Rodent models of AKI-CKD transition

Prolonged unilateral renal ischemia-reperfusion as a model for acute to chronic kidney injury in female mice

Acute kidney injury (AKI) is a significant risk factor for developing chronic kidney disease (CKD). Recent studies have highlighted notable gender differences in the susceptibility and expression of both AKI and CKD. The mechanisms underlying these differences remain unclear, and there is a lack of reliable models for studying the AKI-CKD transition in females. In this study, we evaluated various ischemia times in the unilateral renal ischemia-reperfusion injury (UIR) model in female mice to establish a model for studying the AKI-CKD transition. UIR was induced in the left kidneys of male and female C57Bl/6 mice. Kidney pathology and key injury markers were examined 28 days post-UIR. Comparable pathological changes were observed in female mice subjected to 50- and 60-min ischemia, similar to those in male mice subjected to 30-min UIR. Protein levels of key injury markers, including Vim-1, Krt8, and Acta2, were significantly increased in female mice subjected to 50- and 60-min UIR, comparable to male mice subjected to 30-min UIR, 28 days postinjury. In addition, an increase in mRNA expression of key kidney injury markers Col1a1, Vim-1, FN, and Sox4, along with a decline in Slc34a1 expression, was observed in female mice subjected to 50- and 60-min UIR, similar to male mice subjected to 30-min UIR, at 28 days postinjury. Our findings suggest that the optimal ischemia time for inducing CKD changes in female mice is 50-60 min, compared to much shorter injury times in male mice.NEW & NOTEWORTHY Our findings identify a reliable timepoint at which female mice subjected to unilateral ischemia-reperfusion consistently develop CKD changes relative to much shorter duration in male mice. We provide a novel model to study the AKI-CKD transition in female mice.

Repression of peroxisome proliferation-activated receptor γ coactivator-1α by p53 after kidney injury promotes mitochondrial damage and maladaptive kidney repair

Maladaptive kidney repair after injury is associated with a loss of mitochondrial homeostasis, but the underlying mechanism is largely unknown. Moreover, it remains unclear whether this mitochondrial change contributes to maladaptive kidney repair or the development of chronic kidney problems after injury. Here, we report that the transcriptional coactivator peroxisome proliferation-activated receptor γ coactivator-1α (PGC1a), a master regulator of mitochondrial biogenesis, was persistently downregulated during maladaptive kidney repair after repeated low-dose cisplatin nephrotoxicity or unilateral ischemia/reperfusion injury. Administration of the PGC1α activator ZLN005 after either kidney injury not only preserved mitochondria but also attenuated kidney dysfunction, tubular damage, interstitial fibrosis, and inflammation. PGC1α downregulation in these models was associated with p53 activation. Notably, knockout of p53 from proximal tubules prevented PGC1α downregulation, attenuated chronic kidney pathologies and minimized functional decline. Inhibition of p53 with pifithrin-α, a cell permeable p53 inhibitor, had similar effects. Mechanistically, p53 bound to the PGC1α gene promoter during maladaptive kidney repair, and this binding was suppressed by pifithrin-α. Together, our results indicate that p53 is induced during maladaptive kidney repair to repress PGC1α transcriptionally, resulting in mitochondrial dysfunction for the development of chronic kidney problems. Activation of PGC1α and inhibition of p53 may improve kidney repair after injury and prevent the development of chronic kidney problems.

Expanded discussion of kidney health monitoring for critically ill term and late preterm infants after acute kidney injury: a report from the Neonatal Kidney Health Consensus Workshop

BACKGROUND

Acute kidney injury (AKI) is common in the neonatal intensive care unit (NICU) and is associated with increased morbidity and mortality. Mounting evidence suggests infants with AKI in the NICU have higher risks of long-term kidney dysfunction, such as chronic kidney disease. However, guidelines for outpatient kidney-focused follow-up practices are lacking.

METHODS

As part of the National Institutes of Health-sponsored Consensus Workshop to Address Kidney Health in Neonatal Intensive Care Unit Graduates, a multidisciplinary workgroup within the US performed an in-depth review of the medical literature on term and late preterm (i.e. ≥ 34 weeks gestation) neonates admitted to the NICU with AKI to inform consensus recommendations for outpatient kidney health monitoring for high-risk and at-risk infants.

RESULTS

In this modified Delphi consensus statement, the workgroup developed three consensus recommendations and identified priority research gaps and opportunities for future study. Specific recommendations include completing a NICU discharge kidney health evaluation followed by a comprehensive kidney health assessment six months after discharge for high-risk infants and at two years of age for high-risk and at-risk infants.

CONCLUSIONS

Critically ill term and late preterm infants with AKI have an increased risk of long-term kidney dysfunction and merit evaluation at NICU discharge with subsequent comprehensive kidney health assessments based on risk factors. Current research gaps and opportunities for improved care include identifying optimal pre-discharge planning approaches, examining the impacts of different etiologies and severity of AKI on long-term kidney and overall health, exploring modification to current AKI diagnosis standards, and development of high-yield educational tools for families and providers.

Magnesium Lithospermate B Protects Against Ischemic AKI-to-CKD progression via regulating the KLF5/CDK1/Cyclin B1 pathway

BACKGROUND

Ischemia-reperfusion injury (IRI) is the primary cause of acute kidney injury (AKI), which can result in chronic kidney disease (CKD) with renal fibrosis. Magnesium lithospermate B (Mlb), a bioactive compound produced from Salvia miltiorrhiza Bunge, exerts nephroprotective effects against AKI. However, the significance of Mlb in the evolution of IRI-induced AKI in patients with CKD remains unclear. Notably, the specific mechanisms underlying the putative antifibrotic activities of Mlb during this progression remain to be fully elucidated.

PURPOSE

This study sought to explore the therapeutic benefits of Mlb in AKI-to-CKD progression and uncover the potential mechanisms, with a special interest in its effects on renal fibrosis and cell cycle regulation.

STUDY DESIGN AND METHODS

Unilateral ischemia/reperfusion (UIR)-induced mouse AKI-to-CKD progression (in vivo) and HK-2 cells with TGF-β-induced fibrosis model (in vitro) were used in the study. The beneficial effects of Mlb on renal fibrosis and cell cycle-related signaling pathways were investigated using histological analysis, molecular assays, network pharmacology, and RNA sequencing.

RESULTS

Mlb treatment significantly reduced renal dysfunction, inflammation, apoptosis, and the G2/M phase cell cycle stalling in mice 14 days post-UIR-induced AKI, subsequently improving renal fibrosis. Mechanistically, Mlb promotes the activity of the CDK1/Cyclin B1 signaling pathway, thereby alleviating the G2/M phase cell cycle stalling. Network pharmacology and RNA sequencing analyses identified the KLF5/CDK1/Cyclin B1 signaling pathway as a potential target of the antifibrotic effects of Mlb, which was further verified in both in vivo and in vitro experiments. The KLF5 inhibitor ML264 attenuated the protective effects of Mlb by reducing CDK1/Cyclin B1 expression and reinstating the G2/M phase cell cycle stalling, highlighting the critical role of this pathway in Mlb-mediated renal protection.

CONCLUSIONS

Mlb decreases renal fibrosis by inhibiting the G2/M phase cell cycle stalling via the KLF5/CDK1/Cyclin B1 signaling pathway during AKI-to-CKD progression. Our findings offer new insight into the therapeutic potential of Mlb in preventing CKD progression following AKI and identify a previously unrecognized mechanism involving the KLF5/CDK1/Cyclin B1 pathway.

Metabolic and Microcirculatory Changes in Severe Renal Ischemia-Reperfusion and Ischemic Preconditioning in the Rat: Are They Detectable in the First Hour of Reperfusion?

Ischemia-reperfusion (I/R) strongly affects a graft's function and survival and modulates microcirculatory and hemorheological parameters. However, the boundary between the reversibility and irreversibility of damage is unclear. This study compared the effects of renal I/R and ischemic preconditioning (IPC) to determine whether metabolic, microcirculatory, and micro-rheological changes are already detectable in the first hour of reperfusion. Wistar rats were divided into control (n = 6), I/R (n = 7) and IPC (n = 7) groups. In the ischemic groups the left kidney was subjected to 120 min of ischemia followed by 60 min of reperfusion. In the IPC group, a 3 × 5 min protocol was used prior to the manifest ischemia. Parenchymal microcirculation and renal artery blood flow were measured before ischemia (base) and during reperfusion (R-30, R-60). Hematological, micro-rheological parameters, electrolytes, and metabolites were tested at base and at R-60. Both ischemic groups showed micro-rheological impairment. An increase in potassium, lactate, and creatinine concentrations and a decrease in pH were observed. The blood flow of the IPC group deteriorated less, and microcirculation recordings indicated better values. The 120 min ischemia and the 60 min reperfusion resulted in micro-rheological and metabolic alterations, together with decreased renal blood flow and parenchymal microcirculation. Although the applied IPC protocol showed minor protective effects, its impact was limited in the first hour of reperfusion.

Autologous platelet delivery of siRNAs by autologous plasma protein self-assembled nanoparticles for the treatment of acute kidney injury

Acute kidney injury (AKI) involves the activation of intrarenal hemostatic and inflammatory pathways. Platelets rapidly migrate to affected sites of AKI and release extracellular vesicles (EVs) laden with bioactive mediators that regulate inflammation and hemostasis. While small interfering RNA (siRNA) is a potent gene-silencing tool for biomedical applications, its therapeutic application in vivo remains challenging. We developed an innovative nucleic acid delivery platform by hybridizing synthetic transformation-related protein 53 (p53) siRNA with autologous plasma and incubating the complex with autologous platelets. These engineered platelets selectively delivered p53 siRNA to injured renal tubular cells via EV-mediated cargo release, resulting in targeted p53 suppression in renal cells and subsequent attenuation of AKI progression. This platelet-centric translational strategy demonstrates significant potential for advancing precision therapies in AKI by exploiting endogenous platelet trafficking to deliver therapeutics directly to injury sites.

