Podocyte-derived soluble RARRES1 drives kidney disease progression through direct podocyte and proximal tubular injury.

Retinoic acid receptor responder protein-1 (RARRES1) is a podocyte-enriched transmembrane protein whose increased expression correlates with human glomerular disease progression. RARRES1 promotes podocytopenia and glomerulosclerosis via p53-mediated podocyte apoptosis. Importantly, the cytopathic actions of RARRES1 are entirely dependent on its proteolytic cleavage into a soluble protein (sRARRES1) and subsequent podocyte uptake by endocytosis, as a cleavage mutant RARRES1 exerted no effects in vitro or in vivo. As RARRES1 expression is upregulated in human glomerular diseases, here we investigated the functional consequence of podocyte-specific overexpression of RARRES1 in mice in the experimental focal segmental glomerulosclerosis and diabetic kidney disease. We also examined the effects of long-term RARRES1 overexpression on slowly developing aging-induced kidney injury. As anticipated, the induction of podocyte overexpression of RARRES1 (Pod-RARRES1WT) significantly worsened glomerular injuries and worsened kidney function in all three models, while overexpression of RARRES1 cleavage mutant (Pod-RARRES1MT) did not. Remarkably, direct uptake of sRARRES1 was also seen in proximal tubules of injured Pod-RARRES1WT mice and associated with exacerbated tubular injuries, vacuolation, and lipid accumulation. Single-cell RNA sequence analysis of mouse kidneys demonstrated RARRES1 led to a marked deregulation of lipid metabolism in proximal tubule subsets. We further identified matrix metalloproteinase 23 (MMP23) as a highly podocyte-specific metalloproteinase and responsible for RARRES1 cleavage in disease settings, as adeno-associated virus 9-mediated knockdown of MMP23 abrogated sRARRES1 uptake in tubular cells in vivo. Thus, our study delineates a previously unrecognized mechanism by which a podocyte-derived protein directly facilitates podocyte and tubular injury in glomerular diseases and suggests that podocyte-specific functions of RARRES1 and MMP23 may be targeted to ameliorate glomerular disease progression in vivo.

Macrophage-derived exosomes promote telomere fragility and senescence in tubular epithelial cells by delivering miR-155.

BACKGROUND: Chronic kidney disease (CKD) is highly prevalent worldwide, and its global burden is substantial and growing. CKD displays a number of features of accelerated senescence. Tubular cell senescence is a common biological process that contributes to CKD progression. Tubulointerstitial inflammation is a driver of tubular cell senescence and a common characteristic of CKD. However, the mechanism by which the interstitial inflammation drives tubular cell senescence remains unclear. This paper aims to explore the role of exosomal miRNAs derived from macrophages in the development of tubular cell senescence. METHODS: Among the identified inflammation-related miRNAs, miR-155 is considered to be one of the most important miRNAs involved in the inflammatory response. Macrophages, the primary immune cells that mediate inflammatory processes, contain a high abundance of miR-155 in their released exosomes. We assessed the potential role of miR-155 in tubular cell senescence and renal fibrosis. We subjected miR-155-/- mice and wild-type controls, as well as tubular epithelial cells (TECs), to angiotensin II (AngII)-induced kidney injury. We assessed kidney function and injury using standard techniques. TECs were evaluated for cell senescence and telomere dysfunction in vivo and in vitro. Telomeres were measured by the fluorescence in situ hybridization. RESULTS: Compared with normal controls, miR-155 was up-regulated in proximal renal tubule cells in CKD patients and mouse models of CKD. Moreover, the expression of miR-155 was positively correlated with the extent of renal fibrosis, eGFR decline and p16INK4A expression. The overexpression of miR-155 exacerbated tubular senescence, evidenced by increased detection of p16INK4A/p21expression and senescence-associated ß-galactosidase activity. Notably, miR-155 knockout attenuates renal fibrosis and tubule cell senescence in vivo. Interestingly, once released, macrophages-derived exosomal miR-155 was internalized by TECs, leading to telomere shortening and dysfunction through targeting TRF1. A dual-luciferase reporter assay confirmed that TRF1 was the direct target of miR-155. Thus, our study clearly demonstrates that exosomal miR-155 may mediate communication between macrophages and TECs, subsequently inducing telomere dysfunction and senescence in TECs. CONCLUSIONS: Our work suggests a new mechanism by which macrophage exosomes are involved in the development of tubule senescence and renal fibrosis, in part by delivering miR-155 to target TRF1 to promote telomere dysfunction. Our study may provide novel strategies for the treatment of AngII-induced kidney injury.

