The Medical Technology Blog

PET scan of a human brain with Alzheimer's disease
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Hi and thanks for visiting The Medical Technology blog. Today’s post concerns the news that non-invasive optical imaging of the eyes could lead to earlier diagnosis, intervention and monitoring of Alzheimer’s disease (AD) That is according to new research published online in the journal NeuroImage, showing that the nerve cell-damaging plaque that builds up in the brain with AD also builds up in the retinas of the eyes and shows up there earlier.

Scientists at Cedars-Sinai Medical Center, in collaboration with colleagues from the Weizmann Institute of Science in Israel and the University of Southern California, discovered characteristic amyloid plaques in retinas from deceased AD patients and used a non-invasive optical imaging technique to detect retinal plaques in live laboratory mice genetically modified to model the human disease. The combined results suggest the possibility that non-invasive retinal imaging may be helpful in early diagnosis of the disease.

The researchers considered the retina a better target for non-invasive imaging of AD since it is readily accessible and, unlike other components of the eye, is part of the central nervous system, having a direct connection and therefore many similarities with the brain. Previous studies have documented non-specific visual disturbances, eye disorders and certain types of retinal abnormalities occurring with AD and other neurodegenerative conditions, but this is the first to identify human retinal plaque deposits that could provide a specific diagnostic marker of the condition.

In lab tests, plaques in the retinas of mice genetically modified to model AD could be detected at a very early, pre-symptomatic stage – before the plaque appeared in the brain. A high-resolution, non-invasive optical imaging approach was developed to monitor individual beta-amyloid plaques in the retinas of live mice. The system is based on a specific marker and the adaptation of an existing optical system used to examine rodent eyes.

The research team used a fluorescent compound, called curcumin, to label and detect retinal plaques. This is believed to be the first use of curcumin as an imaging agent to detect AD-related plaques in the retinas of live animals. Curcumin binds to beta-amyloid plaques and makes them visible when viewed microscopically. In the Cedars-Sinai research, curcumin injected into the bloodstream of live mice crossed the blood-retinal barrier and specifically bound to the retinal plaques, allowing them to be viewed in high resolution with a non-invasive procedure.

Curcumin is more commonly known as the main base for the indian spice, turmeric, often used as a colourant is responsible for the yellow colour and was once described as Indian saffron, but of course, being significantly cheaper. Curcumin has been clinically trialled for uses within many diseases including multiple myeloma, pancreatic cancer, myelodysplastic syndromes, colon cancer,  and psoriasis.

Observations from multiple genetically-engineered mouse models of AD demonstrated a correlation between retinal plaques and brain plaques as disease progressed. In the laboratory mice, an immune system-based therapy that reduces the amount of plaques in the brain also reduced plaque load in the retina to the same extent, suggesting that the retina could represent the brain in assessing response to therapy. Beta-amyloid plaques were identified in retinal samples from human patients who had died from AD, and their features correlated with the diagnosed stage of the disease. Importantly, plaques were detected not only in patients who definitely had the disease, but also in the retinas of some people who were suspected of having early-stage AD based on clinical diagnosis and microscopic examination of brain tissue after death.

Collectively, the results are said to offer the first evidence for the existence of Alzheimer’s-specific plaques in the retina of human patients and the ability to detect individual plaques in live mouse models, creating a strong basis for future research building on these findings. According to the authors, these studies establish the potential of direct retinal beta-amyloid plaque imaging in live subjects as a tool for early AD diagnosis and prognosis, as well as assessment of therapies.

Alzheimer’s is a horrendous disease that steals away the people you love and have known perhaps all your life; it recently had strong coverage in the national press in the UK, when John Suchet, well-known journalist, news reader, presenter and author, wrote the moving book ‘My Bonnie’, after his wife was consumed by Alzheimer’s . I welcome this news, and would like to see more money and research spent on AD, though this is unlikely in this present economic climate.

That’s all for now, please drop back soon, or if you would like more information on the medical technology industry visit our main site at Espicom Business Intelligence.

Thanks, Paul.

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