Vocal fold myofibroblast profile of scarring

Nanoparticle-mediated targeting of PGC-1α reveals critical metabolic pathways in bladder cancer metastasis

Metastatic bladder cancer is characterized by its aggressive behavior and complex molecular mechanisms that remain largely undefined. This study explores the therapeutic potential of targeting peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) using liposomal nanoparticles to deliver PGC-1α siRNA to bladder cancer cells. We employed comprehensive transcriptomic, proteomic, and metabolomic analyses to investigate the impact of PGC-1α silencing. Our in vitro results demonstrate that targeting PGC-1α significantly impairs mitochondrial function and disrupts energy metabolism, affecting critical pathways such as glycolysis and the citric acid cycle, as well as altering mRNA nuclear export. In vivo experiments in animal models show that nanoparticles loaded with si-PGC-1α effectively reduce lung metastasis, indicating a significant impact on metastatic progression. These findings highlight PGC-1α as a key regulator of metabolic reprogramming in metastatic bladder cancer and suggest that its inhibition could serve as a promising therapeutic strategy. By elucidating the role of PGC-1α in cancer metabolism, this study provides new insights into the molecular underpinnings of bladder cancer metastasis and offers potential avenues for developing targeted therapies aimed at the metabolic vulnerabilities of this malignancy.

Inhibition of the MRTF-A/SRF signaling axis alleviates vocal fold scarring

Vocal fold scarring, the most common cause of poor voice after airway injury, involves the transition of vocal fold fibroblasts to contractile myofibroblasts. Vocal fold myofibroblasts can be characterized by significant extracellular matrix (ECM) secretion and stress fiber formation. Biochemical signals, such as transforming growth factor (TGF)-β1, and biophysical cues, such as matrix stiffening, have been shown to induce the fibroblast-to-myofibroblast transition. To identify key intracellular pathways that may mediate myofibroblast activation, we performed bulk RNA sequencing of human vocal fold fibroblasts treated with or without TGF-β1 and found that genes downstream of myocardin related transcription factor A (MRTF-A) and serum response factor (SRF) were upregulated in TGFβ1-induced myofibroblasts. We then show that both TGF-β1 and ECM stiffening induce MRTF-A and SRF nuclear translocation during vocal fold myofibroblast activation. Inhibition of MRTF-A via CCG-257,081 reduced pro-fibrotic gene expression, the percentage of α-smooth muscle actin (α-SMA)-positive fibroblasts, and cell contractility in vitro. In a murine model of vocal fold scarring, MRTF-A inhibition reduced vocal fold scarring severity, evidenced by reduced epithelial thickening, decreased glycosaminoglycan content, and collagen deposition, and decreased expression of ACTA2. Our study suggests that the MRTF-A/SRF pathway regulates vocal fold myofibroblast activation, and that inhibition of MRTF-A has a protective effect against vocal fold scarring in mice.

RNA-sequencing demonstrates transcriptional differences between human vocal fold fibroblasts and myofibroblasts

BACKGROUND

Differentiation of fibroblasts into myofibroblasts is necessary for wound healing, but excessive myofibroblast presence and persistence can result in scarring. Treatment for scarring is limited largely due to a lack of comprehensive understanding of how fibroblasts and myofibroblasts differ at the transcript level. The purpose of this study was to characterize transcriptional profiles of injured fibroblasts relative to normal fibroblasts, utilizing fibroblasts from the vocal fold as a model.

RESULTS

Utilizing bulk RNA sequencing technology, we identified differentially expressed genes between four cell lines of normal fibroblasts (cVFF), one line of scarred fibroblasts (sVFF), and four lines of fibroblasts treated with transforming growth factor-beta 1 (TGF-β1), representing an induced-scar phenotype (tVFF). Principal component analysis revealed clustering of normal fibroblasts separate from the clustering of fibroblasts treated with TGF-β1; scarred fibroblasts were more similar to normal fibroblasts than fibroblasts treated with TGF-β1. Enrichment analyses revealed pathways related to cell signaling, receptor-ligand activity, and regulation of cell functions in scarred fibroblasts, pathways related to cell adhesion in normal fibroblasts, and pathways related to ECM binding in fibroblasts treated with TGF-β1. Although transcriptomic profiles between scarred fibroblasts and fibroblasts treated with TGF-β1 were relatively dissimilar, the most highly co-expressed genes were enriched in pathways related to actin cytoskeleton binding, which supports the use of fibroblasts treated with TGF-β1 to represent a scarred cell phenotype.

CONCLUSIONS

Transcriptomics of normal fibroblasts differ from myofibroblasts, including from those retrieved from scar and those treated with TGF-β1. Despite large differences in transcriptomics between tVFF and sVFF, tVFF serve as a useful in vitro model of myofibroblasts and highlight key similarities to myofibroblasts extracted from scar pathology, as well as expected differences related to normal fibroblasts from healthy vocal folds.

