Abstract 778: Cyclophilin A Mediates Vascular Remodeling By Promoting Inflammation And Vascular Smooth Muscle Cell Proliferation
Background - Decreased blood flow generates reactive oxygen species (ROS) in vascular smooth muscle cells (VSMC). Previously we reported that ROS stimulate secretion of VSMC-derived cyclophilin A (CyPA), which promotes proliferation and migration of VSMC in vitro. However, the role CyPA plays in the vascular response to decreased flow remains unknown. In this study, we tested the hypothesis that CyPA contributes to vascular remodeling by analyzing the response to complete carotid ligation in CyPA knockout (KO) mice, wild-type (WT) mice and mice that overexpress CyPA.
Methods and Results - We prepared VSMC-specific transgenic mice (VSMC-Tg) that overexpressed CyPA only in VSMC using a Cre/LoxP system. A LacZflox-CyPA construct was prepared using the pZ/EG vector and the LacZflox-CyPA mice were crossed with SM22-Cre mice to achieve VSMC-specific expression. In response to carotid ligation, CyPA expression in the intima and media of WT mice dramatically increased. The expression of CyPA was significantly increased in VSMC-Tg compared to WT mice. After 2 weeks of carotid ligation, intimal thickness correlated significantly with CyPA expression (KO: 0.5±0.4; WT: 2.8±1.4; and VSMC-Tg: 5.3±3.9 x104 μm2; P<0.05). Cell proliferation measured by Ki67 also correlated significantly with CyPA expression (KO: 1.8±1.2; WT: 9.5±4.1; and VSMC-Tg: 14.8±8.1, P<0.05), suggesting that CyPA was required for proliferation. Additionally, accumulation of CD45-positive cells in the intima correlated with CyPA expression VSMC-Tg>WT>KO, indicating the crucial role of CyPA in the inflammatory response. Finally, to compare cell proliferation, we harvested mouse aortic VSMC from the aorta of WT, KO and VSMC-Tg mice. In response to 10% FBS, Cyclin D1 and Cdk2 levels were significantly increased in mouse VSMC with relative expression VSMC-Tg>WT>KO, indicating the crucial role of CyPA in the proliferation of VSMC.
Conclusions -CyPA promotes a pro-inflammatory response to flow cessation associated with increased VSMC proliferation and neointima formation.