Hobohm L, Kölmel S, Niemann C, Kümpers P, Krieg VJ, Bochenek ML, Lukasz AH, Reiss Y, Plate KH, Liebetrau C, Wiedenroth CB, Guth S, Münzel T, Hasenfuß G, Wenzel P, Mayer E, Konstantinides SV, Schäfer K, and Lankeit M
Background: Defective angiogenesis, incomplete thrombus revascularisation and fibrosis are considered critical pathomechanisms of chronic thromboembolic pulmonary hypertension (CTEPH) after pulmonary embolism. Angiopoietin-2 (ANGPT2) has been shown to regulate angiogenesis, but its importance for thrombus resolution and remodelling is unknown., Methods: ANGPT2 plasma concentrations were measured in patients with CTEPH (n=68) and acute pulmonary embolism (n=84). Tissue removed during pulmonary endarterectomy (PEA) for CTEPH was analysed (immuno)histologically. A mouse model of inferior vena cava ligation was used to study the kinetics of venous thrombus resolution in wild-type mice receiving recombinant ANGPT2 via osmotic pumps, and in transgenic mice overexpressing ANGPT2 in endothelial cells., Results: Circulating ANGPT2 levels were higher in CTEPH patients compared to patients with idiopathic pulmonary arterial hypertension and healthy controls, and decreased after PEA. Plasma ANGPT2 levels were elevated in patients with pulmonary embolism and diagnosis of CTEPH during follow-up. Histological analysis of PEA specimens confirmed increased ANGPT2 expression, and low levels of phosphorylated TIE2 were observed in regions with early-organised pulmonary thrombi, myofibroblasts and fibrosis. Microarray and high-resolution microscopy analysis could localise ANGPT2 overexpression to endothelial cells, and hypoxia and transforming growth factor-β1 were identified as potential stimuli. Gain-of-function experiments in mice demonstrated that exogenous ANGPT2 administration and transgenic endothelial ANGPT2 overexpression resulted in delayed venous thrombus resolution, and thrombi were characterised by lower TIE2 phosphorylation and fewer microvessels., Conclusion: Our findings suggest that ANGPT2 delays venous thrombus resolution and that overexpression of ANGPT2 contributes to thrombofibrosis and may thus support the transition from pulmonary embolism to CTEPH., Competing Interests: Conflict of interest: L. Hobohm reports personal fees for lectures from MSD and Actelion, outside the submitted work. Conflict of interest: S. Kölmel has nothing to disclose. Conflict of interest: C. Niemann has nothing to disclose. Conflict of interest: P. Kümpers has nothing to disclose. Conflict of interest: V.J. Krieg has nothing to disclose. Conflict of interest: M.L. Bochenek has nothing to disclose. Conflict of interest: A.H. Lukasz has nothing to disclose. Conflict of interest: Y. Reiss has nothing to disclose. Conflict of interest: K-H. Plate has nothing to disclose. Conflict of interest: C. Liebetrau reports personal fees for lectures and consultancy from AstraZeneca, Bayer, Berlin Chemie, Boehringer Ingelheim, Daiichi-Sankyo, Pfizer–Bristol-Myers Squibb and Thermo-Fisher, outside the submitted work. Conflict of interest: C.B. Wiedenroth reports personal fees for lectures and consultancy from Actelion, Bayer, Pfizer, BTG and MSD, outside the submitted work. Conflict of interest: S. Guth reports personal fees for lectures and consultancy from Actelion, Bayer, GlaxoSmithKline, Pfizer and MSD, outside the submitted work. Conflict of interest: T. Münzel has nothing to disclose. Conflict of interest: G. Hasenfuß reports personal fees for lectures and consultancy from AstraZeneca, Corvia, Impulse Dynamics, Novartis, Servier, Berlin Chemie and Vifor Pharma; and editor honoraria from Springer International Publishing AG. Conflict of interest: P. Wenzel has nothing to disclose. Conflict of interest: E. Mayer reports personal fees for lectures and consultancy from Actelion, Bayer, MSD and Pfizer, outside the submitted work. Conflict of interest: S.V. Konstantinides reports grants from German Federal Ministry of Education and Research (BMBF 01EO1003 and BMBF 01EO1503), during the conduct of the study; personal fees for consultancy and lectures from Bayer, Boehringer Ingelheim, Daiichi-Sankyo, MSD and Pfizer–Bristol-Myers Squibb; and institutional grants from Actelion, Bayer, Boehringer Ingelheim, Daiichi-Sankyo and Pfizer–Bristol-Myers Squibb, outside the submitted work. Conflict of interest: K. Schäfer has nothing to disclose. Conflict of interest: M. Lankeit reports grants from German Federal Ministry of Education and Research (BMBF 01EO1003 and 01EO1503), during the conduct of the study; personal fees for consultancy and lectures from Actelion, Bayer, BRAHMS–Thermo-Fisher Scientific, Daiichi-Sankyo, MSD and Pfizer–Bristol-Myers Squibb, and research funding from BRAHMS–Thermo-Fisher Scientific., (Copyright ©The authors 2021. For reproduction rights and permissions contact permissions@ersnet.org.)