Arterial Smooth Muscle Cell AKAP150 Mediates Exercise-Induced Repression of CaV1.2 Channel Function in Cerebral Arteries of Hypertensive Rats

BACKGROUND

Hypertension is a major, prevalent risk factor for the development and progression of cerebrovascular disease. Regular exercise has been recommended as an excellent choice for the large population of individuals with mild-to-moderate elevations in blood pressure, but the mechanisms that underlie its vascular-protective and antihypertensive effects remain unknown. Here, we describe a mechanism by which myocyte AKAP150 (A-kinase anchoring protein 150) inhibition induced by exercise training alleviates voltage-dependent L-type Ca2+ channel (CaV1.2) activity and restores cerebral arterial function in hypertension.

METHODS

Spontaneously hypertensive rats and newly generated smooth muscle-specific AKAP150 knockin mice were used to assess the role of myocyte AKAP150/CaV1.2 channel in regulating cerebral artery function after exercise intervention.

RESULTS

Activation of the AKAP150/PKCα (protein kinase Cα) signaling increased CaV1.2 activity and Ca2+ influx of cerebral arterial myocyte, thus enhancing vascular tone in spontaneously hypertensive rats. Smooth muscle-specific AKAP150 knockin mice were hypertensive with higher CaV1.2 channel activity and increased vascular tone. Furthermore, treatment of Ang II (angiotensin II) resulted in a more pronounced increase in blood pressure in smooth muscle-specific AKAP150 knockin mice. Exercise training significantly reduced arterial myocyte AKAP150 expression and alleviated CaV1.2 channel activity, thus restoring cerebral arterial function in spontaneously hypertensive rats and smooth muscle-specific AKAP150 knockin mice. AT1R (AT1 receptor) and AKAP150 were interacted closely in arterial myocytes. Exercise decreased the circulating Ang II and Ang II-involved AT1R-AKAP150 association in myocytes of hypertension.

CONCLUSIONS

The current study demonstrates that aerobic exercise ameliorates CaV1.2 channel function via inhibiting myocyte AKAP150, which contributes to reduced cerebral arterial tone in hypertension.

Paternal preconception alcohol consumption increased Angiotensin II-mediated vasoconstriction in male offspring cerebral arteries via oxidative stress-AT1R pathway

Alcohol consumption is popular worldwidely and closely associated with cardiovascular diseases. Influences of paternal preconception alcohol consumption on offspring cerebral arteries are largely unknown. Male rats were randomly given alcohol or water before being mated with alcohol-naive females to produce alcohol- and control-sired offspring. Middle cerebral artery (MCA) was tested with a Danish Myo Technology wire myograph, patch-clamp, IONOPTIX, immunofluorescence and quantitative PCR. Alcohol consumption enhanced angiotensin II (AngII)-mediated constriction in male offspring MCA mainly via AT1R. PD123,319 only augmented AngII-induced constriction in control offspring. AngII and Bay K8644 induced stronger intracellular calcium transient in vascular smooth muscle cells (VSMCs) from MCA of alcohol offspring. L-type voltage-dependent calcium channel (L-Ca2+ ) current at baseline and after AngII-stimulation was higher in VSMCs. Influence of large-conductance calcium-activated potassium channel (BKC a ) was lower. Caffeine induced stronger constriction and intracellular calcium release in alcohol offspring. Superoxide anion was higher in alcohol MCA than control. Tempol and thenoyltrifluoroacetone alleviated AngII-mediated contractions, while inhibition was significantly higher in alcohol group. The mitochondria were swollen in alcohol MCA. Despite lower Kcnma1 and Prkce expression, many genes expressions were higher in alcohol group. Hypoxia induced reactive oxygen species production and increased AT1R expression in control MCA and rat aorta smooth muscle cell line. In conclusion, this study firstly demonstrated paternal preconception alcohol potentiated AngII-mediated vasoconstriction in offspring MCA via ROS-AT1R. Alcohol consumption increased intracellular calcium via L-Ca2+ channel and endoplasmic reticulum and decreased BKCa function. The present study provided new information for male reproductive health and developmental origin of cerebrovascular diseases.

A Comparative Study of Transcranial Color-Coded Doppler (TCCD) and Transcranial Doppler (TCD) Ultrasonography Techniques in Assessing the Intracranial Cerebral Arteries Haemodynamics

Cerebrovascular disease (CVD) poses a major public health and socio-economic burden worldwide due to its high morbidity and mortality rates. Accurate assessment of cerebral arteries' haemodynamic plays a crucial role in the diagnosis and treatment management of CVD. The study compared a non-imaging transcranial Doppler ultrasound (TCD) and transcranial color-coded Doppler ultrasound (with (cTCCD) and without (ncTCCD)) angle correction in quantifying middle cerebral arteries (MCAs) haemodynamic parameters. A cross-sectional study involving 50 healthy adults aged ≥ 18 years was conducted. The bilateral MCAs were insonated via three trans-temporal windows (TTWs-anterior, middle, and posterior) using TCD, cTCCD, and ncTCCD techniques. The MCA peak systolic velocity (PSV) and mean flow velocity (MFV) were recorded at proximal and distal imaging depths that could be visualised on TCCD with a detectable spectral waveform. A total of 152 measurements were recorded in 41 (82%) subjects with at least one-sided open TTW across the three techniques. The mean PSVs measured using TCD, ncTCCD, and cTCCD were 83 ± 18 cm/s, 81 ± 19 cm/s, and 93 ± 21 cm/s, respectively. There was no significant difference in PSV between TCD and ncTCCD (bias = 2 cm/s, p = 1.000), whereas cTCCD yielded a significantly higher PSV than TCD and ncTCCD (bias = -10 cm/s, p < 0.001; bias = -12 cm/s, p ≤ 0.001, respectively). The bias in MFV between TCD and ncTCCD techniques was (bias = -0.5 cm/s; p = 1.000), whereas cTCCD demonstrated a higher MFV compared to TCD and ncTCCD (bias = -8 cm/s, p < 0.001; bias = -8 cm/s, p ≤ 0.001, respectively). TCCD is a practically applicable imaging technique in assessing MCA blood flow velocities. cTCCD is more accurate and tends to give higher MCA blood flow velocities than non-imaging TCD and ncTCCD techniques. ncTCCD is comparable to non-imaging TCD and should be considered in clinical cases where using both TCD and TCCD measurements is needed.

Multiple dissecting intracranial and extracranial aneurysms in rheumatoid arthritis: a rare case

A 52 year old female with a history of rheumatoid arthritis (RA) and persistently raised levels of serum rheumatoid factor and cyclic citrunillated peptide, presented with dissecting aneurysms at the right internal carotid artery, and intact aneurysms at the supraclinoid segment and opening of the right opthalmic artery. Coil embolization was performed. The patient developed an ischaemic stroke two days later.Intra and extra-cranial large vessel aneurysms in RA have rarely been reported in the literature. RA patients with persistent systemic inflammation are at increased risk of developing vascular complications and ischaemic stroke. Here, high levels of tissue-deposited immune complexes may have resulted in cerebral artery vasculopathy. Risk stratification for the development of vascular complications, including cranial aneurysms and ischaemic stroke, in RA patients with poorly controlled systemic inflammation, is important; especially when we consider the neurological sequelae associated with dissecting cerebral aneurysms, cerebral infarction and surgical intervention.

Proteomic mapping reveals dysregulated angiogenesis in the cerebral arteries of rats with early-onset hypertension

Hypertension is associated with the presence of vascular abnormalities, including remodeling and rarefaction. These processes play an important role in cerebrovascular disease development; however, the mechanistic changes leading to these diseases are not well characterized. Using data-independent acquisition-based mass spectrometry analysis, here we determined the protein changes in cerebral arteries in pre- and early-onset hypertension from the spontaneously hypertensive rat (SHR), a model that resembles essential hypertension in humans. Our analysis identified 125 proteins with expression levels that were significantly upregulated or downregulated in 12-week-old spontaneously hypertensive rats compared to normotensive Wistar Kyoto rats. Using an angiogenesis enrichment analysis, we further identified a critical imbalance in angiogenic proteins that promoted an anti-angiogenic profile in cerebral arteries at early onset of hypertension. In a comparison to previously published data, we demonstrate that this angiogenic imbalance is not present in mesenteric and renal arteries from age-matched SHRs. Finally, we identified two proteins (Fbln5 and Cdh13), whose expression levels were critically altered in cerebral arteries compared to the other arterial beds. The observation of an angiogenic imbalance in cerebral arteries from the SHR reveals critical protein changes in the cerebrovasculature at the early onset of hypertension and provides novel insights into the early pathology of cerebrovascular disease.

Alcohol and pregnenolone interaction on cerebral arteries through targeting of vascular smooth muscle Ca2+- and voltage-gated K+ channels of big conductance

Despite the significant number of people who may be taking pregnenolone supplements while drinking alcohol (ethanol), the widely documented cerebrovascular actions of pregnenolone and ethanol, and the critical dependence of cerebrovascular function on cerebral artery diameter, there are no studies addressing the effect of pregnenolone + ethanol in combination on cerebral artery diameter. We investigated this by evaluating the effect of this combination on middle cerebral artery diameter in male and female C57BL/6J mice, both in vivo and in vitro. The use of de-endothelialized, in vitro pressurized middle cerebral artery segments allowed us to conduct a concentration-response study of constriction induced by pregnenolone ± ethanol, in which drug action could be evaluated independently of circulating and endothelial factors. In both male and female animals, pregnenolone at lower concentrations (≤1 μM) was found to synergize with 50 mM ethanol to cause vasoconstriction. In both sexes, this synergism was lost as one or both vasoconstrictors approached their maximally effective concentrations (75 mM and 10 μM for ethanol and pregnenolone, respectively), whether this was evaluated in vitro or in vivo using a cranial window. Vasoconstriction by pregnenolone + ethanol was abolished by 1 μM paxilline, indicating BK channel involvement. Moreover, cell-free recordings of BK channel activity in cerebral artery myocyte membranes showed that 10 μM pregnenolone and pregnenolone +50 mM ethanol reduced channel activity to an identical extent, suggesting that these drugs inhibit cerebrovascular BK channels via a common mechanism or mechanisms. Indeed, pregnenolone was found to disrupt allosteric coupling to C a 2 + -driven gating, as previously reported for ethanol.

