Mechanisms of maladaptive repair after AKI leading to accelerated kidney ageing and CKD

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.

Role of triggering receptor expressed on myeloid cells-1 in kidney diseases: A biomarker and potential therapeutic target

ABSTRACT

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a member of the immunoglobulin superfamily. As an amplifier of the inflammatory response, TREM-1 is mainly involved in the production of inflammatory mediators and the regulation of cell survival. TREM-1 has been studied in infectious diseases and more recently in non-infectious disorders. More and more studies have shown that TREM-1 plays an important pathogenic role in kidney diseases. There is evidence that TREM-1 can not only be used as a biomarker for diagnosis of disease but also as a potential therapeutic target to guide the development of novel therapeutic agents for kidney disease. This review summarized molecular biology of TREM-1 and its signaling pathways as well as immune response in the progress of acute kidney injury, renal fibrosis, diabetic nephropathy, immune nephropathy, and renal cell carcinoma.

Preconditioning by Moderate-Intensity Exercise Prevents Gentamicin-Induced Acute Kidney Injury

A strict correlation among proximal tubule epithelial cell dysfunction, proteinuria, and modulation of the Renin-Angiotensin System and Kalikrein-Kinin System are crucial factors in the pathogenesis of Acute Kidney Injury (AKI). In this study, we investigated the potential protective effect of preconditioning by moderate-intensity aerobic exercise on gentamicin-induced AKI. Male Wistar rats were submitted to a moderate-intensity treadmill exercise protocol for 8 weeks, and then injected with 80 mg/kg/day s.c. gentamicin for 5 consecutive days. Four groups were generated: 1) NT+SAL (control); 2) NT+AKI (non-trained with AKI); 3) T+SAL (trained); and 4) T+AKI (trained with AKI). The NT+AKI group presented: 1) impairment in glomerular function parameters; 2) increased fractional excretion of Na + , K + , and water; 4) proteinuria and increased urinary γ-glutamyl transferase activity (a marker of tubular injury) accompanied by acute tubular necrosis; 5) an increased renal angiotensin-converting enzyme and bradykinin B1 receptor mRNA expression. Interestingly, the preconditioning by moderate-intensity aerobic exercise attenuated all alterations observed in gentamicin-induced AKI (T+AKI group). Taken together, our results show that the preconditioning by moderate-intensity aerobic exercise ameliorates the development of gentamicin-induced AKI. Our findings help to expand the current knowledge regarding the effect of physical exercise on kidneys during physiological and pathological conditions.

Pathological mechanisms of kidney disease in ageing

The kidney is a metabolically active organ that requires energy to drive processes such as tubular reabsorption and secretion, and shows a decline in function with advancing age. Various molecular mechanisms, including genomic instability, telomere attrition, inflammation, autophagy, mitochondrial function, and changes to the sirtuin and Klotho signalling pathways, are recognized regulators of individual lifespan and pivotal factors that govern kidney ageing. Thus, mechanisms that contribute to ageing not only dictate renal outcomes but also exert a substantial influence over life expectancy. Conversely, kidney dysfunction, in the context of chronic kidney disease (CKD), precipitates an expedited ageing trajectory in individuals, leading to premature ageing and a disconnect between biological and chronological age. As CKD advances, age-related manifestations such as frailty become increasingly conspicuous. Hence, the pursuit of healthy ageing necessitates not only the management of age-related complications but also a comprehensive understanding of the processes and markers that underlie systemic ageing. Here, we examine the hallmarks of ageing, focusing on the mechanisms by which they affect kidney health and contribute to premature organ ageing. We also review diagnostic methodologies and interventions for premature ageing, with special consideration given to the potential of emerging therapeutic avenues to target age-related kidney diseases.

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 β-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.

Loureirin C improves mitochondrial function by promoting NRF2 nuclear translocation to attenuate oxidative damage caused by renal ischemia-reperfusion injury

Acute kidney injury (AKI) is a common clinical syndrome worldwide, with no effective treatment strategy. Renal ischemia-reperfusion (IR) injury is one of the main AKI features, and the excessive reactive oxygen species (ROS) production during reperfusion causes severe oxidative damage to the kidney. Loureirin C (LC), an active ingredient in the traditional Chinese medicine Chinese dragon's blood, possesses excellent antioxidative properties, but its role in renal IR injury is not clear. In this study, we evaluated the protective effects of LC against renal IR injury in vivo and in vitro by establishing a mice renal IR injury model and a human proximal renal tubular epithelial cell (HK-2) hypoxia/reoxygenation (HR) model. We found that LC ameliorated renal function and tissue structure injury and inhibited renal oxidative stress and ferroptosis in vivo. In vitro, LC scavenged ROS and attenuated mitochondrial dysfunction in HK-2 cells, thereby inhibiting oxidative cellular injury. Furthermore, we found that LC effectively promoted nuclear factor erythroid 2-related factor 2 (NRF2) nuclear translocation and activated downstream target genes heme oxygenase 1 (HO-1) and NADPH quinone oxidoreductase-1 (NQO-1) to enhance cellular antioxidant function. Moreover, NRF2 knockdown and pharmacological inhibition of NRF2 partially eliminated the protective effect of LC. These results confirm that LC can effectively inhibit renal IR injury, and the mechanism may be associated with NRF2 activation by LC.

Acute kidney injury in patients with cirrhosis: Acute Disease Quality Initiative (ADQI) and International Club of Ascites (ICA) joint multidisciplinary consensus meeting

Patients with cirrhosis are prone to developing acute kidney injury (AKI), a complication associated with a markedly increased in-hospital morbidity and mortality, along with a risk of progression to chronic kidney disease. Whereas patients with cirrhosis are at increased risk of developing any phenotype of AKI, hepatorenal syndrome (HRS), a specific form of AKI (HRS-AKI) in patients with advanced cirrhosis and ascites, carries an especially high mortality risk. Early recognition of HRS-AKI is crucial since administration of splanchnic vasoconstrictors may reverse the AKI and serve as a bridge to liver transplantation, the only curative option. In 2023, a joint meeting of the International Club of Ascites (ICA) and the Acute Disease Quality Initiative (ADQI) was convened to develop new diagnostic criteria for HRS-AKI, to provide graded recommendations for the work-up, management and post-discharge follow-up of patients with cirrhosis and AKI, and to highlight priorities for further research.

Pediatric acute kidney injury and adverse health outcomes: using a foundational framework to evaluate a causal link

Acute kidney injury (AKI) is a major global health problem, expensive to manage, and its associations with negative pediatric health outcomes have been clearly demonstrated. One of the most fundamental questions to consider as we use previous epidemiological information to advance research and care paradigms is the strength of the causal link between pediatric AKI and health outcomes. In this review, we apply the foundational framework of the Bradford Hill criteria to evaluate the extent to which a causal link exists between AKI and the associated adverse outcomes in children. Available data in children support a causal link between AKI and short-term outcomes including mortality, length of stay, and ventilation time. Clarifying the causal nature of longer term associations requires further high-quality observational studies in children, careful consideration of what defines the most meaningful and measurable longer term outcomes after pediatric AKI, and integration of evolving biological data related to mechanisms of disease. Preventing or mitigating AKI should lead to improved outcomes. Demonstrating such reversibility will solidify confidence in the causal relationship, improve child health, and highlight an aspect which is highly relevant to clinicians, scientists, and policy makers.

From premature birth to premature kidney disease: does accelerated aging play a role?

As the limits of fetal viability have increased over the past 30 years, there has been a growing body of evidence supporting the idea that chronic disease should be taken into greater consideration in addition to survival after preterm birth. Accumulating evidence also suggests there is early onset of biologic aging after preterm birth. Similarly, chronic kidney disease (CKD) is also associated with a phenotype of advanced biologic age which exceeds chronologic age. Yet, significant knowledge gaps remain regarding the link between premature biologic age after preterm birth and kidney disease. This review summarizes the four broad pillars of aging, the evidence of premature aging following preterm birth, and in the setting of CKD. The aim is to provide additional plausible biologic mechanisms to explore the link between preterm birth and CKD. There is a need for more research to further elucidate the biologic mechanisms of the premature aging paradigm and kidney disease after preterm birth. Given the emerging research on therapies for premature aging, this paradigm could create pathways for prevention of advanced CKD.

