Cortical Cerebral Blood Flow Research Articles

CBF changes and cerebral energy metabolism during hypervolemia, hemodilution, and hypertension therapy in patients with poor-grade subarachnoid hemorrhage.

Despite the multifactorial pathogenesis of delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH), augmentation of cerebral blood flow (CBF) is still considered essential in the clinical management of DCI. The aim of this prospective observational study was to investigate cerebral metabolic changes in relation to CBF during therapeutic hypervolemia, hemodilution, and hypertension (HHH) therapy in poor-grade SAH patients with DCI. CBF was assessed by bedside xenon-enhanced CT at days 0-3, 4-7, and 8-12, and the cerebral metabolic state by cerebral microdialysis (CMD), analyzing glucose, lactate, pyruvate, and glutamate hourly. At clinical suspicion of DCI, HHH therapy was instituted for 5 days. CBF measurements and CMD data at baseline and during HHH therapy were required for study inclusion. Non-DCI patients with measurements in corresponding time windows were included as a reference group. In DCI patients receiving HHH therapy (n = 12), global cortical CBF increased from 30.4 ml/100 g/min (IQR 25.1-33.8 ml/100 g/min) to 38.4 ml/100 g/min (IQR 34.2-46.1 ml/100 g/min; p = 0.006). The energy metabolic CMD parameters stayed statistically unchanged with a lactate/pyruvate (L/P) ratio of 26.9 (IQR 22.9-48.5) at baseline and 31.6 (IQR 22.4-35.7) during HHH. Categorized by energy metabolic patterns during HHH, no patient had severe ischemia, 8 showed derangement corresponding to mitochondrial dysfunction, and 4 were normal. The reference group of non-DCI patients (n = 11) had higher CBF and lower L/P ratios at baseline with no change over time, and the metabolic pattern was normal in all these patients. Global and regional CBF improved and the cerebral energy metabolic CMD parameters stayed statistically unchanged during HHH therapy in DCI patients. None of the patients developed metabolic signs of severe ischemia, but a disturbed energy metabolic pattern was a common occurrence, possibly explained by mitochondrial dysfunction despite improved microcirculation.

Anterior Cingulate Structure and Perfusion is Associated with Cerebrospinal Fluid Tau among Cognitively Normal Older Adult APOEɛ4 Carriers.

Evidence suggests the ɛ4 allele of the apolipoprotein E (APOE) gene may accelerate an age-related process of cortical thickening and cerebral blood flow (CBF) reduction in the anterior cingulate cortex (ACC). Although the neural basis of this association remains unclear, evidence suggests it might reflect early neurodegenerative processes. However, to date, associations between cerebrospinal fluid (CSF) biomarkers of neurodegeneration, such as CSF tau, and APOE-related alterations in ACC cortical thickness (CTH) and CBF have yet to be explored. The current study explored the interaction of CSF tau and APOE genotype (ɛ4+, ɛ4-) on FreeSurfer-derived CTH and arterial spin labeling MRI-measured resting CBF in the ACC (caudal ACC [cACC] and rostral ACC [rACC]) among a sample of 45 cognitively normal older adults. Secondary analyses also examined associations between APOE, CTH/CBF, and cognitive performance. In the cACC, higher CSF tau was associated with higher CTH and lower CBF in ɛ4+, whereas these relationships were not evident in ɛ4-. In the rACC, higher CSF tau was associated with higher CTH for both ɛ4+ and ɛ4-, and with lower CBF only in ɛ4+. Significant interactions of CSF tau and APOE on CTH/CBF were not observed in two posterior reference regions implicated in Alzheimer's disease. Secondary analyses revealed a negative relationship between cACC CTH and executive functioning in ɛ4+ and a positive relationship in ɛ4-. Findings suggest the presence of an ɛ4-related pattern of increased CTH and reduced CBF in the ACC that is associated with biomarkers of neurodegeneration and subtle decrements in cognition.

Reduced cerebral blood flow in an α-synuclein transgenic mouse model of Parkinson’s disease

There is increasing evidence that widespread cortical cerebral blood flow deficits occur early in the course of Parkinson’s disease. Although cerebral blood flow measurement has been suggested as a potential biomarker for early diagnosis of Parkinson’s disease, as well as a means for tracking response to treatment, the relationship of cerebral blood flow to α-synucleinopathy, a major pathological hallmark of Parkinson’s disease, remains unclear. Therefore, we performed arterial spin-labeling magnetic resonance imaging and diffusion tensor imaging on transgenic mice overexpressing human wild-type α-synuclein and age-matched controls to measure cerebral blood flow and degenerative changes. As reported for early-stage Parkinson’s disease, α-synuclein mice exhibited a significant reduction in cortical cerebral blood flow, which was accompanied by motor coordination deficits and olfactory dysfunction. Although no overt degenerative changes were apparent in diffusion tensor imaging images, magnetic resonance imaging volumetric analysis revealed a significant reduction in olfactory bulb volume, similar to that seen in Parkinson’s disease patients. Our data, representing the first report of cerebral blood flow deficit in an animal model of Parkinson’s disease, suggest a causative role for α-synucleinopathy in cerebral blood flow deficits in Parkinson’s disease. Thus, α-synuclein transgenic mice comprise a promising model to study Parkinson’s disease-related mechanisms of cerebral blood flow deficits and to investigate further its utility as a potential biomarker for Parkinson’s disease.

