Abstract-In this study, we hypothesized that bone marrow stem cells (BMSCs) protect ischemic myocardium through paracrine effects that can be further augmented with preconditioning. In in vitro experiments, cell survival factors such as Akt and eNOS were significantly increased in BMSCs following anoxia. In the second series of experiments following coronary ligation in mice, left ventricles were randomly injected with the following: DMEM (G-1), BMSCs (G-2), and preconditioned BMSCs (G-3). Four days after myocardial infarction, BMSCs were observed within injured myocardium in G-2 and G-3. Apoptotic cardiomyocytes within periinfarct area were significantly reduced in G-3. Four weeks after myocardial infarction, smaller left ventricular (LV) dimension and increased LV ejection fraction were observed in G-3. Infarct area was significantly reduced in G-3. However, GFP ϩ cardiomyocytes were observed in low numbers within periinfarct area in G-2 and G-3. In conclusion, BMSCs secreted cell survival factors under ischemia, and they prevented apoptosis in cardiomyocytes adjacent to the infarcted area. Preconditioning of BMSCs enhanced their survival and ability to attenuate LV remodeling, which was attributable, in part, to paracrine effects. (Circ Res. 2006;98:1414-1421.)Key Words: stem cells Ⅲ paracrine effect Ⅲ preconditioning Ⅲ ischemia Ⅲ remodeling M yocardial infarction (MI) leads to cardiomyocyte loss and scar formation in the infarcted area. The large transmural infarction is associated with ventricular remodeling after MI. 1 Ventricular remodeling is characterized by changes in left ventricular (LV) geometry, mass, volume, and function, which include hypertrophy and cellular apoptosis of cardiomyocytes, in response to myocardial injury or alteration in load. 2 Ventricular remodeling is also a major factor in the progression of heart failure, and the prognosis for survival is poor.One approach proposed to reverse myocardial remodeling is regeneration of new cardiomyocytes. Recent reports have shown that bone marrow stem cells (BMSCs) have multilineage differentiation potential and potentially cross the lineage restriction to form various nonhematopoietic tissues including heart. 3 Most studies on BMSC therapy in experimental animal heart models 4 -6 and patients with acute MI 7-9 have shown an improvement in cardiac function, signifying the safety and feasibility of this approach. However, the mechanism of BMSC therapy is still controversial. BMSCs repair the ischemic myocardium primarily by angioblast-mediated vasculogenesis, 10,11 prevention of apoptosis of native cardiomyocytes, or direct regeneration of the lost cardiomyocytes.We, therefore, hypothesized that BMSCs protected ischemic myocardium through paracrine effects that could be further augmented with preconditioning. Materials and MethodsAn expanded Materials and Methods section can be found in the online data supplement available at http://circres.ahajournals.org. Coculture of BMSCs and CardiomyocytesIsolation and purification of BMSCs from C57B6 mice ...

It is hypothesized that the protection of bone marrow stem cells (BMSCs) on ischemic myocardium might be related to the anti-apoptotic effect via paracrine mechanisms. In this study, a wide array of cytokines including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), stromal cell derived factor-1 (SDF-1) and insulin growth factor-1 (IGF-1) were detected in the BMSCs cultured medium by ELISA. Myocyte apoptosis was assayed by DNA fragmentation and annexin-V staining. Myocardial infarction model was produced by ligation of mouse left anterior descending coronary arteries (LAD). Before LAD ligation, mice were myoablated by irradiation and transplanted with bone marrow cells from transgenic green fluorescent protein (GFP) mice. After LAD ligation, animals were administered stem cell factor (SCF, 200 μg / day / kg, i.p.) or saline for 6 days. Animals were sacrificed on end of SCF treatment and four weeks later. Apoptotic cardiomyocytes were assayed after treatment finished by TUNEL. Myocardial function was analyzed by echocardiography and pressure-volume loop. Bcl-2 protein was analyzed by western blotting. Our results showed that cultured BMSCs released VEGF, bFGF, SDF-1 and IGF-1. Hypoxia induced cell apoptosis was diminished in cardiomyocytes co-cultured with BMSCs. Smaller LV dimension and increased LV ejection fraction were seen in SCF treated animals. SCF significantly reduced cardiomyocytes apoptosis within peri-infarct area and up-regulation expression of Bcl-2 in ischemic area. Moreover, conditioned medium from cultured BMSCs also induced up-regulation of Bcl-2 protein in cardiomyocytes. It is concluded that paracrine mediators secreted by BMSCs might be involved in early repair of ischemic heart by preventing cardiomyocytes apoptosis and improving cardiac function.

This is the first report clarifying detailed changes in coronary plaque by statin in humans. This study indicated that lipid-lowering therapy changes plaque color and morphology and should then lead to coronary plaque stabilization.

Background-Elevated troponin T levels in non-ST-elevation acute coronary syndromes (NSTE-ACS) have been shown to predict an adverse outcome. Furthermore, it has been reported that troponin T could help improve the effectiveness of such new antithrombotic drugs as platelet GPIIb/IIIa antagonists and low-molecular-weight heparins. We hypothesized that such elevated troponin T levels in NSTE-ACS indicate the presence of thrombus at culprit lesions, and this hypothesis was verified through the use of coronary angioscopy. Methods and Results-We studied 57 consecutive patients with NSTE-ACS who underwent preinterventional angioscopy.Before catheterization, we obtained blood samples to determine troponin positivity, and the patients were then classified as either troponin-positive or troponin-negative groups (diagnostic threshold, 0.1 ng/mL). Using angioscopy at the culprit lesions, we examined the presence of coronary thrombus, yellow plaque, and complex plaque. Moreover, we compared the preinterventional angiographic parameters (thrombus and complexity of the culprit lesion, and TIMI flow) between the two groups. Twenty-two patients were troponin-positive and 35 patients were troponin-negative. Univariate analyses indicated that the TIMI flow and the incidence of coronary thrombus detected with angioscopy correlate with the elevated troponin T levels. A multivariate logistic regression analysis showed the presence of coronary thrombus detected with angioscopy to be the only independent factor associated with elevated troponin T levels in patients with NSTE-ACS (odds ratio, 22.1; 95% CI, 2.59 to 188.42; Pϭ0.0046). Conclusions-Using angioscopy, the elevated troponin T levels in NSTE-ACS were confirmed to be strongly associated with the presence of coronary thrombus.