Neuronal replacement from endogenous precursors in the adult brain after stroke

Alpha‑Asarone Ameliorates Neuronal Injury After Ischemic Stroke and Hemorrhagic Transformation by Attenuating Blood-Brain Barrier Destruction, Promoting Neurogenesis, and Inhibiting Neuroinflammation

Recombinant tissue-type plasminogen activator (rt-PA), the primary drug for acute ischemic stroke (IS), has a narrow therapeutic window and carries a potential risk of hemorrhagic transformation (HT). Without rt-PA administration, patients may suffer permanent cerebral ischemia. Alpha-asarone (ASA), a natural compound derived from Acorus tatarinowii Schott, exhibits diverse neuropharmacological effects. This study aims to investigate whether ASA could improve outcomes in IS and be used to mitigate HT induced by rt-PA. We employed models of permanent middle cerebral artery occlusion (pMCAO) and photothrombotic cortical injury (PCI) to investigate both the therapeutic efficacy and underlying mechanisms of ASA during the acute and recovery periods following IS, respectively. Additionally, Sprague-Dawley rats were subjected to rt-PA treatment at 6-h post-PCI to mimic HT (rt-PA-HT). Our results revealed three key findings: (1) ASA demonstrated therapeutic effects in the acute phase of pMCAO rats by alleviating blood-brain barrier damage through inhibition of glial cell-mediated neuroinflammation; (2) administration of ASA 24 h after stroke ameliorated the neurological damage during the recovery phase in PCI mice by promoting neurogenesis via activation of the BDNF/ERK/CREB signaling pathway; (3) ASA attenuated rt-PA-HT injury by modulating the NLRP3/Caspase1/IL-1β and IL-18 pathways. Overall, our findings suggest that ASA mitigates neuronal injury following IS and HT, positioning it as a promising candidate for treating these conditions.

Circulatory factors in stroke protection and recovery

Over the past decade, the management of acute ischemic stroke has undergone a paradigm shift, especially a longer time-window and a wider indication for endovascular treatments. However, many patients still have long-term dysfunction despite the best medical care at present. Based on findings from innovative proteomic and transcriptomic technologies, researchers have identified an array of novel or previously underappreciated circulatory factors that play pivotal roles in mediating post-injuries brain communication. Thus, the previous concept of the brain as a privileged compartment isolated from the rest of the body has been replaced by the novel consensus that brain bidirectionally interacts with the other organs after brain diseases. In this review, we make a summary of several axes that connect the brain with the rest of the body after stroke. More importantly, we summarize several circulatory factors that play pivotal roles in fostering post-stroke functional recovery in the chronic stage. Special attention is given to the instrumental role of circulatory signals, positing them as significant contributors to the complex process of brain function recovery and as translational therapeutic targets for ischemic stroke in future studies.

The immunomodulatory effects of GLP-1 receptor agonists in neurogenerative diseases and ischemic stroke treatment

Glucagon-like peptide-1 (GLP-1) receptor is widely distributed in the digestive system, cardiovascular system, adipose tissue and central nervous system. Numerous GLP-1 receptor-targeting drugs have been investigated in clinical studies for various indications, including type 2 diabetes and obesity (accounts for 70% of the total studies), non-alcoholic steatohepatitis, Alzheimer's disease, and Parkinson's disease. This review presented fundamental information regarding two categories of GLP-1 receptor agonists (GLP-1RAs): peptide-based and small molecule compounds, and elaborated their potential neuroprotective effects by inhibiting neuroinflammation, reducing neuronal apoptosis, and ultimately improving cognitive function in various neurodegenerative diseases. As a new hypoglycemic drug, GLP-1RA has a unique role in reducing the concurrent risk of stroke in T2D patients. Given the infiltration of various peripheral immune cells into brain tissue, particularly in the areas surrounding the infarct lesion, we further investigated the potential immune regulatory mechanisms. GLP-1RA could not only facilitate the M2 polarization of microglia through both direct and indirect pathways, but also modulate the quantity and function of T cell subtypes, including CD4, CD8, and regulatory T cells, resulting into the inhibition of inflammatory responses and the promotion of neuronal regeneration through interleukin-10 secretion. Therefore, we believe that the "Tregs-microglia-neuron/neural precursor cells" axis is instrumental in mediating immune suppression and neuroprotection in the context of ischemic stroke. Given the benefits of rapid diffusion, favorable blood-brain barrier permeability and versatile administration routes, these small molecule compounds will be one of the important candidates of GLP-1RA. We look forward to the further clinical evidence of small molecule GLP-1RA intervention in ischemic stroke or T2D complicated by ischemic stroke.

Structural pathways related to the subventricular zone are decreased in volume with altered microstructure in young adult males with autism spectrum disorder

Autism spectrum disorder is a neurodevelopmental condition characterized by reduced social communication and repetitive behaviors. Altered neurogenesis, including disturbed neuronal migration, has been implicated in autism spectrum disorder. Using diffusion MRI, we previously identified neuronal migration pathways in the human fetal brain and hypothesized that similar pathways persist into adulthood, with differences in volume and microstructural characteristics between individuals with autism spectrum disorder and controls. We analyzed diffusion MRI-based tractography of subventricular zone-related pathways in 15 young adult men with autism spectrum disorder and 18 controls at Massachusetts General Hospital, with validation through the Autism Imaging Data Exchange II dataset. Participants with autism spectrum disorder had reduced subventricular zone pathway volumes and fractional anisotropy compared to controls. Furthermore, subventricular zone pathway volume was positively correlated (r: 0.68; 95% CI: 0.25 to 0.88) with symptom severity, suggesting that individuals with more severe symptoms tended to have larger subventricular zone pathway volumes, normalized by brain size. Analysis of the Autism Imaging Data Exchange cohort confirmed these findings of reduced subventricular zone pathway volumes in autism spectrum disorder. While some of these pathways may potentially include inaccurately disconnected pathways that go through the subventricular zone, our results suggest that diffusion MRI-based tractography pathways anatomically linked to the periventricular region are associated with certain symptom types in adult males with autism spectrum disorder.

Ghrelin promotes neurologic recovery and neurogenesis in the chronic phase after experimental stroke

BACKGROUND

The neuroprotective and proangiogenic potential of ghrelin in acute ischemic stroke has been demonstrated in experimental studies. However, the transferability of these results is limited as ghrelin was administered either before or very early after stroke onset and follow-up was limited to the first days after stroke. The aim of this study was therefore to close and extend this knowledge gap. To this end, we investigated the effect of ghrelin in two different translational animal models, one investigating acute and one investigating long-term structural and functional recovery after experimental stroke.

METHODS

Middle cerebral artery occlusion (MCAO) or photothrombotic stroke was induced in 65 adult male Wistar rats. Eleven sham-operated animals served as controls. The rats were treated with either ghrelin, the ghrelin receptor antagonist [D-Lys]-GHRP-6 or a control substance. Up to four weeks after ischemia, behavioral tests such as the cylinder test, the tape removal test, and the rotarod test were performed to examine sensorimotor deficits, and the Morris water maze was performed to examine effects on the acquisition and consolidation of new memories. The structural outcome was determined by a differential analysis of neurogenesis in relation to survival and proliferation of newborn neurons in the post-ischemic brain, angiogenesis and determination of infarct size.

RESULTS

Ghrelin treatment improved motor and somatosensory functions and preserved the consolidation of new memories after photothrombotic stroke. As a structural correlate, long-term survival and sustained proliferation of neuronal cells after stroke was significantly increased in ghrelin-treated rats, while angiogenesis remained unaffected. In contrast to these neuroregenerative mechanisms, ghrelin did not induce immediate neuroprotective effects after MCAO.

CONCLUSIONS

Our results suggest that ghrelin has a significant pro-neuroregenerative effect by enhancing long-term survival and sustained proliferation of neurons in the dentate gyrus and peri-infarct area, thus promoting functional recovery. Overall, ghrelin represents a promising target in the subacute and chronic phase after ischemic stroke.

