Successful tracheal replacement in humans using autologous tissues: an 8-year experience. Ann Thorac Surg. 2013;96:1146-1155. [PMID: 23998399 DOI: 10.1016/j.athoracsur.2013.05.073]

Rat Tracheal Cartilage Regeneration Using Mesenchymal Stem Cells Derived From Human iPS Cells

Tracheal cartilage provides structural support to the airways to enable breathing. However, it can become damaged or impaired, sometimes requiring surgical resection and reconstruction. Previously, we clinically applied an artificial trachea composed of a polypropylene mesh and collagen sponge, with a favorable postoperative course. However, the artificial trachea presents a limitation, as the mesh is not biodegradable and cannot be used in pediatric patients. Compared to a polypropylene mesh, regenerated cartilage represents an ideal material for reconstruction of the damaged trachea. The use of mesenchymal stem cells (MSCs) as a source for cartilage regeneration has gained widespread acceptance, but challenges such as the invasiveness of harvesting and limited cell supply persist. Therefore, we focused on the potential of human-induced pluripotent stem cell (hiPSC)-derived mesenchymal stem cells (iMSCs) for tracheal cartilage regeneration. In this study, we aimed to regenerate tracheal cartilage on an artificial trachea as a preliminary step to replace the polypropylene mesh. iMSCs were induced from hiPSCs through neural crest cells and transplanted with a polypropylene mesh covered with a collagen sponge into the damaged tracheal cartilage in immunodeficient rats. Human nuclear antigen (HNA)-positive cells were observed in all six rats at 4 weeks and in six out of seven rats at 12 weeks after transplantation, indicating that transplanted iMSCs survived within the tracheal cartilage defects of rats. The HNA-positive cells coexpressed SOX9, and type II collagen was detected around HNA-positive cells in four of six rats at 4 weeks and in three of seven rats at 12 weeks after transplantation, reflecting cartilage-like tissue regeneration. These results indicate that the transplanted iMSCs could differentiate into chondrogenic cells and promote tracheal cartilage regeneration. iMSC transplantation thus represents a promising approach for human tracheal reconstruction.

Challenges and Opportunities in Developing Tracheal Substitutes for the Recovery of Long-Segment Defects

Tracheal resection and reconstruction procedures are necessary when stenosis, tracheomalacia, tumors, vascular lesions, or tracheal injury cause a tracheal blockage. Replacement with a tracheal substitute is often recommended when the trauma exceeds 50% of the total length of the trachea in adults and 30% in children. Recently, tissue engineering and other advanced techniques have shown promise in fabricating biocompatible tracheal substitutes with physical, morphological, biomechanical, and biological characteristics similar to native trachea. Different polymers and biometals are explored. Even with limited success with tissue-engineered grafts in clinical settings, complete healing of tracheal defects remains a substantial challenge due to low mechanical strength and durability of the graft materials, inadequate re-epithelialization and vascularization, and restenosis. This review has covered a range of reconstructive and regenerative techniques, design criteria, the use of bioprostheses and synthetic grafts for the recovery of tracheal defects, as well as the traditional and cutting-edge methods of their fabrication, surface modification for increased immuno- or biocompatibility, and associated challenges.

Tissue-engineered tracheal implants: Advancements, challenges, and clinical considerations

Restoration of extensive tracheal damage remains a significant challenge in respiratory medicine, particularly in instances stemming from conditions like infection, congenital anomalies, or stenosis. The trachea, an essential element of the lower respiratory tract, constitutes a fibrocartilaginous tube spanning approximately 10-12 cm in length. It is characterized by 18 ± 2 tracheal cartilages distributed anterolaterally with the dynamic trachealis muscle located posteriorly. While tracheotomy is a common approach for patients with short-length defects, situations requiring replacement arise when the extent of lesion exceeds 1/2 of the length in adults (or 1/3 in children). Tissue engineering (TE) holds promise in developing biocompatible airway grafts for addressing challenges in tracheal regeneration. Despite the potential, the extensive clinical application of tissue-engineered tracheal substitutes encounters obstacles, including insufficient revascularization, inadequate re-epithelialization, suboptimal mechanical properties, and insufficient durability. These limitations have led to limited success in implementing tissue-engineered tracheal implants in clinical settings. This review provides a comprehensive exploration of historical attempts and lessons learned in the field of tracheal TE, contextualizing the clinical prerequisites and vital criteria for effective tracheal grafts. The manufacturing approaches employed in TE, along with the clinical application of both tissue-engineered and non-tissue-engineered approaches for tracheal reconstruction, are discussed in detail. By offering a holistic view on TE substitutes and their implications for the clinical management of long-segment tracheal lesions, this review aims to contribute to the understanding and advancement of strategies in this critical area of respiratory medicine.

Full circumferential human tracheal replacement: a systematic review

Full Circumferential Tracheal Replacement (FCTR) is a surgical challenge, indicated in rare cases of extensive tracheal resection, with no consensus on surgical technique or materials. A systematic review according to PRISMA guidelines was carried out from 2000 to 2022 to identify cases of FCTR, to compare surgical indications, the nature of the tracheal substitutes and their immunological characteristics, surgical replacement techniques and vascularization. Thirty-seven patients, including five children, underwent FCTR surgery using 4 different techniques: thyrotracheal complex allograft (n = 2), aorta (n = 12), autologous surgical reconstruction (n = 19), tissue-engineered decellularized trachea (n = 4). The mean follow-up was 4 years. Of the 15 deceased patients, 10 died of the progression of the initial pathology. For the majority of the teams, particular care was given to the vascularization of the substitute, in order to guarantee long-term biointegration. This included either direct vascularization via vascular anastomosis, or an indirect technique involving envelopment of the avascular substitute in a richly vascularized tissue. Stent placement was standard, except for autologous surgical reconstructions where tracheal caliber was stable. Internal stents were frequently complicated by granulation and stenosis. Although epithelial coverage is essential to limit endoluminal proliferation and act as a barrier, fully functional ciliated airway epithelium did not seem to be necessary. In order to facilitate future comparisons, a standardized clinical trial, respecting regulatory constraints, including routine follow-up with tracheal biomechanics assessment and scheduled biopsies could be proposed. It would help collecting information such as dynamics and mechanisms of tracheal bio-integration and regeneration.

