Neurogenesis in Stroke Recovery

Challenges and Improvements of Novel Therapies for Ischemic Stroke

Stroke is the third most common disease all over the world, which is regarded as a hotspot in medical research because of its high mortality and morbidity. Stroke, especially ischemic stroke, causes severe neural cell death, and no effective therapy is currently available for neuroregeneration after stroke. Although many therapies have been shown to be effective in preclinical studies of ischemic stroke, almost none of them passed clinical trials, and the reasons for most failures have not been well identified. In this review, we focus on several novel methods, such as traditional Chinese medicine, stem cell therapy, and exosomes that have not been used for ischemic stroke till recent decades. We summarize the proposed basic mechanisms underlying these therapies and related clinical results, discussing advantages and current limitations for each therapy emphatically. Based on the limitations such as side effects, narrow therapeutic window, and less accumulation at the injury region, structure transformation and drug combination are subsequently applied, providing a deep understanding to develop effective treatment strategies for ischemic stroke in the near future.

Neuroprotective Effects of GV1001 in Animal Stroke Model and Neural Cells Subject to Oxygen-Glucose Deprivation/Reperfusion Injury

Background and Purpose

Previous studies have revealed the diverse neuroprotective effects of GV1001. In this study, we investigated the effects of GV1001 on focal cerebral ischemia-reperfusion injury (IRI) in rats and oxygen-glucose deprivation/reoxygenation (OGD/R)-induced injury in neural stem cells (NSCs) and cortical neurons.

Methods

Focal cerebral IRI was induced by transient middle cerebral artery occlusion (MCAO). Brain diffusion-weighted imaging (DWI) was performed 2 hours after occlusion, and a total of 37 rats were treated by reperfusion with GV1001 or saline 2 hours after occlusion. Fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging, immunohistochemistry, and neurobehavioral function analyses were performed. Additionally, OGD/R-injured NSCs and cortical neurons were treated with different GV1001 concentrations. Cell viability, proliferation, migration, and oxidative stress were determined by diverse molecular analyses.

Results

In the stroke model, GV1001 protected neural cells against IRI. The most effective dose of GV1001 was 60 μM/kg. The infarct volume on FLAIR 48 hours after MCAO compared to lesion volume on DWI showed a significantly smaller ratio in the GV1001-treated group. GV1001-treated rats exhibited better behavioral functions than the saline-treated rats. Treatment with GV1001 increased the viability, proliferation, and migration of the OGD/R-injured NSCs. Free radicals were significantly restored by treatment with GV1001. These neuroprotective effects of GV1001 have also been demonstrated in OGD/R-injured cortical neurons.

Conclusions

The results suggest that GV1001 has neuroprotective effects against IRI in NSCs, cortical neurons, and the rat brain. These effects are mediated through the induction of cellular proliferation, mitochondrial stabilization, and anti-apoptotic, anti-aging, and antioxidant effects.

Emerging roles of growth differentiation factor-15 in brain disorders (Review)

Brain disorders, such as Alzheimer's and Parkinson's disease and cerebral stroke, are an important contributor to mortality and disability worldwide, where their pathogenesis is currently a topic of intense research. The mechanisms underlying the development of brain disorders are complex and vary widely, including aberrant protein aggregation, ischemic cell necrosis and neuronal dysfunction. Previous studies have found that the expression and function of growth differentiation factor-15 (GDF15) is closely associated with the incidence of brain disorders. GDF15 is a member of the TGFβ superfamily, which is a dimer-structured stress-response protein. The expression of GDF15 is regulated by a number of proteins upstream, including p53, early growth response-1, non-coding RNAs and hormones. In particular, GDF15 has been reported to serve an important role in regulating angiogenesis, apoptosis, lipid metabolism and inflammation. For example, GDF15 can promote angiogenesis by promoting the proliferation of human umbilical vein endothelial cells, apoptosis of prostate cancer cells and fat metabolism in fasted mice, and GDF15 can decrease the inflammatory response of lipopolysaccharide-treated mice. The present article reviews the structure and biosynthesis of GDF15, in addition to the possible roles of GDF15 in Alzheimer's disease, cerebral stroke and Parkinson's disease. The purpose of the present review is to summarize the mechanism underlying the role of GDF15 in various brain disorders, which hopes to provide evidence and guide the prevention and treatment of these debilitating conditions.

Compensatory Hippocampal Neurogenesis in the Absence of Cognitive Impairment Following Experimental Hippocampectomy in Adult Rats

Temporal lobe epilepsy (TLE) is the commonest type of focal epilepsy in adult humans, and hippocampal sclerosis (HS) is the main pathological finding in this type of epilepsy. In refractory TLE, patients are indicated for unilateral resection of the affected hippocampus by a surgical procedure called hippocampectomy which generally does not cause any cognitive impairment. Once adult hippocampus is a region of endogenous neurogenesis, even in elderly people, we have hypothesized that a compensatory increase in hippocampal neurogenesis might occur in the remaining hippocampus after unilateral hippocampectomy. To test this hypothesis, we performed unilateral hippocampectomy in adult Wistar rats, which were perfused at 15 (G15) and 30 (G30) days post-surgery. Eighteen Wistar rats were randomly distributed in the following experimental groups: control (no surgery, N = 6), G15 (N = 6), and G30 (N = 6). Adjacent cortex and hippocampus of the left hemisphere were completely removed. Behavioral procedures were performed to address possible cognitive impairments. Brains were collected and fixed from animals belonging to all experimental groups. Gross histopathology was performed using thionine staining. Neuroblasts and mature neurons were immunolabeled using anti-doublecortin (DCX) and anti-NeuN antibodies, respectively. Numbers of DCX and NeuN positive cells were quantified for all experimental groups. Animals submitted to hippocampectomy did not present any cognitive impairment as evaluated by eight-arm radial maze behavioral test. The remaining hippocampus presented a higher number of DCX positive cells compared to control (p < 0.001, ANOVA-Tukey) at both G15 and G30. A higher number of NeuN positive cells were present in the granular layer of dentate gyrus at G30 compared to control and G15 (p < 0.001, ANOVA-Tukey). The data suggest that unilateral hippocampectomy induces compensatory neurogenic effect in the contralateral hippocampus. This may underlie the reported absence of significant cognitive impairment and parallels the findings in human patients submitted to unilateral hippocampectomy to treat refractory TLE.

Microglia as the Critical Regulators of Neuroprotection and Functional Recovery in Cerebral Ischemia

Microglial activation is considered as the critical pathogenic event in diverse central nervous system disorders including cerebral ischemia. Proinflammatory responses of activated microglia have been well reported in the ischemic brain and neuroinflammatory responses of activated microglia have been believed to be the potential therapeutic strategy. However, despite having proinflammatory roles, microglia can have significant anti-inflammatory roles and they are associated with the production of growth factors which are responsible for neuroprotection and recovery after ischemic injury. Microglia can directly promote neuroprotection by preventing ischemic infarct expansion and promoting functional outcomes. Indirectly, microglia are involved in promoting anti-inflammatory responses, neurogenesis, and angiogenesis in the ischemic brain which are crucial pathophysiological events for ischemic recovery. In fact, anti-inflammatory cytokines and growth factors produced by microglia can promote neuroprotection and attenuate neurobehavioral deficits. In addition, microglia regulate phagocytosis, axonal regeneration, blood-brain barrier protection, white matter integrity, and synaptic remodeling, which are essential for ischemic recovery. Microglia can also regulate crosstalk with neurons and other cell types to promote neuroprotection and ischemic recovery. This review mainly focuses on the roles of microglia in neuroprotection and recovery following ischemic injury. Furthermore, this review also sheds the light on the therapeutic potential of microglia in stroke patients.

Silencing lncRNA HOTAIR improves the recovery of neurological function in ischemic stroke via the miR-148a-3p/KLF6 axis

Ischemic stroke (IS), caused by a permanent or transient local reduction in blood supply to the brain, is one of the most widespread causes of public health problems in modern society. Long non-coding RNA (LncRNA) has been reported to be related to angiogenesis following IS. In this study, we explored the effect and potential molecular mechanism of lncRNA homeobox antisense non-coding RNA (HOTAIR) in IS. Permanent middle cerebral artery occlusion (pMCAO) model and oxygen and glucose deprivation (OGD) model were established. HOTAIR was increased in vivo and in vitro models post-ischemic. HOTAIR knockdown promoted neurological function recovery, manifesting in decreased modified neurological severity score, cerebral infarcted area, apoptosis and inflammation, and improved balance ability, spatial learning and memory ability. Silencing HOTAIR also improved the viability of OGD-induced N2a cells, and attenuated apoptosis and inflammation. HOTAIR can compete with KLF6 to bind to miR-148a-3p. miR-148a-3p knockdown or KLF6 overexpression partially reversed the effect of sh-HOTAIR on OGD-induced N2a cells. HOTAIR suppressed the activation of STAT3 pathway via the miR-148a-3p/KLF6 axis. To summarize, this study demonstrated that lncRNA HOTAIR absorbed miR-148a-3p and up-regulated KLF6 expression through ceRNA mechanism, and inhibited STAT3 pathway, promoted apoptosis and inflammation, and aggravated neurological injury post-IS.

