COL1A1 and pemphigus foliaceus: Lung sections from vehicle-treated mice showed regional accumulation of Collagen 1a1 (COL1a1) and alpha-smooth muscle-actin (αSMA), whereas staining was reduced and non-focal in the lungs of PGDHi-treated mice (Fig. 3D), indicating that 15-PGDH inhibition protects against severe fibrosis in bleomycin-induced PF.