Targeting the progression of chronic kidney disease

Advanced Drug Delivery Systems for Renal Disorders

Kidney disease management and treatment are currently causing a substantial global burden. The kidneys are the most important organs in the human urinary system, selectively filtering blood and metabolic waste into urine via the renal glomerulus. Based on charge and/or molecule size, the glomerular filtration apparatus acts as a barrier to therapeutic substances. Therefore, drug distribution to the kidneys is challenging, resulting in therapy failure in a variety of renal illnesses. Hence, different approaches to improve drug delivery across the glomerulus filtration barrier are being investigated. Nanotechnology in medicine has the potential to have a significant impact on human health, from illness prevention to diagnosis and treatment. Nanomaterials with various physicochemical properties, including size, charge, surface and shape, with unique biological attributes, such as low cytotoxicity, high cellular internalization and controllable biodistribution and pharmacokinetics, have demonstrated promising potential in renal therapy. Different types of nanosystems have been employed to deliver drugs to the kidneys. This review highlights the features of the nanomaterials, including the nanoparticles and corresponding hydrogels, in overcoming various barriers of drug delivery to the kidneys. The most common delivery sites and strategies of kidney-targeted drug delivery systems are also discussed.

Targeting inflammation to treat diabetic kidney disease: the road to 2030

Diabetic kidney disease (DKD) is one of the fastest growing causes of chronic kidney disease and associated morbidity and mortality. Preclinical research has demonstrated the involvement of inflammation in its pathogenesis and in the progression of kidney damage, supporting clinical trials designed to explore anti-inflammatory strategies. However, the recent success of sodium-glucose cotransporter-2 inhibitors and the nonsteroidal mineralocorticoid receptor antagonist finerenone has changed both guidelines and standard of care, rendering obsolete older studies directly targeting inflammatory mediators and the clinical development was discontinued for most anti-inflammatory drugs undergoing clinical trials for DKD in 2016. Given the contribution of inflammation to the pathogenesis of DKD, we review the impact on kidney inflammation of the current standard of care, therapies undergoing clinical trials, or repositioned drugs for DKD. Moreover, we review recent advances in the molecular regulation of inflammation in DKD and discuss potential novel therapeutic strategies with clinical relevance. Finally, we provide a road map for future research aimed at integrating the growing knowledge on inflammation and DKD into clinical practice to foster improvement of patient outcomes.

The prediction of in-hospital mortality in chronic kidney disease patients with coronary artery disease using machine learning models

OBJECTIVE

Chronic kidney disease (CKD) patients with coronary artery disease (CAD) in the intensive care unit (ICU) have higher in-hospital mortality and poorer prognosis than patients with either single condition. The objective of this study is to develop a novel model that can predict the in-hospital mortality of that kind of patient in the ICU using machine learning methods.

METHODS

Data of CKD patients with CAD were extracted from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Boruta algorithm was conducted for the feature selection process. Eight machine learning algorithms, such as logistic regression (LR), random forest (RF), Decision Tree, K-nearest neighbors (KNN), Gradient Boosting Decision Tree Machine (GBDT), Support Vector Machine (SVM), Neural Network (NN), and Extreme Gradient Boosting (XGBoost), were conducted to construct the predictive model for in-hospital mortality and performance was evaluated by average precision (AP) and area under the receiver operating characteristic curve (AUC). Shapley Additive Explanations (SHAP) algorithm was applied to explain the model visually. Moreover, data from the Telehealth Intensive Care Unit Collaborative Research Database (eICU-CRD) were acquired as an external validation set.

RESULTS

3590 and 1657 CKD patients with CAD were acquired from MIMIC-IV and eICU-CRD databases, respectively. A total of 78 variables were selected for the machine learning model development process. Comparatively, GBDT had the highest predictive performance according to the results of AUC (0.946) and AP (0.778). The SHAP method reveals the top 20 factors based on the importance ranking. In addition, GBDT had good predictive value and a certain degree of clinical value in the external validation according to the AUC (0.865), AP (0.672), decision curve analysis, and calibration curve.

CONCLUSION

Machine learning algorithms, especially GBDT, can be reliable tools for accurately predicting the in-hospital mortality risk for CKD patients with CAD in the ICU. This contributed to providing optimal resource allocation and reducing in-hospital mortality by tailoring precise management and implementation of early interventions.

Antifibrotic Soluble Thy-1 Correlates with Renal Dysfunction in Chronic Kidney Disease

Kidney fibrosis is a major culprit in the development and progression of chronic kidney disease (CKD), ultimately leading to the irreversible loss of organ function. Thymocyte differentiation antigen-1 (Thy-1) controls many core functions of fibroblasts relevant to fibrogenesis but is also found in a soluble form (sThy-1) in serum and urine. We investigated the association of sThy-1 with clinical parameters in patients with CKD receiving hemodialysis treatment compared to individuals with a preserved renal function. Furthermore, Thy-1 tissue expression was detected in a mouse model of diabetic CKD (eNOS^-/-; db/db) and non-diabetic control mice (eNOS^-/-). Serum and urinary sThy-1 concentrations significantly increased with deteriorating renal function, independent of the presence of diabetes. Serum creatinine is the major, independent, and inverse predictor of serum sThy-1 levels. Moreover, sThy-1 is not only predicted by markers of renal function but is also itself an independent and strong predictor of markers of renal function, i.e., serum creatinine. Mice with severe diabetic CKD show increased Thy-1 mRNA and protein expression in the kidney compared to control animals, as well as elevated urinary sThy-1 levels. Pro-fibrotic mediators, such as interleukin (IL)-4, IL-13, IL-6 and transforming growth factor β, increase Thy-1 gene expression and release of sThy-1 from fibroblasts. Our data underline the role of Thy-1 in the control of kidney fibrosis in CKD and raise the opportunity that Thy-1 may function as a renal antifibrotic factor.

Catalpol Attenuates Oxidative Stress and Inflammation via Mechanisms Involving Sirtuin-1 Activation and NF-κB Inhibition in Experimentally-Induced Chronic Kidney Disease

Chronic kidney disease (CKD) is a stealthy disease, and its development is linked to mechanisms including inflammation and oxidative stress. Catalpol (CAT), an iridoid glucoside from the root of Rehmannia glutinosa, is reported to manifest anti-inflammatory, antioxidant, antiapoptotic and antifibrotic properties. Hence, we studied the possible nephroprotective effects of CAT and its mechanisms in an adenine-induced (0.2% w/w in feed for 4 weeks) murine model of CKD by administering 5 mg/kg CAT to BALB/c mice for the duration of 4 weeks except during weekends. Upon sacrifice, the kidney, plasma and urine were collected and various physiological, biochemical and histological endpoints were assessed. CAT significantly ameliorated the adenine-induced altered body and kidney weight, water intake, urine volume, and concentrations of urea and creatinine in plasma, as well as the creatinine clearance and the albumin and creatinine ratio. Moreover, CAT significantly ameliorated the effect of adenine-induced kidney injury by reducing the kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, cystatin C and adiponectin. Similarly, the augmented concentrations of markers of inflammation and oxidative stress in the adenine-treated group were markedly reduced with CAT pretreatment. Furthermore, CAT prevented adenine-induced deoxyribonucleic acid damage and apoptotic activity in the kidneys. Histologically, CAT significantly reduced the formation of tubular necrosis and dilation, as well as interstitial fibrosis in the kidney. In addition to that, CAT significantly decreased the adenine-induced increase in the phosphorylated NF-κB and reversed the reduced expression of sirtuin-1 in the kidney. In conclusion, CAT exhibits salutary effects against adenine-induced CKD in mice by mitigating inflammation, oxidative stress and fibrosis via mechanisms involving sirtuin-1 activation and NF-κB inhibition. Confirmatory studies are warranted in order to consider CAT as a potent nephroprotective agent against CKD.

The Role of Myofibroblasts in Physiological and Pathological Tissue Repair

Myofibroblasts are the construction workers of wound healing and repair damaged tissues by producing and organizing collagen/extracellular matrix (ECM) into scar tissue. Scar tissue effectively and quickly restores the mechanical integrity of lost tissue architecture but comes at the price of lost tissue functionality. Fibrotic diseases caused by excessive or persistent myofibroblast activity can lead to organ failure. This review defines myofibroblast terminology, phenotypic characteristics, and functions. We will focus on the central role of the cell, ECM, and tissue mechanics in regulating tissue repair by controlling myofibroblast action. Additionally, we will discuss how therapies based on mechanical intervention potentially ameliorate wound healing outcomes. Although myofibroblast physiology and pathology affect all organs, we will emphasize cutaneous wound healing and hypertrophic scarring as paradigms for normal tissue repair versus fibrosis. A central message of this review is that myofibroblasts can be activated from multiple cell sources, varying with local environment and type of injury, to either restore tissue integrity and organ function or create an inappropriate mechanical environment.