Brain Repair by Cell Replacement via In Situ Neuronal Reprogramming

Neurodegenerative diseases, characterized by progressive neural loss, have been some of the most challenging medical problems in aging societies. Treatment strategies such as symptom management have little impact on dis-ease progression, while intervention with specific disease mechanisms may only slow down disease progression. One therapeutic strategy that has the potential to reverse the disease phenotype is to replenish neurons and re-build the pathway lost to degeneration. Although it is generally believed that the central nervous system has lost the capability to regenerate, increasing evidence indicates that the brain is more plastic than previously thought, containing perhaps the biggest repertoire of cells with latent neurogenic programs in the body. This review focuses on key advances in generating new neurons through in situ neuronal reprogramming, which is tied to fun-damental questions regarding adult neurogenesis, cell source, and mecha-nisms for neuronal reprogramming, as well as the ability of new neurons to integrate into the existing circuitry. Expected final online publication date for the Annual Review of Genetics, Volume 55 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Mechanism of ARPP21 antagonistic intron miR-128 on neurological function repair after stroke

OBJECTIVE

Stroke is a cerebrovascular disorder that often causes neurological function defects. ARPP21 is a conserved host gene of miR-128 controlling neurodevelopmental functions. This study investigated the mechanism of ARPP21 antagonistic intron miR-128 on neurological function repair after stroke.

METHODS

Expressions of ARPP21 and miR-128 in stroke patients were detected. The mouse neurons and astrocytes were cultured in vitro and treated with oxygen-glucose deprivation (OGD). The OGD-treated cells were transfected with pc-ARPP21 and miR-128 mimic. The proliferation of astrocytes, and the apoptosis of neurons and astrocytes were detected, and inflammatory factors of astrocytes were measured. The binding relationship between miR-128 and CREB1 was verified. The rat model of middle cerebral artery occlusion (MCAO) was established. ARPP21 expression in model rats was detected. The effects of pc-ARPP21 on neuron injury, brain edema volume, and cerebral infarct in rats were observed.

RESULTS

ARPP21 expression was downregulated and miR-128 expression was upregulated in stroke patients. pc-ARPP21 facilitated the proliferation of astrocytes and inhibited apoptosis of neurons and astrocytes, and reduced inflammation of astrocytes. miR-128 mimic could reverse these effects of pc-ARPP21 on neurons and astrocytes. miR-128 targeted CREB1 and reduced BDNF secretion. In vitro experiments confirmed that ARPP21 expression was decreased in MCAO rats, and pc-ARPP21 promoted neurological function repair after stroke.

CONCLUSION

ARPP21 upregulated CREB1 and BDNF expressions by antagonizing miR-128, thus inhibiting neuronal apoptosis and promoting neurological function repair after stroke. This study may offer a novel target for the management of stroke.

Anti-Inflammatory Dipeptide, a Metabolite from Ambioba Secretion, Protects Cerebral Ischemia Injury by Blocking Apoptosis Via p-JNK/Bax Pathway

MQ (l-methionyl-l-glutamic acid), anti-inflammatory dipeptide, is one of the metabolites of monocyte locomotion inhibitory factor, a thermostable pentapeptide secreted by Entamoeba histolytica. Monocyte locomotion inhibitory factor injection has been approved as an investigational drug for the potential neural protection in acute ischemic stroke. This study further investigated the neuroprotective effect of MQ in ischemic brain damage. Ischemia-reperfusion injury of the brain was induced in the rat model by middle cerebral artery occlusion. 2,3,5-triphenyltetrazolium chloride staining assay was used to measure cerebral infarction areas in rats. Laser Doppler measurement instrument was used to detect blood flow changes in the rat model. Nissl staining and NeuN staining were utilized to observe the numbers and structures of neuron cells, and the pathological changes in the brain tissues were examined by hematoxylin–eosin staining. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) staining was used to assess cell apoptosis. The changes in oxidative stress indexes, superoxide dismutase and malondialdehyde (MDA), were measured in serum. Methyl thiazolyl tetrazolium was used to measure the survival rates of PC12 cells. Flow cytometry assessed the apoptosis rates and the levels of reactive oxygen species. Real-time PCR was used to evaluate the mRNA expression levels, and Western blotting was used to analyze the changes in protein levels of p-JNK, Bax, cleaved Caspase3. We revealed that MQ improved neurobehavior, decreased cerebral infarction areas, altered blood flow volume, and the morphology of the cortex and hippocampus. On the other hand, it decreased the apoptosis of cortical neurons and the levels of MDA, and increased the levels of superoxide dismutase. In vitro studies demonstrated that MQ enhanced the cell survival rates and decreased the levels of reactive oxygen species. Compared to the oxygen-glucose deprivation/reperfusion group, the protein and mRNA expressions of p-JNK, Bax, cleaved Caspase3 was decreased significantly. These findings suggested that MQ exerts a neuroprotective effect in cerebral ischemia by blocking apoptosis via the p-JNK/Bax pathway.

Increased risk of stroke among patients with inflammatory bowel disease: A PRISMA-compliant meta-analysis

BACKGROUND

Previous studies on the association between inflammatory bowel disease (IBD) and stroke showed conflicting results.

METHODS

Articles published before July 2020 were searched in databases (PubMed, Web of Science, Medline, EMBASE, and Google Scholar). We computed all multivariate odds ratios (ORs) or relative risks (RRs) and 95% confidence intervals (CI) by using STATA 12.0 software.

RESULTS

The meta-analysis indicated that IBD was associated with an elevated risk of stroke (OR/RR = 1.21, 95% CI 1.08 to 1.34, I²  = 83.6%, p < .001). In addition, both Crohn's disease (CD) and ulcerative colitis (UC) were associated with a higher risk of stroke (CD: OR/RR = 1.25, 95% CI 1.03 to 1.52, I²  = 86.1%, p < .001; UC: OR/RR = 1.09, 95% CI 1.04 to 1.15, I²  = 54.7%, p = .051). Subgroup study showed that IBD was associated with a higher risk of stroke in cohort studies (RR = 1.21, 95% CI 1.08 to 1.36, I²  = 85.0%, p < .001). Subgroup study showed that IBD was related to an elevated risk of stroke in both Caucasian and Asian groups (Caucasian group: OR/RR = 1.13, 95% CI 1.05 to 1.23, I²  = 44.6%, p = .094; Asian group: OR/RR =1.36, 95% CI 1.07 to 1.74, I²  = 92.5%, p < .001).

CONCLUSION

IBD is a risk factor for stroke. More high-quality large-sample epidemiologic studies about the relationship between IBD and stroke should be further conducted.

Induced Pluripotent Stem Cells for Ischemic Stroke Treatment

Ischemic stroke is one of the main central nervous system diseases and is associated with high disability and mortality rates. Recombinant tissue plasminogen activator (rt-PA) and mechanical thrombectomy are the optimal therapies available currently to restore blood flow in patients with stroke; however, their limitations are well recognized. Therefore, new treatments are urgently required to overcome these shortcomings. Recently, stem cell transplantation technology, involving the transplantation of induced pluripotent stem cells (iPSCs), has drawn the interest of neuroscientists and is considered to be a promising alternative for ischemic stroke treatment. iPSCs are a class of cells produced by introducing specific transcription factors into somatic cells, and are similar to embryonic stem cells in biological function. Here, we have reviewed the current applications of stem cells with a focus on iPSC therapy in ischemic stroke, including the neuroprotective mechanisms, development constraints, major challenges to overcome, and clinical prospects. Based on the current state of research, we believe that stem cells, especially iPSCs, will pave the way for future stroke treatment.

Progranulin promotes functional recovery and neurogenesis in the subventricular zone of adult mice after cerebral ischemia

Progranulin (PGRN), a secreted glycosylated protein, has been reported to attenuate ischemia-induced cerebral injury through anti-inflammation, attenuation of blood-brain barrier disruption and neuroprotection. However, the effect of PGRN on neurogenesis in the subventricular zone (SVZ) after cerebral ischemia remains unclear. In this study, adult C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO), and different doses of recombinant mouse PGRN (r-PGRN, 0.3 ng, 1 ng, 5 ng) were intracerebroventricularly administered 30 min after pMCAO. Results showed that 1 ng r-PGRN markedly reduced infarct volume and rescued functional deficits 24 h after pMCAO. Meanwhile, 1 ng r-PGRN increased SVZ cell proliferation, as shown by a high number of bromodeoxyuridine-positive (BrdU+) cells and Ki-67+ cells in the ischemic ipsilateral SVZ 7 d after pMCAO. Additionally, PGRN increased the percentage of BrdU+/Doublecortin (DCX)+ cells in the ipsilateral SVZ 14 d after pMCAO and increased the percentage of new neurons (BrdU+/NeuN+ cells) in the peri-infarct striatum 28 d after pMCAO, suggesting that PGRN promotes neuronal differentiation. PGRN also upregulated phosphorylation of ERK1/2 and Akt in the ipsilateral SVZ 3 d after pMCAO. Our data indicate that PGRN treatment promotes acute functional recovery; most importantly, it also stimulates neurogenesis in the SVZ, which could be beneficial for long-term recovery after cerebral ischemia. The increase in neurogenesis could be associated with activation of the MAPK/ERK and PI3K/Akt pathways. These results suggest a potential new strategy utilizing PGRN in ischemic stroke therapy.