Brain pericytes and perivascular fibroblasts are stromal progenitors with dual functions in cerebrovascular regeneration after stroke

Functional revascularization is key to stroke recovery and requires remodeling and regeneration of blood vessels around which is located the brain's only stromal compartment. Stromal progenitor cells (SPCs) are critical for tissue regeneration following injury in many organs, yet their identity in the brain remains elusive. Here we show that the perivascular niche of brain SPCs includes pericytes, venular smooth muscle cells and perivascular fibroblasts that together help cerebral microvasculature regenerate following experimental stroke. Ischemic injury triggers amplification of pericytes and perivascular fibroblasts in the infarct region where they associate with endothelial cells inside a reactive astrocyte border. Fate-tracking of Hic1+ SPCs uncovered a transient functional and transcriptional phenotype of stroke-activated pericytes and perivascular fibroblasts. Both populations of these cells remained segregated, displaying distinct angiogenic and fibrogenic profiles. Therefore, pericytes and perivascular fibroblasts are distinct subpopulations of SPCs in the adult brain that coordinate revascularization and scar formation after injury.

Ginsenoside Rb3 Promotes Opa1-Mediated Regenerative Neurogenesis via Activating the Ido1 Pathway in Ischemic Stroke

The activation of neural stem cells (NSCs) residing in the subventricular zone (SVZ) and dentate gyrus (DG) has been shown to promote the restoration of damaged brain tissues. Ginsenoside Rb3 (Rb3) is a bioactive substance known for its pharmacological properties in treating neurological disorders. This study investigated the effects of Rb3 on neural regeneration following ischaemic stroke (IS) and the underlying mechanisms involved. Male C57BL/6 mice were utilized and were subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). Post-ischemia, Rb3 was administered through intraperitoneal (i.p.) injection for either 7 or 28 days. The promotion of Rb3 on regenerative neurogenesis was detected by immunofluorescence staining. NSCs were pretreated with different concentrations of Rb3 for 24 h before oxygen-glucose deprivation/reoxygenation (OGD/R) exposure. Afterward, immunofluorescence staining and flow cytometry were used to detect the migration and proliferation of Rb3 in OGD/R-induced NSCs. Furthermore, Adeno-associated virus (AAV) transduction experiments, siRNA transfection experiments, gene knockout experiments, targeted metabolomics analysis, molecular dynamics simulation, cellular thermal shift assay (CETSA), and drug affinity responsive target stability (DARTS) assays were used to explore the promotion and mechanism of Rb3 on regenerative neurogenesis following IS. Rb3 promoted Opa1-mediated NSCs migration and proliferation. Knockdown of Opa1 blunted the above-promoting effects of Rb3 in both the brains of ischemia-reperfusion (I/R)-treated mice and OGD/R-treated NSCs. Mechanistically, targeted metabolomics, molecular dynamics, molecular docking, CETAS, and DARTS experiments showed that Rb3 promoted Opa1-mediated neural regeneration required the activation of Ido1 and that Ido1 served as a direct target of Rb3 to repair I/R injury. Moreover, studies in siRNA-mediated knockdown and KO mice revealed that inhibition of Ido1 attenuated the enhancing effect of Rb3 on mitochondrial fusion. Our study provides novel evidence that Rb3 promotes neurogenesis through an Ido1/Opa1-mediated pathway involving the interaction between Rb3 and Ido1, leading to improved long-term neurological function. These results indicate that Rb3 or other mitochondrial fusion promoters could be a potential neurorestorative strategy for regenerative neurogenesis following IS.

Neurological function is restored post-ischemic stroke in zebrafish, with aging exerting a deleterious effect on its pathology

Ischemic stroke (IS) is a pathological condition characterized by the cessation of blood flow due to factors such as thrombosis, inflicting severe damage to the cranial nervous system and resulting in numerous disabilities including memory impairments and hemiplegia. Despite the critical nature of this condition, therapeutic options remain limited, with a pressing challenge being the development of treatments aimed at restoring neurological function. In this study, we leveraged zebrafish, renowned for their exceptional regenerative capabilities, to analyze the pathology of IS and the subsequent recovery process. We induced photothrombosis in the telencephalon utilizing rose bengal and conducted a temporal investigation of changes in cerebral vascular function and learning ability. Our findings revealed that blood flow in young zebrafish was restored approximately 7 days post-IS induction (dpi), with brain function recuperating by 14 dpi. Furthermore, we observed an escalation in the expression of the neural stem marker gene at 3dpi, followed by an upregulation of the differentiated neuron marker at 7 and 14dpi. In the aged IS model, symptoms were exacerbated. While cerebral blood flow was restored in 7 days, similar to young zebrafish, the recovery of learning ability was protracted in aged fish. Moreover, an upregulation of the differentiated neuron marker seen in young fish was not observed in the aged model. Collectively, our analysis of the zebrafish IS model and its comparison with existing rodent models may lay the groundwork for novel IS treatment strategies. Furthermore, the zebrafish IS model may prove beneficial for analyzing the impact of aging on the pathology of IS and the recovery process.

Electroconvulsive shock and transcranial magnetic stimulation do not alter the survival or spine density of adult-born striatal neurons

Adult neurogenesis has most often been studied in the hippocampus and subventricular zone-olfactory bulb, where newborn neurons contribute to a variety of behaviors. A handful of studies have also investigated adult neurogenesis in other brain regions, but relatively little is known about the properties of neurons added to non-canonical areas. One such region is the striatum. Adult-born striatal neurons have been described in both rodents and humans, but the regulation of these neurons is poorly understood. Since striatal dysfunction occurs in Parkinson's disease, which is amenable to neurostimulation therapies, we investigated whether electroconvulsive shock (ECS) or transcranial magnetic stimulation (rTMS) modulate neuroplasticity of adult-born striatal neurons. Adult-born cells were labelled in transgenic mice and 8 days later mice were given 10 stimulations over the course of 3 weeks. Adult-born striatal neurons were consistently observed in all groups. Their dendritic morphology and expression of DARPP32 and NeuN indicated a medium spiny neuron phenotype. However, neither ECS nor rTMS altered the number of new neurons, and both treatments also had no effect on the density of dendritic spines compared to unstimulated controls. These results suggest that neither ECS nor rTMS alter early neuronal survival or morphological plasticity at postsynaptic sites in the striatum.

Adult Neurogenesis in the Subventricular Zone of Patients with Huntington's and Parkinson's Diseases and following Long-Term Treatment with Deep Brain Stimulation

OBJECTIVE

Parkinson's and Huntington's diseases are characterized by progressive neuronal loss. Previous studies using human postmortem tissues have shown the impact of neurodegenerative disorders on adult neurogenesis. The extent to which adult neural stem cells are activated in the subventricular zone and whether therapeutic treatments such as deep brain stimulation promote adult neurogenesis remains unclear. The goal of the present study is to assess adult neural stem cells activation and neurogenesis in the subventricular zone of patients with Huntington's and Parkinson's diseases who were treated or not by deep brain stimulation.

METHODS

Postmortem brain samples from Huntington's and Parkinson's disease patients who had received or not long-term deep brain stimulation of the subthalamic nucleus were used.

RESULTS

Our results indicate a significant increase in the thickness of the subventricular zone and in the density of proliferating cells and activated stem cells in the brain of Huntington's disease subjects and Parkinson's disease patients treated with deep brain stimulation. We also observed an increase in the density of immature neurons in the brain of these patients.

INTERPRETATION

Overall, our data indicate that long-term deep brain stimulation of the subthalamic nucleus promotes cell proliferation and neurogenesis in the subventricular zone that are reduced in Parkinson's disease. Taken together, our results also provide a detailed characterization of the cellular composition of the adult human subventricular zone and caudate nucleus in normal condition and in Parkinson's and Huntington's diseases and demonstrate the plasticity of these regions in response to neurodegeneration. ANN NEUROL 2025.

Traumatic Brain Injury Promotes Neurogenesis and Oligodendrogenesis in Subcortical Brain Regions of Mice

Traumatic brain injury (TBI) is one of the major causes of severe neurological disorders and long-term dysfunction in the nervous system. Besides inducing neurodegeneration, TBI alters stem cell activity and neurogenesis within primary neurogenic niches. However, the fate of dividing cells in other brain regions remains unclear despite offering potential targets for therapeutic intervention. Here, we investigated cell division and differentiation in non-neurogenic brain regions during the acute and delayed phases of TBI-induced neurodegeneration. We subjected mice to lateral fluid percussion injury (LFPI) to model TBI and analyzed them 1 or 7 weeks later. To assess cellular proliferation and differentiation, we administered 5-ethinyl-2'-deoxyuridine (EdU) and determined the number and identity of dividing cells 2 h later using markers of neuronal precursors and astro-, micro-, and oligodendroglia. Our results demonstrated a significant proliferative response in several brain regions at one week post-injury that notably diminished by seven weeks, except in the optic tract. In addition to active astro- and microgliosis, we detected oligodendrogenesis in the striatum and optic tract. Furthermore, we observed trauma-induced neurogenesis in the striatum. These findings suggest that subcortical structures, particularly the striatum and optic tract, may possess a potential for self-repair through neuronal regeneration and axon remyelination.

