Role of Genetic Variation in Collateral Circulation in the Evolution of Acute Stroke: A Multimodal Magnetic Resonance Imaging Study

Promising Cerebral Blood Flow Enhancers in Acute Ischemic Stroke

Ischemic stroke presents a major global economic and public health burden. Although recent advances in available endovascular therapies show improved functional outcome, a good number of stroke patients are either ineligible or do not have access to these treatments. Also, robust collateral flow during acute ischemic stroke independently predicts the success of endovascular therapies and the outcome of stroke. Hence, adjunctive therapies for cerebral blood flow (CBF) enhancement are urgently needed. A very clear overview of the pial collaterals and the role of genetics are presented in this review. We review available evidence and advancement for potential therapies aimed at improving CBF during acute ischemic stroke. We identified heme-free soluble guanylate cyclase activators; Sanguinate, remote ischemic perconditioning; Fasudil, S1P agonists; and stimulation of the sphenopalatine ganglion as promising potential CBF-enhancing therapeutics requiring further investigation. Additionally, we outline and discuss the critical steps required to advance research strategies for clinically translatable CBF-enhancing agents in the context of acute ischemic stroke models.

Oatp (Organic Anion Transporting Polypeptide)-Mediated Transport: A Mechanism for Atorvastatin Neuroprotection in Stroke

BACKGROUND

Drug discovery for stroke is challenging as indicated by poor clinical translatability. In contrast, HMG-CoA (3-hydroxy-3-methylglutaryl coenzyme A) reductase inhibitors (ie, statins) improve poststroke neurological outcomes. This property requires transport across the blood-brain barrier via an endogenous uptake transporter (ie, Oatp1a4 [organic anion transporting polypeptide 1a4]). Our goal was to study Oatp1a4 as a drug delivery mechanism because the blood-brain barrier cannot be assumed to be completely open for all drugs in ischemic stroke.

METHODS

Male Sprague-Dawley rats (200-250 g) were subjected to middle cerebral artery occlusion (90 minutes) followed by reperfusion for up to 7 days. Atorvastatin (20 mg/kg, IV) was administered 2 hours following intraluminal suture removal. Involvement of Oatp-mediated transport was determined using fexofenadine (3.2 mg/kg, IV), a competitive Oatp inhibitor. Oatp1a4 transport activity was measured by in situ brain perfusion. Infarction volumes/brain edema ratios and neuronal nuclei expression were determined using 2,3,5-triphenyltetrazolium chloride-stained brain tissue slices and confocal microscopy, respectively. Poststroke functional outcomes were assessed via neurological deficit scores and rotarod analysis.

RESULTS

At 2-hour post-middle cerebral artery occlusion, [3H]atorvastatin uptake was increased in ischemic brain tissue. A single dose of atorvastatin significantly reduced post-middle cerebral artery occlusion infarction volume, decreased brain edema ratio, increased caudoputamen neuronal nuclei expression, and improved functional neurological outcomes. All middle cerebral artery occlusion positive effects of atorvastatin were attenuated by fexofenadine coadministration (ie, an Oatp transport inhibitor).

CONCLUSIONS

Our data demonstrate that neuroprotective effects of atorvastatin may require central nervous system delivery by Oatp-mediated transport at the blood-brain barrier, a mechanism that persists despite increased cerebrovascular permeability in ischemic stroke. These novel and translational findings support utility of blood-brain barrier transporters in drug delivery for neuroprotective agents.

Meta-Analysis of Prognostic Correlation of Thrombectomy for Cerebral Infarction Based on Intelligent Medical Treatment

A meta-analysis is used to investigate the correlation between the status of collateral circulation assessed by head CT angiography (CTA) and the outcome of thrombectomy for cerebral infarction. Meta-analysis is conducted. The experimental results show that the National Institutes of Health Stroke Scale (NIHSS) score, modified Rankin Scale (mRS) score, incidence of cerebral hemorrhage, and mortality in the group with good collateral circulation are significantly lower than those in the group with bad collateral circulation, and the rate of good prognosis is significantly higher (P < 0.05). The evaluation and treatment of patients with cerebral infarction and their prognosis based on CTA intelligent medical technology are related to collateral circulation, and the effect of effectively reducing the risk of death, cerebral hemorrhage, and neurological function injury and improving the prognosis is more obvious in each collateral circulation.

