Regeneration Process of an Autologous Tissue-Engineered Trachea (aTET) in a Rat Patch Tracheoplasty Model.

The treatment of long-tracheal lesion is difficult because there are currently no viable grafts for tracheal replacement. To solve this problem, we have developed an autologous Tissue-Engineered Trachea (aTET), which is made up of collagenous tissues and cartilage-like structures derived from rat chondrocytes. This graft induced successful long-term survival in a small-animal experiment in our previous study. In this study, we investigated the regeneration process of an aTET to attain reproducible success. We prepared an aTET by using a specially designed mold and performed patch tracheoplasty with an aTET. We assigned twenty-seven rats to three groups according to the three types of patch grafts used: aTET patches (the aTET group), fresh tracheal autograft patches (the Ag group), or polylactic acid and polycaprolactone copolymer sheets (the PPc group). In each group, gross and histological evaluations were performed at 1 month (n = 3), 3 months (n = 3), and 6 months (n = 3) after implantation. We obtained high survival rates in all groups, but only the PPc group attained thick tracheal walls with granular tissues and no tracheal regeneration. On the other hand, the aTET and Ag groups reproducibly achieved complete tracheal regeneration in 6 months. So, an aTET could be a promising candidate for tracheal regeneration grafts.

The effect of bioactivity of airway epithelial cells using methacrylated gelatin scaffold loaded with exosomes derived from bone marrow mesenchymal stem cells.

The current evidence provides support for the involvement of bone marrow mesenchymal stem cells (BMSCs) in the regulation of airway epithelial cells. However, a comprehensive understanding of the underlying biological mechanisms remains elusive. This study aimed to isolate and characterize BMSC-derived exosomes (BMSC-Exos) and epithelial cells (ECs) through primary culture. Subsequently, the impact of BMSC-Exos on ECs was assessed in vitro, and sequencing analysis was conducted to identify potential molecular mechanisms involved in these interactions. Finally, the efficacy of BMSC-Exos was evaluated in animal models in vivo. In this study, primary BMSCs and ECs were efficiently isolated and cultured, and high-purity Exos were obtained. Upon uptake of BMSC-Exos, ECs exhibited enhanced proliferation (p < .05), while migration showed no difference (p > .05). Notably, invasion demonstrated significant difference (p < .05). Sequencing analysis suggested that miR-21-5p may be the key molecule responsible for the effects of BMSC-Exos, potentially mediated through the MAPK or PI3k-Akt signaling pathway. The in vivo experiments showed that the presence of methacrylated gelatin (GelMA) loaded with BMSC-Exos in composite scaffold significantly enhanced epithelial crawling in the patches in comparison to the pure decellularized group. In conclusion, this scheme provides a solid theoretical foundation and novel insights for the research and clinical application of tracheal replacement in the field of tissue engineering.

Human tracheal transplantation: A systematic review of case reports.

BACKGROUND: Patients with long-segment airway stenosis not amenable to conventional surgery may benefit from tracheal transplantation. However, this procedure has been only anecdotally reported, and its indications, techniques, and outcomes have not been extensively reviewed. METHODS: We conducted a systematic Literature search to identify all original articles reporting attempts at tracheal transplantation in humans. RESULTS: Of 699 articles found by the initial search, 11 were included in the systematic review, describing 14 cases of tracheal transplantation. Patients underwent transplantation for benign stenosis in nine cases, and for malignancies in five cases. In 12 cases blood supply to the trachea was provided by wrapping the graft in a vascularized recipient's tissue, while in 2 cases the trachea was directly transplanted as a vascularized composite allograft. The transplantation procedure was aborted before orthotopic transplantation in two patients. Among the remaining 12 patients, there was 1 operative mortality, while 4 patients experienced complications. Immunosuppressants drugs were administered to the majority of patients postoperatively, and only one group of authors attempted their withdrawal, in five patients. At the end of follow-up, all 11 patients surviving the operation were alive, but 2 had a recurrent tracheal stenosis requiring an airway appliance for breathing. CONCLUSION: Human tracheal transplantation is still at an embryonic phase. Studies available in the Literature report different surgical techniques, and information on long-term outcomes is still limited. Future research is needed in order to understand the clinical value of this procedure.

Tracheal Replacement Techniques and Associated Mortality: A Systematic Review.

