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Zhang Z, Qiao Y, Ji J, Huang C, Shi H, Gan W, Zhang A. The potential role of differentially expressed tRNA-derived fragments in high glucose-induced podocytes. Ren Fail 2024; 46:2318413. [PMID: 38369750 PMCID: PMC10878346 DOI: 10.1080/0886022x.2024.2318413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 02/08/2024] [Indexed: 02/20/2024] Open
Abstract
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.
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Affiliation(s)
- Zhenxing Zhang
- Department of Pediatrics, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Yunyang Qiao
- Department of Pediatrics, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Jialing Ji
- Department of Pediatrics, The Fourth Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Chan Huang
- Department of Pediatrics, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Huimin Shi
- Department of Pediatrics, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Weihua Gan
- Department of Pediatrics, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Aiqing Zhang
- Department of Pediatrics, The Fourth Affiliated Hospital of Nanjing Medical University, Nanjing, China
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Sasaki T, Tsuboi N, Haruhara K, Okabayashi Y, Kanzaki G, Koike K, Kobayashi A, Yamamoto I, Ogura M, Yokoo T. Bowman Capsule Volume and Related Factors in Adults With Normal Renal Function. Kidney Int Rep 2017; 3:314-320. [PMID: 29725634 PMCID: PMC5932303 DOI: 10.1016/j.ekir.2017.10.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2017] [Revised: 10/07/2017] [Accepted: 10/16/2017] [Indexed: 01/22/2023] Open
Abstract
Introduction Alterations in glomerular filtration can considerably influence the dynamics and functions of the Bowman capsule. Despite the potentially important role in maintaining normal renal functions, few studies have focused on Bowman capsule volume in normal human kidneys. Methods We analyzed specimens from biopsies performed 1 hour after kidney transplantation from living donors without apparent renal disease. The measurements of all cross-sectional areas of the Bowman capsules and glomerular capillaries were used to estimate the mean Bowman capsule volume (BV) and glomerular capillary volume (GV) in each subject. The G/B ratio was defined as the ratio of GV to BV. The morphometric findings were examined in relation to the clinical findings in donors just before kidney transplantation. Results We analyzed 37 adults with a mean creatinine clearance of 111 ml/min. The mean BV and GV of these subjects were 6.10 ± 2.46 × 106 μm3 and 3.83 ± 1.52 × 106 μm3, respectively. Both the BV and GV varied up to 6-fold and were significantly higher in elderly, obese, or hypertensive subjects in comparison to nonelderly, nonobese, or normotensive subjects, whereas the renal function of each subgroup was similar. The G/B ratio (0.63 ± 0.05) was unaffected, and BV and GV were strongly correlated regardless of these clinical factors (r = 0.980 [95% confidence interval = 0.961−0.990], P < 0.001). Conclusion In the normal adult kidney, there may be an optimal BV to GV ratio for maintaining effective filtration in a variety of clinical situations, including advanced age, obesity, and hypertension.
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Affiliation(s)
- Takaya Sasaki
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Nobuo Tsuboi
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
- Correspondence: Nobuo Tsuboi, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi, Minato-Ku, Tokyo, Japan.
