Tubulointerstitial injury and the progression of chronic kidney disease

Clinicopathological findings of tubulointerstitial nephritis: a cross-sectional analysis of the Japan Renal Biopsy Registry (J-RBR)

INTRODUCTION

Tubulointerstitial nephritis (TIN) is an important disease involving a diverse set of factors that can cause both acute kidney injury and chronic kidney disease. The purpose of this cross-sectional study was to clarify the causative diseases and clinicopathological characteristics of TIN using the Japan Renal Biopsy Registry (J-RBR).

METHODS

This cross-sectional study analyzed data from 22,049 cases registered in the J-RBR between 2018 and 2022. Clinicopathological findings at diagnosis were investigated.

RESULTS

Of the enrolled cases, 913 were diagnosed with TIN. "Drug-induced" was the most common (232 cases, 25.7%), followed by "IgG4-related kidney disease" (124 cases, 13.7%). Of "Drug-induced" TIN cases, "Chemotherapy-related" was the most common cause (63 cases, 27.2%), including 47 cases of "immune checkpoint inhibitor (ICI)-associated" TIN. IgM-positive plasma cell-rich TIN (IgMPC-TIN), which has been the focus of much attention in recent years, was also included, with 9 cases.

CONCLUSION

This is the first report of the clinicopathological findings of TIN patients in a large-scale, nationwide registry of renal biopsies. It was possible to identify recent trends in causative diseases, including an increase in chemotherapy-related TIN and IgMPC-TIN.

Dietary Polyunsaturated Fatty Acid Deficiency Impairs Renal Lipid Metabolism and Adaptive Response to Proteinuria in Murine Renal Tubules

Background/Objectives: Kidneys are fatty acid (FA)-consuming organs that use adenosine triphosphate (ATP) for tubular functions, including endocytosis for protein reabsorption to prevent urinary protein loss. Peroxisome proliferator-activated receptor α (PPARα) is a master regulator of FA metabolism and energy production, with high renal expression. Although polyunsaturated fatty acids (PUFAs) are essential nutrients that are natural PPARα ligands, their role in tubular protein reabsorption remains unclear. As clinical PUFA deficiency occurs in humans under various conditions, we used a mouse model that mimics these conditions. Methods: We administered a 2-week intraperitoneal protein-overload (PO) treatment to mice that had been continuously fed a PUFA-deficient diet. We compared the phenotypic changes with those in mice fed a standard diet and those in mice fed a PUFA-deficient diet with PUFA supplementation. Results: In the absence of PO, the PUFA-deficient diet induced increased lysosomal autophagy activation; however, other phenotypic differences were not detected among the diet groups. In the PO experimental condition, the PUFA-deficient diet increased daily urinary protein excretion and tubular lysosomes; suppressed adaptive endocytosis activation, which was probably enhanced by continuous autophagy activation; and worsened FA metabolism and PPARα-mediated responses to PO, which disrupted renal energy homeostasis. However, these changes were attenuated by PUFA supplementation at the physiological intake level. Conclusions: PUFAs are essential nutrients for the tubular adaptive reabsorption response against urinary protein loss. Therefore, active PUFA intake may be important for patients with kidney disease-associated proteinuria, especially those with various PUFA deficiency-inducing conditions.

Associations between iron status and diabetic kidney disease: A nationwide study

BACKGROUND AND AIM

Iron status plays a crucial role in various physiological processes, and its dysregulation is associated with numerous health conditions. However, research on the relationship between iron status and diabetic kidney disease (DKD) is quite limited. Therefore, this study aims to investigate the connection between iron status and DKD.

METHODS AND RESULTS

This population-based cross-sectional survey included adult diabetes patients from five National Health and Nutrition Examination Survey (NHANES) cycles spanning 1999 to 2006 and 2017 to 2018. Regression models were used to assess the impact of iron status on the prevalence of diabetic nephropathy. Restricted cubic spline models further explored potential nonlinear dose-response relationships. Subgroup analyses clarified the effects of other covariates on these associations. Iron and TIBC were negatively correlated with DKD, albuminuria, and low estimated glomerular filtration rate (eGFR). TSAT was negatively correlated with DKD and showed an "L"-shaped nonlinear correlation with albuminuria and low-eGFR. Ferritin exhibited a "J"-shaped nonlinear correlation with DKD, albuminuria, and low-eGFR. Subgroup analysis revealed that the association between TIBC and reduced risk of low eGFR was more pronounced in individuals with hypertension. The associations between iron and TSAT with a reduced risk of DKD were more significant in smokers, while the association between ferritin and an increased risk of albuminuria was also more pronounced in smokers.

CONCLUSIONS

In diabetic patients, iron status is closely associated with DKD. Monitoring these iron status markers can help improve the prevention and management of kidney health in diabetic patients.

Tubulointerstitial nephritis in children and adolescents

The tubulointerstitial compartment comprises most of the kidney parenchyma. Inflammation in this compartment (tubulointerstitial nephritis-TIN) can be acute and resolves if the offending factor is withdrawn or may enter a chronic process leading to irreversible kidney damage. Etiologic factors differ, including different exposures, infections, and autoimmune and genetic tendency, and the initial damage can be acute, recurrent, or permanent, determining whether the acute inflammatory process will lead to complete healing or to a chronic course of inflammation leading to fibrosis. Clinical and laboratory findings of TIN are often nonspecific, which may lead to delayed diagnosis and a poorer clinical outcome. We provide a general review of TIN, with special mention of the molecular pathophysiological mechanisms of the associated kidney damage.

Megalin: A Sidekick or Nemesis of the Kidney?

Megalin is an endocytic receptor in the proximal tubules that reabsorbs filtered proteins in the kidneys. Recycling of megalin after endocytosis and its expression on the apical plasma membrane of the proximal tubule are critical for its function. The expression of megalin in the kidney undergoes dynamic changes under physiologic and pathophysiologic conditions. Receptors and various effector signaling components regulate megalin expression and, potentially, function. Genetic manipulation and rare mutations in megalin suggest that a lack of or deficiency in megalin expression/function promotes tubular proteinuria and albuminuria. However, the role of megalin in kidney diseases associated with obesity, diabetes, hypertension, and nephrotoxicity remains unclear. To address these questions, animal and human studies have indicated megalin as a protective, injurious, and potentially urinary marker of nephropathy. This article reviews the literature on the regulation of megalin expression and the role of megalin in the pathophysiology of the kidney under experimental and clinical conditions. Moreover, this review articulates the need for studies that can clarify whether megalin can serve as a therapeutic target, in one way or the other, to treat kidney disease.

Apical periodontitis and its effects on renal tissue in rats

BACKGROUND

Motivation for the study. Apical periodontitis (AP) can trigger immune responses that affect other organs. Main findings. This animal study examined the effects of AP on renal tissue, finding significant changes in parameters such as renal corpuscle area and Bowman's space, which may have implications for chronic kidney disease. Implications. Future research will provide insight into how dental conditions may affect renal health. If confirmed, regular dental checkups would not only be critical to improve the overall health of patients with kidney disease, but could also serve as a preventive measure.

OBJECTIVES.

To evaluate the effect of apical periodontitis (AP) induced in Wistar rats on histologically examined renal tissue.

MATERIALS AND METHODS.

Fourteen 12-week-old male Wistar rats weighing an average of 250 grams were used. AP was induced with pulp exposure of the upper and lower first molars using a #1011 HL spherical bur in high rotation. The lesions were left exposed to the oral environment for a period of 7 weeks. Blood pressure was measured by the tail-cuff plethysmography method from the fourth week. The kidney was dissected for histological analysis (H&E). Mann-Whitney and Student's t-test were used for non-parametric and parametric data, respectively, with a significance level of 5%.

RESULTS.

A statistically significant increase in both Bowman's space area and renal corpuscle area was found in the AP group (p<0.05). The AP group had a higher percentage of renal tissue with inflammatory infiltrate, but without significant difference. Blood pressure did change during the experimental period and no difference was identified between the groups.

CONCLUSIONS.

Induction of AP in Wistar rats resulted in significant changes of certain renal histological parameters, suggesting a possible interaction between AP and renal tissue that requires further research.

The temporal relationship between mitochondrial quality and renal tissue recovery following ischemia-reperfusion injury

Background

Growing evidence indicates that disruptions in mitochondrial quality management contribute to the development of acute kidney injury (AKI), incomplete or maladaptive kidney repair, and chronic kidney disease. However, the temporal dynamics of mitochondrial quality control alterations in relation to renal injury and its recovery remain poorly understood and are addressed in this manuscript.

Method

ology: Male Wistar rats (n = 60) were subjected to varying durations of ischemia and reperfusion. Ischemia was instigated by clamping both renal arteries and for reperfusion, the clamps were removed to restore the blood flow. Renal injury, physiological function, mitochondrial assessment, and cellular mediators were analyzed.

Results

Prolonging ischemia duration reduces bioenergetic function while disrupting the balance of mitochondrial fusion, fission, and mitophagy at the gene expression level while maintaining intact mitochondrial copy number. However, reperfusing a kidney after 45 min of ischemia with varying reperfusion times exacerbates mitochondrial dysfunction and significantly decreases mitochondrial copy number. These declines are particularly evident at 24 h of reperfusion, with some parameters improving by 7 days of reperfusion. Despite these improvements, 7 days of reperfusion did not correlate with renal injury indicators (CrCl- 0.46 ± 0.01, BUN-86.29 ± 4.9, Cr-1.75 ± 0.16) following 45 min of ischemia. Conversely, 15 min of ischemia followed by 7 days of reperfusion restored mitochondrial quality and renal function (CrCl- 7.33 ± 0.59, BUN-43.6 ± 3.16, Cr-0.93 ± 0.14).

Conclusion

The above findings emphasize that mitochondrial quality control alters with the extent of ischemia and subsequent reperfusion time, impacting not only mitochondrial copy number but also the resilience of mitochondria during tissue repair.

