In vivo performance of decellularized tracheal grafts in the reconstruction of long length tracheal defects: Experimental study

Bioengineered tracheal graft with enhanced vascularization and mechanical stability for functional airway reconstruction

Tracheal reconstruction remains a formidable clinical challenge due to the complex structural, biomechanical, and physiological requirements of the airway. Traditional approaches, including autologous grafts, allografts, and synthetic prostheses, suffer from limitations such as donor site morbidity, immune rejection, and mechanical instability. Tissue-engineered tracheal grafts have emerged as a promising alternative, integrating advanced biomaterials, cellular therapies, and biofabrication techniques to create functional airway replacements. Synthetic polymers, such as polycaprolactone and polylactic acid, provide mechanical stability and tunable degradation properties, while extracellular matrix - derived biomaterials enhance biocompatibility and support cellular integration. Recent advances in stem cell biology, particularly the application of mesenchymal stem cells, induced pluripotent stem cells, and adipose-derived stem cells, have facilitated cartilage regeneration, epithelialization, and immune modulation within engineered constructs. However, achieving adequate vascularization remains a major bottleneck, necessitating the development of pre-vascularized scaffolds, growth factor delivery systems, and in vivo bioreactor strategies. Emerging technologies, including 3D bioprinting, electrospinning, and AI-driven scaffold design, are transforming the landscape of tracheal tissue engineering by enabling precise control over scaffold architecture, cellular distribution, and functional integration. Despite these advances, challenges such as mechanical failure, chronic inflammation, and regulatory hurdles must be addressed to ensure clinical translation. This review critically examines the latest advancements, persisting challenges, and future perspectives in artificial trachea engineering, providing a comprehensive roadmap for its development and clinical implementation.

Enhancing long-segmental tracheal restoration: A self-repairing hydrogel loaded with chondrocytokines for sutureless anastomosis and cartilage regeneration

Artificial tracheal substitutes encounter significant challenges during long-segmental tracheal defects (LSTD) reconstruction, notably early postoperative anastomotic stenosis and tracheal chondromalacia. Mitigating early anastomotic stenosis by creating a compliant sutureless substitute is pivotal. Enhancing its chondrogenic capacity is equally critical for sustained healthy tracheal cartilage regeneration. This study proposes a self-healing hydrogel for sutureless tracheal anastomosis to mitigate anastomotic stenosis, enriched with kartogenin (KGN) and transforming growth factor-β1 (TGFβ1) to bolster chondrogenic properties. Initially, two precursor solutions were prepared: 1) aldehyde-modified hyaluronic acid with sulfonation and β-cyclodextrin-CHO loaded with KGN; 2) hydrazide-grafted gelatin loaded with TGFβ1. Coextrusion of these solutions resulted in a gelated G + TGFβ1/sH-CD + KGN hydrogel, characterized by a robust covalent bonding network of acylhydrazones between hydrazide and aldehyde groups, imparting excellent self-healing properties. The G + TGFβ1/sH-CD + KGN hydrogels, showcasing favorable cytocompatibility, excellent injectability, and rapid gelation, were loaded with bone marrow stem cells. These were customized into O-shaped rings and assembled into a malleable tracheal substitute using our established ring-to-tube method. This resultant compliant substitute facilitated sutureless anastomosis of LSTD in a rabbit model, attributed to the Schiff base reaction between the hydrogel's carbonyl group and the tissue's amino group. Notably, the tracheal substitute reduced early postoperative anastomotic stenosis, maintained tracheal patency, alleviated sputum blockage, promoted reepithelization, and increased the survival rate of the experimental rabbits. The sustained release of chondrocytokines resulted in excellent tracheal cartilage regeneration. Employing chondrocytokines-loaded hydrogels with self-healing properties represents a significant advancement in sutureless tracheal anastomosis and tracheal cartilage regeneration, holding promising potential in inhibiting early postoperative anastomotic stenosis and tracheal chondromalacia when treating LSTD.

Tracheal Tissue Engineering: Principles and State of the Art

Patients affected by long-segment tracheal defects or stenoses represent an unsolved surgical issue, since they cannot be treated with the conventional surgery of tracheal resection and consequent anastomosis. Hence, different strategies for tracheal replacement have been proposed (synthetic materials, aortic allografts, transplantation, autologous tissue composites, and tissue engineering), each with advantages and drawbacks. Tracheal tissue engineering, on the other hand, aims at recreating a fully functional tracheal substitute, without the need for the patient to receive lifelong immunosuppression or endotracheal stents. Tissue engineering approaches involve the use of a scaffold, stem cells, and humoral signals. This paper reviews the main aspects of tracheal TE, starting from the choice of the scaffold to the type of stem cells that can be used to seed the scaffold, the methods for their culture and expansion, the issue of graft revascularization at the moment of in vivo implantation, and experimental models of tracheal research. Moreover, a critical insight on the state of the art of tracheal tissue engineering is also presented.

