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Terinte-Balcan G, Stefan G. A closer look: ultrastructural evaluation of high-risk progression IgA nephropathy. Ultrastruct Pathol 2023; 47:461-469. [PMID: 37700534 DOI: 10.1080/01913123.2023.2256836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 09/05/2023] [Indexed: 09/14/2023]
Abstract
This retrospective, cross-sectional study sought to examine the ultrastructural characteristics of glomerular lesions using Transmission Electron Microscopy (TEM) in IgA nephropathy (IgAN) and their relationship with the high risk of progression phenotype defined by KDIGO guideline as proteinuria ≥1 g/24 hours despite 3 months of optimized supportive care. We analyzed 81 IgAN patients (median age 41 years, 67% male, eGFR 43.8 mL/min, proteinuria 1.04 g/day); 42 (52%) of them had high risk of progression. There were no differences in terms of age, sex, comorbidities, eGFR, and hematuria between the two groups. High-risk patients more often had segmental glomerulosclerosis (29% vs 8%, p 0.01) in optical microscopy, while in TEM had more frequent podocyte hypertrophy (62% vs 26%, p 0.001) and podocyte foot process detachment from the glomerular basement membrane (19% vs 8%, p 0.05), more often thicker (19% vs 5%, p 0.05) and duplicated (26% vs 10%, p 0.05) glomerular basement membrane, and the presence of subendothelial and subepithelial deposits (31% vs 13%, p 0.05). However, in multivariate binary logistic regression analysis, only podocyte hypertrophy (OR 3.14; 95%CI 1.12, 8.79) was an independent risk factor for high-risk progression in IgAN. These findings highlight the importance of podocytopathy in IgAN progression.
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Affiliation(s)
- George Terinte-Balcan
- Department of Nephrology, University of Medicine and Pharmacy "Carol Davila", Bucharest, Romania
- Ultrastructural Pathology Laboratory, "Victor Babes" National Institute of Pathology, Bucharest, Romania
| | - Gabriel Stefan
- Department of Nephrology, University of Medicine and Pharmacy "Carol Davila", Bucharest, Romania
- Department of Nephrology, "Dr. Carol Davila" Teaching Hospital of Nephrology, Bucharest, Romania
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Li F, Fang Y, Zhuang Q, Cheng M, Moronge D, Jue H, Meyuhas O, Ding X, Zhang Z, Chen JK, Wu H. Blocking ribosomal protein S6 phosphorylation inhibits podocyte hypertrophy and focal segmental glomerulosclerosis. Kidney Int 2022; 102:121-135. [PMID: 35483522 PMCID: PMC10711420 DOI: 10.1016/j.kint.2022.02.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 02/01/2022] [Accepted: 02/17/2022] [Indexed: 10/18/2022]
Abstract
Ribosomal protein S6 (rpS6) phosphorylation mediates the hypertrophic growth of kidney proximal tubule cells. However, the role of rpS6 phosphorylation in podocyte hypertrophy and podocyte loss during the pathogenesis of focal segmental glomerulosclerosis (FSGS) remains undefined. Here, we examined rpS6 phosphorylation levels in kidney biopsy specimens from patients with FSGS and in podocytes from mouse kidneys with Adriamycin-induced FSGS. Using genetic and pharmacologic approaches in the mouse model of FSGS, we investigated the role of rpS6 phosphorylation in podocyte hypertrophy and loss during development and progression of FSGS. Phosphorylated rpS6 was found to be markedly increased in the podocytes of patients with FSGS and Adriamycin-induced FSGS mice. Genetic deletion of the Tuberous sclerosis 1 gene in kidney glomerular podocytes activated mammalian target of rapamycin complex 1 signaling to rpS6 phosphorylation, resulting in podocyte hypertrophy and pathologic features similar to those of patients with FSGS including podocyte loss, leading to segmental glomerulosclerosis. Since protein phosphatase 1 is known to negatively regulate rpS6 phosphorylation, treatment with an inhibitor increased phospho-rpS6 levels, promoted podocyte hypertrophy and exacerbated formation of FSGS lesions. Importantly, blocking rpS6 phosphorylation (either by generating congenic rpS6 knock-in mice expressing non-phosphorylatable rpS6 or by inhibiting ribosomal protein S6 kinase 1-mediated rpS6 phosphorylation with an inhibitor) significantly blunted podocyte hypertrophy, inhibited podocyte loss, and attenuated formation of FSGS lesions. Thus, our study provides genetic and pharmacologic evidence indicating that specifically targeting rpS6 phosphorylation can attenuate the development of FSGS lesions by inhibiting podocyte hypertrophy and associated podocyte depletion.
