Angiopoietin-1 Mimetic Peptide Promotes Neuroprotection after Stroke in Type 1 Diabetic Rats

Astrocytes in functional recovery following central nervous system injuries

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

Ischemic stroke and diabetes: a TLR4-mediated neuroinflammatory perspective

Ischemic stroke is the major contributor to morbidity and mortality in people with diabetes mellitus. In ischemic stroke patients, neuroinflammation is now understood to be one of the main underlying mechanisms for cerebral damage and recovery delay. It has been well-established that toll-like receptor 4 (TLR4) signaling pathway plays a key role in neuroinflammation. Emerging research over the last decade has revealed that, compared to ischemic stroke without diabetes mellitus, ischemic stroke with diabetes mellitus significantly upregulates TLR4-mediated neuroinflammation, increasing the risk of cerebral and neuronal damage as well as neurofunctional recovery delay. This review aims to discuss how ischemic stroke with diabetes mellitus amplifies TLR4-mediated neuroinflammation and its consequences. Additionally covered in this review is the potential application of TLR4 antagonists in the management of diabetic ischemic stroke.

MiR-221-5p regulates blood-brain barrier dysfunction through the angiopoietin-1/-2/Tie-2 signaling axis after subarachnoid hemorrhage

AIM

To explore the potential role of microRNA miR-221-5p on the angiopoietin-1 (Ang-1)/Ang-2/Tie-2 signaling axis after subarachnoid hemorrhage (SAH) in a rat model.

METHODS

Aspects of the rat's behavior were measured using the Kaoutzanis scoring system to test neurological responses. This included feeding behavior, body contraction, motor, and eye-opening responses. Brain sections were studied using transmission electron microscopy and Evans blue extravasation. Levels of Ang-1, Ang-2, and Tie-2 were determined by Western blot, while miR-221-5p was quantified using stem-loop real-time quantitative PCR (RT-qPCR).

RESULTS

The SAH group responded worse to the neurological response test than the sham-operated group. The intercellular space was widened in the SAH group, but not in the sham-operated group. Evans blue dye leaked significantly more into brain tissue cells of the SAH group. Stem-loop qRT-PCR showed elevated miR-221-5p levels. Additionally, Ang-1 and Tie-2 were reduced but Ang-2 expression was increased after SAH. This led to a significant reduction of the Ang-1/Ang-2 ratio in the brain tissue, which was associated with the destruction of the blood-brain barrier.

CONCLUSION

The data indicate that miR-221-5p might regulate blood-brain barrier dysfunction through the Ang-1/Ang-2/Tie-2 signaling axis, suggesting that it should be further investigated as a potential novel biomarker.

Astrocytes in ischemic stroke: Crosstalk in central nervous system and therapeutic potential

In the central nervous system (CNS), a large group of glial cells called astrocytes play important roles in both physiological and disease conditions. Astrocytes participate in the formation of neurovascular units and interact closely with other cells of the CNS, such as microglia and neurons. Stroke is a global disease with high mortality and disability rate, most of which are ischemic stroke. Significant strides in understanding astrocytes have been made over the past few decades. Astrocytes respond strongly to ischemic stroke through a process known as activation or reactivity. Given the important role played by reactive astrocytes (RAs) in different spatial and temporal aspects of ischemic stroke, there is a growing interest in the potential therapeutic role of astrocytes. Currently, interventions targeting astrocytes, such as mediating astrocyte polarization, reducing edema, regulating glial scar formation, and reprogramming astrocytes, have been proven in modulating the progression of ischemic stroke. The aforementioned potential interventions on astrocytes and the crosstalk between astrocytes and other cells of the CNS will be summarized in this review.

Pathogenic role of NAMPT in the perivascular regions after ischemic stroke in mice with type 2 diabetes mellitus

Ischemic stroke in patients with abnormal glucose tolerance results in poor outcomes. Nicotinamide phosphoribosyltransferase (NAMPT), an adipocytokine, exerts neuroprotective effects. However, the pathophysiological role of NAMPT after ischemic stroke with diabetes and the relationship of NAMPT with cerebrovascular lesions are unclear. The purpose of this study was to clarify the pathophysiological role of NAMPT in cerebral ischemia with diabetes, using db/db mice as a type 2 diabetes animal model. The number of degenerating neurons increased after middle cerebral artery occlusion and reperfusion (MCAO/R) in db/db mice compared with the degenerating neurons in db/+ mice. Extracellular NAMPT (eNAMPT) levels, especially monomeric eNAMPT, increased significantly in db/db MCAO/R mice but not db/+ mice in isolated brain microvessels. The increased eNAMPT levels were associated with increased expression of inflammatory cytokine mRNA. Immunohistochemical analysis demonstrated that NAMPT colocalized with GFAP-positive cells after MCAO/R. In addition, both dimeric and monomeric eNAMPT levels increased in the conditioned medium of primary cortical astrocytes under high glucose conditions subsequent oxygen/glucose deprivation. Our findings are the first to demonstrate the ability of increased monomeric eNAMPT to induce inflammatory responses in brain microvessels, which may be located near astrocyte foot processes.

