Dual-Targeted NIRF Molecular Imaging Combined With Intravascular OCT for Inflammatory Micro-Calcification in the High-Risk Plaque

Background/Objectives: Micro-calcification is a major target for high-risk plaque but the mechanistic linkage with macrophage-driven inflammation remains questionable. To address this issue, we newly innovated dual-targeted multimodal imaging strategy for calcifying inflammatory activity by integration of intravascular OCT with near-infrared fluorescence (NIRF) molecular imaging. Methods/Results: We fully integrated dual-targeted NIRF molecular imaging with intravascular OCT. Novel NIRF emitting probe targeting micro-calcification was fabricated by chemically coupling alendronate and Cy5.5 to the ends of azide-PEG-NHS ester (Al-Cy5.5). Based on whole body biodistribution, OCT/dual-NIRF in vivo imaging of rabbit aortoiliac atheroma was acquired 48 hrs and 72 hrs after intravenous injection of Al-Cy5.5 (5.0 mg/kg) and macrophage mannose receptor targeted Cy7-emitting probe (7.5 mg/kg), respectively. NIRF signals of Cy5.5 and Cy7 were highly enhanced at the area of micro-calcification and macrophage accumulation within the plaque (Figure) (p<0.01). Fluorescence microscopy and immunostainings from the corresponding sections well corroborated the in vivo findings and concomitantly elevated dual-NIRF signals indicated the presence of calcifying inflammatory activity in atheroma. Intriguingly, osteogenic activity (TRAP stain) was closely interconnected with macrophages in superficial micro-calcification rather inner dense calcification (p<0.01). Conclusions: Our intravascular OCT/dual-NIRF imaging was feasible to simultaneously visualize micro-calcification, osteogenic activity and macrophages in the coronary-sized atheroma. This novel imaging strategy is expected to expand our pathophysiologic insight for the biological behavior of calcifying inflammatory activity existing on the superficial fibrous cap portion of high-risk plaques.