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Histologic examination of cryopreserved aortic allograft at 6 months (sheep model) showing regenerated airway epithelium (hematoxylin and eosin staining; original magnification ×2.5).
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After more than 50 years of research, airway transplantation remains a major challenge in the fields of thoracic surgery and regenerative medicine. Five principal types of tracheobronchial substitutes, including synthetic prostheses, bioprostheses, allografts, autografts and bioengineered conduits have been evaluated experimentally in numerous stud...
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Citations
... Seven preclinical studies on a sheep model showed explored allogeneic aortic grafts as airway substitutes [47]. The aortic scaffold served as a matrix for de novo generation of cartilage. ...
Airway cancers have been increasing in recent years. Tracheal resection is commonly performed during surgery and is burdened from post-operative complications severely affecting quality of life. Tracheal resection is usually carried out in primary tracheal tumors or other neoplasms of the neck region. Regenerative medicine for tracheal replacement using bio-prosthesis is under current research. In recent years, attempts were made to replace and transplant human cadaver trachea. An effective vascular supply is fundamental for a successful tracheal transplantation. The use of biological scaffolds derived from decellularized tissues has the advantage of a three-dimensional structure based on the native extracellular matrix promoting the perfusion, vascularization, and differentiation of the seeded cell typologies. By appropriately modulating some experimental parameters, it is possible to change the characteristics of the surface. The obtained membranes could theoretically be affixed to a decellularized tissue, but, in practice, it needs to ensure adhesion to the biological substrate and/or glue adhesion with biocompatible glues. It is also known that many of the biocompatible glues can be toxic or poorly tolerated and induce inflammatory phenomena or rejection. In tissue and organ transplants, decellularized tissues must not produce adverse immunological reactions and lead to rejection phenomena; at the same time, the transplant tissue must retain the mechanical properties of the original tissue. This review describes the attempts so far developed and the current lines of research in the field of tracheal replacement.
... In most cases, segmentary resection of the damaged trachea and primary anastomosis can be performed, but such methods cannot be used to repair long-segmental tracheal stenosis. In the event of extensive tracheal resection, auto/allograft and prosthetic materials have been used [1][2][3][4]. However, no satisfactory reconstructive option is available for such procedures [5]. ...
Background:
There remains a scarcity of both autografts and allografts for tracheal transplantation after long-segmental resection. Subsequently, tissue engineering has become a promising alternative for tracheal transplantation, which requires successful in vitro chondrogenesis.
Methods:
To optimize the protocol for in situ chondrogenesis using the pig-derived whole Umbilical Cord (UC) as the starting material, it must be performed without using the UC-multipotent stromal cell (MSCs) isolation procedure. Nevertheless, chondrogenic induction is performed under a variety of conditions; with or without TGF-β1 at different concentrations, and also in combination with either a rotatory or hollow organ bioreactor. The engineered explant sections were analyzed using various histochemical and immunohistochemical stains to assess the expression of chondrocyte markers. Cell viability was determined through use of the APO-BrdU TUNEL assay kit.
Results:
The results showed that culture conditions induced heterogeneous chondrogenesis in various compartments of the UC. Moreover, explants cultured with 10 ng/ml TGF-β1 under hypoxic (1% O2) in combination with a bioreactor, significantly enhanced the expression of aggrecan and type II collagen, but were lacking in the production of Glycosaminoglycans (GAGs), as evidenced by alcian blue staining. We speculated that whole segment UCs allowed for the differentiation into premature chondrocytes in our tissue-engineered environments.
Conclusion:
This study has provided exciting preliminary evidence showing that a stem cell-rich UC wrapped around an anatomical tracheal scaffold and implanted in vivo can induce nodes of new cartilage growth into a structurally functional tissue for the repairing of long-segmental tracheal stenosis.
... Since it is extremely difficult to create a capillary network in vitro, implanted TE substitutes can only obtain nutrition via tissue fluid infiltration and vessel in-growth from surrounding recipient tissue (3). Unfortunately, the revascularization process normally takes several months during which the majority of pre-seeded cells located in the central part of the TE substitute die from ischemia (4). ...
