The role of VEGF/VEGFR2 signaling in peripheral stimulation-induced cerebral neurovascular regeneration after ischemic stroke in mice

Pro‑angiogenic activity of salvianolate and its potential therapeutic effect against acute cerebral ischemia

Salvianolate (Sal) is a medicinal composition that is widely used in China for the treatment of coronary heart disease and angina pectoris. The aim of the present study was to investigate the potential macrophage-mediated pro-angiogenic effects of Sal in vitro. In addition, another aim was to explore the effects of Sal in a rat model of transient middle cerebral artery occlusion (tMCAO) along with the potential mechanism by which it promotes angiogenesis. In this study, human umbilical vein endothelial cells (HUVECs) and Raw264.7 macrophages in vitro, and a rat tMCAO model in vivo were used to detect the pro-angiogenic effect and mechanism of Sal. The results of in vitro experiments showed that the viability, migration and tube formation of HUVECs were promoted by the supernatant of Sal-treated Raw264.7 macrophages (s-Sal) but not by Sal alone. s-Sal also increased the levels of phosphorylated (p-)VEGFR-2, p-AKT and p-p38 MAPK in HUVECs while Sal alone did not. In vivo, treatment with Sal significantly reduced the cerebral infarction volume and neurological deficit scores in the rat tMCAO model. Similar to the mechanism observed in the in vitro experiments, Sal treatment upregulated the protein expression of VEGF and VEGFR-2, in addition to the phosphorylation of VEGFR-2, AKT and p38, in the brain tissues of the tMCAO model rats. In summary, the results of the present study suggest that the mechanism of Sal-mediated angiogenesis is associated with stimulation of the VEGF/VEGFR-2 signaling pathway by macrophages. This suggests the potential of Sal as a therapeutic option for the treatment of acute cerebral ischemic injury, which may act via the promotion of angiogenesis.

Pioglitazone Attenuates Ischemic Stroke Aggravation By Blocking PPARγ Reduction and Inhibiting Chronic Inflammation in Diabetic Mice

Diabetes can cause vascular remodeling and is associated with worse outcome after ischemic stroke. Pioglitazone is a commonly used anti-diabetic agent. However, it is not known whether pioglitazone use before ischemia could reduce brain ischemic injury. Pioglitazone was administered to 5-week-old db⁺ or db/db mice. Cerebral vascular remodeling was examined at the age of 9 weeks. Expression of peroxisome proliferator-activated receptor-γ (PPARγ), p-PPARγ (S112 and S273), nucleotide-binding domain (NOD)-like receptor protein 3 (Nlrp3), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) was evaluated in the somatosensory cortex of mice. Neurological outcome was evaluated 24 h after brain ischemia. Results showed that early pioglitazone treatment provided a long-lasting effect of euglycemia but enhanced hyperlipidemia in the db/db mice. Diabetic mice exhibited increased vascular tortuosity, narrower middle cerebral artery (MCA) width and IgG leakage in the brain. These changes were blocked by early pioglitazone treatment. In diabetic animals, PPARγ expression was reduced and p-PPARγ at S273 but not S112, Nlrp3, IL-1β and TNF-α were increased in the somatosensory cortex. PPARγ decrease and Nlrp3 increase were mainly in the neurons of the diabetic brain, which was reversed by early pioglitazone treatment. Pioglitazone attenuated the aggravated neurological outcome after stroke in diabetic mice. But this protective effect was abolished through restoring cerebral inflammation by intracerebroventricular administration of IL-1β and TNF-α in pioglitazone treated diabetic mice before MCAO. In summary, early pioglitazone treatment attenuates cerebral vascular remodeling and ischemic brain injury possibly via blocking chronic neuroinflammation in the db/db mice.

Network Pharmacology and Molecular Docking-Based Mechanism Study to Reveal the Protective Effect of Salvianolic Acid C in a Rat Model of Ischemic Stroke

Salvianolic acid C (SAC) is a major bioactive component of Salvia miltiorrhiza Bunge (Danshen), a Chinese herb for treating ischemic stroke (IS). However, the mechanism by which SAC affects the IS has not yet been evaluated, thus a network pharmacology integrated molecular docking strategy was performed to systematically evaluate its pharmacological mechanisms, which were further validated in rats with cerebral ischemia. A total of 361 potential SAC-related targets were predicted by SwissTargetPrediction and PharmMapper, and a total of 443 IS-related targets were obtained from DisGeNET, DrugBank, OMIM, and Therapeutic Target database (TTD) databases. SAC-related targets were hit by the 60 targets associated with IS. By Gene ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment combined with the protein-protein interaction (PPI) network and cytoHubba plug-ins, nine related signaling pathways (proteoglycans in cancer, pathways in cancer, PI3K-Akt signaling pathway, Focal adhesion, etc.), and 20 hub genes were identified. Consequently, molecular docking indicated that SAC may interact with the nine targets (F2, MMP7, KDR, IGF1, REN, PPARG, PLG, ACE and MMP1). Four of the target proteins (VEGFR2, MMP1, PPARγ and IGF1) were verified using western blot. This study comprehensively analyzed pathways and targets related to the treatment of IS by SAC. The results of western blot also confirmed that the SAC against IS is mainly related to anti-inflammatory and angiogenesis, which provides a reference for us to find and explore the effective anti-IS drugs.

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

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

Sodium tanshinone IIA sulfonate ameliorates cerebral ischemic injury through regulation of angiogenesis

Vascular remodeling and neuroprotection are two major adaptable methods for treating ischemic stroke. Edaravone is a protective agent for the treatment of stroke and was used as a positive control in the present study. Sodium tanshinone IIA sulfonate (STS) has demonstrated therapeutic clinical effects in cerebral infarction in China, while its mechanisms of action in ischemic stroke have remained elusive. The angiogenesis and neuroprotective effects of STS were evaluated in a rat model induced by middle cerebral artery occlusion and 3 days of reperfusion. When used at the same dose, the magnitude of the therapeutic effect of STS was similar to that of edaravone in terms of decreased blood-brain barrier damage as indicated by reduced Evans blue leakage, improved neurological deficits, alleviated cerebral edema and inhibition of histopathological changes caused by ischemia/reperfusion. The TUNEL assay demonstrated that the ability of STS to inhibit neuronal apoptosis was equivalent to that of edaravone. Immunofluorescence detection of CD31 and α-smooth muscle actin indicated that the vascular density was significantly reduced in the vehicle group compared with that in the sham operation group, STS increased the microvessel density in the ischemic area. Furthermore, in the vehicle group the protein expression of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR) as determined by fluorescence microscopy and immunohistochemistry was significantly reduced compared with that in the sham group. However, STS promoted their expression compared to the vehicle group respectively, and increaed the mRNA expression of VEGF, VEGFR, CD31 and angiopoietin-1 as determined by reverse transcription-quantitative PCR, but these changes were not significant or not present for edaravone apart from Ang-1. In conclusion, STS protected against ischemic brain injury by promoting angiogenesis in ischemic areas and inhibiting neuronal apoptosis. These results provide a potential treatment for stroke recovery.

