Airway Transplantation: A Debate Worth Having?

Voice Rehabilitation After Laryngeal Transplantation: Own Experience

BACKGROUND AND PURPOSE

Laryngeal transplantation (LT) remains an infrequently performed procedure due to well-defined and limited medical indications. The challenges include a very complicated surgery, continuous immunosuppressive treatment, as well as post-transplant rehabilitation of voice, speech, and swallowing. The aim of this paper is to describe a model of voice and speech rehabilitation after LT, based on our own experience.

STUDY DESIGN

Observational study.

METHOD

Presented here are the rehabilitation processes of two patients who had previously undergone LT as well as their pre- and postrehabilitation voice outcomes. Both patients underwent voice, speech, and swallowing rehabilitation in the fifth month after LT.

RESULTS

One of the patients had a significant improvement in voice quality. While, the other did not regain his natural, sonorous voice, but he scored very high on a voice self-assessment test.

CONCLUSION

Voice rehabilitation after LT is a complex and long-term process that requires the involvement of a team of specialists. The optimal anatomical conditions restored during surgery, the patient's motivation and the support of professionals make it possible to return to normal verbal communication.

Fetal Lung Tissue Engineering

Lung transplantation may be considered as a final treatment option for diseases such as chronic lung disease, pulmonary hypertension, bronchopulmonary dysplasia, pulmonary fibrosis, and end-stage lung disease. The five-year survival rate of lung transplants is nearly 50%. Unfortunately, many patients will die before a suitable lung donor can be found. Importantly, the shortage of donor organs has been a significant problem in lung transplantation. The tissue engineering approach uses de- and recellularization of lung tissue to create functional lung substitutes to overcome donor lung limitations. Decellularization is hope for generating an intact ECM in the development of the engineered lung. The goal of decellularization is to prepare a suitable scaffold of lung tissue that contains an appropriate framework for the functionality of regenerated lung tissue. In this chapter, we aim to describe the decellularization protocols for lung tissue regenerative purposes.

Tracheal In Vitro Reconstruction Using a Decellularized Bio-Scaffold in Combination with a Rotating Bioreactor

Long-segment airway stenosis as well as their neoplastic transformation is life-threatening and still currently represent unsolved clinical problems. Indeed, despite several attempts, definitive surgical procedures are not presently available, and a suitable tracheal reconstruction or replacement remains an urgent clinical need. A possible innovative strategic solution to restore upper airway function may be represented by the creation of a bioprosthetic trachea, obtained through the combination of tissue engineering and regenerative medicine.Here we describe a two-step protocol for the ex vivo generation of tracheal segments. The first step involves the application of a decellularization technique that allows for the production of a naturally derived extracellular matrix (ECM)-based bio-scaffold, that maintains the macro- and micro-architecture as well as 9 the matrix-related signals distinctive of the original tissue. In the second step chondrocytes are seeded onto decellularized trachea, using a rotating bioreactor to ensure a correct scaffold repopulation.This multi-step approach represents a powerful tool for in vitro reconstruction of a bioengineered trachea that may constitute a promising solution to restore upper airway function. In addition, the procedures here described allow for the creation of a suitable 3D platform that may find useful applications, both for toxicological studies as well as organ transplantation strategies.

A comparison of tracheal scaffold strategies for pediatric transplantation in a rabbit model

OBJECTIVES/HYPOTHESIS

Despite surgical advances, childhood tracheal stenosis is associated with high morbidity and mortality. Various tracheal scaffold strategies have been developed as the basis for bioengineered substitutes, but there is no consensus on which may be superior in vivo. We hypothesized that there would be no difference in morbidity and mortality between three competing scaffold strategies in rabbits.

STUDY DESIGN

Pilot preclinical study.

