Zyxin deficiency aggravates podocyte injury in hypertensive nephropathy.

Reduced podocyte stiffness is a feature of proteinuric kidney disease.

Epidemiological studies suggest that environmental noise is associated with kidney dysfunction in humans; however, the underlying characteristics, such as frequency, intensity, and duration, remain unclear. Effects of exposure to whole environmental noise generated by electric devices (all frequencies), low-frequency noise (LFN; ≤100 Hz), and non-LFN (>100 Hz) for 12-h/day for 5 consecutive days on kidney function were investigated in mice. Exposure to whole environmental noise at ≤ 88 dBA elevated serum creatinine and blood urea nitrogen (BUN). This effect was reproduced by LFN exposure alone (≤70 dBA) but not by non-LFN exposure (≤87 dBA). Biochemically, LFN increased renal expression of endothelin-1 and endothelial nitric oxide synthase, biomarkers of vascular injury. Histologically, LFN increased glomerular and mesangial areas and thickened glomerular basement membranes. Pharmacological inhibition of endothelin signaling reduced serum creatinine and BUN levels and mitigated the LFN-induced glomerular damage. Our findings provide the first direct evidence that the low-frequency component of environmental noise, well below the murine audible range, induces glomerular injury via endothelin signaling and results in kidney dysfunction in mice. Considering prior human cross-sectional studies, these murine findings warrant further investigation to determine their translational relevance in humans.

Persistent hematuria in children with ADAS may therefore represent an early marker of ongoing glomerular vulnerability rather than a completely benign finding, highlighting the importance of longitudinal monitoring before the development of overt proteinuria. • Hematuria is usually the earliest manifestation of autosomal dominant Alport syndrome. • Proteinuria is associated with a higher risk of kidney disease progression. • Sequential emergence of hematuria and proteinuria may reflect progressive impairment of the glomerular filtration barrier in autosomal dominant Alport syndrome. • A pathophysiological model based on injury to the three components of the glomerular filtration barrier-the endothelium, glomerular basement membrane, and podocytes-is proposed.

Reconstructing the glomerular filtration barrier in vitro remains a major challenge in kidney research due to the complexity of cellular interactions and membrane properties that regulate glomerular function. In this study, we developed and characterized a human glomerulus-on-a-chip model that recapitulates podocyte-glomerular endothelial cell (ciGEnC) interactions across a membrane resembling the native glomerular basement membrane (GBM). Using polyethersulfone (PES) and polyethylene terephthalate (PET) membranes with distinct physicochemical characteristics, we systematically evaluated how membrane composition modulates cellular attachment, spatial organization, and extracellular matrix (ECM) accumulation and cellular organization at the podocyte-endothelial interface under static and dynamic conditions. PES membranes promoted enhanced adhesion, spreading, and confluence of both podocytes and ciGEnCs. Quantitative fluorescence image analysis revealed significantly higher total cell areas for both cell types on PES compared to PET, with a more balanced endothelial-to-podocyte area ratio (1.77 for PES vs. 3.11 for PET), suggesting improved co-culture equilibrium. The broader pore size distribution, higher equilibrium water content, and elevated nonfreezable water content in PES membranes contributed to stable hydration layers that facilitated cell migration, interaction, and ECM deposition. Confocal imaging demonstrated the formation of continuous, opposing monolayers on PES membranes and ECM accumulation at the interface between the two cell layers. Under physiologically scaled flow rates, both membranes sustained cell attachment and morphology, but PES provided greater resistance to shear-induced detachment, further confirming its suitability for perfusion-based glomerular models. This study highlights the critical role of membrane material properties especially non-freezable hydration capacity and pore morphology in guiding glomerular cell behavior and tissue architecture formation. Our findings establish PES-based GBM microfluidic chips as a promising platform for modeling glomerular filtration, representing an important step toward the development of more physiologically relevant glomerular microfluidic models.

