Extracellular vesicle

Extracellular vesicles (EVs) are small, membrane-bound particles released by cells into the extracellular environment. They are a heterogeneous group of vesicles, including exosomes, microvesicles, and apoptotic bodies, each varying in size, composition, and biogenesis pathways. EVs play a crucial role in intercellular communication, carrying a diverse cargo of proteins, lipids, RNA, and DNA from their cell of origin to recipient cells. This cargo can influence various physiological and pathological processes, making EVs significant in areas such as immunology, cancer, and regenerative medicine.

Biogenesis and Types

Extracellular vesicles are categorized based on their origin and size.

• Exosomes are typically 30-150 nm in diameter and are formed inside endosomal compartments known as multivesicular bodies (MVBs). Upon fusion of MVBs with the plasma membrane, exosomes are released into the extracellular space.
• Microvesicles or ectosomes, range from 100-1000 nm and are shed directly from the plasma membrane.
• Apoptotic bodies are the largest type of EVs, ranging from 1-5 µm, and are released during apoptosis (programmed cell death).

The mechanisms of EV biogenesis are complex and involve various proteins and lipids. For example, the ESCRT (Endosomal Sorting Complex Required for Transport) machinery plays a significant role in exosome formation, while microvesicles are formed through outward budding and fission of the plasma membrane.

Functions

Extracellular vesicles are involved in a wide range of biological functions, depending on their origin and the molecules they carry. Some of the key functions include:

• Intercellular communication: EVs can transfer molecules such as RNA and proteins to recipient cells, modulating their behavior and function.
• Immune regulation: EVs play roles in both innate and adaptive immune responses, carrying immune-modulatory molecules.
• Disease progression: In diseases like cancer, EVs can promote tumor progression and metastasis by facilitating tumor cell communication and manipulating the tumor microenvironment.
• Tissue repair and regeneration: EVs from stem cells have been shown to promote tissue repair and have therapeutic potential in regenerative medicine.

Clinical Implications

The unique properties of EVs have implications for diagnosis, therapy, and drug delivery. For example, the molecular cargo of EVs can serve as biomarkers for various diseases, including cancer and neurodegenerative diseases. In therapy, engineered EVs are being explored as delivery vehicles for drugs, proteins, and nucleic acids, offering a novel approach to targeted therapy with reduced immunogenicity and toxicity.

Research and Challenges

While the study of extracellular vesicles has expanded rapidly, there are still challenges in the field, including standardization of EV isolation and characterization methods, understanding the mechanisms of EV uptake by recipient cells, and elucidating the full range of functions and therapeutic potential of EVs.

See Also

• Cell signaling
• Membrane biology
• Nanomedicine
• Regenerative medicine