METHODS

Tracheal scaffolds were prepared by three methods that have been applied clinically and reported: preserved cadaveric ("Herberhold") allografts, detergent-enzymatically decellularized allografts, and synthetic scaffolds (nanocomposite polymer [polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU)]). Scaffolds were implanted into cervical trachea of New Zealand White rabbits (n = 4 per group) without cell seeding. Control animals (n = 4) received autotransplanted tracheal segments using the same technique. Animals underwent bronchoscopic monitoring of the grafts for 30 days. Macroscopic evaluation of tissue integration, graft stenosis, and collapsibility and histological examinations were performed on explants at termination.

RESULTS

All surgical controls survived to termination without airway compromise. Mild to moderate anastomotic stenosis from granulation tissue was detected, but there was evidence suggestive of vascular reconnection with minimal fibrous encapsulation. In contrast, three of the four animals in the Herberhold and POSS-PCU groups, and all animals receiving decellularized allografts, required early termination due to respiratory distress. Herberhold grafts showed intense inflammatory reactions, anastomotic stenoses, and mucus plugging. Synthetic graft integration and vascularization were poor, whereas decellularized grafts demonstrated malacia and collapse but had features suggestive of vascular connection or revascularization.

CONCLUSIONS

There are mirror-image benefits and drawbacks to nonrecellularized, decellularized, and synthetic grafts, such that none emerged as the preferred option. Results from prevascularized and/or cell-seeded grafts (as applied clinically) may elucidate clearer advantages of one scaffold type over another.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E449-E457, 2017.

Laryngeal Transplantation

Patients who require laryngectomy usually do not want to completely or partially lose their larynx. Laryngeal transplantation (LT) is a composite tissue transplantation from a cadaver to an alive recipient and requires lifelong immunosuppression in postoperative term. The aims of LT are breathing without tracheostoma, normal swallowing, and voice production. To date, only two successful complete LT have been performed in human despite many researches. The requirement of post-transplant immunosuppressive treatment has ethical concern for the larynx, which is a non-vital organ. However, LT may be an option for improving the quality of life of patients undergoing laryngectomy. In this study, we discussed the LT procedure and researches with the literature.

Seeding of recipient-originated epithelial cells attenuates epithelial to mesenchymal transition in rat tracheal allotransplantation

OBJECTIVE

The specific role and mechanism of epithelium in the progression of obliterative airway disease (OAD) after tracheal allotransplantation remain poorly understood. In this study, we used rat heterotopic tracheal transplantation to investigate the mechanism of epithelial cell seeding during the process of OAD.

STUDY DESIGN

Prospective, basic science.

SETTING

Research laboratory.

SUBJECTS AND METHODS

In total, 120 Sprague Dawley (SD) rats and 90 Wistar rats were used. Tracheas from SD rats were implanted into SD rats (syngeneic, n = 30) or Wistar rats (allogeneic, n = 30), and SD rat tracheas (seeded with Wistar rat-derived epithelial cells 6 days after transplantation) were transplanted into Wistar rats (seeded allogeneic, n = 30). Grafts were harvested at 7, 14, or 30 days after transplantation for histologic, quantitative reverse transcriptional polymerase chain reaction or Western blot analyses.

RESULTS

Syngrafts retained normal histologic structures, while the corresponding allografts demonstrated less ciliated epithelia and more lumenal occlusion. Seeding of epithelial cells ameliorated the histologic changes, reduced the expression of epithelial to mesenchymal transition (EMT)-related transcriptional factors and mesenchymal markers, and dampened the expression of transforming growth factor β1 (TGF-β1) and phosphorylation of smad3.

CONCLUSION

Seeding of recipient epithelial cells inhibits the progression of OAD by attenuating EMT via TGF-β-Smad signaling in rat heterotopic tracheal allografts. Clinically, the injection of recipient-originated epithelial cells might provide new insights into the treatment for OAD after tracheal allotransplantation.

