Endothelial Cell Senescence Exacerbates Pulmonary Fibrosis Potentially Through Accelerated Endothelial to Mesenchymal Transition.

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease characterized by progressive lung fibrosis and obliteration of normal alveolar structures. Myofibroblasts play a central role in the progression of IPF by producing excess amount of extracellular matrix, and these myofibroblasts show heterogenous origins including resident fibroblasts, epithelial cells via epithelial to mesenchymal transition (EMT) and endothelial cell (EC) via endothelial to mesenchymal transition (EndMT). Although lung aging has been considered as essential mechanisms through abnormal activation of epithelial cells and fibroblasts, little is known about a role of EC senescence in the pathogenesis of IPF. Here, we reveal a detrimental role of EC senescence in IPF by utilizing unique EC-specific progeroid mice. EC-specific progeroid mice showed deteriorated pulmonary fibrosis in association with an accelerated EndMT in the lungs after intratracheal bleomycin instillation. We further confirmed that premature senescent ECs were susceptible to EndMT in vitro. Because senescent cells affect nearby cells through senescence-associated secretory phenotype (SASP), we assessed a potential role of the EC-SASP in EMT and myofibroblastic transition of resident fibroblasts. EC-SASP enhanced the myofibroblastic transition in resident fibroblasts, while no effect was detected on EMT. Our data revealed a previously unknown role of EC senescence in the progression of IPF, and thus rejuvenating ECs and/or inhibiting EC-SASP is an attracting therapeutic strategy for the treatment of IPF.