Transplanted human embryonic neural stem cells survive, migrate, differentiate and increase endogenous nestin expression in adult rat cortical peri-infarction zone

Mesenchymal Stem/Stromal Cell Therapy in Blood-Brain Barrier Preservation Following Ischemia: Molecular Mechanisms and Prospects

Ischemic stroke is the leading cause of mortality and long-term disability worldwide. Disruption of the blood-brain barrier (BBB) is a prominent pathophysiological mechanism, responsible for a series of subsequent inflammatory cascades that exacerbate the damage to brain tissue. However, the benefit of recanalization is limited in most patients because of the narrow therapeutic time window. Recently, mesenchymal stem cells (MSCs) have been assessed as excellent candidates for cell-based therapy in cerebral ischemia, including neuroinflammatory alleviation, angiogenesis and neurogenesis promotion through their paracrine actions. In addition, accumulating evidence on how MSC therapy preserves BBB integrity after stroke may open up novel therapeutic targets for treating cerebrovascular diseases. In this review, we focus on the molecular mechanisms of MSC-based therapy in the ischemia-induced prevention of BBB compromise. Currently, therapeutic effects of MSCs for stroke are primarily based on the fundamental pathogenesis of BBB breakdown, such as attenuating leukocyte infiltration, matrix metalloproteinase (MMP) regulation, antioxidant, anti-inflammation, stabilizing morphology and crosstalk between cellular components of the BBB. We also discuss prospective studies to improve the effectiveness of MSC therapy through enhanced migration into defined brain regions of stem cells. Targeted therapy is a promising new direction and is being prioritized for extensive research.

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.

The Effects and Underlying Mechanisms of Cell Therapy on Blood-Brain Barrier Integrity After Ischemic Stroke

Ischemic stroke is one of the main causes of mortality and disability worldwide. However, efficient therapeutic strategies are still lacking. Stem/progenitor cell-based therapy, with its vigorous advantages, has emerged as a promising tool for the treatment of ischemic stroke. The mechanisms involve new neural cells and neuronal circuitry formation, antioxidation, inflammation alleviation, angiogenesis, and neurogenesis promotion. In the past decades, in-depth studies have suggested that cell therapy could promote vascular stabilization and decrease blood-brain barrier (BBB) leakage after ischemic stroke. However, the effects and underlying mechanisms on BBB integrity induced by the engrafted cells in ischemic stroke have not been reviewed yet. Herein, we will update the progress in research on the effects of cell therapy on BBB integrity after ischemic stroke and review the underlying mechanisms. First, we will present an overview of BBB dysfunction under the ischemic condition and cells engraftment for ischemic treatment. Then, we will summarize and discuss the current knowledge about the effects and underlying mechanisms of cell therapy on BBB integrity after ischemic stroke. In particular, we will review the most recent studies in regard to the relationship between cell therapy and BBB in tissue plasminogen activator (t-PA)-mediated therapy and diabetic stroke.

Exogenous neural stem cell transplantation for cerebral ischemia

Cerebral ischemic injury is the main manifestation of stroke, and its incidence in stroke patients is 70–80%. Although ischemic stroke can be treated with tissue-type plasminogen activator, its time window of effectiveness is narrow. Therefore, the incidence of paralysis, hypoesthesia, aphasia, dysphagia, and cognitive impairment caused by cerebral ischemia is high. Nerve tissue regeneration can promote the recovery of the aforementioned dysfunction. Neural stem cells can participate in the reconstruction of the damaged nervous system and promote the recovery of nervous function during self-repair of damaged brain tissue. Neural stem cell transplantation for ischemic stroke has been a hot topic for more than 10 years. This review discusses the treatment of ischemic stroke with neural stem cells, as well as the mechanisms of their involvement in stroke treatment.

Stem cell transplantation therapy for multifaceted therapeutic benefits after stroke

One of the exciting advances in modern medicine and life science is cell-based neurovascular regeneration of damaged brain tissues and repair of neuronal structures. The progress in stem cell biology and creation of adult induced pluripotent stem (iPS) cells has significantly improved basic and pre-clinical research in disease mechanisms and generated enthusiasm for potential applications in the treatment of central nervous system (CNS) diseases including stroke. Endogenous neural stem cells and cultured stem cells are capable of self-renewal and give rise to virtually all types of cells essential for the makeup of neuronal structures. Meanwhile, stem cells and neural progenitor cells are well-known for their potential for trophic support after transplantation into the ischemic brain. Thus, stem cell-based therapies provide an attractive future for protecting and repairing damaged brain tissues after injury and in various disease states. Moreover, basic research on naïve and differentiated stem cells including iPS cells has markedly improved our understanding of cellular and molecular mechanisms of neurological disorders, and provides a platform for the discovery of novel drug targets. The latest advances indicate that combinatorial approaches using cell based therapy with additional treatments such as protective reagents, preconditioning strategies and rehabilitation therapy can significantly improve therapeutic benefits. In this review, we will discuss the characteristics of cell therapy in different ischemic models and the application of stem cells and progenitor cells as regenerative medicine for the treatment of stroke.

