The presence of a vocal ligament in fetuses: a histochemical and ultrastructural study

Tissue-engineered vocal fold replacement in swine: Methods for functional and structural analysis

We have developed a cell-based outer vocal fold replacement (COVR) as a potential therapy to improve voice quality after vocal fold (VF) injury, radiation, or tumor resection. The COVR consists of multipotent human adipose-derived stem cells (hASC) embedded within a three-dimensional fibrin scaffold that resembles vocal fold epithelium and lamina propria layers. Previous work has shown improved wound healing in rabbit studies. In this pilot study in pigs, we sought to develop methods for large animal implantation and phonatory assessment. Feasibility, safety, and structural and functional outcomes of the COVR implant are described. Of eight pigs studied, six animals underwent COVR implantation with harvest between 2 weeks and 6 months. Recovery of laryngeal tissue structure was assessed by vibratory and histologic analyses. Recovery of voice function was assessed by investigating acoustic parameters that were derived specifically for pigs. Results showed improved lamina propria qualities relative to an injured control animal at 6 months. Acoustic parameters reflected voice worsening immediately after surgery as expected; acoustics displayed clear voice recovery in the animal followed for 6 months after COVR. These methods form the basis for a larger-scale long-term pre-clinical safety and efficacy study.

Bioreactors for Vocal Fold Tissue Engineering

It is estimated that almost one-third of the United States population will be affected by a vocal fold (VF) disorder during their lifespan. Promising therapies to treat VF injury and scarring are mostly centered on VF tissue engineering strategies such as the injection of engineered biomaterials and cell therapy. VF tissue engineering, however, is a challenging field as the biomechanical properties, structure, and composition of the VF tissue change upon exposure to mechanical stimulation. As a result, the development of long-term VF treatment strategies relies on the characterization of engineered tissues under a controlled mechanical environment. In this review, we highlight the importance of bioreactors as a powerful tool for VF tissue engineering with a focus on the current state of the art of bioreactors designed to mimic phonation in vitro. We discuss the influence of the phonatory environment on the development, function, injury, and healing of the VF tissue and its importance for the development of efficient therapeutic strategies. A concise and comprehensive overview of bioreactor designs, principles, operating parameters, and scalability are presented. An in-depth analysis of VF bioreactor data to date reveals that mechanical stimulation significantly influences cell viability and the expression of proinflammatory and profibrotic genes in vitro. Although the precision and accuracy of bioreactors contribute to generating reliable results, diverse gene expression profiles across the literature suggest that future efforts should focus on the standardization of bioreactor parameters to enable direct comparisons between studies. Impact statement We present a comprehensive review of bioreactors for vocal fold (VF) tissue engineering with a focus on the influence of the phonatory environment on the development, function, injury, and healing of the VFs and the importance of mimicking phonation on engineered VF tissues in vitro. Furthermore, we put forward a strong argument for the continued development of bioreactors in this area with an emphasis on the standardization of bioreactor designs, principles, operating parameters, and oscillatory regimes to enable comparisons between studies.

The maturational gradient of infant vocalizations: Developmental stages and functional modules

Stage models have been influential in characterizing infant vocalizations in the first year of life. These models are basically descriptive and do not explain why certain types of vocal behaviors occur within a particular stage or why successive patterns of vocalization occur. This review paper summarizes and elaborates a theory of Developmental Functional Modules (DFMs) and discusses how maturational gradients in the DFMs explain age typical vocalizations as well as the transitions between successive stages or other static forms. Maturational gradients are based on biological processes that effect the reconfiguration and remodeling of the respiratory, laryngeal, and craniofacial systems during infancy. From a dynamic systems perspective, DFMs are part of a complex system with multiple degrees of freedom that can achieve stable performance with relatively few control variables by relying on principles such as synergies, self-organization, nonlinear performance, and movement variability.

Evaluation of the Human Vocal Fold Lamina Propria Development Using Optical Coherence Tomography

OBJECTIVES/HYPOTHESIS

Identifying distinctive features of the vocal fold (VF) during development could have significant clinical implications for treating voice disorders. This study investigates the structural organization of the VF microanatomy across gender and age groups using optical coherence tomography (OCT).

STUDY DESIGN

Prospective clinical trial.

MATERIALS AND METHODS

In vivo OCT images were acquired from 97 patients (58 males and 39 females) aged between 6 weeks and 27 years. All patients showed no signs of vocal fold pathology on endoscopy. Morphological features were extracted from OCT images and statistically compared between age groups. This study was performed at Massachusetts Eye and Ear between 2017 and 2019.

RESULTS

All OCT acquisitions show a stratified microanatomy across age groups, even in newborns suggesting the presence of a superficial lamina propria (SLP) at birth. Furthermore, the optical scattering in the VF lamina propria changes according to age, suggesting subepithelial maturation. Although the epithelium thickness was relatively constant across age groups, the SLP showed a significant linear relationship between age and thickness (P = .016). Furthermore, a significant difference (P = .002) in SLP thickness was found between young adult males and females. The overall thickness of the entire mucosa did not change significantly with age.

CONCLUSION

OCT is a noninvasive imaging modality capable of providing quantitative morphological features to describe the VF development. A stratified structure can be observed in OCT from newborns to young adults. Further investigations could combine OCT, acoustic measurements, and molecular sensitive techniques to provide a complete interpretation of the VF development.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:E2558-E2565, 2021.