OBJECTIVE: Tracheal replacement is a crucial operation to enhance the quality of life for patients with extensive tracheal lesions. The most suitable surgical techniques for different clinical conditions remain a topic of debate. Through a reviewing of the relevant literature, this study investigated the association between surgical techniques and mortality rate. DATA SOURCES: Studies were collected from PubMed, Embase, the Web of Science, the Cochrane Center Register of Controlled Trials, and ClinicalTrials.gov. METHODS: This systematic review encompassed literature from the inception of each database to May 10, 2023, focusing on tracheal replacement for patients who underwent circumferential resection of the trachea or partial resection with preservation of the posterior membranous wall. Non-human and non-clinical studies were excluded. RESULTS: About 31 studies were included in the assessment comprising a combination of case reports and case series, and 118 patients underwent tracheal replacement through four underlying methodologies, including tracheal allotransplantation, autologous tissue reconstruction, bioprosthetic reconstruction, or tissue engineering surgery. Each modality exhibits unique advantages and disadvantages, leading to variable outcomes in clinical application. CONCLUSION: Tracheal replacement is challenging due to the absence of an ideal substitution or graft material. Despite limited clinical successes observed across various modalities, we believe autologous tissue reconstruction for tracheal replacement has the advantage of broadest indications, low rejection rate, and avoidance of immunosuppressive agents. Future research should focus on achieving tracheal replacement that preserves mucociliary clearance, lateral rigidity, and longitudinal flexibility. LEVEL OF EVIDENCE: NA Laryngoscope, 134:1517-1522, 2024.

Application of tissue engineering techniques in tracheal repair: a bibliometric study.

Transplantation of tissue-engineered trachea is an effective treatment for long-segment tracheal injury. This technology avoids problems associated with a lack of donor resources and immune rejection, generating an artificial trachea with good biocompatibility. To our knowledge, a systematic summary of basic and clinical research on tissue-engineered trachea in the last 20 years has not been conducted. Here, we analyzed the development trends of tissue-engineered trachea research by bibliometric means and outlined the future perspectives in this field. The Web of Science portal was selected as the data source. CiteSpace, VOSviewer, and the Bibliometric Online Analysis Platform were used to analyze the number of publications, journals, countries, institutions, authors, and keywords from 475 screened studies. Between 2000 and 2023, the number of published studies on tissue-engineered trachea has been increasing. Biomaterials published the largest number of papers. The United States and China have made the largest contributions to this field. University College London published the highest number of studies, and the most productive researcher was an Italian scholar, Paolo Macchiarini. However, close collaborations between various researchers and institutions from different countries were generally lacking. Despite this, keyword analysis showed that manufacturing methods for tracheal stents, hydrogel materials, and 3D bioprinting technology are current popular research topics. Our bibliometric study will help scientists in this field gain an in-depth understanding of the current research progress and development trends to guide their future work, and researchers in related fields will benefit from the introduction to transplantation methods of tissue-engineered trachea.

We conducted a comprehensive bibliometric analysis of tissue-engineered trachea.We systematically outlined the preparation methods and current development forms of tissue-engineered trachea.We predicted future tissue-engineered trachea research trends from the perspectives of countries, institutions, researchers, and popular research topics.

[The first allogenic tracheal transplantation in humans 45 years ago : Procedure, course, and outcome]. / Die erste allogene Trachealtransplantation beim Menschen vor 45 Jahren : Vorgehen, Verlauf und Ergebnis.

In November/December 1978, the first successful tracheal transplantation in humans was performed at the University ENT Clinic in Cologne by the then senior physicians Kurt G. Rose (later chief physician in Dortmund) and Klaus Sesterhenn (later chief physician in Duisburg). Director of the clinic at that time was Prof. Dr. Dr. Fritz Wustrow [10]. The immunological foundations and preliminary work were laid by Sesterhenn in the context of a total of 338 tracheal transplants in Lewis rats in the 1970s (details in the text). The first successful tracheal transplantation was performed on 18 November 1978 in a, then 19-year-old patient who had previously had a motorcycle accident. The donor organ was explanted in the University Hospital Essen and transplanted about 160 min later in the Cologne University ENT Clinic, first into a pocket of the right sternocleidomastoid muscle. The definitive transplantation took place on 06 December 1978. In the article, the circumstances at that time and the perioperative course in the Cologne University ENT Clinic are described by an eyewitness. The former patient is still well and without complications after more than four decades.

Partial decellularization eliminates immunogenicity in tracheal allografts.

