Our bodies’ cells constantly communicate to maintain health and respond to changes. This communication often occurs through microscopic entities called exosomes, released by nearly all cell types, which orchestrate various biological processes throughout the body.
What Exosomes Are
Exosomes are small vesicles, ranging from 30 to 150 nanometers in diameter, released from cells. They originate from late endosomes (MVBs) within the cytoplasm, which fuse with the cell membrane to release exosomes into the extracellular space. Each exosome is enclosed by a lipid bilayer membrane, similar to the parent cell. This membrane protects diverse cargo, including proteins, lipids, and nucleic acids such as messenger RNA (mRNA), microRNA (miRNA), and DNA fragments. The specific cargo depends on the parent cell’s type and physiological state, reflecting its cell of origin.
How Exosomes Work
Exosomes function as biological couriers, traveling between cells to deliver molecular cargo and influence recipient cell behavior, interacting with target cells through various mechanisms after release. They might bind to specific receptors on the recipient cell’s surface, initiating signaling pathways. They can also fuse directly with the recipient cell’s plasma membrane, releasing contents into the cytoplasm. Exosomes can also be internalized by recipient cells through endocytosis, such as receptor-mediated endocytosis. Regardless of the uptake mechanism, the transferred proteins, lipids, and nucleic acids can alter the recipient cell’s gene expression, modulate immune responses, or influence overall function.
Exosomes in the Body
Exosomes participate in physiological functions, contributing to both health and disease. They are involved in immune responses, facilitating communication between immune cells and influencing activation or suppression. For instance, exosomes from dendritic cells can transfer antigens to T-cells, activating the immune system. They also play a role in tissue repair and development, carrying molecules that promote cellular proliferation and differentiation. Their cargo can change in pathological conditions, contributing to various diseases, such as promoting tumor growth and angiogenesis in cancer, and carrying misfolded proteins in neurodegenerative diseases like Alzheimer’s and Parkinson’s.
Exosomes in Medicine
Exosomes are promising tools in medical applications, particularly diagnostics and therapeutics. Present in various bodily fluids (blood, urine, saliva), their disease-specific cargo makes them valuable biomarkers for early disease detection, leading to “liquid biopsies” where exosomes from a fluid sample provide insights into a patient’s health, offering a less invasive alternative to traditional tissue biopsies. Beyond diagnostics, exosomes are being explored as natural delivery vehicles for therapeutic agents. Their capacity to transport molecules and target specific cells makes them suitable for delivering drugs, gene therapies, or regenerative medicine components. Researchers are investigating engineered exosomes tailored to deliver specific payloads (small molecules, nucleic acids, proteins) to precise tissues or cell types with high accuracy, holding promise for treating conditions from cancer to neurodegenerative disorders and cardiac injury.