Different organisms have different lifespans. Under
normal circumstances, the cells that make up an organism will not survive that
creature’s death. Each cell type therefore has the same average lifespan as the
rest of the body. But is this inevitable? In particular, could neurons live
past their usual expiration date?
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The introduced mouse neurons did quite well in their new
homes, integrating themselves into the appropriate positions throughout the
brain. They were recognizable, however, because they remained slightly smaller
than their neighboring rat cells. In other words, the mouse PCs maintained their mouse characteristics.
Despite this, the mouse neurons survived for as long
as their host rat brains did, up to twice as long as they would have done if
they’d stayed in the mice. Perhaps more significantly, they did not decrease in
number as the hybrid rats aged. The grafted PCs looked like mouse neurons, but
they lived like rat neurons.
This could mean one of two things. Either the
type of brain in which a PC neuron finds itself dictates its longevity, or the brain type makes no difference (within reason), other than being alive. In the former case, mouse neurons will never live longer than two years as long as they reside inside mice. However, in the latter case, if we could coax a mouse into
living for three or more years, its PC cells would do just fine. If the same is true for humans, this could have implications for
human longevity. After all, we won’t want to live longer and longer if our
neurons have a strict shelf-life. If, on the other hand, our neurons can chug
along happily for double our average lifespans, then that would make it well worth working to
extend our lives.
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