Nephrology
Abstract
Acute kidney injury (AKI) is a common clinical condition of growing incidence. Patients who suffer severe AKI have a higher risk of developing interstitial fibrosis, chronic kidney disease, and end-stage renal disease later in life. Cellular senescence is a persistent cell cycle arrest and altered gene expression pattern evoked by multiple stressors. The number of senescent cells increases with age and even in small numbers these cells can induce chronic inflammation and fibrosis; indeed, in multiple organs including kidneys, the accumulation of such cells is a hallmark of aging. We hypothesized that cellular senescence might be induced in the kidney after injury and that this might contribute to progressive organ fibrosis. Testing this hypothesis, we found that tubular epithelial cells (TECs) in mice senesce within a few days of kidney injury and that this response is mediated by epithelial Toll-like and interleukin 1 receptors (TLR/IL-1R) of the innate immune system. Epithelial cell–specific inhibition of innate immune signaling in mice by knockout of myeloid differentiation 88 (Myd88) reduced fibrosis as well as damage to kidney tubules, and also prevented the accumulation of senescent TECs. Importantly, although inactivation of Myd88 after injury ameliorated fibrosis, it did not reduce damage to the tubules. Selectively induced apoptosis of senescent cells by two different approaches only partially reduced kidney fibrosis, without ameliorating damage to the tubules. Our data reveal a cell-autonomous role for epithelial innate immunity in controlling TEC senescence after kidney injury, and additionally suggest that early therapeutic intervention is required for effective reduction of long-term sequelae of AKI.
Authors
Heng Jin, Yan Zhang, Qiong Ding, Shan Shan Wang, Prerna Rastogi, Dao-Fu Dai, Dongmei Lu, Madison Purvis, Chao Cao, Angela Wang, Dingxiao Liu, Chongyu Ren, Sarah Elhadi, Ming-Chang Hu, Yanfen Chai, Diana Zepeda-Orozco, Judith Campisi, Massimo Attanasio
Abstract
Acute kidney injury (AKI) is a devastating clinical condition affecting at least two-thirds of critically ill patients, and, among these patients, it is associated with a greater than 60% risk of mortality. Kidney mononuclear phagocytes (MPs) are implicated in pathogenesis and healing in mouse models of AKI and, thus, have been the subject of investigation as potential targets for clinical intervention. We have determined that, after injury, F4/80hi-expressing kidney-resident macrophages (KRMs) are a distinct cellular subpopulation that does not differentiate from nonresident infiltrating MPs. However, if KRMs are depleted using polyinosinic/polycytidylic acid (poly I:C), they can be reconstituted from bone marrow–derived precursors. Further, KRMs lack major histocompatibility complex class II (MHCII) expression before P7 but upregulate it over the next 14 days. This MHCII– KRM phenotype reappears after injury. RNA sequencing shows that injury causes transcriptional reprogramming of KRMs such that they more closely resemble that found at P7. KRMs after injury are also enriched in Wingless-type MMTV integration site family (Wnt) signaling, indicating that a pathway vital for mouse and human kidney development is active. These data indicate that mechanisms involved in kidney development may be functioning after injury in KRMs.
Authors
Jeremie M. Lever, Travis D. Hull, Ravindra Boddu, Mark E. Pepin, Laurence M. Black, Oreoluwa O. Adedoyin, Zhengqin Yang, Amie M. Traylor, Yanlin Jiang, Zhang Li, Jacelyn E. Peabody, Hannah E. Eckenrode, David K. Crossman, Michael R. Crowley, Subhashini Bolisetty, Kurt A. Zimmerman, Adam R. Wende, Michal Mrug, Bradley K. Yoder, Anupam Agarwal, James F. George
Abstract
Podocyte injury is central to many forms of kidney disease, but transcriptional signatures reflecting podocyte injury and compensation mechanisms are challenging to analyze in vivo. Human kidney organoids derived from pluripotent stem cells (PSCs), a potentially new model for disease and regeneration, present an opportunity to explore the transcriptional plasticity of podocytes. Here, transcriptional profiling of more than 12,000 single cells from human PSC–derived kidney organoid cultures was used to identify robust and reproducible cell lineage gene expression signatures shared with developing human kidneys based on trajectory analysis. Surprisingly, the gene expression signature characteristic of developing glomerular epithelial cells was also observed in glomerular tissue from a kidney disease cohort. This signature correlated with proteinuria and inverse eGFR, and it was confirmed in an independent podocytopathy cohort. Three genes in particular were further characterized as potentially novel components of the glomerular disease signature. We conclude that cells in human PSC–derived kidney organoids reliably recapitulate the developmental transcriptional program of podocytes and other cell lineages in the human kidney and that transcriptional profiles seen in developing podocytes are reactivated in glomerular disease. Our findings demonstrate an approach to identifying potentially novel molecular programs involved in the pathogenesis of glomerulopathies.
