Acute exposure to vibration is an apoptosis‐inducing stimulus in the vocal fold epithelium

Abstract

Clinical voice disorders pose significant communication-related challenges to patients. The purpose of this study was to quantify the rate of apoptosis and tumor necrosis factor-alpha (TNF-α) signaling in vocal fold epithelial cells in response to increasing time-doses and cycle-doses of vibration. 20 New Zealand white breeder rabbits were randomized to three groups of time-doses of vibration exposure (30, 60, 120 minutes) or a control group (120 minutes of vocal fold adduction and abduction). Estimated cycle-doses of vocal fold vibration were extrapolated based on mean fundamental frequency. Laryngeal tissue specimens were evaluated for apoptosis and gene transcript and protein levels of TNF-α. Results revealed that terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was significantly higher after 120 minutes of vibration compared to the control. Transmission electron microscopy (TEM) revealed no significant effect of time-dose on the mean area of epithelial cell nuclei. Extrapolated cycle-doses of vibration exposure were closely related to experimental time-dose conditions, although no significant correlations were observed with TUNEL staining or mean area of epithelial cell nuclei. TUNEL staining was positively correlated with TNF-α protein expression. Our findings suggest that apoptosis can be induced in the vocal fold epithelium after 120 minutes of modal intensity phonation. In contrast, shorter durations of vibration exposure do not result in apoptosis signaling. However, morphological features of apoptosis are not observed using TEM. Future studies are necessary to examine the contribution of abnormal apoptosis to vocal fold diseases.

A Method to Administer Agents to the Larynx in an Awake Large Animal

“…This study also evaluated the ultrastructure of true vocal fold epithelium. Previous reports suggest that the ultrastructure of the true vocal fold epithelium is altered with voice use and reflux disease (Franchi et al, 2007;Johnston et al, 2003;Novaleski et al, 2016). Qualitative evaluation of the overall ultrastructure of the true vocal fold epithelium was unremarkable (Figure 3).…”

“…Animal laryngeal tissue is used because it cannot be easily or noninvasively accessed from human beings. For example, recent studies have examined the effects of phonotrauma and acid reflux using in vivo animal models (Durkes & Sivasankar, 2016;Novaleski, Kimball, Mizuta, & Rousseau, 2016). However, these studies typically involved acute exposures, sedation, or animal species with different vocal fold biology than human vocal folds.…”

Apoptosis and Vocal Fold Disease: Clinically Relevant Implications of Epithelial Cell Death

“…The vocal fold epithelium also expressed an immunohistochemical marker for apoptosis that labeled fragmented DNA. Further work using transmission electron microscopy quantified the immunohistochemical marker and morphological sign of cellular shrinkage (Novaleski, Kimball, Mizuta, & Rousseau, 2016). Results revealed that apoptosis occurred in the vocal fold epithelium after 120 min of in vivo vibration exposure compared with the same duration of vocal fold approximation only.…”

Protein Substrate Alters Cell Physiology in Primary Culture of Vocal Fold Epithelial Cells

“…As the most superficial layer of the vocal fold, the epithelium presents a physical barrier to the underlying lamina propria, is often considered the first line of defense against the forces of vibration, and shows structural damage following vibratory trauma [Gray, 2000;Levendoski et al, 2014;Leydon et al, 2014;Mizuta et al, 2017;Rousseau et al, 2017;Kimball et al, 2019]. As such, maintenance and repair of the epithelial barrier is critical to withstanding repeated vibratory stresses in the healthy vocal fold [Rousseau et al, 2011[Rousseau et al, , 2017Kojima et al, 2014;Novaleski et al, 2016]. Several different species have been utilized as in vivo and in vivo models of human vocal fold biology and physiology, and these include pig, dog, sheep, rabbit, and rat [Nakagawa et al, 1998;Akhtar et al, 1999;Rousseau et al, 2003;Hanson et al, 2010;Ling et al, 2010;Sivasankar et al, 2010;Alipour et al, 2011].…”