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Journal ArticleDOI

Live imaging of astrocyte responses to acute injury reveals selective juxtavascular proliferation

TL;DR: In vivo in vivo two-photon laser-scanning microscopy revealed a marked heterogeneity in the reaction of individual astrocytes, with one subset retaining their initial morphology, another directing their processes toward the lesion, and a distinct subset located at juxtavascular sites proliferating.
Abstract: Astrocytes are thought to have important roles after brain injury, but their behavior has largely been inferred from postmortem analysis. To examine the mechanisms that recruit astrocytes to sites of injury, we used in vivo two-photon laser-scanning microscopy to follow the response of GFP-labeled astrocytes in the adult mouse cerebral cortex over several weeks after acute injury. Live imaging revealed a marked heterogeneity in the reaction of individual astrocytes, with one subset retaining their initial morphology, another directing their processes toward the lesion, and a distinct subset located at juxtavascular sites proliferating. Although no astrocytes actively migrated toward the injury site, selective proliferation of juxtavascular astrocytes was observed after the introduction of a lesion and was still the case, even though the extent was reduced, after astrocyte-specific deletion of the RhoGTPase Cdc42. Thus, astrocyte recruitment after injury relies solely on proliferation in a specific niche.

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Citations
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Journal ArticleDOI
22 Jan 2014-Neuron
TL;DR: The contributions of diverse nonneuronal cell types to outcome after acute injury, or to the progression of chronic disease, are of increasing interest as the push toward understanding and ameliorating CNS afflictions accelerates.

1,056 citations


Cites background from "Live imaging of astrocyte responses..."

  • ...become reactive and hypertrophy and in some cases proliferate (Bardehle et al., 2013; Zheng et al., 2010)....

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  • ...…in situ and do not migrate either to or away from injury sites but can swell osmotically and, depending on the severity of injury or ischemia, can die in the center of severe lesions or can become reactive and hypertrophy and in some cases proliferate (Bardehle et al., 2013; Zheng et al., 2010)....

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Journal ArticleDOI
TL;DR: New insights herald the concept that astrocytes represent a diverse population of genetically tractable cells that mediate neural circuit–specific roles in health and disease.
Abstract: Astrocytes tile the entire CNS. They are vital for neural circuit function, but have traditionally been viewed as simple, homogenous cells that serve the same essential supportive roles everywhere. Here, we summarize breakthroughs that instead indicate that astrocytes represent a population of complex and functionally diverse cells. Physiological diversity of astrocytes is apparent between different brain circuits and microcircuits, and individual astrocytes display diverse signaling in subcellular compartments. With respect to injury and disease, astrocytes undergo diverse phenotypic changes that may be protective or causative with regard to pathology in a context-dependent manner. These new insights herald the concept that astrocytes represent a diverse population of genetically tractable cells that mediate neural circuit-specific roles in health and disease.

821 citations

Journal ArticleDOI
Andrea Cossarizza1, Hyun-Dong Chang, Andreas Radbruch, Andreas Acs2  +459 moreInstitutions (160)
TL;DR: These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community providing the theory and key practical aspects offlow cytometry enabling immunologists to avoid the common errors that often undermine immunological data.
Abstract: These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

698 citations

Journal ArticleDOI
TL;DR: Understanding the multifaceted roles of astrocytes in the healthy and diseased CNS will undoubtedly contribute to the development of treatment strategies that will, in a context-dependent manner and at appropriate time points, modulate reactive astrogliosis to promote brain repair and reduce the neurological impairment.
Abstract: Astrocytes are the most abundant cells in the central nervous system (CNS) that provide nutrients, recycle neurotransmitters, as well as fulfill a wide range of other homeostasis maintaining functions During the past two decades, astrocytes emerged also as increasingly important regulators of neuronal functions including the generation of new nerve cells and structural as well as functional synapse remodeling Reactive gliosis or reactive astrogliosis is a term coined for the morphological and functional changes seen in astroglial cells/astrocytes responding to CNS injury and other neurological diseases Whereas this defensive reaction of astrocytes is conceivably aimed at handling the acute stress, limiting tissue damage, and restoring homeostasis, it may also inhibit adaptive neural plasticity mechanisms underlying recovery of function Understanding the multifaceted roles of astrocytes in the healthy and diseased CNS will undoubtedly contribute to the development of treatment strategies that will, in a context-dependent manner and at appropriate time points, modulate reactive astrogliosis to promote brain repair and reduce the neurological impairment

668 citations


Cites background or result from "Live imaging of astrocyte responses..."

