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Marom R, Dau JJ, Ghani KR, Hall TL, Roberts WW. Assessing renal tissue temperature changes and perfusion effects during laser activation in an in vivo porcine model. World J Urol 2024; 42:197. [PMID: 38530484 DOI: 10.1007/s00345-024-04896-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Accepted: 02/21/2024] [Indexed: 03/28/2024] Open
Abstract
INTRODUCTION High fluid temperatures have been seen in both in vitro and in vivo studies with laser lithotripsy, yet the thermal distribution within the renal parenchyma has not been well characterized. Additionally, the heat-sink effect of vascular perfusion remains uncertain. Our objectives were twofold: first, to measure renal tissue temperatures in response to laser activation in a calyx, and second, to assess the effect of vascular perfusion on renal tissue temperatures. METHODS Ureteroscopy was performed in three porcine subjects with a prototype ureteroscope containing a temperature sensor at its tip. A needle with four thermocouples was introduced percutaneously into a kidney with ultrasound guidance to allow temperature measurement in the renal medulla and cortex. Three trials of laser activation (40W) for 60 s were conducted with an irrigation rate of 8 ml/min at room temperature in each subject. After euthanasia, three trials were repeated without vascular perfusion in each subject. RESULTS Substantial temperature elevation was observed in the renal medulla with thermal dose in two of nine trials exceeding threshold for tissue injury. The temperature decay time (t½) of the non-perfused trials was longer than in the perfused trials. The ratio of t½ between them was greater in the cortex than the medulla. CONCLUSION High-power laser settings (40W) can induce potentially injurious temperatures in the in vivo porcine kidney, particularly in the medullary region adjacent to the collecting system. Additionally, the influence of vascular perfusion in mitigating thermal risk in this susceptible area appears to be limited.
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Affiliation(s)
- Ron Marom
- Department of Urology, University of Michigan, 4432 Medical Science I, 1301 Catherine Street, Ann Arbor, MI, 48109-5330, USA.
| | - Julie J Dau
- Department of Urology, University of Michigan, 4432 Medical Science I, 1301 Catherine Street, Ann Arbor, MI, 48109-5330, USA
| | - Khurshid R Ghani
- Department of Urology, University of Michigan, 4432 Medical Science I, 1301 Catherine Street, Ann Arbor, MI, 48109-5330, USA
| | - Timothy L Hall
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - William W Roberts
- Department of Urology, University of Michigan, 4432 Medical Science I, 1301 Catherine Street, Ann Arbor, MI, 48109-5330, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
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Ogurlu B, Hamelink TL, Van Tricht IM, Leuvenink HGD, De Borst MH, Moers C, Pool MBF. Utilizing pathophysiological concepts of ischemia-reperfusion injury to design renoprotective strategies and therapeutic interventions for normothermic ex vivo kidney perfusion. Am J Transplant 2024:S1600-6135(24)00065-0. [PMID: 38184242 DOI: 10.1016/j.ajt.2024.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 12/13/2023] [Accepted: 01/01/2024] [Indexed: 01/08/2024]
Abstract
Normothermic machine perfusion (NMP) has emerged as a promising tool for the preservation, viability assessment, and repair of deceased-donor kidneys prior to transplantation. These kidneys inevitably experience a period of ischemia during donation, which leads to ischemia-reperfusion injury when NMP is subsequently commenced. Ischemia-reperfusion injury has a major impact on the renal vasculature, metabolism, oxygenation, electrolyte balance, and acid-base homeostasis. With an increased understanding of the underlying pathophysiological mechanisms, renoprotective strategies and therapeutic interventions can be devised to minimize additional injury during normothermic reperfusion, ensure the safe implementation of NMP, and improve kidney quality. This review discusses the pathophysiological alterations in the vasculature, metabolism, oxygenation, electrolyte balance, and acid-base homeostasis of deceased-donor kidneys and delineates renoprotective strategies and therapeutic interventions to mitigate renal injury and improve kidney quality during NMP.
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Affiliation(s)
- Baran Ogurlu
- Department of Surgery - Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
| | - Tim L Hamelink
- Department of Surgery - Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Isa M Van Tricht
- Department of Surgery - Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Henri G D Leuvenink
- Department of Surgery - Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Martin H De Borst
- Department of Internal Medicine, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Cyril Moers
- Department of Surgery - Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Merel B F Pool
- Department of Surgery - Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
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3
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McLarnon SR. Pathophysiology of Red Blood Cell Trapping in Ischemic Acute Kidney Injury. Compr Physiol 2023; 14:5325-5343. [PMID: 38158367 DOI: 10.1002/cphy.c230010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Red blood cell (RBC) trapping describes the accumulation of RBCs in the microvasculature of the kidney outer medulla that occurs following ischemic acute kidney injury (AKI). Despite its prominence in human kidneys following AKI, as well as evidence from experimental models demonstrating that the severity of RBC trapping is directly correlated with renal recovery, to date, RBC trapping has not been a primary focus in understanding the pathogenesis of ischemic kidney injury. New evidence from rodent models suggests that RBC trapping is responsible for much of the tubular injury occurring in the initial hours after kidney reperfusion from ischemia. This early injury appears to result from RBC cytotoxicity and closely reflects the injury profile observed in human kidneys, including sloughing of the medullary tubules and the formation of heme casts in the distal tubules. In this review, we discuss what is currently known about RBC trapping. We conclude that RBC trapping is likely avoidable. The primary causes of RBC trapping are thought to include rheologic alterations, blood coagulation, tubular cell swelling, and increased vascular permeability; however, new data indicate that a mismatch in blood flow between the cortex and medulla where medullary perfusion is maintained during cortical ischemia is also likely critical. The mechanism(s) by which RBC trapping contributes to renal functional decline require more investigation. We propose a renewed focus on the mechanisms mediating RBC trapping, and RBC trapping-associated injury is likely to provide important knowledge for improving AKI outcomes. © 2024 American Physiological Society. Compr Physiol 14:5325-5343, 2024.
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Affiliation(s)
- Sarah R McLarnon
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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Lilley RJ, Taylor KD, Wildman SSP, Peppiatt-Wildman CM. Inflammatory mediators act at renal pericytes to elicit contraction of vasa recta and reduce pericyte density along the kidney medullary vascular network. Front Physiol 2023; 14:1194803. [PMID: 37362447 PMCID: PMC10288992 DOI: 10.3389/fphys.2023.1194803] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 06/01/2023] [Indexed: 06/28/2023] Open
Abstract
Introduction: Regardless of initiating cause, renal injury promotes a potent pro-inflammatory environment in the outer medulla and a concomitant sustained decrease in medullary blood flow (MBF). This decline in MBF is believed to be one of the critical events in the pathogenesis of acute kidney injury (AKI), yet the precise cellular mechanism underlying this are still to be fully elucidated. MBF is regulated by contractile pericyte cells that reside on the descending vasa recta (DVR) capillaries, which are the primary source of blood flow to the medulla. Methods: Using the rat and murine live kidney slice models, we investigated the acute effects of key medullary inflammatory mediators TNF-α, IL-1β, IL-33, IL-18, C3a and C5a on vasa recta pericytes, the effect of AT1-R blocker Losartan on pro-inflammatory mediator activity at vasa recta pericytes, and the effect of 4-hour sustained exposure on immunolabelled NG2+ pericytes. Results and discussion: Exposure of rat and mouse kidney slices to TNF-α, IL-18, IL-33, and C5a demonstrated a real-time pericyte-mediated constriction of DVR. When pro-inflammatory mediators were applied in the presence of Losartan the inflammatory mediator-mediated constriction that had previously been observed was significantly attenuated. When live kidney slices were exposed to inflammatory mediators for 4-h, we noted a significant reduction in the number of NG2+ positive pericytes along vasa recta capillaries in both rat and murine kidney slices. Data collected in this study demonstrate that inflammatory mediators can dysregulate pericytes to constrict DVR diameter and reduce the density of pericytes along vasa recta vessels, further diminishing the regulatory capacity of the capillary network. We postulate that preliminary findings here suggest pericytes play a role in AKI.
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Affiliation(s)
- Rebecca J. Lilley
- Division of Natural Sciences, University of Kent, Kent, United Kingdom
| | - Kirsti D. Taylor
- Division of Natural Sciences, University of Kent, Kent, United Kingdom
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Deng J, Li L, Feng Y, Yang J. Comprehensive Management of Blood Pressure in Patients with Septic AKI. J Clin Med 2023; 12:jcm12031018. [PMID: 36769666 PMCID: PMC9917880 DOI: 10.3390/jcm12031018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 01/18/2023] [Accepted: 01/19/2023] [Indexed: 01/31/2023] Open
Abstract
Acute kidney injury (AKI) is one of the serious complications of sepsis in clinical practice, and is an important cause of prolonged hospitalization, death, increased medical costs, and a huge medical burden to society. The pathogenesis of AKI associated with sepsis is relatively complex and includes hemodynamic abnormalities due to inflammatory response, oxidative stress, and shock, which subsequently cause a decrease in renal perfusion pressure and eventually lead to ischemia and hypoxia in renal tissue. Active clinical correction of hypotension can effectively improve renal microcirculatory disorders and promote the recovery of renal function. Furthermore, it has been found that in patients with a previous history of hypertension, small changes in blood pressure may be even more deleterious for kidney function. Therefore, the management of blood pressure in patients with sepsis-related AKI will directly affect the short-term and long-term renal function prognosis. This review summarizes the pathophysiological mechanisms of microcirculatory disorders affecting renal function, fluid management, vasopressor, the clinical blood pressure target, and kidney replacement therapy to provide a reference for the clinical management of sepsis-related AKI, thereby promoting the recovery of renal function for the purpose of improving patient prognosis.
