Segmental Trachea Research Articles

Aptamer‐Directed Bidirectional Modulation of Vascular Niches for Promoted Regeneration of Segmental Trachea Defect

AbstractThe simultaneous regeneration of avascular cartilage ring and vascular connective tissue in one biomimetic tracheal substitute has remained a remarkable challenge in the clinical breakthrough of tissue‐engineered trachea for repairing segmental trachea defect. Herein, an unprecedented strategy based on bidirectional modulation of vascular niches is developed through tailoring the tissue‐specific scaffolds with programmable functional nucleic acids. Namely, the antiangiogenic characteristic of cartilage‐specific scaffold enables development of an avascular niche, and thereby facilitating the regeneration of biomimetic cartilage. Conversely, the angiogenic capability of connective tissue‐specific scaffold fosters the creation of a vascular niche, and thus enhancing the regeneration of biomimetic connective tissue. Importantly, the steadily immobilized nucleic acids in specific scaffolds enable the seamless integration of angiogenic and antiangiogenic functions without mutual interference. As such, biomimetic tracheas are successfully engineered with the vascular connective tissue scattering between avascular cartilage rings using the assembly of tissue‐specific scaffolds. The results from in vivo trachea regeneration and the in situ trachea reconstruction demonstrate the satisfactory tissue‐specific regeneration of (a)vascular niches along with optimal structural, mechanical, and physiological features. This study represents the first demonstration of trachea regeneration promoted by modulation of tissue‐specific vascular niches, which adds an additional dimension for the clinical trachea reconstruction.

Multi-Tissue Integrated Tissue-Engineered Trachea Regeneration Based on 3D Printed Bioelastomer Scaffolds.

Functional segmental trachea reconstruction is a critical concern in thoracic surgery, and tissue-engineered trachea (TET) holds promise as a potential solution. However, current TET falls short in fully restoring physiological function due to the lack of the intricate multi-tissue structure found in natural trachea. In this research, a multi-tissue integrated tissue-engineered trachea (MI-TET) is successfully developed by orderly assembling various cells (chondrocytes, fibroblasts and epithelial cells) on 3D-printed PGS bioelastomer scaffolds. The MI-TET closely resembles the complex structures of natural trachea and achieves the integrated regeneration of four essential tracheal components: C-shaped cartilage ring, O-shaped vascularized fiber ring, axial fiber bundle, and airway epithelium. Overall, the MI-TET demonstrates highly similar multi-tissue structures and physiological functions to natural trachea, showing promise for future clinical advancements in functional TETs.

Instant trachea reconstruction using 3D-bioprinted C-shape biomimetic trachea based on tissue-specific matrix hydrogels

Currently, 3D-bioprinting technique has emerged as a promising strategy to offer native-like tracheal substitutes for segmental trachea reconstruction. However, there has been very limited breakthrough in tracheal repair using 3D-bioprinted biomimetic trachea owing to the lack of ideal bioinks, the requirement for precise structural biomimicking, and the complexity of multi-step surgical procedures by mean of intramuscular pre-implantation. Herein, we propose a one-step surgical technique, namely direct end-to-end anastomosis using C-shape 3D-bioprinted biomimetic trachea, for segmental trachea defect repair. First, two types of tissue-specific matrix hydrogels were exploited to provide mechanical and biological microenvironment conducive to the specific growth ways of cartilage and fibrous tissue respectively. In contrast to our previous O-shape tracheal design, the tubular structure of alternating C-shape cartilage rings and connecting vascularized-fibrous-tissue rings was meticulously designed for rapid 3D-bioprinting of tracheal constructs with optimal printing paths and models. Furthermore, in vivo trachea regeneration in nude mice showed satisfactory mechanical adaptability and efficient physiological regeneration. Finally, in situ segmental trachea reconstruction by direct end-to-end anastomosis in rabbits was successfully achieved using 3D-bioprinted C-shape biomimetic trachea. This study demonstrates the potential of advanced 3D-bioprinting for instant and efficient repair of segmental trachea defects.

Functional Trachea Reconstruction Using 3D-Bioprinted Native-Like Tissue Architecture Based on Designable Tissue-Specific Bioinks.