A novel model of cerebral hyperperfusion with blood-brain barrier breakdown, white matter injury, and cognitive dysfunction.

Cerebral hyperperfusion (CHP) is associated with considerable morbidity. Its pathophysiology involves disruption of the blood-brain barrier (BBB) with subsequent events such as vasogenic brain edema and ischemic and/or hemorrhagic complications. Researchers are trying to mimic the condition of CHP; however, a proper animal model is still lacking. In this paper the authors report a novel surgically induced CHP model that mimics the reported pathophysiology of clinical CHP including BBB breakdown, white matter (WM) injury, inflammation, and cognitive impairment. Male Sprague-Dawley rats were subjected to unilateral common carotid artery (CCA) occlusion and contralateral CCA stenosis. Three days after the initial surgery, the stenosis of CCA was released to induce CHP. Cortical regional cerebral blood flow was measured using laser speckle flowmetry. BBB breakdown was assessed by Evans blue dye extravasation and matrix metalloproteinase-9 levels. WM injury was investigated with Luxol fast blue staining. Cognitive function was assessed using the Barnes circular maze. Other changes pertaining to inflammation were also assessed. Sham-operated animals were prepared and used as controls. Cerebral blood flow was significantly raised in the cerebral cortex after CHP induction. CHP induced BBB breakdown evident by Evans blue dye extravasation, and matrix metalloproteinase-9 was identified as a possible culprit. WM degeneration was evident in the corpus callosum and corpus striatum. Immunohistochemistry revealed macrophage activation and glial cell upregulation as an inflammatory response to CHP in the striatum and cerebral cortex. CHP also caused significant impairments in spatial learning and memory compared with the sham-operated animals. The authors report a novel CHP model in rats that represents the pathophysiology of CHP observed in various clinical scenarios. This model was produced without the use of pharmacological agents; therefore, it is ideal to study the pathology of CHP as well as to perform preclinical drug trials.

Study on the cerebral microcirculation of rats with subarachnoid hemorrhage by using laser speckle technique

Objective To study the value of laser speckle technique in measuring blood flow changes in the cerebral microcirculation of rats with subarachnoid hemorrhage (SAH). Methods Rat double blood injection method was used to establish the model of SAH. Rats were divided into control group, SAH 5-day group, SAH 7-day group, saline 5-day group and saline 7-day group. After sensory nerve function examination, cerebral cortical blood flow was measured by laser speckle technique, and apoptotic index and electron microscopy were detected. SPSS 17.0 statistical software was used to make statistical analysis by variance analysis or non-parametric test. Results SAH 5-day group showed significant sensory dysfunction. There were significant differences between SAH 5-day group (12.100±1.287) and control group (15), SAH 7-day group (14.700±0.675), saline 5-day group (14.900±0.316) and saline 7-day group (15) (Z values were -4.059, -3.655, -3.908, -4.059, respectively; respectively P<0.01); Electron microscopy showed that the morphology of neurons in the control group and saline injection groups was basically normal; neurons in the SAH 5-day group showed obvious edema and extensive neuronal degeneration or necrosis; neurons in the SAH 7-day group showed slight swelling and some neurons had degeneration or necrosis. There were obvious apoptotic cells in cerebral cortex of SAH groups. The apoptotic index of SAH 5-day group [(19.870±1.909)%] and control group [(1.840±0.474)%], SAH 7-day group [(13.770±1.924)%], saline 5-day group [(1.740±0.299)%], saline 7-day group [(1.790±0.407)%] had statistical differences (t values were 28.985, 7.117, 29.670, 29.291, respectively; respectively P<0.01). SAH 7-day group and control group, SAH 5-day group, saline 5-day group, saline 7-day group had statistical differences (t values were 19.037, -7.117, 19.537, 19.263, respectively; respectively P<0.01). Cerebral cortical blood flow in SAH groups decreased, and the most obvious decrease was found in SAH 5-day group (64.000±6.218), compared with control group (106.000±13.081), SAH 7-day group (75.700±8.274), saline 5-day group (105.100±13.169), saline 7-day group (104.100±10.609). There were significant differences (t values were -9.170, -3.575, -8.924, -10.312, respectively; successively P<0.01, 0.05, 0.01, 0.01). There were significant differences between SAH 7-day group and control group, SAH 5-day group, saline 5-day group and saline 7-day group (t values were -6.191, 3.575, -5.978 and -6.675, respectively; successively P<0.01, 0.05, 0.01, 0.01, 0.01). Conclusion Laser speckle technique is suitable for studying the blood flow changes of cerebral microcirculation in SAH rats. Key words: Subarachnoid hemorrhage; Cerebral microcirculation; Cerebral blood flow; Laser speckle

A refined model of chronic cerebral hypoperfusion resulting in cognitive impairment and a low mortality rate in rats.

