Cerebrovascular Remodeling Research Articles

Smooth muscle-specific TMEM16A expression protects against angiotensin II-induced cerebrovascular remodeling via suppressing extracellular matrix deposition

Cerebrovascular remodeling is the leading factor for stroke and characterized by increased extracellular matrix deposition, migration and proliferation of vascular smooth muscle cells, and inhibition of their apoptosis. TMEM16A is an important component of Ca2+-activated Cl− channels. Previously, we showed that downregulation of TMEM16A in the basilar artery was negatively correlated with cerebrovascular remodeling during hypertension. However, it is unclear whether TMEM16A participates in angiotensin II (Ang II)-induced vascular remodeling in mice that have TMEM16A gene modification. In this study, we generated a transgenic mouse that overexpresses TMEM16A specifically in vascular smooth muscle cells. We observed that vascular remodeling in the basilar artery during Ang II-induced hypertension was significantly suppressed upon vascular smooth muscle-specific overexpression of TMEM16A relative to control mice. Specifically, we observed a large reduction in the deposition of fibronectin and collagen I. The expression of matrix metalloproteinases (MMP-2, MMP-9, and MMP-14), and tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) were upregulated in the basilar artery during Ang II-induced hypertension, but this was suppressed upon overexpression of TMEM16A in blood vessels. Furthermore, TMEM16A overexpression alleviated the overactivity of the canonical TGF-β1/Smad3, and non-canonical TGF-β1/ERK and JNK pathways in the basilar artery during Ang II-induced hypertension. These in vivo results were similar to the results derived in vitro with basilar artery smooth muscle cells stimulated by Ang II. Moreover, we observed that the inhibitory effect of TMEM16A on MMPs was mediated by decreasing the activation of WNK1, which is a Cl−-sensitive serine/threonine kinase. In conclusion, this study demonstrates that TMEM16A protects against cerebrovascular remodeling during hypertension by suppressing extracellular matrix deposition. We also showed that TMEM16A exerts this effect by reducing the expression of MMPs via inhibiting WNK1, and decreasing the subsequent activities of TGF-β1/Smad3, ERK, and JNK. Accordingly, our results suggest that TMEM16A may serve as a novel therapeutic target for vascular remodeling.

Inhibition of angiotensin II-induced cerebrovascular smooth muscle cell proliferation by LRRC8A downregulation through suppressing PI3K/AKT activation.

Cerebrovascular smooth muscle cell proliferation is the major contributor to cerebrovascular remodeling and stroke. Chloride channels have been suggested to play an important role in the regulation of smooth muscle cell proliferation. This study aims to investigate the effect of leucine-rich repeat-containing 8A (LRRC8A), an essential component of volume-sensitive chloride channels, on cerebrovascular smooth muscle cell proliferation. The data showed that LRRC8A expression was increased in mouse brain artery during angiotensin II (AngII)-induced cerebrovascular remodeling. Similarly, AngII also increased the expression of LRRC8A in human brain vascular smooth muscle cells (HBVSMCs). Knockdown of LRRC8A by siRNA significantly inhibited AngII-induced the proliferation, migration, and invasion in HBVSMCs. The inhibition of HBVSMCs proliferation by LRRC8A downregulation appeared to be involved in suppression of cell-cycle transition. AngII-induced the decrease in p21 and p27 expression and the increase in CDK4 and cyclin D1 expression were attenuated by LRRC8A downregulation. Moreover, inhibition of LRRC8A suppressed AngII-induced PI3K/AKT activation and reactive oxygen species generation, but had no effect on JNK, ERK, and p38 phosphorylation. In addition, activation of PI3K/AKT-signaling pathways with specific agonists significantly abolished the effect of LRRC8A deficiency on HBVSMC proliferation. This present study demonstrates that knockdown of LRRC8A ameliorates AngII-induced cerebrovascular smooth muscle cell proliferation via inhibiting PI3K/AKT pathway, suggesting that LRRC8A may be a novel molecular target in the treatment of vascular remodeling and stroke.

