Progressive matrix stiffening of tyramine-modified silk fibroin hydrogels governs stage-specific pulmonary fibroblast activation
Fibrosis is a progressive and often fatal pathological process characterized by excessive extracellular matrix deposition, tissue stiffening, and irreversible organ dysfunction. Effective antifibrotic therapies remain limited by the lack of in vitro models that recapitulate the full spectrum of fibrotic disease progression. Here, we leverage tyramine-modified silk fibroin (SF-TA) hydrogels to investigate normal human lung fibroblasts (NHLF) responses to progressively stiffening environments relevant to pulmonary fibrosis. Two hydrogel formulations with distinct stiffening profiles over 14 days were prepared: a gradual-stiffening 0% SF-TA formulation reaching [~]20 kPa, and a rapidly stiffening 50% SF-TA formulation reaching [~]60 kPa. NHLFs were cultured on both formulations, with and without TGF{beta} (5 ng/mL), for 14 days and assessed for viability, metabolic activity, cytokine and collagen secretion, cytoskeletal organization, and mechanotransductive gene expression. The 0% SF-TA hydrogels drove sustained fibroblast proliferation and elevated secretion of IL-6, IL-8, and MCP-1, consistent with early inflammatory fibrosis. The 50% SF-TA hydrogels induced a metabolic plateau without senescence, suppressed inflammatory cytokine secretion, and, in the presence of TGF{beta}, led to significant upregulation of ACTA2 and CTGF, alongside -SMA stress fiber incorporation, consistent with established myofibroblast persistence. Both conditions produced comparable secreted collagen output by day 14. Together, these findings establish dynamically stiffening SF-TA hydrogels as a tunable platform for investigating stage-dependent fibroblast activation and mechanobiological progression in fibrosis.