Dynamic flow for efficient partial decellularization of tracheal grafts: A preliminary rabbit study

Objective

Bioengineered tracheal grafts are a potential solution for the repair of long-segment tracheal defects. A recent advancement is partially decellularized tracheal grafts (PDTGs) which enable regeneration of host epithelium and retain viable donor chondrocytes for hypothesized benefits to mechanical properties. We propose a novel and tunable 3D-printed bioreactor for creating large animal PDTG that brings this technology closer to the bedside.

Methods

Conventional agitated immersion with surfactant and enzymatic activity was used to partially decellularize New Zealand white rabbit (Oryctolagus cuniculus) tracheal segments (n = 3). In parallel, tracheal segments (n = 3) were decellularized in the bioreactor with continuous extraluminal flow of medium and alternating intraluminal flow of surfactant and medium. Unprocessed tracheal segments (n = 3) were also collected as a control. The grafts were assessed using the H&E stain, tissue DNA content, live/dead assay, Masson's trichrome stain, and mechanical testing.

Results

Conventional processing required 10 h to achieve decellularization of the epithelium and submucosa with poor chondrocyte viability and mechanical strength. Using the bioreactor reduced processing time by 6 h and resulted in chondrocyte viability and mechanical strength similar to that of native trachea.

Conclusion

Large animal PDTG created using our novel 3D printed bioreactor is a promising approach to efficiently produce tracheal grafts. The bioreactor offers flexibility and adjustability favorable to creating PDTG for clinical research and use. Future research includes optimizing flow conditions and transplantation to assess post-implant regeneration and mechanical properties.

Level of Evidence

NA.

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.

Extended autologous tracheal replacement by a novel pedicled thoraco-chondro-costal flap: a cadaveric proof of concept

OBJECTIVES

Our aim was to report an anatomic model of an autologous flap based on the internal thoracic blood supply: the pedicled thoraco-chondro-costal flap; and establish the feasibility of various types of extended tracheal replacement with this novel flap, according to a newly proposed topographic classification.

METHODS

In a cadaveric model, a cervicotomy combined with median sternotomy was performed. The incision was extended laterally to expose the chest wall. The internal thoracic pedicle was freed from its origin down to the upper limit of the delineated flap to be elevated. The perichondria and adjacent periostea were incised longitudinally to remove cartilages and adjacent rib segments, preserving perichondria and periostea. A full-thickness quadrangular chest wall flap pedicled on internal thoracic vessels was then elevated and shaped into a neo conduit to replace the trachea with the pleura as an inner lining.

RESULTS

Various types of extended non-circumferential and full-circumferential tracheal replacements were achieved with this composite flap. No anastomosis tension was noticed despite the absence of release manoeuvres.

CONCLUSIONS

This model could represent a suitable autologous tracheal substitute, which is long, longitudinally flexible and eventually transversely rigid. No microsurgical vascular anastomoses are required. The technique is reproducible. The perichondria and periostea would regenerate vascularized neo-cartilaginous rings, potentially decreasing the need for long-term stenting. The inner pleural lining could potentially transform into ciliated epithelium as shown in previous preclinical studies.

Robot-Assisted Correction of a Supra-Long Tracheal Stenosis Using C-Type Nickel-Titanium Alloy Exterior Stenting and Suspension Fixation Technique: A Case Report

T-tubes and airway stents are commonly used but have limited effectiveness and frequent complications. A 50-year-old male patient presented with severe tracheal stenosis, affecting an 8.7 cm length of the airway. We employed an innovative approach known as external suspension fixation of tracheal stent using robotic assistance. This method involves surgically attaching the stent to the exterior of the trachea to provide support and stabilize the softened or collapsed tracheal segments. We designed a C-shaped nickel-titanium alloy exterior stent and successfully fixed it using robotic assistance. This intervention effectively restored tracheal function and led to a favorable postoperative recovery. The technique does not affect tracheal membrane function or airway mucociliary clearance. It could potentially be considered as a new option for treating long-segment benign tracheal softening or collapse.

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.

External Esophageal Stenting Technique in Palliation for Tracheal Agenesis in a Case of Esophageal Lung: A Lesson Learned from the Experience for Tracheomalacia

Tracheal agenesis (TA) is a rare congenital anomaly with an incidence of 1 per 50,000 newborns. It appears at birth with severe respiratory distress, cyanosis, and inaudible crying. Prompt esophageal intubation and long-term management of the esophageal airway are essential to overcome this catastrophic condition. In the long-term management, external stenting of the esophageal airway has been reported as promising to support the fragile esophageal wall; this technique was taken from the surgery for tracheomalacia. We experienced a case of an infant with tracheal agenesis whose respiratory status was stabilized after external esophageal stenting. The stenting was performed based on a lesson learned in the extensive experience in the surgical treatment for tracheomalacia, and the surgical techniques for successful stenting are herein described.

Evaluation of a decellularized bronchial patch transplant in a porcine model

Biological scaffolds for airway reconstruction are an important clinical need and have been extensively investigated experimentally and clinically, but without uniform success. In this study, we evaluated the use of a decellularized bronchus graft for airway reconstruction. Decellularized left bronchi were procured from decellularized porcine lungs and utilized as grafts for airway patch transplantation. A tracheal window was created and the decellularized bronchus was transplanted into the defect in a porcine model. Animals were euthanized at 7 days, 1 month, and 2 months post-operatively. Histological analysis, immunohistochemistry, scanning electron microscopy, and strength tests were conducted in order to evaluate epithelialization, inflammation, and physical strength of the graft. All pigs recovered from general anesthesia and survived without airway obstruction until the planned euthanasia timepoint. Histological and electron microscopy analyses revealed that the decellularized bronchus graft was well integrated with native tissue and covered by an epithelial layer at 1 month. Immunostaining of the decellularized bronchus graft was positive for CD31 and no difference was observed with immune markers (CD3, CD11b, myeloperoxidase) at two months. Although not significant, tensile strength was decreased after one month, but recovered by two months. Decellularized bronchial grafts show promising results for airway patch reconstruction in a porcine model. Revascularization and re-epithelialization were observed and the immunological reaction was comparable with the autografts. This approach is clinically relevant and could potentially be utilized for future applications for tracheal replacement.