Urine-derived stem cells display homing, incorporation, and regeneration in human organoid and mouse models of acute kidney injury

Urine-derived stem cells (USCs) are adult human stem cells that can be collected noninvasively from urine and cultured in vitro. Because of their renal origin and reported therapeutic effects, we hypothesized that USCs would home to the injured kidney in acute kidney injury (AKI) models. We used mouse models of glycerol-induced rhabdomyolysis or unilateral nephrectomy with clamping ischemia reperfusion injury to model AKI. To track USC homing by live animal imaging, we administered luciferase-expressing (Luc) USCs to mice by intraperitoneal injection. We observed USC localization to both the tubules and glomeruli of injured mice within 3 h by histology. We confirmed the presence of Luc-USCs in the kidney at 3 h, 24 h, and 48 h after the injection using biodistribution analysis of quantitative bioluminescence tomography imaging. We performed immunostaining for kidney injury molecule-1 (KIM-1/HAVCR1/TIM-1) for kidney injury and found reduced expression in USC-treated group at 24 h after injection. To evaluate the effects of the human USCs on injured human nephrons, we injured human kidney organoids with the nephrotoxin cisplatin (5 μM) followed by 5 × 104 USC treatment. USCs were incorporated and lowered expression of KIM-1 in the organoids. USCs home to injured nephrons and reduce measures of kidney injury.

Synthetic Bilirubin-Based Nanomedicine Protects Against Renal Ischemia/Reperfusion Injury Through Antioxidant and Immune-Modulating Activity

Renal ischemia/reperfusion injury (IRI) is a common form of acute kidney injury. The basic mechanism underlying renal IRI is acute inflammation, where oxidative stress plays an important role. Although bilirubin exhibits potent reactive oxygen species (ROS)-scavenging properties, its clinical application is hindered by problems associated with solubility, stability, and toxicity. In this study, BX-001N, a synthetic polyethylene glycol-conjugated bilirubin 3α nanoparticle is developed and assessed its renoprotective effects in renal IRI. Intravenous administration of BX-001N led to increase uptake in the kidneys with minimal migration to the brain after IRI. Peri-IRI BX-001N administration improves renal function and attenuates renal tissue injury and tubular apoptosis to a greater extent than free bilirubin on day 1 after IRI. BX-001N suppressed renal infiltration of inflammatory cells and reduced expression of TNF-α and MCP-1. Furthermore, BX-001N increases renal tubular regeneration on day 3 and suppresses renal fibrosis on day 28. BX-001N decreases the renal expressions of dihydroethidium, malondialdehyde, and nitrotyrosine after IRI. In conclusion, BX-001N, the first Good Manufacturing Practice-grade synthetic bilirubin-based nanomedicine attenuates acute renal injury and chronic fibrosis by suppressing ROS generation and inflammation after IRI. It shows adequate safety profiles and holds promise as a new therapy for renal IRI.

Oxidative stress and NRF2 signaling in kidney injury

Oxidative stress plays a crucial role in the pathogenesis of acute kidney injury (AKI), chronic kidney disease (CKD), and the AKI-to-CKD transition. This review examines the intricate relationship between oxidative stress and kidney pathophysiology, emphasizing the potential therapeutic role of nuclear factor erythroid 2-related factor 2 (NRF2), a master regulator of cellular redox homeostasis. In diverse AKI and CKD models, diminished NRF2 activity exacerbates oxidative stress, whereas genetic and pharmacological NRF2 activation alleviates kidney damage induced by nephrotoxic agents, ischemia-reperfusion injury, fibrotic stimuli, and diabetic nephropathy. The renoprotective effects of NRF2 extend beyond antioxidant defense, encompassing its anti-inflammatory and anti-fibrotic properties. The significance of NRF2 in renal fibrosis is further underscored by its interaction with the transforming growth factor-β signaling cascade. Clinical trials using bardoxolone methyl, a potent NRF2 activator, have yielded both encouraging and challenging outcomes, illustrating the intricacy of modulating NRF2 in human subjects. In summary, this overview suggests the therapeutic potential of targeting NRF2 in kidney disorders and highlights the necessity for continued research to refine treatment approaches.

An adoptive cell therapy with TREM2-overexpressing macrophages mitigates the transition from acute kidney injury to chronic kidney disease

BACKGROUND

Macrophages have been shown to contribute to renal injury and fibrosis as well as repair. Recently, Triggering Receptor Expressed on Myeloid Cells 2 (TREM2)-positive macrophages have been shown to play important roles in regulating tissue inflammation and repair. However, it remains unclear whether they can mitigate the transition from acute kidney injury to chronic kidney disease (the AKI-CKD transition).

METHODS

The AKI-CKD transition was generated by unilateral ischaemia-reperfusion injury (UIRI) in wild-type (WT) and Trem2 knockout mice. F4/80 magnetic beads were used to isolate renal macrophages. Flow cytometry was used to determine the levels of TREM2 and CD11b levels. Quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blotting and histological staining were performed to determine the expression of cytokines and fibrotic markers. RNA-seq was used to investigate transcriptomic changes between WT and Trem2 knockout bone marrow-derived macrophages (BMDMs). TREM2-overexpressing macrophages were generated using lentivirus and transferred intravenously to UIRI mice.

RESULTS

TREM2 macrophages exhibited a strong renal protective effect on the AKI-CKD transition. Genetic deletion of Trem2 resulted in increased renal inflammation and exacerbated renal injury and fibrosis in UIRI mice. Interestingly, we found that hypoxia could increase TREM2 expression in macrophages via HIF-1α. Upregulated TREM2 expression enhanced macrophage phagocytosis and suppressed the expression of pro-inflammatory cytokines, resulting in lower levels of apoptosis and fibrosis in tubular epithelial cells. Using RNA-seq analysis, we showed that the regulatory effects of TREM2 were orchestrated by the PI3K-AKT pathway. Pharmacological regulation of the PI3K-AKT pathway could modulate the macrophage-mediated inflammation and phagocytosis. In addition, an adoptive cell therapy using TREM2-overexpressing macrophages effectively reduced the immune cell infiltration, renal injury and fibrosis in UIRI mice.

CONCLUSION

Our study not only provides valuable mechanistic insights into the role of Trem2 in the AKI-CKD transition but also offers a new avenue for TREM2-overexpressing macrophage-based adoptive cell therapy to treat kidney diseases.

KEY POINTS

TREM2 knockout worsens kidney injury and accelerates AKI-CKD transition. TREM2 is upregulated by hypoxia via HIF1α in AKI-CKD transition. An adoptive cell therapy using TREM2-overexpressing macrophages reduces kidney inflammation and fibrosis.

Graphene Quantum Dots as Antifibrotic Therapy for Kidney Disease

Graphene quantum dots (GQDs) have received much attention for their biomedical applications, such as bioimaging and drug delivery. Additionally, they have antioxidant and anti-inflammatory properties. We used GQDs to treat renal fibrosis and confirmed their ability to protect renal cells from excessive oxidative stress in vitro and in vivo. Tubulointerstitial fibrosis was induced by unilateral ureteral obstruction (UUO) in 7- to 8-week-old male C57BL/6 mice. GQDs were administered by intravenous injection to mimic clinical treatment. The levels of oxidative stress, ROS production, apoptosis and proinflammatory cytokines and the activity of the TGFβ1/Smad pathway were evaluated after treatment with GQDs. In vitro, rhTGF-β1 was used to induce fibrosis in primary kidney tubule epithelial cells. GQDs alleviated fibrosis and morphological changes after UUO induction. At the mRNA and protein levels, GQDs significantly reduced the expression of fibrotic markers and proinflammatory cytokines, decreased ROS production and TGF-β1 expression, and affected Smad-dependent signaling pathways. In vitro, GQDs inhibited rhTGF-β1-induced epithelial-to-mesenchymal transition in primary kidney tubule epithelial cells and reduced apoptosis and ROS accumulation. This study revealed the role of GQDs in kidney fibrosis: GQDs effectively attenuated major fibrogenesis events by inhibiting ROS accumulation and the vicious cycle of the ROS and TGF-β1/Smad signaling pathways, as well as alleviating cell apoptosis and inflammation. Thus, GQDs may be a therapeutic option for chronic kidney disease progression.

Temporary bilateral clamping of renal arteries induces ischemia-reperfusion: A new pig model of acute kidney injury using total intravenous anesthesia

Ischemia-reperfusion (IR) is a leading cause of acute kidney injury (AKI), and pigs are commonly used in preclinical AKI models. However, existing models often vary in the methods used to induce ischemia, and the resulting AKI tends to be mild-to-moderate. Moreover, follow-up is often performed under volatile anesthesia, which, in contrast to total intravenous anesthesia (TIVA), can induce malignant hyperthermia and cause hemodynamic instability. Here we present a novel surgical model of IR-induced AKI using bilateral renal artery clamping under TIVA. Anesthesia was induced via TIVA with diazepam, ketamine, and morphine. After retroperitoneal exposure, the renal arteries were isolated and clamped with a plastic tube for 90 min, followed by 8 h of reperfusion. The IR group (n = 6) was compared with a Sham group (n = 5) that underwent the same procedure without IR. The IR group developed moderate-to-severe AKI as evidenced by reduced glomerular filtration, a 158% increase in plasma creatinine versus 21% in the Sham group, and elevated neutrophil gelatinase-associated lipocalin levels (+280% in IR vs. 0% in Sham), indicating tubular injury. Histopathology confirmed these findings. Thus, this preclinical model successfully induced moderate-to-severe AKI in pigs. The TIVA anesthetic protocol offered several advantages compared to halogenated gas anesthesia.

