Haematopoietic stem cells improve cardiac function after infarction without permanent cardiac engraftment

Background: Transplantation of bone marrow derived adult stem cells (BMC) improves cardiac function after acute myocardial infarction (MI). However, the cell population mediating myocardial recovery and the fate of the transplanted cells are still controversial. Aims: We determined the effects of Sca-1+ c-kit+ lin- haematopoietic BMC on cardiac function after MI and the cell fate after transplantation. Methods: Sca-1+ c-kit+ lin- BMC of male donor C57BL/6 mice were transplanted by intravenous injection into syngenic females after permanent MI. LV dimensions and function were determined by echocardiography and cardiac magnetic resonance imaging, transplanted BMC were identified by Y chromosome DNA in situ hybridization. Results: BMC treatment completely prevented LV dilation (LV enddiastolic volume BMC 70±16 μl vs. control 122±41 μl; p <0.05) and improved fractional shortening (BMC 22.9±8% vs. control 15.4±8.4%; p <0.05) and ejection fraction (BMC 68.2±6.6% vs. control 52±14.3%, p <0.05) as early as 3 days after transplantation, but did not decrease infarct size (BMC 27±6% vs. control 28±7%, p =n.s.). After 4 weeks, only sporadic cells of male origin were identified in infarcted hearts (<0.01% of periinfarct cells). Conclusion: Intravenous injection of sca-1+ c-kit+ lin− BMC after MI improves LV dimensions and function without evidence for long term engraftment.