Fig. 5.

A and B: confirmation of hyperoxia-induced activation of pulmonary transforming growth factor (TGF)-β and wingless/Int (Wnt) signaling in TOPGAL mice. Seven-day exposure to 95% O₂ to TOPGAL mice starting on postnatal day 1 resulted in clear evidence of Wnt and TGF-β signaling activation. A shows bluish staining (LacZ positivity) of lung tissue at both macroscopic and microscopic levels. Hyperoxia exposure resulted in increased expression of ALK-5, pSmad3/total Smad3 (T-Smad3), Lef-1, α-SMA, and fibronectin protein levels, clearly indicating activations of TGF-β and Wnt signaling pathways (B; P < 0.05 vs. 21% O₂; n = 4).