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More HL, Braam B, Cupples WA. Reduced tubuloglomerular feedback activity and absence of its synchronization in a connexin40 knockout rat. FRONTIERS IN NETWORK PHYSIOLOGY 2023; 3:1208303. [PMID: 37705697 PMCID: PMC10495682 DOI: 10.3389/fnetp.2023.1208303] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 08/10/2023] [Indexed: 09/15/2023]
Abstract
Introduction: Tubuloglomerular feedback (TGF) is the negative feedback component of renal blood flow (RBF) autoregulation. Neighbouring nephrons often exhibit spontaneous TGF oscillation and synchronization mediated by endothelial communication, largely via connexin40 (Cx40). Methods: We had a knockout (KO) rat made that lacks Cx40. One base pair was altered to create a stop codon in exon 1 of Gja5, the gene that encodes Cx40 (the strain is WKY-Gja55em1Mcwi). Blood pressure (BP)-RBF transfer functions probed RBF dynamics and laser speckle imaging interrogated the dynamics of multiple efferent arterioles that reach the surface (star vessels). Results: The distribution of wild type (WT), heterozygote, and KO pups at weaning approximated the Mendelian ratio of 1:2:1; growth did not differ among the three strains. The KO rats were hypertensive. BP-RBF transfer functions showed low gain of the myogenic mechanism and a smaller TGF resonance peak in KO than in WT rats. Laser speckle imaging showed that myogenic mechanism had higher frequency in KO than in WT rats, but similar maximum spectral power. In contrast, the TGF frequency was similar while peak power of its oscillation was much smaller in KO than in WT rats. In WT rats, plots of instantaneous TGF phase revealed BP-independent TGF synchronization among star vessels. The synchronization could be both prolonged and widespread. In KO rats TGF synchronization was not seen, although BP transients could elicit short-lived TGF entrainment. Discussion: Despite the reduced TGF spectral power in KO rats, there was sufficient TGF gain to induce oscillations and therefore enough gain to be effective locally. We conclude that failure to synchronize is dependent, at least in part, on impaired conducted vasomotor responses.
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Affiliation(s)
- Heather L. More
- Department of Biomedical Physiology and Kinesiology, Faculty of Science Simon Fraser University, Burnaby, BC, Canada
| | - Branko Braam
- Division of Nephrology, Department of Medicine, Edmonton, AB, Canada
- Department of Physiology, University of Alberta, Edmonton, AB, Canada
| | - William A. Cupples
- Department of Biomedical Physiology and Kinesiology, Faculty of Science Simon Fraser University, Burnaby, BC, Canada
- Division of Nephrology, Department of Medicine, Edmonton, AB, Canada
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2
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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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3
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Lee B, Sosnovtseva O, Sørensen CM, Postnov DD. Multi-scale laser speckle contrast imaging of microcirculatory vasoreactivity. BIOMEDICAL OPTICS EXPRESS 2022; 13:2312-2322. [PMID: 35519248 PMCID: PMC9045893 DOI: 10.1364/boe.451014] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 03/07/2022] [Accepted: 03/08/2022] [Indexed: 06/14/2023]
Abstract
Laser speckle contrast imaging is a robust and versatile blood flow imaging tool in basic and clinical research for its relatively simple construction and ease of customization. One of its key features is the scalability of the imaged field of view. With minimal changes to the system or analysis, laser speckle contrast imaging allows for high-resolution blood flow imaging through cranial windows or low-resolution perfusion visualization of perfusion over large areas, e.g. in human skin. We further utilize this feature and introduce a multi-scale laser speckle contrast imaging system, which we apply to study vasoreactivity in renal microcirculation. We combine high resolution (small field of view) to segment blood flow in individual vessels with low resolution (large field of view) to monitor global blood flow changes across the renal surface. Furthermore, we compare their performance when analyzing blood flow dynamics potentially associated with a single nephron and show that the previously published approaches, based on low-zoom imaging alone, provide inaccurate results in such applications.
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Affiliation(s)
- Blaire Lee
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Olga Sosnovtseva
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Charlotte M. Sørensen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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4
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Near-infrared spectrometry: the future of renal graft perfusion monitoring? COR ET VASA 2021. [DOI: 10.33678/cor.2021.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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5
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Heeman W, Maassen H, Calon J, van Goor H, Leuvenink H, van Dam GM, Boerma EC. Real-time visualization of renal microperfusion using laser speckle contrast imaging. JOURNAL OF BIOMEDICAL OPTICS 2021; 26:JBO-200389RR. [PMID: 34024055 PMCID: PMC8140613 DOI: 10.1117/1.jbo.26.5.056004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 05/07/2021] [Indexed: 05/02/2023]
Abstract
SIGNIFICANCE Intraoperative parameters of renal cortical microperfusion (RCM) have been associated with postoperative ischemia/reperfusion injury. Laser speckle contrast imaging (LSCI) could provide valuable information in this regard with the advantage over the current standard of care of being a non-contact and full-field imaging technique. AIM Our study aims to validate the use of LSCI for the visualization of RCM on ex vivo perfused human-sized porcine kidneys in various models of hemodynamic changes. APPROACH A comparison was made between three renal perfusion measures: LSCI, the total arterial renal blood flow (RBF), and sidestream dark-field (SDF) imaging in different settings of ischemia/reperfusion. RESULTS LSCI showed a good correlation with RBF for the reperfusion experiment (0.94 ± 0.02; p < 0.0001) and short- and long-lasting local ischemia (0.90 ± 0.03; p < 0.0001 and 0.81 ± 0.08; p < 0.0001, respectively). The correlation decreased for low flow situations due to RBF redistribution. The correlation between LSCI and SDF (0.81 ± 0.10; p < 0.0001) showed superiority over RBF (0.54 ± 0.22; p < 0.0001). CONCLUSIONS LSCI is capable of imaging RCM with high spatial and temporal resolutions. It can instantaneously detect local perfusion deficits, which is not possible with the current standard of care. Further development of LSCI in transplant surgery could help with clinical decision making.