Effect and Mechanism of Sodium Butyrate on Neuronal Recovery and Prognosis in Diabetic Stroke

Ischemic stroke is a cerebrovascular lesion caused by local ischemia and hypoxia. Diabetes mellitus (DM) is a chronic inflammatory disease that disturbs immune homeostasis and predisposes patients to ischemic stroke. The mechanism by which DM exacerbates stroke remains unclear, although it may involve disturbances in immune homeostasis. Regulatory T cells (Tregs) play a regulatory role in many diseases, but the mechanism of Tregs in diabetes complicated by stroke remains unclear. Sodium butyrate is a short-chain fatty acid that increases Treg levels. This study examined the role of sodium butyrate in the prognosis of neurological function in diabetic stroke and the mechanism by which Tregs are amplified in the bilateral cerebral hemispheres. We evaluated the brain infarct volume, observed 48-h neuronal injury and 28-day behavioral changes, and calculated the 28-day survival rate in mice. We also measured Treg levels in peripheral blood and brain tissue, recorded changes in the blood‒brain barrier and water channel proteins and neurotrophic changes in mice, measured cytokine levels and peripheral B-cell distribution in bilateral hemispheres and peripheral blood, and examined the polarization of microglia and the distribution of peripheral T-cell subpopulations in bilateral hemispheres. Diabetes significantly exacerbated the poor prognosis and neurological deficits in mice with stroke, and sodium butyrate significantly improved infarct volume, prognosis, and neurological function and showed different mechanisms in brain tissue and peripheral blood. The potential regulatory mechanism in brain tissue involved modulating Tregs/TGF-β/microglia to suppress neuroinflammation, while that in peripheral blood involved improving the systemic inflammatory response through Tregs/TGF-β/T cells.

Early therapeutic effects of an Angiopoietin-1 mimetic peptide in middle-aged rats with vascular dementia

Background

Vascular Dementia (VaD) refers to dementia caused by cerebrovascular disease and/or reduced blood flow to the brain and is the second most common form of dementia after Alzheimer's disease. We previously found that in middle-aged rats subjected to a multiple microinfarction (MMI) model of VaD, treatment with AV-001, a Tie2 receptor agonist, significantly improves short-term memory, long-term memory, as well as improves preference for social novelty compared to control MMI rats. In this study, we tested the early therapeutic effects of AV-001 on inflammation and glymphatic function in rats subjected to VaD.

Methods

Male, middle-aged Wistar rats (10-12 m), subjected to MMI, were randomly assigned to MMI and MMI + AV-001 treatment groups. A sham group was included as reference group. MMI was induced by injecting 800 ± 200, 70-100 μm sized, cholesterol crystals into the internal carotid artery. Animals were treated with AV-001 (1 μg/Kg, i.p.) once daily starting at 24 h after MMI. At 14 days after MMI, inflammatory factor expression was evaluated in cerebrospinal fluid (CSF) and brain. Immunostaining was used to evaluate white matter integrity, perivascular space (PVS) and perivascular Aquaporin-4 (AQP4) expression in the brain. An additional set of rats were prepared to test glymphatic function. At 14 days after MMI, 50 μL of 1% Tetramethylrhodamine (3 kD) and FITC conjugated dextran (500 kD) at 1:1 ratio were injected into the CSF. Rats (4-6/group/time point) were sacrificed at 30 min, 3 h, and 6 h from the start of tracer infusion, and brain coronal sections were imaged using a Laser scanning confocal microscope to evaluate tracer intensities in the brain.

Result

Treatment of MMI with AV-001 significantly improves white matter integrity in the corpus callosum at 14 days after MMI. MMI induces significant dilation of the PVS, reduces AQP4 expression and impairs glymphatic function compared to Sham rats. AV-001 treatment significantly reduces PVS, increases perivascular AQP4 expression and improves glymphatic function compared to MMI rats. MMI significantly increases, while AV-001 significantly decreases the expression of inflammatory factors (tumor necrosis factor-α (TNF-α), chemokine ligand 9) and anti-angiogenic factors (endostatin, plasminogen activator inhibitor-1, P-selectin) in CSF. MMI significantly increases, while AV-001 significantly reduces brain tissue expression of endostatin, thrombin, TNF-α, PAI-1, CXCL9, and interleukin-6 (IL-6).

Conclusion

AV-001 treatment of MMI significantly reduces PVS dilation and increases perivascular AQP4 expression which may contribute to improved glymphatic function compared to MMI rats. AV-001 treatment significantly reduces inflammatory factor expression in the CSF and brain which may contribute to AV-001 treatment induced improvement in white matter integrity and cognitive function.

