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Suzuki H, Takeda H, Takuwa H, Ji B, Higuchi M, Kanno I, Masamoto K. Capillary responses to functional and pathological activations rely on the capillary states at rest. J Cereb Blood Flow Metab 2023; 43:1010-1024. [PMID: 36752020 PMCID: PMC10196750 DOI: 10.1177/0271678x231156372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 01/09/2023] [Accepted: 01/19/2023] [Indexed: 02/09/2023]
Abstract
Brain capillaries play a crucial role in maintaining cellular viability and thus preventing neurodegeneration. The aim of this study was to characterize the brain capillary morphology at rest and during neural activation based on a big data analysis from three-dimensional microangiography. Neurovascular responses were measured using a genetic calcium sensor expressed in neurons and microangiography with two-photon microscopy, while neural acivity was modulated by stimulation of contralateral whiskers or by a seizure evoked by kainic acid. For whisker stimulation, 84% of the capillary sites showed no detectable diameter change. The remaining 10% and 6% were dilated and constricted, respectively. Significant differences were observed for capillaries in the diameter at rest between the locations of dilation and constriction. Even the seizures resulted in 44% of the capillaries having no detectable change in diameter, while 56% of the capillaries dilated. The extent of dilation was dependent on the diameter at rest. In conclusion, big data analysis on brain capillary morphology has identified at least two types of capillary states: capillaries with diameters that are relatively large at rest and stable over time regardless of neural activity and capillaries whose diameters are relatively small at rest and vary according to neural activity.
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Affiliation(s)
- Hiroki Suzuki
- Graduate School of
Informatics and Engineering, University of Electro-Communications,
Tokyo, Japan
| | - Hiroshi Takeda
- Graduate School of
Informatics and Engineering, University of Electro-Communications,
Tokyo, Japan
| | - Hiroyuki Takuwa
- Department of Functional
Brain Imaging, National Institutes for Quantum Science and Technology,
Chiba, Japan
| | - Bin Ji
- Department of Functional
Brain Imaging, National Institutes for Quantum Science and Technology,
Chiba, Japan
- Department of Radiopharmacy
and Molecular Imaging, School of Pharmacy, Fudan University, Shanghai,
China
| | - Makoto Higuchi
- Department of Functional
Brain Imaging, National Institutes for Quantum Science and Technology,
Chiba, Japan
| | - Iwao Kanno
- Department of Functional
Brain Imaging, National Institutes for Quantum Science and Technology,
Chiba, Japan
| | - Kazuto Masamoto
- Graduate School of
Informatics and Engineering, University of Electro-Communications,
Tokyo, Japan
- Department of Functional
Brain Imaging, National Institutes for Quantum Science and Technology,
Chiba, Japan
- Center for Neuroscience and
Biomedical Engineering, University of Electro-Communications, Tokyo,
Japan
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2
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Mughal A, Nelson MT, Hill-Eubanks D. The post-arteriole transitional zone: a specialized capillary region that regulates blood flow within the CNS microvasculature. J Physiol 2023; 601:889-901. [PMID: 36751860 PMCID: PMC9992301 DOI: 10.1113/jp282246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 01/13/2023] [Indexed: 02/09/2023] Open
Abstract
The brain is an energy hog, consuming available energy supplies at a rate out of all proportion to its relatively small size. This outsized demand, largely reflecting the unique computational activity of the brain, is met by an ensemble of neurovascular coupling mechanisms that link neuronal activity with local increases in blood delivery. This just-in-time replenishment strategy, made necessary by the limited energy-storage capacity of neurons, complicates the nutrient-delivery task of the cerebral vasculature, layering on a temporo-spatial requirement that invites - and challenges - mechanistic interpretation. The centre of gravity of research efforts to disentangle these mechanisms has shifted from an initial emphasis on astrocyte-arteriole-level processes to mechanisms that operate on the capillary level, a shift that has brought into sharp focus questions regarding the fine control of blood distribution to active neurons. As these investigations have drilled down into finer reaches of the microvasculature, they have revealed an arteriole-proximate subregion of CNS capillary networks that serves a regulatory function in directing blood flow into and within downstream capillaries. They have also illuminated differences in researchers' perspectives on the vascular structures and identity of mural cells in this region that impart the vasomodulatory effects that control blood distribution. In this review, we highlight the regulatory role of a variably named region of the microvasculature, referred to here as the post-arteriole transition zone, in channeling blood flow within CNS capillary networks, and underscore the contribution of dynamically contractile perivascular mural cell - generally, but not universally, recognized as pericytes - to this function.
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Affiliation(s)
- Amreen Mughal
- Department of Pharmacology, University of Vermont, Burlington, VT, USA
| | - Mark T. Nelson
- Department of Pharmacology, University of Vermont, Burlington, VT, USA
- Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
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3
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Chaigneau E, Charpak S. Measurement of Blood Velocity With Laser Scanning Microscopy: Modeling and Comparison of Line-Scan Image-Processing Algorithms. Front Physiol 2022; 13:848002. [PMID: 35464098 PMCID: PMC9022085 DOI: 10.3389/fphys.2022.848002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 02/22/2022] [Indexed: 11/13/2022] Open
Abstract
Laser scanning microscopy is widely used to measure blood hemodynamics with line-scans in physiological and pathological vessels. With scans of broken lines, i.e., lines made of several segments with different orientations, it also allows simultaneous monitoring of vessel diameter dynamics or the activity of specific cells. Analysis of red blood cell (RBC) velocity from line-scans requires specific image-processing algorithms, as angle measurements, Line-Scanning Particle Image Velocimetry (LSPIV) or Fourier transformation of line-scan images. The conditions under which these image-processing algorithms give accurate measurements have not been fully characterized although the accuracy of measurements vary according to specific experimental parameters: the vessel type, the RBC velocity, the scanning parameters, and the image signal to noise ratio. Here, we developed mathematical models for the three previously mentioned line-scan image-processing algorithms. Our models predict the experimental conditions in which RBC velocity measurements are accurate. We illustrate the case of different vessel types and give the parameter space available for each of them. Last, we developed a software generating artificial line-scan images and used it to validate our models.
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Affiliation(s)
- Emmanuelle Chaigneau
- Institut de la Vision, INSERM U968, Paris, France
- Institut de la Vision, CNRS UMR 7210, Paris, France
- Institut de la Vision, Sorbonne Université, Paris, France
- *Correspondence: Emmanuelle Chaigneau,
| | - Serge Charpak
- Institut de la Vision, INSERM U968, Paris, France
- Institut de la Vision, CNRS UMR 7210, Paris, France
- Institut de la Vision, Sorbonne Université, Paris, France
- Serge Charpak,
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4
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Hartmann DA, Coelho-Santos V, Shih AY. Pericyte Control of Blood Flow Across Microvascular Zones in the Central Nervous System. Annu Rev Physiol 2022; 84:331-354. [PMID: 34672718 PMCID: PMC10480047 DOI: 10.1146/annurev-physiol-061121-040127] [Citation(s) in RCA: 70] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The vast majority of the brain's vascular length is composed of capillaries, where our understanding of blood flow control remains incomplete. This review synthesizes current knowledge on the control of blood flow across microvascular zones by addressing issues with nomenclature and drawing on new developments from in vivo optical imaging and single-cell transcriptomics. Recent studies have highlighted important distinctions in mural cell morphology, gene expression, and contractile dynamics, which can explain observed differences in response to vasoactive mediators between arteriole, transitional, and capillary zones. Smooth muscle cells of arterioles and ensheathing pericytes of the arteriole-capillary transitional zone control large-scale, rapid changes in blood flow. In contrast, capillary pericytes downstream of the transitional zone act on slower and smaller scales and are involved in establishing resting capillary tone and flow heterogeneity. Many unresolved issues remain, including the vasoactive mediators that activate the different pericyte types in vivo, the role of pericyte-endothelial communication in conducting signals from capillaries to arterioles, and how neurological disease affects these mechanisms.
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Affiliation(s)
- David A Hartmann
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, California, USA
| | - Vanessa Coelho-Santos
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, Washington, USA;
- Department of Pediatrics, University of Washington, Seattle, Washington, USA
| | - Andy Y Shih
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, Washington, USA;
- Department of Pediatrics, University of Washington, Seattle, Washington, USA
- Department of Bioengineering, University of Washington, Seattle, Washington, USA
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5
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Polimeni JR, Lewis LD. Imaging faster neural dynamics with fast fMRI: A need for updated models of the hemodynamic response. Prog Neurobiol 2021; 207:102174. [PMID: 34525404 PMCID: PMC8688322 DOI: 10.1016/j.pneurobio.2021.102174] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 07/30/2021] [Accepted: 09/08/2021] [Indexed: 12/20/2022]
Abstract
Fast fMRI enables the detection of neural dynamics over timescales of hundreds of milliseconds, suggesting it may provide a new avenue for studying subsecond neural processes in the human brain. The magnitudes of these fast fMRI dynamics are far greater than predicted by canonical models of the hemodynamic response. Several studies have established nonlinear properties of the hemodynamic response that have significant implications for fast fMRI. We first review nonlinear properties of the hemodynamic response function that may underlie fast fMRI signals. We then illustrate the breakdown of canonical hemodynamic response models in the context of fast neural dynamics. We will then argue that the canonical hemodynamic response function is not likely to reflect the BOLD response to neuronal activity driven by sparse or naturalistic stimuli or perhaps to spontaneous neuronal fluctuations in the resting state. These properties suggest that fast fMRI is capable of tracking surprisingly fast neuronal dynamics, and we discuss the neuroscientific questions that could be addressed using this approach.
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Affiliation(s)
- Jonathan R Polimeni
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; Department of Radiology, Harvard Medical School, Boston, MA, USA; Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA.
| | - Laura D Lewis
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; Department of Biomedical Engineering, Boston University, Boston, MA, USA.
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6
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Chen X, Jiang Y, Choi S, Pohmann R, Scheffler K, Kleinfeld D, Yu X. Assessment of single-vessel cerebral blood velocity by phase contrast fMRI. PLoS Biol 2021; 19:e3000923. [PMID: 34499636 PMCID: PMC8454982 DOI: 10.1371/journal.pbio.3000923] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/21/2021] [Accepted: 07/28/2021] [Indexed: 12/30/2022] Open
Abstract
Current approaches to high-field functional MRI (fMRI) provide 2 means to map hemodynamics at the level of single vessels in the brain. One is through changes in deoxyhemoglobin in venules, i.e., blood oxygenation level-dependent (BOLD) fMRI, while the second is through changes in arteriole diameter, i.e., cerebral blood volume (CBV) fMRI. Here, we introduce cerebral blood flow-related velocity-based fMRI, denoted CBFv-fMRI, which uses high-resolution phase contrast (PC) MRI to form velocity measurements of flow. We use CBFv-fMRI in measure changes in blood velocity in single penetrating microvessels across rat parietal cortex. In contrast to the venule-dominated BOLD and arteriole-dominated CBV fMRI signals, CBFv-fMRI is comparable from both arterioles and venules. A single fMRI platform is used to map changes in blood pO2 (BOLD), volume (CBV), and velocity (CBFv). This combined high-resolution single-vessel fMRI mapping scheme enables vessel-specific hemodynamic mapping in animal models of normal and diseased states and further has translational potential to map vascular dementia in diseased or injured human brains with ultra-high-field fMRI.
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Affiliation(s)
- Xuming Chen
- High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Department of Neurology, Wuhan University, Renmin Hospital, Wuhan, China
| | - Yuanyuan Jiang
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - Sangcheon Choi
- High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Graduate Training Centre of Neuroscience, International Max Planck Research School, University of Tübingen, Tübingen, Germany
| | - Rolf Pohmann
- High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Klaus Scheffler
- High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
| | - David Kleinfeld
- Department of Physics, University of California at San Diego, La Jolla, California, United States of America
- Section of Neurobiology, University of California at San Diego, La Jolla, California, United States of America
| | - Xin Yu
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, United States of America
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7
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Huber LR, Poser BA, Kaas AL, Fear EJ, Dresbach S, Berwick J, Goebel R, Turner R, Kennerley AJ. Validating layer-specific VASO across species. Neuroimage 2021; 237:118195. [PMID: 34038769 DOI: 10.1016/j.neuroimage.2021.118195] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 05/17/2021] [Accepted: 05/19/2021] [Indexed: 01/27/2023] Open
Abstract
Cerebral blood volume (CBV) has been shown to be a robust and important physiological parameter for quantitative interpretation of functional (f)MRI, capable of delivering highly localized mapping of neural activity. Indeed, with recent advances in ultra-high-field (≥7T) MRI hardware and associated sequence libraries, it has become possible to capture non-invasive CBV weighted fMRI signals across cortical layers. One of the most widely used approaches to achieve this (in humans) is through vascular-space-occupancy (VASO) fMRI. Unfortunately, the exact contrast mechanisms of layer-dependent VASO fMRI have not been validated for human fMRI and thus interpretation of such data is confounded. Here we validate the signal source of layer-dependent SS-SI VASO fMRI using multi-modal imaging in a rat model in response to neuronal activation (somatosensory cortex) and respiratory challenge (hypercapnia). In particular VASO derived CBV measures are directly compared to concurrent measures of total haemoglobin changes from high resolution intrinsic optical imaging spectroscopy (OIS). Quantified cortical layer profiling is demonstrated to be in agreement between VASO and contrast enhanced fMRI (using monocrystalline iron oxide nanoparticles, MION). Responses show high spatial localisation to layers of cortical processing independent of confounding large draining veins which can hamper BOLD fMRI studies, (depending on slice positioning). Thus, a cross species comparison is enabled using VASO as a common measure. We find increased VASO based CBV reactivity (3.1 ± 1.2 fold increase) in humans compared to rats. Together, our findings confirm that the VASO contrast is indeed a reliable estimate of layer-specific CBV changes. This validation study increases the neuronal interpretability of human layer-dependent VASO fMRI as an appropriate method in neuroscience application studies, in which the presence of large draining intracortical and pial veins limits neuroscientific inference with BOLD fMRI.
