Three-dimensional structural changes in cerebral microvessels after transient focal cerebral ischemia in rats: scanning electron microscopic study of corrosion casts

Post-Ischemic Permeability of the Blood-Brain Barrier to Amyloid and Platelets as a Factor in the Maturation of Alzheimer's Disease-Type Brain Neurodegeneration

The aim of this review is to present evidence of the impact of ischemic changes in the blood-brain barrier on the maturation of post-ischemic brain neurodegeneration with features of Alzheimer's disease. Understanding the processes involved in the permeability of the post-ischemic blood-brain barrier during recirculation will provide clinically relevant knowledge regarding the neuropathological changes that ultimately lead to dementia of the Alzheimer's disease type. In this review, we try to distinguish between primary and secondary neuropathological processes during and after ischemia. Therefore, we can observe two hit stages that contribute to Alzheimer's disease development. The onset of ischemic brain pathology includes primary ischemic neuronal damage and death followed by the ischemic injury of the blood-brain barrier with serum leakage of amyloid into the brain tissue, leading to increased ischemic neuronal susceptibility to amyloid neurotoxicity, culminating in the formation of amyloid plaques and ending in full-blown dementia of the Alzheimer's disease type.

Engineering strategies towards overcoming bleeding and glial scar formation around neural probes

Neural probes are sophisticated electrophysiological tools used for intra-cortical recording and stimulation. These microelectrode arrays, designed to penetrate and interface the brain from within, contribute at the forefront of basic and clinical neuroscience. However, one of the challenges and currently most significant limitations is their ‘seamless’ long-term integration into the surrounding brain tissue. Following implantation, which is typically accompanied by bleeding, the tissue responds with a scarring process, resulting in a gliotic region closest to the probe. This glial scarring is often associated with neuroinflammation, neurodegeneration, and a leaky blood–brain interface (BBI). The engineering progress on minimizing this reaction in the form of improved materials, microfabrication, and surgical techniques is summarized in this review. As research over the past decade has progressed towards a more detailed understanding of the nature of this biological response, it is time to pose the question: Are penetrating probes completely free from glial scarring at all possible?

Hierarchical imaging and computational analysis of three-dimensional vascular network architecture in the entire postnatal and adult mouse brain

The formation of new blood vessels and the establishment of vascular networks are crucial during brain development, in the adult healthy brain, as well as in various diseases of the central nervous system. Here, we describe a step-by-step protocol for our recently developed method that enables hierarchical imaging and computational analysis of vascular networks in postnatal and adult mouse brains. The different stages of the procedure include resin-based vascular corrosion casting, scanning electron microscopy, synchrotron radiation and desktop microcomputed tomography imaging, and computational network analysis. Combining these methods enables detailed visualization and quantification of the 3D brain vasculature. Network features such as vascular volume fraction, branch point density, vessel diameter, length, tortuosity and directionality as well as extravascular distance can be obtained at any developmental stage from the early postnatal to the adult brain. This approach can be used to provide a detailed morphological atlas of the entire mouse brain vasculature at both the postnatal and the adult stage of development. Our protocol allows the characterization of brain vascular networks separately for capillaries and noncapillaries. The entire protocol, from mouse perfusion to vessel network analysis, takes ~10 d.

Does Src Kinase Mediated Vasoconstriction Impair Penumbral Reperfusion?

Despite successful recanalization, a significant number of patients with ischemic stroke experience impaired local brain tissue reperfusion with adverse clinical outcome. The cause and mechanism of this multifactorial complication are yet to be understood. At the current moment, major attention is given to dysfunction in blood-brain barrier and capillary blood flow but contribution of exaggerated constriction of cerebral arterioles has also been suggested. In the brain, arterioles significantly contribute to vascular resistance and thus control of perfusion. Accordingly, pathological changes in arteriolar wall function can, therefore, limit sufficient reperfusion in ischemic stroke, but this has not yet received sufficient attention. Although an increased vascular tone after reperfusion has been demonstrated in several studies, the mechanism behind it remains to be characterized. Importantly, the majority of conventional mechanisms controlling vascular contraction failed to explain elevated cerebrovascular tone after reperfusion. We propose here that the Na,K-ATPase-dependent Src kinase activation are the key mechanisms responsible for elevation of cerebrovascular tone after reperfusion. The Na,K-ATPase, which is essential to control intracellular ion homeostasis, also executes numerous signaling functions. Under hypoxic conditions, the Na,K-ATPase is endocytosed from the membrane of vascular smooth muscle cells. This initiates the Src kinase signaling pathway that sensitizes the contractile machinery to intracellular Ca²⁺ resulting in hypercontractility of vascular smooth muscle cells and, thus, elevated cerebrovascular tone that can contribute to impaired reperfusion after stroke. This mechanism integrates with cerebral edema that was suggested to underlie impaired reperfusion and is further supported by several studies, which are discussed in this article. However, final demonstration of the molecular mechanism behind Src kinase-associated arteriolar hypercontractility in stroke remains to be done.

