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Apparently, you’re only as old as your blood.

Feeling old? Creaking knees, sore back and foggy mind? Find a young-blooded friend and gently broach the subject of a total multi-round blood transfusion or, if they’re a really good friend, parabiosis. 

Nature Communications published a recent article – though not the first - on just such an arrangement in mice. Studying bone morphogenesis and repair, author Baht and colleagues found that while fractured bones healed more slowly in old mice than in younger counterparts (not surprising). Amazingly, when mice were paired in heterochronic parabiosis, a surgical attachment of a young mouse to an old mouse so their circulatory systems were shared, the features of bone repair and health in the older mouse were rejuvenated.  The authors found that the rejuvenating factors could be resolved from young bone morphogenic stem cells (BMSCs, transplantable cells means no need for a whole organism).  More, following bone injury, they found that rejuvenated healing capacity was linked to the dynamic temporal regulation of an important signaling molecule, beta-catenin; lowered levels were important during the healing process, but levels that remained low could negatively impact bone density.

By utilizing the capacity of BMSCs to regulate signaling (in this case beta-catenin) with finer tuning than by coarse therapeutic inhibition / supplementation.

Parabiosis was first successfully demonstrated in rats in the mid-1800s but until recently, has had comparatively little research attention.  Famously, in Spring, 2014, Stanford’s Dr. Wyss-Coray demonstrated that heterochronic parabiosis could positively impact the BRAINS of older mice, an groundbreaking result that led to his formation of the biotech company Alkahest, who are actively (and privately) testing this hypothesis to alleviate Alzheimer’s Disease in humans.

While parabiosis may not be the fountain of youth vampires, aging Hollywood starlets, and Rolling Stones guitarist Keith Richards are hoping for, I’m amazed at the results in animals so far.  Using in vivo imaging, it would be fascinating to see how ‘youthful’ features emerge in the brain of older parabiotic animals to investigate how quickly does parabiosis (or cellular transplantation) work? Are particular regions of the brain more ‘labile’ to change than others?  Will medicine move toward age-grading circulating blood as a metric for overall health?



Baht et al, “Exposure to a youthful circulation rejuvenates bone repair through modulation of β-catenin” Nature Communications 2015 May 19; 6:7131.

Villeda et al, “Young blood reverses age-related impairments in cognitive function and synaptic plasticity in mice” Nature Medicine 2014 Jun; 20(6) 659-63. 

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