Hepatocyte growth factor and its receptor c-met in rat and rabbit vocal folds

Nanofat for Injection Laryngoplasty: A Preliminary Study of a New Substrate

OBJECTIVE

"Nanofat" refers to fat further emulsified into 1-µm sizes. It is commonly used in facial plastic surgery. Nanofat increases the release of adipose-derived stem cells. This study tested whether injection laryngoplasty using nanofat resulted in bulking and vibratory effects comparable to using microfat in treating patients with fold atrophy.

METHODS

This was a randomized, controlled, single-blind, prospective study of 18 patients with vocal atrophy who underwent transoral lipoinjection using microlaryngoscopy. The control group received bilateral microfat injection. The experimental group randomly received microfat in one vocal fold and nanofat in the contralateral vocal fold. The average volume of fat injected was 0.6 mL on each side. The postsurgery evaluation at 3 months included ratings of stroboscopy and acoustic recordings by blinded expert raters. Vibratory behavior, voice ratings, preVoice Handicap Index-10 (VHI-10) and postVHI-10 score, and Cepstral/Spectral Index of Dysphonia (CSID) were compared.

RESULTS

Significant improvement in the VHI at three-month follow-up was noted in all patients (n = 18 total, 12 experimental, six control). In the subgroup analysis, only the nanofat group significantly improved VHI. Improvements in the CSID were observed in both techniques; however, neither group showed statistical significance. Improved glottic closure was comparable in both groups. Expert raters observed an improvement in the voice quality of nanofat individuals but no change in microfat individuals.

CONCLUSION

Lipoinjection laryngoplasty with nanofat may be an alternative to microfat in patients with vocal atrophy.

LEVEL OF EVIDENCE

II.

The Modulation of Fibrosis in Vocal Fold Repair: A Study on c-Met Agonistic Antibodies and Hepatocyte Growth in Animal Studies

Background and Objectives: Damage to the vocal folds frequently results in fibrosis, which can degrade vocal quality due to the buildup of collagen and modifications in the extracellular matrix (ECM). Conventional treatments have shown limited success in reversing fibrotic changes. Hepatocyte growth factor (HGF) and c-Met-targeting antibodies are promising due to their potential to inhibit fibrosis and promote regeneration. This research examines the effectiveness of injections containing c-Met agonistic antibodies relative to HGF in reducing fibrosis within a rat model of vocal fold injury. Materials and Methods: Forty-five Sprague Dawley rats were divided into three groups, which were HGF, c-Met agonistic antibody, and the control (PBS). The right vocal folds were injured and treated with HGF or c-Met agonistic antibody injections. RNA isolation and quantitative real-time PCR were performed to assess mRNA levels of fibrosis-related markers at 1 and 2 weeks post-injury. Histopathological analysis was conducted at 3 weeks to evaluate collagen and hyaluronic acid (HA) deposition. Results: Both the HGF and c-Met groups demonstrated reduced type III collagen mRNA expression compared to the PBS group. The c-Met group uniquely maintained fibronectin levels closer to normal. Additionally, the c-Met group showed significantly upregulated expression of hyaluronan synthase (HAS) 1 and HAS 3 at 2 weeks post-injury, indicating enhanced HA synthesis. Histological analysis showed significantly lower collagen deposition and higher HA in the c-Met group than in PBS, confirming superior anti-fibrotic effects and ECM restoration. Conclusions: c-Met agonistic antibody injections outperformed HGF in reducing fibrosis, upregulating HAS expression, and promoting HA deposition in injured vocal folds, highlighting its potential as a superior therapeutic approach for preventing fibrosis and enhancing ECM quality in vocal fold injuries. Further research on functional outcomes in larger models is recommended to validate these findings.

Platelet-rich plasma in treatment of scar, atrophy, and sulcus: Short- and long-term results

Objective

Platelet-rich plasma (PRP) is rich in growth factors and is easily obtained from blood samples. Long-term data after PRP injection into the larynx should be improved. This study reports the short-term (3 months) and long-term (12 months) voice results after PRP injection.

