Exosomes are a group of extracellular vesicles with a size range of 40-120 nm which can be detected in all body fluids. They play an important role in cell-to-cell communication and can be secreted by all cell types. Since exosomes affect cell proliferation, cellular differentiation, inflammation, aging, angiogenesis, stress response, and cardiovascular remodelling, they became an interesting tool for disease research.
To isolate exosomes from 1 ml of blood plasma an agarose-based size exclusion chromatography in combination with precipitation was chosen. Fluorescence microscopy and live cell imaging were used for the visualization of cellular uptake processes. For this purpose, blood plasma exosomes were dyed with PKH, a fluorescent general membrane marker. The exosomal RNA tracking was performed with SYTO™ RNASelect™ dye. Hoechst staining was chosen to counterstain the nucleus.
During live cell imaging of endothelial cells it was shown that blood plasma exosomes are grabbed by filopodias, cellular actin protrusions, before getting internalized. Furthermore exosomes accumulated in the perinuclear region of human endothelial cells and smooth muscle cells of neonatal rats, with RNA being partially present inside the nucleus, too. Another behaviour could be observed with adult rat cardiomyocytes: exosomes seemed not to reach the nucleus, instead just stick to the membrane, while RNA was present inside the cells.
In this study it was shown that blood plasma exosomes communicate with cells of the cardiovascular system. Because of altered exosomal cargo during disease state, further investigations will take place to get a better understanding of the cellular effects during coronary heart disease and atrial fibrillation.