Integrative cerebral blood flow regulation in ischemic stroke

Optimizing cerebral perfusion is key to rescuing salvageable ischemic brain tissue. Despite being an important determinant of cerebral perfusion, there are no effective guidelines for blood pressure (BP) management in acute stroke. The control of cerebral blood flow (CBF) involves a myriad of complex pathways which are largely unaccounted for in stroke management. Due to its unique anatomy and physiology, the cerebrovascular circulation is often treated as a stand-alone system rather than an integral component of the cardiovascular system. In order to optimize the strategies for BP management in acute ischemic stroke, a critical reappraisal of the mechanisms involved in CBF control is needed. In this review, we highlight the important role of collateral circulation and re-examine the pathophysiology of CBF control, namely the determinants of cerebral perfusion pressure gradient and resistance, in the context of stroke. Finally, we summarize the state of our knowledge regarding cardiovascular and cerebrovascular interaction and explore some potential avenues for future research in ischemic stroke.

Altered diffusivity of the subarachnoid cisterns in the rat brain following neurological disorders

BACKGROUND

Although changes in diffusion characteristics of the brain parenchyma in neurological disorders are widely studied and used in clinical practice, the change in diffusivity in the cerebrospinal fluid (CSF) system is rarely reported. In this study, free water diffusion in the subarachnoid cisterns and ventricles of the rat brain was examined using diffusion magnetic resonance imaging (MRI), and the effects of neurological disorders on diffusivity in CSF system were investigated.

METHODS

Diffusion MRI and T₂-weighted images were obtained in the intact rats, 24 h after ischemic stroke, and 50 days after mild traumatic brain injury (mTBI). We conducted the assessment of diffusivity in the rat brain in the subarachnoid cisterns around the midbrain, as well as the lateral ventricles. One-way ANOVA and Kruskal-Wallis test were used to evaluate the change in mean diffusivity (MD) and MD histogram, respectively, in CSF system following different neurological disease.

RESULTS

A significant decrease in the mean MD value of the subarachnoid cisterns was observed in the stroke rats compared with the intact and mTBI rats (p < 0.005). In addition, the skewness (p < 0.002), maximum MD (p < 0.002), and MD percentiles (p < 0.002) in the stroke rats differed significantly from those in the intact and mTBI rats. By contrast, no difference was observed in the mean MD value of the lateral ventricles among three groups of rats. We proposed that the assessment of the subarachnoid cisterns, rather than the lateral ventricles, in the rat brain would be useful in providing diffusion information in the CSF system.

CONCLUSIONS

Alterations in MD parameters of the subarachnoid cisterns after stroke provide evidence that brain injury may alter the characteristics of free water diffusion not only in the brain parenchyma but also in the CSF system.

A Neuroprotective Locus Modulates Ischemic Stroke Infarction Independent of Collateral Vessel Anatomy

Although studies with inbred strains of mice have shown that infarct size is largely determined by the extent of collateral vessel connections between arteries in the brain that enable reperfusion of the ischemic territory, we have identified strain pairs that do not vary in this vascular phenotype, but which nonetheless exhibit large differences in infarct size. In this study we performed quantitative trait locus (QTL) mapping in mice from an intercross between two such strains, WSB/EiJ (WSB) and C57BL/6J (B6). This QTL mapping revealed only one neuroprotective locus on Chromosome 8 (Chr 8) that co-localizes with a neuroprotective locus we mapped previously from F2 progeny between C3H/HeJ (C3H) and B6. The allele-specific phenotypic effect on infarct volume at the genetic region identified by these two independent mappings was in the opposite direction of the parental strain phenotype; namely, the B6 allele conferred increased susceptibility to ischemic infarction. Through two reciprocal congenic mouse lines with either the C3H or B6 background at the Chr 8 locus, we verified the neuroprotective effects of this genetic region that modulates infarct volume without any effect on the collateral vasculature. Additionally, we surveyed non-synonymous coding SNPs and performed RNA-sequencing analysis to identify potential candidate genes within the genetic interval. Through these approaches, we suggest new genes for future mechanistic studies of infarction following ischemic stroke, which may represent novel gene/protein targets for therapeutic development.

Modified Renshen Yangrong decoction enhances angiogenesis in ischemic stroke through promotion of MicroRNA-210 expression by regulating the HIF/VEGF/Notch signaling pathway

OBJECTIVE

This study aims to investigate the efficacy of modified Ginseng Yangrong decoction (GSYRD) promoting angiogenesis after ischemic stroke.