Real-time imaging of infarction deterioration after ischemic stroke in rats using electrical impedance tomography

OBJECTIVE

This study investigated the feasibility of electrical impedance tomography (EIT) for monitoring the deterioration of ischemic lesion after the onset of stroke.

APPROACH

Fifteen rats were randomly distributed into two groups: rats operated to establish a right middle cerebral artery occlusion (MCAO) (n  =  10), and sham-operated rats (n  =  5). Then, the operated rats were kept 2 h under anesthesia for EIT monitoring. Subsequently, descriptive statistical analysis was performed on whole-brain resistivity changes, and repeated-measures analysis of variance (ANOVA) on the average resistivity variation index. Additionally, pathological examinations were performed after 6 h of infarction.

MAIN RESULTS

The results obtained showed that ischemic damage developed in the right corpus striatum of the rats with MCAO, whereas the brains of the sham group showed no anomalies. The descriptive statistical analysis revealed that the whole-brain resistivity changes after 30, 60, 90, and 120 min of infarction were 0.063  ±  0.038, 0.097  ±  0.046, 0.141  ±  0.062, and 0.204  ±  0.092 for the rats with MCAO and 0.029  ±  0.021, 0.002  ±  0.002, 0.017  ±  0.011, and  -0.001  ±  0.011 for the sham-operated rats, respectively. The repeated-measures ANOVA revealed that the right MCAO model resulted in a significant impedance increase in the right hemisphere, which continued to increase over time after infarction.

SIGNIFICANCE

The overall study results indicate that EIT facilitates monitoring of local impedance variations caused by MCAO and may be a solution for real-time monitoring of intracranial pathological changes in ischemic stroke patients.

Cyclic nucleotide phosphodiesterases (PDEs) and endothelial function in ischaemic stroke. A review

BACKGROUND

Endothelial dysfunction is a hallmark of cerebrovascular disease, including ischemic stroke. Modulating endothelial signalling by cyclic nucleotides, cAMP and cGMP, is a potential therapeutic target in stroke. Inhibitors of the cyclic nucleotide degrading phosphodiesterase (PDE) enzymes may restore cerebral endothelial function. Current knowledge on PDE distribution and function in cerebral endothelial cells is sparse. This review explores data on PDE distribution and effects of PDEi in cerebral endothelial cells and identifies which PDEs are potential treatment targets in stroke.

METHOD

We performed a systematic search of electronic databases (Medline and Embase). Our search terms were cerebral ischaemia, cerebral endothelial cells, cyclic nucleotide, phosphodiesterase and phosphodiesterase inhibitors.

RESULTS

We found 23 publications which described effects of selective inhibitors of only three PDE families on endothelial function in ischemic stroke. PDE3 inhibitors (PDE3i) (11 publications) and PDE4 inhibitors (PDE4i) (3 publications) showed anti-inflammatory, anti-apoptotic or pro-angiogenic effects. PDE3i also reduced leucocyte infiltration and MMP-9 expression. Both PDE3i and PDE4i increased expression of tight junction proteins and protected the blood-brain barrier. PDE5 inhibitors (PDE5i) (6 publications) reduced inflammation and apoptosis. In preclinical models, PDE5i enhanced cGMP/NO signalling associated with microvascular angiogenesis, increased cerebral blood flow and improved functional recovery. Non-specific PDEi (3 publications) had mainly anti-inflammatory effects.

CONCLUSION

This review demonstrates that non-selective and selective PDEi of PDE3, PDE4 and PDE5 modulated endothelial function in cerebral ischemic stroke by regulating processes involved in vascular repair and neuroprotection and thus reduced cell death and inflammation. Of note, they promoted angiogenesis, microcirculation and improved functional recovery; all are important in stroke prevention and recovery, and effects should be further evaluated in humans.