Effects of Path-Finding Algorithms on the Labeling of the Centerlines of Circle of Willis Arteries

Quantitative analysis of intracranial vessel segments typically requires the identification of the vessels' centerlines, and a path-finding algorithm can be used to automatically detect vessel segments' centerlines. This study compared the performance of path-finding algorithms for vessel labeling. Three-dimensional (3D) time-of-flight magnetic resonance angiography (MRA) images from the publicly available dataset were considered for this study. After manual annotations of the endpoints of each vessel segment, three path-finding methods were compared: (Method 1) depth-first search algorithm, (Method 2) Dijkstra's algorithm, and (Method 3) A* algorithm. The rate of correctly found paths was quantified and compared among the three methods in each segment of the circle of Willis arteries. In the analysis of 840 vessel segments, Method 2 showed the highest accuracy (97.1%) of correctly found paths, while Method 1 and 3 showed an accuracy of 83.5% and 96.1%, respectively. The AComm artery was highly inaccurately identified in Method 1, with an accuracy of 43.2%. Incorrect paths by Method 2 were noted in the R-ICA, L-ICA, and R-PCA-P1 segments. The Dijkstra and A* algorithms showed similar accuracy in path-finding, and they were comparable in the speed of path-finding in the circle of Willis arterial segments.

Mapping the branching pattern of the middle cerebral artery in the camel (Camelus dromedarius): a comprehensive anatomical analysis

The complex branching structure of the middle cerebral artery serves as a crucial component in the blood supply to the cerebral cortex, playing a key role in sustaining brain function and overall neurological health in mammals. A thorough understanding of the branching structure of the middle cerebral artery is required for the advancement of veterinary medicine and neuroscience research. In this study, we provide the first comprehensive anatomical analysis of the branching structure of the middle cerebral artery (MCA) in the dromedary brain. To date, no study has examined the MCA branches in dromedaries. By examining 80 cerebral hemispheres from freshly slaughtered male dromedary camels aged 2-6  years, we aimed to explain the origin, course, and branching patterns of the MCA in the dromedary camel. Advanced casting techniques using colored latex, epoxy paint, and liquid plastic have been used to create precise renderings of the MCA structure. Our findings revealed that the MCA is the principal branch of the rostral cerebral artery and serves as the primary blood supply to the telencephalon in dromedaries. The main trunk of the MCA splits into several cortical branches, each supplying blood to a specific cerebral hemisphere. These branches comprise the rostral and caudal olfactory arteries; orbital artery; superior, middle, and inferior frontal arteries; rostral, middle, and caudal parietal arteries; and dorsal, middle, and ventral temporal arteries. This groundbreaking work considerably advances our understanding of the dromedary cerebrovascular system by providing insightful information on the anatomy and topography of the MCA. Our findings open new avenues for advancements in veterinary medicine and neuroscience research, with potential applications in the diagnosis and treatment of neurological disorders in dromedary camels. Furthermore, understanding the unique branching pattern of the MCA may have implications for comparative neuroanatomy and the evolution of cerebrovascular systems across species.

Hypertension Correlates With Stronger Blood Flow Pulsatility in Small Perforating Cerebral Arteries Assessed With 7 Tesla Magnetic Resonance Imaging

BACKGROUND

Hypertension alters the structure and function of cerebral blood vessels, and is an important risk factor for stroke and cerebral small vessel disease (cSVD). However, the pathophysiological process is not yet well understood. This study aimed to investigate the relationship between the pulsatility measures in small perforating arteries and hypertension, since hypertension-induced arterial stiffening may lead to a higher blood flow pulsatility and lower damping.

METHODS

We examined 28 patients with essential hypertension and 25 age- and sex-matched healthy controls (mean age: 63.4, range: 43-81 years, 26 males). Blood flow velocity waveforms were acquired in the lenticulostriate arteries (LSAs) and the middle cerebral artery using phase-contrast MRI at 7 Tesla. Several cSVD markers were scored. The velocity and pulsatility measures were compared between the hypertensives and controls.

RESULTS

A higher pulsatility index (PI) in the LSAs and a lower damping factor (DF) was found in the hypertensive compared to the normotensive group (P=0.015, P=0.015, respectively), but no association was found for the PI in the middle cerebral artery. Higher systolic and mean arterial pressures were associated with higher PI in the LSA and DF. For diastolic blood pressure, only an association with a lower DF was found. Adjusting for cSVD score did not alter these relationships.

CONCLUSIONS

This study shows a higher PI in the LSAs and a lower DF in subjects with hypertension, independent of cSVD presence. This supports the hypothesis that hypertension-induced arterial remodeling may alter the intracerebral blood flow velocity profiles, which could eventually contribute to cerebral tissue damage.

REGISTRATION

URL: https://trialsearch.who.int/; Unique identifier: NL7537 and NL8798.

Effect of Chronically Suppressed Plasma Angiotensin II on Regulation of the CYP4A/20-HETE Pathway in the Dahl Salt-Sensitive Rat

In Dahl salt-sensitive (SS) rats, impaired vascular relaxation can be restored by: (1) minipump infusion of a low (sub-pressor) dose of angiotensin II (ANG II) to restore physiological levels of plasma ANG II, (2) inhibition of 20-HETE production, and (3) introgression of a normally functioning renin allele from the Brown Norway rat (SS-13^BN consomic rat). Unlike SS rats, SS-13^BN rats have normal levels of ANG II on a normal-salt diet and suppressed ANG II on a high-salt (HS) diet. This study tested whether chronically low ANG II levels in SS rats upregulate cytochrome P450-4A (CYP4A) increasing the production of the vasoconstrictor 20-HETE. Although salt-induced suppression of ANG II levels increased reactive oxygen species (ROS) in basilar arteries from SS-13^BN rats in previous studies, this study showed no change in vascular 20-HETE levels in response to ANGII suppression. CYP4A inhibition significantly reduced vascular ROS levels and restored endothelium-dependent relaxation in response to acetylcholine in the middle cerebral artery (MCA) of SS rats and HS-fed SS-13^BN rats. These data demonstrate that both the renin-angiotensin system and the CYP4A/20-HETE pathway play a direct role in the vascular dysfunction of the Dahl SS rat but are independent of each other, even though they may both contribute to vascular dysfunction through ROS production.

Arterial circle of the brain in the common wildebeest (Connochaetes taurinus)

The main aim of this study was to analyze the arterial circle of the brain and rostral epidural rete mirabile in specimens of the common wildebeest (Connochaetes taurinus). The arterial circle of the brain is a circulatory anastomosis that supplies blood to particular lobes of the brain and surrounding structures. The study was conducted on male and female adults (n = 12) by bilateral injection of an acetone solution of vinyl superchloride or latex LBS3060, which resulted in a cast of arteries of the head and encephalic base. We describe the exact structure of the arterial circle of the brain and rostral epidural rete mirabile. The shape of the arterial circle of the brain in the common wildebeest is heart-shaped, as in other Bovidae. It is formed by bilateral rostral cerebral arteries, caudal communicating arteries, and the basilar artery, with a general pattern of vessels forming and branching off from the arterial circle of the brain, as described in other ruminants. The rostral cerebral and caudal communicating arteries emerge from an intracranial segment of the internal carotid artery, which in turn arises from vessels of the rostral epidural rete mirabile. This structure, well developed in the examined individuals, has mechanisms underlying selective cooling of the brain, protecting animals from hyperthermia, and affecting body water balance.

The Stroke Preclinical Assessment Network: Rationale, Design, Feasibility, and Stage 1 Results

Cerebral ischemia and reperfusion initiate cellular events in brain that lead to neurological disability. Investigating these cellular events provides ample targets for developing new treatments. Despite considerable work, no such therapy has translated into successful stroke treatment. Among other issues-such as incomplete mechanistic knowledge and faulty clinical trial design-a key contributor to prior translational failures may be insufficient scientific rigor during preclinical assessment: nonblinded outcome assessment; missing randomization; inappropriate sample sizes; and preclinical assessments in young male animals that ignore relevant biological variables, such as age, sex, and relevant comorbid diseases. Promising results are rarely replicated in multiple laboratories. We sought to address some of these issues with rigorous assessment of candidate treatments across 6 independent research laboratories. The Stroke Preclinical Assessment Network (SPAN) implements state-of-the-art experimental design to test the hypothesis that rigorous preclinical assessment can successfully reduce or eliminate common sources of bias in choosing treatments for evaluation in clinical studies. SPAN is a randomized, placebo-controlled, blinded, multilaboratory trial using a multi-arm multi-stage protocol to select one or more putative stroke treatments with an implied high likelihood of success in human clinical stroke trials. The first stage of SPAN implemented procedural standardization and experimental rigor. All participating research laboratories performed middle cerebral artery occlusion surgery adhering to a common protocol and rapidly enrolled 913 mice in the first of 4 planned stages with excellent protocol adherence, remarkable data completion and low rates of subject loss. SPAN stage 1 successfully implemented treatment masking, randomization, prerandomization inclusion/exclusion criteria, and blinded assessment to exclude bias. Our data suggest that a large, multilaboratory, preclinical assessment effort to reduce known sources of bias is feasible and practical. Subsequent SPAN stages will evaluate candidate treatments for potential success in future stroke clinical trials using aged animals and animals with comorbid conditions.

High-Resolution Vessel Wall MR Imaging in Diagnosis and Length Measurement of Cerebral Arterial Thrombosis: A Feasibility Study

BACKGROUND

Detecting and measuring intraluminal thrombus has prognostic and therapeutic implications for stroke patients.

PURPOSE

To investigate the feasibility of 3D isotropic high-resolution T1w-CUBE imaging to detect and measure intraluminal thrombus in stroke patients.

STUDY TYPE

Retrospective.

SUBJECTS

A total of 93 patients with acute (N = 39) and subacute (N = 54) stroke.

