1 Loss of small airways occurs in mild and moderate Chronic Obstructive Pulmonary Disease Hyun-Kyoung Koo M.D.,* Dragoş M. Vasilescu Ph.D.,* Steven Booth MSc.,* Aileen Hsieh, Orestis L. Katsamenis Ph.D., Nick Fishbane MSc., W. Mark Elliott Ph.D., Miranda Kirby Ph.D., Peter Lackie Ph.D., Ian Sinclair Ph.D., Jane A. Warner Ph.D., Joel D. Cooper M.D., Harvey O. Coxson Ph.D., Peter D. Paré M.D., James C. Hogg M.D., Tillie-Louise Hackett Ph.D. From the University of British Columbia, the Centre for Heart Lung Innovation, and St. Paul’s Hospital, Vancouver, Canada (H.K.K., D.M.V., S.B., A.H., N.F., M.K., W.M.E., H.O.C., P.D.P., J.C.H., T.L.H.); the Department of Anesthesiology, Pharmacology & Therapeutics (H.K.K., S.B., T.L.H.); the Department of Medicine (P.D.P.); the Department of Pathology (J.C.H); - all University of British Columbia, Vancouver, BC, Canada; the μ-VIS X-ray Imaging Centre, Faculty of Engineering and the Environment (O.L.K., I.S.); Clinical & Experimental Sciences, Faculty of Medicine (P.L., J.A.W.) - all University of Southampton, Southampton, U.K.; the Division of Thoracic Surgery (J.D.C.), University of Pennsylvania, Philadelphia, U.S.A. * denotes co-first authors. Reprint requests to Dr. Tillie-Louise Hackett at the University of British Columbia, Centre for Heart Lung Innovation, St. Paul’s Hospital, Rm166, 1081 Burrard Street, Vancouver, B.C., V6Z 1Y6, Canada or at Tillie.Hackett@hli.ubc.ca . TOTAL WORD COUNT = 4075 Manuscript Clean Version