The role of mast cells in ischemic and hemorrhagic brain injury

Stroke, ischemic or hemorrhagic, belongs among the foremost causes of death and disability worldwide. Massive brain swelling is the leading cause of death in large hemispheric strokes and is only modestly alleviated by available treatment. Thrombolysis with tissue plasminogen activator (TPA) is the only approved therapy in acute ischemic stroke, but fear of TPA-mediated hemorrhage is often a reason for withholding this otherwise beneficial treatment. In addition, recanalization of the occluded artery (spontaneously or with thrombolysis) may cause reperfusion injury by promoting brain edema, hemorrhage, and inflammatory cell infiltration. A dominant event underlying these phenomena seems to be disruption of the blood-brain barrier (BBB). In contrast to ischemic stroke, no widely approved clinical therapy exists for intracerebral hemorrhage (ICH), which is associated with poor outcome mainly due to the mass effect of enlarging hematoma and associated brain swelling. Mast cells (MCs) are perivascularly located resident inflammatory cells which contain potent vasoactive, proteolytic, and fibrinolytic substances in their cytoplasmic granules. Experiments from our laboratory showed MC density and their state of granulation to be altered early following focal transient cerebral ischemia, and degranulating MCs were associated with perivascular edema and hemorrhage. (I) Pharmacological MC stabilization led to significantly reduced ischemic brain swelling (40%) and BBB leakage (50%), whereas pharmacological MC degranulation raised these by 90% and 50%, respectively. Pharmacological MC stabilization also revealed a 40% reduction in neutrophil infiltration. Moreover, genetic MC deficiency was associated with an almost 60% reduction in brain swelling, 50% reduction in BBB leakage, and 50% less neutrophil infiltration, compared with controls. (II) TPA induced MC degranulation in vitro. In vivo experiments with post-ischemic TPA administration demonstrated 70- to 100-fold increases in hemorrhage formation (HF) compared with controls HF. HF was significantly reduced by pharmacological MC stabilization at 3 (95%), 6 (75%), and 24 hours (95%) of follow-up. Genetic MC deficiency again supported the role of MCs, leading to 90% reduction in HF at 6 and 24 hours. Pharmacological MC stabilization and genetic MC deficiency were also associated with significant reduction in brain swelling and in neutrophil infiltration. Importantly, these effects translated into a significantly better neurological outcome and lower mortality after 24 hours. (III) Finally, in ICH experiments, pharmacological MC stabilization resulted in significantly less brain swelling, diminished growth in hematoma volume, better neurological scores, and decreased mortality. Pharmacological MC degranulation produced the opposite effects. Genetic MC deficiency revealed a beneficial effect similar to that found with pharmacological MC stabilization. In sum, the role of MCs in these clinically relevant scenarios is supported by a series of experiments performed both in vitro and in vivo. That not only genetic MC deficiency but also drugs targeting MCs could modulate these parameters (translated into better outcome and decreased mortality), suggests a potential therapeutic approach in a number of highly prevalent cerebral insults in which extensive tissue injury is followed by dangerous brain swelling and inflammatory cell infiltration. Furthermore, these experiments could hint at a novel therapy to improve the safety of thrombolytics, and a potential cellular target for those seeking novel forms of treatment for ICH.Aivoinfarkti on yhdessä sydäninfarktin ja syövän kanssa yleisimpiä kuolinsyitä maailmassa. Aivohalvauspotilaiden kuntoutus on kallista eikä se useinkaan estä työkyvyttömyyttä ja elämänlaadun huonontumista. Valtimotukoksen syntymisen ja sen uudelleen avautumisen (spontaanin tai lääkkeellisen) välinen aikaviive ratkaisee kokonaisvaurion laajuuden, koska verenkierron myöhäinen palautuminen johtaa veri-aivo esteen vaurioon, aivoturvotukseen, verenvuotoon ja tulehdussolujen vasteeseen. Valtimotukoksesta aiheutuneen aivoinfarktin ennuste on viime vuosina huomattavasti parantunut liuotushoidon ansioista. Liuotushoito ei kuitenkaan sovellu kaikille potilaille aivoverenvuodon riskin takia. Tämä riski vaihteli kriteereistä riippuen isoissa tutkimuksissa (n. 2-8 %). Jos aivoinfarkti johtuu primäärisestä aivoverenvuodosta, ennuste on tunnetusti huono ja hoitokeinot lähes olemattomat. Syöttösolut on hyvin tunnettuja soluja mm allergia-sairauksissa. Nämä tiettyjen aivoverisuonten ympärille sijoittuvia soluja sisältävät jyväsissään verisuoniin vaikuttavia, valkuaisaineita pilkkovia, fibriiniä hajoittavia sekä muita välittäjäaineita, jotka vapautuvat syöttösolujen aktivaation johdosta. I) Syöttösolujen aktivaatio (yhdiste 48/80) lisäsi veri-aivo esteen vauriota (50 %), aivoturvotusta (90 %) sekä tulehduksellista reaktiota kun taas aktivaation esto (kromoglikaatti) vähensi nämä vasteet seuraavasti: 50 %, 40 % ja 40 % kontrolliryhmään verrattuna. Lisäksi, syöttösolupuutteisilla rotilla oli, villityyppeihin verrattuna, jopa kromoglikaattihoidettuja parempaa löydöstä. II)Liuotushoidon aine (TPA) aktivoi syöttösoluja in vitro. Aivoiskemian mallissa TPA lisäsi aivoverenvuodon 70 100 kertaa kontrolliryhmään verrattuna. TPA:n aiheuttaman aivoverenvuodon vähensi (n. 90 %) syöttösolujen aktivoinnin estämällä 3, 6 sekä 24 tunnin kohdalla. Syttösolupuutteisilla rotilla oli 90 % vähemmän TPA:n aiheuttamaa aivoverenvuotoa kuin villityypeillä. Syöttösolujen aktivoinnin esto ja syöttösolupuutteisuus ilmeni myös vähentyneenä kuolleisuutena ja parempana neurologisena toipumisena. III) Myös primäärisessä aivojen sisäisessä verenvuodossa syöttösolujen aktivoinnin esto merkittävästi vähensi aivoverenvuodon ja aivoturvotuksen kasvua kun taas syöttösolujen aktivointi aiheutti päinvastaisen muutoksen. Syöttösolupuutteisilla rotilla oli samanlaisia löydöksiä kun kromoglikaattihoidetuilla. Tässäkin tutkimuksessa syöttösolujen aktivoinnin esto ja syöttösolupuutteisuus ilmeni vähentyneenä kuolleisuutena ja parempana neurologisena toipumisena. Tulokset viittaavat vahvasti tärkeään syöttösolujen rooliin veri-aivo esteen vaurion, aivoturvotuksen, tulehduksellisen reaktion, liuotushoidon aiheuttaman aivoverenvuodon sekä primäärisen aivojen sisäisen verenvuodon kasvun ja sen aiheuttaman aivoturvotuksen synnyssä