Perlecan Domain V Increases Amyloid Clearance in Co‐Morbid VCID

IntroductionVascular contributions to cognitive impairment and dementia (VCID) is a broad term that encompasses a spectrum of initial asymptomatic cerebrovascular changes (seen in small vessel disease and cerebral amyloid angiopathy) to the profound symptomatic damage following acute stroke(s). Besides aging, metabolic disorders such as type 2 diabetes complicate our understanding of underlying mechanisms. Cerebrovascular remodeling and angiogenesis may represent early compensatory changes to the reduced blood flow seen in VCID by increasing the proteolytic turnover of the surrounding extracellular matrix. We have demonstrated that one such extracellular matrix protein, perlecan, possesses a C terminal domain V (DV) protein that, upon cleavage from perlecan, greatly enhances brain angiogenesis.ObjectiveWe hypothesize that DV therapy can reduce pathological changes in the cerebrovasculature, an underlying component of VCID.MethodsDV's mechanism and therapeutic potential in facilitating Aβ clearance were examined in an ex vivo model of isolated mouse brain capillaries in normal and high glucose environments. We also determined the cerebrovascular changes in a comorbidity mouse model of VCID (diabetic APP/PS1 knock in (db/AD)) that is associated with hemorrhages, aneurysms, Aβ deposition, cognitive decline and increased mortality.ResultsDV (300 and 600 nM) doubled the transport of fluorescently tagged hAβ1‐42 over 24 hours from the bath (abluminal) to luminal side of the brain capillaries. One of Aβ's known transport proteins, P‐glycoprotein (P‐gp), also increased in total protein expression and in transport activity in the presence of DV. At 3–6 months in db/AD mice, we observed a decrease in BBB proteins (claudin‐5) indicating an altered cerebrovascular function correlating with DV expression increase during the asymptomatic angiogenic stage. At 9–12 months, cognitive changes were associated with altered cerebrovascular protein expression in PECAM, Collagen IV, and DV correlating with the aberrant two‐photon vascular imaging, increased saccular aneurysms, and microhemorrhages.ConclusionThese data show that DV increases cerebrovascular Aβ clearance through P‐gp. Increased DV expression correlates with early cerebrovascular changes induced by angiogenic‐remodeling in a diabetic co‐morbid mouse model of VCID. Lower DV expression is associated with aberrant vasculature that contribute to increased mortality, suggesting that DV ‘replacement therapy’ could represent a novel therapeutic for VCID.Support or Funding InformationNIH RO1 N5089515‐01This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract WP558: Benefits of Perlecan Domain V in Diabetic Co-morbid Models of VCID

Introduction: Vascular contributions to cognitive impairment and dementia (VCID) are a major factor in the overall clinical burden of dementia. Besides aging, metabolic disorders such as type 2 diabetes complicate understanding of underlying mechanisms. Despite the complexity, we hypothesize that pathological changes in cerebrovascular extracellular matrix (ECM) are an underlying component of VCID that can be therapeutically targeted to reduce neurodegeneration and improve outcomes . One such ECM component, the terminal domain V (DV) of perlecan, greatly reduces amyloid toxicity and enhances angiogenic cerebrovascular remodeling. Methods: DV’s mechanism and therapeutic potential in facilitating Aβ clearance were examined in an ex vivo model of isolated mouse brain capillaries in normal and high glucose environments. We also determined the cerebrovascular changes in a comorbidity mouse model of VCID (diabetic APP/PS1 knock in (db/AD)) that is associated with hemorrhages, aneurysms, Aβ deposition, cognitive decline and increased mortality. Results: DV (300 and 600 nM) doubled the transport of fluorescently tagged hAβ1-42 over 24 hours from the bath (abluminal) to luminal side of the brain capillaries. One of Aβ’s known transport proteins, P-glycoprotein (P-gp), also increased in total protein expression and in transport activity in the presence of DV. At 3-6 months in db/AD mice, we observed a decrease in BBB proteins (claudin-5) indicating an altered cerebrovascular function correlating with DV expression increase during the asymptomatic angiogenic stage. At 9-12 months, cognitive changes were associated with altered cerebrovascular protein expression in PECAM, Collagen IV, and DV correlating with the aberrant two-photon vascular imaging, increased saccular aneurysms, and microhemorrhages. Conclusion: These data show that DV increases cerebrovascular Aβ clearance through P-gp. Increased DV expression correlates with early cerebrovascular changes induced by angiogenic-remodeling in a diabetic co-morbid mouse model of VCID. Lower DV expression is associated with aberrant vasculature that contribute to increased mortality, suggesting that DV ‘replacement therapy’ could represent a novel therapeutic for VCID.

