Interactive virtual 3D image reconstruction to assist renal surgery in patients with fusion anomalies of the kidney

Objective: Renal fusion anomalies are rare and usually present as horseshoe kidneys or crossed fusion ectopia. The complex renal anatomy seen in patients with these anomalies can present a challenge. Pre-operative planning is therefore paramount in the surgical management of these cases. Herein we report the use of interactive virtual three-dimensional (3D) reconstruction to aid renal surgery in patients with fusion anomalies of the kidney. Materials and Methods: A total of seven cases were performed between May 2016 and October 2020. 3D reconstruction was rendered by Innersight Labs using pre-operative computed tomography (CT) scans. Results: Five patients had malignant disease and two patients had benign pathology. Robotic and open operations were performed in four and three patients, respectively. Conclusion: The use of 3D reconstruction in the cases reported in this series allowed for the identification of variations in renal vasculature, and this informed the choice of operative approach. Oxford Centre for Evidence-Based Medicine Evidence Level: 4

Comparative Studies of Renin-Null Zebrafish and Mice Provide New Functional Insights

Background: The renin-angiotensin system is highly conserved across vertebrates, including zebrafish, which possess orthologous genes coding for renin-angiotensin system proteins, and specialized mural cells of the kidney arterioles, capable of synthesising and secreting renin. Methods: We generated zebrafish with CRISPR-Cas9-targeted knockout of renin ( ren −/− ) to investigate renin function in a low blood pressure environment. We used single-cell (10×) RNA sequencing analysis to compare the transcriptome profiles of renin lineage cells from mesonephric kidneys of ren −/− with ren +/+ zebrafish and with the metanephric kidneys of Ren1 c−/− and Ren1 c +/+ mice. Results: The ren −/− larvae exhibited delays in larval growth, glomerular fusion and appearance of a swim bladder, but were viable and withstood low salinity during early larval stages. Optogenetic ablation of renin-expressing cells, located at the anterior mesenteric artery of 3-day-old larvae, caused a loss of tone, due to diminished contractility. The ren −/− mesonephric kidney exhibited vacuolated cells in the proximal tubule, which were also observed in Ren1 c−/− mouse kidney. Fluorescent reporters for renin and smooth muscle actin ( tg(ren:LifeAct-RFP; acta2:EGFP )), revealed a dramatic recruitment of renin lineage cells along the renal vasculature of adult ren −/− fish, suggesting a continued requirement for renin, in the absence of detectable angiotensin metabolites, as seen in the Ren1 YFP Ren1 c−/− mouse. Both phenotypes were rescued by alleles lacking the potential for glycosylation at exon 2, suggesting that glycosylation is not essential for normal physiological function. Conclusions: Phenotypic similarities and transcriptional variations between mouse and zebrafish renin knockouts suggests evolution of renin cell function with terrestrial survival.

Development of a Novel Perfusable Solution for ex vivo Preservation: Towards Photosynthetic Oxygenation for Organ Transplantation

Oxygen is the key molecule for aerobic metabolism, but no animal cells can produce it, creating an extreme dependency on external supply. In contrast, microalgae are photosynthetic microorganisms, therefore, they are able to produce oxygen as plant cells do. As hypoxia is one of the main issues in organ transplantation, especially during preservation, the main goal of this work was to develop the first generation of perfusable photosynthetic solutions, exploring its feasibility for ex vivo organ preservation. Here, the microalgae Chlamydomonas reinhardtii was incorporated in a standard preservation solution, and key aspects such as alterations in cell size, oxygen production and survival were studied. Osmolarity and rheological features of the photosynthetic solution were comparable to human blood. In terms of functionality, the photosynthetic solution proved to be not harmful and to provide sufficient oxygen to support the metabolic requirement of zebrafish larvae and rat kidney slices. Thereafter, isolated porcine kidneys were perfused, and microalgae reached all renal vasculature, without inducing damage. After perfusion and flushing, no signs of tissue damage were detected, and recovered microalgae survived the process. Altogether, this work proposes the use of photosynthetic microorganisms as vascular oxygen factories to generate and deliver oxygen in isolated organs, representing a novel and promising strategy for organ preservation.

