A rabbit vocal fold laser scarring model for testing lamina propria tissue-engineering therapies

Objectives/Hypothesis: To develop a vocal fold scarring model using an ablative laser in the rabbit as a platform for testing bioengineered therapies for missing or damaged lamina propria. Study Design: Prospective controlled animal study. Methods: An optimal laser energy level was first determined by assessing the depths of vocal fold injury created by a Holmium:YAG laser at various energy levels on fresh cadaveric rabbit larynges. The selected energy level was then used to create controlled unilateral injuries in vocal folds of New Zealand white rabbits, with the contralateral folds serving as uninjured controls. After 4 weeks, the larynges were harvested and subjected to excised-larynx phonation with high-speed imaging and immunohistochemical staining for collagen types I and III, elastin, and hyaluronic acid (HA) with quantitative histological analysis. Results: A total of 1.8 joules produced full-thickness injury of the lamina propria without extensive muscle injury. After 4 weeks, the injured vocal folds vibrated with reduced amplitude (P = 0.036) in excised-larynx phonation compared to normal vocal folds. The injured vocal folds contained a higher relative density of collagen type I (P = 0.004), higher elastin (P = 0.022), and lower HA (P = 0.030) compared to normal controls. Collagen type III was unchanged. Conclusions: With its potential for higher precision of injury, this laser vocal fold scarring model may serve as an alternative to scarring produced by cold instruments for studying the effects of vocal fold lamina propria bioengineered therapies.