Research Published December 23 2015
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The identification of blood markers to diagnose Alzheimer’s disease at an early stage and predict its evolution is a major challenge. A study of Marie-Claude Potier’s team shows for the first time that blood cells from patients with Alzheimer’s disease develop specific morphological alterations. This discovery raises the hope of being able to diagnose the disease through a simple blood test.

Today the diagnosis of Alzheimer’s disease is established through a clinical examination associated to the visualization of lesions in the brain with MRI or Positron emission tomography and the determination of certain proteins in the cerebrospinal fluid after a lumbar puncture. This approach provides a diagnosis on a stage where cognitive deficit is mild but is invasive and expensive.

Establish this diagnosis through a simple blood test is a major challenge for Institut du Cerveau – ICM researchers. For this purpose, it is necessary to identify early altered blood markers in Alzheimer’s patients’ blood.

Neuropathological and clinical data have shown that patients’ neurons contained abnormally enlarged endosomes.  Endosomes are cellular compartments which function is to ensure membrane proteins trafficking inside the cell. Interestingly, the increase in the volume of endosomes occurs before the onset of symptoms. These endosomes have a role in the abnormal production of Aβ peptides, which accumulation is typical with Alzheimer’s disease.

Marie-Claude Potier’s team wanted to check whether blood cells also contained abnormally enlarged endosomes. In a collaborative study conducted with Professors Sarazin and Dubois at the Salpêtrière and Sainte-Anne hospitals in 71 patients with Alzheimer’s disease, on mild cognitive impairment or dementia stages, morphological alterations were observed in blood cells’ endosomal compartment. These changes are correlated to the presence of amyloid plaques in the brain. However, no Aβ peptide is detected on the blood cell level. The reason for the increase in the volume of blood cell endosomes remains unexplained but could be related to a general inflammation caused by the disease.

For the first time, this study demonstrates a correlation between blood cell specific alterations and the presence of amyloid plaques in patients’ brains. Marie-Claude Potier’s team now aims at determining these alterations’ evolution in the development of the disease and to assess their relevance as diagnostic tools for Alzheimer’s disease. This discovery raises a great hope to identify the disease at an early stage through a simple blood test, in order to slow its progression, even before the onset of disabling clinical symptoms.

Reference : Modifications of the endosomal compartment in peripheral blood mononuclear cells and fibroblasts from Alzheimer’s disease patients