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Affiliation(s)
- Junhui Deng
- Department of Nephrology, The Third Affiliated Hospital of Chongqing Medical University, Chongqing 400120, China
| | - Lina Li
- Department of Nephrology, The Third Affiliated Hospital of Chongqing Medical University, Chongqing 400120, China
| | - Yuanjun Feng
- Department of Renal Rheumatology, Space Hospital Affiliated to Zunyi Medical University, Zunyi 563002, China
| | - Jurong Yang
- Department of Nephrology, The Third Affiliated Hospital of Chongqing Medical University, Chongqing 400120, China
- Correspondence: or
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Hu RT, Lankadeva YR, Yanase F, Osawa EA, Evans RG, Bellomo R. Continuous bladder urinary oxygen tension as a new tool to monitor medullary oxygenation in the critically ill. Crit Care 2022; 26:389. [PMID: 36527088 PMCID: PMC9758873 DOI: 10.1186/s13054-022-04230-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 11/09/2022] [Indexed: 12/23/2022] Open
Abstract
Acute kidney injury (AKI) is common in the critically ill. Inadequate renal medullary tissue oxygenation has been linked to its pathogenesis. Moreover, renal medullary tissue hypoxia can be detected before biochemical evidence of AKI in large mammalian models of critical illness. This justifies medullary hypoxia as a pathophysiological biomarker for early detection of impending AKI, thereby providing an opportunity to avert its evolution. Evidence from both animal and human studies supports the view that non-invasively measured bladder urinary oxygen tension (PuO2) can provide a reliable estimate of renal medullary tissue oxygen tension (tPO2), which can only be measured invasively. Furthermore, therapies that modify medullary tPO2 produce corresponding changes in bladder PuO2. Clinical studies have shown that bladder PuO2 correlates with cardiac output, and that it increases in response to elevated cardiopulmonary bypass (CPB) flow and mean arterial pressure. Clinical observational studies in patients undergoing cardiac surgery involving CPB have shown that bladder PuO2 has prognostic value for subsequent AKI. Thus, continuous bladder PuO2 holds promise as a new clinical tool for monitoring the adequacy of renal medullary oxygenation, with its implications for the recognition and prevention of medullary hypoxia and thus AKI.
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Affiliation(s)
- Raymond T. Hu
- grid.410678.c0000 0000 9374 3516Department of Anaesthesia, Austin Health, Heidelberg, VIC Australia ,grid.1008.90000 0001 2179 088XDepartment of Critical Care, Melbourne Medical School, The University of Melbourne, Parkville, VIC Australia
| | - Yugeesh R. Lankadeva
- grid.1008.90000 0001 2179 088XDepartment of Critical Care, Melbourne Medical School, The University of Melbourne, Parkville, VIC Australia ,grid.1008.90000 0001 2179 088XPre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC Australia
| | - Fumitake Yanase
- grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Heidelberg, Australia
| | - Eduardo A. Osawa
- Cardiology Intensive Care Unit, DF Star Hospital, Brasília, Brazil ,grid.472984.4D’Or Institute for Research and Education (IDOR), DF Star Hospital, Brasília, Brazil
| | - Roger G. Evans
- grid.1008.90000 0001 2179 088XPre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC Australia ,grid.1002.30000 0004 1936 7857Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, VIC Australia
| | - Rinaldo Bellomo
- grid.1008.90000 0001 2179 088XDepartment of Critical Care, Melbourne Medical School, The University of Melbourne, Parkville, VIC Australia ,grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Heidelberg, Australia ,grid.1002.30000 0004 1936 7857Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia ,grid.416153.40000 0004 0624 1200Department of Intensive Care, Royal Melbourne Hospital, Parkville, Australia
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7
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Nitric Oxide Signalling in Descending Vasa Recta after Hypoxia/Re-Oxygenation. Int J Mol Sci 2022; 23:ijms23137016. [PMID: 35806018 PMCID: PMC9266395 DOI: 10.3390/ijms23137016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 06/20/2022] [Accepted: 06/21/2022] [Indexed: 01/27/2023] Open
Abstract
Reduced renal medullary oxygen supply is a key factor in the pathogenesis of acute kidney injury (AKI). As the medulla exclusively receives blood through descending vasa recta (DVR), dilating these microvessels after AKI may help in renoprotection by restoring renal medullary blood flow. We stimulated the NO-sGC-cGMP signalling pathway in DVR at three different levels before and after hypoxia/re-oxygenation (H/R). Rat DVR were isolated and perfused under isobaric conditions. The phosphodiesterase 5 (PDE5) inhibitor sildenafil (10−6 mol/L) impaired cGMP degradation and dilated DVR pre-constricted with angiotensin II (Ang II, 10−6 mol/L). Dilations by the soluble guanylyl cyclase (sGC) activator BAY 60-2770 as well as the nitric oxide donor sodium nitroprusside (SNP, 10−3 mol/L) were equally effective. Hypoxia (0.1% O2) augmented DVR constriction by Ang II, thus potentially aggravating tissue hypoxia. H/R left DVR unresponsive to sildenafil, yet sGC activation by BAY 60-2770 effectively dilated DVR. Dilation to SNP under H/R is delayed. In conclusion, H/R renders PDE5 inhibition ineffective in dilating the crucial vessels supplying the area at risk for hypoxic damage. Stimulating sGC appears to be the most effective in restoring renal medullary blood flow after H/R and may prove to be the best target for maintaining oxygenation to this vulnerable area of the kidney.
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8
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Ning Z, Chen S, Chen Z, Han H, Qiao H, Zhang N, Wang R, Shen R, Zhao X. Saturated multi-delay renal arterial spin labeling technique for simultaneous perfusion and T 1 quantification in kidneys. Magn Reson Med 2022; 88:1055-1067. [PMID: 35506512 DOI: 10.1002/mrm.29268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 03/22/2022] [Accepted: 03/24/2022] [Indexed: 11/06/2022]
Abstract
PURPOSE To propose a free-breathing simultaneous multi-delay arterial spin labeling (ASL) and T1 mapping technique with a stepwise kinetic model for renal assessment in a single 4-min scan at 3 T. METHODS The proposed saturated multi-delay renal arterial spin labeling (SAMURAI) sequence used flow-sensitive alternating inversion recovery (FAIR) preparation, followed by acquisition of 9 images with Look-Locker spoiled gradient recalled echo (SPGR). Pre-saturation at the imaging slice was used to achieve saturation-based T1 mapping. A 4-step 2-compartment kinetic model was proposed to characterize water transition through artery- and tissue-compartment. The impact of the Look-Locker sampling scheme on the ASL signal was corrected in this model. T1 estimation with dictionary searching method and perfusion quantification based on the proposed kinetic model fitting were conducted after groupwise registration of the acquired images. The feasibility and repeatability of SAMURAI were validated in healthy subjects (n = 11) and patients with different renal diseases (n = 4). RESULTS The proposed SAMURAI technique can provide accurate T1 map with strong correlation (R2 = 0.98) with inversion recovery spin echo (IR-SE) on phantom. SAMURAI provided equally reliable whole kidney and cortical ASL and T1 quantification results compared with multi-TI FAIR (intraclass correlation coefficient [ICC], 0.880-0.958) and IR-SPGR (ICC, 0.875-0.912), respectively. Low renal blood flow and increased T1 were detected by SAMURAI in the affected kidneys of the patients. SAMURAI had excellent scan-rescan repeatability (ICC, 0.905-0.992) and significantly reduced scan time (4 min 6 s vs. 45 min for 9 TIs) compared to multi-TI FAIR. CONCLUSION The proposed SAMURAI technique is feasible and repeatable for simultaneously quantifying T1 and perfusion of kidneys with high time-efficiency.