Confrontation with kidney inflammation through a HMGB1-targeted peptide augments anti-fibrosis therapy

Damage to the renal tubular epithelial cells (TEC) is a key cellular event in kidney inflammation and subsequent fibrosis. However, drugs targeting renal TEC (RTEC) are limited to the alleviation of kidney fibrosis. Lethal giant larvae 1 (Lgl1) plays a key role in epithelial cell polarity and proliferation. Here, we report that the renal tubule epithelial-specific deletion of Lgl1 significantly ameliorated intrarenal inflammation and kidney fibrosis. Mechanistically, Lgl1 suppressed the activity of the deacetylase sirtuin 1 (SIRT1) and augmented the acetylation of high-mobility group box 1 (HMGB1) at the lysine 90 (K90) site. Consequently, HMGB1 migrated from the nucleus to the cytoplasm, activating an inflammatory cascade. Our renoprotective strategy was to construct a mimic peptide, TAT-K90WT, that targets HMGB1 K90 acetylation. Administration of this peptide significantly ameliorated inflammation and fibrosis in the kidneys. In summary, the Lgl1-HMGB1 axis plays an important role in renal fibrosis, and targeting HMGB1 acetylation by mimicking peptides is a potential strategy to prevent fibrosis.

Butyrolactone I blocks the transition of acute kidney injury to chronic kidney disease in mice by targeting JAK1

Chronic kidney disease (CKD) is a disease that affects more than 850 million people. Acute kidney injury (AKI) is a common cause of CKD, and blocking the AKI-CKD transition shows promising therapeutic potential. Herein, we found that butyrolactone I (BLI), a natural product, exerts significant nephroprotective effects, including maintenance of kidney function, inhibition of inflammatory response, and prevention of fibrosis, in both folic acid- and ureteral obstruction-induced AKI-CKD transition mouse models. Notably, BLI showed greater blood urea nitrogen reduction and anti-inflammatory effects than telmisartan. Bioinformatics analysis and target confirmation assays suggested that BLI directly binds to JAK1, and kinase inhibition assay confirmed it is a potent JAK1inhibitor with an IC50 of 0.376 µM. Experiments in JAK1-knockdown mice also proved that BLI targets JAK1 to work. Furthermore, BLI demonstrated nephroprotective effects and safety comparable to ivarmacitinib, the well-known JAK1 inhibitor. Mechanistically, BLI targets JAK1 and inhibits its phosphorylation and JAK-STAT activation, subsequently regulating the downstream signaling pathways to inhibit reactive oxygen species production, inflammation, and ferroptosis, thereby preventing the occurrence of kidney fibrosis and blocking the AKI-CKD transition process. This study demonstrates for the first time that BLI is a JAK1 inhibitor and a promising candidate for delaying CKD progression, which warrants further investigation.

Weekly administration of betulinic acid prevents development of chronic renal failure from acute renal failure in folic acid-induced mouse model of kidney injury

Betulinic acid (BA) has been shown to exhibit various pharmacological activities and it has shown the protective effect on acute renal failure (ARF) and chronic renal failure (CRF); however, no reports are available on its effect on ARF-CRF transition. Therefore, we aimed to investigate the effects of BA on ARF-CRF transition. A single dose of 250 mg/kg body weight (BW) intraperitoneal injection of folic acid was given in mice for inducing ARF-CRF transition (injury group; I) on day 1. Further, excess of these mice received BA at 30 mg/kg BW dose for 3 days (on days 1, 2, 3) in one group (IT3) and for 7 days (on days 1, 2, 3, 7, 14, 21, 28) in another group (IT7). All mice were sacrificed on day 28. Mice in injury group (I) showed elevated serum creatinine along with oxidative stress markers like urine nitrite, tissue lipid peroxidation, nitrotyrosine and fibrotic markers such as tissue α-smooth muscle actin and matrix metalloproteinase-2 activity. They had attenuated levels of urine creatinine and tissue reparative cytokines viz. interleukin-4 and interleukin-13. Excess of fibroblasts and extracellular matrix in the interstitia and periglomerular area in microscopy further support these findings. Seven days of BA treatment regimen (IT7) significantly improved serum and urine parameters accompanied by reduced oxidative stress, improved reparative cytokines and lesser maladaptive matrix deposition. The above findings reveal that weekly BA treatment regimen has potential to prevent development of CRF after ARF.

Panax Notoginseng Saponins Inhibit Apoptosis and Alleviate Renal Ischemia-Reperfusion Injury Through the ROCK2/NF-κB Pathway

Renal ischemia-reperfusion injury (RIRI) is a primary cause of acute kidney injury (AKI), frequently resulting in high mortality rates and progression to chronic kidney disease (CKD). This study aimed to investigate the therapeutic potential of total saponins from Panax notoginseng (PNS) in the context of RIRI. Utilizing a murine RIRI model, the efficacy of PNS was evaluated, demonstrating a significant reduction in renal inflammation and cellular pyroptosis. Furthermore, PNS was found to modulate the ROCK2/NF-κB signaling pathway, thereby attenuating the inflammatory response. Importantly, in vitro experiments with hypoxia/reoxygenation cell models corroborated these findings, showing that PNS inhibited pyroptosis and regulated the ROCK2/NF-κB pathway. This research underscores the therapeutic potential of PNS in the treatment of RIRI, providing a robust scientific basis for its consideration as a prospective clinical therapy.

Hyaluronic Acid-Nanocoated Bacteria Generate an Anti-Inflammatory Tissue-Repair Effect in Impaired Gut and Extraintestinal Organs

Diverse extraintestinal diseases are characterized by localized inflammatory responses and tissue damage, accompanied with intestinal inflammation and injury. Here, a dual-functionality and dual-location intervention strategy is reported, which is the use of hyaluronic acid-nanocoated Clostridium butyricum to generate an anti-inflammatory tissue-repair effect in the impaired gut and extraintestinal organs. Nanocoated bacteria attenuate intestinal mucosal inflammation and recover gut barrier integrity by leveraging the immunosuppressive nature of hyaluronic acid and the butyrate-producing ability of Clostridium butyricum. Nanocoated bacteria also alleviate the interstitial inflammation and pathological damage of extraintestinal organs via remodeling microbial metabolites and decreasing microbial translocation. In murine models of acute kidney injury and chronic kidney disease, oral delivery of nanocoated bacteria demonstrates the potency to restore renal function and eliminate renal fibrosis. This work proposes a type of next-generation living therapeutics for treating extraintestinal diseases.

Propionate and butyrate counteract renal damage and progression to chronic kidney disease

BACKGROUND

Short-chain fatty acids (SCFAs), mainly acetate, propionate and butyrate, are produced by gut microbiota through fermentation of complex carbohydrates that cannot be digested by the human host. They affect gut health and can contribute at the distal level to the pathophysiology of several diseases, including renal pathologies.

METHODS

SCFA levels were measured in chronic kidney disease (CKD) patients (n = 54) at different stages of the disease, and associations with renal function and inflammation parameters were examined. The impact of propionate and butyrate in pathways triggered in tubular cells under inflammatory conditions was analysed using genome-wide expression assays. Finally, a pre-clinical mouse model of folic acid-induced transition from acute kidney injury to CKD was used to analyse the preventive and therapeutic potential of these microbial metabolites in the development of CKD.

RESULTS

Faecal levels of propionate and butyrate in CKD patients gradually reduce as the disease progresses, and do so in close association with established clinical parameters for serum creatinine, blood urea nitrogen and the estimated glomerular filtration rate. Propionate and butyrate jointly downregulated the expression of 103 genes related to inflammatory processes and immune system activation triggered by tumour necrosis factor-α in tubular cells. In vivo, the administration of propionate and butyrate, either before or soon after injury, respectively, prevented and slowed the progression of damage. This was indicated by a decrease in renal injury markers, the expression of pro-inflammatory and pro-fibrotic markers, and recovery of renal function over the long term.

CONCLUSIONS

Propionate and butyrate levels are associated with a progressive loss of renal function in CKD patients. Early administration of these SCFAs prevents disease advancement in a pre-clinical model of acute renal damage, demonstrating their therapeutic potential independently of the gut microbiota.

Metabolomic and transcriptomic insights into the mechanisms of renal ischemia-reperfusion injury progression

Renal ischemia-reperfusion injury (IRI) is an important cause of acute kidney injury (AKI). However, the pathophysiological changes and mechanisms during IRI-AKI progression remain unclear. This study aims toinvestigate the potential mechanisms in the progression of IRI-AKI by integrating metabolomics and transcriptomics data, providing a reference for the subsequent identification of biomarkers and therapeutic targets. IRI-AKI rat models with 30 min of ischemia and 24-72 h of reperfusion surgery simulating the progression of AKI were established. Compared to the control group underwent sham surgery (NC group), most of the differentially expressed metabolites (DEMs) in IRI-AKI 24 h and IRI-AKI 72 h decreased, mainly including amino acids, organic acids, and carnitines. Additionally, we found that DEMs were mainly enriched in amino acid-related pathways, among which valine, leucine, and isoleucine biosynthesis were dramatically altered in all comparisons. Transcriptomics revealed that differentially expressed genes (DEGs) were primarily involved in amino acid, lipid, and fatty acid metabolism. By integrating metabolomics and transcriptomics, we found valine, leucine, and isoleucine biosynthesis play key roles in IRI-AKI development. Our findings concluded that valine, leucine, and isoleucine pathways are hubs that potentially connect transcriptomes to metabolomes, providing new insights regarding the pathogenesis of IRI-AKI and its potential biomarkers and therapeutic strategies.