Vascular Sema3E-Plexin-D1 Signaling Reactivation Promotes Post-stroke Recovery through VEGF Downregulation in Mice

Post-stroke vascular remodeling, including angiogenesis, facilitates functional recovery. Proper vascular repair is important for efficient post-stroke recovery; however, the underlying mechanisms coordinating the diverse signaling pathways involved in vascular remodeling remain largely unknown. Recently, axon guidance molecules were revealed as key players in injured vessel remodeling. One such molecule, Semaphorin 3E (Sema3E), and its receptor, Plexin-D1, control vascular development by regulating vascular endothelial growth factor (VEGF) signaling. In this study, using a mouse model of transient brain infarction, we aimed to investigate whether Sema3E-Plexin-D1 signaling was involved in cerebrovascular remodeling after ischemic injury. We found that ischemic damage rapidly induced Sema3e expression in the neurons of peri-infarct regions, followed by Plexin-D1 upregulation in remodeling vessels. Interestingly, Plexin-D1 reemergence was concurrent with brain vessels entering an active angiogenic process. In line with this, Plxnd1 ablation worsened neurological deficits, infarct volume, neuronal survival rate, and blood flow recovery. Furthermore, reduced and abnormal vascular morphogenesis was caused by aberrantly increased VEGF signaling. In Plxnd1 knockout mice, we observed significant extravasation of intravenously administered tracers in the brain parenchyma, junctional protein downregulation, and mislocalization in regenerating vessels. This suggested that the absence of Sema3E-Plexin-D1 signaling is associated with blood–brain barrier (BBB) impairment. Finally, the abnormal behavioral performance, aberrant vascular phenotype, and BBB breakdown defects in Plxnd1 knockout mice were restored following the inhibition of VEGF signaling during vascular remodeling. These findings demonstrate that Sema3E-Plexin-D1 signaling can promote functional recovery by downregulating VEGF signaling in the injured adult brain.

Traditional Chinese Medicine Shenmayizhi Decoction Ameliorates Memory and Cognitive Impairment Induced by Multiple Cerebral Infarctions

This study aimed to illustrate the mechanism by which Shenmayizhi decoction (SMYZD) improves the learning memory of rats with vascular cognitive impairment (VCI). Fifty male and female Wistar rats of specific pathogen-free grade (SPF grade) were used to establish the model by the administration of a microsphere embolization. This was accomplished by injecting sterile, standardized, mass-produced microspheres of uniform particle size (100–200 µm in diameter) in a sodium alginate microsphere vascular embolic agent suspension to induce VCI. The VCI model was successfully established in 40 rats, including both male and female rats, and the rats were randomly divided into 4 groups of 10 rats each. The model group was administered an equal volume of distilled water. The donepezil group was administered 0.45 mg/kg/d donepezil, which is equivalent to the clinical dosage. The SMYZ-H group was administered 11.88 g/kg/d SMYZ, which is 4 times higher than the clinically equivalent dosage. The SMYZ-L group was administered 2.97 g/kg/d SMYZ, which is the clinically equivalent dosage. A sham-operated group was used as the control group and administered an equal volume of distilled water. The rats in the 4 groups were treated by gavage with equal volumes of liquid and the indicated concentration of drug diluted in distilled water for 8 consecutive weeks. Two months later, the Morris water maze (MWM) was used to evaluate the spatial memory of all the rats. Ultrastructural and ultrapathological changes in the capillaries of the cerebral cortex were observed by transmission electron microscopy. Furthermore, Western blot and RT-PCR analyses were used to assess the levels of platelet-derived growth factor receptor-β (PDGFR-β), neuron-glial antigen 2 (NG2), vascular endothelial growth factor A (VEGF-A), and angiopoietin 1 (Ang1) in the cerebral cortex of the rats. The results showed that SMYZD at concentrations of 11.88 g/kg/d and 2.97 g/kg/d (SMYZ-H and SMYZ-L) significantly shortened the escape latency (EL). In addition, SMYZ-H significantly prolonged the distance traveled and the time spent in the original platform quadrant by the rats with VCI. SMYZ-H significantly increased the NG2 and Ang1 protein expression levels and increased the PDGFR-β and Ang1 mRNA levels. These results demonstrated that Shenmayizhi decoction can improve the memory abilities of rats with VCI induced by multiple cerebral infarctions by preventing pericyte degeneration.

Roles of β-Endorphin in Stress, Behavior, Neuroinflammation, and Brain Energy Metabolism

β-Endorphins are peptides that exert a wide variety of effects throughout the body. Produced through the cleavage pro-opiomelanocortin (POMC), β-endorphins are the primarily agonist of mu opioid receptors, which can be found throughout the body, brain, and cells of the immune system that regulate a diverse set of systems. As an agonist of the body's opioid receptors, β-endorphins are most noted for their potent analgesic effects, but they also have their involvement in reward-centric and homeostasis-restoring behaviors, among other effects. These effects have implicated the peptide in psychiatric and neurodegenerative disorders, making it a research target of interest. This review briefly summarizes the basics of endorphin function, goes over the behaviors and regulatory pathways it governs, and examines the variability of β-endorphin levels observed between normal and disease/disorder affected individuals.

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.

The Protective Effects of Juglanin in Cerebral Ischemia Reduce Blood-Brain Barrier Permeability via Inhibition of VEGF/VEGFR2 Signaling

Introduction

Ischemic brain injury due to stroke or other pathologies is a major contributor to disability and mortality worldwide. Upon the occurrence of stroke, neuronal cells undergo apoptosis due to the deprivation of oxygen and nutrients and failure of the blood–brain barrier (BBB). In the moments immediately following a stroke, widespread perfusion resulting from hyperpermeability is accompanied by an acute inflammatory response, which induces neovascularization and often permanent neurological injury. Vascular endothelial growth factor (VEGF) and its receptor VEGF receptor 2 (VEGFR2) have been targeted to suppress cerebral ischemia. Recently, natural products including flavonoids, such as juglanin, have been receiving increasing attention for their impressive physiological effects.

