ABSTRACT
Nephrotic syndrome (NS) is a common chronic glomerular disease in children characterized by significant proteinuria with resulting hypoalbuminemia, edema, and hyperlipidemia. Renal biopsy findings of diffuse foot processes effacement on electron microscopy and minimal change disease, focal segmental glomerulosclerosis (FSGS), or diffuse mesangial proliferation on light microscopy. It has been speculated that circulating permeability factors would be implicated in the pathogenesis of NS because they have been reportedly detected in the sera of patients and in experimental models of induced proteinuria. Moreover, a substantial portion of the patients with primary FSGS recurrence shortly after transplantation. This report reviews the current knowledge regarding the role of circulating permeability factors in the pathogenesis of proteinuria in NS and suggests future targeted therapeutic approaches for NS.
Subject(s)
Child , Humans , Biopsy , Edema , Foot , Glomerulosclerosis, Focal Segmental , Hyperlipidemias , Hypoalbuminemia , Microscopy , Microscopy, Electron , Models, Theoretical , Nephrosis, Lipoid , Nephrotic Syndrome , Permeability , Proteinuria , RecurrenceABSTRACT
Focal segmental glomerulosclerosis (FSGS) is characterized by focal and segmental obliteration of glomerular capillary tufts with increased matrix. FSGS is classified as collapsing, tip, cellular, perihilar and not otherwise specified variants according to the location and character of the sclerotic lesion. Primary or idiopathic FSGS is considered to be related to podocyte injury, and the pathogenesis of podocyte injury has been actively investigated. Several circulating factors affecting podocyte permeability barrier have been proposed, but not proven to cause FSGS. FSGS may also be caused by genetic alterations. These genes are mainly those regulating slit diaphragm structure, actin cytoskeleton of podocytes, and foot process structure. The mode of inheritance and age of onset are different according to the gene involved. Recently, the role of parietal epithelial cells (PECs) has been highlighted. Podocytes and PECs have common mesenchymal progenitors, therefore, PECs could be a source of podocyte repopulation after podocyte injury. Activated PECs migrate along adhesion to the glomerular tuft and may also contribute to the progression of sclerosis. Markers of activated PECs, including CD44, could be used to distinguish FSGS from minimal change disease. The pathogenesis of FSGS is very complex; however, understanding basic mechanisms of podocyte injury is important not only for basic research, but also for daily diagnostic pathology practice.