High spatial resolution gene expression profiling and characterization of neuroblasts migrating in the peri-injured cortex using photo-isolation chemistry

In the ventricular-subventricular-zone (V-SVZ) of the postnatal mammalian brain, immature neurons (neuroblasts) are generated from neural stem cells throughout their lifetime. These V-SVZ-derived neuroblasts normally migrate to the olfactory bulb through the rostral migratory stream, differentiate into interneurons, and are integrated into the preexisting olfactory circuit. When the brain is injured, some neuroblasts initiate migration toward the lesion and attempt to repair the damaged neuronal circuitry, but their low regeneration efficiency prevents functional recovery. Elucidation of the molecular basis of neuroblast migration toward lesions is expected to lead to the development of new therapeutic strategies for brain regenerative medicine. Here, we show gene expression profiles of neuroblasts migrating in the peri-injured cortex compared with those migrating in the V-SVZ using photo-isolation chemistry, a method for spatial transcriptome analysis. Differentially expressed gene analysis showed that the expression levels of 215 genes (97 upregulated and 118 downregulated genes) were significantly different in neuroblasts migrating in the peri-injured cortex from those migrating in the V-SVZ. Gene Ontology analysis revealed that in neuroblasts migrating in the peri-injured cortex, expression of genes involved in regulating migration direction and preventing cell death was upregulated, while the expression of genes involved in cell proliferation and maintenance of the immature state was downregulated. Indeed, neuroblasts migrating in the peri-injured cortex had significantly lower Cyclin D2 mRNA and Ki67 protein expression levels than those in the V-SVZ. In the injured brain, amoeboid microglia/macrophages expressed transforming growth factor-β (TGF-β), and neuroblasts migrating in the peri-injured cortex expressed TGF-β receptors. Experiments using primary cultured neuroblasts showed that application of TGF-β significantly decreased proliferating cells labeled with BrdU. These data suggest that the proliferative activity of neuroblasts migrating toward lesions is suppressed by TGF-β secreted from cells surrounding the lesion. This is the first comprehensive study characterizing the gene expression profiles of neuroblasts migrating in the peri-injured cortex.

The subventricular zone neurogenic niche provides adult born functional neurons to repair cortical brain injuries in response to diterpenoid therapy

INTRODUCTION

Neural stem cells from the subventricular zone (SVZ) neurogenic niche provide neurons that integrate in the olfactory bulb circuitry. However, in response to cortical injuries, the neurogenic activity of the SVZ is significantly altered, leading to increased number of neuroblasts with a modified migration pattern that leads cells towards the site of injury. Despite the increased neurogenesis and migration, many newly generated neurons fail to survive or functionally integrate into the cortical circuitry. Providing the injured area with the adequate signaling molecules may improve both migration and functional integration of newly generated neurons.

METHODS

In here, we have studied the effect of a diterpene with the capacity to induce neuregulin release at promoting neurogenesis in a murine model of cortical brain injury. Using green fluorescent protein expressing vectors we have labeled SVZ cells and have studied the migration of newly generated neuroblasts toward the injury in response the treatment. In addition, using electrophysiological recordings we have studied the differentiation of these neuroblasts into mature neurons and their functional integration into the cortical circuitry. We have studied their electrical properties, their morphology and cortical location.

RESULTS

We have found that EOF2 treatment of adult mice with mechanical cortical injuries facilitates the delivery of neuroblasts into these injuries. The newly generated neurons develop features of fully functional neurons. Our results show that the newly generated neurons receive electrical inputs, fire action potentials, and undergo complete differentiation into neurons recapitulating the stages that distinguish ontogenic differentiation. These neurons develop features representative of neurons belonging the cortical layer in which they are situated. We have also studied that EOF2 facilitates neuregulin release in SVZ cells, a signaling factor that promotes neuronal differentiation. Neuregulin is expressed in microglial cells that reach the injury in response to the damage and its release is increased by EOF2 treatment.

CONCLUSION

Promoting neuregulin release via diterpene treatment facilitates migration of SVZ-derived neuroblasts to cortical injuries stimulating their differentiation into mature functional neurons, which receive electrical inputs and develop features of cortical neurons. These findings highlight the role of diterpenoids as a potential therapy to repair cortical brain injuries.

Long non-coding RNA OIP5-AS1 protects neurons from ischemia-reperfusion injury and inhibits neuronal apoptosis through TAB-2

Ischemic stroke represents a highly perilous cerebrovascular disorder, involving a variety of complex pathophysiological mechanisms. OIP5 antisense RNA 1 (OIP5-AS1) is a long non-coding RNA (LncRNA) that has been shown to play a pivotal role in a variety of disease systems. However, there are relatively few studies on ischemic stroke. This research aimed to elucidate the direct impact of OIP5-AS1 on neuronal cells following cerebral ischemia-reperfusion. Our study revealed a significant reduction in OIP5-AS1 expression in mouse neurons following middle cerebral artery occlusion/reperfusion (MCAO/R). Overexpression of OIP5-AS1 in neurons inhibits neuronal apoptosis induced by cerebral ischemia-reperfusion injury (CIRI) and exerts a neuroprotective role. Mechanistically, OIP5-AS1 may play a neuroprotective role after CIRI by up-regulating the expression of TAK1 binding protein 2 (TAB-2), reducing neuronal mitochondrial damage, and inhibiting apoptosis. OIP5-AS1 may become a novel therapeutic target for ischemic stroke.

The Glial Scar: To Penetrate or Not for Motor Pathway Restoration?

Although notable progress has been made, restoring motor function from the brain to the muscles continues to be a substantial clinical challenge in motor neuron diseases/disorders such as spinal cord injury (SCI). While cell transplantation has been widely explored as a potential therapeutic method for reconstructing functional motor pathways, there remains considerable opportunity for enhancing its therapeutic effectiveness. We reviewed studies on motor pathway regeneration to identify molecular and ultrastructural cues that could enhance the efficacy of cell transplantation. While the glial scar is often cited as an intractable barrier to axon regeneration, this mainly applies to axons trying to penetrate its "core" to reach the opposite side. However, the glial scar exhibits a "duality," with an anti-regenerative core and a pro-regenerative "surface." This surface permissiveness is attributed to pro-regenerative molecules, such as laminin in the basement membrane (BM). Transplanting donor cells onto the BM, which forms plastically after injury, may significantly enhance the efficacy of cell transplantation. Specifically, forming detour pathways between transplanted cells and endogenous propriospinal neurons on the pro-regenerative BM may efficiently bypass the intractable scar core and promote motor pathway regeneration. We believe harnessing the tissue's innate repair capacity is crucial, and targeting post-injury plasticity in astrocytes and Schwann cells, especially those associated with the BM that has predominantly been overlooked in the field of SCI research, can advance motor system restoration to a new stage. A shift in cell delivery routes-from the traditional intra-parenchymal (InP) route to the transplantation of donor cells onto the pro-regenerative BM via the extra-parenchymal (ExP) route-may signify a transformative step forward in neuro-regeneration research. Practically, however, the complementary use of both InP and ExP methods may offer the most substantial benefit for restoring motor pathways. We aim for this review to deepen the understanding of cell transplantation and provide a framework for evaluating the efficacy of this therapeutic modality in comparison to others.

Stroke-induced neuroplasticity in spiny mice in the absence of tissue regeneration

Stroke is a major cause of disability for adults over 40 years of age. While research into animal models has prioritized treatments aimed at diminishing post-stroke damage, no studies have investigated the response to a severe stroke injury in a highly regenerative adult mammal. Here we investigate the effects of transient ischemia on adult spiny mice, Acomys cahirinus, due to their ability to regenerate multiple tissues without scarring. Transient middle cerebral artery occlusion was performed and Acomys showed rapid behavioral recovery post-stroke yet failed to regenerate impacted brain regions. An Acomys brain atlas in combination with functional (f)MRI demonstrated recovery coincides with neuroplasticity. The strength and quality of the global connectome are preserved post-injury with distinct contralateral and ipsilateral brain regions compensating for lost tissue. Thus, we propose Acomys recovers functionally from an ischemic stroke injury not by tissue regeneration but by altering its brain connectome.