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Affiliation(s)
- Zihan Ning
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University School of Medicine, Beijing, China
| | - Shuo Chen
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University School of Medicine, Beijing, China.,Tsinghua University-Peking University Joint Center for Life Sciences, Beijing, China
| | - Zhensen Chen
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China
| | - Hualu Han
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University School of Medicine, Beijing, China
| | - Huiyu Qiao
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University School of Medicine, Beijing, China.,Tsinghua University-Peking University Joint Center for Life Sciences, Beijing, China
| | - Nan Zhang
- Department of Radiology, Beijing Anzhen Hospital, Beijing, China
| | - Rui Wang
- Department of Radiology, Peking University First Hospital, Beijing, China
| | - Rui Shen
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University School of Medicine, Beijing, China
| | - Xihai Zhao
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University School of Medicine, Beijing, China
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Lankadeva YR, May CN, Bellomo R, Evans RG. Role of perioperative hypotension in postoperative acute kidney injury: a narrative review. Br J Anaesth 2022; 128:931-948. [DOI: 10.1016/j.bja.2022.03.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 02/17/2022] [Accepted: 03/01/2022] [Indexed: 12/20/2022] Open
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10
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The hypoxia-inducible factor prolyl hydroxylase inhibitor FG4592 promotes natriuresis through upregulation of COX2 in the renal medulla. Hypertens Res 2022; 45:814-823. [PMID: 35304594 DOI: 10.1038/s41440-022-00889-1] [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: 07/01/2021] [Revised: 12/03/2021] [Accepted: 01/09/2022] [Indexed: 11/08/2022]
Abstract
The renal medulla is a key site for the regulation of renal sodium excretion. However, the molecular mechanism remains unclear. Cyclooxygenase 2 (COX2) is specifically expressed in the renal medulla and contributes to the maintenance of the electrolyte/water balance in the body. Hypoxia-inducible factors (HIFs) have also been found to be expressed in the renal medulla, probably owing to the hypoxic conditions in the renal medulla. This study was designed to test the effects of HIF activation on renal sodium handling and renal medullary COX2 expression. Our data showed that HIF activation by the prolyl hydroxylase inhibitor (PHI) FG4592 enhanced natriuresis in mice challenged with a high-salt diet. In addition, FG4592 upregulated the expression of COX2 in the renal medulla. An in vitro study further supported the finding that HIF can induce the expression of COX2 and that this induction is mediated through direct binding to the promoter region of the Cox2 gene, facilitating its transcription. In addition, the COX2 inhibitor celecoxib diminished the natriuretic effect of FG4592. Together, these results suggest that HIF activation promotes sodium excretion through upregulation of COX2 in the renal medulla and therefore maintains sodium homeostasis in the body.
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Freitas F, Attwell D. Pericyte-mediated constriction of renal capillaries evokes no-reflow and kidney injury following ischaemia. eLife 2022; 11:74211. [PMID: 35285797 PMCID: PMC8947765 DOI: 10.7554/elife.74211] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Accepted: 03/09/2022] [Indexed: 12/12/2022] Open
Abstract
Acute kidney injury is common, with ~13 million cases and 1.7 million deaths/year worldwide. A major cause is renal ischaemia, typically following cardiac surgery, renal transplant or severe haemorrhage. We examined the cause of the sustained reduction in renal blood flow ('no-reflow'), which exacerbates kidney injury even after an initial cause of compromised blood supply is removed. Adult male Sprague-Dawley rats, or NG2-dsRed male mice were used in this study. After 60 min kidney ischaemia and 30-60 min reperfusion, renal blood flow remained reduced, especially in the medulla, and kidney tubule damage was detected as Kim-1 expression. Constriction of the medullary descending vasa recta and cortical peritubular capillaries occurred near pericyte somata, and led to capillary blockages, yet glomerular arterioles and perfusion were unaffected, implying that the long-lasting decrease of renal blood flow contributing to kidney damage was generated by pericytes. Blocking Rho kinase to decrease pericyte contractility from the start of reperfusion increased the post-ischaemic diameter of the descending vasa recta capillaries at pericytes, reduced the percentage of capillaries that remained blocked, increased medullary blood flow and reduced kidney injury. Thus, post-ischaemic renal no-reflow, contributing to acute kidney injury, reflects pericytes constricting the descending vasa recta and peritubular capillaries. Pericytes are therefore an important therapeutic target for treating acute kidney injury.
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Affiliation(s)
- Felipe Freitas
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - David Attwell
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
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Kumar N, Saraber P, Ding Z, Kusumbe AP. Diversity of Vascular Niches in Bones and Joints During Homeostasis, Ageing, and Diseases. Front Immunol 2021; 12:798211. [PMID: 34975909 PMCID: PMC8718446 DOI: 10.3389/fimmu.2021.798211] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 11/19/2021] [Indexed: 12/29/2022] Open
Abstract
The bones and joints in the skeletal system are composed of diverse cell types, including vascular niches, bone cells, connective tissue cells and mineral deposits and regulate whole-body homeostasis. The capacity of maintaining strength and generation of blood lineages lies within the skeletal system. Bone harbours blood and immune cells and their progenitors, and vascular cells provide several immune cell type niches. Blood vessels in bone are phenotypically and functionally diverse, with distinct capillary subtypes exhibiting striking changes with age. The bone vasculature has a special impact on osteogenesis and haematopoiesis, and dysregulation of the vasculature is associated with diverse blood and bone diseases. Ageing is associated with perturbed haematopoiesis, loss of osteogenesis, increased adipogenesis and diminished immune response and immune cell production. Endothelial and perivascular cells impact immune cell production and play a crucial role during inflammation. Here, we discuss normal and maladapted vascular niches in bone during development, homeostasis, ageing and bone diseases such as rheumatoid arthritis and osteoarthritis. Further, we discuss the role of vascular niches during bone malignancy.
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Affiliation(s)
| | | | | | - Anjali P. Kusumbe
- Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), Tissue and Tumor Microenvironments Group, University of Oxford, Oxford, United Kingdom
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Kidney Microcirculation as a Target for Innovative Therapies in AKI. J Clin Med 2021; 10:jcm10184041. [PMID: 34575154 PMCID: PMC8471583 DOI: 10.3390/jcm10184041] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 08/29/2021] [Accepted: 09/02/2021] [Indexed: 12/19/2022] Open
Abstract
Acute kidney injury (AKI) is a serious multifactorial conditions accompanied by the loss of function and damage. The renal microcirculation plays a crucial role in maintaining the kidney’s functional and structural integrity for oxygen and nutrient supply and waste product removal. However, alterations in microcirculation and oxygenation due to renal perfusion defects, hypoxia, renal tubular, and endothelial damage can result in AKI and the loss of renal function regardless of systemic hemodynamic changes. The unique structural organization of the renal microvasculature and the presence of autoregulation make it difficult to understand the mechanisms and the occurrence of AKI following disorders such as septic, hemorrhagic, or cardiogenic shock; ischemia/reperfusion; chronic heart failure; cardiorenal syndrome; and hemodilution. In this review, we describe the organization of microcirculation, autoregulation, and pathophysiological alterations leading to AKI. We then suggest innovative therapies focused on the protection of the renal microcirculation and oxygenation to prevent AKI.
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Pool MBF, Hamelink TL, van Goor H, van den Heuvel MC, Leuvenink HGD, Moers C. Prolonged ex-vivo normothermic kidney perfusion: The impact of perfusate composition. PLoS One 2021; 16:e0251595. [PMID: 34003874 PMCID: PMC8130974 DOI: 10.1371/journal.pone.0251595] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/29/2021] [Indexed: 12/22/2022] Open
Abstract
Normothermic machine perfusion (NMP) of donor kidneys provides the opportunity for improved graft preservation and objective pre-transplant ex-vivo organ assessment. Currently, a multitude of perfusion solutions exist for renal NMP. This study aimed to evaluate four different perfusion solutions side-by-side and determine the influence of different perfusate compositions on measured renal perfusion parameters. Porcine kidneys and blood were obtained from a slaughterhouse. Kidneys underwent NMP at 37°C for 7 hours, with 4 different perfusion solutions (n = 5 per group). Group 1 consisted of red blood cells (RBCs) and a perfusion solution based on Williams’ Medium E. Group 2 consisted of RBCs, albumin and a balanced electrolyte composition. Group 3 contained RBCs and a medium based on a British clinical NMP solution. Group 4 contained RBCs and a medium used in 24-hour perfusion experiments. NMP flow patterns for solutions 1 and 2 were similar, solutions 3 and 4 showed lower but more stable flow rates. Thiobarbituric acid reactive substances were significantly higher in solution 1 and 4 compared to the other groups. Levels of injury marker N-acetyl-β-D glucosaminidase were significantly lower in solution 2 in comparison with solution 3 and 4. This study illustrates that the perfusate composition during NMP significantly impacts the measured perfusion and injury parameters and thus affects the interpretation of potential viability markers. Further research is required to investigate the individual influences of principal perfusate components to determine the most optimal conditions during NMP and eventually develop universal organ assessment criteria.