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Affiliation(s)
- Laurentius Renzo Huber
- MBIC, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, the Netherlands.
| | - Benedikt A Poser
- MBIC, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, the Netherlands
| | - Amanda L Kaas
- MBIC, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, the Netherlands
| | - Elizabeth J Fear
- Hull-York-Medical-School (HYMS), University of York, York, United Kingdom
| | - Sebastian Dresbach
- MBIC, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, the Netherlands
| | - Jason Berwick
- Department of Psychology, University of Sheffield, Sheffield, United Kingdom
| | - Rainer Goebel
- MBIC, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, the Netherlands
| | - Robert Turner
- Neurophysics Department Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, United Kingdom
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8
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Early fMRI responses to somatosensory and optogenetic stimulation reflect neural information flow. Proc Natl Acad Sci U S A 2021; 118:2023265118. [PMID: 33836602 PMCID: PMC7980397 DOI: 10.1073/pnas.2023265118] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
fMRI has revolutionized how neuroscientists investigate human brain functions and networks. To further advance understanding of brain functions, identifying the direction of information flow, such as thalamocortical versus corticothalamic projections, is critical. Because the early hemodynamic response at microvessels near active neurons can be detected by ultrahigh field fMRI, we propose using the onset times of fMRI responses to discern the information flow. This approach was confirmed by observing the ultrahigh spatiotemporal resolution BOLD fMRI responses to bottom-up somatosensory stimulation and top-down optogenetic stimulation of the primary motor cortex in anesthetized mice. Because ultrahigh field MRI is increasingly available, ultrahigh spatiotemporal fMRI will significantly facilitate the investigation of functional circuits in humans. Blood oxygenation level–dependent (BOLD) functional magnetic resonance imaging (fMRI) has been widely used to localize brain functions. To further advance understanding of brain functions, it is critical to understand the direction of information flow, such as thalamocortical versus corticothalamic projections. For this work, we performed ultrahigh spatiotemporal resolution fMRI at 15.2 T of the mouse somatosensory network during forepaw somatosensory stimulation and optogenetic stimulation of the primary motor cortex (M1). Somatosensory stimulation induced the earliest BOLD response in the ventral posterolateral nucleus (VPL), followed by the primary somatosensory cortex (S1) and then M1 and posterior thalamic nucleus. Optogenetic stimulation of excitatory neurons in M1 induced the earliest BOLD response in M1, followed by S1 and then VPL. Within S1, the middle cortical layers responded to somatosensory stimulation earlier than the upper or lower layers, whereas the upper cortical layers responded earlier than the other two layers to optogenetic stimulation in M1. The order of early BOLD responses was consistent with the canonical understanding of somatosensory network connections and cannot be explained by regional variabilities in the hemodynamic response functions measured using hypercapnic stimulation. Our data demonstrate that early BOLD responses reflect the information flow in the mouse somatosensory network, suggesting that high-field fMRI can be used for systems-level network analyses.
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9
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Park K, Liyanage AC, Koretsky AP, Pan Y, Du C. Optical imaging of stimulation-evoked cortical activity using GCaMP6f and jRGECO1a. Quant Imaging Med Surg 2021; 11:998-1009. [PMID: 33654672 PMCID: PMC7829166 DOI: 10.21037/qims-20-921] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Genetically encoded calcium indicators (GECIs), especially the GCaMP-based green fluorescence GECIs have been widely used for in vivo detection of neuronal activity in rodents by measuring intracellular neuronal Ca2+ changes. More recently, jRGECO1a, a red shifted GECI, has been reported to detect neuronal Ca2+ activation. This opens the possibility of using dual-color GECIs for simultaneous interrogation of different cell populations. However, there has been no report to compare the functional difference between these two GECIs for in vivo imaging. Here, a comparative study is reported on neuronal responses to sensory stimulation using GCaMP6f and jRGECO1a that were virally delivered into the neurons in the somatosensory cortex of two different groups of animals, respectively. METHODS GCaMP6f and jRGECO1a GECI were virally delivered to sensory cortex. After 3-4 weeks, the animals were imaged to capture the spatiotemporal changes of neuronal Ca2+ and the hemodynamic responses to forepaw electrical stimulation (0.3 mA, 0.3 ms/pulse, 0.03 Hz). The stimulation-evoked neuronal Ca2+ transients expressed with GCaMP6f or jRGECO1a were recorded during the baseline period and after an acute cocaine administration (1 mg/kg, i.v.). RESULTS Histology confirmed that the efficiency of jRGECO1a and GCaMP6f expression into the cortical neurons was similar, i.e., 34%±3% and 32.7%±1.6%, respectively. Our imaging in vivo showed that the hemodynamic responses to the stimulation were the same between jRGECO1a and GCaMP6f expressed groups. Although the stimulation-evoked fluorescence change (∆F/F) and the time-to-peak of the neuronal Ca2+ transients were not significantly different between these two indicators, the full-width-half-maximum (FWHM) duration of the ∆F/F rise in the jRGECO1a-expressed group (0.16±0.02 s) was ~50 ms or 46% longer than that of the GCaMP6f group (0.11±0.003 s), indicating a longer recovery time in jRGECO1a than in GCaMP6f transients (P<0.01). This is likely due to the longer off rate of jRGECO1a than that of GCaMP6f. After cocaine, the time-to-peak of Ca2+ transients was delayed and their FWHM duration was prolonged for both expression groups, indicating that these are cocaine's effects on neuronal Ca2+ signaling and not artifacts due to the property differences of the GCEIs. CONCLUSIONS This study shows that both jRGECO1a and GCaMP6f have sufficient sensitivity for tracking single-stimulation-evoked Ca2+ transients to detect neuronal activities from the brain. Since these GECIs are emitted at the different wavelengths, it will be possible to use them together to characterize the activity of different cell types (e.g., neurons and astrocytes) to study brain activation and brain functional changes in normal or diseased brains.
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Affiliation(s)
- Kicheon Park
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Anuki C. Liyanage
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Alan P. Koretsky
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Yingtian Pan
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Congwu Du
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
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10
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Chen X, Chen C, Ji F, Xu Y, Wang W, Lin X, Jiang D, Song X, Gao X, Tian H, Zhuo C, Zhang J. Irreversible Primary Visual Cortex Impairment in a Mouse Model of High-Risk Schizophrenia. Neuropsychiatr Dis Treat 2021; 17:277-282. [PMID: 33542631 PMCID: PMC7853429 DOI: 10.2147/ndt.s246163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 12/29/2020] [Indexed: 11/23/2022] Open
Abstract
PURPOSE Although visual deficits can be observed at any stage of schizophrenia, few studies have focused on visual cortex alterations in individuals at high risk of schizophrenia. This study aimed to investigate the pathological changes of the primary visual cortex in a prenatal mouse model of MK801-induced high-risk schizophrenia. METHODS The high-risk schizophrenia model was generated by MK801 injection into pregnant mice. The male offspring without schizophrenia-like behaviors in early adulthood were defined as the high-risk mouse model of schizophrenia (HRMMS) and divided into two groups. One HRMMS group received the antipsychotic agent risperidone beginning at postnatal week 4 and another group did not receive any treatment. After treatment for 4 weeks, in vivo two-photon calcium imaging was performed to characterize the primary visual cortex activity. The novel object recognition test and the prepulse inhibition apparatus test were also implemented to assess the cognitive and behavioral performance, respectively. RESULTS Both groups of HRMMS mice, with or without antipsychotic treatment, had decreased neuronal calcium activity, demonstrating primary visual cortex impairment. More notably, antipsychotic treatment did not normalize the impaired neuronal activities in the primary visual cortex. Correspondingly, the treatment did not improve the cognitive or behavioral impairment. CONCLUSION Visual cortex impairment might be a prominent feature of individuals at high risk of schizophrenia that cannot be normalized by early treatment with antipsychotic medication, indicating the presence of independent regulatory pathways for visual perception disturbance in schizophrenia. Thus, visual system impairment in schizophrenic patients must be further studied.
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Affiliation(s)
- Xinying Chen
- Psychiatric-Neuroimaging-Genetics-Comorbidity Laboratory (PNGC_Lab), Tianjin Mental Health Centre, Mental Health Teaching Hospital of Tianjin Medical University, Tianjin Anding Hospital, Tianjin 300222, People's Republic of China
| | - Ce Chen
- Psychiatric-Neuroimaging-Genetics Laboratory, Wenzhou Seventh People's Hospital, Wenzhou, Zhejiang Province 325000, People's Republic of China
| | - Feng Ji
- Department of Psychiatry, School of Mental Health, Jining Medical University, Jining 272119, Shandong Province, People's Republic of China
| | - Yong Xu
- Department of Psychiatry, First Hospital/First Clinical Medical College of Shanxi Medical University, MDT Center for Cognitive Impairment and Sleep Disorders, First Hospital of Shanxi Medical University, Taiyuan 030001, People's Republic of China
| | - Wenqiang Wang
- Co-Collaboration Laboratory of China and Canada, Xiamen Xianyue Hospital and University of Alberta, Xiamen 361000, People's Republic of China
| | - Xiaodong Lin
- Psychiatric-Neuroimaging-Genetics Laboratory, Wenzhou Seventh People's Hospital, Wenzhou, Zhejiang Province 325000, People's Republic of China
| | - Deguo Jiang
- Psychiatric-Neuroimaging-Genetics Laboratory, Wenzhou Seventh People's Hospital, Wenzhou, Zhejiang Province 325000, People's Republic of China
| | - Xueqin Song
- The First Affiliated Hospital/Zhengzhou University, Biological Psychiatry International Joint Laboratory of Henan/Zhengzhou University, Henan Psychiatric Transformation Research Key Laboratory/Zhengzhou University, Zhengzhou 450052, People's Republic of China
| | - Xiangyang Gao
- Health Management Institute, Center for Statistical Analysis of Medical Data, Medical Big Data Analysis Center, Chinese PLA General Hospital, Beijing 100191, People's Republic of China
| | - Hongjun Tian
- Department of Neurology and Psychiatry Biological Imaging Laboratory (NPBI_Lab), Tianjin Fourth Center Hospital, Tianjin 200024, People's Republic of China
| | - Chuanjun Zhuo
- Department of Neurology and Psychiatry Biological Imaging Laboratory (NPBI_Lab), Tianjin Fourth Center Hospital, Tianjin 200024, People's Republic of China
| | - Jingliang Zhang
- Department of Psychiatry, Wenzhou Kangning Hospital, Wenzhou, Zhejiang Province 325007, People's Republic of China
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11
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Dodd AB, Lu H, Wertz CJ, Ling JM, Shaff NA, Wasserott BC, Meier TB, Park G, Oglesbee SJ, Phillips JP, Campbell RA, Liu P, Mayer AR. Persistent alterations in cerebrovascular reactivity in response to hypercapnia following pediatric mild traumatic brain injury. J Cereb Blood Flow Metab 2020; 40:2491-2504. [PMID: 31903838 PMCID: PMC7820694 DOI: 10.1177/0271678x19896883] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 10/15/2019] [Accepted: 11/21/2019] [Indexed: 12/31/2022]
Abstract
Much attention has been paid to the effects of mild traumatic brain injury (mTBI) on cerebrovascular reactivity in adult populations, yet it remains understudied in pediatric injury. In this study, 30 adolescents (12-18 years old) with pediatric mTBI (pmTBI) and 35 age- and sex-matched healthy controls (HC) underwent clinical and neuroimaging assessments during sub-acute (6.9 ± 2.2 days) and early chronic (120.4 ± 11.7 days) phases of injury. Relative to controls, pmTBI reported greater initial post-concussion symptoms, headache, pain, and anxiety, resolving by four months post-injury. Patients reported increased sleep issues and exhibited deficits in processing speed and attention across both visits. In grey-white matter interface areas throughout the brain, pmTBI displayed increased maximal fit/amplitude of a time-shifted end-tidal CO2 regressor to blood oxygen-level dependent response relative to HC, as well as increased latency to maximal fit. The alterations persisted through the early chronic phase of injury, with maximal fit being associated with complaints of ongoing sleep disturbances during post hoc analyses but not cognitive measures of processing speed or attention. Collectively, these findings suggest that deficits in the speed and degree of cerebrovascular reactivity may persist longer than current conceptualizations about clinical recovery within 30 days.
