Hollow fiber bioreactor allows sustained production of immortalized mesenchymal stromal cell-derived extracellular vesicles.

Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) have been reported to hold great potential as cell-free therapies due to their low immunogenicity and minimal toxicity. However, the large doses of MSC-EVs that are required for their clinical application highlight the urgency of finding a large-scale system for MSC-EV manufacture. In this study, we aimed to set up a hollow fiber bioreactor system for the continuous homogenous production of functional and high-quality MSC-EVs. MSC lines from two donors were immortalized (iMSC) and inoculated into hollow fiber bioreactors. Throughout 4 weeks, conditioned medium was daily harvested. iMSC-EVs were purified and characterized for content, immunophenotype, size, and functionality and compared to 2D cultured iMSC. The iMSC inoculated into the bioreactor remained viable during the whole culture period, and they maintained their MSC phenotype at the end of EV production. Our results showed that the bioreactor system allows to obtain 3D-cultured iMSC-derived EVs (3D-EVs) that are comparable to flask (2D)-cultured iMSC-derived EVs (2D-EVs) in terms of protein and lipid content, size, and phenotype. We also confirm that 3D-derived EVs exhibit comparable functionality to 2D-EVs, showing pro-angiogenic potential in a dose-dependent manner. These findings suggest that setting up a hollow fiber bioreactor system inoculating immortalized MSC lines facilitates the large-scale, functional, and high-quality production of iMSC-EVs. Our results emphasize the great potential of this production methodology to standardize EV production in the pursuit of clinical applications.