Predominant fusion of bone marrow-derived cardiomyocytes

Objectives: Here we address the capacity of bone marrow-derived cells (BMDCs) to trans-differentiate into mature myocytes under the physiological stimulus of exercise training. Methods: For this purpose, we have transplanted bone marrow from mice ubiquitously expressing enhanced green fluorescence protein (eGFP) into host mice that have been subjected to a prolonged program of exercise. Results: In all successful bone marrow reconstitutions (greater than 80%), we observed rare but consistent events of bone marrow-derived cardiomyocytes, the frequency of which was unchanged upon exercise training. We have further determined whether these recruited myocytes are a product of trans-differentiation or fusion by the use of a genetic system that distinguishes cell fusion from trans-differentiation in a single-cell assay. Conclusions: We concluded that both in the unchallenged mouse and in the trained specimens, fusion is the most prominent mechanism by which bone marrow-derived cells are observed in the myocyte compartment. (c) 2005 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.