IGF2BP3/NCBP1 complex inhibits renal tubular senescence through regulation of CDK6 mRNA stability

Renal aging and the subsequent rise in kidney-related diseases are attributed to senescence in renal tubular epithelial cells (RTECs). Our study revealed that the abnormal expression of insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3), a reader of RNA N6-methyladenosine, is critically involved in cisplatin-induced renal tubular senescence. In cisplatin-induced senescence of RTECs, the promoter activity and transcription of IGF2BP3 is markedly suppressed. It was due to the down regulation of MYC proto-oncogene (MYC), which regulates IGF2BP3 transcription by binding to the putative site at 1852-1863 of the IGF2BP3 promoter. Overexpression of IGF2BP3 ameliorated cisplatin-induced renal tubular senescence in vitro. Mechanistic studies revealed that IGF2BP3 inhibits cellular senescence in RTECs by enhancing cyclin-dependent kinase 6 (CDK6) mRNA stability and increasing its expression. The inhibition effect of IGF2BP3 on tubular senescence is partially reversed by the knockdown of CDK6. Further, IGF2BP3 recruits nuclear cap binding protein subunit 1 (NCBP1) and inhibits CDK6 mRNA decay, by recognizing m6A modification. Specifically, IGF2BP3 recognizes m6A motif "GGACU" at nucleotides 110-114 in the 5' untranslated region (UTR) field of CDK6 mRNA. The involvement of IGF2BP3/CDK6 in alleviating tubular senescence was confirmed in a cisplatin-induced acute kidney injury (AKI)-to-chronic kidney disease (CKD) model. Clinical data also suggests an age-related decrease in IGF2BP3 and CDK6 levels in renal tissue or serum samples from patients. These findings suggest that IGF2BP3/CDK6 may be a promising target in cisplatin-induced tubular senescence and renal failure.

Mendelian Randomization Analysis of Systemic Iron Status and Risk of Different Types of Kidney Disease

With rapid increases in incidence, diverse subtypes, and complicated etiologies, kidney disease remains a global public health problem. Iron, as an essential trace element, has pleiotropic effects on renal function and the progression of kidney diseases. A two-sample Mendelian randomization (MR) analysis was implemented to determine the potential causal effects between systemic iron status on different kidney diseases. Systemic iron status was represented by four iron-related biomarkers: serum iron, ferritin, transferrin saturation (TfSat), and total iron binding capacity (TIBC). For systemic iron status, 163,511, 246,139, 131,471, and 135,430 individuals were included in the genome-wide association study (GWAS) of serum iron, ferritin, TfSat, and TIBC, respectively. For kidney diseases, 653,143 individuals (15,658 cases and 637,485 controls), 657,076 individuals (8160 cases and 648,916 controls), and 659,320 individuals (10,404 cases and 648,916 controls) were included for immunoglobulin A nephropathy (IgAN), acute kidney disease (AKD), and chronic kidney disease (CKD), respectively. Our MR results showed that increased serum iron [odds ratio (OR): 1.10; 95% confidence interval (95% CI): 1.04, 1.16; p < 0.0042], ferritin (OR: 1.30; 95% CI: 1.14, 1.48; p < 0.0042), and TfSat (OR: 1.07; 95% CI: 1.04, 1.11; p < 0.0042)] and decreased TIBC (OR: 0.92; 95% CI: 0.88, 0.97; p < 0.0042) were associated with elevated IgAN risk. However, no significant associations were found between systemic iron status and AKD or CKD. In our MR study, the genetic evidence supports elevated systemic iron status as a causal effect on IgAN, which suggests a potential protective effect of iron chelation on IgAN patients.

Traditional Chinese Medicine and renal regeneration: experimental evidence and future perspectives

Repair of acute kidney injury (AKI) is a typical example of renal regeneration. AKI is characterized by tubular cell death, peritubular capillary (PTC) thinning, and immune system activation. After renal tubule injury, resident renal progenitor cells, or renal tubule dedifferentiation, give rise to renal progenitor cells and repair the damaged renal tubule through proliferation and differentiation. Mesenchymal stem cells (MSCs) also play an important role in renal tubular repair. AKI leads to sparse PTC, affecting the supply of nutrients and oxygen and indirectly aggravating AKI. Therefore, repairing PTC is important for the prognosis of AKI. The activation of the immune system is conducive for the body to clear the necrotic cells and debris generated by AKI; however, if the immune activation is too strong or lengthy, it will cause damage to renal tubule cells or inhibit their repair. Macrophages have been shown to play an important role in the repair of kidney injury. Traditional Chinese medicine (TCM) has unique advantages in the treatment of AKI and a series of studies have been conducted on the topic in recent years. Herein, the role of TCM in promoting the repair of renal injury and its molecular mechanism is discussed from three perspectives: repair of renal tubular epithelial cells, repair of PTC, and regulation of macrophages to provide a reference for the treatment and mechanistic research of AKI.

Critical roles of tubular mitochondrial ATP synthase dysfunction in maleic acid-induced acute kidney injury

Maleic acid (MA) induces renal tubular cell dysfunction directed to acute kidney injury (AKI). AKI is an increasing global health burden due to its association with mortality and morbidity. However, targeted therapy for AKI is lacking. Previously, we determined mitochondrial-associated proteins are MA-induced AKI affinity proteins. We hypothesized that mitochondrial dysfunction in tubular epithelial cells plays a critical role in AKI. In vivo and in vitro systems have been used to test this hypothesis. For the in vivo model, C57BL/6 mice were intraperitoneally injected with 400 mg/kg body weight MA. For the in vitro model, HK-2 human proximal tubular epithelial cells were treated with 2 mM or 5 mM MA for 24 h. AKI can be induced by administration of MA. In the mice injected with MA, the levels of blood urea nitrogen (BUN) and creatinine in the sera were significantly increased (p < 0.005). From the pathological analysis, MA-induced AKI aggravated renal tubular injuries, increased kidney injury molecule-1 (KIM-1) expression and caused renal tubular cell apoptosis. At the cellular level, mitochondrial dysfunction was found with increasing mitochondrial reactive oxygen species (ROS) (p < 0.001), uncoupled mitochondrial respiration with decreasing electron transfer system activity (p < 0.001), and decreasing ATP production (p < 0.05). Under transmission electron microscope (TEM) examination, the cristae formation of mitochondria was defective in MA-induced AKI. To unveil the potential target in mitochondria, gene expression analysis revealed a significantly lower level of ATPase6 (p < 0.001). Renal mitochondrial protein levels of ATP subunits 5A1 and 5C1 (p < 0.05) were significantly decreased, as confirmed by protein analysis. Our study demonstrated that dysfunction of mitochondria resulting from altered expression of ATP synthase in renal tubular cells is associated with MA-induced AKI. This finding provides a potential novel target to develop new strategies for better prevention and treatment of MA-induced AKI.

Proximal tubular FHL2, a novel downstream target of hypoxia inducible factor 1, is a protector against ischemic acute kidney injury

Four-and-a-half LIM domains protein 2 (FHL2) is an adaptor protein that may interact with hypoxia inducible factor 1α (HIF-1α) or β-catenin, two pivotal protective signaling in acute kidney injury (AKI). However, little is known about the regulation and function of FHL2 during AKI. We found that FHL2 was induced in renal tubular cells in patients with acute tubular necrosis and mice model of ischemia-reperfusion injury (IRI). In cultured renal proximal tubular cells (PTCs), hypoxia induced FHL2 expression and promoted the binding of HIF-1 to FHL2 promoter. Compared with control littermates, mice with PTC-specific deletion of FHL2 gene displayed worse renal function, more severe morphologic lesion, more tubular cell death and less cell proliferation, accompanying by downregulation of AQP1 and Na, K-ATPase after IRI. Consistently, loss of FHL2 in PTCs restricted activation of HIF-1 and β-catenin signaling simultaneously, leading to attenuation of glycolysis, upregulation of apoptosis-related proteins and downregulation of proliferation-related proteins during IRI. In vitro, knockdown of FHL2 suppressed hypoxia-induced activation of HIF-1α and β-catenin signaling pathways. Overexpression of FHL2 induced physical interactions between FHL2 and HIF-1α, β-catenin, GSK-3β or p300, and the combination of these interactions favored the stabilization and nuclear translocation of HIF-1α and β-catenin, enhancing their mediated gene transcription. Collectively, these findings identify FHL2 as a direct downstream target gene of HIF-1 signaling and demonstrate that FHL2 could play a critical role in protecting against ischemic AKI by promoting the activation of HIF-1 and β-catenin signaling through the interactions with its multiple protein partners.

Does cardiac impairment develop in ischemic renal surgery in rats depending on the reperfusion time?

Background

Renal dysfunction is known to cause heart failure. However, renal dysfunction associated with kidney surgeries (mediated by reperfusion injury) that affects the cardiac physiological function, especially during the recovery and repair phase of renal surgery is unknown.

Method

Male Wistar rats (238 ± 18 g) were subjected to renal sham and ischemia-reperfusion (IR-bilateral clamping for 15 min/45 min and reperfusion for 24 h/48 h/7 days) surgeries. At the end of the experiment, the heart was isolated from the animal (to exclude neurohormonal influence) and perfused for 60 min with Krebs-Hanseleit buffer to study the physiological changes.

Result

Renal artery bilateral occlusion for 45 min that creates ischemia, followed by 24 h of reperfusion did not impart any significant cardiac physiological functional decline but 48 h of reperfusion exhibited a significant decline in cardiac hemodynamic indices (Rate pressure product in x104 mmHg*beats/min: Sham- 3.53 ± 0.19, I45_R48-2.82 ± 0.21) with mild tissue injury. However, 7 days of reperfusion inflict significant physiological decline (Rate pressure product in x104 mmHg*beats/min - 2.5 ± 0.14) and tissue injury (Injury score- 4 ± 1.5) in isolated rat hearts. Interestingly, when the renal artery bilateral occlusion time was reduced to 15 min the changes in the hearts were negligible after 7 days. Cellular level exploration reveals a positive relation between functional deterioration of mitochondria and elevated mitochondrial oxidative stress and inflammation with cardiac physiological decline and injury linked with renal ischemia-reperfusion surgery.

