Extracellular Vesicles Slow Down A(1-42) Aggregation by Interfering with the Amyloid Fibril Elongation Step

Formation of amyloid-beta (A beta) fibrils is a central pathogenic feature of Alzheimer's disease. Cell-secreted extracellular vesicles (EVs) have been suggested as disease modulators, although their exact roles and relations to A beta pathology remain unclear. We combined kinetics assays and biophysical analyses to explore how small (<220 nm) EVs from neuronal and non-neuronal human cell lines affected the aggregation of the disease-associated A beta variant A beta(1-42) into amyloid fibrils. Using thioflavin-T monitored kinetics and seeding assays, we found that EVs reduced A beta(1-42) aggregation by inhibiting fibril elongation. Morphological analyses revealed this to result in the formation of short fibril fragments with increased thicknesses and less apparent twists. We suggest that EVs may have protective roles by reducing A beta(1-42) amyloid loads, but also note that the formation of small amyloid fragments could be problematic from a neurotoxicity perspective. EVs may therefore have double-edged roles in the regulation of A beta pathology in Alzheimer's disease.