Materials and Methods

Sixty-three patients with scars (n = 34), sulcus vocalis (n = 17), recalcitrant nodules (n = 5), atrophy (n = 4), or a combination of these (n = 3) were included (158 injections; median follow-up = 12.3 months). Stroboscopy, voice handicap index (VHI-10), and cepstral spectral index of dysphonia (CSID) before and after treatment (3 months) and at 12 months were tabulated.

Results

VHI-10 changed from 19.5 to 14 at 3 months and 21 to 15 in the long term. The CSID scores improved from 31 to 21 in the short term and 31 to 26 in the long term (p < 0.001, paired t-test). Patients reported improved vocal effort and stamina with slight VHI or CSID score changes. Stroboscopy revealed improved closure and mucosal waves. Patients with severe dysphonia were less likely to improve compared to those with mild to moderate dysphonia. Some patients showed short-term improvements and then deteriorated back to baseline CSID over time (p < .05, paired t-test).

Conclusion

Both short- and long-term improvements in voice following PRP injection have been reported. Patients with mild-to-moderate dysphonia had better outcomes. PRP injection is an alternative treatment for patients with mild-to-moderate dysphonia due to vocal fold scarring, sulcus, and atrophy.

Level of evidence

II Prospective case series treatment.

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.

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

BACKGROUND

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

OBJECTIVE

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

RESULTS

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

CONCLUSION

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

Characterizing Vocal Fold Injury Recovery in a Rabbit Model With Three-Dimensional Virtual Histology

OBJECTIVES/HYPOTHESIS

In animal studies of vocal fold scarring and treatment, imaging-based evaluation is most often conducted by tissue slicing and histological staining. Given variation in anatomy, injury type, severity, and sacrifice timepoints, planar histological sections provide limited spatiotemporal details of tissue repair. Three-dimensional (3D) virtual histology may provide additional contextual spatial information, enhancing objective interpretation. The study's aim was to evaluate the suitability of magnetic resonance imaging (MRI), microscale computed tomography (CT), and nonlinear laser-scanning microscopy (NM) as virtual histology approaches for rabbit studies of vocal fold scarring.

METHODS

A unilateral injury was created using microcup forceps in the left vocal fold of three New Zealand White rabbits. Animals were sacrificed at 3, 10, and 39 days postinjury. ex vivo imaging of excised larynges was performed with MRI, CT, and NM modalities.

RESULTS

The MRI modality allowed visualization of injury location and morphological internal features with 100-μm spatial resolution. The CT modality provided a view of the injury defect surface with 12-μm spatial resolution. The NM modality with optical clearing resolved second-harmonic generation signal of collagen fibers and two-photon autofluorescence in vocal fold lamina propria, muscle, and surrounding cartilage structures at submicrometer spatial scales.

CONCLUSIONS

Features of vocal fold injury and wound healing were observed with MRI, CT, and NM. The MRI and CT modalities provided contextual spatial information and dissection guidance, whereas NM resolved extracellular matrix structure. The results serve as a proof of concept to motivate incorporation of 3D virtual histology techniques in future vocal fold injury animal studies.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:1578-1587, 2021.

Prolactin may serve as a regulator to promote vocal fold wound healing

Reduced prolactin (PRL) has been shown to delay wound healing with a limited understanding of the underlying mechanisms. Here, we aim to explore the role of PRL in the repair of vocal fold (VF) injury. A microarray was used to detect the expressed levels of PRL in rat VF tissue at 1, 4, and 8 weeks after VF injury compared with normal uninjured rats. Then, a systematic bioinformatics analysis has been conducted to explore the literature-based biology network and signaling pathways involved in the repair of VF injury. The expression of PRL was significantly decreased in all VF injury groups (week 1, 4, and 8) compared with the control group (F stats = 280.34; P=4.88e-14), with no significant difference among the three VF injury groups (F stats = 1.97; P=0.18). Wounding has been shown to interfere with both PRL-promoting and inhibiting pathways that were involved in wound healing, including 11 PRL inhibitors and 6 PRL promoters. Our results reveal decreased PRL expression levels in VF injury, which is not in favor of the wound healing. The pathways identified may help in understanding the role of PRL as a treatment target for VF wound healing.