Targeting Fibrosis: From Molecular Mechanisms to Advanced Therapies

As the final stage of disease-related tissue injury and repair, fibrosis is characterized by excessive accumulation of the extracellular matrix. Unrestricted accumulation of stromal cells and matrix during fibrosis impairs the structure and function of organs, ultimately leading to organ failure. The major etiology of fibrosis is an injury caused by genetic heterogeneity, trauma, virus infection, alcohol, mechanical stimuli, and drug. Persistent abnormal activation of "quiescent" fibroblasts that interact with or do not interact with the immune system via complicated signaling cascades, in which parenchymal cells are also triggered, is identified as the main mechanism involved in the initiation and progression of fibrosis. Although the mechanisms of fibrosis are still largely unknown, multiple therapeutic strategies targeting identified molecular mechanisms have greatly attenuated fibrotic lesions in clinical trials. In this review, the organ-specific molecular mechanisms of fibrosis is systematically summarized, including cardiac fibrosis, hepatic fibrosis, renal fibrosis, and pulmonary fibrosis. Some important signaling pathways associated with fibrosis are also introduced. Finally, the current antifibrotic strategies based on therapeutic targets and clinical trials are discussed. A comprehensive interpretation of the current mechanisms and therapeutic strategies targeting fibrosis will provide the fundamental theoretical basis not only for fibrosis but also for the development of antifibrotic therapies.

Coexisting Tubulointerstitial Inflammation and Damage Is a Risk Factor for Chronic Kidney Disease in Patients With Lupus Nephritis

OBJECTIVE

This study aims to determine whether the concurrent presence of tubulointerstitial inflammation (TII) and tubulointerstitial damage (TID) predicts the progression of chronic kidney disease (CKD) in patients with lupus nephritis (LN).

METHODS

Data from 175 LN patients, collected at the time of renal biopsy, were analyzed. Patients were stratified into two groups based on the presence or absence of coexisting TII/TID. Uni- and multivariable Cox proportional hazard regression models were utilized to identify independent risk factors for CKD in LN patients.

RESULTS

Of 175 patients, 110 (62.9%) exhibited coexisting TII/TID, whereas 65 (37.1%) did not. Patients with coexisting TII/TID tended to be older and presented with higher levels of ESR and 24-h proteinuria, as well as lower levels of eGFR and hemoglobin compared to those without coexisting TII/TID. Over a mean follow-up period of 89.9 months, CKD and end-stage renal disease occurred more frequently in patients with coexisting TII/TID. Notably, the presence of coexisting TII/TID was associated with a higher risk of CKD progression, with adjusted hazard ratios of 2.667 (95% CI: 1.333, 5.335, p = 0.006) for all LN patients, 3.265 (95% CI: 1.451, 7.345, p = 0.004) for those with class III, IV, and V LN, and 3.045 (95% CI: 1.289, 7.195, p = 0.011) for those with class III, IV, V LN, and eGFR ≥ 30 mL/min/1.73 m2.

CONCLUSIONS

LN patients with coexisting TII/TID are at a heightened risk of kidney function deterioration at LN onset and subsequent development of CKD over the long term.

Renal preservation in immediate bifurcation of the renal artery in a solitary kidney using inner branch in a physician-modified, fenestrated-branched endovascular graft

For high-risk patients with complex aortic aneurysms and post-dissection aneurysms, fenestrated and branched endovascular aortic repair (F/BEVAR) offers minimally invasive options customized to each individual's anatomy. Company-manufactured devices or physician-modified endovascular grafts performed under the purview of an investigational device exemption are two United States Food and Drug Administration-approved avenues to perform fenestrated and branched endovascular aortic repair. This case report describes a creative use of physician-modified endograft to salvage renal function in a solitary kidney with a near immediate bifurcation of the renal artery in a patient with post-dissection extent II thoracoabdominal aortic aneurysm. In our patient, the immediate bifurcation (2 mm distal to the common left renal artery orifice) of the left renal artery in the setting of a known long-standing occlusion of a remotely placed right renal stent presented a clinical and technical challenge to maintaining this patient's kidney function without sacrificing a significant portion of his remaining solitary kidney. Additionally, each branch was sizeable (5 and 7 mm), perfusing the cranial and caudal half of the kidney, respectively. Early bifurcation of renal arteries often results in sacrifice of the smaller branch to obtain adequate target vessel seal. Although some analyses have shown no change in glomerular filtration rate from coverage of accessory renal arteries, more recent studies have indicated clinically significant drops in both glomerular filtration rate and kidney length at 2-year follow-up. Herein, we describe use of a combination of an inner and external branch modification to stent both branches to preserve renal parenchyma and function. The patient has provided written informed consent for publication of this case report and their associated imaging studies.

miR-542-5p targets GREM1 to affect the progression of renal fibrosis

Renal fibrosis (RF) is a typical pathological presentation of end-stage chronic kidney disease (CKD) and autosomal dominant polycystic kidney disease (ADPKD). However, the precise regulatory mechanisms governing this re-expression process remain unclear. Differentially expressed microRNAs (miRNAs) associated with RF were screened by microarray analysis using the Gene Expression Omnibus (GEO) database. The miRNAs upstream of the genes in question were predicted using the miRWalk database. The miRNAs involved in the two GEO data sets were intersected to identify key miRNAs; their regulatory pathways were investigated using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Subsequently, the effects and the underlying mechanisms of target miRNA on RF were examined in a unilateral ureteral obstruction (UUO)-induced mice renal fibrotic model and a transforming growth factor-β1 (TGF-β1)-induced tubular epithelium (HK-2) fibrotic cell model. In total, 109 and 32 differentially expressed miRNAs were identified in the GSE133530 and GSE80247 data sets, respectively. GREM1 was identified as a hub gene, where its 2196 upstream miRNAs were predicted; miR-574-5p was found to be downregulated and closely related to fibrosis after data set intersection and enrichment analyses, thus was selected for further investigation. A differential expression heatmap (GSE162794) showed that miR-542-5p was downregulated. The expression of GREM1 mRNA was upregulated, whereas that of miR-542-5p was downregulated in UUO mice and fibrotic HK-2 cells as compared with the relevant controls. The binding site of miR-542-5p was predicted at the 3'UTR region of GREM1 and was confirmed by subsequent dual luciferase reporter gene assay. Western blot analysis showed that Gremlin-1 and Fibronectin were significantly upregulated after induction of TGF-β1; when miR-542-5p was overexpressed or GREM1 mRNA was interfered, the upregulations of Gremlin-1 and Fibronectin were significantly reduced. Our research demonstrates that miR-542-5p plays a critical role in the progression of RF, and thus may be a promising therapeutic target for CKD and ADPKD.

Serum and urinary monocyte chemoattractant protein-1 as markers of inflammation and renal damage in dogs with naturally occurring leishmaniosis

BACKGROUND

Renal disease in canine leishmaniosis is of great importance owing to increased risk of mortality. In human visceral leishmaniosis, monocyte chemoattractant protein-1 (MCP-1) has been used as a marker of renal damage and inflammation. The purpose of this study was first to determine the serum MCP-1 and urinary MCP-1-to-creatinine ratio (uMCP-1/Cr) in healthy dogs and dogs with leishmaniosis at diagnosis, and second to determine whether these markers can differentiate disease severity at diagnosis.

METHODS

In total, 19 healthy seronegative dogs and 38 dogs with leishmaniosis were included in the study. Dogs with leishmaniosis were classified as LeishVet clinical staging and as International Renal Interest Society (IRIS) staging. Serum and urinary MCP-1 concentrations were measured with an enzyme-linked immunosorbent assay. A receiver operating characteristic (ROC) curve determined disease severity at diagnosis between two LeishVet groups (Stage II versus stage III and IV).

RESULTS

Dogs in Leishvet stages IIb, III, and IV had a median serum MCP-1 and uMCP-1/Cr concentration higher than healthy dogs (P < 0.0001). No statistical differences were found in serum MCP-1 and uMCP-1/Cr between dogs in LeishVet stage IIa and healthy dogs. The dogs in LeishVet stage IV had significantly higher serum MCP-1 and uMCP-1/Cr compared with the dogs in LeishVet stage IIa (P < 0.0001). Serum MCP-1 and uMCP-1 were significantly higher in dogs in IRIS stage I and II + III + IV compared with healthy dogs. Dogs stage II + III + IV of IRIS had a significantly higher serum MCP-1 compared with dogs in IRIS stage I (P < 0.0001). The area under the ROC curve for serum MCP-1 was 0.78 [95% confidence interval (CI) 0.64-0.93] and for uMCP-1/Cr it was 0.86 (95% CI, 0.74-0.99). The optimal cutoff value for serum MCP-1 and uMCP-1/Cr was 336.85 pg/ml (sensitivity of 79% and specificity of 68%) and 6.89 × 10-7 (sensitivity of 84% and specificity of 79%), respectively.

CONCLUSIONS

Serum MCP-1 and uMCP-1/Cr are increased in dogs with leishmaniosis compared with healthy dogs, suggesting the presence of inflammation and renal injury. Serum MCP-1 and uMCP-1/Cr were more elevated in the advanced stages of the disease compared with the moderate stages and, therefore, can be markers of the severity of the disease process.