Methods

Twenty mg/kg body weight juglanin was administrated for 3 weeks before inducing middle cerebral artery occlusion (MCAO) in mice. The animal brain infarction volume, neurological deficit score, blood–brain barrier permeability, and the expression of tight junction proteins were evaluated. Endothelial permeability and tight junction protein expression were also assessed in brain microvascular endothelial cells (HMBVECs) exposed to oxygen–glucose deprivation/reperfusion (OGD/R).

Results

Juglanin significantly reduced occlusion-induced infarct volume and improved neurological score by suppressing BBB hyperpermeability. Juglanin inhibited both the mRNA and protein expression of VEGF and VEGFR2 and restored the normal expression of occludin and zonula occludens-1 (ZO-1), two important tight junction proteins, in MCAO mice. Meanwhile, the results of in vitro experiments show that the protective effects of juglanin against increased BBB permeability and reduced tight junction functionality are dependent on the VEGF/VEGFR2 signaling pathway, as evidenced by the capacity of exogenous VEGF-A to abolish the effects of juglanin.

Conclusion

Our findings indicate a potent ability of juglanin to prevent neuronal injury resulting from cerebral ischemia by modulating the VEGF/VEGFR2 signaling pathway. Further research will help elucidate the exact mechanisms behind the protective effects of juglanin.

Granulocyte colony-stimulating factor and stromal cell-derived factor-1 combination therapy: A more effective treatment for cerebral ischemic stroke

BACKGROUND

Drugs that promote angiogenesis include statins, recombinant human granulocyte colony-stimulating factor, and stromal cell-derived factor-1. Low doses of atorvastatin could significantly increase the vascular expressions of endothelial growth factor, and the number of peripheral blood endothelial progenitor cells (EPCs), thus improving angiogenesis and local blood flow. G-CSF is an EPC-mobilization agent used in ischemia studies for targeting angiogenesis after cerebral ischemia via EPCs. In previous clinical trials, consistent conclusions have not been reached about the effectiveness of G-CSF on ischemic stroke. Therefore, the therapeutic effect of G-CSF and its combination with other medicines need further experimental verification. It is known that atorvastatin, rhG-CSF, and SDF-1 are considered the most promising neuroprotective candidates, but a comprehensive comparison of their effects is lacking.

AIMS

To compare the effects of atorvastatin, stromal cell-derived factor-1, and recombinant human granulocyte colony-stimulating factor on ischemic stroke.

METHODS

Adult male Sprague-Dawley rats were randomly allocated to three groups: normal, sham-operated, and middle cerebral artery occlusion operated. Middle cerebral artery occlusion operated rats were further allocated into saline, atorvastatin, recombinant human granulocyte colony-stimulating factor, and recombinant human granulocyte colony-stimulating factor + stromal cell-derived factor-1 groups. Neurological function evaluation, cerebral infarction and the blood-brain barrier integrity analysis, identification of angiogenic factors, assessment of angiogenesis, expression of growth-associated protein-43, neuroglobin, glial cell-derived neurotrophic factor, and cleaved caspase 3, were performed.

RESULTS

Compared with atorvastatin or recombinant human granulocyte colony-stimulating factor alone, recombinant human granulocyte colony-stimulating factor + stromal cell-derived factor-1 treatment improved neurological performance, reduced cerebral infarction and blood-brain barrier disruption after stroke, and increased the content of stromal cell-derived factor-1, vascular endothelial growth factor, monocyte chemotactic protein 1, and basic fibroblast growth factor in peripheral blood. In addition, recombinant human granulocyte colony-stimulating factor + stromal cell-derived factor-1 promoted greater angiogenesis than atorvastatin or recombinant human granulocyte colony-stimulating factor alone and increased the expression of growth-associated protein-43, neuroglobin, and glial cell-derived neurotrophic factor, while decreasing the levels of cleaved caspase 3 in the brain after ischemic stroke.

CONCLUSIONS

Combination therapy with recombinant human granulocyte colony-stimulating factor and stromal cell-derived factor-1 is more effective than atorvastatin or recombinant human granulocyte colony-stimulating factor alone in protecting against stroke-induced damage and could be an optimal therapeutic strategy for stroke.

Promoting therapeutic angiogenesis of focal cerebral ischemia using thrombospondin-4 (TSP4) gene-modified bone marrow stromal cells (BMSCs) in a rat model

Background

A stroke caused by angiostenosis always has a poor prognosis. Bone marrow stromal cells (BMSC) are widely applied in vascular regeneration. Recently, thrombospondin-4 (TSP4) was reported to promote the regeneration of blood vessels and enhance the function of endothelial cells in angiogenesis. In this work, we observed the therapeutic effect of TSP4-overexpressing BMSCs on angiogenesis post-stroke.

Methods

We subcloned the tsp4 gene into a lentivirus expression vector system and harvested the tsp4 lentivirus using 293FT cells. Primary BMSCs were then successfully infected by the tsp4 virus, and overexpression of GFP-fused TSP4 was confirmed by both western blot and immunofluorescence. In vitro, TSP4-overexpressing BMSCs and wild-type BMSCs were co-cultured with human umbilical vein endothelial cells (HUVECs). The expression level of TSP4, vascular endothelial growth factor (VEGF) and transforming growth factor-β (TGF-β) in the supernatant were detected by enzyme-linked immunosorbent assay (ELISA). Wound healing, tube formation and an arterial ring test were performed to estimate the ability of TSP4-overexpressing BMSCs to promote the angiogenesis of endothelial cells. Using a rat permanent middle cerebral artery occlusion (MCAO) model, the effect of TSP4-overexpressing BMSCs on the regeneration of blood vessels was systematically tested by the neurological function score, immunohistochemistry and immunofluorescence staining assays.

Results

Our results demonstrated that TSP4-overexpressing BMSCs largely increased the expression of VEGF, angiopoietin-1 (Ang-1), matrix metalloprotein 9 (MMP9), matrix metalloprotein 2 (MMP2) and p-Cdc42/Rac1 in endothelial cells. TSP4-BMSC treatment notably up-regulated the TGF-β/Smad2/3 signalling pathway in HUVECs. In vivo, the TSP4-BMSC infusion improved the neurological function score of MCAO rats and expanded the expression of the von Willebrand factor (vWF), Ang-1, MMP2 and MMP9 proteins in cerebral ischemic penumbra.

