Evaluation of Dying Vocal Fold Epithelial Cells by Ultrastructural Features and TUNEL Method

Comparative Three-Dimensional Fine Structures of the Rabbit Vocal Fold Using Correlative Light and Electron Microscopy

OBJECTIVES

The comparative fine structures of the rabbit vocal fold (VF) were investigated using the technique combined with correlative light and electron microscopy (CLEM) and transmission electron microscopy (TEM) to elucidate the functional mechanisms.

METHODS

Seven normal New Zealand White Rabbit vocal folds were examined using CLEM technique and TEM to investigate their fine structures.

RESULTS

In contrast to the human VF, the rabbit VF lacked the macula flava and vocal ligament. However, the distribution of fibrous components of the lamina propria (LP) of the rabbit VF was similar to the human VF. Spindle-shaped and oval-shaped cells were identified in the LP of the membranous portion of the rabbit VF using CLEM. Furthermore, amorphous materials were produced from vesicles positioned at the periphery of fibroblast cytoplasm. Unlike the human macula flava, stellate cells containing lipid droplets in the cytoplasm were absent in the rabbit VF.

CONCLUSION

The potential utilization of the CLEM technique facilitates the observation of these fine structures in other species commonly employed in animal experiments. Rabbits are considered a suitable species for animal experiments due to the characteristics of the fibrous components of the VF, but it is crucial for researchers to understand the structural and functional distinctions of VF in other species utilized for animal experiments. As the CLEM is a useful technique to evaluate the fine structures of the VF across small species, it is expected to be applied in animal experiments in future studies.

LEVEL OF EVIDENCE

NA Laryngoscope, 2025.

Does Vocal Fatigue Negatively Affect Low Vocal Range in Professional, Female Opera Singers? A Survey Study and Single-Subject Pilot Study

OBJECTIVE

1. To survey how vocal fatigue manifests itself in the vocal range of a sample of professional, female opera singers. 2. To assess laryngeal videostroboscopic changes of one professional, female opera singer before and after extended operatic singing.

METHODS

Survey study: 296 professional, female opera singers were recruited to participate in an anonymous research survey querying the temporary impact of vocal fatigue in professional, female opera singers. 46.3% of participants described themselves as singing mainstage roles at large, A-level opera houses. Singers were asked to report where in their vocal range they experienced the effects of vocal fatigue and could choose more than one response. Single-subject study: One professional, female opera singer (the author) underwent two laryngeal videostroboscopic exams pre and post vocal loading. The exams were evaluated and compared independently by two blinded laryngologists.

RESULTS

The results of the survey found that 42.9% of the total responses from professional, female opera singers indicated a temporary impact on the lower middle range (≈C4-F4) as a result of vocal fatigue. 36.5% of participants experienced a temporary impact on their lowest range (≈below C4) and 19.6% reported a temporary impact on their higher range due to vocal fatigue. The results of the single-subject study showed reduced glottal closure pattern in the postloading, lower middle range, head voice condition.

CONCLUSIONS

A large proportion (64.9%) of the professional, female opera singers surveyed reported increased difficulty navigating their lower middle range and/or lowest range after extended operatic singing. These results support the single-subject study, which found that after vocal loading, there was a decrease in glottal competence while singing in head voice in the lower middle range.

Singer’s Nodules: Investigating the Etiopathogenetic Markers Progressing Their Pathogenesis and Clinical Manifestations

Simple Summary

Vocal nodules, together with vocal polyps, are the most common benign vocal cord structures that are thought to be caused by extensive vocal abuse (shouting, talking loudly for prolonged periods) and are routinely treated surgically. However, surgical excision of these nodules, does not exclude the possibility of recurrence of these nodules, especially if lifestyle changes are not adapted to prevent phonetic trauma. Furthermore, the etiopathogenetic pathways governing the formation and maintenance of these nodules are not known. Herein, we investigated the etiopathogenetic markers for proliferation, apoptosis, growth, ischemia (tissue hypoxia), inflammation and innervation to elucidate the causative pathways. We found a profound and significant intensification of apoptosis in tissue epithelium, which strongly correlated with proliferative, ischemic, and inflammatory changes, highlighting the underlying complex interactions between various mechanisms on a cellular and tissue level, which occur during the morpho-pathogenesis of vocal nodules.

