Vascular remodeling after ischemic stroke: mechanisms and therapeutic potentials

Normalisation of glucose metabolism by exendin-4 in the chronic phase after stroke promotes functional recovery in male diabetic mice

BACKGROUND AND PURPOSE

Glucagon-like peptide-1 (GLP-1) receptor activation decreases stroke risk in people with Type 2 diabetes (T2D), while animal studies have shown the efficacy of this strategy to counteract stroke-induced acute brain damage. However, whether GLP-1 receptor activation also improves recovery in the chronic phase after stroke is unknown. We investigated whether post-acute, chronic administration of the GLP-1 receptor agonist, exendin-4, improves post-stroke recovery and examined possible underlying mechanisms in T2D and non-T2D mice.

EXPERIMENTAL APPROACH

We induced stroke via transient middle cerebral artery occlusion (tMCAO) in T2D/obese mice (8 months of high-fat diet) and age-matched controls. Exendin-4 was administered for 8 weeks from Day 3 post-tMCAO. We assessed functional recovery by weekly upper-limb grip strength tests. Insulin sensitivity and glycaemia were evaluated at 4 and 8 weeks post-tMCAO. Neuronal survival, stroke-induced neurogenesis, neuroinflammation, atrophy of GABAergic parvalbumin+ interneurons, post-stroke vascular remodelling and fibrotic scar formation were investigated by immunohistochemistry.

KEY RESULTS

Exendin-4 normalised T2D-induced impairment of forepaw grip strength recovery in correlation with normalised glycaemia and insulin sensitivity. Moreover, exendin-4 counteracted T2D-induced atrophy of parvalbumin+ interneurons and decreased microglia activation. Finally, exendin-4 normalised density and pericyte coverage of micro-vessels and restored fibrotic scar formation in T2D mice. In non-T2D mice, the exendin-4-mediated recovery was minor.

CONCLUSION AND IMPLICATIONS

Chronic GLP-1 receptor activation mediates post-stroke functional recovery in T2D mice by normalising glucose metabolism and improving neuroplasticity and vascular remodelling in the recovery phase. The results warrant clinical trial of GLP-1 receptor agonists for rehabilitation after stroke in T2D.

Galectin-1 Contributes to Vascular Remodeling and Blood Flow Recovery After Cerebral Ischemia in Mice

Galectin-1 is found in the vasculature and has been confirmed to promote angiogenesis in several cancer models. Furthermore, galectin-1 has been demonstrated to improve the recovery of cerebral ischemia. However, whether vascular remodeling contributes to this improvement is still unknown. In the present study, photochemical cerebral ischemia was induced in both galectin-1-treated (2 μg/day, i.c.v, 3 days) and galectin-1 knockout mice. Laser speckle imaging and immunofluorescent staining demonstrated that circulation and vascular remodeling in the ischemic cortex were improved by galectin-1 treatment but disrupted in galectin-1 knockout mice. Western blot analysis showed that the expression of matrix metallopeptidase-9 and vascular endothelial growth factor (VEGF) was regulated by galectin-1 in vivo. To determine how galectin-1 influences endothelial cells, the expression of galectin-1 in bEnd.3 cells was increased by transfection with an expression plasmid and knocked down by siRNA. As demonstrated by quantitative RT-PCR and western blot analysis, the expression of metallopeptidase-9, VEGF, and VEGF receptors was upregulated by galectin-1 overexpression but downregulated after galectin-1 knockdown. Flow cytometry, Transwell assay, and capillary-like tube formation assay were performed on cells after gene manipulation as well as cells treated by exogenous galectin-1 after anoxia. It demonstrated that galectin-1 potentiated the cell proliferation, migration capacity, and tube formation ability. Taken together, these data suggest that by targeting vascular remodeling, galectin-1 contributes to the restoration of blood flow, which promotes the recovery of mice after cerebral ischemic insults.

Neuroprotective Effect of a New Free Radical Scavenger HL-008 in an Ischemia-Reperfusion Injury Rat Model

Oxidative stress plays a critical role in cerebral ischemia-reperfusion injury. We have previously developed a powerful antioxidant, HL-008. This study aimed to investigate the neuroprotective function of HL-008. HL-008 efficacy in vitro and in vivo was evaluated using a PC-12 cell oxidative stress model induced by hydrogen peroxide and a rat model of middle cerebral artery occlusion, respectively. The MTT assay was used to analyze cell viability. 2,3,5-Triphenyltetrazolium chloride and Hematoxylin and Eosin staining, immunofluorescence, western blot, and proteomics were used to evaluate the infarction volume, brain tissue morphology, apoptosis, inflammation, and related pathways. Indicators related to oxidative levels were also detected. HL-008 significantly reduced the cerebral infarction volume induced by ischemia-reperfusion, improved the neurological score, alleviated oxidative stress and inflammation in the brain tissue, reduced glial cell activation, inhibited brain tissue apoptosis by influencing multiple signaling pathways, and had a neuroprotective effect. If HL-008 is successfully developed, it could significantly improve stroke patients' quality of life.

The bidirectional role of the JAK2/STAT3 signaling pathway and related mechanisms in cerebral ischemia-reperfusion injury

The Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway, a well-conserved and basic intracellular signaling cascade, is mostly inactivated under basal conditions, although it can be phosphorylated under extracellular stimulation; in addition, it can influence the transcription and expression of multiple genes involved in biological processes such as cellular growth, metabolism, differentiation, degradation and angiogenesis. The inflammatory response, apoptosis, oxidative stress and angiogenesis are the main factors involved in the pathogenesis of ischemic stroke. Numerous studies have confirmed that the JAK2/STAT3 axis can be activated rapidly by ischemic stress, which is closely related to the regulation of these important pathological processes. However, different opinions on the specific role of this signaling pathway remain. In this paper, we review and summarize previous studies on the JAK2/STAT3 pathway in ischemic stroke.

Adiponectin-Transfected Endothelial Progenitor Cells Have Protective Effects After 2-Hour Middle-Cerebral Artery Occlusion in Rats With Type 2 Diabetes Mellitus

Objectives: This present study aimed to examine the effects of adiponectin-transfected endothelial progenitor cells (LV-APN-EPCs) on cerebral ischemia-reperfusion injury in rats with type 2 diabetes mellitus (T2DM) and to explore the underlying mechanisms. Methods: Seventy male Sprague-Dawley rats with T2DM were randomly divided into sham, phosphate-buffered saline (PBS), LV-APN-EPCs, LV-EPCs, and EPCs groups. Transient middle cerebral artery occlusion (MCAO) was induced by the intraluminal suture method. After 1 h of reperfusion, the five interventions were performed by tail-vein injections. The modified neurological severity score (mNSS) was used to assess neurological function before and on days 1, 7, and 14 after MCAO. After 14 days, magnetic resonance imaging scanning, hematoxylin and eosin staining, terminal dUTP nick-end labeling staining, Western blotting analysis, cluster of differentiation (CD) 31 immunofluorescence, and enzyme-linked immunosorbent assay were used to evaluate infarct rate, morphological damage, cell apoptosis, and microvessel density. Results: Compared with PBS, LV-EPCs, and EPCs groups, the LV-APN-EPCs group showed significantly lower mNSS score, lower infarct rate, and less morphological damage (all P < 0.05). In addition, compared with other groups, the LV-APN-EPCs group had significantly increased levels of B cell lymphoma/leukemia-2 (Bcl-2) protein, CD31+ microvessels, endothelial nitric oxide synthase, and vascular endothelial growth factor, and decreased levels of Bcl-2-associated X protein and neuronal apoptosis in the peri-infarct cortex (all P < 0.05). Conclusion: These results suggest that LV-APN-EPCs exert protective effects against cerebral ischemia-reperfusion injury in T2DM rats by increasing angiogenesis.

Clarifying the effects of diabetes on the cerebral circulation: Implications for stroke recovery and beyond

Given the sheer increased number of victims per year and the availability of only one effective treatment, acute ischemic stroke (AIS) remains to be one of the most under-treated serious diseases. Diabetes not only increases the incidence of ischemic stroke, but amplifies the ischemic damage, upon which if patients with diabetes suffer from stroke, he/she will confront increased risks of long-term functional deficits. The grim reality makes it a pressing need to intensify efforts at the basic science level to understand how diabetes impairs stroke recovery. This review retrospects the clinical and experimental studies in order to elucidate the detrimental effect of diabetes on cerebrovascular circulation including the major arteries/arterioles, collateral circulation, and neovascularization to shed light on further exploration of novel strategies for cerebral circulation protection before and after AIS in patients with diabetes.

Angiopoietin-like 4 promotes angiogenesis and neurogenesis in a mouse model of acute ischemic stroke

OBJECTIVE

The purpose of the present study is to investigate whether angiopoietin-like 4 (ANGPTL4) can promote angiogenesis and neurogenesis following stroke, as well as to explore the potential underlying mechanisms.

