Young bone marrow improves memory
Researchers at Cedars Sinai Medical Center have demonstrated that bone marrow transplantation of young laboratory mice to old animals prevented the extinction of cognitive function of the latter, preserving the ability to memorize and learn. This observation confirms the recently proposed model, according to which the extinction of cognitive function is partly due to the aging of blood cells formed from hematopoietic stem cells in the bone marrow.
According to one of the leaders of the study, associate Professor Helen Goodridge, earlier studies have shown that the introduction of blood from young mice makes it possible to eliminate the manifestations of age-related decline in cognitive function. In their work, the authors managed to partially uncover the mechanisms underlying this phenomenon.
As part of their experiments, they injected 18-month-old laboratory mice with the bone marrow of 4-month-old mice or animals of the same age. Six months after that, both groups passed standard laboratory tests for activity level and learning ability, as well as for the state of spatial and short-term memory. Mice that received an injection of young bone marrow showed much better results compared to animals that received injections of old bone marrow, as well as with animals of the control group.
After that, the researchers analyzed the state of the hippocampus of animals – the region of the brain responsible for memory. Analysis of the results showed that more synapses were preserved in the hippocampus of young bone marrow recipients than in the hippocampus of old bone marrow recipients, despite the comparable number of neurons in the hippocampus of animals of both groups. Synapses are necessary for the functioning of the brain, and their number is an indicator of its functional state.
The microglial cells of the brain of old mice have larger bodies with fewer shorter processes than the cells of young mice. However, the microglia of old mice injected with the bone marrow of young animals outwardly resembled the cells of young mice, whereas transplantation of old bone marrow did not have such an effect.
Further studies revealed a possible cause of synapse loss. The blood cells that emerged from the cells of the young bone marrow suppressed the activity of microglia – auxiliary brain cells. Microglial cells maintain the functional state of brain neurons, but in some cases they can be overly activated and involved in the destruction of synapses. With a smaller number of hyperactive microglial cells, neurons retain their functional state, which contributes to the preservation of synapses.
If in the future the results obtained can be reproduced in clinical studies, they can form the basis of methods to slow the progression of neurodegenerative diseases, including Alzheimer's disease, which affects millions of people around the world. However, given the impossibility of applying modern approaches to bone marrow transplantation for the described purposes, the authors are working on a method for creating "personalized" young hematopoietic stem cells. In the future, such cells can be used to replace their own aging hematopoietic stem cells as a prevention of cognitive decline and, possibly, age-related neurodegenerative diseases.
Article by Melanie M. Das et al. Young bone marrow transplantation preserves learning and memory in old mice published in the journal Communications Biology.
Evgenia Ryabtseva, portal "Eternal Youth" http://vechnayamolodost.ru