Adenine-induced animal model of chronic kidney disease: current applications and future perspectives

Chronic kidney disease (CKD) with high morbidity and mortality all over the world is characterized by decreased kidney function, a condition which can result from numerous risk factors, including diabetes, hypertension and obesity. Despite significant advances in our understanding of the pathogenesis of CKD, there are still no treatments that can effectively combat CKD, which underscores the urgent need for further study into the pathological mechanisms underlying this condition. In this regard, animal models of CKD are indispensable. This article reviews a widely used animal model of CKD, which is induced by adenine. While a physiologic dose of adenine is beneficial in terms of biological activity, a high dose of adenine is known to induce renal disease in the organism. Following a brief description of the procedure for disease induction by adenine, major mechanisms of adenine-induced CKD are then reviewed, including inflammation, oxidative stress, programmed cell death, metabolic disorders, and fibrillation. Finally, the application and future perspective of this adenine-induced CKD model as a platform for testing the efficacy of a variety of therapeutic approaches is also discussed. Given the simplicity and reproducibility of this animal model, it remains a valuable tool for studying the pathological mechanisms of CKD and identifying therapeutic targets to fight CKD.

Knockdown of nicotinamide N-methyltransferase ameliorates renal fibrosis caused by ischemia-reperfusion injury and remodels sphingosine metabolism

BACKGROUND

CKD currently affects 8.2% to 9.1% of the global population and the CKD mortality rate has increased during recent decades, making it necessary to identify new therapeutic targets. This study investigated the role of nicotinamide N-methyltransferase (NNMT) in renal fibrosis following ischemia-reperfusion injury (IRI), a key factor in chronic kidney disease (CKD) progression.

METHODS

We established a mouse model with a knockdown of NNMT to investigate the impact of this enzyme on renal fibrosis after unilateral IRI. We then utilized histology, immunohistochemistry, and metabolomic analyses to investigate fibrosis markers and sphingolipid metabolism in NNMT-deficient mice. We also utilized an Nnmt lentivirus interference vector or an Nnmt overexpression plasmid to transfect mouse kidney proximal tubule cells, stimulated these cells with TGF-β1, and then measured the pro-fibrotic response and the expression of the methylated and unmethylated forms of Sphk1.

RESULTS

The results demonstrated that reducing NNMT expression mitigated fibrosis, inflammation, and lipid deposition, potentially through the modulation of sphingolipid metabolism. Histology, immunohistochemistry, and metabolomic analyses provided evidence of decreased fibrosis and enhanced sphingolipid metabolism in NNMT-deficient mice. NNMT mediated the TGF-β1-induced pro-fibrotic response, knockdown of Nnmt decreased the level of unmethylated Sphk1 and increased the level of methylated Sphk1 in renal tubular epithelial cells.

CONCLUSIONS

Our findings suggest that NNMT functions in sphingolipid metabolism and has potential as a therapeutic target for CKD. Further research is needed to elucidate the mechanisms linking NNMT to sphingolipid metabolism and renal fibrosis.

Chromodomain Y-like (CDYL) inhibition ameliorates acute kidney injury in mice by regulating tubular pyroptosis

Acute kidney injury (AKI) is a common disease, but lacking effective drug treatments. Chromodomain Y-like (CDYL) is a kind of chromodomain protein that has been implicated in transcription regulation of autosomal dominant polycystic kidney disease. Benzo[d]oxazol-2(3H)-one derivative (compound D03) is the first potent and selective small-molecule inhibitor of CDYL (KD = 0.5 μM). In this study, we investigated the expression of CDYL in three different models of cisplatin (Cis)-, lipopolysaccharide (LPS)- and ischemia/reperfusion injury (IRI)-induced AKI mice. By conducting RNA sequencing and difference analysis of kidney samples, we found that tubular CDYL was abnormally and highly expressed in injured kidneys of AKI patients and mice. Overexpression of CDYL in cisplatin-induced AKI mice aggravated tubular injury and pyroptosis via regulating fatty acid binding protein 4 (FABP4)-mediated reactive oxygen species production. Treatment of cisplatin-induced AKI mice with compound D03 (2.5 mg·kg-1·d-1, i.p.) effectively attenuated the kidney dysfunction, pathological damages and tubular pyroptosis without side effects on liver or kidney function and other tissue injuries. Collectively, this study has, for the first time, explored a novel aspect of CDYL for tubular epithelial cell pyroptosis in kidney injury, and confirmed that inhibition of CDYL might be a promising therapeutic strategy against AKI.

Gucy1α1 specifically marks kidney, heart, lung and liver fibroblasts

Fibrosis is a common outcome of numerous pathologies, including chronic kidney disease (CKD), a progressive renal function deterioration. Current approaches to target activated fibroblasts, key effector contributors to fibrotic tissue remodeling, lack specificity. Here, we report Gucy1α1 as a specific kidney fibroblast marker. Gucy1α1 levels significantly increased over the course of two clinically relevant murine CKD models and directly correlated with established fibrosis markers. Immunofluorescent (IF) imaging showed that Gucy1α1 comprehensively labelled cortical and medullary quiescent and activated fibroblasts in the control kidney and throughout injury progression, respectively. Unlike traditionally used markers platelet derived growth factor receptor beta (Pdgfrβ) and vimentin (Vim), Gucy1α1 did not overlap with off-target populations such as podocytes. Notably, Gucy1α1 labelled kidney fibroblasts in both male and female mice. Furthermore, we observed elevated GUCY1α1 expression in the human fibrotic kidney and lung. Studies in the murine models of cardiac and liver fibrosis revealed Gucy1α1 elevation in activated Pdgfrβ-, Vim- and alpha smooth muscle actin (αSma)-expressing fibroblasts paralleling injury progression and resolution. Overall, we demonstrate Gucy1α1 as an exclusive fibroblast marker in both sexes. Due to its multiorgan translational potential, GUCY1α1 might provide a novel promising strategy to specifically target and mechanistically examine fibroblasts.

A novel model of cardiovascular-kidney-metabolic syndrome combining unilateral nephrectomy and high-salt-sugar-fat diet in mice

The aim of this study was to explore biological interaction and pathophysiology mechanisms in a new mouse model of cardiovascular-kidney-metabolic (CKM) syndrome, induced by chronic moderate renal failure in combination with consumption of a customized Western diet rich in carbohydrates, fat and salt. Male C57BL/6J mice were subjected to unilateral nephrectomy, fed a customized Western diet rich not only in sugar and fat but also in salt, and followed for 12 weeks or 20 weeks. Sham-operated mice on a standard chow served as healthy controls. Body composition, weight gain, glucose metabolism, fat distribution, blood pressure, cardiac function, vascular reactivity, renal function, inflammation and mitochondrial function were measured and combined with biochemical and histopathological analyses. The novel triple-hit model of CKM syndrome showed signs and symptoms of metabolic syndrome, disturbed glucose metabolism, impaired adipocyte physiology and fat redistribution, cardiovascular dysfunction, renal damage and dysfunction, systemic inflammation, elevated blood pressure and cardiac remodeling. The pathological changes were more pronounced in mice after prolonged exposure for 20 weeks, but no deaths occurred. In the present mouse model of CKM syndrome, profound and significant metabolic, cardiac, vascular and renal dysfunctions and injuries emerged by using a Western diet rich not only in fat and carbohydrates but also in salt. This multisystem disease model could be used for mechanistic studies and the evaluation of new therapeutic strategies.

The clinical efficacy of cGMP-specific sildenafil on mitochondrial biogenesis induction and renal damage in cats with acute on chronic kidney disease

BACKGROUND

Mitochondrial biogenesis (MB) induction has recently emerged as potential therapeutic approaches in kidney pathology and the mitochondria-targeted therapies should be investigated to improve treatment of animals with kidney diseases. This study aimed to investigate the effects of MB induction with sildenafil citrate on the cGMP/NO pathway, glomerular filtration, and reduction of kidney damage and fibrosis (TGF-β/SMAD pathway) in cats with acute on chronic kidney disease (ACKD). Thirty-three cats were divided into the non-azotemic (healthy) group (n:8) and the ACKD group (n:25), comprising different breeds, sexes, and ages. Sildenafil citrate was administered to the non-azotemic and ACKD groups (2.5 mg/kg, PO, q12 hours) for 30 days. Serum and urine NO, MDA, NGAL, KIM-1, TGF-β1, IL-18, FGF 23, PGC-1α and cGMP concentrations were measured.