Conclusions

Our data illustrate that TSP4-BMSCs can promote the proliferation and migration of endothelial cells and tube formation. We found that TSP4-BMSC infusion can promote the recovery of neural function post-stroke. The tsp4 gene-modified BMSCs provides a better therapeutic effect than that of wild-type BMSCs.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1845-z) contains supplementary material, which is available to authorized users.

PTEN inhibition enhances angiogenesis in an in vitro model of ischemic injury by promoting Akt phosphorylation and subsequent hypoxia inducible factor-1α upregulation

Angiogenesis is an important pathophysiological response to cerebral ischemia. PTEN is a lipid phosphatase whose loss activates PI3K/Akt signaling, which is related to HIF-1α upregulation and enhanced angiogenesis in human cancer cells. However, the specific roles of PTEN in endothelial cell functions and angiogenesis after cerebral ischemia remain unknown. Therefore, we sought to examine the potential effects of PTEN inhibition on post-ischemic angiogenesis in human blood vessel cells and to determine the underlying mechanism. In this present study, human umbilical vein endothelial cells (HUVECs) were exposed to oxygen-glucose deprivation (OGD), cell proliferation, migration and apoptosis, in vitro tube formation and expression of PTEN/Akt pathway and angiogenic factors were examined in HUVECs after treatment with PTEN inhibitor bisperoxovanadium (bpV) at different doses. The results showed that bpV significantly increased the cell proliferation and reduced cell apoptosis indicating that the drug exerts a cytoprotective effect on HUVECs with OGD exposure. bpV also enhanced cell migration and tube formation in HUVECs following OGD, and upregulated HIF-1α and VEGF expressions, but attenuated endostatin expression. Additionally, western blotting analysis demonstrated that Akt phosphorylation in HUVECs was significantly increased after bpV treatment. These findings suggest that PTEN inhibition promotes post-ischemic angiogenesis in HUVECs after exposure to OGD and this enhancing effect might be achieved through activation of the Akt signal cascade.

The Janus Face of VEGF in Stroke

The family of vascular endothelial growth factors (VEGFs) are known for their regulation of vascularization. In the brain, VEGFs are important regulators of angiogenesis, neuroprotection and neurogenesis. Dysregulation of VEGFs is involved in a large number of neurodegenerative diseases and acute neurological insults, including stroke. Stroke is the main cause of acquired disabilities, and normally results from an occlusion of a cerebral artery or a hemorrhage, both leading to focal ischemia. Neurons in the ischemic core rapidly undergo necrosis. Cells in the penumbra are exposed to ischemia, but may be rescued if adequate perfusion is restored in time. The neuroprotective and angiogenic effects of VEGFs would theoretically make VEGFs ideal candidates for drug therapy in stroke. However, contradictory to what one might expect, endogenously upregulated levels of VEGF as well as the administration of exogenous VEGF is detrimental in acute stroke. This is probably due to VEGF-mediated blood–brain-barrier breakdown and vascular leakage, leading to edema and increased intracranial pressure as well as neuroinflammation. The key to understanding this Janus face of VEGF function in stroke may lie in the timing; the harmful effect of VEGFs on vessel integrity is transient, as both VEGF preconditioning and increased VEGF after the acute phase has a neuroprotective effect. The present review discusses the multifaceted action of VEGFs in stroke prevention and therapy.

Diverse Functions and Mechanisms of Pericytes in Ischemic Stroke

Background:

Every year, strokes take millions of lives and leave millions of individuals living with permanent disabilities. Recently more researchers embrace the concept of the neurovascular unit (NVU), which encompasses neurons, endothelial cells (ECs), pericytes, astrocyte, microglia, and the extracellular matrix. It has been well-documented that NVU emerged as a new paradigm for the exploration of mechanisms and therapies in ischemic stroke. To better understand the complex NVU and broaden therapeutic targets, we must probe the roles of multiple cell types in ischemic stroke. The aims of this paper are to introduce the biological characteristics of brain pericytes and the available evidence on the diverse functions and mechanisms involving the pericytes in the context of ischemic stroke.

Methods:

Research and online content related to the biological characteristics and pathophysiological roles of pericytes is review. The new research direction on the Pericytes in ischemic stroke, and the potential therapeutic targets are provided.

Results:

During the different stages of ischemic stroke, pericytes play different roles: 1) On the hyperacute phase of stroke, pericytes constriction and death may be a cause of the no-reflow phenomenon in brain capillaries; 2) During the acute phase, pericytes detach from microvessels and participate in inflammatory-immunological response, resulting in the BBB damage and brain edema. Pericytes also provide benefit for neuroprotection by protecting endothelium, stabilizing BBB and releasing neurotrophins; 3) Similarly, during the later recovery phase of stroke, pericytes also contribute to angiogenesis, neurogenesis, and thereby promote neurological recovery.

Conclusion:

This emphasis on the NVU concept has shifted the focus of ischemic stroke research from neuro-centric views to the complex interactions within NVU. With this new perspective, pericytes that are centrally positioned in the NVU have been widely studied in ischemic stroke. More work is needed to elucidate the beneficial and detrimental roles of brain pericytes in ischemic stroke that may serve as a basis for potential therapeutic targets.

MicroRNA-210 Promotes Accumulation of Neural Precursor Cells Around Ischemic Foci After Cerebral Ischemia by Regulating the SOCS1-STAT3-VEGF-C Pathway

Background

Neural precursor cell (NPC) migration toward lesions is key for neurological functional recovery. The neovasculature plays an important role in guiding NPC migration. MicroRNA‐210 (miR‐210) promotes angiogenesis and neurogenesis in the subventricular zone and hippocampus after cerebral ischemia; however, whether miR‐210 regulates NPC migration and the underlying mechanism is still unclear. This study investigated the role of miR‐210 in NPC migration.

Methods and Results

Neovascularization and NPC accumulation was detected around ischemic foci in a mouse model of middle cerebral artery occlusion (MCAO) and reperfusion. Bone marrow–derived endothelial progenitor cells (EPCs) were found to participate in neovascularization. miR‐210 was markedly upregulated after focal cerebral ischemia/reperfusion. Overexpressed miR‐210 enhanced neovascularization and NPC accumulation around the ischemic lesion and vice versa, strongly suggesting that miR‐210 might be involved in neovascularization and NPC accumulation after focal cerebral ischemia/reperfusion. In vitro experiments were conducted to explore the underlying mechanism. The transwell assay showed that EPCs facilitated NPC migration, which was further promoted by miR‐210 overexpression in EPCs. In addition, miR‐210 facilitated VEGF‐C (vascular endothelial growth factor C) expression both in vitro and in vivo. Moreover, the luciferase reporter assay demonstrated that miR‐210 directly targeted the 3′ untranslated region of SOCS1 (suppressor of cytokine signaling 1), and miR‐210 overexpression in HEK293 cells or EPCs decreased SOCS1 and increased STAT3 (signal transducer and activator of transcription 3) and VEGF‐C expression. When EPCs were simultaneously transfected with miR‐210 mimics and SOCS1, the expression of STAT3 and VEGF‐C was reversed.

