Intraamniotic vitamin D preserves lung development and prevents pulmonary hypertension in experimental bronchopulmonary dysplasia due to intraamniotic sFlt-1

Preterm infants born to mothers with preeclampsia, a disease of vascular dysfunction, are at increased risk for bronchopulmonary dysplasia (BPD). Endothelial cells are critical in both maintaining proper vascular function and coordinating lung development. Understanding the mechanisms contributing to BPD in the setting of preeclampsia and how preeclampsia impacts pulmonary endothelial cells (PECs) in the newborn lung are required to decrease the burden of BPD. Vitamin D has been shown to improve lung angiogenesis and lung development in inflammatory models of BPD, but its therapeutic potential in the setting of preeclampsia is unknown. We hypothesized that intraamniotic (IA) treatment with the biologically active form of vitamin D, 1,25 dihydroxyvitamin D [1,25(OH)₂D], will preserve lung growth in an experimental model of BPD induced by antenatal exposure to soluble vascular endothelial growth factor receptor-1 [sFlt-1 (soluble fms-like tyrosine kinase 1)]. Fetal rats were exposed to saline (control), sFlt-1 alone, 1,25(OH)₂D alone, or simultaneous sFlt-1 + 1,25(OH)₂D via IA injection during the late canalicular stage of lung development and delivered 2 days later. IA treatment with 1,25(OH)₂D in sFlt-1-exposed pups improved lung alveolar and vascular growth and function at 14 days of life. PECs orchestrate alveolar development, and we demonstrate that IA sFlt-1 exposure alone decreased in vitro growth and tube formation of PECs isolated from newborn pups and that PECs from pups coexposed to IA sFlt-1 and 1,25(OH)₂D demonstrated increased growth and tube formation. We conclude that IA 1,25(OH)₂D treatment improves distal lung development during sFlt-1 exposure through preservation of angiogenesis in the developing lung.<b>NEW & NOTEWORTHY</b> This study highlights that experimental BPD induced by intraamniotic sFlt-1 is associated with impaired growth in postnatal pulmonary endothelial cells. We demonstrate that 1,25(OH)₂D may be a therapeutic option to improve lung development through enhancement of VEGF signaling and preservation of early pulmonary endothelial growth in the newborn rat lung.