"Heterochronic parabiosis" rejuvenates the brain

What's the news: A bizarre procedure, "heterochronic parabiosis," rejuvenated the brains of old mice in a variety of measures.

Why should we believe it? This news comes from a study published in Nature Aging earlier this month, March 2023. The study was performed by scientists at Harvard University.

So what is "heterochronic parabiosis"? In short, it's a bizarre, almost monstrous procedure. Scientists surgically sew together two mice of different ages (heterochronic) so their cardiovascular systems function as one (parabiosis). In other words, the blood of the old mouse goes into the young mouse, the blood of the young mouse into the old one, and it all gets mixed up.

This might sound like a truly perverse experiment, but it has been performed a number of times over the past few years, and by reputable scientists at top institutions. Studies published last year showed heterochronic parabiosis rejuvenates blood stem cells as well as liver cells. This new study has now shown that brain cells can also be rejuvenated — and all you need is a young, genetically identical partner who is willing to get surgically grafted onto you.

Why are scientists doing this? The point of this gruesome research is to show that there's something in the blood that can actually trigger rejuvenation, including in the brain. Perhaps that something is a kind of stem cell. Perhaps it's other, simpler signalling factors — some protein or metabolite.

The ultimate goal: Once scientists identify what those rejuvenating factors are, they might be able to trigger rejuvenation — first in mice, then in humans — without having to sew two unfortunate creatures together. Let’s hope that day comes soon.