Vascular smooth muscle cell-derived osteoprotegerin drives pulmonary arterial hypertension via AKT activation and is attenuated by monoclonal antibody therapy

Pulmonary arterial hypertension (PAH) is driven by sustained vasoconstriction and structural remodelling of distal pulmonary arteries. We have previously demonstrated that osteoprotegerin (OPG, tnfrsf11b) is upregulated in PAH animal models and patient tissues, with circulating levels being prognostic. OPG knock-out (KO) mice exhibit an attenuated PAH phenotype, and therapeutic inhibition using a human monoclonal anti-OPG antibody reduces disease severity in multiple rodent models. However, the key cellular source of pathogenic OPG and the mechanism underlying therapeutic blockade remain unknown.

To define the main cellular source of OPG, conditional Tnfrsf11b deletion was generated by crossing OPG^fl/fl mice with PGKcre^tg/+ (global), LysMcre^tg/+ (myeloid), Myl2cre^tg/+ (cardiac myocytes), Cdh5cre^tg/+ (endothelial cells), smMHCcre^tg/+ [vascular smooth muscle cell (VSMCs)], Col1a2cre^tg/+ (fibroblasts). KOs were induced by tamoxifen injection, and PAH established using Sugen5416/hypoxia (SuHx) model. Cardiopulmonary phenotyping included echocardiography, cardiac catheterization, and histological analysis. Mechanistic studies were performed in VSMCs using peptide-based kinase activity profiling (PamStation).

PGKcre^tg/+/OPG^fl/fl mice phenocopied the previous results obtained with global OPG KO (OPG^−/−). Only VSMC-specific deletion (smMHCcre^tg/0/OPG^fl/fl) resulted in significantly improved haemodynamic parameters, evidenced by reduced right ventricular systolic pressure and pulmonary vascular resistance, and reduced pulmonary vascular remodelling demonstrating that VSMC-derived OPG is the primary driver of PAH pathogenesis.

Kinome profiling of control and idiopathic PAH (IPAH)-pulmonary artery smooth muscle cells (PASMCs) treated with OPG^+/− anti-OPG antibody revealed IPAH-specific regulation of PI3K–Akt and enrichment of pathways involving autophagy, and longevity regulation linked to cellular stress resistance and growth. Anti-OPG antibody treatment reduced AKT phosphorylation in IPAH-PASMCs. Knock-down of AKT1 by siRNA reduced OPG-induced proliferation and migration of human PASMCs. These results align with emerging data implicating OPG in cellular senescence and vascular ageing.

Together, these findings highlight VSMC-derived OPG as a critical mediator of pulmonary vascular remodelling in PAH pathogenesis and suggest that targeting OPG via a therapeutic antibody is mediated through PI3K–Akt signalling.