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Affiliation(s)
- Andrew B Dodd
- The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, Albuquerque, NM, USA
| | - Hanzhang Lu
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Christopher J Wertz
- The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, Albuquerque, NM, USA
| | - Josef M Ling
- The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, Albuquerque, NM, USA
| | - Nicholas A Shaff
- The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, Albuquerque, NM, USA
| | - Benjamin C Wasserott
- The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, Albuquerque, NM, USA
| | - Timothy B Meier
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, USA
- Departments of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
- Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Grace Park
- Department of Pediatric Emergency Medicine, University of New Mexico, Albuquerque, NM, USA
| | - Scott J Oglesbee
- Department of Pediatric Emergency Medicine, University of New Mexico, Albuquerque, NM, USA
| | - John P Phillips
- The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, Albuquerque, NM, USA
- Department of Neurology, University of New Mexico, Albuquerque, NM, USA
| | - Richard A Campbell
- Department of Psychiatry, University of New Mexico, Albuquerque, NM, USA
| | - Peiying Liu
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Andrew R Mayer
- The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, Albuquerque, NM, USA
- Department of Neurology, University of New Mexico, Albuquerque, NM, USA
- Department of Psychiatry, University of New Mexico, Albuquerque, NM, USA
- Department of Psychology, University of New Mexico, Albuquerque, NM, USA
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12
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Gil R, Fernandes FF, Shemesh N. Neuroplasticity-driven timing modulations revealed by ultrafast functional magnetic resonance imaging. Neuroimage 2020; 225:117446. [PMID: 33069861 DOI: 10.1016/j.neuroimage.2020.117446] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 09/14/2020] [Accepted: 10/07/2020] [Indexed: 12/13/2022] Open
Abstract
Detecting neuroplasticity in global brain circuits in vivo is key for understanding myriad processes such as memory, learning, and recovery from injury. Functional Magnetic Resonance Imaging (fMRI) is instrumental for such in vivo mappings, yet it typically relies on mapping changes in spatial extent of activation or via signal amplitude modulations, whose interpretation can be highly ambiguous. Importantly, a central aspect of neuroplasticity involves modulation of neural activity timing properties. We thus hypothesized that this temporal dimension could serve as a new marker for neuroplasticity. To detect fMRI signals more associated with the underlying neural dynamics, we developed an ultrafast fMRI (ufMRI) approach facilitating high spatiotemporal sensitivity and resolution in distributed neural pathways. When neuroplasticity was induced in the mouse visual pathway via dark rearing, ufMRI indeed mapped temporal modulations in the entire visual pathway. Our findings therefore suggest a new dimension for exploring neuroplasticity in vivo.
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Affiliation(s)
- Rita Gil
- Champalimaud Research, Champalimaud Centre for the Unknown, Lisbon, Portugal
| | | | - Noam Shemesh
- Champalimaud Research, Champalimaud Centre for the Unknown, Lisbon, Portugal.
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13
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Echagarruga CT, Gheres KW, Norwood JN, Drew PJ. nNOS-expressing interneurons control basal and behaviorally evoked arterial dilation in somatosensory cortex of mice. eLife 2020; 9:e60533. [PMID: 33016877 PMCID: PMC7556878 DOI: 10.7554/elife.60533] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 10/02/2020] [Indexed: 12/19/2022] Open
Abstract
Cortical neural activity is coupled to local arterial diameter and blood flow. However, which neurons control the dynamics of cerebral arteries is not well understood. We dissected the cellular mechanisms controlling the basal diameter and evoked dilation in cortical arteries in awake, head-fixed mice. Locomotion drove robust arterial dilation, increases in gamma band power in the local field potential (LFP), and increases calcium signals in pyramidal and neuronal nitric oxide synthase (nNOS)-expressing neurons. Chemogenetic or pharmocological modulation of overall neural activity up or down caused corresponding increases or decreases in basal arterial diameter. Modulation of pyramidal neuron activity alone had little effect on basal or evoked arterial dilation, despite pronounced changes in the LFP. Modulation of the activity of nNOS-expressing neurons drove changes in the basal and evoked arterial diameter without corresponding changes in population neural activity.
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Affiliation(s)
| | - Kyle W Gheres
- Molecular, Cellular, and Integrative Biology Graduate Program, Pennsylvania State UniversityUniversity ParkUnited States
| | - Jordan N Norwood
- Cell and Developmental Biology Graduate Program, Pennsylvania State UniversityUniversity ParkUnited States
| | - Patrick J Drew
- Bioengineering Graduate Program, Pennsylvania State UniversityUniversity ParkUnited States
- Molecular, Cellular, and Integrative Biology Graduate Program, Pennsylvania State UniversityUniversity ParkUnited States
- Cell and Developmental Biology Graduate Program, Pennsylvania State UniversityUniversity ParkUnited States
- Departments of Engineering Science and Mechanics, Biomedical Engineering, and Neurosurgery, Pennsylvania State UniversityUniversity ParkUnited States
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14
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Vendel E, Rottschäfer V, de Lange ECM. A 3D brain unit model to further improve prediction of local drug distribution within the brain. PLoS One 2020; 15:e0238397. [PMID: 32966285 PMCID: PMC7511021 DOI: 10.1371/journal.pone.0238397] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 08/15/2020] [Indexed: 12/14/2022] Open
Abstract
The development of drugs targeting the brain still faces a high failure rate. One of the reasons is a lack of quantitative understanding of the complex processes that govern the pharmacokinetics (PK) of a drug within the brain. While a number of models on drug distribution into and within the brain is available, none of these addresses the combination of factors that affect local drug concentrations in brain extracellular fluid (brain ECF). Here, we develop a 3D brain unit model, which builds on our previous proof-of-concept 2D brain unit model, to understand the factors that govern local unbound and bound drug PK within the brain. The 3D brain unit is a cube, in which the brain capillaries surround the brain ECF. Drug concentration-time profiles are described in both a blood-plasma-domain and a brain-ECF-domain by a set of differential equations. The model includes descriptions of blood plasma PK, transport through the blood-brain barrier (BBB), by passive transport via paracellular and transcellular routes, and by active transport, and drug binding kinetics. The impact of all these factors on ultimate local brain ECF unbound and bound drug concentrations is assessed. In this article we show that all the above mentioned factors affect brain ECF PK in an interdependent manner. This indicates that for a quantitative understanding of local drug concentrations within the brain ECF, interdependencies of all transport and binding processes should be understood. To that end, the 3D brain unit model is an excellent tool, and can be used to build a larger network of 3D brain units, in which the properties for each unit can be defined independently to reflect local differences in characteristics of the brain.
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Affiliation(s)
- Esmée Vendel
- Mathematical Institute, Leiden University, Leiden, The Netherlands
| | - Vivi Rottschäfer
- Mathematical Institute, Leiden University, Leiden, The Netherlands
- * E-mail: (VR); (EL)
| | - Elizabeth C. M. de Lange
- Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
- * E-mail: (VR); (EL)
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15
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Chen W, Park K, Pan Y, Koretsky AP, Du C. Interactions between stimuli-evoked cortical activity and spontaneous low frequency oscillations measured with neuronal calcium. Neuroimage 2020; 210:116554. [PMID: 31972283 DOI: 10.1016/j.neuroimage.2020.116554] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 12/07/2019] [Accepted: 01/14/2020] [Indexed: 02/06/2023] Open
Abstract
Spontaneous brain activity has been widely used to map brain connectivity. The interactions between task-evoked brain responses and the spontaneous cortical oscillations, especially within the low frequency range of ~0.1 Hz, are not fully understood. Trial-to-trial variabilities in brain's response to sensory stimuli and the ability for brain to detect under noisy conditions suggest an appreciable impact of the brain state. Using a multimodality imaging platform, we simultaneously imaged neuronal Ca2+ and cerebral hemodynamics at baseline and in response to single-pulse forepaw stimuli in rat's somatosensory cortex. The high sensitivity of this system enables detection of responses to very weak and strong stimuli and real time determination of low frequency oscillations without averaging. Results show that the ongoing neuronal oscillations inversely modulate Ca2+ transients evoked by sensory stimuli. High intensity stimuli reset the spontaneous neuronal oscillations to an unpreferable excitability following the stimulus. Cerebral hemodynamic responses also inversely interact with the spontaneous hemodynamic oscillations, correlating with the neuronal Ca2+ transient changes. The results reveal competing interactions between spontaneous oscillations and stimulation-evoked brain activities in somatosensory cortex and the resultant hemodynamics.
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Affiliation(s)
- Wei Chen
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Kicheon Park
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Yingtian Pan
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Alan P Koretsky
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Congwu Du
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA.
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16
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Reiff T, Barthel O, Schönenberger S, Mundiyanapurath S. High-normal P aCO 2 values might be associated with worse outcome in patients with subarachnoid hemorrhage - a retrospective cohort study. BMC Neurol 2020; 20:31. [PMID: 31959120 PMCID: PMC6972024 DOI: 10.1186/s12883-020-1603-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 01/06/2020] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND While both hypercapnia and hypocapnia are harmful in patients with subarachnoid hemorrhage (SAH), it is unknown whether high-normal PaCO2 values are better than low-normal values. We hypothesized that high-normal PaCO2 values have more detrimental than beneficial effects on outcome. METHODS Consecutive patients with aneurysmal subarachnoid hemorrhage (aSAH) requiring mechanical ventilation treated in a tertiary care university hospital were retrospectively analyzed regarding the influence of PaCO2 on favorable outcome, defined as modified Rankin scale score < 3 at discharge. Primary endpoint was the difference in the proportion of PaCO2 values above 40 mmHg in relation to all measured PaCO2 values between patients with favorable and unfavorable outcome. RESULTS 150 patients were included. Median age was 57 years (p25:50, p75:64), median Hunt-Hess score was 4 (p25:3, p75:5). PaCO2 values were mainly within normal range (median 39.0, p25:37.5, p75:41.4). Patients with favorable outcome had a lower proportion of high-normal PaCO2 values above 40 mmHg compared to patients with unfavorable outcome (0.21 (p25:0.13, p75:0.50) vs. 0.4 (p25:0.29, p75:0.59)) resulting in a lower chance for favorable outcome (OR 0.04, 95% CI 0.00-0.55, p = 0.017). In multivariable analysis adjusted for Hunt-Hess score, pneumonia and length of stay, elevated PaCO2 remained an independent predictor of outcome (OR 0.05, 95% CI 0.00-0.81, p = 0.035). CONCLUSIONS A higher proportion of PaCO2 values above 40 mmHg was an independent predictor of outcome in patients with aSAH in our study. The results need to be confirmed in a prospective trial.
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Affiliation(s)
- Tilman Reiff
- Department of Neurology, Heidelberg University Hospital, Im Neuenheimer Feld 400, D-69120, Heidelberg, Germany
| | - Oliver Barthel
- Department of Neurology, Heidelberg University Hospital, Im Neuenheimer Feld 400, D-69120, Heidelberg, Germany
| | - Silvia Schönenberger
- Department of Neurology, Heidelberg University Hospital, Im Neuenheimer Feld 400, D-69120, Heidelberg, Germany
| | - Sibu Mundiyanapurath
- Department of Neurology, Heidelberg University Hospital, Im Neuenheimer Feld 400, D-69120, Heidelberg, Germany.