Decellularized tracheal extracellular matrix supports epithelial migration, differentiation, and function

Tracheal loss is a source of significant morbidity for affected patients with no acceptable solution. Interest in engineering tracheal transplants has created a demand for small animal models of orthotopic tracheal transplantation. Here, we examine the use of a decellularized graft in a murine model of tracheal replacement. Fresh or decellularized tracheas harvested from age-matched female donor C57BL/6 mice were transplanted into syngeneic recipients. Tracheas were decellularized using repeated washes of water, 3% Triton X-100, and 3 M NaCl under cyclic pressure changes, followed by disinfection with 0.1% peracetic acid/4% ethanol, and terminal sterilization by gamma irradiation. Tracheas were explanted for immunolabeling at 1, 4, and 8 weeks following surgery. Video microscopy and computed tomography were performed to assess function and structure. Decellularized grafts supported complete reepithelialization by 8 weeks and motile cilia were observed. Cartilaginous portions of the trachea were maintained in mice receiving fresh transplants, but repopulation of the cartilage was not seen in mice receiving decellularized transplants. We observed superior postsurgical survival, weight gain, and ciliary function in mice receiving fresh transplants compared with those receiving decellularized transplants. The murine orthotopic tracheal transplant provides an appropriate model to assess the repopulation and functional regeneration of decellularized tracheal grafts.

Airway tissue engineering: an update

INTRODUCTION

Prosthetic materials, autologous tissues, cryopreserved homografts and allogeneic tissues have thus far proven unsuccessful in providing long-term functional solutions to extensive upper airway disease and damage. Research is therefore focusing on the rapidly expanding fields of regenerative medicine and tissue engineering in order to provide stem cell-based constructs for airway reconstruction, substitution and/or regeneration.

AREAS COVERED

Advances in stem cell technology, biomaterials and growth factor interactions have been instrumental in guiding optimization of tissue-engineered airways, leading to several first-in-man studies investigating stem cell-based tissue-engineered tracheal transplants in patients. Here, we summarize current progress, outstanding research questions, as well as future directions within the field.

EXPERT OPINION

The complex immune interaction between the transplant and host in vivo is only beginning to be untangled. Recent progress in our understanding of stem cell biology, decellularization techniques, biomaterials and transplantation immunobiology offers the prospect of transplanting airways without the need for lifelong immunosuppression. In addition, progress in airway revascularization, reinnervation and ever-increasingly sophisticated bioreactor design is opening up new avenues for the construction of a tissue-engineered larynx. Finally, 3D printing is a novel technique with the potential to render microscopic control over how cells are incorporated and grown onto the tissue-engineered airway.

Stem cell-based organ replacements-airway and lung tissue engineering

Tissue engineering requires the use of cells seeded onto scaffolds, often in conjunction with bioactive molecules, to regenerate or replace tissues. Significant advances have been made in recent years within the fields of stem cell biology and biomaterials, leading to some exciting developments in airway tissue engineering, including the first use of stem cell-based tissue-engineered tracheal replacements in humans. In addition, recent advances within the fields of scaffold biology and decellularization offer the potential to transplant patients without the use of immunosuppression.

Voice disorders in children

This article reviews the management of voice disorders in children. We describe the relevant anatomy and development of the larynx throughout childhood, which affects voice. We consider the epidemiologic data to establish the size of the problem. The assessment of the patient in the clinic is described stepwise through the history, examination, laryngoscopy, and extra tests. We then review the common voice disorders encountered and their management, concluding with discussion of future directions, which may herald advances in this field.

Tacrolimus enhances the recovery of normal laryngeal muscle fibre distribution after reinnervation

OBJECTIVES

To assess the recovery of various muscle fibre types in the posterior cricoarytenoid muscle after laryngeal reinnervation in the rat, and to determine the influence of tacrolimus on this process.

METHODS

Four groups of rats underwent resection and anastomosis of the left vagus nerve, and were administered either tacrolimus at a low dose or an immunosuppressive dose, or cyclosporin A at a low dose or an immunosuppressive dose. A fifth group received surgery alone, and a sixth group received neither surgery nor drug treatment (healthy group). Muscles were removed for immunohistochemical analysis 45 days after surgery.

