) Although receiving significantly growing attention, reconstruction of long-segment tracheal defect still remains challenging in many non-malignant tracheal diseases. Transplantation of trachea can be exceptionally difficult given the recalcitrant restoration of blood supply to the graft. Tissue-engineering approaches, on the other hand, have been met with failure due to the complex anatomy and functions of trachea. To date, engineered solutions, where either synthetic or decellularized scaffolds are used, have still been confronted with a variety of insurmountable hurdles, including: 1) inadequate length and diameter, 2) incomplete endoluminal healing (epithelialization) that result in perforations/air leaks/strictures/infection, 3) absence of glandular function, 4) limited vascularity, 5) inadequate mechanical properties to accommodate luminal pressure changes, and 6) inability to grow with the patient. Here we propose a new design of a hybrid trachea that integrates the complementary strengths from autologous grafting, allogeneic tissue niches, and synthetic scaffolding to form a novel construct.
We aim to use the hybrid trachea to address simultaneously all these hurdles. The unique helical design of the hybrid trachea enables the construct with increased flexibility to adapt to desired dimensions, avoiding complications seen with incompatible transplants. To test the concept and preliminary efficacy of the designed hybrid, two overarching aims have been developed. The first objective of the project is to utilize an image-based technique we have developed to design the structure of a synthetic scaffold as the spiral backbone that will be fabricated with polycaprolactone by 3-D printing. The scaffold will then be coated with decellularized, morselized tracheal matrix to form a bio-inspired substrate. In the meantime, a decellularized trachea allograft will be prepared as a complimentary helix to the backbone scaffold. Both components will then be assembled into a tracheal construct for the following implantation. The final assembly will be mechanically assessed to ensure the initial structural integrity. The second objective is to test the efficacy of the designed hybrid trachea in a porcine model with complete tracheal resection. This will be performed with the two-staged homograft technique that has been shown to retain functional cilia and mucin production in our previous work in a rabbit model. Reconstructed tracheas will be harvested and assessed for restoration of structure and functions. Although these aims have an enormous potential to address the major hurdles identified in long-segment tracheal reconstruction, the idea also has a high level of risk with the uncertainty for how both synthetic and naturally derived components can be integrated in an optimal way to facilitate the tracheal reconstruction. We hope to utilize this unique funding opportunity to explore the development phase of the new hybrid trachea. If successful, the venture may lead to the future phase of pursuing larger scale funding support through Bioengineering Research Grants.
(Lay Summary) Currently there are no reliable clinical options for complete tracheal replacement in patients with end-stage tracheal disease. This application seeks to develop a newly designed tracheal hybrid that combines the strengths of native, decellularized trachea and our capacity to create 3D printed trachea. The end goal is to create a bio-inspired trachea with the structure and function of uninjured trachea.
