Podocytes are firmly attached to glomerular basement membrane in kidneys with heavy proteinuria. 2004

Anne-Tiina Lahdenkari, and Kari Lounatmaa, and Jaakko Patrakka, and Christer Holmberg, and Jorma Wartiovaara, and Marjo Kestilä, and Olli Koskimies, and Hannu Jalanko
Hospital for Children and Adolescents, University of Helsinki, 00290, Finland.

Glomerular epithelial cells (podocytes) play an important role in the pathogenesis of proteinuria. Podocyte foot process effacement is characteristic for proteinuric kidneys, and genetic defects in podocyte slit diaphragm proteins may cause nephrotic syndrome. In this work, a systematic electron microscopic analysis was performed of the structural changes of podocytes in two important nephrotic kidney diseases, congenital nephrotic syndrome of the Finnish type and minimal-change nephrotic syndrome (MCNS). The results showed that (1) podocyte foot process effacement was present not only in proteinuric glomeruli but also in nonproteinuric MCNS kidneys; (2) podocytes in proteinuric glomeruli did not show detachment from the basement membrane or cell membrane ruptures; (3) the number of pinocytic membrane invaginations in the basal and apical parts of the podocytes was comparable in proteinuric and control kidneys; (4) in proteinuric kidneys, the podocyte slit pore density was decreased by 69 to 80% and up to half of the slits were so "tight" that no visible space between foot processes was seen; thus, the filtration surface area between podocytes was dramatically reduced; and (5) in the narrow MCNS slit pores, nephrin was located in the apical part of the podocyte foot process, indicating vertical transfer of the slit diaphragm complex in proteinuria. In conclusion, these results suggest that protein leakage in the two nephrotic syndromes studied occurs through defective podocyte slits, and the other structural alterations commonly seen in electron microscopy are secondary to, not a prerequisite for, the development of proteinuria.

UI MeSH Term Description Entries
D007678 Kidney Glomerulus A cluster of convoluted capillaries beginning at each nephric tubule in the kidney and held together by connective tissue. Glomerulus, Kidney
D008297 Male Males
D009404 Nephrotic Syndrome A condition characterized by severe PROTEINURIA, greater than 3.5 g/day in an average adult. The substantial loss of protein in the urine results in complications such as HYPOPROTEINEMIA; generalized EDEMA; HYPERTENSION; and HYPERLIPIDEMIAS. Diseases associated with nephrotic syndrome generally cause chronic kidney dysfunction. Childhood Idiopathic Nephrotic Syndrome,Frequently Relapsing Nephrotic Syndrome,Multi-Drug Resistant Nephrotic Syndrome,Pediatric Idiopathic Nephrotic Syndrome,Steroid-Dependent Nephrotic Syndrome,Steroid-Resistant Nephrotic Syndrome,Steroid-Sensitive Nephrotic Syndrome,Multi Drug Resistant Nephrotic Syndrome,Nephrotic Syndrome, Steroid-Dependent,Nephrotic Syndrome, Steroid-Resistant,Nephrotic Syndrome, Steroid-Sensitive,Nephrotic Syndromes,Steroid Dependent Nephrotic Syndrome,Steroid Resistant Nephrotic Syndrome,Steroid Sensitive Nephrotic Syndrome,Steroid-Dependent Nephrotic Syndromes,Steroid-Resistant Nephrotic Syndromes,Steroid-Sensitive Nephrotic Syndromes,Syndrome, Nephrotic,Syndrome, Steroid-Sensitive Nephrotic
D011507 Proteinuria The presence of proteins in the urine, an indicator of KIDNEY DISEASES. Proteinurias
D012016 Reference Values The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality. Normal Range,Normal Values,Reference Ranges,Normal Ranges,Normal Value,Range, Normal,Range, Reference,Ranges, Normal,Ranges, Reference,Reference Range,Reference Value,Value, Normal,Value, Reference,Values, Normal,Values, Reference
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001485 Basement Membrane A darkly stained mat-like EXTRACELLULAR MATRIX (ECM) that separates cell layers, such as EPITHELIUM from ENDOTHELIUM or a layer of CONNECTIVE TISSUE. The ECM layer that supports an overlying EPITHELIUM or ENDOTHELIUM is called basal lamina. Basement membrane (BM) can be formed by the fusion of either two adjacent basal laminae or a basal lamina with an adjacent reticular lamina of connective tissue. BM, composed mainly of TYPE IV COLLAGEN; glycoprotein LAMININ; and PROTEOGLYCAN, provides barriers as well as channels between interacting cell layers. Basal Lamina,Basement Lamina,Lamina Densa,Lamina Lucida,Lamina Reticularis,Basement Membranes,Densas, Lamina,Lamina, Basal,Lamina, Basement,Lucida, Lamina,Membrane, Basement,Membranes, Basement,Reticularis, Lamina
D012680 Sensitivity and Specificity Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed) Specificity,Sensitivity,Specificity and Sensitivity

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