Obstacles and opportunities in the functional analysis of extracellular vesicle RNA – an ISEV position paper by Mateescu, B, Kowal, E, van Balkom, B, Bartel, S, Bhattacharyya, S, Buzás, E, Buck, A, de Candia, P, Chow, F, Das, S, Driedonks, T, Fernández-Messina, L, Haderk, F, Hill, A, Jones, J, Van Keuren-Jensen, K, Lai, C, Lässer, C, Liegro, I, Lunavat, T, Lorenowicz, M, Maas, S, Mäger, I, Mittelbrunn, M, Momma, S, Mukherjee, K, Nawaz, M, Pegtel, D, Pfaffl, M, Schiffelers, R, Tahara, H, Théry, C, Tosar, J, Wauben, M, Witwer, K, Nolte-'t Hoen, E