Cryotherapy Modifies Extracellular Matrix Expression of Vocal Fold in Rat Models

OBJECTIVES

Vocal fold (VF) scarring is the major cause of voice disorders. Cryotherapy is an effective anti-scarring therapy for skin lesions. The aim of this study was to explore the anti-scarring potential of cryotherapy in vocal folds.

METHODS

The extracellular matrix (ECM) mRNA expression of cryotherapy on normal VF tissue and the histologic results of cryotherapy on vocal fold healing were studied. Fifteen rats were introduced cryotherapy on the normal VF bilaterally and were harvested for real-time polymerase chain reaction (RT-PCR) analysis for collagen I, collagen III, TGFβ1, decorin, fibronectin and HAS1 at 1 day, 3 days and 7 days. Ten rats were unilaterally injured by stripping lamina propria and immediately treated with or without cryotherapy and were harvested at 2 months for histological and immunohistochemical analysis.

RESULTS

Regenerative effect of cryotherapy was validated of ECM gene expression. Histological and immunohistochemical analysis showed significantly increased hyaluronan, decreased collagen, and increased decorin deposition in injury-cryotherapy cohort compared with injury control cohort and normal control cohort.

CONCLUSIONS

Cryotherapy may provide an optimal environment for vocal fold tissue regeneration. The results of the present investigation suggest that cryotherapy has therapeutic potential in prevention and treatment of vocal fold scarring.

Biophysical aspects of mechanotransduction in cells and their physiological/biological implications in vocal fold vibration: a narrative review

Mechanotransduction is a crucial property in all organisms, modulating cellular behaviors in response to external mechanical stimuli. Given the high mobility of vocal folds, it is hypothesized that mechanotransduction significantly contributes to their tissue homeostasis. Recent studies have identified mechanosensitive proteins in vocal fold epithelia, supporting this hypothesis. Voice therapy, which, involves the mobilization of vocal folds, aims to rehabilitate vocal function and restore homeostasis. However, establishing a direct causal link between specific mechanical stimuli and therapeutic benefits is challenging due to the variability in voice therapy techniques. This challenge is further compounded when investigating biological benefits in humans. Vocal fold tissue cannot be biopsied without significant impairment of the vibratory characteristics of the vocal folds. Conversely, studies using vocal fold mimetic bioreactors have demonstrated that mechanical stimulation of vocal fold fibroblasts can lead to highly heterogeneous responses, depending on the nature and parameters of the induced vibration. These responses can either aid or impede vocal fold vibration at the physiological level. Future research is needed to determine the specific mechanical parameters that are biologically beneficial for vocal fold function.

Transient Receptor Potential Ankyrin 1 Channel Alters Transforming Growth Factor Beta 1/Smad Signaling in Rat Vocal Fold Fibroblasts

OBJECTIVES

Vocal fold scar remains a therapeutic challenge. Vocal fold fibroblasts (VFFs) secrete extracellular matrix (ECM), and transforming growth factor-beta 1 (TGF-β1)-mediated fibroblast to myofibroblast differentiation is central to the development of fibrosis. The transient receptor potential (TRP) channel superfamily is a group of nonselective cation channels, and activation of TRP ankyrin 1 (TRPA1) channel has been shown to have antifibrotic effects through TGF-β1/Smad signaling in various organs. This study aimed to elucidate expression of TRPA1 and the impact of TRPA1 activation on TGF-β1/Smad signaling in VFFs.

METHODS

Vocal folds were dissected from 10-week-old, male Sprague-Dawley rats and primary VFFs were established. TRPA1 was examined in VFFs and lamina propria via immunostaining. VFFs were treated with allyl isothiocyanate (AITC, TRP channel agonist, 10-5 M) ± TGF-β1 (10 ng/ml) ± A-967079 (selective TRPA1 channel antagonist, 5.0 × 10-7 M) for 4 or 24 h. Trpa1, Smad3, Smad7, Col1a1, Acta2, and Has1 mRNA expression were quantified via qPCR.

RESULTS

TRPA1 was expressed in cultured VFFs and the lamina propria. TGF-β1 administration significantly increased Trpa1 compared to control. AITC alone did not alter Smad3, Smad7, Acta2, or ECM related genes. However, the combination of AITC and TGF-β1 significantly increased Smad3 and decreased Smad7 and Acta2 compared to TGF-β1 alone; A-967079 significantly reduced this response.

