re: Bone Marrow Donation questions?

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Transplant doctors prefer younger donors for their patients
In our previous post, we stated that one reason for the upper age limit is to provide the best treatment for patients. Doctors weigh many factors when selecting a donor for one of their patients; the age of the potential donors is one of them. Transplant doctors want younger donors. Some of this is data-driven; there are publications suggesting that patients with younger donors do better. See for example, https://bloodjournal.hematologylibrary.org/content/98/7/2043. Some of it is judgment. It is very clear that the bone marrow ages just like other organs; the cellularity of bone marrow declines with age. You can’t get as many cells out of an older donor as you can from a younger one, and higher cell dose improves the chances of success.

Additionally, there are little parts of each cell’s chromosomes, called telomeres, whose length reflects the residual ability of the cell to divide. Guess what? — the telomeres of bone marrow cells get shorter with aging. If you do bone marrow transplants serially in mice, the bone marrow poops out when the telomeres are gone. Can bone marrow from a 65-year-old donor last another 45 years or more in a 20-year-old recipient? We don’t know, but a lot of doctors are reluctant to do the experiment. Most would like to put young bone marrow in young patients, and older patients, too, for that matter. Finally, it is also true that diseases of the bone marrow, like myeloproliferative syndrome, myelosdysplastic disease and acute leukemia, are diseases of aging; their frequency begins to increase around age 45 and continues relentlessly throughout older age.

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