RESULTS

Serum cGMP concentrations increased (P < 0.05) in the non-azotemic group during the 2nd (median 475.99 pmol/mL) and 3rd (median 405.01 pmol/mL) weeks of the study, whereas serum cGMP concentrations decreased in the ACKD group during the 4th(median 188.52 pmol/mL) week compared to the non-azotemic group (P < 0.05). No difference was observed in serum biomarker concentrations except NO, which increased in the 4th week (P < 0.05). The urinary concentrations of NO, MDA, PGC-1α, TGF-β1, NGAL, KIM-1, IL-18, and FGF 23 in the ACKD group were found to be higher compared to those in the non-azotemic group from the 1st to the 4th week (P  < 0.05). In the ACKD group, the urine PGC-1α concentration in the 2nd (median 6.10 ng/mL) week was lower compared to that in the 0 and 1st (median 7.65 and 7.21 ng/mL, respectively) week, and the NO concentration in the 3rd (median 28.94 µmol/mL) week was lower than that in the 0th (median 37.43 µmol/mL) week (P < 0.05).

CONCLUSIONS

While sildenafil citrate has been determined to induce a low level of MB and to have a beneficial effect on glomerular filtration, it is observed to be ineffective in mitigating renal damage and fibrosis via the TGF-β/SMAD pathway in cats with ACKD.

Sivelestat Sodium Alleviates Ischemia-Reperfusion-Induced Acute Kidney Injury via Suppressing TLR4/Myd88/NF-κB Signaling Pathway in Mice

Purpose

We aim to detect the effects of sivelestat on renal ischemia-reperfusion associated with AKI and also explore the underlying mechanism.

Materials and Methods

Mice, aged between 8 and 12 weeks, were randomly allocated among four distinct groups, respectively normal saline sham group(C), normal saline surgery group(I), sivelestat (50 mg/kg) sham group(S), sivelestat (50 mg/kg) surgery group(SI) (n=6, each group). In the surgical groups, the renal pedicles of mice were clamped with non-traumatic micro-aneurysm clamps, resulting in ischemia of the kidneys for 45 minutes. This was followed by a period of reperfusion lasting 24 hours. Sham group mice underwent the identical surgery produced without clamping renal pedicles. Mice blood was obtained from eyeballs, and Serum creatinine and blood urea nitrogen levels were measured. After a 24-hour period of reperfusion, the mice were euthanized, and their kidneys were gathered for various analyses, including Western Blot (WB) analysis, RT-PCR, immunofluorescence (IF), hematoxylin and eosin (H&E) staining, and Tunel assay.

Results

Pretreatments with sivelestat decreased renal Neutrophil elastase (NE), serum creatinine, and blood urea nitrogen levels after renal ischemia-reperfusion. Sivelestat also reduced histological damage and cell apoptosis in kidneys following ischemia-reperfusion injury (IRI). In addition, the sivelestat administration diminished the levels of mRNA expression of interleukin 6 (IL-6), Macrophage inflammatory protein-2 (MIP-2), monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor (TNF)-α in the kidneys during IRI. The kidney tissues of the SI group had significantly mitigated TLR4, Myd88, and NF-κB p-p65 protein expression levels compared to the I group (all P<0.05).

Conclusion

We demonstrated a previously unidentified mechanism that sivelestat effectively attenuates AKI-induced renal dysfunction, possibly through suppressing the TLR4/Myd88/ NF-κB pathway.

Experimental models for preclinical research in kidney disease

Acute kidney injury (AKI) and chronic kidney disease (CKD) are significant public health issues associated with a long-term increase in mortality risk, resulting from various etiologies including renal ischemia, sepsis, drug toxicity, and diabetes mellitus. Numerous preclinical models have been developed to deepen our understanding of the pathophysiological mechanisms and therapeutic approaches for kidney diseases. Among these, rodent models have proven to be powerful tools in the discovery of novel therapeutics, while the development of kidney organoids has emerged as a promising advancement in the field. This review provides a comprehensive analysis of the construction methodologies, underlying biological mechanisms, and recent therapeutic developments across different AKI and CKD models. Additionally, this review summarizes the advantages, limitations, and challenges inherent in these preclinical models, thereby contributing robust evidence to support the development of effective therapeutic strategies.

Deficiency of flavin-containing monooxygenase 3 protects kidney function after ischemia-reperfusion in mice

The kidney is vulnerable to ischemia and reperfusion (I/R) injury that can be fatal after major surgery. Currently, there are no effective treatments for I/R-induced kidney injury. Trimethylamine N-oxide (TMAO) is a gut-derived metabolite linked to many diseases, but its role in I/R-induced kidney injury remains unclear. Here, our clinical data reveals an association between preoperative systemic TMAO levels and postoperative kidney injury in patients after post-cardiopulmonary bypass surgery. By genetic deletion of TMAO-producing enzyme flavin-containing monooxygenase 3 (FMO3) and dietary supplementation of choline to modulate TMAO levels, we found that TMAO aggravated acute kidney injury through the triggering of endoplasmic reticulum (ER) stress and worsened subsequent renal fibrosis through TGFβ/Smad signaling activation. Together, our study underscores the negative role of TMAO in I/R-induced kidney injury and highlights the therapeutic potential through the modulation of TMAO levels by targeting FMO3, thereby mitigating acute kidney injury and preventing subsequent renal fibrosis.

Gucy1α1 specifically marks kidney, heart, lung and liver fibroblasts

Fibrosis is a common outcome of numerous pathologies, including chronic kidney disease (CKD), a progressive renal function deterioration. Current approaches to target activated fibroblasts, key effector contributors to fibrotic tissue remodeling, lack specificity. Here, we report Gucy1α1 as a specific kidney fibroblast marker. Gucy1α1 levels significantly increased over the course of two clinically relevant murine CKD models and directly correlated with established fibrosis markers. Immunofluorescent (IF) imaging showed that Gucy1α1 comprehensively labelled cortical and medullary quiescent and activated fibroblasts in the control kidney and throughout injury progression, respectively. Unlike traditionally used markers platelet derived growth factor receptor beta (Pdgfrβ) and vimentin (Vim), Gucy1α1 did not overlap with off-target populations such as podocytes. Notably, Gucy1α1 labelled kidney fibroblasts in both male and female mice. Furthermore, we observed elevated GUCY1α1 expression in the human fibrotic kidney and lung. Studies in the murine models of cardiac and liver fibrosis revealed Gucy1α1 elevation in activated Pdgfrβ-, Vim- and alpha smooth muscle actin (αSma)-expressing fibroblasts paralleling injury progression and resolution. Overall, we demonstrate Gucy1α1 as an exclusive fibroblast marker in both sexes. Due to its multiorgan translational potential, GUCY1α1 might provide a novel promising strategy to specifically target and mechanistically examine fibroblasts.

PTEN in kidney diseases: a potential therapeutic target in preventing AKI-to-CKD transition

Renal fibrosis, a critical factor in the development of chronic kidney disease (CKD), is predominantly initiated by acute kidney injury (AKI) and subsequent maladaptive repair resulting from pharmacological or pathological stimuli. Phosphatase and tensin homolog (PTEN), also known as phosphatase and tensin-associated phosphatase, plays a pivotal role in regulating the physiological behavior of renal tubular epithelial cells, glomeruli, and renal interstitial cells, thereby preserving the homeostasis of renal structure and function. It significantly impacts cell proliferation, apoptosis, fibrosis, and mitochondrial energy metabolism during AKI-to-CKD transition. Despite gradual elucidation of PTEN's involvement in various kidney injuries, its specific role in AKI and maladaptive repair after injury remains unclear. This review endeavors to delineate the multifaceted role of PTEN in renal pathology during AKI and CKD progression along with its underlying mechanisms, emphasizing its influence on oxidative stress, autophagy, non-coding RNA-mediated recruitment and activation of immune cells as well as renal fibrosis. Furthermore, we summarize prospective therapeutic targeting strategies for AKI and CKD-treatment related diseases through modulation of PTEN.

Galectin-8 counteracts folic acid-induced acute kidney injury and prevents its transition to fibrosis

Acute kidney injury (AKI), characterized by a sudden decline in kidney function involving tubular damage and epithelial cell death, can lead to progressive tissue fibrosis and chronic kidney disease due to interstitial fibroblast activation and tissue repair failures that lack direct treatments. After an AKI episode, surviving renal tubular cells undergo cycles of dedifferentiation, proliferation and redifferentiation while fibroblast activity increases and then declines to avoid an exaggerated extracellular matrix deposition. Appropriate tissue recovery versus pathogenic fibrotic progression depends on fine-tuning all these processes. Identifying endogenous factors able to affect any of them may offer new therapeutic opportunities to improve AKI outcomes. Galectin-8 (Gal-8) is an endogenous carbohydrate-binding protein that is secreted through an unconventional mechanism, binds to glycosylated proteins at the cell surface and modifies various cellular activities, including cell proliferation and survival against stress conditions. Here, using a mouse model of AKI induced by folic acid, we show that pre-treatment with Gal-8 protects against cell death, promotes epithelial cell redifferentiation and improves renal function. In addition, Gal-8 decreases fibroblast activation, resulting in less expression of fibrotic genes. Gal-8 added after AKI induction is also effective in maintaining renal function against damage, improving epithelial cell survival. The ability to protect kidneys from injury during both pre- and post-treatments, coupled with its anti-fibrotic effect, highlights Gal-8 as an endogenous factor to be considered in therapeutic strategies aimed at improving renal function and mitigating chronic pathogenic progression.

Lipolysis-Stimulated Lipoprotein Receptor in Proximal Tubule, BMP-SMAD Signaling, and Kidney Disease

Key Points

Background

Lipolysis-stimulated lipoprotein receptor (LSR) is a single-pass membrane protein that plays essential roles in tricellular tight junction organization in the epithelium and endothelium, but its function in kidney physiology and disease development remains unknown.