CONCLUSIONS

VFFs expressed TRPA1, and the activation of TRPA1 regulated TGF-β1/Smad signaling in VFFs. These findings provide preliminary insights into potential anti-fibrotic mechanisms of TRPA1 activation through TGF-β1/Smad signaling in VFFs.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:4593-4598, 2024.

Concentration Effects of Methylprednisolone in Human Vocal Fold Fibroblast-Macrophage Co-Culture

OBJECTIVE

The diversity of glucocorticoid (GC) properties may underlie variability of clinical efficacy for vocal fold (VF) disease. Optimized therapeutic approaches must account for tissue complexity as well as interactions between cell types. We previously reported that reduced GC concentrations inhibited inflammation without eliciting fibrosis in mono-cultured VF fibroblasts and macrophages. These data suggested that a refined approach to GC concentration may improve outcomes. In the current study, co-culture of VF fibroblasts and macrophages was employed to investigate the effects of different concentrations of methylprednisolone on fibrotic and inflammatory response genes in VF fibroblasts to optimize management paradigms.

STUDY DESIGN

In vitro.

METHODS

THP-1 monocyte-derived macrophages were stimulated with interferon-γ (IFN-γ), lipopolysaccharide (LPS), or transforming growth factor-β (TGF-β) to induce inflammatory (M(IFN/LPS)) and fibrotic (M(TGF)) phenotypes. Macrophages were then co-cultured with a human VF fibroblast cell line using a 0.4 μm pore membrane with or without 0.1-3000 nM methylprednisolone. Inflammatory (CXCL10, TNF, and PTGS2) and fibrotic (ACTA2, CCN2, and COL1A1) gene expression was quantified in fibroblasts.

RESULTS

Incubating VF fibroblasts with M(IFN/LPS) macrophages increased expression of TNF and PTGS2, and this effect was inhibited by methylprednisolone. Incubation of VF fibroblasts with M(TGF) macrophages increased expression of ACTA2, CCN2, and COL1A1, and this effect was enhanced by methylprednisolone. The concentration of methylprednisolone required to downregulate inflammatory genes (TNF and PTGS2) was lower than that to upregulate fibrotic genes (ACTA2, CCN2, and COL1A1).

CONCLUSION

Reduced concentration of methylprednisolone effectively suppressed inflammatory genes without enhancing fibrotic genes, suggesting that a refined approach to GC concentration may improve clinical outcomes.

LEVEL OF EVIDENCE

N/A Laryngoscope, 133:3116-3122, 2023.

Dose-Dependent Glucocorticoid Regulation of Transcription Factors in Vocal Fold Fibroblasts and Macrophages

OBJECTIVE

Variable outcomes of glucocorticoid (GC) therapy for laryngeal disease are putatively due to diverse interactions of the GC receptor (GR) with cell signaling pathways, limited consideration regarding concentration-dependent effects, and inconsistent selection of GCs. In the current study, we evaluated the concentration-dependent effects of three frequently administered GCs on transcription factors with an emphasis on the phosphorylation of GR at Ser203 and Ser211 regulating the nuclear translocation of GR. This study provides foundational data regarding the diverse functions of GCs to optimize therapeutic approaches.

STUDY DESIGN

In vitro.

METHODS

Human vocal fold fibroblasts and THP1-derived macrophages were treated with different concentrations of dexamethasone, methylprednisolone, and triamcinolone in combination with IFN-γ, TNF-α, or IL4. Phosphorylated STAT1, NF-κB family molecules, and phosphorylated STAT6 were analyzed by Western blotting. Ser211-phosphorylated GR (S211-pGR) levels relative to GAPDH and Ser203-phosphorylated GR (S203-pGR) were also analyzed.

RESULTS

GCs differentially altered phosphorylated STAT1 and NF-κB family molecules in different cell types under IFN-γ and TNF-α stimuli. GCs did not alter phosphorylated STAT6 in IL4-treated macrophages. The three GCs were nearly equivalent. A lower concentration of dexamethasone increased S211-pGR/GAPDH ratios relative to increased S211-pGR/S203-pGR ratios regardless of cell type and treatment.

CONCLUSION

The three GCs employed in two cell lines had nearly equivalent effects on transcription factor regulation. Relatively high levels of Ser203-phosphorylation at low GC concentrations may be related to concentration-dependent differential effects of GCs in the two cell lines.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:2704-2711, 2023.

Tamoxifen Alters TGF-β1/Smad Signaling in Vocal Fold Injury

OBJECTIVES

Effective treatments for vocal fold fibrosis remain elusive. Tamoxifen (TAM) is a selective estrogen receptor modulator and was recently reported to have antifibrotic actions. We hypothesized that TAM inhibits vocal fold fibrosis via altered transforming growth factor beta 1 (TGF-β1) signaling. Both in vitro and in vivo approaches were employed to address this hypothesis.

