A couple of posts ago I talked about a freaky experiment where a young mouse is surgically attached to an old mouse to create Franken-mice. The two Franken-mice share blood and the young blood reverses heart disease in the old mouse. So scientists looked to see what it is in the young blood that can treat aged hearts. They found that the molecule GDF11 is much higher in young mouse blood than old mouse blood. When they gave GDF11 to old mice, it also reversed age-related heart disease.
Following on from this paper, another group found that the fly version of GDF11, called myoglianin, can extend lifespan in flies.
Now I want to tell you about another Franken-mouse experiment which showed that young blood, or GDF11 alone, can reverse age-related brain degeneration.
As we age, our cognitive skills decline – it becomes harder to remember things or to learn new facts or skills, and we lose the ability to see, hear and smell well. This is largely because there is less blood flow to older brains and less brain cell regeneration. Many people think that the brain can’t regenerate. That we’re born with all the brain cells we are going to get, and every time we drink alcohol or whack our head we are losing precious brain cells that we’ll never get back. Well that is not exactly true. Adult brains have stem cells which can make new neurons. This just happens at a very low rate compared to a more regenerative organ like the liver.
So scientists stitched young, 2 month old, mice to older, 15 month old, mice for 5 weeks to see if young blood could reverse age-related brain changes. The old Franken-mice had 87% more blood vessel volume in their brains than old untreated mice and similar blood flow to their brains as young mice (measured by MRI). The 15 month old Franken-mice had more brain stem cells than untreated old mice, and these stem cells were better at generating brain cells. The old Franken-mice also had more new neurons in the area of brain that controls smell: the olfactory bulb. Once the old mice were separated from their young friends – de-Frankenised – they performed better in a smell test than untreated old mice.
Young serum can stimulate endothelial cells (the cells that line blood vessels) to grow 88% better in vitro than old serum. This shows that the young serum is most likely stimulating endothelial cells in the capillaries of old mouse brains to sprout new blood vessels.
GDF11 can increase endothelial cell growth by 23% in vitro. So scientists gave 21-23 month old mice either saline or GDF11 injections for 4 weeks. GDF11 treated mice had 50% more brain blood vessels and 29% more neural stem cells.
So while GDF11 didn’t completely reproduce the benefits of young blood, it did significantly improve the brains of old mice. So far GDF11 can reverse age-related heart and brain disease in mice and increase life span in flies. It is looking more and more like the elusive elixir of youth.
One interesting side note in the brain Franken-mouse study is that the young mice attached to 15 month old mice did not have any brain defects. However, if young mice were attached to very old mice (21 months old), they had less brain stem cells. So, while young blood can reverse age-related decline, the reverse is also true – old blood can speed up decline in young animals. Understanding the difference between young and old blood may be the key to understanding ageing.
The Scientific Paper: