Endothelial progenitor cells delivered into the pericardial space incorporate into areas of ischemic myocardium.

OBJECTIVE: Our objective was to determine whether autologous endothelial progenitor cells (EPCs) delivered into the pericardial space will migrate to and incorporate into ischemic myocardium in a porcine model. BACKGROUND: Use of EPCs to enhance neovascularization and preserve myocardial function in ischemic tissue is undergoing intense scrutiny as a potential therapy. Delivery into the pericardial sac may overcome some of the limitations of currently employed cell delivery techniques. METHODS: EPCs were immunopurified from peripheral blood of Yorkshire pigs by selecting for the CD31 surface antigen, and adherent cells were cultured for 3-5 days. After myocardial ischemia was induced in the left anterior descending (LAD) artery, either autologous DiI (1,1'-dioctadecyl-1-3,3,3',3'-tetramethylindocarbocyanine perchlorate)-labeled EPCs (n=10) or serum-free medium (SFM; n=8) was delivered into the pericardial space using a percutaneous transatrial approach. Animals were sacrificed on Day 7 or 21. Echocardiography was performed at baseline, during ischemia, and on Day 7 in six SFM group animals and six EPC group animals. RESULTS: On Day 7, EPCs were identified in the left ventricular (LV) anterior wall or anterior septum in all six EPC-treated animals (cell density of 626 ± 122/mm(2)). On Day 21, EPCs were identified in the LV anterior wall or anterior septum in three of four EPC-treated animals (cell density of 267 ± 167/mm(2)). These cells showed dual staining for DiI and Bandeiraea simplicifolia lectin I (a marker of both native and exogenous endothelial cells). At the Day 7 follow-up, echocardiography demonstrated that fractional shortening in the EPC-treated group was 30.6 ± 3.4, compared with 22.6 ± 2.8 in SFM controls (P=.05). CONCLUSIONS: EPCs can migrate from the pericardial space to incorporate exclusively into areas of ischemic myocardium and may have favorable effects on LV function.

Rapid recruitment of temporally distinct vascular gene sets by estrogen.

Cardiovascular disease is the leading cause of mortality for both men and women in developed countries. The sex steroid hormone estrogen is required for normal vascular physiology. Estrogen functions by binding to intracellular estrogen receptors (ER), ERalpha and ERbeta, ligand-activated transcription factors that are expressed in both vascular endothelial and smooth muscle cells. We recently demonstrated that long-term (8 d) estrogen treatment in vivo in mice recruits distinct vascular gene sets mediated by ERalpha and ERbeta and that the promoters from these gene sets are enriched for binding sites of specific transcription factors, leading to the hypothesis that estrogen initiates a cascade of early transcriptional events that modulate gene expression in the vasculature. Here we test this hypothesis using gene expression profiling to examine initial transcriptional events (2-8 h) mediated by estrogen in blood vessels. Our data reveal that 1) estrogen regulates temporally distinct cascades of vascular gene expression, 2) initially, estrogen-mediated vascular gene repression predominates, 3) the earliest estrogen-recruited gene program is enriched in vascular transcription factors that can interact with binding sites present in estrogen-regulated vascular genes recruited subsequently, and 4) estrogen-regulated genes recruited next have specific functions, including lipid metabolism and cellular growth and proliferation that are potentially important for estrogen's known vascular functions. In summary, estrogen directly and rapidly recruits specific transcriptional factors that then propagate distinct cascades of gene expression. These data define the temporal recruitment of specific vascular genes by estrogen and enable further analysis of the mechanisms by which estrogen directly regulates vascular function.

Intravascular imaging of atherosclerotic human coronaries in a porcine model: a feasibility study.

OBJECTIVES: To perform intravascular imaging of atherosclerotic human coronary conduits in an animal model under conditions of flow and cardiac motion that approximate those encountered in vivo. BACKGROUND: Given the lack of animal models of vulnerable plaque, a model which would allow imaging of human disease and simulate coronary motion and blood flow could advance the development of emerging technologies to detect vulnerable plaques. METHODS: Human coronary segments from adult cadaver hearts were prepared as xenografts. In anesthetized Yorkshire pigs (45-50 kg) the chest was opened and the exposed aorta and right atrium were cannulated and attached in an end-to-end fashion to the human coronary xenograft, forming an aorto-atrial conduit. The xenograft was fixed to the anterior wall of the heart to simulate motion. Angiography and intravascular ultrasound (IVUS) of each graft were performed. RESULTS: Twelve human coronary grafts (10 from right coronary segments) were prepared and implanted successfully in seven animals. All animals tolerated the procedure. The average graft length was 39 +/- 2.3 mm. Blood flow rates distal to the graft were >100 ml/min in nine grafts. IVUS was performed in all 12 grafts and documented expansion of arterial (6.9%) and luminal (9.3%) dimensions during the cardiac cycle (P < 0.001 for both). There was a wide range of coronary atherosclerotic pathology within the grafts, including intimal thickening, fibrocalcific plaque, and deep lipid pools. CONCLUSION: This human-to-porcine coronary xenograft model allows intravascular imaging of human coronary pathology under conditions of blood flow and motion, and may be used to develop technologies aimed at identifying high-risk plaques.