A miniature multi-contrast microscope for functional imaging in freely behaving animals

Neurovascular coupling, cerebrovascular remodeling and hemodynamic changes are critical to brain function, and dysregulated in neuropathologies such as brain tumors. Interrogating these phenomena in freely behaving animals requires a portable microscope with multiple optical contrast mechanisms. Therefore, we developed a miniaturized microscope with: a fluorescence (FL) channel for imaging neural activity (e.g., GCaMP) or fluorescent cancer cells (e.g., 9L-GFP); an intrinsic optical signal (IOS) channel for imaging hemoglobin absorption (i.e., cerebral blood volume); and a laser speckle contrast (LSC) channel for imaging perfusion (i.e., cerebral blood flow). Following extensive validation, we demonstrate the microscope’s capabilities via experiments in unanesthetized murine brains that include: (i) multi-contrast imaging of neurovascular changes following auditory stimulation; (ii) wide-area tonotopic mapping; (iii) EEG-synchronized imaging during anesthesia recovery; and (iv) microvascular connectivity mapping over the life-cycle of a brain tumor. This affordable, flexible, plug-and-play microscope heralds a new era in functional imaging of freely behaving animals.

Icariin ameliorates angiotensin II-induced cerebrovascular remodeling by inhibiting Nox2-containing NADPH oxidase activation.

Cerebrovascular smooth muscle cells (SMCs) hyperplasia is an important contributor to cerebrovascular remodeling during hypertension. The aim of present study was to investigate the effects of Icariin on cerebrovascular SMCs proliferation and remodeling and the underlying mechanisms. The results revealed that Icariin administration attenuated the enhanced basilar artery constriction in angiotensin II (AngII)-induced hypertension rat model, as well as the inhibition of basilar artery diameter reduction in response to AngII and phenylephrine. In addition, histological analyses showed that Icariin also significantly ameliorated basilar artery remodeling in AngII hypertensive rats. In human brain vascular SMCs (HBVSMCs), AngII-induced cell proliferation, migration and invasion were markedly inhibited by Icariin treatment. Moreover, Icariin treatment largely limited AngII-induced the increase of reactive oxygen species (ROS) production in HBVSMCs, which was closely associated with cell proliferation. Analysis of the mechanisms showed that Icariin decreased ROS production via inhibiting NADPH oxidase activity but not mitochondria-derived ROS production. Further, Icariin promoted Nox2 degradation and consequently reduced its protein expression. In conclusion, these findings demonstrate that Icariin attenuates cerebrovascular SMCs hyperplasia and subsequent remodeling through inhibiting Nox2-containing NADPH oxidase activation, suggesting Icariin may be a potential therapeutic agent to prevent the onset and progression of stroke.

Transmembrane member 16A participates in hydrogen peroxide-induced apoptosis by facilitating mitochondria-dependent pathway in vascular smooth muscle cells.

Transmembrane member 16A (TMEM16A), an intrinsic constituent of the Ca2+ -activated Cl- channel, is involved in vascular smooth muscle cell (VSMC) proliferation and hypertension-induced cerebrovascular remodelling. However, the functional significance of TMEM16A for apoptosis in basilar artery smooth muscle cells (BASMCs) remains elusive. Here, we investigated whether and how TMEM16A contributes to apoptosis in BASMCs. Cell viability assay, flow cytometry, Western blot, mitochondrial membrane potential assay, immunogold labelling and co-immunoprecipitation (co-IP) were performed. Hydrogen peroxide (H2 O2 ) induced BASMC apoptosis through a mitochondria-dependent pathway, including by increasing the apoptosis rate, down-regulating the ratio of Bcl-2/Bax and potentiating the loss of the mitochondrial membrane potential and release of cytochrome c from the mitochondria to the cytoplasm. These effects were all reversed by the silencing of TMEM16A and were further potentiated by the overexpression of TMEM16A. Endogenous TMEM16A was detected in the mitochondrial fraction. Co-IP revealed an interaction between TMEM16A and cyclophilin D, a component of the mitochondrial permeability transition pore (mPTP). This interaction was up-regulated by H2 O2 but restricted by cyclosporin A, an inhibitor of cyclophilin D. TMEM16A increased mPTP opening, resulting in the activation of caspase-9 and caspase-3. The results obtained with cultured BASMCs from TMEM16A smooth muscle-specific knock-in mice were consistent with those from rat BASMCs. These results suggest that TMEM16A participates in H2 O2 -induced apoptosis via modulation of mitochondrial membrane permeability in VSMCs. This study establishes TMEM16A as a target for therapy of several remodelling-related diseases.

