Purified cardiomyocytes from bone marrow mesenchymal stem cells produce stable intracardiac grafts in mice.

OBJECTIVE: We have previously isolated cardiomyogenic cells from murine bone marrow (CMG cells). Regenerated cardiomyocytes are important candidates for cell transplantation, but as they are stem cell derived, they can be contaminated with various cell types, thereby requiring characterization and purification. Our objectives were to increase the efficiency of cell transplantation and to protect the recipients from possible adverse effects using an efficient and effective purification process as well as to characterize regenerated cardiomyocytes.
METHODS: Noncardiomyocytes were eliminated from a mixture of stem-cell-derived cells using a fluorescence-activated cell sorter to specifically isolate CMG cells transfected with a recombinant plasmid containing enhanced green fluorescent protein (EGFP) cDNA under the control of the myosin light chain-2v (MLC-2v) promoter. Gene expression and the action potential were investigated, and purified cells were transplanted into the heart of adult mice.
RESULTS: Six percent to 24% of transfected CMG cells expressed EGFP after differentiation was induced, and a strong EGFP-positive fraction was selected. All the sorted cells began spontaneous beating after 3 weeks. These cells expressed cardiomyocyte-specific genes such as alpha-skeletal actin, beta-myosin heavy chain, MLC-2v, and CaV1.2 and incorporated bromodeoxyuridine for 5 days. The isolated EGFP-positive cells were expanded for 5 days and then transplanted into the left ventricle of adult mouse hearts. The transplanted cells survived for at least 3 months and were oriented in parallel to the cardiomyocytes of the recipient heart.
CONCLUSIONS: The purification and transplantation of differentiated cardiomyocytes from adult stem cells provides a viable model of tissue engineering for the treatment of heart failure.