Long-Term Culture of Mesenchymal Stem Cell Increased the Secretion of Exosomes

Abstract

Exosomes could be harvested from lots of sources, including mesenchymal stem cells. As biological 'nanocarriers'(30-200nm) they could transport cargo to both nearby and distant cells. These cargoes contain proteins, and RNAs enclosed by a lipid bilayer. Since these cargoes offer opportunities for disease detection and therapeutic applications, they have attracted a great deal of interest to study. Despite significant efforts made in this field, the low yield of isolation of exosomes has still challenged the progress. How to improve the efficiency and quality of exosome isolation remain questions. Most of the exosome studies have been performed without indicating the relation between the yield of exosomes and cell expansion. Therefore, in this study, we aim to investigate whether the exosomes secretion increase or decrease along with long-term cell expansion, and modify an appropriate passage for exosomes isolation. Thus after a long-term expansion of Mesenchymal stem cells, the exosomes were extracted from the culture medium, the total yield of exosomal protein and RNA were compared, and Transmission electron microscopy is applied to above the Morphological characteristics of exosomes. As a result, the concentration of total protein and nuclear acid were increased after long-term expansion. The higher levels of exosome markers, including CD63, TSG101, and exosomal RNA also generate a higher concentration at more upper passages. In summary, our results indicate that late passages result in an increased secretion of exosomes, and reached the highest concentration at eight times passages.