The histologic fate of autologous collagen injected into the canine vocal fold.

Collagen is a functionally essential component of the five-layered structure of the vocal fold. Soluble bovine collagen has previously been shown to be an effective injectable bioimplant for vocal fold defects, paralysis, and, especially, scarred larynges. Although bovine collagen appears to be well tolerated, the concern for possible adverse immunologic responses has deterred approval from the Food and Drug Administration for its clinical use in the larynx. Currently we are investigating the use of injectable autologous collagen for vocal fold augmentation. The purpose of this study is to examine the histologic fate of autologous collagen injected into the canine vocal fold at multiple intervals after injection. An ellipse of skin measuring 3 x 6 cm was harvested from each of three dogs and processed into a naturally cross-linked injectable solution of collagen (Autologen). This autologous collagen was injected into one vocal fold and a control injection of buffer solution was injected contralaterally. The injections were well tolerated and no dog appeared to suffer any immediate or delayed ill effects. The dog larynges were harvested 1, 3, and 6 months after collagen injection and examined grossly and histologically. Injected autologous collagen material persisted in these experimental animals and appeared to be well tolerated. Based on this preliminary study, we anticipate autologous collagen to be at least as suitable as bovine chemically cross-linked collagen as an injectable bioimplant for vocal fold augmentation. It may also have the advantage of added safety and stability.

Autologous collagen vocal fold injection: a preliminary clinical study.

This preliminary study reports the first use of injectable autologous collagen for vocal fold augmentation. In previous studies, the authors showed cross-linked bovine collagen to be effective in more than 150 patients with glottic incompetence, particularly those with focal defects or scarred or atrophic vocal folds. However, concerns about possible adverse immunologic responses to the bovine material have limited its use. The authors studied eight patients with difficult vocal fold pathology, including sulcus vocalis, atrophy, and scarring secondary to trauma and cordectomy. Skin was harvested under local anesthesia, processed into a naturally cross-linked injectable form (Autologen), and injected using indirect laryngoscopy. Voice production was evaluated prior to the injection and at intervals after the injection, using subjective, perceptual, aerodynamic, acoustic, and videostroboscopic assessments. The results indicate that autologous collagen is comparable to injectable bovine collagen in the management of several difficult glottic insufficiency problems and that the likelihood of a hypersensitivity response is negligible. Unlike bovine collagen preparations, Autologen does not require breakdown of the natural collagen molecule, so it is anticipated that this material will be better tolerated and more stable over time.

Effect of substance P on ciliary beat frequency in human adenoid explants.

This study investigated the direct effects of substance P (SP) on ciliary beat frequency of human upper airway mucosa. Human adenoid explant tissue was maintained in serum free culture media, MCDB153. Ciliated epithelial cells were observed with phase-contrast microscopy and ciliary activity was measured using a photometric technique. Oscillations in transmitted light caused by ciliary beating were recorded and modal ciliary beat frequency was determined by fast Fourier transformation. Specimens were treated with SP at concentrations of 10(-4), 10(-5), 10(-6), and 10(-7) mol/L and with equal molar solutions of SP and (D-Pro2,D-Trp7,9)-SP, a SP antagonist. Substance P was found to increase ciliary beat frequency in a dose-dependent manner with a maximum increase of 12.1%. This effect was not seen with solutions containing (D-Pro2,D-Trp7,9)-SP. This suggests that SP exerts a direct stimulatory effect on ciliated cells of the upper airway. Because SP is known to be released in the upper airway in response to chemical irritation, it is presumed that the stimulatory effect of SP on mucosal cells provides a protective mechanism against inhaled irritants.