Submitted on September 11, 2006
Accepted on April 24, 2007
Perinatal Increases in TGF-
Disrupt the Saccular Phase of Lung Morphogenesis & Cause Remodeling: Microarray Analysis
Elizabeth L. Kramer1, Gail H Deutsch2, Maureen A Sartor3, William D Hardie1, Machiko Ikegami1, Thomas R. Korfhagen1, and Timothy D. Le Cras1*
1 Section of Neonatology, Perinatal and Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
2 Division of Pathology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
3 Center for Environmental Genetics, Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio, United States
* To whom correspondence should be addressed. E-mail: tim.lecras{at}cchmc.org.
Transforming growth factor-alpha (TGF-
) and its receptor, the EGF receptor (EGFR), have been associated with lung remodeling in premature infants with bronchopulmonary dysplasia (BPD). The goal of this study was to target TGF- overexpression to the saccular phase of lung morphogenesis and determine early alterations in gene expression. Conditional lung specific TGF- bitransgenic mice and single transgene control mice were generated. TGF- overexpression was induced by doxycycline (Dox) treatment from embryonic day (E)16.5 to E18.5. After birth all bitransgenic pups died by postnatal day 7. Lung histology at E18.5 and postnatal day (P)1 showed abnormal lung morphogenesis in bitransgenic mice, characterized by mesenchymal thickening, vascular remodeling, and poor apposition of capillaries to distal airspaces. Surfactant levels (saturated phosphatidylcholine) were not reduced in bitransgenic mice. Microarray analysis was performed after 1 or 2 days of Dox treatment during the saccular (E17.5, E18.5) and alveolar phases (P4, P5) to identify genes induced by EGFR signaling that were shared or unique to each phase. 196 genes were found to be altered (>1.5 fold change; p<0.01 for at least two time points), with only 32% similarly altered in both saccular and alveolar phases. Western blot analysis and immunostaining showed that five genes selected from the microarrays (egr-1, SP-B, SP-D, S100A4, and pleiotrophin) were also increased at the protein level. Pathologic changes in TGF- overexpressing mice bore similarities to premature infants born in the saccular phase who develop BPD, including remodeling of the distal lung septae and arteries.
