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Endoscopic and biopsy findings have identified two distinct phenotypes among individuals with calcium oxalate (CaOx) kidney stones. The first type has normal renal papillae but shows interstitial mineral deposition, known as Randall's plaque. The other phenotype presents with collecting duct plugging and a higher incidence of loss of papilla tissue mass. With Randall's plaque, renal papilla injury involves the loss of small patches of calcified tissue (Randall's plaque detaching with the stone), which likely results in damage to only a few nephrons. In contrast, collecting duct mineral plugs are very large, causing obstruction to tubular flow. Since each terminal collecting duct drains thousands of nephrons, ductal plugs could lead to the degeneration of many nephrons and a significant loss of renal glomeruli. New visualization techniques for immune cells in papillary biopsies have revealed that the Randall's plaque phenotype is marked by the accumulation of macrophages around the plaque regions. In contrast, preliminary data on the plugging phenotype shows collecting duct damage with mineral plugs and increased T-lymphocytes throughout the papilla. These regions also show tubulitis, i.e., T-cell infiltration into nearby collecting duct epithelium. This suggests that while some CaOx stone formers may have some papillary inflammation but with minimal damage to nephrons, others suffer from obstruction to flow for many nephrons that may also include destructive inflammation in the renal tissue. We propose that CaOx stone formers with the plugging phenotype will have a higher long-term risk for loss of renal function., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Thallium (Tl) is one of the most toxic heavy metals, associated with accidental poisoning and homicide. It causes acute and chronic systemic diseases, including gastrointestinal and cardiovascular diseases and kidney failure. However, few studies have investigated the mechanism by which Tl induces acute kidney injury (AKI). This study investigated the toxic effects of Tl on the histology and function of rat kidneys using biochemical and histopathological assays after intraperitoneal thallium sulfate administration (30 mg/kg). Five days post-administration, rats exhibited severely compromised kidney function. Low-vacuum scanning electron microscopy revealed excessive calcium (Ca) deposition in the outer medulla of Tl-loaded rats, particularly in the medullary thick ascending limb (mTAL) of the loop of Henle. Tl accumulated in the mTAL, accompanied by mitochondrial dysfunction in this segment. Tl-loaded rats showed reduced expression of kidney transporters and channels responsible for Ca 2+ reabsorption in the mTAL. Pre-administration of the Na-K-Cl cotransporter 2 (NKCC2) inhibitor furosemide alleviated Tl accumulation and mitochondrial abnormalities in the mTAL. These findings suggest that Tl nephrotoxicity is associated with preferential Tl reabsorption in the mTAL via NKCC2, leading to mTAL mitochondrial dysfunction and disrupted Ca 2+ reabsorption, culminating in mTAL-predominant Ca crystal deposition and AKI. These findings on the mechanism of Tl nephrotoxicity may contribute to the development of novel therapeutic approaches to counter Tl poisoning. Moreover, the observation of characteristic Ca crystal deposition in the outer medulla provides new insights into diagnostic challenges in Tl intoxication., (© 2024. The Author(s).)

Objectives: Most functional magnetic resonance research has primarily examined alterations in the affected kidney, often neglecting the contralateral kidney. Our study aims to investigate whether imaging parameters accurately depict changes in both the renal cortex and medulla in a unilateral ureteral obstruction rat model, thereby showcasing the utility of intravoxel incoherent motion (IVIM) in evaluating contralateral renal changes., Methods: Six rats underwent MR scans and were subsequently sacrificed for baseline histological examination. Following the induction of left ureteral obstruction, 48 rats were scanned, and the histopathological examinations were conducted on days 3, 7, 10, 14, 21, 28, 35, and 42. The apparent diffusion coefficient (ADC), pure molecular diffusion (D), pseudodiffusion (D*), and perfusion fraction (f) values were measured using IVIM., Results: On the 10 th day of obstruction, both cortical and medullary ADC values differed significantly between the UUO10 group and the sham group ( p  < 0.01). The cortical D values showed statistically significant differences between UUO3 group and sham group ( p  < 0.01) but not among UUO groups at other time point. Additionally, the cortical and medullary f values were statistically significant between the UUO21 group and the sham group ( p  < 0.01). Especially, the cortical f values exhibited significant differences between the UUO21 group and the UUO groups with shorter obstruction time (at time point of 3, 7, 10, 14 day) ( p  < 0.01)., Conclusions: Significant hemodynamic alterations were observed in the contralateral kidney following renal obstruction. IVIM accurately captures changes in the unobstructed kidney. Particularly, the cortical f value exhibits the highest potential for assessing contralateral renal modifications.

We aimed to evaluate the correlation between endoscopic papillary abnormalities (PA) and high renal papilla Hounsfield density (PHD) on CT scan in patients who underwent flexible ureteroscopic treatment (fURS) for renal stones. We retrospectively assessed patients from a prospectively collected database who were treated with fURS for renal stones between May 2016 and October 2020. PHD was measured on preoperative CT-scan by a radiologist blinded from the intraoperative aspect of the papillae. Correlation was examined between high PHD (≥ 43 HU) and PA described in fURS, stone composition, metabolic abnormalities, … Out of 159 consecutive cases, 131 were eligible for analysis with available preoperative CT-scan. Median age was 55 years (IQR 43-67) and median PHD was 40 (IQR 36-45). Eighty patients (61%) had PHD < 43, and 51 patients (39%) had PHD ≥ 43. In univariate and multivariate analysis, only young age (p-value = 0.017) and insufficient diuresis (p-value = 0.008) were correlated with high PHD. No significant correlation was found with PA described during endoscopy, including the intensity of Randall's plaques. In this study, high PHD appears to be only a sign of insufficient diuresis, with no significant correlation with potential PA., (© 2024. The Author(s).)

Alexander Randall first published renal papillary tip findings from stone formers in 1937, paving the way for endoscopic assessment to study stone pathogenesis. We performed a literature search to evaluate the safety of papillary tip biopsy and clinical insights gained from modern renal papillary investigations. A search on the topic of renal papillary biopsy provided an overview of Randall's plaques (RP), classification systems for renal papillary grading, and a summary of procedure type, complications, and outcomes. Within 26 identified manuscripts, 660 individuals underwent papillary tip biopsy percutaneously (n = 562), endoscopically (n = 37), or unspecified (n = 23). Post-operative hemoglobin changes were similar to controls. One individual (0.2%) reported fever > 38°, and long-term mean serum creatinine post-biopsy (n = 32) was unchanged. Biopsies during ureteroscopy or PCNL added ~20-30 min of procedure time. Compared to controls, papillary plaque-containing tissue had upregulation in pro-inflammatory genes, immune cells, and cellular apoptosis. Urinary calcium and papillary plaque coverage were found to differ between RP and non-RP stone formers, suggesting differing underlying pathophysiology for these groups. Two renal papillary scoring systems have been externally validated and are used to classify stone formers. Overall, this review shows that renal papillary biopsies have a low complication profile with high potential for further research. Systematic adaption of a papillary grading scale, newer tissue analysis techniques, and the development of animal models of Randall's plaque may allow further exploration of plaque pathogenesis and identify targets for prevention therapies in patients with nephrolithiasis., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Renal medullary angiitis is characterized by interstitial hemorrhaging in the medulla with neutrophil infiltration. An 81-year-old man presented with a fever, kidney dysfunction, and purpura of the legs, which was diagnosed as leukocytoclastic vasculitis. Proteinase 3 antineutrophil cytoplasmic antibodies were weakly positive. A kidney biopsy showed severe tubulointerstitial hemorrhaging with neutrophilic infiltration in the perivascular areas surrounding the vasa recta in the medulla without crescent formation in the glomeruli. An immunofluorescence analysis was negative, and electron microscopy revealed no immune-dense deposits, ruling out immunoglobulin A vasculitis. Intravenous methylprednisolone for three days and plasma exchange followed by oral prednisolone improved his general condition.