Higher Aortic Stiffness Is Associated With Lower Global Cerebrovascular Reserve Among Older Humans.

Greater aortic stiffness and pulse pressure are associated with cerebrovascular remodeling, reduced white matter microstructure, and cognitive performance with aging in humans. However, it is unclear whether aortic stiffness and pulse pressure are associated with reduced basal global cerebral blood flow (CBF) and cerebrovascular reserve among older adults. Global CBF was quantified in 205 adults (range, 19-87 years; mean±SE: 30.6±1.3 years) using quantitative [15O]water brain positron emission tomography imaging. In a subset of older adults (n=24; 70.0±2.0 years), aortic stiffness (carotid femoral pulse wave velocity) and cerebrovascular reserve (change in global CBF after intravenous infusion of acetazolamide) were assessed. In the entire cohort, global CBF was lower in older compared with young adults (36.5±1.1 versus 50.5±0.7 mL/min per 100 mL; P<0.001). Global CBF was higher in young women compared with young men (51.0±0.30 versus 47.4±0.03 mL/min per 100 mL; P<0.001) but did not differ between older women and men (P=0.63). In older adults, greater carotid femoral pulse wave velocity was associated with lower cerebrovascular reserve (r=-0.68; P=0.001 adjusted for age, sex, and mean arterial pressure) but not global CBF (r=0.13; P=0.60). Brachial pulse pressure was not associated with lower cerebrovascular reserve (r=-0.37; P=0.159) when adjusted for age and sex. These data indicate that the age-related increases in aortic stiffness may contribute, in part, to the brain's impaired ability to augment blood flow in response to a stimulus with aging in humans.

Acetylshikonin attenuates angiotensin II-induced proliferation and motility of human brain smooth muscle cells by inhibiting Wnt/β-catenin signaling.

Cerebrovascular smooth muscle cell proliferation and migration contribute to hyperplasia in case of cerebrovascular remodeling and stroke. In the present study, we investigated the effects of acetylshikonin, the main ingredient of a Chinese traditional medicine Zicao, on human brain vascular smooth muscle cell (HBVSMCs) proliferation and migration induced by angiotensin II (AngII), and the underlying mechanisms. We found that acetylshikonin treatment significantly inhibited AngII-induced HBVSMCs proliferation and cell cycle transition from G1 to S phase. Wound-healing assay and Transwell assay showed that AngII-induced cell migration and invasion were markedly attenuated by acetylshikonin. In addition, AngII challenge significantly induced Wnt/β-catenin signaling activation, as evidenced by increased β-catenin phosphorylation and nuclear translocation and GSK-3β phosphorylation. However, acetylshikonin treatment inhibited the activation of Wnt/β-catenin signaling. Consequently, western blotting analysis revealed that acetylshikonin effectively reduced the expression of downstream target genes in AngII-treated cells, including c-myc, survivin and cyclin D1, which contributed to the inhibitory effect of acetylshikonin on HBVSMCs proliferation. Further, stimulation with recombinant Wnt3a dramatically reversed acetylshikonin-mediated inhibition of proliferation and cell cycle transition in HBVSMCs. Our study demonstrates that acetylshikonin prevents AngII-induced cerebrovascular smooth muscle cells proliferation and migration through inhibition of Wnt/β-catenin pathway, indicating that acetylshikonin may present a potential option for the treatment of cerebrovascular remodeling.

Growth Hormone Improves Cognitive Function After Experimental Stroke.

Cognitive impairment is a common outcome for stroke survivors. Growth hormone (GH) could represent a potential therapeutic option as this peptide hormone has been shown to improve cognition in various clinical conditions. In this study, we evaluated the effects of peripheral administration of GH at 48 hours poststroke for 28 days on cognitive function and the underlying mechanisms. Experimental stroke was induced by photothrombotic occlusion in young adult mice. We assessed the associative memory cognitive domain using mouse touchscreen platform for paired-associate learning task. We also evaluated neural tissue loss, neurotrophic factors, and markers of neuroplasticity and cerebrovascular remodeling using biochemical and histology analyses. Our results show that GH-treated stroked mice made a significant improvement on the paired-associate learning task relative to non-GH-treated mice at the end of the study. Furthermore, we observed reduction of neural tissue loss in GH-treated stroked mice. We identified that GH treatment resulted in significantly higher levels of neurotrophic factors (IGF-1 [insulin-like growth factor-1] and VEGF [vascular endothelial growth factor]) in both the circulatory and peri-infarct regions. GH treatment in stroked mice not only promoted protein levels and density of presynaptic marker (SYN-1 [synapsin-1]) and marker of myelination (MBP [myelin basic protein]) but also increased the density and area coverage of 2 major vasculature markers (CD31 and collagen-IV), within the peri-infarct region. These findings provide compelling preclinical evidence for the usage of GH as a potential therapeutic tool in the recovery phase of patients after stroke.

