Mechanical properties of de-epithelialized tracheal allografts

De-Epithelialized Viable Tracheal Allotransplantation Without Immunosuppressants: 5-Year Follow-Up

OBJECTIVE

Tracheal transplantation could be a better option for patients with long segmental laryngotracheal stenosis or defects, but the need for immunosuppressants limits its widespread use due to the antigenicity of the tracheal epithelium. Chemically treated or cryopreserved nonviable tracheal allografts have no immunogenicity but lead to necrosis and stenosis in long-term outcomes. The present report describes the 5-year outcomes of de-epithelialized viable tracheal allotransplantation without immunosuppressants in a patient with severe laryngotracheal stenosis.

METHODS

The recipient was a 47-year-old female with relapsing polychondritis affecting the larynx and cervical trachea and producing a 5 cm long stenosis that could not be repaired using resection and anastomosis. A tracheal allograft was obtained from a 45-year-old male donor and treated with a combination of 3% sodium dodecyl sulfate (SDS) and organ preservation solution for 138 hours. The allograft was revascularized by heterotopical implantation in the infrahyoid muscles of the recipient for 3 months and then transplantation to the laryngotracheal defect with a split-thickness skin graft sutured to the lumen and a silicon T-tube. No immunosuppressants were used postoperatively.

RESULTS

The allograft was de-epithelialized, and most of the cartilage rings remained viable after the treatment. The allograft was revascularized, viable, and mechanically stable after 3 months of heterotopic implantation. No apparent signs of rejection or destruction were observed. The T-tube was removed, and the internal lining of the allograft was repopulated 4 months after orthotopic transplantation, despite the skin graft necrotizing at 2 weeks. Endoscopy and computed tomography showed a patent airway 5 years after orthotopic transplantation. The patient was able to resume her usual quality of life.

CONCLUSION

The present study demonstrates that transplantation of the de-epithelialized viable tracheal allograft without immunosuppressants is safe and promising for patients with long laryngotracheal stenosis or defects, especially for those with malignant tumor resections.

Synergistic Effects of SDS and H2O2 Combinations on Tracheal Scaffold Development: An In Vitro Study Using Goat Trachea

Currently, a tissue-engineered trachea has been popularly used as a biological graft for tracheal replacement in severe respiratory diseases. In the development of tissue-engineered tracheal scaffolds, in vitro studies play a crucial role in allowing researchers to evaluate the efficacy and safety of scaffold designs and fabrication techniques before progressing to in vivo or clinical trials. This research involved the decellularization of goat trachea using SDS, H2O2, and their combinations. Various quantitative and qualitative assessments were performed, including histological analysis, immunohistochemistry, and biomechanical testing. Hematoxylin and eosin staining evaluated the cellular content, while safranin O-fast green and Masson's trichrome staining assessed glycosaminoglycan content and collagen distribution, respectively. The immunohistochemical analysis focused on detecting MHC-1 antigen presence. Tensile strength measurements were conducted to evaluate the biomechanical properties of the decellularized scaffolds. The results demonstrated that the combination of SDS and H2O2 for goat tracheal decellularization yielded scaffolds with minimal cellular remnants, low toxicity, preserved ECM, and high tensile strength and elasticity. This method holds promise for developing functional tracheal scaffolds to address severe respiratory diseases effectively.

Pre-epithelialized cryopreserved tracheal allograft for neo-trachea flap engineering

Background: Tracheal reconstruction presents a challenge because of the difficulty in maintaining the rigidity of the trachea to ensure an open lumen and in achieving an intact luminal lining that secretes mucus to protect against infection. Methods: On the basis of the finding that tracheal cartilage has immune privilege, researchers recently started subjecting tracheal allografts to "partial decellularization" (in which only the epithelium and its antigenicity are removed), rather than complete decellularization, to maintain the tracheal cartilage as an ideal scaffold for tracheal tissue engineering and reconstruction. In the present study, we combined a bioengineering approach and a cryopreservation technique to fabricate a neo-trachea using pre-epithelialized cryopreserved tracheal allograft (ReCTA). Results: Our findings in rat heterotopic and orthotopic implantation models confirmed that tracheal cartilage has sufficient mechanical properties to bear neck movement and compression; indicated that pre-epithelialization with respiratory epithelial cells can prevent fibrosis obliteration and maintain lumen/airway patency; and showed that a pedicled adipose tissue flap can be easily integrated with a tracheal construct to achieve neovascularization. Conclusion: ReCTA can be pre-epithelialized and pre-vascularized using a 2-stage bioengineering approach and thus provides a promising strategy for tracheal tissue engineering.

Partial Decellularized Scaffold Combined with Autologous Nasal Epithelial Cell Sheet for Tracheal Tissue Engineering

Decellularization has emerged as a potential solution for tracheal replacement. As a fully decellularized graft failed to achieve its purposes, the de-epithelialization partial decellularization protocol appeared to be a promising approach for fabricating scaffolds with preserved mechanical properties and few immune rejection responses after transplantation. Nevertheless, a lack of appropriate concurrent epithelialization treatment can lead to luminal stenosis of the transplant and impede its eventual success. To improve re-epithelialization, autologous nasal epithelial cell sheets generated by our cell sheet engineering platform were utilized in this study under an in vivo rabbit model. The newly created cell sheets have an intact and transplantable appearance, with their specific characteristics of airway epithelial origin being highly expressed upon histological and immunohistochemical analysis. Subsequently, those cell sheets were incorporated with a partially decellularized tracheal graft for autograft transplantation under tracheal partial resection models. The preliminary results two months post operation demonstrated that the transplanted patches appeared to be wholly integrated into the host trachea with adequate healing of the luminal surface, which was confirmed via endoscopic and histologic evaluations. The satisfactory result of this hybrid scaffold protocol could serve as a potential solution for tracheal reconstructions in the future.