Characterization of human vocal fold fibroblasts derived from chronic scar

Early Initiation of Voice Therapy After Microlaryngeal Surgery - A Randomized Control Study

OBJECTIVE

A prospective single blinded randomized control trial was conducted to study if early initiation of voice therapy after microlaryngeal produces a better voice outcome in patients with benign vocal fold lesions.

METHODS

In this Patients undergoing microlaryngeal surgery for benign vocal fold lesions were recruited for the study and underwent voice evaluation and videostroboscopy preoperatively. Participants were randomised into two groups depending on the duration of voice rest-A (2 days voice rest) and B (5 days voice rest). Following the period of voice rest, voice therapy (tube phonation) was carried out for a month. Postoperative evaluation was done at 6 weeks (over telephone) and 3 months (in person visit) follow up. Outcome measures included the VHI-10, auditory-perceptual voice ratings, acoustic analysis and videostroboscopic vibratory ratings.

RESULTS

Of the 50 subjects, 35 completed the follow up evaluation. The overall compliance to absolute voice rest was 43%. Among the various parameters used for voice evaluation, there was no statistically significant difference between the two groups except for jitter, where the improvement in 5 day voice rest group compared to the 2 day voice rest group was statistically significant.

CONCLUSION

Prolonged voice rest after microlaryngeal surgery is difficult to comply with. As there was no significant difference between the two study groups, clinicians may prescribe a shorter duration of voice rest followed by early initiation of voice therapy after microlaryngeal surgery.

High-Resolution Profiling of Human Vocal Fold Cellular Landscapes With Single-Nuclei RNA Sequencing

INTRODUCTION

The function of the vocal folds (VFs) is determined by the phenotype, abundance, and distribution of differentiated cells within specific microenvironments. Identifying this histologic framework is crucial in understanding laryngeal disease. A paucity of studies investigating VF cellular heterogeneity has been undertaken. Here, we examined the cellular landscape of human VFs by utilizing single-nuclei RNA-sequencing.

METHODS

Normal true VF tissue was excised from five patients undergoing pitch elevation surgery. Tissue was snap frozen in liquid nitrogen and subjected to cellular digestion and nuclear extraction. Nuclei were processed for single-nucleus sequencing using the 10X Genomics Chromium platform. Sequencing reads were assembled using cellranger and analyzed with the scanpy package in python.

RESULTS

RNA sequencing revealed 18 global cell clusters. While many were of epithelial origin, expected cell types, such as fibroblasts, immune cells, muscle cells, and endothelial cells were present. Subcluster analysis defined unique epithelial, immune, and fibroblast subpopulations.

CONCLUSION

This study evaluated the cellular heterogeneity of normal human VFs by utilizing single-nuclei RNA-sequencing. With further confirmation through additional spatial sequencing and microscopic imaging, a novel cellular map of the VFs may provide insight into new cellular targets for VF disease.

LEVEL OF EVIDENCE

NA Laryngoscope, 2024.

Introducing a new type of alternative laryngeal mucosa model

Research of human vocal fold (VF) biology is hampered by several factors. The sensitive microstructure of the VF mucosa is one of them and limits the in vivo research, as biopsies carry a very high risk of scarring. A laryngeal organotypic model consisting of VF epithelial cells and VF fibroblasts (VFF) may overcome some of these limitations. In contrast to human VFF, which are available in several forms, availability of VF epithelial cells is scarce. Buccal mucosa might be a good alternative source for epithelial cells, as it is easily accessible, and biopsies heal without scarring. For this project, we thus generated alternative constructs consisting of immortalized human VF fibroblasts and primary human buccal epithelial cells. The constructs (n = 3) were compared to native laryngeal mucosa at the histological and proteomic level. The engineered constructs reassembled into a mucosa-like structure after a cultivation period of 35 days. Immunohistochemical staining confirmed a multi-layered stratified epithelium, a collagen type IV positive barrier-like structure resembling the basement membrane, and an underlying layer containing VFF. Proteomic analysis resulted in a total number of 1961 identified and quantified proteins. Of these, 83.8% were detected in both native VF and constructs, with only 53 proteins having significantly different abundance. 15.3% of detected proteins were identified in native VF mucosa only, most likely due to endothelial, immune and muscle cells within the VF samples, while 0.9% were found only in the constructs. Based on easily available cell sources, we demonstrate that our laryngeal mucosa model shares many characteristics with native VF mucosa. It provides an alternative and reproducible in vitro model and offers many research opportunities ranging from the study of VF biology to the testing of interventions (e.g. drug testing).