Background: Renal steatosis is an abnormal accumulation of fat in the kidney and may cause chronic kidney disease (CKD) or CKD progression., Objectives: This pilot study aimed to evaluate the quantitative measurability of the parenchymal distribution of lipid deposition in the renal cortex and medulla using chemical shift magnetic resonance imaging (MRI) and investigate its relationship with clinical stages in CKD patients., Material and Methods: The study groups included CKD patients with diabetes (CKD-d) (n = 42), CKD patients without diabetes (CKD-nd) (n = 31) and control subjects (n = 15), all of whom underwent a 1.5T MRI of the abdomen using the Dixon two-point method. The fat fraction (FF) values in the renal cortex and medulla were calculated from measurements made on Dixon sequences, and then compared between the groups., Results: The cortical FF value was higher than the medullary FF value in control (0.057 (0.053-0.064) compared to 0.045 (0.039-0.052)), CKD-nd (0.066 (0.059-0.071) compared to 0.063 (0.054-0.071)), and CKD-d (0.081 (0.071-0.091) compared to 0.069 (0.061-0.077)) groups (all p < 0.001). The CKD-d group cortical FF values were higher than those of the CKD-nd group (p < 0.001). The FF values began increasing at CKD stages 2 and 3, and reached statistical significance at stages 4 and 5 in CKD patients (p < 0.001)., Conclusions: Renal parenchymal lipid deposition can be quantified separately in the cortex and medulla using chemical shift MRI. Fat accumulation occurred in cortical and medullary parenchyma in CKD patients, though predominantly in the cortex. This accumulation increased proportionally with the disease stage.

Effective prevention of recurrent kidney stone disease requires the understanding of the mechanisms of its formation. Numerous in vivo observations have demonstrated that a large number of pathological calcium oxalate kidney stones develop on an apatitic calcium phosphate deposit, known as Randall's plaque. In an attempt to understand the role of the inorganic hydroxyapatite phase in the formation and habits of calcium oxalates, we confined their growth under dynamic physicochemical and flow conditions in a reversible microfluidic channel coated with hydroxyapatite. Using multi-scale characterization techniques including scanning electron and Raman microscopy, we showed the successful formation of carbonated hydroxyapatite as found in Randall's plaque. This was possible due to a new two-step flow seed-mediated growth strategy which allowed us to coat the channel with carbonated hydroxyapatite. Precipitation of calcium oxalates under laminar flow from supersaturated solutions of oxalate and calcium ions showed that the formation of crystals is a substrate and time dependent complex process where diffusion of oxalate ions to the surface of carbonated hydroxyapatite and the solubility of the latter are among the most important steps for the formation of calcium oxalate crystals. Indeed when an oxalate solution was flushed for 24 h, dissolution of the apatite layer and formation of calcium carbonate calcite crystals occurred which seems to promote calcium oxalate crystal formation. Such a growth route has never been observed in vivo in the context of kidney stones. Under our experimental conditions, our results do not show any direct promoting role of carbonated hydroxyapatite in the formation of calcium oxalate crystals, consolidating therefore the important role that macromolecules can play in the process of nucleation and growth of calcium oxalate crystals on Randall's plaque.

Mass spectrometry-based proteomics has been extensively applied to current biomedical research. From such large-scale identification of proteins, several computational tools have been developed for determining protein-protein interactions (PPI) network and functional significance of the identified proteins and their complex. Analyses of PPI network and functional enrichment have been widely applied to various fields of biomedical research. Herein, we summarize commonly used tools for PPI network analysis and functional enrichment in kidney stone research and discuss their applications to kidney stone disease (KSD). Such computational approach has been used mainly to investigate PPI networks and functional significance of the proteins derived from urine of patients with kidney stone (stone formers), stone matrix, Randall's plaque, renal papilla, renal tubular cells, mitochondria and immune cells. The data obtained from computational biotechnology leads to experimental validation and investigations that offer new knowledge on kidney stone formation processes. Moreover, the computational approach may also lead to defining new therapeutic targets and preventive strategies for better outcome in KSD management., Competing Interests: Conflicts of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Chang Gung University. Published by Elsevier B.V. All rights reserved.)

Background: Randall's plaques (RP) are identified as anchored sites for kidney calcium oxalate stones, but the mechanism remains unclear. Given the importance of osteogenic-like cells in RP formation and OCT4 in reprogramming differentiated cells to osteoblasts, the current study explored the potential role of OCT4 in RP formation., Methods: OCT4 and biomineralization were evaluated in RP, and immunofluorescence co-staining was performed to identify these cells with alteration of OCT4 and osteogenic markers. Based on the analysis of tissue, we further investigated the mechanism of OCT4 in regulating osteogenic-like differentiation of primary human renal interstitial fibroblasts (hRIFs) in vitro and vivo., Results: We identified the upregulated OCT4 in RP, with a positive correlation to osteogenic markers. Interestingly, fibroblast marker Vimentin was partially co-localized with upregulated OCT4 and osteogenic markers in RP. Further investigations revealed that OCT4 significantly enhanced the osteogenic-like phenotype of hRIFs in vitro and in vivo. Mechanically, OCT4 directly bound to BMP2 promoter and facilitated its CpG island demethylation to transcriptionally promote BMP2 expression. Furthermore, combination of RIP and RNA profiling uncovered that lncRNA OLMALINC physically interacted with OCT4 to promote its stabilization via disrupting the ubiquitination. Additionally, OLMALINC was upregulated in fibroblasts in RP visualized by FISH, and a positive correlation was revealed between OLMALINC and OCT4 in RP., Conclusions: The upregulation of OCT4 in hRIFs was a pathological feature of RP formation, and OLMALINC/OCT4/BMP2 axis facilitated hRIFs to acquire osteogenic-like phenotype under osteogenic conditions, through which the pathway might participate in RP formation. Our findings opened up a new avenue to better understand RP formation in which osteogenic-like process was partially triggered by lncRNAs and pluripotency maintenance related genes., (© 2022. The Author(s).)

Calcium oxalate (CaOx) stones can grow attached to the renal papillary calcification known as Randall's plaque. Although stone growth on Randall's plaque is a common phenomenon, this mechanism of stone formation is still poorly understood. The objective of this study was to investigate the microenvironment of mature Randall's plaque, explore its molecular composition and differentiate plaque from CaOx overgrowth using multimodal imaging on demineralized stone sections. Fluorescence imaging showed consistent differences in autofluorescence patterns between Randall's plaque and calcium oxalate overgrowth regions. Second harmonic generation imaging established the presence of collagen only in regions of decalcified Randall's plaque but not in regions of CaOx overgrowth matrix. Surprisingly, in these stone sections we observed cell nuclei with preserved morphology within regions of mature Randall's plaque. These conserved cells had variable expression of vimentin and CD45. The presence of nuclei in mature plaque indicates that mineralization is not necessarily associated with cell death. The markers identified suggest that some of the entrapped cells may be undergoing dedifferentiation or could emanate from a mesenchymal or immune origin. We propose that entrapped cells may play an important role in the growth and maintenance of Randall's plaque. Further characterization of these cells and thorough analyses of the mineralized stone forming renal papilla will be fundamental in understanding the pathogenesis of Randall's plaque and CaOx stone formation., (© 2021 American Association for Anatomy.)

Introduction: About 1 in 11 Americans will experience a kidney stone, but underlying causes remain obscure. The objective of the present study was to separate idiopathic calcium oxalate stone formers by whether or not they showed positive evidence of forming a stone on Randall's plaque (RP). Materials and Methods: In patients undergoing either percutaneous or ureteroscopic procedures for kidney stone removal, all stone material was extracted and analyzed using micro-CT imaging to identify those attached to RP. Twenty-four-hour urine samples were collected weeks after the stone removal procedure and patients were off of medications that would affect urine composition. The endoscopic video was analyzed for papillary pathology (RP, pitting, plugging, dilated ducts, and loss of papillary shape) by an observer blinded to the data on stone type. The percent papillary area occupied by RP and ductal plugging was quantified using image analysis software. Results: Patients having even one stone on RP ( N  = 36) did not differ from non-RP patients ( N  = 37) in age, sex, BMI, or other clinical characteristics. Compared with the non-RP group, RP stone formers had more numerous, but smaller, stones, more abundant papillary RP formation, and fewer ductal plugs, both by quantitative measurement of surface area (on average, three times more plaque area, but only 41% as much plug area as in non-RP patients) and by semiquantitative visual grading. Serum and blood values did not differ between RP and non-RP stone formers by any measure. Conclusions: Growth of many small stones on plaque seems the pathogenetic scheme for the RP stone-forming phenotype, whereas the non-RP phenotype stone pathogenesis pathway is less obvious. Higher papillary plugging in non-RP patients suggests that plugs play a role in stone formation and that these patients have a greater degree of papillary damage. Underlying mechanisms that create these distinctive phenotypes are presently unknown.