Minimally Invasive Microelectrode Biosensors Based on Platinized Carbon Fibers for in Vivo Brain Monitoring

The ability to monitor the chemical composition of brain interstitial fluid remains an important challenge in the field of bioanalytical chemistry. In particular, microelectrode biosensors are a promising resource for the detection of neurochemicals in interstitial fluid in both animals and humans. These biosensors can provide second-by-second temporal resolution and enzymatic recognition of virtually any redox or nonredox molecule. However, despite miniaturization of these sensors to 50-250 μm in diameter to avoid vascular and cellular injury, inflammation and foreign-body reactions still occur following their implantation. Here, we fabricated microelectrodes with platinized carbon fibers to create biosensors that have an external diameter that is less than 15 μm. Platinization was achieved with physical vapor deposition, and increased sensitivity to hydrogen peroxide and improved enzymatic detection were observed for these carbon fiber microelectrodes. When these devices were implanted in the brains of rats, no injuries to the parenchyma or brain blood vessels were detected. In addition, these microelectrodes provided different estimates of basal glucose, lactate, and oxygen concentrations compared to conventional biosensors. Induction of spreading depolarization in the cerebral cortex further demonstrated the greater sensitivity of our microelectrodes to dynamic neurochemical changes. Thus, these minimally invasive devices represent a major advance in our ability to analyze brain interstitial fluid.

Optical imaging and modulation of neurovascular responses

The cerebral microvasculature consists of pial vascular networks, parenchymal descending arterioles, ascending venules and parenchymal capillaries. This vascular compartmentalization is vital to precisely deliver blood to balance continuously varying neural demands in multiple brain regions. Optical imaging techniques have facilitated the investigation of dynamic spatial and temporal properties of microvascular functions in real time. Their combination with transgenic animal models encoding specific genetic targets have further strengthened the importance of optical methods for neurovascular research by allowing for the modulation and monitoring of neuro vascular function. Image analysis methods with three-dimensional reconstruction are also helping to understand the complexity of microscopic observations. Here, we review the compartmentalized cerebral microvascular responses to global perturbations as well as regional changes in response to neural activity to highlight the differences in vascular action sites. In addition, microvascular responses elicited by optical modulation of different cell-type targets are summarized with emphasis on variable spatiotemporal dynamics of microvascular responses. Finally, long-term changes in microvascular compartmentalization are discussed to help understand potential relationships between CBF disturbances and the development of neurodegenerative diseases and cognitive decline.

Early Blood-Brain Barrier Disruption in Ischemic Stroke Initiates Multifocally Around Capillaries/Venules

BACKGROUND AND PURPOSE

Detection and localization of the early phase of blood-brain barrier disruption (BBBD) in vivo during cerebral ischemia/reperfusion injury remain a major challenge but may be a relevant outcome parameter in stroke.

METHODS

We studied early BBBD in mice after transient middle cerebral artery occlusion by multimodal, high-field (9.4T) in vivo magnetic resonance imaging, including the contrast agent gadofluorineM as an albumin-binding tracer. GadofluorineM contrast-enhanced magnetic resonance imaging was performed to determine BBBD at 2, 6, and 24 hours after reperfusion. BBBD was confirmed and localized along the microvascular tree by using fluorescent gadofluorineM and immunofluorescence stainings (cluster of differentiation 31, ephrin type-B receptor 4, alpha smooth muscle actin, ionized calcium binding adaptor molecule 1).

RESULTS

GadofluorineM contrast-enhanced magnetic resonance imaging revealed a multifocal spatial distribution of early BBBD and its close association with the microvasculature at a resolution of 40 μm. GadofluorineM leakage was closely associated with ephrin type-B receptor 4-positive but not alpha smooth muscle actin-positive vessels. The multifocal pattern of early BBBD (already at 2 hours after reperfusion) thus occurred in the distal capillary and venular microvascular bed. These multifocal zones showed distinct imaging signs indicative of early vasogenic edema. The total volume of multifocal early BBBD accurately predicted infarct size at 24 hours after reperfusion.

CONCLUSIONS

Early BBBD in focal cerebral ischemia initiates multifocally in the distal capillary and venular bed of the cerebral microvasculature. It is closely associated with perimicrovascular vasogenic edema and microglial activation and predicts the extent of final infarction.

