Exosomes are the extracellular vesicles secreted by various cells. Exosomes mediate intercellular
communication by delivering a variety of molecules between cells. Cancer cell derived exosomes seem to
be related with tumor progression and metastasis. Tumor microenvironment is thought to be acidic and
this low pH controls exosome physiology, leading to tumor progression. Despite the importance of
microenvironmental pH on exosome, most of exosome studies have been performed without regard to pH.
Therefore, the difference of exosome stability and yield of isolation by different pH need to be studied. In
this research, weinvestigated the yield of total exosomal protein and RNA after incubation in acidic, neutral
and alkaline conditioned medium. Representative exosome markers were investigated by western blot
after incubation of exosomes in different pH. As a result, the concentrations of exosomal protein and
nucleic acid were significantly increased after incubation in the acidic medium compared with neutral
medium. The higher levels of exosome markers including CD9, CD63 and HSP70 were observed after incubation
in an acidic environment. On the other hand, no exosomal protein, exosomal RNA and exosome
markers have been detected after incubation in an alkaline condition. In summary, our results indicate that
the acidic condition is the favorable environment for existence and isolation of exosomes.