Randall's plaques (RP) are well established as precursor lesions of idiopathic calcium oxalate (CaOx) stones, and the process of biomineralization driven by osteogenic-like cells has been highlighted in RP formation, but the mechanism is poorly understood. Given the inhibitory role of α-Klotho (KL), an aging suppressor protein with high expression in kidneys, in ectopic calcification and the close association between KL gene polymorphisms and urolithiasis susceptibility, we determined the potential role of KL in RP formation. This study found that both soluble KL (s-KL) and transmembrane KL (m-KL) were downregulated, and that s-KL but not m-KL was inversely correlated with upregulation of osteogenic markers in RP tissues. Additionally, s-KL expression was markedly suppressed in human renal interstitial fibroblasts (hRIFs) and slightly suppressed in HK-2 cells after osteogenic induction, intriguingly, which was echoed to the greater osteogenic capability of hRIFs than HK-2 cells. Further investigations showed the inhibitory effect of s-KL on hRIF osteogenic differentiation in vitro and in vivo. Moreover, coculture with recombinant human KL (r-KL) or HK-2 cells suppressed osteogenic differentiation of hRIFs, and this effect was abolished by coculture with KL-silenced HK-2 cells or the β-catenin agonist SKL2001. Mechanistically, s-KL inactivated the Wnt-β-catenin pathway by directly binding to Wnt2 and upregulating SFRP1. Further investigations identified activation of the Wnt-β-catenin pathway and downregulation of SFRP1 and DKK1 in RP tissues. In summary, this study identified s-KL deficiency as a pathological feature of RP and revealed that s-KL released from HK-2 cells inhibited osteogenic differentiation of hRIFs by inactivating the Wnt-β-catenin pathway, not only providing in-depth insight into the role of s-KL in renal interstitial biomineralization but also shedding new light on the interaction of renal tubular epithelial cells with interstitial cells to clarify RP formation., (© 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Context.—: Renal malignancies can be divided into cortical- and medullary-based tumors, the latter of which classically infiltrate the renal parenchyma by extending between nonneoplastic structures. Although high-grade cortical tumors can rarely exhibit the same growth pattern, the infiltrative morphology should elicit a differential diagnosis to be considered in each case. However, these diagnoses can be challenging to distinguish, especially on small renal biopsy samples., Objective.—: To provide an overview of the clinical, gross, and microscopic findings; genetic and molecular alterations; and immunohistochemical evaluation of medullary-based renal tumors and other tumor types with overlapping morphologies and growth patterns., Data Sources.—: Literature review and personal observations were used to compile the information in this review., Conclusions.—: Collecting duct carcinoma is a prototypical medullary-based tumor, and although diagnostic criteria exist, it remains a diagnosis of exclusion, especially with ancillary techniques aiding the recognition of established as well as more recently described neoplasms. Other medullary-based malignancies included in the differential diagnosis include renal medullary carcinoma/renal cell carcinoma unclassified with medullary phenotype, fumarate hydratase-deficient renal cell carcinoma, and upper tract urothelial carcinoma. Moreover, other rare entities should be excluded, including metastatic carcinoma, lymphoma, and melanoma. In addition to potential prognostic differences, accurate diagnoses can have important surgical and clinical management implications.

The fluid in the 14 distinct segments of the renal tubule undergoes sequential transport processes that gradually convert the glomerular filtrate into the final urine. The solute carrier (SLC) family of proteins is responsible for much of the transport of ions and organic molecules along the renal tubule. In addition, some SLC family proteins mediate housekeeping functions by transporting substrates for metabolism. Here, we have developed a curated list of SLC family proteins. We used the list to produce resource webpages that map these proteins and their transcripts to specific segments along the renal tubule. The data were used to highlight some interesting features of expression along the renal tubule including sex-specific expression in the proximal tubule and the role of accessory proteins (β-subunit proteins) that are thought to be important for polarized targeting in renal tubule epithelia. Also, as an example of application of the data resource, we describe the patterns of acid-base transporter expression along the renal tubule.

Idiopathic calcium oxalate (CaOx) stones often develop attached to Randall's plaque present on kidney papillary surfaces. Similar to the plaques formed during vascular calcification, Randall's plaques consist of calcium phosphate crystals mixed with an organic matrix that is rich in proteins, such as inter-α-trypsin inhibitor, as well as lipids, and includes membrane-bound vesicles or exosomes, collagen fibres and other components of the extracellular matrix. Kidney tissue surrounding Randall's plaques is associated with the presence of classically activated, pro-inflammatory macrophages (also termed M1) and downregulation of alternatively activated, anti-inflammatory macrophages (also termed M2). In animal models, crystal deposition in the kidneys has been associated with the production of reactive oxygen species, inflammasome activation and increased expression of molecules implicated in the inflammatory cascade, including osteopontin, matrix Gla protein and fetuin A (also known as α2-HS-glycoprotein). Many of these molecules, including osteopontin and matrix Gla protein, are well known inhibitors of vascular calcification. We propose that conditions of urine supersaturation promote kidney damage by inducing the production of reactive oxygen species and oxidative stress, and that the ensuing inflammatory immune response promotes Randall's plaque initiation and calcium stone formation.

The nuclear factor of activated T cells 5 (NFAT5) is well known for its sensitivity to cellular osmolarity changes, such as in the kidney medulla. Accumulated evidence indicates that NFAT5 is also a sensitive factor to stress signals caused by non-hypertonic stimuli such as heat shock, biomechanical stretch stress, ischaemia, infection, etc. These osmolality-related and -unrelated stimuli can induce NFAT5 upregulation, activation and nuclear accumulation, leading to its protective role against various detrimental effects. However, dysregulation of NFAT5 expression may cause pathological conditions in different tissues, leading to a variety of diseases. These protective or pathogenic effects of NFAT5 are dictated by the regulation of its target gene expression and activation of its signalling pathways. Recent studies have found a number of kinases that participate in the phosphorylation/activation of NFAT5 and related signal proteins. Thus, this review will focus on the NFAT5-mediated signal transduction pathways. As for the stimuli that upregulate NFAT5, in addition to the stresses caused by hyperosmotic and non-hyperosmotic environments, other factors such as miRNA, long non-coding RNA, epigenetic modification and viral infection also play an important role in regulating NFAT5 expression; thus, the discussion in this regard is another focus of this review. As the heart, unlike the kidneys, is not normally exposed to hypertonic environments, studies on NFAT5-mediated cardiovascular diseases are just emerging and rapidly progressing. Therefore, we have also added a review on the progress made in this field of research.

Kidney stones frequently develop as an overgrowth on Randall's plaque (RP) which is formed in the papillary interstitium. The organic composition of RP is distinct from stone matrix in that RP contains fibrillar collagen; RP in tissue has also been shown to have two proteins that are also found in stones, but otherwise the molecular constituents of RP are unstudied. We hypothesized that RP contains unique organic molecules that can be differentiated from the stone overgrowth by fluorescence. To test this, we used micro-CT-guided polishing to expose the interior of kidney stones for multimodal imaging with multiphoton, confocal and infrared microscopy. We detected a blue autofluorescence signature unique to RP, the specificity of which was also confirmed in papillary tissue from patients with stone disease. High-resolution mineral mapping of the stone also showed a transition from the apatite within RP to the calcium oxalate in the overgrowth, demonstrating the molecular and spatial transition from the tissue to the urine. This work provides a systematic and practical approach to uncover specific fluorescence signatures which correlate with mineral type, verifies previous observations regarding mineral overgrowth onto RP and identifies a novel autofluorescence signature of RP demonstrating RP's unique molecular composition.