Conclusions

miR‐210 promoted neovascularization and NPC migration via the SOCS1–STAT3–VEGF‐C pathway.

VEGFR2 is activated by high-density lipoproteins and plays a key role in the proangiogenic action of HDL in ischemia

High-density lipoproteins augment hypoxia-induced angiogenesis by inducing the key angiogenic vascular endothelial growth factor A (VEGFA) and total protein levels of its receptor 2 (VEGFR2). The activation/phosphorylation of VEGFR2 is critical for mediating downstream, angiogenic signaling events. This study aimed to determine whether reconstituted high-density lipoprotein (rHDL) activates VEGFR2 phosphorylation and the downstream signaling events and the importance of VEGFR2 in the proangiogenic effects of rHDL in hypoxia. In vitro, rHDL increased VEGFR2 activation and enhanced phosphorylation of downstream, angiogenic signaling proteins ERK1/2 and p38 MAPK in hypoxia. Incubation with a VEGFR2-neutralizing antibody attenuated rHDL-induced phosphorylation of VEGFR2, ERK1/2, p38 MAPK, and tubule formation. In a murine model of ischemia-driven neovascularization, rHDL infusions enhanced blood perfusion and augmented capillary and arteriolar density. Infusion of a VEGFR2-neutralizing antibody ablated those proangiogenic effects of rHDL. Circulating Sca1⁺/CXCR4⁺ angiogenic progenitor cell levels, important for neovascularization in response to ischemia, were higher in rHDL-infused mice 3 d after ischemic induction, but that did not occur in mice that also received the VEGFR2-neutralizing antibody. In summary, VEGFR2 has a key role in the proangiogenic effects of rHDL in hypoxia/ischemia. These findings have therapeutic implications for angiogenic diseases associated with an impaired response to tissue ischemia.-Cannizzo, C. M., Adonopulos, A. A., Solly, E. L., Ridiandries, A., Vanags, L. Z., Mulangala, J., Yuen, S. C. G., Tsatralis, T., Henriquez, R., Robertson, S., Nicholls, S. J., Di Bartolo, B. A., Ng, M. K. C., Lam, Y. T., Bursill, C. A., Tan, J. T. M. VEGFR2 is activated by high-density lipoproteins and plays a key role in the proangiogenic action of HDL in ischemia.

Stem cell transplantation therapy for multifaceted therapeutic benefits after stroke

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

Hypoxia Response Element-Regulated MMP-9 Promotes Neurological Recovery via Glial Scar Degradation and Angiogenesis in Delayed Stroke

Matrix metalloproteinase 9 (MMP-9) plays a beneficial role in the delayed phase of middle cerebral artery occlusion (MCAO). However, the mechanism is obscure. Here, we constructed hypoxia response element (HRE)-regulated MMP-9 to explore its effect on glial scars and neurogenesis in delayed ischemic stroke. Adult male Institute of Cancer Research (ICR) mice underwent MCAO and received a stereotactic injection of lentivirus carrying HRE-MMP-9 or normal saline (NS)/lentivirus-GFP 7 days after ischemia. We found that HRE-MMP-9 improved neurological outcomes, reduced ischemia-induced brain atrophy, and degraded glial scars (p < 0.05). Furthermore, HRE-MMP-9 increased the number of microvessels in the peri-infarct area (p < 0.001), which may have been due to the accumulation of endogenous endothelial progenitor cells (EPCs) in the peri-infarct area after glial scar degradation. Finally, HRE-MMP-9 increased the number of bromodeoxyuridine-positive (BrdU⁺)/NeuN⁺ cells and the expression of PSD-95 in the peri-infarct area (p < 0.01). These changes could be blocked by vascular endothelial growth factor receptor 2 (VEGFR2) inhibitor SU5416 and MMP-9 inhibitor 2-[[(4-phenoxyphenyl)sulfonyl]methyl]-thiirane (SB-3CT). Our results provided a novel mechanism by which glial scar degradation and vascular endothelial growth factor (VEGF)/VEGFR2-dependent angiogenesis may be key procedures for neurological recovery in delayed ischemic stroke after HRE-MMP-9 treatment. Therefore, HRE-MMP-9 overexpression in the delayed ischemic brain is a promising approach for neurological recovery.

Apelin-13 protects neurovascular unit against ischemic injuries through the effects of vascular endothelial growth factor

Apelin-13 has protective effects on many neurological diseases, including cerebral ischemia. Here, we aimed to test Apelin-13's effects on ischemic neurovascular unit (NVU) injuries and investigate whether the effects were dependent on vascular endothelial growth factor (VEGF). We detected the expression of VEGF and its receptors (VEGFRs) induced by Apelin-13 injection at 1d, 3d, 7d and 14d after middle cerebral artery occlusion (MCAO). Meanwhile, we examined the effects of Apelin-13 on NVU in both in vivo and in vitro experiments as well as whether the effects were VEGF dependent by using VEGF antibody. We also assessed the related signal transduction pathways via multiple inhibitors. We demonstrated Apelin-13 highly increased VEGF and VEGFR-2 expression, not VEGFR-1. Importantly, Apelin-13 led to neurological functions improvement by associating with promotion of angiogenesis as well as reduction of neuronal death and astrocyte activation, which was markedly blocked by VEGF antibody. In cell cultures, Apelin-13 protected neurons, astrocytes and endothelial cells against oxygen-glucose deprivation (OGD) injuries. Moreover, the effect of Apelin-13 to up-regulate VEGF was suppressed by extracellular signal-regulated kinase (ERK) inhibitor U0126 and phosphatidylinositol 3'-kinase (PI3K) inhibitor LY294002. Our data suggest protective effects of Apelin-13 on ischemic NVU injuries are highly associated with the increase of VEGF binding to VEGFR-2, possibly acting through activation of ERK and PI3K/Akt pathways.

