TGF-β: Titan of Lung Fibrogenesis

Pulmonary fibrosis is characterized by epithelial cell injury, accumulation of myofibroblasts, and excessive deposition of collagen and other extracellular matrix elements, leading to loss of pulmonary function. Studies in both humans and animal models strongly suggest that TGF-β1 plays a pivotal role in the pathogenesis of pulmonary fibrosis. This review will first give an overview of TGF-β signaling and the effects of its inhibition on lung fibrogenesis. This overview includes information on TGF-β signal transduction pathways, the importance of TGF-β in the accumulation of myofibroblasts, the role of TGF-β in epithelial injury and apoptosis, the role of TGF-β in extracellular matrix remodeling, and the effects of inhibiting TGF-β signaling in animal models of lung fibrosis. Subsequently this review will highlight recent advances in two areas of particular interest to our research group: (1) TGF-β and proteoglycans; (2) TGF-β and histone deacetylases. Although our understanding of the role of TGF-β and its mechanisms of action in lung fibrogenesis has increased dramatically in recent years, there is still much to be learned about this important molecule, especially how TGF-β function is modulated in vivo, and its complex interactions with other factors expressed during lung injury and repair. Research in these areas will help identify novel therapeutic targets for the treatment of pulmonary fibrosis that will hopefully improve the prognosis of this devastating illness.