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Affiliation(s)
- Wido Heeman
- University of Groningen, Faculty Campus Fryslân, Leeuwarden, The Netherlands
- University Medical Centre Groningen, Department of Surgery, Groningen, The Netherlands
- LIMIS Development BV, Leeuwarden, The Netherlands
- Address all correspondence to Wido Heeman,
| | - Hanno Maassen
- University Medical Centre Groningen, Department of Surgery, Groningen, The Netherlands
- University Medical Centre Groningen, Department of Pathology and Medical Biology, Groningen, The Netherlands
| | - Joost Calon
- ZiuZ Visual Intelligence, Gorredijk, The Netherlands
| | - Harry van Goor
- University Medical Centre Groningen, Department of Pathology and Medical Biology, Groningen, The Netherlands
| | - Henri Leuvenink
- University Medical Centre Groningen, Department of Surgery, Groningen, The Netherlands
| | - Gooitzen M. van Dam
- University Medical Centre Groningen, Department of Surgery, Groningen, The Netherlands
| | - E. Christiaan Boerma
- Medical Centre Leeuwarden, Department of Intensive Care, Leeuwarden, The Netherlands
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6
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van Loon LM, Rongen GA, van der Hoeven JG, Veltink PH, Lemson J. β-Blockade attenuates renal blood flow in experimental endotoxic shock by reducing perfusion pressure. Physiol Rep 2019; 7:e14301. [PMID: 31814327 PMCID: PMC6900489 DOI: 10.14814/phy2.14301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Clinical data suggests that heart rate (HR) control with selective β1-blockers may improve cardiac function during septic shock. However, it seems counterintuitive to start β-blocker infusion in a shock state when organ blood flow is already low or insufficient. Therefore, we studied the effects of HR control with esmolol, an ultrashort- acting β1-selective adrenoceptor antagonist, on renal blood flow (RBF) and renal autoregulation during early septic shock. In 10 healthy sheep, sepsis was induced by continuous i.v. administration of lipopolysaccharide, while maintained under anesthesia and mechanically ventilated. After successful resuscitation of the septic shock with fluids and vasoactive drugs, esmolol was infused to reduce HR with 30% and was stopped 30-min after reaching this target. Arterial and venous pressures, and RBF were recorded continuously. Renal autoregulation was evaluated by the response in RBF to renal perfusion pressure (RPP) in both the time domain and frequency domain. During septic shock, β-blockade with esmolol significantly increased the pressure dependency of RBF to RPP. Stopping esmolol showed the reversibility of the impaired renal autoregulation. Showing that clinical diligence and caution are necessary when treating septic shock with esmolol in the acute phase since esmolol reduced RPP to critical values thereby significantly reducing RBF.
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Affiliation(s)
- Lex M. van Loon
- Cardiovascular and Respiratory Physiology GroupFaculty of Science and TechnologyUniversity of TwenteEnschedeThe Netherlands
- Department of Intensive Care MedicineRadboud University Medical CenterRadboud Institute for Health SciencesNijmegenThe Netherlands
| | - Gerard A. Rongen
- Department of Pharmacology and ToxicologyRadboud University Medical CenterNijmegenThe Netherlands
| | - Johannes G. van der Hoeven
- Department of Intensive Care MedicineRadboud University Medical CenterRadboud Institute for Health SciencesNijmegenThe Netherlands
- Radboud Center for Infectious diseasesNijmegenThe Netherlands
| | - Peter H. Veltink
- Biomedical Signals and SystemsFaculty of Electrical Engineering, Mathematics and Computer ScienceTechnical Medical CentreUniversity of TwenteEnschedeThe Netherlands
| | - Joris Lemson
- Department of Intensive Care MedicineRadboud University Medical CenterRadboud Institute for Health SciencesNijmegenThe Netherlands
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7
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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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8
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Postnov DD, Erdener SE, Kilic K, Boas DA. Cardiac pulsatility mapping and vessel type identification using laser speckle contrast imaging. BIOMEDICAL OPTICS EXPRESS 2018; 9:6388-6397. [PMID: 31065436 PMCID: PMC6491022 DOI: 10.1364/boe.9.006388] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 11/07/2018] [Indexed: 05/02/2023]
Abstract
Systemic flow variations caused by the cardiac cycle can play a role or be an important marker in both normal and pathological conditions. The shape, magnitude and propagation speed of the flow pulse reflect mechanical properties of the vasculature and are known to vary significantly with vascular diseases. Most conventional techniques are not capable of imaging cardiac activity in the microcirculation due to spatial and/or temporal resolution limitations and instead make inferences about propagation speed by making measurements at two points along an artery. Here, we apply laser speckle contrast imaging to images with high spatial resolution in the high frequency harmonics of cardiac activity in the cerebral cortex of a mouse. We reveal vessel dependent variation in the cardiac pulse activity and use this information to automatically identify arteries and veins.