| | - Kotaro Haruhara
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Yusuke Okabayashi
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Go Kanzaki
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Kentaro Koike
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Akimitsu Kobayashi
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Izumi Yamamoto
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Makoto Ogura
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Takashi Yokoo
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
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Combined use of electron microscopy and intravital imaging captures morphological and functional features of podocyte detachment. Pflugers Arch 2017; 469:965-974. [PMID: 28664407 DOI: 10.1007/s00424-017-2020-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 06/13/2017] [Accepted: 06/14/2017] [Indexed: 12/12/2022]
Abstract
The development of podocyte injury and albuminuria in various glomerular pathologies is still incompletely understood due to technical limitations in studying the glomerular filtration barrier (GFB) in real-time. We aimed to directly visualize the early morphological and functional changes of the GFB during the development of focal segmental glomerulosclerosis (FSGS) using a combination of transmission electron microscopy (TEM) and in vivo multiphoton microscopy (MPM) in the rat puromycin aminonucleoside (PAN) model. We hypothesized that this combined TEM + MPM experimental approach would provide a major technical improvement that would benefit our mechanistic understanding of podocyte detachment. Male Sprague-Dawley (for TEM) or Munich-Wistar-Frömter (for MPM) rats were given a single dose of 100-150 mg/kg body weight PAN i.p. and were either sacrificed and the kidneys processed for TEM or surgically instrumented for in vivo MPM imaging at various times 2-14 days after PAN administration. Both techniques demonstrated hypertrophy and cystic dilatations of the subpodocyte space that developed as early as 2-3 days after PAN. Adhesions of the visceral epithelium to the parietal Bowman's capsule (synechiae) appeared at days 8-10. TEM provided unmatched resolution of podocyte foot process remodeling, while MPM revealed the rapid dynamics of pseudocyst filling, emptying, and rupture, as well as endothelial and podocyte injury, misdirected filtration, and podocyte shedding. Due to the complementary advantages of TEM and MPM, this combined approach can provide an unusally comprehensive and dynamic portrayal of the alterations in podocyte morphology and function during FSGS development. The results advance our understanding of the role and importance of the various cell types, hemodynamics, and mechanical forces in the development of glomerular pathology.
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Abstract
Podocytes are highly specialized cells of the kidney glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule. When it comes to glomerular filtration, podocytes play an active role in preventing plasma proteins from entering the urinary ultrafiltrate by providing a barrier comprising filtration slits between foot processes, which in aggregate represent a dynamic network of cellular extensions. Foot processes interdigitate with foot processes from adjacent podocytes and form a network of narrow and rather uniform gaps. The fenestrated endothelial cells retain blood cells but permit passage of small solutes and an overlying basement membrane less permeable to macromolecules, in particular to albumin. The cytoskeletal dynamics and structural plasticity of podocytes as well as the signaling between each of these distinct layers are essential for an efficient glomerular filtration and thus for proper renal function. The genetic or acquired impairment of podocytes may lead to foot process effacement (podocyte fusion or retraction), a morphological hallmark of proteinuric renal diseases. Here, we briefly discuss aspects of a contemporary view of podocytes in glomerular filtration, the patterns of structural changes in podocytes associated with common glomerular diseases, and the current state of basic and clinical research.
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Affiliation(s)
- Jochen Reiser
- Department of Medicine, Rush University Medical Center, Chicago, IL, USA
| | - Mehmet M Altintas
- Department of Medicine, Rush University Medical Center, Chicago, IL, USA
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Matsusaka T, Sandgren E, Shintani A, Kon V, Pastan I, Fogo AB, Ichikawa I. Podocyte injury damages other podocytes. J Am Soc Nephrol 2011; 22:1275-85. [PMID: 21719786 DOI: 10.1681/asn.2010090963] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Loss of podocytes promotes glomerulosclerosis, but whether this results from a continued primary insult or a secondary mechanism triggered by the initial loss of podocytes is unknown. We generated chimeric mice in which only a subpopulation of podocytes expressed hCD25, which is the receptor for the immunotoxin LMB2. In addition, genetic labeling of hCD25-negative cells with human placental alkaline phosphatase allowed the study of these two distinct podocyte populations. Administration of LMB2 did not cause podocyte injury in hCD25-negative control mice. In contrast, LMB2 severely damaged or sloughed off the subpopulation of hCD25-positive podocytes within the chimeric glomeruli. Moreover, hCD25-negative podocytes, which were immune to the initial toxin injury, developed injury as early as 4 d after LMB2 injection, evidenced by foot process effacement, upregulation of desmin, and downregulation of nephrin, podocin, and podocalyxin. Furthermore, the magnitude of secondary injury correlated with the magnitude of primary injury, supporting the concept of an amplified cascade of podocyte injury. In conclusion, podocyte damage can propagate injury by triggering secondary damage of "remnant" intact podocytes, even when the primary insult is short-lived. This transmission of podocyte injury may form a vicious cycle leading to accelerated podocyte deterioration and glomerulosclerosis.
