Tissue-engineered trachea: A review.

Tracheal replacement is performed after resection of a portion of the trachea that was impossible to reconnect via direct anastomosis. A tissue-engineered trachea is one of the available options that offer many advantages compared to other types of graft. Fabrication of a functional tissue-engineered trachea for grafting is very challenging, as it is a complex organ with important components, including cartilage, epithelium and vasculature. A number of studies have been reported on the preparation of a graftable trachea. A laterally rigid but longitudinally flexible hollow cylindrical scaffold which supports cartilage and epithelial tissue formation is the key element. The scaffold can be prepared via decellularization of an allograft or fabricated using biodegradable or non-biodegradable biomaterials. Commonly, the scaffold is seeded with chondrocytes and epithelial cells at the outer and luminal surfaces, respectively, to hasten tissue formation and improve functionality. To date, several clinical trials of tracheal replacement with tissue-engineered trachea have been performed. This article reviews the formation of cartilage tissue, epithelium and neovascularization of tissue-engineered trachea, together with the obstacles, possible solutions and future. Furthermore, the role of the bioreactor for in vitro tracheal graft formation and recently reported clinical applications of tracheal graft were also discussed. Generally, although encouraging results have been achieved, however, some obstacles remain to be resolved before the tissue-engineered trachea can be widely used in clinical settings.