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Albuminuria is characterized by a disruption of the glomerular filtration barrier, which is composed of the fenestrated endothelium, the glomerular basement membrane, and the slit diaphragm. Nephrin is a major component of the slit diaphragm. Apart from hemodynamic effects, Ang II enhances albuminuria by β‐Arrestin2‐mediated nephrin endocytosis. Blocking the AT1 receptor with candesartan and irbesartan reduces the Ang II‐mediated nephrin‐β‐Arrestin2 interaction. The inhibition of MAPK ERK 1/2 blocks Ang II‐enhanced nephrin‐β‐Arrestin2 binding. ERK 1/2 signaling, which follows AT1 receptor activation, is mediated by G‐protein signaling, EGFR transactivation, and β‐Arrestin2 recruitment. A mutant AT1 receptor defective in EGFR transactivation and β‐Arrestin2 recruitment reduces the Ang II‐mediated increase in nephrin β‐Arrestin2 binding. The mutation of β‐Arrestin2K11,K12, critical for AT1 receptor binding, completely abrogates the interaction with nephrin, independent of Ang II stimulation. β‐Arrestin2K11R,K12R does not influence nephrin cell surface expression. The data presented here deepen our molecular understanding of a blood‐pressure‐independent molecular mechanism of AT‐1 receptor blockers (ARBs) in reducing albuminuria. [ABSTRACT FROM AUTHOR]

Objective: Diabetic nephropathy (DN) is the leading cause of end-stage renal disease in diabetic patients. Astragalus polysaccharide (APS) is a natural active ingredient in Astragalus membranaceus with anti-hypertensive and anti-oxidative properties. This study aimed to explore the protective roles of APS and its underlying mechanisms in DN. Methods: After the establishment of a rat model of DN by a high-fat diet and treatment with 30 mg/kg streptozotocin (STZ), the effects of 100 mg/kg APS on the levels of serum creatinine, blood urea nitrogen, blood glucose, and urinary albumin-to-creatinine ratio were measured. Histopathological alterations in renal tissues, renal cell apoptosis, renal inflammation, and oxidative stress were examined. The impacts of 0–200 μg/mL APS on the viability and apoptosis in high glucose (HG)-stimulated podocytes were measured by Cell Counting Kit-8 assays and flow cytometry, respectively. The expression of genes was tested by immunoblotting, quantitative real-time PCR, and immunofluorescence staining. Results: APS enhanced the expression of podocin and nephrin, increased viability, and reduced apoptosis in HG-induced podocytes. APS treatment abrogated high glucose-mediate suppression of autophagy in podocytes by activating the Sirt1/FoxO1 pathway. The Sirt1 inhibitor EX-527 eliminated the ameliorative effects of APS on renal dysfunction and renal tissue damage, as well as the inhibitory effects of APS on oxidative stress, inflammation, and apoptosis in DN rats. Moreover, EX-527 inhibited APS-induced autophagy activation in DN rats. Conclusion: APS mitigated DN under hyperglycemic conditions by activating the Sirt1/FoxO1 autophagy pathway, suggesting that APS is a promising agent for DN treatment. [ABSTRACT FROM AUTHOR]

In the past few decades, the global prevalence of diabetes has provided us with a warning about future chronic complications. Diabetic nephropathy (DN) is the main cause of end-stage kidney disease. Podocytes in the glomerulus play a critical role in regulating glomerular permeability, and podocyte injury is one of the main causes of DN. Extracellular signal-regulated kinase (ERK) is a member of the mitogen-activated protein kinase family that plays critical roles in intracellular signal transduction. In human patients with DN, phosphorylated ERK (pERK), the active form of ERK, is increased in the glomeruli. However, information on the expression of pERK, specifically in podocytes in DN, is limited. Meanwhile, high glucose induces ERK activation in immortalized podocyte cell lines, suggesting the involvement of podocytic ERK in DN. We performed an immunohistochemical study using Wilms' tumor-1 (WT-1) as a podocyte-specific marker to investigate whether podocytic pERK levels are increased in patients with DN. In the glomeruli of the DN group, we observed remarkable co-staining for WT-1 and pERK. In contrast, the glomeruli of the control group contained only a few pERK-positive podocytes. Statistical analyses revealed that, relative to healthy controls, patients with DN showed significantly increased pERK expression levels in cells that were positive for WT-1 (DN: 51.3 ± 13.1% vs. control: 7.3 ± 1.6%, p = 0.0158, t-test, n = 4 for each group). This suggests that ERK activation in podocytes is involved in the pathogenesis of DN. [ABSTRACT FROM AUTHOR]

Cell deaths maintain the normal function of tissues and organs. In pathological conditions, the abnormal activation or disruption of cell death often leads to pathophysiological effects. Diabetic kidney disease (DKD), a significant microvascular complication of diabetes, is linked to high mortality and morbidity rates, imposing a substantial burden on global healthcare systems and economies. Loss and detachment of podocytes are key pathological changes in the progression of DKD. This review explores the potential mechanisms of apoptosis, necrosis, autophagy, pyroptosis, ferroptosis, cuproptosis, and podoptosis in podocytes, focusing on how different cell death modes contribute to the progression of DKD. It recognizes the limitations of current research and presents the latest basic and clinical research studies targeting podocyte death pathways in DKD. Lastly, it focuses on the future of targeting podocyte cell death to treat DKD, with the intention of inspiring further research and the development of therapeutic strategies. [ABSTRACT FROM AUTHOR]

Objective: Diabetic nephropathy (DN) is a serious complication that may occur during the later stages of diabetes, and can be further exacerbated by podocyte damage. Piperazine ferulate (PF) has well-defined nephroprotective effects and is used clinically in the treatment of chronic nephritis and other kidney diseases. However, the renoprotective effects and mechanisms of PF on DN are not clear. This study aims to investigate the protective effect of PF on DN and its mechanism of action, to inform the clinical application of PF in DN treatment. Methods: Network pharmacology was performed to predict themechanism of action of PF in DN. Male Sprague Dawley rats were intraperitoneally injected with STZ (60 mg/kg) to establish a DN model, and then assessed for renal injury after 12 weeks of administration. In vitro, rat podocytes were treated with 25 mmol/L glucose and cultured for 24 h, followed by an assessment of cell injury. Results: Our results showed that PF significantly improved renal function, reduced renal pathological changes, decreased inflammatory response, and alleviated podocyte damage in DN rats. PF also attenuated glucose-induced podocyte injury in vitro. Regarding molecular mechanisms, our study demonstrated that PF downregulated the expression of genes and proteins related to AGE-RAGE-mediated inflammatory signaling. Conclusion: In summary, PF exerts its renoprotective effects by decreasing inflammation and protecting against podocyte injury through the inhibition of the AGE/RAGE/NF-κB/NLRP3 pathway. Overall, these data support the clinical potential of PF as a renoprotective agent in DN. [ABSTRACT FROM AUTHOR]

Primary membranous nephropathy (PMN) is one of the leading causes of end‐stage renal disease, and the most frequent cause of massive proteinuria in nondiabetic adults, resulting in fatal complications. However, the underlying pathomechanisms of PMN remain largely unclear. Here, single‐cell RNA sequencing is employed to analyze kidney biopsies from eleven PMN patients and seven healthy subjects. Profiling 44 060 cells from patients allowed us to characterize the cellular composition and cell‐type‐specific gene expression in the PMN kidney. The complement‐induced BMP2/pSMAD1/COL4 pathway is identified as the pathogenic pathway in podocytes, bridging two key events, i.e., complement system activation and glomerular basement membrane thickening in PMN. Augmented infiltration and activation of myeloid leukocytes and B lymphocytes are found, profiling delicate crosstalk of immune cells in PMN kidneys. Overall, these results provide valuable insights into the roles of podocytes and immune cells in PMN, and comprehensive resources toward the complete understanding of PMN pathophysiology. [ABSTRACT FROM AUTHOR]

The fine structure of echiurid blood vessels in the proboscis is known in detail, but the circulatory system of the trunk is still understood mainly at the level of general anatomy. The trunk circulatory system was studied in Bonellia viridis females, and specialized podocytes were found to form the walls of the ring vessel and the anterior part of the ventral vessel. Podocytes were for the first time described in the echiurid circulatory system. Podocytes of B. viridis displayed a typical cell architecture, which is known for other bilaterians. A podocyte consists of a cell body; primary processes; and pedicels, which extend from the primary processes and are interconnected via specialized slit diaphragms. The presence of podocytes indicates that the ventral and ring vessels act as ultrafiltration sites, where the plasma is filtered through the basal lamina into the body cavity. [ABSTRACT FROM AUTHOR]

