- Exosomes are small extracellular vesicles (30-150 nm in diameter) released by most cell types that play crucial roles in intercellular communication. These membrane-bound vesicles carry diverse molecular cargo, including proteins, lipids, and nucleic acids (mRNA, microRNA, and other non-coding RNAs), which can influence the behavior of recipient cells both locally and systemically.
- The biogenesis of exosomes occurs through a complex cellular process. They originate from the endosomal system, specifically through the formation of multivesicular bodies (MVBs). As early endosomes mature into late endosomes, they form intraluminal vesicles through inward budding of the endosomal membrane. The ESCRT (Endosomal Sorting Complex Required for Transport) machinery plays a crucial role in this process, though ESCRT-independent mechanisms also exist. When MVBs fuse with the plasma membrane, these vesicles are released as exosomes into the extracellular space.
- Exosomes have emerged as important mediators in both physiological and pathological processes. In the immune system, they participate in antigen presentation, immune activation, and immune suppression. Cancer cells often exploit exosomal signaling to promote tumor growth, metastasis, and drug resistance by modifying the tumor microenvironment and influencing distant organs. In neurodegenerative diseases, exosomes may contribute to the spread of pathogenic proteins like beta-amyloid and alpha-synuclein.
- The therapeutic potential of exosomes is increasingly recognized. They can be engineered as delivery vehicles for drugs, proteins, or nucleic acids, offering advantages over traditional drug delivery systems due to their natural origin and ability to cross biological barriers. In regenerative medicine, stem cell-derived exosomes show promise in tissue repair and regeneration. Additionally, exosomes are being investigated as biomarkers for various diseases, as their content can reflect the state of their cell of origin.
- Recent technological advances have improved our ability to isolate and characterize exosomes, leading to better understanding of their roles in health and disease. However, challenges remain in standardizing isolation methods, characterizing exosome subpopulations, and optimizing their therapeutic applications. The field continues to evolve rapidly, with new discoveries regularly emerging about exosome biology and potential clinical applications.
