Glomerular permeability barrier in the rat. Functional assessment by in vitro methods.

Daniels, Barbara S.; Deen, William M.; Mayer, Gert; Meyer, Timothy W.; Hostetter, Thomas H.

doi:10.1172/jci116668

Cited by 60 publications

(38 citation statements)

References 22 publications

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“…40,41 Our present observation of podocyte ultrastructure at EM shows that in MWF rats, podocyte body extends around glomerular capillary segment and peripheral glomerular membrane. These morphological observations were confirmed by morphometrical analysis showing a reduction in the peripheral capillary membrane directly in contact with the urinary space while the remaining peripheral membrane is covered by podocyte body.…”

Section: Discussionmentioning

confidence: 57%

Pathophysiologic Implications of Reduced Podocyte Number in a Rat Model of Progressive Glomerular Injury

Macconi

Bonomelli

Benigni

et al. 2006

The American Journal of Pathology

129

118

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Changes in podocyte number or density have been suggested to play an important role in renal disease progression. Here , we investigated the temporal relationship between glomerular podocyte number and development of proteinuria and glomerulosclerosis in the male Munich Wistar Fromter (MWF) rat. We also assessed whether changes in podocyte number affect podocyte function and focused specifically on the slit diaphragm-associated protein nephrin. Age-matched Wistar rats were used as controls. Estimation of podocyte number per glomerulus was determined by digital morphometry of WT1-positive cells. MWF rats developed moderate hypertension , massive proteinuria , and glomerulosclerosis with age. Glomerular hypertrophy was already observed at 10 weeks of age and progressively increased thereafter. By contrast , mean podocyte number per glomerulus was lower than normal in young animals and further decreased with time. As a consequence , the capillary tuft volume per podocyte was more than threefold increased in older rats. Electron microscopy showed important changes in podocyte structure of MWF rats , with expansion of podocyte bodies surrounding glomerular filtration membrane. Glomerular nephrin expression was markedly altered in MWF rats and inversely correlated with both podocyte loss and proteinuria. Our findings suggest that reduction in podocyte number is an important determinant of podocyte dysfunction and progressive impairment of the glomerular permselectivity that lead to the development of massive proteinuria and ultimately to renal scarring. Proteinuric nephropathies progress toward end-stage renal failure independently of the primary insult. Proteinuria is the leakage of plasma proteins into the urine due to dysfunction of the glomerular barrier, which loses its permselective properties. Increasing evidence suggests that the visceral glomerular epithelial cell is a key determinant in the maintenance of the permselective function of the glomerular capillary.1-5 Podocytes are highly differentiated and specialized epithelial cells anchored to the glomerular basement membrane (GBM). Foot processes of neighboring podocytes interdigitate each other over the capillary wall and are bridged by the slit diaphragm forming the filtration barrier. The most characteristic structural change of damaged podocytes, concomitant with proteinuria, consists of foot process effacement, reorganization of actin cytoskeleton, and apical dislocation of the slit diaphragm. [5][6][7][8] We have recently demonstrated that in a genetic model of spontaneous glomerulosclerosis, the male Munich Wistar Fromter (MWF) rat, 9 proteinuria paralleled redistribution of the slit diaphragm protein zonula occludens-1 in the absence of changes in the ultrastructure of the podocyte foot processes as measured by mean foot process width.

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Section: Discussionmentioning

confidence: 57%

Pathophysiologic Implications of Reduced Podocyte Number in a Rat Model of Progressive Glomerular Injury

Macconi

Bonomelli

Benigni

et al. 2006

The American Journal of Pathology

129

118

View full text Add to dashboard Cite

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“…Although the role of the GBM in restricting the presence of macromolecules has been emphasized for nearly two decades (1,2), several recent studies have shown that slit diaphragms located between the foot processes play the critical role of a barrier to retain macromolecules (3)(4)(5)(6)(7). In the past several years, some molecules were reported to be associated with the slit diaphragm (8 -11).…”