Advances in regenerative medicine for otolaryngology/head and neck surgery

Head and neck structures govern the vital functions of breathing and swallowing. Additionally, these structures facilitate our sense of self through vocal communication, hearing, facial animation, and physical appearance. Loss of these functions can lead to loss of life or greatly affect quality of life. Regenerative medicine is a rapidly developing field that aims to repair or replace damaged cells, tissues, and organs. Although the field is largely in its nascence, regenerative medicine holds promise for improving on conventional treatments for head and neck disorders or providing therapies where no current standard exists. This review presents milestones in the research of regenerative medicine in head and neck surgery.

A phase I/II exploratory clinical trial for intracordal injection of recombinant hepatocyte growth factor for vocal fold scar and sulcus

Vocal fold scar and sulcus are intractable diseases with no effective established treatments. Hepatocyte growth factor (HGF) has preclinically proven to have potent antifibrotic and regenerative effects on vocal fold scar. The current Phase I/II clinical trial aims to examine the safety and effectiveness of intracordal injection of a recombinant human HGF drug for patients with vocal fold scar or sulcus. This is an open-label, dose-escalating, first-in-human clinical trial. Eighteen patients with bilateral vocal fold scar or sulcus were enrolled and divided into three groups: Step I received 1 μg of HGF per vocal fold; Step II received 3 μg of HGF; and Step III received 10 μg of HGF. Injections were administered once weekly for 4 weeks. The protocol treatment was performed starting with Step I and escalating to Step III. Patients were followed for 6 months post-treatment. Local and systemic safety aspects were examined as primary endpoints, and therapeutic effects were assessed as secondary endpoints using voice handicap index-10; maximum phonation time; vocal fold vibratory amplitude; grade, rough, breathy, asthenic, strained scale; and jitter. The results indicated no serious drug-related adverse events in either the systemic or local examinations. In whole-subject analysis, voice handicap index-10, vocal fold vibratory amplitude, and grade, rough, breathy, asthenic, strained scale were significantly improved at 6 months, whereas maximum phonation time and jitter varied. There were no significant differences in phonatory data between the step groups. In conclusion, intracordal injection of a recombinant human HGF drug was safe, feasible, and potentially effective for human patients with vocal fold scar or sulcus.

Epidermal growth factor mediated healing in stem cell-derived vocal fold mucosa

BACKGROUND

The goal of vocal fold wound healing is the reconstitution of functional tissue, including a structurally and functionally intact epithelium. Mechanisms underlying reepithelialization in vocal folds are not known, although it is suspected that healing involves the interplay between several growth factors. We used a three-dimensional human embryonic stem cell-derived model of vocal fold mucosa to examine the effects of one growth factor, exogenous epidermal growth factor (EGF), on wound healing.

MATERIALS AND METHODS

A scratch wound was created in the in vitro model. Rate of wound healing, epidermal growth factor receptor (EGFR) activation, and cell proliferation after injury were analyzed with and without application of both exogenous EGF and an EGFR inhibitor, gefitinib.

RESULTS

Wound repair after injury was significantly hastened by application of exogenous EGF (13.3 μm/h, ± 2.63) compared with absence of exogenous EGF (7.1 μm/h ± 2.84), but inhibited with concurrent addition of Gefitinib (5.2 μm/h, ± 2.23), indicating that EGF mediates wound healing in an EGFR-dependent manner. Immunohistochemistry revealed that EGFR activation occurred only in the presence of exogenous EGF. Although not statistically significant, increased density of Ki67 staining in the epithelium adjacent to the scratch wound was observed after treatment with EGF, suggesting a tendency for exogenous EGF to increase epithelial cell proliferation.