Current proceedings of cerebral palsy

Cerebral palsy (CP) is a complicated disease with varying causes and outcomes. It has created significant burden to both affected families and societies, not to mention the quality of life of the patients themselves. There is no cure for the disease; therefore, development of effective therapeutic strategies is in great demand. Recent advances in regenerative medicine suggest that the transplantation of stem cells, including embryonic stem cells, neural stem cells, bone marrow mesenchymal stem cells, induced pluripotent stem cells, umbilical cord blood cells, and human embryonic germ cells, focusing on the root of the problem, may provide the possibility of developing a complete cure in treating CP. However, safety is the first factor to be considered because some stem cells may cause tumorigenesis. Additionally, more preclinical and clinical studies are needed to determine the type of cells, route of delivery, cell dose, timing of transplantation, and combinatorial strategies to achieve an optimal outcome.

Therapeutic potential of human embryonic stem cell transplantation in patients with cerebral palsy

Background

The present study evaluated the efficacy and safety of human embryonic stem cell (hESC) therapy in patients with CP.

Materials and methods

This analysis included patients (30 days-18 yr) with documented diagnosis of CP. The study consisted of four treatment phases (T1, T2, T3, T4) separated by gap phases. Efficacy of hESC therapy was evaluated based on Gross Motor Function Classification Scores Expanded and Revised (GMFCS-E & R; 1-good to 5-bad).

Results

Ninety one patients were included and all received hESC therapy in T1, 66 patients returned for T2, 38 patients for T3, and 15 patients for T4. Overall, 30.2% patients achieved GMFCS-E & R score 1 during the study with different number of patients achieving GMFCS score 1 by the end of each treatment phase (T1: 6 [6.6%]; T2: 7 [10.6%]; T3: 11 [28.9%]; and T4: 5 [33.3%]). All patients in up to 2 yr (n = 10), 2-4 yr (n = 10), 4-6 yr (n = 9), and 6-12 yr (n = 8) age groups except one of the 5 patients in the age group of 12-18 yr transitioned from GMFCS-E & R score 5 to lower scores by end of T1. Most patients transitioned to GMFCS-E & R score 2 (n = 34) from higher scores by end of T2. Eleven patients achieved GMFCS-E & R score 1 by end of T3. No serious adverse events were observed.

Conclusion

Use of hESC therapy in patients with CP is effective and safe. hESC therapy has demonstrated significant improvement in GMFCS-E & R scale.

Ipsilateral versus bilateral limb-training in promoting the proliferation and differentiation of endogenous neural stem cells following cerebral infarction in rats

We investigated the effects of ipsilateral versus bilateral limb-training on promotion of endogenous neural stem cells in the peripheral infarct zone and the corresponding cerebral region in the unaffected hemisphere of rats with cerebral infarction. Middle cerebral artery occlusion was induced in Wistar rats. The rat forelimb on the unaffected side was either wrapped up with tape to force the use of the paretic forelimb in rats or not braked to allow bilateral forelimbs to participate in training. Daily training consisted of mesh drum training, balance beam training, and stick rolling training for a total of 40 minutes, once per day. Control rats received no training. At 14 days after functional training, rats receiving bilateral limb-training exhibited milder neurological impairment than that in the ipsilateral limb-training group or the control group. The number of nestin/glial fibrillary acidic protein-positive and nestin/microtubule-associated protein 2-positive cells in the peripheral infarct zone and in the corresponding cerebral region in the unaffected hemisphere was significantly higher in rats receiving bilateral limb-training than in rats receiving ipsilateral limb-training. These data suggest that bilateral limb-training can promote the proliferation and differentiation of endogenous neural stem cells in the bilateral hemispheres after cerebral infarction and accelerate the recovery of neurologic function. In addition, bilateral limb-training produces better therapeutic effects than ipsilateral limb-training.

