Histologic study of acute vocal fold wound healing after corticosteroid injection in a rabbit model

Factors Associated With Improvement Following In-office Steroid Injections for Vocal Fold Scar

OBJECTIVE

This study aims to evaluate the clinical outcomes of patients receiving in-office vocal fold steroid injections (VFSI), highlighting relatively new measures around vocal pitch.

METHODS

Patients with a diagnosis of vocal fold scar who received in-office VFSI from 2013 to 2024 were evaluated. Pre- and post-steroid Voice Handicap Index (VHI-10) scores, stroboscopic vibratory parameters, acoustic measures of cepstral peak prominence (CPP), and fundamental frequency coefficient of variation (F0CoV) during sustained phonation were analyzed using Wilcoxon signed-rank tests and McNemar's tests.

RESULTS

Twenty-two patients had follow-up data 1-3 months after steroid injection. The median decrease in VHI-10 after one injection was 4 points (p = 0.02). We found no difference in CPP and F0CoV measures at follow-up. Forty-five percent of patients improved in mucosal wave and amplitude of at least one vocal fold. Earlier presentation from vocal injury was associated with improvement in mucosal wave and amplitude of the left vocal fold (p = 0.03). We found no difference in sex, tobacco smoking history, singing status, secondary diagnosis, and baseline VHI-10 score between patients who improved in vibratory parameters and those who did not.

CONCLUSION

This single-center study is one of the largest exploring patient outcomes following in-office VFSI. Though patients reported modest improvement in voice use after VFSI, this may not be as impactful as previously believed. Improvement in videostroboscopy is expected in about half of the patients, with recency from vocal injury a likely predictor of success. These partially negative results provide insight into counseling patients regarding benefits from in-office VFSI.

LEVEL OF EVIDENCE

4 Laryngoscope, 2024.

Drug delivery systems for wound healing treatment of upper airway injury

INTRODUCTION

Endotracheal intubation is a common procedure to maintain an open airway with risks for traumatic injury. Pathological changes resulting from intubation can cause upper airway complications, including vocal fold scarring, laryngotracheal stenosis, and granulomas and present with symptoms such as dysphonia, dysphagia, and dyspnea. Current intubation-related laryngotracheal injury treatment approaches lack standardized guidelines, relying on individual clinician experience, and surgical and medical interventions have limitations and carry risks.

AREAS COVERED

The clinical and preclinical therapeutics for wound healing in the upper airway are described. This review discusses the current developments on local drug delivery systems in the upper airway utilizing particle-based delivery systems, including nanoparticles and microparticles, and bulk-based delivery systems, encompassing hydrogels and polymer-based approaches.

EXPERT OPINION

Complex laryngotracheal diseases pose challenges for effective treatment, struggling due to the intricate anatomy, limited access, and recurrence. Symptomatic management often requires invasive surgical procedures or medications that are unable to achieve lasting effects. Recent advances in nanotechnology and biocompatible materials provide potential solutions, enabling precise drug delivery, personalization, and extended treatment efficacy. Combining these technologies could lead to groundbreaking treatments for upper airways diseases, significantly improving patients' quality of life. Research and innovation in this field are crucial for further advancements.

Histological Effect of Emodin on Acute Vocal Fold Injury in a Rat Model

OBJECTIVES

Emodin has beneficial effects on wound healing and reduces excessive fibrosis during tissue regeneration. Its positive effects on the wound-healing process were demonstrated on human fibroblasts. The aim of the present study was to evaluate the effectiveness of emodin application on acute vocal fold injury.

MATERIALS AND METHODS

Twenty-four Wistar albino rats were divided into three groups: control, sham, and emodin group. The glottis was examined using a 30°-2.7 mm diameter telescope, and vocal folds was unilaterally wounded by a microscissor through the entire layer of the lamina propria down to the vocalis muscle. While no procedure(no acute injury of the vocal fold or an injection of saline/emodin) was applied to the control group, 0.5 cc of saline was injected into the sham group and 0.5 cc of emodin in the emodin group, just lateral to the vocal folds, with 27 gauge injectors. Animals were sacrificed on the 21st day after the procedure. After excised larynx experiments, serial sections were prepared from the vocal fold. Hematoxylin eosin and immunohistochemical staining were performed and fibroblast density, lamina propria thickness, and vessel formation were graded from 0 (none) to 3 (severe reaction). Transforming growth factor-beta 1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) staining was used for immunohistochemical examinations. Four-point scoring scale for intensity being scored as 0 (no staining) to 3 (severeley stained) to quantify immonuhistochemical reaction. This scoring system was applied to vocal fold epithelium, lamina propria, vessel wall, and vocalis muscle tissues. The groups were compared with the Kruskal Wallis and Dunn tests.

RESULTS

Histologically, there was no significant difference (P > 0.05) between the sham group and the emodin group in terms of fibroblast density, vessel formation, and lamina propria thickness. These parameters were higher (P < 0.05) in both groups compared to the control group. In the lamina propria and vessel wall, MMP-9 staining was more intense in the emodin group than in the sham group. TGF-β1 staining of lamina propria, epithelial tissue, and vocalis muscle was significantly more intense in the emodin group than in the other groups.