Anastomotic stenosis of bioengineered trachea grafts is driven by transforming growth factor β1-induced signaling, proinflammatory macrophages, and delayed epithelialization

Objective

Anastomotic stenosis caused by hypertrophic granulation tissue often develops in response to orthotopically implanted bioengineered tracheal grafts. To determine mechanisms responsible for the development and persistence of this granulation tissue, we looked for changes in gene expression from tissue specimens from the graft-native interface.

Methods

RNA was isolated from paraffin-embedded tissue samples of the anastomotic sites of orthotopically implanted bioengineered tracheal grafts of 9 animals. Tissue samples were binned into 3 groups based on degree of stenosis: no stenosis (<5%), mild stenosis (25%-50%), and moderate and severe stenosis (≥75%). Sections of healthy trachea tissue were used as control. The expression levels of ∼200 genes related to wound healing, plus several endogenous controls, were measured with a pathway-focused predesigned primer array.

Results

Expression of ARG2, IL4, RPL13 A, TGFBR3, and EGFR decreased, whereas expression of RUNX2 was increased in stenotic wounds compared with nonstenotic tissue. Based on the cell types present in the trachea and wound healing, this expression profile indicates a lack of M2 anti-inflammatory macrophages, absent epithelial cells, and transforming growth factor β1-induced signaling.

Conclusions

These findings represent a significant step for tracheal tissue engineering by identifying several key mechanisms present in stenotic granulation tissue. Further research must be conducted to determine what modifications of the graft substrate and which coadministered therapeutics can be used to prevent the development of hypertrophic granulation tissue.

Tracheal Transection After Prolonged Intubation and Tracheostomy: A Case Report

Tracheal transection is a rare, life-threatening complication after tracheal injury. Most commonly, tracheal transection presents after blunt trauma, but iatrogenic tracheal transection after tracheotomy has not been well described. Here, we present a case without a history of trauma that presented with signs of symptoms of tracheal stenosis. She was taken to the operating room for tracheal resection and anastomosis and was incidentally found to have a complete tracheal transection intraoperatively.

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.

Laryngotracheal Reconstruction for Subglottic and Tracheal Stenosis

Laryngotracheal stenosis is the common endpoint for any process that results in the narrowing of the airway at the level of the glottis, subglottis, or trachea. Although endoscopic procedures are effective in opening the airway lumen, open resection and reconstruction can be necessary to reconstitute a functional airway. When resection and anastomosis are insufficient due to extensive length or location of the stenosis, autologous grafts can be used to expand the airway. Future directions in airway reconstruction include tissue engineering and allotransplantation.

Preclinical and clinical orthotopic transplantation of decellularized/engineered tracheal scaffolds: A systematic literature review

Severe tracheal injuries that cannot be managed by mobilization and end-to-end anastomosis represent an unmet clinical need and an urgent challenge to face in surgical practice; within this scenario, decellularized scaffolds (eventually bioengineered) are currently a tempting option among tissue engineered substitutes. The success of a decellularized trachea is expression of a balanced approach in cells removal while preserving the extracellular matrix (ECM) architecture/mechanical properties. Revising the literature, many Authors report about different methods for acellular tracheal ECMs development; however, only few of them verified the devices effectiveness by an orthotopic implant in animal models of disease. To support translational medicine in this field, here we provide a systematic review on studies recurring to decellularized/bioengineered tracheas implantation. After describing the specific methodological aspects, orthotopic implant results are verified. Furtherly, the only three clinical cases of compassionate use of tissue engineered tracheas are reported with a focus on outcomes.

Airway replacement using stented aortic matrices: Long-term follow-up and results of the TRITON-01 study in 35 adult patients

Over the past 25 years, we have demonstrated the feasibility of airway bioengineering using stented aortic matrices experimentally then in a first-in-human trial (n = 13). The present TRITON-01 study analyzed all the patients who had airway replacement at our center to confirm that this innovative approach can be now used as usual care. For each patient, the following data were prospectively collected: postoperative mortality and morbidity, late airway complications, stent removal and status at last follow-up on November 2, 2021. From October 2009 to October 2021, 35 patients had airway replacement for malignant (n = 29) or benign (n = 6) lesions. The 30-day postoperative mortality and morbidity rates were 2.9% (n = 1/35) and 22.9% (n = 8/35) respectively. At a median follow-up of 29.5 months (range 1-133 months), 27 patients were alive. There have been no deaths directly related to the implanted bioprosthesis. Eighteen patients (52.9%) had stent-related granulomas requiring a bronchoscopic treatment. Ten among 35 patients (28.6%) achieved a stent free survival. The actuarial 2- and 5-year survival rates (Kaplan-Meier estimates) were respectively 88% and 75%. The TRITON-01 study confirmed that airway replacement using stented aortic matrices can be proposed as usual care at our center. Clinicaltrials.gov Identifier: NCT04263129.

Novel Therapy for Acquired Tracheomalacia with a Tissue-Engineered Extraluminal Tracheal Splint and Autologous Mesenchymal-Derived Chondrocytes

Introduction Acquired tracheomalacia (ATM) is characterized by a loss of structural strength of the tracheal framework, resulting in airway collapse during breathing. Near half of the patients undergoing prolonged invasive mechanical ventilation will suffer tracheal lesions. Treatment for ATM includes external splinting with rib grafts, prosthetic materials, and tracheal resection. Failure in the use of prosthetic materials has made reconsidering natural origin scaffolds and tissue engineering as a suitable alternative.

