Alzheimer’s may disrupt immune cell production in bone marrow

For decades, research has focused primarily on changes occurring inside the brain, particularly the accumulation of amyloid-beta protein and the formation of tau protein tangles. However, the new study suggests that part of the dysfunction may originate in the bone marrow, which produces stem cells that develop into various types of blood and immune cells.

The researchers focused on a type of immune cell known as monocytes, which circulate in the bloodstream and can transform into macrophages after reaching tissues, helping remove harmful substances.

In experiments involving mice and studies of patients with Alzheimer’s disease, the researchers found that the disease affects the production of these cells in the bone marrow. It also disrupts a mechanism that normally acts as an alarm signal, prompting the bone marrow to release more monocytes into the bloodstream and ultimately toward the brain when they are needed.

The experiments showed that bone marrow stem cells in mice with Alzheimer’s disease lose part of their ability to self-renew and begin differentiating into specialized cells earlier than normal, accompanied by abnormalities in monocyte production.

The researchers also found that restoring the production of these cells in the bone marrow through targeted treatment improved some pathological features in the mice and was accompanied by increased migration of macrophages into the brain.

The researchers suggest that this dysfunction may be linked to an early depletion of the stem cells’ capacity for self-renewal, pointing to aging-related changes in the blood-forming system of people with Alzheimer’s disease.

The findings add to growing evidence that Alzheimer’s disease may not be confined to the brain but may also be associated with changes in the immune and blood systems. However, the researchers emphasize that most of the experiments were conducted in mice and that further studies are needed to determine whether targeting this mechanism could eventually lead to new treatments for humans.