A core scientific problem in the treatment of central nervous system diseases: newborn neurons

It has long been asserted that failure to recover from central nervous system diseases is due to the system's intricate structure and the regenerative incapacity of adult neurons. Yet over recent decades, numerous studies have established that endogenous neurogenesis occurs in the adult central nervous system, including humans'. This has challenged the long-held scientific consensus that the number of adult neurons remains constant, and that new central nervous system neurons cannot be created or renewed. Herein, we present a comprehensive overview of the alterations and regulatory mechanisms of endogenous neurogenesis following central nervous system injury, and describe novel treatment strategies that target endogenous neurogenesis and newborn neurons in the treatment of central nervous system injury. Central nervous system injury frequently results in alterations of endogenous neurogenesis, encompassing the activation, proliferation, ectopic migration, differentiation, and functional integration of endogenous neural stem cells. Because of the unfavorable local microenvironment, most activated neural stem cells differentiate into glial cells rather than neurons. Consequently, the injury-induced endogenous neurogenesis response is inadequate for repairing impaired neural function. Scientists have attempted to enhance endogenous neurogenesis using various strategies, including using neurotrophic factors, bioactive materials, and cell reprogramming techniques. Used alone or in combination, these therapeutic strategies can promote targeted migration of neural stem cells to an injured area, ensure their survival and differentiation into mature functional neurons, and facilitate their integration into the neural circuit. Thus can integration replenish lost neurons after central nervous system injury, by improving the local microenvironment. By regulating each phase of endogenous neurogenesis, endogenous neural stem cells can be harnessed to promote effective regeneration of newborn neurons. This offers a novel approach for treating central nervous system injury.

Blood-derived factors to brain communication in brain diseases

Brain diseases, mainly including acute brain injuries, neurodegenerative diseases, and mental disorders, have posed a significant threat to human health worldwide. Due to the limited regenerative capability and the existence of the blood-brain barrier, the brain was previously thought to be separated from the rest of the body. Currently, various cross-talks between the central nervous system and peripheral organs have been widely described, including the brain-gut axis, the brain-liver axis, the brain-skeletal muscle axis, and the brain-bone axis. Moreover, several lines of evidence indicate that leveraging systemic biology intervention approaches, including but not limited to lifestyle interventions, exercise, diet, blood administration, and peripheral immune responses, have demonstrated a significant influence on the progress and prognosis of brain diseases. The advancement of innovative proteomic and transcriptomic technologies has enriched our understanding of the nuanced interplay between peripheral organs and brain diseases. An array of novel or previously underappreciated blood-derived factors have been identified to play pivotal roles in mediating these communications. In this review, we provide a comprehensive summary of blood-to-brain communication following brain diseases. Special attention is given to the instrumental role of blood-derived signals, positing them as significant contributors to the complex process of brain diseases. The insights presented here aim to bridge the current knowledge gaps and inspire novel therapeutic strategies for brain diseases.

Tlx Promotes Stroke-Induced Neurogenesis and Neuronal Repair in Young and Aged Mice

Stroke is one of the leading causes of chronic disability in humans. It has been proposed that the endogenous neural stem/progenitor cells generate new neurons in the damaged area. Still, the contribution of these cells is negligible because a low number of newborn mature neurons are formed. Tlx conventional knock-out mice, Tlx-CreERT2 mice, and Tlx-overexpressing (Tlx-OE) mice were specifically chosen for their unique genetic characteristics, which were crucial for the experiments. Permanent and transient middle cerebral artery occlusion was used to induce stroke in the mice. Immunostainings for doublecortin and GFP/BrdU/NeuN were performed to study neurogenesis and fate mapping. The rotarod test was performed to assess motor deficits. Here, we show that stroke-induced neurogenesis is dramatically increased with the additional expression of two copies of the nuclear receptor-coding gene tailless (Tlx, also known as Nr2e1), which has been shown to be a master regulator of subventricular zone (SVZ) neural stem cells (NSCs). We show that Tlx expression is upregulated after stroke, and stroke-induced neurogenesis is blocked when Tlx is inactivated. Tlx overexpression in NSCs leads to massive induction of neurogenesis via stroke. More newborn mature neurons are formed in Tlx-overexpressing mice, leading to improved coordination and motor function recovery. Most importantly, we also demonstrate that this process is sustained in aged mice, where stroke-induced neurogenesis is nearly undetectable in wild-type animals. This study provides the first stem cell-specific genetic evidence that endogenous NSCs can be exploited by manipulating their master regulator, Tlx, and thus suggests a novel therapeutic strategy for neuronal repair.

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

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

Interaction between subventricular zone microglia and neural stem cells impacts the neurogenic response in a mouse model of cortical ischemic stroke

After a stroke, the neurogenic response from the subventricular zone (SVZ) to repair the brain is limited. Microglia, as an integral part of the distinctive SVZ microenvironment, control neural stem / precursor cell (NSPC) behavior. Here, we show that discrete stroke-associated SVZ microglial clusters negatively impact the innate neurogenic response, and we propose a repository of relevant microglia-NSPC ligand-receptor pairs. After photothrombosis, a mouse model of ischemic stroke, the altered SVZ niche environment leads to immediate activation of microglia in the niche and an abnormal neurogenic response, with cell-cycle arrest of neural stem cells and neuroblast cell death. Pharmacological restoration of the niche environment increases the SVZ-derived neurogenic repair and microglial depletion increases the formation and survival of newborn neuroblasts in the SVZ. Therefore, we propose that altered cross-communication between microglial subclusters and NSPCs regulates the extent of the innate neurogenic repair response in the SVZ after stroke.

Radixin: Roles in the Nervous System and Beyond

BACKGROUND

Radixin is an ERM family protein that includes radixin, moesin, and ezrin. The importance of ERM family proteins has been attracting more attention, and studies on the roles of ERM in biological function and the pathogenesis of some diseases are accumulating. In particular, we have found that radixin is the most dramatically changed ERM protein in elevated glucose-treated Schwann cells.

METHOD

We systemically review the literature on ERM, radixin in focus, and update the roles of radixin in regulating cell morphology, interaction, and cell signaling pathways. The potential of radixin as a therapeutic target in neurodegenerative diseases and cancer was also discussed.

RESULTS

Radixin research has focused on its cell functions, activation, and pathogenic roles in some diseases. Radixin and other ERM proteins maintain cell shape, growth, and motility. In the nervous system, radixin has been shown to prevent neurodegeneration and axonal growth. The activation of radixin is through phosphorylation of its conserved threonine residues. Radixin functions in cell signaling pathways by binding to membrane proteins and relaying the cell signals into the cells. Deficiency of radixin has been involved in the pathogenic process of diseases in the central nervous system and diabetic peripheral nerve injury. Moreover, radixin also plays a role in cell growth and drug resistance in multiple cancers. The trials of therapeutic potential through radixin modulation have been accumulating. However, the exact mechanisms underlying the roles of radixin are far from clarification.

CONCLUSIONS

Radixin plays various roles in cells and is involved in developing neurodegenerative diseases and many types of cancers. Therefore, radixin may be considered a potential target for developing therapeutic strategies for its related diseases. Further elucidation of the function and the cell signaling pathways that are linked to radixin may open the avenue to finding novel therapeutic strategies for diseases in the nervous system and other body systems.