Network Pharmacology Approach to Investigate the Mechanism of Danggui-Shaoyao-San against Diabetic Kidney Disease

Background

Danggui-Shaoyao-San (DSS) is a traditional Chinese medicine formula that has been widely used to treat a variety of disorders, including renal diseases. Despite being well-established in clinical practice, the mechanisms behind the therapeutic effects of DSS on diabetic nephropathy (DN) remain elusive.

Methods

To explore the therapeutic mechanism, we explored the action mechanism of DSS on DN using network pharmacology strategies. All ingredients were selected from the relevant databases, and active ingredients were chosen on the basis of their oral bioavailability prediction and drug-likeness evaluation. The putative proteins of DSS were obtained from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database, whereas the potential genes of DN were obtained from the GeneCards and OMIM databases. Enrichment analysis using gene ontology (GO) and the Kyoto encyclopedia of genes and genomes (KEGG) was performed to discover possible hub targets and gene-related pathways. Afterwards, the underlying molecular mechanisms of DSS against DN were validated experimentally in vivo against db/db mice.

Results

We identified 91 phytochemicals using the comprehensive network pharmacology technique, 51 of which were chosen as bioactive components. There were 40 proteins and 20 pathways in the target-pathway network. The experimental validation results demonstrated that DSS may reduce the expression of TNF-α, IL-6, and ICAM-1, as well as extracellular matrix deposition, by blocking the JNK pathway activation, which protects against kidney injury.

Conclusion

This study discovered the putative molecular mechanisms of action of DSS against diabetic kidney damage through a network pharmacology approach and experimental validation.

Cellular senescence of renal tubular epithelial cells in renal fibrosis

Renal fibrosis (RF) is the common pathological manifestation of virtually all chronic kidney diseases (CKD) and one of the major causes of end-stage renal disease (ESRD), but the pathogenesis of which is still unclear. Renal tubulointerstitial lesions have been identified as a key pathological hallmark of RF pathology. Renal tubular epithelial cells are the resident cells of the tubulointerstitium and play an important role in kidney recovery versus renal fibrosis following injury. Studies in recent years have shown that senescence of renal tubular epithelial cells can accelerate the progression of renal fibrosis. Oxidative stress(OS), telomere attrition and DNA damage are the major causes of renal tubular epithelial cell senescence. Current interventions and therapeutic strategies for cellular senescence include calorie restriction and routine exercise, Klotho, senolytics, senostatics, and other related drugs. This paper provides an overview of the mechanisms and the key signaling pathways including Wnt/β-catenin/RAS, Nrf2/ARE and STAT-3/NF-κB pathway involved in renal tubular epithelial cell senescence in RF and therapies targeting renal tubular epithelial cell senescence future therapeutic potential for RF patients. These findings may offer promise for the further treatment of RF and CKD.

Role of sex hormones in diabetic nephropathy

Diabetic nephropathy (DN) is the most common microvascular complication in diabetes and one of the leading causes of end-stage renal disease. The standard treatments for patients with classic DN focus on blood glucose and blood pressure control, but these treatments can only slow the progression of DN instead of stopping or reversing the disease. In recent years, new drugs targeting the pathological mechanisms of DN (e.g., blocking oxidative stress or inflammation) have emerged, and new therapeutic strategies targeting pathological mechanisms are gaining increasing attention. A growing number of epidemiological and clinical studies suggest that sex hormones play an important role in the onset and progression of DN. Testosterone is the main sex hormone in males and is thought to accelerate the occurrence and progression of DN. Estrogen is the main sex hormone in females and is thought to have renoprotective effects. However, the underlying molecular mechanism by which sex hormones regulate DN has not been fully elucidated and summarized. This review aims to summarize the correlation between sex hormones and DN and evaluate the value of hormonotherapy in DN.

Obesity and chronic kidney disease

The prevalence of obesity has increased dramatically during the past decades, which has been a major health problem. Since 1975, the number of people with obesity worldwide has nearly tripled. An increasing number of studies find obesity as a driver of chronic kidney disease (CKD) progression, and the mechanisms are complex and include hemodynamic changes, inflammation, oxidative stress, and activation of the renin-angiotensin-aldosterone system (RAAS). Obesity-related kidney disease is characterized by glomerulomegaly, which is often accompanied by localized and segmental glomerulosclerosis lesions. In these patients, the early symptoms are atypical, with microproteinuria being the main clinical manifestation and nephrotic syndrome being rare. Weight loss and RAAS blockers have a protective effect on obesity-related CKD, but even so, a significant proportion of patients eventually progress to end-stage renal disease despite treatment. Thus, it is critical to comprehend the mechanisms underlying obesity-related CKD to create new tactics for slowing or stopping disease progression. In this review, we summarize current knowledge on the mechanisms of obesity-related kidney disease, its pathological changes, and future perspectives on its treatment.

Construction and Validation of a Nomogram for Predicting Acute Kidney Injury After Hip Fracture Surgery

Background

Acute kidney injury (AKI), characterized by sudden impairment of kidney function, is an uncommon complication following hip fracture surgery that is associated with increased morbidity and mortality. We constructed a nomogram to stratify patients according to risk of AKI after hip fracture surgery to guide clinicians in the implementation of timely interventions.

Methods

Patients who received hip fracture surgery from January 2015 to December 2021 were retrospectively identified and divided into a training set (n=448, surgery from January 2015 to December 2019) and a validation set (n=200, surgery from January 2020 to December 2021). Univariate and multivariate logistic regression were used to identify risk factors for AKI after surgery in the training set. A nomogram was constructed based the risk factors for AKI, and was evaluated by receiver operating characteristic (ROC) analysis, calibration curves, and decision curve analysis (DCA).

Results

The mean age was 82.0±6.22 years-old and the prevalence of post-surgical AKI was 13.3%. Age, American Society of Anesthesiologists (ASA) score, the preexistence of chronic kidney disease (CKD), cemented surgery and the decrease of hemoglobin on the first day after surgery were identified as independent risk factors of AKI after hip fracture surgery, and a predictive nomogram was established based on the multivariable model. The predictive nomogram had good discrimination ability (training set: AUC: 0.784, 95% CI: 0.720-0.848; validation set: AUC: 0.804, 95% CI: 0.704-0.903), and showed good validation ability and clinical usefulness based on a calibration plot and decision curve analysis.

Conclusion

A nomogram that incorporated five risk factors including age, ASA score, preexisting CKD, cemented surgery and the decrease of hemoglobin on the first day after surgery had good predictive performance and discrimination. Use of our results for early stratification and intervention has the potential to improve the outcomes of patients receiving hip fracture surgery. Future large, multicenter cohorts are needed to verify the model's performance.

Role of the Circadian Clock and Effect of Time-Restricted Feeding in Adenine-Induced Chronic Kidney Disease

Most physiological functions exhibit circadian rhythmicity that is partly regulated by the molecular circadian clock. Herein, we investigated the relationship between the circadian clock and chronic kidney disease (CKD). The role of the clock gene in adenine-induced CKD and the mechanisms of interaction were investigated in mice in which Bmal1, the master regulator of the clock gene, was knocked out, and Bmal1 knockout (KO) tubule cells. We also determined whether the renoprotective effect of time-restricted feeding (TRF), a dietary strategy to enhance circadian rhythm, is clock gene-dependent. The mice with CKD showed altered expression of the core clock genes with a loss of diurnal variations in renal functions and key tubular transporter gene expression. Bmal1 KO mice developed more severe fibrosis, and transcriptome profiling followed by gene ontology analysis suggested that genes associated with the cell cycle, inflammation, and fatty acid oxidation pathways were significantly affected in the mutant mice. Tubule-specific deletion of BMAL1 in HK-2 cells by CRISPR/Cas9 led to upregulation of p21 and tumor necrosis α and exacerbated epithelial-mesenchymal transition-related gene expression upon transforming growth factor β stimulation. Finally, TRF in the mice with CKD partially restored the disrupted oscillation of the kidney clock genes, accompanied by improved cell cycle arrest and inflammation, leading to decreased fibrosis. However, the renoprotective effect of TRF was abolished in Bmal1 KO mice, suggesting that TRF is partially dependent on the clock gene. Our data demonstrate that the molecular clock system plays an important role in CKD via cell cycle regulation and inflammation. Understanding the role of the circadian clock in kidney diseases can be a new research field for developing novel therapeutic targets.