Introduction: Renal medullary carcinoma (RMC) is a highly lethal adenocarcinoma with a propensity for widespread metastatic disease in young patients. It is strongly associated with sickle cell trait and shows the loss of SMARCB1 (also known as INI1 or BAF47) protein expression. In the present study, we reviewed a series of 12 patients for whom the cytology specimens played a significant role in patient treatment., Materials and Methods: We performed a retrospective case review of patients with a history of RMC from 3 large tertiary care pathology practices., Results: A total of 12 patients were identified with histologically confirmed RMC who had had pleural, pericardial, or urine specimens involved by their disease or had undergone initial kidney fine needle aspiration. Patient age ranged from 13 to 37 years (median, 21.5 years). All 12 patients were black or of African descent, and 10 had a confirmed history of sickle cell trait. Of the 12 patients, 11 (92%) had fluid specimens involved by metastatic tumor at some point in their clinical course, and 4 (33%) had initially presented with pericardial and/or pleural effusions or urine specimens that were positive for malignancy. Cytologic examination predominantly showed fragments of 3-dimensional "tumor balls" with smooth borders, fine pale cytoplasm with vacuolization, and highly pleomorphic nuclei with irregular nuclear membranes and coarse to vesicular chromatin and single prominent nucleoli., Conclusions: The cytomorphology of RMC involving serous fluids is nonspecific and in keeping with metastatic high-grade adenocarcinoma. In a young patient presenting with no history of malignancy and a pleural or pericardial effusion, triaging the material for ancillary studies and a nuanced assessment of patient history and radiologic findings will be critical., (Copyright © 2021 American Society of Cytopathology. Published by Elsevier Inc. All rights reserved.)

High salt diet (HSD, 8% NaCl) contributes to salt-sensitive hypertension, this study aimed to determine the effect of HSD on salt-sensitive hypertension by combining proteomic with metabolomics methods. Salt-sensitive rats were fed on HSD and normal salt diet (NSD, 0.4% NaCl) for two weeks before further analysis. Proteomic analysis showed the differential expression proteins (DEPs) were primarily mapped in the tricarboxylic acid (TCA)-cycle, glycolysis/gluconeogenesis, and other pathways associated with multiple amino acids. HSD decreased the medullary activities and protein expression level of two key enzymes of TCA-cycle, MDH and NADP + -IDH. Metabolomics showed three serous TCA-cycle-associated compounds, including decreased malic acid, decreased citric acid, and increased fumaric acid were differentially detected, which resulted in a decrease in NO content and an increase in H 2 O 2 content in serum. The content of GSH, GSH/GSSG ratio, and synthesis substrates of GSH-cysteine and glycine, were significantly decreased by HSD, thus attenuated the antioxidant system in the renal medulla. HSD enhanced the medullary pentose phosphate pathway, which finally increased the concentration of NADPH and NADP + , NADPH/NADP +, and the activity of NADPH oxidase in the renal medulla. Additionally, HSD enhanced the glycolysis pathway in the renal medulla. In summary, HSD significantly weakened the TCA cycle, and attenuated the antioxidant system in the renal medulla, which finally contributed to salt-sensitive hypertension., Competing Interests: Declaration of competing interest The authors have nothing to disclose., (Copyright © 2020 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

Background: Single-cell transcriptomes from dissociated tissues provide insights into cell types and their gene expression and may harbor additional information on spatial position and the local microenvironment. The kidney's cells are embedded into a gradient of increasing tissue osmolality from the cortex to the medulla, which may alter their transcriptomes and provide cues for spatial reconstruction., Methods: Single-cell or single-nuclei mRNA sequencing of dissociated mouse kidneys and of dissected cortex, outer, and inner medulla, to represent the corticomedullary axis, was performed. Computational approaches predicted the spatial ordering of cells along the corticomedullary axis and quantitated expression levels of osmo-responsive genes. In situ hybridization validated computational predictions of spatial gene-expression patterns. The strategy was used to compare single-cell transcriptomes from wild-type mice to those of mice with a collecting duct-specific knockout of the transcription factor grainyhead-like 2 (Grhl2 CD-/- ), which display reduced renal medullary osmolality., Results: Single-cell transcriptomics from dissociated kidneys provided sufficient information to approximately reconstruct the spatial position of kidney tubule cells and to predict corticomedullary gene expression. Spatial gene expression in the kidney changes gradually and osmo-responsive genes follow the physiologic corticomedullary gradient of tissue osmolality. Single-nuclei transcriptomes from Grhl2 CD-/- mice indicated a flattened expression gradient of osmo-responsive genes compared with control mice, consistent with their physiologic phenotype., Conclusions: Single-cell transcriptomics from dissociated kidneys facilitated the prediction of spatial gene expression along the corticomedullary axis and quantitation of osmotically regulated genes, allowing the prediction of a physiologic phenotype., (Copyright © 2021 by the American Society of Nephrology.)

Retrograde intrarenal surgery (RIRS) is one of the minimally invasive main treatment modalities in renal stone disease. There are many factors which affect stone-free rate (SFR). Our study was based on the hypothesis that higher renal parenchymal thickness (RPT) which may include higher average number of nephrons provides better diuresis. We investigated the efficacy of RPT on success of RIRS. This study is a single-centered prospective surgical cohort study. A total of 383 patients were analyzed. Regularly followed 304 patients with unilateral kidney stone at single pole or renal pelvis and who underwent single-session RIRS were included in the final analysis, and the patients' preoperative and postoperative 1st and 3rd months' data were evaluated. RPT was measured on the non-contrast computed tomography (CT) images. ROC analysis was performed to estimate the cutoff value of RPT for SFR. Univariate and multivariate logistic regression analyses were used to model the relationship between RPT and SFR after RIRS. ROC analysis revealed the best cutoff value of the RPT for predicting residual stone as 19 mm for both the 1st and 3rd month visits with Youden indexes of 0.397 and 0.406, respectively. To the best of our knowledge, this is the first study which evaluated the effect of RPT on the efficacy of RIRS. RPT measurement is a cost-effective method that can be easily performed on routinely applied non-contrast CT and may have predictive value for the surgical success in patients with nephrolithiasis.

Numerous evidence corroborates roles of gap junctions/hemichannels in proper kidney development. We analyzed how Dab1 gene functional silencing influences expression and localization of Cx37, Cx40, Cx43, Cx45, Panx1 and renin in postnatal kidneys of yotari mice, by using immunohistochemistry and electron microscopy. Dab1 Δ102/221 might lead to the activation of c-Src tyrosine kinase, causing the upregulation of Cx43 in the medulla of yotari mice. The expression of renin was more prominent in yotari mice ( p < 0.001). Renin granules were unusually present inside the vascular walls of glomeruli capillaries, in proximal and distal convoluted tubules and in the medulla. Disfunction of Cx40 is likely responsible for increased atypically positioned renin cells which release renin in an uncontrolled fashion, but this doesn't rule out simultaneous involvement of other Cxs, such as Cx45 which was significantly increased in the yotari cortex. The decreased Cx37 expression in yotari medulla might contribute to hypertension reduction provoked by high renin expression. These findings imply the relevance of Cxs/Panx1 as markers of impaired kidney function (high renin) in yotari mice and that they have a role in the preservation of intercellular signaling and implicate connexopathies as the cause of premature death of yotari mice.

Background: Medullary sponge kidney (MSK) is a rare disease characterized by cystic dilatation of papillary collecting ducts. Intravenous urography is still considered the gold standard for diagnosis. We identified a cohort of patients from our outpatient clinic with established diagnosis of MSK to outline some ultrasonographic characteristics that may help establish a diagnosis., Methods: We conducted a retrospective study of patients seen between January 1st 2009 and January 1st 2019 in our clinic. Out of 4321 patients, 18 had a diagnosis of MSK. We reviewed their clinical and family history, laboratory data and imaging studies. Specifically, we focused on ultrasound imaging., Results: Patients were referred to our outpatient clinic because of renal impairment (44%), family history of nephropathy (17%), nephrolithiasis or an established diagnosis of MSK (39%). Seventy-two percent of patients presented with chronic kidney disease, 22% required hemodialysis. Urinary tract infections (44%), nephrolithiasis (33%), microscopic hematuria (50%) and proteinuria (44%) were reported. Seven patients underwent computed tomography; all of them received ultrasound. Ultrasound examination showed bilateral renal cysts, usually small and located in the renal medulla, and microcalcifications located in the medulla or within the cysts., Conclusion: We identified a peculiar tetrad associated with MSK: 1) hypoechoic medullary areas, 2) hyperechoic spots, 3) microcystic dilatation of papillary zone, 4) multiple calcifications (linear, small stones or calcified intracystic sediment) in each papilla. The presence of this diagnostic tetrad, added to laboratory data and clinical history, could be helpful in the differential diagnosis to identify patients with MSK.