Hydrogel-Supported, Engineered Model of Vocal Fold Epithelium

There is a critical need for the establishment of an engineered model of the vocal fold epithelium that can be used to gain understanding of its role in vocal fold health, disease, and facilitate the development of new treatment options. Toward this goal, we isolated primary vocal fold epithelial cells (VFECs) from healthy porcine larynxes and used them within passage 3. Culture-expanded VFECs expressed the suprabasal epithelial marker cytokeratin 13 and intercellular junctional proteins occludin, E-cadherin, and zonula occludens-1. To establish the engineered model, we cultured VFECs on a hyaluronic acid-derived synthetic basement membrane displaying fibronectin-derived integrin-binding peptide (RGDSP) and/or laminin 111-derived syndecan-binding peptide AG73 (RKRLQVQLSIRT). Our results show that matrix stiffness and composition cooperatively regulate the adhesion, proliferation, and stratification of VFECs. Cells cultured on hydrogels with physiological stiffness (elastic shear modulus, G' = 1828 Pa) adopted a cobblestone morphology with close cell-cell contacts, whereas those on softer matrices (G' = 41 Pa) were spindle shaped with extensive intracellular stress fibers. The development of stratified epithelium with proliferating basal cells and additional (1-2) suprabasal layers requires the presence of both RGDSP and AG73 peptide signals. Supplementation of cytokines produced by vimentin positive primary porcine vocal fold fibroblasts in the VFEC culture led to the establishment of 4-5 distinct cell layers. The engineered vocal fold epithelium resembled native tissue morphologically; expressed cytokeratin 13, mucin 1, and tight/adherens junction markers; and secreted basement membrane proteins collagen IV and laminin 5. Collectively, our results demonstrate that stiffness matching, cell-matrix engagement, and paracrine signaling cooperatively contribute to the stratification of VFECs. The engineered epithelium can be used as a versatile tool for investigations of genetic and molecular mechanisms in vocal fold health and disease.

Concurrent YAP/TAZ and SMAD signaling mediate vocal fold fibrosis

Vocal fold (VF) fibrosis is a major cause of intractable voice-related disability and reduced quality of life. Excision of fibrotic regions is suboptimal and associated with scar recurrence and/or further iatrogenic damage. Non-surgical interventions are limited, putatively related to limited insight regarding biochemical events underlying fibrosis, and downstream, the lack of therapeutic targets. YAP/TAZ integrates diverse cell signaling events and interacts with signaling pathways related to fibrosis, including the TGF-β/SMAD pathway. We investigated the expression of YAP/TAZ following vocal fold injury in vivo as well as the effects of TGF-β1 on YAP/TAZ activity in human vocal fold fibroblasts, fibroblast-myofibroblast transition, and TGF-β/SMAD signaling. Iatrogenic injury increased nuclear localization of YAP and TAZ in fibrotic rat vocal folds. In vitro, TGF-β1 activated YAP and TAZ in human VF fibroblasts, and inhibition of YAP/TAZ reversed TGF-β1-stimulated fibroplastic gene upregulation. Additionally, TGF-β1 induced localization of YAP and TAZ in close proximity to SMAD2/3, and nuclear accumulation of SMAD2/3 was inhibited by a YAP/TAZ inhibitor. Collectively, YAP and TAZ were synergistically activated with the TGF-β/SMAD pathway, and likely essential for the fibroplastic phenotypic shift in VF fibroblasts. Based on these data, YAP/TAZ may evolve as an attractive therapeutic target for VF fibrosis.

In vitro mechanical vibration down-regulates pro-inflammatory and pro-fibrotic signaling in human vocal fold fibroblasts

INTRODUCTION

Voice rest following phonotrauma or phonosurgery has a considerable clinical impact, but clinical recommendations are inconsistent due to inconclusive data. As biopsies of the vocal folds (VF) for molecular biology studies in humans are unethical, we established a new in vitro model to explore the effects of vibration on human vocal fold fibroblasts (hVFF) in an inflammatory and normal state, which is based on previously published models.

METHODS

By using a phonomimetic bioreactor we were able to apply predefined vibrational stress patterns on hVFF cultured under inflammatory or normal conditions. Inflammatory and pro-fibrotic stimuli were induced by interleukin (IL)1β and transforming growth factor (TGF)β1, respectively. Mechanical stimulation was applied four hours daily, over a period of 72 hours. Outcome measurements comprised assessment of extracellular matrix (ECM)-related components, angiogenic factors, and inflammatory and fibrogenic markers on gene expression and protein levels.

RESULTS

Under inflammatory conditions, the inflammatory cytokine IL11, as well as the myofibroblast marker alpha smooth muscle actin (α-SMA) were significantly reduced when additional vibration was applied. The desirable anti-fibrotic ECM component hyaluronic acid was increased following cytokine treatment, but was not diminished following vibration.

CONCLUSION

Our experiments revealed the effect of vibrational stress on hVFF in an inflammatory state. Elevated levels of certain pro-inflammatory/pro-fibrotic factors could be mitigated by additional vibrational excitation in an in vitro setting. These findings corroborate clinical studies which recommend early voice activation following an acute event.

Culture of Mesenchymal Stem Cells in a Hydrogel Model of Vocal Fold Lamina Propria

Stem cell injection has been proposed as an alternative approach for the restoration of vocal fold (VF) function in patients with VF scarring. To assess the therapeutic efficacy of this treatment strategy, we evaluated the behaviors of human mesenchymal stem cells (hMSCs) in hydrogels derived from thiolated hyaluronic acid (HA-SH) and poly(ethylene glycol) diacrylate (PEG-DA) entrapping assembled collagen fibrils (abbreviated as HPC gels). Three hydrogel formulations with varying amounts of collagen (0, 1 and 2 mg/mL) but a fixed HA-SH (5 mg/mL) and PEG-DA (2 mg/mL) concentration, designated as HPC0, HPC1 and HPC2, were investigated. The HPC gels exhibit similar pore sizes (35-50 nm) and AFM indentation moduli (~175 Pa), although the elastic shear modulus for HPC1 (~32 Pa) is lower than HPC0 and HPC2 (~55 Pa). Although HPC1 and HPC2 gels both promoted the development of an elongated cell morphology, greater cell spreading was observed in HPC2 than in HPC1 by day 7. At the transcript level, cells cultured in HPC1 and HPC2 gels had an increased expression of fibronectin and integrin β1, but a decreased expression of tissue inhibitor of metalloproteinase-1, collagen types I/III and HA synthase-1 when compared to cells cultured in HPC0 gels. Cellular expression of connective tissue growth factor was also elevated in HPC1 and HPC2 cultures. Importantly, the HPC2 hydrogels promoted a signficant up-regulation of matrix metalloproteinase 1, transforming growth factor β1, and epithelial growth factor receptor, indicating an increased tissue turnover. Overall, hMSCs cultured in HPC2 gels adopt a phenotype reminiscent of cells involved in the wound healing process, providing a platform to study the effectiveness of therapeutic stem cell treatments for VF scarring.