The cognitive deficits of vascular dementia and the vasoocclusive state of moyamoya disease have often been mimicked with bilateral stenosis/occlusion of the common carotid artery (CCA) or internal carotid artery. However, the cerebral blood flow (CBF) declines abruptly in these models after ligation of the CCA, which differs from "chronic" cerebral hypoperfusion. While some modified but time-consuming techniques have used staged occlusion of both CCAs, others used microcoils for CCA stenosis, producing an adverse effect on the arterial endothelium. Thus, the authors developed a new chronic cerebral hypoperfusion (CCH) model with cognitive impairment and a low mortality rate in rats. Male Sprague-Dawley rats were subjected to unilateral CCA occlusion and contralateral induction of CCA stenosis (modified CCA occlusion [mCCAO]) or a sham operation. Cortical regional CBF (rCBF) was measured using laser speckle flowmetry. Cognitive function was assessed using a Barnes circular maze (BCM). MRI studies were performed 4 weeks after the operation to evaluate cervical and intracranial arteries and parenchymal injury. Behavioral and histological studies were performed at 4 and 8 weeks after surgery. The mCCAO group revealed a gradual CBF reduction with a low mortality rate (2.3%). White matter degeneration was evident in the corpus callosum and corpus striatum. Although the cellular density declined in the hippocampus, MRI revealed no cerebral infarctions after mCCAO. Immunohistochemistry revealed upregulated inflammatory cells and angiogenesis in the hippocampus and cerebral cortex. Results of the BCM assessment indicated significant impairment in spatial learning and memory in the mCCAO group. Although some resolution of white matter injury was observed at 8 weeks, the animals still had cognitive impairment. The mCCAO is a straightforward method of producing a CCH model in rats. It is associated with a low mortality rate and could potentially be used to investigate vascular disease, moyamoya disease, and CCH. This model was verified for an extended time point of 8 weeks after surgery.

Establishment of transparent cranial window after cerebral subarachnoid hemorrhage and studying of cerebral cortical blood flow in rats

Objective Establishment of a transparent cranial window model of subarachnoid hemorrhage in rats for 7 days of continuous monitoring of cortical blood flow after subarachnoid hemorrhage Methods Thirty SD male rats were randomly divided into normal control group (n=10), saline group (n=10)and blood injection group (n=10). The transcranial subarachnoid hemorrhage transparent cranial window observation model was established by injecting autologous non-anticoagulation tail artery blood 0.3 ml twice in the occipital large pool and using a transparent flexible material made of silicon-based polydimethylsiloxane. Seven-day dynamic changes in cerebral cortical blood flow within the cranial window were monitored by laser speckle imaging. Results The imaging of 27 rats were clear; the blood flow velocity of the cortex decreased after SAH, which was statistically different from the control group and the saline group (P<0.01), and the blood flow on the 3rd, 5th, and 7th day after SAH. The percentage speeds were (83.20±4.16)%, (64.00±3.05)%, (75.70±3.79)%, and the 5 d was statistically different from the 3rd and 7 d (P<0.01); cortical blood perfusion after SAH The amount decreased, which was statistically different from the control group and the saline group (P<0.05). The percentage blood perfusion of the cortex on the 3rd, 5th, and 7th after SAH was (75.40±4.18)%, (31.80±5.34)%, (68.90±6.31)%, the 5th was statistically different from the 3rd and 7 d (P<0.01). Conclusion Through the use of a new flexible transparent material to establish a subarachnoid hemorrhage transparent cranial window imaging model, combined with laser speckle imaging technology can clearly detect the decline of cortical blood flow velocity and cortical blood perfusion in rats after subarachnoid hemorrhage 5 d is the peak of decline, and recovery begins on the 7th day, providing a new method for studying the pathophysiological changes in the acute and subacute phases after subarachnoid hemorrhage. Key words: Subarachnoid hemorrhage; Transparent cranial window imaging; Cerebral cortex blood flow; Laser speckle imaging technique; Rat

Anti-high mobility group box-1 antibody attenuated vascular smooth muscle cell phenotypic switching and vascular remodelling after subarachnoid haemorrhage in rats

