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Rahmani S, Jafree DJ, Lee PD, Tafforeau P, Brunet J, Nandanwar S, Jacob J, Bellier A, Ackermann M, Jonigk DD, Shipley RJ, Long DA, Walsh CL. Mapping the blood vasculature in an intact human kidney using hierarchical phase-contrast tomography. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.03.28.534566. [PMID: 37034801 PMCID: PMC10081185 DOI: 10.1101/2023.03.28.534566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The architecture of the kidney vasculature is essential for its function. Although structural profiling of the intact rodent kidney vasculature has been performed, it is challenging to map vascular architecture of larger human organs. We hypothesised that hierarchical phase-contrast tomography (HiP-CT) would enable quantitative analysis of the entire human kidney vasculature. Combining label-free HiP-CT imaging of an intact kidney from a 63-year-old male with topology network analysis, we quantitated vasculature architecture in the human kidney down to the scale of arterioles. Although human and rat kidney vascular topologies are comparable, vascular radius decreases at a significantly faster rate in humans as vessels branch from artery towards the cortex. At branching points of large vessels, radii are theoretically optimised to minimise flow resistance, an observation not found for smaller arterioles. Structural differences in the vasculature were found in different spatial zones of the kidney reflecting their unique functional roles. Overall, this represents the first time the entire arterial vasculature of a human kidney has been mapped providing essential inputs for computational models of kidney vascular flow and synthetic vascular architectures, with implications for understanding how the structure of individual blood vessels collectively scales to facilitate organ function.
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Affiliation(s)
- Shahrokh Rahmani
- Department of Mechanical Engineering, University College London, London, UK, WC1E 6BT
- National Heart & Lung Institute, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Daniyal J Jafree
- Developmental Biology and Cancer Research & Teaching Department, UCL Great Ormond Street Institute of Child Health, University College London, London, UK, WC1N 1EH
- UCL MB/PhD Programme, Faculty of Medical Science, University College London, London, UK, WC1E 6BT
- UCL Centre of Kidney and Bladder Health, UCL London UK
| | - Peter D Lee
- Department of Mechanical Engineering, University College London, London, UK, WC1E 6BT
| | - Paul Tafforeau
- European Synchrotron Radiation Facility, Grenoble, France, 38043
| | - Joseph Brunet
- Department of Mechanical Engineering, University College London, London, UK, WC1E 6BT
- European Synchrotron Radiation Facility, Grenoble, France, 38043
| | - Sonal Nandanwar
- Department of Mechanical Engineering, University College London, London, UK, WC1E 6BT
| | - Joseph Jacob
- Satsuma Lab, Centre for Medical Image Computing, UCL, London, UK
- Lungs for Living Research Centre, UCL, London, UK
| | - Alexandre Bellier
- Department of Anatomy (LADAF), Grenoble Alpes University, Grenoble, France, 38058
| | - Maximilian Ackermann
- Institute of Anatomy, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
- Institute of Pathology and Department of Molecular Pathology, Helios University Clinic Wuppertal, University of Witten-Herdecke, Wuppertal, Germany
- Institute of Pathology, RWTH Aachen Medical University, Aachen, Germany
| | - Danny D Jonigk
- Institute of Pathology, RWTH Aachen Medical University, Aachen, Germany
- German Center for Lung Research (DZL), Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Hannover, Germany
| | - Rebecca J Shipley
- Department of Mechanical Engineering, University College London, London, UK, WC1E 6BT
| | - David A Long
- Developmental Biology and Cancer Research & Teaching Department, UCL Great Ormond Street Institute of Child Health, University College London, London, UK, WC1N 1EH
- UCL Centre of Kidney and Bladder Health, UCL London UK
| | - Claire L Walsh
- Department of Mechanical Engineering, University College London, London, UK, WC1E 6BT
