# Assessing the Nature of Human Brain‐Derived Extracellular Vesicles on Synaptic Activity Via the Development of an Air‐liquid Microfluidic Platform

## TL;DR

This study introduces a new microfluidic platform to study brain-derived extracellular vesicles and their effects on human brain activity.

## Contribution

The novel air-liquid microfluidic platform enables real-time monitoring of BDEVs and their impact on human brain explants.

## Key findings

- BDEVs are enriched with synaptic proteins like Neural cell adhesion molecule and Syntaxin-1A.
- BDEVs injection reduces high-frequency oscillations in brain electrical activity.
- Combining BDEVs with GW4869 counteracts their electrical perturbations.

## Abstract

Brain‐Derived Extracellular Vesicles (BDEVs) have been associated with important roles in functional neuron networks. However, the various models that have been used to study these roles fail to account for all the specificities of the human brain. This study presents a microfluidic platform capable of injecting and/or collecting BDEVs from Organotypic culture of Post‐mortem Adult human Brain explants (OPAB) cultured at the air‐liquid interface, while measuring electrical activity in real‐time on 3D‐microelectrode arrays (MEA). The platform design and custom‐made program to control the system allows the automatic collection of BDEVs over days. Mass spectrometry analyses highlight that BDEVs are significantly enriched with synaptic proteins, such as Neural cell adhesion molecule, Syntaxin‐1A, and Synaptopodin, known to regulate synaptic plasticity. Using the MEA‐embedded air‐liquid microfluidic platform, it is shown that BDEVs injection on OPAB induces a significant decrease of local field potential compared to mock conditions, in particular for high frequency oscillations. Finally, a machine learning framework, experimentally validated, revealed that the co‐treatment of OPAB with BDEVs and GW4869, an inhibitor of exosome production, can counteract electrical perturbations induced by BDEVs alone. Together, this work provides innovative methodological developments, that contributed to reveal the diverse biological functions of BDEVs on neural activity.

This seminal study highlights the interwoven and tightly regulated functions of brain‐derived extracellular vesicles. Using microfluidics, proteomics, and AI‐based electric signal analyses of cortical brain explants, this work provides a useful resource dataset revealing the composition of human brain‐derived extracellular vesicles obtained from different isolation methods.