Targeting NK-1R attenuates renal fibrosis via modulating inflammatory responses and cell fate in chronic kidney disease

Background

Renal fibrosis is the final common pathway of chronic kidney disease (CKD), which is clinically irreversible and without effective therapy. Renal tubules are vulnerable to various insults, and tubular injury is involving in the initiation and evolution of renal inflammation and fibrosis. Neurokinin-1 receptor (NK-1R) functions by interacting with proinflammatory neuropeptide substance P (SP), exerting crucial roles in various neurological and non-neurological diseases. However, its roles in renal inflammation and fibrosis are still unknown.

Methods

We collected renal biopsy specimens and serum samples of individuals with or without CKD. Additionally, knockout mice lacking NK-1R expression, SP addition and NK-1R pharmacological antagonist treatment in the unilateral ureteral obstruction (UUO) model, and NK-1R-overexpressed HK-2 cells were employed.

Results

Renal SP/NK-1R and serum SP were increased in patients with CKD and mice experiencing UUO and correlated with renal fibrosis and function. SP addition enhanced UUO-induced progressive inflammatory responses and renal fibrosis, whereas genetically or pharmacologically targeting NK-1R attenuated these effects. Mechanistically, TFAP4 promoted NK-1R transcription by binding to its promoter, which was abolished by mutation of the binding site between TFAP4 and NK-1R promoter. Furthermore, SP acted through the NK-1R to activate the JNK/p38 pathways to modulate cell fate of tubular epithelial cells including growth arrest, apoptosis, and expression of profibrogenic genes.

Conclusion

Our data reveals that SP/NK-1R signaling promotes renal inflammatory responses and fibrosis, suggesting NK-1R could be a potential therapeutic target for the patients with CKD.

Inhibition of MLL1-menin interaction attenuates renal fibrosis in obstructive nephropathy

Mixed lineage leukemia 1 (MLL1), a histone H3 lysine 4 (H3K4) methyltransferase, exerts its enzymatic activity by interacting with menin and other proteins. It is unclear whether inhibition of the MLL1-menin interaction influences epithelial-mesenchymal transition (EMT), renal fibroblast activation, and renal fibrosis. In this study, we investigated the effect of disrupting MLL1-menin interaction on those events and mechanisms involved in a murine model of renal fibrosis induced by unilateral ureteral obstruction (UUO), in cultured mouse proximal tubular cells and renal interstitial fibroblasts. Injury to the kidney increased the expression of MLL1 and menin and H3K4 monomethylation (H3K4me1); MLL1 and menin were expressed in renal epithelial cells and renal interstitial fibroblasts. Inhibition of the MLL1-menin interaction by MI-503 administration or siRNA-mediated silencing of MLL1 attenuated UUO-induced renal fibrosis, and reduced expression of α-smooth muscle actin (α-SMA) and fibronectin. These treatments also inhibited UUO-induced expression of transcription factors Snail and Twist and transforming growth factor β1 (TGF-β1) while expression of E-cadherin was preserved. Moreover, treatment with MI-503 and transfection with either MLL siRNA or menin siRNA inhibited TGF-β1-induced upregulation of α-SMA, fibronectin and Snail, phosphorylation of Smad3 and AKT, and downregulation of E-cadherin in cultured renal epithelial cells. Finally, MI-503 was effective in abrogating serum or TGFβ1-induced transformation of renal interstitial fibroblasts to myofibroblasts in vitro. Taken together, these results suggest that targeting disruption of the MLL1-menin interaction attenuates renal fibrosis through inhibition of partial EMT and renal fibroblast activation.

Astragaloside IV alleviates 1-deoxysphinganine-induced mitochondrial dysfunction during the progression of chronic kidney disease through p62-Nrf2 antioxidant pathway

Introduction: Chronic kidney disease (CKD) can lead to significant elevation of 1-deoxysphingolipids (1-deoxySL). The increase of 1-deoxySL in turn can result in mitochondrial damage and oxidative stress, which can cause further progression of CKD. Methods: This study assessed the therapeutic effect of Astragaloside IV (AST) against 1-deoxySL-induced cytotoxicity in vitro and in rats with CKD. HK-2 cells were exposed to 1-deoxysphinganine (doxSA) or doxSA + AST. doxSA-induced mitochondrial dysfunction and oxidative stress were evaluated by immunostaining, real-time PCR, oxidative stress sensor, and transmission electron microscopy. The potential effects of AST on kidney damage were evaluated in a rat 5/6 nephrectomy (5/6 Nx) model of CKD. Results: The findings of in vitro experiments showed that doxSA induced mitochondrial damage, oxidative stress, and apoptosis. AST markedly reduced the level of mitochondrial reactive oxygen species, lowered apoptosis, and improved mitochondrial function. In addition, exposure to AST significantly induced the phosphorylation of p62 and the nuclear translocation of Nrf2 as well as its downstream anti-oxidant genes. p62 knock-down fully abolished Nrf2 nuclear translocation in cells after AST treatment. However, p62 knock-down did not affect TBHQ-induced Nrf2 nuclear translocation, indicating that AST can ameliorate doxSA-induced oxidative stress through modulation of p62 phosphorylation and Nrf2 nuclear translocation. Conclusion: The findings indicate that AST can activate Nrf2 antioxidant pathway in a p62 dependent manner. The anti-oxidative stress effect and the further mitochondrial protective effect of AST represent a promising therapeutic strategy for the progression of CKD.

Renal Endothelial Cell-Targeted Extracellular Vesicles Protect the Kidney from Ischemic Injury

Endothelial cell injury plays a critical part in ischemic acute kidney injury (AKI) and participates in the progression of AKI. Targeting renal endothelial cell therapy may ameliorate vascular injury and further improve the prognosis of ischemic AKI. Here, P-selectin as a biomarker of ischemic AKI in endothelial cells is identified and P-selectin binding peptide (PBP)-engineered extracellular vesicles (PBP-EVs) with imaging and therapeutic functions are developed. The results show that PBP-EVs exhibit a selective targeting tendency to injured kidneys, while providing spatiotemporal information for the early diagnosis of AKI by quantifying the expression of P-selectin in the kidneys by molecular imaging. Meanwhile, PBP-EVs reveal superior nephroprotective functions in the promotion of renal repair and inhibition of fibrosis by alleviating inflammatory infiltration, improving reparative angiogenesis, and ameliorating maladaptive repair of the renal parenchyma. In conclusion, PBP-EVs, as an ischemic AKI theranostic system that is designed in this study, provide a spatiotemporal diagnosis in the early stages of AKI to help guide personalized therapy and exhibit superior nephroprotective effects, offering proof-of-concept data to design EV-based theranostic strategies to promote renal recovery and further improve long-term outcomes following AKI.

Role of endoplasmic reticulum stress and autophagy in the transition from acute kidney injury to chronic kidney disease

Acute kidney injury (AKI) and chronic kidney disease (CKD) are global health concerns with increasing rates in morbidity and mortality. Transition from AKI-to-CKD is common and requires awareness in the management of AKI survivors. AKI-to-CKD transition is a main risk factor for the development of cardiovascular disease and progression to end-stage kidney disease. The mechanisms driving AKI-to-CKD transition are being explored to identify potential molecular and cellular targets for renoprotective drug interventions. Endoplasmic reticulum (ER) stress and autophagy are involved in the process of AKI-to-CKD transition. Excessive ER stress results in the persistent activation of unfolded protein response, which is an underneath cause of kidney cell death. Moreover, ER stress modulates autophagy and vice-versa. Autophagy is a degradation defensive mechanism protecting cells from malfunction. However, the underlying pathological mechanism involved in this interplay in the context of AKI-to-CKD transition is still unclear. In this review, we discuss the crosstalk between ER stress and autophagy in AKI, AKI-to-CKD transition, and CKD progression. In addition, we explore possible therapeutic targets that can regulate ER stress and autophagy to prevent AKI-to-CKD transition to improve the long-term prognosis of AKI survivors.

