Plasma and urine proteomic profiles in childhood idiopathic nephrotic syndrome.

Purpose: Idiopathic nephrotic syndrome (NS) is characterized by proteinuria, edema, and hypoalbuminemia. The aim of the study was to identify differentially expressed proteins in urine and plasma during NS compared with remission.

Experimental Design: Plasma and urine samples were collected during NS and at remission. Proteomic profiling was performed by iTRAQ labeling followed by nano-LC-MS/MS to yield data on relative protein amounts. Protein validation was performed by ELISA.

Results: A total of 388 and 425 proteins were detected in plasma and urine, respectively. In total, 18 plasma and 38 urinary proteins were significantly altered (p <0.05). E-cadherin was one of the proteins with reduced urinary concentration during NS, a finding validated by ELISA. The slit diaphragm protein P-cadherin was identified by nano-LC-MS/MS and shown to be reduced in urine during NS by ELISA.

Conclusions And Clinical Relevance: The present study identified more than 50 differentially altered proteins comparing NS with remission. Several proteins were found to be linked to the major clinical symptoms of NS, and further studies must elucidate if P-cadherin is involved in proteinuria during NS, and if low urinary E-cadherin level is linked to altered epithelial cell to cell contact in the distal part of the nephron.