METHODS

In vitro, vocal fold fibroblasts were treated with TAM (10-8 or 10-9  M) ± TGF-β1 (10 ng/ml) to quantify cell proliferation. The effects of TAM on genes related to fibrosis were quantified via quantitative real-time polymerase chain reaction. In vivo, rat vocal folds were unilaterally injured, and TAM was administered by oral gavage from pre-injury day 5 to post-injury day 7. The rats were randomized into two groups: 0 mg/kg/day (sham) and 50 mg/kg/day (TAM). Histological changes were examined on day 56 to assess tissue architecture.

RESULTS

TAM (10-8  M) did not affect Smad3, Smad7, Acta2, or genes related to extracellular matrix metabolism. TAM (10-8 or 10-9  M) + TGF-β1, however, significantly increased Smad7 and Has3 expression and decreased Col1a1 and Acta2 expression compared to TGF-β1 alone. In vivo, TAM significantly increased lamina propria area, hyaluronic acid concentration, and reduced collagen deposition compared to sham treatment.

CONCLUSIONS

TAM has antifibrotic potential via the regulation of TGF-β1/Smad signaling in vocal fold injury. These findings provide foundational data to develop innovative therapeutic options for vocal fold fibrosis.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:2248-2254, 2023.

A roadmap for developing and engineering in vitro pulmonary fibrosis models

Idiopathic pulmonary fibrosis (IPF) is a severe form of pulmonary fibrosis. IPF is a fatal disease with no cure and is challenging to diagnose. Unfortunately, due to the elusive etiology of IPF and a late diagnosis, there are no cures for IPF. Two FDA-approved drugs for IPF, nintedanib and pirfenidone, slow the progression of the disease, yet fail to cure or reverse it. Furthermore, most animal models have been unable to completely recapitulate the physiology of human IPF, resulting in the failure of many drug candidates in preclinical studies. In the last few decades, the development of new IPF drugs focused on changes at the cellular level, as it was believed that the cells were the main players in IPF development and progression. However, recent studies have shed light on the critical role of the extracellular matrix (ECM) in IPF development, where the ECM communicates with cells and initiates a positive feedback loop to promote fibrotic processes. Stemming from this shift in the understanding of fibrosis, there is a need to develop in vitro model systems that mimic the human lung microenvironment to better understand how biochemical and biomechanical cues drive fibrotic processes in IPF. However, current in vitro cell culture platforms, which may include substrates with different stiffness or natural hydrogels, have shortcomings in recapitulating the complexity of fibrosis. This review aims to draw a roadmap for developing advanced in vitro pulmonary fibrosis models, which can be leveraged to understand better different mechanisms involved in IPF and develop drug candidates with improved efficacy. We begin with a brief overview defining pulmonary fibrosis and highlight the importance of ECM components in the disease progression. We focus on fibroblasts and myofibroblasts in the context of ECM biology and fibrotic processes, as most conventional advanced in vitro models of pulmonary fibrosis use these cell types. We transition to discussing the parameters of the 3D microenvironment that are relevant in pulmonary fibrosis progression. Finally, the review ends by summarizing the state of the art in the field and future directions.

Glucocorticoid Dose Dependency on Gene Expression in Vocal Fold Fibroblasts and Macrophages

OBJECTIVE

Glucocorticoids (GCs) modulate multiple cellular activities including inflammatory and fibrotic responses. Outcomes of GC treatment for laryngeal disease vary, affording opportunity to optimize treatment. In the current study, three clinically employed GCs were evaluated to identify optimal in vitro concentrations at which GCs mediate favorable anti-inflammatory and fibrotic effects in multiple cell types. We hypothesize a therapeutic window will emerge as a foundation for optimized therapeutic strategies for patients with laryngeal disease.

STUDY DESIGN

In vitro.

METHODS

Human vocal fold fibroblasts and human macrophages derived from THP-1 monocytes were treated with 0.03-1000 nM dexamethasone, 0.3-10,000 nM methylprednisolone, and 0.3-10,000 nM triamcinolone in combination with interferon-γ, tumor necrosis factor-α, or interleukin-4. Real-time polymerase chain reaction was performed to analyze inflammatory (CXCL10, CXCl11, PTGS2, TNF, IL1B) and fibrotic (CCN2, LOX, TGM2) genes, and TSC22D3, a target gene of GC signaling. EC50 and IC50 to alter inflammatory and fibrotic gene expression was calculated.

RESULTS

Interferon-γ and tumor necrosis factor-α increased inflammatory gene expression in both cell types; this response was reduced by GCs. Interleukin-4 increased LOX and TGM2 expression in macrophages; this response was also reduced by GCs. GCs induced TSC22D3 and CCN2 expression independent of cytokine treatment. EC50 for each GC to upregulate CCN2 was higher than the IC50 to downregulate other genes.