Bibliometric and visualization analysis of kidney repair associated with acute kidney injury from 2002 to 2022

Background: Renal repair is closely related to the prognosis of acute kidney injury (AKI) and has attracted increasing attention in the research field. However, there is a lack of a comprehensive bibliometric analysis in this research area. This study aims at exploring the current status and hotspots of renal repair research in AKI from the perspective of bibliometrics. Methods: Studies published between 2002 and 2022 related to kidney repair after AKI were collected from Web of Science core collection (WoSCC) database. Bibliometric measurement and knowledge graph analysis to predict the latest research trends in the field were performed using bibliometrics software CiteSpace and VOSviewer. Results: The number of documents related to kidney repair after AKI has steadily increased over 20 years. The United States and China contribute more than 60% of documents and are the main drivers of research in this field. Harvard University is the most active academic institution that contributes the most documents. Humphreys BD and Bonventre JV are the most prolific authors and co-cited authors in the field. The American Journal of Physiology-Renal Physiology and Journal of the American Society of Nephrology are the most popular journals in the field with the greatest number of documents. "exosome", "macrophage polarization", "fibroblast", and" aki-ckd transition" are high-frequency keywords in this field in recent years. Extracellular vesicles (including exosomes), macrophage polarization, cell cycle arrest, hippo pathway, and sox9 are current research hotspots and potential targets in this field. Conclusion: This is the first comprehensive bibliometric study on the knowledge structure and development trend of AKI-related renal repair research in recent years. The results of the study comprehensively summarize and identify research frontiers in AKI-related renal repair.

Identification of shared gene signatures and molecular mechanisms between chronic kidney disease and ulcerative colitis

Background

There is a complex interaction between chronic kidney disease (CKD) and ulcerative colitis (UC), but the pathophysiological mechanisms underlying the coexistence of CKD and UC are unclear. This study aimed to investigate the key molecules and pathways that may mediate the co-occurrence of CKD and UC through quantitative bioinformatics analysis based on a public RNA-sequencing database.

Methods

The discovery datasets of CKD (GSE66494) and UC (GSE4183), as well as validation datasets of CKD (GSE115857) and UC (GSE10616), were downloaded from the Gene Expression Omnibus (GEO) database. After identifying differentially expressed genes (DEGs) with GEO2R online tool, the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses for the DEGs were performed. Next, protein-protein interaction network was constructed with Search Tool for the Retrieval of Interacting Genes (STRING) and visualized by Cytoscape. Gene modules were identified by the plug-in MCODE and hub genes were screened using the plug-in CytoHubba. Then, correlation between immune cell infiltration and hub genes was analyzed, and the receiver operating characteristic curves were used to assess the predictive value of hub genes. Finally, immunostaining of human specimens was used to validate the relevant findings.

Results

A total of 462 common DEGs were identified and selected for further analyses. GO and KEGG enrichment analyses indicated that these DEGs were primarily enriched in immune- and inflammation-related pathways. Among them, the PI3K-Akt signaling pathway ranked top in both discovery and validation cohorts, and the key signal molecule phosphorylated Akt (p-Akt) was shown to be significantly overexpressed in human CKD kidneys and UC colons, and further elevated in CKD-UC comorbidity specimens. Moreover, nine candidate hub genes, including CXCL8, CCL2, CD44, ICAM1, IL1A, CXCR2, PTPRC, ITGAX, and CSF3, were identified, of which ICAM1 was validated as a common hub gene. Besides, immune infiltration analysis revealed that neutrophils, macrophages, and CD4⁺ T memory cells significantly accumulated in both diseases, and ICAM1 was remarkably associated with neutrophil infiltration. Furthermore, intercellular adhesion molecule1 (ICAM1)-mediated neutrophil infiltration was validated to be upregulated in kidney and colon biopsies of CKD and UC patients, and further increased in patients diagnosed with both CKD and UC. Finally, ICAM1 had shown critical value as a diagnostic marker for the co-occurrence of CKD and UC.

Conclusions

Our study elucidated that immune response, PI3K-Akt signaling pathway, and ICAM1-mediated neutrophil infiltration might be the common pathogenesis of CKD and UC, and identified ICAM1 as a key potential biomarker and therapeutic target for the comorbidity of these two diseases.

The Effect of Family-Centered and Peer-Centered Education on the Sleep Quality of Hemodialysis Patients: A Randomized Clinical Trial

Introduction

Sleep disorders in hemodialysis patients are of high prevalence affecting the lives of these patients.

Objective

The present study was conducted to investigate the effect of family-centered and peer-centered education on the sleep quality of hemodialysis patients.

Methods

In this controlled clinical trial, 90 patients were randomly assigned to three groups (control, family-centered, and peer-centered). All three groups completed Pittsburgh Sleep Quality Index before the intervention. The intervention included five training sessions conducted by the researcher according to the patients' needs to improve their sleep quality. Routine ward interventions were performed for the control group. At the end of the study, the Pittsburgh Sleep Quality Index was completed by all three groups once again. Data were collected and analyzed using SPSS version 24 software and statistical tests.

Results

No significant difference was found between the two intervention and control groups regarding demographic variables and variables related to sleep quality before the intervention (p < .05). However, based on the results of the Wilcoxon test, there was a statistically significant difference between the mean rank of sleep quality in the intervention and control groups after the intervention (p-value = .008), indicating that sleep hygiene education was effective in the two intervention groups.

Conclusion

According to the findings, the mean rank of sleep quality in the two intervention groups was significant after the training, indicating the effectiveness of family-centered and peer-centered education. Accordingly, medical healthcare managers, policymakers, and planners, including nurses, are recommended to employ these convenient, safe, and cost-free training methods and provide better sleep quality and more comfort to patients by spending a short period of time for training.

Zhen Wu decoction represses renal fibrosis by invigorating tubular NRF2 and TFAM to fuel mitochondrial bioenergetics

BACKGROUND

Zhen Wu Decoction (ZWD) is a prescription from the classical text "Treatise on Exogenous Febrile Disease" and has been extensively used to control kidney diseases since the time of the Eastern Han Dynasty.

HYPOTHESIS

We hypothesized that ZWD limits tubular fibrogenesis by reinvigorating tubular bio-energetic capacity.

STUDY DESIGN / METHODS

A mouse model of chronic kidney disease (CKD) was established using unilateral ureteral obstruction (UUO). Three concentrations of ZWD, namely 25.2 g/kg (high dosage), 12.6 g/kg (middle dosage), and 6.3 g/kg (low dosage), were included to study the dose-effect relationship. Real-time qPCR was used to observe gene transcription in blood samples from patients with CKD. Different siRNAs were designed to study the role of mitochondrial transcription factor A (TFAM) and nuclear factor (erythroid-derived 2)-related factor 2 (NRF2) in transforming growth factor (TGF)-β1 induced fibrogenesis and mitochondrial damage.

RESULTS

We showed that ZWD efficiently attenuates renal function impairment and reduces renal interstitial fibrosis. TFAM and NRF2 were repressed, and the stimulator of interferon genes (STING) was activated in CKD patient blood sample. We further confirmed that ZWD activated TFAM depended on NRF2 as an important negative regulator of STING in mouse kidneys. Treatment with ZWD significantly reduced oxidative stress and inflammation by regulating the levels of oxidative phosphorylation (OXPHOS) and pro-inflammatory factors, such as interleukin-6, interleukin-1β, tumor necrosis factor receptor 1, and mitochondrial respiratory chain subunits. NRF2 inhibitors can weaken the ability of ZWD to increase TFAM expression and heal injured mitochondria, playing a similar role to that of STING inhibitors. Our study showed that ZWD elevates the expression of TFAM and mitochondrial respiratory chain subunits by promoting NRF2 activation, after suppressing mitochondrial membrane damage and cristae breakdown and restricting mitochondrial DNA (mtDNA) leakage into the cytoplasm to reduce STING activation.

CONCLUSION

ZWD maintains mitochondrial integrity and improves OXPHOS which represents an innovative insight into "strengthening Yang-Qi" theory. ZWD limits tubular fibrogenesis by reinvigorating tubular bioenergetic capacity.