Although cerebral vascular smooth muscle cell (VSMC) phenotypic switching is involved in the vascular dysfunction after subarachnoid haemorrhage (SAH), the precise mechanisms are still unclear. High mobility group box-1 (HMGB1) has been identified as a modulator in VSMC proliferation. The purpose of this study was to investigate the potential role of HMGB1 in the VSMC phenotypic switching following SAH. An endovascular perforation SAH model was used in our experiments. The expression levels of HMGB1, α­smooth muscle actin (α-SMA), osteopontin (OPN), smooth muscle myosin heavy chain (SM-MHC), embryonic smooth muscle myosin heavy chain (Smemb), TXA2, PAR-1 and AT1 receptor were evaluated by Western blot analyses. Iba1-positive cells and apoptotic cells were determined by immunofluorescence staining and TUNEL staining, respectively. Vasoconstriction of the isolated basilar artery was stimulated by thrombin and KCl. We found that HMGB1 expression was markedly increased following SAH, and anti-HMGB1 mAb significantly reversed VSMC phenotypic switching and vascular remodelling in rats. However, the effects of HMGB1 on VSMC phenotypic switching were partly blocked in the presence of SC79, a potent activator of phosphatidylinositol-3-kinase-AKT (PI3K/AKT). Furthermore, the enhanced vasoconstriction and decreased cerebral cortical blood flow induced by SAH were reversed by anti-HMGB1 mAb. Finally, we found that anti-HMGB1 mAb attenuated microglial activation and brain oedema, ameliorating neurological dysfunction. These results indicated that HMGB1 is a useful regulator of VSMC phenotypic switching and vascular remodelling following SAH and might be exploited as a novel therapeutic target for delayed cerebral ischaemia.

403-P: Cerebral Blood Flow Responses to Hypoglycemia in Healthy Humans Treated with Induction Protocol to Produce Impaired Awareness of Hypoglycemia

In this study, we sought to determine by 3T MRI the cerebral blood flow (CBF) responses to hypoglycemia (HG) in nondiabetic controls exposed to either two euglycemic or two hypoglycemic clamps on the day before the MRI (EU- or HYPO-preconditioning, respectively). Under the belief that HYPO-preconditioning induces hypoglycemia-associated autonomic failure (HAAF) with blunting of the counter-regulatory hormone and symptom responses to HG (Arbelaez et al, 2008), we hypothesized that CBF responses after HYPO-preconditioning would resemble those reported in T1D subjects with impaired awareness of hypoglycemia (IAH) (Weigers et al, 2017). CBF was measured by arterial spin labeling during a 2-step hyperinsulinemic clamp [step 1 = 95 mg/dL normoglycemia (NG), step 2 = 50 mg/dL (HG)]. Symptom and counter-regulatory hormone were also measured. Full CBF datasets were obtained from 10 participants who underwent EU-preconditioning (7F/3M, age 37 ± 14 years, BMI 27.2 ± 3.7 kg/m2) and 9 who underwent HYPO-preconditioning (5F/4M, age 40 ± 14 years, BMI 26.2 ± 2.6 kg/m2). In contrast with our assumption, the HYPO-preconditioning did not induce blunting of symptom or counter-regulatory hormone responses to HG other than for glucagon (33 ± 19 and 14 ± 21 pg/mL for EU- and HYPO-preconditioning, respectively, p=0.04 uncorr). CBF responses did not differ between the two pre-conditionings, and resembled those reported in the literature in naïve nondiabetic controls (Weigers et al, 2017). In particular, the cortical grey matter CBF did not change during HG vs. NG for either the EU- or HYPO-preconditioning settings (1 ± 10% and 2 ± 10%, respectively), while thalamic CBF increased in both settings (21 ± 20%, p=0.012 corr, and 27 ± 30%, p=0.06 corr, respectively). We conclude that the preconditioning protocols should be used with caution in nondiabetic controls for investigating IAH, as the mechanisms of HAAF in T1D patients may be specific to their disease condition. Disclosure A. Canna: None. H. Grohn: None. D. Mascali: None. P. Filip: None. A. Moheet: None. A. Kumar: None. X. Li: None. E.A. Olawsky: None. L.E. Eberly: None. F. Esposito: None. E.R. Seaquist: Advisory Panel; Self; Eli Lilly and Company, Zucara Therapeutics Inc. Consultant; Self; 360 Consulting, MannKind Corporation. Research Support; Self; Eli Lilly and Company, JDRF, National Institutes of Health. Other Relationship; Self; American Diabetes Association, Sanofi, WebMD. S. Mangia: None. Funding National Institutes of Health

Increased TRPM4 Activity in Cerebral Artery Myocytes Contributes to Cerebral Blood Flow Reduction After Subarachnoid Hemorrhage in Rats.