FIELD STRENGTH/SEQUENCE

A 3.0 T/spin-echo echo-planar diffusion-weighted imaging (DWI), high-resolution T1w-CUBE imaging and 3D flow compensated gradient-echo susceptibility-weighted imaging (SWI).

ASSESSMENT

Data assessment was performed by three neuroradiologists with 11, 13, and 20 years of clinical experience. The accuracy of T1W-CUBE and SWI in diagnosing thrombosis was compared by using digital subtraction angiography (DSA) as the reference. For thrombus length measurement, the image quality of proximal and distal thrombus of T1w-CUBE images was first evaluated with a 4-point rating system. Then, the proximal and distal positions to lesions were determined on T1w-CUBE images and compared with those from DSA acquired during endovascular reperfusion therapy. If comparable both locations were found between CUBE and DSA, CUBE imaging can thus be considered for accurate measurement of thrombus length.

STATISTICAL TESTS

Fleiss' Kappa; the area under the receiver operating characteristic (ROC) curve (AUC); Pearson's chi-squared test with Yates' continuity correction.

RESULTS

Moderate-to-good interobserver agreements were validated with all Kappa coefficients higher than 0.40 in thrombus diagnosis and measurement. CUBE imaging showed higher clinical efficacy than SWI (AUC: 0.966 vs. 0.850) in thrombus diagnosis. Additionally, high quality of CUBE imaging was confirmed with 3 or 4 points rated by all three observers. Compared to intraoperative DSA, T1w CUBE showed consistent proximal and distal positions of thrombi in 16 of the 18 patients, validating the accuracy of T1w-CUBE in measuring thrombus length.

DATA CONCLUSION

T1w-CUBE imaging has potential to facilitate diagnosis and measurement of intraluminal thrombus.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: Stage 2.

CircOGDH Is a Penumbra Biomarker and Therapeutic Target in Acute Ischemic Stroke

BACKGROUND

Acute ischemic stroke (AIS) is a leading cause of disability and mortality worldwide. Prediction of penumbra existence after AIS is crucial for making decision on reperfusion therapy. Yet a fast, inexpensive, simple, and noninvasive predictive biomarker for the poststroke penumbra with clinical translational potential is still lacking. We aim to investigate whether the CircOGDH (circular RNA derived from oxoglutarate dehydrogenase) is a potential biomarker for penumbra in patients with AIS and its role in ischemic neuronal damage.

METHODS

CircOGDH was screened from penumbra of middle cerebral artery occlusion mice and was assessed in plasma of patients with AIS by quantitative polymerase chain reaction. Magnetic resonance imaging was used to examine the penumbra volumes. CircOGDH interacted with miR-5112 in primary cortical neurons was detected by fluorescence in situ hybridization, RNA immunoprecipitation, and luciferase reporter assay. ADV-mediated CircOGDH knockdown ameliorated neuronal apoptosis induced by COL4A4 (Gallus collagen, type VI, alpha VI) overexpression. Transmission electron microscope, nanoparticle tracking analysis, and Western blot were performed to confirm exosomes.

RESULTS

CircOGDH expression was dramatically and selectively upregulated in the penumbra tissue of middle cerebral artery occlusion mice and in the plasma of 45 patients with AIS showing a 54-fold enhancement versus noncerebrovascular disease controls. Partial regression analysis revealed that CircOGDH expression was positively correlated with the size of penumbra in patients with AIS. Sequestering of miR-5112 by CircOGDH enhanced COL4A4 expression to elevate neuron damage. Additionally, knockdown of CircOGDH significantly enhanced neuronal cell viability under ischemic conditions. Furthermore, the expression of CircOGDH in brain tissue was closely related to that in the serum of middle cerebral artery occlusion mice. Finally, we found that CircOGDH was highly expressed in plasma exosomes of patients with AIS compared with those in noncerebrovascular disease individuals.

CONCLUSIONS

These results demonstrate that CircOGDH is a potential therapeutic target for regulating ischemia neuronal viability, and is enriched in neuron-derived exosomes in the peripheral blood, exhibiting a predictive biomarker of penumbra in patients with AIS.

Measuring Arterial Pulsatility With Dynamic Inflow Magnitude Contrast

The pulsatility of blood flow through cerebral arteries is clinically important, as it is intrinsically associated with cerebrovascular health. In this study we outline a new MRI approach to measuring the real-time pulsatile flow in cerebral arteries, which is based on the inflow phenomenon associated with fast gradient-recalled-echo acquisitions. Unlike traditional phase-contrast techniques, this new method, which we dub dynamic inflow magnitude contrast (DIMAC), does not require velocity-encoding gradients as sensitivity to flow velocity is derived purely from the inflow effect. We achieved this using a highly accelerated single slice EPI acquisition with a very short TR (15 ms) and a 90° flip angle, thus maximizing inflow contrast. We simulate the spoiled GRE signal in the presence of large arteries and perform a sensitivity analysis. The sensitivity analysis demonstrates that in the regime of high inflow contrast, DIMAC shows much greater sensitivity to flow velocity over blood volume changes. We support this theoretical prediction with in-vivo data collected in two separate experiments designed to demonstrate the utility of the DIMAC signal contrast. We perform a hypercapnia challenge experiment in order to experimentally modulate arterial tone within subjects, and thus modulate the arterial pulsatile flow waveform. We also perform a thigh-cuff release challenge, designed to induce a transient drop in blood pressure, and demonstrate that the continuous DIMAC signal captures the complex transient change in the pulsatile and non-pulsatile components of flow. In summary, this study proposes a new role for a well-established source of MR image contrast and demonstrates its potential for measuring both steady-state and dynamic changes in arterial tone.

Pathological Investigations of Intracranial Atherosclerosis Using Multiple Hypercholesterolemic Rabbit Models

BACKGROUND

Intracranial atherosclerosis (ICAS) is one of the most common causes of ischemic stroke, but there are few animal models that can recapitulate its pathological features. In this study, we examined ICAS pathological features and anatomic distributions using three types of hyperlipidemic rabbit models. We also investigated the effect of different lipoprotein profiles and hypertension on ICAS.

MATERIALS AND METHODS

We examined Watanabe heritable hyperlipidemic (WHHL) rabbits, apoE knockout (KO) rabbits and wild-type rabbits (WT) fed a cholesterol diet, in addition to WT rabbits fed a standard diet as a control. The whole brain was dissected and embedded in paraffin. Serial sections were stained with either hematoxylin/eosin or elastica van Gieson, or immunohistochemically stained with monoclonal antibodies against macrophages and smooth muscle cells. We investigated (1) the presence of cerebral atherosclerosis; (2) the lesion locations in the cerebral arteries; (3) the degree of lumen stenosis; (4) pathological features and cellular components of the lesions in these rabbits; and (5) whether hypertension affects ICAS.

RESULTS

ICAS was detected in apoE and WHHL rabbits, but not in WT rabbits. Compared with apoE KO rabbits, WHHL rabbits had greater ICAS. The lesions of cerebral atherosclerosis were mainly distributed at the bifurcations of the posterior cerebral artery, basilar artery and vertebral artery, and they were basically characterized by smooth muscle cells and extracellular matrix with few macrophages. The extent of the ICAS in WHHL rabbits was significantly increased by hypertension.

CONCLUSIONS

ICAS was detected in WHHL and apoE KO rabbits, and occurred in specific locations in the cerebral arteries. Hypertension promotes the development of ICAS in the setting of hypercholesterolemia.

Associations of Monocytes and the Monocyte/High-Density Lipoprotein Ratio With Extracranial and Intracranial Atherosclerotic Stenosis

Background: Although the monocyte/high-density lipoprotein ratio (MHR) has been shown to be a potential marker of inflammatory of cardiovascular and cerebrovascular diseases, there are few studies on its relationships with the degree of intracranial and extracranial atherosclerotic stenosis and the stenosis distribution.

Methods: In total, 271 patients were admitted for digital subtraction angiography (DSA) examination and were classified into a non-stenosis group and a stenosis group. (1) The two groups were compared and the arteries were categorized according to the degree of intracranial or extracranial atherosclerotic stenosis (if ≥two branches were stenotic, the artery with the most severe stenosis was used). (2) Clinical baseline data and laboratory indexes of patients grouped according to stenosis location (intracranial vs. extracranial) were collected.

Results: (1) MHR × 10² [odds ratio (OR) = 1.119, p < 0.001], age (OR = 1.057, p = 0.007), and lymphocyte count (OR = 0.273, p = 0.002) significantly affected the presence of cerebral atherosclerotic stenosis, with an MHR area of 0.82 under the receiver operating characteristic (ROC) curve (AUC) and an optimal diagnostic value of 0.486. Analyses of the moderate, mild, and severe stenosis groups showed that MHR × 10² (OR = 1.07, p < 0.001) significantly affected the severity of stenosis in patients. (2) In the analysis of stenosis at different sites, the rate of extracranial artery stenosis in patients who smoked (OR = 3.86, p = 0.023) and had a reduced lymphocyte level (OR = 0.202, p = 0.001) was remarkably greater than that in patients who smoked (OR = 3.86, p = 0.023). With increasing age, the rate of extracranial artery stenosis raised sharply. With the increase in the MHR level, the stenosis rate of each group was highly greater than that of the non-stenosis group.

Conclusion: The MHR has a predictive value for the diagnosis of extracranial and intracranial atherosclerotic stenosis and is correlated with the degree and distribution of stenosis.

Trial Registration: Clinical Medical Research Center Project of Qinghai Province (2017-SF-L1). Qinghai Provincial Health Commission Project (Grant #2020-wjzdx-29).