CRISPR-Cas9 screens reveal regulators of ageing in neural stem cells

Ageing impairs the ability of neural stem cells (NSCs) to transition from quiescence to proliferation in the adult mammalian brain. Functional decline of NSCs results in the decreased production of new neurons and defective regeneration following injury during ageing1-4. Several genetic interventions have been found to ameliorate old brain function5-8, but systematic functional testing of genes in old NSCs-and more generally in old cells-has not been done. Here we develop in vitro and in vivo high-throughput CRISPR-Cas9 screening platforms to systematically uncover gene knockouts that boost NSC activation in old mice. Our genome-wide screens in primary cultures of young and old NSCs uncovered more than 300 gene knockouts that specifically restore the activation of old NSCs. The top gene knockouts are involved in cilium organization and glucose import. We also establish a scalable CRISPR-Cas9 screening platform in vivo, which identified 24 gene knockouts that boost NSC activation and the production of new neurons in old brains. Notably, the knockout of Slc2a4, which encodes the GLUT4 glucose transporter, is a top intervention that improves the function of old NSCs. Glucose uptake increases in NSCs during ageing, and transient glucose starvation restores the ability of old NSCs to activate. Thus, an increase in glucose uptake may contribute to the decline in NSC activation with age. Our work provides scalable platforms to systematically identify genetic interventions that boost the function of old NSCs, including in vivo, with important implications for countering regenerative decline during ageing.

The Organism as the Niche: Physiological States Crack the Code of Adult Neural Stem Cell Heterogeneity

Neural stem cells (NSCs) persist in the adult mammalian brain and are able to give rise to new neurons and glia throughout life. The largest stem cell niche in the adult mouse brain is the ventricular-subventricular zone (V-SVZ) lining the lateral ventricles. Adult NSCs in the V-SVZ coexist in quiescent and actively proliferating states, and they exhibit a regionalized molecular identity. The importance of such spatial diversity is just emerging, as depending on their position within the niche, adult NSCs give rise to distinct subtypes of olfactory bulb interneurons and different types of glia. However, the functional relevance of stem cell heterogeneity in the V-SVZ is still poorly understood. Here, we put into perspective findings highlighting the importance of adult NSC diversity for brain plasticity, and how the body signals to brain stem cells in different physiological states to regulate their behavior.

SDF-1 Bound Heparin Nanoparticles Recruit Progenitor Cells for Their Differentiation and Promotion of Angiogenesis after Stroke

Angiogenesis after stroke is correlated with enhanced tissue repair and functional outcomes. The existing body of research in biomaterials for stroke focuses on hydrogels for the delivery of stem cells, growth factors, or small molecules or drugs. Despite the ability of hydrogels to enhance all these delivery methods, no material has significantly regrown vasculature within the translatable timeline of days to weeks after stroke. Here, two novel biomaterial formulations of granular hydrogels are developed for tissue regeneration after stroke: highly porous microgels (i.e., Cryo microgels) and microgels bound with heparin-norbornene nanoparticles with covalently bound SDF-1α. The combination of these materials results in perfused vessels throughout the stroke core in only 10 days, in addition to increased neural progenitor cell recruitment, maintenance, and increased neuronal differentiation.

Inflammation and Elevated Osteopontin in Plasma and CSF in Cerebral Malaria Compared to Plasmodium-Negative Neurological Infections

Cerebral malaria in young African children is associated with high mortality, and persisting neurological deficits often remain in survivors. Sequestered Plasmodium-infected red blood cells lead to cerebrovascular inflammation and subsequent neuroinflammation. Brain inflammation can play a role in the pathogenesis of neurologic sequelae. Therefore, we assessed a select set of proinflammatory analytes (IP10, IL23, MIP3α, GRO, MCP-1, and osteopontin in both the plasma and cerebrospinal fluid(CSF) of Zambian children with cerebral malaria and compared this with children with neurological symptoms that were negative for Plasmodium falciparum (non-cerebral malaria). Several similarities in plasma and CSF levels were found, as were some striking differences. We confirmed that IP10 levels were higher in the plasma of cerebral malaria patients, but this was not found in CSF. Levels of osteopontin were elevated in both the plasma and CSF of CM patients compared to the non-CM patients. These results show again a highly inflammatory environment in both groups but a different profile for CM when compared to non-cerebral malaria. Osteopontin may play an important role in neurological inflammation in CM and the resulting sequelae. Therefore, osteopontin could be a valid target for further biomarker research and potentially for therapeutic interventions in neuroinflammatory infections.

Suppression of PTBP1 in hippocampal astrocytes promotes neurogenesis and ameliorates recognition memory in mice with cerebral ischemia

The therapeutic potential of suppressing polypyrimidine tract-binding protein 1 (Ptbp1) messenger RNA by viral transduction in a post-stroke dementia mouse model has not yet been examined. In this study, 3 days after cerebral ischemia, we injected a viral vector cocktail containing adeno-associated virus (AAV)-pGFAP-mCherry and AAV-pGFAP-CasRx (control vector) or a cocktail of AAV-pGFAP-mCherry and AAV-pGFAP-CasRx-SgRNA-(Ptbp1) (1:5, 1.0 × 1011 viral genomes) into post-stroke mice via the tail vein. We observed new mCherry/NeuN double-positive neuron-like cells in the hippocampus 56 days after cerebral ischemia. A portion of mCherry/GFAP double-positive astrocyte-like glia could have been converted into new mCherry/NeuN double-positive neuron-like cells with morphological changes. The new neuronal cells integrated into the dentate gyrus and recognition memory was significantly ameliorated. These results demonstrated that the in vivo conversion of hippocampal astrocyte-like glia into functional new neurons by the suppression of Ptbp1 might be a therapeutic strategy for post-stroke dementia.

Role of STAT3-FOXO3 Signaling in the Modulation of Neuroplasticity by PD-L1-HGF-Decorated Mesenchymal Stem Cell-Derived Exosomes in a Murine Stroke Model

The limited therapeutic strategies available for stroke leave many patients disabled for life. This study assessed the potential of programmed death-ligand 1 (PD-L1) and hepatocyte growth factor (HGF)-engineered mesenchymal stem cell-derived exosomes (EXO-PD-L1-HGF) in enhancing neurological recovery post-stroke. EXO-PD-L1-HGF, which efficiently endocytosed into target cells, significantly diminishes the H2O2-induced neurotoxicity and increased the antiapoptotic proteins in vitro. EXO-PD-L1-HGF attenuates inflammation by inhibiting T-cell proliferation and increasing the number of CD8+CD122+IL-10+ regulatory T cells. Intravenous injection of EXO-PD-L1-HGF could target stromal cell-derived factor-1α (SDF-1α+) cells over the peri-infarcted area of the ischemic brain through CXCR4 upregulation and accumulation in neuroglial cells post-stroke. EXO-PD-L1-HGF facilitates endogenous nestin+ neural progenitor cell (NPC)-induced neurogenesis via STAT3-FOXO3 signaling cascade, which plays a pivotal role in cell survival and neuroprotection, thereby mitigating infarct size and enhancing neurological recovery in a murine stroke model. Moreover, increasing populations of the immune-regulatory CD19+IL-10+ and CD8+CD122+IL-10+ cells, together with reducing populations of proinflammatory cells, created an anti-inflammatory microenvironment in the ischemic brain. Thus, innovative approaches employing EXO-PD-L1-HGF intervention, which targets SDF-1α+ expression, modulates the immune system, and enhances the activation of resident nestin+ NPCs, might significantly alter the brain microenvironment and create a niche conducive to inducing neuroplastic regeneration post-stroke.

The impact of flavonoids and BDNF on neurogenic process in various physiological/pathological conditions including ischemic insults: a narrative review

OBJECTIVE

Ischemic stroke is the leading cause of mortality and disability worldwide with more than half of survivors living with serious neurological sequelae thus, it has recently attracted considerable attention in the field of medical research. Neurogenesis is the process of formation of new neurons in the brain, including the human brain, from neural stem/progenitor cells [NS/PCs] which reside in neurogenic niches that contain the necessary substances for NS/PC proliferation, differentiation, migration, and maturation into functioning neurons which can integrate into a pre-existing neural network.Neurogenesis can be modulated by many exogenous and endogenous factors, pathological conditions. Both brain-derived neurotrophic factor, and flavonoids can modulate the neurogenic process in physiological conditions and after various pathological conditions including ischemic insults.

AIM

This review aims to discuss neurogenesis after ischemic insults and to determine the role of flavonoids and BDNF on neurogenesis under physiological and pathological conditions with a concentration on ischemic insults to the brain in particular.

METHOD

Relevant articles assessing the impact of flavonoids and BDNF on neurogenic processes in various physiological/pathological conditions including ischemic insults within the timeline of 1965 until 2023 were searched using the PubMed database.