Objective To restore adequate airway patency in an ovine model with surgically-induced ATM employing a tissue-engineered extraluminal tracheal splint (TE-ETS).

Methods In the present prospective pilot study, tracheal rings were partially resected to induce airway collapse in 16 Suffolk sheep (Ovis aries). The TE-ETS was developed with autologous mesenchymal-derived chondrocytes and allogenic decellularized tracheal segments and was implanted above debilitated tracheal rings. The animals were followed-up at 8, 12, and 16 weeks and at 1-year postinsertion. Flexible tracheoscopies were performed at each stage. After sacrifice, a histopathological study of the trachea and the splint were performed.

Results The TE-ETS prevented airway collapse for 16 weeks and up to 1-year postinsertion. Tracheoscopies revealed a noncollapsing airway during inspiration. Histopathological analyses showed the organization of mesenchymal-derived chondrocytes in lacunae, the proliferation of blood vessels, and recovery of epithelial tissue subjacent to the splint. Splints without autologous cells did not prevent airway collapse.

Conclusion It is possible to treat acquired tracheomalacia with TE-ETS without further surgical removal since it undergoes physiological degradation. The present study supports the development of tissue-engineered tracheal substitutes for airway disease.

Skin-derived epithelial lining facilitates orthotopic tracheal transplantation by protecting the tracheal cartilage and inhibiting granulation hyperplasia

Long-segment tracheal defects caused by tumours, inflammation or trauma can cause serious damage to the quality of life of patients. Although many novel neotracheas have been constructed, the therapeutic effect of orthotopic transplantation was compromised mainly because of the lack of an epithelial lining in those neotracheas. In this study, we aimed to investigate the therapeutic function of skin-derived epithelial lining for orthotopic tracheal transplantation. Strips of auricular cartilage with fixed interval were interrupted sutured on a silicone tube to mimic the cartilage rings of the native trachea. Neotrachea in the with epithelium group retained the unilateral skin as the epithelial lining in the lumen, whereas the neotrachea in the without epithelium group consisted solely of cartilage strips. After revascularized in the sternohyoid muscle, 2-cm-long tracheal defects were made and were reconstructed using these neotracheas. Our results showed that the skin-derived epithelial lining simultaneously protected the engineered tracheal cartilage and inhibited granulation hyperplasia in the tracheal lumen; further, compared with the without epithelium group, the group with epithelium showed a marked improvement in the tracheal lumen patency and the survival rate of rabbits. Our study provides a critical cue for improvements in the repair of tracheal defects via skin-derived epithelial lining and may significantly advance the clinical translation of tissue-engineered trachea.

Enhancing Stem Cell-Based Therapeutic Potential by Combining Various Bioengineering Technologies

Stem cell-based therapeutics have gained tremendous attention in recent years due to their wide range of applications in various degenerative diseases, injuries, and other health-related conditions. Therapeutically effective bone marrow stem cells, cord blood- or adipose tissue-derived mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and more recently, induced pluripotent stem cells (iPSCs) have been widely reported in many preclinical and clinical studies with some promising results. However, these stem cell-only transplantation strategies are hindered by the harsh microenvironment, limited cell viability, and poor retention of transplanted cells at the sites of injury. In fact, a number of studies have reported that less than 5% of the transplanted cells are retained at the site of injury on the first day after transplantation, suggesting extremely low (<1%) viability of transplanted cells. In this context, 3D porous or fibrous national polymers (collagen, fibrin, hyaluronic acid, and chitosan)-based scaffold with appropriate mechanical features and biocompatibility can be used to overcome various limitations of stem cell-only transplantation by supporting their adhesion, survival, proliferation, and differentiation as well as providing elegant 3-dimensional (3D) tissue microenvironment. Therefore, stem cell-based tissue engineering using natural or synthetic biomimetics provides novel clinical and therapeutic opportunities for a number of degenerative diseases or tissue injury. Here, we summarized recent studies involving various types of stem cell-based tissue-engineering strategies for different degenerative diseases. We also reviewed recent studies for preclinical and clinical use of stem cell-based scaffolds and various optimization strategies.

The Growing Medical Need for Tracheal Replacement: Reconstructive Strategies Should Overcome Their Limits

Breathing, being predominantly an automatic action, is often taken for granted. However, respiratory diseases affect millions of people globally, emerging as one of the major causes of disability and death overall. Among the respiratory dysfunctions, tracheal alterations have always represented a primary challenge for clinicians, biologists, and engineers. Indeed, in the case of wide structural alterations involving more than 50% of the tracheal length in adults or 30% in children, the available medical treatments are ineffective or inapplicable. So far, a plethora of reconstructive approaches have been proposed and clinically applied to face this growing, unmet medical need. Unfortunately, none of them has become a well-established and routinely applied clinical procedure to date. This review summarizes the main clinical reconstructive attempts and classifies them as non-tissue engineering and tissue engineering strategies. The analysis of the achievements and the main difficulties that still hinder this field, together with the evaluation of the forefront preclinical experiences in tracheal repair/replacement, is functional to promote a safer and more effective clinical translation in the near future.

Tissue Engineering for Tracheal Replacement: Strategies and Challenges

The critical feature in trachea replacement is to provide a hollow cylindrical framework that is laterally stable and longitudinally flexible, facilitating cartilage and epithelial tissue formation. Despite advanced techniques and sources of materials used, most inherent challenges are related to the complexity of its anatomy. Limited blood supply leads to insufficient regenerative capacity for cartilage and epithelium. Natural and synthetic scaffolds, different types of cells, and growth factors are part of tissue engineering approaches with varying outcomes. Pre-vascularization remains one of the crucial factors to expedite the regenerative process in tracheal reconstruction. This review discusses the challenges and strategies used in tracheal tissue engineering, focusing on scaffold implantation in clinical and preclinical studies conducted in recent decades.