Circular RNA circ_HECTD1 regulates cell injury after cerebral infarction by miR-27a-3p/FSTL1 axis

Cerebral infarction is a common cerebrovascular disease caused by neural cell injury, with high mortality worldwide. Circular RNAs HECT domain E3 ubiquitin-protein ligase 1 (circ_HECTD1) has been reported to be related to the oxygen-glucose deprivation/reperfusion (OGD/R)-caused neuronal damage in cerebral ischemia. This study is designed to explore the role and mechanism of circ_HECTD1 in OGD/R-induced cell injury in cerebral ischemia. Circ_HECTD1, microRNA-27a-3p (miR-27a-3p), and Follistatin-like 1 (FSTL1) level were detected by real-time quantitative polymerase chain reaction (RT-qPCR). The localization of circ_HECTD1 was analyzed by subcellular fractionation assay. Cell proliferative ability and apoptosis were assessed by 5-ethynyl-2'-deoxyuridine (EdU), 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT), and flow cytometry assays. The protein levels of proliferating cell nuclear antigen (PCNA), B-cell lymphoma-2 (Bcl-2), Bcl-2 related X protein (Bax), Cleaved poly-ADP-ribose polymerase (PARP), and FSTL1 were examined by western blot assay. The binding relationship between miR-27a-3p and circ_HECTD1 or FSTL1 was predicted by starbase 3.0 then verified by a dual-luciferase reporter assay. Circ_HECTD1 and FSTL1 were highly expressed, and miR-27a-3p was decreased in OGD/R-treated HT22 cells. Moreover, circ_HECTD1 knockdown could boost cell proliferative ability and repress apoptosis in OGD/R-triggered HT22 cells in vitro. Mechanical analysis discovered that circ_HECTD1 could regulate FSTL1 expression by sponging miR-27a-3p. Circ_HECTD1 deficiency could mitigate OGD/R-induced HT22 cell damage by modulating the miR-27a-3p/FSTL1 axis, providing a promising therapeutic target for cerebral infarction treatment.

Tyrosol as a Neuroprotector: Strong Effects of a "Weak" Antioxidant

The use of neuroprotective agents for stroke is pathogenetically justified, but the translation of the results of preclinical studies of neuroprotectors into clinical practice has been a noticeable failure. One of the leading reasons for these failures is the one-target mechanism of their activity. p-Tyrosol (Tyr), a biophenol, is present in a variety of natural sources, mainly in foods, such as olive oil and wine. Tyr has a wide spectrum of biological activity: antioxidant, stress-protective, anti-inflammatory, anticancer, cardioprotective, neuroprotective and many others. This review analyzes data on the neuroprotective, antioxidant, anti-inflammatory, anti-apoptotic and other kinds of Tyr activity as well as data on the pharmacokinetics of the substance. The data presented in the review substantiate the acceptability of tyr as the basis for the development of a new neuroprotective drug with multitarget activity for the treatment of ischemic stroke. Tyr is a promising molecule for the development of an effective neuroprotective agent for use in ischemic stroke.

Telmisartan Inhibits the NLRP3 Inflammasome by Activating the PI3K Pathway in Neural Stem Cells Injured by Oxygen-Glucose Deprivation

Angiotensin II receptor blockers (ARBs) have been shown to exert neuroprotective effects by suppressing inflammatory and apoptotic responses. In the present study, the effects of the ARB telmisartan on the NLRP3 inflammasome induced by oxygen-glucose deprivation (OGD) in neural stem cells (NSCs) were investigated, as well as their possible association with the activation of the PI3K pathway. Cultured NSCs were treated with different concentrations of telmisartan and subjected to various durations of OGD. Cell counting, lactate dehydrogenase, bromodeoxyuridine, and colony-forming unit assays were performed to measure cell viability and proliferation. In addition, the activity of intracellular signaling pathways associated with the PI3K pathway and NLRP3 inflammasome was evaluated. Telmisartan alone did not affect NSCs up to a concentration of 10 μM under normal conditions but showed toxicity at a concentration of 100 μM. Moreover, OGD reduced the viability of NSCs in a time-dependent manner. Nevertheless, treatment with telmisartan increased the viability and proliferation of OGD-injured NSCs. Furthermore, telmisartan promoted the expression of survival-related proteins and mRNA while inhibiting the expression of death-related proteins induced by OGD. In particular, telmisartan attenuated OGD-dependent expression of the NLRP3 inflammasome and its related signaling proteins. These beneficial effects of telmisartan were blocked by a PI3K inhibitor. Together, these results indicate that telmisartan attenuated the activation of the NLRP3 inflammasome by triggering the PI3K pathway, thereby contributing to neuroprotection.

An updated review of autophagy in ischemic stroke: From mechanisms to therapies

Stroke is a leading cause of mortality and morbidity worldwide. Understanding the underlying mechanisms is important for developing effective therapies for treating stroke. Autophagy is a self-eating cellular catabolic pathway, which plays a crucial homeostatic role in the regulation of cell survival. Increasing evidence shows that autophagy, observed in various cell types, plays a critical role in brain pathology after ischemic stroke. Therefore, the regulation of autophagy can be a potential target for ischemic stroke treatment. In the present review, we summarize the recent progress that research has made regarding autophagy and ischemic stroke, including common signaling pathways, the role of autophagic subtypes (e.g. mitophagy, pexophagy, aggrephagy, endoplasmic reticulum-phagy, and lipophagy) in ischemic stroke, as well as the current methods for autophagy detection and potential therapeutic strategy.

Promotion of Momordica Charantia polysaccharides on neural stem cell proliferation by increasing SIRT1 activity after cerebral ischemia/reperfusion in rats

The deacetylase SIRT1 has been reported to play a critical role in regulating neurogenesis, which may be an adaptive processes contributing to recovery after stroke. Our previous work showed that the antioxidant capacity of Momordica charantia polysaccharides (MCPs) could protect against cerebral ischemia/reperfusion (I/R) after stroke. However, whether the protective effect of MCPs on I/R injury is related to neural stem cell (NSC) proliferation remains unclear. In the present study, we designed invivo and invitro experiments to elucidate the underlying mechanisms by which MCPs promote endogenous NSC proliferation during cerebral I/R. Invivo results showed that MCPs rescued the memory and learning abilities of rats after I/R damage and enhanced NSC proliferation in the rat subventricular zone (SVZ) and subgrannular zone (SGZ) during I/R. Invitro experiments demonstrated that MCPs could stimulate the proliferation of C17.2 cells under oxygen-glucose deprivation (OGD) conditions. Further studies revealed that the proliferation-promoting mechanism of MCPs relied on increasing the activity of SIRT1, decreasing the level of acetylation of β-catenin in the cytoplasm, and then triggering the translocation of β-catenin into the nucleus. These data provide experimental evidence that the up-regulation of SIRT1 activity by MCPs led to an increased cytoplasmic deacetylation of β-catenin, which promoted translocation of β-catenin to the nucleus to participate in the signaling pathway involved in NSC proliferation. The present study reveals that MCPs function as a therapeutic drug to promote stroke recovery by increasing the activity of SIRT1, decreasing the level of acetylated β-catenin, promoting the nuclear translocation of β-catenin and thereby increasing endogenous NSC proliferation.

Neutrophil-like Cell-Membrane-Coated Nanozyme Therapy for Ischemic Brain Damage and Long-Term Neurological Functional Recovery

Oxidative stress and a series of excessive inflammatory responses are major obstacles for neurological functional recovery after ischemic stroke. Effective noninvasive anti-inflammatory therapies are urgently needed. However, unsatisfactory therapeutic efficacy of current drugs and inadequate drug delivery to the damaged brain are major problems. Nanozymes with robust anti-inflammatory and antioxidative stress properties possess therapeutic possibility for ischemic stroke. However, insufficiency of nanozyme accumulation in the ischemic brain by noninvasive administration hindered their application. Herein, we report a neutrophil-like cell-membrane-coated mesoporous Prussian blue nanozyme (MPBzyme@NCM) to realize noninvasive active-targeting therapy for ischemic stroke by improving the delivery of a nanozyme to the damaged brain based on the innate connection between inflamed brain microvascular endothelial cells and neutrophils after stroke. The long-term in vivo therapeutic efficacy of MPBzyme@NCM for ischemic stroke was illustrated in detail after being delivered into the damaged brain and uptake by microglia. Moreover, the detailed mechanism of ischemic stroke therapy via MPBzyme@NCM uptake by microglia was further studied, including microglia polarization toward M2, reduced recruitment of neutrophils, decreased apoptosis of neurons, and proliferation of neural stem cells, neuronal precursors, and neurons. This strategy may provide an applicative perspective for nanozyme therapy in brain diseases.

