Background-To enable intravascular detection of inflammation in atherosclerosis, we developed a near-infrared fluorescence (NIRF) catheter-based strategy to sense cysteine protease activity during vascular catheterization. Methods and Results-The NIRF catheter design was based on a clinical coronary artery guidewire. In phantom studies of NIRF plaques, blood produced only a mild (Ͻ30%) attenuation of the fluorescence signal compared with saline, affirming the favorable optical properties of the NIR window. Catheter evaluation in vivo used atherosclerotic rabbits (nϭ11). Rabbits received an injection of a cysteine protease-activatable NIRF imaging agent (Prosense750; excitation/emission, 750/770 nm) or saline. Catheter pullbacks through the blood-filled iliac artery detected NIRF signals 24 hours after injection of the probe. In the protease agent group, the in vivo peak plaque target-to-background ratio was 558% greater than controls (6.8Ϯ1.9 versus 1.3Ϯ0.3, meanϮSEM; PϽ0.05). Ex vivo fluorescence reflectance imaging corroborated these results (target-tobackground ratio, 10.3Ϯ1.8 for agent versus 1.8Ϯ0.3 for saline group; PϽ0.01). In the protease group only, saline flush-modulated NIRF signal profiles further distinguished atheromata from normal segments in vivo (PϽ0.01). Good correlation between the in vivo and ex vivo plaque target-to-background ratio was present (rϭ0.82, PϽ0.01). Histopathological analyses demonstrated strong NIRF signal in plaques only from the protease agent group. NIRF signals colocalized with immunoreactive macrophages and the cysteine protease cathepsin B. Conclusions-An intravascular fluorescence catheter can detect cysteine protease activity in vessels the size of human coronary arteries in real time with an activatable NIRF agent. This strategy could aid in the detection of inflammation and high-risk plaques in small arteries.

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Background— Rapamycin (sirolimus)-eluting stents are associated with reduced restenosis rates in animal studies and initial human trials. The present study evaluated whether orally administered everolimus (a macrolide of the same family as sirolimus) inhibits in-stent neointimal growth in rabbit iliac arteries. Methods and Results— New Zealand white rabbits were randomized to everolimus 1.5 mg/kg per day starting 3 days before stenting and reduced to 1 mg/kg per day from days 14 to 28 (group 1), everolimus 1.5 mg/kg given 1 day before stenting followed by 0.75 mg/kg per day for 28 days (group 2), or matching placebo for each group. Drugs were administered by oral gavage. Stents were deployed in both iliac arteries, and arteries were harvested 28 days after stenting. Group 1 everolimus-treated rabbits experienced weight loss and anorexia, which resolved after the everolimus dose was lowered on day 14. Group 2 animals were healthy for the duration of everolimus dosing. Both everolimus treatment groups significantly reduced in-stent neointimal growth (46% reduction and 42% reduction in intimal thickness in groups 1 and 2, respectively). In group 2 everolimus-treated animals, the neointima was healed or healing, characterized by stent struts covered by a thin neointima, overlying endothelial cells, and only small foci of fibrin. Scanning electron microscopy showed >80% stent surface endothelialization in group 2 everolimus-treated rabbits. Conclusions— Oral everolimus suppresses in-stent neointimal growth in the rabbit iliac artery. At a dose of 1.5 mg/kg given 1 day before stenting followed by 0.75 mg/kg per day for 28 days, everolimus was well tolerated and was associated with significant neointimal healing.