Exosomal-like vesicles are present in human blood plasma

Area of Science:

• Biochemistry
• Cell Biology
• Immunology

Background:

• Exosomes are small membrane vesicles (50-90 nm) secreted by hematopoietic cells.
• Their presence and function in vivo, particularly in circulation, remain largely uncharacterized.

Purpose of the Study:

• To provide the first evidence for the presence of exosomes in vivo within human blood.
• To characterize the biochemical and physical properties of these blood-derived vesicles.

Main Methods:

• Isolation of vesicles from plasma using differential ultracentrifugation and immunoisolation (CD63-coated beads).
• Identification via electron microscopy.
• Biochemical characterization using western blot and flow cytometry.
• Density analysis via sucrose gradient.

Main Results:

• Plasma from healthy donors contains vesicles consistent with exosomes in size, shape, and density.
• These vesicles were identified using electron microscopy and isolated via ultracentrifugation or immunoisolation.
• Biochemical analysis confirmed the presence of exosome-enriched proteins, including tetraspanins (CD63, CD9, CD81), MHC class I and II molecules, and Lamp-2.
• Vesicles exhibited a density similar to exosomes on sucrose gradients.

Conclusions:

• Blood serves as a physiological fluid for exosome circulation in the body.
• Blood exosomes may function as carriers in cell-cell or organ-organ communication, transporting molecules to distant targets.