Subventricular zone-derived neural stem cell grafts protect against hippocampal degeneration and restore cognitive function in the mouse following intrahippocampal kainic acid administration

Selective Neuronal Knockout of STAT3 Function Inhibits Epilepsy Progression, Improves Cognition, and Restores Dysregulated Gene Networks in a Temporal Lobe Epilepsy Model

OBJECTIVE

Temporal lobe epilepsy (TLE) is a progressive disorder mediated by pathological changes in molecular cascades and hippocampal neural circuit remodeling that results in spontaneous seizures and cognitive dysfunction. Targeting these cascades may provide disease-modifying treatments for TLE patients. Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) inhibitors have emerged as potential disease-modifying therapies; a more detailed understanding of JAK/STAT participation in epileptogenic responses is required, however, to increase the therapeutic efficacy and reduce adverse effects associated with global inhibition.

METHODS

We developed a mouse line in which tamoxifen treatment conditionally abolishes STAT3 signaling from forebrain excitatory neurons (nSTAT3KO). Seizure frequency (continuous in vivo electroencephalography) and memory (contextual fear conditioning and motor learning) were analyzed in wild-type and nSTAT3KO mice after intrahippocampal kainate (IHKA) injection as a model of TLE. Hippocampal RNA was obtained 24 h after IHKA and subjected to deep sequencing.

RESULTS

Selective STAT3 knock-out in excitatory neurons reduced seizure progression and hippocampal memory deficits without reducing the extent of cell death or mossy fiber sprouting induced by IHKA injection. Gene expression was rescued in major networks associated with response to brain injury, neuronal plasticity, and learning and memory. We also provide the first evidence that neuronal STAT3 may directly influence brain inflammation.

INTERPRETATION

Inhibiting neuronal STAT3 signaling improved outcomes in an animal model of TLE, prevented progression of seizures and cognitive co-morbidities while rescuing pathogenic changes in gene expression of major networks associated with epileptogenesis. Specifically targeting neuronal STAT3 may be an effective disease-modifying strategy for TLE. ANN NEUROL 2023;94:106-122.

Stem Cell Therapy in Treating Epilepsy

Epilepsy is a common disabling chronic neurological disorder characterized by an enduring propensity for the generation of seizures that result from abnormal hypersynchronous firing of neurons in the brain. Over 20–30% of epilepsy patients fail to achieve seizure control or soon become resistant to currently available therapies. Prolonged seizures or uncontrolled chronic seizures would give rise to neuronal damage or death, astrocyte activation, reactive oxygen species production, and mitochondrial dysfunction. Stem cell therapy is potentially a promising novel therapeutic strategy for epilepsy. The regenerative properties of stem cell-based treatment provide an attractive approach for long-term seizure control, particularly in drug-resistant epilepsy. Embryonic stem cells (ESCs), mesenchymal stem cells (MSCs), neural stem cells (NSCs), induced pluripotent stem cells (iPSCs), and adipose-derived regenerative cells (ADRCs) are capable of differentiating into specialized cell types has been applied for epilepsy treatment in preclinical animal research and clinical trials. In this review, we focused on the advances in stem cell therapy for epilepsies. The goals of stem cell transplantation, its mechanisms underlying graft effects, the types of grafts, and their therapeutic effects were discussed. The cell and animal models used for investigating stem cell technology in epilepsy treatment were summarized.

Life and death in the hippocampus: What's bad?

The hippocampal formation is crucial for the generation and regulation of several brain functions, including memory and learning processes; however, it is vulnerable to neurological disorders, such as epilepsy. Temporal lobe epilepsy (TLE), the most common type of epilepsy, changes the hippocampal circuitry and excitability, under the contribution of both neuronal degeneration and abnormal neurogenesis. Classically, neurodegeneration affects sensitive areas of the hippocampus, such as dentate gyrus (DG) hilus, as well as specific fields of the Ammon's horn, CA3, and CA1. In addition, the proliferation, migration, and abnormal integration of newly generated hippocampal granular cells (GCs) into the brain characterize TLE neurogenesis. Robust studies over the years have intensely discussed the effects of death and life in the hippocampus, though there are still questions to be answered about their possible benefits and risks. Here, we review the impacts of death and life in the hippocampus, discussing its influence on TLE, providing new perspectives or insights for the implementation of new possible therapeutic targets. This article is part of the Special Issue "NEWroscience 2018".

