Activated Endothelial TGF?1 Signaling Promotes Venous Thrombus Nonresolution in Mice Via Endothelin-1: Potential Role for Chronic Thromboembolic Pulmonary Hypertension.

ABSTRACT:

Rationale

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by defective thrombus resolution, pulmonary artery obstruction, and vasculopathy. TGF? (transforming growth factor-?) signaling mutations have been implicated in pulmonary arterial hypertension, whereas the role of TGF? in the pathophysiology of CTEPH is unknown.

Objective

To determine whether defective TGF? signaling in endothelial cells contributes to thrombus nonresolution and fibrosis.

Methods and results

Venous thrombosis was induced by inferior vena cava ligation in mice with genetic deletion of TGF?1 in platelets (Plt.TGF?-KO) or TGF? type II receptors in endothelial cells (End.TGF?RII-KO). Pulmonary endarterectomy specimens from CTEPH patients were analyzed using immunohistochemistry. Primary human and mouse endothelial cells were studied using confocal microscopy, quantitative polymerase chain reaction, and Western blot. Absence of TGF?1 in platelets did not alter platelet number or function but was associated with faster venous thrombus resolution, whereas endothelial TGF?RII deletion resulted in larger, more fibrotic and higher vascularized venous thrombi. Increased circulating active TGF?1 levels, endothelial TGF?RI/ALK1 (activin receptor-like kinase), and TGF?RI/ALK5 expression were detected in End.TGF?RII-KO mice, and activated TGF? signaling was present in vessel-rich areas of CTEPH specimens. CTEPH-endothelial cells and murine endothelial cells lacking TGF?RII simultaneously expressed endothelial and mesenchymal markers and transcription factors regulating endothelial-to-mesenchymal transition, similar to TGF?1-stimulated endothelial cells. Mechanistically, increased endothelin-1 levels were detected in TGF?RII-KO endothelial cells, murine venous thrombi, or endarterectomy specimens and plasma of CTEPH patients, and endothelin-1 overexpression was prevented by inhibition of ALK5, and to a lesser extent of ALK1. ALK5 inhibition and endothelin receptor antagonization inhibited mesenchymal lineage conversion in TGF?1-exposed human and murine endothelial cells and improved venous thrombus resolution and pulmonary vaso-occlusions in End.TGF?RII-KO mice.

Conclusions

Endothelial TGF?1 signaling via type I receptors and endothelin-1 contribute to mesenchymal lineage transition and thrombofibrosis, which were prevented by blocking endothelin receptors. Our findings may have relevant implications for the prevention and management of CTEPH.

SUBMITTER: Bochenek ML 

PROVIDER: S-EPMC7101077 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature