Extracellular vesicles in the crosstalk between glioblastoma multiforme and BV2 microglia: from the morphological characterization to the role in the tumour microenvironment

Extracellular vesicles (EVs) are integral players in the crosstalk between the tumour cells and the cells of the surrounding microenvironment (TME). EVs as nano- and microsized membrane enclosed vesicles transport bioactive cargo that can affect the recipient cells in a specific way. The role of EVs in the resistance and progression of glioblastoma multiforme (GBM) has gained more attention in the last years. In this research we focused on both the GBM- and microglial BV2-derived EVs and the effect of a chemotherapeutic drug temozolomide (TMZ) on their crosstalk. Morphological characterization is important to understand the role of EVs that is why in addition to previous data (TEM, AFM, etc.), we profoundly characterized the size and morphology of GBM-derived EVs using Cryo-EM. A high morphological heterogeneity between GBM cell lines (U87MG, U373MG, U251MG, and T98G) was revealed including the differences in shape, the number of membrane layers in a single EV, membrane thickens and so on. Next, we have evaluated the effect of TMZ on BV2 cells as well as characterized BV2-derived EVs by TEM and western blot. It was shown that TMZ-treatment affects the size distribution of BV2 EVs. Further, to get an insight into the EV-mediated cell-cell communication we analysed the effect of U87MG- and U251MG-derived EVs on the activation of BV2 cells. Finally, we have treated GBM cells with BV2-derived EVs and showed a significant effect on the proliferation and migration, especially in a more sensitive U87MG cell line. This research underlines the importance of EVs in the GBM TME and highlights the necessity to study the cells of the microenvironment in order to find new ways to influence GBM.