Abstract 13950: Osteogenic Conditions Increase Expression of Dynamin Related Protein 1, a Novel Therapeutic Target for Cardiovascular Calcification
Introduction: We have previously demonstrated that matrix vesicles are precursors to microcalcifications within the atherosclerotic plaque. Dynamin Related Protein 1 (DRP1), a GTPase involved in mitochondrial fission, has been associated with cellular exocytosis and cell differentiation. We hypothesized that the calcification process, including the release of matrix vesicles and the phenotypic switching of smooth muscle cells to osteoblast-like cells involves DRP1.
Methods and Results: In apolipoprotein E-deficient mice given a high fat diet for 18 weeks, immunohistochemical analysis showed strong DRP1 staining around calcified and pre-calcified regions of the vasculature. Electron microscopy revealed mitochondrial abnormalities in calcified human tissue. Examination of DRP1 expression in primary human coronary artery smooth muscle cells (HCASMC) cultured in osteogenic differentiation media (OM) revealed a 3-fold increase in mRNA (p=0.03) and a 2-fold increase protein (p=0.04; N= 4 experiments). The use of a DRP1 specific inhibitor, MDIVI-1, or DRP1 siRNA attenuated matrix mineralization, visualized through Alizarin Red staining, in HCASMC cultured in OM for three weeks (Figure).
HCASMC treated with DRP1 inhibitor had reduced Runx2 protein expression, a marker of osteoblast-like cells. Cellular alkaline phosphatase activity decreased by 36% (p=0.0004) in cells cultured for two weeks in OM containing DRP1 inhibitor (N=3 experiments). Additionally, matrix vesicle release, measured by total protein content, was significantly decreased in cells treated with DRP1 inhibitor (p=0.03).
Conclusions: Our data suggests that in SMC, DRP1 inhibition reduces matrix vesicle release, blocks the switching of cells to an osteoblast-like state, and leads to the amelioration of matrix mineralization pathology. The results support the potential of DRP1 as a novel therapeutic target for cardiovascular calcification.
- © 2013 by American Heart Association, Inc.