Stroke remains a leading cause of death and disability in the world. Over the past few decades our understanding of the pathophysiology of stroke has increased, but greater insight is required to ...advance the field of stroke recovery. Clinical treatments have improved in the acute time window, but long-term therapeutics remain limited. Complex neural circuits damaged by ischemia make restoration of function after stroke difficult. New therapeutic approaches, including cell transplantation or stimulation, focus on reestablishing these circuits through multiple mechanisms to improve circuit plasticity and remodeling. Other research targets intact networks to compensate for damaged regions. This review highlights several important mechanisms of stroke injury and describes emerging therapies aimed at improving clinical outcomes.
Stroke continues to cause immense burdens on millions throughout the world. George and Steinberg discuss the growing understanding of stroke pathophysiology and the established and novel treatment methods being developed to combat this serious disease.
Brain endothelial cells form a paracellular and transcellular barrier to many blood-borne solutes via tight junctions (TJs) and scarce endocytotic vesicles. The blood-brain barrier (BBB) plays a ...pivotal role in the healthy and diseased CNS. BBB damage after ischemic stroke contributes to increased mortality, yet the contributions of paracellular and transcellular mechanisms to this process in vivo are unknown. We have created a transgenic mouse strain whose endothelial TJs are labeled with eGFP and have imaged dynamic TJ changes and fluorescent tracer leakage across the BBB in vivo, using two-photon microscopy in the t-MCAO stroke model. Although barrier function is impaired as early as 6 hr after stroke, TJs display profound structural defects only after 2 days. Conversely, the number of endothelial caveolae and transcytosis rate increase as early as 6 hr after stroke. Therefore, stepwise impairment of transcellular followed by paracellular barrier mechanisms accounts for the BBB deficits in stroke.
•Transgenic eGFP-Claudin5 mice enable continual time-lapse imaging of BBB TJs•TJ structural abnormalities are present at late but not early phases after stroke•EC endocytosis and transcytosis are both increased at early phases after stroke•Stroke impairs progressively the transcellular then paracellular endothelial barrier
Knowland et al. generate a transgenic mouse line to image dynamic changes in tight junctions at the blood-brain barrier in vivo with two-photon microscopy and identify a mechanism of how endothelial cells respond to ischemic stroke with potential therapeutic implications.
Moyamoya disease is characterized by chronic stenoocclusive vasculopathy involving the distal supraclinoid internal carotid arteries and presents with ischemic or hemorrhagic symptoms. We review ...advances in the understanding and management of moyamoya disease.
Cerebral revascularization, either direct or indirect, is the cornerstone of treatment for moyamoya disease. Recent advances have been made in understanding the molecular biology and pathophysiology of moyamoya disease, and new genetic mutations and deletions have been identified. Imaging for moyamoya disease is also rapidly improving with new sequences of MRI and better methods of assessing ischemia and cerebrovascular reserve. Positron emission tomography has emerged as an important tool to measure cerebrovascular reserve. Novel surgical techniques assess patency and ischemia during superficial temporal to middle cerebral artery bypass, including indocyanine green videoangiography to evaluate anastomosis patency, and various methods to monitor intraoperative blood flow. Newer methods of indirect revascularization have been described with placement of more tissues supplied by the external carotid artery on the brain surface. Postoperative hyperperfusion to the chronically ischemic brain tissue is a recently identified causative factor of complications. Interestingly, complications from hyperperfusion mimic those caused by ischemia, although they have different treatments, making the role of postoperative blood flow assessment important in distinguishing between the two. Awareness has also increased that even asymptomatic patients can experience significant cognitive decline attributable to chronic ischemia. Whether this reverts after successful revascularization requires investigation.
Surgical revascularization with direct, indirect, and combined methods remains the preferred procedure for patients with moyamoya disease.
The functional and molecular similarities and distinctions between human and murine astrocytes are poorly understood. Here, we report the development of an immunopanning method to acutely purify ...astrocytes from fetal, juvenile, and adult human brains and to maintain these cells in serum-free cultures. We found that human astrocytes have abilities similar to those of murine astrocytes in promoting neuronal survival, inducing functional synapse formation, and engulfing synaptosomes. In contrast to existing observations in mice, we found that mature human astrocytes respond robustly to glutamate. Next, we performed RNA sequencing of healthy human astrocytes along with astrocytes from epileptic and tumor foci and compared these to human neurons, oligodendrocytes, microglia, and endothelial cells (available at http://www.brainrnaseq.org). With these profiles, we identified novel human-specific astrocyte genes and discovered a transcriptome-wide transformation between astrocyte precursor cells and mature post-mitotic astrocytes. These data represent some of the first cell-type-specific molecular profiles of the healthy and diseased human brain.
