Nephrology
Abstract
BACKGROUND. Assessment of risk for chronic kidney disease (CKD) after acute kidney injury (AKI) is based on a limited set of markers primarily reflecting glomerular function. We evaluated markers of cell integrity (EGF) and inflammation (monocyte chemoattractant protein-1 [MCP-1]) for predicting long-term kidney outcomes after cardiac surgery. METHODS. We measured the urinary biomarkers EGF and MCP-1 in pre- and post-operative urine samples from 865 adult patients who underwent cardiac surgery from 2007–2010 at 2 sites in Canada and the United States and assessed their associations with the composite outcome of CKD incidence or progression. We also used single-cell (Sc) RNAseq of biopsies from patients with AKI to perform a transcriptomic analysis of programs that are coregulated with the genes encoding the 2 biomarkers. RESULTS. Over a median (IQR) follow-up of 5.8 (4.2-7.1) years, 266 (30.8%) patients developed the composite CKD outcome. Post-operatively, higher levels of urinary EGF were protective and higher levels of MCP-1 were associated with the composite CKD outcome (adjusted HR 0.83, 95% CI 0.73-0.95 and 1.10, 95% CI 1.00-1.21, respectively). Intrarenal scRNAseq transcriptomes in patients with AKI-defined cell populations revealed concordant changes in EGF and MCP-1 levels and identified underlying molecular processes associated with loss of EGF expression and gain of CCL2 (encoding MCP-1) expression. CONCLUSION. Urinary EGF and MCP-1 were each independently associated with CKD incidence or progression after cardiac surgery. These markers may serve as noninvasive indicators of tubular damage, supported by tissue transcriptomes and provide opportunity for novel interventions in cardiac surgery. TRIAL REGISTRATION. ClinicalTrials.gov NCT00774137 FUNDING. NIH (R01HL085757 to CRP) funded the TRIBE-AKI Consortium.
Authors
Steven Menez, Wenjun Ju, Rajasree Menon, Dennis G. Moledina, Heather Thiessen Philbrook, Eric McArthur, Yaqi Jia, Wassim Obeid, Sherry G. Mansour, Jay K. Koyner, Michael G. Shlipak, Steven G. Coca, Amit X. Garg, John A. Kellum, Andrew S Bomback, Matthias Kretzler, Chirag R. Parikh
Abstract
Loss of function of the lipid kinase diacylglycerol kinase ε (DGKε), encoded by the gene DGKE, causes a form of atypical hemolytic uremic syndrome that is not related to abnormalities of the alternative pathway of the complement, by mechanisms that are not understood. By generating a potentially novel endothelial specific Dgke-knockout mouse, we demonstrate that loss of Dgke in the endothelium results in impaired signaling downstream of VEGFR2 due to cellular shortage of phosphatidylinositol 4,5-biphosphate. Mechanistically, we found that, in the absence of DGKε in the endothelium, Akt fails to be activated upon VEGFR2 stimulation, resulting in defective induction of the enzyme cyclooxygenase 2 and production of prostaglandin E2 (PGE2). Treating the endothelial specific Dgke-knockout mice with a stable PGE2 analog was sufficient to reverse the clinical manifestations of thrombotic microangiopathy and proteinuria, possibly by suppressing the expression of matrix metalloproteinase 2 through PGE2-dependent upregulation of the chemokine receptor CXCR4. Our study reveals a complex array of autocrine signaling events downstream of VEGFR2 that are mediated by PGE2, that control endothelial activation and thrombogenic state, and that result in abnormalities of the glomerular filtration barrier.