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Affiliation(s)
- Dmitry D. Postnov
- Department of Biomedical Engineering, Boston University, 24 Cummington Mall, Boston, MA 02215,
USA
- Department of Biomedical Sciences, Copenhagen University, Blegdamsvej 3, 2200 Copenhagen N,
Denmark
| | - Sefik Evren Erdener
- Department of Biomedical Engineering, Boston University, 24 Cummington Mall, Boston, MA 02215,
USA
| | - Kivilcim Kilic
- Department of Biomedical Engineering, Boston University, 24 Cummington Mall, Boston, MA 02215,
USA
| | - David A. Boas
- Department of Biomedical Engineering, Boston University, 24 Cummington Mall, Boston, MA 02215,
USA
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9
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Mastantuono T, Starita N, Battiloro L, Di Maro M, Chiurazzi M, Nasti G, Muscariello E, Cesarelli M, Iuppariello L, D'Addio G, Gorbach A, Colantuoni A, Lapi D. Laser Speckle Imaging of Rat Pial Microvasculature during Hypoperfusion-Reperfusion Damage. Front Cell Neurosci 2017; 11:298. [PMID: 28993725 PMCID: PMC5622169 DOI: 10.3389/fncel.2017.00298] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Accepted: 09/06/2017] [Indexed: 11/13/2022] Open
Abstract
The present study was aimed to in vivo assess the blood flow oscillatory patterns in rat pial microvessels during 30 min bilateral common carotid artery occlusion (BCCAO) and 60 min reperfusion by laser speckle imaging (LSI). Pial microcirculation was visualized by fluorescence microscopy. The blood flow oscillations of single microvessels were recorded by LSI; spectral analysis was performed by Wavelet transform. Under baseline conditions, arterioles and venules were characterized by blood flow oscillations in the frequency ranges 0.005-0.0095 Hz, 0.0095-0.021 Hz, 0.021-0.052 Hz, 0.052-0.150 Hz and 0.150-0.500 Hz. Arterioles showed oscillations with the highest spectral density when compared with venules. Moreover, the frequency components in the ranges 0.052-0.150 Hz and 0.150-0.500 were predominant in the arteriolar total power spectrum; while, the frequency component in the range 0.150-0.500 Hz showed the highest spectral density in venules. After 30 min BCCAO, the arteriolar spectral density decreased compared to baseline; moreover, the arteriolar frequency component in the range 0.052-0.150 Hz significantly decreased in percent spectral density, while the frequency component in the range 0.150-0.500 Hz significantly increased in percent spectral density. However, an increase in arteriolar spectral density was detected at 60 min reperfusion compared to BCCAO values; consequently, an increase in percent spectral density of the frequency component in the range 0.052-0.150 Hz was observed, while the percent spectral density of the frequency component in the range 0.150-0.500 Hz significantly decreased. The remaining frequency components did not significantly change during hypoperfusion and reperfusion. The changes in blood flow during hypoperfusion/reperfusion caused tissue damage in the cortex and striatum of all animals. In conclusion, our data demonstrate that the frequency component in the range 0.052-0.150 Hz, related to myogenic activity, was significantly impaired by hypoperfusion and reperfusion, affecting cerebral blood flow distribution and causing tissue damage.
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Affiliation(s)
- Teresa Mastantuono
- Department of Clinical Medicine and Surgery, "Federico II" University Medical SchoolNaples, Italy
| | - Noemy Starita
- Molecular Biology and Viral Oncology Unit, Istituto Nazionale Tumori IRCCS-"Fondazione G.Pascale"Naples, Italy
| | - Laura Battiloro
- Department of Clinical Medicine and Surgery, "Federico II" University Medical SchoolNaples, Italy
| | - Martina Di Maro
- Department of Clinical Medicine and Surgery, "Federico II" University Medical SchoolNaples, Italy
| | - Martina Chiurazzi
- Department of Clinical Medicine and Surgery, "Federico II" University Medical SchoolNaples, Italy
| | - Gilda Nasti
- Department of Clinical Medicine and Surgery, "Federico II" University Medical SchoolNaples, Italy
| | - Espedita Muscariello
- Department of Clinical Medicine and Surgery, "Federico II" University Medical SchoolNaples, Italy
| | - Mario Cesarelli
- Department of Biomedical, Electronics and TLC Engineering, University of Naples, "Federico II"Naples, Italy
| | - Luigi Iuppariello
- Department of Biomedical, Electronics and TLC Engineering, University of Naples, "Federico II"Naples, Italy
| | | | - Alexander Gorbach
- Infrared Imaging & Thermometry Unit, NIBIB, National Institutes of HealthBethesda, MD, United States
| | - Antonio Colantuoni
- Department of Clinical Medicine and Surgery, "Federico II" University Medical SchoolNaples, Italy
| | - Dominga Lapi
- Department of Clinical Medicine and Surgery, "Federico II" University Medical SchoolNaples, Italy
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11
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Postnov DD, Salomonsson M, Sorensen CM, Sosnovtseva O. A simple method to ensure homogeneous drug distribution during intrarenal infusion. Am J Physiol Renal Physiol 2016; 312:F543-F548. [PMID: 27881397 DOI: 10.1152/ajprenal.00417.2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 11/17/2016] [Accepted: 11/22/2016] [Indexed: 11/22/2022] Open
Abstract
Intrarenal drug infusion plays an important role in renal experimental research. Laminar flow of the blood can cause streaming and inhomogeneous intrarenal distribution of infused drugs. We suggest a simple method to achieve a homogeneous intravascular distribution of drugs infused into the renal artery of anesthetized rats. The method employs a multiple sidehole catheter inserted into the renal artery, which enables an efficient drug mixing with the arterial blood. To verify the efficiency of this method, we use laser speckle imaging and renal artery flowmetry. The results show that, compared with the conventional single-hole catheter, the multiple sidehole catheter provides a more uniform drug distribution and a homogenous vascular response on the surface of the kidney.
