Cell-based in vitro models for pulmonary permeability studies

Over the past 30years the possibility of using pulmonary administration as a means to deliver systemically acting drugs and biopharmaceuticals has begun to attract the interest of researchers and to be considered an alternative to traditional administration routes such as oral or intravenous. With such rising interest also came the necessity of better understanding the interactions between the drugs and the lung tissue, as well as the mechanisms involved in drug absorption. These mechanisms are similar to those that occur in most organs, such as paracellular or transcellular transport, which will be described in detail. Considering that traditional in vivo studies can be expensive and complex, in vitro models have been proposed to study cellular processes in an attempt to provide an easier and more simplified understanding of biological mechanisms. In this chapter, several in vitro cell-based models using both immortalized cell-lines and primary cells from both bronchial and alveolar lineages are presented and compared, in terms of their strengths and weaknesses, with other models and the in vivo systems that they intend to mimic.