Microvascular transfer of long tracheal autograft segments in the canine model

Case Report: Human Tracheal Transplantation Undergoes Progressive Reepithelialization Over Time

OBJECTIVES

Tracheal transplantation is an ideal option for the reconstruction of long-segment circumferential tracheal defects. Our group performed the first successful vascularized single-staged tracheal transplantation in January 2021. Although a rigid biocompatible structure is necessary for a functioning tracheal replacement, the importance of ciliated epithelium, which allows for critical mucociliary clearance, is now being appreciated. Here, we examined the histological changes of the first single-staged human tracheal transplant from serial endoscopic biopsies.

METHODS

Biopsies of the tracheal mucosa were serially obtained since the time of the tracheal transplantation. Samples were examined via hematoxylin and eosin, electron microscopy, and immunohistochemistry.

RESULTS

One week after transplantation, there is loss of ciliated epithelium and seromucinous cells, with only a basal layer of epithelium remaining. By 2 weeks, however, the epithelium begins to recover, albeit differently depending on the location of the biopsy. Near the site of tracheal anastomosis, there is epithelial proliferation, with the appearance of early ciliated cells. However, in the midgraft, there appears to be evidence of squamous metaplasia. Over time, however, normal ciliated epithelium and mucous cells appear without signs of chronic inflammation.

CONCLUSIONS

Critically, the tracheal allograft regained normal appearing respiratory epithelium after initial ischemic injury. The histologic differences at the midgraft versus anastomosis may suggest unique mechanisms of reepithelialization. At the recipient-donor interface, there may be a faster direct migration of recipient-derived epithelial cells, in line with preclinical studies. The midgraft, in contrast, responds with epithelial proliferation from the donor basal cells or dedifferentiated mucous cells.

LEVEL OF EVIDENCE

N/A Laryngoscope, 134:2664-2671, 2024.

Human Tracheal Transplantation

Long-segment tracheal airway defects may be congenital or result from burns, trauma, iatrogenic intubation damage, or tumor invasion. Although airway defects <6 cm in length may be reconstructed using existing end-to-end reconstructive techniques, defects >6 cm continue to challenge surgeons worldwide. The reconstruction of long-segment tracheal defects has long been a reconstructive dilemma, and these defects are associated with significant morbidity and mortality. Many of these defects are not compatible with life or require a permanent extended-length tracheostomy that is fraught with complications including mucus plugging and tracheoesophageal fistula. Extensive circumferential tracheal defects require a reconstructive technique that provides a rigid structure able to withstand the inspiratory pressures, a structure that will biologically integrate, and contain functional ciliated epithelium to allow for normal mucociliary clearance. Tracheal transplantation has been considered the reconstructive "Holy Grail;" however, there has been a long-held scientific dogma that revascularization of the trachea was not possible. This dogma stifled research to achieve single-staged vascularized tracheal transplantation and prompted the introduction of many creative and inventive alternatives. Throughout history, alloplastic material, nonvascularized allografts, and homografts have been used to address this dilemma. However, these techniques have largely been unsuccessful. The recent introduction of a technique for single-staged vascularized tracheal transplantation may offer a solution to this dilemma and potentially a solution to management of the fatal tracheoesophageal fistula.

Vascularized Tracheal Transplantation: A Twenty Month Follow Up

BACKGROUND

Tracheal transplantation has been considered the ideal option for the reconstruction of long-segment circumferential tracheal defects. Our group developed a technique for vascularized single-staged tracheal transplantation. Twenty months ago, we performed the first-in-human tracheal transplantation. Herein, we report a twenty-month follow-up.

METHODS

The recipient presented with a 9.0 cm airway tracheal stenosis and complete cricoid stenosis. The patient previously failed six major conventional surgical procedures. Prior to transplantation, the patient's airway was maintained with an extended tracheostomy and stent. The patient experienced repeated life-threatening airway obstruction because of mucous plugging and obstructive granulation tissue. In January 2020 the patient underwent a single-staged tracheal transplantation treated with triple-therapy immunosuppression. Organ rejection was monitored with endoscopic tracheoscopy, narrow-band imaging, free-cell DNA assessment, and histological and cytogenetic analysis of tracheal biopsies. Mucociliary function was assessed with dye motility studies.

RESULTS

Twenty months following transplantation, there has been no evidence of acute or chronic rejection. Since day 60, there has been no detectable free cell DNA, a surrogate marker for immune-mediated allograft rejection. Fluorescence in situ hybridization (FISH) cytogenetics demonstrated that the donor trachea was repopulated with recipient epithelium establishing a chimeric allograft. Narrow-band imaging demonstrates a well-vascularized epithelial mucosa and bronchoscopic biopsies demonstrate normal ciliated epithelial architecture and viable epithelial lining with functional ciliated epithelium. The patient has resumed a normal life without a stent or tracheostomy and has returned to work.

