Decreased Serum miR-503 Level in Children with Nephrotic Syndrome

Serum microRNAs (miRNA, miR) are suggested to have great potential to serve as biomarkers. In this study, we explored the clinical role of serum miRNAs which may play key roles in childhood nephrotic syndrome (NS).

Serum samples were obtained from 150 NS children and 109 age/gender-matched healthy controls. The levels of serum miRNAs were analyzed using the TaqMan Low Density Array and then validated with RT-qPCR assay. Pathological changes were examined in NS children with immunohistochemical analysis. The effects of miR-503 on cell proliferation and cell cycle were explored using MTT assay and flow cytometry in rat mesangial cells (RMCs). Western blot analysis was applied to determine the effect of miR-503 on cell cycle-related proteins.

The concentration of serum miR-503 was highly decreased in NS children compared with controls (p < 0.0001). In NS children, we found obvious enhancement of cell proliferation marker Ki-67 by immunohisto- chemistry. Moreover miR-503 mimics significantly extended the G0/G1 phase and decreased the G2/M phase in comparison with the negative control group. Overexpression of miR-503 obviously reduced the levels of cyclin E. Luciferase reporter assay revealed that cyclin E was the target of miR-503.

In this study, we determined that serum miR-503 was significantly decreased in NS children. MiR-503 contributes to the aberrant proliferation of RMCs by targeting cyclin E, which may represent potential diagnostic and prognostic biomarkers for idiopathic pediatric NS.