Abstract

Vocal nodules (or Singer’s nodules) are benign vocal cord structures which are commonly encountered by clinicians. Though phonetic trauma/abuse is thought to be the main cause of the development of vocal nodules, the exact etiopathogenesis remains unknown. Hence, we compared the immunohistochemical markers for proliferation (Ki-67), apoptosis (TUNEL), growth (EGFR), ischemia (VEGF), inflammation (IL-1α and 10), and immunoreactive innervation (PGP 9.5), in vocal nodule tissue samples obtained from 10 females (17–56 years) and vocal cord tissue from seven controls. A statistically significant increase in Ki-67, TUNEL, EGFR, VEGF and IL-1α expression was noted (p < 0.05) between nodule tissue and control tissue in both epithelial and subepithelial layers. However, the difference was non-significant for both IL-10 and PGP 9.5 (p > 0.05). All markers demonstrated moderate to strong positive correlations, except for IL-10. These findings suggest increased cellular growth and proliferation in vocal nodules coupled with a persistent presence of inflammatory and ischemic environment. Furthermore, global prevalence of apoptotic cells and decreased anti-inflammatory cytokines highlight the presence of underlying complex mechanisms in the etiopathogenesis of vocal nodules, with age having a negligible impact on the marker levels. Our results could potentially further our knowledge in understanding the effects of different treatment modalities available at the cellular level.

Cadmium induced skeletal underdevelopment, liver cell apoptosis and hepatic energy metabolism disorder in Bufo gargarizans larvae by disrupting thyroid hormone signaling

Cadmium (Cd) is hazardous to human health and it is also highly detrimental to amphibian life. In this study, Bufo gargarizans larvae were exposed to environmentally relevant Cd concentrations of 5, 100 and 200 μg L^-1 from Gosner stage (Gs) 26 to Gs 42 of metamorphic climax about 6 weeks. The results showed thyroid structural injuries and thyroid signaling disruption were induced by high Cd exposure (100 and 200 μg L^-1). Moreover, tadpole skeleton including whole body, vertebrata, forelimb and hindlimb was developmentally delayed by high Cd exposure through downregulating the mRNA expressions of genes involved with skeletal ossification and growth pathway. Moreover, liver histopathological injuries were caused by high Cd exposure featured by hepatocytes malformation, nuclear degeneration and increasing melanomacrophage centers. Meanwhile, liver apoptosis rate showed on the rise in a dose-dependent way and Cd stimulated liver apoptosis by upregulating mRNA expressions of genes related to extrinsic and intrinsic apoptosis pathways. Furthermore, high Cd caused hepatic glucometabolism disorder by decreasing the genetic expressions associated with glycolysis and mitochondrial oxidative phosphorylation. In addition, liver lipid metabolism was disrupted by high Cd exposure through downregulating mRNA levels of genes related to fatty oxidation and upregulating mRNA levels of genes related to fatty acid synthesis. We suggested that Cd did great harm to tadpole health by disturbing thyroid function, skeletal growth, liver cell apoptosis signaling and hepatic energy metabolism pathway.

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

PURPOSE

Vocal fold diseases affecting the epithelium have a detrimental impact on vocal function. This review article provides an overview of apoptosis, the most commonly studied type of programmed cell death. Because apoptosis can damage epithelial cells, this article examines the implications of apoptosis on diseases affecting the vocal fold cover.

METHOD

A review of the extant literature was performed. We summarized the topics of epithelial tissue properties and apoptotic cell death, described what is currently understood about apoptosis in the vocal fold, and proposed several possible explanations for how the role of abnormal apoptosis during wound healing may be involved in vocal pathology.

RESULTS AND CONCLUSIONS

Apoptosis plays an important role in maintaining normal epithelial tissue function. The biological mechanisms responsible for vocal fold diseases of epithelial origin are only beginning to emerge. This article discusses speculations to explain the potential role of deficient versus excessive rates of apoptosis and how disorganized apoptosis may contribute to the development of common diseases of the vocal folds.

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

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, 120min) or a control group (120min 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 120min 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 120min 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.