We investigated the impact of the mesenchymal stem cell (MSC) source, passage number, incubation time in serum-free medium, and isolation procedure on the yield of
extracellular vesicles (EV). We cultured MSC from bone marrow (BM-MSC), adipose tissue (AT-MSC), and umbilical cord (UC-MSC), and analysed EV using nanoparticle tracking analysis (NTA) and imaging flow cytometry (IFC). Our results showed that UC-MSC produced the highest yield of extracellular vesicles, that prolonged incubation in serum-free medium (48 h) resulted in a higher number of EV compared to 24 h, and that higher passages yielded more EV. At the same time, EV size and size distribution were comparable across different sources and passages. Double ultracentrifugation with washing resulted in a lower EV yield compared to single ultracentrifugation.
Comparison of NTA and IFC results revealed a linear correlation between both methods, although NTA yielded higher values. When establishing protocols for optimising EV
isolation, it is essential to consider the MSC source, culture conditions, and the choice of centrifugation method. The obtained data are relevant for the further application of EV in regenerative medicine, including the treatment of corneal injuries.
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