Older donor hearts may adapt to younger recipients

Older donor hearts may undergo biological changes that bring them closer to the age of their new host, a study reported by ERR suggests. The findings could eventually widen the pool of potential heart donors.

Researchers at Harvard University tracked cellular damage in transplanted hearts using experiments in mice and health data from people who had received transplants. In the animal experiments, hearts from young, middle-aged and old mice were transplanted into other mice in different age combinations. The recipients lived for a time with two hearts.

After several months, researchers analysed tissue samples for chemical markers linked to cells’ biological wear. A similar pattern appeared in tissue samples from 11 patients at a Boston hospital, whose donors and recipients differed in age by as much as 50 years.

Medical records from hundreds of patients also showed that measures including heart rate, heart muscle wall thickness and exercise capacity after transplantation were more closely associated with the age of the recipient than with that of the original donor.

The researchers say the effect may be linked to the recipient’s internal environment and blood circulation. Earlier experiments connecting the blood circulation of young and old mice found that young blood stimulated tissue and brain function in older animals, while old blood had adverse effects on younger ones. A similar biochemical environment may influence how transplanted heart cells renew and age.

The results are preliminary and need to be confirmed in larger patient groups. Donors are currently generally recommended to be younger than 45, but understanding how transplanted hearts adapt could eventually help safely raise that age limit. The findings were published on the bioRxiv research network.