METHODS

In an in vivo study, rats that survived surgery were allocated into four groups: the control group and model group were treated with normal saline, the GSYRD group was treated with 18.9 mg/kg of GSYRD daily, and the positive control group was treated with Tongxinluo (TXL) (1 g/kg/d). At the end of the seven-day treatment, the area of cerebral infarction, the expression changes of miRNA-210 and ephrin A3 were determined. In an in vitro study, HUVECs were divided into a normal control serum group (NC group), normal control serum OGD group (Oxygen Glucose Deprivation group) (OGD group), OGD + drug-containing serum group (OGD+GSYRD group), and OGD + drug-containing serum + ES group (Endostatin group) (OGD+GSYRD+ES group). The cells in all groups except the NC group were cultured in a sugar-free DMEM medium under hypoxia for 48 h. Cell proliferation, angiogenic structure formation ability, the expression changes of miRNA-210, ephrin A3, and the HIF/VEGF/Notch signaling pathway-related molecules were determined.

RESULTS

In vivo, GSYRD significantly reduced infarct size (p < .01), the expression of miRNA-210 and ephrin A3 were decreased in the GSYRD group (p < .05). In vitro, the cell proliferation and tube formation ability were significantly increased in the GSYRD group (p < .05), and the expression of miRNA-210 and ephrin A3 was decreased (p < .05). In addition, in the GSYRD group, the expression of the HIF/VEGF/Notch signaling pathway-related molecules was significantly increased (p < .01 or p < .05).

CONCLUSION

GSYRD promotes cerebral protection following angiogenesis and ischemic brain injury. The specific mechanism was activating the HIF/VEGF/Notch signaling pathway via miRNA-210.

Early neuroimaging and ultrastructural correlates of injury outcome after neonatal hypoxic-ischaemia

Hypoxic ischaemia encephalopathy is the major cause of brain injury in new-borns. However, to date, useful biomarkers which may be used to early predict neurodevelopmental impairment for proper commencement of hypothermia therapy is still lacking. This study aimed to determine whether the early neuroimaging characteristics and ultrastructural correlates were associated with different injury progressions and brain damage severity outcomes after neonatal hypoxic ischaemia. Longitudinal 7 T MRI was performed within 6 h, 24 h and 7 days after hypoxic ischaemia in rat pups. The brain damage outcome at 7 days post-hypoxic ischaemia assessed using histopathology and MRI were classified as mild, moderate and severe. We found there was a spectrum of different brain damage severity outcomes after the same duration of hypoxic ischaemia. The severity of brain damage determined using MRI correlated well with that assessed by histopathology. Quantitative MRI characteristics denoting water diffusivity in the tissue showed significant differences in the apparent diffusion coefficient deficit volume and deficit ratios within 6 h, at 24 h and 7 days after hypoxic ischaemia among the 3 different outcome groups. The susceptible brain areas to hypoxic ischaemia were revealed by the temporal changes in regional apparent diffusion coefficient values among three outcome groups. Within 6 h post-hypoxic ischaemia, a larger apparent diffusion coefficient deficit volume and deficit ratios and lower apparent diffusion coefficient values were highly associated with adverse brain damage outcome. In the apparent diffusion coefficient deficit areas detected early after hypoxic ischaemia which were highly associated with severe damage outcome, transmission electron microscopy revealed fragmented nuclei; swollen rough endoplasmic reticulum and degenerating mitochondria in the cortex and prominent myelin loss and axon detraction in the white matter. Taken together, different apparent diffusion coefficient patterns obtained early after hypoxic ischaemia are highly associated with different injury progression leading to different brain damage severity outcomes, suggesting the apparent diffusion coefficient characteristics may be applicable to early identify the high-risk neonates for hypothermia therapy.

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

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

Endovascular Treatment After Stroke Due to Large Vessel Occlusion for Patients Presenting Very Late From Time Last Known Well

IMPORTANCE

Endovascular treatment (EVT) after ischemic stroke due to emergent large vessel occlusion is usually constrained by a specific window of less than 16 to 24 hours from the time the patient was last known well (LKW). Patients with slow progression and tenacious collateral circulation may persist beyond 16 hours.

OBJECTIVES

To estimate the prevalence of salvageable tissues 16 hours or more from LKW after ischemic stroke due to emergent large vessel occlusion and investigate the effectiveness of EVT in delayed large vessel occlusion.