The influence of premature birth on laryngeal development for phonation

INTRODUCTION

Dysphonia is a known consequence of premature birth, and is usually associated with endotracheal intubation in the neonatal period or surgical ligation of persistent patent ductus arteriosus. Recently, cases of dysphonia, in the absence of these causative factors, have been reported.

OBJECTIVES

This review seeks to identify literature pertaining to those aspects of laryngeal development that may potentially be disrupted by premature birth. The purpose of the review is to determine whether there is any possible anatomical or physiological explanation for dysphonia to arose solely from premature birth.

METHODS

This scoping review was conducted in accordance with the guidelines prescribed by Arskey and O'Malley (2005). Fifteen relevant papers were identified. Results were categorized into age-related categories, to identify changes in the developmental trajectory. Based on the results of the literature search, a further category of unphonated larynges was added.

RESULTS

Potential differences in the laryngeal framework (e.g., the development of the cricoid cartilage and the shape of the glottis) and vocal fold histology, depending on gestational age and post-natal phonation were identified. Much literature focused on the macula flavae, however, the layers of the lamina propria were also discussed.

DISCUSSION

It is unclear whether the process of differentiation of the layers of the lamina propria, which commences in the second to third months of life in term-born infants, is disrupted by prematurity. Further, development of the macula flavae continues until at least 28 weeks' gestation. Preterm children may not phonate immediately after birth, which may also affect laryngeal development.

Insights Into the Role of Collagen in Vocal Fold Health and Disease

As one of the key fibrous proteins in the extracellular matrix, collagen plays a significant role in the structural and biomechanical characteristics of the vocal fold. Anchored fibrils of collagen create secure structural regions within the vocal folds and are strong enough to sustain vibratory impact and stretch during phonation. This contributes tensile strength, density, and organization to the vocal folds and influences health and pathogenesis. This review offers a comprehensive summary for a current understanding of collagen within normal vocal fold tissues throughout the life span as well as vocal pathology and wound repair. Further, collagen's molecular structure and biosynthesis are discussed. Finally, collagen alterations in tissue injury and repair and the incorporation of collagen-based biomaterials as a method of treating voice disorders are reviewed.

A quantitative study of the relationship between the distribution of different types of collagen and the mechanical behavior of rabbit medial collateral ligaments

The mechanical properties of ligaments are key contributors to the stability and function of musculoskeletal joints. Ligaments are generally composed of ground substance, collagen (mainly type I and III collagen), and minimal elastin fibers. However, no consensus has been reached about whether the distribution of different types of collagen correlates with the mechanical behaviors of ligaments. The main objective of this study was to determine whether the collagen type distribution is correlated with the mechanical properties of ligaments. Using axial tensile tests and picrosirius red staining-polarization observations, the mechanical behaviors and the ratios of the various types of collagen were investigated for twenty-four rabbit medial collateral ligaments from twenty-four rabbits of different ages, respectively. One-way analysis of variance was used in the comparison of the Young's modulus in the linear region of the stress-strain curves and the ratios of type I and III collagen for the specimens (the mid-substance specimens of the ligaments) with different ages. A multiple linear regression was performed using the collagen contents (the ratios of type I and III collagen) and the Young's modulus of the specimens. During the maturation of the ligaments, the type I collagen content increased, and the type III collagen content decreased. A significant and strong correlation () was identified by multiple linear regression between the collagen contents (i.e., the ratios of type I and type III collagen) and the mechanical properties of the specimens. The collagen content of ligaments might provide a new perspective for evaluating the linear modulus of global stress-strain curves for ligaments and open a new door for studying the mechanical behaviors and functions of connective tissues.

Aging voice: presbyphonia

Presbyphonia is a physiological process of aging voice that includes morphological changes in the coverage mucosa, muscle, and cartilage. We revised the morphological, endoscopic, and vocal acoustic changes that occur in presbyphonia and discussed some treatments proposed to minimize glottal incompetence and improve vocal performance of the elderly.

Voice disorders in children and its relationship with auditory, acoustic and vocal behavior parameters

OBJECTIVE

Parameters to distinguish normal from deviant voices in early childhood have not been established. The current study sought to auditorily and acoustically characterize voices of children, and to study the relationship between vocal behavior reported by teachers and the presence of vocal aberrations.

METHODS

One hundred children between four and 6 years and 11 months, who attended early childhood educational institutions, were included. The sample comprised 50 children with normal voices (NVG) and 50 with deviant voices (DVG) matched by gender and age. All participants were submitted to auditory and acoustic analysis of vocal quality and had their vocal behaviors assessed by teachers through a specific protocol.

RESULTS

DVG had a higher incidence of breathiness (p<0.001) and roughness (p<0.001), but not vocal strain (p=0.546), which was similar in both groups. The average F(0) was lower in the DVG and a higher noise component was observed in this group as well. Regarding the protocol used "Aspects Related to Phonotrauma - Children's Protocol", higher means were observed for children from DVG in all analyzed aspects and also on the overall means (DVG=2.15; NVG=1.12, p<0.001). In NVG, a higher incidence of vocal behavior without alterations or with discrete alterations was observed, whereas a higher incidence of moderate, severe or extreme alterations of vocal behavior was observed in DVG.

CONCLUSIONS

Perceptual assessment of voice, vocal acoustic parameters (F(0), noise and GNE), and aspects related to vocal trauma and vocal behavior differentiated the groups of children with normal voice and deviant voice.