Exosomes are tiny extracellular vesicles, ranging from 30 to 150 nanometers in diameter, that are released by cells into the extracellular space to facilitate communication between cells. Originating from the inward budding of endosomal membranes, exosomes form multivesicular bodies that then fuse with the plasma membrane to release their contents. These vesicles, which include proteins, lipids, and nucleic acids such as RNA and DNA, play a crucial role in intercellular communication and influence various physiological and pathological processes.

Exosomes work through a series of steps that facilitate communication between cells and influence various biological processes:

• Formation: Exosomes are created within cells. They form inside the cell as small vesicles by budding off from internal compartments called early endosomes. These vesicles mature into multivesicular bodies (MVBs) which contain many smaller vesicles known as intraluminal vesicles (ILVs). MVBs then fuse with the cell membrane, releasing these ILVs as exosomes into the extracellular space

• Release: Once they reach the cell membrane, exosomes are expelled from the cell into the surrounding environment or bloodstream. This release process involves the fusion of the MVBs with the cell membrane, which allows the exosomes to be released

• Transport: Exosomes circulate through bodily fluids like blood, lymph, or tissue fluids. They can travel to various locations within the body, including distant organs and tissues

• Uptake: Target cells take up exosomes through different methods, such as endocytosis (engulfing the exosome) or direct fusion with the cell membrane. This process allows the contents of the exosomes to enter the recipient cells

• Cargo Delivery: Inside the recipient cell, the molecules contained in exosomes—including proteins, lipids, and RNA—are released and can interact with the cell’s machinery. These molecules can influence the cell’s behavior, such as altering gene expression, modulating immune responses, or initiating repair processes

• Functional Impact: By delivering their cargo, exosomes can affect various cellular functions. For instance, they can help regulate immune responses, promote tissue repair, or influence cell growth and metabolism

*Exosomes can significantly complement MSC (mesenchymal stem cell) treatments by enhancing their therapeutic efficacy.