Quantified kidney echogenicity in mice with renal ischemia reperfusion injury: evaluation as a noninvasive biomarker of acute kidney injury

Prolonged depletion of renal tubular thioredoxin following severe acute kidney injury is associated with transition to chronic kidney disease via G2/M cell cycle arrest

Acute kidney injury (AKI) is a potentially life-threatening event, particularly when there is transition from AKI to chronic kidney disease (CKD). Thioredoxin (TRX) is a key regulator of the intracellular redox environment. Among its redox-sensitive target proteins is the G2/M cell cycle regulator cell division cycle 25 C (Cdc25C). After AKI, tubular TRX levels are decreased, while urinary levels are increased. The aim of this study was to investigate the impact of tubular TRX depletion on AKI-to-CKD transition in mouse models of mild and severe AKI and in renal epithelial cell lines. Mice with severe AKI from reperfusion after 30 min of ischemia showed prolonged tubular TRX depletion with increased urinary TRX excretion and impaired TRX mRNA synthesis. After mild AKI (10 min-ischemia and reperfusion), urinary TRX excretion was limited and tubular TRX levels quickly recovered with marked TRX mRNA synthesis. In mice with severe AKI, phosphorylation and cytoplasmic translocation of Cdc25C and cell cycle arrest at G2/M phase were observed. In addition, levels of the profibrotic factors transforming growth factor beta and connective tissue growth factor were increased, suggesting progression of AKI-to-CKD transition. Treatment with TRX inducers or TRX overexpression ameliorated AKI-induced Cdc25C-mediated G2/M arrest and progression of AKI-to-CKD transition. Redox-dependent G2/M arrest and increased levels of profibrotic factors were also observed in renal epithelial cells after treatment with TRX reductase inhibitors or TRX knockdown. These findings suggest that tubular TRX depletion after severe AKI is associated with redox-dependent G2/M arrest and progression of AKI-to-CKD transition.

Prediction model of postnatal renal function in fetuses with lower urinary tract obstruction (LUTO)-Development and internal validation

OBJECTIVE

To develop a prediction model of postnatal renal function in fetuses with lower urinary tract obstruction (LUTO) based on fetal ultrasound parameters and amniotic fluid volume.

METHODS

Retrospective nationwide cohort study of fetuses with postnatally confirmed LUTO and known eGFR. Fetuses treated with fetal interventions such as vesico-amniotic shunting or cystoscopy were excluded. Logistic regression analysis was used to identify prognostic ultrasound variables with respect to renal outcome following multiple imputation of missing data. On the basis of these fetal renal parameters and amniotic fluid volume, a model was developed to predict postnatal renal function in fetuses with LUTO. The main study outcome was an eGFR less than 60 mL/min * 1.73 m² based on the creatinine nadir during the first year following diagnosis. Model performance was evaluated by receiver operator characteristic (ROC) curve analysis, calibration plots, and bootstrapping.

RESULTS

Hundred one fetuses with a confirmed diagnosis of LUTO were included, eGFR less than 60 was observed in 40 (39.6%) of them. Variables predicting an eGFR less than 60 mL/min * 1.73m² included the following sonographic parameters: hyperechogenicity of the renal cortex and abnormal amniotic fluid volume. The model showed fair discrimination, with an area under the ROC curve of 0.70 (95% confidence interval, 0.59-0.81, 0.66 after bootstrapping) and was overall well-calibrated.

CONCLUSION

This study shows that a prediction model incorporating ultrasound parameters such as cortical appearance and abnormal amniotic fluid volume can fairly discriminate an eGFR above or below 60 mL/min * 1.73m² . This clinical information can be used in identifying fetuses eligible for prenatal interventions and improve counseling of parents.

A nephron model for study of drug-induced acute kidney injury and assessment of drug-induced nephrotoxicity

In this study, we developed a multilayer microfluidic device to simulate nephron, which was formed by "glomerulus", "Bowman's capsule", "proximal tubular lumen" and "peritubular capillary". In this microdevice, artificial renal blood flow was circulating and glomerular filtrate flow was single passing through, mimicking the behavior of a nephron. In this dynamic artificial nephron, we observed typical renal physiology, including the glomerular size-selective barrier, glomerular basement membrane charge-selective barrier, glucose reabsorption and para-aminohippuric acid secretion. To demonstrate the capability of our microdevice, we used it to investigate the pathophysiology of drug-induced acute kidney injury (AKI) and give assessment of drug-induced nephrotoxicity, with cisplatin and doxorubicin as model drugs. In the experiment, we loaded the doxorubicin or cisplatin in the "renal blood flow", recorded the injury of primary glomerular endothelial cells, podocytes, tubular epithelial cells and peritubular endothelial cells by fluorescence imaging, and identified the time-dependence, dose-dependence and the death order of four types of renal cells. Then by measuring multiple biomarkers, including E-cadherin, VEGF, VCAM-1, Nephrin, and ZO-1, we studied the mechanism of cell injuries caused by doxorubicin or cisplatin. Also, we investigated the effect of BSA in the "renal blood flow" on doxorubicin-or-cisplatin-induced nephrotoxicity, and found that BSA enhanced the tight junctions between cells and eased cisplatin-induced nephrotoxicity. In addition, we compared the nephron model and traditional tubule models for assessment of drug-induced nephrotoxicity. And it can be inferred that our biomimetic microdevice simulated the complex, dynamic microenvironment of nephron, yielded abundant information about drug-induced-AKI at the preclinical stage, boosted the drug safety evaluation, and provided a reliable reference for clinical therapy.