Development of a Model of Tubulointerstitial Fibrosis Using Transient Unilateral Renal Ischemia and Delayed Contralateral Nephrectomy in Domesticated Cats

Tubulointerstitial fibrosis is a classic histologic feature of chronic kidney disease (CKD) in cats and a final common pathway toward end-stage renal disease. Domesticated cats have been used in models of ischemia-induced renal fibrosis. The objective of this study was to evaluate the performance of 2 variations of a transient unilateral renal ischemia and delayed contralateral nephrectomy model of tubulointerstitial fibrosis in cats. Purpose-bred, young adult, domesticated cats underwent 90 min of surgically induced ischemia to the right kidney followed by delayed contralateral nephrectomy performed 21 d (RI-CN21d group; n = 10) or 90 d postischemia (RI-CN90d group; n = 12). Control cats underwent sham surgery followed by left nephrectomy 21 d after (sham-CN group; n = 3). Renal functional parameters, including glomerular filtration rate and serum creatinine concentration, were evaluated before and after surgeries. The right kidneys were harvested 120 d postischemia/ sham. Renal histology with lesion scoring and histomorphometry for quantification of smooth muscle actin immunolabeling and collagen staining were performed on harvested kidneys. Severe acute kidney injury prompted euthanasia after left nephrectomy in 5/10 (50.0%), 2/12 (16.7%), and 0/3 (0%) of cats in the RI-CN21d, RI-CN90d, and sham-CN groups, respectively. A significant decrease in glomerular filtration rate by day 120, relative to baseline, occurred in cats in the RI-CN21d group (P < 0.001) and RI-CN90d group (P < 0.001) but not the sham-CN group (P = 0.76). All but one cat in the ischemia groups were azotemic at the study end. Kidneys subjected to ischemia had higher interstitial inflammation, tubular atrophy, and fibrosis scores compared with sham-operated kidneys. There were significant increases in smooth muscle actin immunolabeling and collagen staining in these kidneys, relative to the contralateral kidneys. In summary, 90 min of unilateral renal ischemia and delayed contralateral nephrectomy induced histologic and biochemical changes consistent with CKD in cats. A 90-d period between ischemia and nephrectomy resulted in improved survivability of the model.

Urine Epidermal Growth Factor and Kidney Function Decline in Middle-Aged Adults

Rationale & Objective

The diagnosis and prognostication of chronic kidney disease (CKD) largely rely on glomerular measures that may not reflect tubular damage. We investigated the associations of urine kidney tubule biomarkers with estimated glomerular filtration rate (eGFR) change among middle-aged adults, when chronic diseases typically emerge.

Study Design

An observational cohort study.

Setting & Participants

A total of 1,145 participants of the Coronary Artery Risk Development in Young Adults (CARDIA) study without CKD, hypertension, or cardiovascular disease at the year 20 visit.

Exposures

Seven different biomarkers of tubular health: urine epidermal growth factor (EGF), alpha-1-microglobulin (α1m), interleukin-18, kidney injury molecule-1, monocyte chemoattractant protein-1, uromodulin, and chitinase-3-like protein 1.

Outcomes

Ten-year eGFR change and incident reduced eGFR (new onset of eGFR < 60 mL/min/1.73 m2).

Analytical Approach

We examined associations of tubular health biomarkers with 10-year eGFR change and incident reduced eGFR with linear mixed models and interval-censored proportional hazards regression models, respectively. Both minimally and fully adjusted models were controlled for urine creatinine levels.

Results

The mean age of participants was 44.8 ± 3.7 years, with 39% African American and 56% female. The average 10-year change in eGFR was -18.6 mL/min/1.73 m2 (95% CI, -19.4 to -17.8). In contrast to the other tubular biomarkers, which showed conflicting results, EGF demonstrated strong, consistent associations with both kidney outcomes. Each 1-standard deviation (SD) higher EGF was associated with a 2.37 mL/min/1.73 m2 (95% CI, 0.64-4.10) smaller 10-year decrease in eGFR and a 42% (95% CI, 4%-64%) lower risk of incident reduced eGFR in the fully adjusted model.

Limitations

Observational design, measurements of eGFR were done only at 5-year intervals during follow-up.

Conclusions

In middle-aged, community-dwelling adults without hypertension, cardiovascular disease or CKD, higher urine EGF concentrations are associated with slower eGFR decline, whereas other kidney tubule biomarkers lacked a consistent association with kidney function decline.

Modified Zhenwu Tang delays chronic renal failure progression by modulating oxidative stress and hypoxic responses in renal proximal tubular epithelial cells

Background

Tubulointerstitial fibrosis (TIF) is a critical pathological feature of chronic renal failure (CRF), with oxidative stress (OS) and hypoxic responses in renal proximal tubular epithelial cells playing pivotal roles in disease progression. This study explores the effects of Modified Zhenwu Tang (MZWT) on these processes, aiming to uncover its potential mechanisms in slowing CRF progression.

Methods

We used adenine (Ade) to induce CRF in rats, which were then treated with benazepril hydrochloride (Lotensin) and MZWT for 8 weeks. Assessments included liver and renal function, electrolytes, blood lipids, renal tissue pathology, OS levels, the hypoxia-inducible factor (HIF) pathway, inflammatory markers, and other relevant indicators. In vitro, human renal cortical proximal tubular epithelial cells were subjected to hypoxia and lipopolysaccharide for 72 h, with concurrent treatment using MZWT, FM19G11, and N-acetyl-l-cysteine. Measurements taken included reactive oxygen species (ROS), HIF pathway activity, inflammatory markers, and other relevant indicators.

Results

Ade treatment induced significant disruptions in renal function, blood lipids, electrolytes, and tubulointerstitial architecture, alongside heightened OS, HIF pathway activation, and inflammatory responses in rats. In vivo, MZWT effectively ameliorated proteinuria, renal dysfunction, lipid and electrolyte imbalances, and renal tissue damage; it also suppressed OS, HIF pathway activation, epithelial-mesenchymal transition (EMT) in proximal tubular epithelial cells, and reduced the production of inflammatory cytokines and collagen fibers. In vitro findings demonstrated that MZWT decreased apoptosis, reduced ROS production, curbed OS, HIF pathway activation, and EMT in proximal tubular epithelial cells, and diminished the output of inflammatory cytokines and collagen.

Conclusion

OS and hypoxic responses significantly contribute to TIF development. MZWT mitigates these responses in renal proximal tubular epithelial cells, thereby delaying the progression of CRF.

TMAO enhances TNF-α mediated fibrosis and release of inflammatory mediators from renal fibroblasts

Trimethylamine-N-oxide (TMAO) is a gut microbiota-derived metabolite and TNF-α is proinflammatory cytokine, both known to be associated with renal inflammation, fibrosis and chronic kidney disease. However, today there are no data showing the combined effect of TMAO and TNF-α on renal fibrosis-and inflammation. The aim of this study was to investigate whether TMAO can enhance the inflammatory and fibrotic effects of TNF-α on renal fibroblasts. We found that the combination of TNF-α and TMAO synergistically increased fibronectin release and total collagen production from renal fibroblasts. The combination of TMAO and TNF-α also promoted increased cell proliferation. Both renal proliferation and collagen production were mediated through Akt/mTOR/ERK signaling. We also found that TMAO enhanced TNF-α mediated renal inflammation by inducing the release of several cytokines (IL-6, LAP TGF-beta-1), chemokines (CXCL-6, MCP-3), inflammatory-and growth mediators (VEGFA, CD40, HGF) from renal fibroblasts. In conclusion, we showed that TMAO can enhance TNF-α mediated renal fibrosis and release of inflammatory mediators from renal fibroblasts in vitro. Our results can promote further research evaluating the combined effect of TMAO and inflammatory mediators on the development of kidney disease.

Single-cell transcriptomics reveals the ameliorative effect of rosmarinic acid on diabetic nephropathy-induced kidney injury by modulating oxidative stress and inflammation

Diabetic nephropathy (DN) is a severe complication of diabetes, characterized by changes in kidney structure and function. The natural product rosmarinic acid (RA) has demonstrated therapeutic effects, including anti-inflammation and anti-oxidative-stress, in renal damage or dysfunction. In this study, we characterized the heterogeneity of the cellular response in kidneys to DN-induced injury and RA treatment at single cell levels. Our results demonstrated that RA significantly alleviated renal tubular epithelial injury, particularly in the proximal tubular S1 segment and on glomerular epithelial cells known as podocytes, while attenuating the inflammatory response of macrophages, oxidative stress, and cytotoxicity of natural killer cells. These findings provide a comprehensive understanding of the mechanisms by which RA alleviates kidney damage, oxidative stress, and inflammation, offering valuable guidance for the clinical application of RA in the treatment of DN.

Role of ferroptosis in chronic kidney disease

Chronic kidney disease (CKD) has historically been a significant global health concern, profoundly impacting both life and well-being. In the process of CKD, with the gradual loss of renal function, the incidence of various life-threatening complications, such as cardiovascular diseases, cerebrovascular accident, infection and stroke, is also increasing rapidly. Unfortunately, existing treatments exhibit limited ability to halt the progression of kidney injury in CKD, emphasizing the urgent need to delve into the precise molecular mechanisms governing the occurrence and development of CKD while identifying novel therapeutic targets. Renal fibrosis, a typical pathological feature of CKD, plays a pivotal role in disrupting normal renal structures and the loss of renal function. Ferroptosis is a recently discovered iron-dependent form of cell death characterized by lipid peroxide accumulation. Ferroptosis has emerged as a potential key player in various diseases and the initiation of organ fibrosis. Substantial evidence suggests that ferroptosis may significantly contribute to the intricate interplay between CKD and its progression. This review comprehensively outlines the intricate relationship between CKD and ferroptosis in terms of iron metabolism and lipid peroxidation, and discusses the current landscape of pharmacological research on ferroptosis, shedding light on promising avenues for intervention. It further illustrates recent breakthroughs in ferroptosis-related regulatory mechanisms implicated in the progression of CKD, thereby providing new insights for CKD treatment. Video Abstract.

The Molecular Mechanism of Renal Tubulointerstitial Inflammation Promoting Diabetic Nephropathy

Diabetic nephropathy (DN) is a common complication affecting many diabetic patients, leading to end-stage renal disease. However, its pathogenesis still needs to be fully understood to enhance the effectiveness of treatment methods. Traditional theories are predominantly centered on glomerular injuries and need more explicit explanations of recent clinical observations suggesting that renal tubules equally contribute to renal function and that tubular lesions are early features of DN, even occurring before glomerular lesions. Although the conventional view is that DN is not an inflammatory disease, recent studies indicate that systemic and local inflammation, including tubulointerstitial inflammation, contributes to the development of DN. In patients with DN, intrinsic tubulointerstitial cells produce many proinflammatory factors, leading to medullary inflammatory cell infiltration and activation of inflammatory cells in the interstitial region. Therefore, understanding the molecular mechanism of renal tubulointerstitial inflammation contributing to DN injury is of great significance and will help further identify key factors regulating renal tubulointerstitial inflammation in the high glucose environment. This will aid in developing new targets for DN diagnosis and treatment and expanding new DN treatment methods.