Gliotransmitters and cytokines in the control of blood-brain barrier permeability.

The contribution of astrocytes and microglia to the regulation of neuroplasticity or neurovascular unit (NVU) is based on the coordinated secretion of gliotransmitters and cytokines and the release and uptake of metabolites. Blood-brain barrier (BBB) integrity and angiogenesis are influenced by perivascular cells contacting with the abluminal side of brain microvessel endothelial cells (pericytes, astrocytes) or by immune cells existing (microglia) or invading the NVU (macrophages) under pathologic conditions. The release of gliotransmitters or cytokines by activated astroglial and microglial cells is provided by distinct mechanisms, affects intercellular communication, and results in the establishment of microenvironment controlling BBB permeability and neuroinflammation. Glial glutamate transporters and connexin and pannexin hemichannels working in the tight functional coupling with the purinergic system serve as promising molecular targets for manipulating the intercellular communications that control BBB permeability in brain pathologies associated with excessive angiogenesis, cerebrovascular remodeling, and BBB-mediated neuroinflammation. Substantial progress in deciphering the molecular mechanisms underlying the (patho)physiology of perivascular glia provides promising approaches to novel clinically relevant therapies for brain disorders. The present review summarizes the current understandings on the secretory machinery expressed in glial cells (glutamate transporters, connexin and pannexin hemichannels, exocytosis mechanisms, membrane-derived microvesicles, and inflammasomes) and the role of secreted gliotransmitters and cytokines in the regulation of NVU and BBB permeability in (patho)physiologic conditions.

Ca2+/Calmodulin-Dependent Protein Kinase II γ-Dependent Serine727 Phosphorylation Is Required for TMEM16A Ca2+-Activated Cl- Channel Regulation in Cerebrovascular Cells.

TMEM16A is a critical component of Ca2+-activated chloride channels (CaCCs) and mediates basilar arterial smooth muscle cell (BASMC) proliferation in hypertensive cerebrovascular remodeling. CaMKII is a negative regulator of CaCC, and four CaMKII isoforms (α, β, γ and δ) are expressed in vasculature; however, it is unknown which and how CaMKII isoforms affect TMEM16A-associated CaCC and BASMC proliferation.Methods and Results:Patch clamp and small interfering RNA (siRNA) knockdown of different CaMKII isoforms revealed that only CaMKIIγ inhibited native Ca2+-activated chloride currents (ICl.Ca) in BASMCs. The TMEM16A overexpression evoked TMEM16A Cl-current and inhibited angiotensin II (Ang II)-induced proliferation in BASMCs. The co-immunoprecipitation and pull-down assay indicated an interaction between CaMKIIγ and TMEM16A protein. TMEM16A Cl-current was modulated by CaMKIIγ phosphorylation at serine residues in TMEM16A. Serine525 and Serine727 in TMEM16A were mutated to alanine, and only mutation at Ser727 (S727A) reversed the CaMKIIγ inhibition of the TMEM16A Cl-current. Phosphomimetic mutation S727D markedly decreased TMEM16A Cl-current and reversed TMEM16A-mediated suppression of BASMC proliferation, mimicking the inhibitory effects of CaMKIIγ on TMEM16A. A significant increase in CaMKIIγ isoform content was observed in parallel to the decrease of TMEM16A and ICl.Cain basilar artery proliferative remodeling in Ang II-infused mice. Serine 727 phosphorylation in TMEM16A by CaMKIIγ provides a new mechanism for regulating TMEM16A CaCC activity and Ang II-induced BASMC proliferation.

