Tyramine-Based Hyaluronan as a Tracheal Cartilage Substitute

Abstract

Objective: To investigate and characterize a novel tyramine-based hyaluronan/gelatin (THA/G) composite material. First, we demonstrate the ability of THA/G to adhere and maintain respiratory epithelial cells in an in vitro model. Second, we assess the feasibility of THA/G as a biologic cartilage substitute in a rabbit model of tracheal reconstruction.

Method: Immortalized human tracheal epithelial cells were grown on various concentrations of THA/G composites in vitro. Cricotracheal resection with replacement by THA/G was performed in 4 New Zealand white rabbits with auricular cartilage as control in 2 animals. Tracheal patency, graft retention, and mucosalization were evaluated via endoscopy, imaging, and histopathology.

Results: Epithelial cell growth was demonstrated on THA/G composites in vitro. In the rabbit model, all composites remained intact within the tracheal resection. However, the limited shear strength of the THA/G posed difficulties in securing the construct. At 3 and 6 weeks postimplantation, composites revealed minimal histologic evidence of macrophage or lymphocyte infiltration and were without apparent degradation. Tracheal lumen diameter was preserved in all animals. No experimental animals had evidence of dynamic airway collapse or chondromalacia. On endoscopy, there was no evidence of tracheal inflammation or granulation. However, at 6 weeks there was limited respiratory mucosa present on histology.

Conclusion: THA/G composites are a promising material for cartilage substitution. We demonstrate an ability to support epithelial cells and maintain tracheal structure. Improvements to increase the material’s shear strength are necessary so that it may have potential as an airway cartilage substitute.