Targetability of the neurovascular unit in inflammatory diseases of the central nervous system

The blood-brain barrier (BBB) is a selectively permeable barrier separating the periphery from the central nervous system (CNS). The BBB restricts the flow of most material into and out of the CNS, including many drugs that could be used as potent therapies. BBB permeability is modulated by several cells that are collectively called the neurovascular unit (NVU). The NVU consists of specialized CNS endothelial cells (ECs), pericytes, astrocytes, microglia, and neurons. CNS ECs maintain a complex "seal" via tight junctions, forming the BBB; breakdown of these tight junctions leads to BBB disruption. Pericytes control the vascular flow within capillaries and help maintain the basal lamina. Astrocytes control much of the flow of material that has moved beyond the CNS EC layer and can form a secondary barrier under inflammatory conditions. Microglia survey the border of the NVU for noxious material. Neuronal activity also plays a role in the maintenance of the BBB. Since astrocytes, pericytes, microglia, and neurons are all able to modulate the permeability of the BBB, understating the complex contributions of each member of the NVU will potentially uncover novel and effective methods for delivery of neurotherapies to the CNS.

Adjunctive therapy with the Tie2 agonist Vasculotide reduces pulmonary permeability in Streptococcus pneumoniae infected and mechanically ventilated mice

Community acquired pneumonia, mainly caused by Streptococcus pneumoniae (S.pn.), is a common cause of death worldwide. Despite adequate antibiotic therapy, pneumococcal pneumonia can induce pulmonary endothelial hyperpermeability leading to acute lung injury, which often requires mechanical ventilation (MV) causing ventilator-induced lung injury (VILI). Endothelial stabilization is mediated by angiopoietin-1 induced Tie2 activation. PEGylated (polyethylene glycol) Tie2-agonist Vasculotide (VT) mimics Angiopietin-1 effects. Recently, VT has been shown to reduce pulmonary hyperpermeability in murine pneumococcal pneumonia. The aim of this study was to determine whether VT reduces lung damage in S.pn. infected and mechanically ventilated mice. Pulmonary hyperpermeability, immune response and bacterial load were quantified in S.pn. infected mice treated with Ampicillin + /−VT and undergoing six hours of MV 24 h post infection. Histopathological lung changes, Tie2-expression and -phosphorylation were evaluated. VT did not alter immune response or bacterial burden, but interestingly combination treatment with ampicillin significantly reduced pulmonary hyperpermeability, histological lung damage and edema formation. Tie2-mRNA expression was reduced by S.pn. infection and/or MV but not restored by VT. Moreover, Tie2 phosphorylation was not affected by VT. These findings indicate that VT may be a promising adjunctive treatment option for prevention of VILI in severe pneumococcal pneumonia.

Treatment With an Angiopoietin-1 Mimetic Peptide Improves Cognitive Outcome in Rats With Vascular Dementia

Background and Purpose

Vascular dementia (VaD) is a complex neurodegenerative disease affecting cognition and memory. There is a lack of approved pharmacological treatments specifically for VaD. In this study, we investigate the therapeutic effects of AV-001, a Tie2 receptor agonist, in middle-aged rats subjected to a multiple microinfarct (MMI) model of VaD.

Methods

Male, 10-12 month-old, Wistar rats were employed. The following experimental groups were used: Sham, MMI, MMI+1 μg/Kg AV-001, MMI+3 μg/Kg AV-001, MMI+6 μg/Kg AV-001. AV-001 treatment was initiated at 1 day after MMI and administered once daily via intraperitoneal injection. An investigator blinded to the experimental groups conducted a battery of neuro-cognitive tests including modified neurological severity score (mNSS) test, novel object recognition test, novel odor recognition test, three chamber social interaction test, and Morris water maze test. Rats were sacrificed at 6 weeks after MMI.

Results

There was no mortality observed after 1, 3, or 6 μg/Kg AV-001 treatment in middle-aged rats subjected to MMI. AV-001 treatment (1, 3, or 6 μg/Kg) does not significantly alter blood pressure or heart rate at 6 weeks after MMI compared to baseline values or the MMI control group. Treatment of MMI with 1 or 3 μg/Kg AV-001 treatment does not significantly alter body weight compared to Sham or MMI control group. While 6 μg/Kg AV-001 treated group exhibit significantly lower body weight compared to Sham and MMI control group, the weight loss is evident starting at 1 day after MMI when treatment was initiated and is not significantly different compared to its baseline values at day 0 or day 1 after MMI. AV-001 treatment significantly decreases serum alanine aminotransferase, serum creatinine, and serum troponin I levels compared to the MMI control group; however, all values are within normal range. MMI induces mild neurological deficits in middle-aged rats indicated by low mNSS scores (<6 on a scale of 0-18). Compared to control MMI group, 1 μg/Kg AV-001 treatment group did not exhibit significantly different mNSS scores, while 3 and 6 μg/Kg AV-001 treatment induced significantly worse mNSS scores on days 21-42 and 14-42 after MMI, respectively. MMI in middle-aged rats induces significant cognitive impairment including short-term memory loss, long-term memory loss, reduced preference for social novelty and impaired spatial learning and memory compared to sham control rats. Rats treated with 1 μg/Kg AV-001 exhibit significantly improved short-term and long-term memory, increased preference for social novelty, and improved spatial learning and memory compared to MMI rats. Treatment with 3 μg/Kg AV-001 improves short-term memory and preference for social novelty but does not improve long-term memory or spatial learning and memory compared to MMI rats. Treatment with 6 μg/Kg AV-001 improves only long-term memory compared to MMI rats. Thus, 1 μg/Kg AV-001 treatment was selected as an optimal dose. Treatment of middle-aged rats subjected to MMI with 1 μg/Kg AV-001 significantly increases axon density, myelin density and myelin thickness in the corpus callosum, as well as increases synaptic protein expression, neuronal branching and dendritic spine density in the cortex, oligodendrocytes and oligodendrocyte progenitor cell number in the cortex and striatum and promotes neurogenesis in the subventricular zone compared to control MMI rats.

