Differentiation and angiogenesis of central nervous system stem cells implanted with mesenchyme into ischemic rat brain

Neuroprotective Strategies for Ischemic Stroke-Future Perspectives

Ischemic stroke is the main cause of death and the most common cause of acquired physical disability worldwide. Recent demographic changes increase the relevance of stroke and its sequelae. The acute treatment for stroke is restricted to causative recanalization and restoration of cerebral blood flow, including both intravenous thrombolysis and mechanical thrombectomy. Still, only a limited number of patients are eligible for these time-sensitive treatments. Hence, new neuroprotective approaches are urgently needed. Neuroprotection is thus defined as an intervention resulting in the preservation, recovery, and/or regeneration of the nervous system by interfering with the ischemic-triggered stroke cascade. Despite numerous preclinical studies generating promising data for several neuroprotective agents, successful bench-to-bedside translations are still lacking. The present study provides an overview of current approaches in the research field of neuroprotective stroke treatment. Aside from "traditional" neuroprotective drugs focusing on inflammation, cell death, and excitotoxicity, stem-cell-based treatment methods are also considered. Furthermore, an overview of a prospective neuroprotective method using extracellular vesicles that are secreted from various stem cell sources, including neural stem cells and bone marrow stem cells, is also given. The review concludes with a short discussion on the microbiota-gut-brain axis that may serve as a potential target for future neuroprotective therapies.

Protective Effects of 4-Trifluoromethyl-(E)-cinnamoyl]-L-4-F-phenylalanine Acid against Chronic Cerebral Hypoperfusion Injury through Promoting Brain-Derived Neurotrophic Factor-Mediated Neurogenesis

Vascular dementia (VaD), one of the major consequences after stroke, is the second reason for the cognitive decline in aged people. Chronic cerebral hypoperfusion (CCH) is considered as the main cause for cognitive impairment in VaD patients. In our previous study, a synthetic compound, 4-trifluoromethyl-(E)-cinnamoyl]-L-4-F-phenylalanine acid (AE-18), has been proven to decrease infarct volume and to recover the insufficient blood supply after ischemia-reperfusion in rats, which was reminded that AE-18 may possess the ameliorative effect in CCH. In this study, the bilateral common carotid artery occlusion was performed to establish the CCH model in rats to evaluate the effect and mechanisms of AE-18 in CCH. Results showed that AE-18 (5 and 10 mg/kg, i.g.) could recover the learning and memory and increase the number of neurons in the hippocampus, which may be attributed to its neurogenesis effects and its recovery of cerebral blood flow in CCH rats. In addition, the in vitro studies showed that AE-18 promoted neuronal proliferation, induced differentiation of Neuro-2a cells into a neuron-like morphology, and accelerated the establishment of axon-dendrite polarization of primary hippocampal neurons through upregulating brain-derived neurotrophic factor via the PI3K/Akt/CREB pathway. In conclusion, AE-18 is a promising candidate for the treatment of cognitive decline after CCH injury by restoring blood supply to the brain and promoting neurogenesis in the hippocampus.

Overexpression of vascular endothelial growth factor enhances the neuroprotective effects of bone marrow mesenchymal stem cell transplantation in ischemic stroke

Although bone marrow mesenchymal stem cells (BMSCs) might have therapeutic potency in ischemic stroke, the benefits are limited. The current study investigated the effects of BMSCs engineered to overexpress vascular endothelial growth factor (VEGF) on behavioral defects in a rat model of transient cerebral ischemia, which was induced by middle cerebral artery occlusion. VEGF-BMSCs or control grafts were injected into the left striatum of the infarcted hemisphere 24 hours after stroke. We found that compared with the stroke-only group and the vehicle- and BMSCs-control groups, the VEGF-BMSCs treated animals displayed the largest benefits, as evidenced by attenuated behavioral defects and smaller infarct volume 7 days after stroke. Additionally, VEGF-BMSCs greatly inhibited destruction of the blood-brain barrier, increased the regeneration of blood vessels in the region of ischemic penumbra, and reducedneuronal degeneration surrounding the infarct core. Further mechanistic studies showed that among all transplant groups, VEGF-BMSCs transplantation induced the highest level of brain-derived neurotrophic factor. These results suggest that BMSCs transplantation with vascular endothelial growth factor has the potential to treat ischemic stroke with better results than are currently available.

Heliox Preconditioning Exerts Neuroprotective Effects on Neonatal Ischemia/Hypoxia Injury by Inhibiting Necroptosis Induced by Ca2+ Elevation

Our previous studies have indicated that heliox preconditioning (HePC) may exert neuroprotective effects on neonatal hypoxic-ischemic encephalopathy (HIE). The present study was to investigate whether HePC alleviates neonatal HIE by inhibiting necroptosis and explore the potential mechanism. Seven-day-old rat pups were randomly divided into Sham group, HIE group, HIE + HePC group, HIE + Dantrolene (DAN) group, and HIE + Necrostatin-1 (Nec-1) group. HIE was induced by common carotid artery ligation and subsequent hypoxia exposure. The neurological function, brain injury, and molecular mechanism were evaluated by histological staining, neurobehavioral test, Western blotting, Ca²⁺, immunofluorescence staining, co-immunoprecipitation (Co-IP), and transmission electron microscopy (TEM). Results supported that the expression of necroptosis markers and p-RyR2 in the brain increased significantly after HIE. HePC, DAN, or Nec-1 was found to improve the neurological deficits after H/I and inhibit neuronal necroptosis. Interestingly, both HePC and DAN inhibited the increases in cytoplasmic Ca²⁺ and CaMK-II phosphorylation in the brain secondary to HIE, but Nec-1 failed to affect Ca²⁺. In conclusion, our results suggest HePC may alleviate cytoplasmic Ca²⁺ overload by regulating p-RyR2, which inhibits the necroptosis in the brain, exerting neuroprotective effects on HIE.

