Vocal Fold Fibroblast Response to Growth Factor Treatment is Age Dependent: Results From an In Vitro Study

Tissue Engineering and Regenerative Medicine in the Field of Otorhinolaryngology

BACKGROUND

Otorhinolaryngology is a medical specialty that focuses on the clinical study and treatments of diseases within head and neck regions, specifically including the ear, nose, and throat (ENT), but excluding eyes and brain. These anatomical structures play significant roles in a person's daily life, including eating, speaking as well as facial appearance and expression, thus greatly impacting one's overall satisfaction and quality of life. Consequently, injuries to these regions can significantly impact a person's well-being, leading to extensive research in the field of tissue engineering and regenerative medicine over many years.

METHODS

This chapter provides an overview of the anatomical characteristics of otorhinolaryngologic tissues and explores the tissue engineering and regenerative medicine research in otology (ear), rhinology (nose), facial bone, larynx, and trachea.

RESULTS AND CONCLUSION

The integration of tissue engineering and regenerative medicine in otorhinolaryngology holds the promise of broadening the therapeutic choices for a wide range of conditions, ultimately improving quality of a patient's life.

The life-cycle and restoration of the human vocal fold

Objective

To better understand the challenges of designing therapies to treat damaged vocal fold lamina propria, it is essential to understand the biophysical and pathophysiological mechanisms involved in vocal fold development, maintenance, injury, and aging. This review critically analyses these points to try and direct future efforts and new strategies toward science-based solutions.

Data Sources & Review Methods

MEDLINE, Ovid Embase, and Wed of Science databases were used to identify relevant literature. A scoping review was performed following the preferred reporting items for systematic reviews and meta-analyses extension for scoping reviews checklist.

Results

The layered arrangement of the vocal fold, develops during early childhood and is maintained during adulthood unless injury occurs. The stellate cells of the macular flava are likely to be important in this process. The capacity for vocal fold regeneration and growth is lost during adulthood and repair results in the deposition of fibrous tissue from resident fibroblasts. With advancing age, viscoelastic tissue declines, possibly due to cell senescence. Strategies aimed at replacing fibrous tissue within the vocal folds must either stimulate resident cells or implant new cells to secrete healthy extracellular protein. Injection of basic fibroblast growth factor is the most widely reported therapy that aims to achieve this.

Conclusions

The pathways involved in vocal fold development, maintenance and aging are incompletely understood. Improved understanding has the potential to identify new treatment targets that could potentially overcome loss of vocal fold vibratory tissue.

[Molecular laryngology : A new chapter in the understanding of laryngeal diseases]

BACKGROUND

Despite considerable advances in laryngological research, there is still a plethora of (benign) vocal fold pathologies that cannot be treated causally. This is due to the limited accessibility and sensitive microarchitecture of the vocal folds, which cannot be investigated at a cellular level. Consequently, current pathophysiological knowledge is frequently based on macroscopic findings. The impact of interventions is mainly evaluated endoscopically or via indirect diagnostic methods.

OBJECTIVE

The aim of this article is to discuss state-of-the-art biotechnological methods used in laryngological research, illustrated by practical examples.

RESULTS

In recent years, animal and in vitro experiments have significantly contributed to a continuous expansion of knowledge in this field, particularly regarding vocal fold inflammation and scar formation. Vocal fold fibroblasts, the most important cellular component of the lamina propria, can be accredited a central role in these processes.

CONCLUSION

Our knowledge regarding macroanatomy and macropathophysiology of several pathologies has increased considerably in recent years. In vitro trials have shown, e.g., that vocal fold fibroblasts in an inflammatory setting secrete less profibrotic and proinflammatory cytokines when exposed to vibration. Early vocal exercises after surgical interventions on the vocal folds may therefore promote better wound healing and consequently improved phonation. Research in molecular laryngology should create a solid basis of knowledge for subsequent clinical studies.

Office-Based Autologous Fat Injection Laryngoplasty for Glottic Insufficiency in Patients Under 50 Years Old

OBJECTIVE

We sought to determine the outcomes of office-based autologous fat injection laryngoplasty in the treatment of patients under 50 years old with glottic insufficiency but without neurological problems or acquired organic lesions in the vocal fold.

METHODS

We conducted a retrospective chart review of consecutive patients under 50 years of age who underwent office-based autologous fat injection laryngoplasty for glottic insufficiency. None of the patients presented neurological problems or acquired organic lesions in the vocal fold. Videolaryngostroboscopic data, objective voice assessment, perceptual measurements of vocal quality, and subjective ratings of voice quality were evaluated before and after treatment.

RESULTS

The 23 patients (7 men and 16 women) in this study presented significant improvements in phonatory function in terms of maximum phonation time, jitter, grade, asthenia, and Voice Handicap Index-10 (VHI-10) values at 3 months. Significant improvements in terms of jitter, noise-to-harmonic ratio, grade, roughness, breathiness, asthenia, and the VHI-10 values were also observed at 6 months.