CONCLUSIONS

Twenty months after single-staged vascularized tracheal transplantation, the trachea is functional and the patient breathes without the need for a tracheostomy or stent. Single-staged long-segment tracheal transplantation is a viable option for tracheal defects that are not amenable to conventional reconstructive techniques.

LEVEL OF EVIDENCE

4 Laryngoscope, 2022.

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.

Single-stage long-segment tracheal transplantation

Tracheal transplantation has been envisioned as a viable option for reconstruction of long-segment tracheal defects. We report the first human single-stage long-segment tracheal transplantation. Narrow-band imaging and bronchoscopic biopsies demonstrate allograft vascularization and viable epithelial lining. The recipient was immunosuppressed with Tacrolimus, Mycophenolate mofetil, and corticosteroids. Six months after transplantation, the trachea is both functional and the patient is breathing without the need of a tracheostomy or stent.

Large animal models for long-segment tracheal reconstruction: a systematic review

BACKGROUND

The reconstruction of extensive tracheal defects is an unresolved problem. Despite decades of research, a reliable and practical substitute remains to be found. While there have been clinical reports of successful long-segment tracheal reconstruction, reproducibility and widespread applicability of these techniques have yet to be achieved. Large animals such as the dog, pig, sheep, and goat have comparable tracheal morphology and physiology to humans making them useful preclinical models to screen potential therapeutic strategies.

MATERIALS AND METHODS

The literature was reviewed to identify large animal models commonly used for tracheal reconstruction. A systematic search of PubMed and EMBASE was performed for large animal studies reporting on the reconstruction of long-segment tracheal and carinal defects. Fifty-seven studies were identified for analysis.

RESULTS

There is no standard large animal model available for tracheal research. In recent years, livestock species have gained favor over dogs as animal models in this field. The minimum requirements for successful tracheal replacement are rigidity, vascularity, and epithelial lining. Early attempts with synthetic prostheses were met with disappointing results. An autologous tracheal substitute is ideal but hindered by limited donor site availability and the lack of a dominant vascular pedicle for microsurgical reconstruction. Although tracheal allotransplantation enables like-for-like replacement, there are unresolved issues relating to graft vascularity, immunosuppression, and graft preservation. Tissue engineering holds great promise; however, the optimal combination of scaffold, cells, and culture conditions is still indeterminate.

CONCLUSIONS

Despite impressive advances in tracheal reconstruction, a durable substitute for extended tracheal defects continues to be elusive.

Free thyroid transfer: Short-term results of a novel procedure to prevent post-radiation hypothyroidism

Background

The incidence of radiation‐induced hypothyroidism (RIH) in patients with head and neck cancer is >50%. The purpose of this study was to assess the long‐term efficacy of free thyroid transfer (FTT) for prevention of RIH in patients with head and neck cancer.

Methods

Hemithyroid dissection was completed in 10 patients with advanced head and neck cancer undergoing ablation, radial forearm free flap (RFFF) reconstruction, and postoperative radiotherapy (RT). The hemithyroid was anastomosed to the donor site vessels in the forearm. Thyroid laboratory testing and technetium (Tc) scans were performed 6 weeks and 12 months postoperatively to establish functional integrity.

Results

FTT was successfully performed in 9 of 10 recruited patients. Postoperative Tc scans demonstrated strong Tc uptake in the forearm donor site at 6 weeks and 12 months in all patients who underwent transplantations.

Conclusion

FTT is feasible with maintenance of function, and may represent a novel strategy for prevention of RIH. © 2016 Elsevier Head & Neck Published by Wiley Periodicals, Inc. Head Neck39: 1234–1238, 2017

Reepithelialization of Orthotopic Tracheal Allografts Prevents Rejection after Withdrawal of Immunosuppression

