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RESEARCH PRODUCT

Can bone marrow-derived multipotent adult progenitor cells regenerate infarcted myocardium?

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Objectives: To assess the functional effects of multipotent adult progenitor cells (MAPCs) transplanted in a rat model of chronic myocardial infarction. Methods: Forty-four rats underwent coronary ligation and, 14 days later, were randomly allocated to receive in-scar injections (5×106 cells/150 μL) of green fluorescent protein (eGFP)-transduced allogeneic MAPCs ( n =25) or culture medium (controls, n =19). Nine of the MAPC-treated hearts were employed for functional studies while the remaining 16 received cells co-labeled with Resovist™ and were only used for serial histological assessments. Left ventricular (LV) function was assessed echocardiographically before transplantation and 1 month thereafter in a blinded manner. Immunohistochemistry, electron microscopy and PCR were used to detect grafted cells. All data were compared by nonparametric tests. Results: Baseline ejection fractions (EF, median;[interquartile range]) did not differ significantly among the groups: 30% [0.23;0.37] and 37% [0.32;0.38] in control and rMAPC-transplanted hearts, respectively. One month later, LV function of control hearts was found to have deteriorated, as reflected by a decline in EF to 24% [0.21;0.30], and although EF tended to remain more stable after cell transplantation (37% [0.27;0.41]), the difference between the two groups failed to achieve statistical significance ( p =0.06). While MAPCs could be identified early post-transplant, no evidence of engraftment was further observed at 1 month by immunohistochemistry, electron microscopy or PCR. Conclusions: In this model, MAPCs did not improve global pump function, and although some of these cells expressed endothelial markers during the early post-transplant period, we could not detect any evidence for differentiation into cardiomyocytes and no engraftment was further identified beyond 2 weeks after cell injections.