Cost-effective Strategies for Depletion of Endogenous Extracellular Vesicles from Fetal Bovine Serum

Despite the prominent therapeutic potentials of stem cells, their use in cell therapy has been challenged with some unreproducible and inconsistent outcomes in addition to the risk of rejection and tumorigenesis. Gaining novel insights to the importance of the conditioned medium, secretory factors and extracellular vesicles as the functional components of the cultured stem cells, suggested the idea of substituting the cells with their cell-free counterparts. Biological properties of these products are influenced by the cues received from their microenvironment. Hence, providing optimal and fully defined culture conditions is essential for their preparation. Fetal bovine serum (FBS), one of the most routine supplements of cell culture, is enriched by endogenous extracellular vesicles (EVs). These EVs will affect the yield, purity and functional features of the cell-free products. Here, we endeavored to examine and compare three different methods including ultrasonication, ultrafiltration and polymer-based precipitation, to deplete EVs from FBS. We chose easy to perform and fast methods with the capacity for high-throughput applications. Based on our observations, although all examined methods were able to deplete EVs from FBS to some extent, polymer-based precipitation could be considered as the method of choice with minimal consequences on the biological requirements of FBS to support cell growth and characteristics. Due to similarities between FBS and some other biological solutions, this strategy would be suitable for EV-depletion from other liquids with high concentrations of proteins and nutrients. Moreover, it could be applied for preparation of optimal culture conditions for nanoparticle applications.