A new mouse model of immune-mediated podocyte injury (original) (raw)
Role of Podocyte in Kidney Disease
Podocytes are epithelial cells lining the outer surface of the renal glomerular capillaries and they play a pivotal role in maintaining the structural and functional integrity of the glomerular filtration barrier. Podocytes react to injury in various ways and any injury to these highly specialized cells can progress to podocyte dysfunction, resulting in a group of proteinuric renal diseases called podocytopathies. Podocytopathies include a wide spectrum of primary and secondary kidney diseases, including minimal change disease, diffuse mesangial sclerosis, focal segmental glomerulosclerosis, collapsing glomerulopathy, diabetic, membranous and lupus nephropathies. Etiologically, they can be idiopathic, genetic or secondary to infections and drugs, metabolic diseases, hemodynamic factors or associated with various immune and non-immune systemic diseases. This manuscript provides a basic understanding of podocyte structure, causes of podocyte injury, response to the injury and the subsequent progression to podocytopathies. The pathogenesis of these diseases is set around podocytes. The clinical and morphological manifestations, the commonality and heterogeneity of these podocytopathies are also discussed. As our knowledge of podocyte biology improves, so will our treatment avenues with a more podocyte-centric personalized approach.
Unraveling the Role of Podocyte Turnover in Glomerular Aging and Injury
Journal of the American Society of Nephrology, 2014
Podocyte loss is a major determinant of progressive CKD. Although recent studies showed that a subset of parietal epithelial cells can serve as podocyte progenitors, the role of podocyte turnover and regeneration in repair, aging, and nephron loss remains unclear. Here, we combined genetic fate mapping with highly efficient podocyte isolation protocols to precisely quantify podocyte turnover and regeneration. We demonstrate that parietal epithelial cells can give rise to fully differentiated visceral epithelial cells indistinguishable from resident podocytes and that limited podocyte renewal occurs in a diphtheria toxin model of acute podocyte ablation. In contrast, the compensatory programs initiated in response to nephron loss evoke glomerular hypertrophy, but not de novo podocyte generation. In addition, no turnover of podocytes could be detected in aging mice under physiologic conditions. In the absence of podocyte replacement, characteristic features of aging mouse kidneys included progressive accumulation of oxidized proteins, deposits of protein aggregates, loss of podocytes, and glomerulosclerosis. In summary, quantitative investigation of podocyte regeneration in vivo provides novel insights into the mechanism and capacity of podocyte turnover and regeneration in mice. Our data reveal that podocyte generation is mainly confined to glomerular development and may occur after acute glomerular injury, but it fails to regenerate podocytes in aging kidneys or in response to nephron loss.
American Journal of Physiology-Renal Physiology, 2012
Inflammation conveys the development of glomerular injury and is a major cause of progressive kidney disease. NF-κB signaling is among the most important regulators of proinflammatory signaling. Its role in podocytes, the epithelial cells at the kidney filtration barrier, is poorly understood. Here, we inhibited NF-κB signaling in podocytes by specific ablation of the NF-κB essential modulator (NEMO, IKKγ). Podocyte-specific NEMO-deficient mice (NEMOpko) were viable and did not show proteinuria or overt changes in kidney morphology. After induction of glomerulonephritis, both NEMOpkoand control mice developed significant proteinuria. However, NEMOpkomice recovered much faster, showing rapid remission of proteinuria and restoration of podocyte morphology. Interestingly, quantification of infiltrating macrophages, T-lymphocytes, and granulocytes at day 7 revealed no significant difference between wild-type and NEMOpko. To further investigate the underlying mechanisms, we created a sta...
Autoimmunity, 2018
Toll-like receptors (Tlrs) are sensors of danger signals which promote the activation of immune cells and intrinsic renal cells. Podocytes, the intrinsic cells of glomerulus, are continuously exposed to various plasma solutes and danger signals due to their unique location in the glomerulus. Herein, we show that Tlr9 is overexpressed in podocytes and the mechanisms which cause its injury and development of membranoproliferative glomerulonephritis (MPGN) in model BXSB/MpJ-Yaa (Yaa) mice. Yaa mice developed typical lesions of MPGN and showed strong expression of Tlr9 mRNA throughout the glomerulus particularly toward the periphery of the glomerulus. However, BXSB/MpJ (BXSB) mice showed no lesion for MPGN but a very weak expression of Tlr9 mRNA. Relative mRNA expression of Tlr9 and its downstream cytokines, including interleukin 1 beta (Il1b), Il6, interferon gamma (Ifng) and tumour necrosis factor alpha (Tnfa) was markedly increased in glomeruli isolated from Yaa mice. Tlr9 protein expression was almost absent in BXSB mice but intense expression was found in Yaa mice. Podocyte protein expression was normal in BXSB mice but decreased in Yaa mice and colocalized with Tlr9 protein. Furthermore, electron microscopy examination revealed podocyte injury and electron-dense materials in thickened glomerular basement membrane of Yaa mice. Glomerular Tlr9 mRNA expression was significantly correlated with anti-dsDNA antibody, proteinuria, renal function indices (sBUN and sCr), glomerular histopathology indices, downstream factors of Tlr family (Ilb and Tnfa), podocyte injury parameters (p < .05 and p < .01). In conclusion, overexpression of TLR9 correlates with podocyte injury and development of MPGN.