Section: Kawachi@medniigata-uacjpmentioning

confidence: 99%

Cloning of Rat Homologue of Podocin

Kawachi¹,

Koike²,

Kurihara

et al. 2003

Journal of the American Society of Nephrology

107

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Abstract. Podocin is identified as a product of the gene mutated in a patient with autosomal recessive steroid-resistant nephrotic syndrome. Although podocin is reported to be located at the slit diaphragm area, the precise role of podocin for maintaining the barrier function of the slit diaphragm has not been clearly elucidated. A rat homologue of podocin was cloned, and the expression of podocin was investigated and then compared with the nephrin and the ZO-1 expressions in rat experimental proteinuric models and in developing glomeruli. Amino acid sequences of rat and human podocin are highly homologous (84.3% identity). The domain structure of podocin is also highly conserved between rat and human. The mRNA expression for podocin was detected in glomeruli and the nerve tissues. The localization of podocin has close proximity to that of nephrin in normal adult rat glomeruli. Podocin staining was restricted to the basal side of the podocyte of the early developing stage, whereas nephrin staining was detected on the basolateral surface of podocyte. The redistribution of podocin was observed in the anti-nephrin antibody (ANA)-induced nephropathy and puromycin aminonucleoside (PAN) nephropathy. The redistribution of podocin paralleled with nephrin in ANA nephropathy but not in PAN nephropathy. Podocin is observed at the site of tight junction newly formed in proteinuric state in PAN nephropathy. It is postulated that podocin is one of the critical components of a slit diaphragm for maintaining the barrier function of the glomerular capillary wall. kawachi@med.niigata-u.ac.jpThe primary barrier for ultrafiltration of plasma in a glomerular capillary wall comprises three layers: a fenestrated endothelial cell, a glomerular basement membrane (GBM), and a glomerular epithelial cell (podocyte). Although the role of the GBM in restricting the presence of macromolecules has been emphasized for nearly two decades (1,2), several recent studies have shown that slit diaphragms located between the foot processes play the critical role of a barrier to retain macromolecules (3-7). In the past several years, some molecules were reported to be associated with the slit diaphragm (8 -11). Nephrin is considered to be a critical component of the slit diaphragm for maintaining the barrier function (9,(12)(13)(14)(15). CD2AP is reported to be associated with nephrin (16). Boute et al. (17) cloned a novel gene, NPHS2, mutated in patients with autosomal recessive steroid-resistant nephrotic syndrome and reported that this gene product, podocin, is located at the slit diaphragm area (18). Podocin is an integral membrane protein of 383 amino acids, with a single membrane domain forming a hairpin-like structure and with both N-and C-terminal domains in the cytosol. Recent reports indicate that podocin interacts with CD2AP and nephrin (19,20); however, the precise role of podocin for maintaining the barrier function of the slit diaphragm is not yet clarified. To address this, more studies using experimental models would be necessary. We cl...

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“…2 The underlying pathologic change responsible for proteinuria in various glomerular diseases is the loss of size-selective and/or charge-selective properties of the glomerular filtration barrier. [3][4][5][6][7] The glomerular filtration barrier is composed of three layers: A fenestrated endothelial layer, a glomerular basement membrane (GBM), and podocyte foot processes connected by a slit diaphragm. Traditionally, the GBM has been considered a coarse filter that restricts large molecules, whereas the slit diaphragm was thought to function as a fine filter that contributes to ultimate size selec-tivity, permitting permeability only to molecules that are smaller than albumin.…”

mentioning

confidence: 99%

Differential Expression of Nephrin According to Glomerular Size in Early Diabetic Kidney Disease

Kim

Jung

et al. 2007

Journal of the American Society of Nephrology

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Diabetic nephropathy (DN) is clinically characterized by proteinuria. Many studies tried to demonstrate a relationship between proteinuria and changes in nephrin in various forms of glomerular diseases including DN, but the results are not consistent. Glomerular hypertrophy occurs in DN, yet hypertrophy does not develop in all glomeruli concurrently. For investigation of the differences in nephrin expression according to glomerular size, glomeruli were isolated from 10 control and 10 streptozotocin-induced diabetic rats at 6 wk after the induction of diabetes by a sieving technique using sieves with pore sizes of 250, 150, 125, and 75 m. Glomeruli then were classified into large glomeruli (LG; on the 125-m sieve) and small glomeruli (SG; on the 75-m sieve) groups. Glomerular volumes were determined using an image analyzer, and mRNA and protein expression was determined by real-time PCR and Western blot, respectively. The mean volumes of diabetic LG (1.51 Ϯ 0.06 ϫ 10 6 m 3 ) and control LG (1.37 Ϯ 0.05 ϫ 10 6 m 3 ) were significantly higher than those of diabetic SG (0.94 Ϯ 0.03 ϫ 10 6 m 3 ) and control SG (0.87 Ϯ 0.03 ϫ 10 6 m 3 ; P Ͻ 0.01). Nephrin mRNA expression was significantly reduced in the diabetic LG group compared with the diabetic SG and control glomeruli groups (P Ͻ 0.05). In contrast, nephrin mRNA expression was significantly higher in the diabetic SG group compared with the diabetic LG and control glomeruli groups (P Ͻ 0.05). Even after correction for 18s rRNA and Wilms' tumor-1 mRNA expression, the differences in nephrin mRNA expression remained significant. The expression of nephrin protein showed a similar pattern to the mRNA expression. In conclusion, these data suggest that the nephrin gene is differentially expressed according to glomerular size. Furthermore, more hypertrophied glomeruli with lesser nephrin expression may be responsible for albuminuria in the early stage of DN.

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Glomerular permeability barrier in the rat. Functional assessment by in vitro methods.

Cited by 60 publications

References 22 publications

Pathophysiologic Implications of Reduced Podocyte Number in a Rat Model of Progressive Glomerular Injury

Pathophysiologic Implications of Reduced Podocyte Number in a Rat Model of Progressive Glomerular Injury

Cloning of Rat Homologue of Podocin

Differential Expression of Nephrin According to Glomerular Size in Early Diabetic Kidney Disease

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