Something in elderly blood is bad for brains. Plasma from old mice or humans worsens cognition and biological indicators of brain health, when infused into young mice. Conversely, plasma from young mice (or humans) rejuvenates old brains.
Much of this research has come from neurobiologist Tony Wyss-Coray’s group at Stanford University, which is pursuing what constituents of blood might be responsible. One previous study identified a protein, which declines with age, that has powerful beneficial effects. That protein can cross from the blood into the brain, but Wyss-Coray wondered how certain molecules contained in blood typically “talk” to the brain. Must they interact with neurons directly, or can they communicate indirectly, through the gateway to the brain, the blood-brain barrier?