Conclusion

Cardiac functional decline associated with renal surgery is manifested during renal repair or recovery. This decline depends on cardiac mitochondrial health, which is negatively influenced by the renal IR mediators and kidney function.

Renoprotective effects of laxative linaclotide: Inhibition of acute kidney injury and fibrosis in a rat model of renal ischemia-reperfusion

Ischemia-reperfusion (I/R) leads to tissue damage in transplanted kidneys, resulting in acute kidney injury (AKI) and chronic graft dysfunction, which critically compromises transplant outcomes, such as graft loss. Linaclotide, a guanylate cyclase C agonist clinically approved as a laxative, has recently been identified to exhibit renoprotective effects in a chronic kidney disease (CKD) model. This study evaluates the therapeutic effects of linaclotide on AKI triggered by I/R in a rat model with an initial comparison with other laxatives. Here, we show that linaclotide administration resulted in substantial reduction in serum creatinine levels, reflective of enhanced renal function. Histological examination revealed diminished tubular damage, and Sirius Red staining confirmed less collagen deposition, collectively indicating preserved structural integrity and mitigation of fibrosis. Further analysis demonstrated lowered expression of TGF-β and associated fibrotic markers, α-SMA, MMP2, and TIMP1, implicating the downregulation of the fibrogenic TGF-β pathway by linaclotide. Furthermore, one day after I/R insult, linaclotide profoundly diminished macrophage infiltration and suppressed critical pro-inflammatory cytokines such as TNF, IL-1β, and IL-6, signifying its potential to disrupt initial inflammatory mechanisms integral to AKI pathology. These findings suggest that linaclotide, with its established safety profile, could extend its benefits beyond gastrointestinal issues and potentially serve as a therapeutic intervention for organ transplantation. Additionally, it could provide immediate and practical insights into selecting laxatives for managing patients with AKI or CKD, regardless of the cause, and for those receiving dialysis or transplant therapy.

Identification of ligand and receptor interactions in CKD and MASH through the integration of single cell and spatial transcriptomics

BACKGROUND

Chronic Kidney Disease (CKD) and Metabolic dysfunction-associated steatohepatitis (MASH) are metabolic fibroinflammatory diseases. Combining single-cell (scRNAseq) and spatial transcriptomics (ST) could give unprecedented molecular disease understanding at single-cell resolution. A more comprehensive analysis of the cell-specific ligand-receptor (L-R) interactions could provide pivotal information about signaling pathways in CKD and MASH. To achieve this, we created an integrative analysis framework in CKD and MASH from two available human cohorts.

RESULTS

The analytical framework identified L-R pairs involved in cellular crosstalk in CKD and MASH. Interactions between cell types identified using scRNAseq data were validated by checking the spatial co-presence using the ST data and the co-expression of the communicating targets. Multiple L-R protein pairs identified are known key players in CKD and MASH, while others are novel potential targets previously observed only in animal models.

CONCLUSION

Our study highlights the importance of integrating different modalities of transcriptomic data for a better understanding of the molecular mechanisms. The combination of single-cell resolution from scRNAseq data, combined with tissue slide investigations and visualization of cell-cell interactions obtained through ST, paves the way for the identification of future potential therapeutic targets and developing effective therapies.

Cellular dynamics in pig-to-human kidney xenotransplantation

BACKGROUND

Xenotransplantation of genetically engineered porcine organs has the potential to address the challenge of organ donor shortage. Two cases of porcine-to-human kidney xenotransplantation were performed, yet the physiological effects on the xenografts and the recipients' immune responses remain largely uncharacterized.

METHODS

We performed single-cell RNA sequencing (scRNA-seq) and longitudinal RNA-seq analyses of the porcine kidneys to dissect xenotransplantation-associated cellular dynamics and xenograft-recipient interactions. We additionally performed longitudinal scRNA-seq of the peripheral blood mononuclear cells (PBMCs) to detect recipient immune responses across time.

FINDINGS

Although no hyperacute rejection signals were detected, scRNA-seq analyses of the xenografts found evidence of endothelial cell and immune response activation, indicating early signs of antibody-mediated rejection. Tracing the cells' species origin, we found human immune cell infiltration in both xenografts. Human transcripts in the longitudinal bulk RNA-seq revealed that human immune cell infiltration and the activation of interferon-gamma-induced chemokine expression occurred by 12 and 48 h post-xenotransplantation, respectively. Concordantly, longitudinal scRNA-seq of PBMCs also revealed two phases of the recipients' immune responses at 12 and 48-53 h. Lastly, we observed global expression signatures of xenotransplantation-associated kidney tissue damage in the xenografts. Surprisingly, we detected a rapid increase of proliferative cells in both xenografts, indicating the activation of the porcine tissue repair program.

CONCLUSIONS

Longitudinal and single-cell transcriptomic analyses of porcine kidneys and the recipient's PBMCs revealed time-resolved cellular dynamics of xenograft-recipient interactions during xenotransplantation. These cues can be leveraged for designing gene edits and immunosuppression regimens to optimize xenotransplantation outcomes.

FUNDING

This work was supported by NIH RM1HG009491 and DP5OD033430.

Transcriptome Analysis of BAFF/BAFF-R System in Murine Nephrotoxic Serum Nephritis

Chronic kidney disease (CKD) is an emerging cause for morbidity and mortality worldwide. Acute kidney injury (AKI) can transition to CKD and finally to end-stage renal disease (ESRD). Targeted treatment is still unavailable. NF-κB signaling is associated with CKD and activated by B cell activating factor (BAFF) via BAFF-R binding. In turn, renal tubular epithelial cells (TECs) are critical for the progression of fibrosis and producing BAFF. Therefore, the direct involvement of the BAFF/BAFF-R system to the pathogenesis of CKD is conceivable. We performed non-accelerated nephrotoxic serum nephritis (NTN) as the CKD model in BAFF KO (B6.129S2-Tnfsf13btm1Msc/J), BAFF-R KO (B6(Cg)-Tnfrsf13ctm1Mass/J) and wildtype (C57BL/6J) mice to analyze the BAFF/BAFF-R system in anti-glomerular basement membrane (GBM) disease using high throughput RNA sequencing. We found that BAFF signaling is directly involved in the upregulation of collagen III as BAFF ko mice showed a reduced expression. However, these effects were not mediated via BAFF-R. We identified several upregulated genes that could explain the effects of BAFF in chronic kidney injury such as Txnip, Gpx3, Igfbp7, Ccn2, Kap, Umod and Ren1. Thus, we conclude that targeted treatment with anti-BAFF drugs such as belimumab may reduce chronic kidney damage. Furthermore, upregulated genes may be useful prognostic CKD biomarkers.

ELMO1 ameliorates intestinal epithelial cellular senescence via SIRT1/p65 signaling in inflammatory bowel disease-related fibrosis

Background

Intestinal fibrosis is a common complication in inflammatory bowel disease (IBD), which still lacks of reliable markers and therapeutic options. Cellular senescence has been considered an important mechanism of intestinal fibrosis, but the underlying molecular link remains elusive.

Methods

Tissues were stained using α-smooth muscle actin (α-SMA), fibronectin, and collagen I as markers of myofibroblastic differentiation. Cellular senescence was confirmed through Lamin B1 staining, senescence-associated β-galactosidase staining, and the expression of senescence-associated secretory phenotype (SASP) factors. We explored the relationship between senescence of intestinal epithelial cells (IECs) and intestinal fibrosis, as well as the molecular mechanism underlying this interaction. The effects of irisin on cellular senescence and fibrosis were determined.

Results

Here, we identify engulfment and cell motility protein 1 (ELMO1) as a novel biomarker for intestinal cellular senescence and fibrosis. In fibrostrictured tissues from patients and murine models with IBD, significantly high levels of cellular senescence score and factors were noted, which positively correlated with the fibrotic regulator fibronectin. Senescent IECs, not fibroblast itself, released SASP factors to regulate fibroblast activation. Prolonging exposure to severe and persistent injurious stimuli decreased ELMO1 expression, which dampened SIRT1 deacetylase activity, enhanced NF-κB (p65) acetylation, and thereby accelerated cellular senescence. Deletion of ELMO1 led to senescent IECs accumulation and triggered premature fibrosis in murine colitis. Furthermore, irisin, inhibiting the degradation of ELMO1, could downregulate p65 acetylation, reduce IECs senescence, and prevent incipient intestinal fibrosis in murine colitis models.

Conclusions

This study reveals ELMO1 downregulation is an early symbol of intestinal senescence and fibrosis, and the altered ELMO1-SIRT1-p65 pathway plays an important role in intestinal cellular senescence and IBD-related fibrosis.