KIM-1 augments hypoxia-induced tubulointerstitial inflammation through uptake of small extracellular vesicles by tubular epithelial cells.

Tubular epithelial cells (TECs) exposed to hypoxia incite tubulointerstitial inflammation (TII), while the exact mechanism is unclear. In this study, we identified that hypoxia evoked tubule injury as evidenced by tubular hypoxia-inducible factor-1α and kidney injury molecule-1 (KIM-1) expression and that renal small extracellular vesicle (sEV) production was increased with the development of TII after ischemia-reperfusion injury (IRI). Intriguingly, KIM-1-positive tubules were surrounded by macrophages and co-localized with sEVs. In vitro, KIM-1 expression and sEV release were increased in hypoxic TECs and the hypoxia-induced inflammatory response was ameliorated when KIM-1 or Rab27a, a master regulator of sEV secretion, was silenced. Furthermore, KIM-1 was identified to mediate hypoxic TEC-derived sEV (Hypo-sEV) uptake by TECs. Phosphatidylserine (PS), a ligand of KIM-1, was present in Hypo-sEVs as detected by nanoflow cytometry. Correspondingly, the inflammatory response induced by exogenous Hypo-sEVs was attenuated when KIM-1 was knocked down. In vivo, exogenous-applied Hypo-sEVs localized to KIM-1-positive tubules and exacerbated TII in IRI mice. Our study demonstrated that KIM-1 expressed by injured tubules mediated sEV uptake via recognizing PS, which participated in the amplification of tubule inflammation induced by hypoxia, leading to the development of TII in ischemic acute kidney injury.

A Chinese Multi-Specialty Delphi Consensus to Optimize RAASi Usage and Hyperkalaemia Management in Patients with Chronic Kidney Disease and Heart Failure.

Objective Variations are present in common clinical practices regarding best practice in managing hyperkalaemia (HK), there is therefore a need to establish a multi-specialty approach to optimal renin-angiotension-aldosterone system inhibitors (RAASi) usage and HK management in patients with chronic kidney disease (CKD) & heart failure (HF).This study aimed to establish a multi-speciality approach to the optimal use of RAASi and the management of HK in patients with CKD and HF. Methods A steering expert group of cardiology and nephrology experts across China were convened to discuss challenges to HK management through a nominal group technique. The group then created a list of 41 statements for a consensus questionnaire, which was distributed for a further survey in extended panel group of cardiologists and nephrologists across China. Consensus was assessed using a modified Delphi technique, with agreement defined as "strong" (≥75% and <90%) and "very strong" (≥90%). The steering group, data collection, and analysis were aided by an independent facilitator. Results A total of 150 responses from 21 provinces across China were recruited in the survey. Respondents were comprised of an even split (n=75, 50%) between cardiologists and nephrologists. All 41 statements achieved the 75% consensus agreement threshold, of which 27 statements attained very strong consensus (≥90% agreement) and 14 attained strong consensus (agreement between 75% and 90%). Conclusion Based on the agreement levels from respondents, the steering group agreed a set of recommendations intended to improve patient outcomes in the use of RAASi therapy and HK management in China.

Quercetin alleviates tubulointerstitial inflammation by inhibiting exosomes-mediated crosstalk between tubular epithelial cells and macrophages.

BACKGROUND: Tubulointerstitial inflammation (TII) is a critical pathological feature of kidney disease leading to renal fibrosis, and its treatment remains a major clinical challenge. We sought to explore the role of quercetin, a potential exosomes inhibitor, in exosomes release and TII. METHODS: The effects of quercetin on exosomes release and TII were examined by two TII mouse models: the unilateral ureteral obstruction (UUO) models and the LPS-induced mouse models. In vitro, exosomes-mediated crosstalk between tubular epithelial cells (TECs) and macrophages was performed to investigate the mechanisms by which quercetin inhibited exosomes and TII. RESULTS: In this study, we found that exosomes-mediated crosstalk between TECs and macrophages contributed to the development of TII. In vitro, exosomes released from LPS-stimulated TECs induced increased expression of inflammatory cytokines and fibrotic markers in Raw264·7 cells and vice versa. Interestingly, heat shock protein 70 (Hsp70) or Hsp90 proteins could control exosomes release from TECs and macrophages both in vivo and in vitro. Importantly, quercetin, a previously recognized heat shock protein inhibitor, could significantly reduce exosomes release in TII models by down-regulating Hsp70 or Hsp90. Quercetin abrogated exosomes-mediated intercellular communication, which attenuated TII and renal fibrosis accordingly. CONCLUSION: Quercetin could serve as a novel strategy for treatment of tubulointerstitial inflammation by inhibiting the exosomes-mediated crosstalk between tubules and macrophages.