CONCLUSIONS

Exogenous EGF increases the rate of wound healing in an EGFR-dependent manner in a three-dimensional stem cell-derived model of vocal fold mucosa. This model of wound healing can be used to gain insight into the mechanisms that regulate vocal fold epithelial repair after injury.

Tissue engineering for otorhinolaryngology-head and neck surgery

Tissue regeneration in otorhinolaryngology-head and neck surgery is a diverse area filled with specialized tissues and functions. Head and neck structures govern many of the 5 senses, swallowing, breathing, communication, facial animation, and aesthetics. Loss of these functions can have a severe negative effect on patient quality of life. Regenerative medicine techniques have the potential to restore these functions while minimizing the risks associated with traditional reconstruction techniques. This article serves as a review and update on some of the regenerative medicine research in this field. A description of the predominant clinical problems is presented, followed by a discussion of some of the most promising research working toward a solution. There are many noteworthy findings appropriate for inclusion, but limitations preclude mention of them all. This article focuses on laryngeal surgery, craniofacial reconstruction and plastic surgery, and otology and hearing.

Functional remodeling after vocal fold injury by small intestinal submucosa gel containing hepatocyte growth factor

A biomaterial derived from porcine small intestinal submucosa (SIS) was used in smart drug delivery and tissue remodeling. SIS suspensions were easily formulated by simple mixing with the drug of choice and formed an in situ gel upon injection into tissues, enabling them to act as protein drug depots. This study was conducted to determine whether functional remodeling of an injured vocal fold (VF) could be achieved by hepatocyte growth factor (HGF)-containing SIS in situ-forming gel after VF injury in a rabbit model. To accomplish this, we loaded HGF in SIS suspensions and observed a gradual, sustained release of HGF for at least 21 days in vitro. Evaluation of the in vivo efficacy demonstrated that the HGF and HGF-loaded SIS treated VFs showed improved mucosal healing when compared with the PBS-injected VFs. Histopathological evaluations revealed that treatment with the HGF/SIS group alone successfully ameliorated the deposition of type I collagen and increased synthesis of hyaluronic acids relative to the PBS group at three months post-injury. Functional analyses showed that the HGF/SIS group prevented deterioration of mucosal vibration and induced significant improvement in the mean viscoelastic modulus, but that other groups failed to achieve functional rescue of VF biomechanics. Additionally, the VF oscillation in the HGF/SIS group was superior to that in the HGF group. The results of this study suggest that SIS in situ gel has the potential for use as an HGF delivery carrier for enhancement of wound healing and improvement of functional remodeling following VF injury.

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

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

[Treatment of glottal gap]

Glottal gaps can be either physiological or pathological. The latter are multifactorial, predominantly organic in origin and occasionally functional. Organic causes include vocal fold paralysis or scarring, as well as a deficiency or excess of tissue. In addition to loss of the mucosal wave, the degree of hoarseness is primarily determined by the circumferential area of the glottal gap. It is thus important to quantify the extent of glottal insufficiency. Although a patient's symptoms form the basis for treatment decisions, these may be subjective and inadequately reflected by the results of auditory-perceptual evaluation, voice analysis and voice performance tests. The therapeutic approach should always combine phonosurgery with conventional voice therapy methods. Voice therapy utilises all the resources made available by the sphincter model of the aerodigestive tract and knowledge on the mechanism of voice production. The aim of phonosurgery is medialization, reconstruction or reinnervation by injection laryngoplasty or larynx framework surgery. These different methods can be combined and often applied directly after vocal fold surgery (primary reconstruction). In conclusion, the techniques described here can be effectively employed to compensate for glottal gaps.

Regulation of wound healing by granulocyte-macrophage colony-stimulating factor after vocal fold injury

Objectives

Vocal fold (VF) scarring remains a therapeutic challenge. Granulocyte-macrophage colony-stimulating factor (GM-CSF) facilitates epithelial wound healing, and recently, growth factor therapy has been applied to promote tissue repair. This study was undertaken to investigate the effect of GM-CSF on VF wound healing in vivo and in vitro.