Membranous nephropathy (MN) continues to be a leading cause of nephrotic syndrome in non-diabetic adults. As a unique subtype in the serology-based classification of MN, thrombospondin type 1 domain containing 7A (THSD7A)- associatedMNhas attracted increasing interest, because, unlike other autoantigens, THSD7A is also expressed in preclinical species, facilitating the study of its role in MN. A heterologous mouse model of THSD7A-associated MN was previously established using a proprietary in-house antibody that was unfortunately not available to the research community. Here, we developed a mouse model of THSD7A-associated MN by administering a commercially available antibody targeting the most N-terminal part of THSD7A. Our model was characterized by heavy proteinuria and pathological features of human MN without sex differences. Complement depletion with cobra venom factor only partially attenuated proteinuria and glomerular injury in this model, entailing that complementindependent pathomechanisms also contribute. Consistently, in vitro in primary podocytes, exposure to the anti-THSD7A antibody caused evident podocytopathic changes, including disruption of actin cytoskeleton integrity, podocyte hypermobility, oxidative stress, and apoptotic cell death. These signs of podocytopathy were preserved, albeit to a lesser extent, after complement inactivation, indicating autonomous podocyte injury. Furthermore, as the first FDA-approved treatment for primary MN, adrenocorticotropic hormone therapy with repository corticotropin injection (Purified Cortrophin Gel®) appeared to be beneficial and significantly attenuated proteinuria and glomerular injury, suggesting that this modelmay be useful for developing novel treatments or understanding the pathogenesis of MN. Collectively, our model, based on the use of a commercially available anti-THSD7A antibody, will be an important tool for MN research. [ABSTRACT FROM AUTHOR]

Purpose: Podocyte injury plays a crucial role in the development of diabetic nephropathy (DN). A high serum level of insulin‐like growth factor 1 (IGF‐1) has been observed in patients with DN. This paper is to study the role and mechanism of IGF‐1 in high glucose (HG)‐induced podocyte injury. Methods: Mouse podocytes MPC‐5 were treated with HG to establish a DN model in vitro. db/db diabetic mice and db/m nondiabetic mice were used to evaluate the IGF‐1 role in vivo. Western blotting was used for measuring protein levels of IGF‐1 receptor, Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling pathway‐related markers, podocyte markers podocin and nephrin, apoptosis‐ and autophagy‐related markers in MPC‐5 cells. Immunofluorescence staining was implemented for measuring the expression of nephrin and the autophagy marker LC3. Flow cytometry was used for detecting podocyte apoptosis. Results: IGF‐1 expression was increased in HG‐stimulated MPC‐5 cells and the kidney of db/db diabetic mice compared with corresponding controls. Knocking down IGF‐1 downregulated IGF‐1R and inhibited JAK2/STAT signalling pathway in HG‐treated MPC‐5 cells and db/db diabetic mice. IGF‐1 silencing attenuated HG‐induced podocyte injury, apoptosis and reduction in autophagy. Activating the JAK2/STAT signalling pathway or inhibiting autophagy reversed the effects of IGF‐1 silencing on HG‐treated MPC‐5 cells. Conclusion: Knocking down IGF‐1 alleviates HG‐induced podocyte injury and apoptosis by inactivating the JAK2/STAT signalling pathway and enhancing autophagy. [ABSTRACT FROM AUTHOR]

Previous studies have shown that podocyte injury is involved in the development of proteinuria in rats under hypobaric hypoxia conditions. Prolyl hydroxylase inhibitors (PHIs) may reduce proteinuria. This study aimed to further investigate whether the protective effects of hypoxia‐inducible factor 1α (HIF1α) on podocyte injury induced by hypobaric hypoxia are related to Krüppel‐like factor 4 (KLF4). Rats were housed in a low‐pressure oxygen chamber to simulate a high‐altitude environment (5000 m), and a PHI was intraperitoneally injected. Urinary protein electrophoresis was performed and the morphology of the podocytes was observed by electron microscopy. Rat podocytes were cultured under 1% O2, and siRNA was used to interfere with KLF4 expression. The protein expression levels of HIF1α, KLF4, CD2‐associated protein (CD2AP) and nephrin were determined by western blotting. Compared with those in the experimental group, the rats in the intervention group on day 14 had lower urinary protein levels, increased protein expression levels of CD2AP and nephrin, and reduced podocyte injury. The results of in vitro experiments showed that the protein expression levels of KLF4, CD2AP and nephrin were greater in the PHI intervention group and lower in the HIF1α inhibitors group than in the low‐oxygen group. The protein expression of CD2AP and nephrin in the siKLF4‐transfected podocytes treated with PHI and HIF1α inhibitors did not differ significantly from that in the low‐oxygen group. HIF1α may be involved in reducing progressive high‐altitude proteinuria by regulating KLF4 expression and contributing to the repair of podocyte injury induced by hypobaric hypoxia. What is the central question of this study?Podocyte injury is involved in the development of proteinuria in rats under simulated high‐altitude environments and prolyl‐hydroxylase inhibitors (PHI) may have a potential role in reducing proteinuria: what are the effects of PHIs on podocytes and what are the mechanisms?What is the main finding and its importance?PHIs may have a potential role in reducing proteinuria by upregulating local hypoxia‐inducible factor 1α (HIF1α) expression in the kidney to alleviate podocyte injury. HIF1α plays a potential role in regulating Krüppel‐like factor 4 expression and contributing to the repair of podocyte injury induced by hypobaric hypoxia. [ABSTRACT FROM AUTHOR]

Accumulating evidence indicates that inflammatory and immunologic processes play a significant role in the development and progression of glomerular diseases. Podocytes, the terminally differentiated epithelial cells, are crucial for maintaining the integrity of the glomerular filtration barrier. Once injured, podocytes cannot regenerate, leading to progressive proteinuric glomerular diseases. However, emerging evidence suggests that podocytes not only maintain the glomerular filtration barrier and are important targets of immune responses but also exhibit many features of immune-like cells, where they are involved in the modulation of the activity of innate and adaptive immunity. This dual role of podocytes may lead to the discovery and development of new therapeutic targets for treating glomerular diseases. This review aims to provide an overview of the innate immunity mechanisms involved in podocyte injury and the progression of proteinuric glomerular diseases. [ABSTRACT FROM AUTHOR]

Objective. To further clarify the mechanism of podocyte damage by studying the expression of cartilage oligomeric matrix protein (COMP) in glomerular podocytes and its relationship with podocyte autophagy under high glucose environment. Methods. The gene expression dataset GSE104948 was downloaded from the GENE EXPRESSION OMNIBUS (GEO) database, and differentially expressed genes (DEGs) were obtained via GEO2R. The molecular functions and signaling pathways related to differential genes were summarized. The most correlated key genes (hub genes) were acquired by Weighted Gene Co-Expression Network Analysis (WGCNA) and the protein-protein interaction network (PPI) of DEGs was constructed with STRING database. The enrichment analysis was performed again. Conditionally immortalized mouse podocyte cells were cultured in vitro. After being fully differentiated, they were stimulated with high glucose, and the expressions of COMP, mammalian target of rapamycin (mTOR), microtubule-associated protein 1 light chain3 (LC3) and other proteins in podocytes were detected by Western blotting. The shRNA constructed by lentiviral vector was further used to infect podocytes to inhibit the expression of COMP, and the stable cell strains were screened by puromycin. The expression of COMP, mTOR, and LC3 of stable strains were detected by Western blotting, in order to observe the effect of COMP on autophagy. Results. A total of 362 DEGs were filtered for subsequent analysis. Among these DEGs, 284 genes were up-regulated and 78 genes were down-regulated. The results of Gene Onotology (GO) term analysis showed that DEGs in diabetic nephropathy (DN) were mainly enriched in cell surface receptor signaling pathway, receptor binding, etc. The main enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways included phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT) signaling pathway, extracellular matrix (ECM)-receptor interaction, etc. Sixty-four hub genes were refined through the intersection of WGCNA and PPI hub genes, and the hub genes with significantly increased or decreased expression were sifted. The hub genes were annotated with KEGG again, and it was found that most of the hub genes were enriched in "ECM-receptor interaction" and "PI3K/AKT signaling pathway". The PI3K/AKT/mTOR signaling pathway is a classic autophagy pathway, and COMP was absolutely overexpressed (logFC>2) in the 64 hub genes, suggesting that it may affect autophagy through this pathway. Western blotting showed that compared with the mannitol control group and the low glucose group, the expression of COMP in podocytes was significantly increased under high glucose stimulation. Compared with the control group, the expression of LC3-II in the high glucose group was significantly decreased, indicating that the autophagy initiation of podocytes was inhibited under the high glucose environment. Compared with the negative control, the expression of LC3-II in renal podocytes of mice with knockdown of COMP was significantly increased, and the mTOR decreased with the decrease of the expression of COMP, indicating that inhibiting COMP contributed to the recovery of autophagy in podocytes. Conclusion. COMP is highly expressed in DN patients and highly enriched in ECM receptor and PI3K/AKT signaling pathway. Autophagy in mouse renal podocytes is inhibited under high glucose conditions, and the high expression of COMP induced by high glucose may be a key factor in autophagy inhibition. Inhibiting COMP helps to restore autophagy in mouse renal podocytes. [ABSTRACT FROM AUTHOR]