CONCLUSIONS

The selected studies have shown that ischemic insults to the brain induce NS/PC proliferation, differentiation, migration, and maturation into functioning neurons integrating into a pre-existing neural network. Flavonoids and BDNF can modulate neurogenesis in the brain in various physiological/pathological conditions including ischemic insults. In conclusion, flavonoids and BDNF may be involved in post-ischemic brain repair processes through enhancing endogenous neurogenesis.

Stereotactically intracerebral transplantation of neural stem cells for ischemic stroke attenuated inflammatory responses and promoted neurogenesis: an experimental study with monkeys

BACKGROUND

Ischemic stroke is a common neurovascular disorder with high morbidity and mortality. However, the underlying mechanism of stereotactically intracerebral transplantation of human neural stem cells (hNSCs) is not well elucidated.

MATERIALS AND METHODS

Four days after ischemic stroke induced by Rose Bengal photothrombosis, seven cynomolgus monkeys were transplanted with hNSCs or vehicles stereotactically and followed up for 84 days. Behavioral assessments, magnetic resonance imaging, blood tests, and pathological analysis were performed before and after treatment. The proteome profiles of the left and right precentral gyrus and hippocampus were evaluated. Extracellular vesicle micro-RNA (miRNA) from the peripheral blood was extracted and analyzed.

RESULTS

hNSC transplantation reduced the remaining infarcted lesion volume of cynomolgus monkeys with ischemic stroke without remarkable side effects. Proteomic analyses indicated that hNSC transplantation promoted GABAergic and glutamatergic neurogenesis and restored the mitochondrial electron transport chain function in the ischemic infarcted left precentral gyrus or hippocampus. Immunohistochemical staining and quantitative real-time reverse transcription PCR confirmed the promoting effects on neurogenesis and revealed that hNSCs attenuated post-infarct inflammatory responses by suppressing resident glia activation and mediating peripheral immune cell infiltration. Consistently, miRNA-sequencing revealed the miRNAs that were related to these pathways were downregulated after hNSC transplantation.

CONCLUSIONS

This study indicates that hNSCs can be effectively and safely used to treat ischemic stroke by promoting neurogenesis, regulating post-infarct inflammatory responses, and restoring mitochondrial function in both the infarct region and hippocampus.

Decompressive Hemicraniectomy without Evacuation of Acute Intraparenchymal Hemorrhage

BACKGROUND

Intracerebral hemorrhages (ICHs) are prevalent, with high morbidity and mortality. We analyzed whether decompressive craniectomy (DC) without evacuation of the acute intraparenchymal hematoma could produce better functional outcomes than treatment with evacuation.

METHODS

Patients with acute ICH treated with DC without clot evacuation, or evacuation with or without associated craniectomy were included. Matched univariate analyses were performed, and a binary logistic regression model was constructed using the Glasgow Outcome Scale (GOS) and modified Rankin scale (mRS) as dependent variables.

RESULTS

27 patients treated with DC without clot evacuation were compared to 36 patients with clot evacuation; eleven of the first group were matched with 18 patients with evacuation. A significantly better functional prognosis in the group treated with DC without clot evacuation was found. Patients aged < 55 years and treated with DC without clot evacuation had a significantly better functional prognosis (p = 0.008 and p = 0.039, respectively). In multivariate analysis, the intervention performed was the greatest predictor of functional status at the end of follow-up.

CONCLUSIONS

DC without clot evacuation improves the functional prognosis of patients with acute intraparenchymal hematomas. Larger multicenter studies are warranted to determine whether a change in the management of acute ICH should be recommended.

LRIG1 controls proliferation of adult neural stem cells by facilitating TGFβ and BMP signalling pathways

Adult Neural Stem Cells (aNSCs) in the ventricular-subventricular zone (V-SVZ) are largely quiescent. Here, we characterize the mechanism underlying the functional role of a cell-signalling inhibitory protein, LRIG1, in the control of aNSCs proliferation. Using Lrig1 knockout models, we show that Lrig1 ablation results in increased aNSCs proliferation with no change in neuronal progeny and that this hyperproliferation likely does not result solely from activation of the epidermal growth factor receptor (EGFR). Loss of LRIG1, however, also leads to impaired activation of transforming growth factor beta (TGFβ) and bone morphogenic protein (BMP) signalling. Biochemically, we show that LRIG1 binds TGFβ/BMP receptors and the TGFβ1 ligand. Finally, we show that the consequences of these interactions are to facilitate SMAD phosphorylation. Collectively, these data suggest that unlike in embryonic NSCs where EGFR may be the primary mechanism of action, in aNSCs, LRIG1 and TGFβ pathways function together to fulfill their inhibitory roles.

Cell Therapy and Functional Recovery of Stroke

Stroke is the most common cause of disability. Brain repair mechanisms are often insufficient to allow a full recovery. Stroke damage involve all brain cell type and extracellular matrix which represent the crucial "glio-neurovascular niche" useful for brain plasticity. Regenerative medicine including cell therapies hold great promise to decrease post-stroke disability of many patients, by promoting both neuroprotection and neural repair through direct effects on brain lesion and/or systemic effects such as immunomodulation. Mechanisms of action vary according to each grafted cell type: "peripheral" stem cells, such as mesenchymal stem cells (MSC), can provide paracrine trophic support, and neural stem/progenitor cells (NSC) or neurons can act as direct cells' replacements. Optimal time window, route, and doses are still debated, and may depend on the chosen medicinal product and its expected mechanism such as neuroprotection, delayed brain repair, systemic effects, or graft survival and integration in host network. MSC, mononuclear cells (MNC), umbilical cord stem cells and NSC are the most investigated. Innovative approaches are implemented concerning combinatorial approaches with growth factors and biomaterials such as injectable hydrogels which could protect a cell graft and/or deliver drugs into the post-stroke cavity at chronic stages. Through main publications of the last two decades, we provide in this review concepts and suggestions to improve future translational researches and larger clinical trials of cell therapy in stroke.

Astrocytes in functional recovery following central nervous system injuries

Astrocytes are increasingly recognised as partaking in complex homeostatic mechanisms critical for regulating neuronal plasticity following central nervous system (CNS) insults. Ischaemic stroke and traumatic brain injury are associated with high rates of disability and mortality. Depending on the context and type of injury, reactive astrocytes respond with diverse morphological, proliferative and functional changes collectively known as astrogliosis, which results in both pathogenic and protective effects. There is a large body of research on the negative consequences of astrogliosis following brain injuries. There is also growing interest in how astrogliosis might in some contexts be protective and help to limit the spread of the injury. However, little is known about how astrocytes contribute to the chronic functional recovery phase following traumatic and ischaemic brain insults. In this review, we explore the protective functions of astrocytes in various aspects of secondary brain injury such as oedema, inflammation and blood-brain barrier dysfunction. We also discuss the current knowledge on astrocyte contribution to tissue regeneration, including angiogenesis, neurogenesis, synaptogenesis, dendrogenesis and axogenesis. Finally, we discuss diverse astrocyte-related factors that, if selectively targeted, could form the basis of astrocyte-targeted therapeutic strategies to better address currently untreatable CNS disorders.

Translational Medicine in Acute Ischemic Stroke and Traumatic Brain Injury-NeuroAiD Trials, from Traditional Beliefs to Evidence-Based Therapy

Acute ischemic stroke (AIS) and traumatic brain injury (TBI) are two severe neurological events, both being major causes of death and prolonged impairment. Their incidence continues to rise due to the global increase in the number of people at risk, representing a significant burden on those remaining impaired, their families, and society. These molecular and cellular mechanisms of both stroke and TBI present similarities that can be targeted by treatments with a multimodal mode of action, such as traditional Chinese medicine. Therefore, we performed a detailed review of the preclinical and clinical development of MLC901 (NeuroAiDTMII), a natural multi-herbal formulation targeting several biological pathways at the origin of the clinical deficits. The endogenous neurobiological processes of self-repair initiated by the brain in response to the onset of brain injury are often insufficient to achieve complete recovery of impaired functions. This review of MLC901 and its parent formulation MLC601 confirms that it amplifies the natural self-repair process of brain tissue after AIS or TBI. Following AIS and TBI where "time is brain", many patients enter the post-acute phase with their functions still impaired, a period when "the brain needs time to repair itself". The treatment goal must be to accelerate recovery as much as possible. MLC901/601 demonstrated a significant reduction by 18 months of recovery time compared to a placebo, indicating strong potential for facilitating the improvement of health outcomes and the more efficient use of healthcare resources.