CONCLUSION

Lower concentrations of GCs repressed inflammatory gene expression and only moderately induced genes involved in fibrosis. These data warrant consideration as a foundation for optimized clinical care paradigms to reduce inflammation and mitigate fibrosis.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:1169-1175, 2023.

Antifibrotic effects of Quercetin on TGF-β1-induced vocal fold fibroblasts

OBJECTIVE

To investigate the effects of Quercetin on vocal fold fibroblasts induced by TGF-β1 and vocal fold injury.

METHODS

The effects of Quercetin on collagen type I (COL-I), collagen type III (COL-III), and fibronectin (FN) expressions in transforming growth factor-β1 (TGF-β1)-induced human vocal fold fibroblasts were examined by the quantitative reverse transcription-polymerase chain reaction and the enzyme-linked immunosorbent assay. The Cell Counting Kit-8 was used to assess the influence of Quercetin on cell proliferation. A rat vocal fold injury model was developed. These rats were divided into a control group, a model group, and a Quercetin group. Pathorphological observations from Hematoxylin-eosin staining, the density of fibroblasts, and hypertrophic index were compared among the three groups.

RESULTS

Compared with cells untreated with TGF-β1, the mRNA and protein expression levels of COL-I, COL-II, and FN and proliferation ability in TGF-β1-induced human vocal fold fibroblasts were increased (all P<0.05). Compared with human vocal fold fibroblasts induced by TGF-β1, the mRNA and protein expression levels of COL-I, COL-II, and FN and proliferation ability in TGF-β1-induced human vocal fold fibroblasts following Quercetin stimulation were decreased (all P<0.05). There were no statistical differences between human vocal fold fibroblasts treated with or without Quercetin regarding cell proliferation and COL-I, COL-II, and FN expressions. Compared with the model group, Quercetin suppressed the fibrosis of the vocal fold following injury and the protein levels of COL-I, COL-II, and FN in tissue samples (all P<0.001). The density of fibroblasts and hypertrophic index in the vocal fold scar from the Quercetin group were lower than those in the model group (all P<0.05).

CONCLUSIONS

Quercetin inhibited TGF-β1-induced fibrotic changes and proliferation in human vocal fold fibroblasts and had an antifibrotic effect in vocal fold after injuries.

Larynx proteomics after jellyfish collagen IL: Increased ECM/collagen and suppressed inflammation

Objectives/Hypothesis

Compare proteomic profiles of rabbit vocal folds (VFs) injected with micronized cross-linked jellyfish collagen "collagen Type 0" (MX-JC) against two clinical products for injection medialization laryngoplasty (IL).

Study Design

Animal model.

Methods

Left recurrent laryngeal nerve sectioning and IL were performed in New Zealand White rabbits (N = 6/group). Group 1 received (MX-JC) and adipose-derived stem cells (ADSCs), Group 2, MX-JC alone; Group 3, cross-linked hyaluronic acid; and Group 4, micronized acellular dermis. Animals were sacrificed at 4 and 12 weeks. Proteomic profiling of injected versus noninjected VFs by nano-liquid chromatography, tandem mass spectrometry, and reactome gene ontology analysis was performed.

Results

Overall, 37-61 proteins were found to be upregulated and 60-284 downregulated in injected versus non-injected VFs (>1.5 fold, false discovery rate-adjusted p < .05). Over-representation analysis (% of total) revealed top up-regulated pathways at 4 and 12 weeks, respectively: Group 1, keratan sulfate metabolism (46%) and cellular processes (29%); Group 2, extracellular matrix (ECM)/collagen processes (33%) and beta oxidation (39%); Group 3, cellular processes (50%) and energy metabolism (100%); and Group 4, keratan sulfate metabolism (31%) and inflammation (50%). Top downregulated pathways were: Group 1, Inflammation (36%) and glucose/citric acid metabolism (42%); Group 2, cell signaling (38%) and glucose/citric acid metabolism (35%); Group 3, keratan sulfate metabolism (31%) and ECM/collagen processes (48%); and Group 4, glucose/citric acid metabolism (33%) and ECM/collagen processes (43%).

Conclusions

MX-JC "collagen Type 0" upregulates pathways related to ECM/collagen formation and downregulates pathways related to inflammation suggesting that it is promising biomaterial for IL.

Level of Evidence

NA.

