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Matsushita et al. describe a model of acute kidney injury to chronic kidney disease progression in mice surviving cardiac arrest: mice develop severe acute kidney injury that initially recovers but is followed by the onset of impaired renal function on longer-term follow-up. These findings suggest that distinct cardiorenal toxicities and/or injury dynamics are operative in this cardiac arrest model that do not occur in traditional models of acute kidney injury, providing new opportunities for therapeutic and biomarker discovery for an important clinical problem.
Copyright © 2019 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Acute kidney injury (AKI) is a strong independent predictor of mortality and often results in incomplete recovery of renal function, leading to progressive chronic kidney disease (CKD). Many clinical trials have been conducted on the basis of promising preclinical data, but no therapeutic interventions have been shown to improve long-term outcomes after AKI. This is partly due to the failure of preclinical studies to accurately model clinically relevant injury and long-term outcomes on CKD progression. Here, we evaluated the long-term effects of AKI on CKD progression in three animal models reflecting diverse etiologies of AKI: repeat-dose cisplatin, rhabdomyolysis, and ischemia-reperfusion injury. Using transdermal measurement of glomerular filtration rate as a clinically relevant measure of kidney function and quantification of peritubular capillary density to measure capillary rarefaction, we showed that repeat-dose cisplatin caused capillary rarefaction and decreased renal function in mice without a significant increase in interstitial fibrosis, whereas rhabdomyolysis-induced AKI led to severe interstitial fibrosis, but renal function and peritubular capillary density were preserved. Furthermore, long-term experiments in mice with unilateral ischemia-reperfusion injury showed that restoration of renal function 12 wk after a contralateral nephrectomy was associated with increasing fibrosis, but a reversal of capillary rarefaction was seen at 4 wk. These data demonstrate that clear dissociation between kidney function and fibrosis in these models of AKI to CKD progression and suggest that peritubular capillary rarefaction is more strongly associated with CKD progression than renal fibrosis.

Prolyl hydroxylase domain oxygen sensors are dioxygenases that regulate the activity of hypoxia-inducible factor (HIF), which controls renal and hepatic erythropoietin production and coordinates erythropoiesis with iron metabolism. Small molecule inhibitors of prolyl hydroxylase domain dioxygenases (HIF-PHI [prolyl hydroxylase inhibitor]) stimulate the production of endogenous erythropoietin and improve iron metabolism resulting in efficacious anemia management in patients with CKD. Three oral HIF-PHIs-daprodustat, roxadustat, and vadadustat-have now advanced to global phase III clinical development culminating in the recent licensing of roxadustat for oral anemia therapy in China. Here, we survey current clinical experience with HIF-PHIs, discuss potential therapeutic advantages, and deliberate over safety concerns regarding long-term administration in patients with renal anemia.
Copyright © 2019 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Chronic kidney disease (CKD), defined by low estimated glomerular filtration rate (eGFR), contributes to global morbidity and mortality. Here we conduct a transethnic Genome-Wide Association Study of eGFR in 280,722 participants of the Million Veteran Program (MVP), with replication in 765,289 participants from the Chronic Kidney Disease Genetics (CKDGen) Consortium. We identify 82 previously unreported variants, confirm 54 loci, and report interesting findings including association of the sickle cell allele of betaglobin among non-Hispanic blacks. Our transcriptome-wide association study of kidney function in healthy kidney tissue identifies 36 previously unreported and nine known genes, and maps gene expression to renal cell types. In a Phenome-Wide Association Study in 192,868 MVP participants using a weighted genetic score we detect associations with CKD stages and complications and kidney stones. This investigation reinterprets the genetic architecture of kidney function to identify the gene, tissue, and anatomical context of renal homeostasis and the clinical consequences of dysregulation.