Angiogenesis in Ischemic Stroke and Angiogenic Effects of Chinese Herbal Medicine

Stroke is one of the major causes of death and adult disability worldwide. The underlying pathophysiology of stroke is highly complicated, consisting of impairments of multiple signalling pathways, and numerous pathological processes such as acidosis, glutamate excitotoxicity, calcium overload, cerebral inflammation and reactive oxygen species (ROS) generation. The current treatment for ischemic stroke is limited to thromolytics such as recombinant tissue plasminogen activator (tPA). tPA has a very narrow therapeutic window, making it suitable to only a minority of stroke patients. Hence, there is great urgency to develop new therapies that can protect brain tissue from ischemic damage. Recent studies have shown that new vessel formation after stroke not only replenishes blood flow to the ischemic area of the brain, but also promotes neurogenesis and improves neurological functions in both animal models and patients. Therefore, drugs that can promote angiogenesis after ischemic stroke can provide therapeutic benefits in stroke management. In this regard, Chinese herbal medicine (CHM) has a long history in treating stroke and the associated diseases. A number of studies have demonstrated the pro-angiogenic effects of various Chinese herbs and herbal formulations in both in vitro and in vivo settings. In this article, we present a comprehensive review of the current knowledge on angiogenesis in the context of ischemic stroke and discuss the potential use of CHM in stroke management through modulation of angiogenesis.

The role of vascular endothelial growth factor in the regulation of development and functioning of the brain: new target molecules for pharmacotherapy

Vascular endothelial growth factors (VEGFs) have been shown to participate in atherosclerosis, arteriogenesis, cerebral edema, neuroprotection, neurogenesis, angiogenesis, postischemic brain and vessel repair. Most of these actions involve VEGF-A and the VEGFR-2 receptor. VEGF signaling pathways represent an important potential for treatment of neurological diseases affecting the brain

Adaptation of the cortical somatosensory evoked potential following pulsed pneumatic stimulation of the lower face in adults

Cortical adaptation to sustained sensory input is a pervasive form of short-term plasticity in neurological systems. Its role in sensory perception in health and disease, or predicting long-term plastic changes resulting from sensory training offers insight into the mechanisms of somatosensory and sensorimotor processing. A 4-channel electroencephalography (EEG) recording montage was placed bilaterally (C3-P3, C4-P4, F7-P3, F8-P4) to characterize the short-term effects of pulsed pneumatic orofacial stimulation on the cortical somatosensory evoked potential (cSEP) in twenty neurotypical adults (mean age=21±2.88 years). A servo-controlled pneumatic amplifier was used to deliver a repetitive series of pneumatic pulse trains (six 50-ms pulses, 5-second intertrain interval) through a linked pair of custom acetal homopolymer probes (aka TAC-Cells) adhered to the nonglabrous skin of the lower face proximal to the right oral angle to synchronously activate mechanoreceptive afferents in the trigeminal nerve. Blocks of pulse trains were counterbalanced among participants and delivered at two rates, 2 and 4Hz. TAC-Cell stimulation of the lower face consistently evoked a series of cSEPs at P7, N20, P28, N38, P75, N85, and P115. The spatial organization and adaptation of the evoked cSEP was dependent on stimulus pulse index (1-6 within the pulse train, p=.012), frequency of stimulus presentation (2 vs 4Hz, p<.001), component (P7-P115, p<.001), and recording montage (channels 1-4, p<.001). Early component latencies (P7-N20) were highly stable in polarity (sign) and latency, and consistent with putative far-field generators (e.g., trigeminal brainstem, ventroposteromedial thalamus).

Vasoactive intestinal peptide administration after stroke in rats enhances neurogenesis and improves neurological function

The aim of this study was to investigate the effects of vasoactive intestinal peptide (VIP) on neurogenesis and neurological function after cerebral ischemia. Rats were intracerebroventricular administered with VIP after a 2h middle cerebral artery occlusion (MCAO) and sacrificed at 7, 14 and 28 days after MCAO. Functional outcome was studied with the modified neurological severity score. The infarct volume was evaluated via histology. Neurogenesis, angiogenesis and the protein expression of vascular endothelial growth factor (VEGF) were measured by immunohistochemistry and Western blotting analysis, respectively. The treatment with VIP significantly reduced the neurological severity score and the infarc volume, and increased the numbers of bromodeoxyuridine (BrdU) immunoreactive cells and doublecortin immunoreactive area in the subventricular zone (SVZ) at 7, 14 and 28 days after ischemia. The cerebral protein levels of VEGF and VEGF expression in the SVZ were also enhanced in VIP-treated rats at 7 days after stroke. VIP treatment obviously increased the number of BrdU positive endothelial cells in the SVZ and density of cerebral microvessels in the ischemic boundary at 28 days after ischemia. Our study suggests that in the ischemic rat brain VIP reduces brain damage and promotes neurogenesis by increasing VEGF. VIP-enhanced neurogenesis is associated with angiogenesis. These changes may contribute to improvement in functional outcome.

Neuronal and vascular interactions

The brain, which represents 2% of body mass but consumes 20% of body energy at rest, has a limited capacity to store energy and is therefore highly dependent on oxygen and glucose supply from the blood stream. Normal functioning of neural circuits thus relies on adequate matching between metabolic needs and blood supply. Moreover, not only does the brain need to be densely vascularized, it also requires a tightly controlled environment free of toxins and pathogens to provide the proper chemical composition for synaptic transmission and neuronal function. In this review, we focus on three major factors that ensure optimal brain perfusion and function: the patterning of vascular networks to efficiently deliver blood and nutrients, the function of the blood-brain barrier to maintain brain homeostasis, and the regulation of cerebral blood flow to adequately couple energy supply to neural function.

Control of cerebrovascular patterning by neural activity during postnatal development

The brain represents only a small portion of the body mass and yet consumes almost a quarter of the available energy, and has a limited ability to store energy. The brain is therefore highly dependent on oxygen and nutrient supply from the blood circulation, which makes it vulnerable to vascular pathologies. Key vascular determinants will ensure proper brain maturation and function: the establishment of vascular networks, the formation of the blood-brain barrier, and the regulation of blood flow. Recent evidence suggests that the phenomenon of neurovascular coupling, during which increased neural activity normally leads to increased blood flow, is not functional until few weeks after birth, implying that the developing brain must rely on alternative mechanisms to adequately couple blood supply to increasing energy demands. This review will focus on these alternative mechanisms, which have been partly elucidated recently via the demonstration that neural activity influences the maturation of cerebrovascular networks. We also propose possible mechanisms underlying activity-induced vascular plasticity.

