Abstract 1726: Dual Targeted Microparticles of Iron Oxide Detect Endothelial Adhesion Molecule Expression in Mouse Atherosclerosis by Magnetic Resonance Imaging
Superparamagnetic microparticles of iron oxide (MPIOs) distort magnetic field homogeneity and create marked contrast effects in a volume far exceeding their physical size. Our objectives were to determine whether conjugation of antibodies to MPIOs would allow targeted MRI of endothelial adhesion molecule expression in mouse atherosclerosis.
Methods and Results Monoclonal antibodies against VCAM-1 or P-Selectin were covalently conjugated to 4.5 μm MPIOs (1x107 MPIOs/5 μg antibody). Anti-VCAM-1 MPIOs bound specifically in a dose-dependent manner to TNF-α stimulated murine endothelial cells in vitro, quantified by light microscopy (R2 =0.94, P =0.03) and by high resolution MRI at 11.7 T (R2 =0.98, P =0.01). Under simulated blood flow conditions of direct left ventricular injection, both anti-P-Selectin MPIOs and anti-VCAM-1 MPIOs bound to endothelium overlying atheromatous plaque in aortic roots of ApoE−/− mice. More closely to mimic physiological leukocyte binding, dual antibody MPIOs targeting both VCAM-1 and P-selectin were prepared. This increased binding efficiency 6.9 fold vs. anti-P-selectin (P =0.027) and 5.5 fold vs. anti-VCAM-1 (P =0.005) MPIOs alone. Following intravenous injection under normal circulation, dual targeted MPIOs were observed by high resolution MRI to bind specifically to endothelium overlying atherosclerotic plaque in aortic root compared to IgG control (P<0.01) (Fig. 1⇓).
Conclusions Dual anti-VCAM-1 and anti-P-Selectin targeted MPIOs bound specifically to atherosclerotic plaque endothelium and were readily identifiable with MRI. This approach provides a platform for endovascular molecular MRI in a range of pathologies.