Fig. 9.

Periostin induces plasminogen activator inhibitor (PAI)-1 expression in vitro by mesenchymal cells and epithelial cells. A: mesenchymal cells from wild-type mice were isolated and plated at 4 × 10⁵ cells/well. One set of wells was left untreated as a control group in serum-free medium, and the other set was treated with 100 ng/ml recombinant mouse periostin. After 24 h, supernatant was collected from the wells, and total PAI-1 and active PAI-1 ELISAs were run (n = 5/group). B: PAIL cells (mink lung epithelial cells with a PAI-1 promoter driving luciferase) were plated at 4 × 10⁵ cells/well. One set of wells remained untreated in serum-free medium as a negative control, and another set of wells was treated with 2 ng/ml TGF-β as a positive control. The remaining sets of wells were treated with 100 ng/ml recombinant mouse periostin or 1 μg/ml periostin. After 24 h, cells were harvested, and luminescence was measured using the luciferase reporter assay as a measure of PAI-1 transcription (n = 3 wells/group representative of 2 experiments). **P < 0.01, ***P < 0.001.