Background and Objectives: The published tissue adequacy requirement of kidney medulla for BK virus allograft nephropathy diagnosis lacks systematic verification and competes against potential increased procedural risks from deeper sampling., Design, Setting, Participants, & Measurements: We evaluated whether the presence of kidney medulla improved the diagnostic rate of BK nephropathy in 2244 consecutive biopsy samples from 856 kidney transplants with detailed histologic and virologic results., Results: Medulla was present in 821 samples (37%) and correlated with maximal core length ( r =0.35; P <0.001). BK virus allograft nephropathy occurred in 74 (3% overall) but increased to 5% (42 of 821) with medulla compared with 2% (32 of 1423) for cortical samples ( P <0.001). Biopsy medulla was associated with infection after comprehensive multivariable adjustment of confounders, including core length, glomerular number, and number of cores (adjusted odds ratio, 1.81; 95% confidence interval, 1.02 to 3.21; P =0.04). In viremic cases ( n =275), medulla was associated with BK virus nephropathy diagnosis (39% versus 19% for cortex; P <0.001) and tissue polyomavirus load (Banff polyomavirus score 0.64±0.96 versus 0.33±1.00; P =0.006). Biopsy medulla was associated with BK virus allograft nephropathy using generalized estimating equation (odds ratio, 2.04; 95% confidence interval, 1.05 to 3.96; n =275) and propensity matched score comparison (odds ratio, 2.24; 95% confidence interval, 1.11 to 4.54; P =0.03 for 156 balanced pairs). Morphometric evaluation of Simian virus 40 large T immunohistochemistry found maximal infected tubules within the inner cortex and medullary regions ( P <0.001 versus outer cortex)., Conclusions: Active BK virus replication concentrated around the corticomedullary junction can explain the higher detection rates for BK virus allograft nephropathy with deep sampling. The current adequacy requirement specifying targeting medulla can be justified to minimize a missed diagnosis from undersampling., (Copyright © 2020 by the American Society of Nephrology.)

Background: Kidney cortical interstitial fibrosis (IF) is highly predictive of renal prognosis and is currently assessed by the evaluation of a biopsy. Diffusion magnetic resonance imaging (MRI) is a promising tool to evaluate kidney fibrosis via the apparent diffusion coefficient (ADC), but suffers from inter-individual variability. We recently applied a novel MRI protocol to allow calculation of the corticomedullary ADC difference (ΔADC). We here present the validation of ΔADC for fibrosis assessment in a cohort of 164 patients undergoing biopsy and compare it with estimated glomerular filtration rate (eGFR) and other plasmatic parameters for the detection of fibrosis., Methods: This monocentric cross-sectional study included 164 patients undergoing renal biopsy at the Nephrology Department of the University Hospital of Geneva between October 2014 and May 2018. Patients underwent diffusion-weighted imaging, and T1 and T2 mappings, within 1 week after biopsy. MRI results were compared with gold standard histology for fibrosis assessment., Results: Absolute cortical ADC or cortical T1 values correlated poorly to IF assessed by the biopsy, whereas ΔADC was highly correlated to IF (r=-0.52, P < 0.001) and eGFR (r = 0.37, P < 0.01), in both native and allograft patients. ΔT1 displayed a lower, but significant, correlation to IF and eGFR, whereas T2 did not correlate to IF nor to eGFR. ΔADC, ΔT1 and eGFR were independently associated with kidney fibrosis, and their combination allowed detection of extensive fibrosis with good specificity., Conclusion: ΔADC is better correlated to IF than absolute cortical or medullary ADC values. ΔADC, ΔT1 and eGFR are independently associated to IF and allow the identification of patients with extensive IF., (© The Author(s) 2019. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.)

Objective: To investigate the value of combined chemical exchange saturation transfer (CEST) and conventional magnetization transfer imaging (MT) in detecting metabolic and structural changes of renal fibrosis in rats with unilateral ureteral obstruction (UUO) at 3T MRI., Materials and Methods: Thirty-five Sprague-Dawley rats underwent UUO surgery (n = 25) or sham surgery (n = 10). The obstructed and contralateral kidneys were evaluated on days 1, 3, 5, and 7 after surgery. After CEST and MT examinations, 18F-labeled fluoro-2-deoxyglucose positron emission tomography was performed to quantify glucose metabolism. Fibrosis was measured by histology and western blots. Correlations were compared between asymmetrical magnetization transfer ratio at 1.2 ppm (MTR asym(1.2ppm) ) derived from CEST and maximum standard uptake value (SUV max ) and between magnetization transfer ratio (MTR) derived from MT and alpha-smooth muscle actin (α-SMA)., Results: On days 3 and 7, MTR asym(1.2ppm) and MTR of UUO renal cortex and medulla were significantly different from those of contralateral kidneys ( p < 0.05). On day 7, MTR asym(1.2ppm) and MTR of UUO renal cortex and medulla were significantly different from those of sham-operated kidneys ( p < 0.05). The MTR asym(1.2ppm) of UUO renal medulla was fairly negatively correlated with SUV max ( r = -0.350, p = 0.021), whereas MTR of UUO renal medulla was strongly negatively correlated with α-SMA ( r = -0.744, p < 0.001)., Conclusion: CEST and MT could provide metabolic and structural information for comprehensive assessment of renal fibrosis in UUO rats in 3T MRI and may aid in clinical monitoring of renal fibrosis in patients with chronic kidney disease., Competing Interests: The authors have no potential conflicts of interest to disclose., (Copyright © 2020 The Korean Society of Radiology.)

Potassium depletion affects AQP2 expression and the cellular composition of the kidney collecting duct. This, in turn, contributes to the development of a secondary form of nephrogenic diabetes insipidus and hypokalemic nephropathy. Here we show that after 14 days of potassium depletion, the cellular fraction of A-type intercalated cells increases while the fraction of principal cells decreases along the outer medullary collecting duct in rats. The intercalated cells acquired a novel distribution pattern forming rows of cells attached to each other. These morphological changes occur progressively and reverse after 7 days of recovery on normal rat chow diet. The cellular remodeling mainly occurred in the inner stripe of outer medulla similar to the previously seen effect of lithium on the collecting duct cellular profile. The cellular remodeling is associated with the appearance of cells double labelled with both specific markers of principal and type-A intercalated cells. The appearance of this cell type was associated with the downregulation of the Notch signaling via the Hes1 pathways. These results show that the epithelium of the collecting duct has a high degree of plasticity and that Notch signaling likely plays a key role during hypokalemia.

Aim: Medullary ray injury was recently reported in renal transplant biopsies. This study was performed to clarify the clinicopathological features of medullary ray injury in paediatric living renal transplant recipients., Methods: Paediatric recipients who completed a 5-year follow-up after living renal transplantation were enroled. We evaluated the clinical and pathological parameters of the presence or absence of medullary ray injury in their 1-year protocol biopsies., Results: Of 48 1-year protocol biopsies, 18 (37.5%) showed histological evidence of medullary ray injury. The 48 paediatric recipients were classified as those with medullary ray injury (n = 18; MRI-1Y [+] group) and those without medullary ray injury (n = 30; MRI-1Y [-] group) in the 1-year protocol biopsies. The prevalence of histological evidence of calcineurin inhibitor (CNI) nephrotoxicity, chronic obstruction or reflux nephropathy, and imaging findings of vesicoureteral reflux was 66.7, 22.2, and 7.7% in the MRI-1Y (+) group and 33.3, 13.3, and 15.4% in the MRI-1Y (-) group, respectively. Only the prevalence of CNI nephrotoxicity was significantly different between the 2 groups. There was no significant difference in the mean estimated glomerular filtration rate at 1, 3, or 5 years after transplantation between the 2 groups., Conclusion: In total, 37.5% of 1-year protocol biopsies showed histological evidence of medullary ray injury. This finding suggests that CNI nephrotoxicity might be the main contributor to medullary ray injury in 1-year protocol biopsies. The presence of medullary ray injury had little influence on renal function, at least during the first 5 years after transplantation., (© 2020 The Author(s) Published by S. Karger AG, Basel.)