Arterial and microvascular supply of cerebral hemispheres in the nude mouse revealed using corrosion casting and scanning electron microscopy

Morphological analyses of cerebral vascularization are not only important for the characterization of the anatomical and physiological relationships between vascular and nervous tissue, but also required to understand structural modifications that occur in many pathological conditions affecting the brain. The aim of this study was to generate a three-dimensional vascular map of the cerebral hemispheres in the nude mouse brain, a widely used animal model for studying tumour biology. We used the corrosion casting (CC) technique to isolate blood vessels from 30 nude mouse brains. All casts were analysed using scanning electron microscopy (SEM), which generated quantitative data regarding vessel length and diameter as well as inter-vascular and inter-branching distances. We identified three different topographical regions: (i) the cortical region, characterized by a superficial wide sheet of vessels giving rise to terminal perforant vessels that penetrate the grey matter; (ii) the inner part of the grey matter, in which dense capillary nets form many flake-like structures extending towards the grey-white matter boundary, where perforant vessels finally change direction and form a well-defined vascular sheet; and (iii) the white matter layer, characterized by a more disorganized vascular architecture. In this study, we demonstrate the accuracy of the CC-SEM method in revealing the 3D-topographical organization of the vascular network of the normal nude mouse brain. These baseline data will serve as a reference for future anatomical investigations of pathological alterations, such as tumour infiltrations, using the nude mouse model.

Pericytes as Inducers of Rapid, Matrix Metalloproteinase-9-Dependent Capillary Damage during Ischemia

Blood-brain barrier disruption (BBB) and release of toxic blood molecules into the brain contributes to neuronal injury during stroke and other cerebrovascular diseases. While pericytes are builders and custodians of the BBB in the normal brain, their impact on BBB integrity during ischemia remains unclear. We imaged pericyte-labeled transgenic mice with in vivo two-photon microscopy to examine the relationship between pericytes and blood plasma leakage during photothrombotic occlusion of cortical capillaries. Upon cessation of capillary flow, we observed that plasma leakage occurred with three times greater frequency in regions where pericyte somata adjoined the endothelium. Pericyte somata covered only 7% of the total capillary length in cortex, indicating that a disproportionate amount of leakage occurred from a small fraction of the capillary bed. Plasma leakage was preceded by rapid activation of matrix metalloproteinase (MMP) at pericyte somata, which was visualized at high resolution in vivo using a fluorescent probe for matrix metalloproteinase-2/9 activity, fluorescein isothiocyanate (FITC)-gelatin. Coinjection of an MMP-9 inhibitor, but not an MMP-2 inhibitor, reduced pericyte-associated FITC-gelatin fluorescence and plasma leakage. These results suggest that pericytes contribute to rapid and localized proteolytic degradation of the BBB during cerebral ischemia.

SIGNIFICANCE STATEMENT

Pericytes are a key component of the neurovascular unit and are essential for normal BBB function. However, during acute ischemia, we find that pericytes are involved in creating rapid and heterogeneous BBB disruption in the capillary bed. The mechanism by which pericytes contribute to BBB damage warrants further investigation, as it may yield new therapeutic targets for acute stroke injury and other neurological diseases involving capillary flow impairment.

Corrosion casting of the subglottis following endotracheal tube intubation injury: a pilot study in Yorkshire piglets

PURPOSE

Subglottic stenosis can result from endotracheal tube injury. The mechanism by which this occurs, however, is not well understood. The purpose of this study was to examine the role of angiogenesis, hypoxia and ischemia in subglottic mucosal injury following endotracheal intubation.

METHODS

Six Yorkshire piglets were randomized to either a control group (N=3, ventilated through laryngeal mask airway for corrosion casting) or accelerated subglottic injury group through intubation and induced hypoxia as per a previously described model (N=3). The vasculature of all animals was injected with liquid methyl methacrylate. After polymerization, the surrounding tissue was corroded with potassium hydroxide. The subglottic region was evaluated using scanning electron microscopy looking for angiogenic and hypoxic or degenerative features and groups were compared using Mann-Whitney tests and Friedman's 2-way ANOVA.