Progress in Vocal Fold Regenerative Biomaterials: An Immunological Perspective

Vocal folds, housed in the upper respiratory tract, are important to daily breathing, speech and swallowing functions. Irreversible changes to the vocal fold mucosae, such as scarring and atrophy, require a regenerative medicine approach to promote a controlled regrowth of the extracellular matrix (ECM)-rich mucosa. Various biomaterial systems have been engineered with an emphasis on stimulating local vocal fold fibroblasts to produce new ECM. At the same time, it is imperative to limit the foreign body reaction and associated immune components that can hinder the integration of the biomaterial into the host tissue. Modern biomaterial designs have become increasingly focused on actively harnessing the immune system to accelerate and optimize the process of tissue regeneration. An array of physical and chemical biomaterial parameters have been reported to effectively modulate local immune cells, such as macrophages, to initiate tissue repair, stimulate ECM production, promote biomaterial-tissue integration, and restore the function of the vocal folds. In this perspective paper, the unique immunological profile of the vocal folds will first be reviewed. Key physical and chemical biomaterial properties relevant to immunomodulation will then be highlighted and discussed. A further examination of the physicochemical properties of recent vocal fold biomaterials will follow to generate deeper insights into corresponding immune-related outcomes. Lastly, a perspective will be offered on the opportunity of integrating material-led immunomodulatory strategies into future vocal fold tissue engineering therapies.

Bioreactors for Vocal Fold Tissue Engineering

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

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.

Core-Shell Microfibers via Bioorthogonal Layer-by-Layer Assembly

A new technique is described for the construction of core-shell microfibers for biomedical applications. Fibrous scaffolds were fabricated by electrospinning, followed by covalent layer-by-layer deposition based on the rapid bioorthogonal reaction between s-tetrazines (Tz) and trans-cyclooctenes (TCOs). Electrospun poly(ε-caprolactone) (PCL) scaffolds were subjected to surface modifications to install tetrazine groups. The scaffolds were iteratively submerged in aqueous solutions of TCO-modified hyaluronic acid (HA-TCO) and tetrazine-modified hyaluronic acid (HA-Tz), resulting in the controlled growth of a cross-linked HA gel around individual microfibers. Integrin-binding motifs were covalently attached to the surface of the microfibers using TCO-conjugated RGD peptide. The scaffolds fostered the attachment and growth of primary porcine vocal fold fibroblasts without a significant induction of the myofibroblast phenotype. Stimulation with transforming growth factor beta (TGF-β) moderately enhanced fibroblast activation, and inhibition of the Rho/ROCK signaling pathway using Y27632 further decreased the expression of myofibroblastic markers. The bioorthogonally assembled scaffolds with a stiff PCL core and a soft HA shell may find application as therapeutic implants for the treatment of vocal fold scarring.

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.

The Role of Cytokines in Modulating Vocal Fold Fibrosis: A Contemporary Review

OBJECTIVES

Vocal fold (VF) scarring and laryngeal stenosis are a significant clinical challenge. Excessive scar formation causes low voice quality or even life-threatening obstructions. Cytokines are thought to modulate multiple steps of the establishment of VF fibrosis, but there is no systematic report regarding their role in modulating VF fibrosis. This review aims to investigate the role of cytokines in modulating vocal fold fibrosis.

STUDY DESIGN

Literature review.

METHODS

This review searched for all relevant peer publications in English for the period 2009 to 2019 in the PubMed database using search terms: "laryngeal stenosis," "vocal fold scarring," and "cytokines." A thorough investigation of the methods and results of the reviewed studies was performed.

RESULTS

Comprehensive research in various studies, including analyses of prostaglandin E2 (PGE2), granulocyte-macrophage colony-stimulating factor (GM-CSF), hepatocyte growth factor (HGF), basic fibroblast growth factor (bFGF), transforming growth factor-β3 (TGF-β3), and interleukin-10 (IL-10), supports cytokine therapy for VF scarring and laryngeal stenosis to some extent. A few clinical studies on this topic support the conclusion that HGF and bFGF can be selected as effective drugs, and no serious side effects were found.

CONCLUSIONS

This review describes the potential of cytokines for modulating the process of VF fibrogenesis, although cytokines are still an unproven treatment method. As no ideal drugs exist, cytokines may be considered the candidate treatment for preventing VF fibrogenesis. Laryngoscope, 131:139-145, 2021.