METHODS

ANGPTL4 (40 μg/kg) or a vehicle was administered via tail vein beginning 5 min prior to electrocoagulation-induced stroke in male C57/B6 J mice. Infarct volume was measured via Nissl staining at day 3 post-stroke. Angiogenesis, neurogenesis and activation of microglia were evaluated by immunofluorescence co-labelling bromodeoxyuridine (BrdU) with von Willebrand factor (vWF), doublecortin (DCX), neuronal nuclei (NeuN) and Iba1 at day 7 post-stroke. The levels of p-AKT, T-AKT, VEGF, MPO, Fas and FasL in the ipsilesional brain were detected by Western blot analysis at day 1 post-stroke.

RESULTS

Compared with the Vehicle group, ANGPTL4 reduced infarct volume significantly at day 3 post-stroke. ANGPTL4 significantly increased the number of BrdU+, BrdU+/vWF+and BrdU+/DCX+ cells in the peri-infarct zone, subventricular zone and subgranular zone and inhibited BrdU+/Iba1+ cells in the peri-infarct zone at day 7 post-stroke. The level of p-AKT and the ratio of phospho-AKT to total-AKT in the ipsilesional brain were significantly elevated, the levels of MPO, Fas and FasL were significantly declined; however, there was no significant difference at day 1 post-stroke between the VEGF and total-AKT levels in both groups.

CONCLUSIONS

ANGPTL4 enhances angiogenesis and neurogenesis post-stroke by upregulating the phosphorylation of AKT, reduces neuronal death and inhibits inflammatory response, which resultes from the inhibition of FasL/Fas expression and its downstream pathway.

Endothelial Progenitor Cell-Derived Microvesicles Promote Angiogenesis in Rat Brain Microvascular Endothelial Cells In vitro

Brain microvascular endothelial cells (BMECs) are a major component of the blood-brain barrier that maintains brain homeostasis. Preserving and restoring the normal biological functions of BMECs can reverse or reduce brain injury. Endothelial progenitor cells (EPCs) may promote brain vascular remodeling and restore normal endothelial function. As a novel vehicle for cell-cell communication, microvesicles (MVs) have varied biological functions. The present study investigated the biological effects of EPC-derived MVs (EPC-MVs) on BMECs in vitro. We isolated MVs from the supernatant of EPCs in a serum-depleted medium. BMECs were cultured alone or in the presence of EPC-MVs. BMEC viability and proliferation were evaluated with the Cell Counting Kit-8 and by flow cytometry, and the proangiogenic effect of EPC-MVs on BMECs was assessed with the transwell migration, wound healing, and tube formation assays. Our results showed that EPC-derived MVs labeled with DiI were internalized by cultured BMECs; this enhanced BMEC viability and promoted their proliferation. EPC-MVs also stimulated migration and tube formation in BMECs. These results demonstrate that EPC-derived MVs exert a proangiogenic effect on BMECs, which has potential applications in cell-free therapy for brain injury.

Automatic segmentation, feature extraction and comparison of healthy and stroke cerebral vasculature

Accurate segmentation of cerebral vasculature and a quantitative assessment of its morphology is critical to various diagnostic and therapeutic purposes and is pertinent to studying brain health and disease. However, this is still a challenging task due to the complexity of the vascular imaging data. We propose an automated method for cerebral vascular segmentation without the need of any manual intervention as well as a method to skeletonize the binary segmented map to extract vascular geometric features and characterize vessel structure. We combine a Hessian-based probabilistic vessel-enhancing filtering with an active-contour-based technique to segment magnetic resonance and computed tomography angiograms (MRA and CTA) and subsequently extract the vessel centerlines and diameters to calculate the geometrical properties of the vasculature. Our method was validated using a 3D phantom of the Circle-of-Willis region, demonstrating 84% mean Dice similarity coefficient (DSC) and 85% mean Pearson's correlation coefficient (PCC) with minimal modified Hausdorff distance (MHD) error (3 surface pixels at most), and showed superior performance compared to existing segmentation algorithms upon quantitative comparison using DSC, PCC and MHD. We subsequently applied our algorithm to a dataset of 40 subjects, including 1) MRA scans of healthy subjects (n = 10, age = 30 ± 9), 2) MRA scans of stroke patients (n = 10, age = 51 ± 15), 3) CTA scans of healthy subjects (n = 10, age = 62 ± 12), and 4) CTA scans of stroke patients (n = 10, age = 68 ± 11), and obtained a quantitative comparison between the stroke and normal vasculature for both imaging modalities. The vascular network in stroke patients compared to age-adjusted healthy subjects was found to have a significantly (p < 0.05) higher tortuosity (3.24 ± 0.88 rad/cm vs. 7.17 ± 1.61 rad/cm for MRA, and 4.36 ± 1.32 rad/cm vs. 7.80 ± 0.92 rad/cm for CTA), higher fractal dimension (1.36 ± 0.28 vs. 1.71 ± 0.14 for MRA, and 1.56 ± 0.05 vs. 1.69 ± 0.20 for CTA), lower total length (3.46 ± 0.99 m vs. 2.20 ± 0.67 m for CTA), lower total volume (61.80 ± 18.79 ml vs. 34.43 ± 22.9 ml for CTA), lower average diameter (2.4 ± 0.21 mm vs. 2.18 ± 0.07 mm for CTA), and lower average branch length (4.81 ± 1.97 mm vs. 8.68 ± 2.03 mm for MRA), respectively. We additionally studied the change in vascular features with respect to aging and imaging modality. While we observed differences between features as a result of aging, statistical analysis did not show any significant differences, whereas we found that the number of branches were significantly different (p < 0.05) between the two imaging modalities (201 ± 73 for MRA vs. 189 ± 69 for CTA). Our segmentation and feature extraction algorithm can be applied on any imaging modality and can be used in the future to automatically obtain the 3D segmented vasculature for diagnosis and treatment planning as well as to study morphological changes due to stroke and other cerebrovascular diseases (CVD) in the clinic.

Network Pharmacology Reveals the Mechanism of Activity of Tongqiao Huoxue Decoction Extract Against Middle Cerebral Artery Occlusion-Induced Cerebral Ischemia-Reperfusion Injury

Several clinical therapies such as tissue repair by replacing injured tissues with functional ones have been reported; however, there is great potential for exploring traditional herbal-induced regeneration with good safety. Tongqiao Huoxue Decoction (TQHXD), a well-known classical traditional Chinese medicinal formula, has been widely used for clinical treatment of stroke. However, biological activity and mechanisms of action of its constituents toward conferring protection against cerebral ischemia-reperfusion (I/R) injury remain unclear. In this present study, we evaluated TQHXD quality using HPLC; then, it was screened for its potential active ingredients using a series of indices, such as their drug-likeness and oral bioavailability. Subsequently, we analyzed the potential mechanisms of TQHXD anti-I/R using gene ontology functional enrichment analyses. The network pharmacological approach enabled us to screen 265 common targets associated with I/R, indicating that TQHXD had remarkable protective effects on infarction volume, neurological function scores, and blood-brain barrier (BBB) injury. In addition, TQHXD significantly promoted the recovery of regional cerebral blood flow (rCBF) 7 days after reperfusion compared to rats in the vehicle group. Immunofluorescence results revealed a significantly higher CD34 expression in TQHXD-treated rats 7 days after reperfusion. TQHXD is not merely effective but eventually develops a secretory profile composed of VEGF and cerebral blood flow, a typical signature termed the angiogenesis-associated phenotype. Mechanistically, our data revealed that TQHXD (6 g/kg) treatment resulted in a marked increase in expression of p-focal adhesion kinase (FAK) and p-Paxillin proteins. However, Ki8751-mediated inhibition of VEGFR2 activity repealed its angiogenesis and protective effects and decreased both p-FAK and p-Paxillin protein levels. Taken together, these findings affirmed the potential of TQHXD as a drug for the management of stroke, which might be exerted by increasing the angiogenesis via the VEGF pathway. Therefore, these results provide proof-of-concept evidence that angiogenesis is a major contributor to TQHXD-treated I/R and that TQHXD is a promising traditional ethnic medicine for the management of this condition.

Exosomes Derived from CXCR4-Overexpressing BMSC Promoted Activation of Microvascular Endothelial Cells in Cerebral Ischemia/Reperfusion Injury

Background

Ischemic stroke is a severe acute cerebrovascular disease which can be improved with neuroprotective therapies at an early stage. However, due to the lack of effective neuroprotective drugs, most stroke patients have varying degrees of long-term disability. In the present study, we investigated the role of exosomes derived from CXCR4-overexpressing BMSCs in restoring vascular function and neural repair after ischemic cerebral infarction.