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Baldelomar EJ, Morozov D, Wilson LD, Eldeniz C, An H, Charlton JR, Bauer AQ, Keilholz SD, Hulbert ML, Bennett KM. Resting-state MRI reveals spontaneous physiological fluctuations in the kidney and tracks diabetic nephropathy in rats. Am J Physiol Renal Physiol 2024; 327:F113-F127. [PMID: 38660712 DOI: 10.1152/ajprenal.00423.2023] [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: 12/25/2023] [Revised: 04/16/2024] [Accepted: 04/16/2024] [Indexed: 04/26/2024] Open
Abstract
The kidneys maintain fluid-electrolyte balance and excrete waste in the presence of constant fluctuations in plasma volume and systemic blood pressure. The kidneys perform these functions to control capillary perfusion and glomerular filtration by modulating the mechanisms of autoregulation. An effect of these modulations are spontaneous, natural fluctuations in glomerular perfusion. Numerous other mechanisms can lead to fluctuations in perfusion and flow. The ability to monitor these spontaneous physiological fluctuations in vivo could facilitate the early detection of kidney disease. The goal of this work was to investigate the use of resting-state magnetic resonance imaging (rsMRI) to detect spontaneous physiological fluctuations in the kidney. We performed rsMRI of rat kidneys in vivo over 10 min, applying motion correction to resolve time series in each voxel. We observed spatially variable, spontaneous fluctuations in rsMRI signal between 0 and 0.3 Hz, in frequency bands associated with autoregulatory mechanisms. We further applied rsMRI to investigate changes in these fluctuations in a rat model of diabetic nephropathy. Spectral analysis was performed on time series of rsMRI signals in the kidney cortex and medulla. The power from spectra in specific frequency bands from the cortex correlated with severity of glomerular pathology caused by diabetic nephropathy. Finally, we investigated the feasibility of using rsMRI of the human kidney in two participants, observing the presence of similar, spatially variable fluctuations. This approach may enable a range of preclinical and clinical investigations of kidney function and facilitate the development of new therapies to improve outcomes in patients with kidney disease.NEW & NOTEWORTHY This work demonstrates the development and use of resting-state MRI to detect low-frequency, spontaneous physiological fluctuations in the kidney consistent with previously observed fluctuations in perfusion and potentially due to autoregulatory function. These fluctuations are detectable in rat and human kidneys, and the power of these fluctuations is affected by diabetic nephropathy in rats.
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Affiliation(s)
- Edwin J Baldelomar
- Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, United States
| | - Darya Morozov
- Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, United States
| | - Leslie D Wilson
- Division of Comparative Medicine, Washington University School of Medicine in St. Louis, St. Louis, Missouri, United States
| | - Cihat Eldeniz
- Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, United States
| | - Hongyu An
- Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, United States
| | - Jennifer R Charlton
- Division of Nephrology, Department of Pediatrics, University of Virginia, Charlottesville, Virginia, United States
| | - Adam Q Bauer
- Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, United States
| | - Shella D Keilholz
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
| | - Monica L Hulbert
- Division of Pediatric Hematology/Oncology, Washington University School of Medicine in St. Louis, Missouri, United States
| | - Kevin M Bennett
- Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, United States
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Marsh DJ, Wexler AS, Holstein-Rathlou NH. Interacting information streams on the nephron arterial network. FRONTIERS IN NETWORK PHYSIOLOGY 2023; 3:1254964. [PMID: 37928058 PMCID: PMC10620968 DOI: 10.3389/fnetp.2023.1254964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 09/27/2023] [Indexed: 11/07/2023]
Abstract