Current concept in neural regeneration research: NSCs isolation, characterization and transplantation in various neurodegenerative diseases and stroke: A review

Since last few years, an impressive amount of data has been generated regarding the basic in vitro and in vivo biology of neural stem cells (NSCs) and there is much far hope for the success in cell replacement therapies for several human neurodegenerative diseases and stroke. The discovery of adult neurogenesis (the endogenous production of new neurons) in the mammalian brain more than 40 years ago has resulted in a wealth of knowledge about stem cells biology in neuroscience research. Various studies have done in search of a suitable source for NSCs which could be used in animal models to understand the basic and transplantation biology before treating to human. The difficulties in isolating pure population of NSCs limit the study of neural stem behavior and factors that regulate them. Several studies on human fetal brain and spinal cord derived NSCs in animal models have shown some interesting results for cell replacement therapies in many neurodegenerative diseases and stroke models. Also the methods and conditions used for in vitro culture of these cells provide an important base for their applicability and specificity in a definite target of the disease. Various important developments and modifications have been made in stem cells research which is needed to be more specified and enrolment in clinical studies using advanced approaches. This review explains about the current perspectives and suitable sources for NSCs isolation, characterization, in vitro proliferation and their use in cell replacement therapies for the treatment of various neurodegenerative diseases and strokes.

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.

Highly efficient differentiation of neural precursors from human embryonic stem cells and benefits of transplantation after ischemic stroke in mice

Introduction

Ischemic stroke is a leading cause of death and disability, but treatment options are severely limited. Cell therapy offers an attractive strategy for regenerating lost tissues and enhancing the endogenous healing process. In this study, we investigated the use of human embryonic stem cell-derived neural precursors as a cell therapy in a murine stroke model.

Methods

Neural precursors were derived from human embryonic stem cells by using a fully adherent SMAD inhibition protocol employing small molecules. The efficiency of neural induction and the ability of these cells to further differentiate into neurons were assessed by using immunocytochemistry. Whole-cell patch-clamp recording was used to demonstrate the electrophysiological activity of human embryonic stem cell-derived neurons. Neural precursors were transplanted into the core and penumbra regions of a focal ischemic stroke in the barrel cortex of mice. Animals received injections of bromodeoxyuridine to track regeneration. Neural differentiation of the transplanted cells and regenerative markers were measured by using immunohistochemistry. The adhesive removal test was used to determine functional improvement after stroke and intervention.

Results

After 11 days of neural induction by using the small-molecule protocol, over 95% of human embryonic stem-derived cells expressed at least one neural marker. Further in vitro differentiation yielded cells that stained for mature neuronal markers and exhibited high-amplitude, repetitive action potentials in response to depolarization. Neuronal differentiation also occurred after transplantation into the ischemic cortex. A greater level of bromodeoxyuridine co-localization with neurons was observed in the penumbra region of animals receiving cell transplantation. Transplantation also improved sensory recovery in transplant animals over that in control animals.

Conclusions

Human embryonic stem cell-derived neural precursors derived by using a highly efficient small-molecule SMAD inhibition protocol can differentiate into electrophysiologically functional neurons in vitro. These cells also differentiate into neurons in vivo, enhance regenerative activities, and improve sensory recovery after ischemic stroke.

Pitfalls and fallacies interfering with correct identification of embryonic stem cells implanted into the brain after experimental traumatic injury

Cell-therapy was proposed to be a promising tool in case of death or impairment of specific cell types. Correct identification of implanted cells became crucial when evaluating the success of transplantation therapy. Various methods of cell labeling have been employed in previously published studies. The use of intrinsic signaling of green fluorescent protein (GFP) has led to a well known controversy in the field of cardiovascular research. We encountered similar methodological pitfalls after transplantation of GFP-transfected embryonic stem cells into rat brains following traumatic brain injury (TBI). As the identification of implanted graft by intrinsic autofluorescence failed, anti-GFP labeling coupled to fluorescent and conventional antibodies was needed to visualize the implanted cells. Furthermore, different cell types with strong intrinsic autofluorescence were found at the sites of injury and transplantation, thus mimicking the implanted stem cells. GFP-positive stem cells were correctly localized, using advanced histological techniques. The activation of microglia/macrophages, accompanying the transplantation post TBI, was shown to be a significant source of artefacts, interfering with correct identification of implanted stem cells. Dependent on the strategy of stem cell tracking, the phagocytosis of implanted cells as observed in this study, might also impede the interpretation of results. Critical appraisal of previously published data as well as a review of different histological techniques provide tools for a more accurate identification of transplanted stem cells.