Biomimetic Trachea Engineering via a Modular Ring Strategy Based on Bone-Marrow Stem Cells and Atelocollagen for Use in Extensive Tracheal Reconstruction

The fabrication of biomimetic tracheas with a architecture of cartilaginous rings alternately interspersed between vascularized fibrous tissue (CRVFT) has the potential to perfectly recapitulate the normal tracheal structure and function. Herein, the development of a customized chondroitin-sulfate-incorporating type-II atelocollagen (COL II/CS) scaffold with excellent chondrogenic capacity and a type-I atelocollagen (COL I) scaffold to facilitate the formation of vascularized fibrous tissue is described. An efficient modular ring strategy is then adopted to develop a CRVFT-based biomimetic trachea. The in vitro engineering of cartilaginous rings is achieved via the recellularization of ring-shaped COL II/CS scaffolds using bone marrow stem cells as a mimetic for native cartilaginous ring tissue. A CRVFT-based trachea with biomimetic mechanical properties, composed of bionic biochemical components, is additionally successfully generated in vivo via the alternating stacking of cartilaginous rings and ring-shaped COL I scaffolds on a silicone pipe. The resultant biomimetic trachea with pedicled muscular flaps is used for extensive tracheal reconstruction and exhibits satisfactory therapeutic outcomes with structural and functional properties similar to those of native trachea. This is the first study to utilize stem cells for long-segmental tracheal cartilaginous regeneration and this represents a promising method for extensive tracheal reconstruction.

Three-Dimensional Printing Strategies for Irregularly Shaped Cartilage Tissue Engineering: Current State and Challenges

Although there have been remarkable advances in cartilage tissue engineering, construction of irregularly shaped cartilage, including auricular, nasal, tracheal, and meniscus cartilages, remains challenging because of the difficulty in reproducing its precise structure and specific function. Among the advanced fabrication methods, three-dimensional (3D) printing technology offers great potential for achieving shape imitation and bionic performance in cartilage tissue engineering. This review discusses requirements for 3D printing of various irregularly shaped cartilage tissues, as well as selection of appropriate printing materials and seed cells. Current advances in 3D printing of irregularly shaped cartilage are also highlighted. Finally, developments in various types of cartilage tissue are described. This review is intended to provide guidance for future research in tissue engineering of irregularly shaped cartilage.

Development and clinical translation of tubular constructs for tracheal tissue engineering: a review

Effective restoration of extensive tracheal damage arising from cancer, stenosis, infection or congenital abnormalities remains an unmet clinical need in respiratory medicine. The trachea is a 10-11 cm long fibrocartilaginous tube of the lower respiratory tract, with 16-20 tracheal cartilages anterolaterally and a dynamic trachealis muscle posteriorly. Tracheal resection is commonly offered to patients suffering from short-length tracheal defects, but replacement is required when the trauma exceeds 50% of total length of the trachea in adults and 30% in children. Recently, tissue engineering (TE) has shown promise to fabricate biocompatible tissue-engineered tracheal implants for tracheal replacement and regeneration. However, its widespread use is hampered by inadequate re-epithelialisation, poor mechanical properties, insufficient revascularisation and unsatisfactory durability, leading to little success in the clinical use of tissue-engineered tracheal implants to date. Here, we describe in detail the historical attempts and the lessons learned for tracheal TE approaches by contextualising the clinical needs and essential requirements for a functional tracheal graft. TE manufacturing approaches explored to date and the clinical translation of both TE and non-TE strategies for tracheal regeneration are summarised to fully understand the big picture of tracheal TE and its impact on clinical treatment of extensive tracheal defects.

Decellularized tracheal scaffolds in tracheal reconstruction: An evaluation of different techniques

In humans, the trachea is a conduit for ventilation connecting the throat and lungs. However, certain congenital or acquired diseases may cause long-term tracheal defects that require replacement. Tissue engineering is considered a promising method to reconstruct long-segment tracheal lesions and restore the structure and function of the trachea. Decellularization technology retains the natural structure of the trachea, has good biocompatibility and mechanical properties, and is currently a hotspot in tissue engineering studies. This article lists various recent representative protocols for the generation of decellularized tracheal scaffolds (DTSs), as well as their validity and limitations. Based on the advancements in decellularization methods, we discussed the impact and importance of mechanical properties, revascularization, recellularization, and biocompatibility in the production and implantation of DTS. This review provides a basis for future research on DTS and its application in clinical therapy.

Successful Total Tracheal Replacement by Cryopreserved Aortic Allograft in a Patient Post-COVID-19 Infection

This is the first report to our knowledge of a successful total tracheal replacement in a post-COVID-19 patient by cryopreserved aortic allograft. The graft was anastomosed to the cricoid and carina; a silicon stent was inserted to ensure patency. The patient was extubated on the operative table and was immediately able to breathe, speak, and swallow. No immunosuppression was administered. Three weeks after surgery, the patient was discharged from hospital in excellent health, and was able to resume his normal lifestyle, work, and activity as an amateur cyclist. Two months after surgery, the patient assumes aerosol with saline solution three times per day and no other therapy; routine bronchoscopy to clear secretions is no longer needed.

Temporoparietal Fascial Free Flap: A Systematic Review

ABSTRACT

The temporoparietal fascial flap (TPFF) is a versatile tool used in head and neck reconstructive surgeries as well as distal upper and lower extremity reconstructions. Depending on the anatomical location and characteristics of the recipient site soft tissue defects, harvesting techniques for TPFF retrieval may include elevation as a pedicle or a free flap, inclusion of the temporalis muscle and/or adjacent calvarial bone as a composite flap. The TPFF as a free flap is not only used for soft tissue coverage of various defects, and it can be used as a joint gliding surface with coverage of nerve and tendons after repair or trauma. This article includes a systematic search of the medical literature for indications, historical background, techniques, current perspective, and complications along with the pros and cons of the free TPFF compared with other potential reconstructive options.