Authors
Jennifer L. Harder, Rajasree Menon, Edgar A. Otto, Jian Zhou, Sean Eddy, Noel L. Wys, Christopher O’Connor, Jinghui Luo, Viji Nair, Cristina Cebrian, Jason R. Spence, Markus Bitzer, Olga G. Troyanskaya, Jeffrey B. Hodgin, Roger C. Wiggins, Benjamin S. Freedman, Matthias Kretzler, European Renal cDNA Bank (ERCB), Nephrotic Syndrome Study Network (NEPTUNE)
Abstract
Drug-induced kidney injury, largely caused by proximal tubular intoxicants, limits development and clinical use of new and approved drugs. Assessing preclinical nephrotoxicity relies on animal models that are frequently insensitive; thus, potentially novel techniques — including human microphysiological systems, or “organs on chips” — are proposed to accelerate drug development and predict safety. Polymyxins are potent antibiotics against multidrug-resistant microorganisms; however, clinical use remains restricted because of high risk of nephrotoxicity and limited understanding of toxicological mechanisms. To mitigate risks, structural analogs of polymyxins (NAB739 and NAB741) are currently in clinical development. Using a microphysiological system to model human kidney proximal tubule, we exposed cells to polymyxin B (PMB) and observed significant increases of injury signals, including kidney injury molecule-1 KIM-1and a panel of injury-associated miRNAs (each P < 0.001). Surprisingly, transcriptional profiling identified cholesterol biosynthesis as the primary cellular pathway induced by PMB (P = 1.22 ×10–16), and effluent cholesterol concentrations were significantly increased after exposure (P < 0.01). Additionally, we observed no upregulation of the nuclear factor (erythroid derived-2)–like 2 pathway, despite this being a common pathway upregulated in response to proximal tubule toxicants. In contrast with PMB exposure, minimal changes in gene expression, injury biomarkers, and cholesterol concentrations were observed in response to NAB739 and NAB741. Our findings demonstrate the preclinical safety of NAB739 and NAB741 and reveal cholesterol biosynthesis as a potentially novel pathway for PMB-induced injury. To our knowledge, this is the first demonstration of a human-on-chip platform used for simultaneous safety testing of new chemical entities and defining unique toxicological pathway responses of an FDA-approved molecule.
Authors
Elijah J. Weber, Kevin A. Lidberg, Lu Wang, Theo K. Bammler, James W. MacDonald, Mavis J. Li, Michelle Redhair, William M. Atkins, Cecilia Tran, Kelly M. Hines, Josi Herron, Libin Xu, Maria Beatriz Monteiro, Susanne Ramm, Vishal Vaidya, Martti Vaara, Timo Vaara, Jonathan Himmelfarb, Edward J. Kelly
Abstract
BACKGROUND. The molecular understanding of the progression from acute to chronic organ injury is limited. Ischemia/reperfusion injury (IRI) triggered during kidney transplantation can contribute to progressive allograft dysfunction. METHODS. Protocol biopsies (n = 163) were obtained from 42 kidney allografts at 4 time points after transplantation. RNA sequencing–mediated (RNA-seq–mediated) transcriptional profiling and machine learning computational approaches were employed to analyze the molecular responses to IRI and to identify shared and divergent transcriptional trajectories associated with distinct clinical outcomes. The data were compared with the response to IRI in a mouse model of the acute to chronic kidney injury transition. RESULTS. In the first hours after reperfusion, all patients exhibited a similar transcriptional program under the control of immediate-early response genes. In the following months, we identified 2 main transcriptional trajectories leading to kidney recovery or to sustained injury with associated fibrosis and renal dysfunction. The molecular map generated by this computational approach highlighted early markers of kidney disease progression and delineated transcriptional programs associated with the transition to chronic injury. The characterization of a similar process in a mouse IRI model extended the relevance of our findings beyond transplantation. CONCLUSIONS. The integration of multiple transcriptomes from serial biopsies with advanced computational algorithms overcame the analytical hurdles related to variability between individuals and identified shared transcriptional elements of kidney disease progression in humans, which may prove as useful predictors of disease progression following kidney transplantation and kidney injury. This generally applicable approach opens the way for an unbiased analysis of human disease progression. FUNDING. The study was supported by the California Institute for Regenerative Medicine and by the Swiss National Science Foundation.
