Ontogeny of the mouse vocal fold epithelium

Abstract

This investigation provides the first systematic determination of the cellular and molecular progression of vocal fold (VF) epithelium development in a murine model. We define five principal developmental events that constitute the progression from VF initiation in the embryonic anterior foregut tube to fully differentiated and functional adult tissue. These developmental events include (1) the initiation of the larynx and vocal folds with apposition of the lateral walls of the primitive laryngopharynx (embryonic (E) day 10.5); (2) the establishment of the epithelial lamina with fusion of the lateral walls of the primitive laryngopharynx (E11.5); (3) the epithelial lamina recanalization and separation of VFs (E13.5–18.5); (4) the stratification of the vocal folds (E13.5–18.5); and (5) the maturation of vocal fold epithelium (postnatal stages). The illustration of these morphogenetic events is substantiated by dynamic changes in cell proliferation and apoptosis, as well as the expression pattern of key transcription factors, FOXA2, SOX2 and NKX2-1 that specify and pattern the foregut endoderm. Furthermore, we documented the gradual conversion of VF epithelial cells from simple precursors expressing cytokeratins 8 and 18 in the embryo into mature stratified epithelial cells also expressing cytokeratins 5 and 14 in the adult. Interestingly, in the adult, cytokeratins 5 and 14 appear to be expressed in all cell layers in the VF, in contrast to their preferential localization to the basal cell layer in surrounding epithelium. To begin investigating the role of signaling molecules in vocal fold development, we characterized the expression pattern of SHH pathway genes, and how loss of Shh affects vocal fold development in the mutant. This study defines the cellular and molecular context and serves as the necessary foundation for future functional investigations of VF formation.

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

“…During the lifecycle of all cells, cell death is a regulated mechanism that eliminates unnecessary cells to maintain homeostasis. Previous studies revealed that vocal fold epithelial cells and fibroblasts undergo apoptotic cell death [Hellquist, 1997; Hirvikoski et al, 1999; Gaston et al, 2012; Bartlett et al, 2015; Lungova et al, 2015]. However, there remains a limited acknowledgement of cell death as a consequence of different types of vocal fold damage and a lack of consistent language to describe dying cells.…”

“…During embryologic development, Lungova and colleagues [2015] reported that apoptosis is responsible for terminating murine vocal fold epithelial cells. In vocal fold disease, apoptotic events were observed in primary tumor and resection biopsies from patients with laryngeal squamous cell carcinoma and epithelial hyperplasia [Hellquist, 1997; Hirvikoski et al, 1999].…”

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

“…Their work revealed that during the fusion of the lateral epithelial walls and separation of the epithelial lamina, epithelial cells of prospective vocal folds die by apoptosis. Lungova et al (2015) found that although apoptotic cell death was observed during embryogenesis, rates of apoptosis did not seem to be associated with any of the investigated developmental events. Thus, apoptosis may play a primary functional role in eliminating vocal fold epithelial cells to assist with tissue remodeling and sculpting.…”

“…Apoptosis occurs during the embryologic development of murine vocal fold epithelium. Lungova, Verheyden, Herriges, Sun, and Thibeault (2015) investigated the mechanisms by which the vocal fold epithelium is formed during major developmental events. Their work revealed that during the fusion of the lateral epithelial walls and separation of the epithelial lamina, epithelial cells of prospective vocal folds die by apoptosis.…”

RNA sequencing identifies transcriptional changes in the rabbit larynx in response to low humidity challenge

“…Although there was no gross in ammation observed, some level of epithelial cellular response to surface dehydration is expected. The vocal folds are covered by a non-keratinized strati ed squamous epithelium for which some aspects of development are well understood, such as embryological developmental factors and differentially expressed structural components (90,91), but a comprehensive molecular description is not available as for other epithelia like the epidermis. It is interesting that several keratinocyte developmental factors were identi ed with RNA-Seq and as a protein interaction cluster in the STRING analysis: CDSN, CNFN, CRNN, KRT80, KRTDAP, and TGM3.…”