Transplanted Hearts Appear to Take On the Recipient’s Biological Age
Mouse experiments and human biopsy data suggest transplanted hearts adopt the recipient’s biological age, raising questions about aging and donor selection.
Research into transplanted hearts challenges the idea that replacing an older organ with a younger one could rejuvenate the body. Experiments in mice, supported by an analysis of human heart-transplant tissue, suggest that donor hearts soon reflect the biological age of their recipients—regardless of how old the donors were.
The findings do not settle every question about organ aging. They rely on molecular “aging clocks,” which capture only certain aspects of biological age, and the mouse research was published as a preprint. Still, the work may have practical implications for transplantation, including how clinicians evaluate organs from older donors.
Testing whether an organ can change the rest of the body
The research was led by Jesse Poganik of Brigham and Women’s Hospital in Boston. His team wanted to understand whether the age of a transplanted organ could influence the biological age of its recipient.
Previous experiments in aging research have connected the circulatory systems of young and old mice. Those studies indicated that factors associated with young blood could have rejuvenating effects in older animals. That raised a related question: Could a young organ benefit an older body, or could an older organ accelerate aging in a younger recipient?
Poganik’s group investigated the question by performing heart transplants in mice. The procedure differed from a conventional human heart transplant. Instead of replacing the animal’s original heart, the researchers implanted a second heart in its neck. This allowed them to compare the transplanted organ with the mouse’s existing heart.
The experiments included:
- Young adult mice receiving hearts from middle-aged donors.
- Middle-aged mice receiving hearts from young donors.
- Assessments of the transplanted heart, the original heart, blood, and other organs.
Donor hearts shifted toward the recipient’s age
The researchers used three molecular aging clocks to estimate the biological ages of tissues and animals. These tools were able to predict the chronological ages of mice that had not undergone transplantation.
When the team examined transplanted hearts four to six months after surgery, it found an unexpected pattern. Young hearts placed in middle-aged mice appeared biologically older, while middle-aged hearts placed in young mice appeared younger. In both directions, the transplanted organs shifted toward the biological age of the recipient.
The study was published online as a bioRxiv preprint.
Poganik had expected that the exchange might produce effects across the body. Earlier work by other members of his team found that young mice receiving old hearts accumulated senescent cells in other organs. Senescent cells are believed to contribute to aging, suggesting that an older organ might negatively affect a younger animal.
In the new work, however, the recipient’s broader biological environment appeared to have the stronger influence. The transplanted heart changed, while the recipient’s blood, original heart, and other examined organs did not appear to be meaningfully affected by the donor heart’s age.
Human transplant samples showed a similar pattern
The researchers also analyzed tissue from human heart-transplant recipients. After transplantation, patients typically undergo a series of heart biopsies. Brigham and Women’s Hospital had stored small samples from these procedures for decades, giving the team material that could be tested with the same types of aging clocks.
The human results aligned with the mouse findings. Donor hearts appeared to adopt the biological age of their recipients, regardless of the donor’s age.
Hospital records assessed by Poganik showed that heart recipients were generally around 20 years older than their donors. Even with this age difference, the molecular measurements suggested that the transplanted hearts adjusted to the recipients’ biological state rather than retaining their original age profile.
Why the recipient may determine an organ’s age
The study does not establish what causes a transplanted heart to take on the recipient’s biological age. João Pedro de Magalhães, an aging researcher at the University of Birmingham who was not involved in the work, suggested that the immune system could play a role. Immune cells circulating in the recipient’s blood might influence aging markers in the transplanted tissue.
Other possibilities remain. The effects of a single young heart may be overwhelmed by the many older components of an aging body. It is also possible that transplanting one organ is simply insufficient to produce measurable rejuvenation elsewhere.
The findings therefore do not prove that young organs have no benefits. Instead, they indicate that the biological condition of the recipient may be more influential than the donor organ’s starting age, at least according to the molecular clocks used in this research.
Potential consequences for donor-heart decisions
Poganik hopes the results will encourage transplant surgeons to consider more hearts from older donors. Some of these organs are discarded because of an assumption that they will not function as well as younger hearts. If aspects of biological age can reset after transplantation, donor age alone may not provide a complete picture of an organ’s potential.
Organ-preservation technology is already changing how donated organs are assessed and treated. Poganik has also worked on research indicating that preservation machines may make donated livers biologically younger to some extent.
Any application to transplant policy would still need to account for the limitations of biological-age measurements. An organ can appear younger or older according to one molecular measure without showing the same change through another. Aging clocks provide useful signals, but they do not capture every form of cellular or structural deterioration.
Aging remains a whole-body problem
The research weakens the notion that repeatedly replacing individual organs could allow people to become progressively younger. Fully reversing aging would require addressing DNA damage, structural damage, cellular wear, and other forms of deterioration across many tissues at once.
Some components of biological aging may be reversible, while others may not be. For now, transplanted hearts appear to illustrate the power of the recipient’s internal environment: Rather than making the body younger, the organ itself adjusts to the body it joins.
Original source: revew
Originally reported by revew.