Review ArticlesPodocyte and Parietal Epithelial Cell Interactions in Health and DiseaseAl Hussain, Turki MD*,†; Al Mana, Hadeel MD*,†; Hussein, Maged H. MD*,†; Akhtar, Mohammed MD, FCAP, FRCPA, FRCPath*,†Author Information Departments of *Pathology and Laboratory Medicine †Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Kingdom of Saudi Arabia The authors have no funding or conflicts of interest to disclose. Reprints: Mohammed Akhtar, MD, FCAP, FRCPA, FRCPath, Department of Pathology and Laboratory Medicine (MBC 10), King Faisal Specialist Hospital and Research Centre, P.O. Box 3354, Riyadh 11211, Kingdom of Saudi Arabia (e-mails: [email protected]; [email protected]). All figures can be viewed online in color at http://www.anatomicpathology.com Advances In Anatomic Pathology: January 2017 - Volume 24 - Issue 1 - p 24-34 doi: 10.1097/PAP.0000000000000125 Buy Metrics Abstract The glomerulus has 3 resident cells namely mesangial cells that produce the mesangial matrix, endothelial cells that line the glomerular capillaries, and podocytes that cover the outer surface of the glomerular basement membrane. Parietal epithelial cells (PrECs), which line the Bowman’s capsule are not part of the glomerular tuft but may have an important role in the normal function of the glomerulus. A significant progress has been made in recent years regarding our understanding of the role and function of these cells in normal kidney and in kidneys with various types of glomerulopathy. In crescentic glomerulonephritis necrotizing injury of the glomerular tuft results in activation and leakage of fibrinogen which provides the trigger for excessive proliferation of PrECs giving rise to glomerular crescents. In cases of collapsing glomerulopathy, podocyte injury causes collapse of the glomerular capillaries and activation and proliferation of PrECs, which accumulate within the urinary space in the form of pseudocrescents. Many of the noninflammatory glomerular lesions such as focal segmental glomerulosclerosis and global glomerulosclerosis also result from podocyte injury which causes variable loss of podocytes. In these cases podocyte injury leads to activation of PrECs that extend on to the glomerular tuft where they cause segmental and/or global sclerosis by producing excess matrix, resulting in obliteration of the capillary lumina. In diabetic nephropathy, in addition to increased matrix production in the mesangium and glomerular basement membranes, increased loss of podocytes is an important determinant of long-term prognosis. Contrary to prior belief there is no convincing evidence for an active podocyte proliferation in any of the above mentioned glomerulopathies. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.