Mechanisms Underlying the Antifibrotic Potential of Estradiol for Vocal Fold Fibrosis

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.

Cellular and Molecular Effects of Steroid Sex Hormones on the Vocal Folds: A Scoping Review

OBJECTIVE

Steroid sex hormones (SSH) target cell nuclei to affect transcription. Although laryngeal tissue is theorized to be hormonally responsive, SSH receptor presence and cellular effects on the vocal folds are not well-established. A scoping review of this literature might inform future research.

DATA SOURCES

Medline, Embase, Scopus, and Web of Science were searched.

REVIEW METHODS

This review followed JBI and PRISMA-ScR Guidelines. Two independent reviewers screened each title/abstract and full text according to eligibility criteria. Exclusion criteria included primary outcomes based on subjective interpretation and secondary effects on the vocal folds (e.g., voice).

RESULTS

Three hundred and sixty one articles were screened at the title/abstract level, 83 at the full-text level, and 32 met inclusion criteria. Fourteen studies were performed in humans and 15 in animals; 3 were review articles. In studies directly examining receptors (n = 17), estrogen receptors (ER) were found in 10 of 15 studies, progesterone receptors (PR) in 6/10, and androgen receptors (AR) in 6/9. When the effects of SSH on vocal folds were studied (n = 16), estrogen had effects in 10/13, progesterone in 3/3, and androgens in 4/5. ER and PR were mostly identified in epithelium and fibroblasts of lamina propria (LP) while AR was found in muscle, lamina propria, and epithelium.

CONCLUSIONS

Existing evidence variably supports the presence of SSH receptors in vocal fold tissue; therefore, further clarification is needed. Estrogen and progesterone were most identified in mucosal tissue, where they decrease fibrosis and help maintain the epithelial barrier. Androgens appear to be pro-fibrotic in epithelium and hypertrophic in muscle. Laryngoscope, 2024.

Vocal fold fibroblasts and exposure to vibration in vitro: Does sex matter?

Studies have shown that certain vocal fold pathologies are more common in one sex than the other. This is often explained by differences in the composition of the lamina propria and anatomical differences between female and male vocal folds, resulting in e.g. different fundamental frequencies. Here, we investigated a potential sex-specific voice frequency effect in an in vitro setting using vocal fold fibroblasts from one male and one female donor with and without cigarette smoke extract (CSE) addition. After exposure to either male or female vibration frequency with or without CSE, cells and supernatants were harvested. Gene and protein analysis were performed by means of qPCR, western blot, ELISA and Luminex. We found that exposure of cells to both male and female vibration pattern did not elicit significant changes in the expression of extracellular matrix-, inflammation-, and fibrosis-related genes, compared to control cells. The addition of CSE to vibration downregulated the gene expression of COL1A1 in cells exposed to the female vibration pattern, as well as induced MMP1 and PTGS2 in cells exposed to both female and male vibration pattern. The protein expression of MMP1 and COX2 was found to be significantly upregulated only in cells exposed to CSE and female vibration pattern. To conclude, different vibration patterns alone did not cause different responses of the cells. However, the female vibration pattern in combination with CSE had a tendency to elicit/maintain more pro-inflammatory responses in cells than the male vibration pattern.

Effect of Locally Administered Estradiol on Wound Healing in a Nasal Septal Perforation Animal Model

We aimed to investigate the effect of estradiol on wound healing in an experimental nasal septal perforation (NSP) model created in rats. Twenty-two Sprague Dawley healthy male rats were separated into two groups. NSP, approximately 2 mm in diameter, was created in each animal. The 0.1 mL 0.12% estradiol (12 g/L) (study group) and 0.1 mL 0.9% saline (9 g/L) (control group) were applied topically once a day for 14 days. The rats were sacrificed on the 14th day and the cartilage nasal septum of each animal was excised for histopathological examination. The nasal mucosal epithelial regeneration and degeneration, acute inflammatory cell count, fibroblast number, vascularization, granulation tissue formation, giant cell number, eosinophil number, degeneration and regeneration of the nasal cartilage, and collagen density were examined. The macroscopic closure rate of the perforations and histopathological parameters were evaluated statistically. In this study, the epithelial regeneration, the fibroblast count, the granulation tissue formation, and the amount of collagen were significantly higher in the study group than in the saline group (p < 0.05). The acute inflammatory activity was lower in the estradiol group than in the saline group (p < 0.05). There was no statistically significant difference in the closure rate of perforation between the two groups (p = 0.163). No significant difference was found in other comparisons (p > 0.05). The locally administered estradiol may improve wound healing of the nasal septum in an experimental NSP animal model. LEVEL OF EVIDENCE:  Not applicable.