There is currently no suitable autologous tissue to bridge large tracheal defects. As a result, no standard of care exists for long-segment tracheal reconstruction. Tissue engineering has the potential to create a scaffold from allografts or xenografts that can support neotissue regeneration identical to the native trachea. Recent advances in tissue engineering have led to the idea of partial decellularization that allows for the creation of tracheal scaffolds that supports tracheal epithelial formation while preserving mechanical properties. However, the ability of partial decellularization to eliminate graft immunogenicity remains unknown, and understanding the immunogenic properties of partially decellularized tracheal grafts (PDTG) is a critical step toward clinical translation. Here, we determined that tracheal allograft immunogenicity results in epithelial cell sloughing and replacement with dysplastic columnar epithelium and that partial decellularization creates grafts that are able to support an epithelium without histologic signs of rejection. Moreover, allograft implantation elicits CD8+ T-cell infiltration, a mediator of rejection, while PDTG did not. Hence, we establish that partial decellularization eliminates allograft immunogenicity while creating a scaffold for implantation that can support spatially appropriate airway regeneration.

Biomimetic in situ tracheal microvascularization for segmental tracheal reconstruction in one-step.

Formation of functional and perfusable vascular network is critical to ensure the long-term survival and functionality of the engineered tissue tracheae after transplantation. However, the greatest challenge in tracheal-replacement therapy is the promotion of tissue regeneration by rapid graft vascularization. Traditional prevascularization methods for tracheal grafts typically utilize omentum or muscle flap wrapping, which requires a second operation; vascularized segment tracheal orthotopic transplantation in one step remains difficult. This study proposes a method to construct a tissue-engineered tracheal graft, which directly forms the microvascular network after orthotopic transplantation in vivo. The focus of this study was the preparation of a hybrid tracheal graft that is non-immunogenic, has good biomechanical properties, supports cell proliferation, and quickly vascularizes. The results showed that vacuum-assisted decellularized trachea-polycaprolactone hybrid scaffold could match most of the above requirements as closely as possible. Furthermore, endothelial progenitor cells (EPCs) were extracted and used as vascularized seed cells and seeded on the surfaces of hybrid grafts before and during the tracheal orthotopic transplantation. The results showed that the microvascularized tracheal grafts formed maintained the survival of the recipient, showing a satisfactory therapeutic outcome. This is the first study to utilize EPCs for microvascular construction of long-segment trachea in one-step; the approach represents a promising method for microvascular tracheal reconstruction.

Hydrogel modification of 3D printing hybrid tracheal scaffold to construct an orthotopic transplantation.

OBJECTIVE: To evaluate the biological properties of modified 3D printing scaffold (PTS) and applied the hybrid graft for in situ transplantation. METHODS: PTS was prepared via 3D printing and modified by Pluronic F-127. Biocompatibility of the scaffold was examined in vitro to ascertain its benefit in attachment and proliferation of bone marrow mesenchymal stem cells (BMSCs). Moreover, a hybrid trachea was constructed by combining the modified PTS with decellularized matrix. Finally, two animal models of in situ transplantation were established, one for repairing tracheal local window-shape defects and the other for tracheal segmental replacement. RESULTS: The rough surface and chemical elements of the scaffold were improved after modification by Pluronic F-127. Results of BMSCs inoculation showed that the modified scaffold was beneficial to attachment and proliferation. The epithelial cells were seen crawling on and attaching to the patch, 30 days following prothetic surgery of the local tracheal defects. Furthermore, the advantages of the modified PTS and decellularized matrix were combined to generate a hybrid graft, which was subsequently applied to a tracheal segmental replacement model. CONCLUSION: Pluronic F-127-based modification generated a PTS with excellent biocompatibility. The modified scaffold has great potential in development of future therapies for tracheal replacement and reconstruction.

Bioinspired carbon monoxide delivery using artificial blood attenuates the progression of obliterative bronchiolitis via suppression of macrophage activation by IL-17A.