Puromycin-induced kidney injury and subsequent regeneration in adult zebrafish

Puromycin treatment can cause glomerular injury to the kidney, leading to proteinuria. However, the pathogenesis of acute kidney injury and subsequent regeneration after puromycin administration in animal models remain unclear. In this work, we examined the characteristics of kidney injury and subsequent regeneration following puromycin treatment in adult zebrafish. We intraperitoneally injected 100 μg of puromycin into zebrafish; sacrificed them at 1, 3, 5, 7, or 14 days post-injection (dpi); and examined the morphological, functional, and molecular changes in the kidney. Puromycin-treated zebrafish presented more rapid clearance of rhodamine dextran than control animals. Morphological changes were observed immediately after the puromycin injection (1-7 dpi) and had recovered by 14 dpi. The mRNA production of lhx1a, a renal progenitor marker, increased during recovery from kidney injury. Levels of NFκB, TNFα, Nampt, and p-ERK increased significantly during nephron injury and regeneration, and Sirt1, FOXO1, pax2, and wt1b showed an increasing tendency. However, TGF-β1 and smad5 production did not show any changes after puromycin treatment. This study provides evidence that puromycin-induced injury in adult zebrafish kidneys is a potential tool for evaluating the mechanism of nephron injury and subsequent regeneration.

Enlarging the Stokes Shift by Weakening the π-Conjugation of Cyanines for High Signal-to-Noise Ratiometric Imaging

The signal-to-noise ratio (SNR) is one of the key features of a fluorescent probe and one that often defines its potential utility for in vivo labeling and analyte detection applications. Here, it is reported that introducing a pyridine group into traditional cyanine-7 dyes in an asymmetric manner provides a series of tunable NIR fluorescent dyes (Cy-Mu-7) characterized by enhanced Stokes shifts (≈230 nm) compared to the parent cyanine 7 dye (<25 nm). The observed Stokes shift increase is ascribed to symmetry breaking of the Cy-Mu-7 core and a reduction in the extent of conjugation. The fluorescence signals of the Cy-Mu-7 dyes are enhanced upon confinement within the hydrophobic cavity of albumin or via spontaneous encapsulation within micelles in aqueous media. Utilizing the Cy-Mu-7, ultra-fast in vivo kidney labeling in mice is realized, and it is found that the liver injury will aggravate the burden of kidney by monitoring the fluorescence intensity ratio of kidney to liver. In addition, Cy-Mu-7 could be used as efficient chemiluminescence resonance energy transfer acceptor for the reaction between H₂ O₂ and bisoxalate. The potential utility of Cy-Mu-7 is illustrated via direct monitoring fluctuations in endogenous H₂ O₂ levels in a mouse model to mimic emergency room trauma.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

Oxidative Stress and Mitochondrial Dysfunction in Chronic Kidney Disease

The kidney contains many mitochondria that generate ATP to provide energy for cellular processes. Oxidative stress injury can be caused by impaired mitochondria with excessive levels of reactive oxygen species. Accumulating evidence has indicated a relationship between oxidative stress and kidney diseases, and revealed new insights into mitochondria-targeted therapeutics for renal injury. Improving mitochondrial homeostasis, increasing mitochondrial biogenesis, and balancing mitochondrial turnover has the potential to protect renal function against oxidative stress. Although there are some reviews that addressed this issue, the articles summarizing the relationship between mitochondria-targeted effects and the risk factors of renal failure are still few. In this review, we integrate recent studies on oxidative stress and mitochondrial function in kidney diseases, especially chronic kidney disease. We organized the causes and risk factors of oxidative stress in the kidneys based in their mitochondria-targeted effects. This review also listed the possible candidates for clinical therapeutics of kidney diseases by modulating mitochondrial function.

A monoclonal antibody targeting nonjunctional claudin-1 inhibits fibrosis in patient-derived models by modulating cell plasticity

Tissue fibrosis is a key driver of end-stage organ failure and cancer, overall accounting for up to 45% of deaths in developed countries. There is a large unmet medical need for antifibrotic therapies. Claudin-1 (CLDN1) is a member of the tight junction protein family. Although the role of CLDN1 incorporated in tight junctions is well established, the function of nonjunctional CLDN1 (njCLDN1) is largely unknown. Using highly specific monoclonal antibodies targeting a conformation-dependent epitope of exposed njCLDN1, we show in patient-derived liver three-dimensional fibrosis and human liver chimeric mouse models that CLDN1 is a mediator and target for liver fibrosis. Targeting CLDN1 reverted inflammation-induced hepatocyte profibrogenic signaling and cell fate and suppressed the myofibroblast differentiation of hepatic stellate cells. Safety studies of a fully humanized antibody in nonhuman primates did not reveal any serious adverse events even at high steady-state concentrations. Our results provide preclinical proof of concept for CLDN1-specific monoclonal antibodies for the treatment of advanced liver fibrosis and cancer prevention. Antifibrotic effects in lung and kidney fibrosis models further indicate a role of CLDN1 as a therapeutic target for tissue fibrosis across organs. In conclusion, our data pave the way for further therapeutic exploration of CLDN1-targeting therapies for fibrotic diseases in patients.

NAD+ Metabolism and Interventions in Premature Renal Aging and Chronic Kidney Disease

Premature aging causes morphological and functional changes in the kidney, leading to chronic kidney disease (CKD). CKD is a global public health issue with far-reaching consequences, including cardio-vascular complications, increased frailty, shortened lifespan and a heightened risk of kidney failure. Dialysis or transplantation are lifesaving therapies, but they can also be debilitating. Currently, no cure is available for CKD, despite ongoing efforts to identify clinical biomarkers of premature renal aging and molecular pathways of disease progression. Kidney proximal tubular epithelial cells (PTECs) have high energy demand, and disruption of their energy homeostasis has been linked to the progression of kidney disease. Consequently, metabolic reprogramming of PTECs is gaining interest as a therapeutic tool. Preclinical and clinical evidence is emerging that NAD⁺ homeostasis, crucial for PTECs' oxidative metabolism, is impaired in CKD, and administration of dietary NAD⁺ precursors could have a prophylactic role against age-related kidney disease. This review describes the biology of NAD⁺ in the kidney, including its precursors and cellular roles, and discusses the importance of NAD⁺ homeostasis for renal health. Furthermore, we provide a comprehensive summary of preclinical and clinical studies aimed at increasing NAD⁺ levels in premature renal aging and CKD.

New Landmarks to Slow the Progression of Chronic Kidney Disease

Chronic kidney disease (CKD) is a serious condition whose incidence is steadily rising, particularly in the Western world, due to the increasing prevalence of diabetes, hypertension, and obesity, which are nowadays the major causes of CKD in the Western population, as well as the aging of the population [...].

Improving the circulation time and renal therapeutic potency of extracellular vesicles using an endogenous ligand binding strategy

Kidney diseases are a serious health issue worldwide, and novel therapeutics are urgently needed. Extracellular vesicles (EVs) have emerged as potent drug delivery systems (DDSs), but their therapeutic potential is limited by short circulation times and insufficient renal retention. Here, we report that endogenous ligand (albumin, ALB) binding is an efficient modification strategy to improve the therapeutic potency of EV-based DDSs for kidney diseases. Surface albumin-binding peptide (ABP)-displayed EVs (ABP-EVs) were produced by transfecting parent cells with the ABP-Lamp2b fusion plasmid. Compared with unmodified EVs (NC-EVs), ABP-EVs showed increased binding to ALB in vitro and elevated circulation time and multiple organ retention in vivo after systemic (iv) injection. Moreover, ABP-EVs had higher renal retention than NC-EVs in mice with acute kidney injury through a complex mechanism involving microvascular injury and megalin-mediated endocytosis. As a result, delivery of small molecule drugs (e.g., curcumin) or proteins (e.g., hepatocyte growth factor) by ABP-EVs had superior therapeutic (e.g., anti-apoptotic, antioxidant, anti-inflammatory) effects in vitro and in vivo. This study highlights that ABP-EVs are versatile DDSs for kidney diseases and provides insights into the new strategies of engineering EVs for drug delivery.

Remote ischemic postconditioning protects against crush-induced acute kidney injury via down-regulation of apoptosis and senescence

BACKGROUND

Acute renal failure due to crush syndrome is one of the leading causes of death in disasters. Ischemic Postconditioning (IPC) is a potentially effective strategy to protect against ischemic reperfusion injury, but a few studies noted its protective effect in crush induced acute kidney injury (AKI). Hence, this study investigated the optimal IPC strategy to prevent crush induced AKI and reveal related cellular mechanisms.

