Implantation of Esterified Hyaluronic Acid in Microdissected Reinke's Space After Vocal Fold Microsurgery: Short- and Long-Term Results

Versatile fiber-reinforced hydrogels to mimic the microstructure and mechanics of human vocal-fold upper layers

Human vocal folds are remarkable soft laryngeal structures that enable phonation due to their unique vibro-mechanical performances. These properties are tied to their specific fibrous architecture, especially in the upper layers, which comprise a gel-like composite called lamina propria. The lamina propria can withstand large and reversible deformations under various multiaxial loadings. Despite their importance, the relationships between the microstructure of vocal folds and their resulting macroscopic properties remain poorly understood. There is a need for versatile models that encompass their structural complexity while mimicking their mechanical features. In this study, we present a candidate model inspired by histological measurements of the upper layers of human vocal folds. Bi-photonic observations were used to quantify the distribution, orientation, width, and volume fraction of collagen and elastin fibers between histological layers. Using established biomaterials, polymer fiber-reinforced hydrogels were developed to replicate the fibrillar network and ground substance of native vocal fold tissue. To achieve this, jet-sprayed poly(ε-caprolactone) fibrillar mats were successfully impregnated with poly(L-lysine) dendrimers/polyethylene glycol hydrogels. The resulting composites exhibited versatile structural, physical and mechanical properties that could be customized through variations in the chemical formulation of their hydrogel matrix, the microstructural architecture of their fibrous networks (i.e., fiber diameter, orientation and volume fraction) and their assembly process. By mimicking the collagen network of the lamina propria with polymer fibers and the elastin/ground substance with the hydrogel composition, we successfully replicated the non-linear, anisotropic, and viscoelastic mechanical behavior of the vocal-fold upper layers, accounting for inter/intra-individual variations. The development of this mimetic model offers promising avenues for a better understanding of the complex mechanisms involved in voice production. STATEMENT OF SIGNIFICANCE: Human vocal folds are outstanding vibrating soft living tissues allowing phonation. Simple physical models that take into account the histological structure of the vocal fold and recapitulate its mechanical features are scarce. As a result, the relations between tissue components, organisation and vibro-mechanical performances still remain an open question. We describe here the development and the characterization of fiber-reinforced hydrogels inspired from the vocal-fold microstructure. These systems are able to reproduce the mechanics of vocal-fold tissues upon realistic cyclic and large strains under various multi-axial loadings, thus providing a mimetic model to further understand the impact of the fibrous network microstructure in phonation.

Pre and Post-operative Voice Therapy Intervention for Benign Vocal Fold Lesions: A Systematic Review

Benign vocal fold lesions cause dysphonia by preventing vocal fold closure, causing irregular vibration and increasing compensatory muscle tension. Voice therapy delivered in addition to phonosurgery may improve voice and quality of life outcomes but the evidence base is lacking and what constitutes voice therapy for this population is not defined. The purpose of this systematic review is to critically evaluate the evidence for pre and post-operative voice therapy to inform the development of an evidence based intervention.

STUDY DESIGN

Systematic Review.

METHODS

Electronic databases were searched using key terms including dysphonia, phonosurgery, voice therapy and outcomes. Eligible articles were extracted and reviewed by the authors for risk of bias and for information regarding the content, timing and intensity of any pre and post-operative voice therapy intervention.

RESULTS

Of the 432 articles identified, 35 met the inclusion criteria and were included in the review. 5 were RCTs, 2 were individual cohort studies, 1 was a case control study and 26 were case series. There was considerable heterogeneity in participant characteristics. Information was frequently lacking regarding the content timing and intensity of the reported voice therapy intervention, and where present, interventions were highly variable.

CONCLUSION

Reporting in relevant literature is limited in all aspects of content, timing and intensity of intervention. Further intervention development work is required to develop a robust voice therapy treatment intervention for this population, before effectiveness work can commence.

