Modeling fibrosis using fibroblasts isolated from scarred rat vocal folds

Prostaglandin I2 signaling prevents angiotensin II-induced atrial remodeling and vulnerability to atrial fibrillation in mice

Atrial fibrillation (AF) is the most common arrhythmia, and atrial fibrosis is a pathological hallmark of structural remodeling in AF. Prostaglandin I2 (PGI2) can prevent the process of fibrosis in various tissues via cell surface Prostaglandin I2 receptor (IP). However, the role of PGI2 in AF and atrial fibrosis remains unclear. The present study aimed to clarify the role of PGI2 in angiotensin II (Ang II)-induced AF and the underlying molecular mechanism. PGI2 content was decreased in both plasma and atrial tissue from patients with AF and mice treated with Ang II. Treatment with the PGI2 analog, iloprost, reduced Ang II-induced AF and atrial fibrosis. Iloprost prevented Ang II-induced atrial fibroblast collagen synthesis and differentiation. RNA-sequencing analysis revealed that iloprost significantly attenuated transcriptome changes in Ang II-treated atrial fibroblasts, especially mitogen-activated protein kinase (MAPK)-regulated genes. We demonstrated that iloprost elevated cAMP levels and then activated protein kinase A, resulting in a suppression of extracellular signal-regulated kinase1/2 and P38 activation, and ultimately inhibiting MAPK-dependent interleukin-6 transcription. In contrast, cardiac fibroblast-specific IP-knockdown mice had increased Ang II-induced AF inducibility and aggravated atrial fibrosis. Together, our study suggests that PGI2/IP system protects against atrial fibrosis and that PGI2 is a therapeutic target for treating AF.The prospectively registered trial was approved by the Chinese Clinical Trial Registry. The trial registration number is ChiCTR2200056733. Data of registration was 2022/02/12.

Matrix Adhesiveness Regulates Myofibroblast Differentiation from Vocal Fold Fibroblasts in a Bio-orthogonally Cross-linked Hydrogel

Repeated mechanical and chemical insults cause an irreversible alteration of extracellular matrix (ECM) composition and properties, giving rise to vocal fold scarring that is refractory to treatment. Although it is well known that fibroblast activation to myofibroblast is the key to the development of the pathology, the lack of a physiologically relevant in vitro model of vocal folds impedes mechanistic investigations on how ECM cues promote myofibroblast differentiation. Herein, we describe a bio-orthogonally cross-linked hydrogel platform that recapitulates the alteration of matrix adhesiveness due to enhanced fibronectin deposition when vocal fold wound healing is initiated. The synthetic ECM (sECM) was established via the cycloaddition reaction of tetrazine (Tz) with slow (norbornene, Nb)- and fast (trans-cyclooctene, TCO)-reacting dienophiles. The relatively slow Tz-Nb ligation allowed the establishment of the covalent hydrogel network for 3D cell encapsulation, while the rapid and efficient Tz-TCO reaction enabled precise conjugation of the cell-adhesive RGDSP peptide in the hydrogel network. To mimic the dynamic changes of ECM composition during wound healing, RGDSP was conjugated to cell-laden hydrogel constructs via a diffusion-controlled bioorthognal ligation method 3 days post encapsulation. At a low RGDSP concentration (0.2 mM), fibroblasts residing in the hydrogel remained quiescent when maintained in transforming growth factor beta 1 (TGF-β1)-conditioned media. However, at a high concentration (2 mM), RGDSP potentiated TGF-β1-induced myofibroblast differentiation, as evidenced by the formation of an actin cytoskeleton network, including F-actin and alpha-smooth muscle actin. The RGDSP-driven fibroblast activation to myofibroblast was accompanied with an increase in the expression of wound healing-related genes, the secretion of profibrotic cytokines, and matrix contraction required for tissue remodeling. This work represents the first step toward the establishment of a 3D hydrogel-based cellular model for studying myofibroblast differentiation in a defined niche associated with vocal fold scarring.

Peroxisome Proliferator-Activated Receptor-γ Agonist Attenuates Vocal Fold Fibrosis in Rats via Regulation of Macrophage Activation

Macrophages aid in wound healing by changing their phenotype and can be a key driver of fibrosis. However, the contribution of macrophage phenotype to fibrosis following vocal fold injury remains unclear. Peroxisome proliferator-activated receptor-γ (PPARγ) is expressed mainly by macrophages during early wound healing and regulates the macrophage phenotype. This study aimed to evaluate the effects of pioglitazone (PIO), a PPARγ agonist, on the macrophage phenotype and fibrosis following vocal fold injury in rats. PIO was injected into the rat vocal folds on days 1, 3, 5, and 7 after injury, and the vocal fold lamina propria was evaluated on days 4 and 56 after injury. Moreover, THP-1-derived macrophages were treated with PIO, and the expression of proinflammatory cytokines under lipopolysaccharide/interferon-γ stimulation was analyzed. PIO reduced the expression of Ccl2 both in vivo and in vitro. Furthermore, PIO decreased the density of inducible nitric oxide synthase⁺ CD68⁺ macrophages and inhibited the expression of fibrosis-related factors on day 4 after injury. On day 56 after injury, PIO inhibited fibrosis, tissue contracture, and hyaluronic acid loss in a PPARγ-dependent manner. These results indicate that PPARγ activation could inhibit accumulation of inflammatory macrophages and improve tissue repair. Taken together, these findings imply that inflammatory macrophages play a key role in vocal fold fibrosis.