Maternal high-fat diet programs cerebrovascular remodeling in adult rat offspring

Maternal environmental factors such as diet have consequences on later health of the offspring. We found that maternal high-fat diet (HFD) exposure renders adult offspring brain more susceptible to ischemic injury. The present study was further to investigate whether HFD consumption during rat pregnancy and lactation influences the cerebral vasculature in adult male offspring. Besides the endothelial damage observed in the transmission electron microscopy, the MCAs of offspring from fat-fed dams fed with control diet (HFD/C) also displayed increased wall thickness and media/lumen ratio, suggesting that cerebrovascular hypertrophy or hyperplasia occurs. Moreover, smaller lumen diameter and elevated myogenic tone of the MCAs over a range of intralumenal pressures indicate inward cerebrovascular remodeling in HFD/C rats, with a concomitant increase in vessel stiffness. More importantly, both wire and pressure myography demonstrated that maternal HFD intake also enhanced the MCAs contractility to ET-1, accompanied by increases in ET types A receptor (ETAR) but not B (ETBR) density in the arteries. Furthermore, ETAR antagonism but not ETBR antagonism restored maternal HFD-induced cerebrovascular dysfunction in adult offspring. Taken together, maternal diet can substantially influence adult offspring cerebrovascular health, through remodeling of both structure and function, at least partially in an ET-1 manner.

Chronic Remote Ischemic Conditioning Is Cerebroprotective and Induces Vascular Remodeling in a VCID Model

Vascular contributions to cognitive impairment and dementia (VCID) make up 50% of the cases of dementia. The purpose of this study was to determine the effect of chronic remote ischemic conditioning (C-RIC) on improving long-term (6 months) outcomes and cerebral blood flow (CBF) and collateral formation in a mouse model of VCID. Adult C57BL/6J male mice (10 weeks) were randomly assigned to four different groups: (1) sham-bilateral carotid artery stenosis (BCAS), (2) BCAS + sham RIC, (3) BCAS+C-RIC for 1 month (1MO), and (4) BCAS+C-RIC-4 months (4MO). CBF, cognitive impairment, and functional outcomes were performed up for 6 months after BCAS surgery. The expression of CD31, α-SMA, and myelin basic protein (MBP) was assessed by immunohistochemistry (IHC). Additional set of mice were randomized to sham, BCAS, and BCAS+C-RIC. The cerebrovascular angioarchitecture was studied with micro-CT. RIC therapy for either 1 or 4 months significantly improved CBF, new collateral formation, functional and cognitive outcomes, and prevented white matter damage. There was no difference between C-RIC for 1 or 4 months; IHC studies at 6 months showed an increase in brain CD31 and α-SMA expression indicating increased angiogenesis and MBP indicating preservation of white matter in animals receiving RIC. One month of daily RIC is as effective as 4 months of daily RIC in improving CBF, angiogenesis, and long-term functional outcomes (6 months) in a VCID model. This suggests that 1 month of RIC is sufficient to reduce cognitive impairment and induce beneficial cerebrovascular remodeling.

IGF‐1 deficiency alters hypertension induced cerebrovascular remodeling in mice

Hypertension induced cerebral microhemorrhages (CMHs) may contribute to cognitive decline and predict larger strokes. Previous studies of our group found evidence that IGF‐1 deficiency exacerbates hypertension‐induced cerebral microhemorrhages (CMHs) mimicing an age‐related phenotype, but the underlying mechanisms remain elusive. We hypothesized that increased cerebrovascular stiffness and altered hypertension induced remodeling of the vessels may contribute to higher number of CMHS in IGF‐1 deficiency. Liver‐specific knockdown of IGF‐1 (Igf1f/f + TBG‐iCre‐AAV8) and control mice were chronically treated with angiotensin‐IIleading to similar hypertension in both groups (CTRL syst.: 151.375±2.08, diast.:109.65±3.27; IGF syst.: 150.10±2.00, diast.: 106.48±2.53). Middle cerebral (MCA) arteries of both groups were examined, by fixing them to a canulated isobaric vascular system and loaded with calcein. Smooth muscle cell related characteristics likepressure induced alteration in wall thickness and vessel diameter were measured using confocal microscopy. We found impaired cellular hypertrophic response in the IGF‐1 deficient hypertensive (HT) group, leading to smaller increase in wall thickness (1.43±0.04 μm in CTRL HT vs. 1.25±0.04 μm in IGF‐1 deficient HT). Based on the wall thickness and vessel diameter data circumferential stress and circumferential strain were calculated at different pressure levels (5–160 mmHg). Circumferential stress was higher in the IGF‐1 deficient group at any given pressure comparing to wild type group, while there was no change in the circumferential strain. Young's elastic modulus (Emod) was calculated by linear fitting of the stress‐strain curve. The Emod at lower pressures (describes elastin based elasticity) was higher in IGF‐1 HT group (468.20±73.56 vs. 306.77±36.22) while there was no change in the Emod at higher pressures (describes collagen based elasticity). Based on these data we can conclude that age‐related IGF‐1 deficiency alters hypertension‐induced cellular and extracellular matrix remodeling, which may lead to increased stiffnening of microvessels, possibly leading to incrased risk of pressure‐induced rupture.Support or Funding InformationThis work was supported by grants from the American Heart Association, the National Center for Complementary and Alternative Medicine, and the National Institute on Aging

Cerebrovascular Remodeling and Neuroinflammation is a Late Effect of Radiation-Induced Brain Injury in Non-Human Primates.