METHODS

The right lower extremities of rabbits were constantly compressed for 8 h and then performed five cycles of clamping and releasing the femoral artery and vein before depression using a clip. In terms of the duration of clamping and releasing, the animals were randomly divided into 5 groups, Control, IPC-5sec, IPC-30sec, IPC-1min, and IPC-5min groups; 6 rabbits for each group. Biomarkers of inflammation, renal function, renal tubular injury, and muscular injury, apoptosis, and cellular senescence in kidney were detected.

RESULTS

Six hours after decompression, the levels of Serum Creatine (SCr), Blood Urea Nitrogen (BUN), K+, and Interleukin-6 (IL-6) in IPC-1min and IPC-5min groups were lower than Control, with a statistically significant difference. The morphological study of Periodic Acid-Schiff (PAS) staining demonstrated that 6 h after decompression, IPC-1min can attenuate renal tubular damage renal tubule. Meanwhile, the level of Neutrophil Gelatinase-Associated Lipocalin (NGAL) in circulation in the IPC-30sec, IPC-1min, and IPC-5min groups was significantly decreased compared with the Control group, 2 h after decompression. On the other hand, the levels of serum Creatine Kinase (CK) and Myoglobin (Mb), and the morphological change of muscular damage detected by hematoxylin and eosin (H&E) staining in IPC-1min-treated group were significantly lower than Control group 6 hours after decompression. Further results of the cellular mechanism showed that the apoptotic markers of Terminal deoxynucleotidyl Transferase-mediated dUTP Nick End Labeling (TUNEL) and Caspase3 and the cell senescent markers of senescence-associated β-galactosidase (SA-β-Gal) and nuclear LAMNB1 have changed significantly in the IPC-1min group, compared with the control group.

CONCLUSIONS

Performing 5 cycles of 1-min IPC would be a convenient, time-saving, and effective method to prevent crush-induced AKI by attenuating the release of nephrotoxic substances after decompression and downregulation of the expression of apoptosis and cellular senescence biomarkers.

Assessment of Kidney Function in Children

A good understanding of kidney function tests is essential for patient care. Urinalysis is the commonest used test for screening purposes in ambulatory settings. Glomerular function is assessed further by urine protein excretion and estimated glomerular filtration rate and tubular function by various tests such as urine anion gap and excretion of sodium, calcium, and phosphate. In addition, kidney biopsy and/or genetic analyses may be required to further characterize the underlying kidney disease. In this article, we discuss maturation and the assessment of kidney function in children.

Transcriptional profile changes after treatment of ischemia reperfusion injury-induced kidney fibrosis with 18β-glycyrrhetinic acid

Introduction

Chronic kidney disease (CKD) is characterized by renal fibrosis without effective therapy. 18β-Glycyrrhetinic acid (GA) is reported to have detoxification and anti-inflammatory functions and promotes tissue repair. However, the role of GA in CKD remains unclear. In this study, we investigated whether GA has a potential therapeutic effect in kidney fibrosis.

Methods

A renal fibrosis mouse model was established by ischemia/reperfusion (I/R) injury via clamping unilateral left renal pedicle for 45 min; then, the mice were treated with vehicle or GA. Kidney tissues and blood samples were extracted 14 days after reperfusion and renal function, histopathological staining, quantitative PCR, and western blotting were performed. RNA-seq was performed to explore the changes in the transcriptional profile after GA treatment.

Results

Renal function, pathological and molecular analysis displayed that fibrosis was successfully induced in the I/R model. In the GA treatment group, the severity of fibrosis gradually reduced with the best effect seen at a concentration of 25 mg kg ⁻¹. A total of 970 differentially expressed genes were identified. Pathway enrichment showed that reduced activation and migration of inflammatory cells and decreased chemokine interaction in significant pathways. Protein–protein interaction networks were constructed and 15 hub genes were selected by degree rank, including chemokines, such as C3, Ccl6, Ccr2, Ptafr, Timp1, and Pf4.

Conclusions

GA may alleviate renal fibrosis by inhibiting the inflammatory response. GA is a promising therapy that may perhaps be used in treating renal fibrosis and CKD.

Point-of-Care Urinalysis with One Drop of Sample Using an Aggregation-Induced Emission Luminogen under the Coffee-Ring Effect

Development of a practical point-of-care test for urinalysis is crucial for early diagnosis and treatment of chronic kidney disease (CKD). However, the classical gold standard detection method depends on sophisticated instruments and complicated procedures, impeding them from being utilized in resource-limited settings and daily screening. Herein, we report a rapid point-of-care device for the simultaneous quantification of microalbuminuria and leukocyte using one drop of urine. A luminogen (TTVP) with an aggregation-induced emission property can selectively activate its near-infrared fluorescence in the presence of albumin and leukocyte via hydrophobic or electrostatic interactions. The fluorescence signals from urine albumin and leukocyte could be well-separated combined with the coffee-ring effect. Using a smartphone-based detection device, simultaneous quantification of urine albumin and leukocyte was successfully achieved, which only took 20 min and required one drop of urine. The performance of this system is also verified with 120 clinical samples, which might serve as a simple, low-cost, and rapid tool for CKD screening and disease monitoring at the point of care.

A nomogram based on shear wave elastography for assessment of renal fibrosis in patients with chronic kidney disease

BACKGROUND

Non-invasive evaluation of renal fibrosis is still challenging. This study aimed to establish a nomogram based on shear wave elastography (SWE) and clinical features for the assessment of the severity of renal fibrosis in patients with chronic kidney disease (CKD).

METHODS

One hundred and sixty-two patients with CKD who underwent kidney biopsy and SWE examination were prospectively enrolled between April 2019 and December 2021. Patients were classified into mildly or moderately-severely impaired group based on pathology results. All patients were randomly divided into a training (n = 113) or validation cohort (n = 49). Least absolute shrinkage and selection operator (LASSO) algorithm was used for data dimensionality reduction and feature selection. Then, a diagnostic nomogram incorporating the selected features was constructed using multivariable logistic regression analysis. Nomogram performance was evaluated for discrimination, calibration, and clinical utility in training and validation cohorts.

RESULTS

The established SWE nomogram, which integrated SWE value, hypertension, and estimated glomerular filtration rate, showed fine calibration and discrimination in both training (area under the receiver operator characteristic curve (AUC) = 0.94; 95% confidence interval (CI) 0.89-0.98) and validation cohorts (AUC = 0.84; 95% CI 0.71-0.96). Significant improvement in net reclassification and integrated discrimination indicated that the SWE value is a valuable biomarker to assess moderate-severe renal impairment. Furthermore, decision curve analysis revealed that the SWE nomogram has clinical value.

CONCLUSION

The proposed SWE nomogram showed favorable performance in determining individualized risk of moderate-severe renal pathological impairment in patients with CKD, which will help to facilitate clinical decision-making.

Association of mean platelet volume/lymphocyte ratio with inflammation in non-dialysis patients with chronic kidney disease stages 1-4: A retrospective study

OBJECTIVE

The mean platelet volume/ratio (MPVLR) is recognized as a novel marker of inflammation. We evaluated whether the MPVLR is associated with inflammation in non-dialysis patients with chronic kidney disease (CKD) stages 1-4.

METHODS

A total of 402 non-dialysis patients with CKD stages 1-4 were included. The indicators of hematological, renal function (urea, serum creatinine [Scr], estimated glomerular filtration rate [eGFR], and urine albumin to creatinine ratio [ACR]) and the markers of inflammation (high-sensitivity C-reactive protein [hsCRP] and fibrinogen [FIB]) were recorded. The MPVLR values at different CKD stages were analyzed. Next, based on the absence (hsCRP level < 5 mg/L) and presence (hsCRP level > 5 mg/L) of inflammation, the patients were categorized, and the differences in indices between the two groups were observed. The patients were divided into two groups based on the median MPVLR value (6.39) at admission. The laboratory indices of patients with CKD were compared. Simultaneously, a correlation analysis was performed to identify the association between the MPVLR and each parameter. A binary logistic regression analysis was performed to test whether the MPVLR was associated independently with the presence of inflammation in non-dialysis patients with CKD. The receiver operating characteristic (ROC) curve was used to analyzed diagnostic performance of the MPVLR in evaluating the inflammation of non-dialysis patients with CKD stages 1-4.