The Efficacy of Topical Lactoferrin on Wound Healing in an Experimental Animal Model of Nasal Septum Perforation

The aim of the present experimental animal study was to investigate the efficacy of bovine lactoferrin (LF) on wound healing in an animal model of nasal septum perforation (NSP).Twenty-two, 8 to 10 weeks of age, male Sprague-Dawley rats were separated into two groups. Nasal septum perforation was created in each rat. The saline (control) and 0.05 mg LF (study) groups were delivered locally for 14 days. On the 14th day of the study, after the sacrifice, the cartilage nasal septa of the animals were excised. The degeneration and regeneration observed in the nasal septum epithelium and cartilage, the number of acute inflammatory cells, the number of eosinophils, the amount of new vessel formation, the amount of granulation, and the collagen density were examined microscopically. The microscopic parameters and macroscopic healing of NSPs were analyzed. The epithelium regeneration, the fibroblast number, the granulation tissue formation, the collagen density, and the macroscopic healing were significantly higher in the LF group (p < 0.05). Besides, the acute inflammatory cell count was lower in the LF group (p = 0.034). In conclusion, the topically delivered LF can improve wound healing in an experimental rat model of NSP.

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.

The Effect of Melatonin on Nasal Septal Wound Healing in an Experimental Animal Model

The purpose of our study was to examine the effect of melatonin (MLT) on wound healing in the nasal septum. Twenty-two Sprague-Dawley rats of the male sex were included in this experimental study. Nasal septal perforation (NSP), about 2 mm in diameter, was formed in each rat. MLT was applied topically to the subjects in the study group and saline was applied topically to the subjects in the control group once a day for 14 days. On day 14, the rats were sacrificed and the nasal septums of the subjects were resected for pathological evaluation. In the NSP area, degeneration and regeneration of nasal septal epithelium; degeneration and regeneration of the septal cartilage; number of cells involved in wound healing such as acute inflammatory cells (leukocytes), fibroblast, eosinophil, and giant cell; capillary vessel intensity; granulation tissue formation; and collagen intensity parameters were evaluated histopathologically. The macroscopic size and histopathologic examination results of NSPs were statistically analyzed. In the MLT group, the epithelium regeneration, cartilage regeneration, fibroblast number, collagen density, vascularity, and granulation formation were significantly higher, and the epithelial degeneration and acute inflammatory cells density were significantly lower, in the NSP area (p < 0.05). In addition, macroscopic healing was significantly higher in the MLT group (p = 0.044 and <0.05). Local application of MLT accelerates nasal septal wound healing. With this feature, the usage of MLT can be promising to prevent the formation of NSP.

Scarless Healing of Injured Vocal Folds Using an Injectable Hyaluronic Acid-Waterborne Polyurethane Hybrid Hydrogel to Tune Inflammation and Collagen Deposition

Vocal fold (VF) scarring results from injury to the unique layered structure and is one of the main reasons for long-lasting dysphonia. A minimally invasive procedure with injectable hydrogels is a promising method for therapy. However, current surgical techniques or standard injectable fillers do not yield satisfactory outcomes. In this work, an injectable hybrid hydrogel consisting of oxide hyaluronic acid and hydrazide-modified waterborne polyurethane emulsion was injected precisely into the injury site and cross-linked in situ by a dynamic hydrazone bond. The prepared hydrogel displays excellent injectability and self-healing ability, showing favorable biocompatibility and biodegradability to facilitate endogenous newborn cell migration and growth for tissue regeneration. With the aim of evaluating the antifibrosis and regeneration capacity of the hybrid hydrogel in the VF scarring model, the morphology and vibration characteristics of VFs, inflammatory response, and healing status were collected. The hybrid hydrogel can decrease the inflammation and increase the ratio of collagen III/collagen I to heal damaged scar-free tissue. Fascinatingly, the mucosal wave oscillations of healing VF by injecting the hybrid hydrogel were vibrated like the normal VF, achieving functional restoration. This work highlights the utility of hybrid hydrogels consisting of synthetic biodegradable waterborne polyurethane emulsions and natural hyaluronic acid as promising biomaterials for scarless healing of damaged VFs.

Comparison of the effects of platelet-rich plasma and dexamethasone ınjection on scar formation after vocal fold ınjury in rabbits

OBJECTIVES

In this study, a histopathological comparison was aimed between platelet-rich plasma (PRP) injection and dexamethasone injection in the prevention of scar formation after vocal fold injury.

MATERIALS AND METHODS

Electrocautery was applied to damage the right and left vocal folds of a total of 12 New Zealand rabbits. PRP obtained from the rabbit's own blood was injected into the right vocal fold, and dexamethasone was injected into the left vocal fold. After 8 weeks, the experimental animals were euthanized, and the levels of inflammatory cell infiltration, vascularization, collagen, elastin, and hyaluronic acid (HA) were compared in histopathological evaluation.

RESULTS

In statistical comparison of histopathological data obtained; in terms of plasma cell infiltration, vascularization, and edema parameters, statistically significant results were obtained in favor of the PRP group. Although the difference between collagen, elastin and HA, which are critical in vocal fold scar healing, was more positive in favor of PRP, no significant result was revealed in the statistical evaluation.

CONCLUSIONS

PRP injection in rabbits with vocal fold damage reveals similar characteristics with dexamethasone injection in preventing scar formation. PRP injection has favorable effects on vascularization, prevention of edema, and number of plasma cells.