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A5784 - Primary Cilia Are Necessary for Fibroblast Migration and the Development of Pulmonary Fibrosis
Author Block: C. Trempus1, S. Garantziotis2; 1Natl Inst of Environmental Hlth Sciences, Research Triangle Park, NC, United States, 2NIEHS, Natl Inst of Environmental Hlth Sciences, Research Triangle Park, NC, United States.
Introduction: Idiopathic Pulmonary Fibrosis (IPF) is a devastating lung disease caused by a maladaptive response to epithelial injury and characterized by progressive deposition of extracellular matrix in the gas-exchange regions of the lung, ultimately leading to respiratory failure. Fibroblasts (FBs) are hypothesized to contribute to disease pathogenesis through taking on a more invasive phenotype. It is hypothesized that FB behavior is dictated by cues from the microenvironment, sensed in part by primary cilia (PC) - sensory organelles that have been shown to mediate fibrosis-relevant pathways such as mechanotransduction, cell migration, Pdgf and Sonic Hedgehog signaling. The objective of this study was to determine a potential role for PC in the pathogenesis of fibrosis.
Methods: PC expression was assessed sections of formalin-fixed human IPF lung and fibrotic lung from bleomycin-exposed mice using PC-specific antibodies and immunofluorescence staining. In order to investigate the role of FB PC in lung fibrosis, a mouse strain was developed in which FB are deficient in PC (Ift88 fx/fx;SMa22.Cre). Primary lung FBs were established into cell culture, then following 48 hours of serum starvation, primary cilia incidence was determined through immunofluorescence staining, and migration kinetics assessed using the Transwell migration assay. To test the effect of PC deficiency on FB migration in vivo, FxFxCre and control mice were dosed with 2 mg/mouse MIN-U-SIL-5 silica via oropharyngeal instillation and granuloma formation and fibrosis evaluated at up to 6 weeks post-exposure.
Results: PC were detected in FBs populating fibroblastic foci and in cells in adjacent parenchyma in IPF human lungs, in cultured normal and IPF human FBs, and PC-transgelin double positive cells were found in fibrotic areas of mouse lung. PC expressing FBs were overwhelmingly PDGFRA positive. Isolated primary lung FB from FxFxCre mice exhibited reduced migration kinetics compared to controls, as well as reduced markers of invasivity such as versican expression, and finally, FxFxCre mice developed fewer granulomas and reduced fibrosis following silica exposure.
Conclusions: Taken together, our evidence demonstrates that PC are necessary for invasive FB migration into injured lungs and for subsequent fibrosis development.