Nathan V. Welham

Characterization of Vocal Fold Scarring in a Canine Model

Objective The objective was to assess the histological and viscoelastic shear tissue properties of the scarred vocal fold lamina propria at 2 and 6 months postoperatively in a canine model.

Vocal Fatigue: Current Knowledge and Future Directions

Vocal fatigue is a complex multifaceted clinical phenomenon. Several hypotheses exist concerning its underlying mechanism, and a range of empirical studies have examined its manifestation. This article reviews the literature pertaining to the nature, underlying processes, and salient features of vocal fatigue. First, vocal fatigue is defined, its major symptoms are discussed, and hypotheses concerning its primary physiological and biomechanical mechanisms are considered. Second, studies of experimentally induced vocal fatigue in humans are evaluated. Third, research investigating the clinical and occupational manifestations of vocal fatigue is discussed. Fourth, directions for ongoing research in this area are offered.

Growth factor therapy for vocal fold scarring in a canine model.

Vocal fold scarring remains a therapeutic challenge. Hepatocyte growth factor (HGF) has strong antifibrotic activity and has proved to have therapeutic potential in restoration of scar tissues such as liver cirrhosis and lung fibrosis. The present study aimed to clarify the effects of HGF injection into scarred vocal folds in a canine model. Canine vocal folds were stripped unilaterally and treated with intracordal injection of saline solution (sham group), HGF (HGF group), or HGF with cultured autologous normal vocal fold fibroblasts (Fb/HGF group) 1 month after injury. The larynges were harvested 6 months after the initial injury and then subjected to vibratory and histologic examination. The results of vibratory examinations in the excised larynx setup revealed that phonation threshold pressure significantly increased and vocal efficiency was significantly reduced in all treated groups as compared to normal data obtained from normal canine larynges. However, the HGF group presented much better results than both the sham and Fb/HGF groups in terms of mucosal wave amplitude and incidence of vocal fold bowing, glottal incompetence, and phase asymmetry. The histologic data indicated a significant increase of collagen in both the sham and Fb/HGF groups, while normal levels of collagen were found in the HGF group. Tissue contraction of the lamina propria was also observed in both the sham and Fb/HGF groups, but was barely detectable in the HGF group. Although the HGF-treated vocal folds appeared to require more driving forces for vibration, HGF might prevent excessive collagen deposition and tissue contraction and thus reduce the effects of scarring on the vibratory properties of the vocal folds. From these data it is concluded that HGF has considerable potential in the treatment of vocal fold scarring.

Hyaluronan levels in acute vocal fold scar

Objectives/Hypothesis The objective was to measure the level of hyaluronan during the first 15 days after vocal fold biopsy in a rabbit model.

Fibronectin and Adhesion Molecules on Canine Scarred Vocal Folds

Objective To examine the expressions of fibronectin and other adhesion molecules on the scarred vocal folds in a short‐ and long‐term animal model.

Proteomic analysis of naturally-sourced biological scaffolds.

A key challenge to the clinical implementation of decellularized scaffold-based tissue engineering lies in understanding the process of removing cells and immunogenic material from a donor tissue/organ while maintaining the biochemical and biophysical properties of the scaffold that will promote growth of newly seeded cells. Current criteria for evaluating whole organ decellularization are primarily based on nucleic acids, as they are easy to quantify and have been directly correlated to adverse host responses. However, numerous proteins cause immunogenic responses and thus should be measured directly to further understand and quantify the efficacy of decellularization. In addition, there has been increasing appreciation for the role of the various protein components of the extracellular matrix (ECM) in directing cell growth and regulating organ function. We performed in-depth proteomic analysis on four types of biological scaffolds and identified a large number of both remnant cellular and ECM proteins. Measurements of individual protein abundances during the decellularization process revealed significant removal of numerous cellular proteins, but preservation of most structural matrix proteins. The observation that decellularized scaffolds still contain many cellular proteins, although at decreased abundance, indicates that elimination of DNA does not assure adequate removal of all cellular material. Thus, proteomic analysis provides crucial characterization of the decellularization process to create biological scaffolds for future tissue/organ replacement therapies.