Purinergic Receptor Blockade with Suramin Increases Survival of Postnatal Neural Progenitor Cells In Vitro

Neural progenitor cells (NPCs) are self-renewing and multipotent cells that persist in the postnatal and adult brain in the subventricular zone and the hippocampus. NPCs can be expanded in vitro to be used in cell therapy. However, expansion is limited, since the survival and proliferation of adult NPCs decrease with serial passages. Many signaling pathways control NPC survival and renewal. Among these, purinergic receptor activation exerts differential effects on the biology of adult NPCs depending on the cellular context. In this study, we sought to analyze the effect of a general blockade of purinergic receptors with suramin on the proliferation and survival of NPCs isolated from the subventricular zone of postnatal rats, which are cultured as neurospheres. Treatment of neurospheres with suramin induced a significant increase in neurosphere diameter and in NPC number attributed to a decrease in apoptosis. Proliferation and multipotency were not affected. Suramin also induced an increase in the gap junction protein connexin43 and in vascular endothelial growth factor, which might be involved in the anti-apoptotic effect. Our results offer a valuable tool for increasing NPC survival before implantation in the lesioned brain and open the possibility of using this drug as adjunctive therapy to NPC transplantation.

Julian AP, Kopyov O, Kopyov A, Cohen RW. Human neural progenitor cells ameliorate NMDA-induced hippocampal degeneration and related functional deficits

<abstract> <p>It has been established that the CA3 region of the hippocampus is involved in consolidating short-term memory to long-term memory and aids in spatial navigation retention. Seizures and many neurologic diseases induce damage to that region of the hippocampus, resulting in deficits in memory consolidation and spatial navigation. Drug treatments have been proven to have limited effectiveness, but cell replacement therapy has demonstrated to be more promising. Celavie Biosciences have developed a multipotent, nontumorigenic human neural progenitor cell (hNPC) line shown to have the ability to migrate <italic>in situ</italic>, reducing structural and functional deficits in neurodegenerative animal models. Here, we examined whether transplanted hNPCs would reestablish the memories of Han-Wistar rats subjected to hippocampal excitotoxic lesioning. The rats were lesioned in the CA3c regions at 50 days bilaterally with the neurotoxin NMDA (1 µl containing 7.5 mg/ml; −3.5 mm AP; ±2.0 L and −2.5 V). At 54 days of age, live hNPCs (500000 cells in 5 µl cell suspension media), frozen-killed hNPCs (500000 cells/5 µl), HEK293T cells (500000 cells/5 µl) or vehicle (cell suspension media; 5 µl) were bilaterally implanted directly into the NMDA damaged area. The rats were tested two weeks later with three different memory tests: novel and place-object assays and the water-maze task. Results showed that rats receiving live hNPC implantation performed significantly better in the water maze task than control groups; yet, novel and place-object test results showed no significant differences among treatments. Histology confirmed the survival of implanted hNPCs after 28 days post-implantation as well as showing neuroprotective effects. This study showed that Celavie's hNPCs were able to survive and improve some but not all hippocampal functionality, emphasizing the promise for cell replacement therapeutics for neurodegenerative disorders.</p> </abstract>

Heterogeneous fate choice of genetically modulated adult neural stem cells in gray and white matter of the central nervous system

Apart from dedicated oligodendroglial progenitor cells, adult neural stem cells (aNSCs) can also give rise to new oligodendrocytes in the adult central nervous system (CNS). This process mainly confers myelinating glial cell replacement in pathological situations and can hence contribute to glial heterogeneity. Our previous studies demonstrated that the p57kip2 gene encodes an intrinsic regulator of glial fate acquisition and we here investigated to what degree its modulation can affect stem cell-dependent oligodendrogenesis in different CNS environments. We therefore transplanted p57kip2 knockdown aNSCs into white and gray matter (WM and GM) regions of the mouse brain, into uninjured spinal cords as well as in the vicinity of spinal cord injuries and evaluated integration and differentiation in vivo. Our experiments revealed that under healthy conditions intrinsic suppression of p57kip2 as well as WM localization promote differentiation toward myelinating oligodendrocytes at the expense of astrocyte generation. Moreover, p57kip2 knockdown conferred a strong benefit on cell survival augmenting net oligodendrocyte generation. In the vicinity of hemisectioned spinal cords, the gene knockdown led to a similar induction of oligodendroglial features; however, newly generated oligodendrocytes appeared to suffer more from the hostile environment. This study contributes to our understanding of mechanisms of adult oligodendrogenesis and glial heterogeneity and further reveals critical factors when considering aNSC mediated cell replacement in injury and disease.

