Senescent lung fibroblasts delay alveolar epithelial wound repair in IPF
Cellular and molecular mechanisms (English)Introduction: Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease marked by excessive accumulation of fibroblasts (fbs) and collagen in lung parenchyma. In IPF it is thought repeated alveolar epithelial cell injury leads to aberrant re-epithelialisation. IPF fbs demonstrate increased signs of senescence including growth arrest and an activated secretory profile. This study aimed to examine the effect of senescent lung Fbs on the growth and wound repair response of alveolar epithelial cells.
Methods: Primary human fbs were established from lung tissue of patients with (IPF-Fbs) or without IPF (Ctrl-Fbs). Ctrl-fb were treated with H202 (150 µM, 2h) followed by recovery for 3 days. A549 Epithelial cells in transwell inserts were cultured ± fbs conditioned media (CM), or co-cultured with fbs with 5% FCS. After 48 hrs A549 cells were harvested for counting and cycle-analysis. Migratory capacity of Epithelial cells was evaluated using a scratch-wound assay.
Results: Fibroblast senescence was confirmed by increased expression of p21 and senescence-associated β-galactosidase activity. A549 proliferation was attenuated in co-culture with or after transfer of CM from H2O2-treated compared to non-senescent Ctrl-Fbs by 20% (P<0.05). A similar effect was seen with IPF-fbs. Cell-cycle analysis indicated significantly more epithelial cells (P<0.05) co-cultured with IPF-Fbs were arrested in the G2/M phase. Epithelial cell migration was significantly attenuated in the presence of IPF-Fbs but was amplified with Ctrl-Fbs.
Conclusion: Secreted factors from senescent and/or IPF-fbs delay repair of alveolar epithelial cells. These data suggest that senescent fbs contribute to IPF pathology by impeding alveolar epithelial cell regeneration.