Peroxisome proliferator-activated receptor-γ (PPAR-γ) is part of the nuclear hormone receptor family, and PPAR-γ agonists inhibit collagen deposition and TGF-β1-induced collagen secretion in bleomycin-induced pulmonary fibrosis (Milam et al. 2008). Here, TGFB1 is linked to pulmonary fibrosis.