Every day in this country, about 3,000 people are waiting for a heart transplant to save their lives. Ultimately, more than 2,000 receive a new heart -- but more than 1,500 others die before a donor can be identified. This supply-and-demand issue has no easy solution.
Part of the problem is inherent to the heart itself. When injured, this metabolically active organ can't rest as it heals; it must keep working, second after second, beat after beat. This presents unique challenges to regenerative medicine and the development of bioartificial organs as applied to the heart. Although studies have shown that adult heart muscle can be grown from stem cells, these cells do not integrate into existing heart tissue.
In the first report of mammalian cardiac regeneration, we have shown that the fetal sheep heart is capable of regenerating following an in utero heart attack. My colleagues from the University of Pennsylvania and I extended this research in this mammalian model, which more closely tracks the effect regenerated cardiac tissue could have in humans. We examined the role of stem cells in the fetal sheep's regenerative response to a heart attack with the hope of understanding and reproducing that effect in adult sheep. The study, published in the Annals of Thoracic Surgery, showed that even in this large animal model, the fetal heart is capable of regneration because stem cells are "recruited" to replace injured heart tissue.
The finding is a huge step forward. If we can make an adult heart's response mirror the fetal response in utero, we suddenly have the potential to avert heart failure or reverse it after a serious medical event (such as the 935,000 heart attacks suffered annually in the United States). And just think of the impact we could have on the nation's transplant waiting list. Far fewer individuals would ever reach that point of no return where a replacement heart is their only hope.
Scientists are only beginning to understand the basics of cardiac regeneration. While there is not likely to be a sudden breakthrough, this research holds tremendous potential for the many people who otherwise face diminished quality of life or even imminent death.