Conclusions

In this study, we present AV-001 as a novel therapeutic agent to improve cognitive function and reduce white matter injury in middle aged-rats subjected to a MMI model of VaD. Treatment of MMI with 1 μg/Kg AV-001 significantly improves cognitive function, and increases axon density, remyelination and neuroplasticity in the brain of middle-aged rats.

Neuroinflammation, Stem Cells, and Stroke

Stroke remains a significant unmet clinical need with few treatment options that have a very narrow therapeutic window, thereby causing massive mortality and morbidity in the United States and around the world. Accordingly, finding safe and effective novel treatments with a wider therapeutic window stands as an urgent need in stroke. The progressive inflammation that occurs centrally and peripherally after stroke serves as a unique therapeutic target to retard and even halt the secondary cell death. Stem cell therapy represents a potent approach that can diminish inflammation in both the stroke brain and periphery (eg, spleen), advancing a paradigm shift from a traditionally brain-focused therapy to treating stroke as a neurological disorder with a significant peripheral pathology. The purpose of this review article is to highlight the inflammation-mediated secondary cell death that plagues both brain and spleen in stroke and to evaluate the therapeutic potential of stem cell therapy in dampening these inflammatory responses.

Optimized mouse model of embolic MCAO: From cerebral blood flow to neurological outcomes

The embolic middle cerebral artery occlusion (eMCAO) model mimics ischemic stroke due to large vessel occlusion in humans and is amenable to thrombolytic therapy with rtPA. However, two major obstacles, the difficulty of the eMCAO surgery and unpredictable occurrence of clot autolysis, had impeded its application in mice. In this study, we modified catheters to produce suitable fibrin-rich embolus and optimized the eMCAO model using cerebral blood flow (CBF) monitored by both laser Doppler flowmetry (LDF) and 2D laser speckle contrast imaging (LSCI) to confirm occlusion of MCA. The results showed that longer embolus resulted in higher mortality. There was a compensatory increase in MCA territory perfusion after eMCAO associated with decreased infarct volume; however, this was only partly dependent on recanalization as clot autolysis was only observed in ∼30% of mice. Cortical CBF monitoring with LSCI showed that the size of peri-core area at 3 h displayed the best correlation with infarct volume that is attributed to compensatory collateral blood flow. The peri-core area best predicted functional outcome after eMCAO. In summary, we developed a reliable eMCAO mouse model that better mimics embolic ischemic stroke in humans, which will increase the potential for successful translation of stroke neuroprotective therapies.

Neurosurgery at the crossroads of immunology and nanotechnology. New reality in the COVID-19 pandemic

Neurosurgery as one of the most technologically demanding medical fields rapidly adapts the newest developments from multiple scientific disciplines for treating brain tumors. Despite half a century of clinical trials, survival for brain primary tumors such as glioblastoma (GBM), the most common primary brain cancer, or rare ones including primary central nervous system lymphoma (PCNSL), is dismal. Cancer therapy and research have currently shifted toward targeted approaches, and personalized therapies. The orchestration of novel and effective blood-brain barrier (BBB) drug delivery approaches, targeting of cancer cells and regulating tumor microenvironment including the immune system are the key themes of this review. As the global pandemic due to SARS-CoV-2 virus continues, neurosurgery and neuro-oncology must wrestle with the issues related to treatment-related immune dysfunction. The selection of chemotherapeutic treatments, even rare cases of hypersensitivity reactions (HSRs) that occur among immunocompromised people, and number of vaccinations they have to get are emerging as a new chapter for modern Nano neurosurgery.

Endothelial Dysfunction after Hematopoietic Stem Cell Transplantation: A Review Based on Physiopathology

Endothelial dysfunction (ED) is frequently encountered in transplant medicine. ED is an argument of high complexity, and its understanding requires a wide spectrum of knowledge based on many fields of basic sciences such as molecular biology, immunology, and pathology. After hematopoietic stem cell transplantation (HSCT), ED participates in the pathogenesis of various complications such as sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD), graft-versus-host disease (GVHD), transplant-associated thrombotic microangiopathy (TA-TMA), idiopathic pneumonia syndrome (IPS), capillary leak syndrome (CLS), and engraftment syndrome (ES). In the first part of the present manuscript, we briefly review some biological aspects of factors involved in ED: adhesion molecules, cytokines, Toll-like receptors, complement, angiopoietin-1, angiopoietin-2, thrombomodulin, high-mobility group B-1 protein, nitric oxide, glycocalyx, coagulation cascade. In the second part, we review the abnormalities of these factors found in the ED complications associated with HSCT. In the third part, a review of agents used in the treatment of ED after HSCT is presented.

