Last year, Saul Villeda, scientists showed they could boost the growth of new cells in the brains of old mice by giving them a blood infusion from young mice. New work presented at Neuroscience 2012 showed that old mice that had received young blood plasma performed better in tests of memory.
Tissue from the hippocampus of old mice given young blood showed changes in the expression of 200 to 300 genes, particularly in those involved in synaptic plasticity, which underpins learning and memory. They also found changes in some proteins involved in nerve growth. Old mice that had received young blood plasma performed better in tests of memory (memorizing a maze and remembering fear associated locations).
Aging is associated with structural and functional changes in the adult brain that steadily drive cognitive impairments and susceptibility to degenerative disorders in healthy individuals. As human lifespan increases a greater fraction of the population suffers from age-related cognitive impairments, making it crucial to elucidate means by which to combat the effects of aging.
To date, studies in old animals using heterochronic parabiosis - in which the circulatory systems of young and old animals are connected - have demonstrated that young blood can improve stem cell function in aging tissues including the brain. However, whether the enhancements of young blood extend beyond regeneration in either peripheral tissues or the central nervous system remains unknown. We hypothesized that the beneficial effects of young blood could counteract the pre-existing effects of aging in the old brain, and moreover improve higher order cognitive processes. Using heterochronic parabiosis we show that exposure of an old animal to young blood results in an increase in the dendritic spine density of mature granule cell neurons, as well as improvements in synaptic plasticity in the hippocampus of old mice.
Furthermore, intravenous administration of young blood plasma to old mice improved age-related cognitive impairments in both contextual fear conditioning and spatial learning and memory. Together, our data indicate that young blood is capable of reversing some of the structural and functional changes occurring in the adult brain during aging.