Neural stem cells and stroke

Acute ischemic stroke causes a disturbance of neuronal circuitry and disruption of the blood-brain barrier that can lead to functional disabilities. At present, thrombolytic therapy inducing recanalization of the occluded vessels in the cerebral infarcted area is a commonly used therapeutic strategy. However, only a minority of patients have timely access to this kind of therapy. Recently, neural stem cells (NSCs) as therapy for stroke have been developed in preclinical studies. NSCs are harbored in the subventricular zone (SVZ) as well as the subgranular zone of the brain. The microenvironment in the SVZ, including intercellular interactions, extracellular matrix proteins, and soluble factors, can promote NSC proliferation, self-renewal, and multipotency. Endogenous neurogenesis responds to insults of ischemic stroke supporting the existence of remarkable plasticity in the mammalian brain. Homing and integration of NSCs to the sites of damaged brain tissue are complex morphological and physiological processes. This review provides an update on current preclinical cell therapies for stroke, focusing on neurogenesis in the SVZ and dentate gyrus and on recruitment cues that promote NSC homing and integration to the site of the damaged brain.

Transplantation of telencephalic neural progenitors induced from embryonic stem cells into subacute phase of focal cerebral ischemia

Cerebral ischemia causes neuronal death and disruption of neural circuits in the central nervous system. Various neurological disorders caused by cerebral infarction can severely impair quality of life and are potentially fatal. Functional recovery in the chronic stage mainly depends on physical treatment and rehabilitation. We aim to establish cell therapy for cerebral ischemia using embryonic stem (ES) cells, which have self-renewing and pluripotent capacities. We previously reported that the transplanted monkey and mouse ES cell-derived neural progenitors, by stromal cell-derived inducing activity method, could survive and differentiate into various types of neurons and glial cells, and form the neuronal network in basal ganglia. In this report, we induced the differentiation of the neural progenitors from mouse ES cells using the serum-free suspension culture method and confirmed the expression of various basal ganglial neuronal markers and neurotransmitter-related markers both in vitro and in vivo, which was thought to be suitable for replacing damaged striatum after middle cerebral artery occlusion. This is the first report that used selectively induced telencephalic neural progenitors into ischemia model. Furthermore, we purified the progenitors expressing the neural progenitor marker Sox1 by fluorescence-activated cell sorting and Sox1-positive neural progenitors prevented tumor formation in ischemic brain for 2 months. We also analyzed survival and differentiation of transplanted cells and functional recovery from ischemic damage.

Human cord blood for the hypoxic-ischemic neonate

Autologous umbilical cord blood (UCB) is a possible, but unproven, treatment for acute neonatal brain damage. Mesenchymal stem cells (MSCs), which are present in UCB, are likely to be the treating cell type. UCB is effective in the treatment of neonatal rodent hypoxic-ischemic injury (HI) and other types of brain injury when the cells are delivered acutely. Other types of adult stem cells are similarly effective. However, several negative studies have been reported. The most likely mechanisms of action are participation in blood vessel regeneration, improvement of survival of intrinsic cells, perhaps via neurotrophic factors, or suppression of the release of inflammatory cells from the spleen. In the latter case, the splenic inflammatory cells released at the time of injury are thought to have an adverse effect on brain injury. The timing of the administration of the UCB with respect to the time of the injury appears to be the most important issue: the earlier the better. The risks of autologous administration of UCB are minimal. Current clinical trials with UCB are in progress, but there are no peer-reviewed reports as yet. A multicenter trial with specific inclusion criteria is needed.

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.

Update on stem cell therapy for cerebral palsy

INTRODUCTION

Due to the publicity about stem cell transplantation for the treatment of cerebral palsy, many families seek information on treatment, and many travel overseas for cell transplantation. Even so, there is little scientific confirmation of benefit, and therefore existing knowledge in the field must be summarized.

AREAS COVERED

This paper addresses the clinical protocols examining the problem, types of stem cells available for transplant, experimental models used to test the benefit of the cells, possible mechanisms of action, potential complications of cell treatment and what is needed in the field to help accelerate cell-based therapies.

EXPERT OPINION

While stem cells may be beneficial in acute injuries of the CNS the biology of stem cells is not well enough understood in chronic injuries or disorders such as cerebral palsy. More work is required at the basic level of stem cell biology, in the development of animal models, and finally in well-conceived clinical trials.

