Secretome of apoptotic peripheral blood cells (APOSEC) attenuates microvascular obstruction in a porcine closed chest reperfused acute myocardial infarction model: role of platelet aggregation and vasodilation.

Although epicardial blood flow can be restored by an early intervention in most cases, a lack of adequate reperfusion at the microvascular level is often a limiting prognostic factor of acute myocardial infarction (AMI). Our group has recently found that paracrine factors secreted from apoptotic peripheral blood mononuclear cells (APOSEC) attenuate the extent of myocardial injury. The aim of this study was to determine the influence of APOSEC on microvascular obstruction (MVO) in a porcine AMI model. A single dose of APOSEC was intravenously injected in a closed chest reperfused infarction model. MVO was determined by magnetic resonance imaging and cardiac catheterization. Role of platelet function and vasodilation were monitored by means of ELISA, flow cytometry, aggregometry, western blot and myographic experiments in vitro and in vivo. Treatment of AMI with APOSEC resulted in a significant reduction of MVO. Platelet activation markers were reduced in plasma samples obtained during AMI, suggesting an anti-aggregatory capacity of APOSEC. This finding was confirmed by in vitro tests showing that activation and aggregation of both porcine and human platelets were significantly impaired by co-incubation with APOSEC, paralleled by vasodilator-stimulated phosphoprotein (VASP)-mediated inhibition of platelets. In addition, APOSEC evidenced a significant vasodilatory capacity on coronary arteries via p-eNOS and iNOS activation. Our data give first evidence that APOSEC reduces the extent of MVO during AMI, and suggest that modulation of platelet activation and vasodilation in the initial phase after myocardial infarction contributes to the improved long-term outcome in APOSEC treated animals.

Assessment of left ventricular ejection fraction with late-systolic and mid-diastolic cardiac phases using multi-slice computed tomography.

INTRODUCTION: Multi-slice computed tomography (MSCT) is an accurate tool for the assessment of left ventricular ejection fraction (LVEF). However, in order to reduce radiation dose, prospective acquisition protocols are currently used, in which the end-systole and end-diastole are not scanned. Our aim was to study the accuracy of the assessment of LVEF using fixed late-systolic and mid-diastolic cardiac phases compared with echocardiography. METHODS: MSCT-derived LVEF was measured with off-line commercially available software packages, and compared with echocardiography-derived LVEF using the Simpson's method. LVEF was categorized as normal vs. abnormal (50% cut-off) and was also analyzed as a quantitative parameter. Bland-Altman plots and Pearson correlations were used for inter-technique comparisons. RESULTS: 58 patients were included. The sensitivity and specificity of fixed-phase MSCT when compared with echocardiography for detection of LVEF ≤50% was 79% (95% CI = 65-89%) and 43% (10-82%). Misclassification was associated with older age (68 ± 12 vs. 54 ± 13 years, p < 0.01), faster heart rate (79 ± 14 vs. 68 ± 10 bpm, p = 0.01), and LV hypertrophy (86% vs. 52%, p = 0.03). The quantitative comparison revealed no correlation (r = 0.095, p = 0.478) and a significantly different LVEF (median[IQR], 57.0[50.5-63.1]% vs. 61.0[57.3-64.3]%, p = 0.03). The observed bias between the two methods was -3.7% with broad limits of agreement (±25.5%). CONCLUSIONS: Fixed-phase MSCT assessment using late-systole and mid-diastole agreed in defining normal and abnormal LVEF in 76% of patients when compared with echocardiography. Quantitation of LVEF by this method yielded significantly lower values of LVEF and showed no correlation. Thus, accurate quantitation of LVEF by MSCT requires the acquisition of end-systolic and end-diastolic phases.

Protective effect of ischaemic preconditioning on ischaemia/reperfusion-induced microvascular obstruction determined by on-line measurements of coronary pressure and blood flow in pigs.

We investigated the protective effect of ischaemic preconditioning (IP) on the maintenance of coronary patency using on-line measurements of coronary pressures and blood flow in a closed-chest reperfused acute myocardial infarction (MI) model in pigs. Catheter-based 90-min occlusion followed by 60-min reperfusion of the left anterior descending coronary artery (LAD) was performed in anesthetised pigs (MI group). IP was applied (IP group) through two cycles of 5-min occlusion and 5-min reperfusion of the LAD before MI induction. Coronary patency was determined by measurements of coronary wedge pressure, collateral fractional flow reserve (FFRcoll), collateral pressure index (CPI) and absolute coronary blood flow (CBF). Inducible and constitutive nitric oxide synthase (iNOS/cNOS) activities and expressions were determined in the myocardium. Plasma levels of myeloperoxidase (MPO, index of activated leukocytes) and mean platelet volume (MPV, index of activated platelets) were measured. IP resulted in significantly lower levels of MPO (0.52 +/- 0.19 vs. 1.05 +/- 0.24 U/l, p<0.001) and MPV (9.1 +/- 0.6 vs. 9.6 +/- 1.0 fl, p=0.04), higher FFRcoll (0.17 +/- 0.05 vs. 0.04 +/- 0.05, p<0.001), CPI (0.13 +/- 0.05 vs. 0.02 +/- 0.05, p<0.001) and CBF (70.7 +/- 4.2 vs. 50.8 +/- 4.8 m/min, p<0.001) post-reperfusion as compared with the MI group. IP resulted in significantly higher cNOS activity and eNOS expression. Significant negative correlation was found between MPO and measures of coronary patency (FFRcoll, CPI and CBF) and cNOS activity. Moreover, cNOS activity correlated significantly with FFRcoll, CPI and CBF. In conclusion, IP attenuates the release of MPO and platelet activation, thereby contributing to the maintenance of vessel patency at microvascular level after reperfusion of the infarct-related artery.

Tracking the migration of cardially delivered therapeutic stem cells in vivo: state of the art.

Cell-based therapy is a promising, novel therapeutic strategy for cardiovascular disease. The rapid transition of this approach from the benchside to clinical trials has left a gap in the understanding of the mechanisms of cell therapy. Monitoring of cell homing and the fate of cardially delivered stem cells is fundamental for clarification of the myocardial regenerative process. Noninvasive imaging techniques allow an in vivo evaluation of the survival, migration and differentiation of implanted stem cells over time, and by this means, can help to answer unresolved questions. The most promising in vivo tracking methods involve the direct, nonspecific labeling of cells including MRI, radionuclide imaging and the use of reporter-gene imaging. This review summarizes the most important results of animal and human studies in which the fate and biodistribution of cardially delivered stem cells are assessed through different in vivo tracking methods.