Autophagy activates EGR1 via MAPK/ERK to induce FGF2 in renal tubular cells for fibroblast activation and fibrosis during maladaptive kidney repair

Macroautophagy/autophagy contributes to maladaptive kidney repair by inducing pro-fibrotic factors such as FGF2 (fibroblast growth factor 2), but the underlying mechanism remains elusive. Here, we show that EGR1 (early growth response 1) was induced in injured proximal tubules after ischemic acute kidney injury (AKI) and this induction was suppressed by autophagy deficiency in inducible, renal tubule-specific atg7 (autophagy related 7) knockout (iRT-atg7 KO) mice. In cultured proximal tubular cells, TGFB1 (transforming growth factor beta 1) induced EGR1 and this induction was also autophagy dependent. Egr1 knockdown in tubular cells reduced FGF2 expression during TGFB1 treatment, leading to less FGF2 secretion and decreased paracrine effects on fibroblasts. ChIP assay detected an increased binding of EGR1 to the Fgf2 gene promoter in TGFB1-treated tubular cells. Both Fgf2 and Egr1 transcription was inhibited by FGF2 neutralizing antibody, suggesting a positive feedback for EGR1-mediated FGF2 autoregulation. This feedback was confirmed using fgf2-deficient tubular cells and fgf2-deficient mice. Upstream of EGR1, autophagy deficiency in mice suppressed MAPK/ERK (mitogen-activated protein kinase) activation in post-ischemic renal tubules. This inhibition correlated with SQSTM1/p62 (sequestosome 1) aggregation and its sequestration of MAPK/ERK. SQSTM1/p62 interacted with MAPK/ERK and blocked its activation during TGFB1 treatment in autophagy-deficient tubular cells. Inhibition of MAPK/ERK suppressed EGR1 and FGF2 expression in maladaptive tubules, leading to the amelioration of renal fibrosis and improvement of renal function. These results suggest that autophagy activates MAPK/ERK in renal tubular cells, which induces EGR1 to transactivate FGF2. FGF2 is then secreted into the interstitium to stimulate fibroblasts for fibrogenesis.Abbreviation: 3-MA: 3-methyladenine; ACTA2/α-SMA: actin alpha 2, smooth muscle, aorta; ACTB/β-actin: actin, beta; AKI: acute kidney injury; aa: amino acid; ATG/Atg: autophagy related; BUN: blood urea nitrogen; ChIP: chromatin immunoprecipitation; CKD: chronic kidney disease; CM: conditioned medium; COL1A1: collagen, type I, alpha 1; COL4A1: collagen, type IV, alpha 1; CQ: chloroquine; DBA: dolichos biflorus agglutinin; EGR1: early growth response 1; ELK1: ELK1, member of ETS oncogene family; FGF2: fibroblast growth factor 2; FN1: fibronectin 1; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HAVCR1/KIM-1: hepatitis A virus cellular receptor 1; IP: immunoprecipitation; LIR: LC3-interacting region; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MAP2K/MEK: mitogen-activated protein kinase kinase; MAPK: mitogen-activated protein kinase; NFKB: nuclear factor kappa B; PB1: Phox and Bem1; PFT: pifithrin α; PPIB/cyclophilin B: peptidylprolyl isomerase B; RT-qPCR: real time-quantitative PCR; SQSTM1/p62: sequestosome 1; TGFB1/TGF-β1: transforming growth factor beta 1; VIM: vimentin.

[18F] AlF-NOTA-FAPI-04 PET/CT for non-invasive assessment of tubular injury in kidney diseases

Background

[18F] AlF-NOTA-FAPI-04 is a novel positron emission tomography (PET) ligand, which specifically targets fibroblast activation protein (FAP) expression as a FAP inhibitor (FAPI). We analysed the diagnostic value of [18F] AlF-NOTA-FAPI-04 PET/CT for the non-invasive assessment of kidney interstitial inflammation and fibrosis in different renal pathologies.

Methods

Twenty-six patients (14 males and 12 females; mean age, 50.5 ± 16.5 years) with a wide range of kidney diseases and 10 patients (six males and four females; mean age, 55.4 ± 8.6 years) without known evidence of renal disease as disease controls underwent [18F] AlF-NOTA-FAPI-04 PET/CT imaging. Kidney tissues obtained from kidney biopsies were stained with haematoxylin and eosin, periodic acid-Schiff, Masson's trichome, and periodic acid-silver methenamine. Immunohistochemical staining was also performed to assess the expression of α-smooth muscle actin (αSMA) and FAP. Renal parenchymal FAPI uptake reflected by maximum standardized uptake value (SUVmax) and mean standardized uptake value (SUVmean) measurements on PET/CT was analysed against pathohistological findings.

Results

We found that renal parenchymal FAPI uptake was significantly higher in patients with various kidney diseases than in control patients in this study (SUVmax = 4.3 ± 1.8 vs 1.9 ± 0.4, SUVmean=3.9 ± 1.7 vs 1.5 ± 0.4, respectively; all P < 0.001). All kidney diseases, both in acute and chronic kidney disease, had increased renal parenchymal uptake to varying degrees. The correlation analysis indicated a positive association between the SUVmax and the tubulointerstitial inflammation (TII), interstitial fibrosis and tubular atrophy (IF/TA), and TII + IF/TA scores (r = 0.612, 0.681, and 0.754, all P < 0.05), and between the SUVmean and the TII, IF/TA, and TII + IF/TA scores (r = 0.603, 0.700, and 0.748, all P < 0.05). Furthermore, we found significant positive correlations between both SUVmax and the SUVmean with SMA and FAP staining scores (r = 0.686 and 0.732, r = 0.667 and 0.739, respectively; both P < 0.001).

Conclusions

[18F] AlF-NOTA-FAPI-04 PET/CT is clinically available for the comprehensive and non-invasive assessment of tubular injury in various kidney diseases.

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.

BET inhibitor nanotherapy halts kidney damage and reduces chronic kidney disease progression after ischemia-reperfusion injury

Targeting epigenetic mechanisms has emerged as a potential therapeutic approach for the treatment of kidney diseases. Specifically, inhibiting the bromodomain and extra-terminal (BET) domain proteins using the small molecule inhibitor JQ1 has shown promise in preclinical models of acute kidney injury (AKI) and chronic kidney disease (CKD). However, its clinical translation faces challenges due to issues with poor pharmacokinetics and side effects. Here, we developed engineered liposomes loaded with JQ1 with the aim of enhancing kidney drug delivery and reducing the required minimum effective dose by leveraging cargo protection. These liposomes efficiently encapsulated JQ1 in both the membrane and core, demonstrating superior therapeutic efficacy compared to freely delivered JQ1 in a mouse model of kidney ischemia-reperfusion injury. JQ1-loaded liposomes (JQ1-NPs) effectively targeted the kidneys and only one administration, one-hour after injury, was enough to decrease the immune cell (neutrophils and monocytes) infiltration to the kidney-an early and pivotal step to prevent damage progression. By inhibiting BRD4, JQ1-NPs suppress the transcription of pro-inflammatory genes, such as cytokines (il-6) and chemokines (ccl2, ccl5). This success not only improved early the kidney function, as evidenced by decreased serum levels of BUN and creatinine in JQ1-NPs-treated mice, along with reduced tissue expression of the damage marker, NGAL, but also halted the production of extracellular matrix proteins (Fsp-1, Fn-1, α-SMA and Col1a1) and the fibrosis development. In summary, this work presents a promising nanotherapeutic strategy for AKI treatment and its progression and provides new insights into renal drug delivery.

Endothelial to mesenchymal transition in kidney fibrosis

Fibrotic diseases are characterized by the uncontrolled accumulation of extracellular matrix (ECM) components leading to disruption of tissue homeostasis. Myofibroblasts as the main ECM-producing cells can originate from various differentiated cell types after injury. Particularly, the process of endothelial-to-mesenchymal transition (endMT), describing phenotypic shifts of endothelial cells to adopt a fully mesenchymal identity, may contribute to the pool of myofibroblasts in fibrosis, while leading to capillary rarefaction and exacerbation of tissue hypoxia. In renal disease, incomplete recovery from acute kidney injury (AKI) and the ensuing fibrotic reaction stand out as major contributors to chronic kidney disease (CKD) development. While the focus has largely been on impaired tubular epithelial repair as a potential fibrosis-driving mechanism, alterations in the renal microcirculation post-AKI, and in particular endMT as a maladaptive response, could hold equal significance. Dysfunctional interplays among various cell types in the kidney microenvironment can instigate endMT. Transforming growth factor beta (TGF-β) signaling, with its downstream activation of canonical/Smad-mediated and non-canonical pathways, has been identified as primary driver of this process. However, non-TGF-β-mediated pathways involving inflammatory agents and metabolic shifts in intercellular communication within the tissue microenvironment can also trigger endMT. These harmful, maladaptive cell-cell interactions and signaling pathways offer potential targets for therapeutic intervention to impede endMT and decelerate fibrogenesis such as in AKI-CKD progression. Presently, partial reduction of TGF-β signaling using anti-diabetic drugs or statins may hold therapeutic potential in renal context. Nevertheless, further investigation is warranted to validate underlying mechanisms and assess positive effects within a clinical framework.