Fractionated whole-brain irradiation (fWBI) is a mainstay of treatment for patients with intracranial neoplasia; however late-delayed radiation-induced normal tissue injury remains a major adverse consequence of treatment, with deleterious effects on quality of life for affected patients. We hypothesize that cerebrovascular injury and remodeling after fWBI results in ischemic injury to dependent white matter, which contributes to the observed cognitive dysfunction. To evaluate molecular effectors of radiation-induced brain injury (RIBI), real-time quantitative polymerase chain reaction (RT-qPCR) was performed on the dorsolateral prefrontal cortex (DLPFC, Brodmann area 46), hippocampus and temporal white matter of 4 male Rhesus macaques (age 6-11 years), which had received 40 Gray (Gy) fWBI (8 fractions of 5 Gy each, twice per week), and 3 control comparators. All fWBI animals developed neurologic impairment; humane euthanasia was elected at a median of 6 months. Radiation-induced brain injury was confirmed histopathologically in all animals, characterized by white matter degeneration and necrosis, and multifocal cerebrovascular injury consisting of perivascular edema, abnormal angiogenesis and perivascular extracellular matrix deposition. Herein we demonstrate that RIBI is associated with white matter-specific up-regulation of hypoxia-associated lactate dehydrogenase A (LDHA) and that increased gene expression of fibronectin 1 (FN1), SERPINE1 and matrix metalloprotease 2 (MMP2) may contribute to cerebrovascular remodeling in late-delayed RIBI. Additionally, vascular stability and maturation associated tumor necrosis super family member 15 (TNFSF15) and vascular endothelial growth factor beta (VEGFB) mRNAs were increased within temporal white matter. We also demonstrate that radiation-induced brain injury is associated with decreases in white matter-specific expression of neurotransmitter receptors SYP, GRIN2A and GRIA4. We additionally provide evidence that macrophage/microglial mediated neuroinflammation may contribute to RIBI through increased gene expression of the macrophage chemoattractant CCL2 and macrophage/microglia associated CD68. Global patterns in cerebral gene expression varied significantly between regions examined (P < 0.0001, Friedman's test), with effects most prominent within cerebral white matter.

Abstract TMP118: Potential Therapeutic Benefits of Perlecan Domain V in Preclinical Vascular Dementia and Cerebral Angiopathy

Vascular contributions to cognitive impairment and dementia (VCID), the second leading cause of dementia behind Alzheimer’s disease (AD), is a broad term that encompasses a spectrum of initial asymptomatic cerebrovascular changes (seen in small vessel disease and cerebral amyloid angiopathy where pathologic Aβ1-42 protein accumulates around brain blood vessels) to the profound symptomatic damage following acute stroke(s). Cerebrovascular remodeling and new blood vessel growth (angiogenesis) may represent early compensatory changes to reduced cerebral blood flow that can initiate VCID. Angiogenesis, in turn, is supported by various growth factors and the proteolytic turnover of surrounding extracellular matrix. We have demonstrated that one such extracellular matrix protein, perlecan (a heparan sulfate proteoglycan), possesses a C terminal domain V (DV) protein that upon cleavage greatly enhances brain angiogenesis. We characterized VCID induced changes in DV expression in the human parietal cortex and a distinct mouse model (diabetic APP/PS1 knock in (db/AD)), that has a gradual cognitive decline by 9 months with microangiopathy, Aβ1-42 deposition, aneurysms, and microhemorrhages. We also utilized an in vitro model of the blood-brain barrier (BBB) to assess the transport of human Aβ1-42 in the presence of DV. In the human parietal cortex, dementia patients had increased expression of DV despite having fewer cells. In db/AD animals (3-6 months), we observed a decrease in BBB proteins (i.e. claudin-5), indicating that altered function correlated with an increase in brain DV expression during the asymptomatic angiogenic stage, which precedes cognitive changes (9-12 months). In vitro, DV doubled the transport of Aβ1-42 into the lumen of cerebral microvessels over 24 hours with increased activity and total protein expression of P-glycoprotein (P-gp), one of Aβ’s known transport proteins. Collectively, these data indicate that early cerebrovascular changes induce angiogenic-remodeling that correlates with increased expression of DV. DV, in turn, may further enhance angiogenesis and increase brain Aβ clearance into the vascular compartment through P-gp, suggesting that DV could represent a novel therapeutic for VCID.

