Downregulation of microRNA-34b is responsible for the elevation of blood pressure in spontaneously hypertensive rats

The present study aimed to identify the microRNA (miRNA) responsible for the development of primary hypertension, and examine the downstream signaling pathway, which mediates the effect of the miRNA. Reverse transcription-quantitative polymerase chain reaction analysis was performed to identify which miRNA may be involved in the pathogenesis of hypertension. In silico analysis and a luciferase assay were used to validate the target of the selected miRNA, and miRNA mimics and small interfering (si)RNA of the target were transfected into smooth muscle cells to examine its effect on the biological activity of the cells. miR-34b was found to be upregulated in spontaneously hypertensive rats (SHRs), compared with Wistar Kyoto (WKY) rats. Therefore, the present study used online miRNA target prediction tools to predict the candidate target genes of miR-34b in the database, and consequently identified cyclin G1 (CCNG1) and cyclin-dependent kinase 6 (CDK6) as its possible target genes. CDK6 subsequently identified to be the direct target gene of miR-34b using a luciferase reporter assay in vascular smooth muscle cells (VSMCs). The present study also established the possible negative regulatory association between miR-34b and CDK6 via investigating the mRNA and protein expression levels of CDK6 and CCNG1 in VSMCs collected from the SHRs and WKY rats, respectively. To investigate the signaling pathways between miR-34b and CDK6, the mRNA and protein expression levels of CDK6, and the proliferation rates were compared in VSMCs transfected with CDK6 siRNA or miR-34b mimics, the results of which indicated that the miR-34b mimics exerted the same effects on the expression of CDK6 and cell proliferation as CDK6 siRNA. The negative regulatory association between miR-34b and its target, CDK6, was confirmed, which may offer potential as a novel therapeutic target in the treatment of hypertension.