August 16, 2022

I’VE BEEN BLOGGING ABOUT THIS FOR YEARS: Scientists Gave Young Mice The Blood of Old Mice. Then Things Got Weird.

In a new experiment, young mice briefly experienced signs of old age when scientists infused them with the blood of older mice. A similar aging effect occurred when human cells were immersed in the plasma of older individuals.

The young mice – aged three months and all male – were given a blood transfusion from an older mouse, aged 22-24 months. The younger mice were then tested for muscle strength to see whether the old blood created the effect of tissue aging.

Compared to a control group (young mice who received a blood transfusion from another young mouse), the mice that received blood from an old mouse had “decreased maximal twitch force and significantly shorter rates of force development and relaxation during contractions”, the researchers reported.

The mice were tested for their physical endurance on a treadmill at baseline and seven days after the blood infusion. (Mice that refused to run were stimulated by a puff of air that kept them running until they were exhausted.)

Mice that received old blood became fatigued faster and ran a shorter distance on the treadmill than the control group.

These mice also had biomarkers for kidney damage and evidence of liver aging.

When older mice were given younger blood in this experiment, lipids and fibrosis and fatigue declined and muscle endurance increased.

It appears that the problem has more to do with toxic products of aging in old blood than with some youth elixir in the young blood: “The researchers hypothesized that cells from older mice were releasing a ‘senescence-associated secretory phenotype’ (SASP) that promoted aging, like muscle weakness, loss of endurance, and tissue damage.”

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