Methods

BMSCs were transfected with lentivirus encoded by CXCR4 (BMSC^CXCR4). Exosomes derived from BMSC^CXCR4 (Exo^CXCR4) were isolated and characterized by transmission electron microscopy and dynamic light scattering. Western blot and qPCR were used to analyze the expression of CXCR4 in BMSCs and exosomes. The acute middle cerebral artery occlusion (MCAO) model was prepared, Exo^CXCR4 were injected into the rats, and behavioral changes were analyzed. The role of Exo^CXCR4 in promoting the proliferation and tube formation for angiogenesis and protecting brain endothelial cells was determined in vitro.

Results

Compared with the control groups, the Exo^CXCR4 group showed a significantly lower mNSS score at 7 d, 14 d, and 21 d after ischemia/reperfusion (P < 0.05). The bEnd.3 cells in the Exo^CXCR4 group have stronger proliferation ability than other groups (P < 0.05), while the CXCR4 inhibitor can reduce this effect. Exosomes control (Exo^Con) can significantly promote the migration of bEnd.3 cells (P < 0.05), while there was no significant difference between the Exo^CXCR4 and Exo^Con groups (P > 0.05). Exo^CXCR4 can further promote the proliferation and tube formation for the angiogenesis of the endothelium compared with Exo^Con group (P < 0.05). In addition, cobalt chloride (COCl2) can increase the expression of β-catenin and Wnt-3, while Exo^Con can reduce the expression of these proteins (P < 0.05). Exo^CXCR4 can further attenuate the activation of Wnt-3a/β-catenin pathway (P < 0.05).

Conclusions

In ischemia/reperfusion injury, Exo^CXCR4 promoted the proliferation and tube formation of microvascular endothelial cells and play an antiapoptotic role via the Wnt-3a/β-catenin pathway.

N. S. Ethnic variation and the relevance of homozygous RNF 213 p.R4810.K variant in the phenotype of Indian Moya moya disease

Background and purpose

Polymorphisms in Ring Finger Protein 213 (RNF 213) gene have been detected to confer genetic susceptibility to Moya moya disease (MMD) in the East Asian population. We investigated the frequency of RNF 213 gene polymorphism and its association with MMD phenotypes in the Indian population.

Materials and methods

A case-control study for RNF 213 polymorphism involving 65 MMD patients, 75 parents, and 120 controls were performed. A total of 21 SNPs were screened, of which 17 SNPs were monomorphic. Allelic and genotypic frequency of all polymorphic SNPs were assessed and its association with MMD phenotypes was evaluated.

Results

The median age of symptom onset was 9 (range 2–17) and 37 years (range 20–58) in paediatric and adult patients respectively. A strong association was observed with RNF 213 rs112735431(p.R4810K) and MMD. Out of 65 patients with MMD, five patients carried the homozygous risk AA genotype. None of the healthy controls carried this homozygous mutation. The mutant allele was detected in MMD patients from Tamil Nadu and North eastern states of India (p = <0.0001). All the patients carrying the mutant allele had an early age of onset (p = <0.0001), higher incidence of bilateral disease (p = <0.002), positive family history (p = 0.03), higher Suzuki angiographic stage (≥3) (p<0.0006) and recurrent neurological events (ischemic strokes and TIAs) (p = <0.009).

Conclusion

The homozygous rs112735431(p.R4810K) variant in RNF 213 variant not only predicts the risk for MMD but can also predict the phenotypic variants.

The impact of native leptomeningeal collateralization on rapid blood flow recruitment following ischemic stroke

The leptomeningeal collateral status is an independent predictor of stroke outcome. By means of optical coherent tomography angiography to compare two mouse strains with different extent of native leptomeningeal collateralization, we determined the spatiotemporal dynamics of collateral flow and downstream hemodynamics following ischemic stroke. A robust recruitment of leptomeningeal collateral flow was detected immediately after middle cerebral artery (MCA) occlusion in C57BL/6 mice, with continued expansion over the course of seven days. In contrast, little collateral recruitment was seen in Balb/C mice during- and one day after MCAO, which coincided with a greater infarct size and worse functional outcome compared to C57BL/6, despite a slight improvement of cortical perfusion seven days after MCAO. Both strains of mice experienced a reduction of blood flow in the penetrating arterioles (PA) by more than 90% 30-min after dMCAO, although the decrease of PA flow was greater and the recovery was less in the Balb/C mice. Further, Balb/C mice also displayed a prolonged greater heterogeneity of capillary transit time after dMCAO in the MCA territory compared to C57BL/6 mice. Our data suggest that the extent of native leptomeningeal collaterals affects downstream hemodynamics with a long lasting impact in the microvascular bed after cortical stroke.

Catalpol protects vascular structure and promotes angiogenesis in cerebral ischemic rats by targeting HIF-1α/VEGF

BACKGROUND

The initial factor in the occurrence, development, and prognosis of cerebral ischemia is vascular dysfunction in the brain, and vascular remodeling of the brain is the key therapeutic target and strategy for ischemic tissue repair. Catalpol is the main active component of the radix of Rehmannia glutinosa Libosch, and it exhibits potential pleiotropic protective effects in many brain-related diseases, including stroke.

PURPOSE

The present study was designed to investigate whether catalpol protects vascular structure and promotes angiogenesis in cerebral ischemic rats and to identify its possible mechanisms in vivo and in vitro.

STUDY DESIGN

Cerebral ischemic rats and oxygen-glucose deprivation-exposed brain microvascular endothelial cells were used to study the therapeutic potential of catalpol in vivo and in vitro.

METHODS

First, neurological deficits, histopathological morphology, infarct volume, vascular morphology, vessel density, and angiogenesis in focal cerebral ischemic rats were observed to test the potential treatment effects of catalpol. Then, oxygen-glucose deprivation-exposed brain microvascular endothelial cells were used to mimic the pathological changes in vessels during ischemia to study the effects and possible mechanisms of catalpol in protecting vascular structure and promoting angiogenesis.

RESULTS

The in vivo results showed that catalpol reduced neurological deficit scores and infarct volume, protected vascular structure, and promoted angiogenesis in cerebral ischemic rats. The in vitro results showed that catalpol improved oxygen-glucose deprivation-induced damage and promoted proliferation, migration, and in vitro tube formation of brain microvascular endothelial cells. The HIF-1α (hypoxia-inducible factor 1α)/VEGF (vascular endothelial growth factor) pathway was activated by catalpol both in the brains of cerebral ischemic rats and in primary brain microvascular endothelial cells, and the activating effects of catalpol were inhibited by SU1498.

CONCLUSION

The results of both the in vivo and in vitro studies proved that catalpol protects vascular structure and promotes angiogenesis in focal cerebral ischemic rats and that the mechanism is dependent on HIF-1α/VEGF.

LncRNAs Stand as Potent Biomarkers and Therapeutic Targets for Stroke

Stroke is a major public health problem worldwide with a high burden of neurological disability and mortality. Long noncoding RNAs (lncRNAs) have attracted much attention in the past decades because of their newly discovered roles in pathophysiological processes in many diseases. The abundance of lncRNAs in the nervous system indicates that they may be part of a complex regulatory network governing physiology and pathology of the brain. In particular, lncRNAs have been shown to play pivotal roles in the pathogenesis of stroke. In this article, we provide a review of the multifaceted functions of lncRNAs in the pathogenesis of ischemic stroke and intracerebral hemorrhage, highlighting their promising use as stroke diagnostic biomarkers and therapeutics. To this end, we discuss the potential of stem cells in aiding lncRNA applications in stroke.

Circulating MiRNA-195-5p and -451a in Diabetic Patients with Transient and Acute Ischemic Stroke in the Emergency Department

(1) Background: Circulating micro-RNAs (miRNAs) modulate the expression of molecules in diabetes. We evaluated the expression of serum miRNA-195-5p and -451a in diabetic patients with ischemic stroke and correlated them with two markers of brain tissue integrity. (2) Methods: Seventy-eight subjects with acute ischemic stroke (AIS) or transient ischemic attack (TIA) (40 with diabetes) were enrolled. Serum miRNA levels, brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor A (VEGF-A) were assessed at admission and 24 and 72 h after a post-ischemic stroke, and were compared to 20 controls. (3) Results: Both circulating miRNAs were two-fold up-regulated in diabetic AIS and TIA patients compared to non-diabetics. Their levels progressively decreased at 24 and 72 h in both AIS and TIA patients. Interestingly, in the non-diabetic TIA group, both circulating miRNAs, although higher than the controls, tended to achieve a complete decay after 72 h. Furthermore, miRNA-195-5p and miRNA-451a levels inversely correlated with both BDNF and VEGF-A serum levels. (4) Conclusions: These data show a different profile of both micro-RNAs in diabetic versus non-diabetic patients after acute ischemic stroke, suggesting their pivotal role in cerebrovascular ischemic attack.