Comorbidity is common as age increases, and currently prescribed treatments often ignore the interconnectedness of the involved age-related diseases. The presence of any one such disease usually increases the risk of having others, and new approaches will be more effective at increasing an individual's health span by taking this systems-level view into account. In this study, we developed gene therapies based on 3 longevity associated genes (fibroblast growth factor 21 [FGF21], αKlotho, soluble form of mouse transforming growth factor-β receptor 2 [sTGFβR2]) delivered using adeno-associated viruses and explored their ability to mitigate 4 age-related diseases: obesity, type II diabetes, heart failure, and renal failure. Individually and combinatorially, we applied these therapies to disease-specific mouse models and found that this set of diverse pathologies could be effectively treated and in some cases, even reversed with a single dose. We observed a 58% increase in heart function in ascending aortic constriction ensuing heart failure, a 38% reduction in α-smooth muscle actin (αSMA) expression, and a 75% reduction in renal medullary atrophy in mice subjected to unilateral ureteral obstruction and a complete reversal of obesity and diabetes phenotypes in mice fed a constant high-fat diet. Crucially, we discovered that a single formulation combining 2 separate therapies into 1 was able to treat all 4 diseases. These results emphasize the promise of gene therapy for treating diverse age-related ailments and demonstrate the potential of combination gene therapy that may improve health span and longevity by addressing multiple diseases at once., Competing Interests: Conflict of interest statement: N.D., D.O., and G.M.C. are founders of Rejuvenate Bio. N.D. and G.M.C. are named inventors on a patent application related to the technologies described in this article., (Copyright © 2019 the Author(s). Published by PNAS.)

Most kidney stones are made of calcium oxalate crystals. Randall's plaque, an apatite deposit at the tip of the renal papilla, is considered to at the origin of these stones. Hypercalciuria may promote Randall's plaque formation and growth. We analyzed whether long-term exposure of Abcc6 -/- mice (a murine model of Randall's plaque) to vitamin D supplementation, with or without a calcium-rich diet, would accelerate the formation of Randall's plaque. Eight groups of mice (including Abcc6 -/- and wild type) received vitamin D alone (100,000 UI/kg every 2 weeks), a calcium-enriched diet alone (calcium gluconate 2 g/L in drinking water), both vitamin D supplementation and a calcium-rich diet, or a standard diet (controls) for 6 months. Kidney calcifications were assessed by 3-dimensional microcomputed tomography, μ-Fourier transform infrared spectroscopy, field emission-scanning electron microscopy, transmission electron microscopy, and Yasue staining. At 6 months, Abcc6 -/- mice exposed to vitamin D and calcium supplementation developed massive Randall's plaque when compared with control Abcc6 -/- mice (P < 0.01). Wild-type animals did not develop significant calcifications when exposed to vitamin D. Combined administration of vitamin D and calcium significantly accelerates Randall's plaque formation in a murine model. This original model raises concerns about the cumulative risk of vitamin D supplementation and calcium intakes in Randall's plaque formation., (Copyright © 2019 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Excessive tissue scarring, or fibrosis, is a critical contributor to end stage renal disease, but current clinical tests are not sufficient for assessing renal fibrosis. Quantitative magnetization transfer (qMT) MRI provides indirect information about the macromolecular composition of tissues. We evaluated measurements of the pool size ratio (PSR, the ratio of immobilized macromolecular to free water protons) obtained by qMT as a biomarker of tubulointerstitial fibrosis in a well-established murine model with progressive renal disease. MR images were acquired from 16-week-old fibrotic hHB-EGF Tg/Tg mice and normal wild-type (WT) mice (N = 12) at 7 T. QMT parameters were derived using a two-pool five-parameter fitting model. A normal range of PSR values in the cortex and outer stripe of outer medulla (CR + OSOM) was determined by averaging across voxels within WT kidneys (mean ± 2SD). Regions in diseased mice whose PSR values exceeded the normal range above a threshold value (tPSR) were identified and measured. The spatial distribution of fibrosis was confirmed using picrosirius red stains. Compared with normal WT mice, scattered clusters of high PSR regions were observed in the OSOM of hHB-EGF Tg/Tg mouse kidneys. Moderate increases in mean PSR (mPSR) of CR + OSOM regions were observed across fibrotic kidneys. The abnormally high PSR regions (% area) detected by the tPSR were significantly increased in hHB-EGF Tg/Tg mice, and were highly correlated with regions of fibrosis detected by histological fibrosis indices measured from picrosirius red staining. Renal tubulointerstitial fibrosis in OSOM can thus be assessed by qMT MRI using an appropriate analysis of PSR. This technique may be used as an imaging biomarker for chronic kidney diseases., (© 2019 John Wiley & Sons, Ltd.)

Renal ammonia excretion is a critical component of acid-base homeostasis, and changes in ammonia excretion are the predominant component of increased net acid excretion in response to metabolic acidosis. We recently reported substantial sex-dependent differences in basal ammonia metabolism that correlate with sex-dependent differences in renal structure and expression of key proteins involved in ammonia metabolism. The purpose of the present study was to investigate the effect of sex on the renal ammonia response to an exogenous acid load. We studied 4-mo-old C57BL/6 mice. Ammonia excretion, which was less in male mice under basal conditions, increased in response to acid loading to a greater extent in male mice, such that maximal ammonia excretion did not differ between the sexes. Fundamental structural sex differences in the nonacid-loaded kidney persisted after acid loading, with less cortical proximal tubule volume density in the female kidney than in the male kidney, whereas collecting duct volume density was greater in the female kidney. To further investigate sex-dependent differences in the response to acid loading, we examined the expression of proteins involved in ammonia metabolism. The change in expression of phosphoenolpyruvate carboxykinase and Rh family B glycoprotein with acid loading was greater in male mice than in female mice, whereas Na + -K + -2Cl - cotransporter and inner stripe of the outer medulla intercalated cell Rh family C glycoprotein expression were significantly greater in female mice than in male mice. There was no significant sex difference in glutamine synthetase, Na + /H + exchanger isoform 3, or electrogenic Na + -bicarbonate cotransporter 1 variant A protein expression in response to acid loading. We conclude that substantial sex-dependent differences in the renal ammonia response to acid loading enable a similar maximum ammonia excretion response.

Introduction: Randall's plaque (RP) with attached stones is recognized as a primary mechanism for stone formation in adult calcium oxalate stone formers (CaOx SFs). The role of RP in pediatric stone pathogenesis is unknown, with no reported studies to date. The purpose of this study is to investigate renal papillary abnormalities and quantify RP in pediatric CaOx SFs. Methods: Eight pediatric CaOx SFs underwent ureteroscopy for symptomatic urolithiasis. The collecting system was mapped using a digital ureteroscope. Video for each patient was then reviewed using a retrograde pyelogram to confirm the location of each papilla. A single investigator (N.L.M.) reviewed the video to quantify RP. Each papilla was graded as having mild, moderate, or severe amount of RP. Patient history was recorded. Results: An average of nine papillae were mapped per patient. RP was present in 100% of patients and in 88.8% (64/72) of all papillae examined. When present, RP was uniformly distributed throughout the kidney without preferential distribution to a region or pole. The amount of RP on the papillae was graded as mild in 60%, moderate in 20.8%, and severe in 8.3%. The mean fractional RP coverage ranged from 0.39% to 9.34%. No correlation was found between the amount of plaque and age at first stone episode or number of prior stone episodes ( p  = 0.84). Attached stones were rare (1/8 patients). The two patients with severe RP had a small amount of calcium phosphate in their stone analysis. Conclusions: RP is common in pediatric CaOx SFs. Compared with adult CaOx SFs wherein up to 75% of stones are found attached to RP, attached stones were rare. The significance of these findings in the pathogenesis of pediatric stone formation remains unclear and will require longer term follow-up.