Comprehensive analysis of the roles of fatty acid transport related proteins in clear cell renal cell carcinoma.

OBJECTIVE: This study aimed to explore the clinical significance of fatty acid transport-related protein (FATRP) in patients with clear cell renal cell carcinoma(ccRCC). METHODS: RNA-seq data and corresponding clinical data of ccRCC were obtained from TCGA data portal. Seventeen key FATRP genes were comprehensively investigated using bioinformatics approaches to systematically investigate their expression patterns in ccRCC. In addition, the correlation between the expression levels of these genes and clinicopathological features in ccRCC was further explored. RESULTS: Among the 17 key FATRP genes, only FABP5, FABP6, and FABP7 could be regarded as ideal biomarkers for ccRCC, as they were highly expressed in ccRCC tumor tissues, and positively correlates with tumor progression and poor prognosis. FABP6 had the highest copy number variations (CNV) events (63.07 %), and ccRCC patients with FABP6 amplification had a better prognosis than the unaltered group. DNA methylation levels of FABP6 and FABP7 were downregulated in ccRCC tumor tissues compared to those in normal tissues. FABP5 showed the opposite results. Moreover, a novel four FATRP gene (FABP1, FABP5, FABP7, FATP2) and three clinical parameter (age, stage, and grade) prediction model was constructed and that comprised a significant independent prognostic signature. CONCLUSIONS: Only a few FATRP genes are upregulated in ccRCC tumor tissue, and positively correlate with tumor progression and poor prognosis. The accuracy of a single gene of these FATRP genes as predictors of progression and prognosis of ccRCC is limited. The performance of the novel prediction model proposed by this study was much better than that of any single gene.

Tubular-specific CDK12 knockout causes a defect in urine concentration due to premature cleavage of the slc12a1 gene.

Cyclin-dependent kinase 12 (CDK12) plays a critical role in regulating gene transcription. CDK12 inhibition is a potential anticancer therapeutic strategy. However, several clinical trials have shown that CDK inhibitors might cause renal dysfunction and electrolyte disorders. CDK12 is abundant in renal tubular epithelial cells (RTECs), but the exact role of CDK12 in renal physiology remains unclear. Genetic knockout of CDK12 in mouse RTECs causes polydipsia, polyuria, and hydronephrosis. This phenotype is caused by defects in water reabsorption that are the result of reduced Na-K-2Cl cotransporter 2 (NKCC2) levels in the kidney. In addition, CKD12 knockout causes an increase in Slc12a1 (which encodes NKCC2) intronic polyadenylation events, which results in Slc12a1 truncated transcript production and NKCC2 downregulation. These findings provide novel insight into CDK12 being necessary for maintaining renal homeostasis by regulating NKCC2 transcription, which explains the critical water and electrolyte disturbance that occurs during the application of CDK12 inhibitors for cancer treatment. Therefore, there are safety concerns about the clinical use of these new anticancer drugs.

Elevated serum FGF21 is an independent predictor for adverse events in hemodialysis patients from two large centers: a prospective cohort study.

Introduction: We explored the relationship and the predictive value of serum fibroblast growth factor 21 (FGF21) with all-cause mortality, major adverse cardiovascular events (MACEs) and pneumonia in hemodialysis (HD) patients.Methods: A total of 388 Chinese HD patients from two HD centers were finally enrolled in this prospective cohort study (registration number: ChiCTR 1900028249) between January 2018 and December 2018. Serum FGF21 was detected. Patients were followed up with a median period of 47 months to record the MACEs and pneumonia until death or 31 December 2022.Results: The incidence of all-cause mortality, MACEs and pneumonia in HD patients were 20.6%, 29.6%, and 34.8%, respectively. The optimal cutoffs for FGF21 to predict all-cause mortality, MACEs and pneumonia were 437.57 pg/mL, 216.99 pg/mL and 112.79 pg/mL. Multivariate Cox regression analyses showed that FGF21, as a categorical variable, was an independent predictor for all-cause mortality, MACEs and pneumonia (HR, 3.357, 95% CI, 2.128-5.295, p < 0.001; HR, 1.575, 95% CI, 1.046-2.371, p = 0.029; HR, 1.784; 95% CI, 1.124-2.830; p = 0.014, respectively). The survival nomogram, MACEs-free survival nomogram and pneumonia-free survival nomogram based on FGF21 constructed for individualized assessment of HD patients had a high C-index with 0.841, 0.706 and 0.734.Conclusion: Higher serum FGF21 is an independent predictor of all-cause mortality, MACEs and pneumonia in HD patients.

