Safety, Efficacy and Bio-Distribution Analysis of Exosomes Derived From Human Umbilical Cord Mesenchymal Stem Cells for Effective Treatment of Bronchopulmonary Dysplasia by Intranasal Administration in Mice Model

Purpose: Exosomes (Exos) derived from human umbilical cord mesenchymal stem cells (hUC-MSCs) hold great potential for treating bronchopulmonary dysplasia (BPD); however, safety concerns and effects of intranasal administration remain unexplored. This study aimed to explore the safety of hUC-MSCs and Exos and to investigate the efficacy and bio-distribution of repeated intranasal Exos administration in neonatal BPD models. Methods: Characteristics of hUC-MSCs and Exos were analyzed. A subcutaneous tumor formation assay using a single dose of hUC-MSCs or Exos was conducted in Crl:NU-Foxn1nu mice. Vital signs, biochemical indices, pathological alterations, and 18 F-FDG microPET/CT analysis were examined. Pulmonary pathology, three-dimensional reconstructions, ultrastructural structures, in vivo and ex vivo bio-distribution imaging analyses, enzyme-linked immunoassay assays, and reverse transcription-quantitative polymerase chain reaction analyses of lung tissues were all documented following intranasal Exos administration. Results: Characteristics of hUC-MSCs and Exos satisfied specifications. Crl:NU-Foxn1nu mice did not exhibit overt toxicity or carcinogenicity following a single dose of hUC-MSCs or Exos after 60 days of observation. Repeated intranasal Exos administration effectively alleviated pathological injuries, restored pulmonary ventilation in three-dimensional reconstruction, and recovered endothelial cell layer integrity in ultrastructural analysis. Exos steadily accumulated in lung tissues from postnatal day 1 to 14. Exos also interrupted the epithelial–mesenchymal transition and inflammation reactions in BPD models. Conclusion: As a nanoscale, non-cellular therapy, intranasal administration of Exos was an effective, noninvasive treatment for BPD. This approach was free from toxic, tumorigenic risks and repaired alveolar damage while interrupting epithelial–mesenchymal transition and inflammation in neonatal mice with BPD. Plain Language Summary: This study aimed to address the safety concerns surrounding hUC-MSCs and Exos and to investigate, for the first time, the bio-distribution and efficacy of repeated intranasal administration of Exos in a neonatal BPD model. Repeated intranasal Exos administration significantly ameliorated pulmonary pathological injuries and predominantly accumulated in the lungs, as demonstrated by fluorescence tracking from the first day after birth. Furthermore, Exos reduced epithelial–mesenchymal transition and inflammatory cytokines in BPD models. These findings suggest that intranasal administration of Exos is a safe, effective, and noninvasive approach to treat BPD without toxic or tumorigenic risks. Intranasal exos as a nanoscalic, non-cellular therapy has a significant potential for the treatment of BPD, although further examinations are necessary to fully clarify their mechanisms and long-term effects.