Targeting podocyte-associated diseases.

Injury to the podocytes is the initiating cause of many renal diseases, leading to proteinuria with possible progression to end-stage renal disease. Podocytes are highly specialized cells, with an important role in maintaining the glomerular filtration barrier and producing growth factors for both mesangial cells and endothelial cells. With their foot processes they cover the glomerular basement membrane, and form slit diaphragms with neighboring podocytes. Human podocytopathies include focal and segmental glomerulosclerosis, minimal change disease, membranous nephropathy, collapsing glomerulopathy and diabetic nephropathy. Research in the last two decades has demonstrated great progress in understanding the molecular mechanisms leading to podocytopathies. These include single gene defects in slit diaphragm proteins, but also discovery of apoptotic, enzymatic and other pathways involved in podocyte injury. With this progress, a great number of animal models is now available to study either specific podocytopathies, e.g. in mouse models with single gene mutations, or more general podocyte injury patterns, such as the lipopolysaccharide or protamine sulfate model of foot process effacement. In this review, the morphology of the glomerulus will be discussed, with a focus on the podocyte, its interactions with surrounding cells, and the highly differentiated slit diaphragm separating the apical from the basal membrane. We also provide an overview of human podocytopathies and animal models to study these diseases. In the last part we discuss targeted therapies addressing pathways and proteins affected in podocyte injury.