RUNX2 is stabilised by TAZ and drives pulmonary artery calcification and lung vascular remodelling in pulmonary hypertension due to left heart disease.

Background: Calcification is common in chronic vascular disease, yet its role in pulmonary hypertension due to left heart disease is unknown. Here, we probed for the role of runt-related transcription factor-2 (RUNX2), a master transcription factor in osteogenesis, and its regulation by the HIPPO pathway transcriptional coactivator with PDZ-binding motif (TAZ) in the osteogenic reprogramming of pulmonary artery smooth muscle cells and vascular calcification in patients with pulmonary hypertension due to left heart disease. We similarly examined its role using an established rat model of pulmonary hypertension due to left heart disease induced by supracoronary aortic banding.

Methods: Pulmonary artery samples were collected from patients and rats with pulmonary hypertension due to left heart disease. Genome-wide RNA sequencing was performed, and pulmonary artery calcification assessed. Osteogenic signalling via TAZ and RUNX2 was delineated by protein biochemistry. In vivo, the therapeutic potential of RUNX2 or TAZ inhibition by CADD522 or verteporfin was tested in the rat model.

Results: Gene ontology term analysis identified significant enrichment in ossification and osteoblast differentiation genes, including RUNX2, in pulmonary arteries of patients and lungs of rats with pulmonary hypertension due to left heart disease. Pulmonary artery calcification was evident in both patients and rats. Both TAZ and RUNX2 were upregulated and activated in pulmonary artery smooth muscle cells of patients and rats. Co-immunoprecipitation revealed a direct interaction of RUNX2 with TAZ in pulmonary artery smooth muscle cells. TAZ inhibition or knockdown decreased RUNX2 abundance due to accelerated RUNX2 protein degradation rather than reduced de novo synthesis. Inhibition of either TAZ or RUNX2 attenuated pulmonary artery calcification, distal lung vascular remodelling and pulmonary hypertension development in the rat model.

Conclusion: Pulmonary hypertension due to left heart disease is associated with pulmonary artery calcification that is driven by TAZ-dependent stabilisation of RUNX2, causing osteogenic reprogramming of pulmonary artery smooth muscle cells. The TAZ-RUNX2 axis may present a therapeutic target in pulmonary hypertension due to left heart disease.