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Affiliation(s)
- Dmitry D Postnov
- Biomedical Sciences Institute, Copenhagen University, Copenhagen, Denmark
| | - Max Salomonsson
- Biomedical Sciences Institute, Copenhagen University, Copenhagen, Denmark
| | | | - Olga Sosnovtseva
- Biomedical Sciences Institute, Copenhagen University, Copenhagen, Denmark
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12
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Postnov DD, Marsh DJ, Postnov DE, Braunstein TH, Holstein-Rathlou NH, Martens EA, Sosnovtseva O. Modeling of Kidney Hemodynamics: Probability-Based Topology of an Arterial Network. PLoS Comput Biol 2016; 12:e1004922. [PMID: 27447287 PMCID: PMC4957782 DOI: 10.1371/journal.pcbi.1004922] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 04/18/2016] [Indexed: 11/26/2022] Open
Abstract
Through regulation of the extracellular fluid volume, the kidneys provide important long-term regulation of blood pressure. At the level of the individual functional unit (the nephron), pressure and flow control involves two different mechanisms that both produce oscillations. The nephrons are arranged in a complex branching structure that delivers blood to each nephron and, at the same time, provides a basis for an interaction between adjacent nephrons. The functional consequences of this interaction are not understood, and at present it is not possible to address this question experimentally. We provide experimental data and a new modeling approach to clarify this problem. To resolve details of microvascular structure, we collected 3D data from more than 150 afferent arterioles in an optically cleared rat kidney. Using these results together with published micro-computed tomography (μCT) data we develop an algorithm for generating the renal arterial network. We then introduce a mathematical model describing blood flow dynamics and nephron to nephron interaction in the network. The model includes an implementation of electrical signal propagation along a vascular wall. Simulation results show that the renal arterial architecture plays an important role in maintaining adequate pressure levels and the self-sustained dynamics of nephrons. By maintaining the volume and composition of the body fluids within narrow ranges, and by producing a set of hormones that affect the blood vessels, the kidneys provide important long-term regulation of blood pressure. Disturbances of kidney function can cause hypertension, a prevalent disease in modern societies. The kidneys protect their own function against short-term variations in blood pressure at the level of the individual unit (the nephron). In recent years, it has become clear that there is an interaction between nephrons, and that this interaction is mediated through the arterial network of the kidney. The renal vacular network has a complex topology, and at present there are no computational models of this topology, precluding a computational assessment of the consequences of nephron-nephron interactions for renal blood flow control. In this work we focus on understanding how kidney specific vascular structure affects blood flow patterns and nephron-to-nephron interaction in kidney. The paper presents an approach to constructing realistic models of the renal vascular architecture. We developed a computational approach to reproduce the architecture and to examine its consequences for the operating regime of the nephrons.
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Affiliation(s)
- Dmitry D. Postnov
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
| | - Donald J. Marsh
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, Rhode Island
| | - Dmitry E. Postnov
- Physics Department, Saratov State University, Saratov, Russian Federation
| | - Thomas H. Braunstein
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Erik A. Martens
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Olga Sosnovtseva
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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13
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Zhang D, Song XJ, Li SY, Wang SY, Chen BJ, Bai XD, Tang LM. Evaluation of liver function and electroacupuncture efficacy of animals with alcoholic liver injury by the novel imaging methods. Sci Rep 2016; 6:30119. [PMID: 27443832 PMCID: PMC4957079 DOI: 10.1038/srep30119] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 06/29/2016] [Indexed: 12/12/2022] Open
Abstract
Imaging methods to evaluate hepatic microcirculation (HM) and liver function (LF) by directly monitoring overall liver tissue remain lacking. This study establish imaging methods for LF that combines Laser speckle perfusion imaging (LSPI) and in vivo optical imaging (IVOI) technologies to investigate changes of hepatic microcirculation and reserve function in the animals gavaged with 50% ethanol (15 ml/kg·bw) for a model of acute alcoholic liver injury (ALI), and for evaluation of electroacupuncture (EA) effect. The liver blood perfusion and indocyanine green (ICG) distribution were observe by LSPI and IVOI separately. After EA, the livers were collected to measure the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), thromboxane A (TXA2), prostacyclin (PGI2) and endothelin (ET). The acquisitions of newly established LSPI of liver and ICG in vivo fluorescence imaging (ICG-IVFI), combining the results of other indexes showed: hepatic microcirculation perfusion (HMP) significantly reduced, ICG metabolism reduced, and ALT/AST increased in animal model with acute ALI. EA can reverse these changes. The use of LSPI of liver and ICG-IVFI, which was novel imaging methods for LF established in this study, could display the LF characteristics of ALI and the EA efficacy.
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Affiliation(s)
- Dong Zhang
- Department of biomedical engineering, Institute of Acupuncture &Moxibustion, China Academy of Chinese Medical Sciences, 100700, Beijing, China
| | - Xiao-Jing Song
- Department of biomedical engineering, Institute of Acupuncture &Moxibustion, China Academy of Chinese Medical Sciences, 100700, Beijing, China
| | - Shun-Yue Li
- Department of biomedical engineering, Institute of Acupuncture &Moxibustion, China Academy of Chinese Medical Sciences, 100700, Beijing, China
| | - Shu-You Wang
- Department of biomedical engineering, Institute of Acupuncture &Moxibustion, China Academy of Chinese Medical Sciences, 100700, Beijing, China
| | - Bing-Jun Chen
- Department of biomedical engineering, Institute of Acupuncture &Moxibustion, China Academy of Chinese Medical Sciences, 100700, Beijing, China
| | - Xiao-Dong Bai
- Department of biomedical engineering, Institute of Acupuncture &Moxibustion, China Academy of Chinese Medical Sciences, 100700, Beijing, China
| | - Li-Mei Tang
- Department of biomedical engineering, Institute of Acupuncture &Moxibustion, China Academy of Chinese Medical Sciences, 100700, Beijing, China
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14
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Filler G, Ramsaroop A, Stein R, Grant C, Marants R, So A, McIntyre C. Is Testosterone Detrimental to Renal Function? Kidney Int Rep 2016; 1:306-310. [PMID: 29318206 PMCID: PMC5720528 DOI: 10.1016/j.ekir.2016.07.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- Guido Filler
