Biomarkers.

Area of Science:

• Neuroscience
• Biochemistry
• Genetics

Background:

• Exosomes from brain cells (neuron-derived exosomes - NDEs, astrocyte-derived exosomes - ADEs) cross the blood-brain barrier, carrying molecular cargo.
• These vesicles are implicated in intercellular communication but their role in Mild Cognitive Impairment (MCI) and Late-Life Depression (LLD), potential dementia prodromes, is unclear.
• Alzheimer's Disease (AD) research extensively studies exosomes, yet their utility in earlier stages like MCI and LLD requires further investigation.

Purpose of the Study:

• To identify exosome-based biosignatures in NDEs, ADEs, and plasma.
• To explore shared molecular profiles in LLD, MCI, and AD.
• To investigate the role of brain-derived exosomes in the progression of cognitive decline.

Main Methods:

• Recruited participants with LLD, MCI, AD, and healthy controls.
• Isolated and quantified NDEs and ADEs using nanotracking and vesicle flow cytometry.
• Analyzed protein cargo and specific microRNAs (miRNAs) in plasma exosomes.

Main Results:

• Elevated NDEs and ADEs were observed in AD, but not in LLD or MCI compared to controls.
• Five of six assessed miRNAs were significantly reduced in AD exosomes.
• Proteomic analysis indicated persistent neuroinflammation in AD compared to LLD and MCI.

Conclusions:

• Findings suggest impaired brain-periphery communication in LLD, MCI, and AD.
• Exosomes offer a potential window into the molecular pathology of these neurodegenerative conditions.
• Further research into exosome cargo may reveal biomarkers for early detection and diagnosis.