Reinforced Electrospun Polycaprolactone Nanofibers for Tracheal Repair in an In Vivo Ovine Model

Abstract

Tracheal stenosis caused by congenital anomalies, tumors, trauma, or intubation-related damage can cause severe breathing issues, diminishing the quality of life, and potentially becoming fatal. Current treatment methods include laryngotracheal reconstruction or slide tracheoplasty. Laryngotracheal reconstruction utilizes rib cartilage harvested from the patient, requiring a second surgical site. Slide tracheoplasty involves a complex surgical procedure to splay open the trachea and reconnect both segments to widen the lumen. A clear need exists for new and innovative approaches that can be easily adopted by surgeons, and to avoid harvesting autologous tissue from the patient. This study evaluated the use of an electrospun patch, consisting of randomly layered polycaprolactone (PCL) nanofibers enveloping 3D-printed PCL rings, to create a mechanically robust, suturable, air-tight, and bioresorbable graft for the treatment of tracheal defects. The study design incorporated two distinct uses of PCL: electrospun fibers to promote tissue integration, while remaining air-tight when wet, and 3D-printed rings to hold the airway open and provide external support and protection during the healing process. Electrospun, reinforced tracheal patches were evaluated in an ovine model, in which all sheep survived for 10 weeks, although an overgrowth of fibrous tissue surrounding the patch was observed to significantly narrow the airway. Minimal tissue integration of the surrounding tissue and the electrospun fibers suggested the need for further improvement. Potential areas for further improvement include a faster degradation rate, agents to increase cellular adhesion, and/or an antibacterial coating to reduce the initial bacterial load.

Keywords: airway stenosis/reconstruction; trachea; wound healing.

FIG. 1.

(A) Electrospun polycaprolactone (PCL) tracheal patch after fabrication. (B) Tracheal patches were cut to the shape of the defect in the operating room. (C) A 2.5 by 1.5 cm elliptical shape incision was created in the center of each trachea. (D) Tracheal patches were sutured into place over the tracheal defect. Note the sutures placed around the PCL ring extensions. Color images available online at www.liebertpub.com/tea

FIG. 2.

Microcomputed tomography (μCT) reconstructions and analysis of control and treatment groups using Avizo software. (A) Visualized μCT reconstructions where gray coloring indicates the tissue of the trachea and blue coloring indicates the lumen space. All five experimental tracheas are shown, and one representative healthy control trachea is shown. Note the decrease in cross-sectional area at the apex of the stenosis. Scale bar = 25 mm. (B) Quantified lumen volume calculated from reconstructed μCT scans. α = significant difference in lumen volume (p < 0.05). (C) Minimum lumen cross-sectional area calculated from reconstructed μCT scans. β = significant difference in lumen cross-sectional area (p < 0.05). Values represent the mean ± standard deviation. n = 5. Color images available online at www.liebertpub.com/tea

FIG. 3.

Histological analysis of sheep tracheas after 10 weeks postsurgery for two representative samples from the experimental group and one representative sample from the healthy control group. Sections were taken in the transverse plane illustrated by the cross-section through the Avizo reconstruction. Sections were stained using hematoxylin and eosin (H&E), Masson's Trichrome (MT), and Verhoeff-Van Gieson (VG) stain to visualize tissue regeneration. Arrows indicate native cartilage rings of the trachea, and sections have been oriented such that the lumen is at the top of the image. Magnified images correspond to the small window with the same image identifier shown in the bottom left corner (1A–3C). Note fibrous tissue formation surrounding the electrospun scaffolds; however, the tissue did not integrate into the patch. Color images available online at www.liebertpub.com/tea