Blood flow and glomerular filtration in the kidney are regulated by two mechanisms acting on the afferent arteriole of each nephron. The two mechanisms operate as limit cycle oscillators, each responding to a different signal. The myogenic mechanism is sensitive to a transmural pressure difference across the wall of the arteriole, and tubuloglomerular feedback (TGF) responds to the NaCl concentration in tubular fluid flowing into the nephron's distal tubule,. The two mechanisms interact with each other, synchronize, cause oscillations in tubular flow and pressure, and form a bimodal electrical signal that propagates into the arterial network. The electrical signal enables nephrons adjacent to each other in the arterial network to synchronize, but non-adjacent nephrons do not synchronize. The arteries supplying the nephrons have the morphologic characteristics of a rooted tree network, with 3 motifs characterizing nephron distribution. We developed a model of 10 nephrons and their afferent arterioles in an arterial network that reproduced these structural characteristics, with half of its components on the renal surface, where experimental data suitable for model validation is available, and the other half below the surface, from which no experimental data has been reported. The model simulated several interactions: TGF-myogenic in each nephron with TGF modulating amplitude and frequency of the myogenic oscillation; adjacent nephron-nephron with strong coupling; non-adjacent nephron-nephron, with weak coupling because of electrical signal transmission through electrically conductive arterial walls; and coupling involving arterial nodal pressure at the ends of each arterial segment, and between arterial nodes and the afferent arterioles originating at the nodes. The model predicted full synchronization between adjacent nephrons pairs and partial synchronization among weakly coupled nephrons, reproducing experimental findings. The model also predicted aperiodic fluctuations of tubular and arterial pressures lasting longer than TGF oscillations in nephrons, again confirming experimental observations. The model did not predict complete synchronization of all nephrons.
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Affiliation(s)
- Donald J. Marsh
- Department of Medical Sciences, Division of Medicine and Biological Sciences, Brown University, Providence, RI, United States
| | - Anthony S. Wexler
- Departments of Biomedical Engineering, and Mechanical and Aerospace Engineering, University of California Davis, Davis, CA, United States
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Xu P, Holstein-Rathlou NH, Søgaard SB, Gundlach C, Sørensen CM, Erleben K, Sosnovtseva O, Darkner S. A hybrid approach to full-scale reconstruction of renal arterial network. Sci Rep 2023; 13:7569. [PMID: 37160979 PMCID: PMC10169837 DOI: 10.1038/s41598-023-34739-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 05/06/2023] [Indexed: 05/11/2023] Open
Abstract
The renal vasculature, acting as a resource distribution network, plays an important role in both the physiology and pathophysiology of the kidney. However, no imaging techniques allow an assessment of the structure and function of the renal vasculature due to limited spatial and temporal resolution. To develop realistic computer simulations of renal function, and to develop new image-based diagnostic methods based on artificial intelligence, it is necessary to have a realistic full-scale model of the renal vasculature. We propose a hybrid framework to build subject-specific models of the renal vascular network by using semi-automated segmentation of large arteries and estimation of cortex area from a micro-CT scan as a starting point, and by adopting the Global Constructive Optimization algorithm for generating smaller vessels. Our results show a close agreement between the reconstructed vasculature and existing anatomical data obtained from a rat kidney with respect to morphometric and hemodynamic parameters.
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Affiliation(s)
- Peidi Xu
- Department of Computer Science, University of Copenhagen, Universitetsparken 1, Copenhagen, 2100, Denmark.