RESULTS

The MPVLR was higher in patients with CKD stages 3-4 than in those with CKD stages 1 and 2. Significant differences in urea, Scr, eGFR, ACR, lymphocyte (LYM), red blood cell (RBC), hemoglobin (HGB), RBC distribution width (RDW-CV), MPVLR, and FIB values were observed between the groups with and without inflammation. The patients with a higher MPVLR had higher urea, Scr, ACR, WBC, neutrophils (NEU), RDW-CV, platelet distribution width (PDW), mean platelet volume (MPV), and hsCRP values and lower eGFR, LYM, RBC, HGB, and platelet (PLT) values. The MPVLR showed a positive correlation with age, urea, Scr, WBC, NEU, RDW-CV, PDW, MPV, and hsCRP values and a negative correlation with the eGFR, LYM, RBC, HGB, and PLT values. A logistic analysis revealed that the MPVLR was associated independently with the presence of inflammation in non-dialysis patients with CKD, after adjustment for the confounding factors (odds ratio = 1.020; P = 0.024). Furthermore, MPVLR exhibited a modest diagnostic performance for the assessment of inflammation in non-dialysis patients with CKD stages 1-4, with an area under the curve (AUC) of 0.706, and the sensitivity, specificity being 46.2% and 83.2%, respectively.

CONCLUSIONS

The MPVLR was associated independently with the presence of inflammation in non-dialysis patients with CKD and may be useful for monitoring inflammation.

Predicting Progression of Kidney Injury Based on Elastography Ultrasound and Radiomics Signatures

Background: Shear wave elastography ultrasound (SWE) is an emerging non-invasive candidate for assessing kidney stiffness. However, its prognostic value regarding kidney injury is unclear. Methods: A prospective cohort was created from kidney biopsy patients in our hospital from May 2019 to June 2020. The primary outcome was the initiation of renal replacement therapy or death, while the secondary outcome was eGFR < 60 mL/min/1.73 m2. Ultrasound, biochemical, and biopsy examinations were performed on the same day. Radiomics signatures were extracted from the SWE images. Results: In total, 187 patients were included and followed up for 24.57 ± 5.52 months. The median SWE value of the left kidney cortex (L_C_median) is an independent risk factor for kidney prognosis for stage 3 or over (HR 0.890 (0.796−0.994), p < 0.05). The inclusion of 9 out of 2511 extracted radiomics signatures improved the prognostic performance of the Cox regression models containing the SWE and the traditional index (chi-square test, p < 0.001). The traditional Cox regression model had a c-index of 0.9051 (0.8460−0.9196), which was no worse than the machine learning models, Support Vector Machine (SVM), SurvivalTree, Random survival forest (RSF), Coxboost, and Deepsurv. Conclusions: SWE can predict kidney injury progression with an improved performance by radiomics and Cox regression modeling.

Intrarenal 1-methoxypyrene, an aryl hydrocarbon receptor agonist, mediates progressive tubulointerstitial fibrosis in mice

Recent studies have shown that endogenous metabolites act via aryl hydrocarbon receptor (AhR) signalling pathway in tubulointerstitial fibrosis (TIF) pathogenesis. However, the mechanisms underlying endogenous metabolite-mediated AhR activation are poorly characterised. In this study, we conducted untargeted metabolomics analysis to identify the significantly altered intrarenal metabolites in a mouse model of unilateral ureteral obstruction (UUO). We found that the levels of the metabolite 1-methoxypyrene (MP) and the mRNA expression of AhR and its target genes CYP1A1, CYP1A2, CYP1B1 and COX-2 were progressively increased in the obstructed kidney at Weeks 1, 2 and 3. Furthermore, these changes were positively correlated with progressive TIF in UUO mice. In NRK-52E, RAW 264.7 and NRK-49F cells, MP dose-dependently upregulated the mRNA expression of AhR and its four target genes and the protein expression of nuclear AhR, accompanied by the upregulated protein expression of collagen I, α-SMA and fibronectin, as well as downregulated E-cadherin expression. Consistently, oral administration of MP in mice progressively enhanced AhR activity and upregulated profibrotic protein expression in the kidneys; these effects were partially inhibited by AhR knockdown in MP-treated mice and cell lines. In addition, we screened and identified erythro-guaiacylglycerol-β-ferulic acid ether (GFA), which was isolated from Semen plantaginis, as a new AhR antagonist. GFA significantly attenuated TIF in MP-treated NRK-52E cells and mice by partially antagonising AhR activity. Our results suggest that MP activates AhR signalling, thus mediating TIF through epithelial-mesenchymal transition and macrophage-myofibroblast transition. MP is a crucial metabolite that contributes to TIF via AhR signalling pathway.

Urinary extracellular vesicles signature for diagnosis of kidney disease

Congenital disorders characterized by the quantitative and qualitative reduction in the number of functional nephrons are the primary cause of chronic kidney disease (CKD) in children. We aimed to describe the alteration of urinary extracellular vesicles (uEVs) associated with decreased renal function during childhood. By nanoparticle tracking analysis and quantitative proteomics, we identified differentially expressed proteins in uEVs in bilateral renal hypoplasia, which is characterized by a congenitally reduced number of nephrons. This expression signature of uEVs reflected decreased renal function in CKD patients by congenital anomalies of the kidney and urinary tract or ciliopathy. As a proof-of-concept, we constructed a prototype ELISA system that enabled the isolation of uEVs and quantitation of expression of molecules representing the signature. The system identified decreased renal function even in its early stage. The uEVs signature could pave the way for non-invasive methods that can complement existing testing methods for diagnosing kidney diseases.

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Urinary extracellular vesicles (uEVs) are altered in chronic kidney disease (CKD)

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Characteristic expression signatures associated with childhood CKD are identified

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An ELISA utilizing the signature detected decreased renal function

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uEVs signature has potential in diagnosing kidney diseases

Kif26b contributes to the progression of interstitial fibrosis via migration and myofibroblast differentiation in renal fibroblast

Kinesin family member 26b (Kif26b) is essential for kidney development, and its deletion in mice leads to kidney agenesis. However, the roles of this gene in adult settings remain elusive. Thus, this study aims to investigate the role of Kif26b in the progression of renal fibrosis. A renal fibrosis model with adenine administration using Kif26b heterozygous mice and wild-type mice was established. Renal fibrosis and the underlying mechanism were investigated. The underlying pathways and functions of Kif26b were evaluated in an in vitro model using primary renal fibroblasts. Kif26b heterozygous mice were protected from renal fibrosis with adenine administration. Renal expressions of connective tissue growth factor (CTGF) and myofibroblast accumulation were reduced in Kif26b heterozygous mice. The expression of nonmuscle myosin heavy chain II (NMHCII), which binds to the C-terminus of Kif26b protein, was also suppressed in Kif26b heterozygous mice. The in vitro study revealed reduced expressions of CTGF, α-smooth muscle actin, and myosin heavy chain 9 (Myh9) via transfection with siRNAs targeting Kif26b in renal fibroblasts (RFB). RFBs, which were transfected by the expression vector of Kif26b, demonstrated higher expressions of these genes than non-transfected cells. Finally, Kif26b suppression and NMHCII blockage led to reduced abilities of migration and collagen gel contraction in renal fibroblasts. Taken together, Kif26b contributes to the progression of interstitial fibrosis via migration and myofibroblast differentiation through Myh9 in the renal fibrosis model. Blockage of this pathway at appropriate timing might be a therapeutic approach for renal fibrosis.

Association between recovery/occurrence of metabolic syndrome and rapid estimated glomerular filtration rate decline in middle-aged and older populations: evidence from the China Health and Retirement Longitudinal Study

OBJECTIVES

Few studies have explored correlations between metabolic syndrome (MetS) alterations and renal deterioration in longitudinal cohorts. We aim to investigate associations between MetS recovery/development and rapid estimated glomerular filtration rate (eGFR) decline in the China Health and Retirement Longitudinal Study (CHARLS).

DESIGN

Longitudinal cohort study.

SETTING

This study is a secondary analysis of CHARLS.

PARTICIPANTS

After excluding individuals with age <45 years old, eGFR <60 mL/min/1.73 m² and clinician-reported malignant tumour, heart disease, stroke or kidney disease at baseline, 4142 participants with complete data were selected from the CHARLS during the 4-year follow-up period (2011-2015).

OUTCOME MEASURES

MetS were measured at 2011 and 2015 in CHARLS. A rapid eGFR decline was defined as an average annual eGFR decline of >3 mL/min/1.73 m². The associations between rapid eGFR decline and MetS recovery/development were analysed using multivariable adjusted logistic models.

