Has any animal exploited the immortality of its germline to resist ageing indefinitely? The answer is yes. A few examples have been found among simpler organisms, one of the best studied being the hydra, a small freshwater animal up to 20mm long. Hydra appear to be able to regenerate endlessly with none of the recognised signs of ageing. This is possible because their bodies are permeated by germ cells whose primary purpose is to form buds that break off to yield offspring. These germ cells also create new tissue within the body, which in effect is the offspring of itself, constantly forming new cells to replace old ones. The line between reproduction and regeneration is blurred.
There is potential for humans to mimic the biologically immortal hydra, by exploiting our stem cells in the regeneration of organs damaged by age-related diseases. The ability of adult stem cells, which remain in the body throughout life, to regenerate heart muscle cells has already been demonstrated in mice. Organs regenerated this way would in effect be brand new, and "younger" than all the other tissues and organs. Such regeneration might not immediately boost life's span, but should greatly improve its quality in old age.
Possible timelines for regeneration and regenerative medicine in humans are 10-20 years
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