Lifespan of humans might ultimately be limited by the capacity for stem cells to keep replenishing tissues day in day out, analysis of the world's oldest woman's blood has concluded.
Researchers after examining Hendrikje van Andel-Schipper's body suggested that once the stem cells reached a state of exhaustion that imposed a limit on their own lifespan, they themselves gradually die out and gradually reduce the body's capacity to keep regenerating vital tissues and cells, such as blood, New Scientist reported.
Henne Holstege of the VU University Medical Center in Amsterdam said that it was estimated that humans were born with approximate 20,000 blood stem cells, and at any one time, around 1000 were simultaneously active to replenish blood.
Researchers also observed that Andel-Schipper's white blood cells had radically worn-down telomeres, the protective tips on chromosomes that burned down like wicks each time a cell divided.
Holstege added that mutations within the blood cells were not dangerous which resulted from mistaken duplication of DNA during van Andel-Schipper's life, as the "mother" blood stem cells multiplied to provide clones from which blood was repeatedly refilled.