Air-Liquid Interface (ALI) Culture of Human Bronchial Epithelial Cell Monolayers as an In Vitro Model for Airway Drug Transport Studies HONGXIA LIN, 1 HONG LI, 1 HYUN-JONG CHO, 1 SHENGJIE BIAN, 2 HWAN-JUNG ROH, 3 MIN-KI LEE, 3 JUNG SUN KIM, 4 SUK-JAE CHUNG, 1 CHANG-KOO SHIM, 1 DAE-DUK KIM 1 1 College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 151-742, South Korea 2 Department of Biology, Pusan National University, Busan 609-735, South Korea 3 College of Medicine, Pusan National University, Busan 602-739, South Korea 4 Department of Biotechnology, Dongseo University, Busan 617-716, South Korea Received 4 April 2006; revised 9 July 2006; accepted 10 September 2006 Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jps.20803 ABSTRACT: Serially passaged normal human bronchial epithelial (NHBE) cell mono- layers were established on Transwell 1 inserts via an air-liquid interface (ALI) culture method. NHBE cells were seeded on polyester Transwell 1 inserts, followed by an ALI culture from day 3, which resulted in peak TEER value of 766  154 O  cm 2 on the 8th day. Morphological characteristics were observed by light microscopy and SEM, while the formation of tight junctions was visualized by actin staining, and confirmed successful formation of a tight monolayer. The transepithelial permeability (P app ) of model drugs significantly increased with the increase of lipophilicity and showed a good linear relationship, which indicated that lipophilicity is an important factor in determining the P app value. The expression of P-gp transporter in NHBE cell monolayers was confirmed by the significantly higher basolateral to apical permeability of rhodamine123 than that of reverse direction and RT-PCR of MDR1 mRNA. However, the symmetric transport of fexofenadine  HCl in this NHBE cell monolayers study seems to be due to the low expression of P-gp transporter and/or to its saturation with high concentration of fexofenadine  HCl. Thus, the development of tight junction and the expression of P-gp in the NHBE cell monolayers in this study imply that they could be a suitable in vitro model for evaluation of systemic drug absorption via airway delivery, and that they reflect in vivo condition better than P-gp over-expressed cell line models. ß 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:341– 350, 2007 Keywords: drug transport; in vitro model; bronchial epithelial cell; P-glycoprotein; permeability INTRODUCTION Pulmonary drug absorption has been extensively investigated as an attractive route for systemic drug delivery since peptides and protein drugs with poor bioavailability via the oral route apparently show excellent bioavailability when delivered by inhalation as pharmaceutical aero- sols. 1–4 In addition to targeting to the deep lung for systemic absorption, aerosols are also routi- nely used for drug delivery to the bronchial regions of the airways for the treatment of acute or chronic lung diseases, such as asthma, cystic JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 96, NO. 2, FEBRUARY 2007 341 Correspondence to: Dae-Duk Kim (Telephone: þ82-2-880- 7870; Fax: þ82-2-873-9177; E-mail: ddkim@snu.ac.kr) Journal of Pharmaceutical Sciences, Vol. 96, 341–350 (2007) ß 2006 Wiley-Liss, Inc. and the American Pharmacists Association