S138 Nanodiamond Delivery Of Vascular Endothelial Growth Factor Promotes Fetal Lung Development In A Rat Model Of Congenital Diaphragmatic Hernia

<sec> Congenital diaphragmatic hernia (CDH) is a developmental diaphragmatic anomaly resulting in pulmonary hypoplasia and consequent pulmonary hypertension and respiratory failure sequelae. Despite advances in treatment, CDH remains associated with high morbidity and mortality rates. Reduced levels of vascular endothelial growth factor (VEGF) have been implicated in CDH pathogenesis. Animal studies have shown that intrauterine VEGF replacement enhances pulmonary vascularisation and lung epithelial cell proliferation. This study aimed to deliver VEGF through the engineering of a biocompatible and slow releasing nanodiamond (ND) platform, in a rat model of CDH. NDs were either fluorescently labelled (ND-FL) or conjugated to recombinant VEGF164 (ND-VEGF; 2 μg/mL VEGF164). Nitrofen was administered to pregnant Wistar rats at E9 (term=E22) to induce fetal CDH. At E19, maternal hysterotomy was performed, and NDs (75 μg/mL in 50 μL vehicle/saline) were administered intratracheally followed by fetal tracheal occlusion (TO). Blinded assessment of lung-to-body weight ratio (LBWR) and lung morphometric parameters was performed at E21.5 in CDH offspring. Prenatal ND administration did not have overt adverse effects. ND-FL biodistribution indicated that NDs localised in type II pneumocytes. ND-VEGF+TO was associated with improved lung growth (LBWR: 5.9 ± 0.2%), which was greater than that observed in VEGF+TO (3.5 ± 0.4%; p < 0.01), vehicle+TO (3.9 ± 0.1%; p < 0.01), and sham surgery (2.0 ± 0.2%; p < 0.001) groups. Moreover, ND-VEGF+TO resulted in thinner alveolar septa (mean transection length/airspace: 18.9 ± 0.5) and increased alveolar size (mean airspace chord length: 31.4 ± 0.6) compared to other treatment groups (p). This is the first study to show that nanoparticle-mediated prenatal delivery of VEGF induces significant lung growth in CDH and suggests that sustained cargo release is pivotal in mimicking the temporal expression of VEGF in normal lung development. </sec>