The History of Engineered Tracheal Replacements: Interpreting the Past and Guiding the Future

The development of a tracheal graft to replace long-segment defects has thwarted clinicians and engineers alike for over 100 years. To better understand the challenges facing this field today, we have consolidated all published reports of engineered tracheal grafts used to repair long-segment circumferential defects in humans, from the first in 1898 to the most recent in 2018, totaling 290 clinical cases. Distinct trends emerge in the types of grafts used over time, including repair using autologous fascia, rigid tubes of various inert materials, and pretreated cadaveric allografts. Our analysis of maximum clinical follow-up, as a proxy for graft performance, revealed that the Leuven protocol has a significantly longer clinical follow-up time than all other methods of airway reconstruction. This method involves transplanting a cadaveric tracheal allograft that is first prevascularized heterotopically in the recipient. We further quantified graft-related causes of mortality, revealing failure modes that have been resolved, and those that remain a hurdle, such as graft mechanics. Finally, we briefly summarize recent preclinical work in tracheal graft development. In conclusion, we synthesized top clinical care priorities and design criteria to inform and inspire collaboration between engineers and clinicians toward the development of a functional tracheal replacement graft. Impact statement The field of tracheal engineering has floundered in recent years due to multiple article retractions. However, with recent advances in biofabrication and tissue analysis techniques, the field remains ripe for advancement through collaboration between engineers and clinicians. With a long history of clinical application of tracheal replacements, engineered tracheas are arguably the regenerative technology with the greatest potential for translation. This work describes the many phases of engineered tracheal replacements that have been applied in human patients over the past 100 years with the goal of carrying forward critical lessons into development of the next generation of engineered tracheal graft.

State of the art of clinical applications of Tissue Engineering in 2021

Tissue engineering (TE) was introduced almost 30 years ago as a potential technique for regenerating human tissues. However, despite promising laboratory findings, the complexity of the human body, scientific hurdles, and lack of persistent long-term funding still hamper its translation towards clinical applications. In this report, we compile an inventory of clinically applied TE medical products relevant to surgery. A review of the literature, including articles published within the period from 1991 to 2020, was performed according to the PRISMA protocol, using databanks PubMed, Cochrane Library, Web of Science, and Clinicaltrials.gov. We identified 1039 full-length articles as eligible; due to the scarcity of clinical, randomised, controlled trials and case studies, we extended our search towards a broad surgical spectrum. Forty papers involved clinical TE studies. Amongst these, 7 were related to TE protocols for cartilage applied in the reconstruction of nose, ear, and trachea. Nine papers reported TE protocols for articular cartilage, 9 for urological purposes, 7 described TE strategies for cardiovascular aims, and 8 for dermal applications. However, only two clinical studies reported on three-dimensional (3D) and functional long-lasting TE constructs. The concept of generating 3D TE constructs and organs based on autologous molecules and cells is intriguing and promising. The first translational tissue-engineered products and techniques have been clinically implemented. However, despite the 30 years of research and development in this field, TE is still in its clinical infancy. Multiple experimental, ethical, budgetary, and regulatory difficulties hinder its rapid translation. Nevertheless, the first clinical applications show great promise and indicate that the translation towards clinical medical implementation has finally started.

Novel composite trachea grafts using 3-dimensional printing

Objective

Porcine-derived small intestine submucosa (SIS) extracellular matrix (ECM) surgical patches claim to have greater regenerative properties compared with dermal extracellular matrices. We hypothesized that using SIS-ECM in a bioengineered composite tracheal graft would allow better incorporation into the native tissue.

Methods

Two types of size-matched polycaprolactone support scaffolds were designed: rigid and flexible. The SIS-ECM was wrapped around the polycaprolactone supports lining the inside and outside of the graft. The grafts were implanted in 4 Yorkshire pigs, replacing an ∼2 cm segment of native trachea. Airway patency was evaluated with computed tomography scans and explanted grafts were examined grossly and histologically.

Results

All animals survived through the immediate postoperative period. Generally, extraluminal examination showed a smooth transition between native and graft without significant volumetric loss. Animals that received the flexible design survived ∼10 days longer than those that received the rigid design; however, severe perianastomotic intraluminal granulation tissue was observed. The rigid design had less significant intraluminal granulation tissue development at the distal anastomosis, but partial dehiscence had occurred at the proximal anastomosis interrupting graft incorporation.

Conclusions

The generally good extraluminal graft incorporation in our composite tracheal graft highlights some increased regenerative capabilities of SIS-ECM. However, the presence of intraluminal granulation tissue indicates that its use as an off-the-shelf, unaltered substrate in an airway graft is still not ideal. Further research must be conducted to determine whether a modification of the substrate is possible to enhance luminal airway incorporation and to exert control over the mechanisms responsible for granulation tissue development.

Clinical application of pedicled thoracoacromial artery perforator flaps for tracheal reconstruction

Background

Large or complex trachea defects often require some tissue to reconstruct, various flaps have been reported for reconstructing this defect. However, pedicled thoracoacromial artery perforator flap have not been reported in tracheal reconstruction. Therefore, this study is to assess the efficacy and clinical application of pedicled thoracoacromial artery perforator flaps for tracheal reconstruction.

Methods

Eight patients who underwent tracheal reconstructions with pedicled TAAP flaps between December 2017 and October 2019 were retrospectively reviewed.

Results

All of the pedicled TAAP flaps in our study survived. The flap size ranged from 2 cm × 5 cm to 4 cm × 10 cm, and the size of each island of one double-island flap was 2 cm × 2.5 cm. The mean thickness was 0.6 cm, and the pedicle length varied between 6 and 9 cm (mean 7.9 cm). The mean time of flap harvest was 17 min. The mean age of the patients was 62.4 years and five elderly patients had comorbidities, such as diabetes, hypertension and asthma. One patient received a double-island flap for tracheal and esophageal reconstruction, and the other patient received simple tracheal reconstruction. One patient died due to cancer metastasis. Six patients obtained functional recovery of breathing, except one patients who did not experience closure of the tracheostomy opening due to uncompleted I131 treatment.