Microglia and Macrophages in Neuroprotection, Neurogenesis, and Emerging Therapies for Stroke

Stroke remains the number one cause of morbidity in the United States. Within weeks to months after an ischemic event, there is a resolution of inflammation and evidence of neurogenesis; however, years following a stroke, there is evidence of chronic inflammation in the central nervous system, possibly by the persistence of an autoimmune response to brain antigens as a result of ischemia. The mechanisms underlying the involvement of macrophage and microglial activation after stroke are widely acknowledged as having a role in ischemic stroke pathology; thus, modulating inflammation and neurological recovery is a hopeful strategy for treating the long-term outcomes after ischemic injury. Current treatments fail to provide neuroprotective or neurorestorative benefits after stroke; therefore, to ameliorate brain injury-induced deficits, therapies must alter both the initial response to injury and the subsequent inflammatory process. This review will address differences in macrophage and microglia nomenclature and summarize recent work in elucidating the mechanisms of macrophage and microglial participation in antigen presentation, neuroprotection, angiogenesis, neurogenesis, synaptic remodeling, and immune modulating strategies for treating the long-term outcomes after ischemic injury.

Efficacy of stem cell-based therapies for stroke

Stroke remains a prevalent disease with limited treatment options. Available treatments offer little in the way of enhancing neurogenesis and recovery. Because of the limitations of available treatments, new therapies for stroke are needed. Stem cell-based therapies for stroke offer promise because of their potential to provide neurorestorative benefits. Stem cell-based therapies aim to promote neurogenesis and replacement of lost neurons or protect surviving neurons in order to improve neurological recovery. The mechanism through which stem cell treatments mediate their therapeutic effect is largely dependent on the type of stem cell and route of administration. Neural stem cells have been shown in pre-clinical and clinical trials to promote functional recovery when used in intracerebral transplantations. The therapeutic effects of neural stem cells have been attributed to their formation of new neurons and promotion of neuroregeneration. Bone marrow stem cells (BMSC) and mesenchymal stem cells (MSC) have been shown to enhance neurogenesis in pre-clinical models in intracerebral transplantations, but lack clinical evidence to support this therapeutic approach in patients and appear to be less effective than neural stem cells. Intravenous and intra-arterial administration of BMSC and MSC have shown more promise, where their effects are largely mediated through neuroprotective mechanisms. The immune system has been implicated in exacerbating initial damage caused by stroke, and BMSC and MSC have demonstrated immunomodulatory properties capable of dampening post-stroke inflammation and potentially improving recovery. While still in development, stem cell therapies may yield new treatments for stroke which can improve neurological recovery.

Synergistic Improvement in Children with Cerebral Palsy Who Underwent Double-Course Human Wharton's Jelly Stem Cell Transplantation

Background

Our previous studies confirmed that human Wharton's Jelly stem cell (hWJSC) transplantation improved motor function in children with spastic cerebral palsy (CP). This study investigated the dose-effect relationship between the transplanted cell dosage and efficacy in CP children.

Methods

CP children who received one- or two-course (four or eight times lumbar puncture, 4 or 8 × 10⁷ hWJSCs) cell therapy were recruited into this study. Assessments of motor function were performed according to scales for gross motor function measurement (GMFM) and fine motor function measurement (FMFM). The measurement data obtained in the two different groups were analyzed by t-test. Univariate repeated measures analysis of variance was used to compare the data obtained at baseline and 6 or 12 months posttransplantation and met the conditions for Mauchly's sphericity test.

Results

The results for fifty-seven pediatric CP patients (including 35 male and 22 female patients) who completed follow-up showed that gross and fine motor functions improved after cell therapy. Interestingly, the GMFM and FMFM scores in patients who received one course of transplantation were significantly increased at 6 months after treatment. Moreover, another course of transplantation further improved gross and fine motor function in children. The scores for GMFM and FMFM were significantly higher at 6 months posttransplantation than at baseline and showed a linear upward trend. There was no gender difference in GMFM. Interestingly, there was a significant difference between male and female patients in the B and C dimensions of FMFM. These results reveal a gender-related susceptibility to stem cell therapy, especially for movement capability of the upper extremity joint and grasping ability. Similarly, in the group aged ≤3 years old, the improvement observed in dimension A (lying and rolling) of GMFM was nearly exponential and showed a quadratic trend. The results for FMFM were similar to those for GMFM. Moreover, the improvement in motor function was not age dependent.

Conclusions

In this study, our data collectively reveal that CP children display sex- or age-dependent responses to hWJSC therapy; these results shed light on the clinical utility of this approach in specific populations.

Grafted Miniature-Swine Neural Stem Cells of Early Embryonic Mesencephalic Neuroepithelial Origin can Repair the Damaged Neural Circuitry of Parkinson's Disease Model Rats

Although recent progress in the use of human iPS cell-derived midbrain dopaminergic progenitors is remarkable, alternatives are essential in the strategies of treatment of basal-ganglia-related diseases. Attention has been focused on neural stem cells (NSCs) as one of the possible candidates of donor material for neural transplantation, because of their multipotency and self-renewal characteristics. In the present study, miniature-swine (mini-swine) mesencephalic neuroepithelial stem cells (M-NESCs) of embryonic 17 and 18 days grafted in the parkinsonian rat striatum were assessed immunohistochemically, behaviorally and electrophysiologically to confirm their feasibility for the neural xenografting as a donor material. Grafted mini-swine M-NESCs survived in parkinsonian rat striatum at 8 weeks after transplantation and many of them differentiated into tyrosine hydroxylase (TH)-positive cells. The parkinsonian model rats grafted with mini-swine M-NESCs exhibited a functional recovery from their parkinsonian behavioral defects. The majority of donor-derived TH-positive cells exhibited a matured morphology at 8 weeks. Whole-cell recordings from donor-derived neurons in the host rat brain slices incorporating the graft revealed the presence of multiple types of neurons including dopaminergic. Glutamatergic and GABAergic post-synaptic currents were evoked in the donor-derived cells by stimulation of the host site, suggesting they receive both excitatory and inhibitory synaptic inputs from host area. The present study shows that non-rodent mammalian M-NESCs can differentiate into functionally active neurons in the diseased xenogeneic environment and could improve the parkinsonian behavioral defects over the species. Neuroepithelial stem cells could be an attractive candidate as a source of donor material for neural transplantation.

