Endothelial cell senescence exacerbates pulmonary hypertension by inducing juxtacrine Notch signaling in smooth muscle cells

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by a progressive increase in pulmonary artery pressure caused by pathological pulmonary artery remodeling. Here, we demonstrate that endothelial cell (EC) senescence plays a negative role in pulmonary hypertension via juxtacrine interaction with smooth muscle cells (SMCs). By using EC-specific progeroid mice, we discovered that EC progeria deteriorated vascular remodeling in the lungs, and exacerbated pulmonary hypertension in mice. Mechanistically, senescent ECs overexpressed Notch ligands, which resulted in increased Notch signaling and activated proliferation and migration capacities in neighboring SMCs. Pharmacological inhibition of Notch signaling reduced the effects of senescent ECs on SMCs functions in vitro, and improved the worsened pulmonary hypertension in EC-specific progeroid mice in vivo. Our findings show that EC senescence is a critical disease-modifying factor in PAH and that EC-mediated Notch signaling is a pharmacotherapeutic target for the treatment of PAH, particularly in the elderly.

Senescent endothelial cells exacerbate pulmonary hypertension through notch-mediated juxtacrine interaction with pulmonary artery smooth muscle cells

Background

Despite recently developed clinical therapies, vascular remodelling in pulmonary arterial hypertension (PAH) progressively worsen. Hemodynamic unloading has been proposed to normalize the remodelled pulmonary vascular structures in the lungs. Recently, it has been reported that cellular senescence was associated with the irreversibility of pulmonary vascular structures after hemodynamic unloading.

Purpose

This study aims to elucidate the role of senescent endothelial cells (ECs) in the pathogenesis of PAH.

Methods

We generated EC-specific progeroid mice in which ECs undergo premature senescence by overexpressing the dominant-negative form of telomere repeat-binding factor 2 under the control of the VE-cadherin promoter. Following three weeks of hypoxia exposure, the PH phenotypes were assessed by RVSP, lung histology, and RT-qPCR. The interaction of human pulmonary artery ECs (hPAECs) and human pulmonary artery smooth muscle cells (hPASMCs) was indirectly and directly explored through the co-culture system. Gamma-secretase inhibitor (DAPT) was administrated to inhibit Notch signalling both in the in-vitro and in-vivo study.

Results

EC-specific progeroid mice showed exacerbated pulmonary hypertension after chronic hypoxia exposure, accompanied by the enhanced medial SMCs proliferation in the distal pulmonary arteries. Contact-mediated interaction with senescent hPAECs increased proliferation and migration capacities in hPASMCs, while no such effects were detected in the absence of ECs-SMCs contact. Consistently, senescent ECs highly expressed Notch ligands, thus activated Notch signalling in hPASMCs, leading to increased Notch target genes in hPASMCs. Pharmacological inhibition of Notch signalling attenuated the enhanced SMCs proliferation and migration induced by senescent hPAECs, as well as the worsened PH phenotypes in EC-specific progeroid mice.

Conclusions

Our data established a crucial role of senescent ECs in the PAH pathogenesis through the dysregulated SMC functions via juxtacrine signaling. Senescent ECs are attracting targets for further pathological-targeted therapy to cure PAH completely.

Funding Acknowledgement

Type of funding sources: None.

Endothelial cell premature senescence exacerbates pulmonary arterial hypertension through contact-mediated interaction with vascular smooth muscle cells

Introduction

Pulmonary arterial hypertension (PAH) is characterized by remodelling and stenosis of the pulmonary arteries, ultimately leading to the right heart failure and death. Endothelial cell (EC) dysfunction is thought to play a central role in the pathogenesis of PAH by mediating the structural changes in pulmonary vasculatures. Various stresses promote premature senescence in EC, which may modify vascular disorders; however, the role of EC senescence in the development of PAH remains poorly understood.

Purpose

We aimed at investigating the potential role of EC premature senescence in the development of PAH.

Methods

We recently generated EC-specific progeroid mice in which ECs specifically undergo premature senescence by overexpressing the dominant-negative form of telomere repeat-binding factor 2 (published in Nat Commun 2020). These EC-specific progeroid mice were exposed to hypoxia (10% O2 for three weeks) to induce pulmonary hypertension. Also, we prepared premature senescent ECs using human pulmonary artery ECs (hPAECs) and explored their interaction with human pulmonary artery smooth muscle cells (hPASMCs) in two different conditions; direct and indirect interactions. For indirect coculture, hPASMCs were seeded onto the culture insert, while hPAECs were plated on the culture plate, and they were cocultured in the same well and medium so that secreted factors derived from senescent ECs could access to SMCs through the insert pores. For direct coculture, hPAECs were seeded onto the bottom side of the insert, while hPASMCs were cultured on the top side of the same insert, so that cell-to-cell contact could be made through the pores.

Results

After chronic hypoxia exposure, the EC-specific progeroid mice showed higher right ventricular systolic pressure and increased right ventricular mass as compared to wild-type (WT) mice, indicating exacerbated pulmonary hypertension. Histological analysis of the lung revealed a significantly enhanced muscularization in the small pulmonary arteries in EC-specific progeroid mice compared to WT mice. Mechanistically, we identified that direct coculture with premature senescent hPAECs enhanced proliferation and migration in hPASMCs, while no such effects were detected in indirect coculture condition.

Conclusion

To our knowledge, this is the first report that reveals a crucial role of EC premature senescence in the development of PAH. Our in vitro studies suggest that contact-mediated interaction between premature senescent ECs and SMCs is critically involved in its underlying mechanism. Therefore, EC premature senescence is a novel attractive pharmacotherapeutic target for the treatment of PAH.

Funding Acknowledgement

Type of funding source: None