Young Blood in Old Veins: Grasping for Immortality

Tissue from the hippocampus of old mice given young blood showed changes in the expression of 200 to 300 genes, particularly in those involved in synaptic plasticity, which underpins learning and memory. They also found changes in some proteins involved in nerve growth.

The infusion of young blood also boosted the number and strength of neuronal connections in an area of the brain where new cells do not grow. This didn't happen when old mice received old blood. _NewScientist

There is something about young blood that transforms old tissues -- from the genetic level upwards. Those hormonal messengers and other signaling factors that are more prevalent in younger blood make their way into the cell and cell nucleus, transforming gene expression to more closely approximate the gene expression of a younger animal.

But the mystery remains: what exactly is it about young blood that old blood doesn't have? "We have not identified any individual factors responsible for the rejuvenating effects of young plasma yet," says Tony Wyss-Coray, also at Stanford. His team is now trying to identify possible candidates such as lipids and hormones.

Villeda is hopeful the results might one day translate to humans since the components of blood that change with age in mice mirror those in humans. _New Scientist

Abstract of original study from Nature:

In the central nervous system, ageing results in a precipitous decline in adult neural stem/progenitor cells and neurogenesis, with concomitant impairments in cognitive functions1. Interestingly, such impairments can be ameliorated through systemic perturbations such as exercise1. Here, using heterochronic parabiosis we show that blood-borne factors present in the systemic milieu can inhibit or promote adult neurogenesis in an age-dependent fashion in mice. Accordingly, exposing a young mouse to an old systemic environment or to plasma from old mice decreased synaptic plasticity, and impaired contextual fear conditioning and spatial learning and memory. We identify chemokines—including CCL11 (also known as eotaxin)—the plasma levels of which correlate with reduced neurogenesis in heterochronic parabionts and aged mice, and the levels of which are increased in the plasma and cerebrospinal fluid of healthy ageing humans. Lastly, increasing peripheral CCL11 chemokine levels in vivo in young mice decreased adult neurogenesis and impaired learning and memory. Together our data indicate that the decline in neurogenesis and cognitive impairments observed during ageing can be in part attributed to changes in blood-borne factors. _Nature

The study linked above focused on the effect of young blood on brain tissue and neurogenesis. It is likely that humoural factors more prominent in the blood of younger animals are capable of transforming the gene expression of most tissues of older animals -- not just the brain. At the same time, destructive factors -- pro-inflammatory cytokines for example -- that are more prevalent in the blood of older animals, are less likely to be present at high levels in younger animals' blood.

Dr Villeda hopes the results might one day translate to humans.

He told the Guardian newspaper online there was no reason not to think that, at some point in the future, people in their 40s or 50s could take therapies based on the rejuvenating chemical factors in younger people's blood, as a preventative against the degenerative effects of ageing. _Australian

This research should stimulate dozens of new studies, seeking out the good factors in young blood and the bad factors in old blood. Once these entities are identified, the quest to understand each factor -- good and bad -- will trigger dozens of new studies in its own right. In other words, Stanford's research on young blood into old animals is likely to trigger hundreds of new research studies -- a veritable boon for research into dozens of human maladies, including ageing.

More: Another approach to rejuvenating old cells (h/t Brian Wang)

Things are likely to become more interesting, as long as the scientific free for all of conflicting ideas is allowed to proceed unchecked by ideology and politics.