Functional segmental trachea reconstruction remains a remarkable challenge in the clinic. To date, functional trachea regeneration with alternant cartilage‐fibrous tissue‐mimetic structure similar to that of the native trachea relying on the three‐dimensional (3D) bioprinting technology has seen very limited breakthrough. This fact is mostly due to the lack of tissue‐specific bioinks suitable for both cartilage and vascularized fibrous tissue regeneration, as well as the need for firm interfacial integration between stiff and soft tissues. Here, a novel strategy is developed for 3D bioprinting of cartilage‐vascularized fibrous tissue‐integrated trachea (CVFIT), utilizing photocrosslinkable tissue‐specific bioinks. Both cartilage‐ and fibrous tissue‐specific bioinks created by this study provide suitable printability, favorable biocompatibility, and biomimetic microenvironments for chondrogenesis and vascularized fibrogenesis based on the multicomponent synergistic effect through the hybrid photoinitiated polymerization reaction. As such, the tubular analogs are successfully bioprinted and the ring‐to‐ring alternant structure is tightly integrated by the enhancement of interfacial bonding through the amidation reaction. The results from both the trachea regeneration and the in situ trachea reconstruction demonstrate the satisfactory tissue‐specific regeneration along with realization of mechanical and physiological functions. This study thus illustrates the 3D‐bioprinted native tissue‐like trachea as a promising alternative for clinical trachea reconstruction.

Photocrosslinked natural hydrogel composed of hyaluronic acid and gelatin enhances cartilage regeneration of decellularized trachea matrix

Repair of long segmental trachea defects is always a great challenge in the clinic. The key to solving this problem is to develop an ideal trachea substitute with biological function. Using of a decellularized trachea matrix based on laser micropore technique (LDTM) demonstrated the possibility of preparing ideal trachea substitutes with tubular shape and satisfactory cartilage regeneration for tissue-engineered trachea regeneration. However, as a result of the very low cell adhesion of LDTM, an overly high concentration of seeding cell is required, which greatly restricts its clinical translation. To address this issue, the current study proposed a novel strategy using a photocrosslinked natural hydrogel (PNH) carrier to enhance cell retention efficiency and improve tracheal cartilage regeneration. Our results demonstrated that PNH underwent a rapid liquid-solid phase conversion under ultraviolet light. Moreover, the photo-generated aldehyde groups in PNH could rapidly react with inherent amino groups on LDTM surfaces to form imine bonds, which efficiently immobilized the cell-PNH composite to the surfaces of LDTM and/or maintained the composite in the LDTM micropores. Therefore, PNH significantly enhanced cell-seeding efficiency and achieved both stable cell retention and homogenous cell distribution throughout the LDTM. Moreover, PNH exhibited excellent biocompatibility and low cytotoxicity, and provided a natural three-dimensional biomimetic microenvironment to efficiently promote chondrocyte survival and proliferation, extracellular matrix production, and cartilage regeneration. Most importantly, at a relatively low cell-seeding concentration, homogeneous tubular cartilage was successfully regenerated with an accurate tracheal shape, sufficient mechanical strength, good elasticity, typical lacuna structure, and cartilage-specific extracellular matrix deposition. Our findings establish a versatile and efficient cell-seeding strategy for regeneration of various tissue and provide a satisfactory trachea substitute for repair and functional reconstruction of long segmental tracheal defects.

Transplantation of a 3D-printed tracheal graft combined with iPS cell-derived MSCs and chondrocytes

For successful tracheal reconstruction, tissue-engineered artificial trachea should meet several requirements, such as biocompatible constructs comparable to natural trachea, coverage with ciliated respiratory mucosa, and adequate cartilage remodeling to support a cylindrical structure. Here, we designed an artificial trachea with mechanical properties similar to the native trachea that can enhance the regeneration of tracheal mucosa and cartilage through the optimal combination of a two-layered tubular scaffold and human induced pluripotent stem cell (iPSC)-derived cells. The framework of the artificial trachea was fabricated with electrospun polycaprolactone (PCL) nanofibers (inner) and 3D-printed PCL microfibers (outer). Also, human bronchial epithelial cells (hBECs), iPSC-derived mesenchymal stem cells (iPSC-MSCs), and iPSC-derived chondrocytes (iPSC-Chds) were used to maximize the regeneration of tracheal mucosa and cartilage in vivo. After 2 days of cultivation using a bioreactor system, tissue-engineered artificial tracheas were transplanted into a segmental trachea defect (1.5-cm length) rabbit model. Endoscopy did not reveal granulation ingrowth into tracheal lumen. Alcian blue staining clearly showed the formation of ciliated columnar epithelium in iPSC-MSC groups. In addition, micro-CT analysis showed that iPSC-Chd groups were effective in forming neocartilage at defect sites. Therefore, this study describes a promising approach for long-term functional reconstruction of a segmental tracheal defect.