Vigorous Neuronal Differentiation of Amplified and Grafted Basic Fibroblast Growth Factor-Responsive Neurospheres Derived from Neuroepithelial Stem Cells

Neuroepithelial stem cells (NESCs) have emerged as a possible donor material aimed at neural transplantation for the repair of damaged neural circuitry, particularly because of their propensity to differentiate into neurons. We previously ascertained in vitro that NESCs derived from rat early embryos could be amplified in culture containing basic fibroblast growth factors (bFGF), and that neurospheres grown for 7 days in the culture had a strong tendency to differentiate into neurons. In this report, we analyze immunohistochemically the biological nature of bFGF-responsive neurospheres derived from NESCs. We first succeeded in amplifying the number of NESCs from the mesencephalic neural plate of embryonic day 10 Wistar rats with the addition of bFGF. Grown neurospheres were labeled with bromodeoxyuridine (BrdU) in vitro and were stereotactically transplanted into the right striatum of the normal adult Wistar rat. Two weeks after transplantation, a viable graft in the host brain was observed. While many BrdU/Hu double positive cells were seen in the graft, and a few BrdU/nestin double positive cells were also seen, no BrdU/GFAP double positive cells could be identified. These results suggested that bFGF-responsive neurospheres derived from NESCs demonstrated a propensity to differentiate into neurons in the adult brain environment. Furthermore, following in vitro amplification of the original stem cell number with bFGF, the grown neurospheres preserved their propensity to differentiate vigorously into neurons. NESCs are thus suggested as a feasible candidate for intracerebral grafting donor materials aimed at reconstruction of damaged neural circuits.

Feasibility of Using Early Mesencephalic Neural Plate for Intracerebral Grafting

The purpose of this study was to elucidate the biological significance and the possibility of intracerebral grafting of neuroepithelial stem cells derived from the mesencephalic neural plate. Immunohistological studies of embryonic day 10.5 (E10.5) Wister rats revealed strong nestin expression in the mesencephalic part of the neural plate. Mesencephalic neural plates removed from E10.5 rats were processed to either tissue or cell dissociation culture. They were cultured in vitro under various conditions and were analyzed 7 days after the primary culture. When they were cultured as a tissue, cell proliferation and differentiation into neurons extending long neurites were obvious in a serum-free medium, in a medium containing 3% serum, and in a medium containing 20 ng/ml epidermal growth factor. On the other hand, in a medium containing 10 ng/ml basic fibroblast growth factor (bFGF), both vigorous cell proliferation and sphere formation were recognized. Furthermore, marked neurite growth was rarely seen in this culture. When they were plated in a dissociation culture, cell proliferation and neurosphere generation were also recognized only in a medium containing bFGF, depending on the initial cell concentration. The spheres, generated 7 days after the primary cell culture, were positively stained by nestin. These data suggested that bFGF was able to amplify the stem cell population present in the mesencephalic neural plate derived from early embryos. This might make it possible to obtain a large number of stem cells as donor material for neural transplantation on demand.

Protective Effects of UCF-101 on Cerebral Ischemia-Reperfusion (CIR) is Depended on the MAPK/p38/ERK Signaling Pathway

This study was aimed to investigate the treatment mechanisms of 5-[5-(2-nitrophenyl) furfuryliodine]-1,3-diphenyl-2-thiobarbituric acid (UCF-101) in cerebral ischemia-reperfusion (CIR) model rats. Total of 54 healthy male Wistar rats were randomly assigned into three groups, namely sham group, vehicle group, and UCF-101 group. The CIR-injured model was established by right middle cerebral artery occlusion and reperfusion. Neurological function was assessed by an investigator according to the Longa neurologic deficit scores. Meanwhile, the cerebral tissue morphology and apoptotic neurons were evaluated by H&E and TUNEL staining, respectively. Additionally, the expressions of caspase 3, p-p38, and p-ERK were detected by immunohistochemistry or/and Western blotting assays. As results, neurologic deficit and pathological damage were obviously enhanced and TUNEL positive neurons were significantly increased in CIR-injured rats, as compared with those in sham group. Furthermore, the expressions of caspase 3, p-p38, and p-ERK were also significantly increased in vehicle group than those in sham group (P < 0.05). However, UCF-101 treatment could markedly weaken the neurologic deficit with lower scores and improve pathological condition. After UCF-101 treatment, TUNEL positive neurons as well as the expression of caspase 3 were significantly decreased than those in vehicle group (P < 0.05). Besides, p-p38 was decreased while p-ERK was increased in UCF-101 group than those in vehicle group (P < 0.05). Therefore, we concluded that the protective effects of UCF-101 might be associated with apoptosis process and MAPK signaling pathway in the CIR-injured model.

Therapeutic outcomes of transplantation of amniotic fluid-derived stem cells in experimental ischemic stroke

Accumulating preclinical evidence suggests the use of amnion as a source of stem cells for investigations of basic science concepts related to developmental cell biology, but also for stem cells’ therapeutic applications in treating human disorders. We previously reported isolation of viable rat amniotic fluid-derived stem (AFS) cells. Subsequently, we recently reported the therapeutic benefits of intravenous transplantation of AFS cells in a rodent model of ischemic stroke. Parallel lines of investigations have provided safety and efficacy of stem cell therapy for treating stroke and other neurological disorders. This review article highlights the need for investigations of mechanisms underlying AFS cells’ therapeutic benefits and discusses lab-to-clinic translational gating items in an effort to optimize the clinical application of the cell transplantation for stroke.