Pharmacological and stem cell therapy of stroke in animal models: Do they accurately reflect the response of humans?

Cerebrovascular diseases are the second leading cause of death worldwide. Despite significant research investment, the only available therapeutic options are mechanical thrombectomy and tissue plasminogen activator thrombolysis. None of the more than a thousand drugs tested on animal models have proven successful in human clinical trials. Several factors contribute to this poor translation of data from stroke-related animal models to human stroke patients. Firstly, our understanding of the molecular and cellular processes involved in recovering from an ischemic stroke is severely limited. Secondly, although the risk of stroke is particularly high among older patients with comorbidities, most drugs are tested on young, healthy animals in controlled laboratory conditions. Furthermore, in animal models, the tracking of post-stroke recovery typically spans only 3 to 28 days, with occasional extensions to 60 days, whereas human stroke recovery is a more extended and complex process. Thirdly, young animal models often exhibit a considerably higher rate of spontaneous recovery compared to humans following a stroke. Fourth, only a very limited number of animals are utilized for each condition, including control groups. Another contributing factor to the much smaller beneficial effects in humans is that positive outcomes from numerous animal studies are more readily accepted than results reported in human trials that do not show a clear benefit to the patient. Useful recommendations for conducting experiments in animal models, with increased chances of translatability to humans, have been issued by both the STEPS investigative team and the STAIR committee. However, largely, due to economic factors, these recommendations are largely ignored. Furthermore, one might attribute the overall failures in predicting and subsequently developing effective acute stroke therapies beyond thrombolysis to potential design deficiencies in clinical trials.

Endothelial PDGF-D contributes to neurovascular protection after ischemic stroke by rescuing pericyte functions

Ischemic stroke induces neovascularization of the injured tissue as an attempt to promote structural repair and neurological recovery. Angiogenesis is regulated by pericytes that potently react to ischemic stroke stressors, ranging from death to dysfunction. Platelet-derived growth factor (PDGF) receptor (PDGFR)β controls pericyte survival, migration, and interaction with brain endothelial cells. PDGF-D a specific ligand of PDGFRβ is expressed in the brain, yet its regulation and role in ischemic stroke pathobiology remains unexplored. Using experimental ischemic stroke mouse model, we found that PDGF-D is transiently induced in brain endothelial cells at the injury site in the subacute phase. To investigate the biological significance of PDGF-D post-ischemic stroke regulation, its subacute expression was either downregulated using siRNA or upregulated using an active recombinant form. Attenuation of PDGF-D subacute induction exacerbates neuronal loss, impairs microvascular density, alters vascular permeability, and increases microvascular stalling. Increasing PDGF-D subacute bioavailability rescues neuronal survival and improves neurological recovery. PDGF-D subacute enhanced bioavailability promotes stable neovascularization of the injured tissue and improves brain perfusion. Notably, PDGF-D enhanced bioavailability improves pericyte association with brain endothelial cells. Cell-based assays using human brain pericyte and brain endothelial cells exposed to ischemia-like conditions were applied to investigate the underlying mechanisms. PDGF-D stimulation attenuates pericyte loss and fibrotic transition, while increasing the secretion of pro-angiogenic and vascular protective factors. Moreover, PDGF-D stimulates pericyte migration required for optimal endothelial coverage and promotes angiogenesis. Our study unravels new insights into PDGF-D contribution to neurovascular protection after ischemic stroke by rescuing the functions of pericytes.

Stem cell therapy as a promising approach for ischemic stroke treatment

Ischemia as the most common type of stroke is the main cause of death and disability in the world. However, there are few therapeutic approaches to treat ischemic stroke. The common approach to the treatment of ischemia includes surgery-cum-chemical drugs. Surgery and chemical drugs are used to remove blood clots to prevent the deterioration of the nervous system. Given the surgical hazards and the challenges associated with chemical drugs, these cannot be considered safe approaches to the treatment of brain ischemia. Besides surgery-cum-chemical drugs, different types of stem cells including mesenchymal stem cells and neurological stem cells have been considered to treat ischemic stroke. Therapeutic approaches utilizing stem cells to treat strokes are promising because of their neuroprotective and regenerative benefits. However, the mechanisms by which the transplanted stem cells perform their precisely actions are unknown. The purpose of this study is to critically review stem cell-based therapeutic approaches for ischemia along with related challenges.

Lipid organization and turnover in the plasma membrane of human differentiating neural progenitor cells revealed by time-of-flight secondary ion mass spectrometry imaging

Membrane lipids have been known to influence multiple signalling and cellular processes. Dysregulation of lipids at the neuronal membrane is connected to a significant alteration of the brain function and morphology, leading to brain diseases and neurodegeneration. Understanding the lipid composition and turnover of neuronal membrane will provide a significant insight into the molecular events underlying the regulatory effects of these biomolecules in a neuronal system. In this study, we aimed to characterize the composition and turnover of the plasma membrane lipids in human neural progenitor cells (NPCs) at an early differentiation stage into midbrain neurons using ToF-SIMS imaging. Lipid composition of the native plasma membrane was explored, followed by an examination of the lipid turnover using different isotopically labelled lipid precursors, including 13C-choline, 13C-lauric acid, 15N-linoleic, and 13C-stearic. Our results showed that differentiating NPCs contain a high abundance of ceramides, glycerophosphoserines, neutral glycosphingolipids, diradylglycerols, and glycerophosphocholines at the plasma membrane. In addition, different precursors were found to incorporate into different membrane lipids which are specific for the short- or long-carbon chains, and the unsaturation or saturation stage of the precursors. The lipid structure of neuronal membrane reflects the differentiation status of NPCs, and it can be altered significantly using a particular lipid precursor. Our study illustrates a potential of ToF-SIMS imaging to study native plasma membrane lipids and elucidate complex cellular processes by providing molecular -rich information at a single cell level.

Neural regeneration in the human central nervous system-from understanding the underlying mechanisms to developing treatments. Where do we stand today?

Mature neurons in the human central nervous system (CNS) fail to regenerate after injuries. This is a common denominator across different aetiologies, including multiple sclerosis, spinal cord injury and ischemic stroke. The lack of regeneration leads to permanent functional deficits with a substantial impact on patient quality of life, representing a significant socioeconomic burden worldwide. Great efforts have been made to decipher the responsible mechanisms and we now know that potent intra- and extracellular barriers prevent axonal repair. This knowledge has resulted in numerous clinical trials, aiming to promote neuroregeneration through different approaches. Here, we summarize the current understanding of the causes to the poor regeneration within the human CNS. We also review the results of the treatment attempts that have been translated into clinical trials so far.

Targeting brain-peripheral immune responses for secondary brain injury after ischemic and hemorrhagic stroke

The notion that the central nervous system is an immunologically immune-exempt organ has changed over the past two decades, with increasing evidence of strong links and interactions between the central nervous system and the peripheral immune system, both in the healthy state and after ischemic and hemorrhagic stroke. Although primary injury after stroke is certainly important, the limited therapeutic efficacy, poor neurological prognosis and high mortality have led researchers to realize that secondary injury and damage may also play important roles in influencing long-term neurological prognosis and mortality and that the neuroinflammatory process in secondary injury is one of the most important influences on disease progression. Here, we summarize the interactions of the central nervous system with the peripheral immune system after ischemic and hemorrhagic stroke, in particular, how the central nervous system activates and recruits peripheral immune components, and we review recent advances in corresponding therapeutic approaches and clinical studies, emphasizing the importance of the role of the peripheral immune system in ischemic and hemorrhagic stroke.

Versatile strategies for adult neurogenesis: avenues to repair the injured brain

Brain injuries due to trauma or stroke are major causes of adult death and disability. Unfortunately, few interventions are effective for post-injury repair of brain tissue. After a long debate on whether endogenous neurogenesis actually happens in the adult human brain, there is now substantial evidence to support its occurrence. Although neurogenesis is usually significantly stimulated by injury, the reparative potential of endogenous differentiation from neural stem/progenitor cells is usually insufficient. Alternatively, exogenous stem cell transplantation has shown promising results in animal models, but limitations such as poor long-term survival and inefficient neuronal differentiation make it still challenging for clinical use. Recently, a high focus was placed on glia-to-neuron conversion under single-factor regulation. Despite some inspiring results, the validity of this strategy is still controversial. In this review, we summarize historical findings and recent advances on neurogenesis strategies for neurorepair after brain injury. We also discuss their advantages and drawbacks, as to provide a comprehensive account of their potentials for further studies.