Brain morphological and connectivity changes on MRI after stem cell therapy in a rat stroke model

In animal models of stroke, behavioral assessments could be complemented by a variety of neuroimaging studies to correlate them with recovery and better understand mechanisms of improvement after stem cell therapy. We evaluated morphological and connectivity changes after treatment with human mesenchymal stem cells (hMSCs) in a rat stroke model, through quantitative measurement of T₂-weighted images and diffusion tensor imaging (DTI). Transient middle cerebral artery occlusion rats randomly received PBS (PBS-only), FBS cultured hMSCs (FBS-hMSCs), or stroke patients’ serum cultured hMSCs (SS-hMSCs). Functional improvement was assessed using a modified neurological severity score (mNSS). Quantitative analyses of T₂-weighted ischemic lesion and ventricular volume changes were performed. Brain microstructure/connectivity changes were evaluated in the ischemic recovery area by DTI-derived microstructural indices such as relative fractional anisotropy (rFA), relative axial diffusivity (rAD), and relative radial diffusivity (rRD), and relative fiber density (rFD) analyses. According to mNSS results, the SS-hMSCs group showed the most prominent functional improvement. Infarct lesion volume of the SS-hMSCs group was significantly decreased at 2 weeks when compared to the PBS-only groups, but there were no differences between the FBS-hMSCs and SS-hMSCs groups. Brain atrophy was significantly decreased in the SS-hMSCs group compared to the other groups. In DTI, rFA and rFD values were significantly higher and rRD value was significant lower in the SS-hMSCs group and these microstructure/connectivity changes were correlated with T₂-weighted morphological changes. T₂-weighted volume alterations (ischemic lesion and brain atrophy), and DTI microstructural indices and rFD changes, were well matched with the results of behavioral assessment. These quantitative MRI measurements could be potential outcome predictors of functional recovery after treatment with stem cells for stroke.

Phosphofructokinase-1 Inhibition Promotes Neuronal Differentiation of Neural Stem Cells and Functional Recovery After Stroke

Ischemic stroke is a major cause of long-term disability. Neuronal differentiation of neural stem cells (NSCs) is crucial for brain repair after stroke. However, the underlying mechanisms remain unclear. Here, the role and potential mechanisms of phosphofructokinase-1 (PFK-1), the rate-limiting enzyme of glycolysis, was investigated in stroke using middle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation models. We found that stroke increased the PFK-1 expression of NSCs. However, PFK-1 inhibition promoted neuronal differentiation of NSCs and facilitated the dendritic maturation of newborn neurons in vitro and in vivo. Moreover, PFK-1 inhibition also improved the spatial memory performance of MCAO rats. Additionally, we proved that the effect of PFK-1 inhibition above might be achieved by promoting β-catenin nuclear translocation and activating its downstream signaling, independent of Wnt signaling. Thus, these observations reveal a critical role of PFK-1 in stroke, which may provide a novel target for regenerative repair after stroke.

Integrative traditional Korean medicine management, including acupuncture and Chuna-manual therapy, for stroke-related central facial palsy: A study of three case reports

Central facial palsy, which is a sequela of stroke, is associated with decreased quality of life and psychosocial function. Integrative Korean medicine management, including acupuncture and Chuna-manual therapy, has been used to treat neurological diseases, including facial palsy. We report three cases of central facial palsy patients who had these symptoms over three months after a stroke. They had received rehabilitation treatment for the paralyzed upper and lower extremities. However, as their central facial palsy symptom did not improve, Chuna-manual therapy (SJS nonresistance technique) for facial palsy was started along with acupuncture. Oral region movement improved after four weeks of integrative acupuncture and Chuna-manual therapy. After ten to sixteen weeks of treatment, the facial nerve grading system 2.0 grades improved by one in two cases. In one case, although there was no significant change in the grade, she was satisfied with the results after adding Chuna-manual therapy to acupuncture. There were no adverse events. Integrative management, including acupuncture and Chuna-manual therapy, might be an effective treatment strategy for central facial palsy. Further prospective, controlled studies are warranted.

Neurogenesis After Stroke: A Therapeutic Perspective

Stroke is a major cause of death and disability worldwide. Yet therapeutic strategies available to treat stroke are very limited. There is an urgent need to develop novel therapeutics that can effectively facilitate functional recovery. The injury that results from stroke is known to induce neurogenesis in penumbra of the infarct region. There is considerable interest in harnessing this response for therapeutic purposes. This review summarizes what is currently known about stroke-induced neurogenesis and the factors that have been identified to regulate it. Additionally, some key studies in this field have been highlighted and their implications on future of stroke therapy have been discussed. There is a complex interplay between neuroinflammation and neurogenesis that dictates stroke outcome and possibly recovery. This highlights the need for a better understanding of the neuroinflammatory process and how it affects neurogenesis, as well as the need to identify new mechanisms and potential modulators. Neuroinflammatory processes and their impact on post-stroke repair have therefore also been discussed.

The role of exosomal microRNAs in central nervous system diseases

MicroRNAs (miRNA), endogenous non-coding RNAs approximately 22 nucleotides long, regulate gene expression by mediating translational inhibition or mRNA degradation. Exosomes are a tool for intercellular transmission of information in which miRNA exchange plays an important role. Under pathophysiological conditions in the central nervous system (CNS), cellular transmission of exosomal miRNAs can regulate signaling pathways. Exosomal miRNAs are involved in the occurrence and development of diverse CNS diseases, such as traumatic brain injury, spinal cord injury, stroke, neurodegenerative diseases, epilepsy, and glioma. The use of exosomes as transport vehicles for certain miRNAs provides a novel therapeutic strategy for CNS diseases. Furthermore, the exosomes in body fluids change with the occurrence of diseases, indicating that subtle changes in physiological and pathological processes in vivo could be recognized by analyzing exosomes. Exosomal analysis is expected to act as a novel tool for diagnosis and prediction of neurological diseases. In this review, we present the current understanding of the implications of miRNAs in CNS diseases and summarize the role and mechanism of action of exosomal miRNA in nervous system disease models.

Systematic Review of Nicotine Exposure's Effects on Neural Stem and Progenitor Cells

While various modalities of chronic nicotine use have been associated with numerous negative consequences to human health, one possible benefit of nicotine exposure has been uncovered. The discovery of an inverse correlation between smoking and Parkinson's disease, and later Alzheimer's disease as well, motivated investigation of nicotine as a neuroprotective agent. Some studies have demonstrated that nicotine elicits improvements in cognitive function. The hippocampus, along with the subventricular zone (SVZ), is a distinct brain region that allow for ongoing postnatal neurogenesis throughout adulthood and plays a major role in certain cognitive behaviors like learning and memory. Therefore, one hypothesis underlying nicotine-induced neuroprotection is possible effects on neural stem cells and neural precursor cells. On the other hand, nicotine withdrawal frequently leads to cognitive impairments, particularly in hippocampal-dependent behaviors, possibly suggesting an impairment of hippocampal neurogenesis with nicotine exposure. This review discusses the current body of evidence on nicotine's effects on neural stem cells and neural progenitors. Changes in neural stem cell proliferation, survival, intracellular dynamics, and differentiation following acute and chronic nicotine exposure are examined.

Ambroxol Upregulates Glucocerebrosidase Expression to Promote Neural Stem Cells Differentiation Into Neurons Through Wnt/β-Catenin Pathway After Ischemic Stroke

Ischemic stroke has been becoming one of the leading causes resulting in mortality and adult long-term disability worldwide. Post-stroke pneumonia is a common complication in patients with ischemic stroke and always associated with 1-year mortality. Though ambroxol therapy often serves as a supplementary treatment for post-stroke pneumonia in ischemic stroke patients, its effect on functional recovery and potential mechanism after ischemic stroke remain elusive. In the present study, the results indicated that administration of 70 mg/kg and 100 mg/kg enhanced functional recovery by virtue of decreasing infarct volume. The potential mechanism, to some extent, was due to promoting NSCs differentiation into neurons and interfering NSCs differentiation into astrocytes through increasing GCase expression to activate Wnt/β-catenin signaling pathway in penumbra after ischemic stroke, which advanced basic knowledge of ambroxol in regulating NSCs differentiation and provided a feasible therapy for ischemic stroke treatment, even in other brain disorders in clinic.

The Selective SIK2 Inhibitor ARN-3236 Produces Strong Antidepressant-Like Efficacy in Mice via the Hippocampal CRTC1-CREB-BDNF Pathway

Depression is a widespread chronic medical illness affecting thoughts, mood, and physical health. However, the limited and delayed therapeutic efficacy of monoaminergic drugs has led to intensive research efforts to develop novel antidepressants. ARN-3236 is the first potent and selective inhibitor of salt-inducible kinase 2 (SIK2). In this study, a multidisciplinary approach was used to explore the antidepressant-like actions of ARN-3236 in mice. Chronic social defeat stress (CSDS) and chronic unpredictable mild stress (CUMS) models of depression, various behavioral tests, high performance liquid chromatography-tandem mass spectrometry, stereotactic infusion, viral-mediated gene transfer, western blotting, co-immunoprecipitation and immunofluorescence were used together. It was found that ARN-3236 could penetrate the blood-brain barrier. Repeated ARN-3236 administration induced significant antidepressant-like effects in both the CSDS and CUMS models of depression, accompanied with fully preventing the stress-enhanced SIK2 expression and cytoplasmic translocation of cyclic adenosine monophosphate response element binding protein (CREB)-regulated transcription coactivator 1 (CRTC1) in the hippocampus. ARN-3236 treatment also completely reversed the down-regulating effects of CSDS and CUMS on the hippocampal brain-derived neurotrophic factor (BDNF) system and neurogenesis. Moreover, we demonstrated that the hippocampal CRTC1-CREB-BDNF pathway mediated the antidepressant-like efficacy of ARN-3236. Collectively, ARN-3236 possesses strong protecting effects against chronic stress, and could be a novel antidepressant beyond monoaminergic drugs.

