Autophagy Is Impaired in Fetal Hypoplastic Lungs and Rescued by Administration of Amniotic Fluid Stem Cell Extracellular Vesicles.

Rationale: Pulmonary hypoplasia secondary to congenital diaphragmatic hernia is characterized by reduced branching morphogenesis, which is responsible for poor clinical outcomes. Administration of amniotic fluid stem cell extracellular vesicles (AFSC-EVs) rescues branching morphogenesis in rodent fetal models of pulmonary hypoplasia. Herein, we hypothesized that AFSC-EVs exert their regenerative potential by affecting autophagy, a process required for normal lung development. Objectives: To evaluate autophagy in hypoplastic lungs throughout gestation and establish whether AFSC-EV administration improves branching morphogenesis through autophagy-mediated mechanisms. Methods: EVs were isolated from c-kit+ AFSC-conditioned medium by ultracentrifugation and characterized for size, morphology, and EV markers. Branching morphogenesis was inhibited in rat fetuses by nitrofen administration to dams and in human fetal lung explants by blocking RAC1 activity with NSC23766. The expression of autophagy activators (BECN1 and ATG5) and adaptor (SQSTM1/p62) was analyzed in vitro (rat and human fetal lung explants) and in vivo (rat fetal lungs). Mechanistic studies on rat fetal primary lung epithelial cells were conducted using inhibitors for microRNA-17 and -20a contained in the AFSC-EV cargo and known to regulate autophagy. Measurements and Main Results: Rat and human models of fetal pulmonary hypoplasia showed reduced autophagy mainly at pseudoglandular and canalicular stages. AFSC-EV administration restored autophagy in both pulmonary hypoplasia models by transferring miR-17∼92 cluster members contained in the EV cargo. Conclusions: AFSC-EV treatment rescues branching morphogenesis partly by restoring autophagy through microRNA cargo transfer. This study enhances our understanding of pulmonary hypoplasia pathogenesis and creates new opportunities for fetal therapeutic intervention in congenital diaphragmatic hernia babies.