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Affiliation(s)
- Merel B. F. Pool
- Department of Surgery–Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
- * E-mail:
| | - Tim L. Hamelink
- Department of Surgery–Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Harry van Goor
- Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Marius C. van den Heuvel
- Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Henri G. D. Leuvenink
- Department of Surgery–Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Cyril Moers
- Department of Surgery–Organ Donation and Transplantation, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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15
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Apelt K, Bijkerk R, Lebrin F, Rabelink TJ. Imaging the Renal Microcirculation in Cell Therapy. Cells 2021; 10:cells10051087. [PMID: 34063200 PMCID: PMC8147454 DOI: 10.3390/cells10051087] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/23/2021] [Accepted: 04/30/2021] [Indexed: 12/12/2022] Open
Abstract
Renal microvascular rarefaction plays a pivotal role in progressive kidney disease. Therefore, modalities to visualize the microcirculation of the kidney will increase our understanding of disease mechanisms and consequently may provide new approaches for evaluating cell-based therapy. At the moment, however, clinical practice is lacking non-invasive, safe, and efficient imaging modalities to monitor renal microvascular changes over time in patients suffering from renal disease. To emphasize the importance, we summarize current knowledge of the renal microcirculation and discussed the involvement in progressive kidney disease. Moreover, an overview of available imaging techniques to uncover renal microvascular morphology, function, and behavior is presented with the associated benefits and limitations. Ultimately, the necessity to assess and investigate renal disease based on in vivo readouts with a resolution up to capillary level may provide a paradigm shift for diagnosis and therapy in the field of nephrology.
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Affiliation(s)
- Katerina Apelt
- Department of Internal Medicine-Nephrology, Leiden University Medical Center, 2333ZA Leiden, The Netherlands; (K.A.); (R.B.); (F.L.)
- Einthoven Laboratory of Vascular and Regenerative Medicine, Leiden University Medical Center, 2333ZA Leiden, The Netherlands
| | - Roel Bijkerk
- Department of Internal Medicine-Nephrology, Leiden University Medical Center, 2333ZA Leiden, The Netherlands; (K.A.); (R.B.); (F.L.)
- Einthoven Laboratory of Vascular and Regenerative Medicine, Leiden University Medical Center, 2333ZA Leiden, The Netherlands
| | - Franck Lebrin
- Department of Internal Medicine-Nephrology, Leiden University Medical Center, 2333ZA Leiden, The Netherlands; (K.A.); (R.B.); (F.L.)
- Einthoven Laboratory of Vascular and Regenerative Medicine, Leiden University Medical Center, 2333ZA Leiden, The Netherlands
- Physics for Medicine Paris, Inserm, CNRS, ESPCI Paris, Paris Sciences et Lettres University, 75005 Paris, France
| | - Ton J. Rabelink
- Department of Internal Medicine-Nephrology, Leiden University Medical Center, 2333ZA Leiden, The Netherlands; (K.A.); (R.B.); (F.L.)
- Einthoven Laboratory of Vascular and Regenerative Medicine, Leiden University Medical Center, 2333ZA Leiden, The Netherlands
- Correspondence:
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16
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Lu F, Yang J, Yang S, Bernd K, Fu C, Yang C, Xu H, Liu M, Zhan S, Wang C, Guo R, Wu Y. Use of Three-Dimensional Arterial Spin Labeling to Evaluate Renal Perfusion in Patients With Chronic Kidney Disease. J Magn Reson Imaging 2021; 54:1152-1163. [PMID: 33769645 DOI: 10.1002/jmri.27609] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 03/06/2021] [Accepted: 03/09/2021] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND A noninvasive method for evaluating renal blood flow (RBF) in patients with chronic kidney disease (CKD) may have clinical value in disease staging, management, and prognostication. PURPOSE To evaluate effectiveness of three-dimensional pseudocontinuous arterial spin labeling (pCASL) and pulsed arterial spin labeling (PASL) in assessment of cortex and outer medulla (cortex/OM) RBF in CKD patients and healthy volunteers (HVs). STUDY TYPE Prospective, in a single institution. SUBJECTS A total of 48 CKD patients (stage 1, 2, 3, and 4-5: N = 11, 12, 13, and 12, respectively) and 18 HVs FIELD STRENGTH/SEQUENCE: 3 T, pCASL, and PASL with a three-dimensional hybrid gradient echo/spin echo sequence. ASSESSMENT Quality of RBF images derived from pCASL and PASL were evaluated and RBF in cortex/OM measured. Clinical and laboratory data were recorded. STATISTICAL TESTS Image quality differences between pCASL and PASL were evaluated with Wilcoxon signed-rank test. For both methods, analysis of variance, followed by Fisher's LSD-t test, was used to determine whether RBF differed between CKD stages and HVs. Pearson correlation coefficients were calculated to assess strength of relationships between cortex/OM RBF and data from clinical and laboratory tests. RESULTS Image quality differences were significantly higher in pCASL than PASL in both patients and HVs (both P < 0.05). For pCASL, cortex/OM RBF of patients were significantly lower than those of HVs (P < 0.05). Cortex/OM RBF were higher in S1 and S2 patients than those in S3 and S4-5 (P < 0.05). For PASL, only RBF in cortex of S1 and S2 patients were significantly higher than those of S4-5 (P < 0.05). Good correlations between pCASL RBF and estimated glomerular filtration (eGFR) were found in cortex/OM of patients (rho = 0.796 and 0.798, respectively, both P < 0.05), higher than those between PASL RBF and eGFR (rho = 0.430 and 0.374, respectively, both P < 0.05). DATA CONCLUSION Three-dimensional pCASL may potentially be a noninvasive technique to assess renal perfusion in CKD patients in different stages. LEVEL OF EVIDENCE 1 TECHNICAL EFFICACY: Stage 2.
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Affiliation(s)
- Fang Lu
- Department of Radiology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Jing Yang
- Department of Nephrology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Shuohui Yang
- Department of Radiology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Kuehn Bernd
- MR Applications Development, Siemens Healthcare, Erlangen, Germany
| | - Caixia Fu
- MR Applications Development, Siemens Shenzhen Magnetic Resonance Ltd, Shenzhen, China
| | - Chenyao Yang
- Department of Radiology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Huihui Xu
- Department of Radiology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Mengxiao Liu
- MR Scientific Marketing, Siemens Healthcare, Shanghai, China
| | - Songhua Zhan
- Department of Radiology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Chen Wang
- Department of Nephrology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Rongfang Guo
- Department of Radiology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yu Wu
- Department of Radiology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
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17
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Franklin SL, Bones IK, Harteveld AA, Hirschler L, van Stralen M, Qin Q, de Boer A, Hoogduin JM, Bos C, van Osch MJP, Schmid S. Multi-organ comparison of flow-based arterial spin labeling techniques: Spatially non-selective labeling for cerebral and renal perfusion imaging. Magn Reson Med 2020; 85:2580-2594. [PMID: 33251644 PMCID: PMC7898485 DOI: 10.1002/mrm.28603] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 09/21/2020] [Accepted: 10/26/2020] [Indexed: 12/12/2022]
Abstract
Purpose Flow‐based arterial spin labeling (ASL) techniques provide a transit‐time insensitive alternative to the more conventional spatially selective ASL techniques. However, it is not clear which flow‐based ASL technique performs best and also, how these techniques perform outside the brain (taking into account eg, flow‐dynamics, field‐inhomogeneity, and organ motion). In the current study we aimed to compare 4 flow‐based ASL techniques (ie, velocity selective ASL, acceleration selective ASL, multiple velocity selective saturation ASL, and velocity selective inversion prepared ASL [VSI‐ASL]) to the current spatially selective reference techniques in brain (ie, pseudo‐continuous ASL [pCASL]) and kidney (ie, pCASL and flow alternating inversion recovery [FAIR]). Methods Brain (n = 5) and kidney (n = 6) scans were performed in healthy subjects at 3T. Perfusion‐weighted signal (PWS) maps were generated and ASL techniques were compared based on temporal SNR (tSNR), sensitivity to perfusion changes using a visual stimulus (brain) and robustness to respiratory motion by comparing scans acquired in paced‐breathing and free‐breathing (kidney). Results In brain, all flow‐based ASL techniques showed similar tSNR as pCASL, but only VSI‐ASL showed similar sensitivity to perfusion changes. In kidney, all flow‐based ASL techniques had comparable tSNR, although all lower than FAIR. In addition, VSI‐ASL showed a sensitivity to B1‐inhomogeneity. All ASL techniques were relatively robust to respiratory motion. Conclusion In both brain and kidney, flow‐based ASL techniques provide a planning‐free and transit‐time insensitive alternative to spatially selective ASL techniques. VSI‐ASL shows the most potential overall, showing similar performance as the golden standard pCASL in brain. However, in kidney, a reduction of B1‐sensitivity of VSI‐ASL is necessary to match the performance of FAIR.
