Raised intensity phonation compromises vocal fold epithelial barrier integrity

Abstract

Objectives/Hypothesis-We investigated the hypothesis that 30 minutes of raised intensity phonation alters transcript levels of vocal fold intercellular tight junction proteins and disrupts the vocal fold epithelial barrier.Study Design-Prospective animal study. Methods-EighteenNew Zealand white breeder rabbits were randomly assigned to receive 30 minutes of raised intensity phonation or approximation of the vocal folds without phonation. Quantitative polymerase chain reaction (qPCR) was used to investigate transcript levels of the epithelial intercellular tight junction proteins, occludin and zonula occludin-1 (Z0-1), and the adherens junction proteins β-catenin and E-cadherin. Structural alterations to the vocal fold epithelium were further examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results-MannWhitney U revealed significantly decreased occludin (P = .016) and β-catenin (P = .016) gene expression from rabbits undergoing raised intensity phonation, compared to control. There were no significant differences in Z0-1 and E-Cadherin gene expression between groups (P >.025). SEM revealed significant obliteration, desquamation, and evidence of microhole formation in rabbit vocal folds exposed to raised intensity phonation, compared to control, while TEM revealed dilated intercellular morphology between groups.Conclusions-Results provide support for the hypothesis that a transient episode of raised intensity phonation alters transcript levels of vocal fold intercellular tight junction proteins and disrupts integrity of the epithelial barrier. The loss of barrier integrity may have significant consequences on epithelial defenses and compromise protection of the underlying mucosa from damage secondary to prolonged vibration exposure.

Nonlinear Analyses of Elicited Modal, Raised, and Pressed Rabbit Phonation

“…To prepare the rabbits for surgery, the neck was shaved from the submentum down to the chest and the rabbits were placed on an operating platform in the supine position. As described previously 27 , a vertical midline neck incision from the hyoid bone to sternal notch was used to expose the larynx and trachea. The trachea was transected proximal to the sternum and a tracheostomy was performed.…”

Vocal Fold Epithelial Barrier in Health and Injury: A Research Review

“…Collagenous anchoring structures incorporated into the basement membrane secure the epithelium to the lamina propria (Gray, et al, 1994). The surface of the most superficial layer of epithelial cells supports a series of dense microvilli that increase the epithelial surface area (Gray, 2000; Rousseau, Suehiro, Echemendia, & Sivasankar, 2011). The exact function of microvilli in the epithelium of the vocal folds and other tissues including the cornea and airway remain elusive.…”

“…Three major groups of cell junctions include occluding, anchoring, and communicating junctions (Table 1). Members of each junction group have been identified in the vocal fold epithelium of humans and numerous animal models using a combination of cellular and molecular biology techniques (Alper, Fu, Erickson-Levendoski, Zheng, & Sivasankar, 2011; Fisher, et al, 2001; Gill, et al, 2005; Hirano et al, 2003; Ling, Raasch, & Welham, 2011; Rousseau, et al, 2011; Schneider, Teschner, Sudermann, Pikula, & Lautermann, 2002; Sivasankar, Erickson, Rosenblat, & Branski, 2010; Van Deusen & Lyon, 2008; Zhang & Fisher, 2012). Alteration in cell junction formation and distribution, destabilization, or all may lead to epithelial barrier dysfunction.…”

“…It has been suggested that the vocal fold epithelium is important for defending the lamina propria against such mechanical stresses during vocal fold vibration (Rousseau, et al, 2011). To date, three studies, using animal models, have been identified that investigate the effects of simulated phonotrauma, or excessive phonation, on the vocal fold epithelium.…”

“…By four hours, marked tearing of desmosomes and hemidesmosomes was also noted. More recently, Rousseau and colleagues (2011) investigated the effect of 30 minutes of raised intensity phonation, in rabbits, on the expression of cell junction genes and epithelial structure. Significant reductions in the expression of the tight junction protein occludin and the adherens junction protein β-catenin were observed.…”