Evaluating Cellular Response of Different Valve Interstitial Cell (VIC) Phenotypes to Angiotensin I

Calcific Aortic Valve Disease (CAVD), one of the leading causes of death in the United States, is characterized by diminished functioning and limited movement of the aortic valve (AV) due to increased thickening, disorganized extracellular matrix elastin fibers, increased collagen content, and abnormal deposition and formation of calcium nodules on the AV [1, 2]. There are two types of CAVD: i) Aortic valve sclerosis (AVS), in which patients suffer from tissue hardening, fibrosis, and early calcification, and ii) calcific aortic stenosis (CAS), representative by excessive calcification on the AV and reduced AV opening, are the two main forms of CAVD [2]. Three major valve interstitial cells (VICs) involved in CAVD are quiescent VICs, activated VICs, and osteogenic VICs [3]. Angiotensin I (Ang I) is a hormone in the body that has been implicated in CAVD pathophysiology [3]. Angiotensin Converting Enzyme (ACE) inhibitor Quinaprilat has been used to prevent conversion Ang I to Ang II which can lead to fibrosis, an early indicator of CAVD [5,6]. There are certain biomarkers (αSMA and RUNX2) that can be used to determine activation of VICs in the presence of Ang-I or ACE inhibitor [7]. We hypothesized Ang I activity on the VICs will convert Ang I to Ang II and result in higher contractility in the cells in comparison to VICs treated with an ACE inhibitor. To test our hypothesis, VICs were cultured in serum and serum free media in three different environments, quiescent medium (FGF), normal medium (NM), and osteogenic medium (OM), for 7 days to study their effect on VIC phenotype. Protein biomarkers were studied using immunocytochemistry. Results showed increased expression of αSMA in NM VICs and thus a phenotypic change. To further understand the role of the local renin angiotensin system in VICs, a gelatin thin film platform to achieve anisotropic cell growth and quantify contractile function was used. Results from the measurement of contractility response after exposing cells to Ang-I and ACE inhibitor treatments showed that most VICs experienced significantly lower stress in the presence of ACE inhibitor quinaprilat