CONCLUSION

Emodin induced MMP-9 and TGF-1 staining in the vocalis muscle and epithelium, as well as TGF-1 staining in the lamina propria. In terms of fibroblast density, new vascular creation, and LP thickness in acute vocal fold damage, there was no difference between saline administration and emodin injection. It may increase fibroblast activation in the acute phase of wound healing, but its long-term effects should be further investigated.

Functional Analysis of Injectable Substance Treatment on Surgically Injured Rabbit Vocal Folds

OBJECTIVES

The objective of this study was to evaluate the efficacy of immediate injection treatments of dexamethasone, hyaluronic acid (HA)/gelatin (Ge) hydrogel and glycol-chitosan solution on the phonatory function of rabbit larynges at 42 days after surgical injury of the vocal folds, piloting a novel ex vivo phonatory functional analysis protocol.

METHODS

A modified microflap procedure was performed on the left vocal fold of 12 rabbits to induce an acute injury. Animals were randomized into one of four treatment groups with 0.1 mL injections of dexamethasone, HA/Ge hydrogel, glycol-chitosan or saline as control. The left mid vocal fold lamina propria was injected immediately following injury. The right vocal fold served as an uninjured control. Larynges were harvested at Day 42 after injection, then were subjected to airflow-bench evaluation. Acoustic, aerodynamic and laryngeal high-speed videoendoscopy (HSV) analyses were performed. HSV segments of the vibrating vocal folds were rated by three expert laryngologists. Six parameters related to vocal fold vibratory characteristics were evaluated on a Likert scale.

RESULTS

The fundamental frequency, one possible surrogate of vocal fold stiffness and scarring, was lower in the dexamethasone and HA/Ge hydrogel treatment groups compared to that of the saline control (411.52±11.63 Hz). The lowest fundamental frequency value was observed in the dexamethasone group (348.79±14.99 Hz). Expert visual ratings of the HSV segments indicated an overall positive outcome in the dexamethasone treatment group, though the impacts were below statistical significance.

CONCLUSION

Dexamethasone injections might be used as an adjunctive option for iatrogenic vocal fold scarring. An increased sample size, histological correlate, and experimental method improvements will be needed to confirm this finding. Results suggested a promising use of HSV and acoustic analysis techniques to identify and monitor post-surgical vocal fold repair and scarring, providing a useful tool for future studies of vocal fold scar treatments.

Duration of Clinical Response After In-Office Steroid Injection for Vocal Fold Scar

OBJECTIVE

To assess the duration of clinical response after in-office vocal fold steroid injection (VFSI) for vocal fold (VF) scar.

METHODS

Demographic and clinical data for in-office VFSI occurring from 2017 to 2020 were collected. Two Speech-Language Pathologists (SLPs) used perceptual evaluation of voice and functional scales to evaluate blinded voice and laryngovideostroboscopy (LVS) samples collected pre- and post-injection across multiple timepoints.

RESULTS

Blinded SLP ratings were used for 30 individual VFs undergoing initial injection in 18 patients. Persistent improvement in voice past 6 months was seen in 57% of patients after VFSI. Multiple measures of voice and amplitude, percent vibrating tissue, and closed phase predominance significantly improved at various follow-up timepoints on average.

CONCLUSION

Accounting for patient heterogeneity and disease progression, in-office VFSI for VF scar is associated with sustained improvement in a subset of patients. Approximately half of patients can expect to experience a lasting improvement in voice. Future studies of larger scale are required to identify patient factors associated with long-term benefit.

LEVEL OF EVIDENCE

4 Laryngoscope, 133:2333-2339, 2023.

5-Aminolevulinic Acid-Mediated Photodynamic Therapy Improves Vocal Fold Wound Healing in Rats

OBJECTIVE

Studies showed that photodynamic therapy (PDT) might be able to prevent vocal fold scar formation when treating laryngeal lesions. We aim to investigate if PDT improves vocal wound healing and reduces scar formation in both prophylactic and remodeling procedures performed in vivo.

STUDY DESIGN

In vivo.

METHODS

Vocal fold stripping was performed in Sprague-Dawley rats. PDT was performed with intraperitoneal injection of 100 mg/kg 5-Aminolevulinic Acid (5-ALA) and 635 nm laser irradiation of 20, 40, and 60 J/cm² . PDT was performed immediately after surgery to study the prophylactic effect and 4 weeks after surgery to study the remodeling effect. Gene expression was evaluated with real-time PCR at 1 week after PDT. Histologic evaluations were performed 12 weeks after PDT, including hematoxylin-eosin, Masson, Alcian blue staining, and immunohistochemical staining of collagen I and III.

RESULTS

PDT induced similar effects on the vocal fold wound healing outcomes in both prophylactic and remodeling procedures. Expression of MMP8, MMP13, HAS2, and TGFβ1 was significantly elevated. Histologic evaluation revealed significantly increased thickness, decreased density of collagen, and increased deposition of hyaluronic acid in the lamina propria. Immunohistochemistry also revealed better distribution and reduced density of collagen I and III. The most obvious changes were seen in the 60 J/cm² PDT group.