RESULTS

Animals in the accelerated subglottic injury group had less overall angiogenic features (P=.002) and more overall hypoxic/degenerative features (P=.000) compared with controls. Amongst angiogenic features, there was decreased budding (P=.000) and a trend toward decreased sprouting (P=.037) in the accelerated subglottic injury group with an increase in intussusception (P=.004), possibly representing early attempts at rapid revascularization. Amongst hypoxic/degenerative features, extravasation was the only feature that was significantly higher in the accelerated subglottic injury group (P=.000).

CONCLUSIONS

Subglottic injury due to intubation and hypoxia may lead to decreased angiogenesis and increased blood vessel damage resulting in extravasation of fluid and a decreased propensity toward wound healing in this animal model.

Relationship between pulsatility index and clinical course of acute ischemic stroke after thrombolytic treatment

Background. The relationship between the arterial recanalization after intravenous recombinant tissue plasminogen activator (rtPA) and outcomes is still uncertain. The aim of our study was to evaluate whether there is an association between the pulsatility indexes (PI) of the middle cerebral artery (MCA) measured by transcranial Doppler (TCD) after iv rtPA treatment and short- and long-term outcomes in ischemic stroke patients. Methods. Forty-eight patients with acute ischemia in the MCA territory who achieved complete recanalization after the administration of intravenous thrombolytic treatment were included in the study. The TCD was applied to patients after the iv rtPA treatment. Clinical and functional outcomes were assessed by National Institutes of Health Stroke Scale (NIHSS) scores and modified Rankin Scores (mRS), respectively. Results. Significant positive correlations were found between the PI value and NIHSS score at 24 hours, NIHSS score at 3 months, and mRS at 3 months (P < 0.005 for all). The cut-off value for PI in predicting a favorable prognosis and a good prognosis might be less than or equal to 1.1 and less than or equal to 1.4, respectively. Conclusions. PI may play a role in predicting the functional and clinical outcome after thrombolytic therapy in acute ischemic stroke patients.

Distribution of blood-brain barrier disruption in primary blast injury

Traumatic brain injury (TBI) resulting from explosive-related blast overpressure is a topic at the forefront of neurotrauma research. Compromise of the blood-brain barrier (BBB) and other cerebral blood vessel dysfunction is commonly reported in both experimental and clinical studies on blast injury. This study used a rifle primer-driven shock tube to investigate cerebrovascular injury in rats exposed to low-impulse, pure primary blast at three levels of overpressure (145, 232, and 323 kPa) and with three survival times (acute, 24, and 48 h). BBB disruption was quantified immunohistochemically by measuring immunoglobulin G (IgG) extravasation with image analysis techniques. Pure primary blast generated small lesions scattered throughout the brain. The number and size of lesions increased with peak overpressure level, but no significant difference was seen between survival times. Despite laterally directed blast exposure, equal numbers of lesions were found in each hemisphere of the brain. These observations suggest that cerebrovascular injury due to primary blast is distinct from that associated with conventional TBI.

Preservation of Capillary-beds in Rat Lung Tissue Using Optimized Chemical Decellularization

Promoting regeneration using scaffolds created by decellularizing native tissue is becoming a popular technique applied to a variety of tissues. We demonstrate a method to decellularize highly vascular tissue keeping the vascular structure intact down to the capillary scale. Using vascular corrosion casting (VCC), we created a method for quantitatively assessing the functionality of vascular extracellular matrix (ECM) following decellularization. Murine lung tissue was decellularized using a number of techniques, then characterized using standard histological methods, as well as our quantitative VCC (qVCC) technique. Using an optimized acellular method, we successfully decellularized lung tissue while leaving behind a patent vascular network based on qualitative and quantitative histological methods.

Can restoring incomplete microcirculatory reperfusion improve stroke outcome after thrombolysis?

Substantial experimental data and recent clinical evidence suggesting that tissue reperfusion is a better predictor of outcome after thrombolysis than recanalization necessitate that patency of microcirculation after recanalization should be reevaluated. If indeed microcirculatory blood flow cannot be sufficiently reinstituted despite complete recanalization as commonly observed in coronary circulation, it may be one of the factors contributing to low efficacy of thrombolysis in stroke. Although microvascular no-reflow is considered an irreversible process that prevents tissue recovery from injury, emerging evidence suggests that it might be reversed with pharmacological agents administered early during recanalization. Therefore, therapeutic approaches aiming at reducing microvascular obstructions may improve success rate of recanalization therapies. Importantly, promoting oxygen delivery to the tissue, where entrapped erythrocytes cannot circulate in capillaries, with ongoing serum flow may improve survival of the underreperfused tissue. Altogether, these developments bring about the exciting possibility that benefit of reperfusion therapies can be further improved by restoring microcirculatory function because survival in the penumbra critically depends on adequate blood supply. Here, we review the available evidence suggesting presence of an 'incomplete microcirculatory reperfusion' (IMR) after focal cerebral ischemia and discuss potential means that may help investigate IMR in stroke patients after recanalization therapies despite technical limitations.