Neuroregeneration and functional recovery after stroke: advancing neural stem cell therapy toward clinical application

Stroke is a main cause of death and disability worldwide. The ability of the brain to self-repair in the acute and chronic phases after stroke is minimal; however, promising stem cell-based interventions are emerging that may give substantial and possibly complete recovery of brain function after stroke. Many animal models and clinical trials have demonstrated that neural stem cells (NSCs) in the central nervous system can orchestrate neurological repair through nerve regeneration, neuron polarization, axon pruning, neurite outgrowth, repair of myelin, and remodeling of the microenvironment and brain networks. Compared with other types of stem cells, NSCs have unique advantages in cell replacement, paracrine action, inflammatory regulation and neuroprotection. Our review summarizes NSC origins, characteristics, therapeutic mechanisms and repair processes, then highlights current research findings and clinical evidence for NSC therapy. These results may be helpful to inform the direction of future stroke research and to guide clinical decision-making.

Regeneration using endogenous neural stem cells following neonatal brain injury

Despite recent advancements in perinatal care, the incidence of neonatal brain injury has not decreased. No therapies are currently available to repair injured brain tissues. In the postnatal brain, neural stem cells reside in the ventricular-subventricular zone (V-SVZ) and continuously generate new immature neurons (neuroblasts). After brain injury in rodents, V-SVZ-derived neuroblasts migrate toward the injured area using blood vessels as a scaffold. Notably, the neonatal V-SVZ has a remarkable neurogenic capacity. Furthermore, compared with the adult brain, after neonatal brain injury, larger numbers of neuroblasts migrate toward the lesion, raising the possibility that the V-SVZ could be a source for endogenous neuronal regeneration after neonatal brain injury. We recently demonstrated that efficient migration of V-SVZ-derived neuroblasts toward a lesion is supported by neonatal radial glia via neural cadherin (N-cadherin)-mediated neuron-fiber contact, which promotes RhoA activity. Moreover, providing blood vessel- and radial glia-mimetic scaffolds for migrating neuroblasts promotes neuronal migration and improves functional gait behaviors after neonatal brain injury. In the V-SVZ, oligodendrocyte progenitor cells (OPCs) are also generated and migrate toward the surrounding white matter, where they differentiate and form myelin. After white matter injury in rodents, the production and subsequent migration of V-SVZ-derived OPCs are enhanced. In the neonatal period, administration of growth factors at a specific time promotes oligodendrocyte regeneration and functional recovery after brain injury. These findings suggest that activating the high regenerative capacity that is specific to the neonatal period could lead to the development of new therapeutic strategies for neonatal brain injury.

Immunological Responses to Transgene-Modified Neural Stem Cells After Transplantation

Neural stem cell (NSC) therapy is a promising therapeutic strategy for stroke. Researchers have frequently carried out genetic modification or gene editing of stem cells to improve survival or therapeutic function. However, NSC transplantation carries the risk of immune rejection, and genetic modification or gene-editing might further increase this risk. For instance, recent studies have reported on manipulating the stem cell genome and transplantation via the insertion of an exogenous gene derived from magnetotactic bacteria. However, whether transgene-modified stem cells are capable of inducing immunological reactions has not been explored. Although NSCs rarely express the major histocompatibility complex (MHC), they can still cause some immunological issues. To investigate whether transgene-modified NSCs aggravate immunological responses, we detected the changes in peripheral immune organs and intracerebral astrocytes, glial cells, and MHC-I and MHC-II molecules after the injection of GFP-labeled or mms6-GFP-labeled NSCs in a rat model. Xenogeneic human embryonic kidney (HEK-293T) cells were grafted as a positive control group. Our results indicated that xenogeneic cell transplantation resulted in a strong peripheral splenic response, increased astrocytes, enhanced microglial responses, and upregulation of MHC-I and MHC-II expression on the third day of transplantation. But they decreased obviously except Iba-1 positive cells and MHC-II expression. When injection of both mms6-GFP-labeled NSCs and GFP-labeled NSCs also induced similar responses as HEK-293T cells on the third days, but MHC-I and MHC-II expression decreased 3 weeks after transplantation. In addition, mms6 transgene-modified NSCs did not produce peripheral splenic response responses as well as astrocytes, microglial cells, MHC-I and MHC-II positive cells responses when compared with non-modified NSCs. The present study provides preliminary evidence that transgenic modification does not aggravate immunological responses in NSC transplantation.

Protective effects of mesenchymal stem cells on ischemic brain injury: therapeutic perspectives of regenerative medicine

Cerebral ischemic injury as the main manifestation of stroke can occur in stroke patients (70-80%). Nowadays, the main therapeutic strategy used for ischemic brain injury treatment aims to achieve reperfusion, neuroprotection, and neurorecovery. Also, angiogenesis as a therapeutic approach maybe represents a promising tool to enhance the prognosis of cerebral ischemic stroke. Unfortunately, although many therapeutic approaches as a life-saving gateway for cerebral ischemic injuries like pharmacotherapy and surgical treatments are widely used, they all fail to restore or regenerate damaged neurons in the brain. So, the suitable therapeutic approach would focus on regenerating the lost cells and restore the normal function of the brain. Currently, stem cell-based regenerative medicine introduced a new paradigm approach in cerebral ischemic injuries treatment. Today, in experimental researches, different types of stem cells such as mesenchymal stem cells have been applied. Therefore, stem cell-based regenerative medicine provides the opportunity to inquire and develop a more effective and safer therapeutic approach with the capability to produce and regenerate new neurons in damaged tissues.

Inhibition of LPA5 Activity Provides Long-Term Neuroprotection in Mice with Brain Ischemic Stroke

Stroke is a leading cause of long-term disability in ischemic survivors who are suffering from motor, cognitive, and memory impairment. Previously, we have reported suppressing LPA₅ activity with its specific antagonist can attenuate acute brain injuries after ischemic stroke. However, it is unclear whether suppressing LPA₅ activity can also attenuate chronic brain injuries after ischemic stroke. Here, we explored whether effects of LPA₅ antagonist, TCLPA5, could persist a longer time after brain ischemic stroke using a mouse model challenged with tMCAO. TCLPA5 was administered to mice every day for 3 days, starting from the time immediately after reperfusion. TCLPA5 administration improved neurological function up to 21 days after tMCAO challenge. It also reduced brain tissue loss and cell apoptosis in mice at 21 days after tMCAO challenge. Such long-term neuroprotection of TCLPA5 was associated with enhanced neurogenesis and angiogenesis in post-ischemic brain, along with upregulated expression levels of vascular endothelial growth factor. Collectively, results of the current study indicates that suppressing LPA₅ activity can provide long-term neuroprotection to mice with brain ischemic stroke.

Hericium erinaceus potentially rescues behavioural motor deficits through ERK-CREB-PSD95 neuroprotective mechanisms in rat model of 3-acetylpyridine-induced cerebellar ataxia

Cerebellar ataxia is a neurodegenerative disorder with no definitive treatment. Although several studies have demonstrated the neuroprotective effects of Hericium erinaceus (H.E.), its mechanisms in cerebellar ataxia remain largely unknown. Here, we investigated the neuroprotective effects of H.E. treatment in an animal model of 3-acetylpyridine (3-AP)-induced cerebellar ataxia. Animals administered 3-AP injection exhibited remarkable impairments in motor coordination and balance. There were no significant effects of 25 mg/kg H.E. on the 3-AP treatment group compared to the 3-AP saline group. Interestingly, there was also no significant difference in the 3-AP treatment group compared to the non-3-AP control, indicating a potential rescue of motor deficits. Our results revealed that 25 mg/kg H.E. normalised the neuroplasticity-related gene expression to the level of non-3-AP control. These findings were further supported by increased protein expressions of pERK1/2-pCREB-PSD95 as well as neuroprotective effects on cerebellar Purkinje cells in the 3-AP treatment group compared to the 3-AP saline group. In conclusion, our findings suggest that H.E. potentially rescued behavioural motor deficits through the neuroprotective mechanisms of ERK-CREB-PSD95 in an animal model of 3-AP-induced cerebellar ataxia.

Acute kidney injury after a stroke: A PRISMA-compliant meta-analysis

BACKGROUND

The relationship between acute kidney injury (AKI) and stroke needs quantitative summary. Therefore, we analyzed the associations between AKI and stroke including the incidence, risk factors of AKI after stroke, and the influence of AKI after a stroke on prognosis of stroke.

METHODS

Articles published until November 2019 were searched based on the following databases: PubMed, Web of Science, EMBASE, Medline, and Google Scholar. We computed the following results [rates of AKI incidence after a stroke, odds ratios (ORs) or relative risks (RRs) estimates and the 95% confidence intervals (CIs) for the association between risk factors and AKI, ORs or RRs and the CIs for the association between AKI and outcomes after a stroke] by using STATA 13.0 software.