CONCLUSION

PDT could significantly improve vocal wound healing by providing both prophylactic effects and remodeling effects. It may be a minimally invasive treatment for vocal fold lesions with slight vocal scarring, and may be used to treat acute or chronic vocal injury to reduce vocal scarring.

LEVEL OF EVIDENCE

N/A Laryngoscope, 133:1943-1951, 2023.

Voice Outcomes Following Serial Office-Based Steroid Injections and Voice Therapy for Vocal Fold Scar

OBJECTIVE

Previous studies indicate that certain voice outcomes can improve following a single office-based steroid injection with voice therapy for vocal fold scar. We evaluated voice outcomes after a series of three timed office-based steroid injections with voice therapy.

STUDY DESIGN

Retrospective case series with chart review.

SETTING

Academic medical center.

METHODS

We evaluated pre-and postprocedural patient-reported, perceptual, acoustic, aerodynamic, and videostroboscopic parameters. We evaluated 23 patients who underwent three office-based dexamethasone injections into the superficial lamina propria one month apart. All patients pursued voice therapy.

RESULTS

Voice Handicap Index (n = 19; P= .030) decreased after injection series. Total GRBAS score (grade, roughness, breathiness, asthenia, strain) decreased (n = 23; P = 0.001). Dysphonia severity index score improved (n = 20; P = 0.041). Phonation threshold pressure did not decrease significantly (n = 22; P = 0.536). Videostroboscopic parameters of vocal fold edge (P = 0.023), right mucosal wave (P = 0.023) improved or normalized after injection series. Glottic closure (P = 0.134) did not improve.

CONCLUSIONS

Series of three office-based steroid injections combined with voice therapy for vocal fold scar does not appear to provide further benefit than one injection. Despite lack of improvements of PTP and other parameters, injection series is likewise unlikely to worsen dysphonia. A partially negative study provides value in investigation of less invasive treatment alternatives for a disorder that is challenging to treat. Future studies exploring effects of voice therapy alone without other intervention and consideration of sham injection versus steroid injection are warranted.

Effects of compound betamethasone on vocal fold wound healing in rabbit model: A preliminary study

Objectives

The compound betamethasone is widely used to prevent scarring in dermatology. This study aims to explore the effects of compound betamethasone on vocal fold (VF) wound healing.

Study design

Prospective animal study in rabbits.

Methods

Eighteen rabbits underwent bilateral VF stripping and three rabbits served as controls. 0.1 mL of compound betamethasone (1 mL: betamethasone sodium phosphate 5 mg and betamethasone dipropionate 2 mg) was injected into the right VF of each rabbit, and 0.1 mL 0.9% saline was injected into the contralateral VF. Endoscopy was performed for morphologic observation. Six larynges were harvested for histological analysis at 3 days, 7 days, and 1 month. The VFs were stained with hematoxylin and eosin (H&E), Alcian blue, and Masson' trichrome staining.

Results

In morphological analysis, there was no visible difference between betamethasone-treated and saline-treated VFs at 3 and 7 days. After 1 month, more VF scars appeared on the saline-treated VFs than the VFs treated with betamethasone. Inflammatory cell number showed significant difference between both VFs at 3 days (p = .037) and 7 days (p = .045). No significant different was found in epithelial thickness at 1 month between the betamethasone and saline groups. The collagen in the saline-treated VFs was significantly denser than that of the betamethasone-treated group (p = .037). There was also a significant increase in the level of hyaluronic acid (HA) in betamethasone-injected VFs in comparison to the saline-injected VFs (p = .006).

Conclusions

Based on this study, compound betamethasone can improve VF healing. Our findings suggest that VF injection with compound betamethasone helps to minimize scarring by increasing HA level and decreasing collagen density.

The Added Value of Steroid Injection Following Office-based Blue Laser Therapy of Benign Lesions of the Vocal Folds; Short-Term Effect in a Cohort of 43 Patients

OBJECTIVES

To investigate the added value of steroid injection following office-based blue laser therapy of benign lesions of the vocal folds.

STUDY DESIGN

Retrospective cohort analysis.

METHODS

The medical records and video-recordings of patients with benign lesions of the vocal folds who underwent office-based blue laser therapy in a tertiary referral center between February 2020 and October 2022 were reviewed. Patients were divided into two subgroups, those who underwent office-based blue laser therapy alone (n = 23) and those who underwent office-based blue laser therapy with steroid injection (n = 19). Disease regression and voice outcome measures included Voice Handicap Index-10 score, perceptual voice evaluation using the GRB grading, jitter, shimmer, noise to harmonic ratio, voice turbulence index, and maximum phonation time were reviewed.