- Department of Paediatrics, Children’s Hospital at London Health Science Centre, London, Ontario, Canada
- Department of Pathology and Laboratory Medicine, University of Western Ontario, London, Ontario, Canada
- Department of Medicine, University of Western Ontario, London, Ontario, Canada
- Correspondence: Guido Filler, MD, PhD, FRCPC, Department of Paediatrics, Children's Hospital of Western Ontario, 800 Commissioners Rd. E., London, Ontario, Canada N6A 5W9.Department of Paediatrics, Children's Hospital of Western Ontario800 Commissioners Rd. E., LondonOntarioCanada N6A 5W9
| | - Amanda Ramsaroop
- Department of Paediatrics, Children’s Hospital at London Health Science Centre, London, Ontario, Canada
| | - Robert Stein
- Department of Paediatrics, Children’s Hospital at London Health Science Centre, London, Ontario, Canada
| | - Claire Grant
- Department of Medicine, University of Western Ontario, London, Ontario, Canada
| | - Raanan Marants
- Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
| | - Aaron So
- Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
| | - Christopher McIntyre
- Department of Paediatrics, Children’s Hospital at London Health Science Centre, London, Ontario, Canada
- Department of Medicine, University of Western Ontario, London, Ontario, Canada
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15
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Mitrou N, Braam B, Cupples WA. A gap junction inhibitor, carbenoxolone, induces spatiotemporal dispersion of renal cortical perfusion and impairs autoregulation. Am J Physiol Heart Circ Physiol 2016; 311:H582-91. [PMID: 27371687 DOI: 10.1152/ajpheart.00941.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 06/27/2016] [Indexed: 11/22/2022]
Abstract
Renal autoregulation dynamics originating from the myogenic response (MR) and tubuloglomerular feedback (TGF) can synchronize over large regions of the kidney surface, likely through gap junction-mediated electrotonic conduction and reflecting distributed operation of autoregulation. We tested the hypotheses that inhibition of gap junctions reduces spatial synchronization of autoregulation dynamics, abrogates spatial and temporal smoothing of renal perfusion, and impairs renal autoregulation. In male Long-Evans rats, we infused the gap junction inhibitor carbenoxolone (CBX) or the related glycyrrhizic acid (GZA) that does not block gap junctions into the renal artery and monitored renal blood flow (RBF) and surface perfusion by laser speckle contrast imaging. Neither CBX nor GZA altered RBF or mean surface perfusion. CBX preferentially increased spatial and temporal variation in the distribution of surface perfusion, increased spatial variation in the operating frequencies of the MR and TGF, and reduced phase coherence of TGF and increased its dispersion. CBX, but not GZA, impaired dynamic and steady-state autoregulation. Separately, infusion of the Rho kinase inhibitor Y-27632 paralyzed smooth muscle, grossly impaired dynamic autoregulation, and monotonically increased spatial variation of surface perfusion. These data suggest CBX inhibited gap junction communication, which in turn reduced the ability of TGF to synchronize among groups of nephrons. The results indicate that impaired autoregulation resulted from degraded synchronization, rather than the reverse. We show that network behavior in the renal vasculature is necessary for effective RBF autoregulation.
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Affiliation(s)
- Nicholas Mitrou
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada; and
| | - Branko Braam
- Department of Physiology and Department of Medicine, Division of Nephrology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - William A Cupples
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada; and
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16
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Scully CG, Mitrou N, Braam B, Cupples WA, Chon KH. Detecting Interactions between the Renal Autoregulation Mechanisms in Time and Space. IEEE Trans Biomed Eng 2016; 64:690-698. [PMID: 27244712 DOI: 10.1109/tbme.2016.2569453] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Our objective is to identify localized interactions between the renal autoregulation mechanisms over time. METHODS A time-varying phase-randomized wavelet bicoherence detector for quadratic phase coupling between tubuloglomerular feedback and the myogenic response is presented. Through simulations we show its ability to interrogate quadratic phase coupling. The method is applied to kidney blood flow and laser speckle imaging sequences of cortical perfusion from anesthetized rats before and after nonselective inhibition of nitric-oxide synthase. RESULTS Quadratic phase coupling in kidney blood flow data was present in four out of nine animals during the control period for 13.0 ± 5.6% (mean ± SD) of time and in five out of nine animals during inhibition of nitric-oxide synthase for 15.8 ± 8.2% of time. Approximately 60% of time-series extracted from laser speckle imaging pixels of the renal cortex showed significant quadratic phase coupling. Pixels with significant coupling had a median coupling length of 10.8 ± 2.2% and 12.1 ± 3.1% of time with the 95th percentile of pixels being coupled for 25.5 ± 4.4% and 30.9 ± 6.4% of time during control and inhibition of nitric-oxide synthase, respectively. CONCLUSION These results indicate quadratic phase coupling exists in short time intervals between tubuloglomerular feedback and the myogenic response and is detected more often in local renal perfusion signals than whole kidney blood flow in anesthetized rats. SIGNIFICANCE Combining the detector and laser speckle imaging provides identification of coordination between renal autoregulation mechanisms that is localized in time and space.
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17
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Sgouralis I, Maroulas V, Layton AT. Transfer Function Analysis of Dynamic Blood Flow Control in the Rat Kidney. Bull Math Biol 2016; 78:923-60. [PMID: 27173401 DOI: 10.1007/s11538-016-0168-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 04/15/2016] [Indexed: 10/21/2022]
Abstract
Renal blood flow is regulated by the myogenic response (MR) and tubuloglomerular feedback (TGF). Both mechanisms function to buffer not only steady pressure perturbations but also transient ones. In this study, we develop two models of renal autoregulation-a comprehensive model and a simplified model-and use them to analyze the individual contributions of MR and TGF in buffering transient pressure perturbations. Both models represent a single nephron of a rat kidney together with the associated vasculature. The comprehensive model includes detailed representation of the vascular properties and cellular processes. In contrast, the simplified model represents a minimal set of key processes. To assess the degree to which fluctuations in renal perfusion pressure at different frequencies are attenuated, we derive a transfer function for each model. The transfer functions of both models predict resonance at 45 and 180 mHz, which are associated with TGF and MR, respectively, effective autoregulation below [Formula: see text]100 mHz, and amplification of pressure perturbations above [Formula: see text]200 mHz. The predictions are in good agreement with experimental findings.