CD47 deficiency improves neurological outcomes of traumatic brain injury in mice

CD47 is a receptor for signal-regulatory protein alpha (SIRPα) in self-recognition by the innate immune system, and a receptor of thrombospondin-1 (TSP-1) contributing to vascular impairment in response to stress. However, the roles of CD47 in traumatic brain injury (TBI) have not been investigated. In this study we aimed to test our hypothesis that CD47 mediates early neutrophil brain infiltration and late brain vascular remodeling after TBI. Mice were subjected to TBI using a controlled cortical impact (CCI) device. We examined early phase neutrophil infiltration, and late phase brain vessel density, pro-angiogenic markers VEGF and Ang-1 protein expression, neurological function deficits and lesion volumes for up to three weeks after TBI. Our results show that mice deficient in CD47 (CD47 Knockout) had significantly less brain neutrophil infiltration at 24h, upregulated VEGF expression in peri-lesion cortex at 7 and 14days, and increased blood vessel density at 21days after TBI, compared to wild type (WT) mice. CD47 knockout also significantly decreased sensorimotor function deficits and reduced brain lesion volume at 21days after TBI. We conclude that CD47 may play pathological roles in brain neutrophil infiltration, progression of brain tissue damage, impairment of cerebrovascular remodeling and functional recovery after TBI.

OS 11-05 Superior cervical ganglionectomy (SCGx) reduces sympathetic innervation of vertebrobasilar arteries but does not affect cerebrovascular remodelling in the adult spontaneously hypertensive rat (SHR)

Our hypothesis is that hypoperfusion of the brainstem is due to elevated vertebrobasilar artery resistance, triggers hypertension. We asked: is there a functional relationship between the sympathetic innervation to the vertebrobasilar system and its remodelling in the SHR? SHRs (11–12 weeks old) received either sham surgery or bilateral SCGx. Animals recovered for 14 days, were then perfused-fixed with 4% PFA and the vertebrobasilar arteries examined using both immunohistofluorecent staining of sympathetic (anti-DβH) and parasympathetic (anti-VAChT) fibres, and by cross sectional examination of vertebral and basilar arteries. Bilateral SCGx reduced sympathetic innervation to all parts of basilar artery: anterior (SCGx 123 ± 35 vs sham 198 ± 77 fibres/mm2, p < 0.05), middle (86 ± 17 vs 204 ± 62 fibres/mm2, p < 0.001) and posterior (126 ± 29 vs 291 ± 73 fibres/mm2, p < 0.001) as well as both left (L) and right (R) vertebral arteries (VA, LVA 90 ± 33 vs 232 ± 67 fibres/mm2, p < 0.01 and RVA 88 ± 30 vs 238 ± 66 fibres/mm2, p < 0.01). The parasympathetic innervation to the vertebrobasilar arteries was unchanged after SCGx. Despite the reduction of sympathetic input there was no change to vertebrobasilar artery remodelling: the vessels’ external diameter, lumen size and wall thickness were unaffected by the SCGx. The SCG provides a major innervation to the vertebrobasilar arteries in the SHR but it is not the only source of sympathetic innervation. Reduction of sympathetic input to the vertebrobasilar arteries in SHR with established hypertension does not attenuate cerebrovascular remodelling at least over a 14 day period. Acknowledgements – Wellcome Trust, British Heart Foundation

ISH NIA OS-06 PUTATIVE MECHANISMS FOR CEREBROVASCULAR REMODELLING IN THE SPONTANEOUSLY HYPERTENSIVE RAT (SHR) USING TRANSCRIPTOMICS

Objective:Cerebrovascular remodeling in the SHR may be causative to the known brainstem hypoperfusion. Using RNA sequencing, we examined age-related processes that may govern remodeling of the cerebral arteries in the SHR.Design and Method:In SHR and their progenitor (normotensive) control (Wistar K