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Affiliation(s)
- Taiji Matsusaka
- Department of Internal Medicine, Tokai University School of Medicine, Isehara, Kanagawa, Japan
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Nakano Y, Hirano T, Uehara K, Nishibayashi S, Hattori K, Aihara M, Yamada Y. New rat model induced by anti-glomerular basement membrane antibody shows severe glomerular adhesion in early stage and quickly progresses to end-stage renal failure. Pathol Int 2008; 58:361-70. [DOI: 10.1111/j.1440-1827.2008.02237.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Hayashi K, Kaufman L, Ross MD, Klotman PE. Definition of the critical domains required for homophilic targeting of mouse sidekick molecules. FASEB J 2005; 19:614-6. [PMID: 15703275 DOI: 10.1096/fj.04-2947fje] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sidekick-1, a cell adhesion molecule of the immunoglobulin superfamily, is up-regulated in glomerular podocytes in the collapsing glomerulopathy of HIV-associated nephropathy (HIVAN). Sidekick-1 and its ortholog sidekick-2 have also been shown to function as neuronal targeting molecules, guiding developing neurons to specific synapses. In the current work, we overexpress mouse sidekick-1 and -2 in HEK 293 T cells in order to characterize their binding specificities. Cells transiently transfected with either sidekick-1 or -2 cDNA formed separate aggregates when mixed together, demonstrating that sidekicks are homophilic adhesion molecules. The transfection of the short splice variant (lacking the first two Ig domains) or a construct encoding sidekick-1 with the second Ig domain deleted both resulted in nearly abolished adhesion. A beta-sheet strand peptide containing the sequence QLVILA corresponding to an amino acid sequence in the second Ig domain of sidekick-1 showed specific interaction with the recombinant first Ig domain-His protein of sidekick-1. Cells expressing a mutant sidekick-1 where the binding sequence QLVILA is deleted failed to mediate significant adhesion. Furthermore, cells transfected with a chimeric sidekick, where the first two Ig domains of sidekick-2 are replaced with the corresponding two Ig domains of sidekick-1, form aggregates with sidekick-1-transfected cells. The reverse chimera, where the first two Ig domains of sidekick-2 are substituted onto sidekick-1, was similarly able to form aggregates with sidekick-2-transfected cells. These results establish that the first and second Ig domains of sidekick-1 and -2 are necessary and sufficient to mediate and target homophilic adhesion, and the QLVILA sequence is critical to the interaction. Understanding these functional domains has widespread implications in normal development and HIVAN pathogenesis.
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Affiliation(s)
- Kayo Hayashi
- Division of Nephrology, Mount Sinai School of Medicine, Annenberg Bldg., Room 23-38 One Gustave L. Levy Pl., New York, NY 10029, USA.
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Abstract
Spectrin family proteins represent an important group of actin-bundling and membrane-anchoring proteins found in diverse structures from yeast to man. Arising from a common ancestral alpha-actinin gene through duplications and rearrangements, the family has increased to include the spectrins and dystrophin/utrophin. The spectrin family is characterized by the presence of spectrin repeats, actin binding domains, and EF hands. With increasing divergence, new domains and functions have been added such that spectrin and dystrophin also contain specialized protein-protein interaction motifs and regions for interaction with membranes and phospholipids. The acquisition of new domains also increased the functional complexity of the family such that the proteins perform a range of tasks way beyond the simple bundling of actin filaments by alpha-actinin in S. pombe. We discuss the evolutionary, structural, functional, and regulatory roles of the spectrin family of proteins and describe some of the disease traits associated with loss of spectrin family protein function.
