Design and Development of a Novel Bioreactor System for In-Vitro Modelling of Respiratory Tissues

Abstract

Destructive respiratory diseases are predicted to become the 3rd global cause of morbidity and mortality within the next few decades. Despite their high prevalence, there are no treatments due to the limited regenerative capacity of lung tissues. End-stage sufferers of severe respiratory disease ultimately require tissue or whole organ transplantation, which is associated with low success rate and severely offset by donation shortages. The ever-growing field of tissue engineering offers the potential to not only regenerate human tissue equivalents of respiratory epithelia for surgical implantation, but also to provide an ethical research platform for respiratory pathology research, OH&S toxicology studies and more efficient pharmaceutical screening. However, progress has been hindered by difficulties in maintaining lung-specific cell phenotypes in vitro due to poorly understood or neglected cellular requirements. There is opportunity for a biomimetically-inspired bioreactor approach to provide an optimised culture environment for respiratory tissue engineering. This body of work details the development and validation of such an integrated bioreactor system that captures key in vivo conditions experienced by respiratory tissues during breathing. The system incorporates a unique magnetically driven linear actuator, a porous 3-D tissue scaffold and a scaffold straining mechanism that synergistically exposes cultured cells to air and culture medium at physiological strain rates. A modular compatible perfusion unit was designed and developed, and potential control of the immediate gas environment of a cell culture was conceptually developed. Biological studies with a human lung carcinoma cell line cultured on the integrated system successfully demonstrated that the scaffold-straining unit sustained cellular establishment, growth and proliferation in vitro under dynamic culture conditions. Furthermore, actuation at an air-liquid interface was shown to confer superior proliferation, scaffold infiltration and distribution compared to a static submerged control, thus meeting identified design and functional requirements and validating the underlying biomimetic design philosophy. This system overcomes major limitations of current lung tissue models by producing an organotypic, dynamic, air-liquid interfacing environment. In addition, this system is compatible with standard cell culture techniques, enabling potential large-scale use in research. Overall, the system presented shows great potential for use in regeneration of airway tissues in vitro.