An in vitro assessment of the response of THP-1 macrophages to varying stiffness of a glycol-chitosan hydrogel for vocal fold tissue engineering applications

The physical properties of a biomaterial play an essential role in regulating immune and reparative activities within the host tissue. This study aimed to evaluate the immunological impact of material stiffness of a glycol-chitosan hydrogel designed for vocal fold tissue engineering. Hydrogel stiffness was varied via the concentration of glyoxal cross-linker applied. Hydrogel mechanical properties were characterized through atomic force microscopy and shear plate rheometry. Using a transwell setup, macrophages were co-cultured with human vocal fold fibroblasts that were embedded within the hydrogel. Macrophage viability and cytokine secretion were evaluated at 3, 24, and 72 hr of culture. Flow cytometry was applied to evaluate macrophage cell surface markers after 72 hr of cell culture. Results indicated that increasing hydrogel stiffness was associated with increased anti-inflammatory activity compared to relevant controls. In addition, increased anti-inflammatory activity was observed in hydrogel co-cultures. This study highlighted the importance of hydrogel stiffness from an immunological viewpoint when designing novel vocal fold hydrogels.

Regulation of Stem Cell Function in an Engineered Vocal Fold-Mimetic Environment

Human mesenchymal stem cells (hMSCs) have been proposed as therapeutic cells for the treatment of vocal fold (VF) scarring. Although functional recovery was observed in animal models after stem cell injection, it is not clear how injected stem cells interact locally with the extracellular matrix (ECM) of the lamina propria (LP) and how such interactions affect stem cell behaviors to improve function. Herein, we developed an in vitro cell culture platform where hMSCs were encapsulated in a LP-mimetic matrix, derived from hyaluronic acid (HA), poly(ethylene glycol) (PEG) and collagen, and cultured dynamically in a custom-designed VF bioreactor. The cell culture system was characterized by oscillatory shear rheology, laser doppler vibrometry (LDV), and digital image correlation (DIC). A constitutive finite element analysis (FEA) model was further developed to predict vibratory responses of the hydrogel. LDV analysis demonstrated an average displacement of 47 μm in the center of the hydrogel construct at 200 Hz applied frequency without any harmonics. The predicted strains throughout the hydrogel ranged from 0 to 0.03, in good agreement with reported values for the VF. The 3D cellular construct was subjected to vibrational stimulations at 200 Hz for an optimized duration of 1 h, as confirmed by a maximal c-Fos upregulation at the transcript level. Vibrational culture over a 3-day period with a 1h-on/1h-off pattern did not compromise the overall cell viability, but resulted in a significant downregulation of fibrogenic markers and diminished staining for alpha smooth muscle actin (αSMA). Collectively, high frequency mechanical loading resulted in the loss of myofibrogenic potential and a shift away from a fibrotic phenotype.

Pathophysiology of Fibrosis in the Vocal Fold: Current Research, Future Treatment Strategies, and Obstacles to Restoring Vocal Fold Pliability

Communication by voice depends on symmetrical vibrations within the vocal folds (VFs) and is indispensable for various occupations. VF scarring is one of the main reasons for permanent dysphonia and results from injury to the unique layered structure of the VFs. The increased collagen and decreased hyaluronic acid within VF scars lead to a loss of pliability of the VFs and significantly decreases their capacity to vibrate. As there is currently no definitive treatment for VF scarring, regenerative medicine and tissue engineering have become increasingly important research areas within otolaryngology. Several recent reviews have described the problem of VF scarring and various possible solutions, including tissue engineered cells and tissues, biomaterial implants, stem cells, growth factors, anti-inflammatory cytokines antifibrotic agents. Despite considerable research progress, these technical advances have not been established as routine clinical procedures. This review focuses on emerging techniques for restoring VF pliability using various approaches. We discuss our studies on interactions among adipose-derived stem/stromal cells, antifibrotic agents, and VF fibroblasts using an in vitro model. We also identify some obstacles to advances in research.

Liquid-type non-thermal atmospheric plasma ameliorates vocal fold scarring by modulating vocal fold fibroblast

Injection laryngoplasty is a widely used therapeutic option for drug delivery into vocal folds (VFs). Efficient injectable materials are urgently needed for treating intractable VF disease. Liquid-type non-thermal atmospheric plasma (LTP) has been found to be useful for various biological applications, including in regenerative medicine. We evaluated the effects of LTP on VF regeneration. Migration and matrix metalloproteinase-2 expression of lipopolysaccharide (LPS)-treated human vocal fold-derived mesenchymal stem cells (VF-MSCs) were enhanced by LTP treatment. LTP treatment not only ameliorated nuclear factor-κB and interleukin-6 activation, induced by LPS treatment, but also the increased manifestation of α-smooth muscle actin and fibronectin, induced by transforming growth factor-ß. In a rabbit VF scarring animal model, histological analyses showed increased hyaluronic acid deposition and decreased collagen accumulation after LTP injection. Videokymographic analysis showed more improved vibrations in LTP-treated VF mucosa compared to those in non-treated group. In conclusion, LTP treatment enhanced the recruitment and activation of VF-MSCs. Regulated extracellular matrix (ECM) synthesis and eventual functional improvement of scarred VFs were observed upon LTP treatment. The results of this study suggest that LTP injection can enhance wound healing and improve functional remodeling following VF injury.

