Harnessing Tissue Engineering Approaches to Develop Advanced 3D Models for Respiratory Drug Development and Respiratory Regenerative Therapies

Respiratory diseases and major airway trauma represent a global healthcare emergency with most treatment options providing symptomatic relief rather than curative treatment. In addition, they are associated with enormous socioeconomic burden. Respiratory tissue engineering commonly focuses on two broad areas: (i) the development of novel in vitro models for drug discovery and (ii) on artificial constructs for tissue repair and regeneration. The development of physiologically-representative tracheobronchial tissue analogues has the potential to improve the translation of novel inhaled therapies by accurately reflecting in vivo respiratory pharmacological and toxicological responses. On the other hand, effective restoration of extensive tracheal damage arising from cancer, stenosis, infection or congenital abnormalities remains an unmet clinical need in respiratory medicine. In this project, tissue-engineered (TE) collagen hyaluronic acid bilayered (CHyA-B) scaffolds were used to evaluate bacterial and drug induced toxicity and inflammation using Calu-3 bronchial epithelial cells and Wi38 lung fibroblast co-culture under air liquid interface (ALI) conditions as an in vitro model of the upper respiratory tract. After using lipopolysaccharide (LPS) and bleomycin to induce bacterial and drug responses in vitro; differential cell responses were seen between 2D and 3D airway models. Furthermore, the co-culture 3D model provided differential epithelial responses to a number of inhaled nanoparticles compared to 2D models. Based on our understanding of the cell-matrix interactions involved in supporting respiratory epithelial cell growth and differentiation, we sought to harness these CHyA-B scaffolds to develop tubular TE tracheal constructs. A 3Dprinted polymer mesh of thermoplastic polymers with tailored architecture was fabricated and characterised to provide the tubular backbone of the construct. Polyglobalide (PGL), an advanced synthetic polymer that allows for post-processing surface modifications in comparison to commonly used polymers such as polycaprolactone (PCL), was employed as a 3D printable material. This was then covered with CHyA-B scaffolds using a freeze-drying process and Calu-3 epithelial cells were seeded onto its luminal film surface resulting in the formation of a partial epithelial layer. 3D printed PCL- and PGL-CHyA tubular scaffolds are promising biocompatible prototypes for tracheal regeneration with adequate mechanical properties supporting epithelial growth.