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Affiliation(s)
- Suzanne L Franklin
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.,Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands.,Leiden Institute for Brain and Cognition, Leiden University, Leiden, The Netherlands
| | - Isabell K Bones
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Anita A Harteveld
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Lydiane Hirschler
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.,Leiden Institute for Brain and Cognition, Leiden University, Leiden, The Netherlands
| | - Marijn van Stralen
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Qin Qin
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Anneloes de Boer
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Johannes M Hoogduin
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Clemens Bos
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Matthias J P van Osch
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.,Leiden Institute for Brain and Cognition, Leiden University, Leiden, The Netherlands
| | - Sophie Schmid
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.,Leiden Institute for Brain and Cognition, Leiden University, Leiden, The Netherlands
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18
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Gardiner BS, Smith DW, Lee C, Ngo JP, Evans RG. Renal oxygenation: From data to insight. Acta Physiol (Oxf) 2020; 228:e13450. [PMID: 32012449 DOI: 10.1111/apha.13450] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 01/14/2020] [Accepted: 01/30/2020] [Indexed: 12/14/2022]
Abstract
Computational models have made a major contribution to the field of physiology. As the complexity of our understanding of biological systems expands, the need for computational methods only increases. But collaboration between experimental physiologists and computational modellers (ie theoretical physiologists) is not easy. One of the major challenges is to break down the barriers created by differences in vocabulary and approach between the two disciplines. In this review, we have two major aims. Firstly, we wish to contribute to the effort to break down these barriers and so encourage more interdisciplinary collaboration. So, we begin with a "primer" on the ways in which computational models can help us understand physiology and pathophysiology. Second, we aim to provide an update of recent efforts in one specific area of physiology, renal oxygenation. This work is shedding new light on the causes and consequences of renal hypoxia. But as importantly, computational modelling is providing direction for experimental physiologists working in the field of renal oxygenation by: (a) generating new hypotheses that can be tested in experimental studies, (b) allowing experiments that are technically unfeasible to be simulated in silico, or variables that cannot be measured experimentally to be estimated, and (c) providing a means by which the quality of experimental data can be assessed. Critically, based on our experience, we strongly believe that experimental and theoretical physiology should not be seen as separate exercises. Rather, they should be integrated to permit an iterative process between modelling and experimentation.
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Affiliation(s)
- Bruce S. Gardiner
- College of Science Health, Engineering and Education Murdoch University Perth Australia
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Australia
| | - David W. Smith
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Australia
| | - Chang‐Joon Lee
- College of Science Health, Engineering and Education Murdoch University Perth Australia
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Australia
| | - Jennifer P. Ngo
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Australia
- Department of Cardiac Physiology National Cerebral and Cardiovascular Research Center Osaka Japan
| | - Roger G. Evans
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Australia
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19
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Dumas SJ, Meta E, Borri M, Goveia J, Rohlenova K, Conchinha NV, Falkenberg K, Teuwen LA, de Rooij L, Kalucka J, Chen R, Khan S, Taverna F, Lu W, Parys M, De Legher C, Vinckier S, Karakach TK, Schoonjans L, Lin L, Bolund L, Dewerchin M, Eelen G, Rabelink TJ, Li X, Luo Y, Carmeliet P. Single-Cell RNA Sequencing Reveals Renal Endothelium Heterogeneity and Metabolic Adaptation to Water Deprivation. J Am Soc Nephrol 2019; 31:118-138. [PMID: 31818909 DOI: 10.1681/asn.2019080832] [Citation(s) in RCA: 89] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 10/01/2019] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Renal endothelial cells from glomerular, cortical, and medullary kidney compartments are exposed to different microenvironmental conditions and support specific kidney processes. However, the heterogeneous phenotypes of these cells remain incompletely inventoried. Osmotic homeostasis is vitally important for regulating cell volume and function, and in mammals, osmotic equilibrium is regulated through the countercurrent system in the renal medulla, where water exchange through endothelium occurs against an osmotic pressure gradient. Dehydration exposes medullary renal endothelial cells to extreme hyperosmolarity, and how these cells adapt to and survive in this hypertonic milieu is unknown. METHODS We inventoried renal endothelial cell heterogeneity by single-cell RNA sequencing >40,000 mouse renal endothelial cells, and studied transcriptome changes during osmotic adaptation upon water deprivation. We validated our findings by immunostaining and functionally by targeting oxidative phosphorylation in a hyperosmolarity model in vitro and in dehydrated mice in vivo. RESULTS We identified 24 renal endothelial cell phenotypes (of which eight were novel), highlighting extensive heterogeneity of these cells between and within the cortex, glomeruli, and medulla. In response to dehydration and hypertonicity, medullary renal endothelial cells upregulated the expression of genes involved in the hypoxia response, glycolysis, and-surprisingly-oxidative phosphorylation. Endothelial cells increased oxygen consumption when exposed to hyperosmolarity, whereas blocking oxidative phosphorylation compromised endothelial cell viability during hyperosmotic stress and impaired urine concentration during dehydration. CONCLUSIONS This study provides a high-resolution atlas of the renal endothelium and highlights extensive renal endothelial cell phenotypic heterogeneity, as well as a previously unrecognized role of oxidative phosphorylation in the metabolic adaptation of medullary renal endothelial cells to water deprivation.
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Affiliation(s)
- Sébastien J Dumas
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Elda Meta
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Mila Borri
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Jermaine Goveia
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Katerina Rohlenova
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Nadine V Conchinha
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Kim Falkenberg
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Laure-Anne Teuwen
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Laura de Rooij
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Joanna Kalucka
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Rongyuan Chen
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Shawez Khan
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Federico Taverna
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Weisi Lu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Magdalena Parys
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Carla De Legher
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Stefan Vinckier
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Tobias K Karakach
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Luc Schoonjans
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Lin Lin
- Lars Bolund Institute of Regenerative Medicine, Beijing Genomics Institute (BGI)-Qingdao, BGI-Shenzhen, Qingdao, China.,Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Lars Bolund
- Lars Bolund Institute of Regenerative Medicine, Beijing Genomics Institute (BGI)-Qingdao, BGI-Shenzhen, Qingdao, China.,Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Mieke Dewerchin
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Guy Eelen
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Ton J Rabelink
- Division of Nephrology, Department of Internal Medicine, The Einthoven Laboratory for Vascular and Regenerative Medicine, Leiden University Medical Center, Leiden, The Netherlands
| | - Xuri Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China;
| | - Yonglun Luo
- Lars Bolund Institute of Regenerative Medicine, Beijing Genomics Institute (BGI)-Qingdao, BGI-Shenzhen, Qingdao, China; .,Department of Biomedicine, Aarhus University, Aarhus, Denmark.,China National GeneBank, Beijing Genomics Institute (BGI)-Shenzhen, Shenzhen, China; and.,Qingdao-Europe Advanced Institute for Life Sciences, Beijing Genomics Institute (BGI)-Qingdao, Qingdao, China
| | - Peter Carmeliet
- Department of Oncology, Laboratory of Angiogenesis and Vascular Metabolism, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium; .,Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
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20
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Fan L, Wang S, He X, Gonzalez‐Fernandez E, Lechene C, Fan F, Roman RJ. Visualization of the intrarenal distribution of capillary blood flow. Physiol Rep 2019; 7:e14065. [PMID: 31008571 PMCID: PMC6475880 DOI: 10.14814/phy2.14065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 03/11/2019] [Accepted: 03/15/2019] [Indexed: 12/24/2022] Open
Abstract
This study describes a modified technique to fill the renal vasculature with a silicon rubber (Microfil) compound and obtain morphologic information about the intrarenal distribution of capillary blood flow under a variety of conditions. Kidneys and cremaster muscles of rats were perfused in vivo with Microfil using a perfusion pressure equal to the animal's mean arterial pressure at body temperature. Microfil did not alter arteriolar diameter or the pattern of flow in the microcirculation of the cremaster muscle. The modified protocol reproducibly filled the renal vasculature, including; glomerular, peritubular, and vasa recta capillaries. We compared the filling of the renal circulation in control rats with that seen in animals subjected to maneuvers reported to alter the intrarenal distribution of blood flow. Infusion of angiotensin II, hypotension, volume expansion, and mannitol- or furosemide-induced diuresis redistributed flow between renal cortical and medullary capillaries. The advantage of the current technique is that it provides anatomical information regarding the number, diameter, and branching patterns of capillaries in the postglomerular circulation critical in determining the intrarenal distribution of cortical and medullary blood flow.
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Affiliation(s)
- Letao Fan
- Department of Pharmacology and ToxicologyUniversity of Mississippi Medical CenterJacksonMississippi
| | - Shaoxun Wang
- Department of Pharmacology and ToxicologyUniversity of Mississippi Medical CenterJacksonMississippi
| | - Xiaochen He
- Department of Pharmacology and ToxicologyUniversity of Mississippi Medical CenterJacksonMississippi
| | | | - Claude Lechene
- Center of NanoimagingBrigham and Women's HospitalCambridgeMassachusetts
| | - Fan Fan
- Department of Pharmacology and ToxicologyUniversity of Mississippi Medical CenterJacksonMississippi
| | - Richard J. Roman
- Department of Pharmacology and ToxicologyUniversity of Mississippi Medical CenterJacksonMississippi
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Lee CJ, Gardiner BS, Evans RG, Smith DW. A model of oxygen transport in the rat renal medulla. Am J Physiol Renal Physiol 2018; 315:F1787-F1811. [DOI: 10.1152/ajprenal.00363.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The renal medulla is prone to hypoxia. Medullary hypoxia is postulated to be a leading cause of acute kidney injury, so there is considerable interest in predicting the oxygen tension in the medulla. Therefore we have developed a computational model for blood and oxygen transport within a physiologically normal rat renal medulla, using a multilevel modeling approach. For the top-level model we use the theory of porous media and advection-dispersion transport through a realistic three-dimensional representation of the medulla’s gross anatomy to describe blood flow and oxygen transport throughout the renal medulla. For the lower-level models, we employ two-dimensional reaction-diffusion models describing the distribution of oxygen through tissue surrounding the vasculature. Steady-state model predictions at the two levels are satisfied simultaneously, through iteration between the levels. The computational model was validated by simulating eight sets of experimental data regarding renal oxygenation in rats (using 4 sets of control groups and 4 sets of treatment groups, described in 4 independent publications). Predicted medullary tissue oxygen tension or microvascular oxygen tension for control groups and for treatment groups that underwent moderate perturbation in hemodynamic and renal functions is within ±2 SE values observed experimentally. Diffusive shunting between descending and ascending vasa recta is predicted to be only 3% of the oxygen delivered. The validation tests confirm that the computational model is robust and capable of capturing the behavior of renal medullary oxygenation in both normal and early-stage pathological states in the rat.
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Affiliation(s)
- Chang-Joon Lee
- School of Engineering and Information Technology, Murdoch University, Perth, Western Australia, Australia
- Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Bruce S. Gardiner
- School of Engineering and Information Technology, Murdoch University, Perth, Western Australia, Australia
- Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Roger G. Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute, and Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - David W. Smith
- Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Perth, Western Australia, Australia
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22
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Nawata CM, Pannabecker TL. Mammalian urine concentration: a review of renal medullary architecture and membrane transporters. J Comp Physiol B 2018; 188:899-918. [PMID: 29797052 PMCID: PMC6186196 DOI: 10.1007/s00360-018-1164-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 04/23/2018] [Accepted: 05/14/2018] [Indexed: 01/10/2023]
Abstract
Mammalian kidneys play an essential role in balancing internal water and salt concentrations. When water needs to be conserved, the renal medulla produces concentrated urine. Central to this process of urine concentration is an osmotic gradient that increases from the corticomedullary boundary to the inner medullary tip. How this gradient is generated and maintained has been the subject of study since the 1940s. While it is generally accepted that the outer medulla contributes to the gradient by means of an active process involving countercurrent multiplication, the source of the gradient in the inner medulla is unclear. The last two decades have witnessed advances in our understanding of the urine-concentrating mechanism. Details of medullary architecture and permeability properties of the tubules and vessels suggest that the functional and anatomic relationships of these structures may contribute to the osmotic gradient necessary to concentrate urine. Additionally, we are learning more about the membrane transporters involved and their regulatory mechanisms. The role of medullary architecture and membrane transporters in the mammalian urine-concentrating mechanism are the focus of this review.
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Affiliation(s)
- C Michele Nawata
- Department of Physiology, Banner University Medical Center, University of Arizona, 1501 N. Campbell Avenue, Tucson, AZ, 85724-5051, USA.
| | - Thomas L Pannabecker
- Department of Physiology, Banner University Medical Center, University of Arizona, 1501 N. Campbell Avenue, Tucson, AZ, 85724-5051, USA
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23
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Witte J, Mühlbauer M, Braun D, Steinbach A, Golchert J, Rettig R, Grisk O. Renal Soluble Guanylate Cyclase Is Downregulated in Sunitinib-Induced Hypertension. J Am Heart Assoc 2018; 7:e009557. [PMID: 30371202 PMCID: PMC6222942 DOI: 10.1161/jaha.118.009557] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Background The tyrosine kinase inhibitor sunitinib causes hypertension associated with reduced nitric oxide (NO) availability, elevated renal vascular resistance, and decreased fractional sodium excretion. We tested whether (1) nitrate supplementation mitigates sunitinib‐induced hypertension and NO contributes less to renal vascular resistance as well as fractional sodium excretion regulation in sunitinib‐treated rats than in controls; and (2) renal soluble guanylate cyclase (sGC) is downregulated and sGC activation lowers arterial pressure in rats with sunitinib‐induced hypertension. Methods and Results Arterial pressure responses to nitrate supplementation and the effects of systemic and intrarenal NO synthase (NOS) inhibition on renal hemodynamics and fractional sodium excretion were assessed in sunitinib‐treated rats and controls. Renal NOS and sGC mRNA as well as protein abundances were determined by quantitative polymerase chain reaction and Western blot. The effect of the sGC activator cinaciguat on arterial pressure was investigated in sunitinib‐treated rats. Nitrate supplementation did not mitigate sunitinib‐induced hypertension. Endothelium‐dependent reductions in renal vascular resistance were similar in control and sunitinib‐treated animals without and with systemic NOS inhibition. Selective intrarenal NOS inhibition lowered renal medullary blood flow in control but not in sunitinib‐treated rats without significant effects on fractional sodium excretion. Renal cortical sGC mRNA and sGC α1‐subunit protein abundance were less in sunitinib‐treated rats than in controls, and cinaciguat effectively lowered arterial pressure by 15‐20 mm Hg in sunitinib‐treated rats. Conclusions Renal cortical sGC is downregulated in the presence of intact endothelium‐dependent renal vascular resistance regulation in developing sunitinib‐induced hypertension. This suggests that sGC downregulation occurs outside the renal vasculature, increases renal sodium retention, and contributes to nitrate resistance of sunitinib‐induced hypertension.
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Affiliation(s)
- Jeannine Witte
- 1 Institute of Physiology University of Greifswald Greifswald Germany
| | - Melanie Mühlbauer
- 1 Institute of Physiology University of Greifswald Greifswald Germany
| | - Diana Braun
- 1 Institute of Physiology University of Greifswald Greifswald Germany
| | - Antje Steinbach
- 1 Institute of Physiology University of Greifswald Greifswald Germany
| | - Janine Golchert
- 2 Interfaculty Institute for Genetics and Functional Genomics University of Greifswald Greifswald Germany
| | - Rainer Rettig
- 1 Institute of Physiology University of Greifswald Greifswald Germany
| | - Olaf Grisk
- 1 Institute of Physiology University of Greifswald Greifswald Germany
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24
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Odudu A, Nery F, Harteveld AA, Evans RG, Pendse D, Buchanan CE, Francis ST, Fernández-Seara MA. Arterial spin labelling MRI to measure renal perfusion: a systematic review and statement paper. Nephrol Dial Transplant 2018; 33:ii15-ii21. [PMID: 30137581 PMCID: PMC6106644 DOI: 10.1093/ndt/gfy180] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 05/15/2018] [Indexed: 01/03/2023] Open
Abstract
Renal perfusion provides the driving pressure for glomerular filtration and delivers the oxygen and nutrients to fuel solute reabsorption. Renal ischaemia is a major mechanism in acute kidney injury and may promote the progression of chronic kidney disease. Thus, quantifying renal tissue perfusion is critically important for both clinicians and physiologists. Current reference techniques for assessing renal tissue perfusion have significant limitations. Arterial spin labelling (ASL) is a magnetic resonance imaging (MRI) technique that uses magnetic labelling of water in arterial blood as an endogenous tracer to generate maps of absolute regional perfusion without requiring exogenous contrast. The technique holds enormous potential for clinical use but remains restricted to research settings. This statement paper from the PARENCHIMA network briefly outlines the ASL technique and reviews renal perfusion data in 53 studies published in English through January 2018. Renal perfusion by ASL has been validated against reference methods and has good reproducibility. Renal perfusion by ASL reduces with age and excretory function. Technical advancements mean that a renal ASL study can acquire a whole kidney perfusion measurement in less than 5-10 min. The short acquisition time permits combination with other MRI techniques that might inform drug mechanisms and renal physiology. The flexibility of renal ASL has yielded several variants of the technique, but there are limited data comparing these approaches. We make recommendations for acquiring and reporting renal ASL data and outline the knowledge gaps that future research should address.
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Affiliation(s)
- Aghogho Odudu
- Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Fabio Nery
- Developmental Imaging & Biophysics Section, University College London, Great Ormond Street Institute of Child Health, London, UK
| | - Anita A Harteveld
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Roger G Evans
- Department of Physiology, Cardiovascular Disease Program, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Douglas Pendse
- Centre for Medical Imaging, University College London, London, UK
| | - Charlotte E Buchanan
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - Susan T Francis
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK
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25
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Non-Invasive Renal Perfusion Imaging Using Arterial Spin Labeling MRI: Challenges and Opportunities. Diagnostics (Basel) 2018; 8:diagnostics8010002. [PMID: 29303965 PMCID: PMC5871985 DOI: 10.3390/diagnostics8010002] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 12/25/2017] [Accepted: 01/02/2018] [Indexed: 12/28/2022] Open
Abstract
Tissue perfusion allows for delivery of oxygen and nutrients to tissues, and in the kidneys is also a key determinant of glomerular filtration. Quantification of regional renal perfusion provides a potential window into renal (patho) physiology. However, non-invasive, practical, and robust methods to measure renal perfusion remain elusive, particularly in the clinic. Arterial spin labeling (ASL), a magnetic resonance imaging (MRI) technique, is arguably the only available method with potential to meet all these needs. Recent developments suggest its viability for clinical application. This review addresses several of these developments and discusses remaining challenges with the emphasis on renal imaging in human subjects.