CONCLUSIONS

Glottic insufficiency in younger patients without neurological problems or acquired organic lesions in the vocal fold can be treated effectively using office-based autologous fat injection laryngoplasty. Significant improvements in phonatory function were observed even 6 months after surgery.

Prevalence and Risk Factors of Voice Disorders in French Tour Guides

OBJECTIVE/HYPOTHESIS

Voice disorders are frequently observed among professionals using their voice as their main working tool (ie, occupational voice users). The objective of this study is to establish the prevalence of voice disorders in tour guides and to evaluate the risk factors associated with these disorders.

STUDY DESIGN

An online survey, containing the VHI-10 test, was sent to the metropolitan France guides in November 2017. The results were analyzed using answers of tour guides dispatched in all metropolitan French departments.

RESULTS

We received 465 replies. Voice disorders were highly prevalent (up to 21.29%) according to the VHI-10 and were comparable to observed rates in other professional categories (teachers and telecommunicators). The proportion of guides complaining about voice disorders episodes (44.94%) is greater than in the overall general population. Specific work-related factors emerged in this study. First, the use of a high-intensity voice for more than 6 hours a week is a factor significantly associated with a higher risk of having a pathological score at VHI-10. Second, a significant proportion of the guides noted that noise pollution and changes in temperature affected their vocal quality.

CONCLUSIONS

In light of these results, we can conclude that the tour guide profession is subject to voice-related risks. The prevalence of voice disorders is particularly higher than in the general population and risk factors specific to tour guide population exist.

Reversal of Vocal Fold Mucosal Fibrosis Using siRNA against the Collagen-Specific Chaperone Serpinh1

Vocal fold (VF) mucosal fibrosis results in substantial voice impairment and is recalcitrant to current treatments. To reverse this chronic disorder, anti-fibrotic therapies should target the molecular pathology of aberrant collagen accumulation in the extracellular matrix. We investigated the therapeutic potential of siRNA against Serpinh1, a collagen-specific chaperone that enables cotranslational folding and assembly of procollagens in the endoplasmic reticulum. We implemented a previously validated siRNA construct, conducted transfection experiments using in vitro and in vivo rat models, and measured knockdown efficiency, dose responses, delivery strategies, and therapeutic outcomes. Liposome-mediated delivery of Serpinh1-siRNA downregulated collagen production in naive and scar VF fibroblasts as well as naive VF mucosa; moreover, sustained Serpinh1 knockdown in fibrotic VF mucosa reversed scar-associated collagen accumulation within 4 weeks. Analysis of therapeutic effects at the transcriptome level showed evidence of cell cycle upregulation, catabolism, matrix disassembly, and morphogenesis. These findings indicate that Serpinh1-siRNA holds potential as a molecular therapy for chronic VF mucosal fibrosis.

Dual growth factor-immobilized bioactive injection material for enhanced treatment of glottal insufficiency

With increasing demand for treatment of glottal insufficiency, several injection materials have been examined. However, biological resorption, degradation of injected materials, and the subsequent need to perform multiple injections still remain major clinical problems. In this study, we fabricated two different growth factor (GF) [single basic fibroblast growth factor (bFGF), single hepatocyte growth factor (HGF), or dual bFGF/HGF]-immobilized polycaprolactone (PCL)/Pluronic F127 microspheres. These materials were investigated for their potential use as bioactive injection laryngoplasty agents. HGF was found to be continuously released over 20 days and the bFGF was found to be continuously released over 25 days, as demonstrated by ELISA assay. Human vocal fold fibroblasts (hVFFs) showed significantly higher proliferative ability on dual GF-immobilized microspheres. GF-immobilized microspheres (bFGF, HGF, and dual GF) were injected into paralyzed vocal folds of New Zealand white rabbits. Through endoscopic observation and H&E staining, we identified that the microspheres remained localized at the injection site, resulting in constant volume augmentation of the paralyzed vocal fold without significant loss of the initial volume after 4 weeks. The expression of genes related to the extracellular matrix (ECM) in the vocal fold was upregulated by dual GF-immobilized microspheres. Furthermore, dual GF-immobilized microspheres inhibited muscle degeneration and upregulation of myogenic-related genes. In conclusion, dual GF-immobilized microspheres passively augmented the volume of the paralyzed vocal fold while actively inducing ECM synthesis at the injected vocal fold and preserving muscle tissue. Dual GF-immobilized microspheres could be a new and promising injection material for paralyzed vocal folds. STATEMENT OF SIGNIFICANCE: Limitation of prolonged augmentation of vocal fold and degeneration of vocal fold tissue still remain as major clinical problems in the treatment of vocal fold paralysis. Herein, we fabricated the polycaprolactone (PCL)/Pluronic F127 microspheres to augment volume of paralyzed vocal folds. On top of that, we additionally immobilized the growth factors (bFGF, HGF, or dual bFGF/HGF) on the surface of these microspheres. We highlight the efficacy of the dual GF-immobilized microspheres which augmented the volume of the paralyzed vocal fold passively, induced ECM synthesis actively at the injected vocal fold and preserved laryngeal muscle tissue. Our results suggest that the dual GF-immobilized microsphere could be a new promising injection material for injection laryngoplasty to treat paralyzed vocal fold.