X-linked Alport syndrome (XLAS) is a hereditary glomerular basement membrane (GBM) disease caused byCOL4A5 mutations, leading to end-stage renal disease. With unclear pathogenesis and limited treatments, reliable animal models are urgently needed. In this study, the mutation K229X in COL4A5 detected in XLAS patients was introduced into mice model by CRISPR/Cas. The clinical manifestations and pathological changes in the K229X mice were characterized through urinary and serum tests, histopathology, immunofluorescence, and transmission electron microscopy. In K229X male mice, we observed significant hematuria and proteinuria, along with azotemia, and noted a marked decrease in the expression of COL4A5 at both the mRNA and protein levels within the kidneys. Pathological examination revealed glomerulosclerosis, increased mononuclear cells in the renal interstitium, interstitial fibrosis, and absence of α5 collagen IV, with histological abnormalities in the glomeruli, renal tubules, and interstitium progressing with age. Electron microscopy found irregular thickening of the GBM, accompanied by irregular layering. The phenotypic and pathological features of this mouse model are consistent with those observed in XLAS patients and other previously established mouse models. This K229X mouse model is of significant importance for exploring the pathogenic mechanisms of XLAS and researching potential therapeutic approaches.

Inhibition of GLUT1 Ameliorates Thickening of the Glomerular Basement Membrane via the Rheb/mTORC1 Pathway in Diabetic Nephropathy.

Systematic Review of IgA Nephropathy Coexisting With Alport Syndrome.

Diabetic kidney disease (DKD) is one of the most common microvascular complications of diabetes. It can be identified by thickening of the glomerular basement membrane, reduced glomerular filtration rate, and persistent proteinuria. Macrophages play a key role in the pathogenesis of DKD, and their phenotype (M1 and M2) is finely regulated by metabolic reprogramming. M1 macrophages exacerbate inflammatory damage and fibrosis in renal tissue by secreting pro-inflammatory mediators and reactive oxygen species (ROS). M2 macrophages (further subdivided into M2a, M2b, M2c and M2d subtypes) primarily exert anti-inflammatory and tissue-repairing effects. Of these, the M2a and M2c subtypes are particularly crucial for anti-inflammatory repair. This study aimed to systematically review the mechanisms by which glucose, lipid, amino acid, and mitochondrial function-related metabolism influence macrophage polarization. It further explored therapeutic strategies to mitigate renal inflammation and fibrosis by regulating macrophage polarization through targeted metabolic pathways, including inhibiting glycolysis, promoting fatty acid oxidation, modulating amino acid metabolism, and enhancing mitochondrial biogenesis and oxidative phosphorylation (OXPHOS). Several natural compounds and synthetic drugs exhibit the potential to induce M2 polarization and suppress M1 polarization through metabolic reprogramming, thereby offering new directions for optimizing therapeutic strategies for DKD.

X-chromosomal genetic variants have been understudied in end-stage renal disease (ESRD), which holds the promise to provide valuable insights into sexually dimorphic traits and diseases. Here we performed an X chromosome-wide association study (XWAS) in a Chinese cohort (N = 2750), comprising 1489 cases with ESRD and 1261 controls, to identify locus associated with ESRD risk. One locus showing a consistent effect direction across sex but primarily supported by the male cohort was identified in COL4A5 (P = 2.43 × 10-6) in the metaanalysis combining summary statistics from the sex-stratified XWAS. COL4A5 codes for the alpha chain of type IV collagen, which is essential for the integrity of the glomerular basement membrane and normal glomerular function. Two male-specific loci, MIR3202-2 (P = 6.85 × 10-5) and SYTL4 (P = 1.71 × 10-5), were identified in the sex-stratified XWAS in males, and expression of SYTL4, TSPAN6, NOX1, CSTF2, and PCDH19 was found to be influenced by the ESRD loci near SYTL4 based on expression quantitative trait loci (eQTL) results from the Genotype-Tissue Expression (GTEx) project. In summary, our findings revealed three X-chromosome loci linked to ESRD risk, which provided foundational knowledge for genetic risk prediction and advanced our understanding of the molecular underpinnings of ESRD.

