Abstract 18717: The Pro-osteogenic Phenotype of Interstitial Cells of Calcified Human Aortic Valves is Due to Altered Expression of Mir-486 and -204

Abstract

The transition of aortic valve interstitial cells (AVICs) to myofibroblastic and osteoblast-like phenotypes plays a critical role in the progression of calcific aortic valve disease (CAVD). Understanding of the mechanism underlying AVIC phenotypic transition may lead to the development of therapeutic approaches for prevention of CAVD progression. Several microRNAs (miRs) have been implicated in stem cell differentiation into osteoblast. We hypothesized that an epigenetic mechanism regulates the myofibroblastic and osteoblast-like transition in AVICs. This study is to examine miR profile in diseased AVICs and to identify miRs responsible for cell phenotypic transition. Methods and results: AVICs were isolated from normal and diseased human aortic valves. MiR array analysis revealed 16 up-regulated and 14 down-regulated miRs in diseased AVICs, and increased miR-486 and decreased miR-204 were prominent and associated with higher levels of myofibroblastic biomarker α-smooth muscle actin (α-SMA) and osteogenic transcription factors Runx2 and Osx. MiR-486 antagomir and miR-204 mimic reduced the ability of diseased cells to form calcium deposits. While miR-486 antagomir suppressed α-SMA expression in diseased AVICs, miR-204 mimic suppressed the expression of Runx2 and Osx. MiR-486 mimic up-regulated α-SMA expression in normal AVICs through the PTEN-Akt pathway, and miR-204 antagomir up-regulated Runx2 and Osx levels by post-transcriptional modulation. Interestingly, miR-486 mimic and miR-204 antagomir synergistically up-regulated Runx2 and Osx in normal AVICs, resulting in greater calcium deposition. Knockdown of α-SMA attenuated the effect of miR-486 on osteogenic activities. Conclusions: In AVICs of diseased aortic valves, increased expression of miR-486 mediates myofibroblastic transition through the PTEN-Akt pathway, and decreased expression of miR-204 is responsible for the elevated osteogenic activity. MiR-486 also promotes AVIC osteogenic activity by inducing myofibroblastic transition. These novel findings indicate that modulation of the epigenetic mechanism underlying AVIC phenotypic transition and osteogenic activity has therapeutic potential for slowing down CAVD progression.