Impact statement

Voice disorder has a significant impact on life quality, and one of the major causes of this voice disorder is vocal fold scarring. Therefore, various approaches have been tried to treat for voice disorder. However, no method has satisfied all requirements until now. Plasma medicine, which involves the medical application of plasma, is a rapidly developing field. We have confirmed that liquid-type plasma improved vocal fold scarring by mobilizing and activating vocal fold fibroblast. In conclusion, liquid-type plasma is a potential therapeutic agent for promoting vocal fold scarring through simple injection and it may be an alternative therapeutic agent for the current situation to treat voice disorder.

In vitro evaluation of anti-fibrotic effects of select cytokines for vocal fold scar treatment

Scarring of the vocal fold lamina propria (LP) can cause considerable voice disorders due to reduced pliability in scar tissue, attributed in part to abnormal extracellular matrix (ECM) deposition produced by the fibrotic vocal fold fibroblast (fVFF). Cytokines with anti-fibrotic potential have been investigated to limit abnormal LP ECM, but are limited by the need for repeat injections. Moreover, the potentially significant role played by activated macrophages (AMOs) is usually not considered even though the interaction between AMO and fibrotic fibroblasts is known to regulate scar formation across different tissues. AMO are also regulated by cytokines that are used for LP scar removal, but little is known about AMO behaviors in response to these cytokines within the context of LP scar. In the present study, we evaluated anti-fibrotic effects of hepatocyte growth factor (HGF), interleukin-10 (IL-10) and interleukin-6 (IL-6) in a 3D, in vitro fVFF-AMO co-culture system using poly(ethylene glycol) diacrylate (PEGDA) hydrogels. Data from all cytokines was synthesized into a heat-map that enabled assessment of specific associations between AMO and fVFF phenotypes. Cumulatively, our results indicated that both HGF and IL-10 are potentially anti-fibrotic (reduction in fibrotic markers and enhancement in normal, anti-fibrotic VFF markers), while IL-6 displays more complex, marker specific effects. Possible associations between AMO and fVFF phenotypes were found and may highlight a potential desirable macrophage phenotype. These data support the therapeutic potential of HGF and IL-10 for LP scar treatment, and shed light on future strategies aimed at targeting specific AMO phenotypes. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1056-1067, 2019.

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.

Methodology for the establishment of primary porcine vocal fold epithelial cell cultures

OBJECTIVE

A current lack of methods for epithelial cell culture significantly hinders our understanding of the role of the epithelial and mucus barriers in vocal fold health and disease. Our first objective was to establish reproducible techniques for the isolation and culture of primary porcine vocal fold epithelial cells. Our second objective was to evaluate the functional significance of cell cultures using an in vitro exposure to an inflammatory cytokine.

METHODS

Epithelial cells were isolated from porcine vocal folds and expanded in culture. Characterization of cultures was completed by immunostaining with markers for pan-cytokeratin (epithelial cells), vimentin (stromal cells), von Willebrand factor (endothelial cell), and MUC1 and MUC4 (mucin) glycoproteins. Established epithelial cell cultures were then exposed to the inflammatory cytokine tumor necrosis factor alpha (TNF-α) for 24-hours, and transcript expression of MUC1 and MUC4 was evaluated.

RESULTS

Reproducible, porcine vocal fold epithelial cell cultures, demonstrating cobblestone appearance characteristic of the typical morphology of epithelial cell cultures were created. Cells showed positive staining for pan-cytokeratin with limited expression of vimentin and von Willebrand factor. Epithelial cells also expressed MUC1 and MUC4. TNF-α significantly increased transcript expression of MUC4.

CONCLUSION

Here, we present the first report of successful culture of primary porcine vocal fold epithelial cells. Cultures will provide researchers with a valuable new in vitro tool to investigate vocal fold epithelium and mucus as well as the effects of common challenges, including inflammatory cytokines, on these barriers.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E355-E364, 2019.

Cryotherapy has antifibrotic and regenerative effects on human vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Vocal fold scarring remains a major treatment challenge, and scar prevention without residual lesions remains a dilemma. Cryotherapy has shown cosmetic outcomes on skin lesions with minimal scarring. The aim of this study was to clarify the beneficial effects of cryotherapy for the prevention and the treatment of vocal fold scarring.

STUDY DESIGN

In vitro.

METHODS

Primary cultures of human vocal fold fibroblasts (VFFs) were used in this study. Myofibroblast differentiation was stimulated by transforming growth factor β1 (TGF-β1). We mimicked the cryotherapy effect on vocal fold healing in vivo by freezing VFFs ± TGF-β1 in vitro. The influence of freezing on cell viability, proliferation, migration, and contractile properties were analyzed. The expression of collagen I, collagen III, fibronectin, TGF-β1, matrix metallopeptidase 1 (MMP1), hyaluronan synthase 1 (HAS1) were investigated by real-time polymerase chain reaction (RT-PCR), and the expression of alpha smooth muscle actin (α-SMA) and decorin were investigated by RT-PCR and Western blot.