RESULTS

There was no difference in the proportion of types 1, 2a and 2b muscle fibres, comparing the immunosuppressive tacrolimus group and the healthy group, whereas there were fewer type 1 fibres in the group receiving surgery alone, compared with the healthy group (7 vs 12.1 per cent, respectively; p = 0.0303).

CONCLUSION

Tacrolimus enhanced the recovery of normal laryngeal muscle fibres after reinnervation in the rat, indicating a possible role in laryngeal transplantation.

Decellularized rabbit cricoarytenoid dorsalis muscle for laryngeal regeneration

OBJECTIVES

Although considerable progress has been made in regenerative medicine, a quantum step would be the replacement and/or regeneration of functional muscle tissue. For example, although patients' airways can now be successfully replaced with stem cell-based techniques, a much greater patient need would be addressed by regeneration of the muscles required for engineering a functional larynx, in which active movement is critical. The rabbit cricoarytenoid dorsalis muscle was chosen for the present study because it is equivalent to the posterior cricoarytenoid muscle, the only significant abductor muscle in human larynges.

METHODS

Rabbit cricoarytenoid dorsalis muscles were harvested, and different decellularization methods were compared by use of a combination of histologic, immunohistochemical, and molecular techniques. Decellularized scaffolds were implanted into Sprague-Dawley rats as part of a 2-week biocompatibility study to assess immunogenicity.

RESULTS

Decellularization with a combination of latrunculin B, potassium iodide, potassium chloride, and deoxyribonuclease resulted in total DNA clearance and reduced levels of major histocompatibility complex class II expression, with relative preservation of the scaffold's structural integrity (collagen, elastin, and glycosaminoglycan content). The scaffolds showed minimal signs of rejection at 2 weeks in a cross-species (xenotransplantation) study.

CONCLUSIONS

Decellularized laryngeal muscles, which are nonimmunogenic, may provide the optimal scaffold source for the generation of a fully functional tissue-engineered larynx.

Bone marrow-derived mesenchymal stem cells enhance cryopreserved trachea allograft epithelium regeneration and vascular endothelial growth factor expression

BACKGROUND

Epithelium regeneration and revascularization of tracheal implants are challenging issues to be solved in tracheal transplantation research. Bone marrow-derived mesenchymal stem cells (BMSCs) can migrate to the damaged tissue and promote functional restoration. Here, we applied intravenous transplantation of BMSCs combined with a cryopreserved allograft to investigate the role of BMSCs in enhancing implant survival, tracheal epithelium regeneration and revascularization.

METHODS

After transplantation with cryopreserved allografts, PKH-26 labeled 3 to 5 passage BMSCs were injected into recipient rats through the tail vein. Rats in the control groups were injected with a comparable amount of phosphate-buffered saline. We observed the histology of the tracheal allograft and measured vascular endothelial growth factor (VEGF) protein levels in the epithelium to evaluate the effect of BMSCs on epithelium regeneration and revascularization.

RESULTS

Histologic observation of the rats from the BMSCs injection groups showed that the tracheal lumen was covered by pseudostriated ciliated columnar epithelium. The cartilage structure was intact. There were no signs of denaturation or necrosis. PKH-26 labeled BMSCs migrated to the implant site and exhibited red fluorescence, with the brightest red fluorescence at the anastomotic site. VEGF protein levels in the allograft epithelium of the BMSCs injection group were higher than the levels in the phosphate-buffered saline injection group.

CONCLUSIONS

Our results indicate that given systemic administration, BMSCs may enhance epithelium regeneration and revascularization by upregulating VEGF expression.

Airway tissue engineering

INTRODUCTION

Prosthetic replacements, autologous tissue transfer and allografts have so far failed to offer functional solutions for the treatment of long circumferential tracheal defects and loss of a functioning larynx. Interest has therefore turned increasingly to the field of tissue-engineering which applies the principles and methods of bioengineering, material science, cell transplantation and life sciences in an effort to develop in vitro biological substitutes able to restore, maintain or improve tissue and organ function.