RESULTS

A total of 42 patients were included. The mean age was 54.7 ± 10.1 years. Lesions included polyps (n = 21), Reinke's edema (n = 19), and cysts (n = 2). There was partial or complete disease regression in all patients who presented for follow-up (n = 37). In patients who underwent blue laser therapy alone (n = 19), 42.1% had complete regression and 57.9% had partial regression. In those who underwent blue laser therapy followed by steroid injection (n = 18), 77.7% had complete disease regression and 22.3% had partial regression. The difference in disease regression between the two subgroups was statistically significant (P = 0.027). The decrease in the mean Voice Handicap Index-10 score was also statistically significant with a higher mean being noted in the subgroup who underwent blue laser therapy followed by steroid injection (-10.5 ± 6.9 vs. -17.3 ± 11.8, P = 0.031). There was no significant difference in the decrease in the perceptual evaluation scores nor in the decrease in jitter, shimmer, noise to harmonic ratio, and voice turbulence index between the two subgroups. There was also no significant increase in the maximum phonation time.

CONCLUSION

Steroid injection after blue laser therapy improves disease regression and voice outcome of laser therapy.

Intracordal injection therapy for vocal fold scarring: Steroid versus basic fibroblast growth factor

Objectives

Vocal fold scarring is caused by replacement of vocal fold mucosa with fibrous tissue due to repeated inflammation or trauma. It can lead to severe dysphonia. It is currently treated conservatively and with phonosurgery and intracordal injections. Intracordal injection of steroid or basic fibroblast growth factor (bFGF) has been recently found to be useful for treating vocal fold scarring that does not respond to voice therapy.

Methods

This retrospective study involved the administration of steroid injection and bFGF injection bilaterally under local anesthesia in 16 patients each. Laboratory measurements of voice parameters were performed before and 3-6 months after injection.

Results

In the steroid injection group, the Voice Handicap Index (VHI) score significantly improved from 57.1 to 40.5, total Grade, Roughness, Breathiness, Asthenia, Strain (tGRBAS) score significantly improved from 4.2 to 2.6, and mean speech fundamental frequency (SFF) increased from 192.5 to 211.4 dB, but there was no improvement in maximum phonation time (MPT) and mean airflow rate (MFR). In the bFGF injection group, significant improvements in the VHI score (from 53.3 to 35.7), MPT (from 16.9 to 21.8 s) and MFR (from 314.6 to 210.5 ml/s) were seen; however, the tGRBAS score did not improve. In addition, the SFF significantly decreased from 178.1 to 160.5 Hz.

Conclusion

These results suggest that both steroid and bFGF injections are effective for treating vocal fold scarring, with steroids improving voice quality and bFGF improving glottic closure, thereby contributing to improvements in VHI scores.

Level of Evidence

4.

Stem cell therapy for vocal fold regeneration after scarring: a review of experimental approaches

This review aims at becoming a guide which will help to plan the experimental design and to choose adequate methods to assess the outcomes when testing cell-based products in the treatment of the damaged vocal folds. The requirements to preclinical trials of cell-based products remain rather hazy and dictated by the country regulations. Most parameters like the way the cells are administered, selection of the cell source, selection of a carrier, and design of in vivo studies are decided upon by each research team and may differ essentially between studies. The review covers the methodological aspects of preclinical studies such as experimental models, characterization of cell products, assessment of the study outcome using molecular, morphological and immunohistochemical analyses, as well as measuring the tissue physical properties. The unified recommendations to perform preclinical trials could significantly facilitate the translation of cell-based products into the clinical practice.

Comparison of therapeutic effects of steroid injection by benign vocal fold lesion type

BACKGROUND

Benign vocal fold lesions (BVFLs) can cause voice changes, including reduced loudness and pitch range. In recent times, with progression in endoscopic technology, office-based vocal fold steroid injection (VFSI) has been used as an alternative therapy for BVFLs.

AIMS/OBJECTIVES

In this study, we analyzed the efficacy and safety of VFSI to investigate the mechanism underlying its therapeutic effects and determine the conditions in which VFSI will be most effective.

MATERIALS AND METHODS

In this retrospective cohort study, we included 40 condition-matched patients (8 patients per lesion) with chorditis, vocal nodules, vocal polyps, Reinke's edema (RE), or vocal scars who received similar regimens of steroid injection using a commercial preparation of triamcinolone acetonide. Their phonological outcomes were evaluated 2 or 3 months after the injection.

RESULTS

Significant improvements were observed in Voice Handicap Index scores, results of laboratory voice evaluation, and voice quality measured using the Grade, Roughness, Breathiness, Asthenia, Strain scale in all participants. In subgroup analysis, VFSI was highly effective against chorditis and vocal nodules, but less effective against RE and vocal scars.

CONCLUSIONS

Single-dose VFSI is valuable as an alternative to voice rehabilitation and laryngo-microsurgery, but higher concentrations or repeated injections are required for intractable lesions.

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.