RESULTS

Freezing was found to modify extracellular matrix (ECM) synthesis and differentiation of VFFs. Expression of collagen I, collagen III, fibronectin, α-SMA, and TGF-β1 was downregulated, and MMP1 was upregulated in VFFs + TGF-β1 (myofibroblast) by freezing. HAS1 and decorin were upregulated in both VFFs ± TGF-β1 by freezing. Freezing VFFs + TGF-β1 (myofibroblast) with fast thawing had a lower expression of α-SMA when compared with slow thawing. Freezing reduced the migration and collagen contraction of VFFs + TGF-β1 (myofibroblast).

CONCLUSION

Cryotherapy induces antifibrotic and regenerative ECM alterations in VFFs. These data provide insight into the prevention and the treatment of vocal fold scarring with cryotherapy in phonomicrosurgery.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E143-E150, 2019.

Photodynamic therapy induces antifibrotic alterations in primary human vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Photodynamic therapy (PDT) is a promising treatment modality for laryngeal dysplasia, early-stage carcinoma, and papilloma, and was reported to have the ability to preserve laryngeal function and voice quality without clinical fibrotic response. We aimed to investigate the mechanism behind the antifibrotic effects of PDT on primary human vocal fold fibroblasts (VFFs) in vitro.

STUDY DESIGN

In vitro analysis from one human donor.

METHODS

Cell viability of VFFs in response to varying doses of PDT was investigated by the Cell Counting Kit-8 method. Sublethal-dose PDT (SL-PDT) was used for the following experiments. Expression of genes related to vocal fold extracellular matrix formation was analyzed by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blotting. Effects of PDT on cell migration, collagen contraction, and transforming growth factor β-1 (TGF-β1)-induced myofibroblast differentiation were also analyzed.

RESULTS

PDT affects the viability of VFFs in a dose-dependent manner. SL-PDT significantly changed the expression profile of VFFs with antifibrotic effects. It also inhibited cell migration, reduced collagen contraction, and reversed the fibroblast-myofibroblast differentiation induced by TGF-β1.

CONCLUSIONS

SL-PDT induces antifibrotic alterations in VFFs. This could explain the low incidence of vocal fold scar associated with PDT. Moreover, PDT may be useful in treating existing vocal fold scars. Further studies should focus on the in vivo effect of PDT on vocal fold wound healing and scar remodeling.

LEVEL OF EVIDENCE

NA Laryngoscope, 128:E323-E331, 2018.

Metabolic variations in normal and fibrotic human laryngotracheal-derived fibroblasts: A Warburg-like effect

OBJECTIVES/HYPOTHESIS

Laryngotracheal stenosis (LTS) is a chronic fibrotic disease characterized by fibroblast proliferation, collagen deposition, and matrix remodeling in the lamina propria of the larynx and/or trachea. Current medical therapies are limited by a poor understanding of the effector cell's (fibroblasts) cellular biology and metabolism. The purpose of this study was to compare cellular proliferation, function, and metabolism between normal and LTS-derived fibroblasts in vitro. We hypothesize that LTS-derived fibroblasts will demonstrate aberrant behavior with faster proliferation, increased collagen production, and altered metabolic allocation compared with normal fibroblasts.

STUDY DESIGN

In vitro comparative analysis.

METHODS

Human biopsies of normal and iatrogenic LTS tissue (n = 7) were obtained, and fibroblasts were isolated and cultured in vitro. Cellular proliferation, cellular histology, gene expression, and metabolic analyses were performed. Statistical analyses comparing normal and scar-derived fibroblasts were performed.

RESULTS

LTS fibroblast proliferation rate, cellular surface area, and collagen-1 expression were increased compared to normal fibroblasts. Cellular metabolic analysis of LTS-derived fibroblasts demonstrated reduced oxidative phosphorylation and increased glycolysis/oxidative phosphorylation ratio compared with normal fibroblasts.

CONCLUSIONS

Human iatrogenic LTS-derived fibroblasts demonstrated aberrant behavior when compared with normal fibroblasts. A Warburg-like effect was revealed, suggesting human iatrogenic LTS fibroblasts drive their proliferation with aerobic glycolysis. The distinct metabolism suggests metabolic inhibitors could reduce fibroblast hyperplasia and hypertrophy in LTS and fibrosis in general.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:E107-E113, 2017.

Modeling fibrosis using fibroblasts isolated from scarred rat vocal folds

Following injury, pathologically activated vocal fold fibroblasts (VFFs) can engage in disordered extracellular matrix (ECM) remodeling, leading to VF fibrosis and impaired voice function. Given the importance of scar VFFs to phenotypically appropriate in vitro modeling of VF fibrosis, we pursued detailed characterization of scar VFFs obtained from surgically injured rat VF mucosae, compared with those obtained from experimentally naïve, age-matched tissue. Scar VFFs initially exhibited a myofibroblast phenotype characterized by increased proliferation, increased Col1a1 transcription and collagen, type I synthesis, increased Acta2 transcription and α-smooth muscle actin synthesis, and enhanced contractile function. These features were most distinct at passage 1 (P1); we observed a coalescence of the scar and naïve VFF phenotypes at later passages. An empirical Bayes statistical analysis of the P1 cell transcriptome identified 421 genes that were differentially expressed by scar, compared with naïve, VFFs. These genes were primarily associated with the wound response, ECM regulation, and cell proliferation. Follow-up comparison of P1 scar VFFs and their in vivo tissue source showed substantial transcriptomic differences. Finally, P1 scar VFFs responded to treatment with hepatocyte growth factor and transforming growth factor-β3, two biologics with reported therapeutic value. Despite the practical limitations inherent to working with early passage cells, this experimental model is easily implemented in any suitably equipped laboratory and has the potential to improve the applicability of preclinical VF fibrosis research.

