View Abstract

A2224 - Altered Six1 and BMPR2 in Pulmonary Fibrosis
Author Block: C. Wilson, S. Collum, A. M. Hernandez, T. Mertens, L. Headley, K. Rajagopal, S. S. Jyothula, H. Karmouty-Quintana; University of Texas McGovern Medical School, Houston, TX, United States.
Rationale:Idiopathic pulmonary fibrosis (IPF) is a spontaneously occurring chronic and irreversible lung disease with limited treatment options and poor survival rates. Recapitulation of embryonic developmental genes have been reported to play a role in the development of disease, however research on specific genes is lacking.
In this project we have looked at two developmental genes: Sine Oculis Homeobox Homolog 1 (Six1) a transcription factor that is only normally expressed embryonically and is essential for normal lung development but it has also been shown to be elevated in lung cancer. Preliminary data have shown an increase in Six1 protein expression and transcript levels in patients with IPF, as well as increased expression in the lung epithelium. Bone morphogenetic protein receptor (BMPR)-2 an important developmental gene where loss-of-function mutations have been associated with vascular abnormalities in the lung. Previously published data by our group supports a role of BMPR2 dysfunction in macrophages.
Our lab hypothesizes that altered Six1 and BMPR2 expression levels could promote aberrant repair processes that contribute to lung fibrosis.
Methods:
Based on our preliminary data the Cre-Lox system was used to generate conditional KO mice for BMPR2/Six1 in target cells. In order to study the role of Six1 we utilize transgenic mice lacking Six1 in SPC Cre expressing cells that target type II lung epithelial cells. BMPR2f/f LysMCre mice were used to study BMPR2 deletion in alveolar macrophages. These mice were exposed to bleomycin (BLM) 0.035 U, IP twice weekly for 4 weeks or PBS (control). Flash frozen and paraffin-embedded lung tissue was collected after surgery. Immunohistochemistry, RT-PCR, histological analysis, and western blots were performed to evaluate and identify markers of fibrosis and lung function analysis using the Flexivent.
Results and Conclusions:
We demonstrate a significant reduction in fibrosis as in Masson’s Trichrome stained sections and scored using modified Ashcroft in Six1f/f SPC Cre mice when compared to the control SPC Cre mice. These are consistent with improved lung function. Interestingly, BMPR2f/f LysMCre mice did not have a significant change in the level of fibrosis when compared to the LysMCre control mice. Immunohistochemical staining for markers of fibrosis in the BMPR2f/f LysMCre mice did not show significant difference from the LysMCre control mice. These observations suggest that the developmental gene Six1 but not BMPR2 could play a novel role in the pathogenesis of pulmonary fibrosis.