Using a 3D 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. Here, we investigate a graft composed of human airway epithelial stem/progenitor cells and lung fibroblasts embedded within a supportive collagen matrix, that would 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 RAFTTM absorbers. After 48 hours, KRT5+ spheroids formed and BrdU 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 re-vascularized, decellularized tracheal scaffolds in a rabbit model. After one week, constructs had engrafted with signs of re-vascularization 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.