Deconstructing Tissue Engineered Trachea: Assessing the Role of Synthetic Scaffolds, Segmental Replacement and Cell Seeding on Graft Performance

Dharmadhikari, Sayali; Liu, Lumei; Shontz, Kimberly M.; Wiet, Matthew; White, Alan; Goins, Andrew; Akula, Himani; Johnson, Jed; Reynolds, Susan D.; Breuer, Christopher K.; Chiang, Tendy

doi:10.2139/ssrn.3428072

Cited by 8 publications

(48 citation statements)

References 35 publications

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“…In this study, we assessed the presence of host‐cell infiltration in STG implantation over time. Overall, 93.75% of graft recipients following STG implantation survived to planned euthanasia date, consistent with previously published data 4 . Understanding that syngeneic tracheal replacement can incorporate in the absence of graft ischemia, necrosis, stenosis, and collapse, we hypothesized that graft survival resulted in maintenance of graft‐dell populations rather than repopulation of the graft by host tissue.…”

Section: Discussionsupporting

confidence: 82%

“…The ideal tracheal replacement would be nonimmunogenic and permit healing in the absence of graft stenosis and collapse. We developed a mouse model of orthotopic syngeneic segmental tracheal implant and demonstrated that it is a robust model of tracheal replacement 4 . In this study, we assessed the presence of host‐cell infiltration in STG implantation over time.…”

Section: Discussionmentioning

confidence: 99%

“…Postoperative care was the same as our previous study 4 . Animals were evaluated daily during the first 2 weeks monitoring for weight loss >20%, stridor, and respiratory distress.…”

Section: Methodsmentioning

confidence: 99%

“…Mouse models of orthotopic segmental tracheal replacement have been used to study lung transplants as well as tracheal replacement 3–7 . Syngeneic trachea has been used in these models as a surgical control when comparing allografts and TETG constructs 8–10 .…”

Section: Introductionmentioning

confidence: 99%

“…We developed a mouse model of orthotopic tracheal replacement to replicate clinical findings seen in TETGs 3 . We have demonstrated that a syngeneic tracheal graft (STG) implant results in excellent survival without the development of graft stenosis 4 . We hypothesize that a fully functional, living tracheal graft can incorporate with the host with the preservation of native graft tissue and is not replaced by host cells.…”

Section: Introductionmentioning

confidence: 99%

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Spatial and Temporal Analysis of Host Cells in Tracheal Graft Implantation

et al. 2020

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Objectives/Hypothesis The ideal trachea replacement would be a living graft that is genetically identical to the host, avoiding the need for immunosuppression. We have developed a mouse model of syngeneic tracheal transplant that results in long‐term survival without graft stenosis or delayed healing. To understand how host cells contribute to tracheal transplant integration, we quantified the populations of host cells in the graft and native trachea following implant. Study Design: Tracheal transplant, tracheal replacement, regenerative medicine, animal model. Methods Tracheal grafts were obtained from female C57BL/6 mice and orthotopically transplanted into syngeneic male recipients. Cohorts were euthanized on day 14, day 45, and day 90 post‐transplantation. Host and graft tracheas were explanted and analyzed by histology. Male host cells were quantified using fluorescence in situ hybridization, and macrophages were quantified with immunofluorescence. Results Evidence of host‐derived cells was found in the midgraft at the earliest time point (14 days). Host‐derived cells transiently increased in the graft on day 45 and were predominantly found in the submucosa. By day 90, the population of host‐derived cells population declined to a similar level on day 14. Macrophage infiltration of host and graft tissue was observed at all time points and was greatest on day 90. Conclusions Tracheal graft integration occurs by way of subacute transient host‐cell infiltration and is primarily inflammatory in nature. Host‐cell contribution to the graft epithelium is limited. These data indicate that creation of living, nonimmunogenic tracheal graft could serve as a viable solution for long‐segment tracheal defects. Level of Evidence 3 Laryngoscope, 131:E340–E345, 2021

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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

“…Postoperative care was the same as our previous study 4 . Animals were evaluated daily during the first 2 weeks monitoring for weight loss >20%, stridor, and respiratory distress.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatial and Temporal Analysis of Host Cells in Tracheal Graft Implantation

et al. 2020

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Preparation and evaluation of a silk fibroin–polycaprolactone biodegradable biomimetic tracheal scaffold

