Search Results (21)

Podocytopathy, characterized by proteinuria, contributes significantly to kidney diseases, with hypertension playing a key role in damaging podocytes and the glomerular filtration barrier (GFB). The lack of functional in vitro models, however, impedes research and treatment development for hypertensive podocytopathy. We established a novel constant pressure-driven podocyte-on-chip model, utilizing our previously developed dynamic staining self-assembly cell array chip (SACA chip) and 3D printing. This platform features a differentiated podocyte monolayer under controlled hydrostatic pressures, mimicking the epithelial side of the GFB. Using this platform, we investigated mechanical force-dependent permeability to three sizes of fluorescent dextran under varying hydrostatic pressures, comparing the results with a puromycin aminonucleoside (PAN)-induced injury model. We observed that external pressures induced size-dependent permeability changes and altered cell morphology. Higher pressures led to greater macromolecule infiltration, especially for larger dextran (70 kDa, 500 kDa). Mature podocytes exhibited immediate, pressure-dependent cytoskeleton rearrangements, with better recovery at lower pressures (20 mmHg) but irreversible injury at higher pressures (40, 60 mmHg). These morphological changes were also corroborated by dynamic mRNA expression of cytoskeleton-associated proteins, Synaptopodin and ACTN4. This platform offers a promising in vitro tool for investigating the pathomechanisms of hypertension-induced podocytopathy, performing on-chip studies of the GFB, and conducting potential drug screening. Full article

ECIS-based impedance biosensors have been extensively studied in various fields including cancer research, microbiology, and immunology. However, most studies have primarily focused on monitoring cellular behavior through impedance changes, with relatively less emphasis on interpreting the biological significance of impedance signals. In this study, we employed a multi-well array impedance biosensor to conduct IC₅₀ (half-maximal inhibitory concentration) analysis, a widely used metric for evaluating drug efficacy and toxicity in biological and pharmacological research. Specifically, we assessed the IC₅₀ values of puromycin, an aminonucleoside antibiotic known to inhibit protein synthesis. NIH/3T3 fibroblasts were exposed to various concentrations of puromycin, and real-time impedance monitoring was performed. Cell viability was assessed, and the IC₅₀ value of puromycin for NIH/3T3 cells was determined to be 3.96 µM using capacitance-based impedance analysis. Our findings demonstrate that the multi-well array impedance biosensor provides a rapid and quantitative method for drug toxicity evaluation, offering a valuable platform for drug screening and biocompatibility assessment. Full article

Idiopathic childhood nephrotic syndrome is a common glomerulopathy comprising proteinuria, hypoalbuminemia, and edema. Podocyte dysfunction is central to this disease process. Extracellular vesicles are released from stressed cells and can represent a molecular snapshot of the parent cell of origin. We previously showed that urinary large extracellular vesicles (LEVs) derived from podocytes are increased in patients with nephrotic syndrome relapse. Here, we investigated the role of mitochondrial DNA (mtDNA) within LEVs both in vitro and in vivo, revealing the novel finding that podocytes release LEVs containing mtDNA, driven by mitochondrial stress. A puromycin aminonucleoside nephrosis rat model showed foot process effacement on electron microscopy and urinary LEVs with significantly increased mtDNA. Prednisolone, which drives remission in nephrotic syndrome in children, attenuated mitochondrial stress and reduced the amount of mtDNA content within LEVs in vitro. Lastly, urinary LEVs from children with nephrotic syndrome also contain mtDNA, and it is the podocyte LEV-fraction which is preferentially enriched. Overall, these data support a potential mechanism of podocyte mitochondrial stress in non-genetic, idiopathic pediatric nephrotic syndrome. Full article

Background: Podocytes are essential for kidney function, and their dysfunction can result in nephrotic syndrome, such as minimal change disease (MCD). Oxidative stress contributes to podocyte damage. We investigated the therapeutic potential of intravenously infused mesenchymal stem cells (MSCs) in a puromycin aminonucleoside (PAN)-induced rodent MCD model, focusing on oxidative stress modulation. Methods: Sprague-Dawley rats were divided into three groups: intact, PAN-Vehicle, and PAN-MSC. MCD was induced through subcutaneous PAN injection. MSCs were infused intravenously in the PAN-MSC group on day 7. Urinary albumin, serum albumin, and creatinine levels were assessed. Histological analysis of the renal cortex was performed. Podocyte protein (NPHS1, NPHS2, and PODXL) and antioxidant enzyme (SOD1, SOD2, and GPX1) levels were measured using quantitative real-time reverse-transcription PCR (qRT-PCR). Results: MSC infusion significantly reduced proteinuria and restored podocyte structure in the PAN-MSC group. Electron microscopy revealed that infused MSCs could inhibit the fusion of the foot process induced by PAN injection. qRT-PCR showed that intravenous infusion of MSCs rescued the inhibition of GPX1 expression. GFP-labeled MSCs accumulated at the podocyte injury sites. Conclusion: Systemic MSC infusion mitigates PAN-induced MCD by reducing proteinuria, preserving podocyte structure, and modulating oxidative stress via the GPX1 pathway, offering a potential therapeutic approach for nephrotic syndrome. Full article