Is serum hemoglobin level an independent prognostic factor for IgA nephropathy?: a systematic review and meta-analysis of observational cohort studies

BACKGROUND

Decreased serum hemoglobin (Hb) level is associated with Immunoglobulin A nephropathy (IgAN) progression. However, whether serum Hb level is an independent prognostic factor of IgAN remains controversial. Herein, we aimed to investigate the prognostic value of serum Hb level in IgAN.

METHODS

The Cochrane Library, Embase, PubMed and Open Grey databases were systematically searched and reviewed. Kidney disease progression of IgAN was defined as a doubling of serum creatinine (SCr), a 30% reduction in estimated glomerular filtration rate (eGFR), end-stage renal disease (ESRD), or death. We evaluated the hazard ratio (HR) between serum Hb level and the incidence of kidney disease progression in IgAN before and after adjusting for relevant covariates.

RESULTS

We included nine studies with 10006 patients in the meta-analysis. As a continuous variable, we found that serum Hb was an independent prognostic factor of IgAN [unadjusted HR = 0.89, 95% confidence interval (CI) = 0.84-0.95, I² = 98%; adjusted HR = 0.85, 95% CI = 0.79-0.91, I² = 0%]. The sensitivity analysis confirmed the stability of these results. Consistently, as a dichotomous variable defined as the below/above cutoff for anemia, we observed a positive correlation between serum Hb and kidney disease progression in IgAN (unadjusted HR = 2.12, 95% CI = 1.44-3.12, I² = 79%; adjusted HR = 1.65, 95% CI = 1.20-2.27, I² = 0%).

CONCLUSION

Serum Hb level was independently correlated with the incidence of kidney disease progression in IgAN.

Interleukin-6 and epidermal growth factor as noninvasive biomarkers of progression in chronic glomerulonephritis

Several cytokines and chemokines are involved in the pathogenesis and progressive injury of renal tissues in patients with primary chronic glomerulonephritis (CGN). The objective of this study was to determine whether the urinary excretion of interleukin-6 (IL-6), transforming growth factor β1 (TGFβ1), monocytes chemoattractant protein (MCP-1), soluble tumor necrosis factor receptor 1 (sTNFR1), and epidermal growth factor (EGF) in patients with newly recognized CGN can serve as prognostic biomarkers in patients with newly recognized CGN and whether they can be effective in predicting a progressive reduction of renal function in prospective observation. The study included 150 Caucasian patients. UIL-6, UTGFβ1, UMCP-1, UsTNFR1, and UEGF were measured using enzyme-linked immunosorbent assay (ELISA) methods (Quantikine R&D System). UIL-6, UTGFβ1, UMCP-1, and UsTNFR1 were significantly higher, yet UEGF excretion was significantly lower in nephrotic patients, in patients with estimated glomerular filtration rate (eGFR) < 60/min/1.73 m2 at presentation, as well as in the progressor (PG) subgroup. In a multivariate regression analysis basal eGFR correlated with UsTNFR1, UIL-6, and UEGF excretion, although in the follow-up, ΔeGFR (delta estimated glomerular filtration rate) significantly correlated only with UEGF excretion. A logistic regression analysis showed that the most significant independent risk factors for the deterioration of renal function with time are initial high (>11.8 pg/mgCr) UIL-6 excretion, initial low (<15.5 ng/mgCr) urinary UEGF excretion, and male gender. In patients with newly diagnosed CGN, UIL-6, and UEGF can serve as prognostic biomarkers for the progression of the disease.NEW & NOTEWORTHY Baseline high urinary interleukin-6 (IL-6) excretion and low urinary epidermal growth factor (EGF) excretion and particularly high IL-6/EGF ratio were stronger predictive factors of the progression of the deterioration of the kidney function than initial estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 or proteinuria. In patients with newly diagnosed chronic glomerulonephritis, UIL-6 and UEGF can serve as prognostic biomarkers for the progression of the disease.

Renoprotective Effect of TP0472993, a Novel and Selective 20-Hydroxyeicosatetraenoic Acid Synthesis Inhibitor, in Mouse Models of Renal Fibrosis

Kidney fibrosis is considered the essential pathophysiological process for the progression of chronic kidney disease (CKD) toward renal failure. 20-Hydroxyeicosatetraenoic acid (20-HETE) has crucial roles in modulating the vascular response in the kidney and the progression of albuminuria. However, the roles of 20-HETE in kidney fibrosis are largely unexplored. In the current research, we hypothesized that if 20-HETE has important roles in the progression of kidney fibrosis, 20-HETE synthesis inhibitors might be effective against kidney fibrosis. To verify our hypothesis, this study investigated the effect of a novel and selective 20-HETE synthesis inhibitor, TP0472993, on the development of kidney fibrosis after folic acid- and obstructive-induced nephropathy in mice. Chronic treatment with TP0472993 at doses of 0.3 and 3 mg/kg twice a day attenuated the degree of kidney fibrosis in the folic acid nephropathy and the unilateral ureteral obstruction (UUO) mice, as demonstrated by reductions in Masson's trichrome staining and the renal collagen content. In addition, TP0472993 reduced renal inflammation, as demonstrated by markedly reducing interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNF-α) levels in the renal tissue. Chronic treatment with TP0472993 also reduced the activity of extracellular signal-regulated kinase 1/2 (ERK1/2) and signal transducer and activator of transcription 3 (STAT3) in the kidney of UUO mice. Our observations indicate that inhibition of 20-HETE production with TP0472993 suppresses the kidney fibrosis progression via a reduction in the ERK1/2 and STAT3 signaling pathway, suggesting that 20-HETE synthesis inhibitors might be a novel treatment option against CKD. SIGNIFICANCE STATEMENT: In this study, we demonstrate that the pharmacological blockade of 20-hydroxyeicosatetraenoic acid (20-HETE) synthesis using TP0472993 suppresses the progression of kidney fibrosis after folic acid- and obstructive-induced nephropathy in mice, indicating that 20-HETE might have key roles in the pathogenesis of kidney fibrosis. TP0472993 has the potential to be a novel therapeutic approach against chronic kidney disease.

Crotamine/siRNA Nanocomplexes for Functional Downregulation of Syndecan-1 in Renal Proximal Tubular Epithelial Cells

Proteinuria drives progressive tubulointerstitial fibrosis in native and transplanted kidneys, mainly through the activation of proximal tubular epithelial cells (PTECs). During proteinuria, PTEC syndecan-1 functions as a docking platform for properdin-mediated alternative complement activation. Non-viral gene delivery vectors to target PTEC syndecan-1 could be useful to slow down alternative complement activation. In this work, we characterize a PTEC-specific non-viral delivery vector composed of the cell-penetrating peptide crotamine complexed with a syndecan-1 targeting siRNA. Cell biological characterization was performed in the human PTEC HK2 cell line, using confocal microscopy, qRT-PCR, and flow cytometry. PTEC targeting in vivo was carried out in healthy mice. Crotamine/siRNA nanocomplexes are positively charged, about 100 nm in size, resistant to nuclease degradation, and showed in vitro and in vivo specificity and internalization into PTECs. The efficient suppression of syndecan-1 expression in PTECs mediated by these nanocomplexes significantly reduced properdin binding (p < 0.001), as well as the subsequent complement activation by the alternative complement pathway (p < 0.001), as observed in either normal or activated tubular conditions. To conclude, crotamine/siRNA-mediated downregulation of PTEC syndecan-1 reduced the activation of the alternative complement pathway. Therefore, we suggest that the present strategy opens new venues for targeted proximal tubular gene therapy in renal diseases.

Continuous positive airway pressure treatment reduces renal tubular damage in patients with obstructive sleep apnea: A retrospective single-center cohort study

BACKGROUND

Chronic intermittent hypoxia (IH) plays a significant role in the pathogenesis of obstructive sleep apnea (OSA) comorbidities. The prevalence of chronic kidney disease is higher in patients with OSA than the general population, and renal function decline is well correlated with renal tubular injury. However, little is known about the impact of OSA-induced chronic IH on the renal tubules.

METHODS

We conducted a retrospective survey of clinical records performing multiple regression analysis and cluster analysis with particular attention to the 3% oxygen desaturation index (ODI) and urinary N-acetyl-β-d-glucosaminidase (NAG).

RESULTS

In patients with suspicion of OSA, urinary NAG creatinine ratio (UNCR) was elevated as their 3% ODI increased (n = 197, p < 0.001), and the elevated UNCR decreased following CPAP treatment in patients with OSA (n = 46, p = 0.014). Multiple regression analysis showed that 3% ODI was associated with UNCR. Cluster analysis identified three clusters of patients with OSA, including two younger age clusters, one of which was characterized by high BMI, high 3% ODI, and high prevalence of major comorbidities. In a comparative analysis of younger age cases (age ≤ 55, n = 82), the UNCR level was higher in patients with severe 3% ODI (3% ODI > 40 events/h, n = 24) (p = 0.014).

CONCLUSIONS

Our results indicate that even at younger ages, OSA patients with severe chronic IH and major comorbidities are susceptible to renal tubular damage. Early treatment with CPAP may attenuate renal tubular injury and progression toward end-stage renal disease.