Authors
Dingxiao Liu, Qiong Ding, Dao-Fu Dai, Biswajit Padhy, Manasa K. Nayak, Can Li, Madison Purvis, Heng Jin, Chang Shu, Anil K. Chauhan, Chou-Long Huang, Massimo Attanasio
Abstract
BACKGROUND. Serum creatinine concentrations (SCr) are used to determine the presence and severity of acute kidney injury (AKI). SCr is primarily eliminated by glomerular filtration; however, most mechanisms of AKI in critical illness involve kidney proximal tubules, where tubular secretion occurs. Proximal tubular secretory clearance is not currently estimated in the ICU. Our objective was to estimate the kidney clearance of secretory solutes in critically ill adults. METHODS. We collected matched blood and spot urine samples from 170 ICU patients and from a comparison group of 70 adults with normal kidney function. We measured seven endogenously produced secretory solutes using liquid chromatography-tandem mass spectrometry. We computed a composite secretion score incorporating all seven solutes, and evaluated associations with 28-day major adverse kidney events (MAKE28), defined as doubling of SCr, dialysis dependence, or death. RESULTS. The urine/plasma ratio of six of seven secretory solutes were lower in critically ill patients compared with normal individuals after adjustment for SCr. The composite secretion score was moderately correlated with SCr and cystatin C (r = -0.51 and r = -0.53, respectively). Each standard deviation higher composite secretion score was associated with a 25% lower risk of MAKE28 (95% CI 9% - 38% lower) independent of severity of illness, SCr and tubular injury markers. Higher urine to plasma ratios of individual secretory solutes isovalerylglycine and tiglylglycine were associated with MAKE28 after accounting for multiple testing. CONCLUSIONS. Among critically ill adults, tubular secretory clearance is associated with adverse outcomes and measurement could improve assessment of kidney function and dosing of essential ICU medications. TRIAL REGISTRATION. None. FUNDING. PKB was supported by grants from the Digestive and Kidney Diseases K23DK116967, the University of Washington Diabetes Research Center P30DK017047, and an unrestricted gift to the Kidney Research Institute from the Northwest Kidney Centers. EDS was supported by the Vanderbilt O’Brien Kidney Center (NIDDK 5P30 DK114809-03) The funding sources had no role in design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.
Authors
Pavan K. Bhatraju, Xin-Ya Chai, Neha A. Sathe, John Ruzinski, Edward D. Siew, Jonathan Himmelfarb, Andrew N. Hoofnagle, Mark M. Wurfel, Bryan R. Kestenbaum
Abstract
Flow-activated Na+ and HCO3- transport in kidney proximal tubules (PTs) underlies relatively constant fractional reabsorption during changes in glomerular filtration rate (GFR), or glomerulotubular balance (GTB). In view of hypothesized connections of epithelial cilia to flow-sensing, we examined flow-activated transport in three polycystic kidney disease-related mouse models based on inducible conditional knockout (KO) of Pkd1, Pkd2, and Kif3a. PTs. were harvested from mice after gene inactivation but prior to cyst formation, and flow-mediated PTs transport were measured. We confirm that higher flow increases both Na+ and HCO3- absorption in control and observe that this flow effect is preserved in PTs of Pkd1-/- and Kif3a-/-mice. However, flow-activation is absent in Pkd2+/- and Pkd2-/- proximal tubules. In heterozygous (Pkd2+/-) mice, a dopamine receptor (DA1) antagonist (SCH23390) restored transport flow sensitivity. When given chronically, this same antagonist reduced renal cyst formation in Pkd2-/- as evidenced by reduced kidney weight, BUN and the cystic index, when compared to untreated mice. In contrast, SCH23390 did not prevent cyst formation in Pkd1-/- mice. These results indicate that Pkd2 is necessary for normal GTB, and that restoration of flow-activated transport by DA1 antagonist can slow renal cyst formation in Pkd2-/- mice.
Authors
Zhaopeng Du, Xin Tian, Ming Ma, Stefan Somlo, Alan M. Weinstein, Tong Wang
Abstract
Left ventricular hypertrophy (LVH) is a primary feature of cardiovascular complications in chronic kidney disease (CKD) patients. MiRNA-30 is an important posttranscriptional regulator of LVH, but it is unknown whether miRNA-30 participates in the process of CKD-induced LVH. In the present study, we found that CKD not only results in LVH but also suppresses miRNA-30 expression in the myocardium. Rescue of cardiomyocyte-specific miRNA-30 attenuates LVH in CKD rats without altering CKD progression. Importantly, in vivo and in vitro knockdown of miRNA-30 in cardiomyocytes leads to cardiomyocyte hypertrophy by upregulating the calcineurin signalling directly. Furthermore, CKD-related detrimental factors, such as fibroblast growth factor-23 (FGF-23), uraemic toxin, angiotensin-II (Ang-II) and transforming growth factor-β (TGF-β), suppress cardiac miRNA-30 expression, while miRNA-30 supplementation blunts cardiomyocyte hypertrophy induced by such factors. These results uncover a novel mechanism of CKD-induced LVH and provide a potential therapeutic target for CKD patients with LVH.
