Young Mice Blood Extends Life in Old Mice

Surgically joining the circulatory systems of young and old mice slowed cellular aging and increased lifespan in older animals.

The older mice had their physiological abilities improved and lived up to 10% longer than mice that had not undergone the procedure, according to a study published in the journal Nature Aging.

The longer the animals shared circulation, the longer the anti-aging benefits lasted after they were detached from each other.

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A research team led by Duke Health scientists performed heterochronic parabiosis (HPB) — a surgical joining of circulatory systems — of young mice aged three months and older mice aged 20 months. The animals were joined for three months and followed up for another two months after being detached from each other.

The procedure significantly reduced the epigenetic (biological) age of blood and liver. Moreover, the older animals experienced gene expression changes opposite to aging, such as reduced expression of inflammation genes and increased expression of certain metabolism genes. The authors say these cellular-level changes were similar to the effects of lifespan-extending interventions like calorie restriction.

The findings suggest that the young benefit from a cocktail of components and chemicals in their blood that contributes to vitality. These factors could potentially be isolated as therapies to speed healing, rejuvenate the body, and prolong older individuals' lives.

"This is the first evidence that the process, called heterochronic parabiosis, can slow the pace of aging, which is coupled with the extension in lifespan and health," says senior author James White, Ph.D., assistant professor in the departments of Medicine and Cell Biology at Duke University School of Medicine and the Duke Aging Center.

In human terms, the experiment would be the equivalent of pairing a 50-year-old with an 18-year-old for about eight years. This would add eight years to the older person's lifespan. However, performing heterochronic parabiosis in humans is neither practical nor ethical, the authors say.

Moreover, other anti-aging interventions, such as calorie restriction, are more effective in extending longevity in mice.

Scientists have explored the potential of young blood to rejuvenate people, too. In 2016, a California-based startup, Ambrosia, started offering infusions of young plasma, the liquid portion of blood, to treat various conditions such as normal aging, dementia, Alzheimer's disease, and multiple sclerosis.

The startup was closed after the FDA warned that young blood transfusion has no proven clinical benefits while the procedure carries health risks. Nevertheless, the company resumed its activity in 2019.

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Another company, Alkahest, developed a product called GRF6019, a proprietary young blood plasma fraction of about 400 proteins. In the phase 2 clinical trial that involved 40 Alzheimer's patients, the plasma fraction appeared to slow participants' cognitive decline. However, clinical trials in larger populations are necessary to determine the effectiveness of the therapy.

Although the new study has demonstrated that shared circulation extends life and health for older mice, the elements driving these changes are not yet understood.

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