Diseases of the Brain, Head and Neck, Spine 2020–2023

This open access book offers an essential overview of brain, head and neck, and spine imaging. Over the last few years, there have been considerable advances in this area, driven by both clinical and technological developments. Written by leading international experts and teachers, the chapters are disease-oriented and cover all relevant imaging modalities, with a focus on magnetic resonance imaging and computed tomography. The book also includes a synopsis of pediatric imaging. IDKD books are rewritten (not merely updated) every four years, which means they offer a comprehensive review of the state-of-the-art in imaging. The book is clearly structured and features learning objectives, abstracts, subheadings, tables and take-home points, supported by design elements to help readers navigate the text. It will particularly appeal to general radiologists, radiology residents, and interventional radiologists who want to update their diagnostic expertise, as well as clinicians from other specialties who are interested in imaging for their patient care

Vascular Malformations of the Central Nervous System

Vascular malformations of the central nervous system are important pathologies that could present with abrupt onset hemorrhage resulting in devastating neurological deficits. Current knowledge of their biology and natural history is increasing. Diagnostic modalities help clinicians to better evaluate the individual cases, and to decide the best treatment options. Treatment alternatives are various and all treatment options should be evaluated before choosing the final therapeutic modality. The purpose of this book is to review the current knowledge about vascular malformations of the central nervous system and to evaluate the treatment alternatives

Studies of an ischaemic stroke model (middle cerebral artery occlusion in the rat) and modifications to improve its consistency

The work in this study has been mainly directed towards developing consistent protocols for an animal model of ischaemic stroke, suitable for novel drug combination strategies, using the intraluminal suture method of middle cerebral artery occlusion (MCAO) in the rat. Following optimisation of the measurement protocols, it was found that more consistent volumes of cerebral infarction were produced in the animal model when a silicone-coated type of intraluminal suture was used for permanent MCAO in Sprague-Dawley rats (coefficient of variation (cv) 19.9%), compared to an uncoated type (cv 66.6%). This more consistent protocol was used in a therapeutic screening study, combining 619C89, a sodium channel blocker to inhibit glutamate release, with BB-823, a platelet activating factor (PAF) antagonist to inhibit inflammatory responses. Although both agents individually reduced infarct volume, combined administration was only slightly and not significantly more effective. This may have been due to either a ceiling effect or the possibility that both agents targetted the same pathological mechanism. Both glutamate and PAF have been previously shown to induce the expression of cyclo-oxygenase (COX-2). However, molecular studies showed that although COX-2 induction was glutamate-mediated, 619C89 had no effect on the process, and the effect of BB-823 was only slight. A persistent problem with the model was the degree of residual variability, which was possibly obscuring small but significant differences. An attempt was made to improve reproducibility of the protocol further, by investigating the effect of animal strain. In the context of permanent MCAO, Fischer-344 rats had more consistent infarct volumes (cv 10%). Extending this approach to the context of temporary MCAO, Wistar rats had more consistent results (cv 9.5%). The direction of this study turned from investigating novel therapies to developing consistent protocols. Since reliable animal models are essential for preclinical studies, the present findings should significantly benefit stroke research

Brain Injury

The present two volume book "Brain Injury" is distinctive in its presentation and includes a wealth of updated information on many aspects in the field of brain injury. The Book is devoted to the pathogenesis of brain injury, concepts in cerebral blood flow and metabolism, investigative approaches and monitoring of brain injured, different protective mechanisms and recovery and management approach to these individuals, functional and endocrine aspects of brain injuries, approaches to rehabilitation of brain injured and preventive aspects of traumatic brain injuries. The collective contribution from experts in brain injury research area would be successfully conveyed to the readers and readers will find this book to be a valuable guide to further develop their understanding about brain injury

New Insight into Cerebrovascular Diseases

“Brain circulation is a true road map that consists of large extended navigation territories and a number of unimagined and undiscovered routes.” Dr. Patricia Bozzetto Ambrosi This book combines an update on the review of cerebrovascular diseases in the form of textbook chapters, which has been carefully reviewed by Dr. Patricia Bozzetto Ambrosi, Drs. Rufai Ahmad and Auwal Abdullahi and Dr. Amit Agrawal, high-performance academic editors with extensive experience in neurodisciplines, including neurology, neurosurgery, neuroscience, and neuroradiology, covering the best standards of neurological practice involving basic and clinical aspects of cerebrovascular diseases. Each topic was carefully revised and prepared using smooth, structured vocabulary, plus superb graphics and scientific illustrations. In emphasizing the most common aspects of cerebrovascular diseases: stroke burden, pathophysiology, hemodynamics, diagnosis, management, repair, and healing, the book is comprehensive but concise and should become the standard reference guide for this neurological approach