Authors
Pietro E. Cippà, Bo Sun, Jing Liu, Liang Chen, Maarten Naesens, Andrew P. McMahon
Abstract
Our previous work demonstrated a protective role of protein S in early diabetic kidney disease (DKD). Protein S exerts antiinflammatory and antiapoptotic effects through the activation of TYRO3, AXL, and MER (TAM) receptors. Among the 3 TAM receptors, we showed that the biological effects of protein S were mediated largely by TYRO3 in diabetic kidneys. Our data now show that TYRO3 mRNA expression is highly enriched in human glomeruli and that TYRO3 protein is expressed in podocytes. Interestingly, glomerular TYRO3 mRNA expression increased in mild DKD but was suppressed in progressive DKD, as well as in focal segmental glomerulosclerosis (FSGS). Functionally, morpholino-mediated knockdown of tyro3 altered glomerular filtration barrier development in zebrafish larvae, and genetic ablation of Tyro3 in murine models of DKD and Adriamycin-induced nephropathy (ADRN) worsened albuminuria and glomerular injury. Conversely, the induction of TYRO3 overexpression specifically in podocytes significantly attenuated albuminuria and kidney injury in mice with DKD, ADRN, and HIV-associated nephropathy (HIVAN). Mechanistically, TYRO3 expression was suppressed by activation of TNF-α/NF-κB pathway, which may contribute to decreased TYRO3 expression in progressive DKD and FSGS, and TYRO3 signaling conferred antiapoptotic effects through the activation of AKT in podocytes. In conclusion, TYRO3 plays a critical role in maintaining normal podocyte function and may be a potential new drug target to treat glomerular diseases.
Authors
Fang Zhong, Zhaohong Chen, Liwen Zhang, Yifan Xie, Viji Nair, Wenjun Ju, Matthias Kretzler, Robert G. Nelson, Zhengzhe Li, Hongyu Chen, Yongjun Wang, Aihua Zhang, Kyung Lee, Zhihong Liu, John Cijiang He
Abstract
TGF-β signals through a receptor complex composed of 2 type I and 2 type II (TGF-βRII) subunits. We investigated the role of macrophage TGF-β signaling in fibrosis after AKI in mice with selective monocyte/macrophage TGF-βRII deletion (macrophage TGF-βRII–/– mice). Four weeks after injury, renal TGF-β1 expression and fibrosis were higher in WT mice than macrophage TGF-βRII–/– mice, which had decreased renal macrophages. The in vitro chemotactic response to f-Met-Leu-Phe was comparable between bone marrow–derived monocytes (BMMs) from WT and macrophage TGF-βRII–/– mice, but TGF-βRII–/– BMMs did not respond to TGF-β. We then implanted Matrigel plugs suffused with either f-Met-Leu-Phe or TGF-β1 into WT or macrophage TGF-βRII–/– mice. After 6 days, f-Met-Leu-Phe induced similar macrophage infiltration into the Matrigel plugs of WT and macrophage TGF-βRII–/– mice, but TGF-β induced infiltration only in WT mice. We further determined the number of labeled WT or TGF-βRII–/– BMMs infiltrating into WT kidneys 20 days after ischemic injury. There were more labeled WT BMMs than TGF-βRII–/– BMMs. Therefore, macrophage TGF-βRII deletion protects against the development of tubulointerstitial fibrosis following severe ischemic renal injury. Chemoattraction of macrophages to the injured kidney through a TGF-β/TGF-βRII axis is a heretofore undescribed mechanism by which TGF-β can mediate renal fibrosis during progressive renal injury.
Authors
Sungjin Chung, Jessica M. Overstreet, Yan Li, Yinqiu Wang, Aolei Niu, Suwan Wang, Xiaofeng Fan, Kensuke Sasaki, Guan-Nan Jin, Stellor Nlandu Khodo, Leslie Gewin, Ming-Zhi Zhang, Raymond C. Harris
Abstract
Gut microbiota–derived metabolites play important roles in health and disease. D–amino acids and their L-forms are metabolites of gut microbiota with distinct functions. In this study, we show the pathophysiologic role of D–amino acids in association with gut microbiota in humans and mice with acute kidney injury (AKI). In a mouse kidney ischemia/reperfusion model, the gut microbiota protected against tubular injury. AKI-induced gut dysbiosis contributed to the altered metabolism of D–amino acids. Among the D–amino acids, only D-serine was detectable in the kidney. In injured kidneys, the activity of D–amino acid oxidase was decreased. Conversely, the activity of serine racemase was increased. The oral administration of D-serine mitigated the kidney injury in B6 mice and D-serine–depleted mice. D-serine suppressed hypoxia-induced tubular damage and promoted posthypoxic tubular cell proliferation. Finally, the D-serine levels in circulation were significantly correlated with the decrease in kidney function in AKI patients. These results demonstrate the renoprotective effects of gut-derived D-serine in AKI, shed light on the interactions between the gut microbiota and the kidney in both health and AKI, and highlight D-serine as a potential new therapeutic target and biomarker for AKI.
