Nephrology
Abstract
ADAMTS9 mutations cause the ciliopathies nephronophthisis and Joubert syndrome. Here we demonstrated that deletion of ADAMTS9 in the proximal nephron led to polycystic kidney development in mice. In males, Adamts9 deletion caused kidneys to become highly cystic while remaining small without undergoing enlargement. In contrast, female mice developed cystic kidneys at a slower rate. ADAMTS9 deletion disrupted ciliogenesis through the loss of cleavage of the ciliary transition zone (TZ) protein TMEM67, which led to loss of the MKS/B9 module – a key component of the ciliary gate. Functional analysis of all eight ciliopathy patient variants of ADAMTS9 identified to date showed TMEM67 C-terminus failed to localize to the TZ, thus disrupting a key regulatory mechanism in patient renal ciliogenesis. Modeling ADAMTS9-mediated TMEM67 cleavage utilizing TMEM67-cleavage deficient mice revealed loss of TZ formation, but not elevated canonical Wnt signaling as the underlying mechanism driving cystogenesis. Adamts9 deletion led to comparatively intense interstitial collagen deposition, which likely restricted kidney enlargement and resulted in the characteristically small kidney phenotype seen in nephronophthisis. By comparative analysis of four interconnected polycystic kidney models, in addition to Pkd1 and Pkd2 deleted kidneys, we identified differential collagen homeostasis as a principle factor determining cystic kidney size and type.
Authors
Sydney Fischer, Karyn L. Robert, Manu Ahmed, Griffin I. Kane, Matthew A. Kavanaugh, Wei Wang, Pamela V. Tran, Prabhani U. Atukorale, Sumeda Nandadasa
Abstract
Authors
Long Qian, Megan L. Baker, Laura Aponte Becerra, Cathleen Liang, Emma Koval, Kyra Shelton, Daris Javed, Gilbert Moeckel, Deepika Kumar, Avi Z. Rosenberg, Michael Kuperman, Tinyi Chu, Wassim Obeid, Xuefei Tian, Chirag R. Parikh, Leyuan Xu, Jonathan Barasch, Shuta Ishibe, Lloyd G. Cantley, Dennis G. Moledina
Abstract
ACE2 is a membrane-bound monocarboxypeptidase strongly expressed in the renal proximal tubule (PT) with high affinity to degrade the vasopressor angiotensin II (AngII). We employed a mouse model of PT-specific ACE2 deletion (PT ACE2–KO) to demonstrate that the renal PT is a critical site for ACE2 regulation of blood pressure (BP) via modulation of the intrarenal renin-angiotensin system (RAS). While deletion of ACE2 from the PT had a minimal effect on baseline physiology, PT ACE2–KO mice were more susceptible to AngII hypertension than control mice. At day 5 of AngII infusion, the enhanced BP response was associated with cardiac hypertrophy, increased renal AngII levels, failure to suppress epithelial sodium channel (ENaC) γ cleavage, and increased sodium pump activity in PT ACE2–KO mice. Control mice instead increased renal ACE2 expression to reduce renal AngII accumulation and suppress intrarenal RAS activation, which offered protection from hypertension and complications. Transcriptional analysis corroborated changes in intrarenal RAS components and revealed alterations in distinct physiological pathways during AngII hypertension in PT ACE2–KO mice. Our studies provide evidence for alterations in ENaC regulation to contribute to the development of AngII hypertension and support PT-derived ACE2 as an integral member of the intrarenal RAS.
Authors
Jacqueline M. Emathinger, Zhidan Xiang, Jonathan W. Nelson, Matthew W. Hagen, Nakyung Kim, David I. Ortiz-Melo, Natalie Mattocks, Jorge F. Giani, Dexter L. Lee, Hannah Hartman-Houstman, Donna L. Ralph, Alicia A. McDonough, Brianna Chen, Stan G. Louie, Thomas M. Coffman, Susan B. Gurley
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is a leading genetic cause of kidney failure, characterized by progressive cyst growth, inflammation, and interstitial fibrosis. Renal fibrosis, driven by myofibroblast activation and excessive extracellular matrix (ECM) deposition, is increasingly recognized as a key contributor to disease progression, yet targeted antifibrotic therapies remain limited. Here, we evaluated the therapeutic potential of pirfenidone to suppress fibrosis and disease progression in ADPKD. Single-nucleus RNA sequencing of human ADPKD kidneys identified fibroblasts as the predominant source of fibrous and adhesive ECM, with higher ECM-associated gene expression compared with that in normal kidney fibroblasts. In vitro, primary human ADPKD renal myofibroblasts displayed a similar profibrotic gene expression profile, and pirfenidone treatment suppressed ECM gene expression, cell proliferation, migration, and contractility. In the Pkd1RC/RC mouse model of ADPKD, pirfenidone reduced renal fibrosis, myofibroblast accumulation, ECM deposition, profibrotic gene expression, and associated signaling pathways and improved kidney function. Pirfenidone also reduced kidney enlargement but reduced cyst burden only in female mice. Collectively, these findings demonstrate that pirfenidone attenuates renal fibrosis and improves kidney function in ADPKD by suppressing myofibroblast activation and ECM production, supporting fibrosis as a therapeutic target and highlighting pirfenidone as a potential adjunct to cyst-directed therapies.
