Multiphoton endomicroscopy of atherosclerotic plaques – MEAP

A tri-modal optical imaging [1°) coherent anti-stockes Raman scattering (CARS) imaging + 2°) optical second harmonic generation (SHG) imaging + 3°) two-photon excited autofluorescence (2PAF) imaging] will be implemented within an intravascular catheter having an outer diameter below 1 mm. This miniature device will embark a custom-made rotary scanning mechanism similar in its architecture to the one adopted for intravascular optical coherence tomography (OCT) commercial devices. In order optimally fitting to MEAP project’s requirements (i.e. optimally carrying to the tissues the laser excitation signals, efficiently collecting the useful luminescences emitted by the biological species back to the detectors in proximal location), a completely new dual-cladding hollow-core fiber will be designed and manufactured for being installed within the imaging catheter. With such a device, one could thoroughly study in vivo in situ in real-time without staining the natural history of these plaques, which would provide a set of complementary informations required to pre-emptively identify the highest risk lesions in patients so that they may be treated before a fatal event occurs.

The instrument to be developed during MEAP project will deliver, with a high biochemical specificity, in real-time and without exogenous staining, the multimodal evaluation of the main markers of the pathology: (i) occurrence of a large lipidic necrotic core through CARS imaging, (ii) presence of the thin fibrous cap of the plaque through SHG of collagen, while elastin will be screened through its 2PAF and (iii) inflammation through the detection of 2PAF of important intracellular autofluorescent metabolic biomarkers such as NADH highly produced by inflammatory macrophage or FAD highly produced by foamy macrophages. The diagnostic performances of this totally new miniature optical probe will be assessed (a) in vitro on cell cultures (inflammatory, immunoregulatory and foamy macrophages), (b) ex vivo on human and animal biopsy samples and finally (c) in vivo on an animal model of atherosclerosis on the aorta of a rabbit.

As a biomedical imaging project, MEAP, that will develop innovations in optical/electrical engineering, will exploit the valuable assets of multiphoton multimodal imaging as a new tool to detect and study vulnerable plaques of atherosclerosis in vivo.

MEAP results will be published in peer review international journals belonging to the biophotonics and to the biomedical domains. It will be presented during conferences too. The possibility to put patents will be studied carrefully.

MEAP project is about developing a fiber-optic catheter able to accurately detect through intravascular optical imaging vulnerable plaques of coronary atherosclerosis that are among the leading causes of death in the developed countries. Instable atheromatous plaques contain i) a large lipidic necrotic core, ii) covered by a thin fibrous cap consisting of a mixture containing namely fibrillar collagen (while elastin fibers can be founded mostly in the artery wall around the plaque), iii) the upstream shoulder of the plaque containing a high level of pathological macrophages. Because of the multifactorial nature of these lesions, the end-goal of MEAP, that target interventional cardiology research and clinical practice too, is to provide in a single catheter a multi-modal optical imaging intracoronary device that completely characterizes the above-mentioned salient features of coronary lesions. Bringing together medical doctors, biologists and optical/electrical engineers the MEAP consortium aims at developing a totally new catheter-based tri-modal platform using label-free multiphoton imaging. A tri-modal optical imaging [1°) coherent anti-stockes Raman scattering (CARS) imaging + 2°) optical second harmonic generation (SHG) imaging + 3°) two-photon excited autofluorescence (2PAF) imaging] will be implemented within an intravascular catheter having an outer diameter below 1 mm. This miniature device will embark a custom-made rotary scanning mechanism similar in its architecture to the one adopted for intravascular optical coherence tomography (OCT) commercial devices. In order optimally fitting to MEAP project’s requirements (i.e. optimally carrying to the tissues the laser excitation signals, efficiently collecting the useful luminescences emitted by the biological species back to the detectors in proximal location), a completely new dual-cladding hollow-core fiber will be designed and manufactured for being installed within the imaging catheter. With such a device, one could thoroughly study in vivo in situ in real-time without staining the natural history of these plaques, which would provide a set of complementary informations required to pre-emptively identify the highest risk lesions in patients so that they may be treated before a fatal event occurs. The instrument to be developed during MEAP project will deliver, with a high biochemical specificity, in real-time and without exogenous staining, the multimodal evaluation of the main markers of the pathology: (i) occurrence of a large lipidic necrotic core through CARS imaging, (ii) presence of the thin fibrous cap of the plaque through SHG of collagen, while elastin will be screened through its 2PAF and (iii) inflammation through the detection of 2PAF of important intracellular autofluorescent metabolic biomarkers such as NADH highly produced by inflammatory macrophage or FAD highly produced by foamy macrophages. The diagnostic performances of this totally new miniature optical probe will be assessed (a) in vitro on cell cultures (inflammatory, immunoregulatory and foamy macrophages), (b) ex vivo on human and animal biopsy samples and finally (c) in vivo on an animal model of atherosclerosis on the aorta of a rabbit. As a biomedical imaging project, MEAP, that will develop innovations in optical/electrical engineering, will exploit the valuable assets of multiphoton multimodal imaging as a new tool to detect and study vulnerable plaques of atherosclerosis in vivo.