Liu

Feng

et al. 2022

J Biomed Mater Res

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In tracheal tissue engineering, the construction of tracheal scaffolds with adequate biodegradable mechanical capacity and biological functions that mimic the structure of a natural trachea is challenging. To explore the feasibility of preparing biomimetic degradable scaffolds with C‐type cartilage rings and an inner tracheal wall of polycaprolactone and silk fibroin. A mold was made according to the diameter of a rabbit trachea, and a silk fibroin tube and polycaprolactone ring attached to the tube were obtained by solution casting. The ring was fixed to the tube at a specific spacing using electrostatic spinning technology to construct a biomimetic tracheal scaffold; its porous structure was observed by scanning electron microscopy, its degradation properties were determined by in vitro enzymatic hydrolysis and its mechanical properties were obtained by pressure testing. The composite scaffold was transplanted subcutaneously into a rabbit model, and the scaffold was taken at 1, 2, and 4 weeks after surgery for sectioning to observe pre‐vascularization. The Medical Ethics Committee of Guangdong Provincial People's Hospital approved the study. The general view of the biomimetic scaffold: the polycaprolactone ring was fixed firmly on the outer wall of the silk fibroin tube; the two corresponded in size, and they fitted closely. The surface of the polycaprolactone ring was smooth and dense, while the surface of the silk fibroin tube could be seen as a uniform porous structure. Scanning electron microscopy showed that the surface and profile of the fibroin tube had a uniform pore size and distribution. The pores were connected to form a network. In vitro, enzymatic hydrolysis experiments confirmed that the fibroin was degraded easily, with most being degraded at the end of week 1. The degradation slowed at 2, 3, and 4 weeks, while the degradation of polycaprolactone was extremely slow. A compression test showed that the compressive resistance of the silk fibroin–polycaprolactone biomimetic scaffolds was much better than that of the rabbit trachea at close thickness. In the tissue staining experiments, as the material degraded, fibrous tissues and blood vessels grew to replace the material, allowing the scaffold to obtain a blood supply and better mechanical properties. A quantitative analysis of CD31 showed that the results for the vascularization of the scaffold were better at 4 weeks than at 2 weeks following subcutaneous grafting (P < .05). The results confirmed that it is feasible to prepare porous, degradable silk fibroin–polycaprolactone biomimetic scaffolds with good mechanical properties and epithelial biological functions by mold casting.

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Tracheal Macrophages During Regeneration and Repair of Long‐Segment Airway Defects

et al. 2021

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Objectives/Hypothesis: Tissue-engineered tracheal grafts (TETGs) offer a potential solution for repair of long-segment airway defects. However, preclinical and clinical TETGs have been associated with chronic inflammation and macrophage infiltration. Macrophages express great phenotypic heterogeneity (generally characterized as classically activated [M1] vs. alternatively activated [M2]) and can influence tracheal repair and regeneration. We quantified and characterized infiltrating host macrophages using mouse microsurgical tracheal replacement models.Study Design: Translational research, animal model. Methods:We assessed macrophage infiltration and phenotype in animals implanted with syngeneic tracheal grafts, synthetic TETGs, or partially decellularized tracheal scaffolds (DTSs).Results: Macrophage infiltration was observed following tracheal replacement with syngeneic trachea. Both M1 and M2 macrophages were present in native trachea and increased during early tracheal repair (P = .014), with an M1/M2 ratio of 0.48 AE 0.15. In contrast, orthotopic implantation of synthetic TETGs resulted in a shift to M1 predominant macrophage phenotype with an increased M1/M2 ratio of 1.35 AE 0.41 by 6 weeks following implant (P = .035). Modulation of the synthetic scaffold with the addition of polyglycolic acid (PGA) resulted in a reduction of M1/M2 ratio due to an increase in M2 macrophages (P = .006). Using systemic macrophage depletion, the M1/M2 ratio reverted to native values in synthetic TETG recipients and was associated with an increase in graft epithelialization. Macrophage ratios seen in DTSs were similar to native values.Conclusions: M1 and M2 macrophages are present during tracheal repair. Poor epithelialization with synthetic TETG is associated with an elevation of the M1/M2 ratio. Macrophage phenotype can be altered with scaffold composition and hostdirected systemic therapies. DTSs exhibit M1/M2 ratios similar to those seen in native trachea and syngeneic tracheal replacement.

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Deconstructing Tissue Engineered Trachea: Assessing the Role of Synthetic Scaffolds, Segmental Replacement and Cell Seeding on Graft Performance

Cited by 8 publications

References 35 publications

Spatial and Temporal Analysis of Host Cells in Tracheal Graft Implantation

Spatial and Temporal Analysis of Host Cells in Tracheal Graft Implantation

Preparation and evaluation of a silk fibroin–polycaprolactone biodegradable biomimetic tracheal scaffold

Tracheal Macrophages During Regeneration and Repair of Long‐Segment Airway Defects

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