Simvastatin down-regulates osteogenic response in cultured human aortic valve interstitial cells.

ABSTRACT

BACKGROUND: Aortic valve interstitial cells have been implicated in the pathogenesis of aortic stenosis. In response to proinflammatory stimuli, aortic valve interstitial cells undergo an osteogenic phenotypic change. The purpose of this study was to determine whether the anti-inflammatory effects of statins prevent osteogenic activity in cultured aortic valve interstitial cells. METHODS: Human aortic valve interstitial cells were isolated from hearts explanted for cardiac transplantation. To test whether simvastatin down-regulates TLR4-induced osteogenic response, aortic valve interstitial cells were treated with simvastatin with and without TLR4 agonist lipopolysaccharide (LPS), and osteogenic markers were measured. Simvastatin's influence on in vitro calcium deposition was assessed by alizarin red staining. Knockdown of postreceptor signaling proteins (MyD88 and TRIF) was performed to determine which of 2 TLR4-associated pathways mediates the osteogenic response. Expression levels of TLR4-induced nuclear factor kappa light chain enhancer of activated B cells (NF-κB) and TLR4 expression were assessed after treatment with simvastatin. Statistical testing was done by analysis of variance (P < .05). RESULTS: Simvastatin decreased LPS-induced ALP and Runx2 expression and inhibited in vitro calcium deposition in aortic valve interstitial cells. Knockdown of MyD88 and TRIF attenuated the osteogenic response. Simvastatin attenuated TLR4-dependent NF-κB signaling and down-regulated TLR4 levels. CONCLUSIONS: Simvastatin prevented TLR4-induced osteogenic phenotypic changes in isolated aortic valve interstitial cells via down-regulation of TLR4 and inhibition of NF-κB signaling. These data offer mechanistic insight into a possible therapeutic role for simvastatin in the prevention of aortic stenosis.