Further experimental observations of transplantation of canine larynx

Distribution of Class I and II Human Leukocyte Antigens in the Larynx

OBJECTIVE: To examine the antigenic distribution of human leukocyte antigens (HLA) of the human larynx.

STUDY DESIGN AND SETTING: Twelve human larynges were examined for Class I (HLA-A, -B, -C) and Class II (HLA-DR) histocompatibility antigens using mouse monoclonal antibodies in an indirect immunoperoxidase assay. Structures of the larynx and surrounding tissues were examined and given a semiquantitative score based on HLA Class I and II expression.

RESULTS: The mucosal surface epithelium of the larynx stains 2+ or stronger for HLA Class I antigens and 1+ for Class II antigens. The deeper submucosal glands stain 1+ for Class I antigens and 2+ or stronger for Class II antigens. Thyroid cartilage showed 2+ or stronger staining of the chondrocytes for Class I antigens only. Thyroid follicular cells also stain only for Class I antigens. Perichondrium and Schwann cells of nerves stain stronger for Class I antigens than Class II antigens. Cartilage matrix, muscle cells, and axons of nerves do not stain for either class of antigens. Endothelium stains 3+ for both classes of antigens.

CONCLUSIONS: The detailed distribution of major transplantation antigens in the human larynx is elucidated. Class II antigens implicated as initiators of organ transplant rejection were primarily found in 6 areas: mucosal surface epithelium, submucosal glands, ducts, vascular endothelium, perichondrium, and Schwann cells of nerves. The relevance of these findings to the initiation and detection of laryngeal allograft graft rejection is discussed.

The central projections of the laryngeal nerves in the rat

The larynx serves respiratory, protective, and phonatory functions. The motor and sensory innervation to the larynx controlling these functions is provided by the superior laryngeal nerve (SLN) and the recurrent laryngeal nerve (RLN). Classical studies state that the SLN innervates the cricothyroid muscle and provides sensory innervation to the supraglottic cavity, whereas the RLN supplies motor innervation to the remaining intrinsic laryngeal muscles and sensory innervation to the infraglottic cavity, but recent data suggest a more complex anatomical and functional organisation. The current neuroanatomical tracing study was undertaken to provide a comprehensive description of the central brainstem connections of the axons within the SLN and the RLN, including those neurons that innervate the larynx. The study has been carried out in 41 adult male Sprague-Dawley rats. The central projections of the laryngeal nerves were labelled following application of biotinylated dextran amines onto the SLN, the RLN or both. The most remarkable result of the study is that in the rat the RLN does not contain any afferent axons from the larynx, in contrast to the pattern observed in many other species including man. The RLN supplied only special visceromotor innervation to the intrinsic muscles of the larynx from motoneurons in the nucleus ambiguus (Amb). All the afferent axons innervating the larynx are contained within the SLN, and reach the nucleus of the solitary tract. The SLN also contained secretomotor efferents originating from motoneurons in the dorsal motor nucleus of the vagus, and special visceral efferent fibres from the Amb. In conclusion, the present study shows that in the rat the innervation of the larynx differs in significant ways from that described in other species.

Extended canine laryngeal preservation for transplantation

The goal of successfully transplanting the larynx has motivated researchers since the 1960s. Early laryngeal transplant techniques limited the donor larynx to 45 minutes of ischemia. In this study, a method of prolonged laryngeal preservation is employed in three canines. In vivo cold laryngeal perfusion with University of Wisconsin Solution (UWS) was performed. The larynx was removed and placed into cold storage in 4 degrees C UWS. After 24 hours of storage, the same canines underwent laryngeal reimplantation. The animals were sacrificed 7 days after reimplantation. No evidence of necrosis or vascular insufficiency was identified histologically. The results indicate that canine larynges can be successfully reimplanted after 24 hours of preservation. Future studies will assess the application of this technique to laryngeal transplantation.

Functional restoration for recurrent laryngeal paralysis: an experimental study

The purpose of this investigation was to exclude abductor disturbance and to maintain phonation during recurrent laryngeal nerve paralysis through a new surgical design. This new method consists of implantation of the ansa hypoglossi and sternothyroid muscle pedicle which has been shown to provide sufficient abductor function in a recent publication, and the selective severance of the abductor branch after neurorrhaphy of the recurrent laryngeal which is shown to be a sufficient adductor function in another study. The recovery of sufficient abductor function during inspiration and dyspnea was 67% and 89% of adductor function with phonation. However, after cutting an adductor nerve branch of the recurrent laryngeal nerve in cases of insufficient abduction, the vocal cord on the operated-on side regained abduction during inspiration. The effect of the ansa hypoglossi and sternothyroid muscle pedicle is also discussed.

Reconstruction of laryngeal function for recurrent laryngeal nerve paralysis: historical view, advancement of latest investigations and a preliminary experiment

Historical investigations of the functional restoration for recurrent laryngeal nerve paralysis are reviewed and some advancement in recent studies are introduced. A preliminary experiment is reported in which the ansa hypoglossi and the sternothyroid muscle pedicle was implanted into the denervated posterior cricoarytenoid muscle in dogs. From these experiments we have concluded that the ansa hypoglossi and sternothyroid muscle pedicle, which has been shown to transmit efferent inspiratory bursts, is capable of restoring function to the paralyzed posterior cricoarytenoid muscle in some dogs.