**10. Clinical application of tissue-engineered trachea and stem cells**

There have been some reports on the successful implantation of bioengineered tissues like tracheal seeded with stem cells clinically. Macchiarini and colleagues first reported the fabrication of human tissue-engineered trachea seeded with autologous epithelial cells and mesenchymal stem cell-derived chondrocytes. They reported that the engineered scaffold was later transplanted into a bronchomalacia patient to replace her left main bronchus. They concluded that there were evidences of functional airway activities and improved mechanical properties of the scaffold within 4 months [58].

In another clinical report by Otti and co-workers following a 5-year study, transplanted tracheal graft exhibited excellent vascularization and recellularization with respiratory epithelium and normal ciliary functions [59]. However, the authors also reported that because of longer production period of the tracheal graft, it might not be suitable for patients in need of urgent transplantation. In a quest to produce a tracheal graft with reduced production time, Baiguera and colleagues designed a human tracheal graft with production period of 3 weeks. The authors reported that the fabricated graft still possess structural and mechanical properties similar to native trachea [47].

In another innovative clinical study carried out by [60], the authors replaced an adult airway with a stem cell-seeded decellularized tracheal scaffold in a patient suffering from congenital tracheal stenosis. They concluded that the graft scaffold showed accelerated revascularization followed by epithelialization after 12 months. Recently, human-derived decellularized trachea seeded with stem cells was demonstrated to be efficient in terms of stability, epithelialization, neovascularization, and chondrocytes formation in a patient suffering from tracheal stenosis [61].