Capillary remodeling and collateral growth without angiogenesis after unilateral common carotid artery occlusion in mice

OBJECTIVE

To clarify the mechanisms of blood flow restoration after major artery occlusion, we presented first dynamic changes in cortical vessel morphology observed through a cranial window in mice after unilateral common carotid artery (CCA) occlusion.

METHODS

The density and diameter of capillaries, as well as diameters of pial arteries, were measured by confocal laser-scanning microscopy and fluorescent microscopy, respectively. Possible angiogenesis was evaluated by detecting any outgrowth of endothelial cells from pre-existing vessels or intussusception in Tie2-GFP mice.

RESULTS

Immediately after unilateral CCA occlusion, cerebral blood flow (CBF) index, the reciprocal of mean transit time, reduced significantly and returned to the previous level after 14 days. Repeated observation of the cortical vessels did not reveal any angiogenesis, whereas the cortical capillary diameter increased by 74% after 14 days. The anterior cerebral artery (ACA) and collateral vessels connecting ACA and middle cerebral artery also dilated significantly. The capillary dilatation to the size of arteriole in the settings of collateral growth and CBF restoration suggested capillary remodeling.

CONCLUSIONS

Our results indicate that capillary remodeling, pial artery dilatation and collateral growth without angiogenesis are sufficient mechanisms to restore normal cerebral blood flow after unilateral CCA occlusion.

Association between changes in weight and cerebral arteries in rats

The objective of the study was to gain a better understanding of brain artery diameters and anatomical variations for precise modification of cerebral blood supply in ischemic stroke models. Sprague-Dawley rats (n = 35) were used for the experiment. Rats were perfused and resin replicas of cerebral arteries were created using a corrosion casting technique. Resin replicas were measured and analyzed for correlation of vessel lumen with animal sex and weight. A strong correlation between root of aorta diameter and weight was observed (p < 0.0001). We also observed a significant correlation between weight, internal carotid arteries, right external carotid artery, and pterygopalatine arteries. For the common carotid artery, a significant difference between the left and right branches was observed even though there was no association with weight. There was no significant association observed between animal sex and vessel size independent of weight. A better knowledge of vessel lumen in relation to animal sex and weight is essential for adequate blockage of an intracranial artery to induce cerebral ischemia in a rat model of stroke. This study provides a viable reference for choice of rat size in relation to the size of embolic agents such as filaments, microwires, or in vitro thrombus used in ischemic stroke experiments.

Pericyte contraction induced by oxidative-nitrative stress impairs capillary reflow despite successful opening of an occluded cerebral artery

Here we show that ischemia induces sustained contraction of pericytes on microvessels in the intact mouse brain. Pericytes remain contracted despite successful reopening of the middle cerebral artery after 2 h of ischemia. Pericyte contraction causes capillary constriction and obstructs erythrocyte flow. Suppression of oxidative-nitrative stress relieves pericyte contraction, reduces erythrocyte entrapment and restores microvascular patency; hence, tissue survival improves. In contrast, peroxynitrite application causes pericyte contraction. We also show that the microvessel wall is the major source of oxygen and nitrogen radicals causing ischemia and reperfusion-induced microvascular dysfunction. These findings point to a major but previously not recognized pathophysiological mechanism; ischemia and reperfusion-induced injury to pericytes may impair microcirculatory reflow and negatively affect survival by limiting substrate and drug delivery to tissue already under metabolic stress, despite recanalization of an occluded artery. Agents that can restore pericyte dysfunction and microvascular patency may increase the success of thrombolytic and neuroprotective treatments.