The emerging significance of circadian rhythmicity in microvascular resistance

The Earth's rotation generates environmental oscillations (e.g., in light and temperature) that have imposed unique evolutionary pressures over millions of years. Consequently, the circadian clock, a ubiquitously expressed molecular system that aligns cellular function to these environmental cues, has become an integral component of our physiology. The resulting functional rhythms optimize and economize physiological performance: perturbing these rhythms, therefore, is frequently deleterious. This perspective article focuses on circadian rhythms in resistance artery myogenic reactivity, a key mechanism governing tissue perfusion, total peripheral resistance and systemic blood pressure. Emerging evidence suggests that myogenic reactivity rhythms are locally generated in a microvascular bed-specific manner at the level of smooth muscle cells. This implies that there is a distinct interface between the molecular clock and the signalling pathways underlying myogenic reactivity in the microvascular beds of different organs. By understanding the precise nature of these molecular links, it may become possible to therapeutically manipulate microvascular tone in an organ-specific manner. This raises the prospect that interventions for vascular pathologies that are challenging to treat, such as hypertension and brain malperfusion, can be significantly improved.

Feasibility of Ultra-High Resolution Supra-Aortic CT Angiography: An Assessment of Diagnostic Image Quality and Radiation Dose

(1) Background: To evaluate diagnostic image quality and radiation exposure of ultra-high resolution cerebral Computed-Tomography (CT) angiography (CTA) obtained on an ultra-high resolution computed tomography scanner (UHR-CT). (2) Methods: Fifty consecutive patients with UHR-CTA were enrolled. Image reconstruction was processed with a 1024 × 1024 matrix and a slice thickness of 0.25 mm. Quantitative analyses comprising CT values, contrast-noise ratio (CNR) and signal-to-noise ratio (SNR) were performed. Subjective assessment of image quality, vessel contrast, noise, artefacts and delineation of different sized vessels were assessed by two readers on a 4-point scale. Radiation exposure was determined. (3) Results: Hounsfield values (ACI: 461.8 ± 16.8 HU; MCA: 406.1 ± 24.2 HU; BA: 412.2 ± 22.3 HU), SNR (ACI: 35.4 ± 13.1; MCA: 20.8 ± 12.4; BA: 23.7 ± 12.9) and CNR (ACI: 48.7 ± 21; MCA: 63.9 ± 26.9; BA: 48.1 ± 21.4) were remarkably high in all segments. Subjective analysis by two raters (fair agreement, k = 0.26) indicated excellent image qualities (image quality = 4; contrast = 4; noise = 3; artefacts = 4).Our analysis revealed a notably high traceability of the cerebral perforators (3 Points). Radiation exposure was at moderate dose levels (effective dose = 2.5 ± 0.6mSv). (4) Conclusions: UHR-CTA generates highly valuable image qualities that allow the depiction of vessels including cerebral perforators at acceptable dose levels. The UHR-CTA may therefore enhance the detection of small cerebral pathologies and may improve interpretability, especially in settings where high image qualities are crucial for the diagnostic accuracy.

Cerebral white matter vasculature: still uncharted?

White matter vasculature plays a major role in the pathophysiology of permanent neurological deficits following a stroke or progressive cognitive alteration related to small vessel disease. Thus, knowledge of the complex vascularization and functional aspects of the deep white matter territories is paramount to comprehend clinical manifestations of brain ischemia. This review provides a structured presentation of the existing knowledge of the vascularization of the human cerebral white matter from seminal historical studies to the current literature. First, we revisit the highlights of prenatal development of the endoparenchymal telencephalic vascular system that are crucial for the understanding of vessel organization in the adult. Second, we reveal the tangled history of debates on the existence, clinical significance, and physiological role of leptomeningeal anastomoses. Then, we present how conceptions on white matter vascularization transitioned from the mixed ventriculopetal/ventriculofugal theory, in which a low-flow area was interposed in between concurrent arterial flows, to the purely ventriculopetal theory. The latter model explains variable white matter sensitivity to ischemia by various organizations of ventriculopetal vessel terminals having different origin/length properties and interconnection patterns. Next, arteries supplying primarily the white matter are described according to their length and overall structure. Furthermore, the known distribution territories, to date, are studied in relation to primary anatomical structures of the human cerebral white matter, emphasizing the sparsity of the "ground-truth" data available in the literature. Finally, the implications for both large vessel occlusion and chronic small vessel disease are discussed, as well as the insights from neuroimaging. All things considered, we identify the need for further research on deep white matter vascularization, especially regarding the arterial supply of white matter fiber tracts.

Heterogeneity between proximal and distal aspects of occlusive thrombi on pretreatment imaging in acute ischemic stroke

BACKGROUND

The potential heterogeneity in occlusive thrombi caused by in situ propagation by secondary thrombosis after embolic occlusion could obscure the characteristics of original thrombi, preventing the clarification of a specific thrombus signature for the etiology of ischemic stroke. We aimed to investigate the heterogeneity of occlusive thrombi by pretreatment imaging.

METHODS

Among consecutive stroke patients with acute embolic anterior circulation large vessel occlusion treated with thrombectomy, we retrospectively reviewed 104 patients with visible occlusive thrombi on pretreatment non-contrast computed tomography admitted from January 2015 to December 2018. A region of interest was set on the whole thrombus on non-contrast computed tomography under the guidance of computed tomography angiography. The region of interest was divided equally into the proximal and distal segments and the difference in Hounsfield unit densities between the two segments was calculated.

RESULTS

Hounsfield unit density in the proximal segment was higher than that in the distal segment (mean difference 4.45; p < 0.001), regardless of stroke subtypes. On multivariate analysis, thrombus length was positively correlated (β = 0.25; p < 0.001) and time from last-known-well to imaging was inversely correlated (β = -0.0041; p = 0.002) with the difference in Hounsfield unit densities between the proximal and distal segments.

CONCLUSIONS

The difference in density between the proximal and distal segments increased as thrombi became longer and decreased as thrombi became older after embolic occlusion. This time/length-dependent thrombus heterogeneity between the two segments is suggestive of secondary thrombosis initially occurring on the proximal side of the occlusion.

Effects of Levodopa Therapy on Cerebral Arteries and Perfusion in Parkinson's Disease Patients

BACKGROUND

Levodopa is the most-commonly used therapy for Parkinson's Disease (PD). Imaging findings show increased cerebral blood flow (CBF) response to levodopa, but the artery morphological change is less studied.

PURPOSE

To investigate the effect of levodopa on cerebral arteries and CBF.

STUDY TYPE

Prospective.

POPULATION

57 PD patients (56 ± 10 years, 26 males) and 17 age-matched healthy controls (AMC, 57 ± 9 years, 9 males) were scanned at baseline (OFF). Patients were rescanned 50 minutes after taking levodopa (ON).

FIELD STRENGTH AND SEQUENCE

3 T; Simultaneous noncontrast angiography intraplaque imaging (SNAP) based on turbo field echo; Pseudo-continuous arterial spin labeling (PCASL) based on echo-planner imaging.

ASSESSMENT

The Unified Parkinson's Disease Rating Scale (UPDRS-III) was used to assess the disease severity. Length and radius of arteries were measured from SNAP images. CBF was calculated from PCASL images globally and regionally.

STATISTICAL TESTS

Mann Whitney U tests were conducted in comparing PD vs. AMC. Wilcoxon matched-pairs signed rank tests were used in comparing OFF vs. ON, and the more-affected vs. the less-affected hemisphere in PD. Linear regressions were performed to test the correlations of neuroimaging findings with behavioral changes. Significance threshold was P < 0.05 with Bonferroni correction.

RESULTS

PD patients were identified with significantly lower CBF (PD OFF Mean = 40.15 ± 5.99, AMC Mean = 43.48 ± 6.21 mL/100 g/min) and shortened total artery length (PD OFF Mean = 5851.07 ± 1393.45, AMC Mean = 7479.16 ± 1335.93 mm). Levodopa elevated CBF of PD brains (PD ON Mean = 41.48 ± 6.32 mL/100 g/min) and expanded radius of proximal arteries. Artery radius change significantly correlated with CBF change in corresponding territories (r = 0.559 for Internal Carotid Arteries, r = 0.448 for Basilar Artery, and r = 0.464 for Middle Cerebral Artery M1). Global CBF significantly related to UPDRS-III (r = -0.391) post-levodopa.

DATA CONCLUSION

Levodopa can increase CBF by dilating proximal arteries.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 4.

Deep Cerebral Perforators: Anatomical Distribution and Clinical Symptoms: An Overview

The anatomic distribution of the deep cerebral perforators is considered either a given or subject to enormous variability. Most published overviews on this topic only report findings from a limited number of anatomic dissections, and no attempt has been made to date to provide a comprehensive overview of all published data. A comprehensive literature search was performed on MEDLINE, Embase, and Google Scholar with the help of an information specialist. Three types of studies were included: (1) articles that described the anatomy and distribution territories of perforator groups arising from the arteries of the circle of Willis; (2) studies that evaluated the anatomy of the deep cerebral perforators using imaging techniques; and (3) studies that evaluated either microsurgically or radiologically confirmed perforator occlusion and reported the (magnetic resonance imaging-confirmed) distribution territory of the infarction together with a description of the clinical symptoms associated as a result of the infarction. A total of 2715 articles were screened and 53 were included. Of these, 40 dealt with the anatomic and imaging anatomy of perforator groups (37 reported results of dissections and 3 results of imaging studies), with a total of 2421 hemispheres investigated. Another 13 articles with 680 patients were included that evaluated perforator infarction territories. The deep cerebral perforator distribution shows large variability with poor concordance rates among reported studies, with the exception of the posterior communicating and anterior choroidal artery perforators. Despite the assumption that cerebral perforator anatomy is a given, studies show large variability in the anatomic distribution of various perforator groups. Perforator anatomy and relationships between perforator groups, as well as potential collateral circulation in these territories should be prioritized as a research topic in cerebrovascular disease in the near future.

Activation of the Central Renin-Angiotensin System Causes Local Cerebrovascular Dysfunction

[Figure: see text].

Comparison of Hemodynamic Visualization in Cerebral Arteries: Can Magnetic Resonance Imaging Replace Computational Fluid Dynamics?