Experimental model for controlled endoscopic subepithelial vocal fold injury in rats

Purpose:

To present a detailed, reproducible, cost-efficient surgical model for controlled subepithelial endoscopic vocal fold injury in the rat model.

Methods:

Six male Sprague Dawley rats were enrolled in the experiment. The left vocal folds were used to carry out the injury model, and the right vocal fold served as control. After deep sedation, the rats were placed on a custom operating platform. The vocal fold injury by subepithelial stripping was carried out using custom-made microsurgical instruments under endoscopic guidance. Data were analyzed for procedural time and post-procedural pain. Microcomputed tomography (micro-CT) scan and histologic images were obtained to assess the length, area, and depth of injury to the vocal fold.

Results:

The mean procedural time was 112 s. The mean control vocal fold length was 0.96 ± 0.04 mm. The mean vocal fold injury length was 0.53 ± 0.04 mm. The mean vocal fold surface was 0.18 ± 0.01 mm² with a mean lesion area of 0.05 ± 0.00 mm². Mean vocal fold injury depth was 375.4 ± 42.8 μm. The lesion length to vocal fold length ratio was 0.55 ± 0.03, as well as lesion area to vocal fold surface area was 0.29 ± 0.02.

Conclusions:

Our described experimental vocal fold injury model in rats is found to be fast, safe, cost-efficient, and reproducible with a rapid learning curve.

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.

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.

Unraveling the molecular pathobiology of vocal fold systemic dehydration using an in vivo rabbit model

Vocal folds are a viscoelastic multilayered structure responsible for voice production. Vocal fold epithelial damage may weaken the protection of deeper layers of lamina propria and thyroarytenoid muscle and impair voice production. Systemic dehydration can adversely affect vocal function by creating suboptimal biomechanical conditions for vocal fold vibration. However, the molecular pathobiology of systemically dehydrated vocal folds is poorly understood. We used an in vivo rabbit model to investigate the complete gene expression profile of systemically dehydrated vocal folds. The RNA-Seq based transcriptome revealed 203 differentially expressed (DE) vocal fold genes due to systemic dehydration. Interestingly, function enrichment analysis showed downregulation of genes involved in cell adhesion, cell junction, inflammation, and upregulation of genes involved in cell proliferation. RT-qPCR validation was performed for a subset of DE genes and confirmed the downregulation of DSG1, CDH3, NECTIN1, SDC1, S100A9, SPINK5, ECM1, IL1A, and IL36A genes. In addition, the upregulation of the transcription factor NR4A3 gene involved in epithelial cell proliferation was validated. Taken together, these results suggest an alteration of the vocal fold epithelial barrier independent of inflammation, which could indicate a disruption and remodeling of the epithelial barrier integrity. This transcriptome provides a first global picture of the molecular changes in vocal fold tissue in response to systemic dehydration. The alterations observed at the transcriptional level help to understand the pathobiology of dehydration in voice function and highlight the benefits of hydration in voice therapy.

Transcriptomic changes in bovine skeletal muscle cells after resveratrol treatment

Skeletal muscles constitute a high proportion of the cellular mass that is essential for the growth traits in cattle. Resveratrol (RSV) is a natural polyphenol compound involved in pleiotropic biological activities of muscle. Therefore, the aim of our study was to investigate the transcriptome-level effects of RSV on bovine primary myoblast to reveal differentially expressed genes (DEGs). We treated three replicates of primary myoblasts with 20 μM mother solution containing RSV, whereas three other replicates without RSV were used as control group. Then, we conducted genome-wide transcriptome analysis for the two groups. The results of expression analysis identified 3856 DEGs of which 1805 genes were up-regulated and 2051 genes were down-regulated (adjusted P < 0.05). In addition, qRT-PCR analysis of 19 selected DEGs were consistent with the expression levels observed in the transcriptome data. Gene Ontology (GO) and pathway enrichment analysis showed 72 and 66 significant GO terms and KEGG pathways, respectively (adjusted P < 0.05). The most significant GO term was actin cytoskeleton organization (GO:0030036). The top significant KEGG pathway was focal adhesion (bta04510). Predicted protein-protein interactions (PPIs) showed that CDKN1A encoding cyclindependent kinase inhibitor 1A connects several larger protein complexes. In conclusion, our results found a list of DEGs, significant GO terms and pathways, and provided an improved and expanded understanding of the impact of RSV on cattle muscle cells at the transcriptomic level. The study elucidates the potential of using the genes enriched in pathways mediating resveratrol effects as targets in genomic selection for muscle development and growth in beef cattle.