Podocytes express large-conductance Ca²⁺-activated K⁺ channels (BK channels) and at least two different pore-forming KCa1.1 subunit C-terminal splice variants, known as VEDEC and EMVYR, along with auxiliary β and γ subunits. Podocyte KCa1.1 subunits interact directly with TRPC6 channels and BK channels become active in response to Ca²⁺ influx through TRPC6. Here, we confirmed that Ca²⁺ influx through TRPC channels is reduced following the blockade of BK channels by paxilline. The overall abundance of KCa1.1 subunits, as well as that of β4 and γ3 subunits, were increased in glomeruli isolated from Sprague Dawley rats during chronic puromycin aminonucleoside (PAN) nephrosis. Exposing cultured mouse podocytes for 24 h to recombinant TNFα, a circulating factor implicated in pediatric nephrotic syndromes, did not affect the total abundance of KCa1.1, but did evoke significant increases in both β4 and γ3. However, TNFα evoked a marked increase in the surface abundance of KCa1.1 subunits, similar to that of its previously reported effects on TRPC6 channels. The effect of TNFα on the surface expression of KCa1.1 was eliminated following siRNA knockdown of the β4 subunits, suggesting a role for this subunit in KCa1.1 trafficking to the cell surface. By contrast, treating podocytes with suPAR did not affect the total or surface expression of KCa1.1. The coordinated activation of KCa1.1 channels may promote Ca²⁺ influx through TRPC channels during normal and abnormal podocyte function by maintaining a membrane potential that allows for the efficient permeation of divalent cations through TRPC pores. Full article

Puromycin (Puro) is a natural aminonucleoside antibiotic that inhibits protein synthesis by its incorporation into elongating peptide chains. The unique mechanism of Puro finds diverse applications in molecular biology, including the selection of genetically engineered cell lines, in situ protein synthesis monitoring, and studying ribosome functions. However, the key step of Puro biosynthesis remains enigmatic. In this work, pur6-guided genome mining is carried out to explore the natural diversity of Puro-like antibiotics. The diversity of biosynthetic gene cluster (BGC) architectures suggests the existence of distinct structural analogs of puromycin encoded by pur-like clusters. Moreover, the presence of tRNA^Cys in some BGCs, i.e., cst-like clusters, leads us to the hypothesis that Pur6 utilizes aminoacylated tRNA as an activated peptidyl precursor, resulting in cysteine-based analogs. Detailed metabolomic analysis of Streptomyces sp. VKM Ac-502 containing cst-like BGC revealed the production of a cysteinyl-based analog of Puro—cystocin (Cst). Similar to puromycin, cystocin inhibits both prokaryotic and eukaryotic translation by the same mechanism. Aminonucleoside N-acetyltransferase CstC inactivated Cst, mediating antibiotic resistance in genetically modified bacteria and human cells. The substrate specificity of CstC originated from the steric hindrance of its active site. We believe that novel aminonucleosides and their inactivating enzymes can be developed through the directed evolution of the discovered biosynthetic machinery. Full article

GDF15, also known as MIC1, is a member of the TGF-beta superfamily. Previous studies reported elevated serum levels of GDF15 in patients with kidney disorder, and its association with kidney disease progression, while other studies identified GDF15 to have protective effects. To investigate the potential protective role of GDF15 on podocytes, we first performed in vitro studies using a Gdf15-deficient podocyte cell line. The lack of GDF15 intensified puromycin aminonucleoside (PAN)-triggered endoplasmic reticulum stress and induced cell death in cultivated podocytes. This was evidenced by elevated expressions of Xbp1 and ER-associated chaperones, alongside AnnexinV/PI staining and LDH release. Additionally, we subjected mice to nephrotoxic PAN treatment. Our observations revealed a noteworthy increase in both GDF15 expression and secretion subsequent to PAN administration. Gdf15 knockout mice displayed a moderate loss of WT1+ cells (podocytes) in the glomeruli compared to wild-type controls. However, this finding could not be substantiated through digital evaluation. The parameters of kidney function, including serum BUN, creatinine, and albumin–creatinine ratio (ACR), were increased in Gdf15 knockout mice as compared to wild-type mice upon PAN treatment. This was associated with an increase in the number of glomerular macrophages, neutrophils, inflammatory cytokines, and chemokines in Gdf15-deficient mice. In summary, our findings unveil a novel renoprotective effect of GDF15 during kidney injury and inflammation by promoting podocyte survival and regulating endoplasmic reticulum stress in podocytes, and, subsequently, the infiltration of inflammatory cells via paracrine effects on surrounding glomerular cells. Full article