Purpose: Tanshinone IIA (Tan-IIA) is widely used in patients with diabetic nephropathy (DN), but its protective effect on podocytes in DN has not been well studied. In this study, the effects of Tan-IIA on autophagy and inflammation of glomerular podocytes in DN were observed in vivo and in vitro, and the underlying mechanisms were investigated. Irbesartan, an angiotensin II receptor blocker, is a representative medication for the clinical treatment of DN. So irbesartan was chosen as a positive control drug. Methods: Eight-week-old male db/db mice were randomly divided into a DN group, an irbesartan group, and three groups receiving different doses of Tan-IIA. The control group consisted of the db/m littermate mice. Blood, urine, and kidney samples were taken from the mice after 12 weeks of continuous administration. Renal protection of Tan-IIA was evaluated using enzyme-linked immunosorbent assay kits, haematoxylin and eosin staining, transmission electron microscopy, Western blotting, and immunohistochemistry. In vitro, the protective effect of Tan-IIA on podocytes was explored using MPC5 cells cultured with high glucose. Results: Tan-IIA significantly improved renal pathological injury and relieved the renal dysfunction in DN. Compared with the DN group, Tan-IIA could up-regulate the expression of Synaptopodin, Podocin, LC3II/I and Beclin-1 (p < 0.05), and down-regulate the expression of p62, F4/80, NF-κB p65, IL-1β, TNF-α and IL-6 (p < 0.05) both in vivo and in vitro, suggesting that Tan-IIA treatment alleviated podocyte injury by promoting autophagy and inhibiting inflammation during DN. The levels of p-PI3K/PI3K, p-Akt/Akt and p-mTOR/mTOR in Tan-IIA group were lower than those in DN group (p < 0.05), indicating that Tan-IIA inhibited the PI3K/Akt/mTOR signalling pathway in podocytes, which was a key pathway in regulating both autophagy and inflammation. Conclusion: Tan-IIA prevented podocyte injury in DN by fostering autophagy and inhibiting inflammation, at least in part via inhibition of the PI3K/Akt/mTOR signalling pathway. [ABSTRACT FROM AUTHOR]

Abstract Previous studies have shown that podocyte injury is involved in the development of proteinuria in rats under hypobaric hypoxia conditions. Prolyl hydroxylase inhibitors (PHIs) may reduce proteinuria. This study aimed to further investigate whether the protective effects of hypoxia‐inducible factor 1α (HIF1α) on podocyte injury induced by hypobaric hypoxia are related to Krüppel‐like factor 4 (KLF4). Rats were housed in a low‐pressure oxygen chamber to simulate a high‐altitude environment (5000 m), and a PHI was intraperitoneally injected. Urinary protein electrophoresis was performed and the morphology of the podocytes was observed by electron microscopy. Rat podocytes were cultured under 1% O2, and siRNA was used to interfere with KLF4 expression. The protein expression levels of HIF1α, KLF4, CD2‐associated protein (CD2AP) and nephrin were determined by western blotting. Compared with those in the experimental group, the rats in the intervention group on day 14 had lower urinary protein levels, increased protein expression levels of CD2AP and nephrin, and reduced podocyte injury. The results of in vitro experiments showed that the protein expression levels of KLF4, CD2AP and nephrin were greater in the PHI intervention group and lower in the HIF1α inhibitors group than in the low‐oxygen group. The protein expression of CD2AP and nephrin in the siKLF4‐transfected podocytes treated with PHI and HIF1α inhibitors did not differ significantly from that in the low‐oxygen group. HIF1α may be involved in reducing progressive high‐altitude proteinuria by regulating KLF4 expression and contributing to the repair of podocyte injury induced by hypobaric hypoxia.

AbstractContext Membranous glomerulonephritis (MGN) is a leading cause of nephrotic syndrome in adults. Diosgenin (DG) has been reported to exert antioxidative and anti-inflammatory effects.Objective To investigate the renoprotective activity of DG in a cationic bovine serum albumin-induced rat model of MGN.Materials and methods Fourty male Sprague-Dawley rats were randomized into four groups. The MGN model was established and treated with a DG dose (10 mg/kg) and a positive control (TPCA1, 10 mg/kg), while normal control and MGN groups received distilled water by gavage for four consecutive weeks. At the end of the experiment, 24 h urinary protein, biochemical indices, oxidation and antioxidant levels, inflammatory parameters, histopathological examination, immunohistochemistry and immunoblotting were evaluated.Results DG significantly ameliorated kidney dysfunction by decreasing urinary protein (0.56-fold), serum creatinine (SCr) (0.78-fold), BUN (0.71-fold), TC (0.66-fold) and TG (0.73-fold) levels, and increasing ALB (1.44-fold). DG also reduced MDA (0.82-fold) and NO (0.83-fold) levels while increasing the activity of SOD (1.56-fold), CAT (1.25-fold), glutathione peroxidase (GPx) (1.55-fold) and GSH (1.81-fold). Furthermore, DG reduced Keap1 (0.76-fold) expression, Nrf2 nuclear translocation (0.79-fold), and induced NQO1 (1.25-fold) and HO-1 (1.46-fold) expression. Additionally, DG decreased IL-2 (0.55-fold), TNF-α (0.80-fold) and IL-6 (0.75-fold) levels, and reduced protein expression of NF-κB p65 (0.80-fold), IKKβ (0.93-fold), p-IKKβ (0.89-fold), ICAM-1 (0.88-fold), VCAM-1 (0.91-fold), MCP-1 (0.88-fold) and E-selectin (0.87-fold), and also inhibited the nuclear translocation of NF-κB p65 (0.64-fold).Discussion and conclusions The results suggest a potential therapeutic benefit of DG against MGN due to the inhibition of the NF-κB pathway, supporting the need for further clinical trials.

The prevalence of diabetic kidney disease (DKD) is increasing annually. Damage to and loss of podocytes occur early in DKD. tRNA-derived fragments (tRFs), originating from tRNA precursors or mature tRNAs, are associated with various illnesses. In this study, tRFs were identified, and their roles in podocyte injury induced by high-glucose (HG) treatment were explored. High-throughput sequencing of podocytes treated with HG was performed to identify differentially expressed tRFs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed. The expression levels of nephrin, podocin, and desmin were measured in podocytes after overexpression of tRF-1:24-Glu-CTC-1-M2 (tRF-1:24) and concomitant HG treatment. A total of 647 tRFs were identified, and 89 differentially expressed tRFs (|log2FC| ≥ 0.585; p ≤.05) were identified in the HG group, of which 53 tRFs were downregulated and 36 tRFs were upregulated. The 10 tRFs with the highest differential expression were detected by real-time quantitative polymerase chain reaction (RT-qPCR), and these results were consistent with the sequencing results. GO analysis revealed that the biological process, cellular component, and molecular function terms in which the tRFs were the most enriched were cellular processes, cellular anatomical entities, and binding. KEGG pathway analysis revealed that tRFs may be involved in signaling pathways related to growth hormones, phospholipase D, the regulation of stem cell pluripotency, and T-/B-cell receptors. Overexpression of tRF-1:24, one of the most differentially expressed tRFs, attenuated podocyte injury induced by HG. Thus, tRFs might be potential biomarkers for podocyte injury in DKD. [ABSTRACT FROM AUTHOR]