Mesenchymal stem cells have antifibrotic effects on transforming growth factor-β1-stimulated vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Mesenchymal stem cells (MSCs) hold therapeutic promise for vocal fold scar, yet the precise mechanism(s) underlying tissue level changes remain unclear. We hypothesize that MSCs interact with native fibroblasts to favorably affect healing. Furthermore, we hypothesize that these interactions vary based on MSC source.

METHODS

Vocal fold fibroblasts (VFFs), adipose-derived stem cells, and bone marrow-derived stem cells (BMSCs) were extracted from Sprague-Dawley rats; and a coculture model was employed culturing VFFs ± transforming growth factor (TGF-β1) (10 ng/mL) ± MSCs. Monoculture MSCs were also prepared as a control. Both extracellular matrix (ECM) and components of the TGF-β signaling pathway were analyzed via polymerase chain reaction and western blotting.

RESULTS

Significantly decreased TGF-β1 mRNA and α-smooth muscle actin protein was observed in VFFs in response to TGF-β1 in the coculture with both MSCs (P < 0.05, P < 0.01). BMSCs significantly downregulated collagen I (P < 0.05), collagen III (P < 0.05), Smad3 (P < 0.01), and TGF-β1 receptor I (P < 0.01) mRNA in VFFs. Hyaluronic synthase-1 and 2 increased in cocultured BMSCs when compared with monocultured BMSCs at baseline and in response to TGF-β1 (P < 0.01).

CONCLUSION

MSCs had a favorable effect on ECM regulation as well as suppression of TGF-β1 signaling in VFF. Bidirectional paracrine signaling was also observed as VFFs altered ECM regulation in MSCs. These data provide insight into the regenerative effects of MSCs and provide a foundation for clinical application.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:E35-E41, 2017.

Stem cell approaches for vocal fold regeneration

OBJECTIVES/HYPOTHESIS

Current interventions in the management of vocal fold (VF) dysfunction focus on conservative and surgical approaches. However, the complex structure and precise biomechanical properties of the human VF mean that these strategies have their limitations in clinical practice and in some cases offer inadequate levels of success. Regenerative medicine is an exciting development in this field and has the potential to further enhance VF recovery beyond conventional treatments. Our aim in this review is to discuss advances in the field of regenerative medicine; that is, advances in the process of replacing, engineering, or regenerating the VF through utilization of stem cells, with the intention of restoring normal VF structure and function.

DATA SOURCES

English literature (1946-2015) review.

METHODS

We conducted a systematic review of MEDLINE for cases and studies of VF tissue engineering utilizing stem cells.

RESULTS

The three main approaches by which regenerative medicine is currently applied to VF regeneration include cell therapy, scaffold development, and utilization of growth factors.

CONCLUSION

Exciting advances have been made in stem cell biology in recent years, including use of induced pluripotent stem cells. We expect such advances to be translated into the field in the forthcoming years. Laryngoscope, 126:1865-1870, 2016.

Predictors of Posterior Glottic Stenosis: A Multi-Institutional Case-Control Study

OBJECTIVE

To assess intrinsic and extrinsic risk factors in the development of posterior glottic stenosis (PGS) in intubated patients.

METHODS

Patients diagnosed with PGS between September 2012 and May 2014 at 3 tertiary care university hospitals were included. Patient demographics, comorbidities, duration of intubation, endotracheal tube (ETT) size, and indication for intubation were recorded. Patients with PGS were compared to control patients represented by patients intubated in intensive care units (ICU).

RESULTS

Thirty-six PGS patients were identified. After exclusion, 28 PGS patients (14 male, 14 female) and 112 (65 male, 47 female) controls were studied. Multivariate analysis demonstrated ischemia (P < .05), diabetes (P < .01), and length of intubation (P < .01) were significant risk factors for the development of PGS. Fourteen of 14 (100%) males were intubated with a size 8 or larger ETT compared to 47 of 65 (72.3%) male controls (P < .05). Posterior glottic stenosis (P < .01), length of intubation (P < .001), and obstructive sleep apnea (P < .05) were significant risk factors for tracheostomy.

CONCLUSION

Duration of intubation, ischemia, diabetes mellitus, and large ETT size (8 or greater) in males were significant risk factors for the development of PGS. Reducing the use of size 8 ETTs and earlier planned tracheostomy in high-risk patients may reduce the incidence of PGS and improve ICU safety.

Vocal fold myofibroblast profile of scarring

OBJECTIVES/HYPOTHESIS

Vocal fold fibroblasts (VFF) are responsible for extracellular matrix synthesis supporting lamina propria in normal and diseased conditions. When tissue is injured, VFF become activated and differentiate into myofibroblasts to facilitate wound healing response. We investigated if vocal fold myofibroblasts can be utilized as surrogate cells for scarred VFF.

STUDY DESIGN

In vitro.

METHODS

Normal VFF cell lines from a 21-year-old male (N21), 59-year-old female (N59), and a scar VFF cell line from a 56-year-old female (S56) were used in this study. 10 ng/mL of transforming growth factor (TGFβ1) was applied for 5 days to normal VFF. Myofibroblast differentiation was determined with immunocytochemistry and western blot, measuring alpha smooth muscle actin (α-SMA). Cell growth, proliferation, contractile properties, and gene expression profiles were evaluated.