PET imaging of metabolic changes after neural stem cells and GABA progenitor cells transplantation in a rat model of temporal lobe epilepsy

PURPOSE

Stem cell transplantation is promising for temporal lobe epilepsy (TLE) treatment. This study aimed to use PET imaging for the investigation of dynamic metabolic changes after transplantation of human neural stem cells (NSCs) and human GABA progenitor cells (GPCs) in a rat model of TLE.

METHODS

¹⁸F-FDG PET imaging, video-electroencephalography (EEG), whole-cell patch-clamp recordings and immunostaining were performed after transplantation of NSCs and GPCs.

RESULTS

PET imaging demonstrated that glucose metabolism was gradually improved in the NSCs group, but decreased in GPCs and the control. Video-EEG manifested that seizures were suppressed after NSCs or GPCs transplantation; whole-cell patch-clamp confirmed increased inhibitory response of GPC-derived cells; immunostaining studies verified that the transplanted NSCs and GPCs could survive, migrate and differentiate into mature neuronal subtypes.

CONCLUSION

¹⁸F-FDG PET imaging could be a distinguishing approach for evaluation of dynamic glycolytic metabolic changes after transplantation of NSCs and GPCs in TLE. Whole-cell patch-clamp provides evidence for functional maturation and integration of transplanted stem cells within host circuits.

Cend1, a Story with Many Tales: From Regulation of Cell Cycle Progression/Exit of Neural Stem Cells to Brain Structure and Function

Neural stem/precursor cells (NPCs) generate the large variety of neuronal phenotypes comprising the adult brain. The high diversity and complexity of this organ have its origin in embryonic life, during which NPCs undergo symmetric and asymmetric divisions and then exit the cell cycle and differentiate to acquire neuronal identities. During these processes, coordinated regulation of cell cycle progression/exit and differentiation is essential for generation of the appropriate number of neurons and formation of the correct structural and functional neuronal circuits in the adult brain. Cend1 is a neuronal lineage-specific modulator involved in synchronization of cell cycle exit and differentiation of neuronal precursors. It is expressed all along the neuronal lineage, from neural stem/progenitor cells to mature neurons, and is associated with the dynamics of neuron-generating divisions. Functional studies showed that Cend1 has a critical role during neurogenesis in promoting cell cycle exit and neuronal differentiation. Mechanistically, Cend1 acts via the p53-dependent/Cyclin D1/pRb signaling pathway as well as via a p53-independent route involving a tripartite interaction with RanBPM and Dyrk1B. Upon Cend1 function, Notch1 signaling is suppressed and proneural genes such as Mash1 and Neurogenins 1/2 are induced. Due to its neurogenic activity, Cend1 is a promising candidate therapeutic gene for brain repair, while the Cend1 minimal promoter is a valuable tool for neuron-specific gene delivery in the CNS. Mice with Cend1 genetic ablation display increased NPC proliferation, decreased migration, and higher levels of apoptosis during development. As a result, they show in the adult brain deficits in a range of motor and nonmotor behaviors arising from irregularities in cerebellar cortex lamination and impaired Purkinje cell differentiation as well as a paucity in GABAergic interneurons of the cerebral cortex, hippocampus, and amygdala. Taken together, these studies highlight the necessity for Cend1 expression in the formation of a structurally and functionally normal brain.

Co-administration of Anti microRNA-124 and -137 Oligonucleotides Prevents Hippocampal Neural Stem Cell Loss Upon Non-convulsive Seizures

