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Objective We have developed a prosthesis that includes a collagen layer for tracheobronchial reconstruction and applied it in a canine model. In previous studies luminal epithelization remained partial or rather slow because of the early disintegration of the collagen layer. We have improved this type of prosthesis by coating the luminal surface with a biodegradable polymer, which serves to protect the collagen layer. The effect of the polymer coating on the epithelization of the luminal surface of the prosthesis was examined. Methods The main frame consisted of a polypropylene mesh tube, measuring 15 mm in inner diameter and 30 mm in length, with reinforcing rings. Collagen extracted from porcine skin was conjugated to this frame. The luminal surface was coated with a polymer, poly (L-lactic-acid-co-e-caprolactone). In 5 beagle dogs the left main bronchus was replaced with this prosthesis, periodic bronchoscopic observations were conducted, and microscopic evaluations were performed. Results All dogs survived until they were killed, except for 1 animal in which pneumonia developed, and this animal died at 13 months after replacement. None of the dogs showed adverse complications caused by the prosthesis. Bronchoscopic observations revealed that the polymer remained on the luminal surface for 2 weeks. The luminal surface in 4 dogs was completely covered with ciliated columnar epithelium or nonciliated squamous epithelium, and 90% epithelization was achieved in 1 dog. Conclusions The biodegradable polymer coating protected the collagen layer and promoted better epithelization. This improved epithelization on the luminal surface could therefore potentially increase the success rates in airway replacement with artificial prostheses.

Background: Carinal reconstruction by direct suturing is associated with a high mortality because high tension at the anastomosis can lead to tracheobronchial fistula. A new tracheal prosthesis was therefore designed for reconstruction of the tracheal bifurcation and applied for experimental carinal replacement in dogs. Methods: The main frame of the new prosthesis consists of a Y-shaped Marlex mesh tube (C.R. Bard, Inc, Billerica, Mass) reinforced with polypropylene spirals, to which collagen extracted from porcine skin is chemically conjugated to provide biocompatibility and airtightness. This conjugated collagen is composed of amorphous and sponge collagen layers. The tracheobronchial bifurcation was replaced with the prosthesis in 10 beagle dogs. Results: Eight dogs survived the postoperative period, and 2 dogs died within 4 days after the operation. Bronchoscopic examination revealed that the tracheal prosthesis was covered with smooth whitish tissue and that no stenosis or dehiscence was present in the 8 dogs even 6 months after the operation. Slight mesh exposure was recognized in 1 dog. Histologic examination revealed that approximately one half of the luminal surface was covered with ciliated columnar epithelium or nonciliated squamous epithelium. In the remaining lumen, especially in the middle portion of the prosthesis, connective tissue without epithelium was observed. Conclusions: These long-term results indicate that our bifurcated tracheal prosthesis can be used for reconstruction of the tracheobronchial bifurcation with long-term safety. (J Thorac Cardiovasc Surg 2000;119:1162-8)

Objective Epidermal growth factor–loaded gelatin microspheres were tested for potential to accelerate tracheal allograft reepithelialization. Methods Epidermal growth factor–loaded gelatin microspheres were prepared by optimal double-phase emulsified condensation polymerization. One hundred age-matched allogeneic mice were randomly allocated to local administration of 1 mg epidermal growth factor–loaded gelatin microspheres (containing 1 μg epidermal growth factor), 1 mg gelatin microspheres, 1 μg epidermal growth factor, or nothing (control, all groups n=25) during orthotopic transplant of C57BL/6 donor tracheal segments into BALB/c recipients without immunosuppressors. On days 7, 14, 21, 35, and 52 after transplant, 5 mice per group were killed and evaluated by histologic assessment and scanning electronic microscopy for reepithelialization and fibrosis of tracheal grafts. Results Mean diameter of gelatin microspheres was 107 μm. Microspheres could not be fully degraded until 35 days after transplant in vivo. On days 7, 14, and 21, epithelium score and ratio of lamina propria to tracheal cartilage were not statistically different between mice with epidermal growth factor–loaded gelatin microspheres and other groups. On days 35 and 52, however, epithelium score was higher and ratio of lamina propria to tracheal cartilage was lower in epidermal growth factor–loaded gelatin microsphere recipients; these mice also had almost complete differentiation of regenerated epithelium into ciliated columnar epithelium on days 35 and 52, earlier than in other groups. Conclusions Gelatin microspheres act as a functional vector for epidermal growth factor. Sustained local application of epidermal growth factor could accelerate reepithelialization of tracheal allografts.