Rho-associated coiled-coil–containing protein kinase signaling preserves alveolar type II cell identity by antagonizing transforming growth factor-β1–driven epithelial remodeling in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is driven not only by fibroblast activation but also by loss of epithelial identity in alveolar type II (AT2) cells. In fibrotic regions of IPF lungs, AT2 cells frequently transition into cytokeratin 17 (KRT17)-positive alveolar-basal intermediate cells; however, the intracellular mechanisms regulating this fate change remain poorly understood. Although transforming growth factor-β1 (TGF-β1) signaling is a major driver of epithelial remodeling, the regulatory pathways that counterbalance this process in AT2 cells have not been clearly defined. Here, we investigated the interaction between the Rho-associated coiled-coil-containing protein kinase (ROCK) pathway and TGF-β1 signaling using human distal lung-derived alveolar organoids and human IPF lung tissues. ROCK activity was assessed by phosphorylated ezrin/radixin/moesin (pERM), whereas TGF-β1 signaling activity was evaluated by phosphorylated Smad2 (pSmad2). Under basal conditions, AT2 organoids displayed strong pERM expression with minimal pSmad2 activation. TGF-β1 stimulation induced trans-differentiation toward KRT17-positive alveolar-basal intermediate cells, accompanied by loss of surfactant protein C (SFTPC) expression. Inhibition or knockdown of ROCK markedly enhanced this TGF-β1-induced transition, whereas ROCK activation suppressed it. Consistently, human IPF tissues showed pERM-positive/pSmad2-negative AT2 cells in non-fibrotic regions, whereas fibrotic regions were enriched with pSmad2-positive/pERM-negative alveolar-basal intermediate cells. These findings identify ROCK signaling as a key mechanism that preserves AT2 cell identity and antagonizes TGF-β1-driven epithelial remodeling, suggesting epithelial ROCK activity as a potential therapeutic target in IPF. Overall, our results establish ROCK signaling as a gatekeeper of AT2 cell identity during fibrotic lung remodeling.