Convulsive seizures promote adult hippocampal neurogenesis (AHN) through a transient activation of neural stem/progenitor cells (NSPCs) in the subgranular zone (SGZ) of the dentate gyrus (DG). However, in a significant population of epilepsy patients, non-convulsive seizures (ncSZ) are observed. The response of NSPCs to non-convulsive seizure induction has not been characterized before. We here studied first the short-term effects of controlled seizure induction on NSPCs fate and identity. We induced seizures of controlled intensity by intrahippocampally injecting increasing doses of the chemoconvulsant kainic acid (KA) and analyzed their effect on subdural EEG recordings, hippocampal structure, NSPC proliferation and the number and location of immature neurons shortly after seizure onset. After establishing a KA dose that elicits ncSZ, we then analyzed the effects of ncSZ on NSPC proliferation and NSC identity in the hippocampus. ncSZ specifically triggered neuroblast proliferation, but did not induce proliferation of NSPCs in the SGZ, 3 days post seizure onset. However, ncSZ induced significant changes in NSPC composition in the hippocampus, including the generation of reactive NSCs. Interestingly, intrahippocampal injection of a combination of two anti microRNA oligonucleotides targeting microRNA-124 and -137 normalized neuroblast proliferation and prevented NSC loss in the DG upon ncSZ. Our results show for the first time that ncSZ induce significant changes in neuroblast proliferation and NSC composition. Simultaneous antagonism of both microRNA-124 and -137 rescued seizure-induced alterations in NSPC, supporting their coordinated action in the regulation of NSC fate and proliferation and their potential for future seizure therapies.

Do Neural Stem Cells Have a Choice? Heterogenic Outcome of Cell Fate Acquisition in Different Injury Models

The adult mammalian central nervous system (CNS) is generally considered as repair restricted organ with limited capacities to regenerate lost cells and to successfully integrate them into damaged nerve tracts. Despite the presence of endogenous immature cell types that can be activated upon injury or in disease cell replacement generally remains insufficient, undirected, or lost cell types are not properly generated. This limitation also accounts for the myelin repair capacity that still constitutes the default regenerative activity at least in inflammatory demyelinating conditions. Ever since the discovery of endogenous neural stem cells (NSCs) residing within specific niches of the adult brain, as well as the description of procedures to either isolate and propagate or artificially induce NSCs from various origins ex vivo, the field has been rejuvenated. Various sources of NSCs have been investigated and applied in current neuropathological paradigms aiming at the replacement of lost cells and the restoration of functionality based on successful integration. Whereas directing and supporting stem cells residing in brain niches constitutes one possible approach many investigations addressed their potential upon transplantation. Given the heterogeneity of these studies related to the nature of grafted cells, the local CNS environment, and applied implantation procedures we here set out to review and compare their applied protocols in order to evaluate rate-limiting parameters. Based on our compilation, we conclude that in healthy CNS tissue region specific cues dominate cell fate decisions. However, although increasing evidence points to the capacity of transplanted NSCs to reflect the regenerative need of an injury environment, a still heterogenic picture emerges when analyzing transplantation outcomes in injury or disease models. These are likely due to methodological differences despite preserved injury environments. Based on this meta-analysis, we suggest future NSC transplantation experiments to be conducted in a more comparable way to previous studies and that subsequent analyses must emphasize regional heterogeneity such as accounting for differences in gray versus white matter.

Changes in the Blood-Brain Barrier Function Are Associated With Hippocampal Neuron Death in a Kainic Acid Mouse Model of Epilepsy

The kainic acid (KA)-induced epilepsy experimental model is widely used to study the mechanisms underlying this disorder. Recently, the blood-brain barrier (BBB) has become an innovative alternative treatment target for epilepsy patients. KA causes neuronal injury and BBB damage in this experimental epilepsy model but the mechanisms underlying epilepsy-related neuronal injury, autophagy, and BBB damage remain unclear. Therefore, the present study investigated the relationships among neuronal injury, the expressions of autophagy-related proteins, and changes in BBB-related proteins during the acute phase of epilepsy to further understand the mechanisms and pharmacotherapy of epilepsy. NeuN immunohistochemistry and Fluoro-Jade B (FJ-B) staining in the hippocampal CA3 region revealed that neuronal death induced by intraventricular injections of 10 μg/kg KA was greater than that induced by 3 μg/kg KA. In addition, there were transient increases in the levels of microtubule-associated protein light chain 3-II (LC3I/II) and Beclin-1, which are autophagy-related proteins involved in neuronal death, in this region 24 h after the administration of 10 μg/kg KA. There were also morphological changes in BBB-related cells such as astrocytes, endothelial cells (ECs), and tight junctions (TJs). More specifically, there was a significant increase in the activation of astrocytes 72 h after the administration of 10 μg/kg KA as well as continuous increases in the expressions of platelet endothelial cell adhesion molecule-1 (PECAM-1) and BBB-related TJ proteins (Zonula occludens-1 and Claudin-5) until 72 h after KA treatment. These results suggest that the overexpression of autophagy-related proteins and astrocytes and transient increases in the expressions of BBB-related TJ proteins may be closely related to autophagic neuronal injury. These findings provide a basis for the identification of novel therapeutic targets for patients with epilepsy.