A multimodality approach was applied using four-dimensional flow magnetic resonance imaging (4D flow MRI), time-of-flight magnetic resonance angiography (TOF-MRA) signal intensity gradient (SIG), and computational fluid dynamics (CFD) to investigate the 3D blood flow characteristics and wall shear stress (WSS) of the cerebral arteries. TOF-MRA and 4D flow MRI were performed on the major cerebral arteries in 16 healthy volunteers (mean age 34.7 ± 7.6 years). The flow rate measured with 4D flow MRI in the internal carotid artery, middle cerebral artery, and anterior cerebral artery were 3.8, 2.5, and 1.2 mL/s, respectively. The 3D blood flow pattern obtained through CFD and 4D flow MRI on the cerebral arteries showed reasonable consensus. CFD delivered much greater resolution than 4D flow MRI. TOF-MRA SIG and CFD WSS of the major cerebral arteries showed reasonable consensus with the locations where the WSS was relatively high. However, the visualizations were very different between TOF-MRA SIG and CFD WSS at the internal carotid artery bifurcations, the anterior cerebral arteries, and the anterior communicating arteries. 4D flow MRI, TOF-MRA SIG, and CFD are complementary methods that can provide additional insight into the hemodynamics of the human cerebral artery.

Maternal Undernutrition Modulates Neonatal Rat Cerebrovascular Structure, Function, and Vulnerability to Mild Hypoxic-Ischemic Injury via Corticosteroid-Dependent and -Independent Mechanisms

The present study explored the hypothesis that an adverse intrauterine environment caused by maternal undernutrition (MUN) acted through corticosteroid-dependent and -independent mechanisms to program lasting functional changes in the neonatal cerebrovasculature and vulnerability to mild hypoxic-ischemic (HI) injury. From day 10 of gestation until term, MUN and MUN-metyrapone (MUN-MET) group rats consumed a diet restricted to 50% of calories consumed by a pair-fed control; and on gestational day 11 through term, MUN-MET groups received drinking water containing MET (0.5 mg/mL), a corticosteroid synthesis inhibitor. P9/P10 pups underwent unilateral carotid ligation followed 24 h later by 1.5 h exposure to 8% oxygen (HI treatment). An ELISA quantified MUN-, MET-, and HI-induced changes in circulating levels of corticosterone. In P11/P12 pups, MUN programming promoted contractile differentiation in cerebrovascular smooth muscle as determined by confocal microscopy, modulated calcium-dependent contractility as revealed by cerebral artery myography, enhanced vasogenic edema formation as indicated by T2 MRI, and worsened neurobehavior MUN unmasked HI-induced improvements in open-field locomotion and in edema resolution, alterations in calcium-dependent contractility and promotion of contractile differentiation. Overall, MUN imposed multiple interdependent effects on cerebrovascular smooth muscle differentiation, contractility, edema formation, flow-metabolism coupling and neurobehavior through pathways that both required, and were independent of, gestational corticosteroids. In light of growing global patterns of food insecurity, the present study emphasizes that infants born from undernourished mothers may experience greater risk for developing neonatal cerebral edema and sensorimotor impairments possibly through programmed changes in neonatal cerebrovascular function.

Conceptualizing conduction as a pliant electrical response: impact of gap junctions and ion channels

Vasomotor responses conduct among resistance arteries to coordinate blood flow delivery pursuant to energetic demand. Conduction is set by the electrical and mechanical properties of vascular cells, the former tied to how gap junctions and ion channels distribute and dissipate charge, respectively. These membrane proteins are subject to modulation; thus, conduction could be viewed as "pliant" to the current regulatory state. This study used in silico approaches to conceptualize electrical pliancy and to illustrate how gap junctional and ion channel properties distinctly impact conduction along a single skeletal muscle artery or a branching cerebrovascular network. Initial simulations revealed how vascular cells encoded with electrotonic properties best reproduced spreading behavior; the endothelium's importance as a charge source and a longitudinal conduit was readily observed. Alterations in gap junctional conductance produced unique electrical fingerprints: 1) decreased endothelial coupling impaired longitudinal but enhanced radial spread, and 2) reduced myoendothelial coupling limited radial but enhanced longitudinal spread. Subsequent simulations illustrated how tuning ion channel activity, e.g., inward rectifying- and voltage-gated K⁺ channels, modified charge dissipation, resting membrane potential, and the spread of the electrical phenomenon. Restricting ion channel tuning to a network subregion then revealed how electrical spread could be locally shaped in accordance with the aggregate changes in membrane resistance. In summary, our analysis frames and reimagines electrical conduction as a pliable process, with subtle regulatory changes to membrane proteins shaping network spread and tissue perfusion.NEW & NOTEWORTHY Conducted vasomotor responses depend on initiation and spread of electrical phenomena along arterial walls and their translation into contractile responses. Using computational approaches, we show how subtle but widespread regulation of gap junctions and ion channels can modulate the range and amplitude of electrical spread. Ion channels are regulated by endocrine and mechanical signals and may differ regionally in networks. Subregional electrical changes are not spatially confined but may affect electrical conduction in neighboring regions.

αCGRP-Induced Changes in Cerebral and Systemic Circulation; A TCD Study

It is known that perivascular application of CGRP induces cerebral vasodilatation. However, it is unclear whether intravenous alfa CGRP (αCGRP) induces changes in cerebral and systemic hemodynamics. Therefore, we studied the influence of an αCGRP intravenous infusion at a rate of 1.5 mcg/min in 20 min on mean arterial velocity in the middle cerebral artery (vm MCA) and in the posterior cerebral artery (vm PCA) in twenty healthy subjects using transcranial Doppler (TCD). We found out that αCGRP decreased vm MCA (p < 0.001), vm PCA (p < 0.001), mean arterial pressure (MAP) (p < 0.001) and end-tidal CO2 (Et-CO2) (p = 0.030). The heart rate (HR) increased during αCGRP infusion (p < 0.001). In addition, we found a positive relationship between Et-CO2 and vm MCA (p = 0.001) as well as vm PCA (p = 0.043). In our view, αCGRP induces changes in cerebral and systemic circulation in healthy volunteers. It might cause vasodilatation of MCA and PCA and a compensatory decrease of Et-CO2 to αCGRP related hemodynamic changes.

Novel Ultrafast Spiral Head MR Angiography Compared to Standard MR and CT Angiography

BACKGROUND AND PURPOSE

Intracranial vessel imaging by time-of-flight MR angiography (TOF-MRA) is one of the most frequently performed investigations in clinical neuroradiology. Particularly in the acute setting, fast imaging is needed for diagnostics, with a sequence ideally depicting even small vessels. The purpose of this study was to compare image and diagnostic quality of a novel ultrashort TOF-MRA sequence accelerated by spiral imaging (TOF-Spiral-short) to a standard TOF-MRA sequence accelerated by compressed sensing (TOF-CS) and to CT angiography (CTA).

METHODS

Forty-one patients (36.6% showing vessel pathologies) who had undergone TOF-CS (acquisition duration: 4 minutes 8 seconds), TOF-Spiral-short (acquisition duration: 51 seconds; spiral imaging [accelerating factor 1.3], decreased field of view [accelerating factor 1.2], and increased voxel size [accelerating factor 3.3]), and CTA were retrospectively evaluated. Assessment of image quality, diagnostic confidence, and quantification of stenosis or aneurysm diameter were performed by two readers.

RESULTS

Image quality at the skull base was slightly reduced with TOF-Spiral-short compared to CTA and TOF-CS (P < .05). Delineation of small intracranial vessels was improved by TOF-Spiral-short compared to CTA (P < .0001). In TOF-Spiral-short, diagnostic confidence was not reduced compared to TOF-CS in patients with vessel pathologies. We observed no significant difference in quantitative pathology assessment between TOF-Spiral-short and the other two modalities. TOF-Spiral-short enabled the correct identification of all vessel pathologies.

CONCLUSIONS

Accelerating TOF-MRA of brain-feeding arteries by a novel ultrashort spiral imaging sequence shows adequate image quality and sufficient diagnostic performance. Thus, TOF-Spiral-short holds potential for fast and reliable diagnostics of vessel pathologies, particularly in the acute setting.

Analysis of posterior circulation diameters depending on age, sex and side by computed tomography angiography

BACKGROUND

Posterior circulation of brain is important because of vital organs' blood supply provided by them. In this study, we evaluate the relationship of posterior circulation measurements with age, gender and side by using computed tomography angiography (CTA) images.

MATERIALS AND METHODS

A total 199 brain CTA examinations were retrospectively analysed for all posterior circulation arteries (vertebral artery, basilar artery, posterior cerebral artery [PCA], superior cerebellar artery [SCA], anterior inferior cerebellar artery, and posterior inferior cerebellar artery [PICA]) to compare the difference based on age, gender and side.

RESULTS

There is no correlation between age and the mean diameters of all vessels (p > 0.05). The mean diameter of left vertebral artery was higher than right vertebral artery in all genders (p = 0.004 for males and p < 0.001 for females). The mean diameter of left SCA and PICA were higher than right SCA and PICA in females (p = 0.032 and p = 0.027, respectively). The mean diameters of basilar, left PCA, left SCA, left vertebral, right PCA, right SCA, right PICA and right vertebral artery were higher in males and that differences were statistically significant (p < 0.001, p = 0.002, p = 0.006, p = 0.004, p = 0.001, p = 0.003, p = 0.002, and p = 0.006, respectively).

CONCLUSIONS

The posterior circulation vessel diameter is not affected by aging. The mean diameters of basilar artery, both PCAs, both SCAs, right PICA, both vertebral arteries were higher in males. The mean diameter of left vertebral artery is higher than that of right vertebral artery in all genders.

Localization of TRPA1 channels and characterization of TRPA1 mediated responses in dural and pial arteries in vivo after intracarotid infusion of Na2S

BACKGROUND

The Transient Receptor Potential Ankyrin 1 (TRPA1) channel might play a role in migraine. However, different mechanisms for this have been suggested. The purpose of our study was to investigate the localization and significance of TRPA1 channels in rat pial and dural arteries.

METHODS

Immunofluorescence microscopy was used to localize TRPA1 channels in dural arteries, pial arteries, dura mater and trigeminal ganglion. The genuine closed cranial window model was used to examine the effect of Na₂S, a donor of the TRPA1 channel opener H₂S, on the diameter of pial and dural arteries. Further, we performed blocking experiments with TRPA1 antagonist HC-030031, calcitonin gene-related peptide (CGRP) receptor antagonist olcegepant and K_Ca3.1 channel blocker TRAM-34.