Transplantation for stroke

Stroke is the most common cause of disability in the United States, and one of the leading causes of mortality and disability in the world. The hope that damage to the CNS can be reversed or at least ameliorated is the central idea behind the research into neural repair. The ultimate repair for the brain should restore the entire lost structure and it's function. However, partial benefit is possible from addressing some of the needs of the injured brain. These partial solutions are the basis of current research into brain repair after stroke. An opportunity arises for two kinds of intervention: (1) replacement of neurons; (2) support of existing neurons, to prevent excessive degeneration and promote rewiring and plasticity. Transplantation for stroke in the rat model was regularly reported starting in 1992, demonstrating graft survival and even evidence of connection with the host brain. These studies determined several parameters for future work in stroke models, but ultimately had limited efficacy and did not progress to clinical experiments. A variety of cell types have been tried for restoration of brain function after stroke, mostly in rodent models. Human fetal cells had shown some promise in clinical studies for the treatment of Parkinson's disease. The technical and ethical difficulties associated with these cells promoted a search for alternatives. These include porcine fetal cells, human cultured stem cells, immortalized cell lines, marrow stromal cells, Sertoli cells pineal cells, and other sources. Human clonal cell lines have few ethical limitations, but some questions remain regarding their safety and efficacy. Autologous somatic stem cells are a very attractive source--there are no ethical concerns and graft rejection is not an issue. However, it is not clear that somatic cells can are plastic enough and can be safely induced to a neural fate. Restorative treatment for stroke is a new field of study. Naturally, new ideas abound and many strategies have been suggested and tried. Methods and controversies abound, and include: local delivery of cells to the area of the stroke versus grafting to an area of the brain far removed form the stroke; cell therapy for reconstitution of structure and function versus use of cell grafts to support intrinsic repair and recovery mechanisms; intravascular administration of bone marrow or other stem cells; and combination grafts, or co-grafting of several cell types or cells and other substances. The various strategies address the issue of restorative treatments form different perspectives. Some interventions occur early after stroke, or are intended to preserve existing neural structures. For example, treatment strategies that aim to provide trophic support may demonstrate early beneficial results. Other strategies aim for growth and integration of new neurons to replace those lost after stroke. In this case, early beneficial results are not likely. Functional integration of grafted neurons, if it can ever happen, is likely to require training and exercise of the appropriate capacities. Further advances in preclinical studies of neural transplantation will require improved animal models with increased sensitivity to subtle behavioral and imaging changes. Non-human primate models have been established and may increase in importance as a phase before clinical trials. The future of brain repair for stroke is likely to require some form of combination therapy designed to replace the lost cells and supporting structure, attract new blood supply, support and enhance intrinsic repair and plasticity mechanisms.

Intravenous grafts of amniotic fluid-derived stem cells induce endogenous cell proliferation and attenuate behavioral deficits in ischemic stroke rats

We recently reported isolation of viable rat amniotic fluid-derived stem (AFS) cells [1]. Here, we tested the therapeutic benefits of AFS cells in a rodent model of ischemic stroke. Adult male Sprague-Dawley rats received a 60-minute middle cerebral artery occlusion (MCAo). Thirty-five days later, animals exhibiting significant motor deficits received intravenous transplants of rat AFS cells or vehicle. At days 60–63 post-MCAo, significant recovery of motor and cognitive function was seen in stroke animals transplanted with AFS cells compared to vehicle-infused stroke animals. Infarct volume, as revealed by hematoxylin and eosin (H&E) staining, was significantly reduced, coupled with significant increments in the cell proliferation marker, Ki67, and the neuronal marker, MAP2, in the dentate gyrus (DG) [2] and the subventricular zone (SVZ) of AFS cell-transplanted stroke animals compared to vehicle-infused stroke animals. A significantly higher number of double-labeled Ki67/MAP2-positive cells and a similar trend towards increased Ki67/MAP2 double-labeling were observed in the DG and SVZ of AFS cell-transplanted stroke animals, respectively, compared to vehicle-infused stroke animals. This study reports the therapeutic potential of AFS cell transplantation in stroke animals, possibly via enhancement of endogenous repair mechanisms.

Transplantation of human amniotic mesenchymal stem cells in the treatment of focal cerebral ischemia

Cerebrovascular injury is one of the three major causes of death and is the leading cause of adult disability. Despite the increasing progress in emergency treatment and early rehabilitation in patients with cerebrovascular injury, treatment options for neurological dysfunction that presents at a later stage are lacking. This study examined the potential of human amniotic mesenchymal stem cell (hAMSC) transplantation in the repair of neurological deficits in an experimental focal cerebral ischemia model. Following the isolation of hAMSCs, growth characteristics and surface antigen expression were observed. Butylated hydroxyanisole (BHA) was used to induce the cultured cells into neuron-like cells, which were identified by immunocytochemistry. The suture model was used to induce focal cerebral ischemia in rats, which were subsequently randomly divided into experimental and control groups for treatment with BrdU-labeled hAMSCs or PBS, respectively. Neurological deficits were assessed following transplantation using the neurological severity score, beam balance test and elevated body swing test. Eight weeks later, rat brain tissue was analyzed with H&E staining and BrdU immunohistochemistry, and the survival and spatial distribution of the transplanted hAMSCs were determined. The hAMSCs proliferated in vitro, and it was found that neuron-specific enolase (NSE) was expressed in neurons, whereas glial fibrillary acidic protein (GFAP) was expressed in astrocytes. The focal ischemia model caused varying degrees of left limb hemiplegia accompanied by right sided Horner's Syndrome. When examined 1, 3, 6 and 8 weeks later, significant recovery in neurological behavior was detected in the rats treated with hAMSC transplantation compared with the control (P<0.01). BrdU-labeled hAMSCs were concentrated near the graft site and surrounding areas, in certain cases migrating towards the ischemic lesion. Local gliosis and lymphocytic infiltration were not detected. hAMSCs exhibit great potential for proliferation and are induced to differentiate into NSE-expressing neuron-like cells following treatment with BHA. Moreover, hAMSC transplantation may improve neurological symptoms following focal cerebral ischemia.

