Abstract 14631: Pulmonary Artery Calcification: A New Threat in Pulmonary Arterial Hypertension

Background: Pulmonary arterial hypertension (PAH) is associated with imbalance between proliferation and apoptosis of pulmonary artery (PA) smooth muscle cells (PASMCs). Recently, we uncovered a role for microRNA-204 (miR-204), whose downregulation sustains the phenotype in time. In systemic vascular disease, miR-204 downregulation increases the Runt-related transcription factor 2 (RUNX2), a key osteogenic factor inducing calcification. The fact that PAH patients live longer increases the odds of developing PA calcification lesions. Interestingly, the presence and development of calcified lesions in PAH have not been explored. We thus hypothesized that miR-204-dependent upregulation of RUNX2 triggers the development of proliferative and calcified vascular lesions within the lungs, thus worsening PAH. Methods/Results: Using CT-scan, we showed that PAH patients (n=50; p<0.05) had significant increase in distal PA calcification compared to control patients matched for age, sex and comorbidities known to promote vascular calcification. This non-invasive finding was histologically confirmed in the same patients post lung transplantation using Von Kossa staining (n=10; p<0.05). Finally, increase in calcification contributes to worsening of PA compliance and is associated with poorer PAH patients’ survival (n=50; p<0.05). At the molecular level, enhanced calcification in PAH patients correlates (n=43; p<0.05) with a miR-204-dependent up regulation of RUNX2 in lungs, distal PA and primary cultured PASMCs (n=12-40, fold change ≈ 2.5). Using gain and loss of function approaches, we demonstrated in PASMCs from PAH and healthy donors (using siRNA and adenoviruses respectively) that RUNX2, promotes PAH-PASMC proliferation (Ki67), resistance to apoptosis (Annexin-V) and calcification (Alizarin red) (p<0.05). Finally, in Sugen/hypoxia rat model of PAH, we demonstrated that RUNX2 inhibition improves pulmonary hemodynamic and reduces PA remodeling and calcification (n=5-12, p<0.05). Conclusion: We demonstrated for the first time the presence of significant calcification in PAH distal PA contributing to PAH worsening and identified RUNX2 as an attractive new therapeutic strategy to improve PAH. *SC and GR equally contributed.

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