MiR-15a Regulates Bicuspid Aortic Valve Calcification via TGF-β Signaling Pathway via Inhibiting Smad7

Abstract Background Bicuspid aortic valve is a heritable heart valve disease with characteristic early onset of valve calcification and stenosis with rapid progression compared with tricuspid aortic valve. Strong evidence indicates that many miRNAs and their target genes are involved in the development of BAV calcification. This study was designed to investigate miR-15a and Smad7 expressions in BAV and their mechanism of regulating calcification. Methods Immunohistochemistry and western blotting were used to explore the expression levels of Smad7 and Runx2 in human aortic valve tissue. The expression of miR-15a, Smad7 and Runx2 were detected by RT-PCR. The relationship between miR-15a and Smad7 was assessed by dual-luciferase assay. MiR-15a was overexpressed in cultured porcine valve interstitial cells (PVICs) and the variations of Smad7 and Runx2 mRNA were evaluated by RT-PCR, as well as the changes of Smad7 and Runx2 protein. Alizarin reds staining was used to verify the calcification inhibition effect of miR-15a in cultured PVICs under calcification induction. Results Compared with calcified TAV, remarkable higher expression of Smad7 and Runx2 were found in calcified BAV, significantly lower expressions of miR-15a and higher expressions of Smad7 and Runx2 mRNA, along with negative correlation between expressions of miR-15a and mRNA level of Smad7. MiR-15a-overexpressed PVICs shown upregulation of miR-15a, downregulation of Smad7 and Runx2 expression. PVICs under calcification induction shown significantly reduced calcification in miR-15a-overexpressed group Conclusions The lower miR-15a expression in BAV results in the high expression of Smad7, thereby reducing antagonism of Smad2/3–Smad4 complex to runx2 and promoting the progress of BAV calcification.