Abstract 5465: Targeted Protein Cage Nanoparticles Detects Macrophages Accumulation in Mouse Atherosclerosis using Fluorescence Imaging
Macrophages are important imaging targets for detecting high-risk atherosclerotic plaque. Heat shock protein (Hsp) is a promising nanoscale protein cage platform amenable to both genetic and chemical modification for cellular/molecular imaging. Lyp is a peptide that specifically binds to tumor lymphatic vessels. We hypothesized that Lyp-conjugated Hsp (Hsp-Lyp) can effectively target plaque macrophages in vitro and in vivo. Both Hsp-Lyp and Hsp were incubated with activated or non-activated human monocytes for 48 hours and the cellular uptake was analyzed by FACS. Macrophage-rich atherosclerotic lesions were induced in the left common carotid artery by ligation in mice (n=19), with a combination of high fat diet and streptozotocin-induced diabetes. Hsp-Lyp (n=9) and Hsp (n=10) was labeled with the near-infrared (NIR) fluorophore Cy5.5 and injected via tail vein 2 weeks after ligation. Mice were imaged serially by in vivo NIR imaging up to 48 hours, and then followed by in situ and ex vivo NIR imaging. Activated monocytes can take up Hsp-Lyp five times higher than Hsp although no difference was seen in non-activated monocytes. In vivo NIR imaging detected Hsp-Lyp at 10 min after injection, with the predominant signal in the liver, bladder, and neck lymph nodes. In situ (Fig A⇓), the signal in the left carotid artery was significantly higher in mice receiving Hsp-Lyp than Hsp (p=0.002). The enhanced signal of Hsp-Lyp was further confirmed by ex vivo imaging (p=0.0002, Fig B⇓). Hsp-Lyp can effectively target plaque macrophages in vitro and in vivo. Hsp may provide a novel platform for imaging macrophages in atherosclerotic plaques.