Satb2 ablation decreases PTZ-induced seizure susceptibility and pyramidal neuronal excitability

Special AT-rich sequence-binding protein 2 (Satb2) is a transcriptional regulator and people with SATB2 mutation or duplication could display epilepsy. However, whether Satb2 is related with epilepsy and its mechanisms are largely unexplored. Here we found that the expression of Satb2 was decreased following the neuronal hyperactivities. Ablation of Satb2 in mice would decrease incidence and stage of seizure induced by intraperitoneal injection of pentylenetetrazol (PTZ). At cellular levels, we found pyramidal neuronal excitability and excitatory synaptic inputs in CA1 were decreased in Satb2 mutant mice. Taking together, we proved that deletion of Satb2 in mice increased PTZ seizure threshold probably by modulating neuronal excitability.

Sevoflurane Affects Oxidative Stress and Alters Apoptosis Status in Children and Cultured Neural Stem Cells

Anesthesia-induced neurotoxicity in immature animals has raised concerns about similar effects occurring in young children. Our study investigated two commonly used anesthetics-sevoflurane and propofol-for neurotoxicity in young children. Forty-seven children (aged 12-36 months) undergoing hypospadias repair surgery were randomized to receive sevoflurane (SG, n = 24) or propofol (PG, n = 23) general anesthesia. Venous blood was collected at three different times-immediately after induction, 2 h, and 3 days after surgery. The cellular portion was assessed for antioxidant defense and DNA damage, using enzyme assay kits and qRT-PCR, respectively, while serum was used to treat cultured neural stem cells (NSCs). MTT assay and TUNEL staining were performed, and the mRNA levels of antioxidant enzymes and apoptosis indicators were evaluated by qRT-PCR. Antioxidant defense and apoptosis status in the SG group were significantly higher than in the PG group at 2 h after surgery. Additionally, exposure of NSCs to postoperative serum of the SG group resulted in decreased cell density and viability, increased TUNEL-positive cells, elevated mRNA levels of antioxidant enzymes, and cleaved caspase-3 expression. Our data shows for the first time that in young children, administration of sevoflurane, but not propofol, leads to temporally increased antioxidant defense and apoptosis status as well as damage of NSCs.

Protein-Induced Pluripotent Stem Cells Ameliorate Cognitive Dysfunction and Reduce Aβ Deposition in a Mouse Model of Alzheimer's Disease

Transplantation of stem cells into the brain attenuates functional deficits in the central nervous system via cell replacement, the release of specific neurotransmitters, and the production of neurotrophic factors. To identify patient‐specific and safe stem cells for treating Alzheimer's disease (AD), we generated induced pluripotent stem cells (iPSCs) derived from mouse skin fibroblasts by treating protein extracts of embryonic stem cells. These reprogrammed cells were pluripotent but nontumorigenic. Here, we report that protein‐iPSCs differentiated into glial cells and decreased plaque depositions in the 5XFAD transgenic AD mouse model. We also found that transplanted protein‐iPSCs mitigated the cognitive dysfunction observed in these mice. Proteomic analysis revealed that oligodendrocyte‐related genes were upregulated in brains injected with protein‐iPSCs, providing new insights into the potential function of protein‐iPSCs. Taken together, our data indicate that protein‐iPSCs might be a promising therapeutic approach for AD. Stem Cells Translational Medicine2017;6:293–305

Conditional Disabled-1 Deletion in Mice Alters Hippocampal Neurogenesis and Reduces Seizure Threshold