Corneal Healing and Recovery of Ocular Crystallinity with a Dichloromethane Extract of Sedum dendroideum D.C. in a Novel Murine Model of Ocular Pterygium

Pterygium is a corneal alteration that can cause visual impairment, which has been traditionally treated with the sap of Sedum dendroideum D.C. The pharmacological effect of a dichloromethane extract of S. dendroideum was demonstrated and implemented in a pterygium model on the healing process of corneal damage caused by phorbol esters. In mice of the ICR strain, a corneal lesion was caused by intravitreal injection of tetradecanoylphorbol acetate (TPA). The evolution of the corneal scarring process was monitored with vehicle, dexamethasone, and dichloromethane extract of S. dendroideum treatments by daily ophthalmic administration for fifteen days. The lesions were evaluated in situ with highlighted images of fluorescence of the lesions. Following treatment levels in eyeballs of IL-1α, TNF-α, and IL-10 cytokines were measured. The effective dose of TPA to produce a pterygium-like lesion was determined. The follow-up of the evolution of the scarring process allowed us to define that the treatment with S. dendroideum improved the experimental pterygium and had an immunomodulatory effect by decreasing TNF-α, IL-1α, and maintaining the level of IL-10 expression, without difference with respect to the healthy control. Traditional medical use of S. dendroideum sap to treat pterygium is fully justified by its compound composition.

Effects of hyaluronic acid-collagen nanofibers on early wound healing in vocal cord trauma

BACKGROUND

Vocal cord scarring is the most crucial obstacle in voice quality after surgery. This study aimed to evaluate the effectiveness of hyaluronic acid (HA)-collagen nanofibers on the healing of vocal cords after surgical trauma.

METHOD

Right vocal cords of 12 New Zealand white rabbits were traumatized, and the experimental group was received 1.08 mg/75 ml topical HA-collagen nanofiber (Gelfix^® spray) for 3 days. Three animals in each group were sacrificed on the 7th day, and the remaining of the animals were sacrificed on the 21st day. The laryngeal specimens in the experimental and control groups were examined histopathologically.

RESULT

The 7th-day H&E staining evaluation revealed pink, dense, and thin collagen fibers. Besides, the collagen content was scattered and irregular in the experimental group. The 21st-day assessment showed that the collagen bundles in the granulation tissue were almost with the same formation in both of the groups. Masson Trichrome staining on the 7^th day of the study showed that the collagen fiber bundles were less frequent in the control group than the experimental group. The 7th-day Van Gieson staining analysis showed that the pattern of reticular fibers was more regular with the parallel formation in the experimental group than the control group.

CONCLUSION

HA-collagen nanofiber can be used in diseases that impair voice quality due to the thickening of the lamina propria layer in the vocal cord and impaired viscoelasticity due to fibrosis after tissue trauma.

First-line treatment of exudative vocal fold-lesions by in-office local corticosteroid injection: A literature review

OBJECTIVES

There are emerging reports of the effectiveness of in-office awake vocal-fold corticosteroid injection in the treatment of exudative vocal-fold lesions. The aim of this study was to review this therapy and specify indications, practical modalities and outcomes.

STUDY DESIGN

Systematic review of the literature without meta-analysis.

METHODS

A systematic review by PubMed search for the period January 2000 to December 2018 was carried out.

RESULTS

Nine articles were included, for a total of 502 lesions: nodules (46.4%), polyps (31.7%), and Reinke's edema (21.9%). Submucosal injection of low-dose triamcinolone acetonide (0.1 to 0.3mL) was transoral, transcutaneous or transnasal via flexible endoscope with operating channel. Lesion volume was significantly reduced in more than 90% of cases, with significant vocal improvement in all studies. Relapse rates ranged between 4% and 31%, with time to relapse of 1 to 40 months.

CONCLUSIONS

First-line treatment of exudative glottic lesions by submucosal corticosteroid injection provides at least transient significant reduction in lesion volume and vocal improvement. It is consensually reserved to moderate-sized mainly exudative lesions without fibrosis. In-office injection provides an immediate therapeutic response in case of vocal impairment, enabling surgery under general anesthesia to be postponed.

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.

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.

Multimodal virtual histology of rabbit vocal folds by nonlinear microscopy and nano computed tomography

Human vocal folds (VFs) possess a unique anatomical structure and mechanical properties for human communication. However, VFs are prone to scarring as a consequence of overuse, injury, disease or surgery. Accumulation of scar tissue on VFs inhibits proper phonation and leads to partial or complete loss of voice, with significant consequences for the patient's quality of life. VF regeneration after scarring provides a significant challenge for tissue engineering therapies given the complexity of tissue microarchitecture. To establish an effective animal model for VF injury and scarring, new histological methods are required to visualize the wound repair process of the tissue in its three-dimensional native environment. In this work, we propose the use of a combination of nonlinear microscopy and nanotomography as contrast methods for virtual histology of rabbit VFs. We apply these methods to rabbit VF tissue to demonstrate their use as alternatives to conventional VF histology that may enable future clinical studies of this injury model.

Effects of Intracordal Estradiol and Dexamethasone Injection on Wound Healing in Vocal Fold Injuries

OBJECTIVE

The aim of this study was to investigate the effects of intracordal estradiol and dexamethasone injection on wound healing in vocal fold injuries.

STUDY DESIGN

A prospective controlled animal study was carried out.

SETTING

This study was conducted at a tertiary center.