Buyang huanwu decoction promotes angiogenesis via vascular endothelial growth factor receptor-2 activation through the PI3K/Akt pathway in a mouse model of intracerebral hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) is a fatal subtype of stroke that lacks effective treatments. Angiogenesis following ICH is an important response mediating brain recovery and repair. Phosphorylation of vascular endothelial growth factor receptor 2 (pVEGFR2) via PI3K/Akt signaling plays a key role in mediating cellular processes involved in repair, such as mitogenesis, angiogenesis, and vascular permeability. This study aimed to investigate the potential effects of Buyang Huanwu Decoction (BYHWD), a traditional Chinese medicine formula, on angiogenesis by VEGFR2 activation through the phosphatidylinositol 3 kinase (PI3K)/Akt signaling pathway in a mouse model of ICH.

METHODS

Adult male Kunming mice (n = 50) were randomly assigned into sham and ICH-operated groups and treated with one of the followings SU5416 (VEGFR2 inhibitor), BYHWT and BYHWT + SU5416. ICH was induced in mice by injecting collagenase (type VII) into the right globus pallidus of the mouse brain. BYHWD (4.36 g/kg) was administrated in mice by intragastric infusion. Neurological function was evaluated in mice by a modified Neurological Severity Scores (mNSS) as well as corner turn and foot-fault tests. Angiogenesis was examined by intraperitoneal injection of 5-bromodeoxyuridine (BrdU) in mice to quantify new brain vessel growth. SU5416 treatment and assessment of VEGFR2 phosphorylation as well as alterations in PI3K/Akt signaling were performed to determine whether the effect of BYHWD on angiogenesis was partly mediated by phosphorylation of VEGFR2 via the PI3K/Akt signaling pathway.

RESULTS

We show that BYHWD treated mice exhibited (i) significantly better recovery from neurological dysfunction, (ii) increased BrdU(+) nuclei in vWF(+) dilated brain vessels and (iii) higher VEGFR2 phosphorylation immunoreactivity in brain microvessels (P <0.05), (iv) higher expression of PI3K and pAkt at the protein level (P <0.05) when compared to untreated ICH mice. These beneficial effects were reversed by SU5416 (P <0.05).

CONCLUSIONS

BYHWD promoted neurological recovery and angiogenesis after ICH in mice by enhancing VEGFR2 phosphorylation through the PI3K/Akt signaling pathway.

In vivo bioluminescence imaging of vascular remodeling after stroke

Thrombolysis remains the only beneficial therapy for ischemic stroke, but is restricted to a short therapeutic window following the infarct. Currently research is focusing on spontaneous regenerative processes during the sub-acute and chronic phase. Angiogenesis, the formation of new blood vessels from pre-existing ones, was observed in stroke patients, correlates with longer survival and positively affects the formation of new neurons. Angiogenesis takes place in the border zones of the infarct, but further insight into the temporal profile is needed to fully apprehend its therapeutic potential and its relevance for neurogenesis and functional recovery. Angiogenesis is a multistep process, involving extracellular matrix degradation, endothelial cell proliferation, and, finally, new vessel formation. Interaction between vascular endothelial growth factor and its receptor 2 (VEGFR2) plays a central role in these angiogenic signaling cascades. In the present study we investigated non-invasively the dynamics of VEGFR2 expression following cerebral ischemia in a mouse model of middle cerebral artery occlusion (MCAO). We used a transgenic mouse expressing firefly luciferase under the control of the VEGFR2 promotor to non-invasively elucidate the temporal profile of VEGFR2 expression after stroke as a biomarker for VEGF/VEGFR2 signaling. We measured each animal repetitively up to 2 weeks after stroke and found increased VEGFR2 expression starting 3 days after the insult with peak values at 7 days. These were paralleled by increased VEGFR2 protein levels and increased vascular volume in peri-infarct areas at 14 days after the infarct, indicating that signaling via VEGFR2 leads to successful vascular remodeling. This study describes VEGFR2-related signaling is active at least up to 2 weeks after the infarct and results in increased vascular volume. Further, this study presents a novel strategy for the non-invasive evaluation of angiogenesis-based therapies.

Preconditioning strategy in stem cell transplantation therapy

Stem cell transplantation therapy has emerged as a promising regenerative medicine for ischemic stroke and other neurodegenerative disorders. However, many issues and problems remain to be resolved before successful clinical applications of the cell-based therapy. To this end, some recent investigations have sought to benefit from well-known mechanisms of ischemic/hypoxic preconditioning. Ischemic/hypoxic preconditioning activates endogenous defense mechanisms that show marked protective effects against multiple insults found in ischemic stroke and other acute attacks. As in many other cell types, a sub-lethal hypoxic exposure significantly increases the tolerance and regenerative properties of stem cells and progenitor cells. So far, a variety of preconditioning triggers have been tested on different stem cells and progenitor cells. Preconditioned stem cells and progenitors generally show much better cell survival, increased neuronal differentiation, enhanced paracrine effects leading to increased trophic support, and improved homing to the lesion site. Transplantation of preconditioned cells helps to suppress inflammatory factors and immune responses, and promote functional recovery. Although the preconditioning strategy in stem cell therapy is still an emerging research area, accumulating information from reports over the last few years already indicates it as an attractive, if not essential, prerequisite for transplanted cells. It is expected that stem cell preconditioning and its clinical applications will attract more attention in both the basic research field of preconditioning as well as in the field of stem cell translational research. This review summarizes the most important findings in this active research area, covering the preconditioning triggers, potential mechanisms, mediators, and functional benefits for stem cell transplant therapy.

Sensory-related neural activity regulates the structure of vascular networks in the cerebral cortex

Neurovascular interactions are essential for proper brain function. While the effect of neural activity on cerebral blood flow has been extensively studied, whether or not neural activity influences vascular patterning remains elusive. Here, we demonstrate that neural activity promotes the formation of vascular networks in the early postnatal mouse barrel cortex. Using a combination of genetics, imaging, and computational tools to allow simultaneous analysis of neuronal and vascular components, we found that vascular density and branching were decreased in the barrel cortex when sensory input was reduced by either a complete deafferentation, a genetic impairment of neurotransmitter release at thalamocortical synapses, or a selective reduction of sensory-related neural activity by whisker plucking. In contrast, enhancement of neural activity by whisker stimulation led to an increase in vascular density and branching. The finding that neural activity is necessary and sufficient to trigger alterations of vascular networks reveals an important feature of neurovascular interactions.