Lupus nephritis (LN) is characterized by immune system attacks on self-tissues, triggered by the production of pathological autoantibodies, leading to damage in multiple organs and tissues throughout the body. The second-generation calcineurin inhibitor, voclosporin, has recently been recommended in guidelines as an adjunct to basic immunosuppressive interventions for managing active LN in adult patients. However, there are still no real-world data showing that remission was achieved by administering voclosporin in LN using the same protocol as the AURORA trial. We report the case of a 19-year-old woman with proteinuria and microscopic hematuria. The patient developed nephrotic syndrome three years prior to presentation to our department and achieved complete remission with corticosteroids. In the year of presentation, hypocomplementemia and anti-ds-DNA antibodies were detected. Renal biopsy revealed a thickened glomerular basement membrane with spike formation, granular C1q deposition in the mesangial regions, and high electron-density deposits on the epithelial side of the basement membrane. The patient was diagnosed with LN (ISN V) and started treatment with voclosporin combined with corticosteroids, hydroxychloroquine, and mycophenolate mofetil to decrease corticosteroids, which was similar to the regimen as in the AURORA study. Complete remission was achieved 30 days after treatment initiation, and the corticosteroids were discontinued 25 weeks after treatment initiation. This study represents the first clinical case report demonstrating complete remission of LN achieved by implementing the AURORA regimen.

Autosomal dominant Alport syndrome results from heterozygous pathogenic variants in COL4A3 or COL4A4, and is the commonest monogenic kidney disease, affecting about 1% of the population. It is characterised by persistent glomerular hematuria, a thinned glomerular basement membrane and a family history of kidney disease. The typical Alport hearing loss and ocular abnormalities are not present. Autosomal dominant Alport syndrome is common in cohorts with hematuria, proteinuria or steroid-resistant nephrotic syndrome, kidney cysts, or kidney failure. Clinical features vary even in family members with the same genetic change. Overall, only two-thirds of people with a pathogenic COL4A3 or COL4A4 variant have hematuria because of incomplete penetrance. Missense variants that result in Gly substitutions are associated with proteinuria more often than truncating changes which is different from X-linked disease. However missense variants are not consistently associated with kidney failure, or the age at kidney failure. Sometimes genetic testing is negative even where clinicians strongly suspect AD Alport syndrome clinically. Genetic testing distinguishes autosomal dominant Alport syndrome from X-linked disease which is less common but has a higher risk of kidney failure. Autosomal dominant Alport syndrome with more severe features must also be distinguished from digenic disease especially where only one of the two causative variants is identified. People with autosomal dominant Alport syndrome should be monitored for increased albuminuria and treated from its onset with ACE inhibitors and, if necessary, SGLT2 inhibitors. Genetic testing is currently recommended for all first degree family members whether or not they have hematuria.

Renal biopsy remains the gold standard for the diagnosis of kidney diseases, and specimen adequacy is essential for reliable histopathological evaluation. However, confirmation of glomerular yield in routine pathology workflows often relies on histological sections after staining, which may delay feedback when deeper sectioning is required. In this study, we investigated whether virtual staining applied to unstained renal biopsy sections could enable early assessment of glomerular adequacy. Unstained sections prepared under different mounting conditions were virtually transformed into H&E and special stains. The visibility of glomerular structures and the reliability of glomerular assessment were evaluated across multiple scanners. Optimized preparation of unstained sections enabled stable virtual staining with preserved morphological features. Virtual special stains enhanced the visualization of glomerular basement membranes and mesangial regions, allowing reliable identification of glomeruli on unstained tissue sections. This approach demonstrated robustness across different scanning systems, outperforming direct assessment on raw unstained images. Virtual staining of unstained renal biopsy sections provides a rapid and reagent-free strategy for early slide-level assessment of glomerular yield. By enabling feedback at the sectioning stage before routine staining, this method may improve efficiency and quality control in routine renal pathology workflows.

To evaluate kidney biopsy findings to clarify renal disease in patients after hematopoietic stem cell transplantation (HSCT) using unrelated umbilical cord blood transplantation (UCBT). We retrospectively examined 14 patients who underwent UCBT at Toranomon Hospital, Tokyo, Japan, from 2015 to 2023 and subsequently developed kidney injury requiring biopsy. At biopsy, median urinary protein was 0.57 g/day (IQR, 0.27-1.67), median serum creatinine was 1.97 mg/dL (IQR, 1.81-2.6), and median eGFR was 25.3 mL/min/1.73 m2 (IQR, 18.1-34.2). In 13 of 14 patients, mesangiolysis, glomerular basement membrane (GBM) duplication, and subendothelial widening without thrombi were observed-lesions defined as glomerular microangiopathy (GMA). Immunofluorescence and electron microscopy revealed no immune deposits typical of membranous nephropathy. Eleven patients showed distinctive arterial and arteriolar changes termed vascular microangiopathy. Nine exhibited severe interstitial fibrosis and tubular basement membrane duplication involving > 50% of the cortex. Human leukocyte antigen (HLA) incompatibility was found in 13 patients (92.9%) and ABO incompatibility in nine (64.2%). C4d positivity in glomeruli or peritubular capillaries was detected in 12 patients (85.7%). The coexistence of glomerular, vascular, and tubulointerstitial microangiopathic lesions was associated with mild proteinuria and renal dysfunction after UCBT. These findings suggest a chronic endothelial injury process distinct from classical thrombotic microangiopathy.