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Affiliation(s)
- M J F Broderick
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
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Leh S, Vaagnes Ø, Margolin SB, Iversen BM, Forslund T. Pirfenidone and candesartan ameliorate morphological damage in mild chronic anti-GBM nephritis in rats. Nephrol Dial Transplant 2004; 20:71-82. [PMID: 15561744 DOI: 10.1093/ndt/gfh562] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The antifibrotic substance pirfenidone and the angiotensin II type I receptor antagonist candesartan cilexetil, given alone and in combination, were tested in rats with chronic anti-glomerular basement membrane glomerulonephritis (anti-GBM GN). METHODS Male Wistar rats with anti-GBM GN were treated for 8 weeks with candesartan (4 mg/kg body weight/day), pirfenidone (500 mg/kg body weight/day) or a combination of both drugs. One GN group received no treatment and untreated non-GN-rats were used as controls. Blood pressure and urinary protein excretion were measured after 3 and 7 weeks. Kidney histology was complemented by ultrastructural investigation and by quantification of collagen Ialpha mRNA. RESULTS The percentage of glomeruli with adsorption droplets in podocytes correlated well with the amount of proteinuria (r = 0.873, P<0.01) and was significantly lowered in rats treated with candesartan (8.3 vs GN 24.6%), pirfenidone (9.8%) and combined treatment (2.6%, P<0.05 vs candesartan alone). A comparable lowering was seen for segmental sclerosis (GN 11%, candesartan 0.7%, P<0.05 vs GN, pirfenidone 1.8%, P = 0.09 vs GN, candesartan/pirfenidone 0.1%, P>0.5 vs candesartan alone). Cortical collagen Ialpha mRNA expression was significantly decreased in all treatment groups. Ultrastructural investigation showed an amelioration of basement membrane alterations and podocyte damage in the treatment groups. Candesartan caused significant blood pressure reduction and the effect was significantly enhanced by combination therapy after 3 weeks. Rats treated with pirfenidone showed blood pressure values similar to control rats. CONCLUSION Pirfenidone has a beneficial effect on morphological changes in anti-GBM GN comparable with candesartan although with a trend to slightly better results with candesartan treatment. Moreover, our results suggest an additive effect of combination treatment.
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Affiliation(s)
- Sabine Leh
- Renal Research Group, Institute of Internal Medicine, University of Bergen, Bergen, Norway.
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Kriz W. Progression of chronic renal failure in focal segmental glomerulosclerosis: consequence of podocyte damage or of tubulointerstitial fibrosis? Pediatr Nephrol 2003; 18:617-22. [PMID: 12879860 DOI: 10.1007/s00467-003-1172-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The decline in renal function in chronic renal failure is based on the progressive loss of viable nephrons. The pathways to nephron loss in conjunction with chronic renal disease generally start in the glomerulus, extending onto the tubulointerstitium via the urinary pole. Pathways to nephron degeneration starting focally in the tubulointerstitium have yet to be described. The deleterious effects of protein leakage on progression appear to be a result of podocyte damage, the beneficial effects of ACE inhibitors a result of podocyte protection.
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Eremina V, Sood M, Haigh J, Nagy A, Lajoie G, Ferrara N, Gerber HP, Kikkawa Y, Miner JH, Quaggin SE. Glomerular-specific alterations of VEGF-A expression lead to distinct congenital and acquired renal diseases. J Clin Invest 2003. [PMID: 12618525 DOI: 10.1172/jci200317423] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Kidney disease affects over 20 million people in the United States alone. Although the causes of renal failure are diverse, the glomerular filtration barrier is often the target of injury. Dysregulation of VEGF expression within the glomerulus has been demonstrated in a wide range of primary and acquired renal diseases, although the significance of these changes is unknown. In the glomerulus, VEGF-A is highly expressed in podocytes that make up a major portion of the barrier between the blood and urinary spaces. In this paper, we show that glomerular-selective deletion or overexpression of VEGF-A leads to glomerular disease in mice. Podocyte-specific heterozygosity for VEGF-A resulted in renal disease by 2.5 weeks of age, characterized by proteinuria and endotheliosis, the renal lesion seen in preeclampsia. Homozygous deletion of VEGF-A in glomeruli resulted in perinatal lethality. Mutant kidneys failed to develop a filtration barrier due to defects in endothelial cell migration, differentiation, and survival. In contrast, podocyte-specific overexpression of the VEGF-164 isoform led to a striking collapsing glomerulopathy, the lesion seen in HIV-associated nephropathy. Our data demonstrate that tight regulation of VEGF-A signaling is critical for establishment and maintenance of the glomerular filtration barrier and strongly supports a pivotal role for VEGF-A in renal disease.
