5067Dysregulated BMPR/TGF-beta impact fibrotic vascular remodeling during thrombosis

Abstract

Background: Excessive transforming growth factor (TGF)-beta and reduced bone morphogenetic protein receptor (BMPR) signaling have been implicated as key underlying derangements of pulmonary arterial hypertension (PAH). Fibrotic vascular occlusion is a feature of PAH, but also of chronic thromboembolic pulmonary hypertension (CTEPH). Therefore, we aimed to study the role of BMPR and TGF-beta in chronic thrombosis. Method(s): Transgenic mice (BMPR2+/R899X and TBRIIDELTAk) and wild type controls were subjected to subtotal inferior vena cava (IVC) ligation. Thrombus was harvested on days 3, 7, 14 and 21, and histological and molecular analysis were performed. RNA-seq was employed to study the transcriptome of fibroblasts isolated from pairs of pulmonary artery adventitia and thrombus excised during pulmonary endarterectomy (PEA). Result(s): Mice deficient in BMPR2 (BMPR2+/R899X) demonstrated significant increases of thrombus cross sectional area and volume at early time points (days 1, 3 and 7). Compared with wild type controls, transgenic mice also had more fibrin and collagen in their thrombi. In TGF-beta overexpressing mice (TBRIIDELTAk), thrombus burden was significantly greater on days 7, 14 and 21. RNA-seq analysis revealed significant (P < 0.05) fold differences in 39 genes, with substantial increase of MMP-9 in thrombus fibroblasts. Majority of upregulated genes concerned TGF-beta signaling (SMOC1, FERMT3) and endothelial to mesenchymal transition (MMP-9). Conclusion(s): Similar to PAH, the TGF-beta pathway genes are important for pulmonary vascular remodeling in CTEPH. Our results indicate that BMPR2 deficiency seems to impact early thrombosis, while TGF-beta overexpression plays a role in thrombus non-resolution.