SUBJECTS-METHODS

Ten rabbits were randomly divided into two groups. As surgical procedure, cordotomy technique was performed in the middle third of the vocal folds bilaterally. In the first group, 0.1 mL of dexamethasone was injected into the right side, and 0.1 mL of saline was injected into the left side. In the second group, 0.1 mL of estradiol was injected into the right side, and 0.1 mL of saline was injected into the left side. Animals were sacrificed after 1 month and laryngeal specimens were evaluated histopathologically.

RESULTS

No statistically significant difference was observed in terms of inflammatory response, epithelial thickness, type I and III collagen, and hyaluronic acid parameters in dexamethasone and estradiol injections compared to the saline injection. In terms of elastin level, estradiol injection demonstrated statistically higher values compared to the saline injection. Elastin level of dexamethasone injected vocal folds was not statistically different compared to the saline injection. No significant differences were observed in terms of inflammatory response, epithelial thickness, type I and III collagen, and hyaluronic acid parameters between the estradiol and dexamethasone injected vocal folds.

CONCLUSION

It is thought that the effects of estradiol or dexamethasone injections may have similar effects on wound healing in vocal fold injuries. Intracordal estradiol injection has positive effects on tissue elastin levels.

Long-term Surveillance Following Intralesional Steroid Injection for Benign Vocal Fold Lesions

Importance

The short-term outcomes of vocal fold steroid injection (VFSI) are well documented. However, few studies have reported the long-term outcomes following VFSI.

Objective

To investigate the incidence rates of symptom recurrence and secondary interventions following VFSI for benign vocal fold lesions.

Design, Setting, and Participants

This prospective cohort study was conducted at a tertiary referral medical center in Taipei, Taiwan. The cohort included 189 patients with vocal fold lesions who had received VFSI as the primary treatment between August 2011 and September 2013.

Exposures

All participants underwent VFSI.

Main Outcomes and Measures

Long-term surveillance was conducted through structured telephonic interviews and by reviewing medical charts every 6 months over a 2-year period. We assessed the 10-item voice handicap index, dysphonic symptoms, and whether the patients had received any additional interventions after the initial VFSI.

Results

The 189 participants (32 men and 157 women; mean [SD] age, 39 [10] years [range, 20-74 years] included patients who had undergone VFSI for vocal fold nodules (n = 72), polyps (n = 72), or mucus-retention cysts (n = 45). Following VFSI, 141 patients (74.6%; 23 men and 118 women; mean age, 39 years [range, 20-70 years]) showed positive response (ie, clinically significant symptom resolution without the need for additional procedures) and received long-term surveillance. The median follow-up period was 19.4 months, and 2 patients were lost to follow-up postoperatively within 1 year. The cumulative failure rates (subjective symptom recurrence plus secondary treatments) at 6, 12, 18, and 24 months after VFSI were 12%, 17%, 24%, and 32%, respectively. When the initial response rate to VFSI (141 of 189, 74.6%) was considered altogether, VFSI remained effective after 2 years in 50% of the initially recruited 189 patients. The highest rate of long-term effectiveness of VFSI occurred in vocal polyps (54%), followed by nodules (49%) and cysts (43%).

Conclusions and Relevance

This study demonstrates that VFSI can be beneficial in managing benign vocal lesions, especially when first-line treatments are unsuitable. However, the long-term results of this study clarify that a substantial number of patients experience symptom recurrence or receive subsequent interventions within 2 years after VFSI; this should be considered in medical decision making.

Voice Outcomes following a Single Office-Based Steroid Injection for Vocal Fold Scar

OBJECTIVE

Persistent dysphonia from vocal fold scar remains a clinical challenge, with current therapies providing inconsistent outcomes. We evaluated voice outcomes after a single office-based steroid injection.

STUDY DESIGN

Case series with chart review.

SETTING

Academic medical center.

SUBJECTS AND METHODS

This study was based on pre- and postoperative analysis of patient-reported, perceptual, acoustic, aerodynamic, and videostroboscopic parameters. The sample comprised 25 patients undergoing office-based dexamethasone injection into the superficial lamina propria for mild/moderate vocal fold scar. Average follow-up was 13.7 ± 4.4 weeks; patients completed 3.5 ± 2.3 sessions of voice therapy between assessments. Complete data sets were not available for each parameter; sample size is noted with results.

RESULTS

Voice handicap index (n = 24; P < .001) and glottal function index (n = 22; P < .001) decreased after injection. Total GRBAS score (grade, roughness, breathiness, asthenia, strain) decreased (n = 25; P < .001). Fundamental frequency range increased (n = 24; P = .024). Phonation threshold pressure decreased (n = 14; P = .017). Videostroboscopic parameters of vocal fold edge (P = .004), glottic closure (P = .003), and right mucosal wave (P = .016) improved after injection.

CONCLUSIONS

Office-based steroid injection combined with voice therapy for mild/moderate vocal fold scar is associated with improved patient-reported and functional voice measures. These findings provide preliminary support for this approach. Importantly, the procedure is low risk and can be performed in the office, thus offering a simple treatment alternative to patients with a disorder that has traditionally been difficult to manage. Prospective studies evaluating the effects of multiple injections are warranted.