Cerebral blood flow (CBF) reduction underlies unfavorable outcomes after subarachnoid hemorrhage (SAH). Transient receptor potential melastatin-4 (TRPM4) has a pivotal role in cerebral artery myogenic tone maintenance and CBF regulation under physiological conditions. However, the role of TRPM4 in CBF reduction after SAH is unclear. In this study, we aimed at testing whether TRPM4 would contribute to CBF reduction after SAH in vivo and determining underlying mechanisms. Rat SAH model was established by stereotaxic injection of autologous nonheparinized arterial blood at the suprasellar cistern. A TRPM4 blocker, 9-phenanthrol (9-Phe), was infused through an intraventricular catheter connected to a programmed subcutaneous pump to evaluate the contribution of TRPM4 to SAH outcomes. TRPM4 expression and translocation in cerebral artery myocytes were detected by immunoblotting. Macroscopic currents in cerebral artery myocytes were determined by whole-cell patch clamp. Myogenic tone of cerebral arteries was studied by pressurized myography. Cortical and global CBFs were measured via laser Doppler flowmetry and fluorescent microspheres, respectively. After SAH, TRPM4 translocation and macroscopic current density increased significantly. Furthermore, TRPM4 accounted for a greater proportion of myogenic tone after SAH, suggesting an upregulation of TRPM4 activity in response to SAH. Cortical and global CBFs were reduced after SAH, but were restored significantly by 9-Phe, implying that TRPM4 contributed to CBF reduction after SAH. Collectively, these discoveries show that increased TRPM4 activity has a pivotal role in CBF reduction after SAH, and provide a novel target for the management of cerebral perfusion dysfunction following SAH.

Bexarotene Exerts Protective Effects Through Modulation of the Cerebral Vascular Smooth Muscle Cell Phenotypic Transformation by Regulating PPARγ/FLAP/LTB4 After Subarachnoid Hemorrhage in Rats

Vascular smooth muscle cells (VSMCs) play an important role after a subarachnoid hemorrhage (SAH). The changes in VSMCs following bexarotene treatment after SAH are unknown. In the present study, neurological impairment, decreased cerebral cortical blood flow and transformation of cerebral VSMCs from a contractile to a synthetic phenotype were observed after SAH. Bexarotene reduced neurological impairment, improved cerebral cortical blood flow, inhibited VSMC phenotypic transformation and suppressed the expression of 5-lipoxygenase-activating protein (FLAP) and leukotriene B4 (LTB4), which was partly reversed by GW9662, an inhibitor of peroxisome proliferator-activated receptor gamma (PPARγ). Mechanistically, sh-PPARγ-mediated phenotypic transformation of VSMCs was partially suppressed by MK886, an antagonist of FLAP. Therefore, we conclude that bexarotene reduced neurological impairment, improved cerebral cortical blood flow and inhibited the VSMC phenotypic transformation after SAH, which was achieved by activating PPARγ-mediated inhibition of FLAP/LTB4 in VSMCs

Platelet microvesicles promote the recovery of neurological function in mouse model of cerebral infarction by inducing angiogenesis

The aim of this study is to investigate the effect of PMVs on mice with ischemic cerebral infarction and its mechanism. Male C57BL/6 mice were selected, and the right focal cortical infarction model was established via cauterization under a microscope and randomly divided into sham operation (Sham) group, normal saline control (Saline) group and platelet microvesicles intervention (PMVs) group. At 1 h after modeling, 5 μL of PMVs (50 μg/mL) or normal saline was injected into the lateral ventricle. The neurological function of mice in each group was evaluated at 1, 3, 7, 14 and 28 d after modeling. After 28 d, the cerebral infarction area was detected via 2,3,5-triphenyltetrazolium chloride (TTC) staining. At 7 and 28 d after modeling, the blood vessel density, proliferation rate of new vessels and encapsulation rate of pericytes were detected via immunofluorescence staining. Moreover, the changes in cerebral cortical blood flow at the infarction side were detected before modeling and at 7 and 28 d after modeling, respectively. Finally, the expressions of proangiogenic factors vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and N-Cadherin were detected via Western blotting at 3, 7 and 28 d after modeling. PMVs could promote the improvement of neurological function and significantly reduce the cerebral infarction volume in mice with cerebral infarction. PMVs promoted proliferation of new vessels and increased blood vessel density at the infarction edge in mice with cerebral infarction. PMVs could increase the encapsulation rate of pericytes at the infarction edge and improve the permeability of blood-brain barrier in mice with cerebral infarction. PMVs could increase the cerebral cortical blood flow perfusion in mice with cerebral infarction. PMVs could increase proangiogenic factors in brain tissues in mice with cerebral infarction. PMVs could significantly improve the recovery of neurological function in mice with cerebral infarction, which is closely related to the ability of PMVs to promote angiogenesis at the infarction edge. The possible mechanism is that PMVs facilitate angiogenesis after cerebral infarction through promoting the expressions of VEGF, Ang-1 and N-Cadherin. More importantly, the new vessels promoted by PMVs have complete structure and perfect function, and can improve the cerebral blood flow perfusion at the infarction side.

