Nestin promotes pulmonary fibrosis via facilitating recycling of TGF-beta receptor I

Background Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease that is characterised by aberrant proliferation of activated myofibroblasts and pathological remodelling of the extracellular matrix. Previous studies have revealed that the intermediate filament protein nestin plays key roles in tissue regeneration and wound healing in different organs. Whether nestin plays a critical role in the pathogenesis of IPF needs to be clarified. Methods Nestin expression in lung tissues from bleomycin-treated mice and IPF patients was determined. Transfection with nestin short hairpin RNA vectors in vitro that regulated transcription growth factor (TGF)-beta/Smad signalling was conducted. Biotinylation assays to observe plasma membrane T beta RI, T beta RI endocytosis and T beta RI recycling after nestin knockdown were performed. Adeno-associated virus serotype (AAV)6-mediated nestin knockdown was assessed in vivo. Results We found that nestin expression was increased in a murine pulmonary fibrosis model and IPF patients, and that the upregulated protein primarily localised in lung a-smooth muscle actin-positive myofibroblasts. Mechanistically, we determined that nestin knockdown inhibited TGF-beta signalling by suppressing recycling of T beta RI to the cell surface and that Rabll was required for the ability of nestin to promote WI recycling. In vivo, we found that intratracheal administration of AAV6-mediated nestin knockdown significantly alleviated pulmonary fibrosis in multiple experimental mice models. Conclusion Our findings reveal a pro-fibrotic function of nestin partially through facilitating Rab11-dependent recycling of T beta RI and shed new light on pulmonary fibrosis treatment.