Loss of SAV1 in Kidney Proximal Tubule Induces Maladaptive Repair after Ischemia and Reperfusion Injury

Kidney ischemia and reperfusion injury (IRI) is a significant contributor to acute kidney injury (AKI), characterized by tubular injury and kidney dysfunction. Salvador family WW domain containing protein 1 (SAV1) is a key component of the Hippo pathway and plays a crucial role in the regulation of organ size and tissue regeneration. However, whether SAV1 plays a role in kidney IRI is not investigated. In this study, we investigated the role of SAV1 in kidney injury and regeneration following IRI. A proximal tubule-specific knockout of SAV1 in kidneys (SAV1ptKO) was generated, and wild-type and SAV1ptKO mice underwent kidney IRI or sham operation. Plasma creatinine and blood urea nitrogen were measured to assess kidney function. Histological studies, including periodic acid-Schiff staining and immunohistochemistry, were conducted to assess tubular injury, SAV1 expression, and cell proliferation. Western blot analysis was employed to assess the Hippo pathway-related and proliferation-related proteins. SAV1 exhibited faint expression in the proximal tubules and was predominantly expressed in the connecting tubule to the collecting duct. At 48 h after IRI, SAV1ptKO mice continued to exhibit severe kidney dysfunction, compared to attenuated kidney dysfunction in wild-type mice. Consistent with the functional data, severe tubular damage induced by kidney IRI in the cortex was significantly decreased in wild-type mice at 48 h after IRI but not in SAV1ptKO mice. Furthermore, 48 h after IRI, the number of Ki67-positive cells in the cortex was significantly higher in wild-type mice than SAV1ptKO mice. After IRI, activation and expression of Hippo pathway-related proteins were enhanced, with no significant differences observed between wild-type and SAV1ptKO mice. Notably, at 48 h after IRI, protein kinase B activation (AKT) was significantly enhanced in SAV1ptKO mice compared to wild-type mice. This study demonstrates that SAV1 deficiency in the kidney proximal tubule worsens the injury and delays kidney regeneration after IRI, potentially through the overactivation of AKT.

JMJD3 activation contributes to renal protection and regeneration following acute kidney injury in mice

We have recently demonstrated that Jumonji domain-containing protein D3 (JMJD3), a histone demethylase of histone H3 on lysine 27 (H3K27me3), is protective against renal fibrosis, but its role in acute kidney injury (AKI) remains unexplored. Here, we report that JMJD3 activity is required for renal protection and regeneration in murine models of AKI induced by ischemia/reperfusion (I/R) and folic acid (FA). Injury to the kidney upregulated JMJD3 expression and induced expression of H3K27me3, which was coincident with renal dysfunction, renal tubular cell injury/apoptosis, and proliferation. Blocking JMJD3 activity by GSKJ4 led to worsening renal dysfunction and pathological changes by aggravating tubular epithelial cell injury and apoptosis in both murine models of AKI. JMJD3 inhibition by GSKJ4 also reduced renal tubular cell proliferation and suppressed expression of cyclin E and phosphorylation of CDK2, but increased p21 expression in the injured kidney. Furthermore, inactivation of JMJD3 enhanced I/R- or FA-induced expression of TGF-β1, vimentin, and Snail, phosphorylation of Smad3, STAT3, and NF-κB, and increased renal infiltration by F4/80 (+) macrophages. Finally, GSKJ4 treatment caused further downregulation of Klotho, BMP-7, Smad7, and E-cadherin, all of which are associated with renal protection and have anti-fibrotic effects. Therefore, these data provide strong evidence that JMJD3 activation contributes to renal tubular epithelial cell survival and regeneration after AKI.

A short treatment with resveratrol after a renal ischaemia-reperfusion injury prevents maladaptive repair and long-term chronic kidney disease in rats

Acute kidney injury (AKI) often triggers physiological processes aimed at restoring renal function and architecture. However, this response can become maladaptive, leading to nephron loss and fibrosis. Although the therapeutic effects of resveratrol (RSV) are well established, its impact after AKI and for subsequent chronic kidney disease (CKD) remains unclear. This study assessed whether transient administration of RSV following ischaemia-reperfusion injury (IRI) could prevent the progression to CKD. Forty-one male Wistar rats were assigned randomly to sham surgery, bilateral renal ischaemia for 30 min (IR) or IR+RSV. The RSV treatment commenced 24 h after IRI and continued for 10 days. The rats were studied for either 10 days or 5 months, after which kidney function and structure were evaluated. Mitochondrial homeostasis, oxidant defence and renal inflammation state were also evaluated. Despite having the same severity of AKI, rats receiving RSV for 10 days after IRI exhibited significant improvement in kidney histological injury and reduced inflammation, although renal haemodynamic recovery was less pronounced. Resveratrol effectively prevented the elevation of tubular injury-related molecules and profibrotic signalling with reduced myofibroblast proliferation. Furthermore, RSV substantially improved the antioxidant response and mitochondrial homeostasis. After 5 months, RSV prevented the transition to CKD, as evidenced by the prevention of progressive proteinuria, renal dysfunction and tubulointerstitial fibrosis. This study demonstrates that a brief treatment with RSV following IRI is enough to prevent maladaptive repair and the development of CKD. Our findings highlight the importance of the early days of reperfusion, indicating that maladaptive responses can be reduced effectively following severe AKI. KEY POINTS: Physiological processes activated after acute kidney injury (AKI) can lead to maladaptive responses, causing nephron loss and fibrosis. Prophylactic renoprotection with resveratrol (RSV) has been described in experimental AKI, but its impact after AKI and for subsequent chronic kidney disease (CKD) remains unclear. In this study, we found that histological tubular injury persists 10 days after ischaemia-reperfusion injury and contributes to a failed repair phenotype in proximal tubular cells. Short-term RSV intervention influenced the post-ischaemic repair response and accelerated tubular recovery by reducing oxidative stress and mitochondrial damage. Furthermore, RSV targeted inflammation and profibrotic signalling during the maladaptive response, normalizing both processes. Resveratrol effectively prevented AKI-to-CKD transition even 5 months after the intervention. The study serves as a proof of concept, proposing RSV as a valuable candidate for further translational clinical studies to mitigate AKI-to-CKD transition.

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.

Hyperbaric Oxygen Reduces Oxidative Stress Impairment and DNA Damage and Simultaneously Increases HIF-1α in Ischemia-Reperfusion Acute Kidney Injury

The central exacerbating factor in the pathophysiology of ischemic-reperfusion acute kidney injury (AKI) is oxidative stress. Lipid peroxidation and DNA damage in ischemia are accompanied by the formation of 3-nitrotyrosine, a biomarker for oxidative damage. DNA double-strand breaks (DSBs) may also be a result of postischemic AKI. γH2AX(S139) histone has been identified as a potentially useful biomarker of DNA DSBs. On the other hand, hypoxia-inducible factor (HIF) is the "master switch" for hypoxic adaptation in cells and tissues. The aim of this research was to evaluate the influence of hyperbaric oxygen (HBO) preconditioning on antioxidant capacity estimated by FRAP (ferric reducing antioxidant power) and ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assay, as well as on oxidative stress parameter 3-nitrotyrosine, and to assess its effects on γH2AX(S139), HIF-1α, and nuclear factor-κB (NF-κB) expression, in an experimental model of postischemic AKI induced in spontaneously hypertensive rats. The animals were divided randomly into three experimental groups: sham-operated rats (SHAM, n = 6), rats with induced postischemic AKI (AKI, n = 6), and group exposed to HBO preconditioning before AKI induction (AKI + HBO, n = 6). A significant improvement in the estimated glomerular filtration rate, eGFR, in AKI + HBO group (p < 0.05 vs. AKI group) was accompanied with a significant increase in plasma antioxidant capacity estimated by FRAP (p < 0.05 vs. SHAM group) and a reduced immunohistochemical expression of 3-nitrotyrosine and γH2AX(S139). Also, HBO pretreatment significantly increased HIF-1α expression (p < 0.001 vs. AKI group), estimated by Western blot and immunohistochemical analysis in kidney tissue, and decreased immunohistochemical NF-κB renal expression (p < 0.01). Taking all of these results together, we may conclude that HBO preconditioning has beneficial effects on acute kidney injury induced in spontaneously hypertensive rats.

Mice with renal-specific alterations of stem cell-associated signaling develop symptoms of chronic kidney disease but surprisingly no tumors

Previously, we found that Wnt and Notch signaling govern stem cells of clear cell kidney cancer (ccRCC) in patients. To mimic stem cell responses in the normal kidney in vitro in a marker-unbiased fashion, we have established tubular organoids (tubuloids) from total single adult mouse kidney epithelial cells in Matrigel and serum-free conditions. Deep proteomic and phosphoproteomic analyses revealed that tubuloids resembled renewal of adult kidney tubular epithelia, since tubuloid cells displayed activity of Wnt and Notch signaling, long-term proliferation and expression of markers of proximal and distal nephron lineages. In our wish to model stem cell-derived human ccRCC, we have generated two types of genetic double kidney mutants in mice: Wnt-β-catenin-GOF together with Notch-GOF and Wnt-β-catenin-GOF together with a most common alteration in ccRCC, Vhl-LOF. An inducible Pax8-rtTA-LC1-Cre was used to drive recombination specifically in adult kidney epithelial cells. We confirmed mutagenesis of β-catenin, Notch and Vhl alleles on DNA, protein and mRNA target gene levels. Surprisingly, we observed symptoms of chronic kidney disease (CKD) in mutant mice, but no increased proliferation and tumorigenesis. Thus, the responses of kidney stem cells in the tubuloid and genetic systems produced different phenotypes, i.e. enhanced renewal versus CKD.