RESULTS

The study reported an overall incidence of AKI of 12% with a random-effects model. Additionally, the present study showed that higher National Institutes of Health Stroke Scale (NIHSS) score on admission and history of hypertension were associated with higher risk of AKI after stroke. Moreover, the study showed that AKI after stroke was associated with higher in-hospital mortality, higher 1-month mortality, higher long-term mortality, and poorer functional outcome.

CONCLUSIONS

Acute kidney injury appears to be a common complication after stroke and is related to increased mortality and disability in stroke. Additionally, high NIHSS score on admission and history of hypertension were the critical risk factors for the AKI after stroke. More large-scale studies should be made to explore AKI after stroke.

Neuroprotective Effects of Celastrol on Transient Global Cerebral Ischemia Rats via Regulating HMGB1/NF-κB Signaling Pathway

Cerebral ischemia is a major cause of brain dysfunction, neuroinflammation and oxidative stress have been implicated in the pathophysiological process of cerebral ischemia/reperfusion injury. Celastrol is a potent inhibitor of inflammation and oxidative stress that has little toxicity. The present study was designed to evaluate whether celastrol has neuroprotective effects through anti-inflammatory and antioxidant actions, and to elucidate the possible involved mechanisms in transient global cerebral ischemia reperfusion (tGCI/R) rats. Celastrol (1, 2, or 4 mg/kg) was administrated intraperitoneally immediately after reperfusion and the effect of celastrol on reverting spatial learning and memory impairment was determined by Morris water maze (MWM) task. Inflammatory response and oxidative stress, hippocampal neuronal damage and glial activation, and HMGB1/NF-κB signaling pathway proteins were also examined. Our results indicated that celastrol dose-dependently reduced hippocampal and serum concentration of pro-inflammatory markers (TNF-α, IL-1β, and IL-6) and oxidative stress marker (MDA), whereas the anti-inflammatory marker IL-10 and antioxidant markers (GSH, SOD, and CAT) were increased significantly in celastrol treated tGCI/R rats. Celastrol alleviated apoptotic neuronal death, inhibited reactive glial activation and proliferation and improved ischemia-induced neurological deficits. Simultaneously, we found that mechanisms responsible for the neuroprotective effect of celastrol could be attributed to its anti-inflammatory and antioxidant actions via inhibiting HMGB1/NF-κB signaling pathway. These findings provide a proof of concept for the further validation that celastrol may be a superior candidate for the treatment of severe cerebral ischemic patients in clinical practice in the future.

Effect of Wnt signaling pathway on neurogenesis after cerebral ischemia and its therapeutic potential

Neurogenesis process in the chronic phase of ischemic stroke has become the focus of research on stroke treatment recently, mainly through the activation of related pathways to increase the differentiation of neural stem cells (NSCs) in the brain sub-ventricular zone (SVZ) and subgranular zone (SGZ) of hippocampal dentate gyrus (DG) areas into neurons, promoting neurogenesis. While there is still debate about the longevity of active adult neurogenesis in humans, the SVZ and SGZ have the capacity to upregulate neurogenesis in response to cerebral ischemia, which opens discussion about potential treatment strategies to harness this neuronal regenerative response. Wnt signaling pathway is one of the most important approaches potentially targeting on neurogenesis after cerebral ischemia, appropriate activation of which in NSCs may help to improve the sequelae of cerebral ischemia. Various therapeutic approaches are explored on preclinical stage to target endogenous neurogenesis induced by Wnt signaling after stroke onset. This article describes the composition of Wnt signaling pathway and the process of neurogenesis after cerebral ischemia, and emphatically introduces the recent studies on the mechanisms of this pathway for post-stroke neurogenesis and the therapeutic possibility of activating the pathway to improve neurogenesis after stroke.

Proteomics-Guided Study on Buyang Huanwu Decoction for Its Neuroprotective and Neurogenic Mechanisms for Transient Ischemic Stroke: Involvements of EGFR/PI3K/Akt/Bad/14-3-3 and Jak2/Stat3/Cyclin D1 Signaling Cascades

Buyang Huanwu Decoction (BHD), a classic traditional Chinese medicine (TCM) formula, has been used for recovering neurological dysfunctions and treating post-stroke disability in China for 200 years. In the present study, we investigated the effects of BHD on inhibiting neuronal apoptosis, promoting proliferation and differentiation of neural stem cells (NSCs) and neurite formation and enhancing learning and memory functional recovery in an experimental rat ischemic stroke model. BHD significantly reduced infarct volume and decreased cell apoptosis in the ischemic brain. BHD enhanced neuronal cell viability in vitro. BHD dose-dependently promoted the proliferation of NSCs in ischemic rat brains in vivo. Moreover, BHD promoted neuronal and astrocyte differentiation in primary cultured NSCs in vitro. Water maze test revealed that BHD promoted the recovery of learning function but not memory functions in the transient ischemic rats. We then investigated the changes of the cellular signaling molecules by using two-dimension (2D) gel electrophoresis and focused on the PI3K/Akt/Bad and Jak2/Stat3/cyclin D1signaling pathway to uncover its underlying mechanisms for its neuroprotective and neurogenetic effects. BHD significantly upregulated the expression of p-PI3K, p-Akt, and p-Bad as well as the expression of p-Jak, p-Stat3, and cyclin D1 in vitro and in vivo. In addition, BHD upregulated Hes1 and downregulated cav-1 in vitro and in vivo. Taken together, these results suggest that BHD has neuroprotective effects and neurogenesis-promoting effects via activating PI3K/Akt/Bad and Jak2/Stat3/Cyclin D1 signaling pathways. Graphical Abstract Buyang Huanwu Decoction (BHD) activates the PI3K-AKT-BAD pathway in the ischemic brain for neuroprotection. BHD also activates JAK2/STAT3/Cyclin D1 signaling cascades for promoting neurogenesis in the hippocampus of post-ischemic brains. Moreover, BHD inhibits the expression of caveolin-1 and increases the expression of HES1 for promoting neuronal differentiation. The neuroprotective and neurogenesis-promoting effects in the hippocampus of post-ischemic brains promote learning ability.

Glia and Neural Stem and Progenitor Cells of the Healthy and Ischemic Brain: The Workplace for the Wnt Signaling Pathway

Wnt signaling plays an important role in the self-renewal, fate-commitment and survival of the neural stem/progenitor cells (NS/PCs) of the adult central nervous system (CNS). Ischemic stroke impairs the proper functioning of the CNS and, therefore, active Wnt signaling may prevent, ameliorate, or even reverse the negative effects of ischemic brain injury. In this review, we provide the current knowledge of Wnt signaling in the adult CNS, its status in diverse cell types, and the Wnt pathway’s impact on the properties of NS/PCs and glial cells in the context of ischemic injury. Finally, we summarize promising strategies that might be considered for stroke therapy, and we outline possible future directions of the field.

Astragaloside IV improves neurobehavior and promotes hippocampal neurogenesis in MCAO rats though BDNF-TrkB signaling pathway

Astragaloside IV (AST) as the main active ingredient of Astragalus membranaceus. Clinical and laboratory-based studies have demonstrated the effects of AST on cerebral protection and angiogenesis after ischemia stroke. In addition, several reports investigated the effect of AST on proliferation of neural stem cells. The current study was aimed to evaluate the influence of AST on neurogenesis in hippocampal dentate gyrus (DG) of MCAO rats and to explore the possible mechanisms. In this study, the neurobehavioral tests (Ludmila Belayev 12-point scoring, Screen test, fore limb placing test) had been employed to investigate the effect of AST treatment against functional deficit of MCAO rats. The immunofluorescence staining, western-blot and qRT-PCR was performed to evaluate the effects of AST on proliferation, differentiation and maturity of neural stemr cells in hippocampus. Moreover, we investigated the possible mechanism of the AST treatment in promoting neurogenesis after ischemic stroke. The findings indicated that AST treatment ameliorated the neurobehavior of MCAO rats. The results indicated that AST treatment possessed the potential to improve proprioceptive sense and motor function of MCAO rats. AST treatment sustained neuronal viability and stimulates sensorimotor integration functional recovery in MCAO rats. The results suggested that AST improved neurobehavior deficit after ischemic stroke. Furthermore, AST promoted neurogenesis through upregulating the expressing of BNDF/TrkB signaling pathway. Therefore AST might be a promising therapeutic agent for ischemic stroke.

Growth Hormone Treatment Promotes Remote Hippocampal Plasticity after Experimental Cortical Stroke

Cognitive impairment is common after stroke, and disturbances in hippocampal function are often involved, even in remote non-hippocampal injuries. In terms of hippocampal function, growth hormone (GH) is known to affects plasticity and cognition. We aimed to investigate whether GH treatment after an experimental cortical stroke could enhance remote hippocampal plasticity and the hippocampal-dependent visual discrimination task. C57BL6 male mice were subjected to cortical photothrombotic stroke. Stroke mice were then treated with either saline or GH at 48 h after occlusion for 28 days. We assessed learning and memory using mouse touchscreen platform for the visual discrimination task. We also evaluated markers of neural progenitor cells, synaptic plasticity and cerebrovascular remodelling in the hippocampal formation. GH treatment significantly improved the performance on visual discrimination task after stroke. We observed a concomitant increased number of bromodeoxyuridine-positive cells in the dentate gyrus of the hippocampus. We also detected increased protein levels and density of doublecortin, a neuronal precursor cells marker, as well as glutamate receptor 1 (GLuR1), a synaptic marker. These findings provide further neurobiological evidence for how GH treatment could be used to promote hippocampal plasticity in a remote region from the initial cortical injury, and thus enhance cognitive recovery after stroke.