Diabetic nephropathy (DN) is a severe complication of diabetes mellitus, causing a substantive threat to the public, which receives global concern. However, there are limited drugs targeting the treatment of DN. Owing to this, it is highly crucial to investigate the pathogenesis and potential therapeutic targets of DN. The process of ferroptosis is a type of regulated cell death (RCD) involving the presence of iron, distinct from autophagy, apoptosis, and pyroptosis. A primary mechanism of ferroptosis is associated with iron metabolism, lipid metabolism, and the accumulation of ROS. Recently, many studies testified to the significance of ferroptosis in kidney tissue under diabetic conditions and explored the drugs targeting ferroptosis in DN therapy. Our review summarized the most current studies between ferroptosis and DN, along with investigating the significant processes of ferroptosis in different kidney cells, providing a novel target treatment option for DN. [ABSTRACT FROM AUTHOR]

WT1 encodes a podocyte transcription factor whose variants can cause an untreatable glomerular disease in early childhood. Although WT1 regulates many podocyte genes, it is poorly understood which of them are initiators in disease and how they subsequently influence other cell‐types in the glomerulus. We hypothesised that this could be resolved using single‐cell RNA sequencing (scRNA‐seq) and ligand‐receptor analysis to profile glomerular cell–cell communication during the early stages of disease in mice harbouring an orthologous human mutation in WT1 (Wt1R394W/+). Podocytes were the most dysregulated cell‐type in the early stages of Wt1R394W/+ disease, with disrupted angiogenic signalling between podocytes and the endothelium, including the significant downregulation of transcripts for the vascular factors Vegfa and Nrp1. These signalling changes preceded glomerular endothelial cell loss in advancing disease, a feature also observed in biopsy samples from human WT1 glomerulopathies. Addition of conditioned medium from murine Wt1R394W/+ primary podocytes to wild‐type glomerular endothelial cells resulted in impaired endothelial looping and reduced vascular complexity. Despite the loss of key angiogenic molecules in Wt1R394W/+ podocytes, the pro‐vascular molecule adrenomedullin was upregulated in Wt1R394W/+ podocytes and plasma and its further administration was able to rescue the impaired looping observed when glomerular endothelium was exposed to Wt1R394W/+ podocyte medium. In comparative analyses, adrenomedullin upregulation was part of a common injury signature across multiple murine and human glomerular disease datasets, whilst other gene changes were unique to WT1 disease. Collectively, our study describes a novel role for altered angiogenic signalling in the initiation of WT1 glomerulopathy. We also identify adrenomedullin as a proangiogenic factor, which despite being upregulated in early injury, offers an insufficient protective response due to the wider milieu of dampened vascular signalling that results in endothelial cell loss in later disease. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

Acute kidney injury (AKI) is a common clinical condition and is associated with unacceptable morbidity and mortality. Obtusifolin is an anthraquinone extracted from the seeds of Cassia obtusifolia with anti-inflammatory properties. This study focused on the role and mechanism of obtusifolin in AKI. The mouse podocyte cell line MPC5 was exposed to lipopolysaccharide (LPS) to establish a cell model of AKI. The viability of MPC5 cells treated with obtusifolin and/or LPS was detected by 3-(4, 5-Dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay. Cell apoptosis was analyzed by flow cytometry. The levels of podocyte injury- and apoptosis-related proteins as well as the nuclear factor-kappaB (NF-κB) signaling pathway was examined using western blotting analysis. The renal protective effects of obtusifolin were determined using an LPS-induced mouse model of AKI. Serum creatinine and blood urea nitrogen levels were measured. Hematoxylin–eosin staining of kidney sections was performed to evaluate renal histology. We found that MPC5 cells treated with LPS showed suppressed cell viability (p < 0.01) and increased cell apoptosis (p < 0.001). LPS reduced the protein expression of Bcl-2, nephrin, and synaptopodin as well as increased the protein levels of Bax and Cleaved Caspase-3 in podocytes in a concentration-dependent manner (p < 0.01). In addition, 10 μg/ml LPS-repressed cell viability was rescued by obtusifolin in a concentration-dependent manner (p < 0.01). Moreover, LPS-induced increase in MPC5 cell apoptosis was reversed by obtusifolin treatment (p < 0.01). Obtusifolin administration ameliorated LPS-induced kidney injury and reduced blood urea nitrogen and serum creatinine levels in mice (p < 0.001). Additionally, obtusifolin inhibited LPS-induced activation of NF-κB signaling in vitro and in vivo (p < 0.01). Overall, obtusifolin was effective in protecting renal function against LPS-induced AKI via inactivation of NF-κB signaling, which suggested that obtusifolin may act as a valuable agent for AKI therapy. [ABSTRACT FROM AUTHOR]

Objective: Chronic inflammation is a common feature in diabetes, especially when blood sugar levels are poorlycontrolled. This chronic low-grade inflammation can affect various organs, including the kidneys. Podocytedamage play a key role in the development of diabetic nephropathy (DN). The aim of the study was to evaluatethe nephroprotective effect of Boeravinone B (BB) against streptozotocin (STZ) induced DN in rats and explore theunderlying mechanism.Materials and Methods: In this experimental study, the rats received intraperitoneal injections of STZ (60 mg/kg) toinduce DN. Various doses of BB (2.5, 5, and 7.5 mg/kg) were administered orally. Glucose levels, body weights, andorgan weights (hepatic and renal) were assessed. Renal, histomorphological, antioxidant, hepatic, and cytokine levelswere determined, as were the mRNA expression levels of JAK2 and STAT3. At end of the experimental study, the ratswere sacrificed and their renal tissues were removed for histopathological assessment.Results: BB treatment decreased glucose levels and increased body weights. This treatment suppressed hepaticweights, increased renal tissue weights, and also decreased renal parameters like uric acid, urea, bilirubin, creatinine(Cr) and, albumin. There was a decrease (P

Abstract C57BL/6 mice are frequently utilized as murine models with the desired genetic background for altertion in multiple research contexts. So far, there is still a lack of comprehensive kidney morphology and single-cell transcriptome atlas at all stages of growth of C57BL/6 mice. To provide an interactive set of reference standards for the scientific community, we performed the current study to investigate the kidney’s development throughout the capillary-loop stage until senescence. Eight groups, with five to six mice each, represented embryonic stage (embryos 18.5 days), suckling period (1 day after birth), juvenile stage (1 month old), adulthood (containing 3 months old, 6 months old and 10 months old), reproductive senescence stage (20 months old), and post-senescence stage (30 months old), respectively. With age, the thickness of the glomerular basement membrane (GBM) was increased. Notably, GBM knobs appeared at three months and became frequent with age. Using single-cell transcriptome data, we evaluated how various biological process appear in particular cell types and investigated the potential mechanism of formation of GBM konbs. In conclusion, having access to detailed kidney morphology and single-cell transcriptome maps from C57BL/6 mice at various developmental stages of C57BL/6 mice would be a novel and major resource for biological research and testing of prospective therapeutic approaches.

Abstract Focal segmental glomerulosclerosis (FSGS) is a common pathological form of nephrotic syndrome. This study analyzed the value of pathological lesions and clinical prognosis of different segmental glomerulosclerosis ratios in FSGS. Two hundred and six FSGS patients were collected from Dec 2013 to Apr 2016. The patients were divided into two groups according to the proportion of glomerular segmental sclerosis: F1 (SSR ≤ 15%, n = 133) and F2 (SSR > 15%, n = 73). The clinical and pathological data were recorded and analyzed, and statistical differences were observed between the serum uric acid level and the percentage of chronic renal failure. The pathological results showed significant differences in interstitial fibrosis and tubular atrophy (IFTA), degree of mesangial hyperplasia, vascular lesions, synaptopodin intensity, and foot process effacement between the two groups. Multivariate logistic regression analysis showed significant differences in creatinine (OR: 1.008) and F2 group (OR: 1.19). In all patients, the prognoses of urine protein and serum creatinine levels were statistically different. Multivariate Cox regression analysis revealed that F2 (hazard ratio: 2.306, 95% CI 1.022–5.207) was associated with a risk of ESRD (end stage renal disease). The proportion of segmental glomerulosclerosis provides a guiding value in the pathological diagnosis and clinical prognosis of FSGS.

