Abstract 17244: Monocytes and Oxidized Lipids Promote the Destabilization of Calcified Plaque Via Matrix Metalloproteinases(MMP)

Abstract

Objective: Vascular calcification is closely associated with atherosclerosis, but whether it mechanically affects plaque stability remains controversial. We previously showed that calcific nodules produced with cultured calcifying vascular cells (CVC) were destabilized in response to shear stress. Here, we characterized the CVC-derived calcified nodules in ApoE-null mice, and assessed oxLDL and monocytes on the destabilization of CVC-derived calcified nodules under pulsatile shear stress (PSS). Methods and Results: To demonstrate that CVC-derived calcified nodules contain components of calcific atherosclerotic plaque in vivo, CVC was implanted in the ApoE-null mice via a cage. After 6 weeks, histology and immunohistochemsitry revealed a calcified plaque-like structure with fibrous caps, lipids, Collagen II, alkaline phosphotase and friable shoulders. To investigate the calcific nodule destabilization in vitro , CVC nodules were subjected to PSS for two and one-half hours. The percentage of nodules detached was calculated as quantification of nodule destabilization. Computational Fluid Dynamic (CFD) code simulated the instantaneous shear force distribution on the individual nodules and demonstrated accentuated instantaneous shear forces on the shoulder regions of nodules. Treatment with oxLDL or co-culture with monocytic THP-1 cells promoted the destabilization of nodules(Nodules detached: control (PSS) = 24±3%, PSS + THP-1=57±6%, PSS + oxLDL=45±7%, n=4, P <0.001). Both oxLDL and THP-1 significantly up-regulated the expression of MMP-1, MMP-3 and MMP-9 in CVC, and increased the activities of MMP. MMP inhibitor, GM6001, significantly reversed oxLDL- and THP-1-induced nodule destabilization, whereas over-expression of MMP9 increased nodule destabilization. Conclusion: These findings revealed that calcific CVC nodules resembled atherosclerotic plaque in vivo , and active lipids and monocytes induced CVC nodules to express MMP, promoting destabilization of the calcified nodules. This study provides a dynamic model to characterize the destabilization of calcific atherosclerotic plaque in vitro .