Tracheal Transplantation: Cytological Changes Studied by Scanning and Transmission Electron Microscopy in the Rabbit

Objectives Our goal was to offer a comprehensive cytological study of the changes in the trachea after experimental transplantation of the organ. Study Design Autografting of four tracheal rings was done in rabbits and tracheal samples were observed by electron microscopy from 1 week to 6 months after the surgery was performed. Methods Transmission and scanning electron microscopy were used to investigate the fine structure of tracheal samples of rabbits submitted to autotransplantation, and quantitative methods were used to compare several cytological parameters of the different groups of animals. Results We found that tracheal autografting was associated with acute injury of ciliated cells expressed by loss of more than 90% of cilia density on the tracheal epithelium 1 week after the transplantation was performed. The loss of cilia was balanced by an increase in mucous cells present on the tracheal lumen. Recovery of ciliated cells was observed 1 month after the tracheal autografting was performed. In contrast, only mild cytological modifications were seen in the cartilage tissue of the autografted trachea during the first weeks of transplantation; the structural alterations of the cartilage progressed up to the third month after transplantation, resulting in a moderate tracheal stenosis. Conclusions The data indicate that 1) autotransplantation of four tracheal rings is a viable surgical procedure; 2) tracheal grafting causes severe acute changes of the epithelium that are, however, reversible in nature; whereas 3) the initial mild alterations induced by the autografting in the cartilage may evolve into tracheal stenosis. * Although the authors carried out the study they planned, it appears that their experiment was not well thought out from the onset. The clinical goal is to be able to transplant segments of trachea of two or more tracheal rings. In this procedure, as in most true transplants, one must expect some element of ischemia time, temperature changes (usually hypothermia), alterations in the dynamics of blood flow resulting from the inevitable sympathectomy, and the significant effects of lymphatic disruption. Virtually none of these effects were simulated in the “autotransplantation” carried out in this study. Thus, the study provides us with little practical clinical information and is useful primarily as a preliminary step in studying the effects of true transplantation.—Reviewer's Commentary