J Thorac Cardiovasc Surg 2005;129:1208-1209
© 2005 The American Association for Thoracic Surgery
Reply to the Editor
Paolo Macchiarini, MD, PhD
Division of General Thoracic Surgery, Hospital Clinic de Barcelona, University of Barcelona, Barcelona, Spain
It is a distinct privilege to have attracted the interest of Hermes Grillo, and frankly speaking, his comments were expected. In his letter to the Editor, Dr Grillo questions clinical and experimental issues that I am delighted to address.
It is certainly correct that the airway defect could have been closed without the interposition of the engineered airway tissue. However, we all know that (1) it is technically demanding and risky to free (by further devascularizing it) a leaky postradiation (70 Gy) carinal anastomosis, and that (2) an intrathoracic transposed omentum buttressed over an airway defect is almost never immediately tight, and this jeopardizes the spillage of omentum produced fluid into the unique lung and induces a motion- (and foreign body-) temporary cough.
However, and with great respect, we disagree that the addition of an engineered airway tissue was superfluous. From a clinical viewpoint, a repeatedly thoracotomized and previously irradiated (70 Gy) operative field is unlikely to guarantee engrafting (eg, intercostals muscle) or allow harvesting (pericardium) of autogenous tissues. Hence, the closure of the defect with the tissue-engineered graft ensured a tight interface permitting a physiologic secretion transport without having all the complications related to the indirect closure through autogenous tissues. Having experienced the scenario with and without1 this new tool, I must admit my pleasure in having an extremely powerful and valid clinical alternative.
From an experimental viewpoint, our disagreement is even more important because the lessons learned from this clinical application are very important. Because of the concise nature of the chosen article format, we did not report in detail the molecular biologic fate of the patch. However, we did observe ciliar activity as soon as day 3 after implantation, a time frame that is shorter than that reported by other investigators studying autologous pericardial patch tracheoplasty. The objection that one would expect a partial or even entire fibrous scar formation at the patch implantation site is countered with the in vitro observation that the engineered patch underwent a profound tissue remodeling process resulting in a fibromuscular tissue formed by 80% muscle cells and 20% fibroblasts. Because this composition cannot be explained by simple cicatrization, one may suppose that the engineered patch itself and not the transposed omentum was the mesenchymal support of the entire architecture. The late protein, biochemical, and human genetic findings of the engineered airway tissue are currently under review elsewhere and therefore cannot be elucidated here in detail.
I hope that our ongoing experimental tracheal research will at some point overcome some of the clinical barriers of this beautiful organ. I am very grateful to Dr Grillo for his open and very pertinent scientific difference of opinion.
References
- Dartevelle P, Macchiarini P. Carinal resection for bronchogenic carcinomas. Semin Thorac Cardiovasc Surg. 1996;8:414-425.[Medline]