A 10-year-old boy was admitted with facial edema and proteinuria for two months, occurring nine months after hematopoietic stem cell transplantation. He was clinically diagnosed with nephrotic syndrome and showed no remission after four weeks of standard glucocorticoid therapy, suggesting steroid-resistant disease. Renal biopsy was consistent with membranous nephropathy. Mass spectrometry identified granular co-deposition of IgG and semaphorin 3B (Sema3B) along the glomerular basement membrane, establishing the diagnosis of Sema3B-associated membranous nephropathy. Treatment with glucocorticoids combined with tacrolimus led to a marked reduction in proteinuria, resolution of edema, and clinical stabilization over a three-month follow-up, with no recurrence. This case highlights that Sema3B-associated membranous nephropathy may occur after hematopoietic stem cell transplantation in children and underscores the importance of precise diagnostics in pediatric nephropathies. Future multicenter studies are needed to clarify disease course and genetic susceptibility, develop specific biomarkers and therapies, promote individualized treatment, and improve prognosis.

Prevalence Estimates of Predicted Pathogenic COL4A3-COL4A5 Variants in the Chinese Population and Its Implications for Clinical Practice.

We have recently demonstrated that treatment of aged mice with a pan-ERR agonist reverses age-related increase in urinary albumin, decrease in podocyte density, impaired mitochondrial function, and inflammation. The contribution of individual isoforms of ERRs however has not been determined. Since the aging kidney showed a possible compensatory increased expression of ERRγ in the podocytes, in the face of decreased ERRα expression, in the present study we aimed to determine the role of ERRγ in aging podocyte. To this end, we cross bred ERRγ floxed mice with podocin-Cre mice to achieve a podocyte-specific ERRγ deletion. While these mice at 3 months of age showed no effect on albuminuria compared to the wild type, when the mice were aged to 21 months of age, there was a significant increase in albuminuria and decrease in podocyte density. Furthermore, we found that the podocyte deletion of ERRγ primarily targeted the expression of mitochondrial biogenesis regulator PGC-1α, and mitochondrial fatty acid oxidation enzymes CPT1a and MCAD in the kidney. Electron Microscopy (EM) revealed thickened glomerular basement membrane and diffuse podocyte foot process effacement, as well as severe mitochondrial damage including cristae abnormalities, fragmentation, and changes indicative of altered fusion and fission dynamics. Fluorescence Lifetime Imaging Microscopy (FLIM) to determine NADH and FAD lifetimes indicate a metabolic shift from mitochondrial oxidative phosphorylation towards glycolysis, and decrease in mitochondrial redox capacity. Considering a significantly decreased expression of ERRα in aging podocytes plus its traditional role in mitochondrial function, these studies using podocyte ERRγ deletion suggested an overlapping mechanism for ERRα/ERRγ to act as modulators of age-related mitochondrial dysfunction and age-related kidney disease.

