Donor pre-treatment with tacrolimus reduces transplant vasculopathy.

We tested whether transplant arteriosclerosis can be reduced by pre-treatment of the donor with immunosuppressive agents, using a rat allogeneic aorta transplantation model. Donor rats received no pre-treatment, or tacrolimus, methylprednisolone, rapamycin, or mycofenolate mofetil (MMF) 16 and 2h before explantation of the grafts. Eight weeks after transplantation, aorta allografts were harvested.

Gelatinolytic activity in atherosclerotic plaques is highly localized and is associated with both macrophages and smooth muscle cells in vivo.

Background: Atherosclerosis is considered an inflammatory disease. Recent studies provided evidence for a predominant upstream location of plaque inflammation. The present study introduces a novel technique that evaluates the underlying mechanism of this spatial organization.

Intravascular ultrasound tissue harmonic imaging in vivo.

Tissue harmonic imaging (THI) has been shown to increase image quality of medical ultrasound in the frequency range from 2 to 10 MHz and might, therefore, also be used to improve image quality in intravascular ultrasound (IVUS). In this study we constructed a prototype IVUS system that could operate in both fundamental frequency and second harmonic imaging modes. This system uses a conventional, continuously rotating, single-element IVUS catheter and was operated in fundamental 20 MHz, fundamental 40 MHz, and harmonic 40 MHz modes (transmit 20 MHz, receive 40 MHz).

Contrast harmonic intravascular ultrasound: a feasibility study for vasa vasorum imaging.

Objective: We sought to investigate feasibility of vasa vasorum imaging using the novel technique of contrast harmonic intravascular ultrasound.

Methods: Prototype intravascular ultrasound (IVUS) instrumentation was developed for the sensitive detection of micro-bubble contrast agents. The technique, "harmonic" imaging, involves transmitting ultrasound at 20 MHz (fundamental) and detecting contrast signals at 40 MHz (second harmonic).

Three-dimensional palpography of human coronary arteries. Ex vivo validation and in-patient evaluation.

Background: Rupture of thin-cap fibroatheroma is a major cause of acute myocardial infarction and stroke. Identification of these plaques is one of the major challenges in cardiovascular medicine. At present, techniques with sufficient sensitivity and specificity to identify these unstable plaques are not clinically available.

In vivo temperature heterogeneity is associated with plaque regions of increased MMP-9 activity.

Aims: Plaque rupture has been associated with a high matrix metalloproteinase (MMP) activity. Recently, regional temperature variations have been observed in atherosclerotic plaques in vivo and ascribed to the presence of macrophages. As macrophages are a major source of MMPs, we examined whether regional temperature changes are related to local MMP activity and macrophage accumulation.

Shear stress affects the intracellular distribution of eNOS: direct demonstration by a novel in vivo technique.

The focal location of atherosclerosis in the vascular tree is correlated with local variations in shear stress. We developed a method to induce defined variations in shear stress in a straight vessel segment of a mouse. To this end, a cylinder with a tapered lumen was placed around the carotid artery, inducing a high shear stress field.

The role of shear stress in atherosclerosis: action through gene expression and inflammation?

Atherosclerotic lesions preferentially localize near side branches or curved vessels. During the last few decades, research has been shown that low or low and oscillating shear stress is associated with plaque location. Despite ample evidence, the precise mechanism is unknown.

Intravascular thermography: Immediate functional and morphological vascular findings.

Aims: To investigate safety, feasibility, and injurious effect on endothelial cells of a thermography catheter as well as effect of flow on measured temperature in non-obstructive arteries.

Methods And Results: Safety and feasibility were tested in both rabbit aortas and pig coronary arteries. Evaluation of endothelial damage by the catheter (acute, 7 and 14 days) was performed in pig coronaries using Evans Blue, scanning electron microscopy (SEM) and Factor-VIII antibody and compared with normal arteries and arteries that underwent intravascular ultrasound (IVUS).

Functional expression of endothelial nitric oxide synthase fused to green fluorescent protein in transgenic mice.

The activity of endothelial nitric oxide synthase (eNOS) is subject to complex transcriptional and post-translational regulation including the association with several proteins and variations in subcellular distribution. In the present study we describe a transgenic mouse model expressing eNOS fused to green fluorescent protein (GFP), which allows the study of localization and regulation of eNOS expression. We tested the functionality of eNOS in the eNOS-GFP mice.

Augmentation of wall shear stress inhibits neointimal hyperplasia after stent implantation: inhibition through reduction of inflammation?

Background: Low wall shear stress (WSS) increases neointimal hyperplasia (NH) in vein grafts and stents. We studied the causal relationship between WSS and NH formation in stents by locally increasing WSS with a flow divider (Anti-Restenotic Diffuser, Endoart SA) placed in the center of the stent.

Methods And Results: In 9 rabbits fed a high-cholesterol diet for 2 months to induce endothelial dysfunction, 18 stents were implanted in the right and left external iliac arteries (1 stent per vessel).