Researchers develop method to detect Alzheimer’s disease in blood samples

Using biomarkers detected in blood samples, researchers developed a method to detect amyloid buildup in the brain, a hallmark of Alzheimer’s disease.

Alzheimer’s disease is a neurological illness that causes the brain to gradually lose neurons and synapses.

One of the primary causes of Alzheimer’s disease is the accumulation of amyloid b (Ab) in the brain, where it forms plaques. Alzheimer’s disease is mostly seen in individuals over 65 years of age, and cannot currently be stopped or reversed. Thus, Alzheimer’s disease is a major concern for nations with ageing populations, such as Japan.

A team of scientists from Hokkaido University and Toppan, led by Specially Appointed Associate Professor Kohei Yuyama at the Faculty of Advanced Life Science, Hokkaido University, have developed a biosensing technology that can detect Ab-binding exosomes in the blood of mice, which increase as Ab accumulates in the brain. Their research was published in the journal Alzheimer’s Research & Therapy.

When tested on mice models, the Ab-binding exosome Digital ICATM (idICA) showed that the concentration of Ab-binding exosomes increased with the increase in age of the mice. This is significant as the mice used were Alzheimer’s disease model mice, where Ab builds up in the brain with age.

In addition to the lack of effective treatments of Alzheimer’s, there are few methods to diagnose Alzheimer’s. Alzheimer’s can only be definitively diagnosed by direct examination of the brain–which can only be done after death.

Ab accumulation in the brain can be measured by cerebrospinal fluid testing or by positron emission tomography; however, the former is an extremely invasive test that cannot be repeated, and the latter is quite expensive. Thus, there is a need for a diagnostic test that is economical, accurate and widely available.

Previous work by Yuyama’s group has shown that Ab build-up in the brain is associated with Ab-binding exosomes secreted from neurons, which degrade and transport Ab to the microglial cells of the brain. Exosomes are membrane-enclosed sacs secreted by cells that possess cell markers on their surface.

The team adapted Toppan’s proprietary Digital Invasive Cleavage Assay (Digital ICATM) to quantify the concentration of Ab-binding exosomes in as little as 100 uL of blood. The device they developed traps molecules and particles in a sample one-by-one in a million micrometer-sized microscopic wells on a measurement chip and detects the presence or absence of fluorescent signals emitted by the cleaving of the Ab-binding exosomes.

Human clinical studies using the technique are presently underway. This highly sensitive idICA technology is the first ICA application that allows for the highly sensitive detection of exosomes that retain specific surface molecules from a small amount of blood without the need to learn special techniques; because it is applicable to exosome biomarkers in general, it can also be adapted for use in the diagnosis of other diseases.