Potential effect of non-thermal plasma for the inhibition of scar formation: a preliminary report

Non-thermal plasma (NTP) is a promising biomedical tool for application to wound healing. However, there is limited scientific evidence that confirms its efficacy to inhibit scar formation. This study aims to investigate the role of non-thermal plasma in scar formation. Two full-thickness dorsal cutaneous wounds of rats were treated with either a non-thermal helium plasma jet or helium. It was determined that the non-thermal plasma jet accelerated the wound healing process from 5 days after surgery (day 5: 41.27% ± 2.351 vs 54.7% ± 5.314, p < 0.05; day 7: 56.05% ± 1.881 vs 75.28% ± 3.914, p < 0.01; day 14: 89.85% ± 2.991 vs 98.07% ± 0.839, p < 0.05). The width of the scars for the NTP group was narrower than those of control group (4.607 ± 0.416 mm vs 3.260 ± 0.333 mm, p < 0.05). In addition, a lower level of TGF-β1, p-Smad2 and p-Smad3 were detected in the NTP treated wounds (p < 0.05, p < 0.01 and p < 0.01). As expected, α-SMA was also significantly decreased in the NTP treatment group (p < 0.01). Moreover, the expression of type I collagen and the proportion of type I to III collagen were lower in the NTP group (p < 0.05). The results of the study suggest that NTP may play a potential role in scar formation by inhibiting the TGF β1 signal pathway and reducing the levels of α-SMA and type I collagen, and may have clinical utility in the future.

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.

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.

Tissue specific human fibroblast differential expression based on RNAsequencing analysis

Background

Physical forces, such as mechanical stress, are essential for tissue homeostasis and influence gene expression of cells. In particular, the fibroblast has demonstrated sensitivity to extracellular matrices with assumed adaptation upon various mechanical loads. The purpose of this study was to compare the vocal fold fibroblast genotype, known for its unique mechanically stressful tissue environment, with cellular counterparts at various other anatomic locales to identify differences in functional gene expression profiles.

Results

By using RNA-seq technology, we identified differentially expressed gene programs (DEseq2) among seven normal human fibroblast primary cell lines from healthy cadavers, which included: vocal fold, trachea, lung, abdomen, scalp, upper gingiva, and soft palate. Unsupervised gene expression analysis yielded 6216 genes differentially expressed across all anatomic sites. Hierarchical cluster analysis revealed grouping based on anatomic site origin rather than donor, suggesting global fibroblast phenotype heterogeneity. Sex and age-related effects were negligible. Functional enrichment analyses based on separate post-hoc 2-group comparisons revealed several functional themes within the vocal fold fibroblast related to transcription factors for signaling pathways regulating pluripotency of stem cells and extracellular matrix components such as cell signaling, migration, proliferation, and differentiation potential.

Conclusions

Human fibroblasts display a phenomenon of global topographic differentiation, which is maintained in isolation via in vitro assays. Epigenetic mechanical influences on vocal fold tissue may play a role in uniquely modelling and maintaining the local environmental cellular niche during homeostasis with vocal fold fibroblasts distinctly specialized related to their anatomic positional and developmental origins established during embryogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5682-5) contains supplementary material, which is available to authorized users.

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.

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.

Towards an in vitro fibrogenesis model of human vocal fold scarring

Background

Vocal fold (VF) scarring remains a therapeutic dilemma and challenge in modern laryngology. To facilitate corresponding research, we aimed to establish an in vitro fibrogenesis model employing human VF fibroblasts (hVFF) and the principles of macromolecular crowding (MMC).

Methods

Fibrogenesis was promoted by addition of transforming growth factor-β1 to standard medium and medium containing inert macromolecules (MMC). Hepatocyte growth factor (HGF) and Botox type A were tested for their antifibrotic properties in various doses. Experiments were analyzed with respect to the biosynthesis of collagen, fibronectin, and α-smooth muscle actin using immunofluorescence, silver stain and western blot.

Results

MMC led to favourable enhanced deposition of collagen and other extracellular matrix components, reflecting fibrotic conditions. Low doses of HGF were able to dampen profibrotic effects. This could not be observed for higher HGF concentrations. Botox type A did not show any effects.

Conclusion

Based on the principles of MMC we could successfully establish a laryngeal fibrogenesis model employing hVFF. Our finding of dose-dependent HGF effects is important before going into clinical trials in humans and has never been shown before. Our model provides a novel option to screen various potential antifibrotic compounds under standardized conditions in a short time.

Electronic supplementary material

The online version of this article (10.1007/s00405-018-4922-7) contains supplementary material, which is available to authorized users.