Chk2 Modulates Bmi1-Deficiency-Induced Renal Aging and Fibrosis via Oxidative Stress, DNA Damage, and p53/TGFβ1-Induced Epithelial-Mesenchymal Transition

Renal aging may lead to fibrosis and dysfunction, yet underlying mechanisms remain unclear. We explored whether deficiency of the Polycomb protein Bmi1 causes renal aging via DNA damage response (DDR) activation, inducing renal tubular epithelial cell (RTEC) senescence and epithelial-mesenchymal transition (EMT). Bmi1 knockout mice exhibited oxidative stress, DDR activation, RTEC senescence, senescence-associated secretory phenotype (SASP), and age-related fibrosis in kidneys. Bmi1 deficiency impaired renal structure and function, increasing serum creatinine/urea, reducing creatinine clearance, and decreasing cortical thickness and glomerular number. However, knockout of the serine-threonine kinase Chk2 alleviated these aging phenotypes. Transcriptomics identified transforming growth factor beta 1 (TGFβ1) upregulation in Bmi1-deficient RTECs, but TGFβ1 was downregulated upon Chk2 knockout. The tumor suppressor protein p53 transcriptionally activated TGFβ1, promoting EMT in RTECs. Bmi1 knockout or oxidative stress (induced with H2O2) increased TGFβ1 expression, and EMT in RTECs and was partly reversed by p53 inhibition. Together, Bmi1 deficiency causes oxidative stress and DDR-mediated RTEC senescence/SASP, thus activating p53 and TGFβ1 to induce EMT and age-related fibrosis. However, blocking DDR (via Chk2 knockout) or p53 ameliorates these changes. Our study reveals mechanisms whereby Bmi1 preserves renal structure and function during aging by suppressing DDR and p53/TGFβ1-mediated EMT. These pathways represent potential targets for detecting and attenuating age-related renal decline.

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.

Update of pericytes function and their roles in kidney diseases

Studies have highlighted the significant involvement of kidney pericytes in renal fibrosis. Kidney pericytes, classified as interstitial mesenchymal cells, are extensively branched, collagen-producing cells that closely interact with endothelial cells. This article aims to provide an overview of the recent advancements in understanding the physiological functions of pericytes and their roles in kidney diseases. In a healthy kidney, pericytes have essential physiological function in angiogenesis, erythropoietin (EPO) production, and the regulation of renal blood flow. Nevertheless, pericyte-myofibroblast transition has been identified as the primary cause of disease progression in acute kidney injury (AKI)-to-chronic kidney disease (CKD) continuum. Our recent research has demonstrated that hypoxia-inducible factor-2α (HIF-2α) regulates erythropoietin production in pericytes. However, this production is repressed by EPO gene hypermethylation and HIF-2α downregulation which were induced by transforming growth factor-β1-activated DNA methyltransferase and activin receptor-like kinase-5 signaling pathway during renal fibrosis, respectively. Additionally, AKI induces epigenetic modifications in pericytes, rendering them more prone to extracellular matrix production, cell migration and proliferation, thereby contributing to subsequent capillary rarefaction and renal fibrosis. Further investigation into the specific functions and roles of different subpopulations of pericytes may contribute for the development of targeted therapies aimed at attenuating kidney disease and mitigating their adverse effects.

HIF-1 contributes to autophagy activation via BNIP3 to facilitate renal fibrosis in hypoxia in vitro and UUO in vivo

The molecular basis of renal interstitial fibrosis, a major pathological feature of progressive kidney diseases, remains poorly understood. Autophagy has been implicated in renal fibrosis, but whether it promotes or inhibits fibrosis remains controversial. Moreover, it is unclear how autophagy is activated and sustained in renal fibrosis. The present study was designed to address these questions using the in vivo mouse model of unilateral ureteral obstruction and the in vitro model of hypoxia in renal tubular cells. Both models showed the activation of hypoxia-inducible factor-1 (HIF-1) and autophagy along with fibrotic changes. Inhibition of autophagy with chloroquine reduced renal fibrosis in unilateral ureteral obstruction model, whereas chloroquine and autophagy-related gene 7 knockdown decreased fibrotic changes in cultured renal proximal tubular cells, supporting a profibrotic role of autophagy. Notably, pharmacological and genetic inhibition of HIF-1 led to the suppression of autophagy and renal fibrosis in these models. Mechanistically, knock down of BCL2 and adenovirus E1B 19-kDa-interacting protein 3 (BNIP3), a downstream target gene of HIF, decreased autophagy and fibrotic changes during hypoxia in BUMPT cells. Together, these results suggest that HIF-1 may activate autophagy via BNIP3 in renal tubular cells to facilitate the development of renal interstitial fibrosis.NEW & NOTEWORTHY Autophagy has been reported to participate in renal fibrosis, but its role and underlying activation mechanism is unclear. In this study, we report the role of HIF-1 in autophagy activation in models of renal fibrosis and further investigate the underlying mechanism.

Epidemiology of acute kidney injury in children: a report from the 26th Acute Disease Quality Initiative (ADQI) consensus conference

The nephrology and critical care communities have seen an increase in studies exploring acute kidney injury (AKI) epidemiology in children. As a result, we now know that AKI is highly prevalent in critically ill neonates, children, and young adults. Furthermore, children who develop AKI experience greater morbidity and higher mortality. Yet knowledge gaps still exist that suggest a more comprehensive understanding of AKI will form the foundation for future efforts designed to improve outcomes. In particular, the areas of community acquired AKI, AKI in non-critically ill children, and cohorts from low-middle income countries have not been well studied. Longer-term functional outcomes and patient-centric metrics including social determinants of health, quality of life, and healthcare utilization should be the foci of the next phase of scholarship. Current definitions identify AKI-based upon evidence of dysfunction which serves as a proxy for injury; biomarkers capable of identifying injury as it occurs are likely to more accurately define populations with AKI. Despite the strength of the association, the causal and mechanistic relationships between AKI and poorer outcomes remain inadequately examined. A more robust understanding of the relationship represents a potential to identify therapeutic targets. Once established, a more comprehensive understanding of AKI epidemiology in children will allow investigation of preventive, therapeutic, and quality improvement interventions more effectively.

Transient inhibition of sodium-glucose cotransporter 2 after ischemia/reperfusion injury ameliorates chronic kidney disease

Sodium-glucose cotransporter 2 (SGLT2) inhibitor, dapagliflozin (Dapa), exhibited nephroprotective effects in patients with chronic kidney disease (CKD). We assessed the efficacy of short-term Dapa administration following acute kidney injury (AKI) in preventing CKD. Male Wistar rats were randomly assigned to Sham surgery, bilateral ischemia for 30 minutes (abbreviated as IR), and IR + Dapa groups. Daily treatment with Dapa was initiated just 24 hours after IR and maintained for only 10 days. Initially, rats were euthanized at this point to study early renal repair. After severe AKI, Dapa promptly restored creatinine clearance (CrCl) and significantly reduced renal vascular resistance compared with the IR group. Furthermore, Dapa effectively reversed the mitochondrial abnormalities, including increased fission, altered mitophagy, metabolic dysfunction, and proapoptotic signaling. To study this earlier, another set of rats was studied just 5 days after AKI. Despite persistent renal dysfunction, our data reveal a degree of mitochondrial protection. Remarkably, a 10-day treatment with Dapa demonstrated effectiveness in preventing CKD transition in an independent cohort monitored for 5 months after AKI. This was evidenced by improvements in proteinuria, CrCl, glomerulosclerosis, and fibrosis. Our findings underscore the potential of Dapa in preventing maladaptive repair following AKI, emphasizing the crucial role of early intervention in mitigating AKI long-term consequences.

Cellular senescence of renal tubular epithelial cells in acute kidney injury

Cellular senescence represents an irreversible state of cell-cycle arrest during which cells secrete senescence-associated secretory phenotypes, including inflammatory factors and chemokines. Additionally, these cells exhibit an apoptotic resistance phenotype. Cellular senescence serves a pivotal role not only in embryonic development, tissue regeneration, and tumor suppression but also in the pathogenesis of age-related degenerative diseases, malignancies, metabolic diseases, and kidney diseases. The senescence of renal tubular epithelial cells (RTEC) constitutes a critical cellular event in the progression of acute kidney injury (AKI). RTEC senescence inhibits renal regeneration and repair processes and, concurrently, promotes the transition of AKI to chronic kidney disease via the senescence-associated secretory phenotype. The mechanisms underlying cellular senescence are multifaceted and include telomere shortening or damage, DNA damage, mitochondrial autophagy deficiency, cellular metabolic disorders, endoplasmic reticulum stress, and epigenetic regulation. Strategies aimed at inhibiting RTEC senescence, targeting the clearance of senescent RTEC, or promoting the apoptosis of senescent RTEC hold promise for enhancing the renal prognosis of AKI. This review primarily focuses on the characteristics and mechanisms of RTEC senescence, and the impact of intervening RTEC senescence on the prognosis of AKI, aiming to provide a foundation for understanding the pathogenesis and providing potentially effective approaches for AKI treatment.