Conclusion

Pedicled TAAP flaps provide a short harvesting time, thin thickness and stable blood supply, and they do not require microsurgical skills. This flap is a good choice for the reconstruction of tracheal defects, especially in the aged or patients with comorbidities who are not able to tolerate prolonged surgery.

The current status and outlook of trachea transplantation

PURPOSE OF REVIEW

The trachea is an enigmatic organ due to its complex morphology. Although circumferential tracheal defects are extremely difficult to repair with autologous tissue or with an allotransplant, the trachea has been touted as the first organ that could be regenerated. This review provides a comprehensive evaluation of the published evidence in tracheal tissue replacement surgery.

RECENT FINDINGS

In recent years, reports of successful tracheal regeneration have attracted great interest. Despite descriptions of the trachea as a perhaps uniquely regeneratable tissue since 2008, critical reporting provided insights into the more complex realities of tracheal regeneration attempts and led to the retraction of some articles making tracheal regeneration claims. Allotransplantation of the trachea is hindered by numerous difficult obstacles. The most promising approach developed thus far for difficult-to-repair patch airway defects is tracheal allotransplantation, which allows for tapering and withdrawal of immunosuppressive therapy.

SUMMARY

Restoration of a long-segment circumferential tracheal defect remains an unmet challenge. Future clinical studies require thoroughly documented visual evidence of outcomes to reduce confusion surrounding tracheal replacement and to prevent future scandals like those seen previously in the tracheal regeneration story. VIDEO ABSTRACT: http://links.lww.com/COOT/A6.

Tracheal Agenesis: Vertical Division of the Native Esophagus - A Novel Surgical Approach and Review of the Literature

INTRODUCTION

Tracheal agenesis (TA) is rare and usually fatal. Few survivors with concomitant tracheoesophageal fistulae (TEF) who underwent ligation of the distal esophagus with creation of a spit-fistula and neo-trachea from the proximal esophagus exist. We report a novel surgical technique whereby the esophagus is divided longitudinally to preserve a functional alimentation tract and a parallel neo-trachea. We review the literature of reported cases, including survivors beyond 12 months.

METHODS

Case report and literature review.

RESULTS

A female infant with prenatal polyhydramnios was born at 35 weeks gestation with immediate respiratory distress and absent cry. Oxygenation was maintained with a laryngeal mask airway. Despite a normal appearing larynx, she could not be intubated and emergent neck exploration disclosed no cervical trachea. The patient was placed on extra corporeal membranous oxygenation (ECMO), and later diagnosed with TA, Floyd Type I. Parental desire for reconstruction but refusal of a spit-fistula necessitated a novel procedure. The esophagus was divided longitudinally via a microstapler to preserve the original alimentary tract and create a parallel neo-trachea originating from the TEF and terminating as a cervical stoma. The healing process was complicated but the baby was ultimately discharged to home where she developed normally neurologically until succumbing one night to accidental decannulation at 16 months of age.

CONCLUSION

We describe a novel surgical approach to manage TA. This includes avoiding creation of a spit fistula and preserving the native esophagus. We then survey the literature, reporting the survivorship duration and operative management of 174 reported cases of TA.

Bioengineered carina reconstruction using In-Vivo Bioreactor technique in human: proof of concept study

Backgrounds

Long-segment airway defect reconstruction, especially when carina is invaded, remains a challenge in clinical setting. Previous attempts at bioengineered carina reconstruction failed within 90 days due to delayed revascularization and recurrent infection.

Methods

To establish the feasibility of carina bioengineering use In-Vivo Bioreactor technique. Uncontrolled single-center cohort study including three patients with long-segment airway lesions invading carina. Radical resection of the lesions was performed using standard surgical techniques. After resection, In-Vivo Bioreactor airway reconstruction was performed using a nitinol stent wrapped in two layers of acellularized dermis matrix (ADM). Two Port-a-Cath catheters connected to two portable peristaltic pumps were inserted between the ADM layers. The implanted bioengineered airway was continuously perfused with an antibiotic solution via the pump system. Peripheral total nucleated cells (TNCs) were harvested and seeded into the airway substitute via a Port-a-Cath twice a week for 1 month. The patients were treated as a bioreactor for in situ regeneration of their own bioengineered airway substitute.

Results

Three patients were included in the study (mean age, 54.7 years). The first patient underwent 8 cm long trachea and carina reconstruction, the second patient 6 cm long trachea, carina and main bronchus reconstruction. The third patient right main bronchus and carina reconstruction. Major morbidity included gastric retention and pneumonia. All three patients survived till last follow-up and bronchoscopy follow-up showed well-vascularized regenerated tissue without leakage.

Conclusions

In this uncontrolled study, In-Vivo Bioreactor technique demonstrated potential to be applied for long-segment trachea, carina and bronchi reconstruction. Further research is needed to assess efficacy and safety.

3D-bioprinted tracheal reconstruction: an overview

Congenital tracheomalacia and tracheal stenosis are commonly seen in premature infants. In adulthood, are typically related with chronic obstructive pulmonary disease, and can occur secondarily from tracheostomy, prolong intubation, trauma, infection and tumors. Both conditions are life-threatening when not managed properly. There are still some surgical limitations for certain pathologies, however tissue engineering is a promising approach to treat massive airway dysfunctions. 3D-bioprinting have contributed to current preclinical and clinical efforts in airway reconstruction. Several strategies have been used to overcome the difficulty of airway reconstruction such as scaffold materials, construct designs, cellular types, biologic components, hydrogels and animal models used in tracheal reconstruction. Nevertheless, additional long-term in vivo studies need to be performed to assess the efficacy and safety of tissue-engineered tracheal grafts in terms of mechanical properties, behavior and, the possibility of further stenosis development.