Long-segmental tracheal reconstruction in rabbits with pedicled Tissue-engineered trachea based on a 3D-printed scaffold

Long-segmental tracheal defects constitute an intractable clinical problem, due to the lack of satisfactory tracheal substitutes for surgical reconstruction. Tissue engineered artificial substitutes could represent a promising approach to tackle this challenge. In our current study, tissue-engineered trachea, based on a 3D-printed poly (l-lactic acid) (PLLA) scaffold with similar morphology to the native trachea of rabbits, was used for segmental tracheal reconstruction. The 3D-printed scaffolds were seeded with chondrocytes obtained from autologous auricula, dynamically pre-cultured in vitro for 2 weeks, and pre-vascularized in vivo for another 2 weeks to generate an integrated segmental trachea organoid unit. Then, segmental tracheal defects in rabbits were restored by transplanting the engineered tracheal substitute with pedicled muscular flaps. We found that the combination of in vitro pre-culture and in vivo pre-vascularization successfully generated a segmental tracheal substitute with bionic structure and mechanical properties similar to the native trachea of rabbits. Moreover, the stable blood supply provided by the pedicled muscular flaps facilitated the survival of chondrocytes and accelerated epithelialization, thereby improving the survival rate. The segmental trachea substitute engineered by a 3D-printed scaffold, in vitro pre-culture, and in vivo pre-vascularization enhanced survival in an early stage post-operation, presenting a promising approach for surgical reconstruction of long segmental tracheal defects. Statement of SignificanceWe found that the combination of in vitro pre-culture and in vivo pre-vascularization successfully generated a segmental tracheal substitute with bionic structure and mechanical properties similar to the native trachea of rabbits. Moreover, the stable blood supply provided by the pedicled muscular flaps facilitated the survival of chondrocytes and accelerated epithelialization, thereby improving the survival rate of the rabbits. The segmental trachea substitute engineered by a 3D-printed scaffold, in vitro pre-culture, and in vivo pre-vascularization enhanced survival in an early stage post-operation, presenting a promising approach for surgical reconstruction of long segmental tracheal defects.

Tissue engineering of a composite trachea construct using autologous rabbit chondrocytes.

The repair of large tracheal segmental defects remains an unsolved problem. The goal of this study is to apply tissue engineering principles for the fabrication of large segmental trachea replacements. Engineered tracheal replacements composed of autologous cells (neotracheas) were tested in a New Zealand White rabbit model. Neotracheas were formed in the rabbit neck by wrapping a silicone tube with consecutive layers of skin epithelium, platysma muscle, and an engineered cartilage sheet and allowing the construct to mature for 8-12weeks. In total, 28 rabbits were implanted and the neotracheas assessed for tissue morphology. In 11 cases, neotracheas deemed sufficiently strong were used to repair segmental tracheal defects. Initially, the success rate of producing structurally sound neotracheas was impeded by physical disruption of the cartilage sheets during animal handling, but by the end of the study, 15 of 18 neotracheas (83.3%) were structurally sound. Of the 15 structurally sound neotracheas, 11 were used for segmental reconstruction and were left in place for up to 21days. Histological examination showed the presence of variable amounts of viable epithelium, a vascularized platysma flap, and a layer of safranin O-positive cartilage along with evidence of endochondral ossification. Rabbits that had undergone segmental reconstruction showed good tracheal integration, had a viable epithelium with vascular support, and the cartilage was sufficiently strong to maintain a lumen when palpated. The results demonstrated that viable, trilayered, scaffold-free neotracheas could be constructed from autologous cells and could be integrated into native trachea to repair a segmental defect.

In-vivo trachea regeneration: fabrication of a tissue-engineered trachea in nude mice using the body as a natural bioreactor.

To investigate the outcomes of implanting rat decellularized trachea scaffold (DTS) between the paravertebral muscles of nude mice using the body as a bioreactor for total graft recellularization. The tracheas of four rats were aseptically resected and decellularized. To assess the efficiency of the decellularization procedure, all decellularized scaffolds and native control tissues were evaluated with scanning electron microscopy (SEM), DAPI staining, DNA quantification, biomechanical analyses and hydroxyproline measurement. They were then implanted between the paravertebral muscles of four nude mice. The biopsies were precisely evaluated at 1, 3, 6 and 12months postoperatively for tracheal cartilage and soft tissue recellularization by staining for TTF1, CD34, S100 and leukocyte common antibody. Hematoxylin and eosin (H&E) staining, SEM and the tensile test confirmed the preservation of the tissue structure and the biophysical and biochemical properties of the DTS. The present study clearly demonstrated that the hydroxyproline content of the DTS was similar to that of the native tissue. On the other hand, in biopsy samples obtained after 12months, histological evaluation showed superior organization and cell seeding in both the cartilage and connective tissues. This study demonstrated the feasibility of using a natural bioreactor for recellularizing DTS; this may have the potential to facilitate homologous transplantation for repairing segmental trachea defects.

A review of the management and prognosis of thyroid carcinoma with tracheal invasion.