Evaluation of 2D super-resolution ultrasound imaging of the rat renal vasculature using ex vivo micro-computed tomography

Super-resolution ultrasound imaging (SRUS) enables in vivo microvascular imaging of deeper-lying tissues and organs, such as the kidneys or liver. The technique allows new insights into microvascular anatomy and physiology and the development of disease-related microvascular abnormalities. However, the microvascular anatomy is intricate and challenging to depict with the currently available imaging techniques, and validation of the microvascular structures of deeper-lying organs obtained with SRUS remains difficult. Our study aimed to directly compare the vascular anatomy in two in vivo 2D SRUS images of a Sprague–Dawley rat kidney with ex vivo μCT of the same kidney. Co-registering the SRUS images to the μCT volume revealed visually very similar vascular features of vessels ranging from ~ 100 to 1300 μm in diameter and illustrated a high level of vessel branching complexity captured in the 2D SRUS images. Additionally, it was shown that it is difficult to use μCT data of a whole rat kidney specimen to validate the super-resolution capability of our ultrasound scans, i.e., validating the actual microvasculature of the rat kidney. Lastly, by comparing the two imaging modalities, fundamental challenges for 2D SRUS were demonstrated, including the complexity of projecting a 3D vessel network into 2D. These challenges should be considered when interpreting clinical or preclinical SRUS data in future studies.

Emerging Insights Into Chronic Renal Disease Pathogenesis in Hypertension From Human and Animal Genomic Studies

The pathogenic links between elevated blood pressure and chronic kidney disease remain obscure. This article examines progress in population genetics and in animal models of hypertension and chronic kidney disease. It also provides a critique of the application of genome-wide association studies to understanding the heritability of renal function. Emerging themes identified indicate that heritable risk of chronic kidney disease in hypertension can arise from genetic variation in (1) glomerular and tubular protein handling mechanisms; (2) autoregulatory capacity of the renal vasculature; and (3) innate and adaptive immune mechanisms. Increased prevalence of hypertension-associated chronic kidney disease that occurs with aging may reflect amplification of heritable risks by normal aging processes affecting immunity and autoregulation.

Avocado Oil Prevents Kidney Injury and Normalizes Renal Vasodilation after Adrenergic Stimulation in Hypertensive Rats: Probable Role of Improvement in Mitochondrial Dysfunction and Oxidative Stress

Hypertension impairs the function of the kidney and its vasculature. Adrenergic activation is involved in these processes by promoting oxidative stress and mitochondrial dysfunction. Thus, the targeting of mitochondrial function and mitochondrial oxidative stress may be an approach to alleviate hypertensive kidney damage. Avocado oil, a source of oleic acid and antioxidants, improves mitochondrial dysfunction, decreases mitochondrial oxidative stress, and enhances vascular function in hypertensive rats. However, whether avocado oil improves the function of renal vasculature during the adrenergic stimulation, and if this is related to improvement in renal damage and enhancement of mitochondrial activity is unknown. Thus, the effects of avocado oil on renal vascular responses to adrenergic stimulation, mitochondrial dysfunction, oxidative stress, and renal damage were compared with prazosin, an antagonist of α1-adrenoceptors, in hypertensive rats induced by L-NAME. Avocado oil or prazosin decreased blood pressure, improved endothelium—dependent renal vasodilation, prevented mitochondrial dysfunction and kidney damage in hypertensive rats. However, avocado oil, but not prazosin, decreased mitochondrial ROS generation and improved the redox state of mitochondrial glutathione. These results suggest that avocado oil and prazosin prevented hypertensive renal damage due to the improvement in mitochondrial function.

Role of CT Angiography in Diagnosis of Reno-Vascular Abnormalities

Background: Reno-vascular disease is a complex disorder, the most common cause of which is RAS. Multi detector computed tomography angiography (MDCTA) plays an important role in assessment of the renal vasculature. Despite conventional angiography is still considered the gold standard in reno-vascular imaging, MDCTA is increasingly used as it is less invasive, easily applicable and available. Aim of the Study: In our study we aimed to assess the role of CT Angiography in diagnosis of renal vasculature abnormalities. Patients and Methods: This prospective study was carried out at The Radio-diagnosis and Medical Imaging Department in our institute, conducted on 40 Patients who are clinically suspected to have reno-vascular abnormalities in the period from September 2018 to February 2021. Their ages ranged from 33 to 56 years old. Results: Based on CTA findings, out of 40 patients, 6 (15%) patients were confirmed to have accessory renal arteries, 6 (15%) patients had renal artery aneurysm, 6 (15%) patients had nutcracker syndrome, 6 (15%) patients had dual venous drainage of both kidneys, two of them showed retro-aortic left renal vein &10 (25%) patients were confirmed to have renal artery stenosis. Conclusion: CT Angiography with multiplanar reconstruction and three-dimensional display is valuable in studying patients with reno-vascular lesions involving the proximal renal vessels. MDCT angiography is advantageous being a non-invasive technique that can be done on outpatient basis without pre or post-procedure admission, no special post-procedure care and less cost.

