Microphysiological Models for Predictive Pre-Clinical Assessment of Pulmonary Drug Exposure

The communication between the epithelial cells and smooth muscle cells in the airways is a vital characteristic of physiology and pathophysiology, specifically the response of airway smooth muscle to stimulants in the environment and inhaled therapeutics, in both healthy and diseased tissues. However, models currently used to evaluate drugs and environmental stimuli lack the physiological features present in vivo. The lack of respiratory in vitro models that are representative of the human in vivo anatomy, physiology and pathophysiology has resulted in the reliance on models that possess poor predicitve power for the assessment of drugs, resulting in a high attrition rate of new drug candidates in clinical trials due to lack of effiacy or unforseen adverse events. This highlights the need for a more in vivo-like respiratory model. Microphysiological system (MPS) -based in vitro models of the respiratory tissues have the potential to enhance the understanding of disease states and improve drug candidate research through their ability to mimic biomechanical stimuli experienced in vivo.. This thesis investigates the morphological and functional effect of perfusion on a human bronchial epithelium cell line, Calu-3, and primary human bronchial smooth muscle cells in a direct coculture, cultured in the Barrier-12 plate PhysioMimix® Organ-on-a-Chip (OOC) Microphysiological System. Perfusion enhanced the Calu-3 epithelial model’s barrier function and phenotype, whilst decreasing the time needed for differentiation that achieves minimal apparent permeability (Papp) of the paracellular markers lucifer yellow (LY) and sodium fluorescein (NaFL) by up to 7 days compared to the non-perfused comparator. The coculture of the Calu-3 epithelial cells with primary bronchial smooth muscle cells in combination with the perfused condition controlled by the PhysioMimix system further enhanced the barrier functionality of the epithelium, reducing the Papp of NaFL compared to both the non-perfused coculture and both perfused and non-perfused Calu-3 monoculture. Utilising the liquid chromatography tandem mass spectrometry (LC-MS) method that was validated in this thesis, terbutaline transport across the perfused coculture barrier was assessed and the resultant relaxation of the bronchial smooth muscle cells was shown to be more sensitive to the dose-normalized effect of terbutaline than the non-perfused co-culture. This thesis highlighted the benefits of an MPS model for the development and assessment of inhaled therapeutics in a model more representative of the pulmonary in vivo microenvironment.