The CD200/CD200R signaling pathway contributes to spontaneous functional recovery by enhancing synaptic plasticity after stroke

BACKGROUND

Spontaneous functional recovery occurs during the acute phase after stroke onset, but this intrinsic recovery remains limited. Therefore, exploring the mechanism underlying spontaneous recovery and identifying potential strategies to promote functional rehabilitation after stroke are very important. The CD200/CD200R signaling pathway plays an important role in neurological recovery by modulating synaptic plasticity during multiple brain disorders. However, the effect and mechanism of action of the CD200/CD200R pathway in spontaneous functional recovery after stroke are unclear.

METHODS

In this study, we used a transient middle cerebral artery occlusion (MCAO) model in rats to investigate the function of CD200/CD200R signaling in spontaneous functional recovery after stroke. We performed a battery of behavioral tests (Longa test, adhesive removal test, limb-use asymmetry test, and the modified grip-traction test) to evaluate sensorimotor function after intracerebroventricular (i.c.v.) injection with CD200 fusion protein (CD200Fc) or CD200R blocking antibody (CD200R Ab) post-stroke. Density and morphology of dendritic spines were analyzed by Golgi staining. Microglia activation was evaluated by immunofluorescence staining. Western blot was used to detect the levels of protein and the levels of mRNA were measured by qPCR.

RESULTS

Our study demonstrated that sensorimotor function, synaptic proteins, and structures were gradually recovered and CD200R was transiently upregulated in ipsilateral cortex after stroke. Synapse-related proteins and dendritic spines were preserved, accompanied by sensorimotor functional recovery, after stereotaxic CD200Fc injection post-stroke. In addition, CD200Fc restrained microglia activation and pro-inflammatory factor release (such as Il-1, Tnf-α, and Il-6) after MCAO. On the contrary, CD200R Ab aggravated sensory function recovery in adhesive removal test and further promoted microglia activation and pro-inflammatory factor release (such as Il-1) after MCAO. The immune-modulatory effect of CD200/CD200R signaling might be exerted partly by its inhibition of the MAPK pathway.

CONCLUSIONS

This study provides evidence that the CD200/CD200R signaling pathway contributes to spontaneous functional recovery by enhancing synaptic plasticity via inhibition of microglia activation and inflammatory factor release.

Shuxuening injection facilitates neurofunctional recovery via down-regulation of G-CSF-mediated granulocyte adhesion and diapedesis pathway in a subacute stroke mouse model

Post-stroke neural damage is a serious health concern which does not yet have an effective treatment. We have shown previously that Shuxuening injection (SXNI), a Ginkgo biloba extract-based natural medicine, protects brain after an acute ischemic stroke, but its efficacy for post-stroke recovery is not known. This study was to investigate whether SXNI can improve the prognosis of stroke at a subacute phase. Mice with cerebral ischemia-reperfusion injury (CIRI) were established by middle cerebral artery occlusion (MCAO), and drugs or saline were injected by the tail vein every 12 h after reperfusion. The therapeutic effect of SXNI was evaluated by survival rate, modified neurologic severity scores (mNSS), open-field test, locomotive gait patterns, cerebral infarction volume, brain edema and histopathological changes. Subsequently, a combined method of RNA-seq and Ingenuity® Pathway Analysis (IPA) was performed to identify key targets and pathways of SXNI facilitating the prognosis of stroke in mouse brain. The results of the transcriptome analysis were verified by real time reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), western blot (WB) and immunohistochemistry (IHC). The experimental results showed that in the new subacute stroke model, SXNI markedly improves the survival rate, neurological and motor functions and histopathological changes, and significantly reduces cerebral infarction and edema volume. RNA-seq analysis of subacute stroke mice with or without SXNI (3 mL/kg) indicated 963 differentially expressed genes (DEGs) with a fold change ≥ 1.5 and a P-value ≤ 0.01. IPA analysis of DEGs showed that granulocyte adhesion and diapedesis ranked first in the pathway ranking, and the most critical gene regulated by SXNI was G-csf. Simultaneously, RT-PCR, ELISA, WB and IHC results demonstrated that SXNI not only obviously reduced the mRNA expression levels of key genes G-csf, Sele and Mac-1 in this pathway, but also significantly decreased the protein expression levels of G-CSF in serum and E-selectin and MAC-1 in brain tissues. In summary, our research suggested that SXNI can exert a remarkable neurofunctional therapeutic effect on stroke mice via down-regulating G-CSF to inhibit granulocyte adhesion and diapedesis. This study provides experimental evidence that SXNI may fulfill the need for stroke medicine targeting specifically at the recovery stage.

Renshen Shouwu extract enhances neurogenesis and angiogenesis via inhibition of TLR4/NF-κB/NLRP3 signaling pathway following ischemic stroke in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Renshen Shouwu extract (RSSW) is a patented Traditional Chinese Medicine included in Chinese Pharmacopoeia for neurasthenia, forgetfulness, insomnia, inappetence and excessive fatigue. Our previous study had demonstrated the neuroprotective effect of RSSW against ischemic stroke in rats with middle cerebral artery occlusion (MCAO). However, its underlying mechanism remains unknown.

AIM OF THE STUDY

In this study, we investigated the neurogenesis and angiogenesis effects of RSSW in ischemic stroke rats, and further revealed its underlying mechanism focused on TLR4/NF-κB/NLRP3 signaling pathway.

MATERIALS AND METHODS

Firstly, active compounds of RSSW were determined by High Performance Liquid Chromatography (HPLC). Secondly, Middle cerebral artery occlusion (MCAO) was performed to induce ischemic stroke in rats and 2, 3, 5-Triphenyltetrazolium chloride (TTC) staining was employed to evaluate whether MCAO surgery was successfully established. Neurological deficit evaluation was conducted according to the Zea Longa' method. Then, we explored the neurogenesis and angiogenesis effects after oral administration of RSSW (50 mg/kg, 100 mg/kg) in MCAO-induced rats by Immunofluorescence Staining. Moreover, the proteins involved in TLR4/NF-κB/NLRP3 signaling pathway (TLR4, p-NF-κB p65, NF-κB p65, NLRP3, pro-IL-1β, IL-1β, pro-Caspase-1, Caspase-1) were determined by western blotting.

RESULTS

It was observed that RSSW treatment significantly increased the number of newborn neurons and brain microvessel density (MVD) after ischemic stroke. What's more, RSSW treatment significantly downregulated TLR4, p-NF-κB p65/p65, NLRP3, pro-IL-1β, IL-1β, pro-Caspase-1, Caspase-1 proteins involved in TLR4/NF-κB/NLRP3 signaling pathway.

CONCLUSIONS

RSSW enhances neurogenesis and angiogenesis via inhibition of TLR4/NF-κB/NLRP3 inflammatory signaling pathway following ischemic stroke in rats. Hence, RSSW may be a promising Chinese Medicine for the treatment of ischemic stroke.

Intraventricular Medium B Treatment Benefits an Ischemic Stroke Rodent Model via Enhancement of Neurogenesis and Anti-apoptosis

Enhancement of endogenous neurogenesis after ischemic stroke may improve functional recovery. We previously demonstrated that medium B, which is a combination with epidermal growth factor (EGF) and fibronectin, can promote neural stem/progenitor cell (NSPC) proliferation and migration. Here, we showed that medium B promoted proliferation and migration of cultured NSPCs onto various 3-dimentional structures. When rat cortical neurons with oxygen glucose deprivation (OGD) were co-cultured with NSPCs, medium B treatment increased neuronal viability and reduced cell apoptosis. In a rat model with transient middle cerebral artery occlusion (MCAO), post-insult intraventricular medium B treatment enhanced proliferation, migration, and neuronal differentiation of NSPCs and diminished cell apoptosis in the infarct brain. In cultured post-OGD neuronal cells and the infarct brain from MCAO rats, medium B treatment increased protein levels of Bcl-xL, Bcl-2, phospho-Akt, phospho-GSK-3β, and β-catenin and decreased the cleaved caspase-3 level, which may be associated with the effects of anti-apoptosis. Notably, intraventricular medium B treatment increased neuronal density, improved motor function and reduced infarct size in MCAO rats. In summary, medium B treatment results in less neuronal death and better functional outcome in both cellular and rodent models of ischemic stroke, probably via promotion of neurogenesis and reduction of apoptosis.