| | | | - Stinne Byrholdt Søgaard
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3B, Copenhagen, 2200, Denmark
| | - Carsten Gundlach
- Department of Physics, Technical University of Denmark, Kongens Lyngby, Copenhagen, 2800, Denmark
| | - Charlotte Mehlin Sørensen
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3B, Copenhagen, 2200, Denmark
| | - Kenny Erleben
- Department of Computer Science, University of Copenhagen, Universitetsparken 1, Copenhagen, 2100, Denmark
| | - Olga Sosnovtseva
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3B, Copenhagen, 2200, Denmark
| | - Sune Darkner
- Department of Computer Science, University of Copenhagen, Universitetsparken 1, Copenhagen, 2100, Denmark
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5
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Deng W, Tsubota KI. Numerical simulation of the vascular structure dependence of blood flow in the kidney. Med Eng Phys 2022; 104:103809. [PMID: 35641074 DOI: 10.1016/j.medengphy.2022.103809] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 04/18/2022] [Accepted: 04/21/2022] [Indexed: 10/18/2022]
Abstract
A numerical simulation was performed to clarify renal blood flow determination by the vascular structures. Large and small vessels were modeled as symmetric and asymmetric branching vessels, respectively, with simple geometries to parameterize the vascular structures. Modeling individual vessels as straight pipes, Murray's law was used to determine the vessel diameters. Blood flow in the vascular structure was calculated by network analysis based on Hagen-Poiseuille's law. Blood flow simulations for a vascular network segment demonstrated that blood flow rate and pressure vary within the same-generation vessels because of an asymmetric vessel branch while they generally tend to decrease with vessel diameter; thus, the standard deviation of flow rate relative to the mean (relative standard deviation [RSD]) increased from 0.4 to 1.0 when the number of the daughter vessels increased from 3 to 10. Blood flow simulations for an entire vascular network of a kidney showed that the vessel number and branching style, rather than Strahler order, are major parameters in successfully reproducing renal blood flow measured in published experiments. The entire vascular network could generate variation in the physiological flow rate in afferent arterioles at 0.2-0.38 in RSD, which is at least compatible with 0.16 by diameter variation within the same-generation vessels.
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Affiliation(s)
- Wei Deng
- Graduate School of Science and Engineering, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan
| | - Ken-Ichi Tsubota
- Graduate School of Engineering, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan.
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6
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Numerical Modeling and Simulation of Blood Flow in a Rat Kidney: Coupling of the Myogenic Response and the Vascular Structure. Processes (Basel) 2022. [DOI: 10.3390/pr10051005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
A numerical simulation was carried out to investigate the blood flow behavior (i.e., flow rate and pressure) and coupling of a renal vascular network and the myogenic response to various conditions. A vascular segment and an entire kidney vascular network were modeled by assuming one single vessel as a straight pipe whose diameter was determined by Murray’s law. The myogenic response was tested on individual AA (afferent artery)–GC (glomerular capillaries)–EA (efferent artery) systems, thereby regulating blood flow throughout the vascular network. Blood flow in the vascular structure was calculated by network analysis based on Hagen–Poiseuille’s law to various boundary conditions. Simulation results demonstrated that, in the vascular segment, the inlet pressure Pinlet and the vascular structure act together on the myogenic response of each individual AA–GC–EA subsystem, such that the early-branching subsystems in the vascular network reached the well-regulated state first, with an interval of the inlet as Pinlet = 10.5–21.0 kPa, whereas the one that branched last exhibited a later interval with Pinlet = 13.0–24.0 kPa. In the entire vascular network, in contrast to the Pinlet interval (13.0–20.0 kPa) of the unified well-regulated state for all AA–GC–EA subsystems of the symmetric model, the asymmetric model exhibited the differences among subsystems with Pinlet ranging from 12.0–17.0 to 16.0–20.0 kPa, eventually achieving a well-regulated state of 13.0–18.5 kPa for the entire kidney. Furthermore, when Pinlet continued to rise (e.g., 21.0 kPa) beyond the vasoconstriction range of the myogenic response, high glomerular pressure was also related to vascular structure, where PGC of early-branching subsystems was 9.0 kPa and of late-branching one was 7.5 kPa. These findings demonstrate how the myogenic response regulates renal blood flow in vascular network system that comprises a large number of vessel elements.
