In vivo Near Infrared Fluorescentie (NIRF) Intravasculaire Moleculaire Beeldvorming van Inflammatoire Plaque, een multimodale aanpak Imaging Atherosclerose
Summary
We detail een nieuw nabij-infrarood fluorescentie (NIRF) katheter voor twee-dimensionale intravasculaire moleculaire beeldvorming van plaque biologie<em> In vivo</em>. De NIRF katheter kan visualiseren de belangrijkste biologische processen, zoals een ontsteking van rapportage over de aanwezigheid van plaque-activeerbare enthousiaste en doelgerichte NIR fluorochromen. De katheter maakt gebruik van klinische techniek en power-eisen en is bedoeld voor toepassing in de menselijke kransslagaders. De volgende onderzoeksvragen studie beschrijft een multimodale beeldvorming strategie die gebruik maakt van een roman<em> In vivo</em> Intravasculaire katheter NIRF om beeld en te kwantificeren inflammatoire plaque in de proteolytisch actieve ontstoken konijn atheromata.
Abstract
The vascular response to injury is a well-orchestrated inflammatory response triggered by the accumulation of macrophages within the vessel wall leading to an accumulation of lipid-laden intra-luminal plaque, smooth muscle cell proliferation and progressive narrowing of the vessel lumen. The formation of such vulnerable plaques prone to rupture underlies the majority of cases of acute myocardial infarction. The complex molecular and cellular inflammatory cascade is orchestrated by the recruitment of T lymphocytes and macrophages and their paracrine effects on endothelial and smooth muscle cells.1
Molecular imaging in atherosclerosis has evolved into an important clinical and research tool that allows in vivo visualization of inflammation and other biological processes. Several recent examples demonstrate the ability to detect high-risk plaques in patients, and assess the effects of pharmacotherapeutics in atherosclerosis.4 While a number of molecular imaging approaches (in particular MRI and PET) can image biological aspects of large vessels such as the carotid arteries, scant options exist for imaging of coronary arteries.2 The advent of high-resolution optical imaging strategies, in particular near-infrared fluorescence (NIRF), coupled with activatable fluorescent probes, have enhanced sensitivity and led to the development of new intravascular strategies to improve biological imaging of human coronary atherosclerosis.
Near infrared fluorescence (NIRF) molecular imaging utilizes excitation light with a defined band width (650-900 nm) as a source of photons that, when delivered to an optical contrast agent or fluorescent probe, emits fluorescence in the NIR window that can be detected using an appropriate emission filter and a high sensitivity charge-coupled camera. As opposed to visible light, NIR light penetrates deeply into tissue, is markedly less attenuated by endogenous photon absorbers such as hemoglobin, lipid and water, and enables high target-to-background ratios due to reduced autofluorescence in the NIR window. Imaging within the NIR ‘window’ can substantially improve the potential for in vivo imaging.2,5
Inflammatory cysteine proteases have been well studied using activatable NIRF probes10, and play important roles in atherogenesis. Via degradation of the extracellular matrix, cysteine proteases contribute importantly to the progression and complications of atherosclerosis8. In particular, the cysteine protease, cathepsin B, is highly expressed and colocalizes with macrophages in experimental murine, rabbit, and human atheromata.3,6,7 In addition, cathepsin B activity in plaques can be sensed in vivo utilizing a previously described 1-D intravascular near-infrared fluorescence technology6, in conjunction with an injectable nanosensor agent that consists of a poly-lysine polymer backbone derivatized with multiple NIR fluorochromes (VM110/Prosense750, ex/em 750/780nm, VisEn Medical, Woburn, MA) that results in strong intramolecular quenching at baseline.10 Following targeted enzymatic cleavage by cysteine proteases such as cathepsin B (known to colocalize with plaque macrophages), the fluorochromes separate, resulting in substantial amplification of the NIRF signal. Intravascular detection of NIR fluorescence signal by the utilized novel 2D intravascular NIRF catheter now enables high-resolution, geometrically accurate in vivo detection of cathepsin B activity in inflamed plaque.
In vivo molecular imaging of atherosclerosis using catheter-based 2D NIRF imaging, as opposed to a prior 1-D spectroscopic approach,6 is a novel and promising tool that utilizes augmented protease activity in macrophage-rich plaque to detect vascular inflammation.11,12 The following research protocol describes the use of an intravascular 2-dimensional NIRF catheter to image and characterize plaque structure utilizing key aspects of plaque biology. It is a translatable platform that when integrated with existing clinical imaging technologies including angiography and intravascular ultrasound (IVUS), offers a unique and novel integrated multimodal molecular imaging technique that distinguishes inflammatory atheromata, and allows detection of intravascular NIRF signals in human-sized coronary arteries.
Protocol
Discussion
Ontstoken hoog risico of kwetsbare plaques zijn waarschijnlijk verantwoordelijk voor het grootste deel van hartinfarcten. De identificatie van dergelijke plaques voorafgaand aan de aanvang van de symptomen heeft belangrijke klinische implicaties, zowel in het voorspellen van de resultaten en het begeleiden van medische therapie. Conventionele coronaire arteriële beeldvormende technieken, zoals x-ray angiografie meestal gericht op de karakterisering van luminaal vernauwingen in plaats van het verlichten van de onderligg…
Disclosures
The authors have nothing to disclose.
Acknowledgements
Steun voor dit werk werd verzorgd door National Institutes of Health subsidie # R01 HL 108229, American Heart Association Scientist Development Grant # 0830352N, Howard Hughes Medical Institute Career Development Award, Broadview Ventures, zevende Europese Gemeenschap Programme (FP7/2007-2013 onder subsidieovereenkomst overeenkomst # 235689), en de MGH William Schreyer Fellowship.
Materials
| Material Name | Type | Company | Catalogue Number | Comment |
|---|---|---|---|---|
| Prosense 750 | Visen Medical | VM110 | 500 nmol/kg IV injection | |
| Heparin Sodium | APP Pharmaceuticals | 401586D | ||
| Cephazolin | NovaPlus | 46015683 | ||
| Lidocaine HCL 2% | Hospira | NDC 0409-4277-01 | ||
| Buprenorphine | Bedford Laboratories | NDC 55390-100-10 | ||
| Ketamine | Hospira | NDC 0409-2051-05 | ||
| High Cholesterol Diet 1% | Research Diets | C30293 | ||
| HIgh Cholesterol Diet 0.3% | Research Diets | C30255 |
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