I'll say what I always say.
A neuron was transplanted from one species to another with twice the lifespan, it lived as long as the new host. The researchers said it had potentially unlimited lifespan, and could probably live longer in even longer lived species. I believe if you had taken an average human's neuron and put it into Calment it too would have lasted 122+ years, over 50% longer than most any human. While it would be bolder it may be that even if transplanted into a bowhead, a human neuron could last over 200 years.
Some like Michael Fossel, appear to suggest too that a fraction of cells do not show signs of aging, and only fail due to failing supporting tissue, aging supporting cells.
If the body has cells that do not age, as it appears to have, what then? The genes of these cells are shared with virtually all cells in the body, the same repair and maintenance mechanism that allows for an immortal cell exists in all cells.
As a species evolves to be longer lived, and longer lived, there are two positions one 1.) it gets harder and harder requiring ever stronger natural selection to push the longevity. 2.) as it gets longer lived and longer lived the fewer the remaining steps to gain indefinite lifespan or biological immortality, the fewer the steps.
Humans are already very long lived, and as I said it may be some cells within humans are already exhibiting agelessness(their parameters only declining due to aging of supporting cells). It may be that a drug or drug combo could tweak gene expression enough to allow for decades or centuries of added lifespan.-DS, source link