Multimodal optical coherence tomography and fluorescence lifetime imaging with interleaved excitation sources for simultaneous endogenous and exogenous fluorescence.

Multimodal imaging probes a variety of tissue properties in a single image acquisition by merging complimentary imaging technologies. Exploiting synergies amongst the data, algorithms can be developed that lead to better tissue characterization than could be accomplished by the constituent imaging modalities taken alone. The combination of optical coherence tomography (OCT) with fluorescence lifetime imaging microscopy (FLIM) provides access to detailed tissue morphology and local biochemistry. The optical system described here merges 1310 nm swept-source OCT with time-domain FLIM having excitation at 355 and 532 nm. The pulses from 355 and 532 nm lasers have been interleaved to enable simultaneous acquisition of endogenous and exogenous fluorescence signals, respectively. The multimodal imaging system was validated using tissue phantoms. Nonspecific tagging with Alexa Flour 532 in a Watanbe rabbit aorta and active tagging of the LOX-1 receptor in human coronary artery, demonstrate the capacity of the system for simultaneous acquisition of OCT, endogenous FLIM, and exogenous FLIM in tissues.

Delivery of negatively charged liposomes into the atherosclerotic plaque of apolipoprotein E-deficient mouse aortic tissue.

Liposomes have been used to diagnose and treat cancer and, to a lesser extent, cardiovascular disease. We previously showed the uptake of anionic liposomes into the atheromas of Watanabe heritable hyperlipidemic rabbits within lipid pools. However, the cellular distribution of anionic liposomes in atherosclerotic plaque remains undescribed. In addition, how anionic liposomes are absorbed into atherosclerotic plaque is unclear. We investigated the uptake and distribution of anionic liposomes in atherosclerotic plaque in aortic tissues from apolipoprotein E-deficient (ApoE(-/-)) mice. To facilitate the tracking of liposomes, we used liposomes containing fluorescently labeled non-silencing small interfering RNA. Confocal microscopy analysis showed the uptake of anionic liposomes into atherosclerotic plaque and colocalization with macrophages. Transmission electron microscopy analysis revealed anionic liposomal accumulation in macrophages. To investigate how anionic liposomes cross the local endothelial barrier, we examined the role of clathrin-mediated endocytosis in human coronary artery endothelial cells (HCAECs) treated with or without the inflammatory cytokine tumor necrosis factor (TNF)-α. Pretreatment with amantadine, an inhibitor of clathrin-mediated endocytosis, significantly decreased liposomal uptake in HCAECs treated with or without TNF-α by 77% and 46%, respectively. Immunoblot analysis showed that endogenous clathrin expression was significantly increased in HCAECs stimulated with TNF-α but was inhibited by amantadine. These studies indicated that clathrin-mediated endocytosis is partly responsible for the uptake of liposomes by endothelial cells. Our results suggest that anionic liposomes target macrophage-rich areas of vulnerable plaque in ApoE(-)(/)(-) mice; this finding may lead to the development of novel diagnostic and therapeutic strategies for treating vulnerable plaque in humans.

Delivery of negatively charged liposomes into the atheromas of Watanabe heritable hyperlipidemic rabbits.

Liposomes have been used as imaging and therapeutic agents in various tissues but only infrequently in the cardiovascular system. We prepared a liposome to target atheromas in a Watanabe heritable hyperlipidemic (WHHL) rabbit model. Liposomes labeled with rhodamine and nanogold were injected intra-arterially into the descending thoracic aortas of WHHL rabbits. The arterial segments of interest were perfusion-fixed and evaluated with immunohistochemistry, light microscopy, and electron microscopy. Deconvolution microscopy showed that rhodamine label was concentrated in the plaque shoulder regions of advanced-stage atheromas; however, rhodamine label was not found in adjacent, non-atherosclerotic aorta. Transmission electron microscopy revealed liposome remnants and the highest concentration of nanogold label in lipid-laden areas of atheromas. Liposomes were concentrated in areas of lipoprotein-associated phospholipase A(2) expression. We conclude that modified liposomes can be delivered to the shoulder regions of advanced atheromas in WHHL rabbits and may be useful therapeutically for targeting metabolically active plaque.

Percutaneous intervention for the treatment of hypoplastic aortoiliac syndrome.

Hypoplastic aortoiliac syndrome (HAIS) occurs in young women and is characterized by a small infrarenal aorta with a hypoplastic iliofemoral arterial system and advanced atherosclerotic disease. Of 304 aortoiliac interventions (AoI), 30 female patients (mean age, 50 +/- 5 years) had HAIS. HAIS patients were less likely to have coronary disease (33% vs. 88%; P < 0.0001) or diabetes (10% vs. 42%; P < 0.001) compared to their AoI counterparts. Twenty-three patients (73%) had hyperlipidemia with mean cholesterol of 287 +/- 42 mg/dl. Twenty-eight patients (93%) were successfully treated with AoI. The ankle/brachial indices improved from pre-AoI ABI of 0.55 +/- 0.1 to post-AoI ABI of 0.99 +/- 0.1. Complications included one groin hematoma and one case of thrombosis. Follow-up averaged 31 months (range, 3-91 months) with an early (less than 12 months) restenosis rate of 7% and late (greater than 12 months) restenosis of 21%. One patient (3%) required surgical revascularization for persistent symptoms. Percutaneous treatment of HAIS is an alternative to surgical revascularization with satisfactory long-term results.

Diabetic patients treated with abciximab and intracoronary stenting.

Diabetic patients are at greater risk for restenosis, recurrent ischemia, and complications following angioplasty than are their nondiabetic counterparts. This is a retrospective study identifying diabetic patients who were treated with abciximab and intracoronary stenting during the period of January 1997 to December 1999. Abciximab was administered to 268 of 707 diabetic patients who received intracoronary stents from 1997 to 1999. The abciximab group contained a higher number of patients with severe ventricular dysfunction and high-grade lesions. Primary endpoints of all-cause mortality, same-vessel revascularization, CABG, TVR, and postprocedural myocardial infarction were similar for both groups. The abciximab group had reduced rates of readmission for cardiac reasons during all follow-up periods. The trends toward improvement of mortality, surgical or percutaneous revascularization, and cardiac readmissions suggest the effect of abciximab may provide benefit for up to 9 months for higher-risk diabetic patients.