Published by the Students of Johns Hopkins since 1896
August 9, 2022

Bone marrow transplants may slow Alzheimer’s

By RACHEL HUANG | March 7, 2019

Neurocognitive disorders have become more and more prevalent in society. Cognitive disorders can be defined as any disorder that significantly impairs the cognitive function of an individual in motor coordination, learning and memory, and impaired judgement. These disorders make it impossible to function normally in everyday life.

Alzheimer’s is a common neurocognitive disorder that affects an approximated 5.7 million Americans of all ages, with a new case developing every 65 seconds. However, Alzheimer’s is more prevalent in individuals aged 65 and older.

Alzheimer’s is a neurodegenerative disease — a disease that develops because neurons in the brain stop working and/or die. Diseases such as Alzheimer’s worsen over time and have no cure.

However, researchers at Cedars-Sinai Medical Center in Los Angeles may have discovered a new approach to slow the progression of neurodegenerative diseases such as Alzheimer’s using healthy, young bone marrow.

The brain is composed of neurons. Neurons are cells that transmit nerve or neural impulses to other neurons. Neurons communicate with each other by sending action potentials to trigger chemical and electrical synapses. 

A synapse is a gap between two neurons. When there’s more synapses, then there are more connections between neurons, meaning the neurons can communicate more. Synapses, therefore, are very critical for brain function and performance.

In the brain, there are also immune cells called microglia. Microglial cells are known to be responsible for disconnecting the connections between neurons in the brain. By decreasing the number of synapses, cognitive function may be compromised.

The onset of Alzheimer’s disease triggers the overproduction of microglial cells. Microglial cells, in moderation, are responsible for protecting the brain and removing damaged cells. However, when microglia become overactivated, its efficiency decreases, and it begins to cause neuronal damage. The neurodegenerative disease itself begins to progress and worsen.

In a study published in Communications Biology, researchers carried out bone marrow transplants on 18-year-old mice, using the bone marrow from four-month-old mice. In doing so, the researchers found that the mice who received the young bone marrow were able to cognitively outcompete the control group, who didn’t receive a bone marrow transplant, in tasks that tested their working memory and their learning and spatial abilities.

When the team looked at the hippocampus — the brain region associated with learning and memory — they found that the mice that received the young bone marrow transplant had more synapses between their neurons than the controlled counterparts. This finding was consistent with the researchers’ previous observations since synapses are important for normal cognitive functions.

Clive Svendsen is the director of the Cedars-Sinai Board of Governors Regenerative Medicine Institute and a co-author of this study. Helen Goodridge, an associate professor of Medicine and Biomedical Sciences at Cedars-Sinai, was the other co-author in this study.

“Our research suggests one answer [in how introducing blood from young mice can reverse cognitive decline in old mice] lies in specific properties of youthful blood cells,” Goodridge said in a news release. “[The young blood cells] act on the brain to reduce the loss of synapses related to aging,” Svendsen added in the same news release.

This research may prove to be beneficial in slowing the progression of neurodegenerative disorders. However, an issue arises with the use of bone marrow transplants in humans.

Instead, Svendsen hopes to create individualized young blood stem cells that could be used in humans to replace the aging blood stem cells. By reducing the loss of synapses due to aging, it may be possible to prevent the progression of these neurodegenerative disorders.

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