Vocal fold restoration after scarring: biocompatibility and efficacy of an MSC-based bioequivalent

BACKGROUND

There is growing interest to application of regenerative medicine approaches in otorhinolaryngological practice, especially in the framework of the therapy of vocal fold (VF) scar lesions. The used conservative and surgical methods, despite the achieved positive outcomes, are frequently unpredictable and do not result in the restoration of the VF's lamina propria's structure, which provides the mechanical properties necessary for vibration. In this connection, the aim of this study was to ascertain the safety and efficacy of a bioequivalent in the treatment of VF scars using a rabbit model of chronic damage.

METHODS

The bioequivalent consisted of a hydrogel system based on a PEG-fibrin conjugate and human bone marrow-derived MSC. It was characterized and implanted heterotopically into rats and orthotopically into rabbits after VF scar excision.

RESULTS

We showed that the fabricated bioequivalent consisted of viable cells retaining their metabolic and proliferative activity. While being implanted heterotopically, it had induced the low inflammatory reaction in 7 days and was well tolerated. The orthotopic implantation showed that the gel application was characterized by a lower hemorrhage intensity (p = 0.03945). The intensity of stridor and respiratory rate between the groups in total and between separate groups had no statistically significant difference (p = 0.96 and p = 1; p = 0.9593 and p = 0.97…1, respectively). In 3 days post-implantation, MSC were detected only in the tissues closely surrounding the VF defect. The bioequivalent injection caused that the scar collagen fibers were packed looser and more frequently mutually parallel that is inherent in the native tissue (p = 0.018). In all experimental groups, the fibrous tissue's ingrowth in the adjacent exterior muscle tissue was observed; however, in Group 4 (PEG-Fibrin + MSC), it was much less pronounced than it was in Group 1 (normal saline) (p = 0.008). The difference between the thicknesses of the lamina propria in the control group and in Group 4 was not revealed to be statistically significant (p = 0.995). The Young's modulus of the VF after the bioequivalent implantation (1.15 ± 0.25 kPa) did not statistically significantly differ from the intact VF modulus (1.17 ± 0.45 kPa); therefore, the tissue properties in this group more closely resembled the intact VF.

CONCLUSIONS

The developed bioequivalent showed to be biocompatible and highly efficient in the restoration of VF's tissue.

An Exploration of the Risk Factors, Severity, and Sequelae of Vocal Fold Hemorrhage in a Population of Voice Patients Before and After Diagnosis

BACKGROUND

Vocal fold hemorrhage (VFH) is the rupture (usually acute) of a blood vessel within the true vocal fold. The long-term sequelae of VFH on the mucosal wave (MW) and glottic gap on video stroboscopy remain understudied. The primary objective of this study was to investigate the short-term and long-term consequences of VFH through measured and rated analysis of the mucosal wave and glottic gap.

METHODS

The presence of VFH and its extent (limited/moderate vs. extensive VFH) were identified. The primary outcome of this study was mucosal wave, which was assessed on an ordinal scale by three blinded raters pre and posthemorrhage. Only patients who had undergone strobovideolaryngoscopy before sustaining VFH were included. Mucosal wave and glottic gap also were measured using image pixel analysis using the open-access tool, ImageJ (NIH, Bethesda, MD).

RESULTS

Twenty-three subjects were included in this study (mean age 39.78 ± 15.54). Intra-rater reliability for MW ratings was 81.48% ± 6.150% (minimum 77.78%) for all evaluators (κ = 0.519 [0.267-0.772], P < 0.001). Inter-rater reliability analysis revealed 75.56% agreement between evaluators (κ = 0.524 [0.425-0.623], P < 0.001). MWMeasured extrapolated from ImageJ methodology correlated significantly with MWRated (n = 70, r = 0.448, P < 0.001). ΔMWMeasured from baseline to follow-up evaluation were compared for both the initial follow-up visit (FU1) and the second follow-up visit (FU2) [-4.135 ± 31.01 vs. 36.50 ± 39.97, P = 0.025]. Hence, ΔMWMeasured was significantly better by FU2 than FU1, with the larger positive change from baseline representing a greater improvement in the measured mucosal wave. Additionally, there were significant differences in ΔMWRated between those with limited/moderate VFH and those with extensive VFH at FU1. Duration of absolute voice rest correlated significantly with time to VFH resolution. Long-term change in mucosal wave after hemorrhage was assessed using both ΔMWMeasured and MWRated. Based on ΔMWRater, 35.0% of subjects demonstrated ongoing and worse mucosal wave restriction compared to baseline at their most recent follow-up visit. Based on ΔMWMeasured, 50.0% of the subjects showed ongoing and worse mucosal wave restriction compared to baseline at their most recent follow-up visit.

