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Ann Thorac Surg 2000;70:1884-1885
© 2000 The Society of Thoracic Surgeons

Invited commentary

^a Department of Thoracic and Vascular Surgery, Heidehaus Hospital, Am Leineufer 70, D-30419 Hannover, Germany

e-mail: pmacchiarini{at}compuserve.com

Naskanishi and colleagues investigated the tolerable warm ischemia time of tracheal autografts before 3 months cryopreservation. In a rat model, the investigators demonstrate that tracheal autografts are better preserved with warm ischemia periods of less than 18 hours and conclude that human cadavers within 18 hours after cardiac death potentially qualify as viable candidates to be donors in tracheal transplantation.

The utility and track-proven clinical efficacy of cryopreserved heart valves does not per se represent a rationale to anticipate the same benefits for cryopreserved tracheal segments but I must admit that the continuing efforts made by Nakanishi and coauthors must be applauded because they represent in any case an advance in tracheal research. There are, however, several conceptual issues to be addressed. The results presented in this study derive on the viability of 5 rat rings transplanted tracheas and indirectly revascularized through recipient’s omentum for a 3 month period. Yet, all experimental studies so far, including Nakanishi’s previous studies (references 1–8 in the preceding article by Nakanishi and associates), addressing transplantation of indirectly revascularized tracheal auto- or allo-grafts have proven that results are promising at best for tracheal segments no longer than 4 cm but very discouraging for longer segments since chondrolysis and cartilage resorption can not be reversed. If this is the case, one could speculate that the likelihood that the same results presented here would be observed as well as for longer tracheal segments, a circumstance more closer to the clinical scenario, would be extremely low. In as much as this study did not simultaneously evaluate the impact of the reimplantation immune response. Moreover, the concept of harvesting the trachea following the harvesting of other intrathoracic organs is clinically difficult to set up given that during lung harvesting one third of the lower trachea is taken off.

This invited commentary is written as a word of caution towards the potential clinical application of cryopreserved tracheal grafts. The trachea should not be regarded as a simple conduit but as an organ with its own anatomical, physiological and immunological properties. Thanks to the significant progress made in the past, the currently available conservative and surgical techniques have restricted dramatically the indications and needs for the tracheal transplantation, both in adults and children. Yet, we are faced with indications (relapsing polychondritis, Wegener’s granulomatosis, tracheobronchopathia osteochondroplastica, trauma patients, and to a lesser extent, low–grade localized malignancies) where tracheal transplantation may be considered, the rational being that most of the above mentioned diseases are actually treated with palliative measures, and patients already receive immunosuppressive drugs. However, if transplantation of the trachea should be pursued, then it is my strong feeling that only revascularized tracheal allografts would be of clinical benefit. This statement is based on recent advances providing definitive experimental evidence that (a) the seemingly insuperable technical barrier of harvesting and directly revascularizing the native tracheal pedicle has been broken down; (b) the survival and function of up to 12 cm long tracheal allografts depend on their direct revascularization and standard clinical immunosuppression [1]; (c) the trachea is sensible to the same reimplantation response than that involved in other solid organ transplantations [2]. Clinically, the success of the first true human laryngeal transplant in 1998 by Marshal Strome at the Cleveland Clinic reinforces this word of caution. The recipient, whose larynx had been irreversibly damaged by a motorcycle accident received a directly revascularized allograft involving the larynx, thyroid, parathyroids, three tracheal rings and 70% of the pharynx [3]. Two years following transplantation, there is no biopsy sign of rejection and he now speaks full sentences. Since most of the diseases we are faced with extend unavoidably to the larynx, whenever indicated, the concept of a combined laryngotracheal transplantation should emerge, and, to facilitate this, a direct revascularized graft should be transplanted.

References

1. Macchiarini P., Mazmanian G.M., Montpreville V., et al. Experimental tracheal and tracheoesophageal allotransplantation. J Thorac Cardiovasc Surg 1995;110:1-10.
2. Macchiarini P. Tracheal transplantation: beyond the replacement of a simple conduit. Eur J Cardiothoracic Surg 1998;14:621-623.
3. Birshall M.A. Human laryngeal allograft: shift of emphasis in transplantation. Lancet 1998;351:539-540.[Medline]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Paolo Macchiarini Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Macchiarini, P. Search for Related Content PubMed Articles by Macchiarini, P.