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Affiliation(s)
- Ioannis Sgouralis
- National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, TN, USA.
| | | | - Anita T Layton
- Department of Mathematics, Duke University, Durham, NC, USA
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18
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Koeners MP, Ow CPC, Russell DM, Evans RG, Malpas SC. Prolonged and Continuous Measurement of Kidney Oxygenation in Conscious Rats. Methods Mol Biol 2016; 1397:93-111. [PMID: 26676130 DOI: 10.1007/978-1-4939-3353-2_9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A relative deficiency in kidney oxygenation, i.e., renal hypoxia, may contribute to the initiation and progression of acute and chronic kidney disease. A critical barrier to investigate this is the lack of methods allowing measurement of the partial pressure of oxygen in kidney tissue for long periods in vivo. We have developed, validated, and tested a novel telemetric method that can do this. Here we provide details on the calibration, implantation, implementation for data recording, and reuse of this telemetry-based technology for measurement of medullary tissue oxygen tension in conscious, unrestrained rats. This technique provides an important additional tool for investigating the impact of renal hypoxia in biology and pathophysiology.
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Affiliation(s)
- Maarten P Koeners
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK.
- Department of Physiology, Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.
- Department of Nephrology, University Medical Centre Utrecht, Utrecht, The Netherlands.
| | - Connie P C Ow
- Department of Physiology, Monash University, Melbourne, VIC, Australia
| | - David M Russell
- Department of Physiology, Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Millar Ltd, Auckland, New Zealand
| | - Roger G Evans
- Department of Physiology, Monash University, Melbourne, VIC, Australia
| | - Simon C Malpas
- Department of Physiology, Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Millar Ltd, Auckland, New Zealand
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19
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Mitrou N, Morrison S, Mousavi P, Braam B, Cupples WA. Transient impairment of dynamic renal autoregulation in early diabetes mellitus in rats. Am J Physiol Regul Integr Comp Physiol 2015; 309:R892-901. [DOI: 10.1152/ajpregu.00247.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 07/31/2015] [Indexed: 01/01/2023]
Abstract
Renal autoregulation is impaired in early (1 wk) diabetes mellitus (DM) induced by streptozotocin, but effective in established DM (4 wk). Furthermore nitric oxide synthesis (NOS) inhibition with NG-nitro-l-arginine methyl ester (l-NAME) significantly improved autoregulation in early DM but not in established DM. We hypothesized that autoregulation is transiently impaired in early DM because of increased NO availability in the kidney. Because of the conflicting evidence available for a role of NO in DM, we tested the hypothesis that DM reduces autoregulation effectiveness by reducing the spatial similarity of autoregulation. Male Long-Evans rats were divided into control (CON) and diabetic (DM; streptozotocin) groups and followed for either 1 wk (CON1, n = 6; DM1, n = 5) or 4 wk (CON4, n = 7; DM4, n = 7). At the end of the experiment, dynamic autoregulation was assessed in isoflurane-anesthetized rats by whole kidney RBF during baseline, NOS1 inhibition, and nonselective NOS inhibition. Kidney surface perfusion, monitored with laser speckle contrast imaging, was used to assess spatial heterogeneity of autoregulation. Autoregulation was significantly impaired in DM1 rats and not impaired in DM4 rats. l-NAME caused strong renal vasoconstriction in all rats, but did not significantly affect autoregulation dynamics. Autoregulation was more spatially heterogeneous in DM1, but not DM4. Therefore, our results, which are consistent with transient impairment of autoregulation in DM, argue against the hypothesis that this impairment is NO-dependent, and suggest that spatial properties of autoregulation may also contribute to reduced autoregulatory effectiveness in DM1.
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Affiliation(s)
- Nicholas Mitrou
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Sidney Morrison
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Paymon Mousavi
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Branko Braam
- Division of Nephrology and Immunology, University of Alberta, Edmonton, Alberta, Canada; and
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
| | - William A. Cupples
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
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20
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Postnov DD, Sosnovtseva O, Tuchin VV. Improved detectability of microcirculatory dynamics by laser speckle flowmetry. JOURNAL OF BIOPHOTONICS 2015; 8:790-4. [PMID: 26110702 DOI: 10.1002/jbio.201500152] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 06/03/2015] [Accepted: 06/09/2015] [Indexed: 05/16/2023]
Abstract
Mechanisms of renal autoregulation generate oscillations in arterial blood flow at several characteristic frequencies. Full-field laser speckle flowmetry provides a real-time imaging of superficial blood microcirculation. The possibility to detect changes in oscillatory dynamics is an important issue in biomedical applications. In this paper we show how laser power density affects quality of the recorded signal and improves detectability of temporal changes in microvascular perfusion.
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Affiliation(s)
- Dmitry D Postnov
- Department of Biomedical Sciences, Copenhagen University, Blegdamsvej 3, 2200, Copenhagen, Denmark.