Evaluation of prefrontal ischemic lesions on higher order cognitive behaviours in the rat

Stroke is the most common cause of disability worldwide, and it is expected that the global number of stroke survivors will increase significantly over the coming decades. Many survivors of stroke have both short and long-term deficits in function, the most common of which are motor deficits. However, an often forgotten aspect of stroke is its negative and often long-lasting effects on cognitive function. At the moment, there are some effective intervention strategies for treating motor dysfunction post-stroke, but we currently have very limited strategies for treating cognitive dysfunction. Furthermore, there are very few stroke models specifically focusing on higher-order cognitive dysfunctions, also known as executive functions, which have been shown to be affected in a substantial portion of stroke survivors. This makes it difficult to effectively study the effects of potential therapies to alleviate post-stroke cognitive dysfunction. It is also known that the seat of higher-order cognitive function is the prefrontal cortex (PFC), and that damage to this region or by damaging connections to the area can result in executive dysfunction. Therefore, the goal of this thesis is to develop new animal models of post-stroke cognitive dysfunction, targeting specific regions of the rodent PFC. The overarching hypothesis of the project was that injections of the vasoconstrictor, endothelin-1, into particular regions of the prefrontal cortex will cause ischemic lesions in this area, as well as measureable cognitive deficits in higher-order cognitive functions. The overall objectives of the thesis were: 1. To refine and evaluate the effects of endothelin-1 injections into the prefrontal cortex on brain lesion size, and initial behavioural effects in the rat. 2. To measure the effects of refined, focal ischemic lesions within the medial prefrontal cortex on aspects of set-shifting and temporal order memory, both of which are higher-order cognitive functions, in the rat. 3. To further evaluate the model using endothelin-1 to create focal lesions in the orbital prefrontal cortex versus lesions in the medial prefrontal cortex to assess its effects on decision making in the rat. The initial modelling of post-stroke cognitive dysfunction was attempted using the compound endothelin-1 (ET-1), an endogenous polypeptide capable of constricting blood vessels in the brain. Two separate medial prefrontal cortical (mPFC) ET-1 injection protocols (four injections versus two injections into the mPFC) in the rat were examined in an attempt to understand the size and location of the resulting brain lesion. It was found that the two injection protocol, as compared to the four injection protocol, resulted in a more targeted lesion in the mPFC and resulted in fewer animal mortalities. As well, it appeared that mPFC lesions caused anxiogenic behaviours in these animals as assessed through the elevated plus maze, indicating that these lesions were having some effects on post-stroke cognitive behaviour. Further experiments with the two-injection endothelin-1 model previously established assessed for deficits in specific higher-order cognitive domains, specifically set-shifting and temporal order memory. This was done using a modified set-shifting maze and a temporal object recognition task. It was found that lesions to the medial prefrontal cortex caused specific context-dependent set-shifting dysfunctions in stroke animals. However, attempts to determine the lesions effects on temporal order memory did not function as expected, indicating that the methods used to assess this behaviour need to be modified in the future. Finally, two separate models of prefrontal stroke targeting the medial and orbital prefrontal cortices were both examined for their effects on decision making and inhibitory control as assessed through a delay discounting maze, wherein animals would have the choice between an immediately available, but small, food reward or a larger food reward, to which access was delayed. As well, during this testing the animals ultrasonic vocalizations, which can indicate affective or aversive emotional states, were also recorded while the animals were anticipating a food reward. What was found was that lesions to the orbital, but not the medial, prefrontal cortex caused rats to choose the lower food reward as compared to control animals. Interestingly, only the medial prefrontal lesioned animals changed the relative frequency and duration of their ultrasonic vocalization calls post-stroke, indicating that changes in animal vocalizations are not necessarily correlated to changes in behaviour. Overall, the work presented in this thesis suggests that specific higher-order cognitive dysfunctions can be accomplished using endothelin-1, thereby providing a potentially new model for the study of post-stroke cognitive dysfunction