DESIGN, SETTING AND PARTICIPANTS

In this case-control study, from a total of 8032 patients with stroke or transient ischemic attack who were admitted between January 1, 2012, and December 31, 2018, to a single referral university hospital, 150 patients were retrospectively identified who had an acute ischemic stroke with internal carotid artery or middle cerebral artery occlusion, had a baseline National Institutes of Health Stroke Scale score of 6 or more, and arrived 16 hours or more from time LKW. The decision for EVT was made by a treating physician according to the institutional protocol.

MAIN OUTCOMES AND MEASURES

Baseline ischemic core, collateral circulation status, and computed tomographic or magnetic resonance perfusion parameters were retrospectively quantified. Follow-up images, evaluated a median of 93 hours (interquartile range, 66-120 hours) after arrival, were used to assess the final infarct and hemorrhagic transformation. The main outcome was the modified Rankin Scale score at 90 days.

RESULTS

For 150 patients (81 men [54%]; mean [SD] age at onset, 70.1 [13.0] years; median National Institutes of Health Stroke Scale score, 12 [interquartile range, 8-18]), the median ischemic core volume was 11.5 mL (interquartile range, 0-39.1 mL), the median penumbra volume (>6 seconds) was 55.0 mL (interquartile range, 15-128 mL), and the median mismatch ratio was 4.0 (interquartile range, 0.9-18.3). By the imaging inclusion criteria for EVT trials, there were 50 DAWN (DWI or CTP Assessment With Clinical Mismatch in the Triage of Wake-up and Late Presenting Strokes Undergoing Neurointervention With Trevo)-eligible patients (33%), 58 DEFUSE 3 (Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke)-eligible patients (39%), and 57 ESCAPE (Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion With Emphasis on Minimizing CT to Recanalization Times)-eligible patients (38%). Endovascular treatment was performed for 24 patients (16%). In propensity score-matched analyses, EVT was associated with better odds of a 90-day modified Rankin Scale score of 0 to 2 (adjusted odds ratio, 11.08 [95% CI, 1.88-108.60]) and a 90-day modified Rankin Scale score shift (common adjusted odds ratio, 5.17 [95% CI, 1.80-15.62]). Type 2 parenchymal hemorrhage was seen in 3 of 24 patients (13%) who received EVT and in 4 of 126 patients (3%) who received medical management (adjusted odds ratio, 4.06 [95% CI, 0.63-26.30]). In a subgroup of 109 patients who were 24 hours from time LKW, EVT was associated with a favorable mRS shift (common adjusted odds ratio, 10.54 [95% CI, 2.18-59.34]).

CONCLUSIONS AND RELEVANCE

This study suggests that patients with anterior circulation large vessel occlusion presenting very late (>16 hours to 10 days) from the time they were LKW may benefit from EVT.

Predictors and Functional Outcomes of Fast, Intermediate, and Slow Progression Among Patients With Acute Ischemic Stroke

BACKGROUND AND PURPOSE

We aimed to delineate the determinants of the initial speed of infarct progression and the association of speed of infarct progression (SIP) with procedural and functional outcomes.

METHODS

From a prospectively maintained stroke center registry, consecutive anterior circulation ischemic stroke patients with large artery occlusion, National Institutes of Health Stroke Scale score ≥4, and multimodal vessel, ischemic core, and tissue-at-risk imaging within 24 hours of onset were included. Initial SIP was calculated as ischemic core volume at first imaging divided by the time from stroke onset to imaging.

RESULTS

Among the 88 patients, SIP was median 2.2 cc/h (interquartile range, 0-8.7), ranging most widely within the first 6 hours after onset. Faster SIP was positively independently associated with a low collateral score (odds ratio [OR], 3.30 [95% CI, 1.25-10.49]) and arrival by emergency medical services (OR, 3.34 [95% CI, 1.06-10.49]) and negatively associated with prior ischemic stroke (OR, 0.12 [95% CI, 0.03-0.50]) and coronary artery disease (OR, 0.32 [95% CI, 0.10-1.00]). Among the 67 patients who underwent endovascular thrombectomy, slower SIP was associated with a shift to reduced levels of disability at discharge (OR, 3.26 [95% CI, 1.02-10.45]), increased substantial reperfusion by thrombectomy (OR, 8.30 [95% CI, 0.97-70.87]), and reduced radiological hemorrhagic transformation (OR, 0.34 [95% CI, 0.12-0.94]).