| | - Olga Sosnovtseva
- Department of Biomedical Sciences, Copenhagen University, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Valery V Tuchin
- Research-Educational Institute of Optics and Biophotonics, Saratov State University, Astrakhanskaya Str. 83, 410012, Saratov, Russia
- Institute of Precision Mechanics and Control RAS, Rabochaya str. 24, 410028, Saratov, Russia
- Interdisciplinary Laboratory of Biophotonics, National Research Tomsk State University, 634050, Tomsk, Russia
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21
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Scully CG, Mitrou N, Braam B, Cupples WA, Chon KH. Segmentation of renal perfusion signals from laser speckle imaging into clusters with phase synchronized dynamics. IEEE Trans Biomed Eng 2015; 61:1989-97. [PMID: 24956617 DOI: 10.1109/tbme.2014.2311118] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Renal perfusion signals contain dynamics arising from the renal autoregulation feedback mechanisms as the contraction and dilation of vessels alter flow patterns. We can capture the time-varying dynamics at points across the renal surface using laser speckle imaging. We segment an imaged area of the renal cortex into clusters with phase synchronized dynamics. Our approach first uses phase coherence with a surrogate data derived threshold to identify synchronized pixel pairs. Non-negative matrix factorization is then applied to segment phase coherence estimates into phase synchronized regions. The method is applied to laser speckle imaging of the renal cortex of anaesthetized rats to identify regions on the renal surface with phase synchronized myogenic activity. In three out of six animals imaged after bolus infusion of N(ω)-nitro-l-arginine methyl ester (NAM), the renal surfaces are segmented into clusters with high phase coherence. No more than two clusters were identified during control period for any animal. In the remaining three animals, a strong myogenic signal could not be detected in surface perfusion during control or NAM. This method can be used to identify synchronization in renal autoregulation dynamics across the renal surface.
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22
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Abstract
Intrarenal autoregulatory mechanisms maintain renal blood flow (RBF) and glomerular filtration rate (GFR) independent of renal perfusion pressure (RPP) over a defined range (80-180 mmHg). Such autoregulation is mediated largely by the myogenic and the macula densa-tubuloglomerular feedback (MD-TGF) responses that regulate preglomerular vasomotor tone primarily of the afferent arteriole. Differences in response times allow separation of these mechanisms in the time and frequency domains. Mechanotransduction initiating the myogenic response requires a sensing mechanism activated by stretch of vascular smooth muscle cells (VSMCs) and coupled to intracellular signaling pathways eliciting plasma membrane depolarization and a rise in cytosolic free calcium concentration ([Ca(2+)]i). Proposed mechanosensors include epithelial sodium channels (ENaC), integrins, and/or transient receptor potential (TRP) channels. Increased [Ca(2+)]i occurs predominantly by Ca(2+) influx through L-type voltage-operated Ca(2+) channels (VOCC). Increased [Ca(2+)]i activates inositol trisphosphate receptors (IP3R) and ryanodine receptors (RyR) to mobilize Ca(2+) from sarcoplasmic reticular stores. Myogenic vasoconstriction is sustained by increased Ca(2+) sensitivity, mediated by protein kinase C and Rho/Rho-kinase that favors a positive balance between myosin light-chain kinase and phosphatase. Increased RPP activates MD-TGF by transducing a signal of epithelial MD salt reabsorption to adjust afferent arteriolar vasoconstriction. A combination of vascular and tubular mechanisms, novel to the kidney, provides for high autoregulatory efficiency that maintains RBF and GFR, stabilizes sodium excretion, and buffers transmission of RPP to sensitive glomerular capillaries, thereby protecting against hypertensive barotrauma. A unique aspect of the myogenic response in the renal vasculature is modulation of its strength and speed by the MD-TGF and by a connecting tubule glomerular feedback (CT-GF) mechanism. Reactive oxygen species and nitric oxide are modulators of myogenic and MD-TGF mechanisms. Attenuated renal autoregulation contributes to renal damage in many, but not all, models of renal, diabetic, and hypertensive diseases. This review provides a summary of our current knowledge regarding underlying mechanisms enabling renal autoregulation in health and disease and methods used for its study.
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Affiliation(s)
- Mattias Carlström
- Department of Medicine, Division of Nephrology and Hypertension and Hypertension, Kidney and Vascular Research Center, Georgetown University, Washington, District of Columbia; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and Department of Cell Biology and Physiology, UNC Kidney Center, and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Christopher S Wilcox
- Department of Medicine, Division of Nephrology and Hypertension and Hypertension, Kidney and Vascular Research Center, Georgetown University, Washington, District of Columbia; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and Department of Cell Biology and Physiology, UNC Kidney Center, and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - William J Arendshorst
- Department of Medicine, Division of Nephrology and Hypertension and Hypertension, Kidney and Vascular Research Center, Georgetown University, Washington, District of Columbia; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and Department of Cell Biology and Physiology, UNC Kidney Center, and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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23
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Grosenick D, Cantow K, Arakelyan K, Wabnitz H, Flemming B, Skalweit A, Ladwig M, Macdonald R, Niendorf T, Seeliger E. Detailing renal hemodynamics and oxygenation in rats by a combined near-infrared spectroscopy and invasive probe approach. BIOMEDICAL OPTICS EXPRESS 2015; 6:309-23. [PMID: 25780726 PMCID: PMC4354597 DOI: 10.1364/boe.6.000309] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 12/09/2014] [Accepted: 12/11/2014] [Indexed: 05/04/2023]
Abstract
We hypothesize that combining quantitative near-infrared spectroscopy (NIRS) with established invasive techniques will enable advanced insights into renal hemodynamics and oxygenation in small animal models. We developed a NIRS technique to monitor absolute values of oxygenated and deoxygenated hemoglobin and of oxygen saturation of hemoglobin within the renal cortex of rats. This NIRS technique was combined with invasive methods to simultaneously record renal tissue oxygen tension and perfusion. The results of test procedures including occlusions of the aorta or the renal vein, hyperoxia, hypoxia, and hypercapnia demonstrated that the combined approach, by providing different but complementary information, enables a more comprehensive characterization of renal hemodynamics and oxygenation.