Cortical cerebral blood flow in ageing: effects of haematocrit, sex, ethnicity and diabetes

ObjectivesCerebral blood flow (CBF) estimates from arterial spin labelling (ASL) show unexplained variability in older populations. We studied the impact of variation of haematocrit (Hct) on CBF estimates in a tri-ethnic elderly population.Materials and methodsApproval for the study was obtained from the Fulham Research Ethics Committee and participants gave written informed consent. Pseudo-continuous arterial spin labelling was performed on 493 subjects (age 55–90) from a tri-ethnic community-based cohort recruited in London. CBF was estimated using a simplified Buxton equation, with and without correction for Hct measured from blood samples. Differences in perfusion were compared, stratified by sex, ethnicity and diabetes. Results of Student’s t tests were reported with effect size.ResultsHct adjustment decreased CBF estimates in all categories except white European men. The decrease for women was 2.7 (3.0, 2.4) mL/100 g/min) (mean (95% confidence interval (CI)), p < 0.001 d = 0.38. The effect size differed by ethnicity with estimated mean perfusion in South Asian and African Caribbean women found to be lower by 3.0 (3.6, 2.5) mL/100 g/min, p < 0.001 d = 0.56 and 3.1 (3.6, 2.5) mL/100 g/min), p < 0.001 d = 0.48, respectively. Estimates of perfusion in subjects with diabetes decreased by 1.8 (2.3, 1.4) mL/100 g/min, p < 0.001 d = 0.23) following Hct correction. Correction for individual Hct altered sample frequency distributions of CBF values, especially in women of non-European ethnicity.ConclusionASL-derived CBF values in women, non-European ethnicities and individuals with diabetes are overestimated if calculations are not appropriately adjusted for individual Hct.Key Points• CBF quantification from ASL using a fixed Hct of 43.5%, as recommended in the ISMRM white paper, may lead to erroneous CBF estimations particularly in non-European and female subjects.• Individually measured Hct values improve the accuracy of CBF estimation and, if these are not available, an adjusted value according to gender, ethnicity or diabetes status should be considered.• Hct-corrected ASL could be potentially important for CBF threshold decision making in the fields of neurodegenerative disease and neuro-oncology.

Dl-3-n-Butylphthalide regulates the Ang-1/Ang-2/Tie-2 signaling axis to promote neovascularization in chronic cerebral hypoperfusion

Previous findings have demonstrated, in a rat model, that chronic cerebral hypoperfusion (CCH) decreases cortical cerebral blood flow (CBF) while Dl-3-n-Butylphthalide (DNB) accelerates the timely recovery of CBF. However, potential biomarkers, therapeutic targets, and underlying mechanisms for these processes are unclear. In this study, a solid-phase antibody microarray for simultaneously detecting multiple proteins was used to search cortex biotargets in CCH compared to a sham control group, and these results were further examined by biological functional analysis. After DNB treatment, western blot and immunostaining were used to verify candidate protein expression. Importantly, we identified seven proteins that may serve as novel biotargets contributing to CCH. The levels of Tie-2, CNTFRα, IL-4, IL-10, ITGAM, MDC, and TROY were uniquely altered in the CCH. The Tie-2 level was significantly decreased and identified in CCH 2 week (W), CCH 4 W and CCH 8 W. In addition, Ang-1 level and Ang-1/Ang-2 ratio were significantly decreased in CCH 2 W and CCH 4 W while Ang-2 level was increased in the CCH, whereas DNB treatment created the inverse effect to some extent. Moreover, the expression of VEGF and CD34 in the earlier stage of CCH and the diameters of bilateral vertebral arteries (VAs), were significantly enlarged by DNB treatment. Together, we found that the Ang-1/Ang-2/Tie-2 signaling axis was altered in the CCH rat cortex, and DNB treatment could timely regulate this angiopoietin/Tie signaling axis to promote neovascularization in early stages.

Temporal Dynamics of Cerebral Blood Flow During the Acute Course of Severe Subarachnoid Hemorrhage Studied by Bedside Xenon-Enhanced CT

BackgroundCompromised cerebral blood flow (CBF) is a crucial factor in delayed cerebral ischemia after subarachnoid hemorrhage (SAH). Repeated measurement of CBF may improve our understanding of the temporal dynamics following SAH. The aim of this study was to assess CBF at different phases of the acute course in poor-grade SAH patients, hypothesizing more pronounced disturbances at day 4–7, and that the initial level of CBF determines the following course of CBF.MethodsMechanically ventilated SAH patients were scheduled for bedside measurement of regional and global cortical CBF at day 0–3, 4–7, and 8–12, using xenon-enhanced computed tomography in a mobile setup. Patients were dichotomized depending on high or low initial global cortical CBF and cutoff level 30 ml/100 g/min.ResultsEighty-one patients were included, and 51 had measurements at day 0–3 and 4–7. In patients with high initial CBF, the level was unchanged at day 4–7; 37.7 (IQR 32.6–46.7) ml/100 g/min versus 36.8 (IQR 29.5–44.8). The low-CBF group showed a slight increase from 23.6 (IQR 21.0–28.1) ml/100 g/min to 28.4 (IQR 22.7–38.3) (P = 0.025), still markedly lower than the high-CBF group (P = 0.016). In the low-CBF group, CBF increased in patients who received hypertension, hypervolemia, and hemodilution (HHH therapy) but remained low in standard treated patients. For the subset of 27 patients examined also at day 8–12, the differences depending on initial CBF level were no longer statistically significant. Among patients with still low CBF at day 4–7, the proportion who had poor short-term outcome was 55% compared to 35% (n.s.) for patients with high CBF.ConclusionsCBF studied in poor-grade SAH patients at large did not show any statistically significant changes over time. Stratifying patients by high or low initial CBF and whether HHH therapy was given revealed an association between low initial CBF and persistent low CBF at day 4–7. These findings may be of clinical relevance in managing SAH patients with low early CBF.