Methods

Conditional Lsr deletion mice were generated and analyzed to investigate the function of LSR in proximal tubule. Unilateral ischemia-reperfusion was used as an injury model to investigate the role of LSR in AKI and the progression to CKD. Detailed mechanistic analyses were conducted using whole-transcriptome RNA sequencing, immunofluorescence, dual-luciferase reporter gene assay, coimmunoprecipitation, RNA immunoprecipitation, and adeno-associated virus-mediated gene overexpression and knockdown.

Results

The nuclear localization of LSR was found in the kidney. Proximal tubule–specific Lsr knockout mice exhibited alleviated kidney damage and fibrosis compared with those in wild-type mice in response unilateral ischemia-reperfusion injury. Loss of LSR resulted in downregulation of Chrdl1 and activation of bone morphogenetic protein (BMP)-mothers against decapentaplegic homolog (SMAD) signaling in proximal tubules. Treatment with CHRDL1 counteracted the protective effect of LSR deletion in the unilaterally ischemic injured kidney. In addition, the systemic delivery of Chrdl1 short hairpin RNA attenuated injury-induced kidney fibrosis. LSR formed a complex with 14-3-3θ in the nucleus of proximal tubular cells, thereby reducing the interaction between human antigen R and 14-3-3θ, consequently leading to the translocation of unbound human antigen R to the cytoplasm. The absence of LSR promoted the association of 14-3-3θ with human antigen R, potentially resulting in decreased human antigen R levels in the cytoplasm. Reduced human antigen R levels impaired Chrdl1 mRNA stability, subsequently leading to the activation of BMP-SMAD signaling.

Conclusions

Deletion of LSR in proximal tubule deregulated Chrdl1 to activate BMP-SMAD signaling and ameliorated kidney disease.

ISG15 accelerates acute kidney injury and the subsequent AKI-to-CKD transition by promoting TGFβR1 ISGylation

Rationale: Acute kidney injury (AKI) has substantial rates of mortality and morbidity, coupled with an absence of efficacious treatment options. AKI commonly transits into chronic kidney disease (CKD) and ultimately culminates in end-stage renal failure. The interferon-stimulated gene 15 (ISG15) level was upregulated in the kidneys of mice injured by ischemia-reperfusion injury (IRI), cisplatin, or unilateral ureteral obstruction (UUO), however, its role in AKI development and subsequent AKI-to-CKD transition remains unknown. Methods: Isg15 knockout (Isg15 KO) mice challenged with bilateral or unilateral IRI, cisplatin, or UUO were used to investigate its role in AKI. We established cellular models with overexpression or knockout of ISG15 and subjected them to hypoxia-reoxygenation, cisplatin, or transforming growth factor- β1 (TGF-β1) stimulation. Renal RNA-seq data obtained from AKI models sourced from public databases and our studies, were utilized to examine the expression profiles of ISG15 and its associated genes. Additionally, published single cell RNA-seq data from human kidney allograft biopsies and mouse IRI model were analyzed to investigate the expression patterns of ISG15 and the type I TGF-β receptor (TGFβR1). Western blotting, qPCR, co-immunoprecipitation, and immunohistochemical staining assays were performed to validate our findings. Results: Alleviated pathological injury and renal function were observed in Isg15 KO mice with IRI-, cisplatin-, or UUO-induced AKI and the following AKI-to-CKD transition. In hypoxia-reoxygenation, cisplatin or TGF-β1 treated HK-2 cells, knockout ISG15 reduced stimulus-induced cell fibrosis, while overexpression of ISG15 with modification capacity exacerbated cell fibrosis. Immunoprecipitation assays demonstrated that ISG15 promoted ISGylation of TGFβR1, and inhibited its ubiquitination. Moreover, knockout of TGFβR1 blocked ISG15's fibrosis-exacerbating effect in HK-2 cells, while overexpression of TGFβR1 abolished the renal protective effect of ISG15 knockout during IRI-induced kidney injury. Conclusions: ISG15 plays an important role in the development of AKI and subsequent AKI-to-CKD transition by promoting TGFβR1 ISGylation.

Nephron-Specific Lin28A Overexpression Triggers Severe Inflammatory Response and Kidney Damage

The RNA-binding proteins LIN28A and LIN28B contribute to a variety of developmental biological processes. Dysregulation of Lin28A and Lin28B expression is associated with numerous types of tumors. This study demonstrates that Lin28A overexpression in the mouse nephrons leads to severe inflammation and kidney damage rather than to tumorigenesis. Notably, Lin28A overexpression causes inflammation only when expressed in nephrons, but not in the stromal cells of the kidneys, highlighting its cell context-dependent nature. The nephron-specific Lin28A-induced inflammatory response differs from previously described Lin28B-mediated inflammatory feedback loops as it is IL-6 independent. Instead, it is associated with the rapid upregulation of cytokines like Cxcl1 and Ccl2. These findings suggest that the pathophysiological effects of Lin28A overexpression extend beyond cell transformation. Our transgenic mouse model offers a valuable tool for advancing our understanding of the pathophysiology of acute kidney injury, where inflammation is a key factor.

DNA methylation of miR-181a-5p mediated by DNMT3b drives renal interstitial fibrosis developed from acute kidney injury

Aim: To explore the role of miR-181a-5p in the progression of acute kidney injury (AKI) to renal interstitial fibrosis (RIF) from the perspective of DNA methylation.Materials & methods: The role of miR-181a-5p was confirmed by collecting clinical samples, injecting miR-181a-5p agomir into tail vein, and transfecting miR-181a-5p mimic in vitro. The mechanism of miR-181a-5p's influence on AKI induced RIF was investigated by methylation-specific PCR, bioinformatic analysis, transcriptome sequencing and so on.Results: MiR-181a-5p plays an important role in AKI induced RIF. DNMT3b-mediated miR-181a-5p promoter hypermethylation is the main reason for the downregulation of miR-181a-5p. HDAC9 and SNAI2 are direct targets of miR-181a-5p.Conclusion: Hypermethylation of miR-181a-5p promoter mediated by DNMT3b promotes AKI induced RIF by targeting HDAC9 and SNAI2.

Intestinal CXCR6+ ILC3s migrate to the kidney and exacerbate renal fibrosis via IL-23 receptor signaling enhanced by PD-1 expression

Group 3 innate lymphoid cells (ILC3s) regulate inflammation and tissue repair at mucosal sites, but whether these functions pertain to other tissues-like the kidneys-remains unclear. Here, we observed that renal fibrosis in humans was associated with increased ILC3s in the kidneys and blood. In mice, we showed that CXCR6+ ILC3s rapidly migrated from the intestinal mucosa and accumulated in the kidney via CXCL16 released from the injured tubules. Within the fibrotic kidney, ILC3s increased the expression of programmed cell death-1 (PD-1) and subsequent IL-17A production to directly activate myofibroblasts and fibrotic niche formation. ILC3 expression of PD-1 inhibited IL-23R endocytosis and consequently amplified the JAK2/STAT3/RORγt/IL-17A pathway that was essential for the pro-fibrogenic effect of ILC3s. Thus, we reveal a hitherto unrecognized migration pathway of ILC3s from the intestine to the kidney and the PD-1-dependent function of ILC3s in promoting renal fibrosis.

TRPC6 Knockout Alleviates Renal Fibrosis through PI3K/AKT/GSK3B Pathway

OBJECTIVE

Renal fibrosis is the ultimate pathway of various forms of acute and chronic kidney damage. Notably, the knockout of transient receptor potential channel 6 (TRPC6) has shown promise in alleviating renal fibrosis. However, the regulatory impact of TRPC6 on renal fibrosis remains unclear.

METHODS

In vivo, TRPC6 knockout (TRPC6-/-) mice and age-matched 129 SvEv (WT) mice underwent unilateral renal ischemia-reperfusion (uIR) injury surgery on the left renal pedicle or sham operation. Kidneys and serum were collected on days 7, 14, 21, and 28 after euthanasia. In vitro, primary tubular epithelial cells (PTECs) were isolated from TRPC6-/- and WT mice, followed by treatment with transforming growth factor β1 (TGFβ1) for 72 h. The anti-fibrotic effect of TRPC6-/- and the underlying mechanisms were assessed through hematoxylin-eosin staining, Masson staining, immunostaining, qRT-PCR, and Western blotting.

RESULTS

Increased TRPC6 expression was observed in uIR mice and PTECs treated with TGFβ1. TRPC6-/- alleviated renal fibrosis by reducing the expression of fibrotic markers (Col-1, α-SMA, and vimentin), as well as decreasing the apoptosis and inflammation of PTECs during fibrotic progression both in vivo and in vitro. Additionally, we found that the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/glycogen synthase kinase 3 beta (GSK3β) signaling pathway, a pivotal player in renal fibrosis, was down-regulated following TRPC6 deletion.

CONCLUSION

These results suggest that the ablation of TRPC6 may mitigate renal fibrosis by inhibiting the apoptosis and inflammation of PTECs through down-regulation of the PI3K/AKT/GSK3β pathway. Targeting TRPC6 could be a novel therapeutic strategy for preventing chronic kidney disease.