RESULTS

N21, N59, and S56 VFF presented elongated configuration. N21+ and N21- VFF demonstrated significantly greater proliferation compared to N59+, N59-, and S56 VFF at 6 days. α-SMA was expressed in all cells. Fibronectin, alpha smooth actin, connective tissue growth factor, and metallopeptidase inhibitor were the highest genes expression in VFF treated with transforming growth factor β1 (TGFβ1). At 24 hours, S56 VFF showed lower contraction compared to N21+ and N59+ VFF, but at 60 hours S56 VFF had lower collagen contraction compared to all cell groups. Highest collagen contraction matrices were measured with VFF treated with TGFβ1 at 24 hours and N59- VFF at 60 hours.

CONCLUSION

VFF treated with TGFβ1 (myofibroblasts) appear to have similar phenotypic characteristics but different genotypic behavior compared to scar VFF.

LEVEL OF EVIDENCE

N/A. Laryngoscope, 126:E110-E117, 2016.

Varying RGD concentration and cell phenotype alters the expression of extracellular matrix genes in vocal fold fibroblasts

The impact of RGD integrin binding-peptide concentration and cell phenotype on directing extracellular matrix (ECM) gene expression in vocal fold fibroblasts is little understood. Less is known about cell response to RGD concentration on a biomaterial when fibroblasts are in a scar-like environment compared to a healthy environment. We investigated the effects of varying RGD integrin-binding peptide surface concentration on ECM gene expression of elastin, collagen type 3 alpha 1, decorin, fibronectin, hyaluronan synthase 2, and collagen type 1 alpha 2 in scarred and unscarred immortalized human vocal fold fibroblasts (I-HVFFs). Phenotype and RGD concentration affected ECM gene expression. Phenotype change from healthy to myofibroblast-like resulted in ECM gene up-regulation for all genes tested, except for decorin. Systematically altering RGD concentration affected the expression of elastin and collagen type 3 alpha 1 in a myofibroblast phenotype. Specifically greater up-regulation in gene expression was observed with higher RGD concentrations. This research demonstrates that controlling RGD concentration may influence ECM gene expression levels in fibroblasts. Such knowledge is critical in developing the next generation of bioactive materials that, when implanted into sites of tissue damage and scarring, will direct cells to regenerate healthy tissues with normal ECM ratios and morphologies.

Electrospun fiber constructs for vocal fold tissue engineering: effects of alignment and elastomeric polypeptide coating

Vocal fold lamina propria extracellular matrix (ECM) is highly aligned and when injured, becomes disorganized with loss of the tissue's critical biomechanical properties. This study examines the effects of electrospun fiber scaffold architecture and elastin-like polypeptide (ELP4) coating on human vocal fold fibroblast (HVFF) behavior for applications toward tissue engineering the vocal fold lamina propria. Electrospun Tecoflex™ scaffolds were made with aligned and unaligned fibers, and were characterized using scanning electron microscopy and uniaxial tensile testing. ELP4 was successfully adsorbed onto the scaffolds; HVFFs were seeded and their viability, proliferation, morphology and gene expression were characterized. Aligned and unaligned scaffolds had initial elastic moduli of ∼14 MPa, ∼5 MPa and ∼0.3 MPa, ∼0.6 MPa in the preferred and cross-preferred directions, respectively. Scaffold topography had an effect on the orientation of the cells, with HVFFs seeded on aligned scaffolds having a significantly different (p<0.001) angle of orientation than HVFFs cultured on unaligned scaffolds. This same effect and significant difference (p<0.001) was seen on aligned and unaligned scaffolds coated with ELP4. Scaffold alignment and ELP4 coating impacted ECM gene expression. ELP4 coating, and aligned scaffolds upregulated elastin synthesis when tested on day 7 without a concomitant upregulation of collagen III synthesis. Collectively, results indicate that aligned electrospun scaffolds and ELP4 coating are promising candidates in the development of biodegradeable vocal fold lamina propria constructs.

Lipopolysaccharide responsiveness in vocal fold fibroblasts

Background

Vocal fold fibroblast’s (VFF) strategic location in the lamina propria and their ability to respond to external stimuli by producing inflammatory molecules suggest their possible direct involvement in innate immunity. Toll-like receptors (TLRs) are an essential signaling component to this response, as they allow for recognition of various microorganisms, leading to subsequent induction of pro-inflammatory genes. The objective of this study was to elucidate the role of VFF in the host immune response and subsequent influence on inflammatory cytokine secretion.

Methods

VFF derived from polyp, scar, and normal tissue were treated with 5 μg/ml lipopolysaccharide (LPS). TLR1 through 9, CD14, and MD-2 were measured during stable conditions by polymerase chain reaction (PCR). Expression of TLR4 and IL-1R type-1 genes were quantified after 24 hrs LPS stimulation by reverse transcription-PCR. LPS responsiveness was determined by NF-κB nuclear translocation as measured by subunit p65 expression in nucleus with immunocytochemistry. Downstream effects were confirmed with immunoassay measuring IL-8 concentrations in supernatant after 8 hrs.

Results

All VFFs constitutively expressed TLR1 to 6, TLR9, CD14, and MD-2 mRNA. Polyp VFF exhibited significantly higher TLR4 transcript levels (p < 0.001) in comparison to scar and normal VFF. LPS stimulated scar and polyp VFF exhibited increased levels of p65 in the nucleus (p < 0.01) and secreted greater IL-8 protein (p < 0.0001) compared to normal VFF.