Human embryonic neural stem cell transplantation increases subventricular zone cell proliferation and promotes peri-infarct angiogenesis after focal cerebral ischemia

Neurogenesis and angiogenesis are two important processes that may contribute to the repair of brain injury after stroke. This study was designed to investigate whether transplantation of human embryonic neural stem cells (NSCs) into cortical peri-infarction 24h after ischemia effects cell proliferation in the subventricular zone (SVZ) and angiogenesis in the peri-infarct zone. NSCs were prepared from embryonic human brains at 8 weeks gestation. Focal cerebral ischemia was induced by permanent occlusion of the middle cerebral artery of adult rats. Animals were randomly divided into two groups (n=30, each) at 24h after ischemia: NSC-grafted and medium-grafted groups. Toluidine blue staining and 5'-bromo-2'-deoxyuridine (BrdU) or von Willebrand factor (vWF) immunohistochemistry were performed at 7, 14 and 28 days after transplantation. NSC transplantation increased the number of BrdU-positive cells in the ischemic ipsilateral SVZ compared with the medium control at 7 days (P<0.01). This difference in SVZ cell proliferation persisted at 14 days (P<0.01), but was not significant at 28 days (P>0.05). In addition, angiogenesis, as indicated by BrdU and vWF staining in cortical peri-infarct regions, was augmented by 46% and 65% in NSC-grafted rats versus medium-grafted rats at 7 and 14 days, respectively (P<0.05). However, this increase became non-significant at 28 days (P>0.05). Our results indicate that NSC transplantation enhances endogenous cell proliferation in the SVZ and promotes angiogenesis in the peri-infarct zone, even if it is performed in the acute phase of ischemic injury.

Neuroprotective effect of combined hypoxia-induced VEGF and bone marrow-derived mesenchymal stem cell treatment

PURPOSES

To avoid unwanted adverse effects of higher doses of single treatment of stem cells and gene therapy and increase the therapeutic efficacies, we hypothesized the combined therapy with stem cells and gene therapy. This study assessed the neuroprotective effects of combined gene therapy and stem cell treatment under ischemic hypoxia conditions using hypoxia-inducible vascular endothelial growth factor (VEGF) and bone marrow-derived mesenchymal stem cells (BMSC).

METHODS

Experimental groups included the control which was N2A cells transfected with empty vectors, the transfection only group which was N2A cells treated with pEpo-SV-VEGF alone, the BMSC only group which was N2A cells transfected with empty vectors and cocultured with BMSCs, and the combined treatment group which was N2A cells treated with pEpo-SV-VEGF and cocultured with BMSCs. Each group was transfected for 4 h and cultured at 37 degrees C and 5% CO2 for 24 h. Each group was then cultivated under hypoxic conditions (1% O2) for 12 h. Neuroprotective effects were assessed by reverse transcription polymerase chain reaction, annexin V, and cytotoxicity assay.

RESULTS

Neurons exposed to hypoxic conditions exhibited neuronal apoptosis. Compared to single treatments, the combined hypoxia-inducible VEGF and BMSC treatment demonstrated a significant increase in VEGF expression and decreased neuronal apoptosis.

CONCLUSIONS

These results suggest that combined pEpo-SV-VEGF and BMSC treatment is effective in protecting neurons against hypoxic ischemic injury.

Human neural stem cell transplantation attenuates apoptosis and improves neurological functions after cerebral ischemia in rats

BACKGROUND

Neuroprotection is a major therapeutic approach for ischemic brain injury. We investigated the neuroprotective effects induced by transplantation of human embryonic neural stem cells (NSCs) into the cortical penumbra 24 h after focal cerebral ischemia.

METHODS

NSCs were prepared from human embryonic brains obtained at 8 weeks of gestation. Focal cerebral ischemia was induced in adult rats by permanent occlusion of the middle cerebral artery. Animals were randomly divided into two groups: NSCs-grafted group and medium-grafted group (control). Infarct size was assessed 28 days after transplantation by hematoxylin and eosin staining. Neurological severity scores were evaluated before ischemia and at 1, 7, 14, and 28 days after transplantation. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay and immunohistochemical analysis of Bcl-2 and Bax were performed at 7, 14, and 28 days after transplantation.

RESULTS

Physiological parameters of the two groups were comparable, but not significantly different. NSC transplantation significantly improved neurological function (P<0.05) but did not reduce the infarct size significantly (P>0.05). Compared with the control, NSC transplantation significantly reduced the number of TUNEL- and Bax-positive cells in the penumbra at 7 days. Interestingly, the number of Bcl-2-positive cells in the penumbra after NSC transplantation was significantly higher than that after medium transplantation (P<0.05).

CONCLUSIONS

The results indicate that NSC transplantation has anti-apoptotic activity and can improve the neurological function; these effects are mediated by the up-regulation of Bcl-2 expression in the penumbra.