Carbon monoxide (CO) is expected to attenuate the progression of obliterative bronchiolitis (OB), which is a serious complication after lung transplantation. However, issues in terms of feasible exogenous CO supply, such as continuousness and safety, remain unsolved. Here, we applied nano red blood cells, namely hemoglobin vesicles (Hb-V), as a CO cargo based on the biomimetic concept and investigated the therapeutic potential of CO-loaded Hb-V on OB in orthotopic tracheal transplant model mice. The CO-loaded Hb-V was comprised of negatively charged liposomes encapsulating carbonylhemoglobin with a size of ca. 220 nm. The results of histological evaluation showed that allograft luminal occlusion and fibrosis were significantly ameliorated by treatment with CO-loaded Hb-V compared to treatment with saline, cyclosporine, and Hb-V. The therapeutic effects of CO-loaded Hb-V on OB were due to the suppression of M1 macrophage activation in tracheal allografts, resulting from decreased IL-17A production. Furthermore, the expression of TNF-α and TGF-ß in tracheal allografts was decreased by CO-loaded Hb-V treatment but not saline and Hb-V treatment, indicating that CO liberated from CO-loaded Hb-V inhibits epithelial-mesenchymal transition. These findings suggest that CO-loaded Hb-V exerts strong therapeutic efficacy against OB via the regulation of macrophage activation by IL-17A and TGF-ß-driven epithelial-mesenchymal transition.

Partial Decellularization for Segmental Tracheal Scaffold Tissue Engineering: A Preliminary Study in Rabbits.

In this study, we developed a new procedure for the rapid partial decellularization of the harvested trachea. Partial decellularization was performed using a combination of detergent and sonication to completely remove the epithelial layers outside of the cartilage ring. The post-decellularized tracheal segments were assessed with vital staining, which showed that the core cartilage cells remarkably remained intact while the cells outside of the cartilage were no longer viable. The ability of the decellularized tracheal segments to evade immune rejection was evaluated through heterotopic implantation of the segments into the chest muscle of rabbits without any immunosuppressive therapy, which demonstrated no evidence of severe rejection or tissue necrosis under H&E staining, as well as the mechanical stability under stress-pressure testing. Finally, orthotopic transplantation of partially decellularized trachea with no immunosuppression treatment resulted in 2 months of survival in two rabbits and one long-term survival (2 years) in one rabbit. Through evaluations of posttransplantation histology and endoscopy, we confirmed that our partial decellularization method could be a potential method of producing low-immunogenic cartilage scaffolds with viable, functional core cartilage cells that can achieve long-term survival after in vivo transplantation.

Role of CMV chemokine receptor M33 in airway graft rejection in a mouse transplant model.

BACKGROUND: Cytomegalovirus (CMV) infection is a risk factor for bronchiolitis obliterans (BO), one form of chronic lung allograft dysfunction (CLAD). The viral chemokine receptor M33 is essential for successful spread of murine CMV to host salivary glands. In the present study we investigated the impact of M33 on chronic airway rejection. METHODS: MHC I-mismatched tracheas of C·B10-H2b/LilMcdJ mice were transplanted into BALB/c (H2d) recipients and infected at different dates with wild type (WT) or M33-deleted (delM33) MCMV representing clinical settings of viral recipient (R)-donor (D)-serostatus: (D-/R+) or (D+/R-). Grafts were recovered for gene expression and histological / immunofluorescence analysis, respectively. RESULTS: Evaluations showed significantly increased signs of chronic rejection in WT-infected mice compared to uninfected allografts seen in lower epithelium/lamina propria-ratio (ELR) (ELR 0.46 ± 0.07 [WT post] vs. ELR 0.66 ± 0.10 [non-inf.]; p < 0.05). The rejection in delM33-infected groups was significantly reduced vs. WT-infected groups (0.67 ± 0.04 [delM33 post]; vs. WT post p < 0.05). Furthermore, decreased rejection was observed in WT pre-infected compared to post-infected groups (0.56 ± 0.08 [WT pre]; vs. WT post p < 0.05). CD8+ T cell infiltration was significantly higher in WT-post compared to the delM33 infected or non-infected allografts. CONCLUSIONS: These data support the role of the CMV in accelerating CLAD. The deletion of chemokine receptor M33 leads to attenuated rejection.

Deconstructing tissue engineered trachea: Assessing the role of synthetic scaffolds, segmental replacement and cell seeding on graft performance.

