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Smith AF, Doyeux V, Berg M, Peyrounette M, Haft-Javaherian M, Larue AE, Slater JH, Lauwers F, Blinder P, Tsai P, Kleinfeld D, Schaffer CB, Nishimura N, Davit Y, Lorthois S. Brain Capillary Networks Across Species: A few Simple Organizational Requirements Are Sufficient to Reproduce Both Structure and Function. Front Physiol 2019; 10:233. [PMID: 30971935 PMCID: PMC6444172 DOI: 10.3389/fphys.2019.00233] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 02/22/2019] [Indexed: 02/02/2023] Open
Abstract
Despite the key role of the capillaries in neurovascular function, a thorough characterization of cerebral capillary network properties is currently lacking. Here, we define a range of metrics (geometrical, topological, flow, mass transfer, and robustness) for quantification of structural differences between brain areas, organs, species, or patient populations and, in parallel, digitally generate synthetic networks that replicate the key organizational features of anatomical networks (isotropy, connectedness, space-filling nature, convexity of tissue domains, characteristic size). To reach these objectives, we first construct a database of the defined metrics for healthy capillary networks obtained from imaging of mouse and human brains. Results show that anatomical networks are topologically equivalent between the two species and that geometrical metrics only differ in scaling. Based on these results, we then devise a method which employs constrained Voronoi diagrams to generate 3D model synthetic cerebral capillary networks that are locally randomized but homogeneous at the network-scale. With appropriate choice of scaling, these networks have equivalent properties to the anatomical data, demonstrated by comparison of the defined metrics. The ability to synthetically replicate cerebral capillary networks opens a broad range of applications, ranging from systematic computational studies of structure-function relationships in healthy capillary networks to detailed analysis of pathological structural degeneration, or even to the development of templates for fabrication of 3D biomimetic vascular networks embedded in tissue-engineered constructs.
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Affiliation(s)
- Amy F Smith
- Institut de Mécanique des Fluides de Toulouse (IMFT), Université de Toulouse, CNRS, Toulouse, France
| | - Vincent Doyeux
- Institut de Mécanique des Fluides de Toulouse (IMFT), Université de Toulouse, CNRS, Toulouse, France
| | - Maxime Berg
- Institut de Mécanique des Fluides de Toulouse (IMFT), Université de Toulouse, CNRS, Toulouse, France
| | - Myriam Peyrounette
- Institut de Mécanique des Fluides de Toulouse (IMFT), Université de Toulouse, CNRS, Toulouse, France
| | - Mohammad Haft-Javaherian
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, United States
| | - Anne-Edith Larue
- Institut de Mécanique des Fluides de Toulouse (IMFT), Université de Toulouse, CNRS, Toulouse, France
| | - John H Slater
- Department of Biomedical Engineering, University of Delaware, Newark, DE, United States
| | - Frédéric Lauwers
- Toulouse NeuroImaging Center (TONIC), Université de Toulouse, INSERM, Toulouse, France.,Department of Anatomy, LSR44, Faculty of Medicine Toulouse-Purpan, Toulouse, France
| | - Pablo Blinder
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv, Israel
| | - Philbert Tsai
- Department of Physics, University of California, San Diego, La Jolla, CA, United States
| | - David Kleinfeld
- Department of Physics, University of California, San Diego, La Jolla, CA, United States
| | - Chris B Schaffer
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, United States
| | - Nozomi Nishimura
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, United States
| | - Yohan Davit
- Institut de Mécanique des Fluides de Toulouse (IMFT), Université de Toulouse, CNRS, Toulouse, France
| | - Sylvie Lorthois
- Institut de Mécanique des Fluides de Toulouse (IMFT), Université de Toulouse, CNRS, Toulouse, France.,Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, United States
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Dunn JF, Roche MA, Springett R, Abajian M, Merlis J, Daghlian CP, Lu SY, Makki M. Monitoring angiogenesis in brain using steady-state quantification of DeltaR2 with MION infusion. Magn Reson Med 2004; 51:55-61. [PMID: 14705045 DOI: 10.1002/mrm.10660] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
An MRI method for quantification of cerebral blood volume (CBV) in time-course studies of angiogenesis is described. Angiogenesis was stimulated by acclimation to hypoxia. The change in relaxation rate, R2, which is relatively sensitive to the microvasculature, was quantified before and after infusion of a superparamagnetic vascular contrast agent (MION). The DeltaR2 was measured in serum and brain parenchyma with a multiecho sequence. In vitro and in vivo calibration curves of MION concentration vs. R2 were approximated by a linear function. CBV was 3.14 +/- 0.32% (mean +/- SE, n=13) and 6.42 +/- 0.54% (n=4) before and after acclimation. A second acclimated group was hemodiluted to control for polycythemia. CBV was not significantly different between hemodiluted and nonhemodiluted groups. In animals where NMR measurements were taken before and after acclimation, there was a 120% increase in CBV. The NMR technique was validated using quantitative morphometrics, which showed an increase of 147% in CBV with acclimation. We found a linear correlation between MRI and the morphometric results for CBV, as well as demonstrating a quantitative equivalence for relative changes in CBV. This article describes a simple, repeatable method of imaging brain microvascular volume using a plasma-based contrast agent that can be applied to longitudinal studies of angiogenesis.