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17
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Chen X, Cai Z, Ji F, Lin X, Jiang D, Lin C, Ma X, Xu Y, Wang W, Zheng L, Chen C, Zhuo C. Paroxetine can improve primary visual cortex activity in a high-risk mouse model of schizophrenia. BIOTECHNOL BIOTEC EQ 2020. [DOI: 10.1080/13102818.2020.1837009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Affiliation(s)
- Xinying Chen
- Department of Psychiatric-Neuroimging-Genetics and Comorbidity Laboratory (PNGC_Lab), Tianjin Anding Hospital, Tianjin, PR China
| | - Ziyao Cai
- Department of Psychiatry and Micro-imaging Centre, Wenzhou Seventh People’s Hospital, Wenzhou, PR China
| | - Feng Ji
- Department of Psychiatry, School of Mental Health, Jining Medical University, Jining, PR China
| | - Xiaodong Lin
- Department of Psychiatry and Micro-imaging Centre, Wenzhou Seventh People’s Hospital, Wenzhou, PR China
| | - Deguo Jiang
- Department of Psychiatry and Micro-imaging Centre, Wenzhou Seventh People’s Hospital, Wenzhou, PR China
| | - Chongguang Lin
- Department of Psychiatry and Micro-imaging Centre, Wenzhou Seventh People’s Hospital, Wenzhou, PR China
| | - Xiaoyan Ma
- Department of Psychiatric-Neuroimging-Genetics and Comorbidity Laboratory (PNGC_Lab), Tianjin Anding Hospital, Tianjin, PR China
| | - Yong Xu
- Department of Psychiatry, First Hospital/First Clinical Medical College of Shanxi Medical University, Taiyuan, PR China
- MDT Center for Cognitive Impairment and Sleep Disorders, First Hospital of Shanxi Medical University, Taiyuan, PR China
| | - Wenqiang Wang
- Canada and China Joint Laboratory of Biological Psychiatry, Xiamen Xianye Hospital, Xiamen, Fujian, PR China
| | - Lidan Zheng
- Department of Psychiatric-Neuroimging-Genetics and Comorbidity Laboratory (PNGC_Lab), Tianjin Anding Hospital, Tianjin, PR China
| | - Ce Chen
- Department of Psychiatric-Neuroimging-Genetics and Comorbidity Laboratory (PNGC_Lab), Tianjin Anding Hospital, Tianjin, PR China
| | - Chuanjun Zhuo
- Department of Psychiatric-Neuroimging-Genetics and Comorbidity Laboratory (PNGC_Lab), Tianjin Anding Hospital, Tianjin, PR China
- Department of Psychiatry and Micro-imaging Centre, Wenzhou Seventh People’s Hospital, Wenzhou, PR China
- Department of Psychiatry, School of Mental Health, Jining Medical University, Jining, PR China
- Key Laboratory of Real Time Brain Circuits Tracing Of Neurology and Psychiatry (RTBNB_Lab), Tianjin fourth center Hospital, Tianjin Medical affiliated Tianjin Fourth Central Hospital, Nankai University affiliated Tianjin Fourth Center Hospital, Tianjin, PR China
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18
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Havlicek M, Uludağ K. A dynamical model of the laminar BOLD response. Neuroimage 2020; 204:116209. [DOI: 10.1016/j.neuroimage.2019.116209] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 08/11/2019] [Accepted: 09/17/2019] [Indexed: 12/18/2022] Open
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19
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Acute and chronic stage adaptations of vascular architecture and cerebral blood flow in a mouse model of TBI. Neuroimage 2019; 202:116101. [DOI: 10.1016/j.neuroimage.2019.116101] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 08/12/2019] [Accepted: 08/14/2019] [Indexed: 11/18/2022] Open
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20
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Merkle CW, Zhu J, Bernucci MT, Srinivasan VJ. Dynamic Contrast Optical Coherence Tomography reveals laminar microvascular hemodynamics in the mouse neocortex in vivo. Neuroimage 2019; 202:116067. [PMID: 31394180 DOI: 10.1016/j.neuroimage.2019.116067] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 07/01/2019] [Accepted: 08/01/2019] [Indexed: 12/18/2022] Open
Abstract
Studies of flow-metabolism coupling often presume that microvessel architecture is a surrogate for blood flow. To test this assumption, we introduce an in vivo Dynamic Contrast Optical Coherence Tomography (DyC-OCT) method to quantify layer-resolved microvascular blood flow and volume across the full depth of the mouse neocortex, where the angioarchitecture has been previously described. First, we cross-validate average DyC-OCT cortical flow against conventional Doppler OCT flow. Next, with laminar DyC-OCT, we discover that layer 4 consistently exhibits the highest microvascular blood flow, approximately two-fold higher than the outer cortical layers. While flow differences between layers are well-explained by microvascular volume and density, flow differences between subjects are better explained by transit time. Finally, from layer-resolved tracer enhancement, we also infer that microvascular hematocrit increases in deep cortical layers, consistent with predictions of plasma skimming. Altogether, our results show that while the cortical blood supply derives mainly from the pial surface, laminar hemodynamics ensure that the energetic needs of individual cortical layers are met. The laminar trends reported here provide data that links predictions based on the cortical angioarchitecture to cerebrovascular physiology in vivo.
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Affiliation(s)
- Conrad W Merkle
- Department of Biomedical Engineering, University of California Davis, Davis, CA, 95616, USA
| | - Jun Zhu
- Department of Biomedical Engineering, University of California Davis, Davis, CA, 95616, USA
| | - Marcel T Bernucci
- Department of Biomedical Engineering, University of California Davis, Davis, CA, 95616, USA
| | - Vivek J Srinivasan
- Department of Biomedical Engineering, University of California Davis, Davis, CA, 95616, USA; Department of Ophthalmology and Vision Science, University of California Davis School of Medicine, Sacramento, CA, 95817, USA.
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21
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Chaigneau E, Roche M, Charpak S. Unbiased Analysis Method for Measurement of Red Blood Cell Size and Velocity With Laser Scanning Microscopy. Front Neurosci 2019; 13:644. [PMID: 31316334 PMCID: PMC6610068 DOI: 10.3389/fnins.2019.00644] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 06/05/2019] [Indexed: 12/28/2022] Open
Abstract
Two-photon laser scanning microscopy is widely used to measure blood hemodynamics in brain blood vessels. Still, the algorithms used so far to extract red blood cell (RBC) size and velocity from line-scan acquisitions have ignored the extent to which scanning speed influences the measurements. Here, we used a theoretical approach that takes into account the velocity and direction of both scanning mirrors and RBCs during acquisition to provide an algorithm that measures the real RBC size and velocity. We validate our approach in brain vessels of anesthetized mice, and demonstrate that it corrects online measurement errors that can reach several 10s of percent as well as data previously acquired. To conclude, our analysis allows unbiased comparisons of blood hemodynamic parameters from brain capillaries and large vessels in control and pathological animal models.
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Affiliation(s)
| | | | - Serge Charpak
- INSERM U1128, Laboratory of Neurophysiology and New Microscopy, Université Paris Descartes, Paris, France
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22
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Unekawa M, Tomita Y, Toriumi H, Osada T, Masamoto K, Kawaguchi H, Izawa Y, Itoh Y, Kanno I, Suzuki N, Nakahara J. Spatiotemporal dynamics of red blood cells in capillaries in layer I of the cerebral cortex and changes in arterial diameter during cortical spreading depression and response to hypercapnia in anesthetized mice. Microcirculation 2019; 26:e12552. [PMID: 31050358 DOI: 10.1111/micc.12552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 04/21/2019] [Accepted: 04/29/2019] [Indexed: 12/26/2022]
Abstract
OBJECTIVE Control of red blood cell velocity in capillaries is essential to meet local neuronal metabolic requirements, although changes of capillary diameter are limited. To further understand the microcirculatory response during cortical spreading depression, we analyzed the spatiotemporal changes of red blood cell velocity in intraparenchymal capillaries. METHODS In urethane-anesthetized Tie2-green fluorescent protein transgenic mice, the velocity of fluorescence-labeled red blood cells flowing in capillaries in layer I of the cerebral cortex was automatically measured with our Matlab domain software (KEIO-IS2) in sequential images obtained with a high-speed camera laser-scanning confocal fluorescence microscope system. RESULTS Cortical spreading depression repeatedly increased the red blood cell velocity prior to arterial constriction/dilation. During the first cortical spreading depression, red blood cell velocity significantly decreased, and sluggishly moving or retrograde-moving red blood cells were observed, concomitantly with marked arterial constriction. The velocity subsequently returned to around the basal level, while oligemia after cortical spreading depression with slight vasoconstriction remained. After several passages of cortical spreading depression, hypercapnia-induced increase of red blood cell velocity, regional cerebral blood flow and arterial diameter were all significantly reduced, and the correlations among them became extremely weak. CONCLUSIONS Taken together with our previous findings, these simultaneous measurements of red blood cell velocity in multiple capillaries, arterial diameter and regional cerebral blood flow support the idea that red blood cell flow might be altered independently, at least in part, from arterial regulation, that neuro-capillary coupling plays a role in rapidly meeting local neural demand.
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Affiliation(s)
- Miyuki Unekawa
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan.,Tomita Hospital, Okazaki, Japan
| | - Yutaka Tomita
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan.,Tomita Hospital, Okazaki, Japan
| | - Haruki Toriumi
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Takashi Osada
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Kazuto Masamoto
- Brain Science Inspired Life Support Research Center, University of Electro-Communications, Chofu, Japan.,Department of Functional Brain Imaging Research, National Institute of Radiological Sciences, Chiba, Japan
| | - Hiroshi Kawaguchi
- Department of Functional Brain Imaging Research, National Institute of Radiological Sciences, Chiba, Japan.,Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
| | - Yoshikane Izawa
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Yoshiaki Itoh
- Department of Neurology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Iwao Kanno
- Department of Functional Brain Imaging Research, National Institute of Radiological Sciences, Chiba, Japan
| | - Norihiro Suzuki
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan.,Department of Neurology, Shonan Keiiku Hospital, Fujisawa, Japan
| | - Jin Nakahara
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
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23
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Vendel E, Rottschäfer V, de Lange ECM. The need for mathematical modelling of spatial drug distribution within the brain. Fluids Barriers CNS 2019; 16:12. [PMID: 31092261 PMCID: PMC6521438 DOI: 10.1186/s12987-019-0133-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 04/19/2019] [Indexed: 12/17/2022] Open
Abstract
The blood brain barrier (BBB) is the main barrier that separates the blood from the brain. Because of the BBB, the drug concentration-time profile in the brain may be substantially different from that in the blood. Within the brain, the drug is subject to distributional and elimination processes: diffusion, bulk flow of the brain extracellular fluid (ECF), extra-intracellular exchange, bulk flow of the cerebrospinal fluid (CSF), binding and metabolism. Drug effects are driven by the concentration of a drug at the site of its target and by drug-target interactions. Therefore, a quantitative understanding is needed of the distribution of a drug within the brain in order to predict its effect. Mathematical models can help in the understanding of drug distribution within the brain. The aim of this review is to provide a comprehensive overview of system-specific and drug-specific properties that affect the local distribution of drugs in the brain and of currently existing mathematical models that describe local drug distribution within the brain. Furthermore, we provide an overview on which processes have been addressed in these models and which have not. Altogether, we conclude that there is a need for a more comprehensive and integrated model that fills the current gaps in predicting the local drug distribution within the brain.
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Affiliation(s)
- Esmée Vendel
- Mathematical Institute, Leiden University, Niels Bohrweg 1, 2333CA, Leiden, The Netherlands
| | - Vivi Rottschäfer
- Mathematical Institute, Leiden University, Niels Bohrweg 1, 2333CA, Leiden, The Netherlands
| | - Elizabeth C M de Lange
- Leiden Academic Centre for Drug Research, Einsteinweg 55, 2333CC, Leiden, The Netherlands.
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24
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Masamoto K, Vazquez A. Optical imaging and modulation of neurovascular responses. J Cereb Blood Flow Metab 2018; 38:2057-2072. [PMID: 30334644 PMCID: PMC6282226 DOI: 10.1177/0271678x18803372] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 09/02/2018] [Indexed: 12/17/2022]
Abstract
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.
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Affiliation(s)
- Kazuto Masamoto
- Faculty of Informatics and Engineering, University of Electro-Communications, Tokyo, Japan
- Brain Science Inspired Life Support Research Center, University of Electro-Communications, Tokyo, Japan
| | - Alberto Vazquez
- Departments of Radiology and Bioengineering, University of Pittsburgh, PA, USA
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25
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Davoodzadeh N, Cano-Velázquez MS, Halaney DL, Jonak CR, Binder DK, Aguilar G. Evaluation of a transparent cranial implant as a permanent window for cerebral blood flow imaging. BIOMEDICAL OPTICS EXPRESS 2018; 9:4879-4892. [PMID: 30319909 PMCID: PMC6179387 DOI: 10.1364/boe.9.004879] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 08/27/2018] [Accepted: 09/12/2018] [Indexed: 05/11/2023]
Abstract
Laser speckle imaging (LSI) of mouse cerebral blood flow was compared through a transparent nanocrystalline yttria-stabilized zirconia (nc-YSZ) cranial implant over time (at days 0, 14, and 28, n = 3 mice), and vs. LSI through native skull (at day 60, n = 1 mouse). The average sharpness of imaged vessels was found to remain stable, with relative change in sharpness under 7.69% ± 1.2% over 28 days. Through-implant images of vessels at day 60 appeared sharper and smaller on average, with microvessels clearly visible, compared to through-skull images where vessels appeared blurred and distorted. These results suggest that long-term imaging through this implant is feasible.
