Contrary to conventional wisdom, heart muscle cells do regenerate after heart attacks, researchers have found. In recent years, hints that heart cells can perform this healing feat have trickled in. Now the new findings, described today in the New England Journal of Medicine, provide the most compelling indication yet of heart cell regeneration.

Researchers at New York Medical College examined heart muscle cells, or myocytes, taken from patients four to 12 days after they had suffered a heart attack, sampling both the zone near the site of the heart attack and parts farther away from the damaged muscle tissue. To determine whether the heart was healing or not, the team looked for a protein known as Ki67, which is expressed in the nuclei of myocytes during division. Myocytes from the heart attack border zone, they found, multiplied 70 times faster than those in a normal heart; the cells farther away from the diseased zone multiplied 24 times faster than normal.

Future efforts, team leader Piero Anversa suggests, should investigate the source of the dividing myocytes. To that end, preliminary results hint that they might originate from stem cells in the heart, he reports. If so, this could lead to future treatment options. "If we can prove the existence of cardiac stem cells and make these cells migrate to the region of tissue damage," Anversa muses, "we could conceivably improve the repair of damaged heart muscle and reduce heart failure."