CONCLUSIONS

Slower SIP is associated with a high collateral score, prior ischemic stroke, and coronary artery disease, supporting roles for both collateral robustness and ischemic preconditioning in fostering tissue resilience to ischemia. Among patients undergoing endovascular thrombectomy, the speed of infarct progression is a major determinant of clinical outcome.

Application of FLAIR Vascular Hyperintensity-DWI Mismatch in Ischemic Stroke Depending on Semi-Quantitative DWI-Alberta Stroke Program Early CT Score

Objective: Diffusion-weighted imaging (DWI)-Alberta Stroke Program Early CT Score (ASPECTS) is a simple, widely used method to estimate the size of the infarct. Our aim is to determine whether there is a relationship between DWI-ASPECTS and fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH)-DWI mismatch and to better quantify FVH-DWI mismatch to assess the prognosis of cerebral infarction.

Materials and Methods: A retrospective analysis of 109 patients with MCA stenosis or occlusion with cerebral infarction was performed by dividing this cohort into FVH-DWI match group and FVH-DWI mismatch group based on FVH and DWI results. The clinical and imaging data of these two groups of patients were reviewed and analyzed to identify associations between FVH-DWI mismatch and prognosis of patients for preservation of neurological function. Correlation between DWI-ASPECTS and FVH-DWI mismatch was also performed.

Results: FVH-DWI mismatch was present in 66/109 (60.55%) patients, and FVH-DWI match was present in 43/109 (39.45%). Patients with FVH-DWI mismatch had higher DWI-ASPECTS (7.0 vs. 4.0, P < 0.001) and lower mRS at 3 months (3.0 vs. 4.0, P < 0.001) than patients without FVH-DWI mismatch. Multiple regression analysis suggested that DWI-ASPECTS (OR = 4.7, 95% CI = 2.5–9.2, P < 0.001) remained significantly associated with FVH-DWI mismatch. Two threshold points for DWI-ASPECTS of 3 and 8 can be used to distinguish whether there is a mismatch in FVH-DWI by smooth curve fitting.

Conclusions: The DWI-ASPECTS score was an independent predictor of FVH-DWI mismatch. At DWI-ASPECTS ≤ 3, the FVH-DWI mismatch offers no prognostic value; whereas, at DWI-ASPECTS ≥ 8, the FVH-DWI mismatch had the highest prognostic value. DWI-ASPECTS can roughly determine whether there is a FVH-DWI mismatch in order to select optimal clinical treatment and accurately assess prognosis.

Behavioral and Structural Effects of Single and Repeat Closed-Head Injury

BACKGROUND AND PURPOSE

The effects of multiple head impacts, even without detectable primary injury, on subsequent behavioral impairment and structural abnormality is yet well explored. Our aim was to uncover the dynamic changes and long-term effects of single and repetitive head injury without focal contusion on tissue microstructure and macrostructure.

MATERIALS AND METHODS

We introduced a repetitive closed-head injury rodent model (n = 70) without parenchymal lesions. We performed a longitudinal MR imaging study during a 50-day study period (T₂-weighted imaging, susceptibility-weighted imaging, and diffusion tensor imaging) as well as sequential behavioral assessment. Immunohistochemical staining for astrogliosis was examined in a subgroup of animals. Paired and independent t tests were used to evaluate the outcome change after injury and the cumulative effects of impact load, respectively.

RESULTS

There was no gross morphologic evidence for head injury such as skull fracture, contusion, or hemorrhage on micro-CT and MR imaging. A significant decrease of white matter fractional anisotropy from day 21 on and an increase of gray matter fractional anisotropy from day 35 on were observed. Smaller mean cortical volume in the double-injury group was shown at day 50 compared with sham and single injury (P < .05). Behavioral deficits (P < .05) in neurologic outcome, balance, and locomotor activity were also aggravated after double injury. Histologic analysis showed astrogliosis 24 hours after injury, which persisted throughout the study period.

CONCLUSIONS

There are measurable and dynamic changes in microstructure, cortical volume, behavior, and histopathology after both single and double injury, with more severe effects seen after double injury. This work bridges cross-sectional evidence from human subject and pathologic studies using animal models with a multi-time point, longitudinal research paradigm.