Roxadustat for Anemia in Patients with Kidney Disease Not Receiving Dialysis.

BACKGROUND: Roxadustat (FG-4592) is an oral inhibitor of hypoxia-inducible factor (HIF) prolyl hydroxylase that stimulates erythropoiesis and regulates iron metabolism. In phase 2 studies involving patients with chronic kidney disease, roxadustat increased levels of endogenous erythropoietin to within or near the physiologic range, along with increasing hemoglobin levels and improving iron homeostasis. Additional data are needed regarding the efficacy and safety of roxadustat for the treatment of anemia in patients with chronic kidney disease who are not undergoing dialysis. METHODS: In this phase 3 trial conducted at 29 sites in China, we randomly assigned 154 patients with chronic kidney disease in a 2:1 ratio to receive roxadustat or placebo three times a week for 8 weeks in a double-blind manner. All the patients had a hemoglobin level of 7.0 to 10.0 g per deciliter at baseline. The randomized phase of the trial was followed by an 18-week open-label period in which all the patients received roxadustat; parenteral iron was withheld. The primary end point was the mean change from baseline in the hemoglobin level, averaged over weeks 7 through 9. RESULTS: During the primary-analysis period, the mean (±SD) change from baseline in the hemoglobin level was an increase of 1.9±1.2 g per deciliter in the roxadustat group and a decrease of 0.4±0.8 g per deciliter in the placebo group (P<0.001). The mean reduction from baseline in the hepcidin level (associated with greater iron availability) was 56.14±63.40 ng per milliliter in the roxadustat group and 15.10±48.06 ng per milliliter in the placebo group. The reduction from baseline in the total cholesterol level was 40.6 mg per deciliter in the roxadustat group and 7.7 mg per deciliter in the placebo group. Hyperkalemia and metabolic acidosis occurred more frequently in the roxadustat group than in the placebo group. The efficacy of roxadustat in hemoglobin correction and maintenance was maintained during the 18-week open-label period. CONCLUSIONS: In Chinese patients with chronic kidney disease who were not undergoing dialysis, those in the roxadustat group had a higher mean hemoglobin level than those in the placebo group after 8 weeks. During the 18-week open-label phase of the trial, roxadustat was associated with continued efficacy. (Funded by FibroGen and FibroGen [China] Medical Technology Development; ClinicalTrials.gov number, NCT02652819.).

Roxadustat Treatment for Anemia in Patients Undergoing Long-Term Dialysis.

