Fibrotic lung ECM upregulates SDC4/integrin-αvβ1 interaction and the interfering peptide SDC4_87-131 and its...

Fibroblast activation promotes remodeling of the extracellular matrix (ECM), and the fibrotic remodeling ECM further stimulating fibroblast activation and advancing pulmonary fibrosis (PF). syndecan-4 (SDC4) is the key mediator of ECM-cell signaling, but its action in PF remains unclear. Using decellularized lung ECM (dECM), this study found that fibrotic ECM enhanced fibroblast activation via SDC4-regulated integrin-αvβ1 expression and activation, and FAK/AKT phosphorylation. Meanwhile, SDC4 knockdown inhibited fibrotic ECM-induced TGF-β1 synthesis and PKCα activation. A Duolink-proximity ligation assay confirmed extracellular interactions between SDC4 and integrin-αvβ1, and the SDC4 blocking antibody Anti-SDC4_(93-121) prevented this interaction, resulting in an effect consistent with knockdown of SDC4. The interfering peptide SDC4_87-131 diminished the interaction between SDC4 and integrin-αvβ1, subsequently inhibited the activation of FAK/AKT, Smad2/3 and PKCα/NF-κB pathways and exhibited anti-PF activity comparable to that of SDC4 knockdown and Anti-SDC4_(93-121). A docking mode of SDC4_87-131 with the Calf-1/Calf-2 domain of integrin-αv was constructed by using the AlphaFold2-Multimer model, and peptide design was performed to obtain a novel polypeptide chain CS-9 with enhanced anti-PF effect. This study found that the biomaterial, lung ECM, regulates fibroblast activation through the collaboration of SDC4 and integrin-αvβ1, and obtained a novel SDC4_87-131-derived peptide that may prevent fibrotic ECM from promoting PF.