Scientists have called into question previous research that suggested blood of a young mouse can reinvigorate an older one – in fact the opposite may be happening they say.
The technique, parabiosis, involves sewing a young mouse and an old mouse together so that they share a circulatory system. So promising have been the results that it has led to attempts to commercialise the procedure in humans.
In 2013, a team led by Amy Wagers, a stem-cell researcher at Harvard University in Cambridge, Massachusetts, seemed to offer an explanation for this blood-doping effect. The scientists found that levels of a protein called GDF11 decreased in the blood of mice as they grew older. When the researchers injected the protein into the heart muscle of old mice, it became ‘younger’ — thinner and better able to pump blood. Two subsequent studies by Wagers and her colleagues found that GDF11 boosted the growth of new blood vessels and neurons in the brain and spurred stem cells to regenerate skeletal muscle at the sites of injuries.
But another team of scientists has tested the results and found something different going on. They used a combination of chemicals to injure a mouse’s skeletal muscles, and then regularly injected the animal with GDF11. But rather than regenerating the muscle, the protein injections seemed to make the damage worse.
But Wagers stands by her work, believing that there could be multiple forms of GDF11.