Modeling middle cerebral artery stroke in rats : an examination of the skilled reaching impairments

xiii, 345 leaves : ill. ; 29 cm. + 1 CD-ROMMiddle cerebral artery (MCA) stroke can produce chronic incapacitating motor impairments. Understanding the neural basis of the motor syndromes is complicated by the diversity of neural structures damaged but the problem can be addressed in laboratory rats by inducing selective infarcts. Nevertheless, the motor syndromes that ensue from stroke in rats remain poorly understood and undermine its potential as a model for clinical stroke. The objective of the present thesis was to document the skilled reaching impairments from neocortical and subcortical MCA infarcts in rats. In addition, the integrity of the motor system components spared by the infarct was assessed neurophysiologically and neuroanatomically. Characteristic reaching impairments emerged from each infarct but there were also some overlapping features that might be explained by neural dysfunction extending beyond the boundaries of the infarct. The present studies showed that the laboratory rat is an ideal animal model for studying stroke, which should be of interest to both clinical and research scientists studying stroke

Tracking endogenous and grafted neural progenitor cells in normal and ischaemic brains using MRI contrast agents and genetic labelling

Cerebral ischaemia is a major cause of mortality and morbidity globally. Neural stem and progenitor cells (NPC) have the potential to contribute to brain repair and regeneration after an ischaemic event. Both endogenous and grafted NPC have been shown to migrate towards the ischaemic lesion, and differentiate into neurons. This thesis investigates methods of labeling and tracking the migration neural progenitor cells to a site of cerebral ischaemic injury, using magnetic resonance imaging (MRI) contrast agents and transgenic lineage tracing techniques. First, labeling of exogenous NPC populations was investigated, for use in cell tracking in grafting studies. Cell labeling was optimized in vitro with fetal NPC using the iron oxide-based MRI contrast agent. A labeling method was developed using the FePro contrast agent, which maximized iron oxide uptake, was non-toxic to NPC, and did not interfere with NPC proliferation and differentiation. Labelled cells were then grafted into the brain after cerebral ischaemia, and imaged over four weeks using MRI. NPC migration was not observed in vivo, but an endogenous contrast evolved over time within the lesioned tissue, which presented a source of confounding signal for cell tracking. Endogenous ferric iron was observed in the lesion on histological sections. Several limitations of using MRI-based iron oxide contrast agents were highlighted in this study. To circumvent these limitations, we considered the development of gadolinium-based MRI contrast agents for cellular labeling and tracking, in collaboration with Imperial College chemistry department. Polymeric Gd-DOTA chelates were synthesized and designed for maximal r1 relaxivity, and their relaxivity and effects on cell viability were assessed. Through this approach, we identified a number of candidate polymeric Gd-DOTA chelates with high relaxivity and low cytotoxicity for use in cellular imaging and tracking studies. Next, cell tracking of endogenous NPC was investigated, using MRI contrast agent and transgenic lineage tracing approaches. A method of in situ labeling of endogenous NPC with the MRI contrast agent FePro was developed. NPC were labeled with FePro in situ, and their normal migration to the olfactory bulb, where they contribute to neurogenesis, could be imaged in vivo and ex vivo. In a second study, the migration of NPC constitutively expressing green fluorescent protein (GPF) under the promoters of genes of two developmentally distinct cortical and striatal NPC populations, was investigated following cerebral ischaemia. Both cortical and striatal populations of NPC were observed to contribute to the migrating streams of NPC that were observed in the striatum after five weeks post-ischaemia. These studies demonstrate that MRI contrast agents offer the potential for in vivo, longitudinal tracking of NPC migration, in both grafted and endogenous NPC populations. Coupled with transgenic lineage tracing, and used in animal models of CNS injury such as cerebral ischaemia, labeling and tracking the migration of NSC with MRI contrast agents can contribute to our understanding of NPC biology in pathological environments