Mayo Clinic researchers have proven for the first time that cells produced by the bone marrow can form new heart-muscle cells in adults, providing an important boost to research that could enable the body to replace heart muscle damaged by heart attack. The findings are published in Circulation: Journal of the American Heart Association.
"Until recently, the heart has been seen as an organ that cannot be healed," says Noel Caplice, M.D., the Mayo Clinic cardiologist who led the study. "Heart-attack damage to the myocardium, or heart muscle, was considered irreversible. This study points the way to a process that could lead to heart repair."
The researchers studied four female patients with leukemia who had survived 35 to 600 days after receiving bone-marrow transplants from male donors. Heart tissue samples were examined at autopsy using special staining techniques, which showed that a small portion of the heart-muscle cells, or cardiomyocytes, contained male genetic material and had therefore originated from the donor marrow. Of the more than 80,000 cell nuclei examined, about 1 in 425 (.23 percent) contained the y chromosome.
The study is important because it is the first confirmation that progenitor cells from outside the heart are capable of forming new heart muscle cells. "These progenitor cells are produced by the bone marrow and circulate in the blood," explains Dr. Caplice. "They are like stem cells in that they have potential to develop into various kinds of cells. Given the right biological signals, we have now shown they can become heart cells."
Dr. Caplice says the study has significant implications for future research. "Under normal conditions, with less than one percent of heart-muscle cells originating from these progenitor cells, they obviously are not adding much to the heart's pumping strength. But if we can determine the signaling mechanism that causes progenitor cells to develop into cardiomyocytes, we may be able to boost the response and induce more of them to proceed in that direction. A growth hormone delivered to the heart could perhaps lead to formation of new muscle around an area of scar tissue, so the heart could actually be healed after being damaged by heart attack. This study provides an important validation of the potential for this new line of research," Dr. Caplice concludes.