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.
... Based on the pioneering work by Vacanti and colleagues, tissue engineering techniques have become a potential solution [36,37] (Figure 11.2). The challenge is represented by the creation of cartilaginous tubes covered with respiratory cells [38]. ...
... Use of autologous tissues such as the pericardium, skin, costal cartilage, bowel, esophagus, or bladder involve long and complex procedures and did not provide prospective clinical trials. Based on the pioneering work by Vacanti and colleagues, tissue engineering techniques have become a potential solution [36,37] (Figure 11.2). e challenge is represented by the creation of cartilaginous tubes covered with respiratory cells [38]. %*" " lesions. ...
... In 1997, we proposed to evaluate the use of aortic grafts as matrices for airway transplantation. In successive experimental studies, we demonstrated encouraging results with the use of aortic autografts and fresh or cryopreserved allografts [27,38,[43][44][45]. We observed in vivo tissue engineering with epithelial and cartilage regeneration from bonemarrow stem cells [46]. ...
As part of the development of an artificial larynx, in vivo experiments and clinical trials have revealed a defect in re-epithelialization of the endoluminal side of the prosthesis. This respiratory epithelium is absolutely necessary to obtain an implantable device fully integrated into the body but also for the functionality of such an implant. In this work we have developed patches of interpenetrated and reticulated hydrogels based on collagen and hyaluronic acid to ensure rapid epithelial regrowth. These optimized hydrogel patches have sufficient resistance to hydrolysis to limit their early degradation once implanted. They have been functionalized by growth and cell differentiation factors that are released gradually with an objectified result on cell proliferation. Encapsulation of immune cells and the use of cytokines in these gels also modulate the inflammatory response towards a healing process rather than rejection.
... Although various anastomotic operation methods following airway resection have been reported [1,2], these treatments cause postoperative scarring, and granulation is sometimes observed. Autografts and allografts using costal cartilage, auricular cartilage, and skin have also been performed for airway replacement [3][4][5]. However, it is difficult to obtain an adequate quantity and appropriate shape of tissue for airway regeneration. ...
induced pluripotent stem (iPS) cells can be differentiated into various cell types, including airway epithelial cells, since they have the capacity for self-renewal and pluripotency. Thus, airway epithelial cells generated from iPS cells are expected to be potent candidates for use in airway regeneration and the treatment of airway diseases such as cystic fibrosis (CF). Recently, it was reported that iPS cells can be differentiated into airway epithelial cells according to the airway developmental process. These studies demonstrate that airway epithelial cells generated from iPS cells are equivalent to their in vivo counterparts. However, it has not been evaluated in detail whether these cells exhibit physiological functions and are fully mature. Airway epithelial cells adequately control water volume on the airway surface via the function of Cl⁻ channels. Reasonable environments on the airway surface cause ciliary movement with a constant rhythm and maintain airway clearance. Therefore, the generation of functional airway epithelial cells/tissues with Cl⁻ channel function from iPS cells will be indispensable for cell/tissue replacement therapy, the development of a reliable airway disease model, and the treatment of airway disease. This review highlights the generation of functional airway epithelial cells from iPS cells and discusses the remaining challenges to the generation of functional airway epithelial cells for airway regeneration and the treatment of airway disease.
... However, when the tracheal defect is longer than 6 cm in adults (30% of the total length in children), it is difficult to achieve tracheal reconstruction by direct anastomosis, and reconstruction of the trachea must be performed with substitutes (Grillo, 2002;Hinderer and Schenke-Layland, 2013;Wright et al., 2004). Presently, commonly used substitutes for tracheal transplantation include autologous tissue (Martinod et al., 2013), tracheal (Friedman and Mayer, 1992), and artificial materials, but they all have inherent disadvantages. In recent years, rapid development of tissue engineering technology has provided new approaches to resolve such issues (Elliott et al., 2012;Grimmer et al., 2004). ...
