AimsTo investigate the mechanism of exosomes' role in the transformation of MDS to AML.MethodsExosomes in culture supernatants of MDS and AML cell lines, were extracted by ultrafiltration and identified in three ways: morphology, size, and exosome protein surface markers. Exosomes from AML cell lines were then co-cultured with MDS cell lines and their impacts on MDS cell microenvironment, proliferation, differentiation, cell cycle, and apoptosis were analyzed by CCK-8 assay and flow cytometry. Furthermore, exosomes from MSC were extracted for further authentication.ResultsThe transmission electron microscopy, nanoparticle tracking analysis, Western blotting, and flow cytometry methods all verify that ultrafiltration is a reliable method to extract exosomes in the culture medium. Exosomes from AML cell lines inhibit the proliferation of MDS cell lines, block cell cycle progression, and promote apoptosis and cell differentiation. It also leads to increased secretion of tumor necrosis factor-α (TNF-α) and reactive oxygen species (ROS) in MDS cell lines. In addition, MSC-derived exosomes were found to inhibit the proliferation of MDS cell lines, arrest cell cycle progression, promote apoptosis, and inhibit differentiation.ConclusionUltrafiltration is a proper methodology in extracting exosomes. The exosomes of AML origin and MSC origin may play a role in MDS leukemia transformation via targeting TNF-α/ROS-Caspase3 pathway.