A Window of Vascular Plasticity Coupled to Behavioral Recovery after Stroke

Stroke causes remodeling of vasculature surrounding the infarct, but whether and how vascular remodeling contributes to recovery are unclear. We established an approach to monitor and compare changes in vascular structure and blood flow with high spatiotemporal precision after photothrombotic infarcts in motor cortex using longitudinal 2-photon and multiexposure speckle imaging in mice of both sexes. A spatially graded pattern of vascular structural remodeling in peri-infarct cortex unfolded over the first 2 weeks after stroke, characterized by vessel loss and formation, and selective stabilization of a subset of new vessels. This vascular structural plasticity was coincident with transient activation of transcriptional programs relevant for vascular remodeling, reestablishment of peri-infarct blood flow, and large improvements in motor performance. Local vascular plasticity was strongly predictive of restoration of blood flow, which was in turn predictive of behavioral recovery. These findings reveal the spatiotemporal evolution of vascular remodeling after stroke and demonstrate that a window of heightened vascular plasticity is coupled to the reestablishment of blood flow and behavioral recovery. Our findings support that neovascularization contributes to behavioral recovery after stroke by restoring blood flow to peri-infarct regions. These findings may inform strategies for enhancing recovery from stroke and other types of brain injury.SIGNIFICANCE STATEMENT An improved understanding of neural repair could inform strategies for enhancing recovery from stroke and other types of brain injury. Stroke causes remodeling of vasculature surrounding the lesion, but whether and how the process of vascular remodeling contributes to recovery of behavioral function have been unclear. Here we used longitudinal in vivo imaging to track vascular structure and blood flow in residual peri-infarct cortex after ischemic stroke in mice. We found that stroke created a restricted period of heightened vascular plasticity that was associated with restoration of blood flow, which was in turn predictive of recovery of motor function. Therefore, our findings support that vascular remodeling facilitates behavioral recovery after stroke by restoring blood flow to peri-infarct cortex.

Oxytocin Receptor Signaling in Vascular Function and Stroke

The oxytocin receptor (OXTR) is a G protein-coupled receptor with a diverse repertoire of intracellular signaling pathways, which are activated in response to binding oxytocin (OXT) and a similar nonapeptide, vasopressin. This review summarizes the cell and molecular biology of the OXTR and its downstream signaling cascades, particularly focusing on the vasoactive functions of OXTR signaling in humans and animal models, as well as the clinical applications of OXTR targeting cerebrovascular accidents.

Novel Approaches for Omega-3 Fatty Acid Therapeutics: Chronic Versus Acute Administration to Protect Heart, Brain, and Spinal Cord

This article reviews novel approaches for omega-3 fatty acid (FA) therapeutics and the linked molecular mechanisms in cardiovascular and central nervous system (CNS) diseases. In vitro and in vivo research studies indicate that omega-3 FAs affect synergic mechanisms that include modulation of cell membrane fluidity, regulation of intracellular signaling pathways, and production of bioactive mediators. We compare how chronic and acute treatments with omega-3 FAs differentially trigger pathways of protection in heart, brain, and spinal cord injuries. We also summarize recent omega-3 FA randomized clinical trials and meta-analyses and discuss possible reasons for controversial results, with suggestions on improving the study design for future clinical trials. Acute treatment with omega-3 FAs offers a novel approach for preserving cardiac and neurological functions, and the combinations of acute treatment with chronic administration of omega-3 FAs might represent an additional therapeutic strategy for ameliorating adverse cardiovascular and CNS outcomes.

Cerebral collaterals in acute ischaemia: Implications for acute ischaemic stroke patients receiving reperfusion therapy

The cerebral collaterals play an important role in penumbral tissue sustenance after an acute ischaemic stroke. Recent studies have demonstrated the potential role of collaterals in the selection of acute ischaemic stroke patients eligible for reperfusion therapy. However, the understanding of the significance and evidence around the role of collateral status in predicting outcomes in acute ischaemic stroke patients treated with reperfusion therapy is still unclear. Moreover, the use of pre-treatment collaterals in patient selection and prognosis is relatively underappreciated in clinical settings. A focused review of the literature was performed on the various methods of collateral evaluation and the role of collateral status in acute ischaemic stroke patients receiving reperfusion therapy. We discuss the methods of evaluating pre-treatment collaterals in clinical settings. The patient selection based on collateral status as well as the prognostic and therapeutic value of collaterals in acute ischaemic stroke, in settings of intravenous thrombolysis or endovascular therapy alone, and bridge therapy, are summarized. Recommendations for future research and possible pharmacological intervention strategies aimed at collateral enhancement are also discussed. Collaterals may play an important role in identifying acute ischaemic stroke patients who are likely to benefit from endovascular treatment in an extended time window. Future neuroscientific efforts to better improve our understanding of the role of collaterals in acute ischaemia as well as clinical studies to delineate its role in patient selection and acute stroke prognosis are warranted.

Houshiheisan promotes angiogenesis via HIF-1α/VEGF and SDF-1/CXCR4 pathways: in vivo and in vitro

Rationale: Houshiheisan (HSHS), a classic prescription in traditional Chinese medicine (TCM), has remarkable efficacy in the treatment of ischemic stroke.

Objective: To investigate the pro-angiogenic effect and molecular mechanism of HSHS for stroke recovery.

Methods and results: The rat permanent middle cerebral artery occlusion (pMCAO) model was constructed by suture method, HSHS (5.25 or 10.5 g/kg) and Ginaton (28 mg/kg) treatment was intragastrically administrated at 6 h after modeling which remained for 7 consecutive days. Pathological evaluation conducted by Hematoxylin–Eosin (HE) staining and the results showed that HSHS alleviated blood vessel edema, reduced the damage to blood vessels and neurons in the ischemic areas. Immunostaining, quantitative real-time fluorescence PCR results showed that HSHS up-regulated pro-angiogenic factors including platelet endothelial cell adhesion molecule-1 (cluster of differentiation 31 (CD31)), vascular endothelial growth factor (VEGF), vascular endothelial growth factor A (VEGFA), VEGF receptor 2 (VEGFR2), angiopoietin-1 (Ang-1), while down-regulated angiopoietin-2 (Ang-2), stromal cell derived factor-1 (SDF-1), and cxc chemokine receptor 4 (CXCR4) expression in infarct rat cortex, and similar results were obtained in subsequent Western blot experiment. Furthermore, CCK8 assay and transwell migration assay were performed to assess cell proliferation, migration, and tube formation. The medicated serum (MS) of HSHS appeared to have beneficial effects for immortalized human umbilical vein cells (Im-HUVECs) on proliferation and migration after persistence hypoxia. Western blot analysis revealed that the expression of hypoxia inducible factor-1α (HIF-1α), VEGFA, Ang-1, Ang-2, and CXCR4 were significantly up-regulated while Ang-2 was down-regulated by HSHS MS treatment compared with vehicle group in vitro.

Conclusion: The present study suggests a novel application of HSHS as an effective angiogenic formula for stroke recovery.

Can miRNAs Be Considered as Diagnostic and Therapeutic Molecules in Ischemic Stroke Pathogenesis?-Current Status

Ischemic stroke is one of the leading causes of death worldwide. Clinical manifestations of stroke are long-lasting and causing economic burden on the patients and society. Current therapeutic modalities to treat ischemic stroke (IS) are unsatisfactory due to the intricate pathophysiology and poor functional recovery of brain cellular compartment. MicroRNAs (miRNA) are endogenously expressed small non-coding RNA molecules, which can act as translation inhibitors and play a pivotal role in the pathophysiology associated with IS. Moreover, miRNAs may be used as potential diagnostic and therapeutic tools in clinical practice; yet, the complete role of miRNAs is enigmatic during IS. In this review, we explored the role of miRNAs in the regulation of stroke risk factors viz., arterial hypertension, metabolic disorders, and atherosclerosis. Furthermore, the role of miRNAs were reviewed during IS pathogenesis accompanied by excitotoxicity, oxidative stress, inflammation, apoptosis, angiogenesis, neurogenesis, and Alzheimer's disease. The functional role of miRNAs is a double-edged sword effect in cerebral ischemia as they could modulate pathological mechanisms associated with risk factors of IS. miRNAs pertaining to IS pathogenesis could be potential biomarkers for stroke; they could help researchers to identify a particular stroke type and enable medical professionals to evaluate the severity of brain injury. Thus, ascertaining the role of miRNAs may be useful in deciphering their diagnostic role consequently it is plausible to envisage a suitable therapeutic modality against IS.