AREAS COVERED

This article gives an overview of the tissue-engineering approach to airway replacement and will describe the encouraging results obtained so far in tracheal regeneration. The recent advances in the field of tissue-engineering have provided a new attractive approach towards the concept of functional substitutes and may represent an alternative to the shortage of suitable grafts for reconstructive airway surgery. We summarize fundamental questions, as well as future directions in airway tissue engineering.

EXPERT OPINION

The replacement of active movement, as would be necessary to replace an entire larynx introduces another order of magnitude of complexity, although progress in this area is starting to bear fruit. In addition, the stem cell field is advancing rapidly, opening new avenues for this type of therapy.

Regenerative medicine and organ transplantation: past, present, and future

This overview traces the history of regenerative medicine pertinent to organ transplantation, illustrates potential clinical applications reported to date, and highlights progress achieved in the field of complex modular organ engineering. Regenerative medicine can now produce relatively simple tissues such as skin, bladders, vessels, urethras, and upper airways, whereas engineering or generation of complex modular organs remains a major challenge. Ex vivo organ engineering may benefit from complementary investigations in the fields of developmental biology and stem cells and transplantation before its full potential can be realized.

Tissue-engineered larynx using perfusion-decellularized technique and mesenchymal stem cells in a rabbit model

CONCLUSION

Reseeding mesenchymal stem cells (MSCs) into the decellularized laryngeal muscle matrix for construction of a tissue-engineered larynx is feasible. This in vivo maturation in the omentum could be the first step before in situ implantation of the construct. This construct could facilitate a tissue-engineered method for laryngeal reconstruction.

OBJECTIVES

The extracellular matrix (ECM) and MSCs have been widely used for organ reconstruction. Our study aimed to prepare a soft tissue decellularized laryngeal scaffold with intact laryngeal cartilages utilizing a perfusion-decellularized technique, reseeding cells on it, and then construct a recellularized larynx.

METHODS

Perfusion-decellularized larynges were obtained from 20 rabbits by perfusion of the common carotid arteries with detergents. Twelve perfused larynges were observed by macroscopic visualization, histological examination, scanning electron microscopy (SEM), and cartilage viability. The remaining eight perfusion constructs were reseeded with induced MSCs aspirated from eight receptor rabbits. Composites were transferred into greater omentums of receptor rabbits after adherence for 1 day in vitro. Rabbit larynges were harvested after 4 weeks and 8 weeks, respectively. Macroscopic visualization, histological examination, and immunohistochemistry were performed.

RESULTS

Larynges perfused by sodium dodecyl sulfate became transparent after 2 h of perfusion. Histology and SEM indicated that the perfusion method showed a better decullularized effect. Almost no intact cells or nuclei were found, while more pores and collagen fibers were retained in the decellularized matrix. The chondrocyte vitality assay indicated that chondrocyte vitality was high. Vascularization was clearly seen by 4 weeks and relatively integrated cartilage frameworks remained by 8 weeks. Histological and immunohistochemical examinations clearly showed muscle bundles and vessels.

Generation and transplantation of an autologous vascularized bioartificial human tissue

BACKGROUND

The lack of transplant vascularization forecloses the generation and clinical implementation of bioartificial tissues. We developed techniques to generate a bioartificial human tissue with an innate vascularization. The tissue was implanted clinically as proof of concept to evaluate vascular network thrombogenicity and tissue viability after transplantation.

METHODS

A porcine small bowl segment was decellularized in a two-step procedure, preserving its vascular structures. The extracellular matrix was characterized quantitatively for DNA residues and protein composition. The vascular remainings were reseeded with human endothelial cells in a dynamic tissue culture. The engineered tissue was characterized by (1) histology, (2) immune-histology, (3) life-dead assay, and (4) metabolic activity. To evaluate the tissue capabilities, it was implanted clinically and recovered after 1 week.

