Young mouse blood increases the lifespan of an old mouse

This interesting experiment reveals how blood from a young mouse can affect the body, aging process, and health of an old mouse and vice versa, when their circulatory systems are connected.

Explaining the process further, Vadim N Gladyshev, one of the researchers and a professor of medicine at Harvard University, told The Harvard Gazette:

“It’s not just an infusion of young blood: The young and old mice share much more in this procedure. For example, old mice have access to the younger organs and the mice exchange blood factors in both ways so that the damage accumulated with age is distributed, together with other factors that might influence biological age.’

Heterochronic parabiosis triggered changes

Generally, parabiosis experiments last for only a month or 45 days. In contrast, Gladyshev and his team joined the blood vessels of a young and old mouse together and then kept the animals in the same condition for three months.

After three months, they detached the mice and studied the molecular markers in their blood that indicate aging for the following two months. According to the researchers, it was like checking the aging process in an 18-year-old and 50-year-old human being after keeping them alive on a common circulation system for eight years.

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They noticed that during the time the mice were connected the young mouse was aging faster. However, after it got separated from the old mouse, the aging process returned to its usual pace. 

The most surprising changes were observed in the old mouse though. Heterochronic parabiosis reduced the aging of blood cells and liver tissues in the mouse and triggered genetic changes that promoted longevity. 

When the researchers compared the biological markers in the old mouse with other mice of its age who didn’t undergo parabiosis, they were surprised. The mouse attained a 10 percent longer lifespan than the control group mice.

“The older mice became younger, and they lived longer than the controls. The difference in lifespan is significant,” said Gladyshev.

“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,” James White, senior study author and a professor at Duke University, added.

Possibly slow aging in humans? 

The researchers claim that the anti-aging effect in the old mouse lasted even after two months of separation. This was probably because both mice were connected for a longer than usual duration.

Therefore, these findings suggest that if old mice share a common circulatory system with young mice for a long time, they are also likely to experience anti-aging effects for a longer duration when they are disconnected.

Interestingly, if you apply the logic from this study to human aging, you may assume that the same process could increase the lifespan of a person by nearly six years (six to 10 percent increase). However, that’s not how logic and science work. Gladyshev and his team are still not sure what caused the increase in the old mouse’s lifespan. Was it just the blood? A protein? Or some unknown molecule? 

“We don’t know exactly how this happens. It’s probably a combination of different factors that leads to the rejuvenating effect. But it’s clearly not just that an infusion of young blood rejuvenates. It’s more complex than that,” said Gladyshev.

Also, the current results are only based on a two-month follow-up period, so they don’t know if the procedure could lead to any long-term side effects in the mice. 

Moreover, the human body is much more complex than a mouse’s body. So a lot of research needs to be done before scientists start performing surgical procedures like heterochronic parabiosis to rejuvenate humans.

The study is published in the journal Nature Aging.

Study Abstract:

Heterochronic parabiosis (HPB) is known for its functional rejuvenation effects across several mouse tissues. However, its impact on biological age and long-term health is unknown. Here we performed extended (3-month) HPB, followed by a 2-month detachment period of anastomosed pairs. Old detached mice exhibited improved physiological parameters and lived longer than control isochronic mice. HPB drastically reduced the epigenetic age of blood and liver based on several clock models using two independent platforms. Remarkably, this rejuvenation effect persisted even after 2 months of detachment. Transcriptomic and epigenomic profiles of anastomosed mice showed an intermediate phenotype between old and young, suggesting a global multi-omic rejuvenation effect. In addition, old HPB mice showed gene expression changes opposite to aging but akin to several lifespan-extending interventions. Altogether, we reveal that long-term HPB results in lasting epigenetic and transcriptome remodeling, culminating in the extension of life span and health span.