Long non-coding RNA FABP5P3/miR-22 axis improves TGFβ1-induced fatty acid oxidation deregulation and fibrotic changes in proximal tubular epithelial cells of renal fibrosis

Severe hydronephrosis increases the risk of urinary tract infection and irretrievable renal fibrosis. While TGFβ1-mediated fibrotic changes in proximal tubular epithelial cells and fatty acid oxidation (FAO) deregulation contribute to renal fibrosis and hydronephrosis. Firstly, a few elements were analyzed in this paper, including differentially-expressed long non-coding RNAs (lncRNAs), and miRNAs correlated to CPT1A, RXRA, and NCOA1. This paper investigated TGFβ1 effects on lncRNA FABP5P3, CPT1A, RXRA, and NCOA1 expression and fibrotic changes in HK-2 cells and FABP5P3 overexpression effects on TGFβ1-induced changes. Moreover, this paper predicted and proved that miR-22 binding to lncRNA FABP5P3, 3'UTR of CPT1A, RXRA, and NCOA1 was validated. The dynamic effects of the FABP5P3/miR-22 axis on TGFβ1-induced changes were investigated. A Renal fibrosis model was established in unilateral ureteral obstruction (UUO) mice, and FABP5P3 effects were investigated. Eventually, this paper concluded that TGFβ1 inhibited lncRNA FABP5P3, CPT1A, RXRA, and NCOA1 expression, induced fibrotic changes in HK-2 cells, and induced metabolic reprogramming within HK-2 cells, especially lower FAO. FABP5P3 overexpression partially reversed TGFβ1-induced changes. miR-22 targeted lncRNA FABP5P3, CPT1A, RXRA, and NCOA1. LncRNA FABP5P3 counteracted miR-22 inhibition of CPT1A, NCOA1, and RXRA through competitive binding. TGFβ1 stimulation induced the activation of TGFβ/SMAD and JAG/Notch signaling pathways; Nocth2 knockdown reversed TGFβ1 suppression on lncRNA FABP5P3. FABP5P3 overexpression attenuated renal fibrosis in unilateral ureteral obstruction mice. The LncRNA FABP5P3/miR-22 axis might be a potent target for improving the FAO deregulation and fibrotic changes in proximal TECs under TGFβ1 stimulation.

Effects of dietary phosphorus concentration and phosphate salt form on renal tubule function in unilateral nephrectomized rats

Background: Excessive consumption of phosphorus (P) impairs renal tubule function; however, the effects of different dietary phosphate salts on chronic kidney disease (CKD) are unclear. Aim: To examine the effects of potassium dihydrogen phosphate (KH2PO4) and potassium tripolyphosphate (K5P3O10) and P concentration on renal function in a rat model of early CKD. Methods: Male sham-operated Sprague-Dawley rats were fed a diet containing KH2PO4 with a normal P level. Kidney injury was induced by unilateral nephrectomy (UNx), and the rats were divided into four groups fed dietary KH2PO4 or K5P3O10 with a normal (UNx-NKH, UNx-NKP) or high (UNx-HKH, UNx-HKP) P concentration, respectively, for 21 days. Results: UNx-NKH rats showed significantly lower creatinine clearance (CCr) and higher albumin (ALB) compared with those of sham rats, confirming UNx-induced kidney injury. The urinary levels of liver-type fatty acid-binding protein (L-FABP) and ALB were significantly higher in UNx-HKP rats than in UNx-HKH rats. However, other markers of renal tubule function, such as CCr, serum creatinine (CRE), calcium (Ca), and hormones, only differed among groups according to the P concentration and not the dietary phosphate salt form. Histological examination showed higher incidence and severity of tubulointerstitial lesions, tubule regeneration, tubule dilation, and calcification in the high-phosphorus than in the normal-phosphorus UNx groups. These changes were more severe in the UNx-HKP group compared with the UNx-HKH group. Conclusion: This study highlights the importance of controlling dietary P intake in terms of both concentration and source to prevent the progression of CKD.

TMAO Suppresses Megalin Expression and Albumin Uptake in Human Proximal Tubular Cells Via PI3K and ERK Signaling

Trimethylamine-N-oxide (TMAO) is a uremic toxin, which has been associated with chronic kidney disease (CKD). Renal tubular epithelial cells play a central role in the pathophysiology of CKD. Megalin is an albumin-binding surface receptor on tubular epithelial cells, which is indispensable for urine protein reabsorption. To date, no studies have investigated the effect of TMAO on megalin expression and the functional properties of human tubular epithelial cells. The aim of this study was first to identify the functional effect of TMAO on human renal proximal tubular cells and second, to unravel the effects of TMAO on megalin-cubilin receptor expression. We found through global gene expression analysis that TMAO was associated with kidney disease. The microarray analysis also showed that megalin expression was suppressed by TMAO, which was also validated at the gene and protein level. High glucose and TMAO was shown to downregulate megalin expression and albumin uptake similarly. We also found that TMAO suppressed megalin expression via PI3K and ERK signaling. Furthermore, we showed that candesartan, dapagliflozin and enalaprilat counteracted the suppressive effect of TMAO on megalin expression. Our results may further help us unravel the role of TMAO in CKD development and to identify new therapeutic targets to counteract TMAOs effects.

PGC1 plays a pivotal role in renal fibrosis via regulation of fatty acid metabolism in renal tissue

Renal fibrosis is a common and irreversible pathological feature of end-stage renal disease caused by multiple etiologies. The role of inflammation in renal fibrosis tissue has been generally accepted. The latest view is that fatty acid metabolism disorder contributes to renal fibrosis. peroxisome proliferator activated receptor-gamma coactivator 1α (PGC1α) plays a key role in fatty acid metabolism, regulating fatty acid uptake and oxidized protein synthesis, preventing the accumulation of lipid in the cytoplasm, and maintaining a dynamic balanced state of intracellular lipid. In multiple animal models of renal fibrosis caused by acute or chronic kidney disease, or even age-related kidney disease, almost all of the kidney specimens show the down-regulation of PGC1α. Upregulation of PGC1α can reduce the degree of renal fibrosis in animal models, and PGC1α knockout animals exhibit severe renal fibrosis. Studies have demonstrated that AMP-activated protein kinase (AMPK), MAPK, Notch, tumor necrosis factor-like weak inducer of apoptosis (TWEAK), epidermal growth factor receptor (EGFR), non-coding RNA (ncRNAs), liver kinase B1 (LKB1), hairy and enhancer of split 1 (Hes1), and other pathways regulate the expression of PGC1α and affect fatty acid metabolism. But some of these pathways interact with each other, and the effect of the integrated pathway on renal fibrosis is not clear.

Combination of Perindopril Erbumine and Huangqi-Danshen Decoction Protects Against Chronic Kidney Disease via Sirtuin3/Mitochondrial Dynamics Pathway

Background

Chronic kidney disease (CKD) is a major public health problem worldwide. Treatment with renin-angiotensin system inhibitors can achieve only partial efficacy on renal function decline and renal fibrosis in CKD patients. Huangqi-Danshen decoction (HDD) is a basic Chinese herbal pair which is commonly used to treat CKD with good efficacy.

Objectives

The current study aimed to investigate the effect of perindopril erbumine (PE), an angiotensin-converting enzyme inhibitor, combined with HDD on adenine-induced CKD rat model and explore the possible mechanism from Sirtuin3/mitochondrial dynamics pathway.

Method

CKD rat model was established by feeding of 0.75% w/w adenine containing diet for 3 weeks. At the same time, the treatment groups were given PE (0.42 mg/kg/d) or HDD (4.7 g/kg/d) or PE combined with HDD by gavage for 4 weeks. Renal function was evaluated by the levels of serum creatinine (Scr) and blood urea nitrogen (BUN). The renal pathological injury was observed by periodic acid-Schiff (PAS) and Masson's trichrome staining. Proteins expression was determined by Western blot analysis. Mitochondrial morphology was observed by transmission electron microscopy.

Results

PE in combination with HDD significantly improved renal function, reduced tubular injury and interstitial fibrosis in adenine-induced CKD rats. Moreover, PE + HDD treatment mainly activated the Sirtuin3 expression level. In addition, PE + HDD exhibited bidirectional regulation on mitochondrial dynamics by suppressing mitochondrial fission protein dynaminrelated protein 1 expression and elevating mitochondrial fusion protein optic atrophy 1 expression, resulted in restraint of mitochondrial fragmentation.

Conclusion

The combination of PE and HDD attenuated adenine-induced CKD in rats, which was possibly associated with Sirtuin3/mitochondrial dynamics pathway.

Urinary Epidermal Growth Factor: A Promising "Next Generation" Biomarker in Kidney Disease

BACKGROUND

The epidermal growth factor (EGF) is a globular protein that is generated in the kidney, especially in the loop of Henle and the distal convoluted tubule. While EGF is nonexistent or hardly detectable in plasma, it is present in normal people's urine. Until now, risk stratification and chronic kidney disease (CKD) diagnosis have relied on estimated glomerular filtration rate (eGFR) and urine albumin/creatinine ratio (uACR), both of which reflect glomerular function or impairment. Tubular dysfunction, on the other hand, may also be associated with renal failure.

SUMMARY

Because decreased urine EGF (uEGF) indicates tubular atrophy and interstitial fibrosis, this biomarker, together with eGFR and uACR, may be employed in the general population for risk assessment and diagnosis of CKD. uEGF levels have been shown to correlate with intrarenal EGF mRNA expression and have been found to decrease in a variety of glomerular and non-glomerular kidney disorders.

KEY MESSAGE

uEGF, uEGF/creatinine, or uEGF/monocyte chemotactic peptide-1 are possible "new generation" biomarkers linked to a variety of kidney diseases that deserve further investigation as a single biomarker or as part of a multi-biomarker panel.

