The Secret Life of Exosomes: What Bees Can Teach Us About Next-Generation Therapeutics

Abstract

Mechanistic exploration has pinpointed nanosized extracellular vesicles, known as exosomes, as key mediators of the benefits of cell therapy. Exosomes appear to recapitulate the benefits of cells and more. As durable azoic entities, exosomes have numerous practical and conceptual advantages over cells. Will cells end up just being used to manufacture exosomes, or will they find lasting value as primary therapeutic agents? Here, a venerable natural process-the generation of honey-serves as an instructive parable. Flowers make nectar, which bees collect and process into honey. Cells make conditioned medium, which laboratory workers collect and process into exosomes. Unlike flowers, honey is durable, compact, and nutritious, but these facts do not negate the value of flowers themselves. The parallels suggest new ways of thinking about next-generation therapeutics.

Keywords: cell therapy; exosomes; vesicle.

Figure 1. Exosome biology

Left panel: Schematic of exosome biogenesis. Exosomes arise from the fusion of surface membrane invaginations (multivesicular bodies) and products of the Golgi apparatus. The resulting vesicles are either degraded by lysosomes or secreted as exosomes. Right panel: List of cardinal features of exosomes.

Central Illustration. Parallels between exosome manufacturing and the making of honey

Top row: Cells condition the media in which they are grown. Humans collect conditioned media and extract exosomes. Lower row: Flowers make nectar. Bees collect nectar and process it to make honey. The starting points (cells, flowers) are both fragile living entities. The intermediates are fluids (conditioned media, nectar) arising from those living entities. The end products (exosomes, honey) are durable and azoic, with traces of their origins but distinct properties.