  • ...Most astrocytes in the injured cortex become hypertrophic, upregulate GFAP, but stay within their tiled domains with only a limited overlap between domains of neighboring astrocytes (16, 260), while subsets of astrocytes become polarized or proliferate, the latter typically found in close association with blood vessels (16)....

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  • ...Astrocyte polarity and directional migration seem to play a crucial role in astrocyte ability to react to injury: astrocytes depleted of the small RhoGTPase Cdc42, a key regulator of cell polarization, show impaired recruitment to the stab wound lesion despite their upregulation of GFAP and hypertrophic response (192)....

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  • ...Similarly, selective ablation of the small RhoGTPase Cdc42 in astrocytes impaired their recruitment to the stab wound lesion and was accompanied by higher density of microglia in the lesion (192)....

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  • ...It was proposed that these proliferating blood vessel-associated astrocytes regulate migration and proliferation of glial scar forming pericytes (16, 82)....

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  • ...The proliferative response of astrocytes after injury seems to be specific for astrocytes in the juxtavascular space and depends only partially on Cdc42 (16)....

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Journal ArticleDOI
TL;DR: Heterogeneity of reactive astrocytes is demonstrated and scar borders are formed by newly proliferated, elongated astroglia, which organize via STAT3-dependent mechanisms to corral inflammatory and fibrotic cells into discrete areas separated from adjacent tissue that contains viable neurons.
Abstract: Astroglial scars surround damaged tissue after trauma, stroke, infection, or autoimmune inflammation in the CNS. They are essential for wound repair, but also interfere with axonal regrowth. A better understanding of the cellular mechanisms, regulation, and functions of astroglial scar formation is fundamental to developing safe interventions for many CNS disorders. We used wild-type and transgenic mice to quantify and dissect these parameters. Adjacent to crush spinal cord injury (SCI), reactive astrocytes exhibited heterogeneous phenotypes as regards proliferation, morphology, and chemistry, which all varied with distance from lesions. Mature scar borders at 14 d after SCI consisted primarily of newly proliferated astroglia with elongated cell processes that surrounded large and small clusters of inflammatory, fibrotic, and other cells. During scar formation from 5 to 14 d after SCI, cell processes deriving from different astroglia associated into overlapping bundles that quantifiably reoriented and organized into dense mesh-like arrangements. Selective deletion of STAT3 from astroglia quantifiably disrupted the organization of elongated astroglia into scar borders, and caused a failure of astroglia to surround inflammatory cells, resulting in increased spread of these cells and neuronal loss. In cocultures, wild-type astroglia spontaneously corralled inflammatory or fibromeningeal cells into segregated clusters, whereas STAT3-deficient astroglia failed to do so. These findings demonstrate heterogeneity of reactive astroglia and show that scar borders are formed by newly proliferated, elongated astroglia, which organize via STAT3-dependent mechanisms to corral inflammatory and fibrotic cells into discrete areas separated from adjacent tissue that contains viable neurons.

585 citations


Cites result from "Live imaging of astrocyte responses..."

  • ...It deserves mention that this organization occurred without obvious evidence for long distance migration, similar to reports using different transgenic analyses or in vivo imaging to show local derivation and minimal migration of newly generated reactive astroglia after CNS injury (Tsai et al., 2012; Bardehle et al., 2013)....

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  • ...…organization occurred without obvious evidence for long distance migration, similar to reports using different transgenic analyses or in vivo imaging to show local derivation and minimal migration of newly generated reactive astroglia after CNS injury (Tsai et al., 2012; Bardehle et al., 2013)....

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  • ...4 – 6) without long distance migration, in a manner compatible with reports by others using different types of transgenic analyses or in vivo imaging (Tsai et al., 2012; Bardehle et al., 2013)....