RESULTS

According to MetS baseline status and follow-up, participants were divided into four groups: (1) 2460 (59.4%) in the MetS-free group, (2) 361 (8.7%) in the MetS-developed group, (3) 499 (12.0%) in the MetS recovery group and (4) 822 (19.8%) in the MetS chronic group. When compared with the MetS chronic group, the multivariable adjusted OR of rapid eGFR decline in the MetS recovery group was 0.64 (OR: 0.64; 95% CI 0.45 to 0.90, p=0.01). In contrast, when compared with the MetS-free group, the multivariable adjusted OR of rapid eGFR decline in the MetS-developed group was 1.00 (OR: 1.00; 95% CI 0.73 to 1.38, p=0.98).

CONCLUSIONS

Over the 4-year follow-up period, we found that MetS recovery was associated with a reduced risk of rapid eGFR decline in middle-aged and older adults, while MetS occurrence was not related to rapid eGFR decline. Recovery from MetS appeared to protect against a rapid decline in eGFR.

Hepatic and proximal tubule angiotensinogen play distinct roles in kidney dysfunction, glomerular and tubular injury, and fibrosis progression

Components of the renin-angiotensin system, including angiotensinogen (AGT), are critical contributors to chronic kidney disease (CKD) development and progression. However, the specific role of tissue-derived AGTs in CKD has not been fully understood. To define the contribution of liver versus kidney AGT in the CKD development, we performed 5/6 nephrectomy (Nx), an established CKD model, in wild-type (WT), proximal tubule (PT)- or liver-specific AGT knockout (KO) mice. Nx significantly elevated intrarenal AGT expression and elevated blood pressure (BP) in WT mice. The increase of intrarenal AGT protein was completely blocked in liver-specific AGT KO mice with BP reduction, suggesting a crucial role for liver AGT in BP regulation during CKD. Nx-induced glomerular and kidney injury and dysfunction, as well as fibrosis, were all attenuated to a greater extent in liver-specific AGT KO mice compared with PT-specific AGT KO and WT mice. However, the suppression of interstitial fibrosis in PT- and liver-specific AGT KO mouse kidneys was comparable. Our findings demonstrate that liver AGT acts as a critical contributor in driving glomerular and tubular injury, renal dysfunction, and fibrosis progression, whereas the role of PT AGT was limited to interstitial fibrosis progression in chronic renal insufficiency. Our results provide new insights for the development of tissue-targeted renin-angiotensin system intervention in the treatment of CKD.NEW & NOTEWORTHY Chronic kidney disease (CKD) is a major unmet medical need with no effective treatment. Current findings demonstrate that hepatic and proximal tubule angiotensinogen have distinct roles in tubular and glomerular injury, fibrogenesis, and renal dysfunction during CKD development. As renin-angiotensin system components, including angiotensinogen, are important targets for treating CKD in the clinic, the results from our study may be applied to developing better tissue-targeted treatment strategies for CKD and other fibroproliferative diseases.

From AKI to CKD: Maladaptive Repair and the Underlying Mechanisms

Acute kidney injury (AKI) is defined as a pathological condition in which the glomerular filtration rate decreases rapidly over a short period of time, resulting in changes in the physiological function and tissue structure of the kidney. An increasing amount of evidence indicates that there is an inseparable relationship between acute kidney injury and chronic kidney disease (CKD). With the progress in research in this area, researchers have found that the recovery of AKI may also result in the occurrence of CKD due to its own maladaptation and other potential mechanisms, which involve endothelial cell injury, inflammatory reactions, progression to fibrosis and other pathways that promote the progress of the disease. Based on these findings, this review summarizes the occurrence and potential mechanisms of maladaptive repair in the progression of AKI to CKD and explores possible treatment strategies in this process so as to provide a reference for the inhibition of the progression of AKI to CKD.

SIRT6 overexpression retards renal interstitial fibrosis through targeting HIPK2 in chronic kidney disease

Introduction: Renal interstitial fibrosis is a common pathophysiological change in the chronic kidney disease (CKD). Nicotinamide adenine dinucleotide (NAD)-dependent deacetylase sirtuin 6 (SIRT6) is demonstrated to protect against kidney injury. Vitamin B3 is the mostly used form of NAD precursors. However, the role of SIRT6 overexpression in renal interstitial fibrosis of CKD and the association between dietary vitamin B3 intake and renal function remain to be elucidated.

Methods: Wild-type (WT) and SIRT6-transgene (SIRT6-Tg) mice were given with high-adenine diets to establish CKD model. HK2 cells were exposed to transforming growth factor β1 (TGF-β1) in vitro to explore related mechanism. Population data from Multi-Ethnic Study of Atherosclerosis (MESA) was used to examine the association between dietary vitamin B3 intake and renal function decline.

Results: Compared to WT mice, SIRT6-Tg mice exhibited alleviated renal interstitial fibrosis as evidenced by reduced collagen deposit, collagen I and α-smooth muscle actin expression. Renal function was also improved in SIRT6-Tg mice. Homeodomain interacting protein kinase 2 (HIPK2) was induced during the fibrogenesis in CKD, while HIPK2 was downregulated after SIRT6 overexpression. Further assay in vitro confirmed that SIRT6 depletion exacerbated epithelial-to-mesenchymal transition of HK2 cells, which might be linked with HIPK2 upregulation. HIPK2 was inhibited by SIRT6 in the post-transcriptional level. Population study indicated that higher dietary vitamin B3 intake was independently correlated with a lower risk of estimate glomerular filtration rate decline in those ≥65 years old during follow-up.

Conclusion: SIRT6/HIPK2 axis serves as a promising target of renal interstitial fibrosis in CKD. Dietary vitamin B3 intake is beneficial for renal function in the old people.

Targeted biomarkers of progression in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is an increasingly significant health issue worldwide. Early stages of CKD can be asymptomatic and disease trajectory difficult to predict. Not everyone with CKD progresses to kidney failure, where kidney replacement therapy is the only life-sustaining therapy. Predicting which patients will progress to kidney failure would allow better use of targeted treatments and more effective allocation of health resources. Current diagnostic tests to identify patients with progressive disease perform poorly but there is a suite of new and emerging predictive biomarkers with great clinical promise.

METHODS

This narrative review describes new and emerging biomarkers of pathophysiologic processes of CKD development and progression, accessible in blood or urine liquid biopsies. Biomarkers were selected based on their reported pathobiological functions in kidney injury, inflammation, oxidative stress, repair and fibrosis. Biomarker function and evidence of involvement in CKD development and progression are reported.

CONCLUSION

Many biomarkers reviewed here have received little attention to date, perhaps because of conflicting conclusions of their utility in CKD. The functional roles of the selected biomarkers in the underlying pathobiology of progression of CKD are a powerful rationale for advancing and validating these molecules as prognosticators and predictors of CKD trajectory.

Natural products: potential drugs for the treatment of renal fibrosis

With the increasing prevalence and mortality, chronic kidney disease (CKD) has become a world public health problem. As the primary pathological manifestation in CKD, renal fibrosis is often used as a critical target for the treatment of CKD and inhibits the progression of CKD to end-stage renal disease (ESRD). As a potential drug, natural products have been confirmed to have the potential as a routine or supplementary therapy for chronic kidney disease, which may target renal fibrosis and act through various pharmacological activities such as anti-inflammatory and anti-oxidation of natural products. This article briefly introduces the pathological mechanism of renal fibrosis and systematically summarizes the latest research on the treatment of renal fibrosis with natural products of Chinese herbal medicines.

TMAO as a potential biomarker and therapeutic target for chronic kidney disease: A review

The gut microbiota and its metabolites have become a hotspot of recent research. Trimethylamine N-oxide (TMAO) metabolized by the gut microbiota is closely related to many diseases such as cardiovascular disease, chronic kidney disease, type 2 diabetes, etc. Chronic kidney disease (CKD) is an important contributor to morbidity and mortality from non-communicable diseases. Recently, increasing focus has been put on the role of TMAO in the development and progress of chronic kidney disease. The level of TMAO in patients with chronic kidney disease is significantly increased, and a high level of TMAO deteriorates chronic kidney disease. This article describes the relationship between TMAO and chronic kidney disease and the research progress of drugs targeted TMAO, providing a reference for the development of anti-chronic kidney disease drugs targeted TMAO.