Rhein Improves Renal Fibrosis by Restoring Cpt1a-Mediated Fatty Acid Oxidation through SirT1/STAT3/twist1 Pathway

The latest progress in the field of renal fibrosis mainly focuses on the new concept of “partial epithelial-mesenchymal transition (pEMT)” to explain the contribution of renal tubular epithelial (RTE) cells to renal fibrosis and the crucial role of fatty acid oxidation (FAO) dysfunction in RTE cells for the development of renal fibrosis. FAO depression is considered to be secondary or occur simultaneously with pEMT. We explored the relationship between pEMT and FAO and the effect of rhein on them. Intragastric administration of rhein significantly improved the levels of BUN, Scr, α-SMA, collagen 1A and histopathological changes in UUO-rats. Transcriptomic and metabolomic analyses revealed that abnormal signaling pathways were involved in EMT and FAO disorders. RTE cell experiments showed that TGF-β could inhibit the activity of Cpt1a, resulting in ATP depletion and lipid deposition. Cpt1a inhibitor induced EMT, while Cpt1 substrate or rhein inhibited EMT, indicating that Cpt1a-mediated FAO dysfunction is essential for RTE cells EMT. Further studies showed that Cpt1a activity were regulated by SirT1/STAT3/Twist1 pathway. Rhein inhibits RTE cell EMT by promoting Cpt1a-mediated FAO through the SirT1/STAT3/Twist1 pathway. Surprisingly and importantly, our experiments showed that FAO depression occurs before EMT, and EMT is one of the results of FAO depression.

The Signaling Pathway of TNF Receptors: Linking Animal Models of Renal Disease to Human CKD

Chronic kidney disease (CKD) has been recognized as a global public health problem. Despite the current advances in medicine, CKD-associated morbidity and mortality remain unacceptably high. Several studies have highlighted the contribution of inflammation and inflammatory mediators to the development and/or progression of CKD, such as tumor necrosis factor (TNF)-related biomarkers. The inflammation pathway driven by TNF-α, through TNF receptors 1 (TNFR1) and 2 (TNFR2), involves important mediators in the pathogenesis of CKD. Circulating levels of TNFRs were associated with changes in other biomarkers of kidney function and injury, and were described as predictors of disease progression, cardiovascular morbidity, and mortality in several cohorts of patients. Experimental studies describe the possible downstream signaling pathways induced upon TNFR activation and the resulting biological responses. This review will focus on the available data on TNFR1 and TNFR2, and illustrates their contributions to the pathophysiology of kidney diseases, their cellular and molecular roles, as well as their potential as CKD biomarkers. The emerging evidence shows that TNF receptors could act as biomarkers of renal damage and as mediators of the disease. Furthermore, it has been suggested that these biomarkers could significantly improve the discrimination of clinical CKD prognostic models.

Urinary Galectin-3 as a Novel Biomarker for the Prediction of Renal Fibrosis and Kidney Disease Progression

Plasma galectin-3 (Gal-3) is associated with organ fibrosis, but whether urinary Gal-3 is a potential biomarker of kidney disease progression has never been explored. Between 2018 and 2021, we prospectively enrolled 280 patients who underwent renal biopsy and were divided into three groups based on their urinary Gal-3 levels (<354.6, 354.6−510.7, and ≥510.8 pg/mL) to assess kidney disease progression (defined as ≥40% decline in the estimated glomerular filtration rate or end-stage renal disease) and renal histology findings. Patients in the highest urinary Gal-3 tertile had the lowest eGFRs and highest proteinuria levels. In multivariate Cox regression models, patients in the highest tertile had the highest risk of kidney disease progression (adjusted hazard ratio, 4.60; 95% confidence interval, 2.85−7.71) compared to those in the lowest tertile. Higher urinary Gal-3 levels were associated with more severe renal fibrosis. Intrarenal mRNA expression of LGALS3 (Gal-3-encoded gene) was most correlated with the renal stress biomarkers (IGFBP7 and TIMB2), renal function biomarkers (PTGDS) and fibrosis-associated genes (TGFB1). The urinary Gal-3 level may be useful for the identification of patients at high risk of kidney disease progression and renal fibrosis, and for the early initiation of treatments for these patients.

Adverse Effects of fine particulate matter on human kidney functioning: a systematic review

BACKGROUND

Ambient fine particulate matter (PM < 2.5 μm, PM2.5) is gaining increasing attention as an environmental risk factor for health. The kidneys are considered a particularly vulnerable target to the toxic effects that PM2.5 exerts. Alteration of kidney function may lead to a disrupted homeostasis, affecting disparate tissues in the body. This review intends to summarize all relevant knowledge published between January 2000 and December 2021 on the effects of ambient PM2.5 and the adverse effects on kidney function in adults (≥ 18 years).

RESULTS AND DISCUSSION

Studies published in peer-reviewed journals, written in English, regarding the effects of PM2.5 on kidney function and the development and/or exacerbation of kidney disease(s) were included. Of the 587 nonduplicate studies evaluated, 40 were included, comprising of studies on healthy or diagnosed with pre-existing disease (sub)populations. Most of the studies were cohort studies (n = 27), followed by 10 cross-sectional, 1 ecological and 2 time-series studies. One longitudinal study was considered intermediate risk of bias, the other included studies were considered low risk of bias. A large portion of the studies (n = 36) showed that PM2.5 exposure worsened kidney outcome(s) investigated; however, some studies show contradictory results. Measurement of the estimated glomerular filtration rate, for instance, was found to be positively associated (n = 8) as well as negatively associated (n = 4) with PM2.5.

LIMITATIONS AND CONCLUSION

The main limitations of the included studies include residual confounding (e.g., smoking) and lack of individual exposure levels. The majority of included studies focused on specific subpopulations, which may limit generalizability. Evidence of the detrimental effects that ambient PM2.5 may exert on kidney function is emerging. However, further investigations are required to determine how and to what extent air pollution, specifically PM2.5, exerts adverse effects on the kidney and alters its function.

REGISTRATION

The systematic review protocol was submitted and published by the International Prospective Register of Systematic Reviews (PROSPERO; CRD42020175615 ).

The Human Microbiome in Chronic Kidney Disease: A Double-Edged Sword

Chronic kidney disease (CKD) is an increasing global health burden. Current treatments for CKD include therapeutics to target factors that contribute to CKD progression, including renin–angiotensin–aldosterone system inhibitors, and drugs to control blood pressure and proteinuria control. Recently, associations between chronic disease processes and the human microbiota and its metabolites have been demonstrated. Dysbiosis—a change in the microbial diversity—has been observed in patients with CKD. The relationship between CKD and dysbiosis is bidirectional; gut-derived metabolites and toxins affect the progression of CKD, and the uremic milieu affects the microbiota. The accumulation of microbial metabolites and toxins is linked to the loss of kidney functions and increased mortality risk, yet renoprotective metabolites such as short-chain fatty acids and bile acids help restore kidney functions and increase the survival rate in CKD patients. Specific dietary interventions to alter the gut microbiome could improve clinical outcomes in patients with CKD. Low-protein and high-fiber diets increase the abundance of bacteria that produce short-chain fatty acids and anti-inflammatory bacteria. Fluctuations in the urinary microbiome are linked to increased susceptibility to infection and antibiotic resistance. In this review, we describe the potential role of the gut, urinary and blood microbiome in CKD pathophysiology and assess the feasibility of modulating the gut microbiota as a therapeutic tool for treating CKD.

The serum free triiodothyronine to free thyroxine ratio as a potential prognostic biomarker of chronic kidney disease in patients with glomerular crescents: A retrospective study

BACKGROUND

Crescent formation indicates severe glomerular pathology, and hypothyroidism usually predicts poor prognosis for severe diseases. However, the relationship between thyroid function and the progression of chronic kidney disease (CKD) is unclear. This study analysed the prognostic predictive value of the serum free triiodothyronine (FT3) to free thyroxine (FT4) ratio and its correlation with renal function in patients with CKD with crescent formation.

METHODS

This single-centre study included 162 CKD patients with glomerular crescents confirmed by renal pathology between March 2012 and December 2014. According to the first tertile (0.284) of FT3/FT4 ratio, the patients were divided into high and low FT3/FT4 ratio groups. Kaplan-Meier and Cox regression analyses were performed to evaluate the prognostic value of the FT3/FT4 ratio.

RESULTS

The age, haemoglobin, eGFR, urinary albumin-to-creatinine ratio, cardiac troponin T, N-terminal brain natriuretic peptide precursor, FT3, FT4, percentage of total crescents in non-globally sclerotic glomeruli, prevalences of hypertension, moderate to severe renal tubulopathy and crescentic nephritis, and proportion of patients receiving glucocorticoids and immunosuppressants were significantly different between high and low FT3/FT4 ratio groups (P < 0.05). Multivariate Cox regression analysis showed that when compared with patients with a high FT3/FT4 ratio (>0.284), those with intermediate and low FT3/FT4 ratios (≤0.284) had an increased risk of the long-term composite endpoint (P < 0.05 for various adjustment models).

CONCLUSIONS

A low FT3/FT4 ratio is associated with increased mortality and worse outcome risk in CKD patients with crescent pathology.

Development of a unilateral ureteral obstruction model in cynomolgus monkeys

Background

Chronic kidney disease (CKD) has a high global prevalence and large unmet need. Central to developing new CKD therapies are in vivo models in CKD. However, next-generation antibody, protein, and gene therapies are highly specific, meaning some do not cross-react with rodent targets. This complicates preclinical development, as established in vivo rodent models cannot be utilized unless tool therapeutics are also developed. Tool compounds can be difficult to develop and, if available, typically have different epitopes, sequences, and/or altered affinity, making it unclear how efficacious the lead therapeutic may be, or what dosing regimen to investigate. To address this, we aimed to develop a nonhuman primate model of CKD.

Methods

In vivo rodent unilateral ureteral obstruction (UUO) models kidney fibrosis and is commonly used due to its rapidity, consistency, and ease. We describe translation of this model to the cynomolgus monkey, specifically optimizing the model duration to allow adequate time for assessment of novel therapeutics prior to the fibrotic plateau.

Results

We demonstrated that disease developed more slowly in cynomolgus monkeys than in rodents post-UUO, with advanced fibrosis developing by 6 weeks. The tubulointerstitial fibrosis in cynomolgus monkeys was more consistent with human obstructive disease than in rodents, having a more aggressive tubular basement expansion and a higher fibroblast infiltration. The fibrosis was also associated with increased transglutaminase activity, consistent with that seen in patients with CKD.

