Recellularization of decellularized mouse lung airways using negative pressure directed cell delivery

Ahmadipour , Mohammadali 1, 2; Chadwick  , Eric 3; Bazylak , Aimy 1, 3; Karoubi and Waddell, Golnaz and Thomas 1, 2

 1. Institute of Biomaterials and Engineering , University of Toronto; 2. Latner Thoracic Surgery Research Laboratories; 3. Department of mechanical and industrial engineering , University of Toronto

 For end-stage lung disease such as Chronic Obstructive Pulmonary Disease (COPD), lung transplantation remains the only viable treatment approach. Transplantation, however, is highly limited due to the shortage and availability of transplantable lungs. Generation of bioartificial lungs through the process of decellularization and recellularization of transplant rejected donor lungs is an exciting alternative currently under investigation in the field of tissue engineering. While there has been significant progress in the optimization of decellularization methodologies, recellularization of acellular lung scaffolds remains a challenge. In particular, there needs to be an improvement in both cell delivery methods targeting cells to the appropriate regions of the lung (proximal vs. distal) as well as methods to achieve better overall cell coverage. In this project, a novel cell seeding method using negative pressure was used to deliver cells to decellularized mouse lung airways. It was hypothesized that controllable fluid flow generated via negative pressure could direct cell distribution in site-specific areas within proximal and distal regions in the lung airways. Negative pressure opens the lung  airways and decreases the resistance to fluid flow during the seeding process. To analyze the results, the following image analysis techniques were used: 1) cell coverage heat map to demonstrating the cell distribution over the entire scaffold,  2) precise calculation of the area covered by cells and Extracellular matrix (ECM) surface area to measure the cell coverage efficiency and  3) counting cells within different airway sizes, to measure the distribution of the cells in distal and proximal sites. The preliminary qualitative observations demonstrate that this new method results in enhanced overall cell distribution and better distal and proximal coverage in comparison to state of the art, gravity perfusion cell seeding technique. Moreover, increasing the fluid flow during cell delivery appears to increase the delivery of the cells to distal sites whereas lower fluid flow results in more cells within proximal sites. This approach eventually can provide a practical tool to specifically target cells to different sites and will be potentially significant as the field is moving towards the use of pluripotent cell sources that will differentially respond to microenvironmental cues presented by the scaffold. Future work will provide a quantitative evaluation to assess the impact of the negative pressure fluid flow velocity on the airway re-epithelialization as well as optimize directed delivery of proximal and distal progenitor populations to distal and proximal sites in the lung airways.