Hydroxyapatite (HAP) is not only a common component of most idiopathic CaOx stones, but also the core of Randall's plaque. HAP is a nest that can induce the formation of Randall's plaques and even kidney stones. We studied the toxic effects and mechanisms of four different types of nano-HAP crystals (H-Sphere, 72.5 nm × 72.5 nm; H-Needle, 37.2 nm × 162.7 nm; H-Rod, 42.3 nm × 115.3 nm; and H-Plate, 145.5 nm × 272.9 nm) on human renal proximal tubular epithelial cells (HK-2). HAP crystals could cause oxidative stress that triggered a series of cell dysfunction problems, resulting in decreased cell viability, loss of cell membrane integrity, cell swelling, and cell necrosis. The toxic effect of HAP was mainly attributed to its entry into cell by endocytosis and its accumulation in the lysosomes, causing the level of intracellular reactive oxygen species (ROS) to rise, the mitochondrial membrane potential (Δψm) to decrease, the lysosomal integrity to be destroyed, and the cell cycle blocked during the G0/G1 phase. The cytotoxicity of the four kinds of HAP crystals was ranked as follows: H-Sphere > H-Needle > H-Rod > H-Plate. The cytotoxicity of each crystal was positively correlated with low absolute zeta potential, conduciveness to internalized morphology, large specific surface area and aspect ratio, and small particle size. These results indicated that nano-HAP could damage HK-2 cells, and the physical properties of HAP crystals play a vital effect in their cytotoxicity., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In recent years, progress has been made on understanding the relationship between vesicoureteral reflux (VUR) and urinary tract infection (UTI). The findings on recent prospective, randomized, controlled studies have questioned the conventional VUR clinical significance and, therefore, have challenged the traditional diagnostic and therapeutic recommendations. These new studies have redefined the pathogenic role of vesicoureteral reflux in UTI as well as have disputed the routine use of urinary antibiotic prophylaxis to prevent UTI and renal damage in VUR patients. The time to overinvestigate and treat the vast majority of otherwise healthy children who have an uncomplicated UTI with long-term antibiotic prophylaxis seems to be over. Is there a role of severe VUR in the development of chronic renal disease and renal failure? New ideas are needed to answer these questions with the goal to avoid repeating past mistakes when therapeutic choices were based on expert opinions rather than facts.

Mutations in natriuretic peptide receptor 2 (Npr2) gene cause a rare form of short-limbed dwarfism, but its physiological effects have not been well studied. Human and mouse genetic data suggest that Npr2 in the kidney plays a role in salt homeostasis. Herein, we described anatomic changes within renal papilla of Npr2 knockout (Npr2 -/- ) mice. Dramatic reduction was found in diuresis, and albuminuria was evident after administration of 1% NaCl in drinking water in Npr2 -/- and heterozygous (Npr2 +/- ) mice compared with their wild-type (Npr2 +/+ ) littermates. There was indication of renal epithelial damage accompanied by high numbers of red blood cells and inflammatory cells (macrophage surface glycoproteins binding to galectin-3) and an increase of renal epithelial damage marker (T-cell Ig and mucin domain 1) in Npr2 -/- mice. Addition of 1% NaCl tended to increase apoptotic cells (cleaved caspase 3) in the renal papilla of Npr2 -/- mice. In vitro, genetic silencing of the Npr2 abolished protective effects of C-type natriuretic peptide, a ligand for Npr2, against death of M-1 kidney epithelial cells exposed to 360 mmol/L NaCl. Finally, significantly lower levels of expression of the NPR2 protein were detected in renal samples of hypertensive compared with normotensive human subjects. Taken together, these findings suggest that Npr2 is essential to protect renal epithelial cells from high concentrations of salt and prevent kidney injury., (Copyright © 2019 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

To study racial differences in tumor stage at diagnosis among Black and White patients with renal cell carcinoma (RCC) by histologic type and time period. The patients were Black and White patients with RCC from 1999 to 2011 derived from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. Multinomial logistic regression was used to assess the associations between cancer stage and race and then stratified by histology and diagnosis year. Compared to Whites, Blacks were less likely to be diagnosed with regional disease [odds ratio (OR)=0.67; 95% confidence interval (CI)=0.60-0.73] or distant disease (OR=0.82; 95% CI=0.74-0.90) after adjusting for age, sex, year of diagnosis, and tumor grade. When stratified by RCC histology, similar results were observed for clear cell (OR=0.71; 95% CI=0.63-0.80), chromophobe (OR=0.51; 95% CI=0.32-0.81), and other histologic type (OR=0.63; 95% CI=0.42-0.96) while the association was not significant for papillary histology. The analyses by time showed a lower likelihood to have regional disease in Black than White in 2003-2006 (OR=0.66; 95% CI=0.55-0.79) and 2007-2011 (OR=0.57; 95% CI=0.49-0.67). Black patients were also less likely to have distant disease in 2007-2011 period (OR=0.76; 95% CI=0.65-0.88). In conclusion, blacks were less likely to be diagnosed at a later stage RCC than Whites regardless of cancer histology. This racial disparity may exist over time during the study period.

In histopathology, the presence of a tissue change that does not represent the tissue's normal appearance can often lead to an incorrect diagnosis and interpretation. These changes are collectively known as "artifacts" resulting from postmortem autolysis, improper fixation, problems with tissue handling or slide preparation procedures. Most tissue artifacts are obvious, yet some artifacts may be subtle, occur in relatively well-fixed tissue, and demand careful observation to avoid confusion with real biological lesions. The kidney often contains artifacts that may be observed throughout all regions of the renal parenchyma. Cortical tubule artifacts present the greatest challenge when discerning an artifact versus an induced lesion following exposure to a xenobiotic. However, confounding artifacts observed at the tip of the renal papilla may also be problematic for the pathologist. An uncommon artifact involving tinctorial alteration and rarefaction affecting the papillary tip of the rat kidney is described here and differentiated from treatment induced lesions of renal papillary necrosis.

Renal medullary hypoxia may contribute to cardiac surgery-associated acute kidney injury (AKI). However, the effects of cardiopulmonary bypass (CPB) on medullary oxygenation are poorly understood. Here we tested whether CPB causes medullary hypoxia and whether medullary oxygenation during CPB can be improved by increasing pump flow or mean arterial pressure (MAP). Twelve sheep were instrumented to measure whole kidney, medullary, and cortical blood flow and oxygenation. Five days later, under isoflurane anesthesia, CPB was initiated at a pump flow of 80 mL kg -1 min -1 and target MAP of 70 mm Hg. Pump flow was then set at 60 and 100 mL kg -1 min -1 , while MAP was maintained at approximately 70 mm Hg. MAP was then increased by vasopressor (metaraminol, 0.2-0.6 mg/min) infusion at a pump flow of 80 mL kg -1 min -1 . CPB at 80 mL kg -1 min -1 reduced renal blood flow (RBF), -61% less than the conscious state, perfusion in the cortex (-44%) and medulla (-40%), and medullary Po 2 from 43 to 27 mm Hg. Decreasing pump flow from 80 to 60 mL kg -1 min -1 further decreased RBF (-16%) and medullary Po 2 from 25 to 14 mm Hg. Increasing pump flow from 80 to 100 mL kg -1 min -1 increased RBF (17%) and medullary Po 2 from 20 to 29 mm Hg. Metaraminol (0.2 mg/min) increased MAP from 63 to 90 mm Hg, RBF (47%), and medullary Po 2 from 19 to 39 mm Hg. Thus, the renal medulla is susceptible to hypoxia during CPB, but medullary oxygenation can be improved by increasing pump flow or increasing target MAP by infusion of metaraminol., (Copyright © 2019 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Objectives: To elucidate the difference in the lithogenesis of calcium oxalate and calcium phosphate stones., Methods: Renal papillary tissues were obtained from 23 idiopathic calcium oxalate and seven calcium phosphate stone patients who had undergone endoscopic lithotripsy. Samples were individually collected from two different regions in each patient: the papillary mucosa containing Randall's plaque and mucosa not containing Randall's plaque. A microarray analysis was carried out on those tissues to compare their gene expression patterns. Furthermore, a causal pathway analysis comparing their differences was carried out., Results: Cluster analysis showed that gene expression profiles of calcium phosphate stone patients markedly differed from those of calcium oxalate stone patients. Disease and function analysis showed that Randall's plaque-containing tissues of calcium phosphate stone-forming patients had significantly higher movement and migration of mononuclear leukocytes, and lower tendency toward infection and lymph node formation than Randall's plaque-containing tissues of calcium oxalate stone formers. Additional pathway analysis showed increased immune cell signaling in calcium phosphate formers, such as the helper T cell 1 and 2 pathways, which was confirmed by their messenger ribonucleic acid expression., Conclusions: The present results show the upregulation of helper T-cell signaling pathways in Randall's plaque-containing papillae in calcium phosphate, but not in calcium oxalate stone formers. Thus, helper T-cell immune responses and the related inflammatory processes seem to lead to the formation of calcium phosphate stones on Randall's plaques., (© 2019 The Japanese Urological Association.)