CONCLUSION

Overall long-term restrictions in MW after hemorrhage were present in 35.0% of the subjects based on ratings and 50.0% of the patients based on the measured MW using ImageJ, demonstrating the importance of ongoing study into this pathology and how to prevent it, especially in PVU and professional singers. Patients presenting with extensive hemorrhage were at risk for more prominent, detectable changes in mucosal wave compared to those with limited/moderate hemorrhage in the short-term, defined by a mean FU time of 3 months, but not long-term, characterized by a mean FU time 6 months or greater. Whether the severity of VFH is a true indicator of mucosal wave alterations requires additional study, as does the reliability and validity of ImageJ mucosal wave and glottic gap measurement techniques.

Hydration State and Hyaluronidase Treatment Significantly Affect Porcine Vocal Fold Biomechanics

OBJECTIVES

The understanding of vocal fold hydration state, including dehydrated, euhydrated, rehydrated tissue, and how hydration affects vocal fold biomechanical properties is still evolving. Although clinical observations support the benefits of increasing vocal fold hydration after dehydrating events, more mechanistic information on the effects of vocal fold dehydration and the beneficial effects of rehydration are needed. Alterations to hyaluronic acid (HA), an important component of the vocal fold extracellular matrix, are likely to influence the biomechanical properties of vocal folds. In this study, we investigated the influence of hydration state and HA on vocal fold tissue stiffness via biomechanical testing.

STUDY DESIGN

Prospective, ex vivo study design.

METHODS

Fresh porcine vocal folds (N = 18) were examined following sequential immersion in hypertonic (dehydration) and isotonic solutions (rehydration). In a separate experiment, vocal folds were incubated in hyaluronidase (Hyal) to remove HA. Control tissues were not exposed to any challenges. A custom micromechanical system with a microforce sensing probe was used to measure the force-displacement response. Optical strain was calculated, and ultrasound imaging was used to measure tissue cross-sectional area to obtain stress-strain curves.

RESULTS

Significant increases (P ≤ 0.05) were found in tangent moduli between dehydrated and rehydrated vocal folds at strains of ε = 0.15. The tangent moduli of Hyal-digested tissues significantly increased at both ε = 0.15 and 0.3 (P ≤ 0.05).

CONCLUSION

Vocal fold dehydration increased tissue stiffness and rehydration reduced the stiffness. Loss of HA increased vocal fold stiffness, suggesting a potential mechanical role for HA in euhydrated vocal folds.

Dexamethasone for Postoperative Nausea and Vomiting in Papillary Thyroid Carcinoma Patients: A Randomized Clinical Trial

BACKGROUND

Postoperative nausea and vomiting (PONV) frequently occur after thyroidectomy. Previous studies have investigated the effects of preoperative dexamethasone for alleviating PONV in various cancers, but studies focused on papillary thyroid carcinoma (PTC) were limited. This study aimed to determine the efficacy of a single preoperative dose of dexamethasone to prevent PONV in patients with PTC.

METHODS

This single-center, parallel-group, double-blind, placebo-controlled clinical trial was conducted on patients with PTC in West China Hospital. Patients were randomized 1:1 into Group Dex (preoperative 8-mg dexamethasone) or Group Control (0.9% NaCl as control). The primary outcome was the incidence and severity of PONV. The secondary outcomes included postoperative pain, vocal dysfunction, and adverse events.

