MicroRNA 4323 induces human bladder smooth muscle cell proliferation under cyclic hydrodynamic pressure by activation of erk1/2 signaling pathway

We cultivated human bladder smooth muscle cells (HBSMCs) under pressures of 0 or 200cm H2O pressure for 24 h, before using microarray technology to extract and analyze the different expressions of miRNAs and mRNAs in the two groups. We also predicted the target mRNA of the miDNA and performed functional forecasting. Changes in miRNA were identified by quantitative real-time polymerase chain reaction (qRT-PCR) after overexpressing miRNA by transfection. We used flow cytometry to examine HBSMC proliferation, and we used qRT-PCR and Western blot analyses to quantify the expression and activation of mRNAs and proteins. There were nine upregulated and four downregulated miRNAs involved in cell proliferation, including miR 4323, which was identified by qRT-PCR (p = 0.027). In addition, miR 4323 was shown to inhibit LYN (p = 0.031), decrease lyn kinase (p = 0.037), and promotes the phosphorylation of extracellular regulated protein kinases 1 and 2 (Erk1/2) (p = 0.004). Moreover, overexpression of miR 4323 activated the proliferation pathway regulated by Erk1/2. Then, miR 4323 was shown to stimulate the proliferation of HBSMCs, with the proliferation index improving from 30.84 +/- 4.57 to 52.13 +/- 3.41 (p = 0.001). In summary, when the miRNA miR 4323 was overexpressed under cyclic hydrodynamic pressure, LYN is decreased and the Erk1/2 signaling pathway is activated; in addition, miR 4323 is involved in HBSMC proliferation when under hydrodynamic pressure.