Mechanical Characterization of Extracellular Vesicles Derived from Immortalized Adipose Stromal Cells

Adipose stromal/stem cells (ASC) are being intensively studied in the research field of regenerative medicine because of their capacities in immunosuppression, anti-inflammation, and regeneration. Extracellular vesicles (EVs) produced by such cells were shown to support regeneration and angiogenesis. However, little is known about the effect of environmental conditions, e. g. reduced oxygen concentrations, on the produced EVs. Here, cultured immortalized ASCs were incubated under different oxygen concentrations (normoxic and hypoxic oxygen conditions) in order to mimic these extreme conditions. EVs were isolated from supernatant of both conditions and their mechanical properties were studied. For better understanding of the EV functioning and their interaction with target cells and tissue, their mechanical characterization is indispensable. Atomic force microscopy (AFM) was used to image the particles at the single particle level with nanometer resolution and under close-to physiological conditions. In addition, nanoindentation experiments were performed: the scanning probe was pushed to the center of the vesicle and the corresponding force-distance curves were recorded. Analyzing these curves and the topography images provides insights into the EV's elastic behavior, e. g. spring constants and the bending modulus can be estimated. Hereby the effects of environmental conditions on the properties of adipose stromal cell EVs was studied.