The objective of the study was to explore the surgical approaches, treatment significance and prognosis of thyroid carcinoma with tracheal invasion. We retrospectively reviewed 48 patients with tracheal invasion by papillary thyroid carcinoma, follicular thyroid carcinoma and medullary thyroid carcinoma by means of clinical data ranging from 1993 to 2011. The patients were classified into three groups in terms of the depth and extent of tracheal invasion by the tumors, i.e., group A of 18 patients with localized tracheal invasion; group B of 21 patients with intraluminal tracheal invasion, and group C of nine patients with extensive invasion of the trachea, larynx, esophagus and/or mediastinum. Of these patients, 18 received radical tumorectomy and segmental resection of the outer layer of the tracheal wall; 21 had radical tumorectomy, circumferential sleeve trachea resection or segmental tracheal resection plus tracheal repair, and the remaining nine patients underwent radical tumorectomy, segmental trachea resection and esophagolaryngectomy. 46 patients took I(131) oral solution and/or had external radiotherapy postoperatively. A survival analysis was done using Kaplan-Meier Estimator for cumulative survival probability together with Log-Rank test, and Cox Regression Model was used for multivariate analysis. (1) In group A of 18 patients, 10 took I(131)oral solution and 7 received radiotherapy after surgery. The overall 5 and 10-year survival rates were 88.93 and 77.78 %, respectively; (2) In group B of 21 patients, 15 took I(131) oral solution and 7 received radiotherapy after surgery. The overall 5 and 10-year survival rates were 90.47 and 61.87 %, respectively; (3) In group C of 9 patients, 7 received radiotherapy after surgery. The overall 5 and 10-year survival rates were 77.78 and 22.22 %, respectively. Whether they received postsurgical I(131) treatment or radiotherapy, there was a statistical difference between the 5-year survival rates and the 10-year survival rates in all of these three groups (P value in each group is <0.05). In the treatment of thyroid carcinoma with tracheal invasion, radical tumorectomy plus tracheal repair, segmental tracheal resection or circumferential sleeve trachea resection could lengthen the survival time. Radical tumorectomy could enhance the probability of survival of patients with thyroid carcinoma that had extensively invaded the larynx, esophagus and/or mediastinum. Postsurgical I(131) treatment and radiotherapy enhanced the probability of survival.

Tracheal development in the Drosophila brain is constrained by glial cells

The Drosophila brain is tracheated by the cerebral trachea, a branch of the first segmental trachea of the embryo. During larval stages the cerebral trachea splits into several main (primary) branches that grow around the neuropile, forming a perineuropilar tracheal plexus (PNP) at the neuropile surface. Five primary tracheal branches whose spatial relationship to brain compartments is relatively invariant can be distinguished, although the exact trajectories and branching pattern of the brain tracheae are surprisingly variable. Immunohistochemical and electron microscopic studies demonstrate that all brain tracheae grow in direct contact with the glial cell processes that surround the neuropile. To investigate the effect of glia on tracheal development, embryos and larvae lacking glial cells as a result of a genetic mutation or a directed ablation were analyzed. In these animals, the tracheal branching pattern was highly abnormal. In particular, the number of secondary branches entering the central neuropile was increased. Wild-type larvae possess only two central tracheae, typically associated with the mushroom body and the antennocerebral tract. In larvae lacking glial cells, six to ten tracheal branches penetrate the neuropile in a variable pattern. This finding indicates that glia-derived signals constrained tracheal growth in the Drosophila brain and restrict the number of branches entering the neuropile.

Successful Tracheal Autotransplantation With Two-Stage Approach Using the Greater Omentum

Background. Although many studies on reconstruction of extensive circumferential tracheal defects with a segmental trachea have been done, up to date, no reliable and satisfactory tracheal transplantation procedure has been developed. We conducted this experiment to investigate feasibility and efficacy of a staged tracheal transplantation approach for tracheal reconstruction. Methods. Twelve dogs were divided equally into groups I and II. A segment of cervical tracheas (six rings) was harvested as an autograft and implanted heterotopically into the greater omentum. Two weeks later, the autografts with their omental pedicles were transplanted orthotopically to the cervical (group I) or the thoracic portion of the trachea (group II). Bronchoscopic examination were performed monthly during a 5-month follow-up period. After sacrificing the dogs, we had the grafts examined macroscopically and microscopically. Results. The dogs of both groups survived well until the end of the follow-up. No abnormal findings were observed through bronchoscopy. The grafts had normal appearance, without shrinkage, granulation, or necrosis by postmortem gross examination. Histologic examination showed the structures of the grafts were intact. Conclusions. We conclude that the two-stage tracheal transplantation approach using the greater omentum is feasible, and can facilitate the survival of a tracheal graft as well.