RNA-seq analysis of ischemia stroke and normal brain in a tree shrew model with or without type 2 diabetes mellitus

Nowadays, similar strategies have been used for the treatment and prevention of acute stroke in both diabetes mellitus (DM) and non-DM populations. These strategies were analyzed to provide an experimental basis for the clinical prevention and treatment of stroke in patients both with and without DM. Tree shrews were randomly divided into control, DM, ischemic stroke (IS), and DMIS groups with 18 animals in each group. Serum biochemical indicators were used to assess metabolic status. Neural tissue damage was determined using triphenyl tetrazolium chloride staining, H-E staining, and electron microscopy. Differential gene expression of neural tissue between the DM and control groups and the IS and DMIS groups was measured using RNA-seq analysis. The serum glucose levels of the DM and DMIS groups were significantly higher than other groups. In the DMIS group, the infarct size was significantly larger than in the IS group (19.56 ± 1.25%), with a more obvious abnormal ultrastructure of neural cells. RNA-seq analysis showed that the expression of IL-8, C-C motif chemokine 2 (CCL2), and alpha-1-antichymotrypsin was significantly higher in the DM group than in the control group. The CCL7, ATP-binding cassette sub-family A member 12, and adhesion G protein-coupled receptor E2 levels were significantly higher in the DMIS group than in the IS group. For the prevention and treatment of stroke in patients with DM, reducing the inflammatory state of the nervous system may reduce the incidence of stroke and improve the prognosis of neurological function after IS.

Blood-brain barrier dysfunction in ischemic stroke and diabetes: the underlying link, mechanisms and future possible therapeutic targets

Ischemic stroke caused by occlusion of cerebral artery is responsible for the majority of stroke that increases the morbidity and mortality worldwide. Diabetes mellitus (DM) is a crucial risk factor for ischemic stroke. Prolonged DM causes various microvascular and macrovascular changes, and blood-brain barrier (BBB) permeability that facilitates inflammatory response following stroke. In the acute phase following stroke, BBB disruption has been considered the initial step that induces neurological deficit and functional disabilities. Stroke outcomes are significantly worse among DM. In this article, we review stroke with diabetes-induce BBB damage, as well as underlying mechanism and possible therapeutic targets for stroke with diabetes.

Vasculotide restores the blood-brain barrier after focused ultrasound-induced permeability in a mouse model of Alzheimer's disease

Focused ultrasound (FUS) is used to locally and transiently induce blood-brain barrier (BBB) permeability, allowing targeted drug delivery to the brain. The purpose of the current study is to evaluate the potential of Vasculotide to accelerate the recovery of the BBB following FUS disruption in the TgCRND8 mouse model of amyloidosis, characteristic of Alzheimer's disease (AD). Accelerating the restoration of the BBB post-FUS would represent an additional safety procedure, which could be beneficial for clinical applications. Methods: TgCRND8 mice and their non-transgenic littermates were treated with Vasculotide (250 ng, intraperitoneal) every 48 hours for 3 months. BBB permeability was induced using FUS, in presence of intravenously injected microbubbles, in TgCRND8 and non-transgenic mice, and confirmed at time 0 by MRI enhancement using the contrast agent gadolinium. BBB closure was assessed at 6, 12 and 20 hours by MRI. In a separate cohort of animals, BBB closure was assessed at 24-hours post-FUS using Evans blue injected intravenously and followed by histological evaluation. Results: Chronic Vasculotide administration significantly reduces the ultra-harmonic threshold required for FUS-induced BBB permeability in the TgCRND8 mice. In addition, Vasculotide treatment led to a faster restoration of the BBB following FUS in TgCRND8 mice. BBB closure after FUS is not significantly different between TgCRND8 and non-transgenic mice. BBB permeability was assessed by gadolinium up to 20-hours post-FUS, demonstrating 87% closure in Vasculotide treated TgCRND8 mice, as opposed to 52% in PBS treated TgCRND8 mice, 58% in PBS treated non-transgenic mice, and 74% in Vasculotide treated non-transgenic mice. In both TgCRND8 mice and non-transgenic littermates the BBB was impermeable to Evans blue dye at 24-hours post-FUS. Conclusion: Vasculotide reduces the pressure required for microbubble ultra-harmonic onset for FUS-induced BBB permeability and it accelerates BBB restoration in a mouse model of amyloidosis, suggesting its potential clinical utility to promote vascular health, plasticity and repair in AD.

Treatment with an Angiopoietin-1 mimetic peptide promotes neurological recovery after stroke in diabetic rats

Aim

Vasculotide (VT), an angiopoietin‐1 mimetic peptide, exerts neuroprotective effects in type one diabetic (T1DM) rats subjected to ischemic stroke. In this study, we investigated whether delayed VT treatment improves long‐term neurological outcome after stroke in T1DM rats.

Methods

Male Wistar rats were induced with T1DM, subjected to middle cerebral artery occlusion (MCAo) model of stroke, and treated with PBS (control), 2 µg/kg VT, 3 µg/kg VT, or 5.5 µg/kg VT. VT treatment was initiated at 24 h after stroke and administered daily (i.p) for 14 days. We evaluated neurological function, lesion volume, vascular and white matter remodeling, and inflammation in the ischemic brain. In vitro, we evaluated the effects of VT on endothelial cell capillary tube formation and inflammatory responses of primary cortical neurons (PCN) and macrophages.

