MYOCARDIN-DEPENDENT REGULATION OF ADAM12 AND ADAM19 PROMOTES FIBRONECTIN FIBRILLOGENESIS DURING PLEURAL FIBROSIS

Pleural fibrosis involves excessive extracellular matrix (ECM) deposition driven by chronic injury and inflammation. Transforming growth factor-β (TGF-β) induces mesothelial–mesenchymal transition (MesoMT), promoting a myofibroblast phenotype. Our laboratory identified myocardin (Myocd), a transcriptional coactivator, as a key mediator of MesoMT that regulates ECM-remodeling proteases. RNA-seq and qPCR analyses showed that ADAM12 and ADAM19 are upregulated by TGF-β but suppressed by Myocd knockdown in Human pleural mesothelial and IPF-derived cells. Silencing ADAM12 reduced fibrotic markers, including fibronectin and smooth muscle actin (α-SMA), whereas ADAM19 showed relatively minor effects. ADAM12 knockdown also impaired fibronectin fibrillogenesis and insoluble matrix assembly, as confirmed by a deoxycholate (DOC) solubility assay. Confocal colocalization and proximity ligation analyses showed that ADAM12 and ADAM19 were associated with integrin β1 and α-actinin-related adhesion structures, with TGF-β inducing time-dependent changes in their molecular proximity. Knockdown of either protease reduced TGF-β-induced cell migration, with a stronger effect after ADAM12 silencing. In vivo, carbon black/bleomycin- or Streptococcus pneumoniae-induced pleural fibrosis was associated with elevated ADAM12 and ADAM19 expression alongside α-SMA. These findings identify ADAM12, and to a lesser extent ADAM19, as Myocd-dependent regulators of ECM remodeling during pleural fibrosis progression. Pleural fibrosis involves excessive extracellular matrix (ECM) deposition driven by chronic injury and inflammation. Transforming growth factor-β (TGF-β) induces mesothelial–mesenchymal transition (MesoMT), promoting a myofibroblast phenotype. Our laboratory identified myocardin (Myocd), a transcriptional coactivator, as a key mediator of MesoMT that regulates ECM-remodeling proteases. RNA-seq and qPCR analyses showed that ADAM12 and ADAM19 are upregulated by TGF-β but suppressed by Myocd knockdown in Human pleural mesothelial and IPF-derived cells. Silencing ADAM12 reduced fibrotic markers, including fibronectin and smooth muscle actin (α-SMA), whereas ADAM19 showed relatively minor effects. ADAM12 knockdown also impaired fibronectin fibrillogenesis and insoluble matrix assembly, as confirmed by a deoxycholate (DOC) solubility assay. Confocal colocalization and proximity ligation analyses showed that ADAM12 and ADAM19 were associated with integrin β1 and α-actinin-related adhesion structures, with TGF-β inducing time-dependent changes in their molecular proximity. Knockdown of either protease reduced TGF-β-induced cell migration, with a stronger effect after ADAM12 silencing. In vivo, carbon black/bleomycin- or Streptococcus pneumoniae-induced pleural fibrosis was associated with elevated ADAM12 and ADAM19 expression alongside α-SMA. These findings identify ADAM12, and to a lesser extent ADAM19, as Myocd-dependent regulators of ECM remodeling during pleural fibrosis progression.