Authors
Viji Remadevi, Abeda Jamadar, Meekha M. Varghese, Haichun Yang, Sumedha Gunewardena, Darren P. Wallace, Reena Rao
Abstract
TGF-β is a central driver of kidney fibrosis, a common pathological hallmark of chronic kidney disease (CKD). Initiation of TGF-β signaling requires not only its synthesis but also the conversion of latent TGF-β to its bioactive form. However, the mechanisms governing TGF-β activation in the kidney and their contribution to kidney fibrosis remain poorly understood. Glycoprotein A repetitions predominant (GARP) anchors latent TGF-β on the cell surface and facilitates its bioactive release. Here, we show that GARP-mediated TGF‐β activation promotes kidney fibrosis. GARP was upregulated in both human and mouse CKD kidneys, predominantly in fibroblasts, and was induced by TNF in an NF-kB-dependent fashion. In multiple mouse models of kidney fibrosis, either global or fibroblast-specific deletion of GARP significantly reduced fibrosis. Mechanistically, GARP enables sustained production of active TGF-β, thereby amplifying fibroblast stimulation. Deletion of GARP in kidney fibroblasts lowered active TGF-β levels and attenuated fibroblast activation, whereas GARP overexpression enhanced TGF-β signaling. Notably, tamoxifen-induced deletion of GARP after fibrosis onset attenuated kidney fibrosis. Together, our findings identify GARP-mediated release of active TGF‐β as a critical step in sustaining fibroblast activation during kidney fibrosis and highlight GARP as a promising therapeutic target for CKD.
Authors
Yintong Chen, Weiwei Xu, Jieli Yu, Pei Deng, Nianping Liu, Yinyin Li, Hui Zhou, Hong Zhou, Jianchuan Wang, Bo Zhao, Florian Winau, Fan Fan Hou, Yu Hu
Abstract
Early diagnosis of cystinosis is critical to limit disease progression. YKL-40, a protein in the chitinase family, released by inflammatory cells, may be a useful biomarker for cystinosis. In a case-control study of 10 children with cystinosis and 20 without cystinosis, matched by age and baseline eGFR, we measured urine YKL-40, NGAL, and EGF. A lateral flow device (LFD) for YKL-40 was also developed and tested. Urine YKL-40 was over 200-fold higher in children with cystinosis (64.6 ng/mL [IQR: 23.4, 83.8]) compared with controls (0.3 [IQR: 0.3, 0.79]; P = 0.0001) with excellent diagnostic discrimination (AUC = 0.99) that was superior to other biomarkers. LFD measurements for YKL-40 showed similar results (AUC = 0.93). YKL-40 results were verified in 5 cystinosis patients, and YKL-40 staining was markedly higher in kidney biopsies from cystinosis patients than in healthy controls. Urine YKL-40 has excellent diagnostic potential for cystinosis, and point-of-care technologies may facilitate early screening and management of this disease.
Authors
Jason H. Greenberg, Serena D Souza, Heather R. Thiessen Philbrook, Wassim Obeid, Avi Z. Rosenberg, Elena Levtchenko, Koenraad Veys, Susan L. Furth, Chirag R. Parikh
Abstract
Autoimmune kidney diseases can cause glomerulonephritis and tubulointerstitial nephritis, which if unresolved, lead to progressive glomerulosclerosis and tubulointerstitial fibrosis. The IL-1 receptor (IL-1R1) is known to have divergent and cell-specific effects in kidney injury. We hypothesized that IL-1R1 would dampen pro-inflammatory activation of myeloid cells such that deletion of myeloid cell IL-1R1 would exacerbate autoimmune nephritis. Mice with myeloid cell-specific deletion of IL-1R1 (LysMCre(+) / Il1r1fl/fl - MKO) and littermate controls (LysMCre(-) / Il1r1fl/fl - MWT) were subjected to nephrotoxic serum (NTS) nephritis. MKO mice demonstrated worsened glomerular and tubular injury as indicated by increased albuminuria, glomerular injury scores, and kidney mRNA levels of kidney injury molecule (KIM)-1 (Havcr1) and neutrophil gelatinase-associated lipocalin (NGAL/Lcn2). We further found that myeloid IL-1R1 deficiency resulted in increased myeloid cell ER stress and expression of the heterodimeric cytokine Ebi3/Il27a (IL-27). IL-27 then induced increased type I IFN expression by kidney endothelial cells. In turn, anti-IL-27 limited type I IFN expression in endothelial cells and NTS nephritis, and anti-IFNAR1 therapy ameliorated glomerular and tubular injury in MKO mice. Thus, we demonstrated a myeloid cell-endothelial cell immunoregulatory axis whereby myeloid IL-1R1 activity constrained endothelial type I IFN generation to limit chronic kidney damage.
