Under conditions of tissue injury, myocardial replication and regeneration have been reported. A growing number of investigators have implicated adult bone marrow (BM) in this process, suggesting that marrow serves as a reservoir for cardiac precursor cells. It remains unclear which BM cell(s) can contribute to myocardium, and whether they do so by transdifferentiation or cell fusion. Here, we studied the ability of c-kit-enriched BM cells, Lin- c-kit+ BM cells and c-kit+ Thy1.1(lo) Lin- Sca-1+ long-term reconstituting haematopoietic stem cells to regenerate myocardium in an infarct model. Cells were isolated from transgenic mice expressing green fluorescent protein (GFP) and injected directly into ischaemic myocardium of wild-type mice. Abundant GFP+ cells were detected in the myocardium after 10 days, but by 30 days, few cells were detectable. These GFP+ cells did not express cardiac tissue-specific markers, but rather, most of them expressed the haematopoietic marker CD45 and myeloid marker Gr-1. We also studied the role of circulating cells in the repair of ischaemic myocardium using GFP+-GFP- parabiotic mice. Again, we found no evidence of myocardial regeneration from blood-borne partner-derived cells. Our data suggest that even in the microenvironment of the injured heart, c-kit-enriched BM cells, Lin- c-kit+ BM cells and c-kit+ Thy1.1(lo) Lin- Sca-1+ long-term reconstituting haematopoietic stem cells adopt only traditional haematopoietic fates.

Background-A relatively simple, invasive method for quantitatively assessing the status of the coronary microcirculation independent of the epicardial artery is lacking. Methods and Results-By using a coronary pressure wire and modified software, it is possible to calculate the mean transit time of room-temperature saline injected down a coronary artery. The inverse of the hyperemic mean transit time has been shown to correlate with absolute flow. We hypothesize that distal coronary pressure divided by the inverse of the hyperemic mean transit time provides an index of microcirculatory resistance (IMR) that will correlate with true microcirculatory resistance (TMR), defined as the distal left anterior descending (LAD) pressure divided by hyperemic flow, measured with an external ultrasonic flow probe. A total of 61 measurements were made in 9 Yorkshire swine at baseline and after disruption of the coronary microcirculation, both with and without an epicardial LAD stenosis. The mean IMR (16.9Ϯ6.5 U to 25.9Ϯ14.4 U, Pϭ0.002) and TMR (0.51Ϯ0.14 to 0.79Ϯ0.32 mm Hg · mL Ϫ1 · min

Over the past few decades, advances in pharmacological, catheter-based, and surgical reperfusion have improved outcomes for patients with acute myocardial infarctions. However, patients with large infarcts or those who do not receive timely revascularization remain at risk for mechanical complications of acute myocardial infarction. The most commonly encountered mechanical complications are acute mitral regurgitation secondary to papillary muscle rupture, ventricular septal defect, pseudoaneurysm, and free wall rupture; each complication is associated with a significant risk of morbidity, mortality, and hospital resource utilization. The care for patients with mechanical complications is complex and requires a multidisciplinary collaboration for prompt recognition, diagnosis, hemodynamic stabilization, and decision support to assist patients and families in the selection of definitive therapies or palliation. However, because of the relatively small number of high-quality studies that exist to guide clinical practice, there is significant variability in care that mainly depends on local expertise and available resources.

After collateral flow is taken into account, the minimum achievable microvascular resistance is not affected by increasing epicardial artery stenosis.

Insulin-like growth factor-1 (IGF-1) promotes myocyte proliferation and can reverse cardiac abnormalities when it is administered in the early fetal stage. Supplementation of a mouse embryonic stem cell (ESC) suspension with IGF-1 might enhance cellular engraftment and host organ-specific differentiation after injection in the area of acute myocardial injury. In the study reported here, we sought to enhance the restorative effect of ESCs in the injured heart by adding IGF-1 to the injected cell population. Green fluorescent protein (GFP)-labeled sv129 ESCs (2.5 ✕ 10 5 ) were injected into the ischemic area after left anterior descending (LAD) artery ligation in BalbC mice. Recombinant mouse IGF-1 (25 ng) was added to the cell suspension prior to the injection (n = 5).

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Background-Thermodilution coronary flow reserve (CFR thermo

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