Fig. 3.

The biogenesis of MSC-EXOs and their pathways to the target cell. a EXOs biogenesis starts within the endosomal system. Within the endosomal system, internalized loads are encapsulated into early endosomes, b which then mature into late endosomes or MVB. Different compounds are also transported from the trans-Golgi network and presumably from the cytosol. c In addition, MVBs can be transported to lysosomes for decay or d move along microtubules to amalgamate with the cell membrane and discharge EXOs into the extracellular environment. MVB amalgamation with the membrane is a fine-tuned process, which needs various vital agents, including Rab GTPases and SNARE complexes. e) EXOs intercede their effects on the target cells via three essential methods: 1- recipient cell receptor interceded signal amplification, 2- direct connecting to the plasma membrane and fusion, and 3- endocytosis