The Interaction of Podocytes, Glomerular Cells and Mesangial Cells in Glomerulopathies
American Journal of Biomedical Science & Research, 2021
Compared to primary glomerulopathies, secondary glomerulopathies refer to those in which glomerular damage is part of a complex clinical picture, caused by different processes: immunological, tumors, hereditary, infections or drugs, the classic examples are triggered by the systemic lupus erythematosus (SLE), diabetes, among others See Tables 1&2 [4]. During years, glomerulopathies have been closely related to chronic kidney disease (CKD) [5], occupying the first places of CKD triggers according to the 2017 report of the "The United States Renal Data Am J Biomed Sci & Res
The glomerulus – a view from the outside – the podocyte
The International Journal of Biochemistry & Cell Biology, 2010
In the past decade, podocyte research has been greatly aided by the development of powerful new molecular, cellular and animal tools, leading to elucidation of an increasing number of proteins involved in podocyte function and identification of mutated genes in hereditary glomerulopathies. Accumulating evidence indicates that podocyte disorders may not only underlie these hereditary glomerulopathies but also play crucial role in a broad spectrum of acquired glomerular diseases. Genetic susceptibility, environmental influence and systemic responses are all involved in the mediation of the pathogenesis of podocytopathies. Injured podocytes may predisopose to further injury of other podocytes and other adjacent/distant renal cells in a vicious cycle, leading to inexorable progression of glomerular injury. The classic view is that podocytes have a limited ability to proliferate in the normal mature kidney. However, recent research in rodents has provided suggestive evidence for podocyte regeneration resulting from differentiation of progenitor cells within Bowman's capsule.
Podocytes Populate Cellular Crescents in a Murine Model of Inflammatory Glomerulonephritis
Journal of the American Society of Nephrology, 2004
Cellular crescents are a defining histologic finding in many forms of inflammatory glomerulonephritis. Despite numerous studies, the origin of glomerular crescents remains unresolved. A genetic cell lineage-mapping study with a novel transgenic mouse model was performed to investigate whether visceral glomerular epithelial cells, termed podocytes, are precursors of cells that populate cellular crescents. The podocytespecific 2.5P-Cre mouse line was crossed with the ROSA26 reporter line, resulting in irreversible constitutive expression of -galactosidase in doubly transgenic 2.5P-Cre/ROSA26 mice. In these mice, crescentic glomerulonephritis was induced with a previously described rabbit anti-glomerular basement membrane antiserum nephritis approach. Interestingly, -galactosi-dase-positive cells derived from podocytes adhered to the parietal basement membrane and populated glomerular crescents during the early phases of cellular crescent formation, accounting for at least one-fourth of the total cell mass. In cellular crescents, the proliferation marker Ki-67 was expressed in -galactosidase-positive and -galactosidase-negative cells, indicating that both cell types contributed to the formation of cellular crescents through proliferation in situ. Podocyte-specific antigens, including WT-1, synaptopodin, nephrin, and podocin, were not expressed by any cells in glomerular crescents, suggesting that podocytes underwent profound phenotypic changes in this nephritis model.
Podocyte Depletion Causes Glomerulosclerosis
Journal of the American Society of Nephrology, 2005
Glomerular injury and proteinuria in diabetes (types 1 and 2) and IgA nephropathy is related to the degree of podocyte depletion in humans. For determining the causal relationship between podocyte depletion and glomerulosclerosis, a transgenic rat strain in which the human diphtheria toxin receptor is specifically expressed in podocytes was developed. The rodent homologue does not act as a diphtheria toxin (DT) receptor, thereby making rodents resistant to DT. Injection of DT into transgenic rats but not wild-type rats resulted in dose-dependent podocyte depletion from glomeruli. Three stages of glomerular injury caused by podocyte depletion were identified: Stage 1, 0 to 20% depletion showed mesangial expansion, transient proteinuria and normal renal function; stage 2, 21 to 40% depletion showed mesangial expansion, capsular adhesions (synechiae), focal segmental glomerulosclerosis, mild persistent proteinuria, and normal renal function; and stage 3, >40% podocyte depletion showed segmental to global glomerulosclerosis with sustained high-grade proteinuria and reduced renal function. These pathophysiologic consequences of podocyte depletion parallel similar degrees of podocyte depletion, glomerulosclerosis, and proteinuria seen in diabetic glomerulosclerosis. This model system provides strong support for the concept that podocyte depletion could be a major mechanism driving glomerulosclerosis and progressive loss of renal function in human glomerular diseases.
Augmenting podocyte injury promotes advanced diabetic kidney disease in Akita mice
Biochemical and Biophysical Research Communications, 2014
To determine if augmenting podocyte injury promotes the development of advanced diabetic nephropathy (DN), we created mice that expressed the enzyme cytosine deaminase (CD) specifically in podocytes of diabetic Akita mice (Akita-CD mice). In these mice, treatment with the prodrug 5-flucytosine (5-FC) causes podocyte injury as a result of conversion to the toxic metabolite 5-fluorouracil (5-FU). We found that treatment of 4-5 week old Akita mice with 5-FC for 5 days caused robust albuminuria at 16 and 20 weeks of age compared to 5-FC treated Akita controls, which do not express CD (Akita CTLs). By 20 weeks of age, there was a significant increase in mesangial expansion in Akita-CD mice compared to Akita CTLs, which was associated with a variable increase in glomerular basement membrane (GBM) width and interstitial fibrosis. At 20 weeks of age, podocyte number was similarly reduced in both groups of Akita mice, and was inversely correlated with the albuminuria and mesangial expansion. Thus, enhancing podocyte injury early in the disease process promotes the development of prominent mesangial expansion, interstitial fibrosis, increased GBM thickness and robust albuminuria. These data suggest that podocytes play a key role in the development of advanced features of diabetic kidney disease.