Results

Treatment of T1DM‐stroke with 3 µg/kg VT but not 2 µg/kg or 5.5 µg/kg significantly improves neurological function and decreases infarct volume and cell death compared to control T1DM‐stroke rats. Thus, 3 µg/kg VT dose was employed in all subsequent in vivo analysis. VT treatment significantly increases axon and myelin density, decreases demyelination, decreases white matter injury, increases number of oligodendrocytes, and increases vascular density in the ischemic border zone of T1DM stroke rats. VT treatment significantly decreases MMP9 expression and decreases the number of M1 macrophages in the ischemic brain of T1DM‐stroke rats. In vitro, VT treatment significantly decreases endothelial cell death and decreases MCP‐1, endothelin‐1, and VEGF expression under high glucose (HG) and ischemic conditions and significantly increases capillary tube formation under HG conditions when compared to non‐treated control group. VT treatment significantly decreases inflammatory factor expression such as MMP9 and MCP‐1 in macrophages subjected to LPS activation and significantly decreases IL‐1β and MMP9 expression in PCN subjected to ischemia under HG conditions.

Conclusion

Delayed VT treatment (24 h after stroke) significantly improves neurological function, promotes vascular and white matter remodeling, and decreases inflammation in the ischemic brain after stroke in T1DM rats.

Enhancing the Therapeutic Potential of CCL2-Overexpressing Mesenchymal Stem Cells in Acute Stroke

Although intravenous administration of mesenchymal stem cells (MSCs) is effective for experimental stroke, low engraftment and the limited functional capacity of transplanted cells are critical hurdles for clinical applications. C-C motif chemokine ligand 2 (CCL2) is associated with neurological repair after stroke and delivery of various cells into the brain via CCL2/CCR2 (CCL2 receptor) interaction. In this study, after CCL2-overexpressing human umbilical cord-derived MSCs (hUC-MSCs) were intravenously transplanted with mannitol in rats with middle cerebral arterial occlusion, we compared the differences between four different treatment groups: mannitol + CCL2-overexpressing hUC-MSCs (CCL2-MSC), mannitol + naïve hUC-MSCs (M-MSC), mannitol only, and control. At four-weeks post-transplantation, the CCL2-MSC group showed significantly better functional recovery and smaller stroke volume relative to the other groups. Additionally, we observed upregulated levels of CCR2 in acute ischemic brain and the increase of migrated stem cells into these areas in the CCL2-MSC group relative to the M-MSC. Moreover, the CCL2-MSC group displayed increased angiogenesis and endogenous neurogenesis, decreased neuro-inflammation but with increased healing-process inflammatory cells relative to other groups. These findings indicated that CCL2-overexpressing hUC-MSCs showed better functional recovery relative to naïve hUC-MSCs according to the increased migration of these cells into brain areas of higher CCR2 expression, thereby promoting subsequent endogenous brain repair.

Exosomes derived from bone marrow mesenchymal stem cells harvested from type two diabetes rats promotes neurorestorative effects after stroke in type two diabetes rats

BACKGROUND AND PURPOSE

Diabetes elevates the risk of stroke, promotes inflammation, and exacerbates vascular and white matter damage post stroke, thereby hindering long term functional recovery. Here, we investigated the neurorestorative effects and the underlying therapeutic mechanisms of treatment of stroke in type 2 diabetic rats (T2DM) using exosomes harvested from bone marrow stromal cells obtained from T2DM rats (T2DM-MSC-Exo).

METHODS

T2DM was induced in adult male Wistar rats using a combination of high fat diet and Streptozotocin. Rats were subjected to transient 2 h middle cerebral artery occlusion (MCAo) and 3 days later randomized to one of the following treatment groups: 1) phosphate-buffered-saline (PBS, i.v), 2) T2DM-MSC-Exo, (3 × 10¹¹, i.v), 3) T2DM-MSC-Exo with miR-9 over expression (miR9+/+-T2DM-MSC-Exo, 3 × 10¹¹, i.v) or 4) MSC-Exo derived from normoglycemic rats (Nor-MSC-Exo) (3 × 10¹¹, i.v). T2DM sham control group is included as reference. Rats were sacrificed 28 days after MCAo.

RESULTS

T2DM-MSC-Exo treatment does not alter blood glucose, lipid levels, or lesion volume, but significantly improves neurological function and attenuates post-stroke weight loss compared to PBS treated as well as Nor-MSC-Exo treated T2DM-stroke rats. Compared to PBS treatment, T2DM-MSC-Exo treatment of T2DM-stroke rats significantly 1) increases tight junction protein ZO-1 and improves blood brain barrier (BBB) integrity; 2) promotes white matter remodeling indicated by increased axon and myelin density, and increases oligodendrocytes and oligodendrocyte progenitor cell numbers in the ischemic border zone as well as increases primary cortical neuronal axonal outgrowth; 3) decreases activated microglia, M1 macrophages, and inflammatory factors MMP-9 (matrix mettaloproteinase-9) and MCP-1 (monocyte chemoattractant protein-1) expression in the ischemic brain; and 4) decreases miR-9 expression in serum, and increases miR-9 target ABCA1 (ATP-binding cassette transporter 1) and IGFR1 (Insulin-like growth factor 1 receptor) expression in the brain. MiR9+/+-T2DM-MSC-Exo treatment significantly increases serum miR-9 expression compared to PBS treated and T2DM-MSC-Exo treated T2DM stroke rats. Treatment of T2DM stroke with miR9+/+-T2DM-MSC-Exo fails to improve functional outcome and attenuates T2DM-MSC-Exo treatment induced white matter remodeling and anti-inflammatory effects in T2DM stroke rats.

