatory effect of EA on the notch signaling pathway and neurotrophic factor secretion may result in the promotion of NSCs proliferation and consequently a therapeutic effect on cerebral ischemia.