Tracheal replacement with aortic grafts: Bench to clinical practice

Tracheal reconstruction following extensive resection for malignant or benign lesions remains a major challenge in thoracic surgery. Numerous studies have attempted to identify the optimal tracheal replacement with different biological or prosthetic materials, such as various homologous and autologous tissues, with no encouraging outcomes. Recently, a few clinical studies reported attaining favorable outcomes using in vitro or stem cell-based airway engineering and also with tracheal allograft implantation following heterotopic revascularization. However, none of the relevant studies offered a standardized technology for airway replacement. In 1997, a novel approach to airway reconstruction was proposed, which involved using aortic grafts as the biological matrix. Studies on animal models reported achieving in-vivo cartilage and epithelial regeneration using this approach. These encouraging results inspired the subsequent application of cryopreserved aortic allografts in humans for the first time. Cryopreserved aortic allografts offered further advantages, such as easy availability in tissue banks and no requirement for immunosuppressive treatments. Currently, stented aortic matrix-based airway replacement has emerged as a standard approach, and its effectiveness was also verified in the recently reported TRITON-01 study. In this context, the present review aims to summarize the current status of the application of aortic grafts in tracheal replacement, including the latest advancements in experimental and clinical practice.

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.

Successful tracheal regeneration using biofabricated autologous analogues without artificial supports

Tracheas have a tubular structure consisting of cartilage rings continuously joined by a connective tissue membrane comprising a capillary network for tissue survival. Several tissue engineering efforts have been devoted to the design of scaffolds to produce complex structures. In this study, we successfully fabricated an artificial materials-free autologous tracheal analogue with engraftment ability by combining in vitro cell self-aggregation technique and in-body tissue architecture. The cartilage rings prepared by aggregating chondrocytes on designated culture grooves that induce cell self-aggregation were alternately connected to the connective tissues to form tubular tracheal analogues by subcutaneous embedding as in-body tissue architecture. The tracheal analogues allogeneically implanted into the rat trachea matured into native-like tracheal tissue by covering of luminal surfaces by the ciliated epithelium with mucus-producing goblet cells within eight months after implantation, while maintaining their structural integrity. Such autologous tracheal analogues would provide a foundation for further clinical research on the application of tissue-engineered tracheas to ensure their long-term functionality.

A Review of Woven Tracheal Stents: Materials, Structures, and Application

The repair and reconstruction of tracheal defects is a challenging clinical problem. Due to the wide choice of materials and structures, weaving technology has shown unique advantages in simulating the multilayer structure of the trachea and providing reliable performance. Currently, most woven stent-based stents focus only on the effect of materials on stent performance while ignoring the direct effect of woven process parameters on stent performance, and the advantages of weaving technology in tissue regeneration have not been fully exploited. Therefore, this review will introduce the effects of stent materials and fabric construction on the performance of tracheal stents, focusing on the effects of weaving process parameters on stent performance. We will summarize the problems faced by woven stents and possible directions of development in the hope of broadening the technical field of artificial trachea preparation.

Cartilaginous Extracellular Matrix Enriched with Human Gingival Mesenchymal Stem Cells Derived "Matrix Bound Extracellular Vesicles" Enabled Functional Reconstruction of Tracheal Defect

Stem cells derived extracellular vesicles (EVs) conceive cues essential for tissue repair. Mammalian cartilaginous extracellular matrix (cECM) may not be optimally inductive for tracheal regeneration because of the granulomatous, instead of regenerative, responses in injured adult mammalian tracheas. Given the high regenerative capacity of gingiva, it is hypothesized human gingival mesenchymal stem cells derived EVs (gEVs) can induce mammalian tracheal epithelia regeneration. Coculturing chondrocytes with GMSCs produce abundant "matrix bound gEVs (gMVs)" in forming cartilaginous ECM, which are further preserved in acellular cECM (cACM) following mild, short-period decellularization. The results show that gMVs-cACM could be well anchored on polyglycerol sebacate microporous patch thus enforce the surgical suturability and mechanical strength. In rabbit tracheal defect, the gMVs-cACM patch induces rapid regeneration of vascularized ciliated columnar epithelium, which supports long-term survival of animals. gMVs-cACM treated groups exhibit proliferation of tracheal progenitors-basal epithelial cells, as well as, activation of JAK2/STAT1 pathway in reparative cells. This study departs from conventional focuses on tissue derived ECM and introduces a new approach for tracheal tissue regeneration.