Figure 3.

TGF-β induces the expression of ID1 and smooth muscle cell differentiation marker proteins. Top: A representative Western blot for the effect of TGF-β₁ in serum-free conditions on ID1 protein levels up to 6 hours for human fetal lung fibroblasts (HFL1) and primary human adult lung fibroblasts (pHALF) compared with baseline (BL). Also shown are ID2 protein levels that did not change on exposure to TGF-β₁. In contrast, ID3 was undetectable at the protein level. Bottom: Representative Western blots for the effect of TGF-β₁ for 36 hours on the indicated proteins for cultures of HFL-1 and pHALF compared with cultures exposed to serum-free control media (BL).