Authors
Jingfu Bao, Yinghui Lu, Qin-ying She, Weijuan Dou, Rong Tang, Xiaodong Xu, Mingchao Zhang, Ling Zhu, Qing Zhou, Hui Li, Guohua Zhou, Zhongzhou Yang, Shaolin Shi, Zhihong Liu, Chunxia Zheng
Abstract
Endothelial cells are important in the maintenance of healthy blood vessels and in the development of vascular diseases. However, the origin and dynamics of endothelial precursors and remodeling at the single-cell level have been difficult to study in vivo due to technical limitations. We aimed to develop a direct visual approach to track the fate and function of single endothelial cells over several days-weeks in the same vascular bed in vivo using multiphoton microscopy (MPM) of transgenic Cdh5-Confetti mice and the kidney glomerulus as a model. Individual cells of the vascular endothelial lineage were identified and tracked due to their unique color combination, based on the random expression of cyan/green/yellow/red fluorescent proteins. Experimental hypertension, hyperglycemia, and laser-induced endothelial cell ablation rapidly increased the number of new glomerular endothelial cells that appeared in clusters of the same color, suggesting clonal cell remodeling by local precursors at the vascular pole. Furthermore, intravital MPM allowed the detection of distinct structural and functional alterations of proliferating endothelial cells. No circulating Cdh5-Confetti+ cells were found in the renal cortex. The heart, lung, and kidneys showed more significant clonal endothelial cell expansion compared to the brain, pancreas, liver and spleen. Serial MPM of Cdh5-Confetti mice in vivo is a powerful new technical advance to study endothelial remodeling and repair in the kidney and other organs under physiological and disease conditions.
Authors
Dorinne Desposito, Ina Maria Schiessl, Georgina Gyarmati, Anne Riquier-Brison, Audrey Izuhara, Hiroyuki Kadoya, Balint Der, Urvi Nikhil Shroff, Young-Kwon Hong, Janos Peti-Peterdi
Abstract
Despite the recent launch of Tolvaptan, the search for safer polycystic kidney disease (PKD) drugs continues. Ciclopirox (CPX) or its olamine salt (CPX-O) are contained in number of commercially available antifungal agents. CPX is also reported to possess anticancer activity. Several mechanisms of action have been proposed including chelation of iron and inhibition of iron dependent enzymes. Here, we show that CPX-O inhibited in vitro cystogenesis of primary human PKD cyst-lining epithelial cells cultured in a 3D collagen matrix. To assess in vivo role of CPX-O, we treated PKD mice with CPX-O. CPX-O reduced the kidney- to-body weight ratios of PKD mice. This was also associated with decreased cell proliferation, decreased cystic area and improved renal function. Ferritin levels were significantly elevated in cystic kidneys of PKD mice, and CPX-O treatment reduced renal ferritin levels. The reduction in ferritin was associated with increased ferritinophagy marker, NCOA4 which reversed upon CPX-O treatment in PKD mice. Interestingly, these effects on ferritin appeared independent of iron. These data suggest that CPX-O can induce ferritin degradation via ferritinophagy which is associated with decreased cyst growth progression in PKD mice. Most importantly these data indicate that CPX-O has the potential to treat autosomal dominant PKD.
Authors
Priyanka S. Radadiya, Mackenzie M. Thornton, Rajni V. Puri, Sireeesha Yerrathota, Johnny Dinh-Phan, Brenda Magenheimer, Dharmalingam Subramaniam, Pamela V. Tran, Hao Zhu, Subhashini Bolisetty, James P. Calvet, Darren P. Wallace, Madhulika Sharma
Abstract
Mutations in LAMB2, encoding laminin β2, cause Pierson syndrome and occasionally milder nephropathy without extrarenal abnormalities. The most deleterious missense mutations that have been identified affect primarily the N-terminus of laminin β2. On the other hand, those associated with isolated nephropathy are distributed across the entire molecule, and variants in the β2 LEa-LF-LEb domains are exclusively found in cases with isolated nephropathy. Here we report the clinical features of mild isolated nephropathy associated with 3 LAMB2 variants in the LEa-LF-LEb domains (p.R469Q, p.G699R, and p.R1078C) and their biochemical characterization. Although Pierson syndrome missense mutations often inhibit laminin β2 secretion, the 3 recombinant variants were secreted as efficiently as WT. However, the β2 variants lost pH dependency for heparin binding, resulting in aberrant binding under physiologic conditions. This suggests that the binding of laminin β2 to negatively charged molecules is involved in glomerular basement membrane (GBM) permselectivity. Moreover, the excessive binding of the β2 variants to other laminins appears to lead to their increased deposition in the GBM. Laminin β2 also serves as a potentially novel cell-adhesive ligand for integrin α4β1. Our findings define biochemical functions of laminin β2 variants influencing glomerular filtration that may underlie the pathogenesis of isolated nephropathy caused by LAMB2 abnormalities.
Authors
Yamato Kikkawa, Taeko Hashimoto, Keiichi Takizawa, Seiya Urae, Haruka Masuda, Masumi Matsunuma, Yuji Yamada, Keisuke Hamada, Motoyoshi Nomizu, Helen Liapis, Masataka Hisano, Yuko Akioka, Kenichiro Miura, Motoshi Hattori, Jeffrey H. Miner, Yutaka Harita
Abstract
Nephrogenic diabetes insipidus (NDI) patients produce large amounts of dilute urine. NDI can be congenital, resulting from mutations in the type-2 vasopressin receptor (V2R), or acquired, resulting from medications such as lithium. There are no good treatment options for NDI. Activation of PKA is disrupted in both congenital and acquired NDI, resulting in decreased aquaporin-2 phosphorylation and water reabsorption. We showed that adenosine monophosphate-activated protein kinase (AMPK) also phosphorylates aquaporin-2. We identified an activator of AMPK, NDI-5033, and tested its ability to increase urine concentration in animal models of NDI. NDI-5033 increased AMPK phosphorylation by 2.5 fold, confirming activation. It increased urine osmolality in tolvaptan-treated NDI rats by 30-50%, and in V2R knockout mice by 50%. Metformin, another AMPK activator, can cause hypoglycemia. It would be risky to treat NDI patients, especially children, with NDI-5033 if it caused hypoglycemia. Rats with NDI receiving NDI-5033 showed no hypoglycemia in a calorie-restricted, exercise protocol. Congenital NDI therapy needs to be effective long-term. We administered NDI-5033 for 3 weeks and saw no reduction in efficacy. We conclude that NDI-5033 can improve urine concentration in animals with NDI and holds promise as a potential therapy for patients with congenital NDI due to V2R mutations.
Authors
Janet D. Klein, Ish Khanna, Sivaram Pillarisetti, Rachael A. Hagan, Lauren M. LaRocque, Eva L. Rodriguez, Jeff M. Sands
Abstract
Morphologic examination of tissue biopsies is essential for histopathological diagnosis. However, accurate and scalable cellular quantification in human samples remains challenging. Here, we present a deep learning-based approach for antigen-specific cellular morphometrics in human kidney biopsies, which combines indirect immunofluorescence imaging with U-Net-based architectures for image-to-image translation and dual segmentation tasks, achieving human-level accuracy. In the kidney, podocyte loss represents a hallmark of glomerular injury and can be estimated in diagnostic biopsies. Thus, we profiled over 27,000 podocytes from 110 human samples, including patients with anti-neutrophil cytoplasmic antibody-associated glomerulonephritis (ANCA-GN), an immune-mediated disease with aggressive glomerular damage and irreversible loss of kidney function. We identified previously unknown morphometric signatures of podocyte depletion in patients with ANCA-GN, which allowed patient classification and, in combination with routine clinical tools, showed potential for risk stratification. Our approach enables robust and scalable molecular morphometric analysis of human tissues, yielding deeper biological insights into the human kidney pathophysiology.
Authors
Marina Zimmermann, Martin Klaus, Milagros N. Wong, Ann-Katrin Thebille, Lukas Gernhold, Christoph Kuppe, Maurice Halder, Jennifer Kranz, Nicola Wanner, Fabian Braun, Sonia Wulf, Thorsten Wiech, Ulf Panzer, Christian F. Krebs, Elion Hoxha, Rafael Kramann, Tobias B. Huber, Stefan Bonn, Victor G. Puelles
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