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Affiliation(s)
- Nami Davoodzadeh
- Department of Mechanical Engineering, University of California, Riverside, CA, USA
| | | | - David L Halaney
- Department of Mechanical Engineering, University of California, Riverside, CA, USA
| | - Carrie R Jonak
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, CA, USA
| | - Devin K Binder
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, CA, USA
| | - Guillermo Aguilar
- Department of Mechanical Engineering, University of California, Riverside, CA, USA
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26
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Han S, Son JP, Cho H, Park JY, Kim SG. Gradient-echo and spin-echo blood oxygenation level-dependent functional MRI at ultrahigh fields of 9.4 and 15.2 Tesla. Magn Reson Med 2018; 81:1237-1246. [PMID: 30183108 PMCID: PMC6585650 DOI: 10.1002/mrm.27457] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 06/26/2018] [Accepted: 06/27/2018] [Indexed: 01/08/2023]
Abstract
Purpose Sensitivity and specificity of blood oxygenation level–dependent (BOLD) functional MRI (fMRI) is sensitive to magnetic field strength and acquisition methods. We have investigated gradient‐echo (GE)‐ and spin‐echo (SE)‐BOLD fMRI at ultrahigh fields of 9.4 and 15.2 Tesla. Methods BOLD fMRI experiments responding to forepaw stimulation were performed with 3 echo times (TE) at each echo type and B0 in α‐chloralose–anesthetized rats. The contralateral forelimb somatosensory region was selected for quantitative analyses. Results At 9.4 T and 15.2 T, average baseline T2* (n = 9) was 26.6 and 17.1 msec, whereas baseline T2 value (n = 9) was 35.7 and 24.5 msec, respectively. Averaged stimulation‐induced ΔR2* was –1.72 s–1 at 9.4 T and –3.09 s–1 at 15.2 T, whereas ΔR2 was –1.19 s–1 at 9.4 T and –1.97 s–1 at 15.2 T. At the optimal TE of tissue T2* or T2, BOLD percent changes were slightly higher at 15.2 T than at 9.4 T (GE: 7.4% versus 6.4% and SE: 5.7% versus 5.4%). The ΔR2* and ΔR2 ratio of 15.2 T to 9.4 T was 1.8 and 1.66, respectively. The ratio of the macrovessel‐containing superficial to microvessel‐dominant parenchymal BOLD signal was 1.73 to 1.76 for GE‐BOLD versus 1.13 to 1.19 for SE‐BOLD, indicating that the SE‐BOLD contrast is less sensitive to macrovessels than GE‐BOLD. Conclusion SE‐BOLD fMRI improves spatial specificity to microvessels compared to GE‐BOLD at both fields. BOLD sensitivity is similar at the both fields and can be improved at ultrahigh fields only for thermal‐noise–dominant ultrahigh‐resolution fMRI.
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Affiliation(s)
- SoHyun Han
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea.,Athinoula A. Martinos Center for Biomedical Imaging, MGH/Harvard Medical School, Charlestown, Massachusetts
| | - Jeong Pyo Son
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea.,Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul, South Korea
| | - HyungJoon Cho
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea
| | - Jang-Yeon Park
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea.,Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea
| | - Seong-Gi Kim
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea.,Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul, South Korea.,Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea
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27
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Hirano Y, Yen CC, Liu JV, Mackel JB, Merkle H, Nascimento GC, Stefanovic B, Silva AC. Investigation of the BOLD and CBV fMRI responses to somatosensory stimulation in awake marmosets (Callithrix jacchus). NMR IN BIOMEDICINE 2018; 31:10.1002/nbm.3864. [PMID: 29285809 PMCID: PMC5841465 DOI: 10.1002/nbm.3864] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 09/16/2017] [Accepted: 10/24/2017] [Indexed: 06/01/2023]
Abstract
Understanding the spatiotemporal features of the hemodynamic response function (HRF) to brain stimulation is essential for the correct application of neuroimaging methods to study brain function. Here, we investigated the spatiotemporal evolution of the blood oxygen level-dependent (BOLD) and cerebral blood volume (CBV) HRF in conscious, awake marmosets (Callithrix jacchus), a New World non-human primate with a lissencephalic brain and with growing use in biomedical research. The marmosets were acclimatized to head fixation and placed in a 7-T magnetic resonance imaging (MRI) scanner. Somatosensory stimulation (333-μs pulses; amplitude, 2 mA; 64 Hz) was delivered bilaterally via pairs of contact electrodes. A block design paradigm was used in which the stimulus duration increased in pseudo-random order from a single pulse up to 256 electrical pulses (4 s). For CBV measurements, 30 mg/kg of ultrasmall superparamagnetic ironoxide particles (USPIO) injected intravenously, were used. Robust BOLD and CBV HRFs were obtained in the primary somatosensory cortex (S1), secondary somatosensory cortex (S2) and caudate at all stimulus conditions. In particular, BOLD and CBV responses to a single 333-μs-long stimulus were reliably measured, and the CBV HRF presented shorter onset time and time to peak than the BOLD HRF. Both the size of the regions of activation and the peak amplitude of the HRFs grew quickly with increasing stimulus duration, and saturated for stimulus durations greater than 1 s. Onset times in S1 and S2 were faster than in caudate. Finally, the fine spatiotemporal features of the HRF in awake marmosets were similar to those obtained in humans, indicating that the continued refinement of awake non-human primate models is essential to maximize the applicability of animal functional MRI studies to the investigation of human brain function.
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Affiliation(s)
- Yoshiyuki Hirano
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065 USA
| | - Cecil C. Yen
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065 USA
| | - Junjie V. Liu
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065 USA
| | - Julie B. Mackel
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065 USA
| | - Hellmut Merkle
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065 USA
| | - George C. Nascimento
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065 USA
| | - Bojana Stefanovic
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065 USA
| | - Afonso C. Silva
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065 USA
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28
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He Y, Wang M, Chen X, Pohmann R, Polimeni JR, Scheffler K, Rosen BR, Kleinfeld D, Yu X. Ultra-Slow Single-Vessel BOLD and CBV-Based fMRI Spatiotemporal Dynamics and Their Correlation with Neuronal Intracellular Calcium Signals. Neuron 2018; 97:925-939.e5. [PMID: 29398359 PMCID: PMC5845844 DOI: 10.1016/j.neuron.2018.01.025] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 11/14/2017] [Accepted: 01/10/2018] [Indexed: 01/07/2023]
Abstract
Functional MRI has been used to map brain activity and functional connectivity based on the strength and temporal coherence of neurovascular-coupled hemodynamic signals. Here, single-vessel fMRI reveals vessel-specific correlation patterns in both rodents and humans. In anesthetized rats, fluctuations in the vessel-specific fMRI signal are correlated with the intracellular calcium signal measured in neighboring neurons. Further, the blood-oxygen-level-dependent (BOLD) signal from individual venules and the cerebral-blood-volume signal from individual arterioles show correlations at ultra-slow (<0.1 Hz), anesthetic-modulated rhythms. These data support a model that links neuronal activity to intrinsic oscillations in the cerebral vasculature, with a spatial correlation length of ∼2 mm for arterioles. In complementary data from awake human subjects, the BOLD signal is spatially correlated among sulcus veins and specified intracortical veins of the visual cortex at similar ultra-slow rhythms. These data support the use of fMRI to resolve functional connectivity at the level of single vessels.
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Affiliation(s)
- Yi He
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, International Max Planck Research School, University of Tuebingen, 72074 Tuebingen, Germany
| | - Maosen Wang
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, International Max Planck Research School, University of Tuebingen, 72074 Tuebingen, Germany
| | - Xuming Chen
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, International Max Planck Research School, University of Tuebingen, 72074 Tuebingen, Germany
| | - Rolf Pohmann
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany
| | - Jonathan R Polimeni
- MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA 02114, USA
| | - Klaus Scheffler
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Department of Biomedical Magnetic Resonance, University of Tübingen, 72076 Tübingen, Germany
| | - Bruce R Rosen
- MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA 02114, USA
| | - David Kleinfeld
- Department of Physics, University of California at San Diego, La Jolla, CA 92093, USA; Section of Neurobiology, University of California at San Diego, La Jolla, CA 92093, USA
| | - Xin Yu
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany.
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29
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Gutiérrez-Jiménez E, Angleys H, Rasmussen PM, Mikkelsen IK, Mouridsen K, Østergaard L. The effects of hypercapnia on cortical capillary transit time heterogeneity (CTH) in anesthetized mice. J Cereb Blood Flow Metab 2018; 38:290-303. [PMID: 28181842 PMCID: PMC5951010 DOI: 10.1177/0271678x17692598] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Capillary flow patterns are highly heterogeneous in the resting brain. During hyperemia, capillary transit-time heterogeneity (CTH) decreases, in proportion to blood's mean transit time (MTT) in passive, compliant microvascular networks. Previously, we found that functional activation reduces the CTH:MTT ratio, suggesting that additional homogenization takes place through active neurocapillary coupling mechanisms. Here, we examine changes in the CTH:MTT ratio during hypercapnic hyperemia in anesthetized mice (C57Bl/6NTac), expecting that homogenization is smaller than during functional hyperemia. We used an indicator-dilution technique and multiple capillary scans by two-photon microscopy to estimate CTH and MTT. During hypercapnia, MTT and CTH decreased as derived from indicator-dilution between artery and vein, as well as between arterioles and venules. The CTH:MTT ratio, however, increased. The same tendency was observed in the estimates from capillary scans. The parallel reductions of MTT and CTH are consistent with previous data. We speculate that the relative increase in CTH compared to MTT during hypercapnia represents either or both capillary constrictions and blood passage through functional thoroughfare channels. Intriguingly, hemodynamic responses to hypercapnia declined with cortical depth, opposite previous reports of hemodynamic responses to functional activation. Our findings support the role of CTH in cerebral flow-metabolism coupling during hyperemia.
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Affiliation(s)
- Eugenio Gutiérrez-Jiménez
- 1 Center of Functionally Integrative Neuroscience and MINDLab, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Hugo Angleys
- 1 Center of Functionally Integrative Neuroscience and MINDLab, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Peter Mondrup Rasmussen
- 1 Center of Functionally Integrative Neuroscience and MINDLab, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Irene Klærke Mikkelsen
- 1 Center of Functionally Integrative Neuroscience and MINDLab, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Kim Mouridsen
- 1 Center of Functionally Integrative Neuroscience and MINDLab, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Leif Østergaard
- 1 Center of Functionally Integrative Neuroscience and MINDLab, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.,2 Department of Neuroradiology, Aarhus University Hospital, Aarhus, Denmark
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30
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Kisler K, Nelson AR, Montagne A, Zlokovic BV. Cerebral blood flow regulation and neurovascular dysfunction in Alzheimer disease. Nat Rev Neurosci 2017; 18:419-434. [PMID: 28515434 PMCID: PMC5759779 DOI: 10.1038/nrn.2017.48] [Citation(s) in RCA: 759] [Impact Index Per Article: 108.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cerebral blood flow (CBF) regulation is essential for normal brain function. The mammalian brain has evolved a unique mechanism for CBF control known as neurovascular coupling. This mechanism ensures a rapid increase in the rate of CBF and oxygen delivery to activated brain structures. The neurovascular unit is composed of astrocytes, mural vascular smooth muscle cells and pericytes, and endothelia, and regulates neurovascular coupling. This Review article examines the cellular and molecular mechanisms within the neurovascular unit that contribute to CBF control, and neurovascular dysfunction in neurodegenerative disorders such as Alzheimer disease.
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Affiliation(s)
- Kassandra Kisler
- Zilkha Neurogenetic Institute, 1501 San Pablo Street, Los Angeles, California 90089, USA
| | - Amy R Nelson
- Zilkha Neurogenetic Institute, 1501 San Pablo Street, Los Angeles, California 90089, USA
| | - Axel Montagne
- Zilkha Neurogenetic Institute, 1501 San Pablo Street, Los Angeles, California 90089, USA
| | - Berislav V Zlokovic
- Zilkha Neurogenetic Institute, 1501 San Pablo Street, Los Angeles, California 90089, USA
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31
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Reactivity in the human retinal microvasculature measured during acute gas breathing provocations. Sci Rep 2017; 7:2113. [PMID: 28522835 PMCID: PMC5437020 DOI: 10.1038/s41598-017-02344-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 04/10/2017] [Indexed: 11/11/2022] Open
Abstract
Although changes in vessel diameter following gas perturbation have been documented in retinal arterioles and venules, these responses have yet to be quantified in the smallest vessels of the human retina. Here, using in vivo adaptive optics, we imaged 3–25 µm diameter vessels of the human inner retinal circulation and monitored the effects of altered gas-breathing conditions. During isocapnic hyperoxia, definite constrictions were seen in 51% of vessel segments (mean ± SD for pre-capillary arterioles −9.5 ± 3.0%; capillaries −11.8 ± 3.3%; post-capillary venules −6.3 ± 2.8%); these are comparable with responses previously reported in larger vessels. During isoxic hypercapnia, definite dilations were seen in 47% of vessel segments (mean ± SD for pre-capillary arterioles +9.8 ± 1.5%; capillaries +13.7 ± 3.8%; post-capillary venules +7.5 ± 4.2%); these are proportionally greater than responses previously reported in larger vessels. The magnitude of these proportional changes implies that the capillary beds themselves play an important role in the retinal response to changes in carbon dioxide levels. Interestingly, the distribution of microvascular responses shown here differs from our previously reported responses to flicker stimulation, suggesting differences in the way blood supply is coordinated following gas perturbation and altered neural activity.
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32
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Dorr A, Thomason LA, Koletar MM, Joo IL, Steinman J, Cahill LS, Sled JG, Stefanovic B. Effects of voluntary exercise on structure and function of cortical microvasculature. J Cereb Blood Flow Metab 2017; 37:1046-1059. [PMID: 27683451 PMCID: PMC5363487 DOI: 10.1177/0271678x16669514] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Aerobic activity has been shown highly beneficial to brain health, yet much uncertainty still surrounds the effects of exercise on the functioning of cerebral microvasculature. This study used two-photon fluorescence microscopy to examine cerebral hemodynamic alterations as well as accompanying geometric changes in the cortical microvascular network following five weeks of voluntary exercise in transgenic mice endogenously expressing tdTomato in vascular endothelial cells to allow visualization of microvessels irrespective of their perfusion levels. We found a diminished microvascular response to a hypercapnic challenge (10% FiCO2) in running mice when compared to that in nonrunning controls despite commensurate increases in transcutaneous CO2 tension. The flow increase to hypercapnia in runners was 70% lower than that in nonrunners (p = 0.0070) and the runners' arteriolar red blood cell speed changed by only half the amount seen in nonrunners (p = 0.0085). No changes were seen in resting hemodynamics or in the systemic physiological parameters measured. Although a few unperfused new vessels were observed on visual inspection, running did not produce significant morphological differences in the microvascular morphometric parameters, quantified following semiautomated tracking of the microvascular networks. We propose that voluntary running led to increased cortical microvascular efficiency and desensitization to CO2 elevation.