Acid sphingomyelinase (ASM) has been reported to increase tissue ceramide and thereby mediate hyperhomocysteinemia (hHcy)-induced glomerular nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome activation, inflammation, and sclerosis. In the present study, we tested whether somatic podocyte-specific silencing of Smpd1 gene (mouse ASM gene code) attenuates hHcy-induced NLRP3 inflammasome activation and associated extracellular vesicle (EV) release in podocytes and thereby suppresses glomerular inflammatory response and injury. In vivo, somatic podocyte-specific Smpd1 gene silencing almost blocked hHcy-induced glomerular NLRP3 inflammasome activation in Podocre (podocyte-specific expression of cre recombinase) mice compared with control littermates. By nanoparticle tracking analysis (NTA), floxed Smpd1 shRNA transfection was found to abrogate hHcy-induced elevation of urinary EV excretion in Podocre mice. In addition, Smpd1 gene silencing in podocytes prevented hHcy-induced immune cell infiltration into glomeruli, proteinuria, and glomerular sclerosis in Podocre mice. Such protective effects of podocyte-specific Smpd1 gene silencing were mimicked by global knockout of Smpd1 gene in Smpd1−/− mice. On the contrary, podocyte-specific Smpd1 gene overexpression exaggerated hHcy-induced glomerular pathological changes in Smpd1trg/Podocre (podocyte-specific Smpd1 gene overexpression) mice, which were significantly attenuated by transfection of floxed Smpd1 shRNA. In cell studies, we also confirmed that Smpd1 gene knockout or silencing prevented homocysteine (Hcy)-induced elevation of EV release in the primary cultures of podocyte isolated from Smpd1−/− mice or podocytes of Podocre mice transfected with floxed Smpd1 shRNA compared with WT/WT podocytes. Smpd1 gene overexpression amplified Hcy-induced EV secretion from podocytes of Smpd1trg/Podocre mice, which was remarkably attenuated by transfection of floxed Smpd1 shRNA. Mechanistically, Hcy-induced elevation of EV release from podocytes was blocked by ASM inhibitor (amitriptyline, AMI), but not by NLRP3 inflammasome inhibitors (MCC950 and glycyrrhizin, GLY). Super-resolution microscopy also showed that ASM inhibitor, but not NLRP3 inflammasome inhibitors, prevented the inhibition of lysosome-multivesicular body interaction by Hcy in podocytes. Moreover, we found that podocyte-derived inflammatory EVs (released from podocytes treated with Hcy) induced podocyte injury, which was exaggerated by T cell coculture. Interstitial infusion of inflammatory EVs into renal cortex induced glomerular injury and immune cell infiltration. In conclusion, our findings suggest that ASM in podocytes plays a crucial role in the control of NLRP3 inflammasome activation and inflammatory EV release during hHcy and that the development of podocyte-specific ASM inhibition or Smpd1 gene silencing may be a novel therapeutic strategy for treatment of hHcy-induced glomerular disease with minimized side effect. NEW & NOTEWORTHY: In the present study, we tested whether podocyte-specific silencing of Smpd1 gene attenuates hyperhomocysteinemia (hHcy)-induced nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome activation and associated inflammatory extracellular vesicle (EV) release in podocytes and thereby suppresses glomerular inflammatory response and injury. Our findings suggest that acid sphingomyelinase (ASM) in podocytes plays a crucial role in the control of NLRP3 inflammasome activation and inflammatory EV release during hHcy. Based on our findings, it is anticipated that the development of podocyte-specific ASM inhibition or Smpd1 gene silencing may be a novel therapeutic strategy for treatment of hHcy-induced glomerular disease with minimized side effects. [ABSTRACT FROM AUTHOR]

Approximately 30% of steroid-resistant nephrotic syndromes are attributed to monogenic disorders that involve 27 genes. Mutations in KANK family members have also been linked to nephrotic syndrome; however, the precise mechanism remains elusive. To investigate this, podocyte-specific Kank1 knockout mice were generated to examine phenotypic changes. In the initial assessment under normal conditions, Kank1 knockout mice showed no significant differences in the urinary albumin-creatinine ratio, blood urea nitrogen, serum creatinine levels, or histological features compared to controls. However, following kidney injury with adriamycin, podocyte-specific Kank1 knockout mice exhibited a significantly higher albumin-creatinine ratio and a significantly greater sclerotic index than control mice. Electron microscopy revealed more extensive foot process effacement in the knockout mice than in control mice. In addition, KANK1-deficient human podocytes showed increased detachment and apoptosis following adriamycin exposure. These findings suggest that KANK1 may play a protective role in mitigating podocyte damage under pathological conditions. [ABSTRACT FROM AUTHOR]

Podocyte health is vital for maintaining proper glomerular filtration in the kidney. Interdigitating foot processes from podocytes form slit diaphragms which regulate the filtration of molecules through size and charge selectivity. The abundance of lipid rafts, which are ordered membrane domains rich in cholesterol and sphingolipids, near the slit diaphragm highlights the importance of lipid metabolism in podocyte health. Emerging research shows the importance of sphingolipid metabolism to podocyte health through structural and signaling roles. Dysregulation in sphingolipid metabolism has been shown to cause podocyte injury and drive glomerular disease progression. In this review, we discuss the structure and metabolism of sphingolipids, as well as their role in proper podocyte function and how alterations in sphingolipid metabolism contributes to podocyte injury and drives glomerular disease progression. [ABSTRACT FROM AUTHOR]

Migrasomes represent a recently uncovered category of extracellular microvesicles, spanning a diameter range of 500 to 3000 nm. They are emitted by migrating cells and harbour a diverse array of RNAs and proteins. Migrasomes can be readily identified in bodily fluids like serum and urine, rendering them a valuable non‐invasive source for disease diagnosis through liquid biopsy. In this investigation, we introduce a streamlined and effective approach for the capture and quantitative assessment of migrasomes, employing wheat germ agglutinin (WGA)‐coated magnetic beads and flow cytometry (referred to as WBFC). Subsequently, we examined the levels of migrasomes in the urine of kidney disease (KD) patients with podocyte injury and healthy volunteers using WBFC. The outcomes unveiled a substantial increase in urinary podocyte‐derived migrasome concentrations among individuals with KD with podocyte injury compared to the healthy counterparts. Notably, the urinary podocyte‐derived migrasomes were found to express an abundant quantity of phospholipase A2 receptor (PLA2R) proteins. The presence of PLA2R proteins in these migrasomes holds promise for serving as a natural antigen for the quantification of autoantibodies against PLA2R in the serum of patients afflicted by membranous nephropathy. Consequently, our study not only pioneers a novel technique for the isolation and quantification of migrasomes but also underscores the potential of urinary migrasomes as a promising biomarker for the early diagnosis of KD with podocyte injury. [ABSTRACT FROM AUTHOR]

Background Diabetic nephropathy (DN) is the most common microvascular complication of diabetes mellitus (DM), being the second cause of end-stage renal disease globally. Podocyte injury is closely associated with DN developmen. Our study aimed to investigate the role of long non-coding RNA (lncRNA) TTN-AS1 in DN-associated podocyte injury. Methods The mouse podocyte cell line (MPC5) and human primary podocytes were stimulated by high glucose (HG; 30 nM glucose) to establish the cellular model of DN. Before HG stimulation, both podocytes were transfected with sh-TTN-AS1#1/2 or pcDNA3.1/STAT3 to evaluate the influence of TTN-AS1 knockdown or STAT3 overexpression on HG-induced podocyte injury. TTN-AS1 and STAT3 expression in both podocytes was examined by RT-qPCR. Cell viability and death were assessed by CCK-8 and LDH release assay. ELISA was adopted for testing IL-6 and TNF-α contents in cell supernatants. The levels of oxidative stress markers (ROS, MDA, SOD, and GSH) in cell supernatants were determined by commercial kits. Western blotting was used for measuring the expression of fibrosis markers (fibronectin and α-SMA and podocyte function markers (podocin and nephrin) in podocytes. Results HG stimulation led to decreased cell viability, increased cell death, fibrosis, inflammation, cell dysfunction and oxidative stress in podocytes. However, knockdown of TTN-AS1 ameliorated HG-induced podocyte injury. Mechanically, the transcription factor STAT3 interacted with TTN-AS1 promoter and upregulated TTN-AS1 expression. STAT3 overexpression offset the protective effect of TTN-AS1 silencing on HG-induced podocyte damage. Conclusion Overall, STAT3-mediated upregulation of lncRNA TTN-AS1 could exacerbate podocyte injury in DN through suppressing inflammation and oxidative stress. [ABSTRACT FROM AUTHOR]

