Abstract 319: Novel Method to Evaluate Nature of Vessel Wall in Abdominal Aortic Aneurysm by Fluorescent Probes Reacting Specific Protease

Abstract

Background and Objective: Evaluation of the vessel wall condition during vascular surgery is an essential and important for technical success. However, no optimal method has been recommended for the objective assessment of the condition, and evaluation and decision of the suture/anastomotic sites are governed by the surgeon’s experience during surgery. Fluorescence-based visualization is a promising method available for objective assessment; therefore, we aimed to use this technique to distinguish non-aneurysmal wall from an aneurysmal one. Various proteases are known to play a role in aneurysm formation. We synthesized over 250 kinds of aminopeptidase-activatable fluorescent probes. To optimize aneurysmal wall evaluation based on specific fluorescent activity, these probes were investigated. Methods and Results: Vessel wall specimens were clinically obtained during open surgery for the abdominal aortic aneurysm at the University of Tokyo Hospital. Initially, to screen these probes comprehensively, the vessel walls were homogenized and supernatants were obtained. After incubating each probe in the supernatant, the increment of fluorescence was measured (excitation at 485 nm and detection at 535 nm). Among the 250 probes investigated, 6 showed a difference in the fluorescent activity between aneurysmal and non-aneurysmal walls. Next, these 6 probes were applied to freshly resected vessel walls on the from luminal side in the form of a gel, and fluorescent images were obtained using the Maestro® imaging system (PerkinElmer, Waltham, MA). Two probes showed a > 2-fold stronger activity in aneurysmal walls than that observed in non-aneurysmal walls. Conclusion: These probes may be useful for the objective evaluation of the nature of vascular walls. We plan to use small fluorescent detectors for native aortic wall intraoperatively and investigate target proteases that react with these probes.