At Stanford, researchers were investigating whether the blood of young mice altered the brains of old mice. In 2011, Saul Villeda, then a graduate student, and his colleagues reported that it did. When old mice received young blood, they had a burst of new neurons in the hippocampus, a region of the brain that is crucial for forming memories.
In a study published Sunday in the journal Nature Medicine, Dr. Villeda, now a faculty fellow at the University of California, San Francisco, and his colleagues unveiled more details of what young blood does to the brains of old mice.
After parabiosis, Dr. Villeda and his colleagues found that the neurons in the hippocampus of the old mice sprouted new connections. They then moved beyond parabiosis by removing the cells and platelets from the blood of young mice and injecting the plasma that remained into old mice. That injection caused the old mice to perform far better on memory tests.
Dr. Wagerss team has been investigating a specific region of the brain involved in perceiving smells.
In a second study in Science, the team reported that parabiosis spurred the growth of blood vessels in the brain. The new blood supply led to the growth of neurons and gave older mice a sharper sense of smell.
After linking the GDF11 protein to the rejuvenation of skeletal muscle and the heart, Dr. Wagers and her colleagues studied whether the protein was also responsible for the changes in the brain. They injected GDF11 alone into the mice and found that it spurred the growth of blood vessels and neurons in the brain, although the change was not as large as that from parabiosis.
Theres no conflict between the two groups, which is heartening, said Dr. Richard M. Ransohoff, director of the Neuroinflammation Research Center at the Cleveland Clinic.
Dr. Ransohoff and others hope the experiments on mice will lead to studies on people to see if the human version of GDF11, or other molecules in the blood of young people, has a similar effect on older adults.