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26
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Guerci P, Ergin B, Ince C. The macro- and microcirculation of the kidney. Best Pract Res Clin Anaesthesiol 2017; 31:315-329. [PMID: 29248139 DOI: 10.1016/j.bpa.2017.10.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 10/25/2017] [Indexed: 01/22/2023]
Abstract
Acute kidney injury (AKI) remains one of the main causes of morbidity and mortality in the intensive care medicine today. Its pathophysiology and progress to chronic kidney disease is still under investigation. In addition, the lack of techniques to adequately monitor renal function and microcirculation at the bedside makes its therapeutic resolution challenging. In this article, we review current concepts related to renal hemodynamics compromise as being the event underlying AKI. In doing so, we discuss the physiology of the renal circulation and the effects of alterations in systemic hemodynamics that lead to renal injury specifically in the context of reperfusion injury and sepsis. The ultimate key culprit of AKI leading to failure is the dysfunction of the renal microcirculation. The cellular and subcellular components of the renal microcirculation are discussed and how their injury contributes to AKI is described.
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Affiliation(s)
- Philippe Guerci
- Department of Anesthesiology and Critical Care Medicine, University Hospital of Nancy, France; INSERM U1116, University of Lorraine, Vandoeuvre-Les-Nancy, France; Department of Translational Physiology, Academic Medical Centre, Amsterdam, The Netherlands
| | - Bulent Ergin
- Department of Translational Physiology, Academic Medical Centre, Amsterdam, The Netherlands; Department of Intensive Care Medicine, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands
| | - Can Ince
- Department of Translational Physiology, Academic Medical Centre, Amsterdam, The Netherlands; Department of Intensive Care Medicine, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands.
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27
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Pannabecker TL. Renal vascular pericytes: long overlooked and poorly understood, but clearly important, and what about those regulatory pathways? Am J Physiol Renal Physiol 2017; 314:F67-F69. [PMID: 28971993 DOI: 10.1152/ajprenal.00468.2017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Thomas L Pannabecker
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
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28
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Ngo JP, Ow CP, Gardiner BS, Kar S, Pearson JT, Smith DW, Evans RG. Diffusive shunting of gases and other molecules in the renal vasculature: physiological and evolutionary significance. Am J Physiol Regul Integr Comp Physiol 2016; 311:R797-R810. [DOI: 10.1152/ajpregu.00246.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 07/27/2016] [Indexed: 01/22/2023]
Abstract
Countercurrent systems have evolved in a variety of biological systems that allow transfer of heat, gases, and solutes. For example, in the renal medulla, the countercurrent arrangement of vascular and tubular elements facilitates the trapping of urea and other solutes in the inner medulla, which in turn enables the formation of concentrated urine. Arteries and veins in the cortex are also arranged in a countercurrent fashion, as are descending and ascending vasa recta in the medulla. For countercurrent diffusion to occur, barriers to diffusion must be small. This appears to be characteristic of larger vessels in the renal cortex. There must also be gradients in the concentration of molecules between afferent and efferent vessels, with the transport of molecules possible in either direction. Such gradients exist for oxygen in both the cortex and medulla, but there is little evidence that large gradients exist for other molecules such as carbon dioxide, nitric oxide, superoxide, hydrogen sulfide, and ammonia. There is some experimental evidence for arterial-to-venous (AV) oxygen shunting. Mathematical models also provide evidence for oxygen shunting in both the cortex and medulla. However, the quantitative significance of AV oxygen shunting remains a matter of controversy. Thus, whereas the countercurrent arrangement of vasa recta in the medulla appears to have evolved as a consequence of the evolution of Henle’s loop, the evolutionary significance of the intimate countercurrent arrangement of blood vessels in the renal cortex remains an enigma.
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Affiliation(s)
- Jennifer P. Ngo
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology and
| | - Connie P.C. Ow
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology and
| | - Bruce S. Gardiner
- School of Engineering and Information Technology, Murdoch University, Perth, Western Australia
| | - Saptarshi Kar
- School of Computer Science and Software Engineering, The University of Western Australia, Perth, Australia; and
| | - James T. Pearson
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology and
- Monash Biomedical Imaging Facility, Monash University, Melbourne, Australia
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan
| | - David W. Smith
- School of Computer Science and Software Engineering, The University of Western Australia, Perth, Australia; and
| | - Roger G. Evans
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology and
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29
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Pollock DM. Comprehensive Physiology: a tool for advanced education in physiology. ADVANCES IN PHYSIOLOGY EDUCATION 2016; 40:275-277. [PMID: 27445273 DOI: 10.1152/advan.00087.2016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 06/14/2016] [Indexed: 06/06/2023]
Affiliation(s)
- David M Pollock
- Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
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30
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31
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Ahmeda AF, Alzoghaibi M. Factors regulating the renal circulation in spontaneously hypertensive rats. Saudi J Biol Sci 2015; 23:441-51. [PMID: 27298576 PMCID: PMC4890190 DOI: 10.1016/j.sjbs.2015.06.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 06/14/2015] [Accepted: 06/19/2015] [Indexed: 01/17/2023] Open
Abstract
Hypertension is one of the leading causes of health morbidity and mortality which are linked to many life threatening diseases such as stroke heart problems and renal dysfunction. The integrity of renal microcirculation is crucial to maintaining the clearance and the excretory function in the normotensive and hypertensive conditions. Furthermore, any alteration in the renal function is involved in the pathophysiology of hypertension. The aim of this review is to provide a brief discussion of some factors that regulate renal haemodynamics in spontaneously hypertensive rats, an animal model of hypertension, and how these factors are linked to the disease.
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Affiliation(s)
- Ahmad F Ahmeda
- Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Mohammed Alzoghaibi
- Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
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32
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Menzies RI, Unwin RJ, Bailey MA. Renal P2 receptors and hypertension. Acta Physiol (Oxf) 2015; 213:232-41. [PMID: 25345692 DOI: 10.1111/apha.12412] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 09/23/2014] [Accepted: 10/17/2014] [Indexed: 12/11/2022]
Abstract
The regulation of extracellular fluid volume is a key component of blood pressure homeostasis. Long-term blood pressure is stabilized by the acute pressure natriuresis response by which changes in renal perfusion pressure evoke corresponding changes in renal sodium excretion. A wealth of experimental evidence suggests that a defect in the pressure natriuresis response contributes to the development and maintenance of hypertension. The mechanisms underlying the relationship between renal perfusion pressure and sodium excretion are incompletely understood. Increased blood flow through the vasa recta increases renal interstitial hydrostatic pressure, thereby reducing the driving force for transepithelial sodium reabsorption. Paracrine signalling also contributes to the overall natriuretic response by inhibiting tubular sodium reabsorption in several nephron segments. In this brief review, we discuss the role of purinergic signalling in the renal control of blood pressure. ATP is released from renal tubule and vascular cells in response to increased flow and can activate P2 receptor subtypes expressed in both epithelial and vascular endothelial/smooth muscle cells. In concert, these effects integrate the vascular and tubular responses to increased perfusion pressure and targeting P2 receptors, particularly P2X7, may prove beneficial for treatment of hypertension.
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Affiliation(s)
- R. I. Menzies
- University/British Heart Foundation; Centre for Cardiovascular Science; The University of Edinburgh; Edinburgh UK
- MRC Institute for Genetics and Molecular Medicine; The University of Edinburgh; Edinburgh UK
| | - R. J. Unwin
- UCL Centre for Nephrology; University College London; London UK
| | - M. A. Bailey
- University/British Heart Foundation; Centre for Cardiovascular Science; The University of Edinburgh; Edinburgh UK
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33
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Cowley AW, Abe M, Mori T, O'Connor PM, Ohsaki Y, Zheleznova NN. Reactive oxygen species as important determinants of medullary flow, sodium excretion, and hypertension. Am J Physiol Renal Physiol 2014; 308:F179-97. [PMID: 25354941 DOI: 10.1152/ajprenal.00455.2014] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The physiological evidence linking the production of superoxide, hydrogen peroxide, and nitric oxide in the renal medullary thick ascending limb of Henle (mTAL) to regulation of medullary blood flow, sodium homeostasis, and long-term control of blood pressure is summarized in this review. Data obtained largely from rats indicate that experimentally induced elevations of either superoxide or hydrogen peroxide in the renal medulla result in reduction of medullary blood flow, enhanced Na(+) reabsorption, and hypertension. A shift in the redox balance between nitric oxide and reactive oxygen species (ROS) is found to occur naturally in the Dahl salt-sensitive (SS) rat model, where selective reduction of ROS production in the renal medulla reduces salt-induced hypertension. Excess medullary production of ROS in SS rats emanates from the medullary thick ascending limbs of Henle [from both the mitochondria and membrane NAD(P)H oxidases] in response to increased delivery and reabsorption of excess sodium and water. There is evidence that ROS and perhaps other mediators such as ATP diffuse from the mTAL to surrounding vasa recta capillaries, resulting in medullary ischemia, which thereby contributes to hypertension.