Differential responses to steroid hormones in fibroblasts from the vocal fold, trachea, and esophagus

There is accumulating evidence that fibroblasts are target cells for steroids such as sex hormones and corticoids. The characteristics of fibroblasts vary among tissues and organs. Our aim in this study is to examine differences in responses to steroid hormones among fibroblasts from different cervicothoracic regions. We compared the actions of steroid hormones on cultured fibroblasts from the vocal folds, which are considered to be the primary target of steroid hormones, and the trachea and esophagus in adult male rats. Expression of steroid hormone receptors (androgen receptor, estrogen receptor α, and glucocorticoid receptor) was identified by immunofluorescence histochemistry. Androgen receptor was much more frequently expressed in fibroblasts from the vocal fold than in those from the trachea and esophagus. Cell proliferation analysis showed that administration of testosterone, estradiol, or corticosterone suppressed growth of all 3 types of fibroblasts. However, mRNA expression for extracellular matrix-associated genes, including procollagen I and III and elastin, and hyaluronic acid synthase I was elevated only by addition of testosterone to fibroblasts from the vocal fold. These results indicate that each steroid hormone exerts region-specific effects on cervicothoracic fibroblasts with different properties through binding to specific receptors.

Dexamethasone Controlled Release on TGF-β1 Treated Vocal Fold Fibroblasts

OBJECTIVE

Corticosteroids may be beneficial in treating vocal fold scarring. Current drug delivery methods do not permit controlled corticosteroid release. Here we investigate the effects of poly-lactic-co-glycolic acid (PLGA) microparticles loaded with the corticosteroid dexamethasone in reducing collagen synthesis and inflammation in vocal fold fibroblasts treated with and without TGF-β1.

STUDY DESIGN

Experimental, in vitro study.

METHODS

PLGA microparticles of differing molecular weight and terminating moieties were synthesized using a hydrogel template method. The release of dexamethasone was characterized from these microparticles over 4 days. Based on the release studies, ester-terminated low molecular weight PLGA microparticles were loaded with dexamethasone and applied to TGF-β1 treated vocal fold fibroblasts for 4 days. Quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assays (ELISAs) were used to assess the effects of released dexamethasone on collagen synthesis and inflammatory mediators.

RESULTS

COL3A1 and COL1A2 were significantly down-regulated after exposure to ester-terminated low molecular weight PLGA microparticles loaded with dexamethasone. The loaded microparticles also reduced interleukin-6 synthesis.

CONCLUSION

These data show promise in using a PLGA microparticle-based delivery system to control dexamethasone release over 4 days. Our findings lay the groundwork for developing more effective treatments for vocal fold scarring.

Glucocorticoids in laryngology: a review

OBJECTIVES/HYPOTHESIS

To provide the otolaryngologist an evidence-based sound review of glucocorticoid use for laryngeal pathology.

STUDY DESIGN

Review of contemporary peer-reviewed literature as well as review articles.

METHODS

A review of the literature regarding glucocorticoids as a therapeutic intervention for the treatment of benign laryngeal pathology and laryngeal manifestations of systemic disease was performed. Review included both systemic administration as well as local injection.

RESULTS

Glucocorticoids, administered in the critical care setting for planned extubation, markedly reducing the risk of reintubation and remain a rudimentary pharmacologic adjunct in laryngeal manifestations of common autoimmune and inflammatory disorders. Intralesional injection has reduced the rate of surgical intervention for benign inflammatory primary laryngeal pathology.

CONCLUSIONS

Glucocorticoids are effective in the treatment of a number of laryngeal pathologies, through both systemic and intralesional administration. However, a clear consensus for utilization of glucocorticoids in the treatment of specific laryngeal disorders has yet to be published.

Perioperative corticosteroids administration as a risk factor for pressure ulcers in cardiovascular surgical patients: a retrospective study

The aim of this study was to investigate the relationship between perioperative corticosteroids administration and the incidence of pressure ulcers (PUs) in cardiovascular surgical patients. A retrospective analysis was performed on data from consecutive patients who had cardiac surgery in 2012. Univariate and multivariate logistic regression analyses were performed to evaluate the relationship between perioperative corticosteroid administration and the incidence of surgery-related PU (SRPU). A total of 286 cardiac surgery patients were included in this study; of these, 47 patients developed 57 SRPUs, an incidence of 16·4% [95% confidence interval (CI): 12·3-21·2%). The SRPU incidence was significantly higher in corticosteroid-administered group compared with groups not receiving corticosteroids (43·8% versus 14·8%, Pearson's χ(2)  = 9·209, P = 0·002). The crude odds ratio (OR) was 4·472 (95% CI: 1·576-12·694). After performing multivariate logistic regression analysis, the adjusted OR was 2·808 (95% CI: 1·062-11·769). This result showed that perioperative corticosteroid administration was an independent risk factor for PUs in cardiovascular surgical patients. Therefore, it is recommended that in order to prevent PU perioperative corticosteroids should be administered with caution to cardiovascular surgical patients.

