Extracellular vesicles from organoids and 3D culture systems

When discovered, extracellular vesicles (EVs) such as exosomes were thought of as junk carriers and a means by which the cell disposed of its waste material. Over the years, the role of EVs in cell communication has become apparent with the discovery that the nano‐scale vesicles also transport RNA, DNA, and other bioactive components to and from the cells. These findings were originally made in EVs from body fluids of organisms and from in vitro two‐dimensional (2D) cell culture models. Recently, organoids and other 3D multicellular in vitro models are being used to study EVs in the context of both physiologic and pathological states. However, standard, reproducible methods are lacking for EV analysis using these models. As a step toward understanding the implications of these platforms, this review provides a comprehensive picture of the progress using 3D in vitro culture models for EV analysis. Translational efforts and regulatory considerations for EV therapeutics are also briefly overviewed to understand what is needed for scale‐up and, ultimately, commercialization. This review looks at cellular architecture and the implications on extracellular vesicle (EV) cargo and concentration profiles using organoids and other three‐dimensional (3D) in vitro systems. Abdollahi details key findings on 3D EV studies, mainly on cancer, cardiac repair, and stem cells. In general, cancer leads to an increase in EVs, and 3D in vitro systems were found to secrete more EVs than 2D cultures. This piece also highlights challenges in 3D EV assessments and translational efforts toward EV therapeutics.