Human placental trophoblast progenitor cells (hTPCs) promote angiogenesis and neurogenesis after focal cerebral ischemia in rats

INTRODUCTION

Reduction of blood flow below a threshold value in brain regions locally or globally is called cerebral ischemia and proper treatment requires either the restoration of normal blood flow and/or the administration of neuroprotective therapies. Human trophoblast progenitor cells (hTPCs) give rise to the placenta and are responsible for the invasion and vascular remodeling of the maternal vessels within the uterus. Here, we tested whether hTPCs promoted to differentiate along neural lineages may exhibit therapeutic properties in the setting of cerebral ischemia in vivo.

MATERIALS AND METHODS

Cerebral ischemia was generated in rats via middle cerebral artery occlusion and, after 24 h, hTPCs were injected systemically via tail vein. Animals were sacrified at Day 3 or 11.

RESULTS

TTC staining indicated that infarct volumes were smaller in hTPC treated animals. Visible myelin recovery was observed in the hTPC injected group with Luxol Fast Blue staining. On Day 11 after hTPC transplantation, DLX5 and VEGF expression, as well as 2 and 10 d after hTPC transplantation, NKX2.2 were significantly increased; while LHX6, Olig1, PDGFRα, VEGFR1 and VEGFR2 showed trends toward improved expression in brain tissue via immunoblot analysis. Neuron-like differentiated cells were positive for both NeuN and Cresyl Violet staining.

CONCLUSION

Here, we demonstrate for the first time that hTPCs enhance the expression of angiogenic and neurogenic factors in rat brain after stroke. Transplantation of hTPCs could form the basis of novel therapeutic approaches for the treatment of stroke in the clinical setting.

3-Mercaptopyruvate sulfurtransferase/hydrogen sulfide protects cerebral endothelial cells against oxygen-glucose deprivation/reoxygenation-induced injury via mitoprotection and inhibition of the RhoA/ROCK pathway

3-Mercaptopyruvate sulfurtransferase (3-MST) is the major source of hydrogen sulfide (H₂S) production in the brain and participates in many physiological and pathological processes. The present study was designed to investigate the role of 3-MST-derived H₂S (3-MST/H₂S) on oxygen-glucose deprivation/reoxygenation (OGD/R) injury in cerebrovascular endothelial cells (ECs). Using cerebrovascular specimens from patients with acute massive cerebral infarction (MCI), we found abnormal morphology of the endothelium and mitochondria, as well as decreases in H₂S and 3-MST levels. In an OGD/R model of ECs, 3-mercaptopyruvate (3-MP) and l-aspartic acid (l-Asp) were used to stimulate or inhibit the production of 3-MST/H₂S. The results showed that OGD/R induced significant decreases in H₂S and 3-MST levels in both ECs and mitochondria, as well as increases in oxidative stress and mitochondrial energy imbalance. Cellular oxidative stress, destruction of mitochondrial ultrastructure, accumulation of mitochondrial reactive oxygen species (ROS), reduction of mitochondrial adenosine triphosphate (ATP) synthase activity and ATP production, and decreased mitochondrial membrane potential were all significantly ameliorated by 3-MP, whereas they were exacerbated by l-Asp pretreatment. Contrary to the effects of l-Asp, the increase in RhoA activity and expression of ROCK₁ and ROCK₂ induced by OGD/R were markedly inhibited by 3-MP pretreatment in subcellular fractions without mitochondria and mitochondrial fractions. In addition, 3-MST^-/- rat ECs displayed greater oxidative stress than 3-MST^+/+ rat ECs after OGD/R injury. These findings suggest that 3-MST/H₂S protects ECs against OGD/R-induced injury, which may be related to preservation of mitochondrial function and inhibition of the RhoA/ROCK pathway.

Structural and Functional Remodeling of the Brain Vasculature Following Stroke

Maintenance of cerebral blood vessel integrity and regulation of cerebral blood flow ensure proper brain function. The adult human brain represents only a small portion of the body mass, yet about a quarter of the cardiac output is dedicated to energy consumption by brain cells at rest. Due to a low capacity to store energy, brain health is heavily reliant on a steady supply of oxygen and nutrients from the bloodstream, and is thus particularly vulnerable to stroke. Stroke is a leading cause of disability and mortality worldwide. By transiently or permanently limiting tissue perfusion, stroke alters vascular integrity and function, compromising brain homeostasis and leading to widespread consequences from early-onset motor deficits to long-term cognitive decline. While numerous lines of investigation have been undertaken to develop new pharmacological therapies for stroke, only few advances have been made and most clinical trials have failed. Overall, our understanding of the acute and chronic vascular responses to stroke is insufficient, yet a better comprehension of cerebrovascular remodeling following stroke is an essential prerequisite for developing novel therapeutic options. In this review, we present a comprehensive update on post-stroke cerebrovascular remodeling, an important and growing field in neuroscience, by discussing cellular and molecular mechanisms involved, sex differences, limitations of preclinical research design and future directions.

Integrin α5β1 inhibition by ATN-161 reduces neuroinflammation and is neuroprotective in ischemic stroke

Stroke remains a leading cause of death and disability with limited therapeutic options. Endothelial cell β₁ integrin receptors play a direct role in blood-brain barrier (BBB) dysfunction through regulation of tight junction proteins and infiltrating leukocytes, potentially mediated by β1 integrins. Following tandem transient common carotid artery/middle cerebral artery occlusion on wild-type mice, we administered the integrin a5b1 inhibitor, ATN-161, intraperitoneal (IP) injection at 1 mg/kg acutely after reperfusion, on post-stroke day (PSD)1 and PSD2. Systemic changes (heart rate, pulse distension, and body temperature) were determined. Additionally, infarct volume and edema were determined by 2,3-triphenyltetrazolium chloride and magnetic resonance imaging, while neurological changes were evaluated using an 11-point Neuroscore. Brain immunohistochemistry was performed for claudin-5, α5β1, IgG, and CD45 + cells, and quantitative polymerase chain reaction (qPCR) was performed for matrix metalloproteinase-9 (MMP-9), interleukin (IL)-1β, collagen IV, and CXCL12. ATN-161 significantly reduced integrin α5β1 expression in the surrounding peri-infarct region with no systemic changes. Infarct volume, edema, and functional deficit were significantly reduced in ATN-161-treated mice. Furthermore, ATN-161 treatment reduced IgG extravasation into the parenchyma through conserved claudin-5, collagen IV, CXCL12 while reducing MMP-9 transcription. Additionally, IL-1β and CD45 + cells were reduced in the ipsilateral cortex following ATN-161 administration. Collectively, ATN-161 may be a promising novel stroke therapy by reducing post-stroke inflammation and BBB permeability.

Buyang Huanwu Decoction Promotes Angiogenesis after Cerebral Ischemia by Inhibiting the Nox4/ROS Pathway

Background

Buyang Huanwu decoction (BYHWD), an important traditional Chinese medicine (TCM), has been used clinically for centuries for the treatment of various diseases. The study aims to explore the BYHWD effects on angiogenesis and neuroprotection after cerebral ischemia/reperfusion (CI/R) injury in rats and to explore the underlying angiogenic roles and mechanisms of BYHWD in hydrogen peroxide (H₂O₂) induced oxidative stress in human umbilical vein endothelial cells (HUVECs) model.

Methods

The effects of BYHWD on neurological function were screened by measuring neurological deficits, spatial memory function, and angiogenesis (by microvascular density (MVD) and cerebral blood flow (CBF)) after CI/R injury in middle cerebral artery occlusion (MCAO) in vivo in rats. In vitro, we examined the angiogenic roles and mechanisms of action of BYHWD in an H₂O₂-induced oxidative stress HUVECs model by measuring cell viability, apoptosis, vascular tube formation, intracellular ROS generation, NADPH oxidase (Nox) activity, and Nox4 protein expression.

Results

BYHWD significantly improved neurological function, including neurological deficits and spatial learning and memory, and significantly increased MVD and CBF in the ischemic penumbra after CI/R injury in rats. BYHWD significantly increased cell viability, inhibited apoptosis, induced vascular tube formation, decreased intracellular ROS generation, and reduced Nox activity and Nox4 protein expression in H₂O₂-treated HUVECs in a dose-dependent manner.

Conclusions

Our study demonstrates that BYHWD promotes neurological function recovery and increases angiogenesis. BYHWD exerts angiogenic effects against cerebral ischemic injury through the downregulation of Nox4, which results in the reduction of ROS generation.

