Feasibility of Bioengineered Tracheal and Bronchial Reconstruction Using Stented Aortic Matrices

Dr Emmanuel Martinod and colleagues from Hospital Avicenne near Paris France have reported the results of a prospective, single-institution safety and feasibility trial of airway replacement with aorta to reconstruct long-segment defects of the trachea and central bronchi. Over 6.5 years, 13 of 20 patients with end-stage tracheal lesions or proximal lung tumors requiring a pneumonectomy were enrolled in the study and underwent airway reconstruction with cryopreserved aortic allografts following definitive resection. Custom-made stents to support the allografts were used initially to prevent airway collapse but were removed at a postoperative mean duration of 18 months.With a median follow-up of nearly 4 years, 76.9% (10 of 13) of patients were alive and 80% (8 of 10) were breathing normally. Surprisingly – histological and molecular analysis of follow-up endobronchial biopsies showed regeneration of respiratory epithelium and de novo generation of cartilage within the aortic allografts from recipient cells. The study represents the culmination of 20 years of systematic investigation. In earlier animal models, these investigators showed first that aortic autografts, then aortic allografts could be used for circumferential tracheal replacement; that over a period of 6 to 12 months following an initial intense inflammatory response, the allograft developed spontaneous growth of mucociliary epithelium and vascularized cartilage originating from the recipient; and that tissue regeneration was potentially related to involvement of bone marrow-derived mesenchymal stem cells. This is rather difficult to explain – how did this happen ? – how did the the aorta transform itself into a trachea ?. Of course, further studies from different centers are needed to see if the results can be replicated. We also need to understand the mechanisms underlying tissue regeneration and the homing of stem cells. The work is indeed a great illustration of consistent efforts in a bench-to-bedside research. This study represents a major advance in the management of diseases affecting the central airways