Perspective insights into versatile hydrogels for stroke: From molecular mechanisms to functional applications

As the leading killer of life and health, stroke leads to limb paralysis, speech disorder, dysphagia, cognitive impairment, mental depression and other symptoms, which entail a significant financial burden to society and families. At present, physiology, clinical medicine, engineering, and materials science, advanced biomaterials standing on the foothold of these interdisciplinary disciplines provide new opportunities and possibilities for the cure of stroke. Among them, hydrogels have been endowed with more possibilities. It is well-known that hydrogels can be employed as potential biosensors, medication delivery vectors, and cell transporters or matrices in tissue engineering in tissue engineering, and outperform many traditional therapeutic drugs, surgery, and materials. Therefore, hydrogels become a popular scaffolding treatment option for stroke. Diverse synthetic hydrogels were designed according to different pathophysiological mechanisms from the recently reported literature will be thoroughly explored. The biological uses of several types of hydrogels will be highlighted, including pro-angiogenesis, pro-neurogenesis, anti-oxidation, anti-inflammation and anti-apoptosis. Finally, considerations and challenges of using hydrogels in the treatment of stroke are summarized.

Naoxinqing tablet protects against cerebral ischemic/reperfusion injury by regulating ampkα/NAMPT/SIRT1/PGC-1α pathway

AIM OF THE STUDY

Naoxinqing (NXQ) tablets are derived from persimmon leaves and are widely used in China for promoting blood circulation and removing blood stasis in China. We aimed to explore whether NXQ has the therapeutic effect on ischemic stroke and explored its possible mechanism.

MATERIALS AND METHODS

The cerebral artery occlusion/reperfusion (MCAO/R) surgery was used to establish the cerebral ischemic/reperfusion rat model. NXQ (60 mg/kg and 120 mg/kg) were administered orally. The TTC staining, whole brain water content, histopathology staining, immunofluorescent staining, enzyme-linked immunosorbent assay (ELISA) and Western blot analyses were performed to determine the therapeutical effect of NXQ on MCAO/R rats.

RESULTS

The study demonstrated that NXQ reduced the cerebral infarction volumes and neurologic deficits in MCAO/R rats. The neuroprotective effects of NXQ were accompanied by inhibited oxidative stress and inflammation. The nerve regeneration effects of NXQ were related to regulating the AMPKα/NAMPT/SIRT1/PGC-1α pathway.

CONCLUSION

In summary, our results revealed that NXQ had a significant protective effect on cerebral ischemia-reperfusion injury in rats. This study broadens the therapeutic scope of NXQ tablets and provides new neuroprotective mechanisms of NXQ as an anti-stroke therapeutic agent.

Thyroid hormone action in adult neurogliogenic niches: the known and unknown

Over the last decades, thyroid hormones (THs) signaling has been established as a key signaling cue for the proper maintenance of brain functions in adult mammals, including humans. One of the most fascinating roles of THs in the mature mammalian brain is their ability to regulate adult neurogliogenic processes. In this respect, THs control the generation of new neuronal and glial progenitors from neural stem cells (NSCs) as well as their final differentiation and maturation programs. In this review, we summarize current knowledge on the cellular organization of adult rodent neurogliogenic niches encompassing well-established niches in the subventricular zone (SVZ) lining the lateral ventricles, the hippocampal subgranular zone (SGZ), and the hypothalamus, but also less characterized niches in the striatum and the cerebral cortex. We then discuss critical questions regarding how THs availability is regulated in the respective niches in rodents and larger mammals as well as how modulating THs availability in those niches interferes with lineage decision and progression at the molecular, cellular, and functional levels. Based on those alterations, we explore the novel therapeutic avenues aiming at harnessing THs regulatory influences on neurogliogenic output to stimulate repair processes by influencing the generation of either new neurons (i.e. Alzheimer's, Parkinson's diseases), oligodendrocytes (multiple sclerosis) or both (stroke). Finally, we point out future challenges, which will shape research in this exciting field in the upcoming years.

The m6A methylation and expression profiles of mouse neural stem cells after hypoxia/reoxygenation

BACKGROUND

Ischemia-reperfusion injury to the central nervous system often causes severe complications. The activation of endogenous neural stem cells (NSCs) is considered a promising therapeutic strategy for nerve repair. However, the specific biological processes and molecular mechanisms of NSC activation remain unclear, and the role of N6-methyladenosine (m6A) methylation modification in this process has not been explored.

METHODS

NSCs were subjected to hypoxia/reoxygenation (H/R) to simulate ischemia-reperfusion in vivo. m6A RNA methylation quantitative kit was used to measure the total RNA m6A methylation level. Quantitative real-time PCR was used to detect methyltransferase and demethylase mRNA expression levels. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) were conducted for NSCs in control and H/R groups, and the sequencing results were analyzed using bioinformatics. Finally, the migration ability of NSCs was identified by wound healing assays, and the proliferative capacity of NSCs was assessed using the cell counting kit-8, EdU assays and cell spheroidization assays.

RESULTS

Overall of m6A modification level and Mettl14 mRNA expression increased in NSCs after H/R treatment. The m6A methylation and expression profiles of mRNAs in NSCs after H/R are described for the first time. Through the joint analysis of MeRIP-seq and RNA-seq results, we verified the proliferation of NSCs after H/R, which was regulated by m6A methylation modification. Seven hub genes were identified to play key roles in the regulatory process. Knockdown of Mettl14 significantly inhibited the proliferation of NSCs. In addition, separate analysis of the MeRIP-seq results suggested that m6A methylation regulates cell migration and differentiation in ways other than affecting mRNA expression. Subsequent experiments confirmed the migration ability of NSCs was suppressed by knockdown of Mettl14.

CONCLUSION

The biological behaviors of NSCs after H/R are closely related to m6A methylation of mRNAs, and Mettl14 was confirmed to be involved in cell proliferation and migration.

Brain Maturation as a Fundamental Factor in Immune-Neurovascular Interactions in Stroke

Injuries in the developing brain cause significant long-term neurological deficits. Emerging clinical and preclinical data have demonstrated that the pathophysiology of neonatal and childhood stroke share similar mechanisms that regulate brain damage, but also have distinct molecular signatures and cellular pathways. The focus of this review is on two different diseases-neonatal and childhood stroke-with emphasis on similarities and distinctions identified thus far in rodent models of these diseases. This includes the susceptibility of distinct cell types to brain injury with particular emphasis on the role of resident and peripheral immune populations in modulating stroke outcome. Furthermore, we discuss some of the most recent and relevant findings in relation to the immune-neurovascular crosstalk and how the influence of inflammatory mediators is dependent on specific brain maturation stages. Finally, we comment on the current state of treatments geared toward inducing neuroprotection and promoting brain repair after injury and highlight that future prophylactic and therapeutic strategies for stroke should be age-specific and consider gender differences in order to achieve optimal translational success.

Inhibition of Apoptosis in a Model of Ischemic Stroke Leads to Enhanced Cell Survival, Endogenous Neural Precursor Cell Activation and Improved Functional Outcomes

Stroke results in neuronal cell death, which causes long-term disabilities in adults. Treatment options are limited and rely on a narrow window of opportunity. Apoptosis inhibitors demonstrate efficacy in improving neuronal cell survival in animal models of stroke. However, many inhibitors non-specifically target apoptosis pathways and high doses are needed for treatment. We explored the use of a novel caspase-3/7 inhibitor, New World Laboratories (NWL) 283, with a lower IC50 than current caspase-3/7 inhibitors. We performed in vitro and in vivo assays to determine the efficacy of NWL283 in modulating cell death in a preclinical model of stroke. In vitro and in vivo assays show that NWL283 enhances cell survival of neural precursor cells. Delivery of NWL283 following stroke enhances endogenous NPC migration and leads to increased neurogenesis in the stroke-injured cortex. Furthermore, acute NWL283 administration is neuroprotective at the stroke injury site, decreasing neuronal cell death and reducing microglia activation. Coincident with NWL283 delivery for 8 days, stroke-injured mice exhibited improved functional outcomes that persisted following cessation of the drug. Therefore, we propose that NWL283 is a promising therapeutic warranting further investigation to enhance stroke recovery.