Brain ischemia and ischemic blood-brain barrier as etiological factors in sporadic Alzheimer's disease

The development of neuronal death and amyloid plaques is a characteristic feature of ischemic- and Alzheimer-type dementia. An important aspect of neuronal loss and amyloid plaques are their topography and neuropathogenesis. This review was performed to present the hypothesis that different fragments of blood-borne amyloid precursor protein are able to enter the ischemic blood-brain barrier. Chronic disruption of the blood-brain barrier after ischemic injury was shown. As an effect of chronic ischemic blood-brain barrier injury, a visible connection of amyloid plaques with neurovasculature was observed. This neuropathology appears to have similar distribution and mechanisms to Alzheimer's disease. The usefulness of rival ischemic theory in elucidating the neuropathogenesis of amyloid plaques formation and neuronal death in Alzheimer's disorder is discussed.

Quantitative assessments of cerebral vascular damage with a silicon rubber casting method in photochemically-induced thrombotic stroke rat models

Previous studies have described microvascular disturbances downstream of occluded large vessels arising during the acute phase (several hours) following cerebral ischemic insult. Prolonged microvascular disturbances may cause delayed neuronal cell death in ischemic penumbral regions, leading to expanded brain infarctions and poor neurological and functional outcomes. The lack of simple and quantitative methods for investigating this microcirculation failure suggests the need to develop a new method for clarifying the precise distribution and persistence of post-ischemic microvascular disturbances. The present study used a silicone rubber casting method in quantitative analyses of microvascular conditions in photochemically-induced thromboembolic (PIT) stroke rat models. After the casting procedure in rats with PIT stroke, a 6 microm-thick coronal section was obtained, and quantitative analyses of microvascular density and measurements of the infarct area in the serial section were performed. The major findings of the present study are as follows: (1) Silicone rubber casting techniques can be applied to precise quantitative analyses of microvessels in the same individual in whom brain infarct volume was measured; (2) the persistence and spatial distribution of microvascular disturbances assessed at the ischemic core, ischemic penumbra, and non-ischemic regions strongly suggest that microvascular disturbances affect brain infarct expansion; (3) the current method demonstrated the protective effects of MK-801 on microvessels, indicating that the technique may be useful in investigating factors that provide vascular protection. The experimental procedure introduced here would facilitate future evaluations of vascular protective agents.

Three-dimensional cerebral vasculature of the CBA mouse brain: A magnetic resonance imaging and micro computed tomography study

Studies of mouse cerebral vasculature to date have focused on the circle of Willis without examining the morphological distribution of blood vessels through the rest of the brain. Since mouse models are frequently used in brain-related studies, there is a need for a comprehensive cerebral vasculature atlas for the mouse with an emphasis on the location of vessels with respect to neuroanatomical structures, the watershed regions associated with specific arteries, as well as a consistent nomenclature of the cerebral vessels. This article describes such an atlas, based on a combination of magnetic resonance and computed tomography technology to yield high-resolution volumetric and vasculature data on CBA mouse. This three-dimensional vasculature dataset provides an anatomical resource for future mouse studies.

New polyurethane-based material for vascular corrosion casting with improved physical and imaging characteristics

Vascular corrosion casting has been established as a method to reconstruct the three-dimensional (3D) structure of blood vessels of organs and tissues. After replacing the blood volume with a low viscosity resin, the surrounding tissue is removed to replicate the vascular architecture, typically using scanning electron microscopy (SEM). To date available casting resins have had significant limitations such as lack of viscosity, leading to insufficient perfusion of smallest capillaries in organs and tissues of smaller species, interaction with surrounding tissue or fragility of resulting casts. We have reported here about a new polyurethane-based casting resin (PU4ii) with superior physical and imaging characteristics. Low viscosity, timely polymerization, and minimal shrinking of PU4ii produces high quality casts, including the finest capillaries. These casts are highly elastic while retaining their original structure to facilitate postcasting tissue dissection and pruning of casts. SEM images illustrate the high reproduction quality, including endothelial cell imprints, features that allow one to discern arterial and veinal vessels. For quantitative analysis, casts from PU4ii can be imaged using micro-computed tomography to produce digital 3D reconstructions. The inherent fluorescence of PU4ii is sufficient to reproduce casts with or without tissue using confocal microscopy (CM). Because of the simplified casting procedure, the high reproducibility and the superior reproduction quality, a combination of vascular corrosion casting using PU4ii with advanced imaging technologies has great potential to support the description of vascular defects and drug effects in disease models using mutant mice.