Stem cells can secrete extracellular vesicles (EVs), which possess the same therapeutic and regenerative effects as their parent stem cells.

These are nanovesicles containing proteins, lipids, RNAs (mRNA, miRNA, and lncRNA), and other biomolecules that play a vital role in paracrine signaling. EVs, such as exosomes and microvesicles (MVs), are continuously released from all living cells. MVs are released from the cell membrane via direct budding, while exosomes are formed from multivesicular endosomes or multivesicular bodies.    Bioactive molecules, such as RNA, miRNA, lipids, and metabolites, are sorted into EVs through different methods of loading and transport. Differences in EV size and surface composition also affect uptake by target or recipient cells.  

For example, microautophagy technically corresponds to the capture of isolated exocytic vesicles and small exocytic vesicles, but not large exocytic vesicles or clusters of small exocytic vesicles. Exocytic vesicles can be internalized and targeted to the lysosome for degradation or recycled and released into the extracellular fluid. Exocytic vesicles can also transmit information to recipient cells through local action on the cell membrane, particularly for signaling communication at the cell surface.   However, the key feature of exocytic vesicle cargo delivery is fusion with the plasma membrane and the transport of molecules into the cytoplasm. Exocytic vesicles are a form of secreted cells and contain the original cell's secretome. They can be used to treat various reproductive disorders due to their ability to transport various molecules.  Exocytic vesicles can be used in various cell-free therapies to overcome stem cell defects.