BACKGROUND: Roxadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor that stimulates erythropoiesis and regulates iron metabolism. Additional data are needed regarding the effectiveness and safety of roxadustat as compared with standard therapy (epoetin alfa) for the treatment of anemia in patients undergoing dialysis. METHODS: In a trial conducted in China, we randomly assigned (in a 2:1 ratio) patients who had been undergoing dialysis and erythropoiesis-stimulating agent therapy with epoetin alfa for at least 6 weeks to receive roxadustat or epoetin alfa three times per week for 26 weeks. Parenteral iron was withheld except as rescue therapy. The primary end point was the mean change in hemoglobin level from baseline to the average level during weeks 23 through 27. Noninferiority of roxadustat would be established if the lower boundary of the two-sided 95% confidence interval for the difference between the values in the roxadustat group and epoetin alfa group was greater than or equal to -1.0 g per deciliter. Patients in each group had doses adjusted to reach a hemoglobin level of 10.0 to 12.0 g per deciliter. Safety was assessed by analysis of adverse events and clinical laboratory values. RESULTS: A total of 305 patients underwent randomization (204 in the roxadustat group and 101 in the epoetin alfa group), and 256 patients (162 and 94, respectively) completed the 26-week treatment period. The mean baseline hemoglobin level was 10.4 g per deciliter. Roxadustat led to a numerically greater mean (±SD) change in hemoglobin level from baseline to weeks 23 through 27 (0.7±1.1 g per deciliter) than epoetin alfa (0.5±1.0 g per deciliter) and was statistically noninferior (difference, 0.2±1.2 g per deciliter; 95% confidence interval [CI], -0.02 to 0.5). As compared with epoetin alfa, roxadustat increased the transferrin level (difference, 0.43 g per liter; 95% CI, 0.32 to 0.53), maintained the serum iron level (difference, 25 µg per deciliter; 95% CI, 17 to 33), and attenuated decreases in the transferrin saturation (difference, 4.2 percentage points; 95% CI, 1.5 to 6.9). At week 27, the decrease in total cholesterol was greater with roxadustat than with epoetin alfa (difference, -22 mg per deciliter; 95% CI, -29 to -16), as was the decrease in low-density lipoprotein cholesterol (difference, -18 mg per deciliter; 95% CI, -23 to -13). Roxadustat was associated with a mean reduction in hepcidin of 30.2 ng per milliliter (95% CI, -64.8 to -13.6), as compared with 2.3 ng per milliliter (95% CI, -51.6 to 6.2) in the epoetin alfa group. Hyperkalemia and upper respiratory infection occurred at a higher frequency in the roxadustat group, and hypertension occurred at a higher frequency in the epoetin alfa group. CONCLUSIONS: Oral roxadustat was noninferior to parenteral epoetin alfa as therapy for anemia in Chinese patients undergoing dialysis. (Funded by FibroGen and FibroGen [China] Medical Technology Development; ClinicalTrials.gov number, NCT02652806.).

Weekly pattern of dialysis unit blood pressure is a promising marker for prognosis evaluation in hemodialysis population.

BACKGROUND: Dialysis unit blood pressure (BP) pattern showed superiority in prognostic evaluation and interdialytic BP burden assessment. However previous studies mainly focused on the recurrent BP pattern within a session (intradialytic BP change or intradialytic BP slope), the clinical value of the weekly pattern of dialysis unit BP is unknown. METHODS: We performed a prospective cohort study in adult end stage renal disease (ESRD) patients on thrice weekly hemodialysis (HD). The slope and the change of the postdialysis systolic BP (SBP) in the course of a week (post-SBP slope and post-SBP change) were used to characterize the weekly pattern of dialysis unit BP. Outcomes included all-cause mortality, cardiovascular mortality, and first cardiovascular event. We also measured the home BP in our cohort. RESULTS: One hundred and twenty-nine subjects were followed over a median of 31 months. Higher post-SBP slope (≥0.185) was independently associated with increased risk of all-cause mortality, cardiovascular mortality, and first cardiovascular event. Results were similar for increased post-SBP change. HD patients with a higher post-SBP slope or an increased post-SBP change also had significant increased interdialytic BP burden measured by home SBP on both dialysis days and non-dialysis days. CONCLUSIONS: Post-SBP slope and post-SBP change might be promising dialysis unit BP markers for prognostic evaluation and interdialytic BP burden assessment.

Kim-1 Targeted Extracellular Vesicles: A New Therapeutic Platform for RNAi to Treat AKI.

BACKGROUND: AKI is a significant public health problem with high morbidity and mortality. Unfortunately, no definitive treatment is available for AKI. RNA interference (RNAi) provides a new and potent method for gene therapy to tackle this issue. METHODS: We engineered red blood cell-derived extracellular vesicles (REVs) with targeting peptides and therapeutic siRNAs to treat experimental AKI in a mouse model after renal ischemia/reperfusion (I/R) injury and unilateral ureteral obstruction (UUO). Phage display identified peptides that bind to the kidney injury molecule-1 (Kim-1). RNA-sequencing (RNA-seq) characterized the transcriptome of ischemic kidney to explore potential therapeutic targets. RESULTS: REVs targeted with Kim-1-binding LTH peptide (REVLTH) efficiently homed to and accumulated at the injured tubules in kidney after I/R injury. We identified transcription factors P65 and Snai1 that drive inflammation and fibrosis as potential therapeutic targets. Taking advantage of the established REVLTH, siRNAs targeting P65 and Snai1 were efficiently delivered to ischemic kidney and consequently blocked the expression of P-p65 and Snai1 in tubules. Moreover, dual suppression of P65 and Snai1 significantly improved I/R- and UUO-induced kidney injury by alleviating tubulointerstitial inflammation and fibrosis, and potently abrogated the transition to CKD. CONCLUSIONS: A red blood cell-derived extracellular vesicle platform targeted Kim-1 in acutely injured mouse kidney and delivered siRNAs for transcription factors P65 and Snai1, alleviating inflammation and fibrosis in the tubules.