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.

Porcine Vocal Fold Lamina Propria-Derived Biomaterials Modulate TGF-β1-Mediated Fibroblast Activation in Vitro

The vocal fold lamina propria (VFLP), one of the outermost layers of the vocal fold (VF), is composed of tissue-specific extracellular matrix (ECM) proteins and is highly susceptible to injury. Various biomaterials have been clinically tested to treat voice disorders (e.g., hydrogels, fat, and hyaluronic acid), but satisfactory recovery of the VF functionality remains elusive. Fibrosis or scar formation in the VF is a major challenge, and the development and refinement of novel therapeutics that promote the healing and normal function of the VF are needed. Injectable hydrogels derived from native tissues have been previously reported with major advantages over synthetic hydrogels, including constructive tissue remodeling and reduced scar tissue formation. This study aims to characterize the composition of a decellularized porcine VFLP-ECM scaffold and the cytocompatibility and potential antifibrotic properties of a hydrogel derived from VFLP-ECM. In addition, we isolated potential matrix-bound vesicles (MBVs) and macromolecules from the VFLP-ECM that also downregulated smooth muscle actin ACTA2 under transforming growth factor-beta 1 (TGF-β1) stimulation. The results provide evidence of the unique protein composition of the VFLP-ECM and the potential link between the components of the VFLP-ECM and the inhibition of TGF-β1 signaling observed in vitro when transformed into injectable forms.

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.

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.

Alterations in macrophage polarization in injured murine vocal folds

OBJECTIVES

Macrophages are prominent inflammatory cells in wounds, and their phenotypes are altered during wound healing. They are reported to contribute to not only inflammatory responses but also tissue remodeling. However, few studies in vocal fold biology have focused on the function of macrophages. The purpose of this study was to investigate macrophage polarization and distribution in injured murine vocal folds.

STUDY DESIGN

Animal experiments with controls.

METHOD

Unilateral vocal fold stripping was performed on C57BL/6 mice, and larynges were harvested 1, 3, 5, 7, and 14 days postinjury. Immunohistochemical analysis of the vocal fold lamina propria was performed to detect the expression of classically activated (M1) and alternatively activated (M2) macrophage markers (inducible nitric oxide synthase [iNOS] and CD206, respectively) in F4/80+ macrophages.

RESULTS

The proportion of F4/80+ iNOS+ cells out of all F4/80+ cells tended to increase from day 1. F4/80+ iNOS+ cell percentage tended to be high at days 1 through 7 and declined to close to a normal level by day 14. F4/80+ CD206+ cell percentage tended to decrease at day 1 and then to increase the rest of the time. In the normal vocal fold, the majority of F4/80+ macrophages were only positive for CD206. F4/80+ iNOS+ CD206+ cells were observed at days 1 through 7.

CONCLUSION

The main population of injured sites gradually shifted from M1 to M2 marker-positive macrophages in murine vocal folds. However, coexistence of M1 and M2 markers in the same macrophages was observed. Our results suggest that macrophage phenotypes are regulated by complex tissue-derived signals and exhibit dynamic changes during wound healing.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E135-E142, 2019.

Characterization of aged rat vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

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

STUDY DESIGN

In vitro study.

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E94-E101, 2019.

High-Performance Agent-Based Modeling Applied to Vocal Fold Inflammation and Repair

Fast and accurate computational biology models offer the prospect of accelerating the development of personalized medicine. A tool capable of estimating treatment success can help prevent unnecessary and costly treatments and potential harmful side effects. A novel high-performance Agent-Based Model (ABM) was adopted to simulate and visualize multi-scale complex biological processes arising in vocal fold inflammation and repair. The computational scheme was designed to organize the 3D ABM sub-tasks to fully utilize the resources available on current heterogeneous platforms consisting of multi-core CPUs and many-core GPUs. Subtasks are further parallelized and convolution-based diffusion is used to enhance the performance of the ABM simulation. The scheme was implemented using a client-server protocol allowing the results of each iteration to be analyzed and visualized on the server (i.e., in-situ) while the simulation is running on the same server. The resulting simulation and visualization software enables users to interact with and steer the course of the simulation in real-time as needed. This high-resolution 3D ABM framework was used for a case study of surgical vocal fold injury and repair. The new framework is capable of completing the simulation, visualization and remote result delivery in under 7 s per iteration, where each iteration of the simulation represents 30 min in the real world. The case study model was simulated at the physiological scale of a human vocal fold. This simulation tracks 17 million biological cells as well as a total of 1.7 billion signaling chemical and structural protein data points. The visualization component processes and renders all simulated biological cells and 154 million signaling chemical data points. The proposed high-performance 3D ABM was verified through comparisons with empirical vocal fold data. Representative trends of biomarker predictions in surgically injured vocal folds were observed.

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.