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Affiliation(s)
| | | | | | - Illsung L Joo
- 1 Sunnybrook Research Institute, Toronto, Canada.,2 Department of Medical Biophysics, University of Toronto, Toronto, Canada
| | - Joe Steinman
- 2 Department of Medical Biophysics, University of Toronto, Toronto, Canada.,3 Mouse Imaging Centre, The Hospital for Sick Children, Toronto, Canada
| | - Lindsay S Cahill
- 3 Mouse Imaging Centre, The Hospital for Sick Children, Toronto, Canada
| | - John G Sled
- 2 Department of Medical Biophysics, University of Toronto, Toronto, Canada.,3 Mouse Imaging Centre, The Hospital for Sick Children, Toronto, Canada
| | - Bojana Stefanovic
- 1 Sunnybrook Research Institute, Toronto, Canada.,2 Department of Medical Biophysics, University of Toronto, Toronto, Canada
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33
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Schmid F, Tsai PS, Kleinfeld D, Jenny P, Weber B. Depth-dependent flow and pressure characteristics in cortical microvascular networks. PLoS Comput Biol 2017; 13:e1005392. [PMID: 28196095 PMCID: PMC5347440 DOI: 10.1371/journal.pcbi.1005392] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 03/01/2017] [Accepted: 01/31/2017] [Indexed: 01/21/2023] Open
Abstract
A better knowledge of the flow and pressure distribution in realistic microvascular networks is needed for improving our understanding of neurovascular coupling mechanisms and the related measurement techniques. Here, numerical simulations with discrete tracking of red blood cells (RBCs) are performed in three realistic microvascular networks from the mouse cerebral cortex. Our analysis is based on trajectories of individual RBCs and focuses on layer-specific flow phenomena until a cortical depth of 1 mm. The individual RBC trajectories reveal that in the capillary bed RBCs preferentially move in plane. Hence, the capillary flow field shows laminar patterns and a layer-specific analysis is valid. We demonstrate that for RBCs entering the capillary bed close to the cortical surface (< 400 μm) the largest pressure drop takes place in the capillaries (37%), while for deeper regions arterioles are responsible for 61% of the total pressure drop. Further flow characteristics, such as capillary transit time or RBC velocity, also vary significantly over cortical depth. Comparison of purely topological characteristics with flow-based ones shows that a combined interpretation of topology and flow is indispensable. Our results provide evidence that it is crucial to consider layer-specific differences for all investigations related to the flow and pressure distribution in the cortical vasculature. These findings support the hypothesis that for an efficient oxygen up-regulation at least two regulation mechanisms must be playing hand in hand, namely cerebral blood flow increase and microvascular flow homogenization. However, the contribution of both regulation mechanisms to oxygen up-regulation likely varies over depth.
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Affiliation(s)
- Franca Schmid
- Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland
| | - Philbert S. Tsai
- Department of Physics, University of California at San Diego, La Jolla, California, United States of America
| | - David Kleinfeld
- Department of Physics, University of California at San Diego, La Jolla, California, United States of America
- Section of Neurobiology, University of California, La Jolla, California, United States of America
| | - Patrick Jenny
- Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland
| | - Bruno Weber
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
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34
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Li B, Wang H, Fu B, Wang R, Sakadžić S, Boas DA. Impact of temporal resolution on estimating capillary RBC-flux with optical coherence tomography. JOURNAL OF BIOMEDICAL OPTICS 2017; 22:16014. [PMID: 28125157 PMCID: PMC5266917 DOI: 10.1117/1.jbo.22.1.016014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Accepted: 01/09/2017] [Indexed: 05/06/2023]
Abstract
Optical coherence tomography (OCT) has been used to measure capillary red blood cell (RBC) flux. However, one important technical issue is that the accuracy of this method is subject to the temporal resolution ( ? t ) of the repeated RBC-passage B-scans. A ceiling effect arises due to an insufficient ? t limiting the maximum RBC-flux that can be measured. In this letter, we first present simulations demonstrating that ? t = 1.5 ?? ms permits measuring RBC-flux up to 150 ?? RBCs / s with an underestimation of 9%. The simulations further show that measurements with ? t = 3 and 4.5 ms provide relatively less accurate estimates for typical physiological fluxes. We provide experimental data confirming the simulation results showing that reduced temporal resolution (i.e., a longer ? t ) results in an underestimation of mean flux and compresses the distribution of measured fluxes, which potentially confounds physiological interpretation of the results. The results also apply to RBC-passage measurements made with confocal and two-photon microscopy for estimating capillary RBC-flux.
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Affiliation(s)
- Baoqiang Li
- Massachusetts General Hospital/Harvard Medical School, Optics Division, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts 02129, United States
- Address all correspondence to: Baoqiang Li, E-mail:
| | - Hui Wang
- Massachusetts General Hospital/Harvard Medical School, Optics Division, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts 02129, United States
- Massachusetts General Hospital/Harvard Medical School, Laboratory for Computational Neuroimaging, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts 02129, United States
| | - Buyin Fu
- Massachusetts General Hospital/Harvard Medical School, Optics Division, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts 02129, United States
| | - Ruopeng Wang
- Massachusetts General Hospital/Harvard Medical School, Laboratory for Computational Neuroimaging, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts 02129, United States
| | - Sava Sakadžić
- Massachusetts General Hospital/Harvard Medical School, Optics Division, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts 02129, United States
| | - David A. Boas
- Massachusetts General Hospital/Harvard Medical School, Optics Division, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts 02129, United States
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35
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Choi WJ, Li Y, Qin W, Wang RK. Cerebral capillary velocimetry based on temporal OCT speckle contrast. BIOMEDICAL OPTICS EXPRESS 2016; 7:4859-4873. [PMID: 28018711 PMCID: PMC5175537 DOI: 10.1364/boe.7.004859] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 10/21/2016] [Accepted: 10/27/2016] [Indexed: 05/15/2023]
Abstract
We propose a new optical coherence tomography (OCT) based method to measure red blood cell (RBC) velocities of single capillaries in the cortex of rodent brain. This OCT capillary velocimetry exploits quantitative laser speckle contrast analysis to estimate speckle decorrelation rate from the measured temporal OCT speckle signals, which is related to microcirculatory flow velocity. We hypothesize that OCT signal due to sub-surface capillary flow can be treated as the speckle signal in the single scattering regime and thus its time scale of speckle fluctuations can be subjected to single scattering laser speckle contrast analysis to derive characteristic decorrelation time. To validate this hypothesis, OCT measurements are conducted on a single capillary flow phantom operating at preset velocities, in which M-mode B-frames are acquired using a high-speed OCT system. Analysis is then performed on the time-varying OCT signals extracted at the capillary flow, exhibiting a typical inverse relationship between the estimated decorrelation time and absolute RBC velocity, which is then used to deduce the capillary velocities. We apply the method to in vivo measurements of mouse brain, demonstrating that the proposed approach provides additional useful information in the quantitative assessment of capillary hemodynamics, complementary to that of OCT angiography.
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36
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Gutiérrez-Jiménez E, Cai C, Mikkelsen IK, Rasmussen PM, Angleys H, Merrild M, Mouridsen K, Jespersen SN, Lee J, Iversen NK, Sakadzic S, Østergaard L. Effect of electrical forepaw stimulation on capillary transit-time heterogeneity (CTH). J Cereb Blood Flow Metab 2016; 36:2072-2086. [PMID: 26858243 PMCID: PMC5363666 DOI: 10.1177/0271678x16631560] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 11/26/2015] [Accepted: 12/23/2015] [Indexed: 11/16/2022]
Abstract
Functional hyperemia reduces oxygen extraction efficacy unless counteracted by a reduction of capillary transit-time heterogeneity of blood. We adapted a bolus tracking approach to capillary transit-time heterogeneity estimation for two-photon microscopy and then quantified changes in plasma mean transit time and capillary transit-time heterogeneity during forepaw stimulation in anesthetized mice (C57BL/6NTac). In addition, we analyzed transit time coefficient of variance = capillary transit-time heterogeneity/mean transit time, which we expect to remain constant in passive, compliant microvascular networks. Electrical forepaw stimulation reduced, both mean transit time (11.3% ± 1.3%) and capillary transit-time heterogeneity (24.1% ± 3.3%), consistent with earlier literature and model predictions. We observed a coefficient of variance reduction (14.3% ± 3.5%) during functional activation, especially for the arteriolar-to-venular passage. Such coefficient of variance reduction during functional activation suggests homogenization of capillary flows beyond that expected as a passive response to increased blood flow by other stimuli. This finding is consistent with an active neurocapillary coupling mechanism, for example via pericyte dilation. Mean transit time and capillary transit-time heterogeneity reductions were consistent with the relative change inferred from capillary hemodynamics (cell velocity and flux). Our findings support the important role of capillary transit-time heterogeneity in flow-metabolism coupling during functional activation.
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Affiliation(s)
| | - Changsi Cai
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | | | | | - Hugo Angleys
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Mads Merrild
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Kim Mouridsen
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Sune Nørhøj Jespersen
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | - Jonghwan Lee
- Department of Radiology, Harvard Medical School, Boston, USA
| | | | - Sava Sakadzic
- Department of Radiology, Harvard Medical School, Boston, USA
| | - Leif Østergaard
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Neuroradiology, Aarhus University Hospital, Aarhus, Denmark
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Li B, Lee J, Boas DA, Lesage F. Contribution of low- and high-flux capillaries to slow hemodynamic fluctuations in the cerebral cortex of mice. J Cereb Blood Flow Metab 2016; 36:1351-6. [PMID: 27165011 PMCID: PMC4976754 DOI: 10.1177/0271678x16649195] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 04/17/2016] [Indexed: 11/15/2022]
Abstract
We employed optical coherence tomography to measure cerebral cortical capillary red blood cell (RBC) flux in mice. The results suggest that baseline-flux weakly depends on cortical depth. Furthermore, under hypercapnia, low baseline-flux capillaries exhibit greater flux increases while the higher ones saturate, resulting in RBC-flux homogenization. Power-spectrum analysis indicates that higher flux capillaries saw greater flux variability in the low-frequency range (0.01-0.1 Hz) both at baseline and during hypercapnia. These results suggest that lower baseline-flux capillaries have more reserve to deliver oxygen with increased blood flow; but higher ones more strongly impact the low-frequency fluctuations associated with BOLD fMRI measurements of resting state functional connectivity.
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Affiliation(s)
- Baoqiang Li
- Department of Electrical Engineering, École Polytechnique de Montréal, Canada Optics Division, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, USA
| | - Jonghwan Lee
- Optics Division, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, USA
| | - David A Boas
- Optics Division, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, USA
| | - Frederic Lesage
- Department of Electrical Engineering, École Polytechnique de Montréal, Canada
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38
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Santisakultarm TP, Kersbergen CJ, Bandy DK, Ide DC, Choi SH, Silva AC. Two-photon imaging of cerebral hemodynamics and neural activity in awake and anesthetized marmosets. J Neurosci Methods 2016; 271:55-64. [PMID: 27393311 DOI: 10.1016/j.jneumeth.2016.07.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 06/22/2016] [Accepted: 07/03/2016] [Indexed: 10/21/2022]
Abstract
BACKGROUND Marmosets are a powerful, emerging model for human behavior and neurological disorders. However, longitudinal imaging modalities that visualize both cellular structure and function within the cortex are not available in this animal model. Hence, we implemented an approach to quantify vascular topology, hemodynamics, and neural activity in awake marmosets using two-photon microscopy (2PM). NEW METHOD Marmosets were acclimated to a custom stereotaxic system. AAV1-GCaMP5G was injected into somatosensory cortex to optically indicate neural activity, and a cranial chamber was implanted. RESULTS Longitudinal 2PM revealed vasculature and neurons 500μm below the cortical surface. Vascular response and neural activity during sensory stimulation were preserved over 5 and 3 months, respectively, before optical quality deteriorated. Vascular remodeling including increased tortuosity and branching was quantified. However, capillary connectivity from arterioles to venules remained unchanged. Further, behavioral assessment before and after surgery demonstrated no impact on cognitive and motor function. Immunohistochemistry confirmed minimal astrocyte activation with no focal damage. Over 6 months, total cortical depth visualized decreased. When under anesthesia, the most prominent isoflurane-induced vasodilation occurred in capillaries and smaller arterioles. COMPARISON WITH EXISTING METHOD(S) These results demonstrate the capability to repeatedly observe cortical physiology in awake marmosets over months. CONCLUSIONS This work provides a novel and insightful technique to investigate critical mechanisms in neurological disorders in awake marmosets without introducing confounds from anesthesia.
