Abstract Body (Do not enter title and authors here): Rationale: Previously we identified a mouse model Tie2Cre-mediated disruption of Egln1 of Pulmonary arterial hypertension (PAH) with 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 PAH. We hypothesized that Macrophage accumulation and polarization due to crosstalk with endothelial cells contributes to obliterative pulmonary vascular remodeling and severe PAH in Egln1^Tie2Cre (CKO) mice.
Methods: We utilized single-cell RNA sequencing (scRNAseq) to provide transcriptome insights into cellular composition changes in the lungs of in Egln1^Tie2Cre mice. Egln1^Tie2Cre mice with CD68-FlpERT2/CD206-frt-stop-frt-Dre/Rosa26-rox-stop-rox-DTR (CKO/Dep) transgene were generated and received tamoxifen and diphtheria toxin to deplete the CD206+ macrophages during the development of PAH. RVSP and RV/(LV+S) ratio were measured. Russell-Movat pentachrome staining was carried out to assess pulmonary vascular remodeling. Igf1/ Egln1^Tie2Cre double knockout mice and IGF1R inhibitor treatment were employed to delineate the molecular mechanism.
Results: Single cell RNA sequencing and FACS analyses identified marked accumulation of the Adgre+/Chil3-/Cx3cr1+/Cd206+ macrophages (PAH-M) subpopulation in Egln1^Tie2Cre mouse lungs. PAH-Ms were accumulated in the pulmonary vessel adventitia of IPAH patients as well as Egln1^Tie2Cre mice. Genetic depletion of PAH-Ms using the novel generated CKO/Dep transgene mouse model markedly inhibited obliterative pulmonary vascular remodeling and PAH and promoted survival. These PAH-Ms were accumulated due to cross talk with endothelial cells via SDF1 signaling and expressed elevated levels of pro-PAH factors such as IGF1 and thus promoted SMC proliferation in co-culture study. Genetic disruption of the Igf1 in Egln1^Tie2Cre mice inhibited IGF1 production and attenuated PAH and pulmonary vascular remodeling. Treatment of IGF1 receptor inhibitor attenuated PAH in Egln1^Tie2Cre mice and MCT-rats.
Conclusions: Endothelial SDF1 induced accumulation of Adgre+/Chil3-/Cx3cr1+/Cd206+ PAH-Ms in the adventitia of pulmonary vascular lesions of Egln1^Tie2Cre mice and IPAH patients, which contributed to severe PAH though the IGF1 signaling. Thus, targeting abnormal macrophage function and signaling pathways is a potential effective therapeutic strategy for treatment of PAH patients and promotion survival.