Magnetic Resonance Imaging of Cerebral Small Vessel Disease in Men Living with HIV and HIV-Negative Men Aged 50 and Above.

We assessed whether HIV status was associated with white matter hyperintensities (WMH), a neuroimaging correlate of cerebral small vessel disease (CSVD), in men aged ≥50 years. A cross-sectional substudy was nested within a larger cohort study. Virologically suppressed men living with HIV (MLWH) and demographically matched HIV-negative men aged ≥50 underwent magnetic resonance imaging (MRI) at 3 Tesla. Sequences included volumetric three-dimensional (3D) T1-weighted, fluid-attenuated inversion recovery and pseudocontinuous arterial spin labeling. Regional segmentation by automated image processing algorithms was used to extract WMH volume (WMHV) and resting cerebral blood flow (CBF). The association between HIV status and WMHV as a proportion of intracranial volume (ICV; log-transformed) was estimated using a multivariable linear regression model. Thirty-eight MLWH [median age 59 years (interquartile range, IQR 55-64)] and 37 HIV-negative [median 58 years (54-63)] men were analyzed. MLWH had median CD4+ count 570 (470-700) cells/μL and a median time since diagnosis of 20 (14-24) years. Framingham 10-year risk of cardiovascular disease was 6.5% in MLWH and 7.4% in controls. Two (5%) MLWH reported a history of stroke or transient ischemic attack and five (13%) reported coronary heart disease compared with none of the controls. The total WMHV in MLWH was 1,696 μL (IQR 1,229-3,268 μL) or 0.10% of ICV compared with 1,627 μL (IQR 1,032-3,077 μL), also 0.10% of ICV in the HIV-negative group (p = .43). In the multivariable model, WMHV/ICV was not associated with HIV status (p = .86). There was an age-dependent decline in cortical CBF [-3.9 mL/100 mL/min per decade of life (95% confidence interval 1.1-6.7 mL)] but no association between CBF and HIV status (p > .2 in all brain regions analyzed). In conclusion, we found no quantitative MRI evidence of an increased burden of CSVD in MLWH aged 50 years and older.

Abstract 101: ApoE4 Disrupts Cerebrovascular Microcirculation and Undermines White Matter Integrity and Cognitive Function

Background: Small vessel disease leading to subcortical white matter lesions (WML) is the major cause of vascular cognitive impairment. The apolipoprotein E4 (ApoE4) allele, a well-known risk factor for Alzheimer’s disease, is also a risk factor for WML, but the mechanisms of the effect remain unclear. We set out to determine whether the ApoE4 genotype disrupts the cerebral microcirculation and promotes WML and cognitive impairment. Methods: We studied male ApoE4 targeted replacement mice (ApoE4-TR; age 3-4 months). ApoE3 (ApoE3-TR) were used as controls. Cerebral blood flow (CBF) was assessed by ASL-MRI; the CBF increase induced by whisker stimulation (WS) or the endothelium-dependent agent acetylcholine (ACh) was assessed in cranial window preparations by laser-Doppler flowmetry. The corpus callosum (CC) microcirculation was examined by three-photon microscopy (3PM). Bilateral carotid artery stenosis (BCAS) was induced with 0.18 mm microcoils. WML and cognition were tested 4 weeks after BCAS. Results: In ApoE4-TR mice resting cortical CBF was attenuated compared to ApoE3-TR (-13%), as well the increase in CBF produced by WS (-47±3%) or ACh (-38±3%; p&lt;0.05; n=5/group). In the CC, red blood cell (RBC) speed was slower in ApoE4-TR (1.6±0.1) than in ApoE3 mice (1.9±0.1 mm/s; p&lt;0.05; n=5/group). Following 4 weeks of BCAS, cortical CBF was reduced more in ApoE4-TR (-35±4%) than in ApoE3-TR mice (-23±2%; p&lt;0.05; n=8/group). Similarly, in the CC RBC speed was reduced more in ApoE4-TR (-33±3%) than in ApoE3-TR mice (-23±3%; p&lt;0.05; n=5/group). In ApoE4-TR mice BCAS resulted in more marked CC WML (SMI312/MBP ratio, 48%) and cognitive dysfunction (novel object recognition: 18%; Y-maze arm alternation: 14%) than in ApoE3-TR mice (p&lt;0.05; n=8/group). Conclusions: The findings unveil a previously unrecognized ApoE4-dependent failure of critical neurovascular regulatory mechanisms, sufficient to promote white matter damage in the setting of cerebral hypoperfusion. Such alterations may be responsible for the increased susceptibility to hypoxic-ischemic lesions in the subcortical white matter of individuals carrying the ApoE4 allele.