RESULTS

TRPA1 channels were localized to the endothelium of both dural and pial arteries and in nerve fibers in dura mater. Further, we found TRPA1 expression in the membrane of trigeminal ganglia neuronal cells, some of them also staining for CGRP. Na₂S caused dilation of both dural and pial arteries. In dural arteries, this was inhibited by HC-030031 and olcegepant. In pial arteries, the dilation was inhibited by TRAM-34, suggesting involvement of the K_Ca3.1 channel.

CONCLUSION

Na₂S causes a TRPA1- and CGRP-dependent dilation of dural arteries and a K_Ca3.1 channel-dependent dilation of pial arteries in rats.

Comparative morphology of the internal elastic lamina of cerebral and peripheral arteries

BACKGROUND

Atherosclerosis progresses later and with fewer complicated plaques in cerebral arteries than in peripheral arteries. The internal elastic lamina has been proposed to be important for the migration of smooth muscle cells into the intima during intimal thickening and atherosclerosis.

METHODS

A total of 280 segments were retrieved from 14 autopsy specimens. Five sites were selected for analysis in each case: the middle cerebral artery, basilar artery, coronary artery, iliac artery and renal artery. We investigated the differences in the internal elastic lamina of cerebral and peripheral arteries.

RESULTS

The average thickness of the internal elastic lamina of the cerebral arteries was larger than that of the peripheral arteries in both the early and advanced atherosclerotic plaque groups. Among the cerebral arteries, the basilar arteries had a thicker internal elastic lamina than the middle cerebral arteries. Among the peripheral arteries, the renal arteries had the thickest internal elastic lamina, followed by the iliac arteries and coronary arteries. Atherosclerosis led to a reduction in the thickness of the internal elastic lamina of the basilar, middle cerebral, and renal arteries. The stratification of the internal elastic lamina of iliac arteries significantly affected its measurement. The internal elastic lamina of coronary arteries was not affected by atherosclerosis, but it appeared fragmented.

CONCLUSION

The results suggest that the characteristics of atherosclerotic plaques in cerebral and peripheral arteries may be related to the characteristics of the internal elastic lamina.

Demographic age-related variation in Circle of Willis completeness assessed by digital subtraction angiography

OBJECTIVE:

Incomplete circle of Willis (CoW) configuration is an important risk factor for cerebrovascular pathology, namely aneurysm formation and ischemic stroke. This study was performed to characterize CoW variation using digital subtraction angiography and to identify demographic and physiologic features that may influence the risk of having an incomplete CoW configuration.

MATERIALS AND METHODS:

A retrospective review of 274 patients who underwent cerebral angiography by a single surgeon for any indication was conducted. Each CoW branch was graded as normal, hypoplastic, or aplastic. Univariate and multivariate regression analyses were conducted to assess the impact of age, gender, race, and certain comorbidities on CoW configuration.

RESULTS:

A complete CoW was identified in 37.23% of patients. In univariate analysis, patients <40 years old were more likely to have a complete CoW (odds ratio [OR]: 4.973, 95% confidence interval [CI]: 2.610–9.476, P < 0.001) as were patients <70 years old (OR: 2.849, 95% CI: 1.131–7.194, P < 0.05). Univariate analysis on demographic factors and comorbidities revealed CoW completeness to decrease with hypertension (OR: 0.575, 95% CI: 0.347–0.951, P = 0.031) and diabetes mellitus (OR: 0.368, 95% CI: 0.180–0.754, P = 0.006). Multivariable logistic regression analysis used to assess the impact of age on CoW completeness showed age to be an independent predictor of complete CoW, with an inverse correlation between increasing age and CoW completeness (OR: 0.955, 95% CI: 0.937–0.973, P < 0.001) after controlling for potential confounders including hypertension and diabetes mellitus.

CONCLUSIONS:

CoW configuration shows considerable variation with age; however, further investigation is required to elucidate the full impact of other demographic and vascular risk factors on CoW anatomy.

Differential expression of angiotensin II type 1 receptor subtypes within the cerebral microvasculature

Arteries and arterioles constrict in response to intraluminal pressure to generate myogenic tone, but the molecular nature of the vascular force-sensing mechanism is not fully characterized. Here, we investigated the role of angiotensin II type 1 receptors (AT1Rs) on vascular smooth muscle cells in the development of myogenic tone in cerebral parenchymal arterioles from mice. We found that pretreatment with the AT1R blocker losartan inhibited the development of myogenic tone in these vessels but did not alter the luminal diameter of arterioles with preestablished tone. Rodents express two AT1R isotypes: AT1Ra and AT1Rb. We previously demonstrated that AT1Rb is expressed at much higher levels compared with AT1Ra in cerebral pial arteries and is required for myogenic contractility in these vessels, whereas AT1Ra is unnecessary for this function. Here, we found that AT1Ra and AT1Rb are expressed at similar levels in parenchymal arterioles and that genetic knockout of AT1Ra blunted the ability of these vessels to generate myogenic tone. We also found that AT1Rb and total AT1R expression levels are much lower in parenchymal arterioles compared with pial arteries and that parenchymal arterioles are less sensitive to the vasoconstrictive effects of the endogenous AT1R ligand angiotensin II (ANG II). We conclude that 1) AT1Rs are critical for the initiation, but not the maintenance, of myogenic tone in parenchymal arterioles, and 2) lower levels of AT1Rb and total AT1R in parenchymal arterioles compared with pial arteries result in differences in myogenic and ANG II-induced vasoconstriction between these vascular segments.NEW & NOTEWORTHY Myogenic tone is critical for appropriate regulation of cerebral blood flow, but the mechanisms used by vascular smooth muscle cells to detect changes in intraluminal pressure are not fully characterized. Here, we demonstrate angiotensin II receptor type 1 (AT1R) is indispensable to initiation, but not maintenance, of myogenic tone in cerebral parenchymal arterioles. Furthermore, we demonstrate differences in AT1R expression levels lead to critical differences in contractile regulation between parenchymal arterioles and cerebral pial arteries.

Nanoscale coupling of junctophilin-2 and ryanodine receptors regulates vascular smooth muscle cell contractility

Junctophilin proteins maintain close contacts between the endoplasmic/sarcoplasmic reticulum (ER/SR) and the plasma membrane in many types of cells, as typified by junctophilin-2 (JPH2), which is necessary for the formation of the cardiac dyad. Here, we report that JPH2 is the most abundant junctophilin isotype in native smooth muscle cells (SMCs) isolated from cerebral arteries and that acute knockdown diminishes the area of sites of interaction between the SR and plasma membrane. Superresolution microscopy revealed nanometer-scale colocalization of JPH2 clusters with type 2 ryanodine receptor (RyR2) clusters near the cell surface. Knockdown of JPH2 had no effect on the frequency, amplitude, or kinetics of spontaneous Ca²⁺ sparks generated by transient release of Ca²⁺ from the SR through RyR2s, but it did nearly abolish Ca²⁺ spark-activated, large-conductance, Ca²⁺-activated K⁺ (BK) channel currents. We also found that JPH2 knockdown was associated with hypercontractility of intact cerebral arteries. We conclude that JPH2 maintains functional coupling between RyR2s and BK channels and is critically important for cerebral arterial function.

Comparison of blood velocity between Transcranial Doppler and numerical method in the patient-specific Circle of Willis with aneurysm

BACKGROUND

The development of any disturbance in the Circle of Willis (COW) can change the hemodynamics of blood flow and result in damage to the vascular system. Clinical methods such as TCD for diagnosing an aneurysm or growth factors and rupture can measure blood velocity. Several factors influence the accuracy of TCD that can lead to wrong evaluations and affect the treatment planning.

OBJECTIVE

In this study, the conformity between CFD and TCD was accomplished for investigating the accuracy of the clinical method (TCD) in different vessels of the Circle of Willis.

METHODS

The realistic three-dimensional models have been produced from angiography images. Considering fluid-structure interaction, a domain of the blood flow and vessel wall has been simulated by the ANSYS.CFX software. The velocity in the cerebral arteries has been calculated and compared with the velocity acquired from TCD.

RESULTS

According to the findings, there were significant differences between the results obtained from computational fluid dynamics and Doppler test in different vessels of the Circle of Willis. In some areas, differences close to 80 cm/s were also reported.

CONCLUSION

According to the results, there are possibilities of errors in carrying out a Doppler test in some arteries and can lead to wrong estimates and ultimately incorrect decisions.

Effects of prolonged type 2 diabetes on mitochondrial function in cerebral blood vessels

One of the major characteristics of hyperglycemic states such as type 2 diabetes is increased reactive oxygen species (ROS) generation. Since mitochondria are a major source of ROS, it is vital to understand the involvement of these organelles in the pathogenesis of ROS-mediated conditions. Therefore, we investigated mitochondrial function and ROS production in cerebral blood vessels of 21-wk-old Zucker diabetic fatty obese rats and their lean controls. We have previously shown that in the early stages of insulin resistance, and short periods of type 2 diabetes mellitus, only mild differences exist in mitochondrial function. In the present study, we examined mitochondrial respiration, mitochondrial protein expression, and ROS production in large-surface cerebral arteries. We used 21-wk-old animals exposed to peak glucose levels for 7 wk and compared them with our previous studies on younger diabetic animals. We found that the same segments of mitochondrial respiration (basal respiration and proton leak) were diminished in diabetic groups as they were in younger diabetic animals. Levels of rattin, a rat humanin analog, tended to decrease in the diabetic group but did not reach statistical significance (P = 0.08). Other mitochondrial proteins were unaffected, which might indicate the existence of compensatory mechanisms with extension of this relatively mild form of diabetes. Superoxide levels were significantly higher in large cerebral vessels of diabetic animals compared with the control group. In conclusion, prolonged dietary diabetes leads to stabilization, rather than deterioration, of metabolic status in the cerebral circulation, despite continued overproduction of ROS.NEW & NOTEWORTHY We have characterized for the first time the dynamics of mitochondrial function during the progression of type 2 diabetes mellitus with regard to mitochondrial respiration, protein expression, and reactive oxygen species production. In addition, this is the first measurement of rattin levels in the cerebral vasculature, which could potentially lead to novel treatment options.