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Affiliation(s)
- Thom P Santisakultarm
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Calvin J Kersbergen
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Daryl K Bandy
- Section on Instrumentation, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - David C Ide
- Section on Instrumentation, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Sang-Ho Choi
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Afonso C Silva
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA.
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39
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Yu X, He Y, Wang M, Merkle H, Dodd SJ, Silva AC, Koretsky AP. Sensory and optogenetically driven single-vessel fMRI. Nat Methods 2016; 13:337-40. [PMID: 26855362 DOI: 10.1038/nmeth.3765] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 01/07/2016] [Indexed: 01/24/2023]
Abstract
Magnetic resonance imaging (MRI) sensitivity approaches vessel specificity. We developed a single-vessel functional MRI (fMRI) method to image the contribution of vascular components to blood oxygenation level-dependent (BOLD) and cerebral blood volume (CBV) fMRI signal. We mapped individual vessels penetrating the rat somatosensory cortex with 100-ms temporal resolution by MRI with sensory or optogenetic stimulation. The BOLD signal originated primarily from venules, and the CBV signal from arterioles. The single-vessel fMRI method and its combination with optogenetics provide a platform for mapping the hemodynamic signal through the neurovascular network with specificity at the level of individual arterioles and venules.
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Affiliation(s)
- Xin Yu
- High Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | - Yi He
- High Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | - Maosen Wang
- High Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | - Hellmut Merkle
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, US National Institutes of Health, Bethesda, Maryland, USA
| | - Stephen J Dodd
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, US National Institutes of Health, Bethesda, Maryland, USA
| | - Afonso C Silva
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, US National Institutes of Health, Bethesda, Maryland, USA
| | - Alan P Koretsky
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, US National Institutes of Health, Bethesda, Maryland, USA
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Merkle CW, Srinivasan VJ. Laminar microvascular transit time distribution in the mouse somatosensory cortex revealed by Dynamic Contrast Optical Coherence Tomography. Neuroimage 2015; 125:350-362. [PMID: 26477654 DOI: 10.1016/j.neuroimage.2015.10.017] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Revised: 09/15/2015] [Accepted: 10/07/2015] [Indexed: 11/15/2022] Open
Abstract
The transit time distribution of blood through the cerebral microvasculature both constrains oxygen delivery and governs the kinetics of neuroimaging signals such as blood-oxygen-level-dependent functional Magnetic Resonance Imaging (BOLD fMRI). However, in spite of its importance, capillary transit time distribution has been challenging to quantify comprehensively and efficiently at the microscopic level. Here, we introduce a method, called Dynamic Contrast Optical Coherence Tomography (DyC-OCT), based on dynamic cross-sectional OCT imaging of an intravascular tracer as it passes through the field-of-view. Quantitative transit time metrics are derived from temporal analysis of the dynamic scattering signal, closely related to tracer concentration. Since DyC-OCT does not require calibration of the optical focus, quantitative accuracy is achieved even deep in highly scattering brain tissue where the focal spot degrades. After direct validation of DyC-OCT against dilution curves measured using a fluorescent plasma label in surface pial vessels, we used DyC-OCT to investigate the transit time distribution in microvasculature across the entire depth of the mouse somatosensory cortex. Laminar trends were identified, with earlier transit times and less heterogeneity in the middle cortical layers. The early transit times in the middle cortical layers may explain, at least in part, the early BOLD fMRI onset times observed in these layers. The layer-dependencies in heterogeneity may help explain how a single vascular supply manages to deliver oxygen to individual cortical layers with diverse metabolic needs.
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Affiliation(s)
- Conrad W Merkle
- Department of Biomedical Engineering, University of California at Davis 451 E. Health Sciences Dr. GBSF 2303 Davis CA 95616, USA
| | - Vivek J Srinivasan
- Department of Biomedical Engineering, University of California at Davis 451 E. Health Sciences Dr. GBSF 2303 Davis CA 95616, USA.
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41
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Rooney WD, Li X, Sammi MK, Bourdette DN, Neuwelt EA, Springer CS. Mapping human brain capillary water lifetime: high-resolution metabolic neuroimaging. NMR IN BIOMEDICINE 2015; 28:607-23. [PMID: 25914365 PMCID: PMC4920360 DOI: 10.1002/nbm.3294] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 01/28/2015] [Accepted: 03/02/2015] [Indexed: 05/25/2023]
Abstract
Shutter-speed analysis of dynamic-contrast-agent (CA)-enhanced normal, multiple sclerosis (MS), and glioblastoma (GBM) human brain data gives the mean capillary water molecule lifetime (τ(b)) and blood volume fraction (v(b); capillary density-volume product (ρ(†)V)) in a high-resolution (1)H2O MRI voxel (40 μL) or ROI. The equilibrium water extravasation rate constant, k(po) (τ(b)(-1)), averages 3.2 and 2.9 s(-1) in resting-state normal white matter (NWM) and gray matter (NGM), respectively (n = 6). The results (italicized) lead to three major conclusions. (A) k(po) differences are dominated by capillary water permeability (P(W)(†)), not size, differences. NWM and NGM voxel k(po) and v(b) values are independent. Quantitative analyses of concomitant population-averaged k(po), v(b) variations in normal and normal-appearing MS brain ROIs confirm P(W)(†) dominance. (B) P(W)(†) is dominated (>95%) by a trans(endothelial)cellular pathway, not the P(CA)(†) paracellular route. In MS lesions and GBM tumors, P(CA)(†) increases but P(W)(†) decreases. (C) k(po) tracks steady-state ATP production/consumption flux per capillary. In normal, MS, and GBM brain, regional k(po) correlates with literature MRSI ATP (positively) and Na(+) (negatively) tissue concentrations. This suggests that the P(W)(†) pathway is metabolically active. Excellent agreement of the relative NGM/NWM k(po)v(b) product ratio with the literature (31)PMRSI-MT CMR(oxphos) ratio confirms the flux property. We have previously shown that the cellular water molecule efflux rate constant (k(io)) is proportional to plasma membrane P-type ATPase turnover, likely due to active trans-membrane water cycling. With synaptic proximities and synergistic metabolic cooperativities, polar brain endothelial, neuroglial, and neuronal cells form "gliovascular units." We hypothesize that a chain of water cycling processes transmits brain metabolic activity to k(po), letting it report neurogliovascular unit Na(+),K(+)-ATPase activity. Cerebral k(po) maps represent metabolic (functional) neuroimages. The NGM 2.9 s(-1) k(po) means an equilibrium unidirectional water efflux of ~10(15) H2O molecules s(-1) per capillary (in 1 μL tissue): consistent with the known ATP consumption rate and water co-transporting membrane symporter stoichiometries.
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Affiliation(s)
- William D. Rooney
- Advanced Imaging Research CenterOregon Health and Science UniversityPortlandORUSA
- W. M. Keck Foundation High‐Field MRI LaboratoryOregon Health and Science UniversityPortlandORUSA
- Knight Cardiovascular InstituteOregon Health and Science UniversityPortlandORUSA
- Department of NeurologyOregon Health and Science UniversityPortlandORUSA
| | - Xin Li
- Advanced Imaging Research CenterOregon Health and Science UniversityPortlandORUSA
- W. M. Keck Foundation High‐Field MRI LaboratoryOregon Health and Science UniversityPortlandORUSA
| | - Manoj K. Sammi
- Advanced Imaging Research CenterOregon Health and Science UniversityPortlandORUSA
- W. M. Keck Foundation High‐Field MRI LaboratoryOregon Health and Science UniversityPortlandORUSA
| | | | - Edward A. Neuwelt
- Blood‐Brain Barrier ProgramOregon Health and Science UniversityPortlandORUSA
| | - Charles S. Springer
- Advanced Imaging Research CenterOregon Health and Science UniversityPortlandORUSA
- W. M. Keck Foundation High‐Field MRI LaboratoryOregon Health and Science UniversityPortlandORUSA
- Knight Cardiovascular InstituteOregon Health and Science UniversityPortlandORUSA
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Østergaard L, Jespersen SN, Engedahl T, Gutiérrez Jiménez E, Ashkanian M, Hansen MB, Eskildsen S, Mouridsen K. Capillary dysfunction: its detection and causative role in dementias and stroke. Curr Neurol Neurosci Rep 2015; 15:37. [PMID: 25956993 PMCID: PMC4441906 DOI: 10.1007/s11910-015-0557-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In acute ischemic stroke, critical hypoperfusion is a frequent cause of hypoxic tissue injury: As cerebral blood flow (CBF) falls below the ischemic threshold of 20 mL/100 mL/min, neurological symptoms develop and hypoxic tissue injury evolves within minutes or hours unless the oxygen supply is restored. But is ischemia the only hemodynamic source of hypoxic tissue injury? Reanalyses of the equations we traditionally use to describe the relation between CBF and tissue oxygenation suggest that capillary flow patterns are crucial for the efficient extraction of oxygen: without close capillary flow control, "functional shunts" tend to form and some of the blood's oxygen content in effect becomes inaccessible to tissue. This phenomenon raises several questions: Are there in fact two hemodynamic causes of tissue hypoxia: Limited blood supply (ischemia) and limited oxygen extraction due to capillary dysfunction? If so, how do we distinguish the two, experimentally and in patients? Do flow-metabolism coupling mechanisms adjust CBF to optimize tissue oxygenation when capillary dysfunction impairs oxygen extraction downstream? Cardiovascular risk factors such as age, hypertension, diabetes, hypercholesterolemia, and smoking increase the risk of both stroke and dementia. The capillary dysfunction phenomenon therefore forces us to consider whether changes in capillary morphology or blood rheology may play a role in the etiology of some stroke subtypes and in Alzheimer's disease. Here, we discuss whether certain disease characteristics suggest capillary dysfunction rather than primary flow-limiting vascular pathology and how capillary dysfunction may be imaged and managed.
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Affiliation(s)
- Leif Østergaard
- Center of Functionally Integrative Neuroscience and MINDLab, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark,
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Abstract
Blood flow is a useful indicator of the metabolic state of the retina. However, accurate measurement of retinal blood flow is difficult to achieve in practice. Most existing optical techniques used for measuring blood flow require complex assumptions and calculations. We describe here a simple and direct method for calculating absolute blood flow in vessels of all sizes in the rat retina. The method relies on ultrafast confocal line scans to track the passage of fluorescently labeled red blood cells (fRBCs). The accuracy of the blood flow measurements was verified by (1) comparing blood flow calculated independently using either flux or velocity combined with diameter measurements, (2) measuring total retinal blood flow in arterioles and venules, (3) measuring blood flow at vessel branch points, and (4) measuring changes in blood flow in response to hyperoxic and hypercapnic challenge. Confocal line scans oriented parallel and diagonal to vessels were used to compute fRBC velocity and to examine velocity profiles across the width of vessels. We demonstrate that these methods provide accurate measures of absolute blood flow and velocity in retinal vessels of all sizes.
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44
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Modeling the role of osmotic forces in the cerebrovascular response to CO2. Med Hypotheses 2015; 85:25-36. [PMID: 25858437 DOI: 10.1016/j.mehy.2015.03.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Revised: 03/06/2015] [Accepted: 03/12/2015] [Indexed: 12/15/2022]
Abstract
Increases in blood osmolarity have been shown to exert a vasodilatory effect on cerebral and other vasculature, with accompanying increases in blood flow. It has also been shown that, through an influence on blood concentration of the bicarbonate ion and pH, changes in blood levels of CO2 can alter blood osmolarity sufficiently to have an impact on vessel diameter. We propose here that this phenomenon plays a previously unappreciated role in CO2-mediated vasodilation, and present a biophysical model of osmotically driven vasodilation. Our model, which is based on literature data describing CO2-dependent changes in blood osmolarity and hydraulic conductivity (Lp) of the blood-brain barrier, is used to predict the change in cerebral blood flow (CBF) associated with osmotic forces arising from a specific hypercapnic challenge. Modeled changes were then compared with actual CBF changes determined using arterial spin-labeling (ASL) MRI. For changes in the arterial partial pressure of CO2 (PaCO2) of 20 mmHg, our model predicted increases of 80% from baseline CBF with a temporal evolution that was comparable to the measured hemodynamic responses. Our modeling results suggest that osmotic forces could play a significant role in the cerebrovascular response to CO2.
