Heterochronic Parabiosis: Reversing Aging With Young Blood?
The dream of rejuvenating the aged by the infusion of young blood is much older than anyone living. It is said that the Scythians thought to make themselves strong by drinking the blood of their enemies killed in battle. And Dracula kept himself youthful by drinking the blood first of young maidens visiting Transylvania and later of maidens in England once he had moved there.
Blood is not the only tissue that has been thought to protect and rejuvenate the elderly. In the 1920s a Franco-Russian surgeon named Serge Voronoff transplanted monkey testes into men (some of them eminent, for example Kemal Ataturk) whose virility had declined, and claimed that it worked. He made a fortune but soon became the object of mockery and scorn, dying in prosperous obscurity in Switzerland in 1951.
There is always an air of charlatanry about those who claim to be able to turn the biological clock back (it is easy to find smooth-talking promoters of recaptured youth on the internet, for example), but a recent article in the New England Journal of Medicine suggests that some of the old ideas about the rejuvenating qualities of young blood may not have been quite so far-fetched after all. It is early days to proclaim that eternal youth is around the corner, and personally I am not sure I would want it even if it were, but according to the author a technique known as heterochronic parabiosis has retarded or reversed the aging process in mice. It is, of course, some distance from Mouse to Man.
Heterochronic parabiosis is the surgical technique by which the blood supplies of creatures of different ages are linked. Researchers found that the cardiac hypertrophy of older mice could be reduced by this means: their hearts in effect became younger. They identified a factor in the younger mouse blood that was responsible for this, called Growth Differentiation Factor 11. When they gave this factor to old mice without the rest of the blood, they found that it had the same effect. Levels of this factor in blood decline with age.
The effects of heterochronic parabiosis were not confined to the heart. It increased the muscle strength of the old mice, too. The exercise endurance of the old mice became longer, and their grip strength too, though precisely how this was measured was not stated. More important still, there were beneficial neurological effects. It seems that the young blood promoted the activation of neural stem cells and this resulted in a more acute sense of smell (which declines with age). The improvement was not attributable solely to the GDF 11 in the younger blood because heterochronic parabiosis was more effective than GDF 11 alone. This means that there must be other factors in young blood that cause rejuvenation.
GDF 11 exerts its effect, according to the author, at the cellular level. It repairs the damage done by time to the mitochondria of cells, the mitochondria being the sub-cellular structures which generate most of the cell’s energy. It also affects gene expression of the formation of neural cells.
These results, if not merely speculative or fraudulent (for this is a field in which fraud has a long history), suggest possible applications, for example in the muscle-wasting in cancer and in the loss of brain cells in dementia. The author warns that GDF 11 has deleterious effects upon red cell production, but if its promise becomes known to a wider public, can it be long before an enterprising biochemical Serge Voronoff offers GDF 11 therapy in a clinic somewhere in the world where they don’t bother very much with regulation?
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