This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: 29/11/1950    most recent ATVBAHA.109.195271v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Google Scholar Articles by Benton, J. A. Articles by Anseth, K. S. PubMed PubMed Citation Articles by Benton, J. A. Articles by Anseth, K. S.

(Arteriosclerosis, Thrombosis, and Vascular Biology. 2009;29:1950.)
© 2009 American Heart Association, Inc.

Cell Biology/Signaling

Statins Block Calcific Nodule Formation of Valvular Interstitial Cells by Inhibiting -Smooth Muscle Actin Expression

Julie A. Benton; Hanna B. Kern; Leslie A. Leinwand; Peter D. Mariner; Kristi S. Anseth

From the Department of Chemical and Biological Engineering (J.A.B., H.B.K., K.S.A.), the Department of Molecular, Cellular, and Developmental Biology (L.A.L.), and the Howard Hughes Medical Institute (P.D.M., K.S.A.), University of Colorado, Boulder.

Correspondence to Kristi S. Anseth, University of Colorado, Campus Box 424, Boulder, CO 80309-0424. E-mail kristi.anseth{at}colorado.edu

Objective— Calcific aortic stenosis, characterized by excessive fibrosis and deposition of bone-like calcified tissue, affects roughly 2% to 3% of the U.S. population over the age of 65. Recent studies have suggested that statins have a positive effect on the progression of aoritic stenosis, likely because of their ability to affect the resident cell population, known as valvular interstitial cells (VICs). VICs are fibroblastic cells that can differentiate to form activated myofibroblasts, displaying increased alpha smooth muscle actin (SMA) expression, contractility, and collagen production.

Methods and Results— In culture, VICs spontaneously form multicellular aggregates that subsequently develop into calcified nodules, providing an in vitro model for aortic stenosis. Using real-time microscopic tracking, we observed that confluent VIC monolayers spontaneously contract into rounded nodules, suggesting that myofibroblastic contractility is a critical step in the process of nodule formation. Overexpression of SMA increased VIC calcific nodule formation and contractility, whereas knockdown of SMA with siRNAs reduced these phenotypes, suggesting that the expression and contractile properties of SMA are essential to the formation of nodules. Statin treatment of VICs reduced SMA expression, inhibited contractility, and decreased nodule formation. When statins were used to treat preformed nodules, no decrease in the number of calcified nodules was observed, suggesting that statins may play more of a preventative role in aortic stenosis than a cure.

Conclusions— Our studies provide evidence of a causal relationship between VIC myofibroblastic activity and initial VIC calcific nodule formation. Furthermore, we demonstrate that pravastatin inhibition of calcific nodule formation is related to inhibition of myofibroblastic activity.

We observed that VIC monolayers spontaneously contract into nodules, suggesting myofibroblastic contractility is critical. Overexpression of SMA increased nodule formation, whereas knockdown of SMA with siRNAs reduced these phenotypes. Statin treatment reduced SMA expression and decreased nodules. When statins were used to treat preformed nodules, no decrease in nodules was observed.

Key Words: valvular interstitial cells • myofibroblast • calcific nodule • statin • contractility