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Affiliation(s)
- Fang Li
- Department of Pathology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Department of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China; Department of Cellular Biology and Anatomy Medical College of Georgia, Augusta University, Augusta, Georgia, USA; Department of Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Yili Fang
- Department of Pathology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Department of Nephrology, Shanghai General Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Qiyuan Zhuang
- Department of Pathology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Meichu Cheng
- Department of Cellular Biology and Anatomy Medical College of Georgia, Augusta University, Augusta, Georgia, USA; Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Desmond Moronge
- Department of Cellular Biology and Anatomy Medical College of Georgia, Augusta University, Augusta, Georgia, USA; Department of Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Hao Jue
- Department of Pathology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Oded Meyuhas
- Department of Biochemistry and Molecular Biology, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Xiaoqiang Ding
- Department of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Zhigang Zhang
- Department of Pathology, School of Basic Medical Sciences, Fudan University, Shanghai, China.
| | - Jian-Kang Chen
- Department of Cellular Biology and Anatomy Medical College of Georgia, Augusta University, Augusta, Georgia, USA; Department of Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Huijuan Wu
- Department of Pathology, School of Basic Medical Sciences, Fudan University, Shanghai, China.
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Kriz W, Hähnel B, Hosser H, Rösener S, Waldherr R. Structural analysis of how podocytes detach from the glomerular basement membrane under hypertrophic stress. Front Endocrinol (Lausanne) 2014; 5:207. [PMID: 25566184 PMCID: PMC4264519 DOI: 10.3389/fendo.2014.00207] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 11/17/2014] [Indexed: 01/09/2023] Open
Abstract
Podocytes are lost by detachment from the GBM as viable cells; details are largely unknown. We studied this process in the rat after growth stimulation with FGF-2. Endothelial and mesangial cells responded by hyperplasia, podocytes underwent hypertrophy, but, in the long run, developed various changes that could either be interpreted showing progressing stages in detachment from the GBM or stages leading to a tighter attachment by foot process effacement (FPE). This occurred in microdomains within the same podocyte; thus, features of detachment and of reinforced attachment may simultaneously be found in the same podocyte. (1) Initially, hypertrophied podocytes underwent cell body attenuation and formed large pseudocysts, i.e., expansions of the subpodocyte space. (2) Podocytes entered the process of FPE starting with the retraction of foot processes (FPs) and the replacement of the slit diaphragm by occluding junctions, thereby sealing the filtration slits. Successful completion of this process led to broad attachments of podocyte cell bodies to the GBM. (3) Failure of sealing the slits led to gaps of varying width between retracting FPs facilitating the outflow of the filtrate from the GBM. (4) Since those gaps are frequently overarched by broadened primary processes, the drainage of the filtrate into the Bowman's space may be hindered leading to the formation of small pseudocysts associated with bare areas of GBM. (5) The merging of pseudocysts created a system of communicating chambers through which the filtrate has to pass to reach Bowman's space. Multiple flow resistances in series likely generated an expansile force on podocytes contributing to detachment. (6) Such a situation appears to proceed to complete disconnection generally of a group of podocytes owing to the junctional connections between them. (7) Since such groups of detaching podocytes generally make contact to parietal cells, they start the formation of tuft adhesions to Bowman's capsule.