The ideal construct for tracheal replacement remains elusive in the management of long segment airway defects. Tissue engineered tracheal grafts (TETG) have been limited by the development of graft stenosis or collapse, infection, or lack of an epithelial lining. We applied a mouse model of orthotopic airway surgery to assess the impact of three critical barriers encountered in clinical applications: the scaffold, the extent of intervention, and the impact of cell seeding and characterized their impact on graft performance. First, synthetic tracheal scaffolds electrospun from polyethylene terephthalate / polyurethane (PET/PU) were orthotopically implanted in anterior tracheal defects of C57BL/6 mice. Scaffolds demonstrated complete coverage with ciliated respiratory epithelium by 2 weeks. Epithelial migration was accompanied by macrophage infiltration which persisted at long term (>6 weeks) time points. We then assessed the impact of segmental tracheal implantation using syngeneic trachea as a surrogate for the ideal tracheal replacement. Graft recovery involved local upregulation of epithelial progenitor populations and there was no evidence of graft stenosis or necrosis. Implantation of electrospun synthetic tracheal scaffold for segmental replacement resulted in respiratory distress and required euthanasia at an early time point. There was limited epithelial coverage of the scaffold with and without seeded bone marrow-derived mononuclear cells (BM-MNCs). We conclude that synthetic scaffolds support re-epithelialization in orthotopic patch implantation, syngeneic graft integration occurs with focal repair mechanisms, however epithelialization in segmental synthetic scaffolds is limited and is not influenced by cell seeding. STATEMENT OF SIGNIFICANCE: The life-threatening nature of long-segment tracheal defects has led to clinical use of tissue engineered tracheal grafts in the last decade for cases of compassionate use. However, the ideal tracheal reconstruction using tissue-engineered tracheal grafts (TETG) has not been clarified. We addressed the core challenges in tissue engineered tracheal replacement (re-epithelialization and graft patency) by defining the role of cell seeding with autologous bone marrow-derived mononuclear cells, the mechanism of respiratory epithelialization and proliferation, and the role of the inflammatory immune response in regeneration. This research will facilitate comprehensive understanding of cellular regeneration and neotissue formation on TETG, which will permit targeted therapies for accelerating re-epithelialization and attenuating stenosis in tissue engineered airway replacement.

Evaluation of Antigenicity of Components of Tracheal Allotransplant and Effect of Immunosuppressant Regime in a Rodent Model.

Background Tracheal transplantation seems to be the logical step in the process of reconstruction of the trachea following a long-segment resection, which is usually done to treat malignant disease or benign stenosis of the airway caused by a traumatic, congenital, inflammatory, or iatrogenic lesion. Immunosuppression following transplant is essential but not ideal after oncoresection. Methods The tracheal allografts, harvested from Sprague Dawley rats, were implanted in the Wistar strain rat. The harvested tracheal grafts were divided into groups and subgroups, based on the layers of trachea, method of decellularization, and immunosuppression. The antigenicity of different layers of trachea and the effect of various decellularization methods were studied within three time frames, that is, day 3, 9, and 15. Result On structural analysis, the day 3 and day 15 samples showed no meaningful comparison could be made, due to extensive neutrophil infiltration in all three layers. The day 9 tracheal grafts showed loss of epithelium, with no signs of regeneration in most of the allografts. The subepithelial lymphoid infiltration was found to be severe in nonimmunosuppressed allografts. The group in which both inner and outer layers were removed showed moderate-to-severe infiltrate of lymphoid cells in all the allografts, but there was no cartilage loss, irrespective of the method of decellularization. The irradiated specimens retained the cartilage but showed extensive ischemic damage. Conclusion Rat trachea is a good model for tracheal transplant research but not adequately sturdy to sustain mechanical debridement. Irradiation and chemical decellularization eliminates the immune response but causes intense ischemic damage. Out of the three time frames, day 9 seemed to be the best to study the immune response. To substantiate the results obtained in this study, the immunohistochemical study of the allografts is needed to be performed among a larger group of animals.

FK506 combined with GM6001 prevents tracheal obliteration in a mouse model of heterotopic tracheal transplantation.

BACKGROUND: Obliterative bronchiolitis (OB) is the major complication limiting the long-term survival of allografts after lung transplantation. In this study, we investigated the effect of tacrolimus (FK506) combined with GM6001，a matrix metalloproteinase (MMP) inhibitor， on the formation of OB using a mouse heterotopic tracheal transplantation model. METHODS: Syngeneic tracheal grafts were transplanted heterotopically from BALB/c mice to BALB/c mice. Allografts from C57BL/6 mice were transplanted to BALB/c mice. Isograft group, allograft group, allograft+FK506 group, allograft +GM6001 group and allograft+FK506 + GM6001 group was given respectively intraperitoneal injection of saline, saline, FK506, GM6001 and FK506 + GM6001 once a day. At 28 day after transplantation, OB incidence was determined by hematoxylin-eosin staining and the expressions of MMPs and cytokines were assessed using enzyme linked immunosorbent assay, immunohistochemical assays and western blot assay. RESULTS: The tracheal occlusion rates of isograft group, allograft group, allograft+FK506 group, allograft+GM6001 group and allograft+FK506 + GM6001 group were 0, 74.1 ±â€¯9.79%, 34.4 ±â€¯6.04%, 40.3 ±â€¯8.77% and 26.5 ±â€¯5.73% respectively. There were significant differences between the latter two groups (P < .001). The serum MMP-8 and MMP-9 levels of allograft group were significantly higher than those of isograft group (P < .05) and had no significant decrease when treated by FK506. The serum MMP-8 and MMP-9 levels of allograft+FK506 + GM6001 group were significantly lower than those of allograft+FK506 group (P < .05). MMP-8 and MMP-9 protein expression in the grafts of allograft+FK506 + GM6001 group were lower than those of allograft+FK506 group verified by immunohistochemical staining and western blotting. CONCLUSION: FK506 combined with GM6001 could alleviate tracheal obliteration in mouse heterotopic tracheal transplantation model, due to its inhibitory effect on MMPs.