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45
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Low-frequency calcium oscillations accompany deoxyhemoglobin oscillations in rat somatosensory cortex. Proc Natl Acad Sci U S A 2014; 111:E4677-86. [PMID: 25313035 DOI: 10.1073/pnas.1410800111] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Spontaneous low-frequency oscillations (LFOs) of blood-oxygen-level-dependent (BOLD) signals are used to map brain functional connectivity with functional MRI, but their source is not well understood. Here we used optical imaging to assess whether LFOs from vascular signals covary with oscillatory intracellular calcium (Ca(2+)i) and with local field potentials in the rat's somatosensory cortex. We observed that the frequency of Ca(2+)i oscillations in tissue (∼0.07 Hz) was similar to the LFOs of deoxyhemoglobin (HbR) and oxyhemoglobin (HbO2) in both large blood vessels and capillaries. The HbR and HbO2 fluctuations within tissue correlated with Ca(2+)i oscillations with a lag time of ∼5-6 s. The Ca(2+)i and hemoglobin oscillations were insensitive to hypercapnia. In contrast, cerebral-blood-flow velocity (CBFv) in arteries and veins fluctuated at a higher frequency (∼0.12 Hz) and was sensitive to hypercapnia. However, in parenchymal tissue, CBFv oscillated with peaks at both ∼0.06 Hz and ∼0.12 Hz. Although the higher-frequency CBFv oscillation (∼0.12 Hz) was decreased by hypercapnia, its lower-frequency component (∼0.06 Hz) was not. The sensitivity of the higher CBFV oscillations to hypercapnia, which triggers blood vessel vasodilation, suggests its dependence on vascular effects that are distinct from the LFOs detected in HbR, HbO2, Ca(2+)i, and the lower-frequency tissue CBFv, which were insensitive to hypercapnia. Hemodynamic LFOs correlated both with Ca(2+)i and neuronal firing (local field potentials), indicating that they directly reflect neuronal activity (perhaps also glial). These findings show that HbR fluctuations (basis of BOLD oscillations) are linked to oscillatory cellular activity and detectable throughout the vascular tree (arteries, capillaries, and veins).
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46
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Ultrasensitive detection of 3D cerebral microvascular network dynamics in vivo. Neuroimage 2014; 103:492-501. [PMID: 25192654 DOI: 10.1016/j.neuroimage.2014.08.051] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 07/20/2014] [Accepted: 08/24/2014] [Indexed: 11/23/2022] Open
Abstract
Despite widespread applications of multiphoton microscopy in microcirculation, its small field of view and inability to instantaneously quantify cerebral blood flow velocity (CBFv) in vascular networks limit its utility in investigating the heterogeneous responses to brain stimulations. Optical Doppler tomography (ODT) provides 3D images of CBFv networks, but it suffers poor sensitivity for measuring capillary flows. Here we report on a new method, contrast-enhanced ODT with Intralipid that significantly improves quantitative CBFv imaging of capillary networks by obviating the errors from long latency between flowing red blood cells (low hematocrit ~20% in capillaries). This enhanced sensitivity allowed us to measure the ultraslow microcirculation surrounding a brain tumor and the abnormal ingrowth of capillary flows in the tumor as well as in ischemia triggered by chronic cocaine in the mouse brain that could not be detected by regular ODT. It also enabled significantly enhanced sensitivity for quantifying the heterogeneous CBFv responses of vascular networks to acute cocaine exposure. Inasmuch as lipid emulsions are widely used for parenteral nutrition the Intralipid contrast method has translational potential for clinical applications.
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Changes in cortical microvasculature during misery perfusion measured by two-photon laser scanning microscopy. J Cereb Blood Flow Metab 2014; 34:1363-72. [PMID: 24849667 PMCID: PMC4126097 DOI: 10.1038/jcbfm.2014.91] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 04/02/2014] [Accepted: 04/25/2014] [Indexed: 12/29/2022]
Abstract
This study aimed to examine the cortical microvessel diameter response to hypercapnia in misery perfusion using two-photon laser scanning microscopy (TPLSM). We evaluated whether the vascular response to hypercapnia could represent the cerebrovascular reserve. Cerebral blood flow (CBF) during normocapnia and hypercapnia was measured by laser-Doppler flowmetry through cranial windows in awake C57/BL6 mice before and at 1, 7, 14, and 28 days after unilateral common carotid artery occlusion (UCCAO). Diameters of the cortical microvessels during normocapnia and hypercapnia were also measured by TPLSM. Cerebral blood flow and the vascular response to hypercapnia were decreased after UCCAO. Before UCCAO, vasodilation during hypercapnia was found primarily in arterioles (22.9%±3.5%). At 14 days after UCCAO, arterioles, capillaries, and venules were autoregulatorily dilated by 79.5%±19.7%, 57.2%±32.3%, and 32.0%±10.8%, respectively. At the same time, the diameter response to hypercapnia in arterioles was significantly decreased to 1.9%±1.5%. A significant negative correlation was observed between autoregulatory vasodilation and the diameter response to hypercapnia in arterioles. Our findings indicate that arterioles play main roles in both autoregulatory vasodilation and hypercapnic vasodilation, and that the vascular response to hypercapnia can be used to estimate the cerebrovascular reserve.
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48
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Masamoto K, Takuwa H, Seki C, Taniguchi J, Itoh Y, Tomita Y, Toriumi H, Unekawa M, Kawaguchi H, Ito H, Suzuki N, Kanno I. Microvascular sprouting, extension, and creation of new capillary connections with adaptation of the neighboring astrocytes in adult mouse cortex under chronic hypoxia. J Cereb Blood Flow Metab 2014; 34:325-31. [PMID: 24252848 PMCID: PMC3915210 DOI: 10.1038/jcbfm.2013.201] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 10/16/2013] [Accepted: 10/23/2013] [Indexed: 11/09/2022]
Abstract
The present study aimed to determine the spatiotemporal dynamics of microvascular and astrocytic adaptation during hypoxia-induced cerebral angiogenesis. Adult C57BL/6J and Tie2-green fluorescent protein (GFP) mice with vascular endothelial cells expressing GFP were exposed to normobaric hypoxia for 3 weeks, whereas the three-dimensional microvessels and astrocytes were imaged repeatedly using two-photon microscopy. After 7 to 14 days of hypoxia, a vessel sprout appeared from the capillaries with a bump-like head shape (mean diameter 14 μm), and stagnant blood cells were seen inside the sprout. However, no detectable changes in the astrocyte morphology were observed for this early phase of the hypoxia adaptation. More than 50% of the sprouts emerged from capillaries 60 μm away from the center penetrating arteries, which indicates that the capillary distant from the penetrating arteries is a favored site for sprouting. After 14 to 21 days of hypoxia, the sprouting vessels created a new connection with an existing capillary. In this phase, the shape of the new vessel and its blood flow were normalized, and the outside of the vessels were wrapped with numerous processes from the neighboring astrocytes. The findings indicate that hypoxia-induced cerebral angiogenesis provokes the adaptation of neighboring astrocytes, which may stabilize the blood-brain barrier in immature vessels.
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Affiliation(s)
- Kazuto Masamoto
- 1] Brain Science Inspired Life Support Research Center, University of Electro-Communications, Chofu, Tokyo, Japan [2] Molecular Imaging Center, National Institute of Radiological Sciences, Inage, Chiba, Japan
| | - Hiroyuki Takuwa
- Molecular Imaging Center, National Institute of Radiological Sciences, Inage, Chiba, Japan
| | - Chie Seki
- Molecular Imaging Center, National Institute of Radiological Sciences, Inage, Chiba, Japan
| | - Junko Taniguchi
- Molecular Imaging Center, National Institute of Radiological Sciences, Inage, Chiba, Japan
| | - Yoshiaki Itoh
- Department of Neurology, School of Medicine Keio University, Shinjuku, Tokyo, Japan
| | - Yutaka Tomita
- Department of Neurology, School of Medicine Keio University, Shinjuku, Tokyo, Japan
| | - Haruki Toriumi
- Department of Neurology, School of Medicine Keio University, Shinjuku, Tokyo, Japan
| | - Miyuki Unekawa
- Department of Neurology, School of Medicine Keio University, Shinjuku, Tokyo, Japan
| | - Hiroshi Kawaguchi
- Molecular Imaging Center, National Institute of Radiological Sciences, Inage, Chiba, Japan
| | - Hiroshi Ito
- Molecular Imaging Center, National Institute of Radiological Sciences, Inage, Chiba, Japan
| | - Norihiro Suzuki
- Department of Neurology, School of Medicine Keio University, Shinjuku, Tokyo, Japan
| | - Iwao Kanno
- Molecular Imaging Center, National Institute of Radiological Sciences, Inage, Chiba, Japan
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Desjardins M, Berti R, Lefebvre J, Dubeau S, Lesage F. Aging-related differences in cerebral capillary blood flow in anesthetized rats. Neurobiol Aging 2014; 35:1947-55. [PMID: 24612672 DOI: 10.1016/j.neurobiolaging.2014.01.136] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 01/09/2014] [Accepted: 01/27/2014] [Indexed: 11/30/2022]
Abstract
Age-related decreases in baseline cerebral blood flow have been measured with various imaging modalities, however, the contribution of capillary flow to this phenomenon remain to elucidate. This study used 2-photon laser scanning fluorescence microscopy to measure capillary diameter, red blood cell speed, and flux in individual capillaries in the sensory-motor cortex of 12 adult (3-month-old) and 12 old (24-month-old) male Long-Evans rats under isoflurane anesthesia. The average (± standard deviation) diameter and speed over 921 capillaries were 6.4 ± 1.4 μm and 1.3 ± 1.1 mm/s, respectively. Red blood cell speed and flux were significantly higher, by 48% and 15%, respectively, in old compared with young animals (p < 5%). The diameter also showed a similar tendency (7% higher, p = 5.7%). Furthermore, capillary hematocrit and density were significantly lower in the older group (p < 5%), by 32% and 20%, respectively.
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Affiliation(s)
- Michèle Desjardins
- Department de Génie Électrique, Institut de Génie Biomédical, École Polytechnique de Montréal, Montréal, Quebec, Canada; Montreal Heart Institute, Montréal, Quebec, Canada.
| | - Romain Berti
- Department de Génie Électrique, Institut de Génie Biomédical, École Polytechnique de Montréal, Montréal, Quebec, Canada; Montreal Heart Institute, Montréal, Quebec, Canada
| | - Joël Lefebvre
- Department de Génie Électrique, Institut de Génie Biomédical, École Polytechnique de Montréal, Montréal, Quebec, Canada; Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Simon Dubeau
- Department de Génie Électrique, Institut de Génie Biomédical, École Polytechnique de Montréal, Montréal, Quebec, Canada; Montreal Heart Institute, Montréal, Quebec, Canada
| | - Frédéric Lesage
- Department de Génie Électrique, Institut de Génie Biomédical, École Polytechnique de Montréal, Montréal, Quebec, Canada; Montreal Heart Institute, Montréal, Quebec, Canada; Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
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Desjardins M, Berti R, Pouliot P, Dubeau S, Lesage F. Multimodal study of the hemodynamic response to hypercapnia in anesthetized aged rats. Neurosci Lett 2014; 563:33-7. [PMID: 24480251 DOI: 10.1016/j.neulet.2014.01.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 01/13/2014] [Accepted: 01/17/2014] [Indexed: 10/25/2022]
Abstract
With aging, the brain undergoes changes in metabolism and perfusion, both of which influence the widely used blood-oxygenation-level-dependent (BOLD) MRI signal. To isolate the vascular effects associated with age, this study measured the response to a hypercapnic challenge using different imaging modalities in 19 young (3 months-old) and 13 old (24 months-old) Long-Evans rats. Intrinsic optical imaging was used to measure oxy (HbO), deoxy (HbR) and total (HbT) hemoglobin concentration changes, laser speckle for cerebral blood flow (CBF) changes, and MRI for the BOLD signal. Older rats had smaller HbO (41% smaller), HbT (50%) and CBF (34%) responses, but the temporal dynamics did not exhibit significant age differences. The ratio of CBV to CBF responses was also smaller in older adults, potentially indicating a change in the compliance of vessels.
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Affiliation(s)
- Michèle Desjardins
- Institut de Génie Biomédical, Dpt. de Génie Électrique, École Polytechnique de Montréal, C.P. 6079, succ. Centre-ville, Montréal, QC, H3C 3A7, Canada; Montreal Heart Institute, 5000 rue Bélanger, Montréal, QC, H1T 1C8, Canada.
| | - Romain Berti
- Institut de Génie Biomédical, Dpt. de Génie Électrique, École Polytechnique de Montréal, C.P. 6079, succ. Centre-ville, Montréal, QC, H3C 3A7, Canada; Montreal Heart Institute, 5000 rue Bélanger, Montréal, QC, H1T 1C8, Canada
| | - Philippe Pouliot
- Institut de Génie Biomédical, Dpt. de Génie Électrique, École Polytechnique de Montréal, C.P. 6079, succ. Centre-ville, Montréal, QC, H3C 3A7, Canada; Montreal Heart Institute, 5000 rue Bélanger, Montréal, QC, H1T 1C8, Canada
| | - Simon Dubeau
- Institut de Génie Biomédical, Dpt. de Génie Électrique, École Polytechnique de Montréal, C.P. 6079, succ. Centre-ville, Montréal, QC, H3C 3A7, Canada; Montreal Heart Institute, 5000 rue Bélanger, Montréal, QC, H1T 1C8, Canada
| | - Frédéric Lesage
- Institut de Génie Biomédical, Dpt. de Génie Électrique, École Polytechnique de Montréal, C.P. 6079, succ. Centre-ville, Montréal, QC, H3C 3A7, Canada; Montreal Heart Institute, 5000 rue Bélanger, Montréal, QC, H1T 1C8, Canada
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