[Research progress of vascular endothelial growth factor-A and its isoforms in kidney disease].

Vascular endothelial growth factor-A (VEGF-A) is a critical angiogenic factor which is mainly secreted from podocytes and epithelial cells in kidney and plays an important role in renal pathophysiology. In recent years, functions of different isoforms of VEGF-A and the new secretion approach via extracellular vesicles (EVs) have been identified. Thus, further understanding are needed for the role of VEGF-A and its isoforms in renal injury and repair. In this review, we summarized the expression, secretion and regulation of VEGF-A, its biological function, and the role of different isoforms of VEGF-A in the development of different renal diseases. Meanwhile, the research progress of VEGF-A as diagnostic marker and therapeutic target for renal diseases were discussed.

[Research progress of extracellular vesicles in the treatment of renal disease].

Extracellular vesicles (EVs) are lipid bilayer-enclosed structures containing diverse bioactive cargoes that play a major role in intercellular communication in both physiological and pathological conditions. Currently, the field of EV-based therapy has been rapidly growing, and two main therapeutic uses of EVs can be surmised: (i) exploiting stem cell-derived EVs as therapeutic agents; and (ii) employing EVs as natural therapeutic vectors for drug delivery. This review will discuss the recent advances in EV-based therapy in the treatment of renal disease.

HIF-1α is transcriptionally regulated by NF-κB in acute kidney injury.

Oxygen homeostasis disturbances play a critical role in the pathogenesis of acute kidney injury (AKI). The transcription factor hypoxia-inducible factor-1 (HIF-1) is a master regulator of adaptive responses to hypoxia. Aside from posttranslational hydroxylation, the mechanism of HIF-1 regulation in AKI remains largely unclear. In this study, the mechanism of HIF-α regulation in AKI was investigated. We found that tubular HIF-1α expression significantly increased at the transcriptional level in ischemia-reperfusion-, unilateral ureteral obstruction-, and sepsis-induced AKI models, which was closely associated with macrophage-dependent inflammation. Meanwhile, NF-κB, which plays a central role in the inflammation response, was involved in the increasing expression of HIF-1α in AKI, as evidenced by pharmacological modulation (NF-κB inhibitor BAY11-7082). Mechanistically, NF-κB directly bound to the HIF-1α promoter and enhanced its transcription, which occurred not only under hypoxic conditions but also under normoxic conditions. Moreover, the induced HIF-1α by inflammation protected against tubular injury in AKI. Thus, our findings not only provide novel insights into HIF-1 regulation in AKI but also offer to understand the pathophysiology of kidney diseases.NEW & NOTEWORTHY Here, the mechanism of hypoxia-inducible factor-α (HIF-α) regulation in acute kidney injury (AKI) was investigated. We found that tubular HIF-1α expression significantly increased at the transcriptional level, which was closely associated with macrophage-dependent inflammation. Meanwhile, NF-κB was involved in the increasing expression of HIF-1α in AKI. Mechanistically, NF-κB directly bound to the HIF-1α promoter and enhanced its transcription. Our findings not only provide novel insights into HIF-1 regulation in AKI but also offer to understand the pathophysiology of kidney diseases.

Urinary small extracellular vesicles derived CCL21 mRNA as biomarker linked with pathogenesis for diabetic nephropathy.

