Dean Sheppard’s research focuses on the molecular mechanisms underlying pulmonary (and other organ) fibrosis, asthma and acute lung injury. One aim of the research is to identify new therapeutic targets to ultimately improve the treatment of each of these common diseases. The work begins with basic investigation of how cells use members of the integrin family to detect, modify and respond to spatially restricted extracellular clues and how these responses contribute to the development of common lung diseases. Utilizing mice with global or conditional knockouts of five integrins, the epithelial-restricted integrin, avβ6, and the widely expressed integrins a9β1, avβ5, avβ3 and avβ8, the lab has identified important roles for these integrins in models of each common lung disease and key steps upstream and downstream of the integrins that provide potential therapeutic targets. We have also used the knockout mice to develop potent blocking monoclonal antibodies against 4 of these which are in various stages of clinical development.
During the course of these studies we have identified 3 integrins, avβ6, avβ8 and avβ1 that all have as their major in vivo function activation of the extracellular latent form of the pleiotrophic growth factor, transforming growth factor β (TGFβ), through a novel mechanism that depends on cell contraction and integrin-dependent mechanical deformation of latent TGFβ. We have shown that this function plays a central role in pulmonary, hepatic and renal fibrosis, acute lung injury, protection from pulmonary emphysema, tumor invasion and in the induction of airway hyperresponsiveness following allergen challenge. Currently we are identifying pathways that regulate each of these responses. A humanized monoclonal antibody generated by immunizing our itgb6 knockout mice is currently in clinical trials for treatment of pulmonary fibrosis. Together with Bill Degrado we have developed a potent and selective small molecular inhibitor of avβ1 which we are developing as a potential treatment for a wider variety of fibrotic diseases.
The avβ8 integrin also activates TGFβ. Mice we have generated lacking the avβ8 integrin on dendritic cells are dramatically defective in their ability to generate a subset of antigen specific T cells that make IL-17, making these mice an excellent model of Th17 cell deficiency. Mice lacking avβ8 integrin on dendritic cells are dramatically protected from pathology in a number of immune-mediated disease models, including multiple sclerosis and allergic asthma. We are currently characterizing the mechanisms underlying these effects, the mechanisms by which this process is regulated during the induction of adaptive immune responses, and the relevance of this pathway in various models of immune-mediated disease. These mice are also protected in a simple model of acute lung injury, and sequencing T cell receptors on Th17 cells in this model demonstrated marked oligoclonality, suggesting the existence of as yet determined antigens driving an adaptive immune response that contributes to acute lung injury. We are currently attempting to identify these antigens.
a9β1 is expressed by a wide variety of cells and recognizes at least 15 distinct ligands. a9β1 is critical for cell migration, an effect that depends on unique sequences in the α9 cytoplasmic domain. As a9 ko mice are not viable, we have generated mice expressing a conditional null allele to better the role of this integrin in vivo. Mice lacking this integrin in airway smooth muscle cells develop spontaneous airway hyperresponsiveness, resembling asthma. We have used these mice and cells and tissues from their lungs to identify a completely novel pathway regulating airway smooth muscle contraction, and are currently working to develop specific inhibitors of pathway components in the hope of finding new treatments for asthma.
We are also taking advantage of our experience with multiple models of tissue fibrosis to identify shared and distinct molecular characteristics of the fibroblasts that drive fibrosis in different organs. Using single cell RNAseq we have identified multiple distinct subsets of pathologic fibroblasts, surface markers to allow purification of each subset from different organs and novel biomarkers and targets that we hope will ultimately allow us to develop targeted therapies for treatment of the large number of chronic diseases characterized by excessive tissue fibrosis.
Munger JS, Huang XZ , Kawakatsu H , Griffiths MJD, Dalton SL, Wu JF, Pittet JF, Kaminiski N, Garat C, Matthay MA, Rifkin DB, Sheppard D. The integrin avβ6 binds and activates latent TGFβ: a mechanism for regulating pulmonary inflammation and fibrosis. Cell 1999, 96: 319-328.
Morris DG, Huang X, Kaminski N, Wang Y, Shapiro SD, Dolganov G, Glick, A, Sheppard D. Loss of integrin avβ6-mediated TGFβ activation causes Mmp12-dependent emphysema. Nature 2003 422:169-173.
Travis MA, Reizis B, Melton AC Masteller E, Tang Q, Proctor J, Wang Y, Bernstein X, Huang X, Riechardt L, Bluestone J, Sheppard D. Loss of integrin avβ8 on dendritic cells causes autoimmunity and colitis in mice. Nature 2007 449:361-365.
Melton A, Bailey-Bucktrout SL, Travis MA, Fife BT, Bluestone JA, Sheppard D. avβ8 integrin on dendritic cells regulates Th17 cell development and experimental autoimmune encephalomyelitis in mice. J Clin Invest 2010 120:4436-44
Kudo M, Melton AC, Chen C, Engler M, Huang KE, Ren X, Wang Y, Bernstein X, Li J, Atabai K, Huang X, Sheppard D. IL-17A produced by aβ T cells drives airway smooth muscle contraction. Nature Medicine 2012 18:547-554.
Sugimoto K, Kudo M, Sundaram A, Ren X, Huang K, Bernstein X, Wang Y, Raymond WW, Erle D, Abrink M, Caughey GH, Huang X, Sheppard D. The avβ6 integrin modulates airway hyperresponsiveness by regulating intra-epithelial mast cells. J Clin Invest 2012 122:748-758, PMID:22232213
Chen C, Kudo M, Rutaganira F, Takano H, Lee C, Atakilit A, Robinett, KS, Uede T, Wolters P, Shokat KM, Huang X, Sheppard D. Integrin alpha9beta1 in airway smooth muscle regulates a novel brake on exaggerated murine and human airway narrowing J Clin Invest 2012 122:2916-27 PMID 22772469
Henderson NC, Arnold TD, Katamura Y, Giacomini MM, Rodriguez JD, McCarty JH, Ruminiski PG, Griggs DW, Maher JJ, Iredale JP, Lacy-Hulbert A, Adams RH, Sheppard D. Selective av integrin deletion identifies a core, targetable molecular pathway that regulates fibrosis across solid organs. 2013 Nature Medicine 2013 19:1617-1624 NIHMS495176
Li JT, Melton AC, Su G, Hamm DE, LaFemina M, Howard J, Fang X, Bhat S, Huynh K-M, O'Kane CM, Ingram RJ, Muir RR, McAuley DF, Matthay MA, Sheppard D. Unexpected role for adaptive aβ Th 17 cells in acute respiratory failure. K Immunol 2015 185:87-95 NIHMSID: 684976.
Reed NI, Jo H, Chen C, Tsujino K, Arnold TD, DeGrado WF, Sheppard D. The avβ1 integrin plays a critical in vivo role in tissue fibrosis. Science Translational Medicine 2015 7:288-294.