... A glimpse at the literature reveals that this clinical trial is based on years of experience in animal models using aortic allografts as airway substitutes. The concept of using the aorta as a tracheal substitute is based on the facts that the aortic tissue is well-known for its solidity, compliance and resilience to infection (23). The major disadvantage being the propensity towards collapse which can be overcome using stents. ...
The patient population in desperate need for an airway substitute are individuals with long segment tracheal defects that are considered, technically, inoperable. Regardless of the underlying etiology, benign or malignant growing processes, this patient category enters a palliative setting or require tracheal transplantation. Different airway substitutes have been categorized by Grillo as follows; tracheal transplantation, autogenous tissue, non-viable tissue, tissue-engineering and foreign materials. These fields have been explored in the past in animal models and in clinical patients. Research on airway replacement has been exposed to a level of controversies in the past years. The field has been turbulent and apocryphal. In particular, the area of tissue-engineering using stem cells has suffered from a major set-back leaving scientists, clinicians and ethical committees skeptical. Recently, a hopeful study emerged using aortic allografts as tracheal substitutes in patients with airway defects. The initial results seem promising and reliable. The developments of the field at this point seem striking and hopeful. The focus of this review is to shed light on developments in the field of aortic allografts as substitute for tracheal replacement.
... A series of 7 preclinical animal studies using a sheep model showed that autologous and fresh or cryopreserved allogeneic aortic grafts could be valuable airway substitutes. 7 The regeneration of epithelium and de novo generation of cartilage were observed within the aortic matrices, thus allowing stent removal after only 6 months. Although controversial, the hypothesis that bone marrow mesenchymal stem cells play a role in this process of in vivo tissue engineering has been proposed. ...
... The techniques used followed guidelines established during human and other experimental studies. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] In Figure 1, the final aspect of the airways after surgical resection and reconstruction is shown schematically. None of the patients received immunosuppressive therapy per the usual recommendations when cryopreserved aortic allografts are used in vascular surgery. ...
... Since the review of airway transplantation by Grillo, 30 recent advances have been observed and include the development of modern tissue engineering techniques. 7,24,31,32 The results obtained by Macchiarini et al 1 have been critically debated following the revelation that the majority of patients died after the implantation of tissue-engineered airways, which is in contrast to the initial reports. 3,5,[22][23][24] Other case studies have been reported by multiple groups using various conduit types including a Marlex mesh patch with spiral rings covered by a collagen sponge (Omori et al 33,34 ; n = 7), 4 Hamilton et al, 36 and Steinke et al 37 ; n = 2). ...
Importance
Airway transplantation could be an option for patients with proximal lung tumor or with end-stage tracheobronchial disease. New methods for airway transplantation remain highly controversial.
Objective
To establish the feasibility of airway bioengineering using a technique based on the implantation of stented aortic matrices.
Design, Setting, and Participants
Uncontrolled single-center cohort study including 20 patients with end-stage tracheal lesions or with proximal lung tumors requiring a pneumonectomy. The study was conducted in Paris, France, from October 2009 through February 2017; final follow-up for all patients occurred on November 2, 2017.
Exposures
Radical resection of the lesions was performed using standard surgical techniques. After resection, airway reconstruction was performed using a human cryopreserved (−80°C) aortic allograft, which was not matched by the ABO and leukocyte antigen systems. To prevent airway collapse, a custom-made stent was inserted into the allograft. In patients with proximal lung tumors, the lung-sparing intervention of bronchial transplantation was used.
Main Outcomes and Measures
The primary outcome was 90-day mortality. The secondary outcome was 90-day morbidity.