Characterization of aged rat vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

To elucidate the aging physiology of the vocal folds, we examined the characters of aged vocal fold fibroblasts (VFFs) in various conditions.

STUDY DESIGN

In vitro study.

METHODS

VFFs from young (12-week-old) and aged (19-month-old) Sprague-Dawley rats were compared. Proliferative capacity, ratio of myofibroblast to fibroblast, myofibroblast function, and extracellular matrix production were examined in the following conditions: naïve, basic fibroblast growth factor (bFGF) supplemented, and hepatocyte growth factor (HGF) supplemented.

RESULTS

Aged VFFs demonstrated reduced proliferation by cell counting, though the ratio of Ki-67-positive cells showed no difference. Aged VFFs exhibited an increased expression of α-smooth muscle actin (α-SMA); however, they demonstrated no enhanced contractile ability in a gel contraction assay. Type I collagen protein was increased age dependently, accompanied with decreased Mmp1 and unchanged Col1a1 transcription. Type I collagen protein and α-SMA represented quite similar reduction patterns to bFGF or HGF administration.

CONCLUSIONS

The following possible characteristics of aged VFFs were implied: long duration of mitosis, increased myofibroblast population size with certain dysfunctions, reduced type I collagen turnover, and correlation between α-SMA expression and type I collagen metabolism. Further investigations of these features will help to clarify presbyphonia's pathology and establish treatment strategies.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E94-E101, 2019.

Characteristics and Responses of Human Vocal Fold Cells in a Vibrational Culture Model

OBJECTIVES/HYPOTHESIS

This study was conducted to provide a vibrational culture model to investigate the effects of mechanical environments on cellular functions, and elucidate physiological characteristics of two different types of cells in vocal folds under static and vibrational conditions.

STUDY DESIGN

In vitro study of human vocal fold fibroblasts (hVFFs) and human macula flava stellate cells (hMF-SCs).

METHODS

hVFFs and hMF-SCs were exposed to a 2-second-on/2-second-off, 205 Hz vibration regime for 4 hours by using a vibrational culture model. We compared cell morphology, cell viability, and gene expression in extracellular matrix-related components, growth factors, and differentiation markers under static and vibratory conditions.

RESULTS

hVFFs and hMF-SCs differed in their morphologies and gene expression levels under static condition. The applied vibration did not induce changes in morphology and viability of either cell type. However, gene expression levels changed in both cell types in response to vibration; in particular, hMF-SCs exhibited a more sensitive response to vibration than that shown by hVFFs.

CONCLUSIONS

The vibrational culture model developed in this study enabled us to investigate the effects of the applied vibration on two types of vocal fold resident cells. As a result, we could demonstrate that hVFFs and hMF-SCs exhibited distinctively different characteristics under vibrational conditions.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:E258-E264, 2018.

Small Intestinal Submucosa Implantation for the Possible Treatment of Vocal Fold Scar, Sulcus, and Superficial Lamina Propria Atrophy

Objectives:

Evaluate the histologic effects of grafting porcine-derived small intestinal submucosa (SIS) into the vocal fold superficial lamina propria (SLP) layer for the potential treatment of vocal fold scar, sulcus and superficial lamina propria atrophy.

Methods:

Small intestinal submucosa was implanted into the right vocal fold SLP of 6 mongrel dogs. The left vocal fold served as a sham surgical control. At 2, 4, and 6 weeks postoperative, bilateral vocal fold specimens were evaluated histologically.

Results:

At 2 and 4 weeks, respectively, SIS-implanted vocal folds demonstrated moderate and mild inflammation and acute and chronic inflammation. At 6 weeks, inflammation was minimal and chronic. The 6-week specimens showed copious amounts of newly generated hyaluronic acid (HA) within the graft. There was no reactive fibrosis at 6 weeks.

Conclusions:

In the canine model, SIS appears safe for SLP grafting. Inflammation is similar to that of sham surgery. Small intestinal submucosa results in newly generated HA without concomitant fibrosis. Small intestinal submucosa has potential to be used in treatment of disorders with SLP, including vocal fold scar, sulcus, and atrophy. Studies evaluating the effect of SIS implantation on vocal fold function, as well as the ultimate fate of the graft, are required.

The unsolved chapter of vocal fold scars and how tissue engineering could help us solve the problem

Vocal fold scarring is a relatively small field in scar research with prerequisites found nowhere else. The deterioration of the delicate tri-layered micro-structure of the epithelium of the vocal folds leads to impaired vibration characteristics resulting in a permanent hoarse and breathy voice. Tissue engineering approaches could help to restore the pre-injury status. Despite a considerable progress in this field during the last years, routine clinical applications are not available so far. One reason might be that vocal fold fibroblasts, as the responsible cell type for fibrogenesis, have very particular properties that are only poorly characterized. Moreover, in vivo trials are costly and time consuming and a representative in vitro model does not exist so far. These particular circumstances lead to innovative in vitro strategies and concepts such as macro-molecular crowding that can also be applied in adjacent fields.