In vitro evaluation of a basic fibroblast growth factor-containing hydrogel toward vocal fold lamina propria scar treatment

Scarring of the vocal fold lamina propria can lead to debilitating voice disorders that can significantly impair quality of life. The reduced pliability of the scar tissue-which diminishes proper vocal fold vibratory efficiency-results in part from abnormal extracellular matrix (ECM) deposition by vocal fold fibroblasts (VFF) that have taken on a fibrotic phenotype. To address this issue, bioactive materials containing cytokines and/or growth factors may provide a platform to transition fibrotic VFF within the scarred tissue toward an anti-fibrotic phenotype, thereby improving the quality of ECM within the scar tissue. However, for such an approach to be most effective, the acute host response resulting from biomaterial insertion/injection likely also needs to be considered. The goal of the present work was to evaluate the anti-fibrotic and anti-inflammatory capacity of an injectable hydrogel containing tethered basic fibroblast growth factor (bFGF) in the dual context of scar and biomaterial-induced acute inflammation. An in vitro co-culture system was utilized containing both activated, fibrotic VFF and activated, pro-inflammatory macrophages (MΦ) within a 3D poly(ethylene glycol) diacrylate (PEGDA) hydrogel containing tethered bFGF. Following 72 h of culture, alterations in VFF and macrophage phenotype were evaluated relative to mono-culture and co-culture controls. In our co-culture system, bFGF reduced the production of fibrotic markers collagen type I, α smooth muscle actin, and biglycan by activated VFF and promoted wound-healing/anti-inflammatory marker expression in activated MΦ. Cumulatively, these data indicate that bFGF-containing hydrogels warrant further investigation for the treatment of vocal fold lamina propria scar. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1258-1267, 2018.

An in vitro scaffold-free epithelial-fibroblast coculture model for the larynx

OBJECTIVES/HYPOTHESIS

Physiologically relevant, well-characterized in vitro vocal fold coculture models are needed to test the effects of various challenges and therapeutics on vocal fold physiology. We characterize a healthy state coculture model, created by using bronchial/tracheal epithelial cells and immortalized vocal fold fibroblasts. We also demonstrate that this model can be induced into a fibroplastic state to overexpress stress fibers using TGFβ1.

STUDY DESIGN

In vitro.

METHODS

Cell metabolic activity of immortalized human vocal fold fibroblasts incubated in different medium combinations was confirmed with an MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide) assay. Fibroblasts were grown to confluence, and primary bronchial/tracheal epithelial cells suspended in coculture medium were seeded directly over the base layer of the fibroblasts. Cells were treated with transforming growth factor β1 (TGFβ1) to induce myofibroblast formation. Cell shape and position were confirmed by live cell tracking, fibrosis was confirmed by probing for α smooth muscle actin (αSMA), and phenotype was confirmed by immunostaining for vimentin and E-cadherin.

RESULTS

Fibroblasts retain metabolic activity in coculture epithelial medium. Live cell imaging revealed a layer of epithelial cells atop fibroblasts. αSMA expression was enhanced in TGFβ1-treated cells, confirming that both cell types maintained a healthy phenotype in coculture, and can be induced into overexpressing stress fibers. Vimentin and E-cadherin immunostaining show that cells retain phenotype in coculture.

CONCLUSIONS

These data lay effective groundwork for a functional coculture model that retains the reproducibility necessary to serve as a viable diagnostic and therapeutic screening platform.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:E185-E192, 2017.

Cellular source and proinflammatory roles of high-mobility group box 1 in surgically injured rat vocal folds

Objectives/Hypothesis

High‐mobility group box 1 (HMGB1) is a chromatin‐binding protein located in the cell nucleus. Following injury, immunocompetent cells secrete HMGB1 to the extracellular milieu under the stimulation of proinflammatory cytokines. Extracellular HMGB1 acts a danger signal that instigates the innate immunity and tissue repair. We previously reported HMGB1 in the vocal fold extracellular compartment between day 3 and day 7 following surgical injury. In this study, we further investigated the cell source of HMGB1 and the relationship of proinflammatory cytokine expression and HMGB1 translocation in wounded vocal folds.

Study Design

Prospective animal study.

Methods

Bilateral vocal fold injury was performed on 122 Sprague‐Dawley rats. An additional 18 rats served as uninjured controls. Animals were sacrificed at multiple time points up to 4 weeks after surgery. Immunohistochemical costaining was performed to identify the cell source of HMGB1. Cell markers ED1, fibroblast‐specific protein 1 (FSP1), and alpha smooth muscle actin (α‐SMA) were used to identify macrophages, fibroblasts, and myofibroblasts, respectively. Enzyme‐linked immunosorbent assays were performed to measure cytokine levels of interleukin‐1beta (IL‐1β) and tumor necrosis factor‐alpha (TNF‐α) in vocal fold tissue.

Results

Costaining of HMGB1 was strong with ED1 and FSP1 but was minimal with α‐SMA in injured vocal folds. Compared to uninjured controls, IL‐1β and TNF‐α expression increased significantly the first 2 days after injury.

Conclusions

Macrophages and fibroblasts were a major cell source of vocal fold HMGB1. Translocation of HMGB1 may be an active response to the early accumulation of IL‐1β and TNF‐α in the wounded vocal folds.

Level of Evidence

NA Laryngoscope, 127:E193–E200, 2017