A Genome-Wide Analysis of the Penumbral Volume in Inbred Mice following Middle Cerebral Artery Occlusion

Following ischemic stroke, the penumbra, at-risk neural tissue surrounding the core infarct, survives for a variable period of time before progressing to infarction. We investigated genetic determinants of the size of penumbra in mice subjected to middle cerebral artery occlusion (MCAO) using a genome-wide approach. 449 male mice from 33 inbred strains underwent MCAO for 6 hours (215 mice) or 24 hours (234 mice). A genome-wide association study using genetic data from the Mouse HapMap project was performed to examine the effects of genetic variants on the penumbra ratio, defined as the ratio of the infarct volume after 6 hours to the infarct volume after 24 hours of MCAO. Efficient mixed model analysis was used to account for strain interrelatedness. Penumbra ratio differed significantly by strain (F = 2.7, P < 0.001) and was associated with 18 significant SNPs, including 6 protein coding genes. We have identified 6 candidate genes for penumbra ratio: Clint1, Nbea, Smtnl2, Rin3, Dclk1, and Slc24a4.

Substrain- and sex-dependent differences in stroke vulnerability in C57BL/6 mice

The C57BL/6 mouse strain is represented by distinct substrains, increasingly recognized to differ genetically and phenotypically. The current study compared stroke vulnerability among C57BL/6 J (J), C57BL/6JEiJ (JEiJ), C57BL/6ByJ (ByJ), C57BL/6NCrl (NCrl), C57BL/6NJ (NJ) and C57BL/6NTac (NTac) substrains, using a model of permanent distal middle cerebral artery and common carotid artery occlusion. Mean infarct volume was nearly two-fold smaller in J, JEiJ and ByJ substrains relative to NCrl, NJ and NTac (N-lineage) mice. This identifies a previously unrecognized confound in stroke studies involving genetically modified strain comparisons if control substrain background were not rigorously matched. Mean infarct size was smaller in females of J and ByJ substrains than in the corresponding males, but there was no sex difference for NCrl and NJ mice. A higher proportion of small infarcts in J and ByJ substrains was largely responsible for both substrain- and sex-dependent differences. These could not be straightforwardly explained by variations in posterior communicating artery patency, MCA anatomy or acute penumbral blood flow deficits. Their larger and more homogeneously distributed infarcts, together with their established use as the common background for many genetically modified strains, may make N-lineage C57BL/6 substrains the preferred choice for future studies in experimental stroke.

The pial vasculature of the mouse develops according to a sensory-independent program

The cerebral vasculature is organized to supply the brain’s metabolic needs. Sensory deprivation during the early postnatal period causes altered neural activity and lower metabolic demand. Neural activity is instructional for some aspects of vascular development, and deprivation causes changes in capillary density in the deprived brain region. However, it is not known if the pial arteriole network, which contains many leptomeningeal anastomoses (LMAs) that endow the network with redundancy against occlusions, is also affected by sensory deprivation. We quantified the effects of early-life sensory deprivation via whisker plucking on the densities of LMAs and penetrating arterioles (PAs) in anatomically-identified primary sensory regions (vibrissae cortex, forelimb/hindlimb cortex, visual cortex and auditory cortex) in mice. We found that the densities of penetrating arterioles were the same across cortical regions, though the hindlimb representation had a higher density of LMAs than other sensory regions. We found that the densities of PAs and LMAs, as well as quantitative measures of network topology, were not affected by sensory deprivation. Our results show that the postnatal development of the pial arterial network is robust to sensory deprivation.

The cerebral collateral circulation: Relevance to pathophysiology and treatment of stroke

The brain's collateral circulation consists of arterial anastomotic channels capable of providing nutrient perfusion to brain regions whose normal sources of flow have become compromised, as occurs in acute ischemic stroke. Modern CT-based neuroimaging is capable of providing detailed information as to collateral extent and sufficiency and is complemented by magnetic resonance-based methods. In the present era of standard-of-care IV thrombolysis for acute ischemic stroke, and following the recent therapeutic successes of randomized clinical trials of acute endovascular intervention, the sufficiency of the collateral circulation has been convincingly established as a key factor influencing the likelihood of successful reperfusion and favorable clinical outcome. This article reviews the features of the brain's collateral circulation; methods for its evaluation in the acute clinical setting; the relevance of collateral circulation to prognosis in acute ischemic stroke; the specific insights into the collateral circulation learned from recent trials of endovascular intervention; and the major influence of genetic factors. Finally, we emphasize the need to develop therapeutic approaches to augment collateral perfusion as an adjunctive strategy to be employed along with, or prior to, thrombolysis and endovascular interventions, and we highlight the possible potential of inhaled nitric oxide, albumin, and other approaches. This article is part of the Special Issue entitled 'Cerebral Ischemia'.