INTRODUCTION ABSENCE OF MAST CELLS IN AN EXPERIMENTAL MODEL OF PULMONARY AND CARDIAC FIBROSIS, THE CUX-1 MICE Navya A Reddy 1, Farhan Raza 1, Ahmed Said 1, Safia Livingston 2, David Jacobsen 2, Donovan Kearns 2, Richard Baybutt 2, Gregory Van Den Heuvel 3, Agostino Molteni 1, Soheila Hamidpour 1. 1 University of Missouri Kansas City, Kansas City, MO, 2 Wheaton College, Wheaton, IL, 3 Western Michigan University, Kalamazoo, MI Both pulmonary and cardiovascular (CV) fibrosis have a significant role in clinical medicine, however the mechanism of fibrosis in these organs is controversial (1,2). In rat models, injection of triolein (T) a substance comprising 80% of human fat and used for inducing fat embolism (FE), has been associated with an increase of mast cells (MCs) and renin stained cells in the lungs and heart (3,4) In injured pulmonary tissue, MCs are known to produce renin, leading to Angiotensin II mediated fibroblasts proliferation (5). The angiotensin II receptor blocker Losartan is associated with a reduction in lung MCs and fibroblast proliferation, suggesting that MCs may have a correlation with the fibrosis (6). We aimed to understand whether MC may have any role in the development of pulmonary and cardiac fibrosis in another rodent model; the CUX 1 (CUT-like homeobox) transgenic mice. The CUX-1 gene is present in all metazoans. Its constitutive expression (such as in polycystic kidneys) blocks cyclin dependent kinase inhibitors p21 and p27, leading to hepatic, pulmonary and cardiac fibrosis (7). Previous studies of CUX-1 mice have shown severe inflammation of the pulmonary and coronary arteries with media thickening, luminal patency reduction, and adventitial fibrosis (8,9). The presence of MCs in the lungs and heart of CUX-1 mice has not yet been determined. METHODS In our study, 6 Wild type and 6 CUX-1 transgenic mice were sacrificed by isoflurane anesthesia and then necropsied. Lungs and heart were collected, fixed in 10% formalin and stained for detection of mast cells: H&E (morphometric scoring), Trichrome (fibrosis), May-Grünwald-Giemsa (MCs), and CD117 C- kit (MCs). In each organ slide, 10 photographs were taken at random at 400x magnification by 2 pathologists unaware of the slide identity. RESULTS SUMMARY In wild type mice, we observed mild inflammation/fibrosis of the lungs and heart CUX-1 mice presented with very severe fibrosis, particularly in the bronchial basal membrane, peribronchial pulmonary arteries, and branches of the coronary arteries of the heart. May-Grünwald-Giemsa staining of heart tissue showed very few MCs in the wild type and no MCs in CUX-1 mice CD117 staining showed no MCs in either organs of CUX- 1 mice, notwithstanding the severe damage. CONCLUSION The results of these models of pulmonary and cardiac damage suggest that different pathogenetic mechanisms and cellular elements are involved. Further mechanisms of the development fibrotic damage should be explored to identify potential therapeutic options in patients with pulmonary or cardiac fibrosis. REFERENCES 1)Herridge et al. N Engl J Medicine. 2011; 364: )Ajemba O, et al. Case reports in Clinical Pathology: 2015: )Mclff T et al. Journal of Ortho Research )Alhariri et al. Chest )Wilson M. S. et al. Mucosal Immunol. 103– /mi )Silveira K et al. Peptides 2015: )Molteni A et al. International Colloquium on Lung and Respiratory airways fibrosis. Mont Tremblant Quebec, Canada, 2014, September )Helgelson et al. The FASEB Journal: 2015: Supplement )Fletcher A et al. The FASEB Journal: 2015: Supplement LB 439. Fig 1) Representative samples of lung peribronchial arteries & bronchi of WTF (A,B) and CUX-1 (C,D) mice -Trichrome 400x Lungs of WTF & CUX-1 mice (CD117 stain 100x) Lungs: Wild Type and CUX-1 Lungs: Mast Cells in Rats with FE (CD117 stain) A) Saline (Control) B) Triolein C) Triolein+ losartan Heart: Mast Cells in Rats with FE (CD117 stain) A) Saline (Control) B) TrioleinC) Triolein+losartan Heart WTF & CUX-1 mice (May-Grünwald-Giemsa 400x) Fig A) WTF Fig B) CUX-1 Fig A) WTF Fig B) CUX-1 Fig 2) Representative samples of heart of WTF (C) and CUX-1 (D) mice -H&E 400X Representative samples of heart of WTF (E) and CUX-1 (F) mice -Trichrome 400x Heart: Wild Type and CUX-1 Lungs FE model: A significant amount of MCs were evident with the CD117 staining. Losartan treatment was found to significantly reduce this mast cell number in mice with FE, confirming the interaction of mast cells and the renin-angiotensin system in this model. WTF: Mo MCs were evident on CD117 stain. CUX-1: No MCs were evident with both methods of staining despite severe fibrosis. Myocardium FE model: Few MCs were evident with CD117 staining. WTF: Few MCS were evident with May-Grünwald-Giemsa. No MCs were evident with CD117 staining. CUX-1: No MCs were evident either with May-Grünwald-Giemsa or CD117 staining. Acknowledgments 1)Mary Catherine Geldmacher Foundation St. Louis, Missouri, MO 2)Wheaton College Funds, Wheaton, IL 3)Histopathology Laboratory, Truman Medical Center, Kansas City, MO