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Affiliation(s)
- Dirk Grosenick
- Physikalisch-Technische Bundesanstalt (PTB), Berlin,
Germany
| | - Kathleen Cantow
- Institut für Vegetative Physiologie, Charité – Universitätsmedizin Berlin, Berlin,
Germany
| | - Karen Arakelyan
- Institut für Vegetative Physiologie, Charité – Universitätsmedizin Berlin, Berlin,
Germany
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin,
Germany
| | - Heidrun Wabnitz
- Physikalisch-Technische Bundesanstalt (PTB), Berlin,
Germany
| | - Bert Flemming
- Institut für Vegetative Physiologie, Charité – Universitätsmedizin Berlin, Berlin,
Germany
| | - Angela Skalweit
- Institut für Vegetative Physiologie, Charité – Universitätsmedizin Berlin, Berlin,
Germany
| | - Mechthild Ladwig
- Institut für Vegetative Physiologie, Charité – Universitätsmedizin Berlin, Berlin,
Germany
| | | | - Thoralf Niendorf
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin,
Germany
| | - Erdmann Seeliger
- Institut für Vegetative Physiologie, Charité – Universitätsmedizin Berlin, Berlin,
Germany
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24
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Mitrou N, Scully CG, Braam B, Chon KH, Cupples WA. Laser speckle contrast imaging reveals large-scale synchronization of cortical autoregulation dynamics influenced by nitric oxide. Am J Physiol Renal Physiol 2015; 308:F661-70. [PMID: 25587114 DOI: 10.1152/ajprenal.00022.2014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 01/08/2015] [Indexed: 11/22/2022] Open
Abstract
Synchronization of tubuloglomerular feedback (TGF) dynamics in nephrons that share a cortical radial artery is well known. It is less clear whether synchronization extends beyond a single cortical radial artery or whether it extends to the myogenic response (MR). We used LSCI to examine cortical perfusion dynamics in isoflurane-anesthetized, male Long-Evans rats. Inhibition of nitric oxide synthases by N(ω)-nitro-l-arginine methyl ester (l-NAME) was used to alter perfusion dynamics. Phase coherence (PC) was determined between all possible pixel pairs in either the MR or TGF band (0.09-0.3 and 0.015-0.06 Hz, respectively). The field of view (≈4 × 5 mm) was segmented into synchronized clusters based on mutual PC. During the control period, the field of view was often contained within one cluster for both MR and TGF. PC was moderate for TGF and modest for MR, although significant in both. In both MR and TGF, PC exhibited little spatial variation. After l-NAME, the number of clusters increased in both MR and TGF. MR clusters became more strongly synchronized while TGF clusters showed small highly coupled, high-PC regions that were coupled with low PC to the remainder of the cluster. Graph theory analysis probed modularity of synchronization. It confirmed weak synchronization of MR during control that probably was not physiologically relevant. It confirmed extensive and long-distance synchronization of TGF during control and showed increased modularity, albeit with larger modules seen in MR than in TGF after l-NAME. The results show widespread synchronization of MR and TGF that is differentially affected by nitric oxide.
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Affiliation(s)
- Nicholas Mitrou
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Christopher G Scully
- Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts; and
| | - Branko Braam
- Department of Medicine and Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
| | - Ki H Chon
- Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts; and
| | - William A Cupples
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada;
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25
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Brazhe AR, Marsh DJ, Holstein-Rathlou NH, Sosnovtseva O. Synchronized renal blood flow dynamics mapped with wavelet analysis of laser speckle flowmetry data. PLoS One 2014; 9:e105879. [PMID: 25216274 PMCID: PMC4162534 DOI: 10.1371/journal.pone.0105879] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 07/13/2014] [Indexed: 11/18/2022] Open
Abstract
Full-field laser speckle microscopy provides real-time imaging of superficial blood flow rate. Here we apply continuous wavelet transform to time series of speckle-estimated blood flow from each pixel of the images to map synchronous patterns in instantaneous frequency and phase on the surface of rat kidneys. The regulatory mechanism in the renal microcirculation generates oscillations in arterial blood flow at several characteristic frequencies. Our approach to laser speckle image processing allows detection of frequency and phase entrainments, visualization of their patterns, and estimation of the extent of synchronization in renal cortex dynamics.
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Affiliation(s)
- Alexey R. Brazhe
- Department of Biophysics, Biological Faculty, Moscow State University, Moscow, Russia
- * E-mail:
| | - Donald J. Marsh
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, Rhode Island, United States of America
| | | | - Olga Sosnovtseva
- Department of Biomedical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark
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26
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Zhang Z, Lin H, Cao C, Payne K, Pallone TL. Descending vasa recta endothelial cells and pericytes form mural syncytia. Am J Physiol Renal Physiol 2013; 306:F751-63. [PMID: 24381184 DOI: 10.1152/ajprenal.00470.2013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Using patch clamp, we induced depolarization of descending vasa recta (DVR) pericytes or endothelia and tested whether it was conducted to distant cells. Membrane potential was measured with the fluorescent voltage dye di-8-ANEPPS or with a second patch-clamp electrode. Depolarization of an endothelial cell induced responses in other endothelia within a millisecond and was slowed by gap junction blockade with heptanol. Endothelial response to pericyte depolarization was poor, implying high-resistance myo-endothelial coupling. In contrast, dual patch clamp of neighboring pericytes revealed syncytial coupling. At high sampling rate, the spread of depolarization between pericytes and endothelia occurred in 9 ± 2 or 12 ± 2 μs, respectively. Heptanol (2 mM) increased the overall input resistance of the pericyte layer to current flow and prevented transmission of depolarization between neighboring cells. The fluorescent tracer Lucifer yellow (LY), when introduced through ruptured patches, spread between neighboring endothelia in 1 to 7 s, depending on location of the flanking cell. LY diffused to endothelial cells on the ipsilateral but not contralateral side of the DVR wall and minimally between pericytes. We conclude that both DVR pericytes and endothelia are part of individual syncytia. The rate of conduction of membrane potential exceeds that for diffusion of hydrophilic molecules by orders of magnitude. Gap junction coupling of adjacent endothelial cells may be spatially oriented to favor longitudinal transmission along the DVR axis.
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Affiliation(s)
- Zhong Zhang
- Div. of Nephrology, N3W143, 22 S. Greene St., UMMS, Baltimore, MD 21201.
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