# miR-7704-Enriched Stem Cell-Derived Extracellular Vesicles Attenuate Hyperoxia-Induced Apoptosis and Oxidation in Lung Epithelial Cells

## TL;DR

This study shows that extracellular vesicles enriched with miR-7704 from stem cells can reduce lung cell damage caused by high oxygen levels in a model of neonatal lung disease.

## Contribution

The novel contribution is demonstrating that miR-7704-enriched extracellular vesicles from stem cells can mitigate hyperoxia-induced lung epithelial cell injury.

## Key findings

- miR-7704-enriched EVs significantly enhanced cell proliferation and reduced apoptosis in hyperoxic conditions.
- miR-7704 EVs reversed hyperoxia-induced increases in cleaved caspase-3, caspase-7, and FasL, and restored Bcl-2 levels.
- miR-7704 EVs increased antioxidant enzymes SOD1, SOD2, and HO-1, mitigating oxidative stress in lung cells.

## Abstract

Bronchopulmonary dysplasia (BPD) is a significant complication of hyperoxia in preterm neonates. Extracellular vesicle (EV)-based therapies derived from mesenchymal stem cells (MSCs) show regenerative potential. We investigated the therapeutic efficacy of EVs derived from human umbilical cord mesenchymal stem cells (HUCMSCs), particularly those engineered to overexpress miR-7704 in a hyperoxia-induced BPD cell model. EVs were isolated from GFP- and miR-7704-transfected HUCMSCs. A549 alveolar epithelial cells were exposed to normoxic or hyperoxic conditions and treated with HUCMSC-EV or miR-7704-HUCMSC-EV. EV uptake was confirmed using fluorescence microscopy. Cell proliferation was evaluated, and apoptosis was assessed by means of Western blot analysis of caspase family proteins and apoptosis-related markers. Both HUCMSC-EV and miR-7704-HUCMSC-EV enhanced A549 cell proliferation under hyperoxic stress, with miR-7704-HUCMSC-EV showing greater efficacy. Protein-level analyses revealed hyperoxia-induced increases in cleaved caspase-3, caspase-7, and FasL, along with decreased Bcl-2. Treatment with miR-7704-HUCMSC-EV significantly reversed these effects, whereas HUCMSC-EVs minimally impacted apoptotic protein expression. Bioinformatic analysis predicted that hsa-miR-7704 targeted the 3′ UTR of APOPT1. miR-7704-HUCMSC EVs also enhanced the expression of key antioxidant enzymes, including SOD1, SOD2, and HO-1. miR-7704-enriched HUCMSC-derived EV significantly promoted cell survival and mitigated hyperoxia-induced apoptosis and oxidation in a BPD cell model, suggesting their potential therapeutic role in neonatal lung injury.