Reversal of lung lesions in transgenic transforming growth factor alpha mice by expression of mutant epidermal growth factor receptor.

Abstract

Transgenic mice expressing transforming growth factor alpha (TGF-alpha) in type II cells under control of the lung-specific surfactant protein-C (SP-C) promoter develop pulmonary fibrosis and marked airspace hypoplasia. To identify cellular signaling mechanisms involved in lesion formation, we generated transgenic mice expressing a mutant epidermal growth factor receptor lacking a portion of the intracytoplasmic domain (EGF-R-M) under control of the human SP-C promoter. Transcripts of the SP-C-EGF-R-M transgene were detected in distal bronchiolar and type II cells by in situ hybridization. The morphology of lungs from the SP-C-EGF-R-M transgenic mice was normal. Lung fibrosis was not detectable and airspace hypoplasia was significantly corrected in bitransgenic mice derived by breeding SP-C-TGF-alpha and SP-C-EGF-R-M mice. Correction of lung pathology in the bitransgenic mice occurred without altering the level of hTGF-alpha mRNA. To further demonstrate that reversal of TGF-alpha lesions required signaling through the EGF-R, SP-C-TGF-alpha transgenic mice were bred to mice homozygous for the wa-2 mutation which encodes a mutated EGF-R. TGF-alpha-induced lesions were reversed in homozygous wa-2 mice. Amelioration of TGF-alpha-dependent pulmonary lesions in SP-C-EGF-R-M mice or wa-2/wa-2 mice supports the concept that autocrine and paracrine signaling mediate fibrosis and airspace remodeling caused by TGF-alpha.

Disrupted pulmonary vascular development and pulmonary hypertension in transgenic mice overexpressing transforming growth factor-α

“…Bitransgenic mice, TGF-␣ ϩ EGFR-M, were generated by breeding hemizygous TGF-␣(ϩ/Ϫ) mice to homozygous EGFR-M(ϩ/ϩ) mice. Genotyping of TGF-␣, bitransgenic TGF-␣ ϩ EGFR-M, and EGFR-M mice was performed by PCR and Southern blot analysis of tail DNA as previously described (18,24). Hematocrits were measured in adult TGF-␣ mice and WT controls by standard techniques with heparinized blood (28).…”

“…Although TGF-␣ transgenic lungs appeared normal at birth, alveolar simplification occurred during the postnatal phase of lung development and was due to disrupted septation (17,19). Expression of a dominant-negative mutant EGF receptor (SPC-EGFR-M) in the distal epithelial cells, also driven by the human SP-C promoter, prevented the induction of pulmonary fibrosis by TGF-␣ and partially improved postnatal alveolarization (18).…”

Genomic Profile of Matrix and Vasculature Remodeling in TGF-α–Induced Pulmonary Fibrosis

“…Transforming growth factor-a (TGF-a) is a ligand for the EGFR, and constitutive or conditional expression of TGF-a in the respiratory epithelium of transgenic mice caused peribronchial, perivascular, and pleural fibrosis in the absence of inflammation (7)(8)(9). Fibrosis in constitutive TGF-a transgenic mice is prevented in mice in which the EGFR is genetically disrupted, supporting TGF-a as inducing fibrotic lesions primarily through the EGFR signaling pathway (10). To identify genes and pathways influenced by TGF-a during the progression of pulmonary disease in the mouse, we correlated changes in mRNA levels with histologic and functional changes in fibrosis and pulmonary hypertension.…”

Increased Phosphorylated Extracellular Signal-Regulated Kinase Immunoreactivity Associated with Proliferative and Morphologic Lung Alterations after Chrysotile Asbestos Inhalation in Mice

“…Our murine model of asbestosis with quantifiable outcomes of inflammation and cell proliferation will be invaluable in determining whether MAPK signaling is directly related to the development of these endpoints and their relationship to fibrogenesis. Ongoing experiments are using this inhalation model with transgenic mice expressing a mutant form of EGF-R 42 or dominant-negative ERK kinase (MEK-1) in bronchiolar epithelial cells to further delineate the signaling cascades involved in the development of asbestosis.…”