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Affiliation(s)
- Vera Eremina
- The Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
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12
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Eremina V, Sood M, Haigh J, Nagy A, Lajoie G, Ferrara N, Gerber HP, Kikkawa Y, Miner JH, Quaggin SE. Glomerular-specific alterations of VEGF-A expression lead to distinct congenital and acquired renal diseases. J Clin Invest 2003; 111:707-16. [PMID: 12618525 PMCID: PMC151905 DOI: 10.1172/jci17423] [Citation(s) in RCA: 859] [Impact Index Per Article: 40.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Kidney disease affects over 20 million people in the United States alone. Although the causes of renal failure are diverse, the glomerular filtration barrier is often the target of injury. Dysregulation of VEGF expression within the glomerulus has been demonstrated in a wide range of primary and acquired renal diseases, although the significance of these changes is unknown. In the glomerulus, VEGF-A is highly expressed in podocytes that make up a major portion of the barrier between the blood and urinary spaces. In this paper, we show that glomerular-selective deletion or overexpression of VEGF-A leads to glomerular disease in mice. Podocyte-specific heterozygosity for VEGF-A resulted in renal disease by 2.5 weeks of age, characterized by proteinuria and endotheliosis, the renal lesion seen in preeclampsia. Homozygous deletion of VEGF-A in glomeruli resulted in perinatal lethality. Mutant kidneys failed to develop a filtration barrier due to defects in endothelial cell migration, differentiation, and survival. In contrast, podocyte-specific overexpression of the VEGF-164 isoform led to a striking collapsing glomerulopathy, the lesion seen in HIV-associated nephropathy. Our data demonstrate that tight regulation of VEGF-A signaling is critical for establishment and maintenance of the glomerular filtration barrier and strongly supports a pivotal role for VEGF-A in renal disease.
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Affiliation(s)
- Vera Eremina
- The Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
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Abstract
Focal segmental glomerulosclerosis is a pathological hallmark of many forms of progressive renal disease. The 'classic' lesion, based on the adhesion of the capillary tuft to Bowman's capsule, results from the loss of podocytes from the capillary basement membrane. The recently described 'collapsing' variant, in contrast, has an apparent excess of extracapillary cells, which may represent dedifferentiated, 'dysregulated' podocytes.
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Affiliation(s)
- W Kriz
- Institut für Anatomie und Zellbiologie, INF 307, Universität Heidelberg, Germany.
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Kihara I, Yaoita E, Kawasaki K, Yamamoto T, Hara M, Yanagihara T. Origin of hyperplastic epithelial cells in idiopathic collapsing glomerulopathy. Histopathology 1999; 34:537-47. [PMID: 10383699 DOI: 10.1111/j.1365-2559.1999.00670.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIMS Glomerular epithelial cell hypertrophy and hyperplasia are listed as the primary criteria for the diagnosis of collapsing glomerulopathy (CG), a distinct variant of focal segmental glomerulosclerosis. However, the extent of podocyte phenotypic alterations that occur in CG, and the origin of the hyperplastic epithelial cells remain to be established. METHODS AND RESULTS Renal biopsy materials from seven out of three patients with CG were studied by serial section analysis for immunohistochemistry and electron microscopy. Markers for podocytes (PHM5 and synaptopodin), parietal epithelial cells (PECs: cytokeratin) and macrophages (CD68) were used for the immunohistochemistry. Multiple ultrathin sections from a total of 15 glomeruli, including some from patients with CG, were examined by electron microscopy. Glomerular adhesions occurred in 71% of the serially sectioned glomeruli taken from patients with CG. Hyperplastic epithelial cells were immunonegative for podocyte markers and CD68, but invariably immunopositive for cytokeratin. Electron microscopy revealed that detachment of the podocytes from involved glomerular capillary walls was extensive. Many of the detached podocytes appeared to be necrotic and apoptotic. In contrast, junctional complexes of desmosomes and zonula adherens connected hyperplastic epithelial cells to each other. Cilia were also often observed. CONCLUSIONS The results of our ultrastructural and immunohistochemical study suggest that the hyperplastic epithelial cells observed in cases of CG are derived from PECs. Our results raise the possibility that PECs play a general role in covering glomerular tufts from which the podocytes have disappeared.
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Affiliation(s)
- I Kihara
- Department of Pathology, Institute of Nephrology, Niigata University School of Medicine, Niigata, Japan
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