Examination of retinal and brain tissue samples collected from 86 people
Alzheimer’s disease destroys memory and cognitive abilities. Currently, there is no single test that can definitively diagnose a person with Alzheimer’s disease. Newer therapies can only slow the progression, so early diagnosis is very important.
Research has shown that brain and cognitive changes in Alzheimer’s patients can be diagnosed through the retina. A research team at Cedars-Sinai Medical Center in Los Angeles, USA analyzed how retinal changes correspond to brain and cognitive changes in Alzheimer’s patients. This is to understand the complex effects of Alzheimer’s disease on the retina in the early stages of cognitive impairment.
Senior author Professor Maya Coronyo-Hamawi said: “This study is the first to provide an in-depth analysis of the protein profile of Alzheimer’s disease on the human retina and how it responds to molecular, cellular and structural impacts and changes in brain and cognitive function. “It is important for developing imaging techniques that can accurately diagnose diseases earlier and observe disease progression non-invasively through the eyes,” he said.
“The retina, as a progressive extension of the brain, provides a great opportunity to non-invasively monitor the central nervous system,” said researcher Josef Coronyo, first author of the study. We found that this strong protein accumulates and causes severe cell degeneration.”
The research team examined retinal and brain tissue samples collected from 86 donors over 14 years. This is the largest retinal sample of any group of patients with Alzheimer’s disease and mild cognitive impairment studied to date.
The research team compared samples from donors with normal cognitive function to those with early to mild cognitive impairment and late-stage dementia with Alzheimer’s disease. They also explored the patients’ retinal characteristics, measured and mapped markers of inflammation and functional cell loss, and analyzed proteins present in retinal and brain tissue.
As a result, what was found in the retinas of patients with mild cognitive impairment and Alzheimer’s disease was:
-In the brains of patients with Alzheimer’s disease, an excess of the protein ‘amyloid beta 42’, which clumps together to form plaques that interfere with brain function
-Accumulation of amyloid beta protein in ganglion cells, cells that connect visual input from the retina to the optic nerve
-More immune cells called microglia and astrocytes that tightly surround the amyloid beta plaques
-80% fewer microglia that clear amyloid beta protein from the retina and brain
-Specific molecular and biological pathways responsible for inflammation, cell and tissue death
“These changes in the retina correlate with changes in a part of the brain called the visceral and temporal cortex, which are centers for memory, navigation and time perception,” Coronyo said.
Retinal changes are also correlated with the pathological stage of Alzheimer’s disease and the patient’s cognitive status. These changes were also found in people who were cognitively normal or who had very little cognitive impairment. It shows that these factors can be early predictors of later cognitive decline.
Co-authors Ruth and Lawrence Harvey, PhD, said: “This study provides a deeper understanding of the effects of Alzheimer’s disease on the retina. Because these changes coincide with changes in the brain and can be detected in the early stages of the disorder, Alzheimer’s disease “It could lead to new diagnoses for the disease and ways to evaluate new forms of treatment.”
The study was published in Acta Neuropathologica. The original title is ‘Retinal pathological features and proteome signatures of Alzheimer’s disease’.