Prior work has demonstrated that immunosuppressed orthotopic tracheal allografts undergo progressive reepithelialization over a 48-day period with recipient-derived tracheal epithelium. We hypothesized that reepithelialization of tracheal allografts would prevent rejection after withdrawal of immunosuppression. BALB/c murine tracheal grafts were transplanted orthotopically into either syngeneic or allogeneic C57/BL6 recipients. The recipients were either not immunosuppressed, immunosuppressed with cyclosporine A (10 mg/kg per day) continuously, or immunosuppressed for 48 days and then withdrawn from immunosuppression. The grafts were assessed for acute and chronic rejection 10 days and 50 days after immunosuppression withdrawal. The immunosuppressed allograft recipients maintained a ciliated epithelium acutely and chronically after immunosuppression withdrawal. Ten days after immunosuppression withdrawal, there was a mild cellular infiltrate, which resolved 50 days after withdrawal. Electron microscopy, lymphocyte subpopulation assays, and lamina propria analysis demonstrated that immunosuppression withdrawal did not result in tracheal allograft rejection. In vitro and in vivo assessments did not demonstrate evidence of systemic or local immune tolerance. We conclude that reepithelialization of orthotopic tracheal allografts with recipient-derived mucosa prevents rejection of allograft segments. Tracheal transplantation may require only transient immunosuppression, which can be withdrawn after tracheal reepithelialization.

Long-term outcomes of microsurgical reconstruction for large tracheal defects

BACKGROUND

Reconstruction of large tracheal defects has been largely unsuccessful. The purpose of this study was to review the authors' experience with microsurgical reconstruction of these defects.

METHODS

Seven cases of microsurgical tracheal reconstruction were performed between May 2002 and April 2008. All but 1 patient had recurrent thyroid cancer; the other patient had primary adenocystic carcinoma of the trachea. The radial forearm free flap was used for lining in all cases. Rigid support was provided with a variety of prosthetic materials.

RESULTS

All defects involved the cervical trachea, with an average length of 5.8 cm ± 1.0 cm (range, 5 cm-7.5 cm). The width of defects ranged from half of the tracheal circumference to the entire circumference. Major complications included air leak in 4 patients, exposure and removal of prosthesis in 2 patients, and cardiopulmonary complications in 2 patients. One patient with postoperative retroperitoneal hematoma, abdominal compartment syndrome, and multiple organ failure died 2 months after surgery. Two patients died of other causes 1 year and 4 years, respectively, after surgery. The other 4 patients were alive and disease free, with follow-up ranging from 1 to 4.5 years. Four patients are asymptomatic, with normal speech and swallowing functions. Two patients remained tracheostomy dependent, but vocal ability was intact. All patients tolerated a regular diet.

CONCLUSIONS

Microsurgical reconstruction is a viable option in selected patients with large cervical tracheal defects that are beyond primary repair.

Tracheal transplant with a prefabricated microsurgical flap

OBJECTIVE

To test the viability of a tracheal autotransplant, with an original technique using a prefabricated flap from a complete tracheal neovascularized segment (CTNVS) of the sternohyoid muscle anastomosed by a microsurgical technique.

STUDY DESIGN

An experimental study using dogs as an animal model.

METHODS

Ten mongrel dogs weighing 23 to 40 kg were divided into two groups: group I (control), five animals submitted to autotransplant of the CTNVS without a microsurgical vascular anastomosis; and group II, five dogs submitted to autotransplant of the CTNVS with a microsurgical vascular anastomosis.

RESULTS

All group I dogs developed respiratory insufficiency and died because of necrosis and stenosis of the autotransplanted CTNVS, whereas all group II dogs completed a minimum period of 90 days of observation without any clinical changes. Macro- and microscopic analysis revealed intact tracheal structures.

CONCLUSIONS

The present clinical and morphological findings demonstrate that the CTNVS autotransplant is viable, when a microsurgical vascular anastomosis is used.

Engineering a Composite Neotrachea in a Rat Model

BACKGROUND

Attempts to reconstruct the trachea have been largely unsuccessful because of its rigidity and opening to the outside environment. Materials that impart rigidity are usually alloplastic, so they cannot be exposed to the open environment without an unacceptably high risk of infection and rejection. The authors hypothesized that tissue engineering principles can be employed to construct a well-integrated neotrachea with rigid support and an epithelial lining to mimic the structure and function of the native trachea.

METHODS

A 30-mm-long segment of polytetrafluoroethylene vascular graft with a diameter of 10 mm was lined with a fascial flap based on the superficial inferior epigastric artery with full-thickness skin grafts on its luminal surface. The composite unit was then buried under the abdominal skin of 20 rats and harvested 3 weeks later. Microfil and methylene blue dye were injected into the superficial inferior epigastric arteries and histologic analyses were performed to assess microcirculation and polytetrafluoroethylene-tissue integration.

RESULTS

Two composite neotracheas experienced minor damage due to chewing by the rats, but all other neotracheas were viable and without infection. Injection studies demonstrated excellent circulation throughout the fascial flaps and skin grafts and across the polytetrafluoroethylene grafts to the overlying abdominal skin. Histologic analyses revealed abundant muscle-walled blood vessel ingrowth within the polytetrafluoroethylene grafts and all layers of the neotracheas with minimal inflammatory reactions.

