# Bio-Printed PCL Tracheal Graft in a Large Animal Model: Reproducible Short-Segment Regeneration and Preliminary Upgraded Long-Segment Reconstruction

## TL;DR

This study explores 3D bioprinted tracheal grafts in pigs, showing successful short-segment regeneration and initial feasibility for longer segments.

## Contribution

The study demonstrates reproducible short-segment tracheal regeneration and provides preliminary insights into long-segment bioprinted grafts in a large animal model.

## Key findings

- Short-segment (2 cm) PCL tracheal grafts achieved reproducible survival exceeding three months with tissue regeneration.
- Histological analysis showed multi-lineage tissue formation, including cartilage, muscle, glands, and epithelium.
- Long-segment (≥4 cm) grafts were technically feasible but require further investigation for long-term success.

## Abstract

Three-dimensional (3D) bioprinting provides new options for airway reconstruction by enabling the fabrication of customizable, biodegradable scaffolds designed to support in situ tissue regeneration. Building on our established large-animal platform, in which two cm bioprinted tracheal grafts combined with refined surgical techniques and adjunctive laser intervention have achieved long-term survival exceeding three months, the present study aims to explore long-segment (≥four cm) tracheal transplantation. We evaluated the fabrication feasibility and regeneration patterns of extrusion-based 3D bioprinted polycaprolactone (PCL) tracheal grafts in a porcine model. The grafts were implanted via end-to-end anastomosis with adjunctive mechanical stabilization and followed by serial bronchoscopic surveillance, gross examination, and histological analysis. The two cm PCL tracheal grafts achieved reproducible survival exceeding three months when combined with refined surgical techniques, structured postoperative airway management, and optimized wound coverage. Histological analysis revealed multi-lineage tissue formation—including cartilage, muscle, glands, and epithelium—was observed. Cartilage regeneration followed a staged maturation process, compared to epithelial regeneration, although continuous by 12 weeks, remained developmentally immature. A single long-segment transplantation was explored in a single preliminary case, providing an initial technical observation of feasibility; however, definitive conclusions regarding long-term survival or regeneration cannot be drawn. These findings further characterize regenerative responses in a large-animal model and highlight critical translational barriers—fabrication constraints, airway biomechanics, and delayed epithelial maturation—that require systematic investigation before long-segment tracheal reconstruction can advance toward clinical application.