Conclusion

VFF constitutively express genes for the receptors essential to the host immune response. Scar and polyp VFF produced greater LPS responsiveness resulting in over-activated inflammatory patterns. These findings support VFF role in the pathogenesis of inflammatory vocal fold disorders and suggests their presence in the wound bed could lead to chronic inflammation.

CD34-positive fibroblasts in Reinke's edema

OBJECTIVES/HYPOTHESIS

To elucidate whether and to what extent CD34+ fibroblasts (so-called CD34+ fibrocytes, CD34+ dendritic cells, and CD34+ stromal cells) occur in normal human vocal folds and in Reinke's edema.

STUDY DESIGN

Histological study.

METHODS

Conventional, immunohistochemical, and ultrastructural procedures were performed in histological blocks of 18 selected cases of Reinke's edema (with typical findings including acellular edematous spaces in the subepithelial connective tissue of vocal folds, and disarrangement of elastic, collagen, and reticular fibers). For control purposes, four normal vocal folds were analyzed.

RESULTS

In normal vocal folds, most stromal cells were spindle-shaped CD34+ fibroblasts. In Reinke's edema, increased density and changes in the morphology and size of this subpopulation of fibroblasts were demonstrated in the connective tissue surrounding the edematous spaces, particularly in their borders, where together with some macrophages they formed boundaries, mimicking the walls of distended lymphatic vessels when conventional stains were used. These activated CD34+ fibroblasts acquired a dendritic morphology (with long, moniliform, often bifurcated, overlapping multipolar processes), and their cytoplasmic organelles were increased in number. In addition to CD34, they expressed vimentin, CD10 and CD99, but no α-smooth muscle actin (α-SMA), CD31, CD117, CD68, h-caldesmon, desmin, or S-100 protein.

CONCLUSIONS

CD34+ fibroblasts are a major cell component in the stroma of vocal folds in Reinke's edema, and their activation, with increased density and morphologic changes around the edematous spaces, occurs without immunophenotypic transformation toward myofibroblasts (no expression of α-SMA). The mechanisms by which these cells act in Reinke's edema require further study.

Cell-cell interaction between vocal fold fibroblasts and bone marrow mesenchymal stromal cells in three-dimensional hyaluronan hydrogel

Mesenchymal stromal cells (MSCs) are multipotential adult cells present in all tissues. Paracrine effects and differentiating ability make MSCs an ideal cell source for tissue regeneration. However, little is known about how interactions between implanted MSCs and native cells influence cellular growth, proliferation, and behaviour. By using an in vitro three-dimensional (3D) co-culture assay of normal or scarred human vocal fold fibroblasts (VFFs) and bone marrow-derived MSCs (BM-MSCs) in a uniquely suited hyaluronan hydrogel (HyStem-VF), we investigated cell morphology, survival rate, proliferation and protein and gene expression of VFFs and BM-MSCs. BM-MSCs inhibited cell proliferation of both normal and scarred VFFs without changes in VFF morphology or viability. BM-MSCs demonstrated decreased proliferation and survival rate after 7 days of co-culture with VFFs. Interactions between BM-MSCs and VFFs led to a significant increase in protein secretion of collagen I and hepatocyte growth factor (HGF) and a decrease of vascular endothelial growth factor (VEGF), monocyte chemotactic protein-1 (MCP-1) and interleukin-6 (IL-6). In particular, BM-MSCs significantly upregulated matrix metalloproteinase 1 (MMP1) and HGF gene expression for scarred VFFs compared to normal VFFs, indicating the potential for increases in extracellular matrix remodelling and tissue regeneration. Application of BM-MSCs-hydrogels may play a significant role in tissue regeneration, providing a therapeutic approach for vocal fold scarring. Copyright © 2013 John Wiley & Sons, Ltd.

Vocal fold fibroblasts immunoregulate activated macrophage phenotype

Recent evidence suggests that fibroblasts play a critical role in regulating inflammation during wound healing because they express several inflammatory mediators in response to bacteria. The objective of this study was to analyze the effects of lipopolysaccharide (LPS) on the immunomodulatory properties of vocal fold fibroblasts (VFFs) derived from polyps, scar and normal tissue co-cultured with macrophages, to provide insight into their interactions during the inflammatory process. Fibroblasts were co-cultured with CD14+ monocytes and after 7 days, wells were treated with LPS for 24 and 72 h. Culture supernatants were collected and concentrations of TNF-α, IL-6, IL-8, IL-10, IL-12, IL-1β and MCP-1 were quantified by ELISA. Normal VFF and CD14+ monocultures were used as controls. Twenty-four hours after LPS activation, macrophages co-cultured with polyp VFF had significantly increased expression of TNF-α, IL-1β, IL-12 and IL-10 compared to controls (p<0.0001). In contrast, macrophages co-cultured with scar VFF had significantly lower expression of TNF-α, IL-1β and IL-12 with significantly higher IL-10 compared to control (p<0.0001). After 72 h, macrophages co-cultured with polyp VFF increased expression of TNF-α, IL-1β, IL-10, IL-6, IL-8, MCP-1 and TGF-β (p<0.01) and macrophages co-cultured with scar VFF significantly decreased their expression of IL-1β and IL-12 compared to control (p<0.0001). Scar VFF at both time points produced significantly lower levels of IL-8, MCP-1, IL-6 and TGF-β compared to controls (p<0.05). Based on our findings, VFF and macrophages secrete several inflammatory mediators that modify their diverse functions. Polyp and scar VFF may play a role in regulating abnormal inflammatory responses, which could result in excessive ECM deposition that disrupts the function of the vocal folds.