Many animal models of temporal lobe epilepsy (TLE) exhibit altered neurogenesis arising from progenitors within the dentate gyrus subgranular zone (SGZ). Aberrant integration of new neurons into the existing circuit is thought to contribute to epileptogenesis. In particular, adult-born neurons that exhibit ectopic migration and hilar basal dendrites (HBDs) are suggested to be pro-epileptogenic. Loss of reelin signaling may contribute to these morphological changes in patients with epilepsy. We previously demonstrated that conditional deletion of the reelin adaptor protein, disabled-1 (Dab1), from postnatal mouse SGZ progenitors generated dentate granule cells (DGCs) with abnormal dendritic development and ectopic placement. To determine whether the early postnatal loss of reelin signaling is epileptogenic, we conditionally deleted Dab1 in neural progenitors and their progeny on postnatal days 7–8 and performed chronic video-EEG recordings 8–10 weeks later. Dab1-deficient mice did not have spontaneous seizures but exhibited interictal epileptiform abnormalities and a significantly reduced latency to pilocarpine-induced status epilepticus. After chemoconvulsant treatment, over 90% of mice deficient for Dab1 developed generalized motor convulsions with tonic-clonic movements, rearing, and falling compared to <20% of wild-type mice. Recombination efficiency, measured by Cre reporter expression, inversely correlated with time to the first sustained seizure. These pro-epileptogenic changes were associated with decreased neurogenesis and increased numbers of hilar ectopic DGCs. Interestingly, neurons co-expressing the Cre reporter comprised a fraction of these hilar ectopic DGCs cells, suggesting a non-cell autonomous effect for the loss of reelin signaling. We also noted a dispersion of the CA1 pyramidal layer, likely due to hypomorphic effects of the conditional Dab1 allele, but this abnormality did not correlate with seizure susceptibility. These findings suggest that the misplacement or reduction of postnatally-generated DGCs contributes to aberrant circuit development and hyperexcitability, but aberrant neurogenesis after conditional Dab1 deletion alone is not sufficient to produce spontaneous seizures.

Effect of Astragaloside IV on Neural Stem Cell Transplantation in Alzheimer's Disease Rat Models

Stem cell-based therapy is a promising treatment strategy for neurodegenerative diseases such as Alzheimer's disease (AD). However, the mechanism underlying the maintenance of renewal and replacement capabilities of endogenous progenitor cells or engrafted stem cells in a pathological environment remains elusive. To investigate the effect of astragaloside IV (ASI) on the proliferation and differentiation of the engrafted neural stem cells (NSCs), we cultured NSCs from the hippocampus of E14 rat embryos, treated the cells with ASI, and then transplanted the cells into the hippocampus of rat AD models. In vitro experimentation showed that 10⁻⁵ M ASI induced NSCs to differentiate into β-tubulin III⁺ and GFAP⁺ cells. NSCs transplantation into rat AD models resulted in improvements in learning and memory, especially in the ASI-treated groups. ASI treatment resulted in an increase in the number of β-tubulin III⁺ cells in the hippocampus. Further investigation showed that ASI inhibited PS1 expression in vitro and in vivo. The high-dose ASI downregulated the Notch intracellular domain, whereas the low-dose ASI increased Notch-1 and NICD. In conclusion, ASI treatment resulted in improvements in learning and memory of AD models by promoting NSC proliferation and differentiation partly through the Notch signal pathway.

Neural stem/progenitor cells differentiate into oligodendrocytes, reduce inflammation, and ameliorate learning deficits after transplantation in a mouse model of traumatic brain injury

The central nervous system has limited capacity for regeneration after traumatic injury. Transplantation of neural stem/progenitor cells (NPCs) has been proposed as a potential therapeutic approach while insulin-like growth factor I (IGF-I) has neuroprotective properties following various experimental insults to the nervous system. We have previously shown that NPCs transduced with a lentiviral vector for IGF-I overexpression have an enhanced ability to give rise to neurons in vitro but also in vivo, upon transplantation in a mouse model of temporal lobe epilepsy. Here we studied the regenerative potential of NPCs, IGF-I-transduced or not, in a mouse model of hippocampal mechanical injury. NPC transplantation, with or without IGF-I transduction, rescued the injury-induced spatial learning deficits as revealed in the Morris Water Maze. Moreover, it had beneficial effects on the host tissue by reducing astroglial activation and microglial/macrophage accumulation while enhancing generation of endogenous oligodendrocyte precursor cells. One or two months after transplantation the grafted NPCs had migrated towards the lesion site and in the neighboring myelin-rich regions. Transplanted cells differentiated toward the oligodendroglial, but not the neuronal or astrocytic lineages, expressing the early and late oligodendrocyte markers NG2, Olig2, and CNPase. The newly generated oligodendrocytes reached maturity and formed myelin internodes. Our current and previous observations illustrate the high plasticity of transplanted NPCs which can acquire injury-dependent phenotypes within the host CNS, supporting the fact that reciprocal interactions between transplanted cells and the host tissue are an important factor to be considered when designing prospective cell-based therapies for CNS degenerative conditions.