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References
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01 Jan 2004
TL;DR: ImageJ is an open source Java-written program that is used for many imaging applications, including those that that span the gamut from skin analysis to neuroscience, and can read most of the widely used and significant formats used in biomedical images.
Abstract: Wayne Rasband of NIH has created ImageJ, an open source Java-written program that is now at version 1.31 and is used for many imaging applications, including those that that span the gamut from skin analysis to neuroscience. ImageJ is in the public domain and runs on any operating system (OS). ImageJ is easy to use and can do many imaging manipulations. A very large and knowledgeable group makes up the user community for ImageJ. Topics covered are imaging abilities; cross platform; image formats support as of June 2004; extensions, including macros and plug-ins; and imaging library. NIH reports tens of thousands of downloads at a rate of about 24,000 per month currently. ImageJ can read most of the widely used and significant formats used in biomedical images. Manipulations supported are read/write of image files and operations on separate pixels, image regions, entire images, and volumes (stacks in ImageJ). Basic operations supported include convolution, edge detection, Fourier transform, histogram and particle analyses, editing and color manipulation, and more advanced operations, as well as visualization. For assistance in using ImageJ, users e-mail each other, and the user base is highly knowledgeable and will answer requests on the mailing list. A thorough manual with many examples and illustrations has been written by Tony Collins of the Wright Cell Imaging Facility at Toronto Western Research Institute and is available, along with other listed resources, via the Web.

12,060 citations

Journal ArticleDOI
27 May 2005-Science
TL;DR: Using in vivo two-photon imaging in neocortex, it is found that microglial cells are highly active in their presumed resting state, continually surveying their microenvironment with extremely motile processes and protrusions.
Abstract: Microglial cells represent the immune system of the mammalian brain and therefore are critically involved in various injuries and diseases. Little is known about their role in the healthy brain and their immediate reaction to brain damage. By using in vivo two-photon imaging in neocortex, we found that microglial cells are highly active in their presumed resting state, continually surveying their microenvironment with extremely motile processes and protrusions. Furthermore, blood-brain barrier disruption provoked immediate and focal activation of microglia, switching their behavior from patroling to shielding of the injured site. Microglia thus are busy and vigilant housekeepers in the adult brain.

4,458 citations

Journal ArticleDOI
TL;DR: A novel toolbox for subcellular colocalization analysis under ImageJ is created that integrates current global statistic methods and a novel object‐based approach to assess proteins residing on intracellular structures by fluorescence microscopy.
Abstract: Summary It is generally accepted that the functional compartmentalization of eukaryotic cells is reflected by the differential occurrence of proteins in their compartments. The location and physiological function of a protein are closely related; local information of a protein is thus crucial to understanding its role in biological processes. The visualization of proteins residing on intracellular structures by fluorescence microscopy has become a routine approach in cell biology and is increasingly used to assess their colocalization with well-characterized markers. However, imageanalysis methods for colocalization studies are a field of contention and enigma. We have therefore undertaken to review the most currently used colocalization analysis methods, introducing the basic optical concepts important for image acquisition and subsequent analysis. We provide a summary of practical tips for image acquisition and treatment that should precede proper colocalization analysis. Furthermore, we discuss the application and feasibility of colocalization tools for various biological colocalization situations and discuss their respective strengths and weaknesses. We have created a novel toolbox for subcellular colocalization analysis under Image J, named JACoP, that integrates current global statistic methods and a novel object-based approach.

4,195 citations

Journal ArticleDOI
TL;DR: The software consists of a collection of algorithms that are commonly used to solve medical image registration problems, and allows the user to quickly configure, test, and compare different registration methods for a specific application.
Abstract: Medical image registration is an important task in medical image processing. It refers to the process of aligning data sets, possibly from different modalities (e.g., magnetic resonance and computed tomography), different time points (e.g., follow-up scans), and/or different subjects (in case of population studies). A large number of methods for image registration are described in the literature. Unfortunately, there is not one method that works for all applications. We have therefore developed elastix, a publicly available computer program for intensity-based medical image registration. The software consists of a collection of algorithms that are commonly used to solve medical image registration problems. The modular design of elastix allows the user to quickly configure, test, and compare different registration methods for a specific application. The command-line interface enables automated processing of large numbers of data sets, by means of scripting. The usage of elastix for comparing different registration methods is illustrated with three example experiments, in which individual components of the registration method are varied.

3,444 citations

Journal ArticleDOI
TL;DR: Chondroitin and keratan sulphate proteoglycans are among the main inhibitory extracellular matrix molecules that are produced by reactive astrocytes in the glial scar, and they are believed to play a crucial part in regeneration failure.
Abstract: After injury to the adult central nervous system (CNS), injured axons cannot regenerate past the lesion. In this review, we present evidence that this is due to the formation of a glial scar. Chondroitin and keratan sulphate proteoglycans are among the main inhibitory extracellular matrix molecules that are produced by reactive astrocytes in the glial scar, and they are believed to play a crucial part in regeneration failure. We will focus on this role, as well as considering the behaviour of regenerating neurons in the environment of CNS injury.

2,838 citations