Stem cell-based therapy for experimental stroke: a systematic review and meta-analysis

Stem cell therapy holds great promise in medicine, but clinical development should be based on a sound understanding of potential weaknesses in supporting experimental data. The aim of this article was to provide a systematic overview of evidence relating to the efficacy of stem cell-based therapies in animal models of stroke to foster the clinical application of stem cell-based therapies and to inform the design of large-scale clinical trials. We conducted a systematic search for reports of experiments using stem cells in animal models of cerebral ischaemia, and performed DerSimmonian and Laird random effects meta-analysis. We assessed the impact of study characteristics, of publication bias and of measures to reduce bias. We identified 6059 publications, 117 met our prespecified inclusion criteria. One hundred eighty-seven experiments using 2332 animals described changes in structural outcome and 192 experiments using 2704 animals described changes in functional outcome. Median study quality score was 4 (interquartile range 3 to 6) and less than half of studies reported randomization or blinded outcome assessment; only three studies reported a sample size calculation. Nonrandomized studies gave significantly higher estimates of improvement in structural outcome, and there was evidence of a significant publication bias. For structural outcome autologous (i.e. self-derived) stem cells were more effective than allogeneic (donor-derived) cells, but for functional outcome, the reverse was true. A significant dose-response relationship was observed only for structural outcome. For structural outcome, there was an absolute reduction in efficacy of 1·5% (-2·4 to -0·6) for each days delay to treatment; functional outcome was independent of the time of administration. While stem cells appear to be of some benefit in animal models of stroke the internal and external validity of this literature is potentially confounded by poor study quality and by publication bias. The clinical development of stem cell-based therapies, in stroke and elsewhere, should acknowledge these potential weaknesses in the supporting animal data.

Functional recovery after transplantation of neural stem cells modified by brain-derived neurotrophic factor in rats with cerebral ischaemia

Functional recovery after transplantation of brain-derived neurotrophic factor (BDNF)-modified neural stem cells (NSCs) was evaluated in a rat model of cerebral ischaemia damage induced by temporary middle cerebral artery occlusion (tMCAO). Western blotting and enzyme-linked immunosorbent assay demonstrated upregulated BDNF protein expression by rat embryonic NSCs transfected with the human BDNF gene (BDNF-NSCs). BDNF-NSCs stimulated neurite outgrowth in cocultured dorsal root ganglion neurons, suggesting that BDNF increased neurogenesis in vitro. In vivo, BDNF promoted recovery of tMCAO. Phosphate-buffered saline, untransformed NSCs or BDNF-NSCs were introduced into the penumbra zone of the right striatum of tMCAO rats and neurological function deficit was assessed for up to 12 weeks using the neurological severity score (NSS). The NSS was significantly lower in the BDNF-NSC transfected transplant group than in all the other groups from week 10. BDNF-NSCs recovered 1 week after transplantation expressed BDNF protein. Transplanted NSCs had differentiated into mature neurons 12 weeks after transplantation. Transgenic NSCs have potential as a therapeutic agent for brain ischaemia.

Transplantation of neural stem cells modified by human neurotrophin-3 promotes functional recovery after transient focal cerebral ischemia in rats

The study tested the hypothesis that transplantation of human neurotrophin-3 (hNT-3) over-expressing neural stem cells (NSCs) into rat striatum after a severe focal ischemia would promote functional recovery. Rat NSCs, transduced by Flag-tagged hNT-3 gene mediated by lentiviral vector (LV), were transplanted into the striatum ipsilateral to the injury of adult rats 7 days after 2-h occlusion of the middle cerebral artery (MCAO). From 3 days to 2 weeks after transplantation, the modified cells (NSCs-hNT3, as defined by Flag immunofluorencence staining) that survived the transplantation procedures could secrete significantly higher levels of neurotrophin-3 protein in the graft sites than controls (P<0.001). Furthermore, the rats that accepted NSCs-hNT3 exhibited enhanced functional recovery on neurological and behavioral tests, compared with controlled animals transplanted with saline or untransduced NSCs. This study suggests: (1) LV is an ideal vector to transduce foreign gene into the NSCs; (2) modified NSCs could carry therapeutic genes to disease tissues and express effectively; (3) modified cells could survive in the ischemic brains and continue to secrete neurotrophin-3 abundantly for over 2 weeks, which might have values for enhancing functional recovery after stroke.

Role of Endogenous Neural Stem Cells in Neurological Disease and Brain Repair

These examples show that stem-cell-based therapy of neuro-psychiatric disorders will not follow a single scheme, but rather include widely different approaches. This is in accordance with the notion that the impact of stem cell biology on neurology will be fundamental, providing a shift in perspective, rather than introducing just one novel therapeutic tool. Stem cell biology, much like genomics and proteomics, offers a "view from within" with an emphasis on a theoretical or real potential and thereby the inherent openness, which is central to the concept of stem cells. Thus, stem cell biology influences many other, more traditional therapeutic approaches, rather than introducing one distinct novel form of therapy. Substantial advances have been made i n neural stemcell research during the years. With the identification of stem and progenitor cells in the adult brain and the complex interaction of different stem cell compartments in the CNS--both, under physiological and pathological conditions--new questions arise: What is the lineage relationship between t he different progenitor cells in the CNS and how much lineage plasticity exists? What are the signals controlling proliferation and differentiation of neural stem cells and can these be utilized to allow repair of the CNS? Insights in these questions will help to better understand the role of stem cells during development and aging and the possible relation of impaired or disrupted stem cell function and their impact on both the development and treatment of neurological disease. A number o f studies have indicated a limited neuronal and glial regeneration certain pathological conditions. These fundamental observations have already changed our view on understanding neurological disease and the brain's capacity for endogenous repair. The following years will have to show how we can influence andmodulate endogenous repair nisms by increasing the cellular plasticity in the young and aged CNS.

