Old Hearts Rejuvenated

A study led by Jesse Poganik of Harvard Medical School has made a remarkable discovery: older hearts transplanted into younger recipients appear to become biologically younger. The research, which used mice as subjects, found that the biological age of an organ is not fixed, but is instead influenced by the body it is placed in.

The study used an established technique in which the recipient keeps its original heart, while a donor heart is connected to blood vessels in the neck. This allowed the researchers to observe the effects of the transplant on the donor heart's biological age.

The researchers used epigenetic clocks to estimate the biological age of the hearts, which involves looking for characteristic patterns of chemical tags called methyl groups attached to DNA. This method provides a way to measure the biological age of an organ, which can differ from its chronological age.

The study's findings suggest that an organ's biological age is not entirely intrinsic to the organ itself, but is strongly influenced by the body around it. This has significant implications for organ transplantation, as it could potentially expand the pool of available organs for transplants by loosening current constraints on donor age limits.

## Why it matters The discovery that older hearts can become biologically younger when transplanted into younger recipients could have a major impact on the field of organ transplantation. If the findings are confirmed, it could lead to an increase in the number of available organs for transplant, potentially saving thousands of lives. The study's results also highlight the complex relationship between an organ and the body it is placed in, and could lead to a greater understanding of the aging process.

The study has been uploaded to bioRxiv and has not yet been peer-reviewed. However, if the findings are confirmed, they could have a significant impact on the field of organ transplantation and our understanding of the aging process.