Transplant efficacy of pure 3D bio-printed PCL tracheal grafts in a porcine model

Tracheal transplantation remains a significant challenge due to structural complexity and essential function of the trachea in respiration. We subscribe to the theory of using 3D bio-printed grafts parallel to donor organs, orienting tracheal transplantation to circumvent oscillating the utility of graft options. Here, we aim to evaluate, in a porcine model, effectiveness of pure 3D-printed polycaprolactone (PCL) tracheal grafts. The experiment was originally designed to test the feasibility of bio-printed tracheal grafts as an exemplary paradigm. We applied tracheal transplantation in 8 large animals at 2-cm circumferential tracheal resection and end-to-end anastomosis using pure PCL grafts, with 2 cases including modified distal trachea anchoring with strap muscles. Neo-tissue growths included cartilage, muscle, fat, and glands. Furthermore, this burgeoning tissue germinated cartilage islands or templates, processing a complex array of chondrogenesis with gradation in outgrowth over the anastomosis entity. Post-implantation monitoring involved bronchoscopy and laser ablation to manage granulation tissue and ensure graft patency. We recorded complications, like wound infection, graft-tissue infection with dehiscence, and necrosis. Histological analyses of regenerative tissue alongside the graft revealed chondrogenesis, adipogenesis, myogenesis, angiogenesis, glando-genesis, and epithelialization, formulating the scenario of empirical graft implantation. Two long-term surviving animals had a significant weight gain and notable tissue regeneration, including intact cartilage formation. Such outcomes highlighted the potential of PCL as an effective graft material for promoting longer survival and convincing tissue repair, though further research is needed to translate findings to human applications.