Quantitative colorimetry of atherosclerotic plaque using the L*a*b* color space during angioscopy for the detection of lipid cores underneath thin fibrous caps.

OBJECTIVES: Yellow plaques seen during angioscopy are thought to represent lipid cores underneath thin fibrous caps (LCTCs) and may be indicative of vulnerable sites. However, plaque color assessment during angioscopy has been criticized because of its qualitative nature. The purpose of the present study was to test the ability of a quantitative colorimetric system to measure yellow color intensity of atherosclerotic plaques during angioscopy and to characterize the color of LCTCs. METHODS: Using angioscopy and a quantitative colorimetry system based on the L*a*b* color space [L* describes brightness (-100 to +100), b* describes blue to yellow (-100 to +100)], the optimal conditions for measuring plaque color were determined in three flat standard color samples and five artificial plaque models in cylinder porcine carotid arteries. In 88 human tissue samples, the colorimetric characteristics of LCTCs were then evaluated. RESULTS: In in-vitro samples and ex-vivo plaque models, brightness L* between 40 and 80 was determined to be optimal for acquiring b* values, and the variables unique to angioscopy in color perception did not impact b* values after adjusting for brightness L* by manipulating light or distance. In ex-vivo human tissue samples, b* value >/=23 (35.91 +/- 8.13) with L* between 40 and 80 was associated with LCTCs (fibrous caps <100 mum). CONCLUSIONS: Atherosclerotic plaque color can be consistently measured during angioscopy with quantitative colorimetry. High yellow color intensity, determined by this system, was associated with LCTCs. Quantitative colorimetry during angioscopy may be used for detection of LCTCs, which may be markers of vulnerability.

Low power ultrasound delivered through a PTCA-like guidewire: preclinical feasibility and safety of a novel technology for intracoronary thrombolysis.

BACKGROUND: Low power ultrasound delivered through an angioplasty-like guidewire may be effective for intracoronary thrombolysis. We evaluated the preclinical feasibility and safety of such wire. METHODS AND RESULTS: In 15 anesthetized Yucatan minipigs, the ultrasonic wire was advanced percutaneously into all three coronaries. Each coronary was randomized to long activation (6 minutes), short activation (3 minutes), or control (3 minutes indwelling, no activation). The energy delivered was 0.14 +/- 0.01 W/cm of active length (20 kHz). No changes in heart rate, rhythm, or arterial pressure occurred during wire positioning or activation. Mean lumen diameter (MLD) by quantitative angiography was not significantly different pre- and postintervention (2.36 +/- 0.12 mm vs 2.36 +/- 0.11 mm for long activation, P = 0.96; 2.33 +/- 0.15 mm vs 2.34 +/- 0.14 mm for short activation, P = 0.54; 2.30 +/- 0.12 mm vs 2.33 +/- 0.12 mm for control, P = 0.21). There were no angiographic stenoses at 60 or 90 days follow-up. Compared with baseline, MLD at follow-up increased in all the three groups (2.40 +/- 0.13 mm vs 2.53 +/- 0.11 mm, P = 0.004 for long activation; 2.37 +/- 0.17 mm vs 2.52 +/- 0.14 mm, P = 0.023 for short activation; 2.20 +/- 0.12 mm vs 2.33 +/- 0.11 mm, P = 0.001 for the control group). By histology, there were no clinically significant pathologic changes in coronary morphology. CONCLUSION: Use of a transverse cavitation therapeutic wire is feasible and well tolerated acutely in the normal porcine coronary. At 60 and 90 days, no angiographically apparent damage, no clinically significant pathologic changes, and no adverse events were seen. This technology may be safely used during percutaneous coronary intervention. Further studies are justified to evaluate its efficacy for intracoronary thrombus ablation.