When she was successful, Dr. Iram said, the result was about 10 microliters of cerebrospinal fluid — about one-fifth the size of a drop of water. To collect enough for infusions, she had to perform the procedure on many hundreds of mice, taming the technical challenges Dr. Wyss-Coray had warned by sheer force of repetition.
“I like doing these kinds of studies that require a lot of perseverance,” said Dr. iram. “I just set a goal and I’m not stopping.”
To transfer the young cerebrospinal fluid into old mice, Dr. Iram made a small hole in their skulls and implanted a pump under the skin on their upper back. For comparison, a separate group of old mice was infused with artificial cerebrospinal fluid.
A few weeks later, the mice were exposed to cues — a tone and a flashing light — that they had previously learned to associate with shocks to their feet. The animals that had received the young cerebrospinal fluid infusion tended to freeze for longer, suggesting that they retained stronger memories of the original foot shocks.
“This is a really cool study that seems scientifically solid to me,” said Matt Kaeberlein, a biologist who studies aging at the University of Washington and was not involved in the study. “This adds to the growing body of evidence that it is possible, perhaps surprisingly easy, to restore function in senescent tissues by targeting the mechanisms of biological aging.”
dr. Iram tried to determine how the young cerebrospinal fluid helped to preserve memory by analyzing the hippocampus, a part of the brain dedicated to forming and storing memory. She found that treating the old mice with the liquid had a strong effect on cells that act as precursors to oligodendrocytes, which produce layers of fat known as myelin that insulate nerve fibers and provide strong signaling connections between neurons.
The study authors addressed a particular protein in the young cerebrospinal fluid that appeared to be involved in triggering the chain of events that led to stronger nerve isolation. Known as fibroblast growth factor 17, or FGF17, the protein could be delivered into older cerebrospinal fluid and could partially replicate the effects of young fluid, the study found.