Abstract 15227: Egln1 Deficiency Induce Alveolar Macrophages Accumulation and Polarize Lung Interstitial Macrophages to a Pro-pah State Mediating Obliterative Pulmonary Vascular Remodeling and Severe PAH

Introduction: Previously we identified a mouse model (Tie2Cre-mediated disruption of Egln1 ) of Pulmonary arterial hypertension (PAH) with progressive obliterative vascular remodeling including vascular occlusion and plexiform-like lesions and right heart failure. Tie2Cre-meidated disruption of Egln1 in bone marrow contributes to the severity of PAH indicating the importance of the immune cells in the pathogenesis of PH. Hypothesis: Macrophage accumulation and polarization due to Egln1 deficiency contributes to obliterative pulmonary vascular remodeling and severe PAH in Egln1 Tie2Cre mice. Methods: Egln1 Tie2Cre mice with macrophage Fas-Induced apoptosis (MaFIA) transgene were generated (Egln1 Tie2Cre /MaFIA) and received AP20187 treatment to deplete the macrophages during the development of PAH afterwards the RVSP and RV/(LV+S) ratio were measured as the indicator of diseases severity. Flowcytometry and immunostaining were used to quantify different types of macrophages. Bulk RNA-seq and single cell RNA-seq were used to identify PAH-related pathway changes and population changes of lung macrophages in Egln1 Tie2Cre mice. BrdU staining was used to measure the smooth muscle cell (SMC) proliferation co-culturing with macrophages isolated from Egln1 Tie2Cre mice. Results: We observed that CD206+ Alternative Activated Macrophages (AAMs) are accumulated in the pulmonary vessel adventitia of IPAH patients as well as Egln1 Tie2Cre mice. These macrophages are Egln1 deficient and express elevated level of pro-PAH factors and thus promote SMC proliferation in vitro . Moreover, genetic depletion of total macrophages using the Egln1 Tie2Cre /MaFIA mouse model markedly inhibited obliterative pulmonary vascular remodeling and PAH. Single cell RNA-seq revealed that lung resident alveolar macrophages (Siglec-F+/Cd11c+) accumulated due to hyper-proliferation while recruited lung interstitial (Cx3cr1+/Aif1+) macrophages polarize to a pro-PAH state in Egln1 Tie2Cre mice. Conclusions: Egln1 deficiency in the HCs induced proliferation/accumulation of alveolar macrophages and polarized the recruited interstitial macrophages to AAM state which contributes to the vascular remodeling by secreting pro-PAH factors.