BACKGROUND: Diabetic nephropathy (DN) is a leading cause of renal failure, whereas the effective and early diagnostic biomarkers are still lacking. METHODS: Fourteen cytokines and chemokines mRNA were detected in urinary extracellular vesicles (EVs) from the screening cohort including 4 healthy controls (HC), 4 diabetes mellitus (DM) and 4 biopsy-proven DN patients, and was validated in another 16 HC and 15 DM and 28 DN patients. Correlation analysis was performed between the candidate biomarkers and clinic parameters as well as kidney histological changes. The findings were also confirmed in DN rat model with single injection of STZ. RESULTS: The number of small EVs secreted in urine was increased in DN patients compared to DM patients and healthy controls, with expression of AQP1 (a marker of proximal tubules) and AQP2 (a marker of distal/collecting tubules). Small EVs derived CCL21 mRNA increased significantly in DN patients and correlated with level of proteinuria and eGFR. Interestingly, elevated CCL21 mRNA from urine small EVs was observed in DN patients with normal renal function and could discriminate early DN patients from DM more efficiently compared to eGFR and proteinuria. CCL21 also showed an accurate diagnostic ability in distinguishing incipient from overt DN. Histologically, CCL21 mRNA expression increased progressively with the deterioration of tubulointerstitial inflammation and showed the highest level in nodular sclerosis group (class III) in DN patients. Remarkable infiltration of CD3 positive T cells including both CD4 and CD8 positive T cell population were observed in DN patients with high-CCL21 expression. Besides, accumulation of CD3 positive T cells correlated with level of urinary small EVs derived CCL21 and co-localized with CCL21 in the tubulointerstitium in DN patients. Finally, the correlation of CCL21 expression in renal cortex and urinary small EVs was confirmed in STZ-induced DN rat model. CONCLUSIONS: Urinary small EVs derived CCL21 mRNA may serve as early biomarker for identifying DN linked with pathogenesis. CCL21 mRNA mediated T cell infiltration may constitute the key mechanism of chronic inflammation in DN.

FIH-1-modulated HIF-1α C-TAD promotes acute kidney injury to chronic kidney disease progression via regulating KLF5 signaling.

Incomplete recovery from episodes of acute kidney injury (AKI) can predispose patients to develop chronic kidney disease (CKD). Although hypoxia-inducible factor-1α (HIF-1α) is a master regulator of the response to hypoxia/ischemia, the role of HIF-1α in CKD progression following incomplete recovery from AKI is poorly understood. Here, we investigated this issue using moderate and severe ischemia/reperfusion injury (I/RI) mouse models. We found that the outcomes of AKI were highly associated with the time course of tubular HIF-1α expression. Sustained activation of HIF-1α, accompanied by the development of renal fibrotic lesions, was found in kidneys with severe AKI. The AKI to CKD progression was markedly ameliorated when PX-478 (a specific HIF-1α inhibitor, 5 mg· kg-1·d-1, i.p.) was administered starting on day 5 after severe I/RI for 10 consecutive days. Furthermore, we demonstrated that HIF-1α C-terminal transcriptional activation domain (C-TAD) transcriptionally stimulated KLF5, which promoted progression of CKD following severe AKI. The effect of HIF-1α C-TAD activation on promoting AKI to CKD progression was also confirmed in in vivo and in vitro studies. Moreover, we revealed that activation of HIF-1α C-TAD resulted in the loss of FIH-1, which was the key factor governing HIF-1α-driven AKI to CKD progression. Overexpression of FIH-1 inhibited HIF-1α C-TAD and prevented AKI to CKD progression. Thus, FIH-1-modulated HIF-1α C-TAD activation was the key mechanism of AKI to CKD progression by transcriptionally regulating KLF5 pathway. Our results provide new insights into the role of HIF-1α in AKI to CKD progression and also the potential therapeutic strategy for the prevention of renal diseases progression.

Fibroblast growth factor 21 (FGF21) is a sensitive marker of osteoporosis in haemodialysis patients: a cross-sectional observational study.

INTRODUCTION: Osteoporosis is one of the important bone abnormalities in chronic kidney disease-mineral and bone disorder (CKD-MBD) and still lacks a sensitive biomarker to diagnose. Fibroblast growth factor 21 (FGF21) can stimulate bone loss in patients with diabetes and increase in CKD patients. In this study, we investigated whether FGF21 could serve as a biomarker to predict osteoporosis in a haemodialysis cohort. METHODS: We recorded demographic information, biochemical data, and serum FGF21 and FGF23 levels and measured the CT attenuation values of 339 haemodialysis patients from two large medical centres. We assessed the correlation of CT attenuation values with serum FGF21 and FGF23 levels and tested whether they were independent factors for osteoporosis. ROC curves were constructed to compare the prognostic value of FGF21 and FGF23 for osteoporosis. RESULTS: Based on the CT attenuation value, serum FGF21 levels were higher in our osteoporosis group (median 640.86 pg/ml vs. 245.46 pg/ml, P ˂ 0.01). Meanwhile, FGF21 (r = -0.136, P < 0.05) and FGF23 (r = -0.151, P < 0.05) were both negatively associated with osteoporosis. Moreover, FGF21 (ß = -0.067, P < 0.05) was an independent factor for osteoporosis. Furthermore, FGF21 combined with age yielded a marked specificity (90.5 %) and sensitivity (61.8 %) in predicting osteoporosis of haemodialysis patients with less residual renal function. CONCLUSIONS: FGF21 has a positive relationship with the incidence of osteoporosis in patients on haemodialysis. FGF21 combined with age is a good predictive biomarker for osteoporosis in patients on haemodialysis, especially those with less residual renal function.

