Intravenously injected mesenchymal stem cells home to viable myocardium after coronary occlusion and preserve systolic function without altering infarct size.

Background: The purpose of this study was to determine whether murine mesenchymal stem cells (MSC) are able to home to the viable myocardium when injected intravenously and attenuate cardiac dysfunction and ventricular remodeling associated with myocardial infarction.

Methods And Results: Murine bone marrow cells were negatively selected for lineage markers and adherent MSC differentiated into adipocytes and osteocytes following treatment in culture. Two weeks after coronary occlusion that resulted in a permanent transmural infarct we observed a significant drop in LV systolic pressure, dP/dt(max), dP/dt(min), ESPVR and E(max) and a significant increase in end-diastolic volume in vivo. Femoral vein injection of MSC 1 h after occlusion attenuated the cardiac dysfunction without altering infarct size, or end-diastolic volume. Injected MSC pre-labeled with fluorescent paramagnetic microspheres were observed scattered in noninfarcted regions of the myocardium. Flow cytometry of whole heart digests after intravenous injection of MSC labeled with either fluorescent microspheres or fluorescent PKH26 dye demonstrated that infarcted hearts from mice that received MSC injections contained significantly more cells that integrated into the heart (20x) than those from uninfarcted controls.

Conclusion: We conclude that intravenously injected MSC were able to home to viable myocardium and preserve systolic function by 2 weeks following ligation. The preserved contractility is likely an MSC-mediated paracrine response since infarct morphology was unchanged and labeled cells observed at two weeks exhibited the same characteristics as the injected MSC. These data underscore the importance of using MSC as a potential therapeutic intervention in preserving cardiac function following infarction.