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Affiliation(s)
- Wilhelm Kriz
- Institute of Transfusion Medicine and Immunology, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
- Institute of Neuroanatomy, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
- *Correspondence: Wilhelm Kriz, Zentrum für Biomedizin und Medizintechnik Mannheim, Institut für Neuroanatomie, Ludolf-Krehl-Str. 13-17, Tridomus C, Ebene 6, Mannheim D68167, Germany e-mail:
| | - Brunhilde Hähnel
- Institute of Neuroanatomy, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Hiltraud Hosser
- Institute of Neuroanatomy, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
- Pathologie Heidelberg, Heidelberg, Germany
| | - Sigrid Rösener
- Global Non-Clinical Safety, Merck KGaA, Merck Serono, Darmstadt, Germany
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D’Elia JA, Roshan B, Maski M, Weinrauch LA. Manifestation of renal disease in obesity: pathophysiology of obesity-related dysfunction of the kidney. Int J Nephrol Renovasc Dis 2009; 2:39-49. [PMID: 21694920 PMCID: PMC3108758 DOI: 10.2147/ijnrd.s7999] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Indexed: 11/23/2022] Open
Abstract
Albuminuria in individuals whose body mass index exceeds 40 kg/m(2) is associated with the presence of large glomeruli, thickened basement membrane and epithelial cellular (podocyte) distortion. Obstructive sleep apnea magnifies glomerular injury as well, probably through a vasoconstrictive mechanism. Insulin resistance from excess fatty acids is exacerbated by decreased secretion of high molecular weight adiponectin from adipose cells in the obese state. Adiponectin potentiates insulin in its post-receptor signaling resulting in glucose oxidation in mitochondria. Recent studies of podocyte physiology have concentrated on the structural and functional requirements that prevent glomerular albumin leakage. The architecture of the podocyte involves nephrin and podocin, proteins that cooperate to keep slit pores between foot processes competent to retain albumin. Insulin and adiponectin are necessary for high-energy phosphate generation. When fatty acids bind to albumin, the toxicity to proximal renal tubules is magnified. Albumin and fatty acids are elevated in urine of individuals with obesity related nephrotic syndrome. Fatty acid accumulation and resistin inhibit insulin and adiponectin. Study of cytokines produced by adipose tissue (adiponectin and leptin) and macrophages (resistin) has led to a better understanding of the relationship between weight and hypertension. Leptin, is presumably secreted after food intake to inhibit the midbrain/hypothalamic appetite centers. Resistance to leptin results in excess signaling to hypothalamic sympathetics leading to hypertension. Demonstration of the existence of a cerebral receptor mutation provide evidence for a role in hypertension of a central nervous reflex arc in humans. Further understanding of obesity-related renal dysfunction has been accomplished recently using experimental models. Rapid weight loss following bariatric surgery may reverse renal pathology of obesity with restoration of normal blood pressure.
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Affiliation(s)
- John A D’Elia
- Joslin Diabetes Center, Renal Unit, Beth Israel Deaconess Medical Center, Department of Medicine, Mount Auburn Hospital, Harvard Medical School, Boston and Cambridge, Massachusetts
| | - Bijan Roshan
- Joslin Diabetes Center, Renal Unit, Beth Israel Deaconess Medical Center, Department of Medicine, Mount Auburn Hospital, Harvard Medical School, Boston and Cambridge, Massachusetts
| | - Manish Maski
- Joslin Diabetes Center, Renal Unit, Beth Israel Deaconess Medical Center, Department of Medicine, Mount Auburn Hospital, Harvard Medical School, Boston and Cambridge, Massachusetts
| | - Larry A Weinrauch
- Joslin Diabetes Center, Renal Unit, Beth Israel Deaconess Medical Center, Department of Medicine, Mount Auburn Hospital, Harvard Medical School, Boston and Cambridge, Massachusetts
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