The limits of mortality

The blood analysis of a woman who died at 115 reveals why death is life’s eventual certainty

How do seemingly healthy people die of old age? What ensures that all of us come with expiry dates? A new study brings us closer to understanding the limits of human mortality than ever before.

According to a new study published in the journal Genome Research, our lifespans are limited by our cells’ ability to divide. That stem cells, which replenish tissues day in and day out, will eventually reach a state of exhaustion where they gradually die out, diminishing the body’s capacity to regenerate vital tissues and cells, eventually resulting in death.

This finding was made by a group of Dutch researchers who were studying the blood of a dead woman who had once been recognised as the oldest woman in the world. Hendrikje van Andel-Schipper, who was born in 1890 in the Netherlands and died at the age of 115 in 2005, was known to be remarkably healthy for her age. Even in her last few years, she was known to possess clear cognition and her blood circulatory system was disease- free. On her death, her body was bequeathed to medical research.

According to the researchers, most humans are born with 20,000 blood stem cells. The number of active stem cells is known to shrink through the years, and most bodies are known to possess at least 1,000 simultaneously active stem cells to replenish blood at any given time.

When analysing van Andel- Schipper’s blood, the researchers found that around two-thirds of the white blood cells in her body at death originated from just two stem cells. All the blood stem cells she had started her life with had already burnt out. Her white blood cells had also drastically worn-down telomeres, protective caps at the end of chromosomes, which burn down each time a cell divides. These were around 17 times shorter than those found in her brain cells, which are more static in comparison with regularly dividing blood cells. This too pointed towards the level of stem cell exhaustion.

The researchers claim this finding raises hope for longevity. They say it is now theoretically possible that old bodies are rejuvenated by injecting them with stem cells saved from birth or early life.

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