Release of biologically active TGF-1 by alveolar epithelial cells results in pulmonary fibrosis

fibrosis (IPF) is a progressive fatal fibrotic lung disease. Transforming growth factor (TGF)-1 is present in a biolog-ically active conformation in the epithelial cells lining lesions with advanced IPF. To determine the role of aberrant expres-sion of biologically active TGF-1 by alveolar epithelial cells (AECs), the AECs of explanted normal rat lungs were trans-fected with the TGF-1 gene using the retrovirus pMX-L-s223,225-TGF-1. In situ hybridization using a digoxigenin-labeled cDNA of the puromycin resistance gene contained in the pMX demonstrated that pMX-L-s233,225-TGF-1 was selectively transfected into AECs of the explants. Condi-tioned media overlying explants obtained 7 days after being treated with pMX-L-s223,225-TGF-1 contained 14.5 3.15 pg/ml of active TGF-1. With the use of Masson’s trichrome staining of explant sections obtained 14 days after transfec