In short
Exosome therapy is the administration of exosomes — small extracellular vesicles naturally released by cells that carry proteins, lipids, and RNA to communicate with other cells — typically derived from cultured stem cells, and marketed for tissue repair and anti-aging purposes.
Exosomes are a normal part of cell-to-cell communication: cells package molecular cargo into these small (roughly 30–150 nanometer) vesicles and release them into surrounding tissue or the bloodstream, where they can be taken up by other cells and influence their behavior. Interest in exosomes derived specifically from mesenchymal stem cells stems from the observation that much of MSC therapy's benefit may come from this paracrine signaling rather than the stem cells themselves engrafting into tissue — which raised the idea of delivering just the signaling cargo without the cells.
This remains a preclinical and early investigational field: exosome-based products have shown promising results in cell culture and animal models for wound healing and some inflammatory conditions, but exosome therapy has essentially no FDA-approved indications, and the FDA has specifically warned about unapproved exosome products marketed for various conditions, including a warning tied to reported adverse events from unregulated cosmetic and injectable exosome products.
A particular concern with commercially marketed exosome products is manufacturing variability and lack of standardization — exosome content, purity, and dose can vary substantially between suppliers with no equivalent to the batch-consistency standards required of an approved drug, and there is essentially no completed human randomized trial evidence supporting exosome therapy for general anti-aging or systemic rejuvenation use as currently marketed.