BACKGROUND - Sex differences mediating predisposition to kidney injury are well known, with evidence indicating lower CKD incidence rates and slower decline in renal function in nondiabetic CKD for premenopausal women compared with men. However, signaling pathways involved have not been elucidated to date. The EGF receptor (EGFR) is widely expressed in the kidney in glomeruli and tubules, and persistent and dysregulated EGFR activation mediates progressive renal injury.
METHODS - To investigate the sex differences in response to renal injury, we examined EGFR expression in mice, in human kidney tissue, and in cultured cell lines.
RESULTS - In wild type mice, renal mRNA and protein EGFR levels were comparable in males and females at postnatal day 7 but were significantly lower in age-matched adult females than in adult males. Similar gender differences in renal EGFR expression were detected in normal adult human kidneys. In Dsk5 mutant mice with a gain-of-function allele that increases basal EGFR kinase activity, males had progressive glomerulopathy, albuminuria, loss of podocytes, and tubulointerstitial fibrosis, but female Dsk5 mice had minimal kidney injury. Oophorectomy had no effect on renal EGFR levels in female Dsk5 mice, while castration protected against the kidney injury in male Dsk5 mice, in association with a reduction in EGFR expression to levels seen in females. Conversely, testosterone increased EGFR expression and renal injury in female Dsk5 mice. Testosterone directly stimulated EGFR expression in cultured kidney cells.
CONCLUSIONS - These studies indicate that differential renal EGFR expression plays a role in the sex differences in susceptibility to progressive kidney injury that may be mediated at least in part by testosterone.
Copyright © 2019 by the American Society of Nephrology.

Chronic kidney disease (CKD) is responsible for a public health burden with multi-systemic complications. Through trans-ancestry meta-analysis of genome-wide association studies of estimated glomerular filtration rate (eGFR) and independent replication (n = 1,046,070), we identified 264 associated loci (166 new). Of these, 147 were likely to be relevant for kidney function on the basis of associations with the alternative kidney function marker blood urea nitrogen (n = 416,178). Pathway and enrichment analyses, including mouse models with renal phenotypes, support the kidney as the main target organ. A genetic risk score for lower eGFR was associated with clinically diagnosed CKD in 452,264 independent individuals. Colocalization analyses of associations with eGFR among 783,978 European-ancestry individuals and gene expression across 46 human tissues, including tubulo-interstitial and glomerular kidney compartments, identified 17 genes differentially expressed in kidney. Fine-mapping highlighted missense driver variants in 11 genes and kidney-specific regulatory variants. These results provide a comprehensive priority list of molecular targets for translational research.

Transforming growth factor-β (TGF-β) is a key profibrotic growth factor that is activated in acute kidney injury (AKI) and associated with cellular responses that lead to the development of chronic kidney disease (CKD). The persistently injured, de-differentiated tubular epithelial cell is an important mediator of the transition from AKI to CKD. TGF-β signaling may perpetuate proximal tubule injury through de-differentiation, cell cycle arrest, and increased susceptibility to apoptosis. In addition, TGF-β signaling promotes macrophage chemotaxis, endothelial injury, and myofibroblast differentiation after AKI. Future studies that block TGF-β signaling after cessation of AKI are needed to better define its role in the progression of acute to chronic renal injury.
© 2019 S. Karger AG, Basel.

Fibrosis contributes to the progression of chronic kidney disease (CKD). Severe acute kidney injury can lead to CKD through proximal tubular cell (PTC) cycle arrest in the G-M phase, with secretion of profibrotic factors. Here, we show that epithelial cells in the G-M phase form target of rapamycin (TOR)-autophagy spatial coupling compartments (TASCCs), which promote profibrotic secretion similar to the senescence-associated secretory phenotype. Cyclin G1 (CG1), an atypical cyclin, promoted G-M arrest in PTCs and up-regulated TASCC formation. PTC TASCC formation was also present in humans with CKD. Prevention of TASCC formation in cultured PTCs blocked secretion of profibrotic factors. PTC-specific knockout of a key TASCC component reduced the rate of kidney fibrosis progression in mice with CKD. CG1 induction and TASCC formation also occur in liver fibrosis. Deletion of CG1 reduced G-M phase cells and TASCC formation in vivo. This study provides mechanistic evidence supporting how profibrotic G-M arrest is induced in kidney injury and how G-M-arrested PTCs promote fibrosis, identifying new therapeutic targets to mitigate kidney fibrosis.
Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

