This study investigates the effects of a site-directed TG2-selective inhibitor on the lung myofibroblast phenotype and ECM deposition to elucidate TG2 as a novel therapeutic target in idiopathic pulmonary fibrosis (IPF)—an incurable progressive fibrotic disease. IPF fibroblasts showed increased expression of TG2, α smooth muscle actin (αSMA) and fibronectin (FN) with increased extracellular TG2 and transforming growth factor β1 (TGFβ1) compared to normal human lung fibroblasts (NHLFs) which do not express αSMA and express lower levels of FN. The myofibroblast phenotype shown by IPF fibroblasts could be reversed by selective TG2 inhibition with a reduction in matrix FN and TGFβ1 deposition. TG2 transduction or TGFβ1 treatment of NHLFs led to a comparable phenotype to that of IPF fibroblasts which was reversible following selective TG2 inhibition. Addition of exogenous TG2 to NHLFs also induced the myofibroblast phenotype by a mechanism involving TGFβ1 activation which could be ameliorated by selective TG2 inhibition. SMAD3-deleted IPF fibroblasts via CRISPR-cas9 genome editing, showed reduced TG2 protein levels following TGFβ1 stimulation. This study demonstrates a key role for TG2 in the induction of the myofibroblast phenotype and shows the potential for TG2-selective inhibitors as therapeutic agents for the treatment of fibrotic lung diseases like IPF.

本研究调查了定点 TG2 选择性抑制剂对肺肌成纤维细胞表型和 ECM 沉积的影响，以阐明 TG2 作为特发性肺纤维化 (IPF)（一种无法治愈的进行性纤维化疾病）的新治疗靶点。与不表达 αSMA 和表达较低水平的正常人肺成纤维细胞 (NHLF) 相比，IPF 成纤维细胞显示出 TG2、α 平滑肌肌动蛋白 (αSMA) 和纤连蛋白 (FN) 的表达增加，细胞外 TG2 和转化生长因子 β1 (TGFβ1) 增加FN 的。IPF 成纤维细胞显示的肌成纤维细胞表型可以通过选择性 TG2 抑制与基质 FN 和 TGFβ1 沉积的减少来逆转。NHLFs 的 TG2 转导或 TGFβ1 处理导致与 IPF 成纤维细胞相当的表型，在选择性 TG2 抑制后是可逆的。将外源性 TG2 添加到 NHLF 还通过涉及 TGFβ1 激活的机制诱导肌成纤维细胞表型，该机制可以通过选择性 TG2 抑制来改善。通过 CRISPR-cas9 基因组编辑删除 SMAD3 的 IPF 成纤维细胞，在 TGFβ1 刺激后显示 TG2 蛋白水平降低。这项研究证明了 TG2 在诱导肌成纤维细胞表型中的关键作用，并显示了 TG2 选择性抑制剂作为治疗纤维化肺病（如 IPF）的治疗剂的潜力。