Transplantation of vascular endothelial growth factor-transfected neural stem cells into the rat brain provides neuroprotection after transient focal cerebral ischemia

OBJECTIVE

Vascular endothelial growth factor (VEGF) stimulation and neural stem cell (NSC) transplantation have been implicated in the treatment of cerebral ischemia because of their crucial roles in neuroprotection, neurogenesis, and angiogenesis. However, effective delivery of VEGF or NSCs remains difficult. This study attempted to explore whether VEGF121 complementary deoxyribonucleic acid could be transferred into the NSCs and, furthermore, whether transplanting these VEGF121-transfected NSCs into the rat brain provides sufficient neuroprotection after transient focal cerebral ischemia.

METHODS

The VEGF121 gene was transfected to the NSCs isolated from E14 fetal rat hippocampus. In vitro studies revealed that VEGF messenger ribonucleic acid could be consistently expressed in NSCs from 1 day to up to 2 weeks.

RESULTS

After transplantation of VEGF121-transfected NSCs into the perifocal area of the ischemic rat brain, we found that these cells could survive and migrate in the ischemic region for 12 weeks. Furthermore, we observed a significant improvement of the Neurological Severity Scale score in the rats transplanted with VEGF121-transfected NSCs in comparison to the phosphate-buffered saline-injected or the sham-operated rats (P < 0.05). Transplantation of nontransfected NSCs into ischemic rat brain improved the Neurological Severity Scale score as well. Of note, the improvement in the Neurological Severity Scale score occurred earlier in the VEGF121-transfected NSC rats than in the nontransfected NSC rats (range, 2-12 wk versus 8-12 wk), suggesting a potent neuroprotection mediated by additional VEGF121 transfection.

CONCLUSION

We conclude that transplantation of VEGF121-transfected NSCs improved ischemic neurological deficiency. This finding provides a novel approach for the treatment of cerebral ischemia.

Behavioral and histological evaluation of a focal cerebral infarction rat model transplanted with neurons induced from bone marrow stromal cells

Neurons can be specifically induced from bone marrow stromal cells (MSCs) with extremely high efficiency using gene transfection of the Notch intracellular domain and subsequent treatment with basic-fibroblast growth factor, forskolin, and ciliary neurotrophic factor. We investigated the behavioral and histologic efficacy of such bone marrow stromal cell-derived neuronal cell (MSDNC) transplantation into a focal cerebral infarction model in rats. A left middle cerebral artery occlusion (MCAO) was performed on adult Wistar rats. MSDNC transplantation into the ipsilateral hemisphere was performed on day 7 after MCAO. The behavioral analyses were conducted on days 14, 21, 28, 35, and 36-40, and a histologic evaluation was performed on day 41. MSDNC-transplanted rats showed significant recovery compared with controls (MCAO without cell transplantation) in beam balance, limb placing, and Morris water maze tests. Histologically, transplanted cells migrated from the injection site into the ischemic boundary area, including the cortex, corpus callosum, striatum, and hippocampus. Transplanted MSDNCs were positive for MAP-2 (84% +/- 8.11%), whereas only a small number of cells were positive for GFAP (1.0% +/- 0.23%). The survival rates of MSDNCs and MSCs 1 month after transplantation were approximately 45% and 10%, respectively. These results suggest that use of MSDNCs may be a promising therapeutic strategy for cerebral infarction.

Potential functional neural repair with grafted neural stem cells of early embryonic neuroepithelial origin

The fate of grafted neuroepithelial stem cells in the normal mature brain environment was assessed both morphologically and electrophysiologically to confirm their feasibility in the functional repair of damaged neural circuitry. The neuroepithelial stem cells were harvested from the mesencephalic neural plate of transgenic green fluorescence protein-carrying rat embryos, and implanted into the normal adult rat striatum. The short- and long-term differentiation pattern of donor-derived cells was precisely monitored immunohistochemically. The functional abilities of the donor-derived cells and communication between them and the host were investigated using host-rat brain slices incorporating the graft with whole-cell patch-clamp recording. Vigorous differentiation of the neuroepithelial stem cells into mostly neurons was noted in the short-term with positive staining for tyrosine hydroxylase, suggesting that the donor-derived cells were exclusively following their genetically programmed fate, together with gamma-aminobutyric acid (GABA) and glutamate expression. In the long-term, the large number of donor-derived neurons was sustained, but the staining pattern showed expression of dopamine- and adenosine 3':5'-monophosphate-regulated phosphoprotein 32, suggesting that some neurons were following environmental cues, together with the appearance of some cholinergic neurons. Some donor-derived astrocytes were also seen in the graft. Many action potentials indicating the presence of both dopaminergic and non-dopaminergic patterns could be elicited and recorded in the donor-derived neurons in addition to spontaneous glutamatergic and GABAergic post-synaptic currents which were strongly shown to be of host origin. Neuroepithelial stem cells are therefore an attractive candidate as a source of donor material for intracerebral grafting in functional repair.

Neuroglial activation in Niemann-Pick Type C mice is suppressed by intracerebral transplantation of bone marrow-derived mesenchymal stem cells

Glial activation is thought to play a key role in pathogenesis of neurodegenerative disorders. Here we show that direct transplantation of bone marrow-derived mesenchymal stem cells (BM-MSC) results in alleviation of inflammatory responses associated with the cerebellum of Niemann-Pick disease Type C (NP-C) model mice. Immunohistochemical examinations using glial fibrillary acidic protein (GFAP) and F4/80 antibodies revealed that BM-MSC transplantation reduced significantly both of astrocytic and microglial activations in the cerebellum of NP-C mice. Expression of macrophage colony stimulating factor (M-CSF), a microglial activator, was also considerably down-regulated by the BM-MSC transplantation. These findings suggest that BM-MSC transplantation may have potential for a therapeutic role in the treatment of NP-C and other neurodegenerative brain disorders.