Erenumab (AMG 334), a monoclonal antagonist antibody against the canonical CGRP receptor, does not impair vasodilatory or contractile responses to other vasoactive agents in human isolated cranial arteries

BACKGROUND

Calcitonin gene-related peptide (CGRP) is a neuronal transmitter present in intracranial sensory nerves, where it is involved in migraine pathophysiology as well as other biological functions. Recently, the fully human monoclonal antibody erenumab (AMG 334), which targets the canonical calcitonin gene-related peptide receptor, showed significant prophylactic efficacy and favourable safety in phase II and III clinical trials for episodic and chronic migraine and is now approved for migraine prevention in several countries.

OBJECTIVE

Given that calcitonin gene-related peptide can mediate vasodilation, we investigated the effect of erenumab on vasoactive responses in the presence or absence of various vasodilatory and vasocontractile mediators in a model using isolated human cerebral and meningeal arteries.

METHODS

Ring segments of human isolated cerebral and meningeal arteries were mounted in a sensitive myograph. On arterial segments pre-contracted with 30 mM potassium chloride, vasoactive responses to calcitonin gene-related peptide were studied in the presence of different concentrations of erenumab. At the maximal tested inhibitory concentration of erenumab (100 nM), functional arterial relaxation in response to nicardipine or substance P, and the contractile responses to sumatriptan and dihydroergotamine were examined.

RESULTS

30 mM potassium chloride produced a stable contraction of the vessel segments and calcitonin gene-related peptide induced a concentration-dependent relaxation. We observed that (i) erenumab had no direct contractile or relaxant effects per se (by itself), (ii) pre-treatment with erenumab antagonized the calcitonin gene-related peptide-induced relaxation in a competitive manner, (iii) the relaxant responses to nicardipine or substance P were unaffected in the presence of erenumab and (iv) the contraction induced by sumatriptan or dihydroergotamine was not modified by erenumab.

CONCLUSION

Our findings demonstrate that erenumab, while not associated with vasoactive properties per se, specifically inhibits calcitonin gene-related peptide-induced relaxation of cranial arteries without impacting vasodilatory responses or contractile responses of endogenous or pharmacological vasoactive compounds.

Impaired Trafficking of β1 Subunits Inhibits BK Channels in Cerebral Arteries of Hypertensive Rats

Hypertension is a risk factor for cerebrovascular diseases, including stroke and dementia. During hypertension, arteries become constricted and are less responsive to vasodilators, including nitric oxide (NO). The regulation of arterial contractility by smooth muscle cell (myocyte) large-conductance calcium (Ca²⁺)-activated potassium (BK) channels is altered during hypertension, although mechanisms involved are unclear. We tested the hypothesis that dysfunctional trafficking of pore-forming BK channel (BKα) and auxiliary β1 subunits contributes to changes in cerebral artery contractility of stroke-prone spontaneously hypertensive rats (SP-SHRs). Our data indicate that the amounts of total and surface BKα and β1 proteins are similar in unstimulated arteries of age-matched SP-SHRs and normotensive Wistar-Kyoto rats. In contrast, stimulated surface-trafficking of β1 subunits by NO or membrane depolarization is inhibited in SP-SHR myocytes. PKCα (protein kinase C α) and PKCβII total protein and activity were both higher in SP-SHR than in Wistar-Kyoto rat arteries. NO or depolarization robustly activated Rab11, a small trafficking GTPase, in Wistar-Kyoto rat arteries but weakly activated Rab11 in SP-SHRs. Bisindolylmaleimide, a PKC inhibitor, and overexpression of a PKC phosphorylation-deficient Rab11A mutant (Rab11A S177A) restored stimulated β1 subunit surface-trafficking in SP-SHR myocytes. BK channel activation by NO was inhibited in SP-SHR myocytes and restored by Rab11A S177A expression. Vasodilation to NO and lithocholate, a BKα/β1 channel activator, was inhibited in pressurized SP-SHR arteries and reestablished by bisindolylmaleimide. In summary, data indicate that spontaneously active PKC inhibits Rab11A-mediated β1 subunit trafficking in arterial myocytes of SP-SHRs, leading to dysfunctional NO-induced BK channel activation and vasodilation.

Cerebral and skeletal muscle feed artery vasoconstrictor responses in a mouse model with greater large elastic artery stiffness

NEW FINDINGS

What is the central question of this study? Greater large artery stiffness is associated with dysfunctional resistance artery vasodilatory responses, impaired memory and greater risk of Alzheimer's disease. However, it is unknown whether stiffer large arteries affect cerebral and skeletal muscle feed artery responses to vasoconstrictors. What is the main finding and its importance? In a mouse model with greater large artery stiffness (Eln^+/- ), we find an exacerbated vasoconstrictor response to angiotensin II in cerebral arteries, but not skeletal muscle feed arteries, thus implicating altered cerebral artery angiotensin II responsiveness in the poor brain outcomes associated with greater large artery stiffness.

ABSTRACT

Greater stiffness of the large elastic arteries is associated with end-organ damage and dysfunction. At the same time, resistance artery vasoconstrictor responsiveness influences vascular tone and organ blood flow. However, it is unknown whether large elastic artery stiffness modulates the responsiveness to vasoconstrictors in resistance arteries of the cerebral or skeletal muscle circulations. We previously described the elastin haploinsufficient (Eln^+/- ) mouse as a model with greater aortic stiffness, but with similar cerebral and skeletal muscle feed artery stiffness to wild-type (Eln^+/+ ) mice. Here, we used this model to examine the relationship between large elastic artery stiffness and resistance artery vasoconstrictor responses. In middle cerebral arteries (MCAs), vasoconstriction in response to angiotensin II (Ang II) was ∼40% greater in Eln^+/- compared with Eln^+/+ mice (P = 0.02), and this group difference was ameliorated by losartan, indicating a role for Ang II type 1 receptors (AT1Rs). In gastrocnemius feed arteries, Eln^+/- and Eln^+/+ mice did not differ in the response to Ang II. In addition, the vasoconstrictor responses to noradrenaline, endothelin-1 and potassium chloride were not different between Eln^+/- and Eln^+/+ mice for either MCAs or gastrocnemius feed arteries. The MCA AT1R gene expression did not differ between groups, whereas Ang II type 2 receptor gene expression was ∼50% lower in MCAs from Eln^+/- versus Eln^+/+ mice (P = 0.01). In conclusion, greater large elastic artery stiffness is associated with an exacerbated vasoconstriction response to Ang II in cerebral arteries, but is not associated with the responses to other vasoconstrictors in either cerebral or skeletal muscle feed arteries.

Accuracy of blood flow assessment in cerebral arteries with 4D flow MRI: Evaluation with three segmentation methods

Background

Accelerated 4D flow MRI allows for high‐resolution velocity measurements with whole‐brain coverage. Such scans are increasingly used to calculate flow rates of individual arteries in the vascular tree, but detailed information about the accuracy and precision in relation to different postprocessing options is lacking.

Purpose

To evaluate and optimize three proposed segmentation methods and determine the accuracy of in vivo 4D flow MRI blood flow rate assessments in major cerebral arteries, with high‐resolution 2D PCMRI as a reference.

Study Type

Prospective.

Subjects

Thirty‐five subjects (20 women, 79 ± 5 years, range 70–91 years).

Field Strength/Sequence

4D flow MRI with PC‐VIPR and 2D PCMRI acquired with a 3 T scanner.

Assessment

We compared blood flow rates measured with 4D flow MRI, to the reference, in nine main cerebral arteries. Lumen segmentation in the 4D flow MRI was performed with k‐means clustering using four different input datasets, and with two types of thresholding methods. The threshold was defined as a percentage of the maximum intensity value in the complex difference image. Local and global thresholding approaches were used, with evaluated thresholds from 6–26%.

Statistical Tests

Paired t‐test, F‐test, linear correlation (P < 0.05 was considered significant) along with intraclass correlation (ICC).

Results

With the thresholding methods, the lowest average flow difference was obtained for 20% local (0.02 ± 15.0 ml/min, ICC = 0.97, n = 310) or 10% global (0.08 ± 17.3 ml/min, ICC = 0.97, n = 310) thresholding with a significant lower standard deviation for local (F‐test, P = 0.01). For all clustering methods, we found a large systematic underestimation of flow compared with 2D PCMRI (16.1–22.3 ml/min).

Data Conclusion

A locally adapted threshold value gives a more stable result compared with a globally fixed threshold. 4D flow with the proposed segmentation method has the potential to become a useful reliable clinical tool for assessment of blood flow in the major cerebral arteries.

Level of Evidence: 2

Technical Efficacy: Stage 2

J. Magn. Reson. Imaging 2019;50:511–518.

Endothelium-specific amyloid precursor protein deficiency causes endothelial dysfunction in cerebral arteries

The exact physiological function of amyloid-β precursor protein (APP) in endothelial cells is unknown. Endothelium-specific APP-deficient (eAPP^-/-) mice were created to gain new insights into the role of APP in the control of vascular endothelial function. Endothelium-dependent relaxations to acetylcholine were significantly impaired in basilar arteries of global APP knockout (APP^-/-) and eAPP^-/- mice ( P < 0.05). In contrast, endothelium-independent relaxations to nitric oxide (NO)-donor diethylamine-NONOate were unchanged. Western blot analysis revealed that protein expression of endothelial nitric oxide synthase (eNOS) was significantly downregulated in large cerebral arteries of APP^-/- mice and eAPP^-/- mice as compared to respective wild-type littermates ( P < 0.05). Furthermore, basal levels of cyclic guanosine monophosphate (cGMP) were also significantly reduced in large cerebral arteries of APP-deficient mice ( P < 0.05). In contrast, protein expression of prostacyclin synthase as well as levels of cyclic adenosine monophosphate (cAMP) was not affected by genetic inactivation of APP in endothelial cells. By using siRNA to knockdown APP in cultured human brain microvascular endothelial cells we also found a significant downregulation of eNOS mRNA and protein expressions in APP-deficient endothelium ( P < 0.05). These findings indicate that under physiological conditions, expression of APP in cerebral vascular endothelium plays an important protective function by maintaining constitutive expression of eNOS .