CONCLUSIONS

T2DM-MSC-Exo treatment for stroke in T2DM rats promotes neurorestorative effects and improves functional outcome. Down regulation of miR-9 expression and increasing its target ABCA1 pathway may contribute partially to T2DM-MSC-Exo treatment induced white matter remodeling and anti-inflammatory responses.

Beyond barrier functions: Roles of pericytes in homeostasis and regulation of neuroinflammation

Pericytes are contractile cells that extend along the vasculature to mediate key homeostatic functions of endothelial barriers within the body. In the central nervous system (CNS), pericytes are important contributors to the structure and function of the neurovascular unit, which includes endothelial cells, astrocytes and neurons. The understanding of pericytes has been marred by an inability to accurately distinguish pericytes from other stromal cells with similar expression of identifying markers. Evidence is now growing in favor of pericytes being actively involved in both CNS homeostasis and pathology of neurological diseases, including multiple sclerosis, spinal cord injury, and Alzheimer's disease among others. In this review, we discuss the current understanding on the characterization of pericytes, their roles in maintaining the integrity of the blood-brain barrier, and their contributions to neuroinflammation and neurorepair. Owing to its plethora of surface receptors, pericytes respond to inflammatory mediators such as CCL2 (monocyte chemoattractant protein-1) and tumor necrosis factor-α, in turn secreting CCL2, nitric oxide, and several cytokines. Pericytes can therefore act as promoters of both the innate and adaptive arms of the immune system. Much like professional phagocytes, pericytes also have the ability to clear up cellular debris and macromolecular plaques. Moreover, pericytes promote the activities of CNS glia, including in maturation of oligodendrocyte lineage cells for myelination. Conversely, pericytes can impair regenerative processes by contributing to scar formation. A better characterization of CNS pericytes and their functions would bode well for therapeutics aimed at alleviating their undesirable properties and enhancing their benefits.

Angiopoietin-1/Tie-2 signal after focal traumatic brain injury is potentiated by BQ788, an ETB receptor antagonist, in the mouse cerebrum: Involvement in recovery of blood-brain barrier function

Angiopoietin-1, an angiogenic factor, stabilizes brain microvessels through Tie-2 receptor tyrosine kinase. In traumatic brain injury, blood-brain barrier (BBB) disruption is an aggravating factor that induces brain edema and neuroinflammation. We previously showed that BQ788, an endothelin ET_B receptor antagonist, promoted recovery of BBB function after lateral fluid percussion injury (FPI) in mice. To clarify the mechanisms underlying BBB recovery mediated by BQ788, we examined the involvements of the angiopoietin-1/Tie-2 signal. When angiopoietin-1 production and Tie-2 phosphorylation were assayed by quantitative reverse transcription polymerase chain reaction and western blotting, increased angiopoietin-1 production and Tie-2 phosphorylation were observed in 7-10 days after FPI in the mouse cerebrum, whereas no significant effects were obtained at 5 days. When BQ788 (15 nmol/day, i.c.v.) were administered in 2-5 days after FPI, increased angiopoietin-1 production and Tie-2 phosphorylation were observed. Immunohistochemical observations showed that brain microvessels and astrocytes contained angiopoietin-1 after FPI, and brain microvessels also contained phosphorylated Tie-2. Treatment with endothelin-1 (100 nM) decreased angiopoietin-1 production in cultured astrocytes and the effect was inhibited by BQ788 (1 μM). Five days after FPI, increased extravasation of Evans blue dye accompanied by reduction in claudin-5, occludin, and zonula occludens-1 proteins were observed in mouse cerebrum while these effects of FPI were reduced by BQ788 and exogenous angiopoietin-1 (1 μg/day, i.c.v.). The effects of BQ788 were inhibited by co-administration of a Tie-2 kinase inhibitor (40 nmol/day, i.c.v.). These results suggest that BQ788 administration after traumatic brain injury promotes recovery of BBB function through activation of the angiopoietin-1/Tie-2 signal.