Kainic Acid-Induced Excitotoxicity Experimental Model: Protective Merits of Natural Products and Plant Extracts

Excitotoxicity is well recognized as a major pathological process of neuronal death in neurodegenerative diseases involving the central nervous system (CNS). In the animal models of neurodegeneration, excitotoxicity is commonly induced experimentally by chemical convulsants, particularly kainic acid (KA). KA-induced excitotoxicity in rodent models has been shown to result in seizures, behavioral changes, oxidative stress, glial activation, inflammatory mediator production, endoplasmic reticulum stress, mitochondrial dysfunction, and selective neurodegeneration in the brain upon KA administration. Recently, there is an emerging trend to search for natural sources to combat against excitotoxicity-associated neurodegenerative diseases. Natural products and plant extracts had attracted a considerable amount of attention because of their reported beneficial effects on the CNS, particularly their neuroprotective effect against excitotoxicity. They provide significant reduction and/or protection against the development and progression of acute and chronic neurodegeneration. This indicates that natural products and plants extracts may be useful in protecting against excitotoxicity-associated neurodegeneration. Thus, targeting of multiple pathways simultaneously may be the strategy to maximize the neuroprotection effect. This review summarizes the mechanisms involved in KA-induced excitotoxicity and attempts to collate the various researches related to the protective effect of natural products and plant extracts in the KA model of neurodegeneration.

Kainate-induced epileptogenesis alters circular hole board learning strategy but not the performance of C57BL/6J mice

Patients with mesial temporal lobe epilepsy (mTLE) frequently show cognitive deficits. However, the relation between mTLE and cognitive impairment is poorly understood. To gain more insight into epilepsy-associated alterations in cognitive performance, we studied the spatial learning of C57BL/6J mice five weeks after kainate-induced status epilepticus (SE). Typically, structural hippocampal rearrangements take place within five weeks after SE. Mice were monitored by exposing them to four tasks with a focus on spatial memory and anxiety: the circular hole board, modified hole board, novel object-placement task, and elevated plus maze. On the circular hole board, animals showed a higher preference for hippocampus-independent strategies after SE. In contrast, no change in strategy was seen on the modified hole board, but animals with SE were able to finish the task more often. Animals did not have an increased preference for a relocated object in the novel object-placement task but showed an increased locomotion after SE. No indications for altered anxiety were found when tested on the elevated plus maze following SE. These data suggest that the circular hole board is a well-suited paradigm to detect subtle SE-induced hippocampal deficits.

Hippocampal injury-induced cognitive and mood dysfunction, altered neurogenesis, and epilepsy: can early neural stem cell grafting intervention provide protection?

Damage to the hippocampus can occur through many causes including head trauma, ischemia, stroke, status epilepticus, and Alzheimer's disease. Certain changes such as increased levels of neurogenesis and elevated concentrations of multiple neurotrophic factors that ensue in the acute phase after injury seem beneficial for restraining hippocampal dysfunction. However, many alterations that arise in the intermediate to chronic phase after injury such as abnormal migration of newly born neurons, aberrant synaptic reorganization, progressive loss of inhibitory gamma-amino butyric acid positive interneurons including those expressing reelin, greatly declined neurogenesis, and sustained inflammation are detrimental. Consequently, the net effect of postinjury plasticity in the hippocampus remains inadequate for promoting significant functional recovery. Hence, ideal therapeutic interventions ought to be efficient for restraining these detrimental changes in order to block the propensity of most hippocampal injuries to evolve into learning deficits, memory dysfunction, depression, and temporal lobe epilepsy. Neural stem cell (NSC) grafting into the hippocampus early after injury appears alluring from this perspective because several recent studies have demonstrated the therapeutic value of this intervention, especially for preventing/easing memory dysfunction, depression, and temporal lobe epilepsy development in the chronic phase after injury. These beneficial effects of NSC grafting appeared to be mediated through considerable modulation of aberrant hippocampal postinjury plasticity with additions of new inhibitory gamma-amino butyric acid positive interneurons and astrocytes secreting a variety of neurotrophic factors and anticonvulsant proteins. This review presents advancements made in NSC grafting therapy for treating hippocampal injury in animal models of excitotoxic injury, traumatic brain injury, Alzheimer's disease, and status epilepticus; potential mechanisms of functional recovery mediated by NSC grafts placed early after hippocampal injury; and issues that need to be resolved prior to considering clinical application of NSC grafting for hippocampal injury.