Dopamine effects on frontal cortical blood flow and motor inhibition in Parkinson's disease

Parkinson's disease (PD) is characterized by dysfunction in frontal cortical and striatal networks that regulate action control. We investigated the pharmacological effect of dopamine agonist replacement therapy on frontal cortical activity and motor inhibition. Using Arterial Spin Labeling MRI, we examined 26 PD patients in the off- and on-dopamine agonist medication states to assess the effect of dopamine agonists on frontal cortical regional cerebral blood flow. Motor inhibition was measured by the Simon task in both medication states. We applied the dual process activation suppression model to dissociate fast response impulses from motor inhibition of incorrect responses. General linear regression model analyses determined the medication effect on regional cerebral blood flow and motor inhibition, and the relationship between regional cerebral blood flow and motor inhibitory proficiency. We show that dopamine agonist administration increases frontal cerebral blood flow, particularly in the pre-supplementary motor area (pre-SMA) and the dorsolateral prefrontal cortex (DLPFC). Higher regional blood flow in the pre-SMA, DLPFC and motor cortex was associated with better inhibitory control, suggesting that treatments which improve frontal cortical activity could ameliorate motor inhibition deficiency in PD patients.

Low cerebral blood flow is a non-invasive biomarker of neuroinflammation after repetitive mild traumatic brain injury

Previous work has shown that non-invasive optical measurement of low cerebral blood flow (CBF) is an acute biomarker of poor long-term cognitive outcome after repetitive mild traumatic brain injury (rmTBI). Herein, we explore the relationship between acute cerebral blood flow and underlying neuroinflammation. Specifically, because neuroinflammation is a driver of secondary injury after TBI, we hypothesized that both glial activation and inflammatory signaling are associated with acute CBF and, by extension, with long-term cognitive outcome after rmTBI. To test this hypothesis, cortical CBF was non-invasively measured in anesthetized mice 4 h after 3 repetitive closed head injuries spaced once-daily, at which time brains were collected. Right hemispheres were fixed for immunohistochemical staining for glial activation markers Iba1 and GFAP while left hemispheres were used to quantify Iba1 and GFAP expression via Western blot as well as 32 cytokines and 21 phospho-proteins in the MAPK, PI3K/Akt, and NF-κB pathways using a Luminex multiplexed immunoassay. N = 8/7 injured/sham C57/black-6 adult male mice were studied. Within the injured group, CBF inversely correlated with Iba1 expression (R = −0.86, p < .01). Further, partial least squares regression analysis revealed significant correlations between CBF and expression of multiple pro-inflammatory cytokines, including RANTES and IL-17. Finally, within the injured group, phosphorylation of specific signals in the MAPK and NF-κB intracellular signaling pathways (e.g., p38 MAPK and NF-κB) were significantly positively correlated with Iba1. In total, our data indicate that acute cerebral blood flow after rmTBI is a biomarker of underlying neuroinflammatory pathology.

Longitudinal assessment of cerebral perfusion and vascular response to hypoventilation in a bigenic mouse model of Alzheimer's disease with amyloid and tau pathology.

Alzheimer's disease is the most common neurodegenerative disease, and many patients also present with vascular dysfunction. In this study, we aimed to assess cerebral blood flow (CBF) and cerebrovascular response (CVR) as early, pre-symptomatic (3months of age), imaging markers in a bigenic model of Alzheimer's disease (APP.V717IxTau.P301L, biAT) and in the monogenic parental strains. We further developed our previously published combination of pulsed arterial spin labeling perfusion MRI and hypo-ventilation paradigm, which allows weaning of the mice from the ventilator. Furthermore, the commonly used isoflurane anesthesia induces vasodilation and is thereby inherently a vascular challenge. We therefore assessed perfusion differences in the mouse models under free-breathing isoflurane conditions. We report (i) that we can determine CBF and hypoventilation-based CVR under ketamine/midazolam anesthesia and wean mice from the ventilator, making it a valuable tool for assessment of CBF and CVR in mice, (ii) that biAT mice exhibit lower cortical CBF than wild-type mice at age 3months, (iii) that CVR was increased in both biAT and APP.V717I mice but not in Tau.P301L mice, identifying the APP genotype as a strong influencer of brain CVR and (iv) that perfusion differences at baseline are masked by the widely used isoflurane anesthesia.