RESULTS

Six hundred participants were recruited and randomized. The total incidence of PONV was 33.3% (200 of 600 patients; 95% CI, 29.6-37.1). In the intention-to-treat analysis, PONV occurred in 81 of 300 patients (27.0%; 95% CI, 21.9-32.1) in Group Dex and in 119 of 300 patients (39.7%; 95% CI, 34.1-45.2) in Group Control (p = 0.001), and the absolute risk reduction was 12.7% (95% CI, 5.1-20.0). Patients in Group Dex reported fewer antiemetic requirements than those in Group Control (p = 0.004). Multivariate analysis indicated that dexamethasone administration (OR = 0.546; 95% CI, 0.383-0.777; p = 0.001) was associated with a reduced rate of PONV. Dexamethasone treatment also contributed to alleviating postoperative pain and improving subjective vocal dysfunction, with no increase in adverse events.

CONCLUSIONS

A single dose of dexamethasone is effective and safe for preventing PONV in PTC patients.

Vocal-fold leukoplakia and dysplasia. Mini-review by the French Society of Phoniatrics and Laryngology (SFPL)

Vocal-fold leukoplakia and dysplasia are together designated "epithelial hyperplastic laryngeal lesions" (EHLL). Work-up and follow-up are founded on optical examination with high-definition imaging, stroboscopy and narrow-band imaging. Diagnosis is based on pathology, using the new 2017 WHO classification, dichotomizing "low grade" and "high grade". Statistically, the risk of cancerous progression is 20% within 5 to 10 years of diagnosis, or more in over-65 year-old males; risk for any given patient, however, is unpredictable. Research focuses on the genetic criteria of the lesion and characterization of the tumoral microenvironment. Treatment is exclusively microsurgical. Resection depth is adjusted according to infiltration. EHLL is a chronic disease, necessitating long-term follow-up, which may be hampered by residual dysphonia and surgical sequelae in the vocal folds. Sequelae need to be minimized by good mastery of microsurgical technique and indications. When they occur, biomaterials such as autologous fat and hyaluronic acid can be useful. Tissue bio-engineering is a promising field.

Investigation of surgical adhesives for vocal fold wound closure

OBJECTIVES

Surgical adhesives are increasingly used for vocal fold microsurgery to assist wound closure and reduce the risks of scar formation. Currently used vocal fold adhesives such as fibrin glue, however, have thus far not been found to promote wound closure or reduce scarring. The objectives of this study were to investigate the mechanical strength and the cytotoxicity of three commercially available adhesives (Glubran 2, GEM, Viareggio, Italy; BioGlue, CryoLife, Kennesaw, GA; and Tisseel, Baxter Healthcare, Deerfield, IL) for vocal fold wound closure.

METHODS

Shear and tension tests were performed on 150 porcine larynges. The cytotoxicity of the adhesives to immortalized human vocal fold fibroblasts was investigated using neutral red uptake assays.

RESULTS

The average shear adhesive strength for Tisseel, BioGlue, and Glubran 2 was 13.86 ± 5.03 kilopascal (kPa), 40.92 ± 17.94 kPa, and 68.79 ± 13.29 kPa, respectively. The tensile adhesive strength for Tisseel, BioGlue, and Glubran 2 was 10.70 ± 6.42 kPa, 34.27 ± 12.59 kPa, and 46.67 ± 12.13 kPa, respectively. The vocal fold cell viabilities in extracts of Tisseel, BioGlue, and Glubran 2 were 99.27%, 43.05%, and 1.79%, respectively.

CONCLUSION

There was a clear tradeoff between adhesive strength and toxicity. The maximum failure strength in shear or tension of the three surgical adhesives ranked from strongest to the weakest was: 1) Glubran 2, 2) BioGlue, and 3) Tisseel. Tisseel was found to be the least toxic of the three adhesives, whereas Glubran 2 was the most toxic.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:2139-2146, 2019.

