Using a Three-Dimensional Collagen Matrix to Deliver Respiratory Progenitor Cells to Decellularized Trachea In Vivo

Airway epithelial cells are a key barrier to inhaled toxicants, pollutants, and infectious agents. During severe epithelial injury and in transplantation settings, it would be desirable to rapidly reintroduce a functional epithelium through the engraftment of exogenous cells or by promoting host regeneration. However, the three-dimensional surface of the airway and the requirement to maintain airflow using stents, which cause mechanical shear at the tracheal surface, are challenges. In this study, we investigate a graft composed of human airway epithelial stem/progenitor cells and lung fibroblasts embedded within a supportive collagen matrix, which we propose might be more resistant to mechanical shear than cells exposed directly to the lumen surface. Cells were combined in a collagen I hydrogel before it was dehydrated into a mechanically stable sheet using RAFT((TM)) absorbers. After 48 h, KRT5+ spheroids formed and bromodeoxyuridine staining indicated active proliferation. To test whether epithelial cell- and fibroblast-containing grafts were able to successfully engraft on a section of trachea in vivo, they were implanted onto revascularized, decellularized tracheal scaffolds in a rabbit model. After 1 week, constructs had engrafted with signs of revascularization and keratin-positive cells were found throughout the scaffold. Although the long-term fate of these cells in vivo remains uncertain, we envisage that this strategy could improve host epithelial repair and/or contribute directly to mucosal regeneration. Impact Statement This article describes a method for engrafting epithelial progenitor cells to a revascularized scaffold in a protective and supportive collagen-rich environment. This method has the potential to overcome two key limitations of existing grafting techniques as epithelial cells are protected from mechanical shear and the relatively hypoxic phase that occurs while grafts revascularize, offering the opportunity to provide epithelial cells to decellularized allografts at the point of implantation. Advances in this area will improve the safety and efficacy of bioengineered organ transplantation.