A Selective Transforming Growth Factor-β Ligand Trap Attenuates Pulmonary Hypertension

Rationale: Transforming growth factor-beta (TGF-beta)ligands signal via type I and type II serine-threonine kinase receptors to regulate broad transcriptional programs. Excessive TGF-beta-mediated signaling is implicated in the pathogenesis of pulmonary arterial hypertension, based in part on the ability of broad inhibition of activin-like kinase (ALK) receptors 4/5/7 recognizing TGF-beta, activin, growth and differentiation factor, and nodal ligands to attenuate experimental pulmonary hypertension (PH). These broad inhibition strategies do not delineate the specific contribution of TGF-beta versus a multitude of other ligands, and their translation is limited by cardiovascular and systemic toxicity. Objectives: We tested the impact of a soluble TGF-beta type II receptor extracellular domain expressed as an immunoglobulin-Fc fusion protein (TGFBRII-Fc), serving as a selective TGF-beta 1/3 ligand trap, in several experimental PH models. Methods: Signaling studies used cultured human pulmonary artery smooth muscle cells. PH was studied in monocrotaline-treated Sprague-Dawley rats, SU5416/hypoxia-treated Sprague-Dawley rats, and SU5416/hypoxia-treated C57BL/6 mice. PH, cardiac function, vascular remodeling, and valve structure were assessed by ultrasound, invasive hemodynamic measurements, and histomorphometry. Measurements and Main Results: TGFBRII-Fc is an inhibitor of TGF-beta 1 and TGF-beta 3, but not TGF-beta 2, signaling. In vivo treatment with TGFBRII-Fc attenuated Smad2 phosphorylation, normalized expression Of plasminogen activator inhibitor-1, and mitigated PH and pulmonary vascular remodeling in monocrotaline-treated rats, SU5416/hypoxia-treated rats, and SU5416/hypoxia-treated mice. Administration of TGFBRII-Fc to monocrotaline-treated or SU5416/hypmda-treated rats with established PH improved right ventricular systolic pressures, right ventricular function, and survival. No cardiac structural or valvular abnormalities were observed after treatment with TGFBRII-Fc. Conclusions: Our findings are consistent with a pathogenetic role of TGF-beta 1/3, demonstrating the efficacy and tolerability of selective TGF-beta ligand blockade for improving hemodynamics, remodeling, and survival in multiple experimental PH models.