Incorporation of types I and III collagen in tunable hyaluronan hydrogels for vocal fold tissue engineering

Vocal fold scarring is the fibrotic manifestation of a variety of voice disorders, and is difficult to treat. Tissue engineering therapies provide a potential strategy to regenerate the native tissue microenvironment in order to restore vocal fold functionality. However, major challenges remain in capturing the complexity of the native tissue and sustaining regeneration. We hypothesized that hydrogels with tunable viscoelastic properties that present relevant biological cues to cells might be better suited as therapeutics. Herein, we characterized the response of human vocal fold fibroblasts to four different biomimetic hydrogels: thiolated hyaluronan (HA) crosslinked with poly(ethylene glycol) diacrylate (PEGDA), HA-PEGDA with type I collagen (HA-Col I), HA-PEGDA with type III collagen (HA-Col III) and HA-PEGDA with type I and III collagen (HA-Col I-Col III). Collagen incorporation allowed for interpenetrating fibrils of collagen within the non-fibrillar HA network, which increased the mechanical properties of the hydrogels. The addition of collagen fibrils also reduced hyaluronidase degradation of HA and hydrogel swelling ratio. Fibroblasts encapsulated in the HA-Col gels adopted a spindle shaped fibroblastic morphology by day 7 and exhibited extensive cytoskeletal networks by day 21, suggesting that the incorporation of collagen was essential for cell adhesion and spreading. Cells remained viable and synthesized new DNA throughout 21 days of culture. Gene expression levels significantly differed between the cells encapsulated in the different hydrogels. Relative fold changes in gene expression of MMP1, COL1A1, fibronectin and decorin suggest higher degrees of remodeling in HA-Col I-Col III gels in comparison to HA-Col I or HA-Col III hydrogels, suggesting that the former may better serve as a natural biomimetic hydrogel for tissue engineering applications. STATEMENT OF SIGNIFICANCE: Voice disorders affect about 1/3rd of the US population and significantly reduce quality of life. Patients with vocal fold fibrosis have few treatment options. Tissue engineering therapies provide a potential strategy to regenerate the native tissue microenvironment in order to restore vocal fold functionality. Various studies have used collagen or thiolated hyaluronan (HA) with gelatin as potential tissue engineering therapies. However, there is room for improvement in providing cells with more relevant biological cues that mimic the native tissue microenvironment and sustain regeneration. The present study introduces the use of type I collagen and type III collagen along with thiolated HA as a natural biomimetic hydrogel for vocal fold tissue engineering applications.

Collagen fibrillar structures in vocal fold scarring and repair using stem cell therapy: a detailed histological, immunohistochemical and atomic force microscopy study

Regenerative medicine opens new opportunities in the repair of cicatricial lesions of the vocal folds. Here, we present a thorough morphological study, with the focus on the collagen structures in the mucosa of the vocal folds, dedicated to the effects of stem cells on the vocal folds repair after cicatricial lesions. We used a conventional experimental model of a mature scar of the rabbit vocal folds, which was surgically excised with a simultaneous implantation of autologous bone marrow-derived mesenchymal stem cells (MSC) into the defect. The restoration of the vocal folds was studied 3 months postimplantation of stem cells and 6 months after the first surgery. The collagen structure assessment included histology, immunohistochemistry and atomic force microscopy (AFM) studies. According to the data of optical microscopy and AFM, as well as to immunohistochemical analysis, MSC implantation into the vocal fold defect leads not only to the general reduction of scarring, normal ratio of collagens type I and type III, but also to a more complete restoration of architecture and ultrastructure of collagen fibres in the mucosa, as compared to the control. The collagen structures in the scar tissue in the vocal folds with implanted MSC are more similar to those in the normal mucosa of the vocal folds than to those of the untreated scars. AFM has proven to be an instrumental technique in the assessment of the ultrastructure restoration in such studies. LAY DESCRIPTION: Regenerative medicine opens new opportunities in the repair of the vocal fold scars. Because collagen is a main component in the vocal fold mucosa responsible for the scar formation and repair, we focus on the collagen structures in the mucosa of the vocal folds, using a thorough morphological study based on histology and atomic force microscopy (AFM). Atomic force microscopy is a scanning microscopic technique which allows revealing the internal structure of a tissue with a resolution up to nanometres. We used a conventional experimental model of a mature scar of the rabbit vocal folds, surgically excised and treated with a mesenchymal stem cells transplant. Our morphological study, primarily AFM, explicitly shows that the collagen structures in the scarred vocal folds almost completely restore after the stem cell treatment. Thus, the modern microscopic methods, and especially AFM are instrumental tools for monitoring the repair of the vocal folds scars.

