Successful Early Neovascularization in Composite Tracheal Grafts

Proteomic Analysis of Surgery-induced Stress Post-Tracheal Transplantation Highlights Changes in Matrisome

OBJECTIVE

Investigate the impact of Surgery-induced stress (SIS) on the normal airway repair process after airway reconstruction using a mouse microsurgery model, mass spectrometry (MS), and bioinformatic analysis.

METHODS

Tracheal tissue from non-surgical (N = 3) and syngeneic tracheal grafts at 3 months post-replacement (N = 3) were assessed using mass spectrometry. Statistical analysis was done using MASCOT via Proteome Discoverer™. Proteins were categorized into total, dysregulated, suppressed, and evoked proteins in response to SIS. Dysregulated proteins were identified using cut-off values of -1 1 and t-test (p value <0.05). Enriched pathways were determined using STRING and Metascape.

RESULTS

At the three-month post-operation mark, we noted a significant increase in submucosal cellular infiltration (14343 ± 1286 cells/mm2, p = 0.0003), despite reduced overall thickness (30 ± 3 μm, p = 0.01), compared to Native (4578 ± 723 cells/mm2; 42 ± 6 μm). Matrisome composition remained preserved, with proteomic analysis identifying 193 commonly abundant proteins, encompassing 7.2% collagens, 34.2% Extracellular matrix (ECM) glycoproteins, 6.2% proteoglycans, 33.2% ECM regulators, 14.5% Extracellular matrix-affiliated, and 4.7% secreted factors. Additionally, our analysis unveiled a unique proteomic signature of 217 "Surgery-evoked proteins" associated with SIS, revealing intricate connections among neutrophils, ECM remodeling, and vascularization through matrix metalloproteinase-9 interaction.

CONCLUSIONS

Our study demonstrated the impact of SIS on the extracellular matrix, particularly MMP9, after airway reconstruction. The novel identification of MMP9 prompts further investigation into its potential role in repair.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:4052-4059, 2024.

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.

Recent Advances in the Application of 3D-Printing Bioinks Based on Decellularized Extracellular Matrix in Tissue Engineering

In recent years, 3D bioprinting with various types of bioinks has been widely used in tissue engineering to fabricate human tissues and organs with appropriate biological functions. Decellularized extracellular matrix (dECM) is an excellent bioink candidate because it is enriched with a variety of bioactive proteins and bioactive factors and can provide a suitable environment for tissue repair or tissue regeneration while reducing the likelihood of severe immune rejection. In this Review, we systematically review recent advances in 3D bioprinting and decellularization technologies and comprehensively detail the latest research and applications of dECM as a bioink for tissue engineering in various systems, with the aim of providing a reference for researchers in tissue engineering to better understand the properties of dECM bioinks.

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.

The Autonomization Principle in Vascularized Flaps: An Alternative Strategy for Composite Tissue Scaffold In Vivo Revascularization

Autonomization is a physiological process allowing a flap to develop neo-vascularization from the reconstructed wound bed. This phenomenon has been used since the early application of flap surgeries but still remains poorly understood. Reconstructive strategies have greatly evolved since, and fasciocutaneous flaps have progressively replaced muscle-based reconstructions, ensuring better functional outcomes with great reliability. However, plastic surgeons still encounter challenges in complex cases where conventional flap reconstruction reaches its limitations. Furthermore, emerging bioengineering applications, such as decellularized scaffolds allowing a complex extracellular matrix to be repopulated with autologous cells, also face the complexity of revascularization. The objective of this article is to gather evidence of autonomization phenomena. A systematic review of flap autonomization is then performed to document the minimum delay allowing this process. Finally, past and potential applications in bio- and tissue-engineering approaches are discussed, highlighting the potential for in vivo revascularization of acellular scaffolds.

Tissue Engineering: Current Technology for Facial Reconstruction

Facial reconstruction is a complex surgical process that requires intricate three-dimensional (3D) concepts for optimal functional and aesthetic outcomes. Conventional reconstruction of structural facial anomalies, such as those including cartilage or bony defects, typically rely on hand-carving autologous constructs harvested from a separate donor site, and shaping that cartilage or bone into a new structural framework. Tissue engineering has emerged in recent decades as a potential approach to mitigate the need for donor site morbidity while improving precision in the design of reconstructive construct. Computer-aided design and computer-aided manufacturing have allowed for a digital 3D workflow to digitally execute the planned reconstruction in virtual space. 3D printing and other manufacturing techniques can then be utilized to create custom-fabricated scaffolds and guides to improve the reconstructive efficiency. Tissue engineering can be paired with custom 3D-manufactured scaffolds to theoretically create an ideal framework for structural reconstruction. In the past decade, there have been several compelling preclinical studies demonstrating the capacity to induce chondrogenesis or osteogenesis in a custom scaffold. However, to date, these preclinical data have not yet translated into significant clinical experience. This translation has been hindered by a lack of consensus on the ideal materials and cellular progenitors to be utilized in these constructs and a lack of regulatory guidance and control to enable clinical application. In this review, we highlight the current state of tissue engineering in facial reconstruction and exciting potential for future applications as the field continues to advance.