Authors
Yusuke Nakade, Yasunori Iwata, Kengo Furuichi, Masashi Mita, Kenji Hamase, Ryuichi Konno, Taito Miyake, Norihiko Sakai, Shinji Kitajima, Tadashi Toyama, Yasuyuki Shinozaki, Akihiro Sagara, Taro Miyagawa, Akinori Hara, Miho Shimizu, Yasutaka Kamikawa, Kouichi Sato, Megumi Oshima, Shiori Yoneda-Nakagawa, Yuta Yamamura, Shuichi Kaneko, Tetsuya Miyamoto, Masumi Katane, Hiroshi Homma, Hidetoshi Morita, Wataru Suda, Masahira Hattori, Takashi Wada
Abstract
Chronic obstructive pulmonary disease (COPD), associated with cigarette smoke–induced (CS-induced) emphysema, contributes significantly to the global health care burden of disease. Although chronic kidney disease (CKD) may occur in patients with COPD, the relationship between COPD and CKD remains unclear. Using a murine model of experimental COPD, we show that chronic CS exposure resulted in marked kidney injury and fibrosis, as evidenced by histological and ultrastructural changes, altered macrophage subpopulations, and expression of tissue injury, fibrosis, and oxidative stress markers. CS induced mitochondrial dysfunction, and increased autophagic flux in kidney tissues and in kidney tubular epithelial (HK-2) cells, as determined by LC3B turnover assays. Mice heterozygous for Beclin-1 (Becn1+/–) were protected from the development of kidney tissue injury and renal fibrosis in response to CS exposure, and displayed impaired basal and inducible mitochondrial turnover by mitophagy. Interestingly, CS caused a reduction of Beclin-1 expression in mouse kidneys and kidney tubular epithelial cells, attributed to increased autophagy-dependent turnover of Beclin-1. These results suggest that Beclin-1 is required for CS-induced kidney injury and that reduced levels of Beclin-1 may confer renoprotection. These results identify the kidney as a target for CS-induced injury in COPD and the Beclin-1–dependent autophagy pathway as a potential therapeutic target in CKD.
Authors
Maria A. Pabón, Edwin Patino, Divya Bhatia, Jocelyn Quintero, Kevin C. Ma, Eli J. Finkelsztein, Juan C. Osorio, Faryal Malick, Francesca Polverino, Caroline A. Owen, Stefan W. Ryter, Augustine M.K. Choi, Suzanne M. Cloonan, Mary E. Choi
Abstract
Lipocalin-2 is not only a sensitive biomarker, but it also contributes to the pathogenesis of renal injuries. The present study demonstrates that adipose tissue–derived lipocalin-2 plays a critical role in causing both chronic and acute renal injuries. Four-week treatment with aldosterone and high salt after uninephrectomy (ANS) significantly increased both circulating and urinary lipocalin-2, and it induced glomerular and tubular injuries in kidneys of WT mice. Despite increased renal expression of lcn2 and urinary excretion of lipocalin-2, mice with selective deletion of lcn2 alleles in adipose tissue (Adipo-LKO) are protected from ANS- or aldosterone-induced renal injuries. By contrast, selective deletion of lcn2 alleles in kidney did not prevent aldosterone- or ANS-induced renal injuries. Transplantation of fat pads from WT donors increased the sensitivity of mice with complete deletion of Lcn2 alleles (LKO) to aldosterone-induced renal injuries. Aldosterone promoted the urinary excretion of a human lipocalin-2 variant, R81E, in turn causing renal injuries in LKO mice. Chronic treatment with R81E triggered significant renal injuries in LKO, resembling those observed in WT mice following ANS challenge. Taken in conjunction, the present results demonstrate that lipocalin-2 derived from adipose tissue causes acute and chronic renal injuries, largely independent of local lcn2 expression in kidney.
Authors
Wai Yan Sun, Bo Bai, Cuiting Luo, Kangmin Yang, Dahui Li, Donghai Wu, Michel Félétou, Nicole Villeneuve, Yang Zhou, Junwei Yang, Aimin Xu, Paul M. Vanhoutte, Yu Wang
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