Podocyte injury plays a critical role in the progression of diabetic kidney disease (DKD), but the underlying cellular and molecular mechanisms remain poorly understanding. MicroRNAs (miRNAs) can disrupt gene expression by inducing translation inhibition and mRNA degradation, and recent evidence has shown that miRNAs may play a key role in many kidney diseases. In this study, we identified miR‐4645‐3p by global transcriptome expression profiling as one of the major downregulated miRNAs in high glucose‐cultured podocytes. Moreover, whether DKD patients or STZ‐induced diabetic mice, expression of miR‐4645‐3p was also significantly decreased in kidney. In the podocytes cultured by normal glucose, inhibition of miR‐4645‐3p expression promoted mitochondrial damage and podocyte apoptosis. In the podocytes cultured by high glucose (30 mM glucose), overexpression of miR‐4645‐3p significantly attenuated mitochondrial dysfunction and podocyte apoptosis induced by high glucose. Furthermore, we found that miR‐4645‐3p exerted protective roles by targeting Cdk5 inhibition. In vitro, miR‐4645‐3p obviously antagonized podocyte injury by inhibiting overexpression of Cdk5. In vivo of diabetic mice, podocyte injury, proteinuria, and impaired renal function were all effectively ameliorated by treatment with exogenous miR‐4645‐3p. Collectively, these findings demonstrate that miR‐4645‐3p can attenuate podocyte injury and mitochondrial dysfunction in DKD by targeting Cdk5. Sustaining the expression of miR‐4645‐3p in podocytes may be a novel strategy to treat DKD. [ABSTRACT FROM AUTHOR]

Nuclear receptors (NRs) are important transcriptional factors that mediate autophagy, preventing podocyte injury and the progression of diabetic kidney disease (DKD). However, the role of nuclear receptor coactivators that are powerful enhancers for the transcriptional activity of NRs in DKD remains unclear. In this study, a significant decrease in Nuclear Receptor Coactivator 3 (NCOA3) is observed in injured podocytes caused by high glucose treatment. Additionally, NCOA3 overexpression counteracts podocyte damage by improving autophagy. Further, Src family member, Fyn is identified to be the target of NCOA3 that mediates the podocyte autophagy process. Mechanistically, NCOA3 regulates the transcription of Fyn in a nuclear receptor, PPAR‐γ dependent way. Podocyte‐specific NCOA3 knockout aggravates albuminuria, glomerular sclerosis, podocyte injury, and autophagy in DKD mice. However, the Fyn inhibitor, AZD0530, rescues podocyte injury of NCOA3 knockout DKD mice. Renal NCOA3 overexpression with lentivirus can ameliorate podocyte damage and improve podocyte autophagy in DKD mice. Taken together, the findings highlight a novel target, NCOA3, that protects podocytes from high glucose injury by maintaining autophagy. [ABSTRACT FROM AUTHOR]

Background: A previous report showed that the urine output of HPLBII-P in patients with diabetes mellitus and SARS-CoV-2 infection was increased as a sign of glomerular dysfunction. The aim of this report was to investigate the relation of the urine output of HPLBII-P to diabetes mellitus in two large community-based elderly populations, i.e., the ULSAM and PIVUS cohorts. Methods: HPLBII-P was measured by an ELISA in the urine of a community-based cohort of 839 men (ULSAM) collected at 77 years of age and in the urine of a community-based cohort of 75-year-old men, n = 387, and women, n = 401 (PIVUS). KIM-1, NGAL, and albumin were measured in urine and cathepsin S and cystatin C in serum. Results: HPLBII-P was significantly raised among males with diabetes in the ULSAM (p < 0.0001) and PIVUS cohorts (p ≤ 0.02), but not in the female cohort of PIVUS. In the female subpopulation of insulin-treated diabetes, HPLBII-P was raised (p = 0.02) as compared to women treated with oral antidiabetics only. In the ULSAM cohort, HPLBII-P was correlated to NGAL, KIM-1, and albumin in urine both in non-DM (all three biomarkers; p < 0.0001) and in DM (NGAL; p = 0.002, KIM-1; p = 0.02 and albumin; p = 0.01). Plasma glucose and HbA1c in blood showed correlations to U-HPLBII-P (r = 0.58, p < 0.001 and r = 0.42, p = 0.004, respectively). U-HPLBII-P and cathepsin S were correlated in the ULSAM group (r = 0.50, p < 0.001). No correlations were observed between U-HPLBII-P and serum creatinine or cystatin C. Conclusions: The urine measurement of HPLBII-P has the potential to become a novel and useful biomarker in the monitoring of glomerular activity in diabetes mellitus. [ABSTRACT FROM AUTHOR]

Introduction: Urinary extracellular vesicles (uEVs) can be considered biomarkers of kidney diseases. EVs derived from podocytes may reflect podocyte damage in different glomerular diseases. IgA nephropathy (IgAN) is one of the most common forms of glomerulonephritis (GN) characterized by proteinuria and hematuria. This study aimed to analyze the uEVs of IgAN patients to understand the pathophysiological processes of the disease at the protein level. Methods: Patients with GN [biopsy-proven IgAN (n = 16) and membranous glomerulonephritis (MGN, n = 16)], and healthy controls (n = 16) were included in this study. The uEVs were extracted, characterized, and analyzed to evaluate the protein levels of candidate markers of IgAN, including vasorin precursor, aminopeptidase N, and ceruloplasmin by western-blot analysis. Results: Higher levels of both podocytes and EVs-related proteins were observed in the pooled urine samples of GN patients compared to the healthy controls. In IgAN patients, uEV-protein levels of vasorin were statistically lower while levels of ceruloplasmin were significantly higher compared to MGN (P = 0.002, P = 0.06) and healthy controls, respectively (P = 0.020, P= 0.001). Conclusion: Different levels of the studied proteins in uEVs may indicate podocyte injury and represent a direct association with the pathology of IgAN and MGN. [ABSTRACT FROM AUTHOR]

PAX2 regulates kidney development, and its expression persists in parietal epithelial cells (PECs), potentially serving as a podocyte reserve. We hypothesized that mice with a Pax2 pathogenic missense variant (Pax2A220G/þ) have impaired PEC-mediated podocyte regeneration. Embryonic wild-type mouse kidneys showed overlapping expression of PAX2/Wilms' tumor-1 (WT-1) until PEC and podocyte differentiation, reflecting a close lineage relationship. Embryonic and adult Pax2A220G/þ mice have reduced nephron number but demonstrated no glomerular disease under baseline conditions. Pax2A220G/þ mice compared with wildtype mice were more susceptible to glomerular disease after adriamycin (ADR)-induced podocyte injury, as demonstrated by worsened glomerular scarring, increased podocyte foot process effacement, and podocyte loss. There was a decrease in PAX2- expressing PECs in wild-type mice after adriamycin injury accompanied by the occurrence of PAX2/WT-1-coexpressing glomerular tuft cells. In contrast, Pax2A220G/þ mice showed no changes in the numbers of PAX2-expressing PECs after adriamycin injury, associated with fewer PAX2/WT-1-coexpressing glomerular tuft cells compared with injured wild-type mice. A subset of PAX2- expressing glomerular tuft cells after adriamycin injury was increased in Pax2A220G/þ mice, suggesting a pathological process given the worse outcomes observed in this group. Finally, Pax2A220G/þ mice have increased numbers of glomerular tuft cells expressing Ki-67 and cleaved caspase-3 compared with wild-type mice after adriamycin injury, consistent with maladaptive responses to podocyte loss. Collectively, our results suggest that decreased glomerular numbers in Pax2A220G/þ mice are likely compounded with the inability of their mutated PECs to regenerate podocyte loss, and together these two mechanisms drive the worsened focal segmental glomerular sclerosis phenotype in these mice. [ABSTRACT FROM AUTHOR]