Because exosomes have gained attention as a source of biomarkers, we investigated if miRNAs in exosomes (exo-miRs) can report the disease progression of organ injury. Using rat renal ischemia-reperfusion injury (IRI) as a model of acute kidney injury (AKI), we determined temporally-released exo-miRs in urine during IRI and found that these exo-miRs could reliably mirror the progression of AKI. From the longitudinal measurements of miRNA expression in kidney and urine, we found that release of exo- miRs was a regulated sorting process. In the injury state, miR-16, miR-24, and miR-200c were increased in the urine. Interestingly, expression of target mRNAs of these exo-miRs was significantly altered in renal medulla. Next, in the early recovery state, exo-miRs (miR-9a, miR-141, miR-200a, miR-200c, miR-429), which share Zeb1/2 as a common target mRNA, were upregulated together, indicating that they reflect TGF-β-associated renal fibrosis. Finally, release of exo-miRs (miR-125a, miR-351) was regulated by TGF-β1 and was able to differentiate the sham and IRI even after the injured kidneys were recovered. Altogether, these data indicate that exo-miRs released in renal IRI are associated with TGF-β signaling. Temporal release of exo-miRs which share targets might be a regulatory mechanism to control the progression of AKI.

Background: The purpose of the study is to examine the effect of metformin on oxygen metabolism and mitochondrial function in the kidney of an animal model of insulinopenic diabetes in order to isolate any renoprotective effect from any concomitant effect on blood glucose homeostasis., Methods: Sprague-Dawley rats were injected with streptozotocin (STZ) (50 mg kg -1 ) and when stable started on metformin treatment (250 mg kg -1 ) in the drinking water. Rats were prepared for in vivo measurements 25 to 30 days after STZ injection, where renal function, including glomerular filtration rate and sodium transport, was estimated in anesthetized rats. Intrarenal oxygen tension was measured using oxygen sensors. Furthermore, mitochondrial function was assessed in mitochondria isolated from kidney cortex and medulla analysed by high-resolution respirometry, and superoxide production was evaluated using electron paramagnetic resonance., Results: Insulinopenic rats chronically treated with metformin for 4 weeks displayed improved medullary tissue oxygen tension despite of no effect of metformin on blood glucose homeostasis. Metformin reduced UCP2-dependent LEAK and differentially affected medullary mitochondrial superoxide radical production in control and diabetic rats., Conclusions: Metformin attenuates diabetes-induced renal medullary tissue hypoxia in an animal model of insulinopenic type 1 diabetes. The results suggest that the mechanistic pathway to attenuate the diabetes-induced medullary hypoxia is independent of blood glucose homeostasis and includes reduced UCP2-mediated mitochondrial proton LEAK., (© 2018 John Wiley & Sons, Ltd.)

The antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is released from thymosin-β4 (Tβ4) by the meprin-α and prolyl oligopeptidase (POP) enzymes and is hydrolyzed by angiotensin-converting enzyme (ACE). Ac-SDKP is present in urine; however, it is not clear whether de novo tubular release occurs or if glomerular filtration is the main source. We hypothesized that Ac-SDKP is released into the lumen of the nephrons and that it exerts an antifibrotic effect. We determined the presence of Tβ4, meprin-α, and POP in the kidneys of Sprague-Dawley rats. The stop-flow technique was used to evaluate Ac-SDKP formation in different nephron segments. Finally, we decreased Ac-SDKP formation by inhibiting the POP enzyme and evaluated the long-term effect in renal fibrosis. The Tβ4 precursor and the releasing enzymes meprin-α and POP were expressed in the kidneys. POP enzyme activity was almost double that in the renal medulla compared with the renal cortex. With the use of the stop-flow technique, we detected the highest Ac-SDKP concentrations in the distal nephron. The infusion of a POP inhibitor into the kidney decreased the amount of Ac-SDKP in distal nephron segments and in the proximal nephron to a minor extent. An ACE inhibitor increased the Ac-SDKP content in all nephron segments, but the increase was highest in the distal portion. The chronic infusion of a POP inhibitor increased kidney medullary fibrosis, which was prevented by Ac-SDKP. We conclude that Ac-SDKP is released by the nephron and is part of an important antifibrotic system in the kidney.

Objective: To investigate the renal fat fraction and water molecular diffusion features in patients with early-stage DN using Dixon imaging and diffusion tensor imaging (DTI)., Methods: Sixty-one type 2 diabetics (normoalbuminuria: n = 40; microalbuminuria: n = 21) and 34 non-diabetic volunteers were included. All participants received three-point Dixon imaging and DTI using a 3.0-T magnetic resonance imager. The fat fraction [FF] and DTI features [fractional anisotropy (FA), apparent diffusion coefficient (ADC), tract counts and length from DTI tractography] were collected. All image features were compared between cohorts using one-way ANOVA with Bonferroni post-hoc analysis., Results: Renal FF in the microalbuminuric group was significantly higher than in the normoalbuminuric and control groups (5.6% ± 1.3%, 4.7% ± 1.1% and 4.3% ± 0.5%, respectively; p < 0.001). Medullary FA in the microalbuminuric group was the lowest (0.31 ± 0.06) in all cohorts. The tract counts and length in the renal medulla were significantly lower in the microalbuminuric group than in the other two groups., Conclusions: Dixon imaging and DTI are able to detect renal lipid deposition and water molecule diffusion abnormalities in patients with early-stage DN. Both techniques have the potential to noninvasively evaluate early renal impairment in type 2 diabetes., Key Points: • Dixon imaging demonstrated renal fat deposition in early-stage DN; • Renal fractional anisotropy decreased in patients with early-stage DN; • Renal tractography demonstrated reduced track counts and length in early-stage DN.

A main feature of Fabry disease is nephropathy, with polyuria an early manifestation; however, the mechanism that underlies polyuria and affected tubules is unknown. To increase globotriaosylceramide (Gb3) levels, we previously crossbred asymptomatic Gla tm mice with transgenic mice that expressed human Gb3 synthase (A4GALT) and generated the Gla tm Tg(CAG-A4GALT) symptomatic Fabry model mice. Additional analyses revealed that these mice exhibit polyuria and renal dysfunction without remarkable glomerular damage. In the present study, we investigated the mechanism of polyuria and renal dysfunction in these mice. Gb3 accumulation was mostly detected in the medulla; medullary thick ascending limbs (mTALs) were the most vacuolated tubules. mTAL cells contained lamellar bodies and had lost their characteristic structure ( i.e., extensive infolding and numerous elongated mitochondria). Decreased expression of the major molecules-Na + -K + -ATPase, uromodulin, and Na + -K + -2Cl - cotransporter-that are involved in Na + reabsorption in mTALs and the associated loss of urine-concentrating ability resulted in progressive water- and salt-loss phenotypes. Gla tm Tg(CAG-A4GALT) mice exhibited fibrosis around mTALs and renal dysfunction. These and other features were consistent with pathologic findings in patients with Fabry disease. Results demonstrate that mTAL dysfunction causes polyuria and renal impairment and contributes to the pathophysiology of Fabry nephropathy.-Maruyama, H., Taguchi, A., Nishikawa, Y., Guili, C., Mikame, M., Nameta, M., Yamaguchi, Y., Ueno, M., Imai, N., Ito, Y., Nakagawa, T., Narita, I., Ishii, S. Medullary thick ascending limb impairment in the Gla tm Tg(CAG-A4GALT) Fabry model mice.