We still don't know the exact cause of Alzheimer's disease for every patient, but research has increasingly pointed to environmental factors — such as meat and processed foods and particles in car pollution — that seem to lead to the tragic and degenerative condition.
Add another possible culprit to that list: blood.
Results from a new study published in the journal Stem Cell Reports suggest that transfusions and transplants of blood, bone marrow, organs and other biological matter from one person with hereditary Alzheimer's to a healthy person can spread the disease.
Canadian scientists at the University of British Columbia arrived at this conclusion after performing lab experiments with mice and stem cells.
For the study, they bred mice to be carriers of human inheritable Alzheimer's, and specifically a gene that synthesizes amyloid plaques. They then extracted stem cells from their bone marrow and injected this biological tissue into healthy mice that were not carriers.
Within nine months, the normal mice were showing signs of cognitive decline, as well as changes in their brains such as the accumulation of amyloid plaques, fibrous deposits that are classic hallmarks of Alzheimer’s.
The researchers had several takeaways.
One is that Alzheimer's can arise from stem cells outside the body's central nervous system, which overturns some preconceptions about how the disease forms.
"One of the potential outcomes of this study is to spur the field to move away from the conventional central dogma of AD [Alzheimer's disease] pathology, which states that the accumulation of brain-derived Aβ [amyloid], specifically produced by neurons, is the cause of the disease," the researchers write. "This study demonstrates the contribution Aβ, generated outside the brain, in establishing the disease."
Another is that the pathway to developing Alzheimer's could be similar to how people acquire prion brain diseases like Creutzfeldt–Jakob's, which can be transmitted. People eating cows with Mad Cow Disease have been known to develop a version of Creutzfeldt–Jakob disease.
In a nutshell, Alzheimer's could be passed to healthy people through the donation of biological matter. This would mean that potential donors would have to be screened for the condition.
"This supports the idea that Alzheimer's is a systemic disease where amyloids that are expressed outside of the brain contribute to central nervous system pathology," University of British Columbia immunologist and principle author Wilfred Jefferies said in a statement. "As we continue to explore this mechanism, Alzheimer’s disease may be the tip of the iceberg and we need to have far better controls and screening of the donors used in blood, organ and tissue transplants as well as in the transfers of human derived stem cells or blood products."
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