Conclusion

This cynomolgus monkey UUO model can be used to test potential human-specific therapeutics in kidney fibrosis.

Time-Varying Proteinuria and the Risk of Cardiovascular Disease and Graft Failure in Kidney Transplant Recipients

Introduction: Proteinuria is recognized as an independent risk factor for cardiovascular disease in kidney transplant recipients, but previous studies have not considered the impact of changes in urine protein over time. Research Question and Design: We used time-dependent, multivariable Cox proportional hazards models in this observational cohort study of adult kidney transplant recipients to evaluate whether proteinuria measured by dipstick on random spot urine samples starting from 1-month post-transplant was associated with the risk of major adverse cardiac events and graft loss. Results: A total of 144 major adverse cardiac events, defined as acute myocardial infarction, cerebrovascular accident, revascularization, or all-cause mortality, were observed in 1106 patients over 5728.7 person-years. Any level of proteinuria greater or equal to trace resulted in a two-fold increase in the risk of major adverse cardiac events (hazard ratio 2.00 [95% confidence interval 1.41, 2.84]). This relationship was not found to be dose-dependent (hazard ratios of 2.98, 1.76, 1.63, and 1.54 for trace, 1+, 2+, and 3+ urine protein, respectively). There was an increased risk of graft failure with greater urine protein concentration (hazard ratios 2.22, 2.85, 6.41, and 19.71 for trace, 1+, 2+, and 3+, respectively). Conclusion: Urine protein is associated with major adverse cardiac events and graft loss in kidney transplant recipients. The role of interventions to reduce proteinuria on decreasing the risk of adverse cardiovascular and graft outcomes in kidney transplant recipients requires further study.

RTEC-intrinsic IL-17-driven inflammatory circuit amplifies antibody-induced glomerulonephritis and is constrained by Regnase-1

Antibody-mediated glomerulonephritis (AGN) is a clinical manifestation of many autoimmune kidney diseases for which few effective treatments exist. Chronic inflammatory circuits in renal glomerular and tubular cells lead to tissue damage in AGN. These cells are targeted by the cytokine IL-17, which has recently been shown to be a central driver of the pathogenesis of AGN. However, surprisingly little is known about the regulation of pathogenic IL-17 signaling in the kidney. Here, using a well-characterized mouse model of AGN, we show that IL-17 signaling in renal tubular epithelial cells (RTECs) is necessary for AGN development. We also show that Regnase-1, an RNA binding protein with endoribonuclease activity, is a negative regulator of IL-17 signaling in RTECs. Accordingly, mice with a selective Regnase-1 deficiency in RTECs exhibited exacerbated kidney dysfunction in AGN. Mechanistically, Regnase-1 inhibits IL-17-driven expression of the transcription factor IκBξ and, consequently, its downstream gene targets, including Il6 and Lcn2. Moreover, deletion of Regnase-1 in human RTECs reduced inflammatory gene expression in a IκBξ-dependent manner. Overall, these data identify an IL-17-driven inflammatory circuit in RTECs during AGN that is constrained by Regnase-1.

Acetic acid treatment causes renal inflammation and chronic kidney disease in mice

We established a novel mouse model of chronic kidney disease (CKD) using acetic acid and compared it with the 5/6-nephrectomized mouse model. In our novel model, significant increases were observed in blood biochemical values and urinary parameters. Moreover, a decrease in creatinine clearance (Ccr) was observed. This model also demonstrated a higher survival rate than the 5/6-nephrectomized model. Observed histological changes in our model included cell infiltration in the renal interstitium, tubular dilation, regenerated tubules, and glomerulosclerosis. Inflammation of the renal interstitium was particularly remarkable. TNF-α, IL-1β, and ICAM-1 mRNA expression were up-regulated prior to elevation of mean blood pressure and prior to changes in blood biochemical values and urinary parameters. Up-regulation of TGF-β mRNA and down-regulation of nephrin mRNA were also observed at 12 weeks after acetic acid treatment. However, no correlation between the progression of CKD and the decrease in renal blood flow was observed. Finally, repeated losartan administration attenuated the effects of acetic acid-induced renal injury. Our findings suggest that chronic kidney conditions associated with this model may be triggered by interstitial inflammation. Moreover, we suggest that this model is useful for understanding the pathophysiological mechanisms of CKD, and for evaluating the effects of therapeutic agents.

Shen Shuai II Recipe Attenuates Renal Interstitial Fibrosis by Improving Hypoxia via the IL-1β/c-Myc Pathway

Background

Renal interstitial fibrosis is a pathological manifestation of progression of chronic kidney disease induced by various factors. Shen Shuai II Recipe (SSR) has been used in clinical practice for more than 20 years, and clinical studies have confirmed that SSR significantly improves the renal function of patients with chronic kidney disease. However, the specific mechanisms underlying its efficacy require further research. This study aims to explore the influencing factors of renal interstitial fibrosis in the context of hypoxia via the IL-1β/c-Myc pathway and the potential molecular mechanisms of SSR intervention in vivo and in vitro.

Methods

A rat model of chronic renal failure was developed by performing 5/6 (ablation/infarction, A/I) surgery on randomly selected, male Sprague Dawley rats. Thirty-six successfully modeled rats were randomly divided into three groups: 5/6 (A/I), 5/6 (A/I) + SSR, and 5/6 (A/I) + losartan. Another 12 rats were used as the sham group. After 8 weeks of the corresponding intervention, renal function, liver function, and protein expression of renal-fibrosis-related factors, HIF-1α, IL-1β, and c-Myc, were detected. In vitro analysis was performed using hypoxia-induced rat renal tubular epithelial cells (NRK-52E) and IL-1β-stimulated rat renal interstitial fibroblasts (NRK-49F). IL-1β concentration in the culture medium and IL-1β protein expression in hypoxic NRK-52E treated with different concentrations of SSR were investigated. Furthermore, we also studied the changes in protein expression of c-Myc and fibrosis-related factors after c-Myc gene silencing in IL-1β-stimulated NRK-49F treated with SSR.

Results

Shen Shuai II Recipe significantly reduced RIF and downregulated the expression of HIF-1α, c-Myc, and IL-1β proteins in 5/6 (A/I) rats with chronic renal failure. It also inhibited IL-1β secretion from NRK-52E induced by hypoxia, which in turn inhibited fibroblast activation mediated by the IL-1β/c-Myc pathway, and finally reduced the overproduction of the extracellular matrix.

Conclusion

The renoprotective effects of SSR in rats with chronic renal failure may be related to its inhibition of hypoxia via the IL-1β/c-Myc pathway. Thus, SSR is a potentially effective drug for delaying the progression of renal interstitial fibrosis.

A Systematic Review of Renal Pathology in Chronic Kidney Disease of Uncertain Etiology

INTRODUCTION

Despite much research on chronic kidney disease of uncertain etiology (CKDu) in Sri Lanka and the Mesoamerican nephropathy, the etiology and pathogenesis of this disease remains elusive. The pathology has broadly been described as chronic tubulointerstitial nephritis and no specific signature lesions have been identified.

METHODS

A scoping review was conducted through MEDLINE and Google Scholar databases for peer-reviewed publications on biopsy studies related to CKDu - Sri Lanka and Mesoamerican nephropathy to develop a comparative and critical analysis of the renal pathology found in these patients.

RESULTS

Thirteen studies met the selection criteria. Interstitial fibrosis was the predominant lesion in all the studies. Tubulointerstitial and glomerular abnormalities showed a more variable distribution. No characteristic histopathological feature was reported other than a proximal tubular lysosomal inclusion body which was claimed to indicate a toxic etiology. Three main pathogenetic mechanisms were postulated: repeated acute insults leading to scarring, low-grade chronic insults leading to non-inflammatory fibrosis, and tubulointerstitial damage in combination with glomerular injury. The main limitations in the interpretation and comparative analysis of these studies were the heterogeneity in case selection and biopsy reporting.

CONCLUSIONS

Although no characteristic histopathological feature could be found in CKDu-Sri Lanka or Mesoamerican nephropathy, there are noticeable differences between these two groups in the frequency and severity of the glomerular and tubulointerstitial changes which warrant more explorative studies preferably on kidneys in early stages of the disease. Future strategies should ensure that more uniform selection criteria and reporting methods are used.

Aetiology, course and treatment of acute tubulointerstitial nephritis in paediatric patients: a cross-sectional web-based survey

BACKGROUND

Acute tubulointerstitial nephritis (TIN) is a significant cause of acute renal failure in paediatric and adult patients. There are no large paediatric series focusing on the aetiology, treatment and courses of acute TIN.

PATIENTS, DESIGN AND SETTING

We collected retrospective clinical data from paediatric patients with acute biopsy-proven TIN by means of an online survey. Members of four professional societies were invited to participate.

RESULTS

Thirty-nine physicians from 18 countries responded. 171 patients with acute TIN were included (54% female, median age 12 years). The most frequent causes were tubulointerstitial nephritis and uveitis syndrome in 31% and drug-induced TIN in 30% (the majority of these caused by non-steroidal anti-inflammatory drugs). In 28% of patients, no initiating noxae were identified (idiopathic TIN). Median estimated glomerular filtration rate (eGFR) rose significantly from 31 at time of renal biopsy to 86 mL/min/1.73 m² 3-6 months later (p<0.001). After 3-6 months, eGFR normalised in 41% of patients (eGFR ≥90 mL/min/1.73 m²), with only 3% having severe or end-stage impairment of renal function (<30 mL/min/1.73 m²). 80% of patients received corticosteroid therapy. Median eGFR after 3-6 months did not differ between steroid-treated and steroid-untreated patients. Other immunosuppressants were used in 18% (n=31) of patients, 21 of whom received mycophenolate mofetil.

CONCLUSIONS

Despite different aetiologies, acute paediatric TIN had a favourable outcome overall with 88% of patients showing no or mild impairment of eGFR after 3-6 months. Prospective randomised controlled trials are needed to evaluate the efficacy of glucocorticoid treatment in paediatric patients with acute TIN.

