Extracellular HSP90a promotes cellular senescence in pulmonary fibrosis through TGF signaling

Idiopathic pulmonary fibrosis (IPF) is a chronic age-related lung disease, in which cellular senescence have been proposed as an important pathogenesis. However, the mechanisms of fibroblast senescence remain unknown. We previously found that extracellular HSP90α(eHSP90α) promotes severe pulmonary fibrosis. We aimed to determine whether eHSP90α regulates cellular senescence and the impacts of 1G6-D7, anti-HSP90α monoclonal antibody, on pulmonary fibrosis development. We detected HSP90α in serum from IPF patients and healthy controls by ELISA. Bleomycin-induced lung fibrosis in wild-type and 1G6-D7 therapeutic treatment mice was measured by histology, collagen, profibrotic gene expression and pulmonary function testing. Cellular senescence was evaluated by senescence-associated β-galactosidase staining. RNA sequencing analysis was performed on IMR90 after F-5 fragment treatment, the functional fragment of eHSP90α.We found that serum HSP90α levels were elevated in IPF patients compared with healthy controls. α-sma, p16 and p21 expression, collagen deposition and resistance were decreased in 1G6-D7 therapeutic treatment mice. In vitro, F-5 fragment or recombinant HSP90α treatment in IMR90 increased cellular senescence. And 1G6-D7 reduced TGF-β1-induced cellular senescence. Notably, our RNA sequence analysis showed that TGFβ signaling was the most significant up-regulated signaling after F-5 fragment application. These data demonstrate that eHSP90α mediated cellular senescence to promote pulmonary fibrosis development, partially through TGFβ signaling. Therefore, targeting eHSP90α by 1G6-D7 to mitigate fibroblast senescence might be a prospective therapy to resolve pulmonary fibrosis.