Exosome-Mediated Small RNA Delivery: A Novel Therapeutic Approach for Inflammatory Lung Responses

Exosomes (EXOs) are a type of extracellular nanovesicles released from living cells. Accumulating evidence suggests that EXOs are involved in the pathogenesis of human diseases, including lung conditions. In recent years, the potential of EXO-mediated drug delivery has gained increasing interest. In this report, we investigated whether inhaled EXOs serve as an efficient and practical delivery vehicle to activate or inhibit alveolar macrophages (AMs), subsequently modulating pulmonary immune responses. We first identified the recipient cells of the inhaled EXOs, which were labeled with PKH26. We found that only lung macrophages efficiently take up intratracheally instilled EXOs in vivo. Using modified calcium chloride-mediated transformation, we manipulated small RNA molecules in serum-derived EXOs, including siRNAs, microRNA (miRNA) mimics, and miRNA inhibitors. Via intratracheal instillation, we successfully delivered siRNA and miRNA mimics or inhibitors into lung macrophages using the serum-derived EXOs as vehicles. Furthermore, EXO siRNA or miRNA molecules are functional in modulating LPS-induced lung inflammation in vivo. Beneficially, serum-derived EXOs themselves do not trigger lung immune responses, adding more favorable features to serve as drug delivery agents. Collectively, we developed a novel protocol using serum-derived EXOs to deliver designated small RNA molecules into lung macrophages in vivo, potentially shedding light on future gene therapy of human lung diseases.