Parameters and Scales Used to Assess and Report Findings From Stroboscopy: A Systematic Review

OBJECTIVE

Laryngeal endoscopy with stroboscopy, a critical component of the assessment of voice disorders, is rarely used as a treatment outcome measure in the scientific literature. We hypothesized that this is because of the lack of a widely used standardized, validated, and reliable method to assess and report laryngeal anatomy and physiology, and undertook a systematic literature review to determine the extent of the inconsistencies of the parameters and scales used in voice treatment outcome studies.

STUDY DESIGN

Systematic literature review.

METHODS

We searched PubMed, Ovid, and Cochrane for studies where laryngeal endoscopy with stroboscopy was used as a treatment outcome measure with search terms representing "stroboscopy" and "treatment" guided by Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement standards.

RESULTS

In the 62 included articles, we identified 141 terms representing 49 different parameters, which were further classified into 20 broad categories. The six most common parameters were magnitude of glottal gap, mucosal wave amplitude, location or shape of glottal gap, regularity of vibration, phase symmetry, and presence and size of specific lesions. Parameters were assessed on scales ranging from binary to 100 points. The number of scales used for each parameter varied from 1 to 24, with an average of four different scales per parameter.

CONCLUSIONS

There is a lack of agreement in the scientific literature regarding which parameters should be assessed to measure voice treatment outcomes and which terms and scales should be used for each parameter. This greatly diminishes comparison and clinical implementation of the results of treatment outcomes research in voice disorders. We highlight a previously published tool and recommend it for future use in research and clinical settings.

A Review of Hyaluronic Acid and Hyaluronic Acid-based Hydrogels for Vocal Fold Tissue Engineering

Vocal fold scarring is a common cause of dysphonia. Current treatments involving vocal fold augmentation do not yield satisfactory outcomes in the long term. Tissue engineering and regenerative medicine offer an attractive treatment option for vocal fold scarring, with the aim to restore the native extracellular matrix microenvironment and biomechanical properties of the vocal folds by inhibiting progression of scarring and thus leading to restoration of normal vocal function. Hyaluronic acid is a bioactive glycosaminoglycan responsible for maintaining optimum viscoelastic properties of the vocal folds and hence is widely targeted in tissue engineering applications. This review covers advances in hyaluronic acid-based vocal fold tissue engineering and regeneration strategies.

Uso do programa MDVP em diferentes contextos: revisão de literatura

Resumo:Este estudo tem como objetivo descrever, a partir de revisão de literatura, a confiabilidade da análise acústica utilizando o Multi Dimensional Voice Program,comparação de suas medidas com outros programas de análise acústica; caracterização de vozes de diferentes grupos; e sua utilização para verificar os efeitos e eficácia de diferentes procedimentos terapêuticos. Realizou-se levantamento bibliográfico que priorizaram estudos dos últimos cinco anos, incluindo-se artigos cujo objetivo estivesse de acordo com o interesse da presente revisão. A pesquisa foi realizada nos bancos de dados das bases Lilacs, BIREME, PubMed, MedLine, Scielo e Google Schoolar, por meio dos descritores acoustic, speech acoustics e voice. As medidas mais utilizadas são frequência fundamental, jitter, shimmer e proporção harmônico-ruído. As medidas de tremor não apresentam boa confiabilidade. As medidas mais consistentes que apresentam alta concordância com outros programas de análise acústica são as relacionadas com a frequência fundamental. Diversos estudos buscam caracterizar diferentes tipos de vozes tais como as de sujeitos sem alterações vocais de ambos os sexos, buscando estabelecer parâmetro de normalidade para diferentes grupos populacionais. Além disso, alguns estudos caracterizam vozes com diferentes distúrbios. A análise acústica é um recurso objetivo e necessário na avaliação de pacientes com distúrbio vocal e, principalmente, na comparação de diversos tipos de tratamento.

Hyaluronic Acid Behavior in the Lamina Propria of the Larynx with Advancing Age

Objectives

To analyze the hyaluronic acid behavior in the lamina propria of the larynx with advancing age.