PPAR-γ Mediates Ta-VNS-Induced Angiogenesis and Subsequent Functional Recovery after Experimental Stroke in Rats

Background

Neoangiogenesis after cerebral ischemia in mammals is insufficient to restore neurological function, illustrating the need to design better strategies for improving outcomes. Our previous study has suggested that transcutaneous auricular vagus nerve stimulation (ta-VNS) induced angiogenesis and improved neurological functions in a rat model of cerebral ischemia/reperfusion (I/R) injury. However, the mechanisms involved need further exploration. Peroxisome proliferator-activated receptor-γ (PPAR-γ), well known as a ligand-modulated nuclear transcription factor, plays a crucial role in the regulation of cerebrovascular structure and function. Hence, the present study was designed to explore the role of PPAR-γ in ta-VNS-mediated angiogenesis and uncover the possible molecular mechanisms against ischemic stroke.

Methods

Adult male Sprague-Dawley rats were transfected with either PPAR-γ small interfering RNA (siRNA) or lentiviral vector without siRNA prior to surgery and subsequently received ta-VNS treatment. The expression and localization of PPAR-γ in the ischemic boundary after ta-VNS treatment were examined. Subsequently, neurological deficit scores, neuronal damage, and infarct volume were all evaluated. Additionally, microvessel density, endothelial cell proliferation condition, and the expression of angiogenesis-related molecules in the peri-infarct cortex were measured.

Results

We found that the expression of PPAR-γ in the peri-infarct cortex increased at 14 d and reached normal levels at 28 d after reperfusion. Ta-VNS treatment further upregulated PPAR-γ expression in the ischemic cortex. PPAR-γ was mainly expressed in neurons and astrocytes. Furthermore, ta-VNS-treated I/R rats showed better neurobehavioral recovery, alleviated neuronal injury, reduced infarct volume, and increased angiogenesis, as indicated by the elevated levels of brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and phosphorylated endothelial nitric oxide synthase (P-eNOS). Surprisingly, the beneficial effects of ta-VNS were weakened after PPAR-γ silencing.

Conclusions

Our results suggest that PPAR-γ is a potential mediator of ta-VNS-induced angiogenesis and neuroprotection against cerebral I/R injury.

Widefield fluorescence localization microscopy for transcranial imaging of cortical perfusion with capillary resolution

Imaging of cerebral vasculature is impeded with the existing fluorescence microscopy methods due to intense light scattering in living tissues and the need for highly invasive craniotomy procedures to resolve structures on a capillary scale. We propose a widefield fluorescence localization microscopy technique for high-resolution transcranial imaging and quantitative assessment of cortical perfusion in mice. The method is based on tracking single fluorescent microparticles sparsely distributed in the blood stream using a simple CMOS camera and a continuous-wave laser source. We demonstrate quantitative transcranial in vivo mapping of the blood flow velocity and direction at capillary level resolution (5 µm) across the entire cortex. The new technique opens a new high-resolution transcranial window into the brain function in health and disease.

Sestrin2 promotes angiogenesis to alleviate brain injury by activating Nrf2 through regulating the interaction between p62 and Keap1 following photothrombotic stroke in rats

AIMS

The lack of effective treatments for ischemic stroke is concerning. Here, we aimed to examine the protective effects of sestrin2 in ischemic stroke and determine the mechanism by which sestrin2 attenuates cerebral injuries.

MAIN METHODS

Ischemic stroke was induced in Sprague-Dawley rats using a photothrombotic ischemia (PTI) model. After sestrin2 was overexpressed or silenced, neurological deficits and brain infarction were evaluated. Cerebral angiogenesis and the expression of related proteins were examined by Western blotting and immunofluorescence. The interaction between p62 and Keap1 was measured by coimmunoprecipitation (CoIP) and an in situ proximity ligation assay (PLA).

KEY FINDINGS

The overexpression of sestrin2 was found to improve the neurological function of rats 10 days after PTI and to reduce the infarct volume and brain edema in rats 10 days after PTI. It was shown that upregulating sestrin2 enhanced the relative immunofluorescence intensity of CD34, CD31 and DCX. Sestrin2 overexpressionalso increased the number and total length of CD34 and CD31 positive vessels and the expression of nuclear and total Nrf2, HO-1, VEGF and p62. However, downregulating sestrin2 induced almost the opposite results. Furthermore, we demonstrated that sestrin2 increased the interaction between p62 and Keap1.

SIGNIFICANCE

Based on our data, sestrin2 may promote angiogenesis by activating the Nrf2 pathway through increasing the interaction between p62 and Keap1 via upregulating p62 expression.

DL-3-n-butylphthalide improves cerebral hypoperfusion in patients with large cerebral atherosclerotic stenosis: a single-center, randomized, double-blind, placebo-controlled study

BACKGROUND

DL-3-n-butylphthalide (NBP) was demonstrated to increase the cerebral blood flow (CBF) in the animal models, but there are no clinic studies to verify this. We aimed to explore the effect of NBP on improving cerebral hypoperfusion caused by cerebral large-vessel stenosis.

METHODS

In this single-center, randomized, double-blind, placebo-controlled study, 120 patients with severe carotid atherosclerotic stenosis and cerebral hypoperfusion in the ipsilateral middle cerebral artery (MCA) were included and randomly assigned into NBP or placebo group as 1:1 radio. Patients in NBP or placebo group received 200 mg or 20 mg of NBP capsules three times daily for four weeks respectively. Single photon emission computed tomography (SPECT) was used to assess regional CBF (rCBF) in four regions of interest (ROIs) corresponding to MCA before and 12 weeks after the treatment. After therapy, the rCBF change for every ROI and the whole CBF change in MCA territory for every patient were classified into amelioration, stabilization and deterioration respectively.

RESULTS

48 NBP patients (6 with bilateral stenosis) and 46 placebo patients (8 with bilateral stenosis) completed the trial. Overall, both groups had 54 stenotic carotid arteries and 216 ROIs for rCBF change analysis. After therapy, the rCBF in ROIs increased in NBP group (83.5% ± 11.4% vs. 85.8% ± 12.5%, p = 0.000), whereas no change was found in placebo group (86.9% ± 11.6% vs. 87.8% ± 11.7%, p = 0.331). Besides, there was higher percentages of ROIs with rCBF amelioration and stabilization in NBP group than in placebo group (93.1% vs. 79.2%, p = 0.000). Furthermore, ordinal regression analysis showed that compared with placebo, NBP independently made more patients to have whole CBF amelioration in ipsilateral MCA (Wald-χ2 = 5.247, OR = 3.31, p = 0.022).

CONCLUSIONS

NBP might improve the cerebral hypoperfusion in the patients with carotid artery atherosclerotic stenosis.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR1900028005, registered December 8th 2019- Retrospectively registered (http://www.chictr.org.cn/index.aspx).

Neurorestoration Approach by Biomaterials in Ischemic Stroke

Ischemic stroke (IS) is the leading cause of disability in the western world, assuming a high socio-economic cost. One of the most used strategies in the last decade has been biomaterials, which have been initially used with a structural support function. They have been perfected, different compounds have been combined, and they have been used together with cell therapy or controlled release chemical compounds. This double function has driven them as potential candidates for the chronic treatment of IS. In fact, the most developed are in different phases of clinical trial. In this review, we will show the ischemic scenario and address the most important criteria to achieve a successful neuroreparation from the point of view of biomaterials. The spontaneous processes that are activated and how to enhance them is one of the keys that contribute to the success of the therapeutic approach. In addition, the different routes of administration and how they affect the design of biomaterials are analyzed. Future perspectives show where this broad scientific field is heading, which advances every day with the help of technology and advanced therapies.

Impact of stroke co-morbidities on cortical collateral flow following ischaemic stroke

Acute hyperglycaemia and chronic hypertension worsen stroke outcome but their impact on collateral perfusion, a determinant of penumbral life span, is poorly understood. Laser-speckle contrast imaging (LSCI) was used to determine the influence of these stroke comorbidities on cortical perfusion after permanent middle cerebral artery occlusion (pMCAO) in spontaneously hypertensive stroke prone rats (SHRSP) and normotensive Wistar rats. Four independent studies were conducted. In animals without pMCAO, cortical perfusion remained stable over 180 min. Following pMCAO, cortical perfusion was markedly reduced at 30 min then gradually increased, via cortical collaterals, over the subsequent 3.5 h. In the contralateral non-ischaemic hemisphere, perfusion did not change over time. Acute hyperglycaemia (in normotensive Wistar) and chronic hypertension (SHRSP) attenuated the restoration of cortical perfusion after pMCAO. Inhaled nitric oxide did not influence cortical perfusion in SHRSP following pMCAO. Thus, hyperglycaemia at the time of arterial occlusion or pre-existing hypertension impaired the dynamic recruitment of cortical collaterals after pMCAO. The impairment of collateral recruitment may contribute to the detrimental effects these comorbidities have on stroke outcome.

