Blood of world's oldest person hints at limits of life
In van Andel-Schipper's case, it seemed that in the twilight of her life, about two-thirds of the white blood cells remaining in her body at death originated from just two stem cells, implying that most or all of the blood stem cells she started life with had already burned out and died. "Is there a limit to the number of cell divisions, and does that imply that there's a limit to human life?"
Can you get round that by limit by replenishment with cells saved from earlier in your life?
The other evidence for the stem cell fatigue came from observations that van Andel-Schipper's white blood cells had drastically worn-down telomeres, the protective tips on chromosomes that burn down like wicks each time a cell divides.
On average, the telomeres on the white blood cells were 17 times shorter than those on brain cells, which hardly replicate at all throughout life.
The team could establish the number of white blood cell-generating stem cells by studying the pattern of mutations found within the blood cells.
The pattern was so similar in all cells that the researchers could conclude that they all came from one of two closely related "mother" stem cells.