Inhalation & intravenous: umbilical cord mesenchymal stem cell-derived exosomes therapy strategy for acute respiratory distress syndrome in a murine model.

Background: Acute respiratory distress syndrome (ARDS) is a complex syndrome characterized by acute diffuse lung injury and progressive respiratory failure, caused by various intra- and extra-pulmonary factors. The coronavirus disease 2019 (COVID-19) pandemic has significantly increased the incidence of ARDS, posing a tremendous threat to human health due to its high mortality rate and lack of effective therapeutic drugs. In recent years, mesenchymal stem cell-derived exosomes (MSC-exo) have been considered a new hope for the treatment of ARDS due to their potent immunomodulatory characteristics. Although multiple studies have demonstrated their efficacy and safety, the differential therapeutic effects of various administration routes and doses remain unclear. This study aimed to investigate the administration route of MSC-exo for ARDS treatment, with the goal of maximizing therapeutic benefits and providing valuable clinical insights. Methods: This study aims to establish an ARDS disease model by intratracheal instillation of lipopolysaccharide (LPS) in male C57/BL6 mice. Subsequently, umbilical cord mesenchymal stem cell exosomes will be administered via three methods: inhalation, tail vein injection, and combination therapy (inhalation combined with tail vein injection). Following the establishment of the mouse ARDS model via intratracheal instillation of LPS, the animals were randomly divided into seven groups based on the timing and dosage of the treatment administration. Samples were harvested at 24 hours, 72 hours, and 7 days after modeling. The assessments included RNA transcriptome sequencing, cytokine levels in blood and bronchoalveolar lavage fluid, blood oxygen saturation, histopathological staining, and survival analysis. Results: Compared to nebulized exosomes alone, dual-route administration significantly improved respiratory function, as evidenced by prolonged expiratory and inspiratory times and increased minute ventilation (P≤0.05). Furthermore, it decreased the levels of the pro-inflammatory cytokines interleukin-1β (IL-1β) and interleukin-6 (IL-6) in the blood (P=0.01, P=0.041). Compared to intravenous exosomes alone, dual-route administration produced broader improvements. It significantly enhanced lung function by prolonging expiratory time (P=0.01), inspiratory time (P=0.004), and increasing minute ventilation (P=0.02). Additionally, it suppressed inflammation by lowering IL-6 levels in bronchoalveolar lavage fluid (P=0.01) and reduced the death of type II alveolar epithelial cells (P=0.03). Conclusions: The dual-route administration of umbilical cord MSC-exo is more effective in controlling the inflammatory response and alleviating lung injury in LPS-induced ARDS animal models. Inhalation rapidly alleviates pulmonary inflammation with a smaller dose, while intravenous injection better manages the systemic inflammation. This dual-route approach holds promise as a novel ARDS treatment strategy.