Methods

VF scarring was induced in New Zealand white rabbits by direct injury. Immediately thereafter, either GM-CSF or PBS was injected into the VFs of rabbits. Endoscopic, histopathological, immunohistochemical, and biomechanical evaluations of VFs were performed at 3 months post-injury. Human vocal fold fibroblasts (hVFFs) were cultured with GM-CSF. Production of type I and III collagen was examined immunocytochemically, and the synthesis of elastin and hyaluronic acids was evaluated by ELISA. The mRNA levels of genes related to ECM components and ECM production-related growth factors, such as HGF and TGF-ß1, were examined by real time RT-PCR.

Results

The GM-CSF-treated VFs showed reduced collagen deposition in comparison to the PBS-injected controls (P<0.05). Immunohistochemical staining revealed lower amounts of type I collagen and fibronectin in the GM-CSF-treated VFs (P<0.05 and P<0.01, respectively). Viscous and elastic shear moduli of VF samples were significantly lower in the GM-CSF group than in the PBS-injected group (P<0.001 and P<0.01, respectively). Mucosal waves in the GM-CSF group showed significant improvement when compared to the PBS group (P = 0.0446). GM-CSF inhibited TGF-β1-induced collagen synthesis by hVFFs (P<0.05) and the production of hyaluronic acids increased at 72 hours post-treatment (P<0.05). The expressions of HAS-2, tropoelastin, MMP-1, HGF, and c-Met mRNA were significantly increased by GM-CSF, although at different time points (P<0.05).

Conclusion

The present study shows that GM-CSF offers therapeutic potential for the remodeling of VF wounds and the promotion of VF regeneration.

[Vocal fold scars: pathogenesis, diagnosis, therapy]

Scarring of the vocal folds leads to a deterioration of the highly complex microstructure with consecutively impaired vibratory pattern and glottic insufficiency. The resulting dysphonia is predominantly characterized by a reduced vocal capacity. Despite considerable progress in the understanding of the underlying pathophysiology, treatment of scarred vocal folds is still an unresolved chapter in laryngology and phonosurgery. Decisive for successful treatment is an individual, multidimensional concept that comprises the whole armamentarium of surgical and nonsurgical (e.g. voice therapy) modalities. The chosen phonosurgical method is determined by the main clinical feature: medialization techniques for treatment of glottic insufficiency, or epithelium-freeing techniques for improvement of vibration characteristics often combined with injection augmentation or implantation. In severe cases, buccal mucosa grafting can be an option. New developments include treatment with angiolytic lasers [pulse dye laser, PDL; potassium titanyl phosphate (KTP) laser], or techniques of tissue engineering. However, despite promising results with in vitro experiments, animal studies and first clinical trials, application in clinical routine has not yet been achieved.

Advances in biomimetic regeneration of elastic matrix structures

Elastin is a vital component of the extracellular matrix, providing soft connective tissues with the property of elastic recoil following deformation and regulating the cellular response via biomechanical transduction to maintain tissue homeostasis. The limited ability of most adult cells to synthesize elastin precursors and assemble them into mature crosslinked structures has hindered the development of functional tissue-engineered constructs that exhibit the structure and biomechanics of normal native elastic tissues in the body. In diseased tissues, the chronic overexpression of proteolytic enzymes can cause significant matrix degradation, to further limit the accumulation and quality (e.g., fiber formation) of newly deposited elastic matrix. This review provides an overview of the role and importance of elastin and elastic matrix in soft tissues, the challenges to elastic matrix generation in vitro and to regenerative elastic matrix repair in vivo, current biomolecular strategies to enhance elastin deposition and matrix assembly, and the need to concurrently inhibit proteolytic matrix disruption for improving the quantity and quality of elastogenesis. The review further presents biomaterial-based options using scaffolds and nanocarriers for spatio-temporal control over the presentation and release of these biomolecules, to enable biomimetic assembly of clinically relevant native elastic matrix-like superstructures. Finally, this review provides an overview of recent advances and prospects for the application of these strategies to regenerating tissue-type specific elastic matrix structures and superstructures.