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Postnov D, Marsh DJ, Cupples WA, Holstein-Rathlou NH, Sosnovtseva O. Synchronization in renal microcirculation unveiled with high-resolution blood flow imaging. eLife 2022; 11:75284. [PMID: 35522041 PMCID: PMC9113743 DOI: 10.7554/elife.75284] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 05/06/2022] [Indexed: 11/13/2022] Open
Abstract
Internephron interaction is fundamental for kidney function. Earlier studies have shown that nephrons signal to each other, synchronise over short distances, and potentially form large synchronised clusters. Such clusters would play an important role in renal autoregulation, but due to the technological limitations, their presence is yet to be confirmed. In the present study, we introduce an approach for high-resolution laser speckle imaging of renal blood flow and apply it to estimate frequency and phase differences in rat kidney microcirculation under different conditions. The analysis unveiled spatial and temporal evolution of synchronised blood flow clusters of various sizes, including the formation of large (>90 vessels) long-lived clusters (>10 periods) locked at the frequency of the tubular glomerular feedback mechanism. Administration of vasoactive agents caused significant changes in the synchronisation patterns and, thus, in nephrons' co-operative dynamics. Specifically, infusion of vasoconstrictor angiotensin II promoted stronger synchronisation, while acetylcholine caused complete desynchronisation. The results confirm the presence of the local synchronisation in the renal microcirculatory blood flow and that it changes depending on the condition of the vascular network and the blood pressure, which will have further implications for the role of such synchronisation in pathologies development.
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Affiliation(s)
- Dmitry Postnov
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Donald J Marsh
- Division of Biology and Medicine, Brown University, Rhode Island, United States
| | - Will A Cupples
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | | | - Olga Sosnovtseva
- Biomedical Sciences Institute, University of Copenhagen, Copenhagen, Denmark
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Andersen SB, Taghavi I, Kjer HM, Søgaard SB, Gundlach C, Dahl VA, Nielsen MB, Dahl AB, Jensen JA, Sørensen CM. Evaluation of 2D super-resolution ultrasound imaging of the rat renal vasculature using ex vivo micro-computed tomography. Sci Rep 2021; 11:24335. [PMID: 34934089 PMCID: PMC8692475 DOI: 10.1038/s41598-021-03726-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 12/08/2021] [Indexed: 11/29/2022] Open
Abstract
Super-resolution ultrasound imaging (SRUS) enables in vivo microvascular imaging of deeper-lying tissues and organs, such as the kidneys or liver. The technique allows new insights into microvascular anatomy and physiology and the development of disease-related microvascular abnormalities. However, the microvascular anatomy is intricate and challenging to depict with the currently available imaging techniques, and validation of the microvascular structures of deeper-lying organs obtained with SRUS remains difficult. Our study aimed to directly compare the vascular anatomy in two in vivo 2D SRUS images of a Sprague-Dawley rat kidney with ex vivo μCT of the same kidney. Co-registering the SRUS images to the μCT volume revealed visually very similar vascular features of vessels ranging from ~ 100 to 1300 μm in diameter and illustrated a high level of vessel branching complexity captured in the 2D SRUS images. Additionally, it was shown that it is difficult to use μCT data of a whole rat kidney specimen to validate the super-resolution capability of our ultrasound scans, i.e., validating the actual microvasculature of the rat kidney. Lastly, by comparing the two imaging modalities, fundamental challenges for 2D SRUS were demonstrated, including the complexity of projecting a 3D vessel network into 2D. These challenges should be considered when interpreting clinical or preclinical SRUS data in future studies.
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Affiliation(s)
- Sofie Bech Andersen
- Department of Biomedical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
- Department of Radiology, Rigshospitalet, 2100, Copenhagen, Denmark.