•We develop the first method to acutely purify fetal and adult human astrocytes•We obtain transcriptome profiles of human neurons, glia, and vascular cells•While similar, human and mouse astrocytes have unique genomic and functional traits•Human astrocytes exist in at least two distinct developmental stages
Zhang et al. developed a method to acutely purify healthy and diseased human astrocytes and to culture them in serum-free conditions. They obtained transcriptome profiles of purified human CNS cell types and discovered two distinct stages of human astrocyte development.
To derive quantitative image features from magnetic resonance (MR) images that characterize the radiographic phenotype of glioblastoma multiforme (GBM) lesions and to create radiogenomic maps ...associating these features with various molecular data.
Clinical, molecular, and MR imaging data for GBMs in 55 patients were obtained from the Cancer Genome Atlas and the Cancer Imaging Archive after local ethics committee and institutional review board approval. Regions of interest (ROIs) corresponding to enhancing necrotic portions of tumor and peritumoral edema were drawn, and quantitative image features were derived from these ROIs. Robust quantitative image features were defined on the basis of an intraclass correlation coefficient of 0.6 for a digital algorithmic modification and a test-retest analysis. The robust features were visualized by using hierarchic clustering and were correlated with survival by using Cox proportional hazards modeling. Next, these robust image features were correlated with manual radiologist annotations from the Visually Accessible Rembrandt Images (VASARI) feature set and GBM molecular subgroups by using nonparametric statistical tests. A bioinformatic algorithm was used to create gene expression modules, defined as a set of coexpressed genes together with a multivariate model of cancer driver genes predictive of the module's expression pattern. Modules were correlated with robust image features by using the Spearman correlation test to create radiogenomic maps and to link robust image features with molecular pathways.
Eighteen image features passed the robustness analysis and were further analyzed for the three types of ROIs, for a total of 54 image features. Three enhancement features were significantly correlated with survival, 77 significant correlations were found between robust quantitative features and the VASARI feature set, and seven image features were correlated with molecular subgroups (P < .05 for all). A radiogenomics map was created to link image features with gene expression modules and allowed linkage of 56% (30 of 54) of the image features with biologic processes.
Radiogenomic approaches in GBM have the potential to predict clinical and molecular characteristics of tumors noninvasively. Online supplemental material is available for this article.
3D histology, slice-based connectivity atlases, and diffusion MRI are common techniques to map brain wiring. While there are many modality-specific tools to process these data, there is a lack of ...integration across modalities. We develop an automated resource that combines histologically cleared volumes with connectivity atlases and MRI, enabling the analysis of histological features across multiple fiber tracts and networks, and their correlation with in-vivo biomarkers. We apply our pipeline in a murine stroke model, demonstrating not only strong correspondence between MRI abnormalities and CLARITY-tissue staining, but also uncovering acute cellular effects in areas connected to the ischemic core. We provide improved maps of connectivity by quantifying projection terminals from CLARITY viral injections, and integrate diffusion MRI with CLARITY viral tracing to compare connectivity maps across scales. Finally, we demonstrate tract-level histological changes of stroke through this multimodal integration. This resource can propel investigations of network alterations underlying neurological disorders.
Significance Stroke is the leading cause of disability in the United States and has very limited treatment options. Brain stimulation techniques that promote recovery after stroke are a promising ...area of research; however, current stimulation techniques nonspecifically activate/inhibit the target area, which not only leads to undesired side effects but also makes it difficult to understand which cell types and mechanisms drive recovery. We used the optogenetic technique to specifically stimulate only neurons after stroke and demonstrate that selective neuronal stimulations can activate beneficial mechanisms and promote recovery. Understanding the cell type and mechanisms driving recovery may identify potential drug targets for stroke treatment, as well as ultimately help develop precise brain stimulation techniques for stroke therapy.
Neurorestoration after stroke Azad, Tej D; Veeravagu, Anand; Steinberg, Gary K
Neurosurgical focus,
05/2016, Volume:
40, Issue:
5
Journal Article
Peer reviewed
Open access
Recent advancements in stem cell biology and neuromodulation have ushered in a battery of new neurorestorative therapies for ischemic stroke. While the understanding of stroke pathophysiology has ...matured, the ability to restore patients' quality of life remains inadequate. New therapeutic approaches, including cell transplantation and neurostimulation, focus on reestablishing the circuits disrupted by ischemia through multidimensional mechanisms to improve neuroplasticity and remodeling. The authors provide a broad overview of stroke pathophysiology and existing therapies to highlight the scientific and clinical implications of neurorestorative therapies for stroke.
No treatment currently exists to restore lost neurological function after stroke. A growing number of studies highlight the potential of stem cell transplantation as a novel therapeutic approach for ...stroke. In this review we summarize these studies, discuss potential mechanisms of action of the transplanted cells, and emphasize the need to determine parameters that are critical for transplantation success.
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