Lessons Learned from Various 3D-Printed Tracheal Grafts in an Extensive Porcine Model for De Novo Tracheal Regeneration.

Background: Tracheal implants using tissue-engineering and three-dimensional (3D) printing are promising, but challenges remain, including graft composition, anastomosis methods, and tracheal tissue regeneration. This study examines the effectiveness of various tracheal graft materials in a large animal model.

Methods: Thirty-eight tracheal surgeries were performed on a porcine large animal model, involving a 2 cm circumferential tracheal excision with end-to-end anastomosis. The grafts used included translucent plastic material crystal (n=16), silicone (n=8), and polycaprolactone (PCL, n=8). Non-absorbable (n=28) or absorbable (n=4) sutures were applied, and two animals received modified distal trachea anchoring using the strap muscle. Bronchoscopy and laser ablation were used to assess granulation tissue and graft patency in select cases. Postoperative complications, survival rates, and tissue regeneration outcomes were tracked.

Results: Operation times ranged from 91 to 126 minutes. Animals survived between 5 to 92 days, with 29 experiencing complications such as abdominal distress (n=15) and granulation tissue formation (n=18) after 7 days. Postoperative issues included wound infection (n=16), graft infection (n=7), and necrosis (n=14). Histology revealed regenerating tissue with chondrogenesis (n=8), adipogenesis (n=9), myogenesis (n=9), angiogenesis (n=6), glandogenesis (n=2), and epithelialization (n=2). Two PCL graft animals with strap muscle reinforcement survived longer, gaining 101 kg, with one showing heterotopic ossification.

Conclusions: The study highlights critical insights into graft material selection and integration with native tissue. PCL grafts demonstrated improved integration and tissue healing with biodegradable properties, supporting their potential for clinical use in tracheal implants.