Using a Three-Dimensional Collagen Matrix to Deliver Respiratory Progenitor Cells to Decellularized Trachea In Vivo.

IMPACT STATEMENT: This article describes a method for engrafting epithelial progenitor cells to a revascularized scaffold in a protective and supportive collagen-rich environment. This method has the potential to overcome two key limitations of existing grafting techniques as epithelial cells are protected from mechanical shear and the relatively hypoxic phase that occurs while grafts revascularize, offering the opportunity to provide epithelial cells to decellularized allografts at the point of implantation. Advances in this area will improve the safety and efficacy of bioengineered organ transplantation.

[Long-term oucomes of tracheal transplantation: success and unsolved problems]. / Otdalennyi rezul'tat transplantatsii trakhei: uspekh i nereshennye problemy.

AIM: To analyze long-term outcomes of tracheal transplantation. MATERIAL AND METHODS: There were 1128 patients with cicatricial tracheal stenosis who have been operated at the Petrovsky Russian Research Center for Surgery and the Sechenov First Moscow State Medical University for the period 1963-2015. RESULTS: Operations have become safer. Postoperative morbidity and mortality reduced from 41.4% (1963-1980) to 5.6% (2001-2015) and from 21.9% (1963-1980) to 0.5% (2001-2015), respectively. Tracheal transplantation was performed in 2 cases and fundamentally different tracheal structures were applied. Donor thyreotracheal complex with restored blood supply through thyroid vessels was used in the first case (2006). Perennial experimental trials preceded clinical application of this technique. In the second case (2010) we applied scientific results of foreign colleagues (cellular technologies and methods of regenerative medicine to create artificial trachea). Patients are still alive after 12 and 8 years, respectively. Restoration of blood supply of donor trachea is possible through thyroid collaterals. This technique is successful in long-term period. Tissue-engineered trachea cannot be considered true trachea due to no all tracheal components. However, such trachea provides air-conducting, evacuation and protective functions. Tracheomalacia requires further researches as one of the main problems of tracheal transplantation.

Transplantation of the decellularized tracheal allograft in animal model (rabbit).

BACKGROUND: It has been difficult to perform tracheal allotransplantation without immunosuppression. To determine whether decellularized trachea can be used in tracheal replacement, we evaluated the viability of decellularized tracheal allografts in a rabbit model of immunosuppressant-free transplantation. METHOD: Half allograft (Group 1, n = 7) was harvested from adult New Zealand white rabbits, subjected to a detergent-enzymatic method (containing sodium deoxycholate/DNase lavations) of decellularization for as many cycles as needed, and the other half was stored in phosphate-buffered saline at 4°C as a control (Group 2, n = 7). Bioengineered and control tracheas were then implanted in 14 age-matched rabbits. RESULTS: In Group 1 (decellularized), all rabbits survived, whereas in Group 2(control), all rabbits died of airway obstruction between 20 days and 45 days after operation. Histologically, the decellularized allografts displayed complete regeneration of epithelium and cartilage, but the fresh allografts showed inflammatory changes, no epithelium, and no cartilage. CONCLUSIONS: Complete regeneration of epithelium and cartilage tracheal rings occurred after the implantation of decellularized tracheal allografts without immunosuppression. We demonstrate that the decellularized process reduces the allogeneic response to the trachea. Therefore, we believe that the decellularized tracheal allograft is an excellent choice for tracheal replacement. To our knowledge, this is the first study to observe the long-term (1 year) prognosis of this transplanted trachea.