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Affiliation(s)
- Jeff F Dunn
- Department of Radiology, Dartmouth Medical School, HB 7786, Hanover, New Hampshire 03755, USA.
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Houston GC, Papadakis NG, Carpenter TA, Hall LD, Mukherjee B, James MF, Huang CL. Mapping of the cerebral response to hypoxia measured using graded asymmetric spin echo EPI. Magn Reson Imaging 2000; 18:1043-54. [PMID: 11118759 DOI: 10.1016/s0730-725x(00)00196-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Graded asymmetric spin echo-echo planar imaging (ASE-EPI) was used to measure transient alterations in cerebral oxygenation resulting from 60 seconds of anoxia in alpha-chloralose anaesthetised rats. The anoxic period induced a transient fall ( approximately 1 min) in signal intensity followed by a prolonged signal overshoot consistent with an autoregulatory response to oxygen deprivation. The magnitude of signal response, integrated over the entire brain, increased linearly with the echo asymmetry (t(ge)). However, that increase in sensitivity was offset by a reduced signal to noise ratio and quality of the image data. The responses of four regions of interest within the brain to the anoxic stimulus, and the effect of increasing the echo asymmetry, were compared. A comparable magnitude of signal decrease was observed in all brain regions except the superficial cortex that included pial vessels. As t(ge) was incremented differences in signal attenuation between regions became more pronounced. The signal overshoot observed upon restoration of normal breathing gases showed similar trends, producing similar normalised vascular responses for all regions of interest studied. Different regions of interest showed comparable time courses of the signal overshoot suggesting that similar autoregulatory vascular mechanisms operate in all brain regions. These findings additionally show that the use of graded ASE-EPI produced a characteristic profile of maximum signal change measured during and following the anoxic period for each brain region. They suggest that the shape of this profile was determined by the local vasculature within each region of interest; this feature could be exploited in activation studies to eliminate regions with significant signal changes originating from large draining vessels. Finally, the consistent physiological response observed, when the overshoot was compared to the magnitude of the signal drop, demonstrated that modification of the spin echo offset parameter did not mask or detrimentally alter the signal change resulting from the underlying physiological perturbation.
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Affiliation(s)
- G C Houston
- Herchel Smith Laboratory for Medicinal Chemistry, University of Cambridge Clinical School, University Forvie Site, Robinson Way, CB2 2PZ, Cambridge, UK
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Abstract
Blood oxygenation level-dependent (BOLD) magnetic resonance (MR) imaging is sensitive, in part, to the amount of paramagnetic deoxyhemoglobin in a voxel. This project was designed to determine whether there would be differences in the BOLD response between the hippocampus and other brain regions to acute hypoxia. R2* was quantified using a multi-echo gradient-echo sequence. The pyramidal CA1 region of the hippocampus showed a reduced response to changes in arterial oxygenation relative to cortex and basal ganglia and white matter. This difference may relate to the relative hypoxia sensitivity of the hippocampus. It also supports the premise that in functional MR imaging, the magnitude of the MR response to a stimulus may vary with the region of the brain.
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Affiliation(s)
- J F Dunn
- Biomedical NMR Research Center, Diagnostic Radiology, Dartmouth Hitchcock Medical Center, Hanover, New Hampshire, USA.
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