Matrix Nanoscale Mechanics Regulates Exosome Production by Mesenchymal Stem Cells

Complex biotherapeutics such exosomes offer attractive opportunities for cell-free treatment of disease and conditions difficult to address with single, defined compounds. However their production remains challenging as adherent cells proposed to secrete therapeutic extra cellular vesicles require scalable platforms. In addition, the role of biomaterials design parameters on processes regulating vesicular secretory phenotypes is unclear. Here we propose the use of bioactive microdroplets, or bioemulsions, as microcarriers for the culture of mesenchymal stem cells and production of exosomes. We demonstrate 100% increase in the output of extracellular vesicles on bioemulsions. The impact of matrix mechanics on this process is then investigated, and in particular interfacial shear mechanical properties of corresponding liquid-liquid interfaces forming microdroplets. We find that such local nanoscale mechanics regulates not only cell adhesion, but also exosome output. We find that exosomes generated by cells cultured on bioemulsion microdroplets retain a high content of protein and RNA cargos. Finally, we demonstrate that the cold-shock protein YBox 1, previously associated with RNA packaging, is modulated by matrix mechanics and regulates exosome production. Together, these results demonstrate the impact of local interfacial mechanics on the adhesion and secretory machinery and provide a proof of concept for the application of bioemulsions for the production of complex biotherapeutics.