Efficient enzyme-free isolation of brain-derived extracellular vesicles

Abstract

Extracellular vesicles (EVs) have gained significant attention as pathology mediators and potential diagnostic tools for neurodegenerative diseases. However, isolation of brain-derived EVs (BDEVs) from tissue remains challenging, often involving enzymatic digestion steps that may compromise the integrity of EV proteins and overall functionality. Here, we describe that collagenase digestion, commonly used for BDEV isolation, produces undesired protein cleavage of EV-associated proteins in brain tissue homogenates and cell-derived EVs. In order to avoid this effect, we studied the possibility of isolating BDEVs with a reduced amount of collagenase or without any protease. Characterization of the isolated BDEVs revealed their characteristic morphology and size distribution with both approaches. However, we revealed that even minor enzymatic digestion induces 'artificial' proteolytic processing in key BDEV markers, such as Flotillin-1, CD81, and the cellular prion protein (PrPC), whereas avoiding enzymatic treatment completely preserves their integrity. We found no differences in mRNA and protein content between non-enzymatically and enzymatically isolated BDEVs, suggesting that we are purifying the same BDEV populations with both approaches. Intriguingly, the lack of Golgi marker GM130 signal, often referred to as contamination contamination-negative marker in EV preparations, seems to result from enzymatic digestion rather than from its actual absence in BDEV samples. Overall, we show that non-enzymatic isolation of EVs from brain tissue is possible and avoids artificial pruning of proteins while achieving a high BDEV yield and purity. This protocol will help to understand the functions of BDEV in a near-physiological setting, thus opening new research approaches.