Authors
Yanting Chen, Yu Li, Jiafa Ren, Chia-Chun Wu, Xiaohan Lu, Achintya Inumarty, Steven D. Crowley, Jamie R. Privratsky
Abstract
Obesity is a major risk factor for chronic kidney disease. Time-restricted feeding (TRF) shows promise to reduce kidney inflammation in chronic kidney disease. We hypothesized that TRF blunts kidney fibrosis in obese mice by mitigating T cell inflammation. We used a diet-induced obese mouse model fed a high fat diet (DIO, 45% fat) ad libitum for 18 weeks followed by 2 weeks of TRF or ad libitum high fat feeding. We found that TRF reversed kidney fibrosis as well as reduced kidney CD8+ T cells in DIO mice. Our study also revealed that DIO mice had increased kidney CD8+ T cell infiltration from the small intestine that was blunted with TRF. Furthermore, anti-CD8 intervention in DIO showed reduced kidney fibrosis and damage compared to anti-IgG treated DIO mice. Single cell RNA sequencing data revealed that DIO increased, while TRF reduced, the frequency of a specific cluster of CD8+ T cells that featured high expression of exhaustion/activation genes. Spatial analyses showed DIO mice had significant infiltration of PD-1+CD8+ T cells near CD31+ endothelial cells that was diminished by TRF. In conclusion, this study discovered that TRF reverses kidney fibrosis through reducing CD8+ T cell infiltration in obese mice.
Authors
Claudia J. Edell, John D. Erickson, Xiaofen Liu, Savannah C. Walker, Jackson Colson, Michael Heim, Pranav Nagila, Kyle H. Moore, Keri M. Kemp, Kelly Hyndman, Selene Meza-Perez, Troy D. Randall, Annye P. Bennett, Anna G. Sorace, Yu-Hua Dean Fang, David M. Pollock, Carmen De Miguel, Julienne L. Carstens, Jennifer S. Pollock
Abstract
The pathogenesis of Bartter syndrome (BS) has long been attributed to decreased salt reabsorption in the thick ascending limb of Henle’s loop (TAL). By studying Clc-k2 (mouse ortholog of ClC-Kb)-knockout (Clc-k2-/-) mice, we recently uncovered an additional mechanism in which loss of Clc-k2 induces TAL hypoplasia in neonatal kidneys, exacerbating BS severity. Here, we further investigated this mechanism. TALs and distal convoluted tubules (DCTs) isolated from Clc-k2-/- and wild-type mice were used for transcriptome, proteomics, cell cycle, and proliferation assays. Mitochondrial morphology and function were studied using electron microscopy and mitochondrial respiration assays. Our results revealed impairments in cell proliferation, S-to-G2/M cell cycle transition, mitochondrial biogenesis, oxidative phosphorylation, glycolysis, and fatty acid oxidation in Clc-k2-/- TALs and DCTs. Increasing transport function by introducing a gain-of-function with-no-lysine kinase 4 mutation in Clc-k2-/- mice restored these metabolic and proliferative impairments and improved phenotype. Transgenic expression of peroxisome proliferator-activated receptor gamma coactivator-1α, a master regulator of mitochondrial biogenesis, in Clc-k2-/- mice also alleviated mitochondrial dysfunction and phenotype. These findings support the hypothesis that mitochondrial hypofunction, resulting from decreased transport function, contributes to cell cycle arrest and tubular hypoplasia in BS. Targeting mitochondria early in life could be a potential therapeutic approach for BS.
Authors
Chiao-Hui Hsieh, Yu-Jen Chen, Chih-Chien Sung, Emily Morrison, Chou-Long Huang, Chih-Jen Cheng
Abstract
Systemic lupus erythematosus (SLE) is a progressive autoimmune disease that affects multiple organs and tissues, with lupus nephritis (LN) as one of its most severe complications. While LN progression is associated with compromised permeability of human renal glomerular endothelial cells (HRGECs), the underlying mechanisms are not fully defined. Herein, we demonstrate that aberrant glycolysis drives this glomerular endothelial barrier defect by suppressing the transcription of tight junction (TJ) genes. Mechanistically, circulating self-DNA in SLE plasma acts as a ligand that activates the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway in HRGECs, driving aberrant glycolytic adaption. The resulting glycolytic product, lactate, serves as a substrate for protein lactylation, leading to extensive lactylation and subsequent ubiquitination of the enhancer of zeste homolog 2 (EZH2). In consequence, EZH2 deficiency results in reduced H3K27me3 levels, thereby suppressing the transcription of TJ genes. In a self-DNA-induced SLE model, inhibition of cGAS-STING signaling or lactate production effectively restored the integrity of TJs of HRGECs and concurrently alleviated key LN symptoms. Together, lactate programs lactylation and ubiquitination of EZH2 to impair glomerular endothelial barrier in human SLE.
Authors
Jiaxin Lei, Xingyu Zhai, Yixin Wang, Ying Li, Lei Li, Mengdi Liu, Jing Guo, Lingyi Li, Zhezhuyun Chen, Qinghua Cao, Zhichun Liu, Ting Liu, Lin Xu, Zhenke Wen
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