CONCLUSION

The authors successfully have engineered a well-integrated neotrachea in rats that possesses rigid support, an epithelial lining, and reliable coverage-the prerequisites for successful trachea reconstruction.

Tracheal wall for the reconstruction of extended hemilaryngectomy in the rabbit model

OBJECTIVE

To evaluate reconstruction of the surgical wound of extended hemilaryngectomy using the tracheal wall.

STUDY DESIGN AND SETTING

Prospective, nonrandomized experimental study in a rabbit model in which cricothyroid hemilaryngectomy was performed in 10 rabbits. The proximal trachea was tailored to cover the surgical wound and sutured to it. The ipsilateral lobe of the thyroid gland and the medial thyroid vascular pedicle were conserved so as to assure vascular supply to the tracheal flap. After 4 weeks the animals were sacrificed and pathology analysis conducted.

RESULTS

Eight of the 10 rabbits survived without respiratory or deglutitory alterations. Pathologic analysis showed well-healed suture lines together with normal mucosa and cartilage rings in the tracheal flap.

CONCLUSIONS

The tracheal wall appears to be the ideal donor tissue for repair of the larynx.

SIGNIFICANCE

This simple, 1-session surgical procedure demonstrates an effective reconstruction of an extended hemilaryngectomy wound.

Circumferential Tracheal Reconstruction for the Functional Treatment of Airway Compromise

OBJECTIVES/HYPOTHESIS

The objective was to describe a surgical technique for replacement of long tracheal defects with a totally autologous free prefabricated cutaneous chondromucosal forearm tubular flap, applied to humans.

STUDY DESIGN

Surgical reconstruction of the trachea.

METHODS

A three-stage surgery was performed in a 25-year-old patient who presented with a long tracheal defect not resolved by previous resection with primary anastomosis and laser surgery.

RESULTS

The staged surgery has been well tolerated by the patient, and no problems at all were reported. The postoperative computed tomography scan and the bronchofibroscopy examination of the "neo-trachea" at 2 and 6 months revealed normal caliber, good healing of the suture lines, absence of crusts or granulation tissue, and a well-vascularized internal mucosal lining.

CONCLUSION

The modified flap reconstruction technique has the potential to be considered reliable for the definitive circumferential reconstruction of extensive laryngotracheal defects not amenable to being cured by conventional techniques.

Microvascular transplantation of tracheal allografts model in the canine

The inability to reconstruct extensive and often life-threatening tracheal defects is a clinical dilemma. The objective of this study was to achieve microvascular revascularization and transplantation of long-segment circumferential tracheal allografts in a canine model. Fifteen mongrel dogs were randomly assigned to 5 treatment groups. Twelve dogs underwent an excision of an 8-cm tracheal segment followed by transplantation and microvascular revascularization of an 8-cm cervical trachea allograft. Group 1 (n = 4) was treated with 10 mg/kg per day of cyclosporin A (CsA) and 7.5 mg/kg per day of mycophenolate mofetil (MM). Group 2 (n = 4) was treated with 5 mg/kg per day of CsA and 7.5 mg/kg per day of MM. Group 3 (n = 4) was treated with 2.5 mg/kg per day of CsA and 7.5 mg/kg per day of MM. Group 4 (n = 2) underwent an autograft tracheal transplant and received postoperative 2.5 mg/kg perday of CsA and 7.5 mg/kg per day of MM. Group 5 (n = 1) did not undergo surgery, but received postoperative 2.5 mg/kg per day of CsA and 7.5 mg/kg per day of MM. The animals were maintained for a duration of 30 days, during which time the graft was assessed by routine endoscopic examination and tracheal biopsies. Ex vivo, tracheal autografts were examined grossly for graft healing and microscopically for histologic architecture. The mean survival times were 13.25 days (group 1), 16 days (group 2), and 20 days (group 3). There was 1 early allograft failure secondary to microvascular thrombosis, and there were 4 delayed failures secondary to postoperative wound infections. Five dogs were euthanized before the end of the 30-day observation period because of failure to thrive or hypocalcemic tetany. None of the dogs in the study demonstrated endoscopic or histologic evidence of rejection before euthanasia. Postmortem examination of the surviving dogs demonstrated normal histologic architecture without evidence of rejection. For the first time, we have achieved allotransplantation of long tracheal segments based on the cranial thyroid artery and internal jugular vein. Minimal systemic immunosuppression appears to be associated with a higher survival rate and a lower complication rate.