In vivo detection limits of magnetically labeled embryonic stem cells in the rat brain using high-field (17.6 T) magnetic resonance imaging

Stem cell transplantation is a promising therapeutic approach for several neurological disorders. However, it has yet to fulfill its high expectations, partially due to the lack of a reliable noninvasive method for monitoring the biodistribution of the grafted stem cells in vivo. We have used high-resolution magnetic resonance imaging (MRI) at 17.6 T, combined with efficient magnetic labeling of the stem cells with iron oxide nanoparticles, in order to assess the in vivo detection limit in small animal models. Injection of different concentrations of magnetically labeled stem cells in gel phantoms led to significant reductions in image intensity from small cellular clusters of less than 10 cells. To determine the detection limit in vivo, various numbers of both labeled and unlabeled cells were injected stereotactically into the striatum of rats. Significant hypointense signal changes were observed for 100 labeled cells. After injection of approximately 20 labeled cells, signal reduction at the injection site was observed but could not be assigned unambiguously to the cells. Our results show that high-field MRI allows tracking of a minimal number of cells in vivo, well below the number used in previous studies, opening the possibility of gaining new insights into cell migration and differentiation.

Reduction of neural and vascular damage by transplantation of VEGF-secreting neural stem cells after cerebral ischemia

We determined the role of VEGF-transfected neural stem cells (NSCs) transplantation in rat brain subjected to ischemia. Fetal NSCs were cultured from E14 days SD rats and transfected with VEGF121 gene by using lipofectamine technique. Temporary middle cerebral artery occlusion (tMCAO) models were established and randomly divided into 1: control group, 2: PBS transplantation group, 3: NSCs transplantation group and 4: VEGF-secreting NSCs transplantation group. Grafts were transplanted into the penumbra zones 3 days after tMCAO model established. Neurological Severity Score (NSS) was checked in all groups 2-12 weeks after transplantation. By using immunofluorescent staining, VEGF expression of transplanted cells, differentiation and migration of transplanted NSCs after transplantation were detected. VEGF gene-transfected neural stem cells expressed gene products during the first 2 weeks. NSS in this group was significantly lower compared with that in other 3 groups 12 weeks after transplantation. VEGF gene-transfected NSCs migrated and expressed VEGF in hosts' brains, some of them differentiated to neurons 12 weeks after transplantation. VEGF-transfected NSCs expressed gene products during the early time after transplantation, which reduce brain injury through protecting the vascular system against ischemic attack.

Is there a future for neural transplantation?

Traditionally neural transplantation has had as its central tenet the replacement of missing neurons that have been lost because of neurodegenerative processes, as exemplified by diseases such as Parkinson disease (PD). However, the effectiveness and widespread application of this approach clinically has been limited, primarily because of the poor donor supply of human fetal neural tissue and the incomplete neurobiological understanding of the circuit reconstruction required to normalize function in these diseases. So, in PD the progress from promising neural transplantation in animal models to proof-of-principle, open-labeled clinical transplants, to randomized, placebo-controlled studies of neural transplantation has not been straightforward. The emergence of previously undescribed adverse effects and lack of significant functional advantage in recent clinical studies has been disappointing and has served to cast a new, and perhaps more realistic, perspective on this treatment approach. In fact, there have been calls by some involved in neural transplantation to return to the drawing board before pressing on with further clinical trials, and the return to basic experimentation. This therefore precipitates the question - is there a future for neural transplantation? It is important to remember that there are a number of possible explanations for the disappointing results from the recent clinical trials in PD, ranging from the mode of transplantation to patient selection. Nevertheless, almost irrespective of these reasons for the current trial results, there have always been significant practical and ethical problems with using human fetal tissue, and so a number of alternative cell sources have been investigated. These alternative sources include stem cells, which are attractive for cell-based therapies because of their potential ease of isolation, propagation and manipulation, and their ability in some cases to migrate to areas of pathology and differentiate into specific and appropriate cell types. Furthermore, the availability of stem cells derived from non-embryonic sources (e.g. adult stem cells derived from the sub-ventricular zone) has removed some of the ethical limitations associated with the use of embryonic human tissue. These potentially beneficial aspects of stem cells means that there is a future for neural transplantation as a means of treating patients with a range of neurological disorders, although whether this will ever translate into a truly effective, widely available therapy remains unknown.

Genetic and Cellular Therapies for Cerebral Infarction

Neurosurgeons, working as surgical scientists, can have a prominent role in developing and implementing genetic and cellular therapies for cerebral ischemia. The rapid emergence of both genetic and cellular therapies for neural regeneration warrants a careful analysis before implementation of human studies to understand the pitfalls and promises of this strategy. In this article, we review the topic of genetic and cellular therapy for stroke to provide a foundation for practicing neurosurgeons and clinical scientists who may become involved in this type of work. In Part 1, we review preclinical approaches with gene transfer, such as 1) improved energy delivery, 2) reduction of intracellular calcium availability, 3) abrogation of effects of reactive oxygen species, 4) reduction of proinflammatory cytokine signaling, 5) inhibition of apoptosis mediators, and 6) restorative gene therapy, that are paving the way to develop new strategies to treat cerebral infarction. In Part 2, we discuss the results of studies that address the possibility of using cellular therapies for stroke in animal models and in human trials by reviewing 1) the basics of stem cell biology, 2) exogenous and 3) and endogenous cell sources for therapy, and 4) clinical considerations in cell therapy applications. These emerging technologies based on the advancements made in recent years in the fields of genetics, therapeutic cloning, neuroscience, stem cell biology, and gene therapy provide significant potential for new therapies for stroke.