Podocytes play a central role in glomerular diseases such as (idiopathic) nephrotic syndrome (iNS). Glucocorticoids are the gold standard therapy for iNS. Nevertheless, frequent relapses are common. In children with iNS, steroid-sparing agents are used to avoid prolonged steroid use and reduce steroid toxicity. Levamisole is one of these steroid-sparing drugs and although clinical effectiveness has been demonstrated, the molecular mechanisms of how levamisole exerts its beneficial effects remains poorly studied. Apart from immunomodulatory capacities, nonimmunological effects of levamisole on podocytes have also been suggested. We aimed to elaborate on the effects of levamisole on human podocytes in iNS. RNA sequencing data from a human podocyte cell line treated with levamisole showed that levamisole modulates the expression of various genes involved in actin cytoskeleton stabilization and remodeling. Functional experiments showed that podocytes exposed to puromycin aminonucleoside (PAN), lipopolysaccharides (LPS), and NS patient plasma resulted in significant actin cytoskeleton derangement, reduced cell motility, and impaired cellular adhesion when compared to controls, effects that could be restored by levamisole. Mechanistic studies revealed that levamisole exerts its beneficial effects on podocytes by signaling through the glucocorticoid receptor and by regulating the activity of Rho GTPases. In summary, our data show that levamisole exerts beneficial effects on podocytes by stabilizing the actin cytoskeleton in a glucocorticoid receptor-dependent manner. Full article

Podocyte cellular injury and detachment from glomerular capillaries constitute a critical factor contributing to kidney disease. Notably, transcription factors are instrumental in maintaining podocyte differentiation and homeostasis. This study explores the hitherto uninvestigated expression of Nuclear Factor Erythroid 2-related Factor 1 (NFE2L1) in podocytes. We evaluated the podocyte expression of NFE2L1, Nuclear Factor Erythroid 2-related Factor 2 (NFE2L2), and NAD(P)H:quinone Oxidoreductase (NQO1) in 127 human glomerular disease biopsies using multiplexed immunofluorescence and image analysis. We found that both NFE2L1 and NQO1 expressions were significantly diminished across all observed renal diseases. Furthermore, we exposed human immortalized podocytes and ex vivo kidney slices to Puromycin Aminonucleoside (PAN) and characterized the NFE2L1 protein isoform expression. PAN treatment led to a reduction in the nuclear expression of NFE2L1 in ex vivo kidney slices and podocytes. Full article

Podocytes, alternatively called glomerular epithelial cells, are terminally differentiated cells that wrap around glomerular capillaries and function as a part of the glomerular filtration barrier in the kidney. Therefore, podocyte injury with morphological alteration and detachment from glomerular capillaries leads to severe proteinuria and subsequent renal failure through glomerulosclerosis. Previous RNA sequencing analysis of primary rat podocytes exposed to puromycin aminonucleoside (PAN), a well-known experimental model of injured podocytes, identified several transcripts as being aberrantly expressed. However, how the expression of these transcripts is regulated remains unclear. MicroRNAs (miRNAs) are small noncoding RNAs that posttranscriptionally inhibit the expression of their target transcripts. In this study, using small RNA sequencing analysis, miR-217-5p was identified as the most upregulated transcript in PAN-treated rat podocytes. MiR-217-5p overexpression in E11 podocyte cells led to shrunken cells with abnormal actin cytoskeletons. Consistent with these changes in cell morphology, gene ontology (GO) enrichment analysis showed that interactive GO terms related to cell morphogenesis were enriched with the predicted targets of miR-217-5p. Of the predicted targets highly downregulated by PAN, Myosin 1d (Myo1d) is a nonmuscle myosin predicted to be involved in actin filament organization and thought to play a role in podocyte morphogenesis and injury. We demonstrated that miR-217-5p targets Myo1d by luciferase assays, qRT–PCR, and Western blotting. Furthermore, we showed that miR-217-5p was present in urine from PAN- but not saline-administrated rats. Taken together, our data suggest that miR-217-5p may serve as a therapeutic target and a biomarker for podocyte injury. Full article

Kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD), which can progress to end stage renal disease (ESRD), are a worldwide health burden. Organ transplantation or kidney dialysis are the only effective available therapeutic tools. Therefore, in vitro models of kidney diseases and the development of prospective therapeutic options are urgently needed. Within the kidney, the glomeruli are involved in blood filtration and waste excretion and are easily affected by changing cellular conditions. Puromycin aminonucleoside (PAN) is a nephrotoxin, which can be employed to induce acute glomerular damage and to model glomerular disease. For this reason, we generated kidney organoids from three iPSC lines and treated these with PAN in order to induce kidney injury. Morphological observations revealed the disruption of glomerular and tubular structures within the kidney organoids upon PAN treatment, which were confirmed by transcriptome analyses. Subsequent analyses revealed an upregulation of immune response as well as inflammatory and cell-death-related processes. We conclude that the treatment of iPSC-derived kidney organoids with PAN induces kidney injury mediated by an intertwined network of inflammation, cytoskeletal re-arrangement, DNA damage, apoptosis and cell death. Furthermore, urine-stem-cell-derived kidney organoids can be used to model kidney-associated diseases and drug discovery. Full article

Lymphatic vessels are highly responsive to changes in the interstitial environment. Previously, we showed renal lymphatics express the Na-K-2Cl cotransporter. Since interstitial sodium retention is a hallmark of proteinuric injury, we examined whether renal sodium affects NKCC1 expression and the dynamic pumping function of renal lymphatic vessels. Puromycin aminonucleoside (PAN)-injected rats served as a model of proteinuric kidney injury. Sodium ²³Na/¹H-MRI was used to measure renal sodium and water content in live animals. Renal lymph, which reflects the interstitial composition, was collected, and the sodium analyzed. The contractile dynamics of isolated renal lymphatic vessels were studied in a perfusion chamber. Cultured lymphatic endothelial cells (LECs) were used to assess direct sodium effects on NKCC1. MRI showed elevation in renal sodium and water in PAN. In addition, renal lymph contained higher sodium, although the plasma sodium showed no difference between PAN and controls. High sodium decreased contractility of renal collecting lymphatic vessels. In LECs, high sodium reduced phosphorylated NKCC1 and SPAK, an upstream activating kinase of NKCC1, and eNOS, a downstream effector of lymphatic contractility. The NKCC1 inhibitor furosemide showed a weaker effect on ejection fraction in isolated renal lymphatics of PAN vs controls. High sodium within the renal interstitium following proteinuric injury is associated with impaired renal lymphatic pumping that may, in part, involve the SPAK-NKCC1-eNOS pathway, which may contribute to sodium retention and reduce lymphatic responsiveness to furosemide. We propose that this lymphatic vessel dysfunction is a novel mechanism of impaired interstitial clearance and edema in proteinuric kidney disease. Full article

Chronic kidney disease (CKD) is normally related to proteinuria, a common finding in a compromised glomerular filtration barrier (GFB). GFB is a structure composed of glomerular endothelial cells, the basement membrane, and the podocytes. CKD with podocyte damage may be associated with actin cytoskeleton reorganization, resulting in podocyte effacement. Gelsolin plays a critical role in several diseases, including cardiovascular diseases and cancer. Our current study aimed to determine the connection between gelsolin and podocyte, and thus the mechanism underlying podocyte injury in CKD. Experiments were carried out on Drosophila to demonstrate whether gelsolin had a physiological role in maintaining podocyte. Furthermore, the survival rate of gelsolin-knocked down Drosophila larvae was extensively reduced after AgNO₃ exposure. Secondly, the in vitro podocytes treated with puromycin aminonucleoside (PAN) enhanced the gelsolin protein expression, as well as small GTPase RhoA and Rac1, which also regulated actin dynamic expression incrementally with the PAN concentrations. Thirdly, we further demonstrated in vivo that GSN was highly expressed inside the glomeruli with mitochondrial dysfunction in a CKD mouse model. Our findings suggest that an excess of gelsolin may contribute to podocytes damage in glomeruli. Full article

Urinary exosomes, small extracellular vesicles present in urine, are secreted from all types of renal epithelial cells. Aquaporin-2 (AQP2), a vasopressin-regulated water channel protein, is known to be selectively excreted into the urine through exosomes (UE-AQP2), and its renal expression is decreased in nephrotic syndrome. However, it is still unclear whether excretion of UE-AQP2 is altered in nephrotic syndrome. In this study, we examined the excretion of UE-AQP2 in an experimental rat model of nephrotic syndrome induced by the administration of puromycin aminonucleoside (PAN). Rats were assigned to two groups: a control group administered saline and a PAN group given a single intraperitoneal injection of PAN (125 mg/kg) at day 0. The experiment was continued for 8 days, and samples of urine, blood, and tissue were collected on days 2, 5, and 8. The blood and urine parameters revealed that PAN induced nephrotic syndrome on days 5 and 8, and decreases in the excretion of UE-AQP2 were detected on days 2 through 8 in the PAN group. Immunohistochemistry showed that the renal expression of AQP2 was decreased on days 5 and 8. The release of exosomal marker proteins into the urine through UEs was decreased on day 5 and increased on day 8. These data suggest that UE-AQP2 is decreased in PAN-induced nephrotic syndrome and that this reflects its renal expression in the marked proteinuria phase after PAN treatment. Full article