Abstract 9727: Reduced Bmpr2 Causes a Decrease in Foxf1 That Links Unrepaired DNA Damage to Persistent Pulmonary Hypertension

Introduction: B MPR2 mutation is the most common genetic cause of pulmonary arterial hypertension (PAH). Loss of BMPR2 causes pulmonary arterial (PA) endothelial cell (EC) dysfunction and impairs EC-mediated suppression of smooth muscle cells proliferation. These are characteristic features of PAH vascular cells as is the presence of DNA damage that can be induced by oxidative stress. We previously showed that EC- Bmpr2 -/- mice have persistent pulmonary hypertension (PH) with reoxygenation after hypoxia. However, the role of DNA damage in causing persistent PH related to loss of BMPR2 and oxidative stress is unknown. Hypothesis: We hypothesize that loss of BMPR2 causes unrepaired DNA damage and persistent PH by altering the expression of genes that maintain EC homeostasis. Methods and Results: DNA damage assessed by γH2AX foci was observed in PAEC of EC- Bmpr2 -/- mice in room air, that was more extensive after reoxygenation (10% hypoxia for 3 weeks followed by recovery in room-air for 4 weeks). Deletion of the DNA damage sensor ataxia-telangiectasia mutated (ATM) in EC of mice (EC- Atm -/- ) also resulted in persistent DNA damage and PH. RNA sequencing of PAEC after reoxygenation in EC- Bmpr2 -/- and EC- Atm -/- mice vs. controls showed downregulated EC differentiation and development genes enriched in biding motifs for Foxf1, a transcription factor associated with DNA repair and angiogenesis. Foxf1 expression was reduced in PAEC with loss of BMPR2 or ATM. Loss of Foxf1 decreased angiogenic genes Cldn5 and Vegfr2 , and DNA damage response genes Atm and p53 , and impaired PAEC migration and tube formation. Foxf1 overexpression increased these genes in PAEC. Immunohistochemistry showed decreased FOXF1 in PAEC of human pulmonary vascular lesions. Delivery of Foxf1 to EC- Bmpr2 -/- mice with an AAV2-peptide targeting the PA endothelium attenuated DNA damage in PAEC, restored angiogenesis genes and completely reversed persistent PH returning right ventricular systolic pressure to normal levels. Conclusions: We link loss of BMPR2 and DNA damage sensing in PAEC to persistent DNA damage and PAH and show that both are mediated by reduced FOXF1 . In EC- Bmpr2 -/- mice, Foxf1 gene therapy attenuated DNA damage restored angiogenesis genes, and prevented persistent PH.