Proteinuria with and without renal glomerular podocyte effacement.

Renal biopsies of patients with proteinuria and kidney disease most often are associated with podocyte foot process effacement. For several decades, nephrologists have wondered whether proteinuria is a result of podocyte foot process effacement or the cause of it. In the past few years, the author's laboratory has addressed this issue using different mouse models of proteinuria. Although in most cases, podocyte effacement is associated with proteinuria and glomerular disease, in three different mouse models, it was demonstrated that proteinuria can be observed without podocyte foot process effacement. The first model is generated by injection of antibodies to vascular endothelial growth factor or soluble vascular endothelial growth factor receptor 1. The second model is a mouse with deletion of type IV collagen alpha3 chain in the glomerular basement membrane. The third model was generated by genetic deletion of a slit diaphragm protein known as nephrin. Collectively, these experiments and the supporting evidence from several human studies demonstrate that severe defects in either the glomerular basement membrane or the glomerular endothelium can lead to proteinuria without foot process effacement.