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Affiliation(s)
- Allen W Cowley
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Michiaki Abe
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Takefumi Mori
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Paul M O'Connor
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Yusuke Ohsaki
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
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Abstract
Alterations in water homeostasis can disturb cell size and function. Although most cells can internally regulate cell volume in response to osmolar stress, neurons are particularly at risk given a combination of complex cell function and space restriction within the calvarium. Thus, regulating water balance is fundamental to survival. Through specialized neuronal "osmoreceptors" that sense changes in plasma osmolality, vasopressin release and thirst are titrated in order to achieve water balance. Fine-tuning of water absorption occurs along the collecting duct, and depends on unique structural modifications of renal tubular epithelium that confer a wide range of water permeability. In this article, we review the mechanisms that ensure water homeostasis as well as the fundamentals of disorders of water balance.
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Affiliation(s)
- John Danziger
- Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - Mark L Zeidel
- Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
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35
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Zhang Z, Payne K, Pallone TL. Syncytial communication in descending vasa recta includes myoendothelial coupling. Am J Physiol Renal Physiol 2014; 307:F41-52. [PMID: 24785189 DOI: 10.1152/ajprenal.00178.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Using dual cell patch-clamp recording, we examined pericyte, endothelial, and myoendothelial cell-to-cell communication in descending vasa recta. Graded current injections into pericytes or endothelia yielded input resistances of 220 ± 21 and 128 ± 20 MΩ, respectively (P < 0.05). Injection of positive or negative current into an endothelial cell depolarized and hyperpolarized adjacent endothelial cells, respectively. Similarly, current injection into a pericyte depolarized and hyperpolarized adjacent pericytes. During myoendothelial studies, current injection into a pericyte or an endothelial cell yielded small, variable, but significant change of membrane potential in heterologous cells. Membrane potentials of paired pericytes or paired endothelia were highly correlated and identical. Paired measurements of resting potentials in heterologous cells were also correlated, but with slight hyperpolarization of the endothelium relative to the pericyte, -55.2 ± 1.8 vs. -52.9 ± 2.2 mV (P < 0.05). During dual recordings, angiotensin II or bradykinin stimulated temporally identical variations of pericyte and endothelial membrane potential. Similarly, voltage clamp depolarization of pericytes or endothelial cells induced parallel changes of membrane potential in the heterologous cell type. We conclude that the descending vasa recta endothelial syncytium is of lower resistance than the pericyte syncytium and that high-resistance myoendothelial coupling also exists. The myoendothelial communication between pericytes and endothelium maintains near identity of membrane potentials at rest and during agonist stimulation. Finally, endothelia membrane potential lies slightly below pericyte membrane potential, suggesting a tonic role for the former to hyperpolarize the latter and provide a brake on vasoconstriction.
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Affiliation(s)
- Zhong Zhang
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Kristie Payne
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Thomas L Pallone
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
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36
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Moss R, Layton AT. Dominant factors that govern pressure natriuresis in diuresis and antidiuresis: a mathematical model. Am J Physiol Renal Physiol 2014; 306:F952-69. [PMID: 24553433 DOI: 10.1152/ajprenal.00500.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
We have developed a whole kidney model of the urine concentrating mechanism and renal autoregulation. The model represents the tubuloglomerular feedback (TGF) and myogenic mechanisms, which together affect the resistance of the afferent arteriole and thus glomerular filtration rate. TGF is activated by fluctuations in macula densa [Cl(-)] and the myogefnic mechanism by changes in hydrostatic pressure. The model was used to investigate the relative contributions of medullary blood flow autoregulation and inhibition of transport in the proximal convoluted tubule to pressure natriuresis in both diuresis and antidiuresis. The model predicts that medullary blood flow autoregulation, which only affects the interstitial solute composition in the model, has negligible influence on the rate of NaCl excretion. However, it exerts a significant effect on urine flow, particularly in the antidiuretic kidney. This suggests that interstitial washout has significant implications for the maintenance of hydration status but little direct bearing on salt excretion, and that medullary blood flow may only play a signaling role for stimulating a pressure-natriuresis response. Inhibited reabsorption in the model proximal convoluted tubule is capable of driving pressure natriuresis when the known actions of vasopressin on the collecting duct epithelium are taken into account.
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Affiliation(s)
- Robert Moss
- Dept. of Mathematics, Duke Univ., Box 90320, Durham, NC 27708-0320.
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37
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Abstract
The renal medulla produces concentrated urine through the generation of an osmotic gradient that progressively increases from the cortico-medullary boundary to the inner medullary tip. In the outer medulla, the osmolality gradient arises principally from vigorous active transport of NaCl, without accompanying water, from the thick ascending limbs of short- and long-looped nephrons. In the inner medulla, the source of the osmotic gradient has not been identified. Recently, there have been important advances in our understanding of key components of the urine-concentrating mechanism, including (a) better understanding of the regulation of water, urea, and sodium transport proteins; (b) better resolution of the anatomical relationships in the medulla; and (c) improvements in mathematical modeling of the urine-concentrating mechanism. Continued experimental investigation of signaling pathways regulating transepithelial transport, both in normal animals and in knockout mice, and incorporation of the resulting information into mathematical simulations may help to more fully elucidate the mechanism for concentrating urine in the inner medulla.
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Affiliation(s)
- Jeff M. Sands
- Renal Division, Department of Medicine, and Department of Physiology,Emory University School of Medicine, Atlanta, Georgia 30322
| | - Harold E. Layton
- Department of Mathematics, Duke University, Durham, North Carolina 27708-0320
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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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Moss R, Thomas SR. Hormonal regulation of salt and water excretion: a mathematical model of whole kidney function and pressure natriuresis. Am J Physiol Renal Physiol 2013; 306:F224-48. [PMID: 24107423 DOI: 10.1152/ajprenal.00089.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We present a lumped-nephron model that explicitly represents the main features of the underlying physiology, incorporating the major hormonal regulatory effects on both tubular and vascular function, and that accurately simulates hormonal regulation of renal salt and water excretion. This is the first model to explicitly couple glomerulovascular and medullary dynamics, and it is much more detailed in structure than existing whole organ models and renal portions of multiorgan models. In contrast to previous medullary models, which have only considered the antidiuretic state, our model is able to regulate water and sodium excretion over a variety of experimental conditions in good agreement with data from experimental studies of the rat. Since the properties of the vasculature and epithelia are explicitly represented, they can be altered to simulate pathophysiological conditions and pharmacological interventions. The model serves as an appropriate starting point for simulations of physiological, pathophysiological, and pharmacological renal conditions and for exploring the relationship between the extrarenal environment and renal excretory function in physiological and pathophysiological contexts.
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Affiliation(s)
- Robert Moss
- Mathematics Dept., Duke Univ., Box 90320, Durham, NC 27708-0320.
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Mechanisms of pressure-diuresis and pressure-natriuresis in Dahl salt-resistant and Dahl salt-sensitive rats. BMC PHYSIOLOGY 2012; 12:6. [PMID: 22583378 PMCID: PMC3536597 DOI: 10.1186/1472-6793-12-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 04/04/2012] [Indexed: 12/11/2022]
Abstract
Background Data on blood flow regulation, renal filtration, and urine output in salt-sensitive Dahl S rats fed on high-salt (hypertensive) and low-salt (prehypertensive) diets and salt-resistant Dahl R rats fed on high-salt diets were analyzed using a mathematical model of renal blood flow regulation, glomerular filtration, and solute transport in a nephron. Results The mechanism of pressure-diuresis and pressure-natriuresis that emerges from simulation of the integrated systems is that relatively small increases in glomerular filtration that follow from increases in renal arterial pressure cause relatively large increases in urine and sodium output. Furthermore, analysis reveals the minimal differences between the experimental cases necessary to explain the observed data. It is determined that differences in renal afferent and efferent arterial resistances are able to explain all of the qualitative differences in observed flows, filtration rates, and glomerular pressure as well as the differences in the pressure-natriuresis and pressure-diuresis relationships in the three groups. The model is able to satisfactorily explain data from all three groups without varying parameters associated with glomerular filtration or solute transport in the nephron component of the model. Conclusions Thus the differences between the experimental groups are explained solely in terms of difference in blood flow regulation. This finding is consistent with the hypothesis that, if a shift in the pressure-natriuresis relationship is the primary cause of elevated arterial pressure in the Dahl S rat, then alternation in how renal afferent and efferent arterial resistances are regulated represents the primary cause of chronic hypertension in the Dahl S rat.
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