New Criterion to Evaluate Acute-on-Chronic Kidney Injury Based on the Creatinine Reference Change.

BACKGROUND: The lack of consensus criteria of acute on chronic kidney injury (ACKI) affects the judgment for its clinical prognosis. METHODS: In this study, we analyzed the data from 711,615 hospitalized adults who had at least 2 serum creatinine (SCr) tests within 30 days. We estimated the reference change value (RCV) of SCr given initial SCr level in adults without known risks of acute kidney injury other than chronic kidney disease (CKD). We proposed a criterion for ACKI based on the RCV of SCr (cROCK), which defined ACKI as a ≥25% increase in SCr in 7 days. We validated cROCK by its association with the risks of in-hospital mortality, death after discharge, and CKD progression in a large cohort of patients with CKD stage 3. RESULTS: In 21,661 patients with CKD stage 3, a total of 3,145 (14.5%), 1,512 (7.0%), and 221 (1.0%) ACKI events were detected by both cROCK and Kidney Disease Improving Global Outcomes (KDIGO), cROCK only, and KDIGO only, respectively. cROCK detected 40% more ACKI events than KDIGO. Compared with patients without ACKI by both definitions, those with cROCK- but not KDIGO-defined ACKI had a significantly increased risk of in-hospital mortality (hazard ratio [HR] 5.53; 95% CI 3.75-8.16), death after discharge (HR 1.51; 95% CI 1.21-1.83), and CKD progression (OR 5.65; 95% CI 3.05-10.48). CONCLUSIONS: RCV-based criterion (cROCK) for ACKI is clinically valid in that it has a substantially improved sensitivity in identifying patients with high risk of adverse outcomes.

The profibrotic effects of MK-8617 on tubulointerstitial fibrosis mediated by the KLF5 regulating pathway.

The discovery of hypoxia-inducible factor (HIF)-prolyl hydroxylase inhibitor (PHI) has revolutionized the treatment strategy for renal anemia. However, the presence of multiple transcription targets of HIF raises safety concerns regarding HIF-PHI. Here, we explored the dose-dependent effect of MK-8617 (MK), a kind of HIF-PHI, on renal fibrosis. MK was administered by oral gavage to mice for 12 wk at doses of 1.5, 5, and 12.5 mg/kg. In vitro, the human proximal tubule epithelial cell line HK-2 was treated with increasing doses of MK administration. Transcriptome profiling was performed, and fibrogenesis was evaluated. The dose-dependent biphasic effects of MK on tubulointerstitial fibrosis (TIF) were observed in chronic kidney disease mice. Accordingly, high-dose MK treatment could significantly enhance TIF. Using RNA-sequencing, combined with in vivo and in vitro experiments, we found that Krüppel-like factor 5 (KLF5) expression level was significantly increased in the proximal tubular cells, which could be transcriptionally regulated by HIF-1α with high-dose MK treatment but not low-dose MK. Furthermore, our study clarified that HIF-1α-KLF5-TGF-ß1 signaling activation is the potential mechanism of high-dose MK-induced TIF, as knockdown of KLF5 reduced TIF in vivo. Collectively, our study demonstrates that high-dose MK treatment initiates TIF by activating HIF-1α-KLF5-TGF-ß1 signaling. These findings provide novel insights into TIF induction by high-dose MK (HIF-PHI), suggesting that the safety dosage window needs to be emphasized in future clinical applications.-Li, Z.-L., Lv, L.-L., Wang, B., Tang, T.-T., Feng, Y., Cao, J.-Y., Jiang, L.-Q., Sun, Y.-B., Liu, H., Zhang, X.-L., Ma, K.-L., Tang, R.-N., Liu, B.-C. The profibrotic effects of MK-8617 on tubulointerstitial fibrosis mediated by the KLF5 regulating pathway.