There is no debate in one area that the transplanted bone marrow cells are rejuvenating hearts.
According to Joshua Hare MD; a Hopkins University cardiologist on the board of Institute for Cell Engineering.
"Millions of dollars and years of effort can be spent trying to pin down the minutiae of stem cell science when patients need help immediately! Basic scientists say it is premature to do the trials when the mechanisms are unknown, "But I say it's unethical to wait." "Now it is possible to isolate adult stem cells and differentiate them in vitro into actual beating heart cells; that may be reinfused fairly easily back into the donor patient."
Dr, Joshua Hare MD Johns Hopkins - Institute for Cell Engineering , http://heart.sdsu.edu/~website/IRRI/Pages/faculty/untitled-2.html