| | - Iman Taghavi
- Center for Fast Ultrasound Imaging, Department of Health Technology, Technical University of Denmark, 2800, Lyngby, Denmark
| | - Hans Martin Kjer
- Department of Applied Mathematics and Computer Science, Technical University of Denmark, 2800, Lyngby, Denmark
| | - Stinne Byrholdt Søgaard
- Department of Biomedical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
- Department of Radiology, Rigshospitalet, 2100, Copenhagen, Denmark
| | - Carsten Gundlach
- Department of Physics, Technical University of Denmark, 2800, Lyngby, Denmark
| | - Vedrana Andersen Dahl
- Department of Applied Mathematics and Computer Science, Technical University of Denmark, 2800, Lyngby, Denmark
| | - Michael Bachmann Nielsen
- Department of Radiology, Rigshospitalet, 2100, Copenhagen, Denmark
- Department of Clinical Medicine, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Anders Bjorholm Dahl
- Department of Applied Mathematics and Computer Science, Technical University of Denmark, 2800, Lyngby, Denmark
| | - Jørgen Arendt Jensen
- Center for Fast Ultrasound Imaging, Department of Health Technology, Technical University of Denmark, 2800, Lyngby, Denmark
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Zehra T, Cupples WA, Braam B. Tubuloglomerular Feedback Synchronization in Nephrovascular Networks. J Am Soc Nephrol 2021; 32:1293-1304. [PMID: 33833078 PMCID: PMC8259654 DOI: 10.1681/asn.2020040423] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
To perform their functions, the kidneys maintain stable blood perfusion in the face of fluctuations in systemic BP. This is done through autoregulation of blood flow by the generic myogenic response and the kidney-specific tubuloglomerular feedback (TGF) mechanism. The central theme of this paper is that, to achieve autoregulation, nephrons do not work as single units to manage their individual blood flows, but rather communicate electrically over long distances to other nephrons via the vascular tree. Accordingly, we define the nephrovascular unit (NVU) to be a structure consisting of the nephron, glomerulus, afferent arteriole, and efferent arteriole. We discuss features that require and enable distributed autoregulation mediated by TGF across the kidney. These features include the highly variable topology of the renal vasculature which creates variability in circulation and the potential for mismatch between tubular oxygen demand and delivery; the self-sustained oscillations in each NVU arising from the autoregulatory mechanisms; and the presence of extensive gap junctions formed by connexins and their properties that enable long-distance transmission of TGF signals. The existence of TGF synchronization across the renal microvascular network enables an understanding of how NVUs optimize oxygenation-perfusion matching while preventing transmission of high systemic pressure to the glomeruli, which could lead to progressive glomerular and vascular injury.
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Affiliation(s)
- Tayyaba Zehra
- Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - William A. Cupples
- Department of Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Branko Braam
- Department of Medicine, University of Alberta, Edmonton, Alberta, Canada,Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
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Lametschwandtner A, Minnich B. Renal microvasculature in the adult pipid frog, Xenopus laevis: A scanning electron microscope study of vascular corrosion casts. J Morphol 2020; 281:725-736. [PMID: 32374496 PMCID: PMC7383921 DOI: 10.1002/jmor.21132] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/26/2020] [Accepted: 04/09/2020] [Indexed: 12/15/2022]
Abstract
We studied the opisthonephric (mesonephric) kidneys of adult male and female Xenopus laevis using scanning electron microscopy (SEM) of vascular corrosion casts and light microscopy of paraplast embedded tissue sections. Both techniques displayed glomeruli from ventral to mid-dorsal regions of the kidneys with single glomeruli located dorsally close beneath the renal capsule. Glomeruli in general were fed by a single afferent arteriole and drained via a single thinner efferent arteriole into peritubular vessels. Light microscopy and SEM of vascular corrosion casts revealed sphincters at the origins of afferent arterioles, which arose closely, spaced from their parent renal arteries. The second source of renal blood supply via renal portal veins varied interindividually in branching patterns with vessels showing up to five branching orders before they became peritubular vessels. Main trunks and their first- and second-order branches revealed clear longish endothelial cell nuclei imprint patterns oriented parallel to the vessels longitudinal axis, a pattern characteristic for arteries. Peritubular vessels had irregular contours and were never seen as clear cylindrical structures. They ran rather parallel, anastomosed with neighbors and changed into renal venules and veins, which finally emptied into the ventrally located posterior caval vein. A third source of blood supply of the peritubular vessels by straight terminal portions of renal arteries (vasa recta) was not found.
