Endothelial senescence mediates hypoxia-induced vascular remodeling by modulating PDGFB expression

Uncontrolled accumulation of pulmonary artery smooth muscle cells (PASMC) to the non-muscularized distal pulmonary arterioles (PAs) is one of the major characteristics of pulmonary hypertension (PH). Cellular senescence contributes to aging and lung diseases associated with PH and links to PH progression. However, the mechanism by which cellular senescence controls vascular remodeling in PH is not fully understood. Here, we have demonstrated that endothelial senescence mediates PH pathology by increasing platelet-derived growth factor (PDGFB) expression. The levels of senescence markers p16INK4A and senescence-associated ß-galactosidase (SA-ß-gal) are higher in PA endothelial cells (ECs) isolated from IPAH patients compared to those from healthy individuals. Hypoxia-induced accumulation of a-smooth muscle actin (aSMA)-positive cells to the PAs is attenuated in p16INK4Afl/fl-Cdh5(PAC)-CreERT2 mice after tamoxifen induction. We have reported that endothelial TWIST1 mediates hypoxia-induced vascular remodeling by increasing PDGFB expression. Transcriptomic analyses of idiopathic pulmonary arterial hypertension (IPAH) patient lung ECs or hypoxia-induced mouse lung ECs reveal the alteration of senescence-related gene expression and interaction with TWIST1. Increases in the levels of PDGFB and TWIST1 in hypoxia-treated mouse lung ECs or IPAH patient lung ECs are attenuated by knocking down p16INK4A expression or treating with senolytic reagents. Knockdown of p16INK4A also suppresses accumulation of aSMA–positive cells to the supplemented ECs in the gel. Exosomes collected from hypoxia-treated mouse lung ECs stimulate SMC DNA synthesis and migration in vitro and in the gel implanted on the mouse lungs, while p16INK4A knockdown in ECs inhibits the effects. These results suggest that endothelial senescence controls aSMA–positive cell proliferation and migration in PH through TWIST1-PDGFB signaling. Overall design: Mouse lung endothelial cells were isolated from C57Bl6J mouse lungs (8 week old male mice) 3 weeks after hypoxia and normoxia mouse lungs (n=3 per group, each n was pooled from 3 male mice) using anti-CD31 conjugated magnetic beads for transcriptome analysis.