BACKGROUND - Older adults with advanced CKD have significant pain, other symptoms, and disability. To help ensure that care is consistent with patients' values, nephrology providers should understand their patients' priorities when they make clinical recommendations.
METHODS - Patients aged ≥60 years with advanced (stage 4 or 5) non-dialysis-dependent CKD receiving care at a CKD clinic completed a validated health outcome prioritization tool to ascertain their health outcome priorities. For each patient, the nephrology provider completed the same health outcome prioritization tool. Patients also answered questions to self-rate their health and completed an end-of-life scenarios instrument. We examined the associations between priorities and self-reported health status and between priorities and acceptance of common end-of-life scenarios, and also measured concordance between patients' priorities and providers' perceptions of priorities.
RESULTS - Among 271 patients (median age 71 years), the top health outcome priority was maintaining independence (49%), followed by staying alive (35%), reducing pain (9%), and reducing other symptoms (6%). Nearly half of patients ranked staying alive as their third or fourth priority. There was no relationship between patients' self-rated health status and top priority, but acceptance of some end-of-life scenarios differed significantly between groups with different top priorities. Providers' perceptions about patients' top health outcome priorities were correct only 35% of the time. Patient-provider concordance for any individual health outcome ranking was similarly poor.
CONCLUSIONS - Nearly half of older adults with advanced CKD ranked maintaining independence as their top heath outcome priority. Almost as many ranked being alive as their last or second-to-last priority. Nephrology providers demonstrated limited knowledge of their patients' priorities.
Copyright © 2018 by the American Society of Nephrology.

BACKGROUND AND OBJECTIVES - HDL particles obtained from patients on chronic hemodialysis exhibit lower cholesterol efflux capacity and are enriched in inflammatory proteins compared with those in healthy individuals. Observed alterations in HDL proteins could be due to effects of CKD, but also may be influenced by the hemodialysis procedure, which stimulates proinflammatory and prothrombotic pathways.
DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS - We compared HDL-associated proteins in 143 participants who initiated hemodialysis within the previous year with those of 110 participants with advanced CKD from the Hemodialysis Fistula Maturation Study. We quantified concentrations of 38 HDL-associated proteins relative to total HDL protein using targeted mass spectrometry assays that included a stable isotope-labeled internal standard. We used linear regression to compare the relative abundances of HDL-associated proteins after adjustment and required a false discovery rate value ≤10% to control for multiple testing. We further assessed the association between hemodialysis initiation and cholesterol efflux capacity in a subset of 80 participants.
RESULTS - After adjustment for demographics, comorbidities, and other clinical characteristics, eight HDL-associated proteins met the prespecified false discovery threshold for association. Recent hemodialysis initiation was associated with higher HDL-associated concentrations of serum amyloid A1, A2, and A4; hemoglobin-; haptoglobin-related protein; cholesterylester transfer protein; phospholipid transfer protein; and apo E. The trend for participants recently initiating hemodialysis for lower cholesterol efflux capacity compared with individuals with advanced CKD did not reach statistical significance.
CONCLUSIONS - Compared with advanced CKD, hemodialysis initiation within the previous year is associated with higher concentrations of eight HDL proteins related to inflammation and lipid metabolism. Identified associations differ from those recently observed for nondialysis-requiring CKD. Hemodialysis initiation may further impair cholesterol efflux capacity. Further work is needed to clarify the clinical significance of the identified proteins with respect to cardiovascular risk.
PODCAST - This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2018_07_25_CJASNPodcast_18_8_W.mp3.
Copyright © 2018 by the American Society of Nephrology.