Exosomes are small membrane-coated vesicles that are secreted from many human tissues and can be found in body fluids such as blood or urine. When the exosomes are formed proteins from the cells that they originate from are included. By identifying their tissue origins, exosomes detected in body fluids may prove valuable indicators, or biomarkers, for diseases like cancer in specific organs.
However, due to the small size of exosomes, and their low-level protein contents, extremely sensitive analysis methods are required to identify these vesicles and their originating organs. In the present study the researchers have used the PEA technology (proximity extension assay), developed in Uppsala, to examine the protein content of exosomes.
“Using the PEA technology we were able to demonstrate that the protein profiles of exosomes reveal their cells or tissues of origin,” says Masood Kamali-Moghaddam who led the study.
The researchers analyzed exosomes from many different sources. The proteins in exosomes in human milk had several proteins in common with cultivated milk gland cells, while proteins in exosomes from seminal fluid coincided with proteins in cultivated prostate cells. The results establish that analyses of protein in exosomes from body fluids can indeed reveal which tissues they originate from.
“The sensitive PEA technology also has the advantage that many proteins can be analyzed simultaneously in very small sample volumes. We are now adapting the technology to identify and count exosomes from different tissues, which may allow effective and non-invasive strategies for early disease diagnosis,” says Masood Kamali-Moghaddam.
The study has been published online in the journal Molecular & cellular proteomics.