Ischemia-reperfusion injury of brain induces endothelial-mesenchymal transition and vascular fibrosis via activating let-7i/TGF-βR1 double-negative feedback loop

Let-7i modulates the physical function and inflammation in endothelial cells (ECs). However, whether the let-7i of ECs involves in brain vasculature and ischemic stroke is unknown. Using inducible Cadherin5-Cre lineage-tracking mice, a loxp-RNA-sponge conditional knockdown of let-7 in ECs- induced increase of transforming growth factor-β receptor type 1 (TGF-βR1), endothelial-mesenchymal transition (endMT), vascular fibrosis, and opening of the brain-blood barrier (BBB). By this lineage-tracking mice, we found that ECs underwent endMT after transient middle cerebral artery occlusion (MCAO). Through specifically overexpressed let-7i in ECs, we found that it reduced TGF-βR1, endMT, and vascular fibrosis. Furthermore, this overexpression reduced the infarct volume and leakage of the BBB, and improved the neurological function. Further, the expression of let-7i decreased after MCAO, but was reversed by antagonist of TGF-βR1 or inhibition of Mek phosphorylation. And the inhibition of Mek attenuated the vascular fibrosis after MCAO. In summary, we concluded that ischemic stroke activates a let-7i/TGF-βR1 double-negative feedback loop, thereby inducing endMT and vascular fibrosis. These results suggest that endMT is a potential target for the treatment of cerebral vascular fibrosis.

MRI Visualization of Whole Brain Macro- and Microvascular Remodeling in a Rat Model of Ischemic Stroke: A Pilot Study

Using superparamagnetic iron oxide nanoparticles (SPION) as a single contrast agent, we investigated dual contrast cerebrovascular magnetic resonance imaging (MRI) for simultaneously monitoring macro- and microvasculature and their association with ischemic edema status (via apparent diffusion coefficient [ADC]) in transient middle cerebral artery occlusion (tMCAO) rat models. High-resolution T1-contrast based ultra-short echo time MR angiography (UTE-MRA) visualized size remodeling of pial arteries and veins whose mutual association with cortical ischemic edema status is rarely reported. ΔR2-ΔR2*-MRI-derived vessel size index (VSI) and density indices (Q and MVD) mapped morphological changes of microvessels occurring in subcortical ischemic edema lesions. In cortical ischemic edema lesions, significantly dilated pial veins (p = 0.0051) and thinned pial arteries (p = 0.0096) of ipsilateral brains compared to those of contralateral brains were observed from UTE-MRAs. In subcortical regions, ischemic edema lesions had a significantly decreased Q and MVD values (p < 0.001), as well as increased VSI values (p < 0.001) than normal subcortical tissues in contralateral brains. This pilot study suggests that MR-based morphological vessel changes, including but not limited to venous blood vessels, are directly related to corresponding tissue edema status in ischemic stroke rat models.

The hydromechanics in arteriogenesis

Coronary heart diseases are tightly associated with aging. Although current revascularization therapies, such as percutaneous coronary interventions (PCI) and coronary artery bypass graft (CABG), improve the clinical outcomes of patients with coronary diseases, their application and therapeutic effects are limited in elderly patients. Thus, developing novel therapeutic strategies, like prompting collateral development or the process of arteriogenesis, is necessary for the treatment of the elderly with coronary diseases. Arteriogenesis (ie, the vascular remodeling from pre‐existent arterioles to collateral conductance networks) functions as an essential compensation for tissue hypoperfusion caused by artery occlusion or stenosis, and its mechanisms remain to be elucidated. In this review, we will summarize the roles of the major hydromechanical components in laminar conditions in arteriogenesis, and discuss the potential effects of disturbed flow components in non‐laminar conditions.

Endothelium-Targeted Deletion of microRNA-15a/16-1 Promotes Poststroke Angiogenesis and Improves Long-Term Neurological Recovery

RATIONALE

Angiogenesis promotes neurological recovery after stroke and is associated with longer survival of stroke patients. Cerebral angiogenesis is tightly controlled by certain microRNAs (miRs), such as the miR-15a/16-1 cluster, among others. However, the function of the miR-15a/16-1 cluster in endothelium on postischemic cerebral angiogenesis is not known.

OBJECTIVE

To investigate the functional significance and molecular mechanism of endothelial miR-15a/16-1 cluster on angiogenesis in the ischemic brain.

METHODS AND RESULTS

Endothelial cell-selective miR-15a/16-1 conditional knockout (EC-miR-15a/16-1 cKO) mice and wild-type littermate controls were subjected to 1 hour middle cerebral artery occlusion followed by 28-day reperfusion. Deletion of miR-15a/16-1 cluster in endothelium attenuates post-stroke brain infarction and atrophy and improves the long-term sensorimotor and cognitive recovery against ischemic stroke. Endothelium-targeted deletion of the miR-15a/16-1 cluster also enhances post-stroke angiogenesis by promoting vascular remodeling and stimulating the generation of newly formed functional vessels, and increases the ipsilateral cerebral blood flow. Endothelial cell-selective deletion of the miR-15a/16-1 cluster up-regulated the protein expression of pro-angiogenic factors VEGFA (vascular endothelial growth factor), FGF2 (fibroblast growth factor 2), and their receptors VEGFR2 (vascular endothelial growth factor receptor 2) and FGFR1 (fibroblast growth factor receptor 1) after ischemic stroke. Consistently, lentiviral knockdown of the miR-15a/16-1 cluster in primary mouse or human brain microvascular endothelial cell cultures enhanced in vitro angiogenesis and up-regulated pro-angiogenic proteins expression after oxygen-glucose deprivation, whereas lentiviral overexpression of the miR-15a/16-1 cluster suppressed in vitro angiogenesis and down-regulated pro-angiogenic proteins expression. Mechanistically, miR-15a/16-1 translationally represses pro-angiogenic factors VEGFA, FGF2, and their receptors VEGFR2 and FGFR1, respectively, by directly binding to the complementary sequences within 3'-untranslated regions of those messenger RNAs.

CONCLUSIONS

Endothelial miR-15a/16-1 cluster is a negative regulator for postischemic cerebral angiogenesis and long-term neurological recovery. Inhibition of miR-15a/16-1 function in cerebrovascular endothelium may be a legitimate therapeutic approach for stroke recovery.

Cortical Transplantation of Brain-Mimetic Glycosaminoglycan Scaffolds and Neural Progenitor Cells Promotes Vascular Regeneration and Functional Recovery after Ischemic Stroke in Mice

Stroke causes significant mortality and morbidity. Currently, there are no treatments which can regenerate brain tissue lost to infarction. Neural progenitor cells (NPCs) are at the forefront of preclinical studies for regenerative stroke therapies. NPCs can differentiate into and replace neurons and promote endogenous recovery mechanisms such as angiogenesis via trophic factor production and release. The stroke core is hypothetically the ideal location for replacement of neural tissue since it is in situ and develops into a potential space where injections may be targeted with minimal compression of healthy peri-infarct tissue. However, the compromised perfusion and tissue degradation following ischemia create an inhospitable environment resistant to cellular therapy. Overcoming these limitations is critical to advancing cellular therapy. In this work, the therapeutic potential of mouse-induced pluripotent stem cell derived NPCs is tested encapsulated in a basic fibroblast growth factor (bFGF) binding chondroitin sulfate-A (CS-A) hydrogel transplanted into the infarct core in a mouse sensorimotor cortex mini-stroke model. It is shown that CS-A encapsulation significantly improves vascular remodeling, cortical blood flow, and sensorimotor behavioral outcomes after stroke. It is found these improvements are negated by blocking bFGF, suggesting that the sustained trophic signaling endowed by the CS-A hydrogel combined with NPC transplantation can promote tissue repair.

Wheel running for 26 weeks is associated with sustained vascular plasticity in the rat motor cortex

Vascular pathologies represent the leading causes of mortality worldwide. The nervous system has evolved mechanisms to compensate for the cerebral hypoxia caused by many of these conditions. Vessel dilation and growth of new vessels are two prominent responses to hypoxia, both of which play a critical role in maintaining cerebral homeostasis. One way to facilitate cerebrovascular plasticity, and develop neuroprotection against vascular pathologies, is through aerobic exercise. The present study explored the long-term consequences of aerobic exercise on vascular structure and function in the motor cortex. Rats were assigned to a sedentary condition or were provided access to running wheels for 26 weeks. Rats were then anesthetized, and angiograms were captured using spectral domain optical coherence tomography (SD-OCT) to explore cerebrovascular reactivity in response to altered oxygen and carbon dioxide status. Following this procedure, all rats were euthanized, and unbiased stereological quantification of blood vessel density was collected from sections of the primary motor cortex infused with India ink. Results demonstrated that chronic exercise increased capillary and arteriole surface area densities and enhanced arteriole reactivity in response to hypercapnia-hypoxia, as displayed by increased vasodilation within the motor cortex of exercised animals.