Double-negative T cells have a reparative role after experimental severe ischemic acute kidney injury

T cells mediate organ injury and repair. A proportion of unconventional kidney T cells called double-negative (DN) T cells (TCR+ CD4- CD8-), with anti-inflammatory properties, were previously demonstrated to protect from early injury in moderate experimental acute kidney injury (AKI). However, their role in repair after AKI has not been studied. We hypothesized that DN T cells mediate repair after severe AKI. C57B6 mice underwent severe (40 min) unilateral ischemia-reperfusion injury (IRI). Kidney DN T cells were studied by flow cytometry and compared with gold-standard anti-inflammatory CD4+ regulatory T cells (Tregs). In vitro effects of DN T cells and Tregs on renal tubular epithelial cell (RTEC) repair after injury were quantified with live-cell analysis. DN T cells, Tregs, CD4, or vehicle were adoptively transferred after severe AKI. Glomerular filtration rate (GFR) was measured using fluorescein isothiocyanate (FITC)-sinistrin. Fibrosis was assessed with Masson's trichrome staining. Profibrotic genes were measured with qRT-PCR. Percentages and the numbers of DN T cells substantially decreased during repair phase after severe AKI, as well as their activation and proliferation. Both DN T cells and Tregs accelerated RTEC cell repair in vitro. Post-AKI transfer of DN T cells reduced kidney fibrosis and improved GFR, as did Treg transfer. DN T cell transfer lowered transforming growth factor (TGF)β1 and α-smooth muscle actin (αSMA) expression. DN T cells reduced effector-memory CD4+ T cells and IL-17 expression. DN T cells undergo quantitative and phenotypical changes after severe AKI, accelerate RTEC repair in vitro as well as improve GFR and renal fibrosis in vivo. DN T cells have potential as immunotherapy to accelerate repair after AKI.NEW & NOTEWORTHY Double-negative (DN) T cells (CD4- CD8-) are unconventional kidney T cells with regulatory abilities. Their role in repair from acute kidney injury (AKI) is unknown. Kidney DN T cell population decreased during repair after ischemic AKI, in contrast to regulatory T cells (Tregs) which increased. DN T cell administration accelerated tubular repair in vitro, while after severe in vivo ischemic injury reduced kidney fibrosis and increased glomerular filtration rate (GFR). DN T cell infusion is a potential therapeutic agent to improve outcome from severe AKI.

Hippo pathway activated by circulating reactive oxygen species mediates cardiac diastolic dysfunction after acute kidney injury

Acute kidney injury (AKI) can cause distal cardiac dysfunction; however, the underlying mechanism is unknown. Oxidative stress is proved prominent in AKI-induced cardiac dysfunction, and a possible bridge role of oxidative-stress products in cardio-renal interaction has been reported. Therefore, this study aimed to investigate the critical role of circulating reactive oxygen species (ROS) in mediating cardiac dysfunction after bilateral renal ischemia-reperfusion injury (IRI). We observed the diastolic dysfunction in the mice following renal IRI, accompanied by reduced ATP levels, oxidative stress, and branched-chain amino acids (BCAA) accumulation in the heart. Notably, ROS levels showed a sequential increase in the kidneys, circulation, and heart. Treatment with tempol, an ROS scavenger, significantly restored cardiac diastolic function in the renal IRI mice, corroborating the bridge role of circulating ROS. Accumulating evidence has identified oxidative stress as upstream of Mst1/Hippo in cardiac injury, which could regulate the expression of downstream genes related to mitochondrial quality control, leading to lower ATP, higher ROS and metabolic disorder. To verify this, we examined the activation of the Mst1/Hippo pathway in the heart of renal IRI mice, which was alleviated by tempol treatment as well. In vitro, analysis revealed that Mst1-knockdown cardiomyocytes could be activated by hydrogen peroxide (H2O2). Analysis of Mst1-overexpression cardiomyocytes confirmed the critical role of the Mst1/Hippo pathway in oxidative stress and BCAA dysmetabolism. Therefore, our results indicated that circulating ROS following renal IRI activates the Mst1/Hippo pathway of myocardium, leading to cardiac oxidative stress and diastolic dysfunction. This finding provides new insights for the clinical exploration of improved treatment options for cardiorenal syndrome.

miR-486-5p protects against rat ischemic kidney injury and prevents the transition to chronic kidney disease and vascular dysfunction

AIM

Acute kidney injury (AKI) increases the risk for progressive chronic kidney disease (CKD). MicroRNA (miR)-486-5p protects against kidney ischemia-reperfusion (IR) injury in mice, although its long-term effects on the vasculature and development of CKD are unknown. We studied whether miR-486-5p would prevent the AKI to CKD transition in rat, and affect vascular function.

METHODS

Adult male rats were subjected to bilateral kidney IR followed by i.v. injection of liposomal-packaged miR-486-5p (0.5 mg/kg). Kidney function and histologic injury were assessed after 24 h and 10 weeks. Kidney endothelial protein levels were measured by immunoblot and immunofluorescence, and mesenteric artery reactivity was determined by wire myography.

RESULTS

In rats with IR, miR-486-5p blocked kidney endothelial cell increases in intercellular adhesion molecule-1 (ICAM-1), reduced neutrophil infiltration and histologic injury, and normalized plasma creatinine (P<0.001). However, miR-486-5p attenuated IR-induced kidney endothelial nitric oxide synthase (eNOS) expression (P<0.05). At 10 weeks, kidneys from rats with IR alone had decreased peritubular capillary density and increased interstitial collagen deposition (P<0.0001), and mesenteric arteries showed impaired endothelium-dependent vasorelaxation (P<0.001). These changes were inhibited by miR-486-5p. Delayed miR-486-5p administration (96 h, 3 weeks after IR) had no impact on kidney fibrosis, capillary density, or endothelial function.

CONCLUSION

In rats, administration of miR-486-5p early after kidney IR prevents injury, and protects against CKD development and systemic endothelial dysfunction. These protective effects are associated with inhibition of endothelial ICAM-1 and occur despite reduction in eNOS. miR-486-5p holds promise for the prevention of ischemic AKI and its complications.

Gucy1α1 specifically marks kidney, heart, lung and liver fibroblasts

Fibrosis is a common outcome of numerous pathologies, including chronic kidney disease (CKD), a progressive renal function deterioration. Current approaches to target activated fibroblasts, key effector contributors to fibrotic tissue remodeling, lack specificity. Here, we report Gucy1α1 as a specific kidney fibroblast marker. Gucy1α1 levels significantly increased over the course of two clinically relevant murine CKD models and directly correlated with established fibrosis markers. Immunofluorescent (IF) imaging showed that Gucy1α1 comprehensively labelled cortical and medullary quiescent and activated fibroblasts in the control kidney and throughout injury progression, respectively. Unlike traditionally used markers platelet derived growth factor receptor beta (Pdgfrβ) and vimentin (Vim), Gucy1α1 did not overlap with off-target populations such as podocytes. Notably, Gucy1α1 labelled kidney fibroblasts in both male and female mice. Furthermore, we observed elevated GUCY1α1 expression in the human fibrotic kidney and lung. Studies in the murine models of cardiac and liver fibrosis revealed Gucy1α1 elevation in activated Pdgfrβ-, Vim- and alpha smooth muscle actin (αSma)-expressing fibroblasts paralleling injury progression and resolution. Overall, we demonstrate Gucy1α1 as an exclusive fibroblast marker in both sexes. Due to its multiorgan translational potential, GUCY1α1 might provide a novel promising strategy to specifically target and mechanistically examine fibroblasts.

Recent Update on Acute Kidney Injury-to-Chronic Kidney Disease Transition

Acute kidney injury (AKI) is characterized by an abrupt decline of excretory kidney function. The incidence of AKI has increased in the past decades. Patients diagnosed with AKI often undergo diverse clinical trajectories, such as early or late recovery, relapses, and even a potential transition from AKI to chronic kidney disease (CKD). Although recent clinical studies have demonstrated a strong association between AKI and progression of CKD, our understanding of the complex relationship between AKI and CKD is still evolving. No cohort study has succeeded in painting a comprehensive picture of these multi-faceted pathways. To address this lack of understanding, the idea of acute kidney disease (AKD) has recently been proposed. This presents a new perspective to pinpoint a period of heightened vulnerability following AKI, during which a patient could witness a substantial decline in glomerular filtration rate, ultimately leading to CKD transition. Although AKI is included in a range of kidney conditions collectively known as AKD, spanning from mild and self-limiting to severe and persistent, AKD can also occur without a rapid onset usually seen in AKI, such as when kidney dysfunction slowly evolves. In the present review, we summarize the most recent findings about AKD, explore the current state of biomarker discovery related to AKD, discuss the latest insights into pathophysiological underpinnings of AKI to CKD transition, and reflect on therapeutic challenges and opportunities that lie ahead.

<sc>A</sc> multi-hierarchical approach reveals <sc>d</sc>-serine as a hidden substrate of sodium-coupled monocarboxylate transporters

Transporter research primarily relies on the canonical substrates of well-established transporters. This approach has limitations when studying transporters for the low-abundant micromolecules, such as micronutrients, and may not reveal physiological functions of the transporters. While d-serine, a trace enantiomer of serine in the circulation, was discovered as an emerging biomarker of kidney function, its transport mechanisms in the periphery remain unknown. Here, using a multi-hierarchical approach from body fluids to molecules, combining multi-omics, cell-free synthetic biochemistry, and ex vivo transport analyses, we have identified two types of renal d-serine transport systems. We revealed that the small amino acid transporter ASCT2 serves as a d-serine transporter previously uncharacterized in the kidney and discovered d-serine as a non-canonical substrate of the sodium-coupled monocarboxylate transporters (SMCTs). These two systems are physiologically complementary, but ASCT2 dominates the role in the pathological condition. Our findings not only shed light on renal d-serine transport, but also clarify the importance of non-canonical substrate transport. This study provides a framework for investigating multiple transport systems of various trace micromolecules under physiological conditions and in multifactorial diseases.