Results
Twenty patients were included in the study (mean age, 54.9 years; age range, 24-79 years; 13 men [65%]). Thirteen patients underwent tracheal (n = 5), bronchial (n = 7), or carinal (n = 1) transplantation. Airway transplantation was not performed in 7 patients for the following reasons: medical contraindication (n = 1), unavoidable pneumonectomy (n = 1), exploratory thoracotomy only (n = 2), and a lobectomy or bilobectomy was possible (n = 3). Among the 20 patients initially included, the overall 90-day mortality rate was 5% (1 patient underwent a carinal transplantation and died). No mortality at 90 days was observed among patients who underwent tracheal or bronchial reconstruction. Among the 13 patients who underwent airway transplantation, major 90-day morbidity events occurred in 4 (30.8%) and included laryngeal edema, acute lung edema, acute respiratory distress syndrome, and atrial fibrillation. There was no adverse event directly related to the surgical technique. Stent removal was performed at a postoperative mean of 18.2 months. At a median follow-up of 3 years 11 months, 10 of the 13 patients (76.9%) were alive. Of these 10 patients, 8 (80%) breathed normally through newly formed airways after stent removal. Regeneration of epithelium and de novo generation of cartilage were observed within aortic matrices from recipient cells.
Conclusions and Relevance
In this uncontrolled study, airway bioengineering using stented aortic matrices demonstrated feasibility for complex tracheal and bronchial reconstruction. Further research is needed to assess efficacy and safety.
Trial Registration
clinicaltrials.gov Identifier: NCT01331863
... Tracheal replacement is widely proposed as a solution for patients with end-stage upper airway disease for which conventional treatment strategies currently fail [19]. The complexity of upper airway disease has meant there has been no single, clear strategy for replacement. ...
Tracheal replacement for the treatment of end-stage airway disease remains an elusive goal. The use of tissue-engineered tracheae in compassionate use cases suggests that such an approach is a viable option. Here, a stem cell-seeded, decellularized tissue-engineered tracheal graft was used on a compassionate basis for a girl with critical tracheal stenosis after conventional reconstructive techniques failed. The graft represents the first cell-seeded tracheal graft manufactured to full good manufacturing practice (GMP) standards. We report important preclinical and clinical data from the case, which ended in the death of the recipient. Early results were encouraging, but an acute event, hypothesized to be an intrathoracic bleed, caused sudden airway obstruction 3 weeks post-transplantation, resulting in her death. We detail the clinical events and identify areas of priority to improve future grafts. In particular, we advocate the use of stents during the first few months post-implantation. The negative outcome of this case highlights the inherent difficulties in clinical translation where preclinical in vivo models cannot replicate complex clinical scenarios that are encountered. The practical difficulties in delivering GMP grafts underscore the need to refine protocols for phase I clinical trials.
... Based on the pioneering work by Vacanti and colleagues, tissue engineering techniques have become a potential solution [36,37] (Figure 11.2). The challenge is represented by the creation of cartilaginous tubes covered with respiratory cells [38]. ...
... In 1997, we proposed to evaluate the use of aortic grafts as matrices for airway transplantation. In successive experimental studies, we demonstrated encouraging results with the use of aortic autografts and fresh or cryopreserved allografts [27,38,[43][44][45]. We observed in vivo tissue engineering with epithelial and cartilage regeneration from bone-marrow stem cells [46]. ...
This chapter describes the two organs, trachea and larynx, in detail, explains the medical conditions that necessitate their partial resection or removal, and elaborates on the methods for their replacement with a special focus on the clinical larynx and tracheal replacement trials. It also describes the basics of the laryngeal and tracheal anatomy and histology. The goal is to provide the anatomical background in order to understand better the associated clinical problems that would require larynx and trachea replacement. Total laryngectomy is indicated for larynx or hypopharynx cancers, in advanced cases of larynx benign tumors, and in nonfunctioning larynx either post-traumatic or due to neurological diseases. Currently, there are four ways for restoring the laryngeal functions after total laryngectomy: laryngeal transplantation, grafts, biomaterial-based solutions (implants), and tissue engineering. The routine treatment after a laryngectomy in clinical medicine is to perform pharynx-to-esophagus anastomosis and tracheostomy to maintain breathing, causing great pain to the patients.