Study Design

Prospective study.

Setting

UNESP-Univ Estadual Paulista, Botucatu Medical School, Brazil.

Subjects and Methods

Thirty vocal folds were obtained at necropsy from 10 adult males (30–50 years old) and 20 geriatric males (10: 60–75 years old; 10: over 76 years old). Midmembranous vocal fold sections were subjected to immunohistochemical reactions. Digital imaging software (ImageJ) was used to quantify the hyaluronic acid distribution over the lamina propria of vocal folds, from superficial to deep layers.

Results

Hyaluronic acid distribution was homogeneous for the larynges, at both superficial and deep layers (41.6 and 38.5, respectively). For both 30- to 50-year-old men geriatric age groups, hyaluronic acid level was lower at both layers.

Conclusion

Hyaluronic acid level in the lamina propria of the larynx of geriatric men decreases with advancing age at both layers of the lamina.

Vocal fold scars: current concepts and future directions. Consensus report of the Phonosurgery Committee of the European Laryngological Society

Scarring of the vocal folds leads to a deterioration of the highly complex micro-structure with consecutively impaired vibratory pattern and glottic insufficiency. The resulting dysphonia is predominantly characterized by a reduced vocal capacity. Despite the considerable progress in understanding of the underlying pathophysiology, the treatment of scarred vocal folds is still an unresolved chapter in laryngology and phonosurgery. Essential for a successful treatment is an individual, multi-dimensional concept that comprises the whole armamentarium of surgical and non-surgical (i.p. voice therapy) modalities. An ideal approach would be to soften the scar, because the reduced pliability and consequently the increased vibratory rigidity impede the easiness of vibration. The chosen phonosurgical method is determined by the main clinical feature: Medialization techniques for the treatment of glottic gap, or epithelium freeing techniques for improvement of vibration characteristics often combined with injection augmentation or implantation. In severe cases, buccal mucosa grafting can be an option. New developments, include treatment with anxiolytic lasers, laser technology with ultrafine excision/ablation properties avoiding coagulation (Picosecond infrared laser, PIRL), or techniques of tissue engineering. However, despite the promising results by in vitro experiments, animal studies and first clinical trials, the step into clinical routine application has yet to be taken.

Nonlinear laser scanning microscopy of human vocal folds

OBJECTIVES/HYPOTHESIS

The purpose of this work was to apply nonlinear laser scanning microscopy (NLSM) for visualizing the morphology of extracellular matrix proteins within human vocal folds. This technique may potentially assist clinicians in making rapid diagnoses of vocal fold tissue disease or damage. Microstructural characterization based on NLSM provides valuable information for better understanding molecular mechanisms and tissue structure.

STUDY DESIGN

Experimental, ex vivo human vocal fold.

METHODS

A custom-built multimodal nonlinear laser scanning microscope was used to scan fibrillar proteins in three 4% formaldehyde-fixed cadaveric samples. Collagen and elastin, key extracellular matrix proteins in the vocal fold lamina propria, were imaged by two nonlinear microscopy modalities: second harmonic generation (SHG) and two-photon fluorescence (TPF), respectively. An experimental protocol was introduced to characterize the geometrical properties of the imaged fibrous proteins.

RESULTS

NLSM revealed the biomorphology of the human vocal fold fibrous proteins. No photobleaching was observed for the incident laser power of ∼60 mW before the excitation objective. Types I and III fibrillar collagen were imaged without label in the tissue by intrinsic SHG. Imaging while rotating the incident laser light-polarization direction confirmed a helical shape for the collagen fibers. The amplitude, periodicity, and overall orientation were then computed for the helically distributed collagen network. The elastin network was simultaneously imaged via TPF and found to have a basket-like structure. In some regions, particularly close to the epithelium, colocalization of both extracellular matrix components were observed.

CONCLUSIONS

A benchmark study is presented for quantitative real-time, ex vivo, NLSM imaging of the extracellular macromolecules in human vocal fold lamina propria. The results are promising for clinical applications.