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Affiliation(s)
- Alois Lametschwandtner
- Department of BiosciencesUniversity of Salzburg, Vascular and Exercise Biology Research GroupSalzburgAustria
| | - Bernd Minnich
- Department of BiosciencesUniversity of Salzburg, Vascular and Exercise Biology Research GroupSalzburgAustria
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11
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Guan Z, Baty JJ, Zhang S, Remedies CE, Inscho EW. Rho kinase inhibitors reduce voltage-dependent Ca 2+ channel signaling in aortic and renal microvascular smooth muscle cells. Am J Physiol Renal Physiol 2019; 317:F1132-F1141. [PMID: 31432708 DOI: 10.1152/ajprenal.00212.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Voltage-dependent L-type Ca2+ channels (L-VDCCs) and the RhoA/Rho kinase pathway are two predominant intracellular signaling pathways that regulate renal microvascular reactivity. Traditionally, these two pathways have been thought to act independently; however, recent evidence suggests that these pathways could be convergent. We hypothesized that Rho kinase inhibitors can influence L-VDCC signaling. The effects of Rho kinase inhibitors Y-27632 or RKI-1447 on KCl-induced depolarization or the L-VDCC agonist Bay K8644 were assessed in afferent arterioles using an in vitro blood-perfused rat juxtamedullary nephron preparation. Superfusion of KCl (30-90 mM) led to concentration-dependent vasoconstriction of afferent arterioles. Administration of Y-27632 (1, 5, and 10 µM) or RKI-1447 (0.1, 1, and 10 µM) significantly increased the starting diameter by 16-65%. KCl-induced vasoconstriction was markedly attenuated with 5 and 10 µM Y-27632 and with 10 µM RKI-1447 (P < 0.05 vs. KCl alone). Y-27632 (5 µM) also significantly attenuated Bay K8644-induced vasoconstriction (P < 0.05). Changes in intracellular Ca2+ concentration ([Ca2+]i) were estimated by fura-2 fluorescence during KCl-induced depolarization in cultured A7r5 cells and in freshly isolated preglomerular microvascular smooth muscle cells. Administration of 90 mM KCl significantly increased fura-2 fluorescence in both cell types. KCl-mediated elevation of [Ca2+]i in A7r5 cells was suppressed by 1-10 µM Y-27632 (P < 0.05), but 10 µM Y-27632 was required to suppress Ca2+ responses in preglomerular microvascular smooth muscle cells. RKI-1447, however, significantly attenuated KCl-mediated elevation of [Ca2+]i. Y-27632 markedly inhibited Bay K8644-induced elevation of [Ca2+]i in both cell types. The results of the present study indicate that the Rho kinase inhibitors Y-27632 and RKI-1447 can partially inhibit L-VDCC function and participate in L-VDCC signaling.
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Affiliation(s)
- Zhengrong Guan
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Joshua J Baty
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Shali Zhang
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Colton E Remedies
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Edward W Inscho
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
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12
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Sorensen CM, Cupples WA. Myoendothelial communication in the renal vasculature and the impact of drugs used clinically to treat hypertension. Curr Opin Pharmacol 2019; 45:49-56. [PMID: 31071677 DOI: 10.1016/j.coph.2019.04.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 04/04/2019] [Indexed: 12/11/2022]
Abstract
The renal vasculature has many peculiarities including highly irregular branching. Renal blood flow must sustain adequate perfusion and maintain a high glomerular filtration. Renal autoregulation helps control renal blood flow. The local autoregulatory mechanism, tubuloglomerular feedback, elicits a vasoconstriction that can be found not only in neighboring nephrons but over large areas of the kidney indicating that the renal vasculature supports strong conduction of vascular responses. The basis for conduction is intercellular communication through gap junctions. The endothelium is strongly coupled and serves as a vascular conduction highway leading the signal to the vascular smooth muscle cells through myoendothelial coupling. Extensive intercellular coupling is also found in renin secreting cells where gap junctions seem to tie the cells together to improve control of renin secretion. Lack of coupling leads to dysregulation of renin secretion and hypertension. However, the activity of the renin-angiotensin system also controls gap junction expression in the kidney. Treatment reducing angiotensin II activity, as used in hypertension treatment, can affect expression of renal and vascular gap junction.
