It seems that the blood of the young can help the old. A new study shows that when the blood of young mice is injected into the old, some of the effects of age-related cognitive decline are reversed.
The scientists presented their findings at the Society for Neuroscience Conference in New Orleans, Louisiana. The blood has a huge effect on brain cells, but scientists were unsure how if the effects extended beyond cell regeneration. The team tested for changes in cognition by linking the circulatory system of young and old mice, analyzing the blood of each conjoined mouse once the blood had fully mixed.
Tissue from the hippocampus of old mice given young blood showed changes in the expression of 200 to 300 genes, especially in those that involved synaptic plasticity, which is linked to learning and memory. There were also changes in proteins involved in nerve growth.
The strength and number of neuronal connections were also boosted. The team gave 12 old mice shots of intravenous blood plasma from either young or old mice over the course of one month. This allowed them to exclude any effect produced by blood cells.
The old mice which had received young blood plasma performed much better in standard memory tasks than those who received old plasma. Fear conditioning tests were performed to determine which brain areas were involved in the reversal of cognitive decline. Mice with young blood were better at remembering fear associated with tasks that activated the hippocampus, implying that young blood has a specific effect upon this area.
However, the researchers haven’t determined yet what it is about young blood that old blood doesn’t have. The team is currently examining hormones and lipids for rejuvenation capabilities. While it’s plausible that there are similar mechanisms operating in humans, there’s no direct evidence to support such a claim.