Effect of cell seeding on neotissue formation in a tissue engineered trachea

Abstract

Background Surgical management of long segment tracheal disease is limited by a paucity of donor tissue and poor performance of synthetic materials. A potential solution is the development of a tissue-engineered tracheal graft (TETG), which promises an autologous airway conduit with growth capacity. Methods We created a TETG by vacuum seeding bone marrow-derived mononuclear cells (BM-MNCs) on a polymeric nanofiber scaffold. First, we evaluated the role of scaffold porosity on cell seeding efficiency in vitro. We then determined the effect of cell seeding on graft performance in vivo using an ovine model. Results Seeding efficiency of normal porosity (NP) grafts was significantly increased when compared to high porosity (HP) grafts (NP: 360.3 ± 69.19 ×103 cells/mm2; HP: 133.7 ± 22.73 ×103 cells/mm2; p<0.004). Lambs received unseeded (n=2) or seeded (n=3) NP scaffolds as tracheal interposition grafts for 6 weeks. Three animals were terminated early due to respiratory complications (n=2 unseeded, n=1 seeded). Seeded TETG explants demonstrated wound healing, epithelial migration, and delayed stenosis when compared to their unseeded counterparts. Conclusion Vacuum seeding BM-MNCs on nanofiber scaffolds for immediate implantation as tracheal interposition grafts is a viable approach to generate TETGs, but further preclinical research is warranted before advocating this technology for clinical application.

The innate immune response to lower respiratory tract E. Coli infection and the role of the CCL2-CCR2 axis in neonatal mice

“…They noted improved healing of the bone fracture with early administration of recombinant human TNF, whereas inhibition of CCR2 signaling impaired bone healing. Bone marrow-derived mononuclear cells have also been shown to promote cartilage and diabetic wound healing [41,42] and attenuate stenosis of tissue engineered tracheas [43]. Taken together, our data supports the hypothesis that an intact CCL2-CCR2 axis is required to optimize the dynamics and effectiveness of a regulated innate immune response that results in timely resolution of microbial challenge in neonatal lungs.…”

Designing a tissue-engineered tracheal scaffold for preclinical evaluation

“…We have previously investigated a prototype tracheal scaffold seeded with bone marrow derived mononuclear cells prior to implantation in a lamb model, but encountered graft stenosis in all animals [7]. Prior to embarking upon further critical in vivo studies, comprehensive analysis of candidate prototypes is warranted to identify a scaffold that would yield relevant and informative data once applied in an animal model.…”

“…Scaffolds were manufactured by Nanofiber Solutions, Inc. (Hilliard, OH) as previously described [7]. A custom mandrel composed of stainless steel was designed to match the dimensions of native juvenile sheep trachea (lumen diameter = 20 mm).…”

“…TETGs were then affixed on a customized porous mandrel (18 mm outer diameter) using Tegaderm™ (3M). The scaffold was then submerged in a 60 mL aliquot of the pooled, enriched mononuclear cell solution and vacuum seeded as previously described [7,8]. To mimic the scenario of immediate delivery to the operating room for implantation in future preclinical studies, seeded scaffolds were not incubated prior to sampling, rather samples were obtained directly after seeding and processed for DNA assay.…”

“…In 2015, our team described an ovine model that evaluated a biosynthetic scaffold that had previously been used in the clinical realm. All animals in this study suffered from stenosis and deterioration of respiratory function [7]. These grafts were designed to have supra-physiologic biomechanical properties due to concerns regarding malacia, however, it has been demonstrated in other organ systems that a mismatch in the biomechanical properties of graft and native tissue may lead to stenosis.…”