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Ann Thorac Surg 2005;79:949
© 2005 The Society of Thoracic Surgeons

INVITED COMMENTARY

Division of General Thoracic Surgery, Massachusetts General Hospital, Blake 1570, 55 Fruit St, Boston, MA 02114

(E-mail: pguerriero{at}partners.org).

Martinod and associates "report for the first time here that allogenic aortic segments implanted in the tracheal environment after extensive tracheal resection were replaced after a few months by a new trachea comprising mucociliary epithelium, cartilage rings and a posterior membrane [italics added]." They postulate that "the environment plays a major role to induce tissue transformation leading toward a structure as complex as a trachea with cartilage rings and posterior membrane." If confirmed, this work would be very important, and a wholly new biological process will have been discovered.

Migration of tracheal epithelium with dedifferentiation and later redifferentiation has been documented. There is, however, little scientific precedent for reformation of cartilaginous rings, with even absent membranous wall cartilage, except for similar observations by Pressman and Simon [1, 2] after aortic graft reconstruction of trachea. Photographs of their specimens appear similar to photographs previously offered by Martinod. In the present experiments, the involvement of the aortic allograft first by massive inflammation (most likely due to an immune response plus local ischemia) followed by apparent resorption is biologically familiar. We still must ask, however, whether the "new cartilaginous rings" are not previously present marginal rings pulled into a vigorously remodeling and contracting connective tissue mass around the intralumenal stent, which in turn prevents contraction into the lumen.

The "young" cartilage identified might derive from previously present cartilage fragments and rings under the vigorous forces of inflammation, local remodeling, and contraction. Collagen is produced in response to physical stress on tissue. The persistence of the stent may account for the apparent definition of "suture lines" in what would be a complex movement of various portions of the scar and preexistent rings. Indeed, Daniel [3] observed very similar "new" cartilaginous rings regenerated in the presence of a stent across a gap without any aortic graft at all.

With findings as surprising, but possibly as promising, as these seem to be, critical experiments need to be performed. The proximal and distal one or two tracheal cartilaginous rings might be permanently marked to be sure that they are not indeed pulled into the defect by longitudinal contraction guided by the stent. An initial suggestion could be use of multiple very fine wire sutures in these rings or carbon black deposited into the substance of these rings as a kind of tattoo. Repetition of Daniel's experiment also seems to be called for: use of a connecting stent after tracheal resection without an aortic segment at all, allowing epithelium to migrate in time over the tube of scar tissue that forms peripheral to the stent under these circumstances.

	References

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1. Pressman JJ, Simon MB. Observations upon the experimental repair of the trachea using autogenous aorta and polyethylene tubes Surg Gynecol Obstet 1958;106:56.[Medline]
2. Pressman JJ, Simon MB. Tracheal stretching and metaplasia of the tracheal rings from cartilage to bone following the use of aortic homografts Am Surg 1959;25:850-856.
3. Daniel Jr RA. The regeneration of defects of the trachea and bronchiAn experimental study. J Thorac Surg 1948;17:335-349.[Medline]

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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): Hermes Grillo Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Grillo, H. Search for Related Content PubMed Articles by Grillo, H. Related Collections Related Article