Urinary podocyte markers in kidney diseases

Podocytes play an important role in the maintenance of kidney function, and they are the primary focus of many kidney diseases. Podocyte injury results in the shedding of podocyte-derived cellular fragments and podocytespecific molecular targets into the urine, which may serve as biomarkers of kidney diseases. Intact podocytes, either viable or dead, and podocyte-derived microvesicles could be quantified in the urine by various centrifugation, visualization and culture methods. Podocyte-specific protein targets from the nucleus, cytoplasm, slitdiaphragm, glomerular capillary basement membrane, and cytoskeleton, as well as their corresponding messenger RNA (mRNA), in the urine could be quantified by western blotting, ELISA, or quantitative polymerase chain reaction. Although some of these techniques may be expensive or labor-intensive at present, they may become widely available in the future because of the improvement in technology and automation. The application of urinary podocyte markers for the diagnosis and monitoring of various kidney diseases have been explored but the published data in this area are not sufficiently systematic and lack external validation. Further research should focus on standardizing, comparing, and automizing laboratory methods, as well as defining their added value to the routine clinical tests.