3D Bioprinting Artificial Respiratory Tract Tissue

A dependence on the use of animal models and reductionistic in vitro models of the respiratory epithelium in drug discovery has led, amongst others factors, to a high degree of drug attrition in respiratory drug development. Therefore, there is a need to develop and apply novel in vitro respiratory epithelium models which are both predictive and translatable to the human condition. This research aimed to develop and validate complex in vitro models of the respiratory epithelium using a co-culture of normal human lung fibroblasts (NHLFs) and human bronchial epithelial cells (HBECs) differentiated at an air-liquid interface (ALI). 3D Bioprinting was used as a platform to generate these models, in addition to their recent applications in regenerative medicine. Self-assembling peptide hydrogels were identified as a reproducible, synthetic matrix to enable functional bioprinting of primary NHLFs. To this end, the printability, rheological properties, stability, topography and microscale morphology of several self-assembling peptide hydrogels were characterised. The applicability of these synthetic peptides to HBEC ALI differentiation was analysed, in addition to their compatibility with cell-laden bioprinting of human lung fibroblasts. Cell-laden bioprinting in the self-assembling peptide RADA16 (quadruplet of Arginine, Alanine, Aspartic acid and Alanine amino acids) negatively affected cell viability due to a low pH at point of cell encapsulation, which was not seen in native and functionalised Biogelx peptide bioinks. A novel nanocomposite bioink was designed, developed and characterised to enhance the viability of cell-encapsulated bioprinting in synthetic matrices. This systematic approach produced a novel NHLF-HBEC co-culture respiratory epithelium model amenable to use in conjunction with bioprinting technologies. Functional testing of novel NHLF-HBEC co-culture ALI models showed improved morphology and gene expression in comparison to the gold-standard HBEC monoculture ALI models, with proof of concept studies to develop disease-relevant models. The study highlights future potential applications of synthetic self-assembling peptides and 3D bioprinting in complex, in vitro respiratory airway modelling and regenerative medicine applications