Advantages of repeated low dose against single high dose of kainate in C57BL/6J mouse model of status epilepticus: behavioral and electroencephalographic studies

A refined kainate (KA) C57BL/6J mouse model of status epilepticus (SE) using a repeated low dose (RLD) of KA (5 mg/kg, intraperitoneal; at 30 min intervals) was compared with the established single high dose (SHD) of KA (20 mg/kg, intraperitoneal) model. In the RLD group, increased duration of convulsive motor seizures (CMS, Racine scale stage ≥3) with a significant reduction in mortality from 21% to 6% and decreased variability in seizure severity between animals/batches were observed when compared to the SHD group. There was a significant increase in the percentage of animals that reached stage-5 seizures (65% versus 96%) in the RLD group. Integrated real-time video-EEG analysis of both groups, using NeuroScore software, revealed stage-specific spikes and power spectral density characteristics. When the seizures progressed from non-convulsive seizures (NCS, stage 1-2) to CMS (stage 3-5), the delta power decreased which was followed by an increase in gamma and beta power. A transient increase in alpha and sigma power marked the transition from NCS to CMS with characteristic 'high frequency trigger' spikes on the EEG, which had no behavioral expression. During SE the spike rate was higher in the RLD group than in the SHD group. Overall these results confirm that RLD of KA is a more robust and consistent mouse model of SE than the SHD of KA mouse model.

Microarray Analysis of mRNA and MicroRNA Expression Profile Reveals the Role of β -Sitosterol-D-glucoside in the Proliferation of Neural Stem Cell

Neural stem cells (NSCs) are self-regenerating cells, but their regenerative capacity is limited. The present study was conducted to investigate the effect of β-sitosterol-D-glucoside (BSSG) on the proliferation of hippocampal NSCs and to determine the corresponding molecular mechanism. Results of CCK-8 assay showed that BSSG significantly increased NSC proliferation and the effectiveness of BSSG was similar to that of basic fibroblast growth factor and epidermal growth factor. mRNA expression profiling showed that 960 genes were differentially expressed after NSCs were treated with BSSG. Among the 960 genes, IGF1 is considered as a key regulatory gene that functionally promotes NSC proliferation. MicroRNA (miRNA) expression profiling indicated that 30 and 84 miRNAs were upregulated and downregulated, respectively. miRNA-mRNA relevance analysis revealed that numerous mRNAs including IGF1 mRNA were negatively regulated by miRNAs with decreased expression, thereby increasing the corresponding mRNA expression. The increased expression of IGF1 protein was validated by ELISA. Picropodophyllin (PPP, an inhibitor of IGF-1R) inhibition test confirmed that the proliferation-enhancing effect depended on IGF1. This study provided information about BSSG as an efficient and inexpensive growth factor alternative, of which the effect is closely involved in IGF1.

Receptor tyrosine kinase (RTK) signalling in the control of neural stem and progenitor cell (NSPC) development

Important developmental responses are elicited in neural stem and progenitor cells (NSPC) by activation of the receptor tyrosine kinases (RTK), including the fibroblast growth factor receptors, epidermal growth factor receptor, platelet-derived growth factor receptors and insulin-like growth factor receptor (IGF1R). Signalling through these RTK is necessary and sufficient for driving a number of developmental processes in the central nervous system. Within each of the four RTK families discussed here, receptors are activated by sets of ligands that do not cross-activate receptors of the other three families, and therefore, their activation can be independently regulated by ligand availability. These RTK pathways converge on a conserved core of signalling molecules, but differences between the receptors in utilisation of signalling molecules and molecular adaptors for intracellular signal propagation become increasingly apparent. Intracellular inhibitors of RTK signalling are widely involved in the regulation of developmental signalling in NSPC and often determine developmental outcomes of RTK activation. In addition, cellular responses of NSPC to the activation of a given RTK may be significantly modulated by signal strength. Cellular propensity to respond also plays a role in developmental outcomes of RTK signalling. In combination, these mechanisms regulate the balance between NSPC maintenance and differentiation during development and in adulthood. Attribution of particular developmental responses of NSPC to specific pathways of RTK signalling becomes increasingly elucidated. Co-activation of several RTK in developing NSPC is common, and analysis of co-operation between their signalling pathways may advance knowledge of RTK role in NSPC development.