New Delhi: Whether distance makes the heart grow fonder or not is debatable, but scientists have now proven that a younger body can definitely make a transplanted heart young again.
The findings, yet to be peer-reviewed, were posted on the pre-print server bioRxiv by researchers at Harvard University, who were trying to understand how donor hearts adapt their biological age when they are transplanted.
“Organ transplantation offers a unique platform to investigate ageing biology as it uniquely enables delineating effects of grafting a tissue of a particular age into an environment of differing age. Compelling results…have recently shown that biological age of an organism may be modulated by an age-disparate environment, with exposure to a youthful physiological environment resulting in rejuvenation and lifespan extension,” read the study.
Over the years, as the average human lifespan increases, heart transplants have gotten far more frequent than they once were. In India, the number of organ transplants has grown fourfold in the past decade, from less than 5,000 in 2013 to nearly 20,000 in 2025. However, thousands of people still die every year, stuck on endless waiting lists for organ donation.
For heart transplants particular medical guidelines recommend that the donor’s age be less than 45 years old. However, the team of researchers found that the cell damage accumulated in donor hearts does not remain the same once the heart is in a new body. The heart adapts to the body’s age.
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New hearts for mice
For the study, the team grafted hearts from young, middle aged, and old mice, aged three months, 1 year, and 1.5 years, respectively. These hearts were then transplanted into mice of all three age groups. About four to six months later, the researchers took tissue samples from their heart to study the genetic changes linked to ageing.
Their analysis revealed that within the span of a few months, the biological age of the donated heart had shifted closer to the age of the recipient. Younger hearts inside older bodies proved to age faster, and older hearts in younger bodies were “rejuvenated”.
When the team looked into data about heart transplants at the Brigham and Women’s Hospital in Boston, they studied 11 cases of heart transplants with a significant age gap. They found the same effects that they had observed in the mice.
Researchers are still unsure why this happens, but they highlighted that the study only proves how complex ageing is. They plan to dedicate further research to understand exactly what is behind the biological ageing of a person.