Anatomy of the feeding arteries of the cerebral arteriovenous malformations

BACKGROUND

Identification and anatomic features of the feeding arteries of the arteriovenous malformations (AVMs) is very important due to neurologic, radiologic, and surgical reasons.

MATERIALS AND METHODS

Seventy-seven patients with AVMs were examined by using a digital subtraction angiographic (DSA) and computerised tomographic (CT) examination, including three-dimensional reconstruction of the brain vessels. In addition, the arteries of 4 human brain stems and 8 cerebral hemispheres were microdissected.

RESULTS

The anatomic examination showed a sporadic hypoplasia, hyperplasia, early bifurcation and duplication of certain cerebral arteries. The perforating arteries varied from 1 to 8 in number. The features of the leptomeningeal and choroidal vessels were presented. The radiologic examination revealed singular (22.08%), double (32.48%) or multiple primary feeding arteries (45.45%), which were dilated and elongated in 58.44% of the patients. The feeders most often originated from the middle cerebral artery (MCA; (23.38%), less frequently from the anterior cerebral artery (ACA; 12.99%), and the posterior cerebral artery (PCA; 10.39%). Multiple feeders commonly originated from the ACA and MCA (11.69%), the MCA and PCA (10.39%), the ACA and PCA (7.79%), and the ACA, MCA and PCA (5.19%). The infratentorial feeders were found in 9.1% of the AVMs. Contribution from the middle meningeal and occipital arteries was seen in 3.9% angiograms. Two cerebral arteries had a saccular aneurysm. The AVM haemorrhage appeared in 63.6% of patients.

CONCLUSIONS

The knowledge of the origin and anatomic features of the AVMs feeders is important in the explanation of neurologic signs, and in a decision regarding the endovascular embolisation, neurosurgical and radiosurgical treatments.

Impact of pulse pressure on cerebrovascular events leading to age-related cognitive decline

Aging is a modern concept: human life expectancy has more than doubled in less than 150 yr in Western countries. Longer life span, however, reveals age-related diseases, including cerebrovascular diseases. The vascular system is a prime target of aging: the "wear and tear" of large elastic arteries exposed to a lifelong pulsatile pressure causes arterial stiffening by fragmentation of elastin fibers and replacement by stiffer collagen. This arterial stiffening increases in return the amplitude of the pulse pressure (PP), its wave penetrating deeper into the microcirculation of low-resistance, high-flow organs such as the brain. Several studies have associated peripheral arterial stiffness responsible for the sustained increase in PP, with brain microvascular diseases such as cerebral small vessel disease, cortical gray matter thinning, white matter atrophy, and cognitive dysfunction in older individuals and prematurely in hypertensive and diabetic patients. The rarefaction of white matter is also associated with middle cerebral artery pulsatility that is strongly dependent on PP and artery stiffness. PP and brain damage are likely associated, but the sequence of mechanistic events has not been established. Elevated PP promotes endothelial dysfunction that may slowly develop in parallel with the accumulation of proinflammatory senescent cells and oxidative stress, generating cerebrovascular damage and remodeling, as well as brain structural changes. Here, we review data suggesting that age-related increased peripheral artery stiffness may promote the penetration of a high PP to cerebral microvessels, likely causing functional, structural, metabolic, and hemodynamic alterations that could ultimately promote neuronal dysfunction and cognitive decline.

Cerebral blood flow velocities and cerebrovascular resistance in normal-term neonates in the first 72 hours

AIM

To determine the range of cerebral blood flow velocities (CBFVs) and Doppler indices of cerebrovascular resistance in normal-term neonates as a baseline for a study of hypoxic-ischaemic encephalopathy.

METHODS

The CBFVs, resistive index (RI) and pulsatility index (PI) were measured in the anterior and middle cerebral arteries (ACA and MCA) of 38 normal neonates.

RESULTS

The mean peak systolic, end diastolic and time-averaged velocities (PSV, EDV and TAV) were 36.3 ± 6.6, 12.4 ± 3.9 and 22.0 ± 4.0 cm/s (ACA) and 41.4 ± 13.2, 13.0 ± 5.5 and 25.8 ± 7.9 cm/s (MCA), respectively. All CBFVs in the ACA correlated with gestation; only EDV was correlated to post-natal age. The RI in the ACA (0.67 ± 0.06) and MCA (0.68 ± 0.07) were correlated (r = 0.72, P < 0.001); RI correlated to post-natal age. Two infants with RI < 0.55 were both fed within 25 mins of the study; RI correlated with post-prandial time (dichotomous, pivot 25 min). The mean PI was 1.11 ± 0.18 (ACA) and 1.17 ± 0.23 (MCA). Correlations were observed with post-natal age and post-prandial time (dichotomous). The average angle of insonation was greater in the ACA than in the MCA (median of 5° vs. 18°).

CONCLUSIONS

Results corresponded with previous published studies. No correlation was observed between Doppler indices and gestation as component velocities all increase with advancing gestation. Less variation and smaller standard deviation of CBFV's was associated with a smaller angle of insonation. Low RIs (<0.55), without a pathological cause, warrants further study.

Clinical Significance of the Cerebral Perforating Arteries

There is scarce data in the contemporary literature regarding the correlation of the microanatomy of the perforating arteries, their atherosclerosis, and the ischemia in their territory. In order to examine, at least partially, those parameters, the perforating arteries of 12 brains were microdissected or their vascular casts were obtained. In addition, 30 specimens of the perforators were used for a histological and immunohistochemical study. Finally, radiological images of 14 patients with deep cerebral infarcts were examined following a selection among 62 subjects. It was found out that certain groups of the perforators ranged in number between 0 to 11 (1.1-8.4 on average). In addition to the origin from the parent vessels, some of the perforators also arose from the leptomeningeal branches. Occlusion of such a branch may result in both a superficial and a deep ischemic lesion. Besides, the common stems of certain perforators supplied both right and left portions of the corresponding brain regions. Occlusion of such a common trunk leads to bilateral infarction. The atherosclerosis of the perforating vessels, which was found in one third of the specimens, is the basis for the ischemic lesions development on their territory. Among the 62 patients with ischemic lesions, 14 had a deep cerebral infarcts, most often within the thalamus, as well as on the territory of the middle cerebral and the anterior choroidal artery perforators of the hemispheres. Our study showed that a strong correlation exists between certain microanatomical features, atherosclerosis, and region of supply of the perforating arteries, on the one hand, and location of the ischemic lesions on the other hand.

Aerobic exercise prevents rarefaction of pial collaterals and increased stroke severity that occur with aging

Variation in extent of the brain's collateral circulation is an important determinant of variation in the severity of stroke and efficacy of revascularization therapies. However, the number and diameter of pial collateral "arterioles" decrease with aging in associated with reduced eNOS and increased oxidative stress. We tested whether exercise reduces this aging-induced rarefaction. Twelve-month-old mice were randomized to sedentary or voluntary wheel-running. At 26 months' age, permanent MCA occlusion was followed 72 h later by determination of infarct volume and vascular casting after maximal dilation. The decline in collateral number and diameter and 2.4-fold increase in infarct volume evident in 26-versus 3-month-old sedentary mice were prevented by exercise-training. In contrast, number and diameter of the posterior communicating collateral "arteries" were unaffected by aging or exercise. Interestingly, diameter of the primary intracranial arteries increased with aging. Mechanistically, genetic overexpression of eNOS inhibited age-induced collateral rarefaction, and exercise increased eNOS and SOD2 and decreased the inflammatory marker NFkB assessed in hindlimb arteries. In conclusion, exercise prevented age-induced rarefaction of pial collaterals and reduced infarct volume. Aging also promoted outward remodeling of intracranial arteries. These effects were associated with increased eNOS and reduced markers of inflammation and aging in the vascular wall.

Carotid artery stenosis in hypertensive rats impairs dilatory pathways in parenchymal arterioles

Hypertension is a leading risk factor for vascular cognitive impairment and is strongly associated with carotid artery stenosis. In normotensive rats, chronic cerebral hypoperfusion induced by bilateral common carotid artery stenosis (BCAS) leads to cognitive impairment that is associated with impaired endothelium-dependent dilation in parenchymal arterioles (PAs). The aim of this study was to assess the effects of BCAS on PA function and structure in stroke-prone spontaneously hypertensive rats, a model of human essential hypertension. Understanding the effects of hypoperfusion on PAs in a hypertensive model could lead to the identification of therapeutic targets for cognitive decline in a model that reflects the at-risk population. We hypothesized that BCAS would impair endothelium-dependent dilation in PAs and induce artery remodeling compared with sham rats. PAs from BCAS rats had endothelial dysfunction, as assessed using pressure myography. Inhibition of nitric oxide and prostaglandin production had no effect on PA dilation in sham or BCAS rats. Surprisingly, inhibition of epoxyeicosatrienoic acid production increased dilation in PAs from BCAS rats but not from sham rats. Similar results were observed in the presence of inhibitors for all three dilatory pathways, suggesting that epoxygenase inhibition may have restored a nitric oxide/prostaglandin-independent dilatory pathway in PAs from BCAS rats. PAs from BCAS rats underwent remodeling with a reduced wall thickness. These data suggest that marked endothelial dysfunction in PAs from stroke-prone spontaneously hypertensive rats with BCAS may be associated with the development of vascular cognitive impairment. NEW & NOTEWORTHY The present study assessed the structure and function of parenchymal arterioles in a model of chronic cerebral hypoperfusion and hypertension, both of which are risk factors for cognitive impairment. We observed that impaired dilation and artery remodeling in parenchymal arterioles and abolished cerebrovascular reserve capacity may mediate cognitive deficits.