Alcohol promotes mammary tumor growth through activation of VEGF-dependent tumor angiogenesis

Alcohol consumption has been recognized as a risk factor for breast cancer. Experimental studies demonstrate that alcohol exposure promotes the progression of existing mammary tumors. However, the mechanisms underlying this effect remain unclear. In the present study, the role of vascular endothelial growth factor (VEGF) in alcohol promotion of breast cancer development was investigated using a mouse xenograft model of mammary tumors and a three-dimensional (3D) tumor/endothelial cell co-culture system. For the mouse xenograft model, mouse E0771 breast cancer cells were implanted into the mammary fat pad of C57BL6 mice. These mice were exposed to alcohol in their drinking water. For the 3D co-culture system, E0771 cells and MDA-MB231 breast cancer cells were co-cultured with SVEC4-10EE2 and human umbilical vein endothelial cells, respectively. The results demonstrated that alcohol increased tumor angiogenesis and accelerated tumor growth. Furthermore, it appeared that alcohol induced VEGF expression in breast cancer cells in vitro and in vivo. Blocking VEGF signaling by SU5416 inhibited tumor angiogenesis in the 3D tumor/endothelial cell co-culture system. Furthermore, injection of SU5416 into mice inhibited alcohol-promoted mammary tumor growth in vivo. These results indicate that alcohol may promote mammary tumor growth by stimulating VEGF-dependent angiogenesis.

Cerebral neovascularization in diabetes: implications for stroke recovery and beyond

Neovascularization is an innate physiologic response by which tissues respond to various stimuli through collateral remodeling (arteriogenesis) and new vessel formation from existing vessels (angiogenesis) or from endothelial progenitor cells (vasculogenesis). Diabetes has a major impact on the neovascularization process but the response varies between different organ systems. While excessive angiogenesis complicates diabetic retinopathy, impaired neovascularization contributes to coronary and peripheral complications of diabetes. How diabetes influences cerebral neovascularization remained unresolved until recently. Diabetes is also a major risk factor for stroke and poor recovery after stroke. In this review, we discuss the impact of diabetes, stroke, and diabetic stroke on cerebral neovascularization, explore potential mechanisms involved in diabetes-mediated neovascularization as well as the effects of the diabetic milieu on poststroke neovascularization and recovery, and finally discuss the clinical implications of these effects.

Histological quantification of angiogenesis after focal cerebral infarction: a systematic review

Ischemic stroke is a leading cause of disability, and current treatments to improve recovery are limited. Part of the natural recovery process after brain injury is angiogenesis. The formation of new blood vessels around the infarct appears to be important for restoration of adequate perfusion to allow for healing of brain tissue. Many potential restorative treatments may affect, and be affected by, angiogenesis, so accurate quantification of this outcome is needed. We performed a systematic review of histological methods to quantify angiogenesis after cerebral infarction. We found reports of the use of a variety of histological and general and immunostaining techniques in conjunction with a variety of analysis methods. We found no direct comparison studies and concluded that more research is needed to optimize the assessment of this important stroke outcome.

Systemic administration of low dosage of tetanus toxin decreases cell proliferation and neuroblast differentiation in the mouse hippocampal dentate gyrus

In the present study, we investigated the effect of Tetaus toxin (TeT) on cell proliferation and neuroblast differentiation using specific markers: 5-bromo-2-deoxyuridine (BrdU) as an exogenous marker for cell proliferation, Ki-67 as an endogenous marker for cell proliferation and doublecortin (DCX) as a marker for neuroblasts in the mouse hippocampal dentate gyrus (DG) after TeT treatment. Mice were intraperitoneally administered 2.5 and 10 ng/kg TeT and sacrificed 15 days after the treatment. In both the TeT-treated groups, no neuronal death occurred in any layers of the DG using neuronal nuclei (NeuN, a neuron nuclei maker) and Fluoro-Jade B (F-J B, a high-affinity fluorescent marker for the localization of neuronal degeneration). In addition, no significant change in glial activation in both the 2.5 and 10 ng/kg TeT-treated-groups was found by GFAP (a marker for astrocytes) and Iba-1 (a marker for microglia) immunohistochemistry. However, in the 2.5 ng/kg TeT-treated-group, the mean number of BrdU, Ki-67 and DCX immunoreactive cells, respectively, were apparently decreased compared to the control group, and the mean number of each in the 10 ng/kg TeT-treated-group was much more decreased. In addition, processes of DCX-immunoreactive cells, which projected into the molecular layer, were short compared to those in the control group. In brief, our present results show that low dosage (10 ng/kg) TeT treatment apparently decreased cell proliferation and neuroblast differentiation in the mouse hippocampal DG without distinct gliosis as well as any loss of adult neurons.

Histological quantification of brain tissue inflammatory cell infiltration after focal cerebral infarction: a systematic review

Ischemic stroke is a leading cause of death and disability, and current treatments to limit tissue injury and improve recovery are limited. Cerebral infarction is accompanied by intense brain tissue inflammation involving many inflammatory cell types that may cause both negative and positive effects on outcomes. Many potential neuroprotective and neurorestorative treatments may affect, and be affected by, this inflammatory cell infiltration, so that accurate quantification of this tissue response is needed. We performed a systematic review of histological methods to quantify brain tissue inflammatory cell infiltration after cerebral infarction. We found reports of multiple techniques to quantify different inflammatory cell types. We found no direct comparison studies and conclude that more research is needed to optimize the assessment of this important stroke outcome.

Role of neural precursor cells in promoting repair following stroke

Stem cell-based therapies for the treatment of stroke have received considerable attention. Two broad approaches to stem cell-based therapies have been taken: the transplantation of exogenous stem cells, and the activation of endogenous neural stem and progenitor cells (together termed neural precursors). Studies examining the transplantation of exogenous cells have demonstrated that neural stem and progenitor cells lead to the most clinically promising results. Endogenous activation of neural precursors has also been explored based on the fact that resident precursor cells have the inherent capacity to proliferate, migrate and differentiate into mature neurons in the uninjured adult brain. Studies have revealed that these neural precursor cell behaviours can be activated following stroke, whereby neural precursors will expand in number, migrate to the infarct site and differentiate into neurons. However, this innate response is insufficient to lead to functional recovery, making it necessary to enhance the activation of endogenous precursors to promote tissue repair and functional recovery. Herein we will discuss the current state of the stem cell-based approaches with a focus on endogenous repair to treat the stroke injured brain.