Mapping the Fine-Scale Organization and Plasticity of the Brain Vasculature

The cerebral vasculature is a dense network of arteries, capillaries, and veins. Quantifying variations of the vascular organization across individuals, brain regions, or disease models is challenging. We used immunolabeling and tissue clearing to image the vascular network of adult mouse brains and developed a pipeline to segment terabyte-sized multichannel images from light sheet microscopy, enabling the construction, analysis, and visualization of vascular graphs composed of over 100 million vessel segments. We generated datasets from over 20 mouse brains, with labeled arteries, veins, and capillaries according to their anatomical regions. We characterized the organization of the vascular network across brain regions, highlighting local adaptations and functional correlates. We propose a classification of cortical regions based on the vascular topology. Finally, we analysed brain-wide rearrangements of the vasculature in animal models of congenital deafness and ischemic stroke, revealing that vascular plasticity and remodeling adopt diverging rules in different models.

LncRNA DANCR attenuates brain microvascular endothelial cell damage induced by oxygen-glucose deprivation through regulating of miR-33a-5p/XBP1s

Brain microvascular endothelial cell (BMEC) survival and angiogenesis after ischemic stroke has great significance for improving the prognosis of stroke. Abnormal variants of lncRNAs are closely associated with stroke. In this study, we examined the effects and molecular mechanisms of differentiation antagonizing non-protein coding RNA (DANCR) on apoptosis, migration, and angiogenesis of oxygen-glucose deprivation (OGD)-treated BMECs. We found that DANCR expression significantly increased at 2, 4, 6, 8, and 10 h after OGD. DANCR overexpression promoted cell viability, migration, and angiogenesis in OGD-treated BMECs. Additionally, we found that X-box binding protein l splicing (XBP1s) expression was positively correlated with DANCR expression. DANCR overexpression promoted XBP1s expression in OGD-treated BMECs. Silenced XBP1s reversed the effect of DANCR in OGD-treated BMECs. Furthermore, we found that microRNA (miR)-33a-5p bound to DANCR and the 3'-UTR of XBP1. miR-33a-5p overexpression inhibited proliferation, migration, angiogenesis, and XBP1s expression in OGD-treated DANCR-overexpressing BMECs, reversing the protective effect of DANCR. Finally, we found that XBP1s expression promoted proliferation, migration, and angiogenesis, reversing the damaging effect of miR-33a-5p. In conclusion, DANCR enhanced survival and angiogenesis in OGD-treated BMECs through the miR-33a-5p/XBP1s axis.

Effects of Remote Ischemic Conditioning on Cerebral Hemodynamics in Ischemic Stroke

Ischemic stroke is one of the most common cerebrovascular diseases and is the leading cause of disability all over the world. It is well known that cerebral blood flow (CBF) is disturbed or even disrupted when ischemic stroke happens. The imbalance between demand and shortage of blood supply makes ischemic stroke take place or worsen. The search for treatments that can preserve CBF, especially during the acute phase of ischemic stroke, has become a research hotspot. Animal and clinical experiments have proven that remote ischemic conditioning (RIC) is a beneficial therapeutic strategy for the treatment of ischemic stroke. However, the mechanism by which RIC affects CBF has not been fully understood. This review aims to discuss several possible mechanisms of RIC on the cerebral hemodynamics in ischemic stroke, such as the improvement of cardiac function and collateral circulation of cerebral vessels, the protection of neurovascular units, the formation of gas molecules, the effect on the function of vascular endothelial cells and the nervous system. RIC has the potential to become a therapeutic treatment to improve CBF in ischemic stroke. Future studies are needed to highlight our understanding of RIC as well as accelerate its clinical translation.

Translating concepts of neural repair after stroke: Structural and functional targets for recovery

Stroke is among the most common causes of adult disability worldwide, and its disease burden is shifting towards that of a long-term condition. Therefore, the development of approaches to enhance recovery and augment neural repair after stroke will be critical. Recovery after stroke involves complex interrelated systems of neural repair. There are changes in both structure (at the molecular, cellular, and tissue levels) and function (in terms of excitability, cortical maps, and networks) that occur spontaneously within the brain. Several approaches to augment neural repair through enhancing these changes are under study. These include identifying novel drug targets, implementing rehabilitation strategies, and developing new neurotechnologies. Each of these approaches has its own array of different proposed mechanisms. Current investigation has emphasized both cellular and circuit-based targets in both gray and white matter, including axon sprouting, dendritic branching, neurogenesis, axon preservation, remyelination, blood brain barrier integrity, blockade of extracellular inhibitory signals, alteration of excitability, and promotion of new brain cortical maps and networks. Herein, we review for clinicians recovery after stroke, basic elements of spontaneous neural repair, and ongoing work to augment neural repair. Future study requires alignment of basic, translational, and clinical research. The field continues to grow while becoming more clearly defined. As thrombolysis changed stroke care in the 1990 s and thrombectomy in the 2010 s, the augmentation of neural repair and recovery after stroke may revolutionize care for these patients in the coming decade.

Experiences and needs of patients on the endovascular therapy pathway after acute ischaemic stroke: Being helpless and next to yourself

Aims

To explore the experiences and needs of patients on the endovascular therapy pathway.

Design

A qualitative design using a phenomenological-hermeneutic approach.

Methods

Semi-structured interviews and participant observations were carried out. Data were collected from April 2016-January 2017. Data were analysed using Ricoeur's theory of interpretation, capturing meaning and ensuring comprehensive understanding. The Consolidated Criteria for Reporting Qualitative Research checklist was used as a guideline.

Results

The findings of this study show that the impact of stroke goes far beyond physical disability. During the structural analysis, four themes were identified: (1) Acute admission to a stroke unit - an overwhelming and blurred experience. (2) Being helpless and next to yourself. (3) The important care when you worry about dying. (4) Poststroke feelings of loneliness and uncertainty.

Catalpol Enhances Neurogenesis And Inhibits Apoptosis Of New Neurons Via BDNF, But Not The BDNF/Trkb Pathway

Background

The role of catalpol in brain neurogenesis and newborn neuron survival has not been previously determined in permanent middle cerebral artery occlusion (pMCAO).

Methods

Fifty-four rats were divided into 6 groups: pMCAO (model, n=9); sham operation (NS, n=9); catalpol treatment (5 mg/kg and 10 mg/kg subgroups, n=9 each); K252a (n=9); and K252a+catalpol 5 mg/kg (n=9) with stroke. The effects of catalpol on behavior, neurogenesis surrounding the infarction ipsilateral to pMCAO, and the expression of brain-derived neurotrophic factor (BDNF) and its receptor (TrkB) were evaluated. Vehicle or, K252a (i.p.), an inhibitor of TrkB phosphorylase.

Results

Repeated administration of catalpol reduced neurological deficits and significantly improved neurogenesis. Catalpol increased the number of newborn immature neurons, as determined by BrdU⁺-Nestin⁺ and BrdU⁺-Tuj-1⁺ staining, and downregulated cleaved caspase 3 in Tuj-1⁺ cells at day 7 following stroke. Moreover, catalpol increased the protein expression of Tuj-1, MAP2, and the Bcl-2/Bax ratio, as determined using Western blot. Catalpol also significantly increased brain levels of BDNF, but not TrkB, resulting in enhanced survival of newborn neurons via inhibition of apoptosis.

Conclusion

Catalpol may contribute to neurogenesis in infarcted brain regions and help promote the survival of newborn neurons by activating BDNF, but not BDNF/TrkB signaling.

Effects of mesencephalic astrocyte-derived neurotrophic factor on cerebral angiogenesis in a rat model of cerebral ischemia

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum stress-related protein that exhibits neuroprotective effects. Recent studies have shown that MANF promotes poststroke functional recovery in rats. However, the underlying mechanisms have not yet been fully understood. Here, we examined the effects of MANF on cerebral angiogenesis in a permanent middle cerebral artery occlusion model in rats. Recombinant human MANF was administered intracerebroventricularly 24 h after stroke. We performed neurobehavioral tests and assessed microvessel density, functional microvessels, and regional cerebral blood flow (rCBF), as well as detected angiogenic factors in the peri-infarct cerebral cortex. Results showed that MANF ameliorated neurobehavioral scores, promoted rCBF, upregulated the expression of CD34, as well as the total vessel surface area and the number of microvessel branch points, and activated the vascular endothelial growth factor (VEGF) pathway. In conclusion, our findings provide insight into the mechanisms of MANF in promoting functional recovery from ischemic stroke. Our results suggest that MANF improves neurobehavioral recovery from cerebral ischemic injury, and that this effect is mediated partly by its proangiogenic effects and augmentation of rCBF, which are possibly associated with VEGF.