SPP1 and pulmonary fibrosis: We also analyzed the expression of apoptosis-linked genes in the lungs of TGFα transgenic mice on Dox and observed a progressive increase in transcripts of Grem1, Spp1, Ptgs2, and Mdk during TGFα-induced pulmonary fibrosis, while Fas expression was significantly downregulated in TGFα mice on Dox for 4 weeks (Figure 4D).