The effect of angiopoietin-1 upregulation on the outcome of acute ischaemic stroke in rodent models: A meta-analysis

Clinical studies report that low circulating angiopoietin-1 concentration at presentation predicts worse outcomes after ischaemic stroke. Upregulating angiopoietin-1 may therefore have therapeutic benefit for ischaemic stroke. This systematic review assessed whether upregulating angiopoietin-1 improved outcomes in rodent models of ischaemic stroke. Random-effects models quantified the effect of angiopoietin-1 upregulation on stroke severity in terms of the size of cerebral infarction and the extent of blood-brain barrier permeability. Eleven studies utilising rat and mouse models of ischaemic stroke fulfilled the inclusion criteria. Meta-analyses demonstrated that angiopoietin-1 upregulation significantly reduced cerebral infarction size (standardised mean difference: -3.02; 95% confidence intervals: -4.41, -1.63; p < 0.001; n = 171 animals) and improved blood-brain barrier integrity (standardized mean difference: -2.02; 95% confidence intervals: -3.27, -0.77; p = 0.002; n = 129 animals). Subgroup analyses demonstrated that angiopoietin-1 upregulation improved outcomes in models of transient, not permanent cerebral ischaemia. Six studies assessed the effect of angiopoietin-1 upregulation on neurological function; however, inter-study heterogeneity prevented meta-analysis. In conclusion, published rodent data suggest that angiopoietin-1 upregulation improves outcome following temporary cerebral ischaemia by reducing cerebral infarction size and improving blood-brain barrier integrity. Additional research is required to examine the effect of angiopoietin-1 upregulation on neurological function during stroke recovery and investigate the benefit and risks in patients.

Long noncoding RNA HAS2-AS1 promotes tumor progression in glioblastoma via functioning as a competing endogenous RNA

Glioblastoma multiforme (GBM) is a refractory tumor with poor prognosis and requires more effective treatment regimens. It has been confirmed that long noncoding RNAs (lncRNAs) substantially regulate various human disease including GBM. However, the biological roles and its underlying molecular mechanisms still need to be further investigated. In this study, the biological function and potential molecular mechanism of lncHAS2-AS1 in GBM were explored. It was discovered that HAS2-AS1 was elevated in glioma tissues and correlated with the prognosis of patients with glioma. Reduction of HAS2-AS1 suppressed the migration and invasion in vitro and in vivo. The transcription factor STAT1 could raise HAS2-AS1 by binding to its promoter region. Besides, HAS2-AS1 could adjust PRPS1 via sponging miR-608 in a direct manner. On the whole, the results of this study evidence that HAS2-AS1 is an oncogene and a potential therapeutic target for GBM.

Improving CNS Delivery to Brain Metastases by Blood-Tumor Barrier Disruption

Brain metastases encompass nearly 80% of all intracranial tumors. A late stage diagnosis confers a poor prognosis, with patients typically surviving less than 2 years. Poor survival can be equated to limited effective treatment modalities. One reason for the failure rates is the presence of the blood-brain barrier (BBB) and blood-tumor barrier (BTB) that limit the access of potentially effective chemotherapeutics to metastatic lesions. Strategies to overcome these barriers include new small molecule entities capable of crossing into the brain parenchyma, novel formulations of existing chemotherapies, and disruptive techniques. Here, we review BBB physiology and BTB pathophysiology. Additionally, we review the limitations of routinely practiced therapies and three current methods being explored for BBB/BTB disruption for improved delivery of chemotherapy to brain tumors.

Angiopoietin: A Novel Neuroprotective/Neurotrophic Agent

Angiopoietin (Ang) is an angiogenic factor, but its neuroprotective and neurotrophic effects have recently come to light. Ang exerts neuroprotective effects by inhibiting neuronal apoptosis, protecting the blood-brain/blood-spinal cord barrier, reducing inflammation and promoting neovascularization. In addition, Ang can also promote neural development and neurite outgrowth via activation of the PI3K/Akt signaling pathway and binding to the Tie2 receptor and/or integrin receptor. In addition, Ang and vascular endothelial growth factor (VEGF) are known to interact in blood vessels in the nervous system and the combination of Ang and VEGF can mitigate the negative effects of VEGF, such as inflammation and local edema. These data indicated that Ang is a novel neuroprotective/neurotrophic factor, which may become a new tool for the treatment of nerve injury.

Dual Roles of Astrocyte-Derived Factors in Regulation of Blood-Brain Barrier Function after Brain Damage

The blood-brain barrier (BBB) is a major functional barrier in the central nervous system (CNS), and inhibits the extravasation of intravascular contents and transports various essential nutrients between the blood and the brain. After brain damage by traumatic brain injury, cerebral ischemia and several other CNS disorders, the functions of the BBB are disrupted, resulting in severe secondary damage including brain edema and inflammatory injury. Therefore, BBB protection and recovery are considered novel therapeutic strategies for reducing brain damage. Emerging evidence suggests key roles of astrocyte-derived factors in BBB disruption and recovery after brain damage. The astrocyte-derived vascular permeability factors include vascular endothelial growth factors, matrix metalloproteinases, nitric oxide, glutamate and endothelin-1, which enhance BBB permeability leading to BBB disruption. By contrast, the astrocyte-derived protective factors include angiopoietin-1, sonic hedgehog, glial-derived neurotrophic factor, retinoic acid and insulin-like growth factor-1 and apolipoprotein E which attenuate BBB permeability resulting in recovery of BBB function. In this review, the roles of these astrocyte-derived factors in BBB function are summarized, and their significance as therapeutic targets for BBB protection and recovery after brain damage are discussed.