Oleoylethanolamide attenuates acute-to-chronic kidney injury: in vivo and in vitro evidence of PPAR-α involvement

Chronic kidney disease (CKD) development after acute kidney injury (AKI) involves multiple mechanisms, including inflammation, epithelial-mesenchymal transition (EMT), and extracellular matrix deposition, leading to progressive tubulointerstitial fibrosis. Recently, a central role for peroxisome-proliferator activated receptor (PPAR)-α has been addressed in preserving kidney function during AKI. Among endogenous lipid mediators, oleoylethanolamide (OEA), a PPAR-α agonist, has been studied for its metabolic and anti-inflammatory effects. Here, we have investigated OEA effects on folic acid (FA)-induced kidney injury in mice and the underlying mechanisms. OEA improved kidney function, normalized urine output, and reduced serum BUN, creatinine, and albuminuria. Moreover, OEA attenuated tubular epithelial injury, as shown by histological analysis, and decreased expression of neutrophil gelatinase-associated lipocalin and kidney injury molecule-1. Gene expression analysis of kidney tissue indicated that OEA limited immune cell infiltration and inflammation. Moreover, OEA significantly inhibited Wnt7b and Catnb1 gene transcription and α-smooth muscle actin expression, indicating suppression of EMT. Accordingly, OEA exhibited an anti-fibrotic effect, as shown by Masson staining and the reduced levels of transforming growth factor (TGF)-β1, fibronectin, and collagen IV. Mechanistically, the nephroprotective effect of OEA was related to PPAR-α activation since OEA failed to exert its beneficial activity in FA-insulted PPAR-α-/- mice. PPAR-α involvement was also confirmed in HK2 cells where GW6471, a PPAR-α antagonist, blunted OEA activity on the TGF-β1 signalling pathway and associated pro-inflammatory and fibrotic patterns. Our findings revealed that OEA counteracts kidney injury by controlling inflammation and fibrosis, making it an effective therapeutic tool for limiting AKI to CKD progression.

Discovery of PRDM16-Mediated TRPA1 Induction as the Mechanism for Low Tubulo-Interstitial Fibrosis in Diabetic Kidney Disease

The pathogenesis of Diabetic kidney disease(DKD) involves pathological changes in both tubulo-interstitium and the glomerulus. Surprisingly, tubulo-interstitial fibrosis (TIF), does not develop significantly until the late stage of DKD. Here, it is demonstrated that PR domain-containing 16 (PRDM16) is a key to the low level of TIF in DKD. In the experiments, PRDM16 is upregulated in high glucose-treated renal tubular cells, DKD mouse kidneys, and renal biopsy of human DKD patients via activation of NF-κB signal pathway. High glucose-induced expression of fibrotic proteins in renal tubular cells is suppressed by PRDM16. Mechanistically, PRDM16 bound to the promotor region of Transient receptor potential ankyrin 1 (TRPA1) to transactivate its expression and then suppressed MAPK (P38, ERK1/2) activation and downstream expression of TGF-β1. Knockout of PRDM16 from kidney proximal tubules in mice blocked TRPA1 expression and enhanced MAPK activation, TGF-β1 production, TIF development, and DKD progression, whereas knock-in of PRDM16 has opposite effects. In addition, overexpression of PRDM16 or its induction by formononetin ameliorated renal dysfunction and fibrosis in db/db diabetic mice. Finally, the above finding are detected in renal biopsies of DKD patients. Together, these results unveil PRDM16/TRPA1 as the mechanism responsible for the low level of TIF in the early stage of DKD by suppressing and TGF-β1 expression.

Pax protein depletion in proximal tubules triggers conserved mechanisms of resistance to acute ischemic kidney injury preventing transition to chronic kidney disease

Acute kidney injury (AKI) is a common condition that lacks effective treatments. In part, this shortcoming is due to an incomplete understanding of the genetic mechanisms that control pathogenesis and recovery. Identifying the molecular and genetic regulators unique to nephron segments that dictate vulnerability to injury and regenerative potential could lead to new therapeutic targets to treat ischemic kidney injury. Pax2 and Pax8 are homologous transcription factors with overlapping functions that are critical for kidney development and are re-activated in AKI. Here, we examined the role of Pax2 and Pax8 in recovery from ischemic AKI and found them upregulated after severe AKI and correlated with chronic injury. Surprisingly, proximal-tubule-selective deletion of Pax2 and Pax8 resulted in a less severe chronic injury phenotype. This effect was mediated by protection against the acute insult, similar to pre-conditioning. Prior to injury, Pax2 and Pax8 mutant mice develop a unique subpopulation of proximal tubule cells in the S3 segment that displayed features usually seen only in acute or chronic injury. The expression signature of these cells was strongly enriched with genes associated with other mechanisms of protection against ischemic AKI including caloric restriction, hypoxic pre-conditioning, and female sex. Thus, our results identified a novel role for Pax2 and Pax8 in mature proximal tubules that regulates critical genes and pathways involved in both the injury response and protection from ischemic AKI.

Macrophages polarization in renal inflammation and fibrosis animal models (Review)

Chronic kidney disease (CKD) is a significant public health concern. Renal fibrosis is the final common pathway in the progression of kidney diseases, irrespective of the initial injury. Substantial evidence underscores the pivotal role of renal inflammation in the genesis of renal fibrosis. The presence of macrophages within normal renal tissue is significantly increased within diseased renal tissue, indicative of their crucial regulatory function in inflammation and fibrosis. Macrophages manifest a high degree of heterogeneity, exhibiting distinct phenotypic and functional traits in response to diverse stimuli within the local microenvironment in various types of kidney diseases. Broadly, macrophages are categorized into two principal groups: Classically activated, designated as M1 macrophages and alternatively activated, designated as M2 macrophages. A number of experimental models are widely used to study the underlying mechanisms driving renal inflammation and fibrosis progression. The present review delineated the phenotypic and functional attributes of macrophages present in diverse induced models, analyzing their disposition in relation to M1 and M2 polarization states.

From Acute to Chronic: Unraveling the Pathophysiological Mechanisms of the Progression from Acute Kidney Injury to Acute Kidney Disease to Chronic Kidney Disease

This article provides a thorough overview of the biomarkers, pathophysiology, and molecular pathways involved in the transition from acute kidney injury (AKI) and acute kidney disease (AKD) to chronic kidney disease (CKD). It categorizes the biomarkers of AKI into stress, damage, and functional markers, highlighting their importance in early detection, prognosis, and clinical applications. This review also highlights the links between renal injury and the pathophysiological mechanisms underlying AKI and AKD, including renal hypoperfusion, sepsis, nephrotoxicity, and immune responses. In addition, various molecules play pivotal roles in inflammation and hypoxia, triggering maladaptive repair, mitochondrial dysfunction, immune system reactions, and the cellular senescence of renal cells. Key signaling pathways, such as Wnt/β-catenin, TGF-β/SMAD, and Hippo/YAP/TAZ, promote fibrosis and impact renal function. The renin-angiotensin-aldosterone system (RAAS) triggers a cascade leading to renal fibrosis, with aldosterone exacerbating the oxidative stress and cellular changes that promote fibrosis. The clinical evidence suggests that RAS inhibitors may protect against CKD progression, especially post-AKI, though more extensive trials are needed to confirm their full impact.

Spatial multi-omics: novel tools to study the complexity of cardiovascular diseases

Spatial multi-omic studies have emerged as a promising approach to comprehensively analyze cells in tissues, enabling the joint analysis of multiple data modalities like transcriptome, epigenome, proteome, and metabolome in parallel or even the same tissue section. This review focuses on the recent advancements in spatial multi-omics technologies, including novel data modalities and computational approaches. We discuss the advancements in low-resolution and high-resolution spatial multi-omics methods which can resolve up to 10,000 of individual molecules at subcellular level. By applying and integrating these techniques, researchers have recently gained valuable insights into the molecular circuits and mechanisms which govern cell biology along the cardiovascular disease spectrum. We provide an overview of current data analysis approaches, with a focus on data integration of multi-omic datasets, highlighting strengths and weaknesses of various computational pipelines. These tools play a crucial role in analyzing and interpreting spatial multi-omics datasets, facilitating the discovery of new findings, and enhancing translational cardiovascular research. Despite nontrivial challenges, such as the need for standardization of experimental setups, data analysis, and improved computational tools, the application of spatial multi-omics holds tremendous potential in revolutionizing our understanding of human disease processes and the identification of novel biomarkers and therapeutic targets. Exciting opportunities lie ahead for the spatial multi-omics field and will likely contribute to the advancement of personalized medicine for cardiovascular diseases.

