Airway transplantation: a challenge for regenerative medicine

Abstract

After more than 50 years of research, airway transplantation remains a major challenge in the fields of thoracic surgery and regenerative medicine. Five principal types of tracheobronchial substitutes, including synthetic prostheses, bioprostheses, allografts, autografts and bioengineered conduits have been evaluated experimentally in numerous studies. However, none of these works have provided a standardized technique for the replacement of the airways. More recently, few clinical attempts have offered encouraging results with ex vivo or stem cell-based engineered airways and tracheal allografts implanted after heterotopic revascularization. In 1997, we proposed a novel approach: the use of aortic grafts as a biological matrix for extensive airway reconstruction. In vivo regeneration of epithelium and cartilage were demonstrated in animal models. This led to the first human applications using cryopreserved aortic allografts that present key advantages because they are available in tissue banks and do not require immunosuppressive therapy. Favorable results obtained in pioneering cases have to be confirmed in larger series of patients with extensive tracheobronchial diseases.

Figure 1

Histologic examination of cryopreserved aortic allograft at 6 months (sheep model) showing regenerated airway epithelium (hematoxylin and eosin staining; original magnification ×2.5).

Figure 2

Histologic examination of cryopreserved aortic allograft at 2 months (sheep model) showing regenerated cartilage (hematoxylin and eosin staining; original magnification ×10).