Study Reveals Young Bone Marrow Regenerates Aging Mouse Brain



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LOS ANGELES (EMBARGOED UNTIL 5:00 AM EST FEBRUARY 20, 2019) – A new study found that bone marrow transplantation of young laboratory mice on old mice prevented the cognitive decline of old mice, preserved their memory and their learning abilities. The results support an emerging model that attributes cognitive decline, in part, to the aging of blood cells, which are produced in the bone marrow.

"Previous studies have shown that introducing young mice 's blood can reverse cognitive decline in older mice, but it is not clear how this happens," said Helen Goodridge, PhD, associate professor of medicine. and biomedical sciences at Cedars-Sinai. lead author of the study. "Our research suggests that the answer lies in the specific properties of young blood cells."

If new research confirms similar processes in humans, the findings could provide a pathway for designing therapies aimed at slowing the progression of neurodegenerative diseases, including Alzheimer's disease, which affect millions of people. Americans, said Goodridge.

In the study, published in the journal Biology of communicationLab mice, 18 months old, received bone marrow transplants from either 4-month-old mice or mice of their age. Six months later, both transplant groups underwent standard laboratory tests of activity and learning level, as well as spatial and work memory. Mice that received young bone marrow outperformed mice that received old bone marrow. They also outperformed a control group of old mice that were not transplanted.

The research team then examined the hippocampus, a region associated with memory, in the brain of mice. Young bone marrow recipients have retained more connections, called synapses, between hippocampal neurons than recipients of old bone marrow, although they have about the same number of neurons. Synapses are essential for brain performance.

Other tests have shown a possible reason for the missing synapses. The blood cells made by the young bone marrow have reduced the activation of microglia, a type of immune cell of the brain. Microglia promote the health of neurons but can become hyperactive and participate in the disconnection of synapses. With less hyperactive microglia, the neurons would stay healthy and more synapses would survive.

"We are entering a time when there will be more elderly people in the population, as well as an increased incidence of Alzheimer's disease, which will significantly increase the health care system," said Clive Svendsen, PhD, director of Cedars-Sinai's board of directors. of the Governors Regenerative Medicine Institute, professor of biomedical sciences and medicine and co-lead author of the new study. "Our work indicates that the cognitive decline of mice can be dramatically reduced by simply providing young blood cells, which act on the brain to reduce the loss of synapses associated with aging."

Translating the results, if they are confirmed in human samples, in potential treatments can prove difficult, since bone marrow transplants are currently not feasible for this use. Svendsen is working on the creation of "personalized" young blood stem cells for an individual using stem cell technology. These cells could eventually be used to replace the person's aging blood stem cells and prevent cognitive decline and possibly neurodegenerative diseases such as Alzheimer's disease.

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