ABSTRACT Background C3 glomerulopathy (C3G) is a rare type of glomerular disease characterized by predominant deposits of C3 complement. Although dominant C3 immunofluorescent (IF) staining has become well known as a diagnostic criterion, the findings of electron microscopy (EM) are not well specified. The goal of this study was to scrutinize the characteristic features of C3 deposits on EM and to correlate with C3 IF staining patterns. Methods We examined the EM images of a cohort of 24 cases of C3G (22 C3 dominant glomerulonephritis [C3GN] and 2 dense deposit disease [DDD]) to determine their characteristic features when compared to a cohort of patients with immune complex-mediated glomerulonephritis. Results In our patients with C3G, the C3 deposits were present in all three glomerular compartments (mesangial, subendothelial, and subepithelial spaces) and they had the following features: (1) Smear pattern of C3 deposits along glomerular basement membranes (GBM) and subepithelial spaces; (2) C3 deposits were mostly lighter in gray colors as opposed to the dark black appearance of immune complex deposits (ICD); (3) C3 aggregates revealed smooth contours with a homogeneous fine granular appearance when compared to the humpy and bumpy appearance of ICD, and (4) C3 deposits rarely showed either retraction artifacts around the deposits or vacuolization within the GBM or mesangial areas. Conclusions In our cohort, C3 deposits exhibit reproducible EM features that are well correlated with clinical data and dominant C3 staining by IF and are different from ICD upon securitized review.

Dirofilaria repens is a mosquito-borne filarial nematode that causes subcutaneous dirofilariasis in dogs and is closely related to Dirofilaria immitis. Infection with D. immitis can lead to immune-mediated glomerulonephritis characterized by immune complex deposition along the glomerular basement membrane, resulting in proteinuria and renal dysfunction. Reported histopathological changes include membranous glomerulonephritis with potential chronic progression to chronic interstitial nephritis, glomerulosclerosis, and amyloidosis. Despite the close relationship between these two Dirofilaria species, renal clinicopathological changes associated with D. repens infection have been only rarely investigated, and renal ultrastructural and immunofluorescence findings have not been described in naturally infected dogs. The objective of this study was to collect clinicopathological data and evaluate kidneys from dogs naturally infected with D. repens for structural abnormalities using light microscopy (LM), immunofluorescence (IF), and transmission electron microscopy (TEM). Seventy-two shelter dogs from the university neutering program were screened for D. repens infection. Six infected dogs were identified, and renal biopsies were obtained during neutering. Serum urea, creatinine, and SDMA concentrations were measured, and comprehensive urinalysis was performed, including urinary protein-to-creatinine and albumin-to-creatinine ratios. None of the dogs had increased serum creatinine or SDMA; two of six dogs had mildly increased urea. Mean urine specific gravity was 1.029 ± 0.011, and urine sediment was unremarkable in all dogs. Two dogs were borderline proteinuric and one was proteinuric; the mean urine protein-to-creatinine ratio was 0.29 ± 0.15. Microalbuminuria was detected in one case (median: 0.001). Histopathology predominantly demonstrated podocyte injury with variable podocyte foot process effacement, without evidence supporting an immune complex-mediated glomerulopathy. Two dogs had mild focal and segmental glomerulosclerosis (FSGS). IF was available for two dogs and did not support immune complex-mediated disease, in agreement with TEM findings. In this cohort, dogs naturally infected with D. repens showed predominantly mild renal lesions characterized mainly by podocyte injury and, less frequently, focal segmental glomerulosclerosis. These findings differ from the immune-complex-dominant renal pathology commonly described in D. immitis infection and highlight the value of ultrastructural and immunofluorescence assessment for characterizing renal changes associated with D. repens infection.

Published data on podocyte morphology in young domesticated pigs are scarce. The current study aimed to characterize the histological and ultrastructural characteristics of the podocyte in Sus domesticus. This study depended on kidney samples from seven healthy two-month-old domestic pigs, which were collected immediately after slaughter and processed for histological and transmission electron microscopy (TEM) examination. The renal cortical tissue consisted of nephron components, including renal corpuscles, proximal convoluted tubules, distal convoluted tubules and collecting tubules. TEM analysis showed that the cytoplasm contained few mitochondria and poorly developed endoplasmic reticulum cisternae. Some podocytes have a primary process that wraps around the basal lamina of the blood capillary and gives rise to small secondary cytoplasmic processes known as pedicels. The podocytes exhibited numerous pedicels resting on the glomerular basement membrane, closely associated with the underlying glomerular endothelium, and projecting towards the capillary lumen. The filtration barrier consisted of fenestrated endothelial cells, a trilaminar glomerular basement membrane and an intact podocyte layer. In conclusion, this study provides a detailed histological and ultrastructural description of podocytes in young Landrace pigs and establishes baseline morphological data that may support future comparative, developmental and functional renal investigations in Sus domesticus.