Investigating the role of podocytes in proteinuric disease is imperative to address the increasing global burden of chronic kidney disease (CKD). Studies strongly implicate increased levels of monocyte chemoattractant protein-1 (MCP-1/CCL2) in proteinuric CKD. Since podocytes express the receptor for MCP-1 (i.e., CCR2), we hypothesized that podocyte-specific MCP-1 production in response to stimuli could activate its receptor in an autocrine manner, leading to further podocyte injury. To test this hypothesis, we generated podocyte-specific MCP-1 knockout mice (Podo-Mcp-1fl/fl) and exposed them to proteinuric injury induced by either angiotensin II (Ang II; 1.5 mg/kg/d, osmotic minipump) or Adriamycin (Adr; 18 mg/kg, intravenous bolus). At baseline, there were no between-group differences in body weight, histology, albuminuria, and podocyte markers. After 28 days, there were no between-group differences in survival, change in body weight, albuminuria, kidney function, glomerular injury, and tubulointerstitial fibrosis. The lack of protection in the knockout mice suggests that podocyte-specific MCP-1 production is not a major contributor to either Ang II- or Adr-induced glomerular disease, implicating that another cell type is the source of pathogenic MCP-1 production in CKD. [ABSTRACT FROM AUTHOR]

C57BL/6 mice are frequently utilized as murine models with the desired genetic background for altertion in multiple research contexts. So far, there is still a lack of comprehensive kidney morphology and single-cell transcriptome atlas at all stages of growth of C57BL/6 mice. To provide an interactive set of reference standards for the scientific community, we performed the current study to investigate the kidney's development throughout the capillary-loop stage until senescence. Eight groups, with five to six mice each, represented embryonic stage (embryos 18.5 days), suckling period (1 day after birth), juvenile stage (1 month old), adulthood (containing 3 months old, 6 months old and 10 months old), reproductive senescence stage (20 months old), and post-senescence stage (30 months old), respectively. With age, the thickness of the glomerular basement membrane (GBM) was increased. Notably, GBM knobs appeared at three months and became frequent with age. Using single-cell transcriptome data, we evaluated how various biological process appear in particular cell types and investigated the potential mechanism of formation of GBM konbs. In conclusion, having access to detailed kidney morphology and single-cell transcriptome maps from C57BL/6 mice at various developmental stages of C57BL/6 mice would be a novel and major resource for biological research and testing of prospective therapeutic approaches. [ABSTRACT FROM AUTHOR]

Focal segmental glomerulosclerosis (FSGS) is a common pathological form of nephrotic syndrome. This study analyzed the value of pathological lesions and clinical prognosis of different segmental glomerulosclerosis ratios in FSGS. Two hundred and six FSGS patients were collected from Dec 2013 to Apr 2016. The patients were divided into two groups according to the proportion of glomerular segmental sclerosis: F1 (SSR ≤ 15%, n = 133) and F2 (SSR > 15%, n = 73). The clinical and pathological data were recorded and analyzed, and statistical differences were observed between the serum uric acid level and the percentage of chronic renal failure. The pathological results showed significant differences in interstitial fibrosis and tubular atrophy (IFTA), degree of mesangial hyperplasia, vascular lesions, synaptopodin intensity, and foot process effacement between the two groups. Multivariate logistic regression analysis showed significant differences in creatinine (OR: 1.008) and F2 group (OR: 1.19). In all patients, the prognoses of urine protein and serum creatinine levels were statistically different. Multivariate Cox regression analysis revealed that F2 (hazard ratio: 2.306, 95% CI 1.022–5.207) was associated with a risk of ESRD (end stage renal disease). The proportion of segmental glomerulosclerosis provides a guiding value in the pathological diagnosis and clinical prognosis of FSGS. [ABSTRACT FROM AUTHOR]

Aims: Diabetic nephropathy (DN), a destructive complication of diabetes mellitus (DM), is one of the leading causes of end-stage renal disease (ESRD). This study aimed to investigate the role of long non-coding RNA (lncRNA) MIAT in high-glucose (HG)-induced podocyte injury associated with DN. Methods: Three human kidney podocyte (HKP) cultures were treated with HG to mimic DN. Expression of lncRNA MIAT, podocyte-specific and injury-related proteins, and apoptosis were assessed before and after MIAT knockdown using MIAT shRNAs. Results: MIAT expression was upregulated in HKPs in response to glucose stress. HG treatment resulted in a significant increase in the apoptotic rate, Bax level, and levels of injury-related proteins desmin, fibroblast-specific protein 1 (FSP-1), and smooth muscle α-actin (α-SMA), and a significant reduction in Bcl-2 levels and the levels of podocyte-specific proteins synaptopodin and podocin. Transfection of HKPs with shRNAs significantly reduced MIAT levels (p < 0.05) and attenuated apoptosis in HG-medium. Correspondingly, the levels of synaptopodin and podocin were upregulated, and desmin, FSP-1, and α-SMA were reduced (p < 0.05). Western blot analysis also showed that anti-apoptotic active caspase-3 and Bax and proapoptotic Bcl-2 were elevated and decreased, respectively, after MIAT knockdown, suggesting that apoptosis pathways are deactivated after MIAT downregulation. Conclusions: High glucose upregulates MIAT level in HKPs and induces cellular injury. Knockdown of MIAT alleviates the injury likely via deactivating apoptosis pathways. [ABSTRACT FROM AUTHOR]

Podocytes maintain renal filtration integrity when the glomerular filtration barrier (GFB) is integrated. Impairment or attrition of podocytes, leading to compromised GFB permeability, constitutes the primary etiology of proteinuria and is a hallmark pathological feature of diabetic nephropathy (DN). This study centers on Heterogeneous Nuclear Ribonucleoprotein I (HNRNP I), an RNA-binding protein, delineating its role in facilitating DN-induced renal damage by modulating podocyte health. Comparative analyses in renal biopsy specimens from DN patients and high-glucose-challenged podocyte models in vitro revealed a marked downregulation of HNRNP I expression relative to normal renal tissues and podocytes. In vitro assays demonstrated that high-glucose conditions precipitated a significant reduction in podocyte viability and an escalation in markers indicative of apoptosis. Conversely, HNRNP I overexpression was found to restore podocyte viability and attenuate apoptotic indices. IRAK1, a gene encoding a protein integral to inflammatory signaling, was shown to interact with HNRNP I, which promotes IRAK1 degradation. This interaction culminates in suppressing the PI3K/AKT/mTOR signaling pathway, thereby diminishing podocyte apoptosis and mitigating renal damage in DN. This investigation unveils the mechanistic role of HNRNP I in DN for the first time, potentially informing novel therapeutic strategies for DN renal impairment.

Podocytopathies encompass kidney diseases where direct or indirect podocyte injury leads to proteinuria or nephrotic syndrome. Although Semaphorin3A (Sema3A) is expressed in podocytes and tubular cells in adult mammalian kidneys and has a common effect on the progression of podocyte injury, its mechanism remains unclear. Previous studies have shown increased Sema3A expression in various glomerulopathies, indicating a gap in understanding its role. In this study, analysis of human data revealed a positive correlation between the levels of urinary Sema3A and Podocalyxin (PCX), suggesting a close relationship between Sema3A and podocyte loss. Furthermore, the impact of Adriamycin on podocytes was investigated. Adriamycin induced podocyte migration and apoptosis, along with an increase in Sema3A expression, all of which were ameliorated by the inhibition of Sema3A. Importantly, TRPC5 was found to increase the overexpression of Sema3A in podocytes. A TRPC5 inhibitor, AC1903, alleviated podocyte migration and apoptosis, inhibiting the formation of lamellar pseudopodia in the podocyte cytoskeleton by lowering the expression of Rac1. Furthermore, AC1903 relieved massive albuminuria and foot process effacement in the kidneys of Adriamycin-treated mice in vivo. In conclusion, our findings suggest that Sema3A may impact the cytoskeletal stability of podocytes through TRPC5 ion channels, mediated by Rac1, ultimately leading to foot process effacement. Notably, AC1903 demonstrates the potential to reverse Adriamycin-induced foot process fusion and urine protein. These results contribute to a deeper understanding of the mechanisms involved in podocytopathies and highlight the therapeutic potential of targeting the Sema3A-TRPC5 pathway.

Abstract Primary membranous nephropathy (PMN) is one of the leading causes of end‐stage renal disease, and the most frequent cause of massive proteinuria in nondiabetic adults, resulting in fatal complications. However, the underlying pathomechanisms of PMN remain largely unclear. Here, single‐cell RNA sequencing is employed to analyze kidney biopsies from eleven PMN patients and seven healthy subjects. Profiling 44 060 cells from patients allowed us to characterize the cellular composition and cell‐type‐specific gene expression in the PMN kidney. The complement‐induced BMP2/pSMAD1/COL4 pathway is identified as the pathogenic pathway in podocytes, bridging two key events, i.e., complement system activation and glomerular basement membrane thickening in PMN. Augmented infiltration and activation of myeloid leukocytes and B lymphocytes are found, profiling delicate crosstalk of immune cells in PMN kidneys. Overall, these results provide valuable insights into the roles of podocytes and immune cells in PMN, and comprehensive resources toward the complete understanding of PMN pathophysiology.