Implantation of atelocollagen sheet for vocal fold scar

PURPOSE OF REVIEW

This article reviews recent advances in scaffold-based interventions for the treatment of vocal fold scarring, with a particular emphasis on atelocollagen sheet implantation in the vocal fold lamina propria.

RECENT FINDINGS

Scaffold-based therapies have demonstrated therapeutic promise in both preclinical and early clinical studies. Recent research has begun to shed light on the interactions between scaffold material properties, encapsulated and infiltrating cells, stimulatory molecules such as growth factors, and external regulatory variables such as stress, strain, and vibration. The atelocollagen sheet, a cross-linked collagen material with abundant micropores, has an established clinical track record as a scaffold for dermal and epidermal repair and exhibited potential therapeutic benefit in a recent study of patients with vocal fold scarring and sulcus vocalis.

SUMMARY

Scaffolding is one of the useful tools in tissue engineering and atelocollagen sheet implantation has been shown to be effective in vocal fold regeneration. However, many of the scaffold materials under investigation still await clinical translation and those that have been investigated in human patients (such as the atelocollagen sheet) require additional research in appropriately powered placebo-controlled studies.

Hyaluronic acid for the treatment of vocal fold scars

PURPOSE OF REVIEW

In vocal fold scars the lamina propria layer is lost or deficient. Lamina propria replacement therapy remains a clinical challenge because this layer has a highly specialized three-dimensional organization of extracellular matrix molecules and unique viscoelastic properties. Use of a polymer such as hyaluronic acid appears most promising for replacement therapy because it has the optimal viscoelasticity and also plays a role in the maturation and maintenance of vocal fold lamina propria.

RECENT FINDINGS

A variety of cross-linked hyaluronic acid formulations and growth factor therapies targeted to increase hyaluronic acid production have been used in the treatment of both acute and established vocal fold scars. Therapeutic strategies have focused on prevention of scar at the time of initial injury, and rejuvenation of lamina propria layer in established scars. Both strategies show improved histologic, viscoelastic, acoustic, and aerodynamic measures.

SUMMARY

Cross-linked hyaluronic acid formulations appear useful in the treatment of vocal fold scarring. Their use at the time of acute injury especially appears to lessen the degree of long-term scar formation and appears promising. While animal studies have demonstrated the safety profile of many hyaluronic acid formulations, further improvement in these materials and well designed and controlled human trials are needed to further establish the safety and efficacy of these materials and therapeutic approaches.

Assessment of canine vocal fold function after injection of a new biomaterial designed to treat phonatory mucosal scarring

OBJECTIVES

Most cases of irresolvable hoarseness are due to deficiencies in the pliability and volume of the superficial lamina propria of the phonatory mucosa. By using a US Food and Drug Administration-approved polymer, polyethylene glycol (PEG), we created a novel hydrogel (PEG30) and investigated its effects on multiple vocal fold structural and functional parameters.

METHODS

We injected PEG30 unilaterally into 16 normal canine vocal folds with survival times of 1 to 4 months. High-speed videos of vocal fold vibration, induced by intratracheal airflow, and phonation threshold pressures were recorded at 4 time points per subject. Three-dimensional reconstruction analysis of 11.7 T magnetic resonance images and histologic analysis identified 3 cases wherein PEG30 injections were the most superficial, so as to maximally impact vibratory function. These cases were subjected to in-depth analyses.

RESULTS

High-speed video analysis of the 3 selected cases showed minimal to no reduction in the maximum vibratory amplitudes of vocal folds injected with PEG30 compared to the non-injected, contralateral vocal fold. All PEG30-injected vocal folds displayed mucosal wave activity with low average phonation threshold pressures. No significant inflammation was observed on microlaryngoscopic examination. Magnetic resonance imaging and histologic analyses revealed time-dependent resorption of the PEG30 hydrogel by phagocytosis with minimal tissue reaction or fibrosis.

CONCLUSIONS

The PEG30 hydrogel is a promising biocompatible candidate biomaterial to restore form and function to deficient phonatory mucosa, while not mechanically impeding residual endogenous superficial lamina propria.