Effect of exogenous hepatocyte growth factor on vocal fold fibroblasts

OBJECTIVES

We have previously demonstrated the therapeutic potential of hepatocyte growth factor (HGF) in the treatment of vocal fold scarring, although how exogenous HGF affects gene expression of endogenous HGF or extracellular matrix components in the vocal fold fibroblasts remains unclear. In this in vitro study, we aimed to clarify this aspect in order to better understand the effects of HGF on the vocal folds.

METHODS

Fibroblasts were obtained from the lamina propria of the vocal folds of 5 Sprague-Dawley rats and were cultured with HGF at concentrations of 100, 10, 1, and 0 ng/mL. The cells were collected on days 1, 3, and 7, and the expression of endogenous HGF, its receptor c-Met, transforming growth factor-beta1 (TGF-beta1), procollagen types I and III, and hyaluronic acid synthase (HAS)-1 and HAS-2 messenger RNAs (mRNAs) was examined by real-time reverse transcription-polymerase chain reaction.

RESULTS

The expression of endogenous HGF and HAS-1 mRNAs increased significantly when exogenous HGF was administered at a concentration of 1 ng/mL. On day 1, the expression of TGF-beta1 and HAS-2 mRNAs increased significantly in response to 1 ng/mL HGF.

CONCLUSIONS

Exogenous HGF triggered the up-regulation of endogenous HGF, TGF-beta1, HAS-1, and HAS-2 mRNAs in vocal fold fibroblasts.

Gene expression of transforming growth factor-beta1 and hepatocyte growth factor during wound healing of injured rat vocal fold

OBJECTIVES/HYPOTHESIS

To investigate the expression of genes coding transforming growth factor (TGF)-beta1, hepatocyte growth factor (HGF), and c-Met, its membrane-spanning tyrosine kinase receptor, during the inflammatory, proliferative, and remodeling phases of wound healing in the injured rat vocal fold.

STUDY DESIGN

Prospective animal study.

METHODS

Thirty five rats were involved in this study. Bilateral vocal fold wounds were created in 30 rats. Injured vocal fold specimens were harvested on postinjury day 1, 3, 7, 14, 28, and 56. Real-time polymerase chain reaction (PCR) was used to quantify mRNA expression of TGF-beta1, HGF, and c-Met. Five uninjured rats were used to establish PCR control.

RESULTS

Results of analysis of variance revealed a significant main effect for TGF-beta1 (P = .000), HGF (P = .000), and c-Met (P = .000) expression across time points. Post-hoc testing revealed that TGF-beta1 expression increased significantly on postinjury day 7 (P = .001) compared to control. HGF expression decreased significantly on postinjury day 1 (P = .001), and increased significantly on postinjury day 14 (P = .000). c-Met expression decreased significantly on postinjury day 1 (P = .000), day 3 (P = .000), and day 56 (P = .000), and increased significantly on postinjury day 28 (P = .000).

CONCLUSIONS

Results revealed time-dependent changes in the regulation of genes coding TGF-beta1, HGF, and c-Met during wound healing in the injured rat vocal fold. These patterns of gene expression correspond well with previously reported histologic changes of the rat vocal fold after injury.

Current understanding and review of the literature: vocal fold scarring

Vocal fold scarring is the greatest cause of poor voice after vocal fold injury. Scarring causes a disruption of the viscoelastic layered structure of the lamina propria, an increase in stiffness of the vibratory structure, and glottic incompetence. Current treatments for this complex condition are inconsistent and often produce suboptimal results. Research investigating this condition has dramatically increased over the last several years. The literature has been directed toward understanding vocal fold scarring at the biological level and translating this to the clinical forum. We present an up-to-date, thorough, and scholarly review of the literature in vocal fold scarring since 1996.