Diabetic kidney disease (DKD) is the primary cause of chronic kidney and end-stage renal disease. Glomerular podocyte loss and death are pathological hallmarks of DKD, and programmed cell death (PCD) in podocytes is crucial in DKD progression. PCD involves apoptosis, autophagy, ferroptosis, pyroptosis, and necroptosis. During DKD, PCD in podocytes is severely impacted and primarily characterized by accelerated podocyte apoptosis and suppressed autophagy. These changes lead to a gradual decrease in podocyte numbers, impairing the glomerular filtration barrier function and accelerating DKD progression. However, research on the interactions between the different types of PCD in podocytes is lacking. This review focuses on the novel roles and mechanisms of PCD in the podocytes of patients with DKD. Additionally, we summarize clinical drugs capable of regulating podocyte PCD, present challenges and prospects faced in developing drugs related to podocyte PCD and suggest that future research should further explore the detailed mechanisms of podocyte PCD and interactions among different types of PCD.

Abstract Renal involvement is one of the most severe morbidities of Fabry disease (FD), a multisystemic lysosomal storage disease with an X-linked inheritance pattern. It results from pathogenic variants in the GLA gene (Xq22.2), which encodes the production of alpha-galactosidase A (α-Gal), responsible for glycosphingolipid metabolism. Insufficient activity of this lysosomal enzyme generates deposits of unprocessed intermediate substrates, especially globotriaosylceramide (Gb3) and derivatives, triggering cellular injury and subsequently, multiple organ dysfunction, including chronic nephropathy. Kidney injury in FD is classically attributed to Gb3 deposits in renal cells, with podocytes being the main target of the pathological process, in which structural and functional alterations are established early and severely. This configures a typical hereditary metabolic podocytopathy, whose clinical manifestations are proteinuria and progressive renal failure. Although late clinical outcomes and morphological changes are well established in this nephropathy, the molecular mechanisms that trigger and accelerate podocyte injury have not yet been fully elucidated. Podocytes are highly specialized and differentiated cells that cover the outer surface of glomerular capillaries, playing a crucial role in preserving the structure and function of the glomerular filtration barrier. They are frequent targets of injury in many nephropathies. Furthermore, dysfunction and depletion of glomerular podocytes are essential events implicated in the pathogenesis of chronic kidney disease progression. We will review the biology of podocytes and their crucial role in regulating the glomerular filtration barrier, analyzing the main pathogenic pathways involved in podocyte injury, especially related to FD nephropathy.

Fabry disease (FD) is an X-linked lysosomal disease caused by an enzyme deficiency of alpha-galactosidase A (α-gal A). This deficiency leads to the accumulation of glycosphingolipids in lysosomes, resulting in a range of clinical symptoms. The complex pathogenesis of FD involves lysosomal dysfunction, altered autophagy, and mitochondrial abnormalities. Omics sciences, particularly transcriptomic analysis, comprehensively understand molecular mechanisms underlying diseases. This study focuses on genome-wide expression analysis in an FD human podocyte model to gain insights into the underlying mechanisms of podocyte dysfunction. Human control and GLA-edited podocytes were used. Gene expression data was generated using RNA-seq analysis, and differentially expressed genes were identified using DESeq2. Principal component analysis and Spearman correlation have explored gene expression trends. Functional enrichment and Reporter metabolite analyses were conducted to identify significantly affected metabolites and metabolic pathways. Differential expression analysis revealed 247 genes with altered expression levels in GLA-edited podocytes compared to control podocytes. Among these genes, 136 were underexpressed, and 111 were overexpressed in GLA-edited cells. Functional analysis of differentially expressed genes showed their involvement in various pathways related to oxidative stress, inflammation, fatty acid metabolism, collagen and extracellular matrix homeostasis, kidney injury, apoptosis, autophagy, and cellular stress response. The study provides insights into molecular mechanisms underlying Fabry podocyte dysfunction. Integrating transcriptomics data with genome-scale metabolic modeling further unveiled metabolic alterations in GLA-edited podocytes. This comprehensive approach contributes to a better understanding of Fabry disease and may lead to identifying new biomarkers and therapeutic targets for this rare lysosomal disorder.

BackgroundPrimary FSGS manifests with nephrotic syndrome and may recur following KT. Failure to respond to conventional therapy after recurrence results in poor outcomes. Evaluation of podocyte B7-1 expression and treatment with abatacept (a B7-1 antagonist) has shown promise but remains controversial.MethodsFrom 2012 to 2020, twelve patients developed post-KT FSGS with nephrotic range proteinuria, failed conventional therapy, and were treated with abatacept. Nine/twelve (

Lipid metabolism disorders lead to lipotoxicity. The hyperlipidemia-induced early stage of renal injury mainly manifests as podocyte damage. CD36 mediates fatty acid uptake and the subsequent accumulation of toxic lipid metabolites, resulting in podocyte lipotoxicity.

Background: Deposition of immune complexes drives podocyte injury acting in the initial phase of lupus nephritis (LN), a process mediated by B cell involvement. Accordingly, targeting B cell subsets represents a potential therapeutic approach for LN. Ginsenoside compound K (CK), a bioavailable component of ginseng, possesses nephritis benefits in lupus-prone mice; however, the underlying mechanisms involving B cell subpopulations remain elusive. Methods: Female MRL/lpr mice were administered CK (40 mg/kg) intragastrically for 10 weeks, followed by measurements of anti-dsDNA antibodies, inflammatory chemokines, and metabolite profiles on renal samples. Podocyte function and ultrastructure were detected. Publicly available single-cell RNA sequencing data and flow cytometry analysis were employed to investigate B cell subpopulations. Metabolomics analysis was adopted. SIRT1 and AMPK expression were analyzed by immunoblotting and immunofluorescence assays. Results: CK reduced proteinuria and protected podocyte ultrastructure in MRL/lpr mice by suppressing circulating anti-dsDNA antibodies and mitigating systemic inflammation. It activated B cell-specific SIRT1 and AMPK with Rhamnose accumulation, hindering the conversion of renal B cells into plasma cells. This cascade facilitated the resolution of local renal inflammation. CK facilitated the clearance of deposited immune complexes, thus reinstating podocyte morphology and mobility by normalizing the expression of nephrin and SYNPO. Conclusions: Our study reveals the synergistic interplay between SIRT1 and AMPK, orchestrating the restoration of renal B cell subsets. This process effectively mitigates immune complex deposition and preserves podocyte function. Accordingly, CK emerges as a promising therapeutic agent, potentially alleviating the hyperactivity of renal B cell subsets during LN.

Abstract Sirtuins, which are NAD+-dependent class III histone deacetylases, are involved in various biological processes, including DNA damage repair, immune inflammation, oxidative stress, mitochondrial homeostasis, autophagy, and apoptosis. Sirtuins are essential regulators of cellular function and organismal health. Increasing evidence suggests that the development of age-related diseases, including kidney diseases, is associated with aberrant expression of sirtuins, and that regulation of sirtuins expression and activity can effectively improve kidney function and delay the progression of kidney disease. In this review, we summarise current studies highlighting the role of sirtuins in renal diseases. First, we discuss sirtuin family members and their main mechanisms of action. We then outline the possible roles of sirtuins in various cell types in kidney diseases. Finally, we summarise the compounds that activate or inhibit sirtuin activity and that consequently ameliorate renal diseases. In conclusion, targeted modulation of sirtuins is a potential therapeutic strategy for kidney diseases. Video Abstract

Diabetic kidney disease (DKD) is a disease of abnormal renal structure and function due to long-term hyperglycemia. Podocyte injury is a major cause of renal inflammation, glomerular filtration barrier injury and renal fibrosis. Ubiquitin proteasome system is involved in intracellular protein clearance. Recent studies have confirmed that it plays an important role in podocyte injury of DKD. High glucose-related injury factors cause an abnormal function of podocyte proteasome, an altered expression level of ubiquitin ligase and an enhancement of deubiquitinating enzyme activity. As a result, an accumulation of injurious protein or an abnormal degradation of protective protein in podocyte may accentuate podocyte injury. This review focused upon the mechanisms of podocyte injury and ubiquitin proteasome involvement in DKD.