Ex vivo gene therapy using bone marrow-derived cells: combined effects of intracerebral and intravenous transplantation in a mouse model of niemann–pick disease

Normal murine bone marrow cells were transduced with a retroviral vector to overexpress and release human acid sphingomyelinase (ASM). The transduced cells were then transplanted intravenously into 3-day-old, irradiated ASM-deficient mice, a model of human Niemann-Pick disease (NPD). At 4 weeks, engrafted mice received intracerebral injections of mesenchymal stem cells obtained from the original, transduced bone marrow. By 16 weeks, most of the treated NPD mice had near-normal levels of ASM activity in their tissues, including the brain; dramatically improved histology; and marked reductions in sphingomyelin. Cerebellar function also was normal, and the number of Purkinje cells was > 80% of normal. Remarkably, in certain regions of the cerebellum many of the surviving Purkinje cells expressed human ASM RNA, suggesting that either they were donor-derived or that the transplanted bone marrow cells had fused with existing Purkinje cells. However, despite these positive results, by 24 weeks the ASM activities were dramatically reduced and cerebellar function began to decline, coincident with the detection of anti-human ASM antibodies in the plasma. We conclude that this gene therapy procedure might be useful in Type A NPD and other neurological lysosomal storage disorders, particularly since it is an approach that could be beneficial for both the neurological and the visceral organ features of these diseases.

Neural stem cells in aging and disease

Aging in the central nervous system is associated with progressive loss of function which is exacerbated by neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. The two primary cell replacement strategies involve transplantation of exogenous tissue, and activation of proliferation of endogenous cells. Transplanted tissue is used to either directly replace lost tissue, or to implant genetically engineered cells that secrete factors which promote survival and/or proliferation. However, successful application of any cell replacement therapy requires knowledge of the complex relationships between neural stem cells and the more restricted neural and glial progenitor cells. This review focuses on recent advances in the field of stem cell biology of the central nervous system, with an emphasis on cellular and molecular approaches to replacing cells lost in neurodegenerative disorders.

Intracerebral transplantation of mesenchymal stem cells into acid sphingomyelinase-deficient mice delays the onset of neurological abnormalities and extends their life span

Types A and B Niemann-Pick disease (NPD) are lysosomal storage disorders resulting from loss of acid sphingomyelinase (ASM) activity. We have used a knockout mouse model of NPD (ASMKO mice) to evaluate the effects of direct intracerebral transplantation of bone marrow-derived mesenchymal stem cells (MSCs) on the progression of neurological disease in this disorder. MSCs were transduced with a retroviral vector to overexpress ASM and were injected into the hippocampus and cerebellum of 3-week-old ASMKO pups. Transplanted cells migrated away from the injection sites and survived at least 6 months after transplantation. Seven of 8 treated mice, but none of the untreated controls, survived for > or = 7 months after transplant. Survival times were greater in sex-matched than in sex-mismatched transplants. Transplantation significantly delayed the Purkinje cell loss that is characteristic of NPD, although the protective effect declined with distance from the injection site. Overall ASM activity in brain homogenates was low, but surviving Purkinje cells contained the retrovirally expressed human enzyme, and transplanted animals showed a reduction in cerebral sphingomyelin. These results reveal the potential of treating neurodegenerative lysosomal storage disorders by intracerebral transplantation of bone marrow-derived MSCs.

CNS stem cell transplantation: clinical and ethical perspectives

Central nervous system disorders evoke special fear though their varied and unrelenting threats to memory, cognition, mobility, and every aspect of personal integrity and independence. Understandably, neurologic patients and their families become desperate for help, making fully free, informed consent problematic but not impossible. This desperation mandates our anticipatory attention to ethical questions related to any aggressive new therapy, including central nervous system grafting. In the United States, the right-to-life issue dominates ethical discussions on neural grafting. A variety of alternative tissue sources may permit technically suitable preparations, at least for some uses. If plentiful supplies of grafting cells can be made commercially, this should reduce problems related to allocating scarce resources, although financial and other scarcity barriers may still raise ethical problems. Many contemporary conceptions of selfhood depend on the identity and intactness of the mind and, by implication, the brain as substrate of mind. How much can we reweave the cerebral tapestry without creating a new self, a new identity? These philosophical questions will probably be approached pragmatically and incrementally, in the context of many other developments in human genetics and biomedicine. Our vision of the self will evolve amidst conflicting religious, ethical and pragmatic perspectives.

Stem cell grafting for epilepsy: clinical promise and ethical concerns

The recent explosion of research on stem cells and neural grafting holds great promise for many neurological conditions, including epilepsy. Potential roles for cell grafting in epilepsy include remodeling of dysfunctional neuronal circuits and local delivery of neuromodulatory or neuroprotective factors. While many basic questions remain to be answered, initial human trials are underway in epilepsy as well as Parkinson's disease, Alzheimer's disease, stroke, and other conditions. It is not too early to begin ethical reflection on this dynamic field. Donor cells are often derived from human embryos, raising scarcity concerns as well as opposition from anti-abortion forces. Alternative donor sources are being actively developed. Safety concerns, adequate consent, and equitable access to care will also become important issues. Ethical issues most unique to neural grafting will revolve around redefining self-identity when personality and cognition may be altered by therapy. Views of selfhood and of being human have evolved in a historically contingent process, so that neural grafting and other consequences of the genetic revolution fall within a series of reductionist scientific developments that lead to an increasing instrumentation of our self-image. Neuroscientists and clinicians must interact with other cultural, religious, and academic groups to promote mutual understanding and richer, but scientifically accurate, views of what it means to be human. A good starting point may come by telling patients' stories, connecting scientific knowledge with the density of lived experience.