Pre-clinical evaluation of biomarkers for the early detection of nephrotoxicity following alpha-particle radioligand therapy

PURPOSE

Cancer treatment with alpha-emitter-based radioligand therapies (α-RLTs) demonstrates promising tumor responses. Radiolabeled peptides are filtered through glomeruli, followed by potential reabsorption of a fraction by proximal tubules, which may cause acute kidney injury (AKI) and chronic kidney disease (CKD). Because tubular cells are considered the primary site of radiopeptides' renal reabsorption and potential injury, the current use of kidney biomarkers of glomerular functional loss limits the evaluation of possible nephrotoxicity and its early detection. This study aimed to investigate whether urinary secretion of tubular injury biomarkers could be used as an additional non-invasive sensitive diagnostic tool to identify unrecognizable tubular damage and risk of long-term α-RLT nephrotoxicity.

METHODS

A bifunctional cyclic peptide, melanocortin 1 ligand (MC1L), labeled with [203Pb]Pb-MC1L, was used for [212Pb]Pb-MC1L biodistribution and absorbed dose measurements in CD-1 Elite mice. Mice were treated with [212Pb]Pb-MC1L in a dose-escalation study up to levels of radioactivity intended to induce kidney injury. The approach enabled prospective kidney functional and injury biomarker evaluation and late kidney histological analysis to validate these biomarkers.

RESULTS

Biodistribution analysis identified [212Pb]Pb-MC1L reabsorption in kidneys with a dose deposition of 2.8, 8.9, and 20 Gy for 0.9, 3.0, and 6.7 MBq injected [212Pb]Pb-MC1L doses, respectively. As expected, mice receiving 6.7 MBq had significant weight loss and CKD evidence based on serum creatinine, cystatin C, and kidney histological alterations 28 weeks after treatment. A dose-dependent urinary neutrophil gelatinase-associated lipocalin (NGAL, tubular injury biomarker) urinary excretion the day after [212Pb]Pb-MC1L treatment highly correlated with the severity of late tubulointerstitial injury and histological findings.

CONCLUSION

Urine NGAL secretion could be a potential early diagnostic tool to identify unrecognized tubular damage and predict long-term α-RLT-related nephrotoxicity.

Rodent models of AKI and AKI-CKD transition: an update in 2024

Despite known drawbacks, rodent models are essential tools in the research of renal development, physiology, and pathogenesis. In the past decade, rodent models have been developed and used to mimic different etiologies of acute kidney injury (AKI), AKI to chronic kidney disease (CKD) transition or progression, and AKI with comorbidities. These models have been applied for both mechanistic research and preclinical drug development. However, current rodent models have their limitations, especially since they often do not fully recapitulate the pathophysiology of AKI in human patients, and thus need further refinement. Here, we discuss the present status of these rodent models, including the pathophysiologic compatibility, clinical translational significance, key factors affecting model consistency, and their main limitations. Future efforts should focus on establishing robust models that simulate the major clinical and molecular phenotypes of human AKI and its progression.

The therapeutic effect of Picroside II in renal ischemia-reperfusion induced acute kidney injury: An experimental study

The microcirculation hemodynamics change and inflammatory response are the two main pathophysiological mechanisms of renal ischemia-reperfusion injury (IRI) induced acute kidney injury (AKI). The treatment of microcirculation hemodynamics and inflammatory response can effectively alleviate renal injury and correct renal function. Picroside II (P II) has a wide range of pharmacological effects. Still, there are few studies on protecting IRI-AKI, and whether P II can improve renal microcirculation perfusion is still being determined. This study aims to explore the protective effect of P II on IRI-AKI and evaluate its ability to enhance renal microcirculation perfusion. In this study, a bilateral renal IRI-AKI model in mice was established, and the changes in renal microcirculation and inflammatory response were quantitatively evaluated before and after P II intervention by contrast-enhanced ultrasound (CEUS). At the same time, serum and tissue markers were measured to assess the changes in renal function. The results showed that after P II intervention, the levels of serum creatinine (Scr), blood urea nitrogen (BUN), serum cystatin C (Cys-C), kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), malondialdehyde (MDA), and superoxide dismutase (SOD), as well as the time-to-peak (TTP), peak intensity (PI) and area under the curve (AUC), and the normalized intensity difference (NID) were all alleviated. In conclusion, P II can improve renal microcirculation perfusion changes caused by IRI-AKI, reduce inflammatory reactions during AKI, and enhance renal antioxidant stress capacity. P II may be a new and promising drug for treating IRI-AKI.

Remimazolam attenuates inflammation and kidney fibrosis following folic acid injury

The transition of acute kidney injury (AKI) to chronic kidney disease (CKD) is characterized by intense inflammation and progressive fibrosis. Remimazolam is widely used for procedural sedation in intensive care units, such as AKI patients. Remimazolam has been shown to possess anti-inflammatory and organ-protective properties. However, the role of remimazolam in inflammation and renal fibrosis following AKI remains unclear. Here, we explored the effects of remimazolam on the inflammatory response and kidney fibrogenesis of mice subjected to folic acid (FA) injury. Our results showed that remimazolam treatment alleviated kidney damage and dysfunction. Mice treated with remimazolam presented less collagen deposition in FA-injured kidneys compared with FA controls, which was accompanied by a reduction of extracellular matrix proteins accumulation and fibroblasts activation. Furthermore, remimazolam treatment reduced inflammatory cells infiltration into the kidneys of mice with FA injury and inhibited proinflammatory or profibrotic molecules expression. Finally, remimazolam treatment impaired the activation of bone marrow-derived fibroblasts and blunted the transformation of macrophages to myofibroblasts in FA nephropathy. Additionally, the benzodiazepine receptor antagonist PK-11195 partially reversed the protective effect of remimazolam on the FA-injured kidneys. Overall, remimazolam attenuates the inflammatory response and renal fibrosis development following FA-induced AKI, which may be related to the peripheral benzodiazepine receptor pathway.

Establishment of a novel mouse model of renal artery coiling-based chronic hypoperfusion-related kidney injury

Renal artery stenosis-induced chronic renal ischemia is an important cause of renal dysfunction, especially in older adults, and its incidence is currently increasing. To elucidate the mechanisms underlying chronic renal hypoperfusion-induced kidney damage, we developed a novel mouse model of renal artery coiling-based chronic hypoperfusion-related kidney injury. This model exhibits decreased renal blood flow and function, atrophy, and parenchymal injury in the coiled kidney, along with compensatory hypertrophy in the non-coiled kidney, without chronic hypertension. The availability of this mouse model, which can develop renal ischemia without genetic modification, will enhance kidney disease research by serving as a new tool to investigate the effects of acquired factors (e.g., obesity and aging) and genetic factors on renal artery stenosis-related renal parenchymal damage.

Therapeutic potential for renal fibrosis by targeting Smad3-dependent noncoding RNAs

Renal fibrosis is a characteristic hallmark of chronic kidney disease (CKD) that ultimately results in renal failure, leaving patients with few therapeutic options. TGF-β is a master regulator of renal fibrosis and mediates progressive renal fibrosis via both canonical and noncanonical signaling pathways. In the canonical Smad signaling, Smad3 is a key mediator in tissue fibrosis and mediates renal fibrosis via a number of noncoding RNAs (ncRNAs). In this regard, targeting Smad3-dependent ncRNAs may offer a specific therapy for renal fibrosis. This review highlights the significance and innovation of TGF-β/Smad3-associated ncRNAs as biomarkers and therapeutic targets in renal fibrogenesis. In addition, the underlying mechanisms of these ncRNAs and their future perspectives in the treatment of renal fibrosis are discussed.

Renal-specific loss of ferroportin disrupts iron homeostasis and attenuates recovery from acute kidney injury

Chronic kidney disease is increasing at an alarming rate and correlates with the increase in diabetes, obesity, and hypertension that disproportionately impact socioeconomically disadvantaged communities. Iron plays essential roles in many biological processes including oxygen transport, mitochondrial function, cell proliferation, and regeneration. However, excess iron induces the generation and propagation of reactive oxygen species, which lead to oxidative stress, cellular damage, and ferroptosis. Iron homeostasis is regulated in part by the kidney through iron resorption from the glomerular filtrate and exports into the plasma by ferroportin (FPN). Yet, the impact of iron overload in the kidney has not been addressed. To test more directly whether excess iron accumulation is toxic to kidneys, we generated a kidney proximal tubule-specific knockout of FPN. Despite significant intracellular iron accumulation in FPN mutant tubules, basal kidney function was not measurably different from wild type kidneys. However, upon induction of acute kidney injury (AKI), FPN mutant kidneys exhibited significantly more damage and failed recovery, evidence for ferroptosis, and increased fibrosis. Thus, disruption of iron export in proximal tubules, leading to iron overload, can significantly impair recovery from AKI and can contribute to progressive renal damage indicative of chronic kidney disease. Understanding the mechanisms that regulate iron homeostasis in the kidney may provide new therapeutic strategies for progressive kidney disease and other ferroptosis-associated disorders.NEW & NOTEWORTHY Physiological iron homeostasis depends in part on renal resorption and export into the plasma. We show that specific deletion of iron exporters in the proximal tubules sensitizes cells to injury and inhibits recovery. This can promote a chronic kidney disease phenotype. Our paper demonstrates the need for iron balance in the proximal tubules to maintain and promote healthy recovery after acute kidney injury.