RESULTS

Tissue preparation with sodium desoxycholate monohydrate solution resulted in an incomplete decellularization. Cell residues were removed by additional tissue incubation with DNAse. The human endothelial cells formed a viable endothelium inside the primarily porcine extracellular matrix, expressing CD31, Flk-1, and vascular endothelium-cadherin. The metabolic activity of the bioartificial tissue increased continuously over time in vitro. Clinical tissue transplantation confirmed vessel patency and tissue viability for 1 week.

CONCLUSIONS

The feasibility to bioengineer a human tissue with an innate vascularization has been shown in vitro and the clinical setting. These results may open the door for the clinical application of various sophisticated bioartificial tissue substitutes and organ replacements.

Structural and morphologic evaluation of a novel detergent-enzymatic tissue-engineered tracheal tubular matrix

OBJECTIVE

We sought to bioengineer a nonimmunogenic tracheal tubular matrix of 6 cm in length and test its structural, functional, and immunologic properties in vitro and in vivo.

METHODS

Twelve-centimeter tracheal segments were harvested from Yorkshire boars. Half of each segment was 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 degrees C as a control. Bioengineered and control tracheas were then implanted in major histocompatibility complex-unmatched pigs (allograft) or mice (xenograft) heterotopically for 30 days. Structural and functional analysis and immunostaining were performed after each detergent-enzymatic method cycle and transplantation.

RESULTS

Compared with control tracheas, bioengineered matrices displayed no major histocompatibility complex class I and II antigens after 17 detergent-enzymatic method cycles, without significant (P > .05) differences in their strain ability (rupture force, 56.1 +/- 3.3 vs 55.5 +/- 2.4 N; tissue deformation at 203% +/- 13% vs 200% +/- 8% or 12.2 +/- 0.8 vs 12 +/- 0.5 cm; and applied maximum force, 173.4 +/- 3.2 vs 171.5 +/- 4.6 N). Thirty days after implantation, significantly (P < .01) smaller inflammatory reactions (392 vs 15 macrophages/mm(2) and 874 vs 167 T lymphocytes/mm(2)) and P-selectin expressions (1/6 vs 6/6) were observed in both the xenograft and allograft models with bioengineered matrices compared with those seen with control tracheas. There was no development of anti-pig leukocyte antigen antibodies or increase in both IgM and IgG content in mice implanted with bioengineered tracheas.

CONCLUSIONS

Bioengineered tracheal matrices displayed similar structural and mechanical characteristics to native tracheas and excite no immune response to 30 days when implanted as allografts or xenografts. This method holds great promise for the future of tissue-engineered airway replacement.

Clinical transplantation of a tissue-engineered airway

BACKGROUND

The loss of a normal airway is devastating. Attempts to replace large airways have met with serious problems. Prerequisites for a tissue-engineered replacement are a suitable matrix, cells, ideal mechanical properties, and the absence of antigenicity. We aimed to bioengineer tubular tracheal matrices, using a tissue-engineering protocol, and to assess the application of this technology in a patient with end-stage airway disease.

METHODS

We removed cells and MHC antigens from a human donor trachea, which was then readily colonised by epithelial cells and mesenchymal stem-cell-derived chondrocytes that had been cultured from cells taken from the recipient (a 30-year old woman with end-stage bronchomalacia). This graft was then used to replace the recipient's left main bronchus.

FINDINGS

The graft immediately provided the recipient with a functional airway, improved her quality of life, and had a normal appearance and mechanical properties at 4 months. The patient had no anti-donor antibodies and was not on immunosuppressive drugs.

INTERPRETATION

The results show that we can produce a cellular, tissue-engineered airway with mechanical properties that allow normal functioning, and which is free from the risks of rejection. The findings suggest that autologous cells combined with appropriate biomaterials might provide successful treatment for patients with serious clinical disorders.