Renal and non-renal response of ABC and SLC transporters in chronic kidney disease

INTRODUCTION

The solute carrier (SLC) and the ATP-binding cassette (ABC) transporter superfamilies play essential roles in the disposition of small molecules (endogenous metabolites, uremic toxins, drugs) in the blood, kidney, liver, intestine, and other organs. In chronic kidney disease (CKD), the loss of renal function is associated with altered function of remote organs. As renal function declines, many molecules accumulate in the plasma. Many studies now support the view that ABC and SLC transporters as well as drug metabolizing enzymes (DMEs) in renal and non-renal tissues are directly or indirectly affected by the presence of various types of uremic toxins, including those derived from the gut microbiome; this can lead to aberrant inter-organ communication.

AREAS COVERED

Here, the expression, localization and/or function of various SLC and ABC transporters as well as DMEs in the kidney and other organs are discussed in the context of CKD and systemic pathophysiology.

EXPERT OPINION

According to the Remote Sensing and Signaling Theory (RSST), a transporter and DME-centric network that optimizes local and systemic metabolism maintains homeostasis in the steady state and resets homeostasis following perturbations due to renal dysfunction. The implications of this view for pharmacotherapy of CKD are also discussed.

Chronic treatment with the (iso-)glutaminyl cyclase inhibitor PQ529 is a novel and effective approach for glomerulonephritis in chronic kidney disease

Glomeruli and renal tubule injury in chronic kidney disease (CKD) is reported to involve induction of macrophage activation through the CCL2/CCR2 axis. The effects of inhibitors of the CCL2/CCR2 axis, such as anti-CCL2 antibody and CCR2 antagonist, on kidney function in animal models or humans with kidney dysfunction have been demonstrated. The N-terminal glutamine on immature CCL2 is replaced with pyroglutamate (pE) by glutaminyl cyclase (QC) and isoQC. pE-CCL2 is stable and resistant to peptidases. We hypothesized that inhibiting QC/isoQC activity would lead to the degradation of CCL2, thereby ameliorating CKD and reducing kidney inflammation. To test this hypothesis, we investigated the renoprotective properties of the QC/isoQC inhibitor PQ529 in anti-glomerular basement membrane (GBM) antibody-induced glomerulonephritis Wistar Kyoto (WKY) rats. Three-week repeated administration of PQ529 (30 and 100 mg/kg, twice daily) significantly reduced the serum and urine CCL2 and urinary protein excretion in a dose-dependent manner. Correlations between the urinary protein level and serum or urinary CCL2 levels were confirmed in tested animals. Repeated administration of PQ529 significantly reduced the expression of CD68, a macrophage marker, in the kidney cortex and mononuclear infiltration into the tubulointerstitium. In addition, decreased levels of urinary KIM-1, β2 microglobulin, and clusterin were detected, suggesting the inhibition of inflammation in both the proximal and distal tubules. These results suggest that PQ529 suppresses the progression of inflammation-induced renal dysfunction by inhibiting the CCL2/CCR2 axis. Inhibition of QC/isoQC may thus be a viable alternative therapeutic approach for treating glomerulonephritis and CKD patients.

Relation between Vitamin D Level and Cyclin-Dependent Kinase-1 Gene Expression in Egyptian Patients with Lupus Nephritis and their Impact on Disease Activity

Introduction:

Lupus nephritis (LN) is a common complication of systemic lupus erythematosus. Vitamin D and cycline-dependent kinase-1 (CDK1) have been implicated in its pathogenesis. The aim of this study was to determine the relation between vitamin D level and CDK-1 in lupus nephritis patients and their impact on disease activity.

Patients and Methods:

The current study was conducted on 50 LN patients and 20 control subjects from Egyptian population using ELISA to assess vitamin D level in serum and TaqMan assay for CDK1 gene expression.

Results:

Serum vitamin D level was significantly lower in LN patients and CDK-1 gene was down expressed in the majority of LN patients. A significant inverse correlation was found between vitamin D level and 24 h protein in urine, ANA, anti-dsDNA, CRP, with a significant positive correlation with renal biopsy indices, eGFR. There was a non-significant inverse correlation between vitamin D and CDK-1 (before RO-3306 addition) and a positive correlation after RO-3306. A significant positive correlation was found between CDK-1 gene expressions with urinary albumin/creatinine ratio. However, a significant positive correlation was found between CDK-1 (after RO-3306 addition) and proteinuria. While a significant positive correlation was found between CDK-1 expression (after RO-3306 addition) and ANA, a significant positive correlation was found between CDK-1 expression (before RO-3306 addition) and anti-dsDNA but CDK-1 is not associated with renal biopsy indices nor with activity indices of SLE. There was a positive correlation between CDK-1 gene expression and CRP before and after RO-3306 addition.

Conclusions:

Vitamin D deficiency acts as a risk factor for developing LN. CDK-1 may have an association with the diagnosis of LN but its association with the progression of staging of LN is still confusing

Netrin-1 and clusterin: Innovative potential diagnostic biomarkers for early renal damage in β-thalassemia major children

BACKGROUND

Children with β-thalassemia major (β-TM) suffer from tubular dysfunction even before the onset of any renal impairment symptoms and/or clinical signs. Therefore, identifying innovative biomarkers allowing early renal damage detection has focused attention.

AIM

This study aims to preliminary assess Netrin-1(NTN-1) and clusterin (CLU) in β-TM children and explore their possible roles as surrogate noninvasive biomarkers of renal tubular dysfunction.

SUBJECTS AND METHODS

In this study, 40 β-TM children and 30 healthy children were enrolled. Routine serum and urinary biochemical variables were determined. Urinary NTN-1 and CLU levels were measured using ELISA and their mRNA expression in PBMCs were assayed using real-time PCR. Serum TNF-α, MDA levels and GST activity were measured.

RESULTS

Urinary NTN-1 and CLU concentrations and mRNA relative expression levels in PBMCs were significantly increased in β-TM children relative to controls. Oxidative stress and inflammatory markers revealed significant elevation in β-TM children compared to controls. The change in these parameters correlated significantly with other renal parameters. ROC curves analysis showed that urinary NTN-1 and CLU levels are of promising diagnostic performance.

CONCLUSION

Our results suggest that NTN-1 and CLU are qualified as new noninvasive biomarker panels for early detection of renal injury in β-TM children. Moreover, urinary NTN-1 is recommended as a precise one during the clinical practices.

Increased Levels of Renal Lysophosphatidic Acid in Rodent Models with Renal Disease

Lysophosphatidic acid (LPA) is a bioactive lipid mediator that has been implicated in the pathophysiology of kidney disease. However, few studies have attempted to measure changes in the levels of various LPA species in the kidney after the development of renal disease. The present study measured the renal LPA levels during the development of kidney disease in rat models of hypertension, diabetes, and obstructive nephropathy using liquid chromatography/mass spectrometry/mass spectrometry. LPA levels (sum of 16:0, 18:0, 18:1, 18:2, and 20:4 LPA) were higher in the renal cortex of hypertensive Dahl salt-sensitive (Dahl S) rats fed a high-salt diet than those in normotensive rats fed a low-salt diet (296.6 ± 22.9 vs. 196.3 ± 8.5 nmol/g protein). LPA levels were elevated in the outer medulla of the kidney of streptozotocin-induced type 1 diabetic Dahl S rats compared with control rats (624.6 ± 129.5 vs. 318.8 ± 17.1 nmol/g protein). LPA levels were also higher in the renal cortex of 18-month-old, type 2 diabetic nephropathy (T2DN) rats with more severe renal injury than in 6-month-old T2DN rats (184.9 ± 20.9 vs. 116.9 ± 6.0 nmol/g protein). LPA levels also paralleled the progression of renal fibrosis in the renal cortex of Sprague-Dawley rats after unilateral ureteral obstruction (UUO). Administration of an LPA receptor antagonist, Ki16425, reduced the degree of renal fibrosis in UUO rats. These results suggest that the production of renal LPA increases during the development of renal injury and contributes to renal fibrosis. SIGNIFICANCE STATEMENT: The present study reveals that the lysophosphatidic acid (LPA) levels increase in the kidney in rat models of hypertension, diabetes, and obstructive nephropathy, and administration of an LPA receptor antagonist attenuates renal fibrosis. Therapeutic approaches that target the formation or actions of renal LPA might be renoprotective and have therapeutic potential.

MR Elastography of the Abdomen: Basic Concepts

Magnetic resonance elastography (MRE) is an emerging imaging modality that maps the elastic properties of tissue such as the shear modulus. It allows for noninvasive assessment of stiffness, which is a surrogate for fibrosis. MRE has been shown to accurately distinguish absent or low stage fibrosis from high stage fibrosis, primarily in the liver. Like other elasticity imaging modalities, it follows the general steps of elastography: (1) apply a known cyclic mechanical vibration to the tissue; (2) measure the internal tissue displacements caused by the mechanical wave using magnetic resonance phase encoding method; and (3) infer the mechanical properties from the measured mechanical response (displacement), by generating a simplified displacement map. The generated map is called an elastogram.While the key interest of MRE has traditionally been in its application to liver, where in humans it is FDA approved and commercially available for clinical use to noninvasively assess degree of fibrosis, this is an area of active research and there are novel upcoming applications in brain, kidney, pancreas, spleen, heart, lungs, and so on. A detailed review of all the efforts is beyond the scope of this chapter, but a few specific examples are provided. Recent application of MRE for noninvasive evaluation of renal fibrosis has great potential for noninvasive assessment in patients with chronic kidney diseases. Development and applications of MRE in preclinical models is necessary primarily to validate the measurement against "gold-standard" invasive methods, to better understand physiology and pathophysiology, and to evaluate novel interventions. Application of MRE acquisitions in preclinical settings involves challenges in terms of available hardware, logistics, and data acquisition. This chapter will introduce the concepts of MRE and provide some illustrative applications.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by another separate chapter describing the experimental protocol and data analysis.