Electroacupuncture Ameliorates Cerebral I/R-Induced Inflammation through DOR-BDNF/TrkB Pathway

The beneficial effects of electroacupuncture (EA) at Shuigou (GV26) and Neiguan (PC6) on poststroke rehabilitation are critically related to the activation of the delta-opioid receptor (DOR). The underlying anti-inflammatory mechanisms in DOR activation and EA-mediated neuroprotection in cerebral ischemia/reperfusion (I/R) injury were investigated in the current study. Cell proliferation and apoptosis were detected by morphological changes, cell counting kit-8 (CCK-8) assay, lactate dehydrogenase (LDH) release, and TUNEL staining. The mRNA levels were evaluated by using real-time quantitative polymerase chain reaction (RT-qPCR), and the protein expression was measured by western blot or enzyme-linked immunosorbent assay (ELISA) in vitro. Infarct volume was examined by cresyl violet (CV) staining, neurologic recovery was assessed by neurological deficit scores, and pro- and anti-inflammatory cytokines were determined by immunofluorescence in vivo. DOR activation greatly ameliorated morphological injury, reduced LDH leakage and apoptosis, and increased cell viability. It reversed the oxygen-glucose deprivation/reoxygenation- (OGD/R-) induced downregulation of DOR mRNA and protein, as well as BDNF protein. DOR activation also reduced proinflammatory cytokine gene expression, including TNF-α, IL-1β, and IL-6, and at the same time, increased anti-inflammatory cytokines IL-4 and IL-10 in OGD/R challenged PC12 cells. EA significantly reduced middle cerebral artery occlusion/reperfusion- (MCAO/R-) induced infarct volume and attenuated neurologic deficit scores. It markedly increased the expression of IL-10 and decreased IL-1β, while sham EA did not have any protective effect in MCAO/R-injured rats. DOR activation plays an important role in neuroprotection against OGD/R injury by inhibiting inflammation via the brain-derived neurotrophic factor/tropomyosin-related kinase B (BDNF/TrkB) pathway. The neuroprotective efficacy of EA at Shuigou (GV26) and Neiguan (PC6) on cerebral I/R injury may be also related to the inhibition of inflammatory response through the DOR-BDNF/TrkB pathway.

Effects of RO27-3225 on neurogenesis, PDGFRβ+ cells and neuroinflammation after cerebral infarction

Cerebral infarction causes severe social and economic burdens to patients due to its high morbidity and mortality rates, and the available treatments are limited. RO27-3225 is a highly selective melanocortin receptor 4 agonist that alleviates damage in many nervous system diseases, such as cerebral hemorrhage, traumatic brain injury and chronic neurodegenerative diseases. However, the effect of RO27-3225 on cerebral infarction remains unclear. In this study, we used a mouse model of transient middle cerebral artery occlusion (tMCAO) and administered RO27-3225 or saline to the mice through intraperitoneal injection. RO27-3225 increased the number of Nestin⁺/BrdU⁺ cells and doublecortin (DCX)⁺/BrdU⁺ cells in the subventricular zone (SVZ) and the number of DCX⁺/BrdU⁺ cells in the peri-infarct area on day 7 after tMCAO. Furthermore, RO27-3225 decreased the number of activated microglia (Iba1⁺ cells with a specific morphology) and the expression levels of Iba1, TNFα, IL6, and iNOS proteins and increased the number of PDGFRβ⁺ cells in the peri-infarct region on day 3 after tMCAO. Finally, RO27-3225-treated mice exhibited significantly decreased infarct volumes, brain water contents, and neurological deficits after cerebral infarction. Thus, RO27-3225 can improve the outcomes following cerebral infarction, partially by regulating neurogenesis in the SVZ, PDGFRβ⁺ cell survival and neuroinflammation in the peri-infarct zone. Our research reveals that RO27-3225 is a potential new treatment for cerebral infarction.

Early increment of soluble triggering receptor expressed on myeloid cells 2 in plasma might be a predictor of poor outcome after ischemic stroke

Soluble triggering receptor expressed on myeloid cells 2 (sTREM2) is derived from cleavage of TREM2, which is expressed on the cell surface of microlgia and other tissue-specific macrophages. In the present study, the changes in the sTREM2 levels after ischemic stroke (IS) and their association with clinical outcomes were evaluated. A total of 43 patients diagnosed with non-cardioembolic IS between June 2011 and May 2014 were consecutively included in this study. Patients treated with intravenous thrombolysis or intra-arterial thrombectomy were excluded. Plasma samples were collected three times (days 1, 7, and 90) after ictus. The sTREM2 level was measured in the samples using the highly sensitive solid-phase proximity ligation assay (SP-PLA). Among the 43 subjects, higher initial NIH stroke scale (NIHSS) score (P = 0.005), early increment of sTREM2 (P < 0.001), and late decrement of sTREM2 (P = 0.002), were more common in patients with poor outcome. Based on multivariate analysis, initial NIHSS score (P = 0.015) and early increment of sTREM2 (P = 0.032) were independently associated with poor outcome. The results from the present study indicate that increment of sTREM2 level at the early phase was a predictor of poor outcome. Serial follow-up of sTREM2 may aid prognosis after stroke.

Prognostic Value of NT-proBNP After Ischemic Stroke: A Systematic Review and Meta-analysis of Prospective Cohort Studies

BACKGROUND

Many studies have evaluated the relationship between N-terminal pro-brain natriuretic peptide (NT-proBNP) and its prognostic value in ischemic stroke. However, a widespread consensus has not been reached. Therefore, we completed a meta-analysis to evaluate the prognostic significance of NT-proBNP for mortality and functional outcome in patients with ischemic stroke.

METHODS

We performed a systematic search and review using the PubMed and EMBASE databases to identify literature that reported a correlation between NT-proBNP and mortality and functional outcome in ischemic stroke patients.

RESULTS

Eleven studies inclusive of 10,498 patients met the inclusion criteria. Elevated plasma NT-proBNP levels were associated with increased risk of mortality in ischemic stroke patients (all-cause mortality: odds ratio [OR] = 2.43, 95% confidence interval [CI] 1.62-3.64, P < .001, I²=74.3%; cardiovascular mortality: OR = 2.01, 95% CI 1.55-2.61, P < .001, I² = 42.6%). In addition, unfavorable functional outcomes were observed in patients with higher levels of NT-proBNP (OR = 1.68, 95% CI 1.13-2.50, P = .01, I² = 90.8%) after ischemic stroke.

CONCLUSIONS

This meta-analysis demonstrates that NT-proBNP could be a predictor of mortality and functional outcome in ischemic stroke patients.

Cerebral Organoids Repair Ischemic Stroke Brain Injury

Stroke is the second leading cause of death and main cause of disability worldwide, but with few effective therapies. Although stem cell-based therapy has been proposed as an exciting regenerative medicine strategy for brain injury, there are limitations. The developed cerebral organoids (COs) represent a promising transplantation source for stroke that remains to be answered. Here, we transplanted COs at 55 days and explored the feasibility in the rat middle cerebral artery occlusion (MCAO) model of stroke. COs transplantation at 6 h or even 24 h after MCAO significantly reduces brain infarct volume and improves neurological motor function. Transplanted COs show the potential of multilineage differentiation to mimic in vivo cortical development, support motor cortex region-specific reconstruction, form neurotransmitter-related neurons, and achieve synaptic connection with host brain via in situ differentiation and cell replacement in stroke. Cells from transplanted COs show extensive migration into different brain regions along corpus callosum. The mechanisms underlying COs transplantation therapy are also associated with enhanced neurogenesis, synaptic reconstruction, axonal regeneration and angiogenesis, and decreased neural apoptosis with more survival neurons after stroke. Moreover, COs transplantation promotes predominantly exogenous neurogenesis in the transplantation periphery of ipsilateral cortex and predominantly endogenous neurogenesis in the hippocampus and subventricular zone. Together, we demonstrate the efficacy and underlying mechanisms of COs transplantation in stroke. This preliminary but promising study provides first-hand preclinical evidence for COs transplantation as a potential and effective intervention for stroke treatment.

Cystatin C improves blood-brain barrier integrity after ischemic brain injury in mice

Cystatin C, a well-established biomarker of renal function, has been associated with a protective effect against stroke. However, the potential neuroprotective mechanism of cystatin C in ischemic brain injury remains unclear. Our study hypothesized that cystatin C can ameliorate blood-brain barrier (BBB) disruption by up-regulating caveolin-1 expression, thereby improving neurological outcomes in cerebral ischemic injury. Western blotting, immunohistochemistry, immunofluorescence staining, and immunoprecipitation were performed to investigate target proteins. Evans Blue and gelatin zymography were used to examine the effect of cystatin C on BBB disruption. Plasmid and small interfering RNA transfection was used to observe alterations in caveolin-1 and occludin expression induced by changes in cystatin C expression. Intriguingly, our study showed that the expression of both cystatin C and caveolin-1 was increased in middle cerebral artery occlusion-injured mice, and pretreatment with exogenous cystatin C significantly increased caveolin-1 expression, reduced Evans Blue leakage in the injured brain region, and decreased the enzymatic activity of matrix metallopeptidase-9. Meanwhile, our study also showed that the over-expression of cystatin C greatly enhanced caveolin-1 expression, which later increased occludin expression in oxygen-glucose deprivation-exposed brain microvascular endothelial cells. The knockdown of cystatin C induced the opposite outcomes. These experimental results indicate a positive role for cystatin C in the regulation of caveolin-1 and occludin expression in cerebral ischemic injury. Taken together, these data unveil a new mechanism of the regulation of caveolin-1 expression by cystatin C in the maintenance of BBB integrity after ischemic brain injury and provide new clues for the identification of potential therapeutic strategies for stroke.