Abstract MP25: Defining The Role Of Renin Lineage Cells During Regeneration After Release Of Partial Ureteral Obstruction In Neonatal Mice.

Our previous study on a partial unilateral ureteral obstruction (pUUO) model in neonatal mice showed that the release of obstruction halts the progression of kidney damage and leads to a remarkable repair of the kidney with improvement in renal blood flow. In the current study, we aim to understand the role of mural cells of the renin lineage during kidney damage and repair in the neonatal pUUO model. Our results show a marked increase in renin-positive areas in kidneys obstructed for 3W (Sham-3W: 0.70±0.10%, n=3; Obstructed-3W: 1.82±0.43%, n=3). However, relief of obstruction at 1W restored the renin-positive areas to sham levels (Post-release-2W: 0.70±0.09%; n=3). Lineage tracing using Ren1 d Cre;mTmG mice revealed a significant increase in GFP+ cells in the obstructed kidneys, with a decrease post-release. To understand further the dynamic changes in cells of renin lineage due to obstruction, we ablated the renin cells using DTA (Diphtheria toxin subunit A). We crossed the DTA fl/fl mice with Ren1 d -DTA het ;Ren1 d Cre;mTmG mice and performed pUUO in the resultant pups with DTA in the renin cells (DTA+). DTA+ animals showed thinning of the renal vasculature and a 90% reduction in renin-positive area compared to controls [Control: 0.70±0.10% (n=3); DTA+: 0.06±0.03% (n=3)]. In addition, there was no significant increase in the renin-positive area post-obstruction [Sham-3W: 0.06±0.04% (n=3); Obstructed-3W: 0.12±0.05% (n=4); Post-release-2W: 0.08±0.03% (n=4)]. These results indicate that ablation of renin cells abolished the obstruction-mediated surge in the renin expression. However, measurement of interstitial collagen positive area indicated that despite the absence of renin cells, the fibrotic damage due to obstruction recovered remarkably post-release [Collagen positive area: Sham-3W: 3.38±0.67% (n=3) Obstructed-3W: 62.98±31.50% (n=3); Post-release-2W: 10.93±5.46% (n=4)]. Similarly, vascular damage induced by persistent obstruction and recovery following the relief of obstruction was similar between the DTA+ and non-DTA animals. Our results imply that though the renin and renin lineage cells increase in obstructed kidneys, ablation of renin cells does not affect the regeneration capacity of kidneys following the relief of obstruction.

Connexin mRNA distribution in adult mouse kidneys

Kidneys are thought to express eight different connexin isoforms (i.e., Cx 26, 30, 32, 37, 40, 43, 45, and 46), which form either hemichannels or gap junctions serving to intercellular communication and functional synchronization. Proper function of connexins has already been shown to be crucial for regulation of renal hemodynamics and renin secretion, and there is also growing evidence for connexins to play a role in pathologic conditions such as renal fibrosis or diabetic nephropathy. Therefore, exact intrarenal localization of the different connexin isoforms gains particular interest. Until now intrarenal expression of connexins has mainly been examined by immunohistochemistry, which in part generated conflicting results depending on antibodies and fixation protocols used. In this work, we used fluorescent RNAscope as an alternative technical approach to localize renal connexin mRNAs in healthy mouse kidneys. Addition of RNAscope probes for cell type specific mRNAs was used to assign connexin mRNA signals to specific cell types. We hereby found Cx26 mRNA strongly expressed in proximal tubules, Cx30 mRNA was selectively detected in the urothelium, and Cx32 mRNA was found in proximal tubules and to a lesser extent also in collecting ducts. Cx37 mRNA was mainly associated with vascular endothelium, Cx40 mRNA was largely found in glomerular mesangial and less in vascular endothelial cells, Cx43 mRNA was sparsely expressed by interstitial cells of all kidney zones, and Cx45 mRNA was predominantly found in smooth muscle cell layers of both blood vessels and ureter as well as in mesangial and interstitial (fibroblastic) cells. Cx46 mRNA could not be detected. In summary our results essentially confirm previous data on connexin expression in the renal vasculature and in glomeruli. In addition, they demonstrate strong connexin gene expression in proximal tubules, and they suggest significant connexin expression in resident tubulointerstitial cells.