The metabolic pathway regulation in kidney injury and repair

Kidney injury and repair are accompanied by significant disruptions in metabolic pathways, leading to renal cell dysfunction and further contributing to the progression of renal pathology. This review outlines the complex involvement of various energy production pathways in glucose, lipid, amino acid, and ketone body metabolism within the kidney. We provide a comprehensive summary of the aberrant regulation of these metabolic pathways in kidney injury and repair. After acute kidney injury (AKI), there is notable mitochondrial damage and oxygen/nutrient deprivation, leading to reduced activity in glycolysis and mitochondrial bioenergetics. Additionally, disruptions occur in the pentose phosphate pathway (PPP), amino acid metabolism, and the supply of ketone bodies. The subsequent kidney repair phase is characterized by a metabolic shift toward glycolysis, along with decreased fatty acid β-oxidation and continued disturbances in amino acid metabolism. Furthermore, the impact of metabolism dysfunction on renal cell injury, regeneration, and the development of renal fibrosis is analyzed. Finally, we discuss the potential therapeutic strategies by targeting renal metabolic regulation to ameliorate kidney injury and fibrosis and promote kidney repair.

Impaired hemodynamic renal reserve response following recovery from established acute kidney injury and improvement by hydrodynamic isotonic fluid delivery

Renal reserve capacity may be compromised following recovery from acute kidney injury (AKI) and could be used to identify impaired renal function in the face of restored glomerular filtration rate (GFR) or plasma creatinine. To investigate the loss of hemodynamic renal reserve responses following recovery in a model of AKI, rats were subjected to left unilateral renal ischemia-reperfusion (I/R) injury and contralateral nephrectomy and allowed to recover for 5 wk. Some rats were treated 24 h post-I/R by hydrodynamic isotonic fluid delivery (AKI-HIFD) of saline through the renal vein, previously shown to improve recovery and inflammation relative to control rats that received saline through the vena cava (AKI-VC). At 5 wk after surgery, plasma creatinine and GFR recovered to levels observed in uninephrectomized sham controls. Baseline renal blood flow (RBF) was not different between AKI or sham groups, but infusion of l-arginine (7.5 mg/kg/min) significantly increased RBF in sham controls, whereas the RBF response to l-arginine was significantly reduced in AKI-VC rats relative to sham rats (22.6 ± 2.2% vs. 13.8 ± 1.8%, P < 0.05). RBF responses were partially protected in AKI-HIFD rats relative to AKI-VC rats (17.0 ± 2.2%) and were not significantly different from sham rats. Capillary rarefaction observed in AKI-VC rats was significantly protected in AKI-HIFD rats. There was also a significant increase in T helper 17 cell infiltration and interstitial fibrosis in AKI-VC rats versus sham rats, which was not present in AKI-HIFD rats. These data suggest that recovery from AKI results in impaired hemodynamic reserve and that associated CKD progression may be mitigated by HIFD in the early post-AKI period.NEW & NOTEWORTHY Despite the apparent recovery of renal filtration function following acute kidney injury (AKI) in rats, the renal hemodynamic reserve response is significantly attenuated, suggesting that clinical evaluation of this parameter may provide information on the potential development of chronic kidney disease. Treatments such as hydrodynamic isotonic fluid delivery, or other treatments in the early post-AKI period, could minimize chronic inflammation or loss of microvessels with the potential to promote a more favorable outcome on long-term function.

Multiparametric Magnetic Resonance Investigations on Acute and Long-Term Kidney Injury

Acute kidney injury (AKI) is a frequent complication of critical illness and carries a significant risk of short- and long-term mortality. The prediction of the progression of AKI to long-term injury has been difficult for renal disease treatment. Radiologists are keen for the early detection of transition from AKI to long-term kidney injury, which would help in the preventive measures. The lack of established methods for early detection of long-term kidney injury underscores the pressing needs of advanced imaging technology that reveals microscopic tissue alterations during the progression of AKI. Fueled by recent advances in data acquisition and post-processing methods of magnetic resonance imaging (MRI), multiparametric MRI is showing great potential as a diagnostic tool for many kidney diseases. Multiparametric MRI studies offer a precious opportunity for real-time noninvasive monitoring of pathological development and progression of AKI to long-term injury. It provides insight into renal vasculature and function (arterial spin labeling, intravoxel incoherent motion), tissue oxygenation (blood oxygen level-dependent), tissue injury and fibrosis (diffusion tensor imaging, diffusion kurtosis imaging, T1 and T2 mapping, quantitative susceptibility mapping). The multiparametric MRI approach is highly promising but the longitudinal investigation on the transition of AKI to irreversible long-term impairment is largely ignored. Further optimization and implementation of renal MR methods in clinical practice will enhance our comprehension of not only AKI but chronic kidney diseases. Novel imaging biomarkers for microscopic renal tissue alterations could be discovered and benefit the preventative interventions. This review explores recent MRI applications on acute and long-term kidney injury while addressing lingering challenges, with emphasis on the potential value of the development of multiparametric MRI for renal imaging on clinical systems. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2.

Acute Kidney Injury: Definition, Management, and Promising Therapeutic Target

Acute kidney injury (AKI) is caused by a sudden loss of renal function, resulting in the build-up of waste products and a significant increase in mortality and morbidity. It is commonly diagnosed in critically ill patients, with its occurrence estimated at up to 50% in patients hospitalized in the intensive critical unit. Despite ongoing efforts, the death rate associated with AKI has remained high over the past half-century. Thus, it is critical to investigate novel therapy options for preventing the epidemic. Many studies have found that inflammation and Toll-like receptor-4 (TLR-4) activation have a significant role in the pathogenesis of AKI. Noteworthy, challenges in the search for efficient pharmacological therapy for AKI have arisen due to the multifaceted origin and complexity of the clinical history of people with the disease. This article focuses on kidney injury's epidemiology, risk factors, and pathophysiological processes. Specifically, it focuses on the role of TLRs especially type 4 in disease development.

Endogenous stimuli-responsive drug delivery nanoplatforms for kidney disease therapy

Kidney disease is one of the most life-threatening health problems, affecting millions of people in the world. Commonly used steroids and immunosuppressants often fall exceptionally short of outcomes with inescapable systemic toxicity. With the booming research in nanobiotechnology, stimuli-responsive nanoplatform has come an appealing therapeutic strategy for kidney disease. Endogenous stimuli-responsive materials have shown profuse promise owing to their enhanced spatiotemporal control and precise to the location of the lesion. This review focuses on recent advances stimuli-responsive drug delivery nano-architectonics for kidney disease. First, a brief introduction of pathogenesis of kidney disease and pathological microenvironment were provided. Then, various endogenous stimulus involved in drug delivery nanoplatforms including pH, ROS, enzymes, and glucose were categorized based on the pathological mechanisms of kidney disease. Next, we separately summarized literature examples of endogenous stimuli-responsive nanomaterials, and outlined the design strategies and response mechanisms. Finally, the paper was concluded by discussing remaining challenges and future perspectives of endogenous stimuli-responsive drug delivery nanoplatform for expediting the speed of development and clinical applications.

4-Octyl itaconate alleviates renal ischemia reperfusion injury by ameliorating endoplasmic reticulum stress via Nrf2 pathway

Renal ischemia-reperfusion injury (IRI) is a common clinical complication of multiple severe diseases. Owing to its high mortality and the lack of effective treatment, renal IRI is still an intractable problem for clinicians. Itaconate, which is a metabolite of cis-aconitate, can exert anti-inflammatory and antioxidant roles in many diseases. As a derivative of itaconate with high cell membrane permeability, 4-octyl itaconate (4-OI) could provide a protective effect for various diseases. However, the role of 4-OI in renal IRI is still unclear. Herein, we examined whether 4-OI afforded kidney protection through attenuating endoplasmic reticulum stress (ERS) via nuclear factor erythroid-2-related factor 2 (Nrf2) pathway. To observe the effects of 4-OI on alleviating renal pathologic injury, improving renal dysfunction, decreasing inflammatory cytokines, and reducing oxidative stress, we utilized C57BL/6J mice with bilateral renal pedicle clamped and HK-2 cells with hypoxia/reoxygenation (H/R) exposure in our study. In addition, through western blot assay, we found 4-OI ameliorated renal IRI-induced ERS, and activated Nrf2 pathway. Moreover, Nrf2-knockout (KO) mice and Nrf2 knockdown HK-2 cells were used to validate the role of Nrf2 signaling pathway in 4-OI-mediated alleviation of ERS caused by renal IRI. We demonstrated that 4-OI relieved renal injury and suppressed ERS in wild-type mice, while the therapeutic role was not shown in Nrf2-KO mice. Similarly, 4-OI could exert cytoprotective effect and inhibit ERS in HK-2 cells after H/R, but not in Nrf2 knockdown cells. Our in vivo and in vitro studies revealed that 4-OI protected renal IRI through attenuating ERS via Nrf2 pathway.