Long-Segment Tracheal Reconstruction With Free Radial Forearm Flap Reinforced by Rib Cartilage

Long-segment tracheal reconstruction remains a challenge. The ideal tracheal substitute should be an epithelialized tube to prevent stenosis and sufficiently rigid to maintain airflow patency. An autologous technique using a radial forearm free flap reinforced by rib cartilage has been recently described for tracheal reconstruction. We report here two cases of complex tracheal reconstruction with a modification of this technique, which consists of the creation of two independent skin paddles to allow the reconstruction of the trachea and a second adjacent defect (eg, cervical skin, esophagus). Airway patency was achieved with no stenosis, prolonged stenting, fistula, or necrosis after 26 and 44 months, respectively. We suggest that the satisfactory outcome obtained with this modified technique is a valuable option for tracheal and adjacent defect reconstruction without the need for a second flap.

Carinal resection

Tracheobronchial tumors with involvement of the carina represent a challenging problem in the pulmonary surgery. Carinal resection is referred to removal and reconstruction of the airway itself, whereas concomitant removal of the lung parenchyma (usually a whole lung) is termed as carinal pneumonectomy. Thorough preoperative workup of these patients is mandatory. Meticulous surgical technique and aggressive postoperative management is required for the best outcomes in these difficult cases. In the paper authors review surgical technique, evaluation and management of this challenging patient population.

Regeneration of trachea graft with cartilage support, vascularization, and epithelization

The repair and functional reconstruction of long-segment tracheal defects is always a great challenge in the clinic. Finding an ideal substitute for tracheal transplantation is the only way to solve this problem. The current study proposed a series of novel strategies for constructing a bionic living trachea substitute. For the issue of tubular cartilage support, cartilage sheet technique based on high-density culture of chondrocytes was adopted to avoid the inflammatory reaction triggered by the materials and thus formed mature cartilage-like tissue in autologous goat model. For the issue of epithelialization, the autologous transplantation of oral mucosal epithelium was used to realize mucosa coverage of the constructed trachea lumen. Finally, the flat trapezius fascia flap with double blood supply was separated by microsurgical techniques to achieve stable pre-vascularization of both the regenerated cartilage and the grafted epithelium simultaneously. By integrating the above strategies, the vascularized and epithelialized tracheal substitute with tubular cartilage support was successfully constructed in a goat model. The reconstructed trachea possessed a multiple layer structure of muscle-cartilage-fascia-mucosa comparable to the native trachea, and thus might realize stable survival and long-term airway function maintenance, providing a promising tracheal substitute for the repair and permanent functional reconstruction of long-segment tracheal defects. STATEMENT OF SIGNIFICANCE: The repair of long-segment tracheal defects is always a great challenge in the clinic. Finding an ideal substitute for tracheal transplantation is the only way to solve this problem. In the current study, by technical integration of cartilage regeneration, microsurgery, and oral mucosa transplantation, a complex tracheal substitute with satisfactory vascularization, epithelialization, and tubular cartilage support was successfully constructed in a goat autologous model. The reconstructed trachea substitute possessed a multiple layer structure of muscle-cartilage-fascia-mucosa exactly similar to native trachea, and thus might realize stable survival and long-term airway function maintenance. The current study provides feasible strategies and ideal tracheal substitutes for permanent functional reconstruction of long-segmental trachea defects.

Replacement of Rat Tracheas by Layered, Trachea-Like, Scaffold-Free Structures of Human Cells Using a Bio-3D Printing System

Current scaffold-based tissue engineering approaches are subject to several limitations, such as design inflexibility, poor cytocompatibility, toxicity, and post-transplant degradation. Thus, scaffold-free tissue-engineered structures can be a promising solution to overcome the issues associated with classical scaffold-based materials in clinical transplantation. The present study seeks to optimize the culture conditions and cell combinations used to generate scaffold-free structures using a Bio-3D printing system. Human cartilage cells, human fibroblasts, human umbilical vein endothelial cells, and human mesenchymal stem cells from bone marrow are aggregated into spheroids and placed into a Bio-3D printing system with dedicated needles positioned according to 3D configuration data, to develop scaffold-free trachea-like tubes. Culturing the Bio-3D-printed structures with proper flow of specific medium in a bioreactor facilitates the rearrangement and self-organization of cells, improving physical strength and tissue function. The Bio-3D-printed tissue forms small-diameter trachea-like tubes that are implanted into rats with the support of catheters. It is confirmed that the tubes are viable in vivo and that the tracheal epithelium and capillaries proliferate. This tissue-engineered, scaffold-free, tubular structure can represent a significant step toward clinical application of bioengineered organs.

Experimental Tracheal Replacement Using 3-dimensional Bioprinted Artificial Trachea with Autologous Epithelial Cells and Chondrocytes

Various treatment methods for tracheal defects have been attempted, such as artificial implants, allografts, autogenous grafts, and tissue engineering; however, no perfect method has been established. We attempted to create an effective artificial trachea via a tissue engineering method using 3D bio-printing. A multi-layered scaffold was fabricated using a 3D printer. Polycaprolactone (PCL) and hydrogel were used with nasal epithelial and auricular cartilage cells in the printing process. An artificial trachea was transplanted into 15 rabbits and a PCL scaffold without the addition of cells was transplanted into 6 rabbits (controls). All animals were followed up with radiography, CT, and endoscopy at 3, 6, and 12 months. In the control group, 3 out of 6 rabbits died from respiratory symptoms. Surviving rabbits in control group had narrowed tracheas due to the formation of granulation tissue and absence of epithelium regeneration. In the experimental group, 13 of 15 animals survived, and the histologic examination confirmed the regeneration of epithelial cells. Neonatal cartilage was also confirmed at 6 and 12 months. Our artificial trachea was effective in the regeneration of respiratory epithelium, but not in cartilage regeneration. Additional studies are needed to promote cartilage regeneration and improve implant stability.