Transforming growth factor-β1 (TGF-(β1) is a 25-kDa homodimeric protein secreted by numerous cells including platelets, monocytes, macrophages, epithelial cells, and fibroblasts (1 –3 ). Active TGF-(β1 exerts multiple and divergent effects on mesenchymal and epithelial cell cycle regulation (1 ). In addition, TGF-(β1 influences the expression of multiple genes, which act in concert to enhance the synthesis of extracellular matrix components with resulting fibrosis (1 ,2 ). In vitro studies have demonstrated that TGF-(β1 regulates the genetic expression of extracellular matrix components, including fibronectin (FN), the α5β1 fibronectin receptor (FNR), collagen, and proteoglycans (4 –7 ).