Inflammatory factor profiles one hour following vocal fold injury.

Objectives Inflammatory factors are key mediators of wound healing processes following injury, and their modulation may improve healing outcomes. The objective of this study was to characterize in vivo inflammatory factor and extracellular matrix (ECM) messenger RNA (mRNA) expression levels 1 hour after vocal fold injury. Methods Five Sprague-Dawley rats were subjected to bilateral vocal fold injury, 5 rats were reserved as uninjured controls, and 1 rat was subjected to unilateral vocal fold injury and reserved for histology. Tissue was harvested 1 hour after injury. Real-time reverse transcription–polymerase chain reaction was performed to examine the mRNA expression profiles of inflammatory factors nuclear factor kappa beta (NF-κ β), interferon gamma (IFN-γ), cyclooxygenase 2 (COX-2), transforming growth factor beta isoform 1 (TGF-β1), tumor necrosis factor alpha (TNF-α), and interleukin 1 beta (IL-1β), as well as ECM genes hyaluronic acid synthase (HAS) 1, HAS-2, procollagen 1, procollagen 3, and elastin, in the injured samples compared with the uninjured controls. Results Injury resulted in subepithelial bleeding throughout the vocal fold. The COX-2, TNF-α, IL-1β, and HAS-1 mRNA expression levels were significantly up-regulated 1 hour after injury compared with the uninjured controls. Conclusions Inflammatory factor and ECM gene expression changes occur in vocal fold wound sites as early as 1 hour after injury. These results should inform future efforts to attenuate vocal fold scarring via the modulation of inflammatory factors.

Prospective Multi-arm Evaluation of Surgical Treatments for Vocal Fold Scar and Pathologic Sulcus Vocalis

The purpose of this study was to compare the clinical effectiveness of type I thyroplasty, injection laryngoplasty, and graft implantation for the treatment of vocal fold scar and pathologic sulcus vocalis.

TGF-β3 modulates the inflammatory environment and reduces scar formation following vocal fold mucosal injury in rats.

Transforming growth factor (TGF)-β1 and TGF-β3 have been reported to exert differential effects on wound healing, and possibly even account for tissue-specific differences in scar formation. Scarring is particularly detrimental in the vocal fold mucosa (VFM), where destruction of the native extracellular matrix causes irreparable biomechanical changes and voice impairment. Here, in a series of in vitro and in vivo experiments, we identified differences in TGF-β1 and TGF-β3 transcription and immunolocalization to various cell subpopulations in naïve and injured rat VFM, compared with oral mucosa (which undergoes rapid healing with minimal scar) and skin (which typically heals with scar). Treatment of cultured human vocal fold fibroblasts with TGF-β3 resulted in less potent induction of profibrotic gene transcription, extracellular matrix synthesis and fibroblast-myofibroblast differentiation, compared with treatment with TGF-β1 and TGF-β2. Finally, delivery of exogenous TGF-β3 to rat VFM during the acute injury phase modulated the early inflammatory environment and reduced eventual scar formation. These experiments show that the TGF-β isoforms have distinct roles in VFM maintenance and repair, and that TGF-β3 redirects wound healing to improve VFM scar outcomes in vivo.

Alteration in cellular morphology, density and distribution in rat vocal fold mucosa following injury.

The vocal fold mucosa plays an important role in voice production. Its cellular composition and density frequently change under various pathological conditions, often contributing to altered extracellular matrix production, tissue viscoelasticity, and voice quality. In this study, cellular changes in the rat mucosa following a unilateral stripping injury were investigated and analyzed semi‐quantitatively. Distinctive and sequential changes in cellular morphology, composition, and density were observed in the mucosa post‐injury. Cellular recruitment was a major event during the early stage of injury and reached its peak level by day 5 post‐injury. Several types of cells, including neutrophil‐like cells, epithelial cells, and fibroblast‐like cells, were sequentially recruited. The sequential emergence of reactive cell populations following injury and subsequent reconstruction of the mucosa suggests their involvement in vocal fold tissue repair and scar formation processes.