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Affiliation(s)
| | - William A Cupples
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Canada
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Marsh DJ, Postnov DD, Sosnovtseva OV, Holstein-Rathlou NH. The nephron-arterial network and its interactions. Am J Physiol Renal Physiol 2019; 316:F769-F784. [DOI: 10.1152/ajprenal.00484.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Tubuloglomerular feedback and the myogenic mechanism form an ensemble in renal afferent arterioles that regulate single-nephron blood flow and glomerular filtration. Each mechanism generates a self-sustained oscillation, the mechanisms interact, and the oscillations synchronize. The synchronization generates a bimodal electrical signal in the arteriolar wall that propagates retrograde to a vascular node, where it meets similar electrical signals from other nephrons. Each signal carries information about the time-dependent behavior of the regulatory ensemble. The converging signals support synchronization of the nephrons participating in the information exchange, and the synchronization can lead to formation of nephron clusters. We review the experimental evidence and the theoretical implications of these interactions and consider additional interactions that can limit the size of nephron clusters. The architecture of the arterial tree figures prominently in these interactions.
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Affiliation(s)
- Donald J. Marsh
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, Rhode Island
| | - Dmitry D. Postnov
- Neurophotonics Center, Boston University, Boston, Massachusetts
- Department of Biomedical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Olga V. Sosnovtseva
- Department of Biomedical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark
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Khan Z, Ngo JP, Le B, Evans RG, Pearson JT, Gardiner BS, Smith DW. Three-dimensional morphometric analysis of the renal vasculature. Am J Physiol Renal Physiol 2018; 314:F715-F725. [DOI: 10.1152/ajprenal.00339.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vascular topology and morphology are critical in the regulation of blood flow and the transport of small solutes, including oxygen, carbon dioxide, nitric oxide, and hydrogen sulfide. Renal vascular morphology is particularly challenging, since many arterial walls are partially wrapped by the walls of veins. In the absence of a precise characterization of three-dimensional branching vascular geometry, accurate computational modeling of the intrarenal transport of small diffusible molecules is impossible. An enormous manual effort was required to achieve a relatively precise characterization of rat renal vascular geometry, highlighting the need for an automated method for analysis of branched vasculature morphology to allow characterization of the renal vascular geometry of other species, including humans. We present a semisupervised method for three-dimensional morphometric analysis of renal vasculature images generated by computed tomography. We derive quantitative vascular attributes important to mass transport between arteries, veins, and the renal tissue and present methods for their computation for a three-dimensional vascular geometry. To validate the algorithm, we compare automated vascular estimates with subjective manual measurements for a portion of rabbit kidney. Although increased image resolution can improve outcomes, our results demonstrate that the method can quantify the morphological characteristics of artery-vein pairs, comparing favorably with manual measurements. Similar to the rat, we show that rabbit artery-vein pairs become less intimate along the course of the renal vasculature, but the total wrapped mass transfer coefficient increases and then decreases. This new method will facilitate new quantitative physiological models describing the transport of small molecules within the kidney.
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Affiliation(s)
- Zohaib Khan
- School of Information Technology and Mathematical Sciences, University of South Australia, Adelaide, Australia
| | - Jennifer P. Ngo
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia
| | - Bianca Le
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia
| | - Roger G. Evans
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia
| | - James T. Pearson
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan
| | - Bruce S. Gardiner
- School of Engineering and Information Technology, Murdoch University, Perth, Australia
| | - David W. Smith
- Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Perth, Australia
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Cupples WA. At last! Quantitative cortical vascular anatomy. Am J Physiol Renal Physiol 2018; 314:F928-F929. [DOI: 10.1152/ajprenal.00623.2017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Affiliation(s)
- William A. Cupples
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
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