Morphological and Histological Changes of Rabbit Vocal Fold after Steroid Injection

Objectives/Hypothesis

The purpose of this study was to investigate the morphological and histological change of vocal folds (VFs) after steroid injection in a rabbit model.

Study Design

Prospective animal study.

Setting

Tertiary academic medical center.

Subjects and Methods

Twenty-four New Zealand white rabbits were used in this study. We randomly classified rabbits into the 3 groups and triamcinolone acetonide suspension was injected to the right VF with different concentrations. Left VF was injected with the same volume of phosphate-buffered saline as control. Endoscopic evaluation was performed to measure morphological changes. The larynges were collected for histological analysis, and the VFs were stained with hematoxylin-eosin for assessing inflammatory response, glandular atrophy, and muscular atrophy and with Masson’s trichrome for assessing collagen deposition.

Results

In morphological assessment, there were no differences in VF mass reduction, mucosal atrophy, and granulation formation between both VFs. Histological assessments showed no significant difference in inflammatory response, glandular atrophy, and collagen deposition between both VFs. However, there was a difference in muscular atrophy and epithelial layer thinning in steroid injected right VFs. Muscular atrophy had been completely recovered over time, but mild epithelial thinning was continued until 12 weeks. The longer exposure time and larger dose did not increase the intensity of muscular atrophy or epithelial thinning.

Conclusion

We demonstrated that the VF steroid injection resulted in no significant changes in morphology and histology of rabbit VF. However, steroid injection may induce several VF histological changes and these results are needed to be considered when treating humans.

Transnasal endoscopic steroid injection: a practical and effective alternative treatment for benign vocal fold disorders

OBJECTIVES/HYPOTHESIS

Emerging literature has documented the effectiveness of intralesional steroid injection as an alternative treatment for benign vocal fold disorders. However, clinical application is frequently limited by the associated technical demands for adequate anesthesia and precise needle placement. This study investigated the applicability and effectiveness of the more practical and less technically demanding method of transnasal endoscopic steroid injection (TESI).

STUDY DESIGN

Prospective case series.

METHODS

This study recruited 30 patients with vocal nodules and polyps. Dexamethasone was injected into the Reinke's space under local anesthesia via the operating channel of a transnasal flexible laryngoscope in an office setting. Treatment outcome were measured before, 1 month after, and 3 months after the injection, using videolaryngostroboscopy (VLS), maximal phonation time (MPT), 10-item voice handicap index (VHI-10), acoustic analysis, and perceptual evaluation.

RESULTS

VLS examinations at 3 months post-treatment demonstrated that vocal lesions of 10 and 19 patients were resolved or reduced, respectively. Objective measurements showed increased MPT and decreased VHI-10 (P < .05 and P < .01, respectively). Acoustic analysis revealed significant decrease in jitter and shimmer (P < .05). Perceptual evaluation using the GRB (grade, roughness, breathiness) scale also showed improved voice quality (P < .01). Treatment outcomes were similar between vocal nodules and polyps (P > .05). Mild vocal hematoma occurred in three patients following TESI, but resolved spontaneously within 1 month.

CONCLUSIONS

TESI is a simple and practical office-based treatment modality for benign vocal fold lesions, suitable for most otolaryngologists. Treatment outcomes showed significant subjective and objective improvements that were comparable to the results of other injection procedures reported in the literature.

LEVEL OF EVIDENCE

4.

Modulation of inflammatory and profibrotic signaling in a rabbit model of acute phonotrauma using triamcinolone

OBJECTIVE

To investigate the hypothesis that prophylactic triamcinolone modulates acute vocal fold inflammatory and profibrotic signaling during acute phonotrauma.

STUDY DESIGN

In vivo rabbit phonation model.

SETTING

Academic medical center.

SUBJECTS AND METHODS

Forty New Zealand white breeder rabbits were randomly assigned to 1 of 4 groups: control (no intervention), no treatment (30 minutes of raised intensity phonation), sham treatment (bilateral intralaryngeal triamcinolone acetonide injection at 0 µg/25 µL followed by 30 minutes of raised intensity phonation), or steroid treatment (bilateral intralaryngeal triamcinolone acetonide injection at 400 µg/25 µL followed by 30 minutes of raised intensity phonation). Quantitative polymerase chain reaction (qPCR) was used to investigate gene expression levels of cyclooxygenase-2 (COX-2), interleukin (IL)-1β, and transforming growth factor (TGF)-β1.

RESULTS

Results revealed a significant main effect for COX-2 (P = .002). Post hoc testing revealed that rabbits receiving no treatment (15.10) had higher COX-2 gene expression than control (5.90; P < .001). There were no significant differences in COX-2 expression between treatment groups. Results revealed a significant main effect for IL-1β (P < .001). Post hoc testing revealed that rabbits receiving no treatment (14.70) had higher IL-1β gene expression than control (6.30) (P = .001). There were no significant differences in IL-1β gene expression between treatment groups. There were no significant differences in TGF-β1 gene expression (P = .525) between treatment and control groups.

CONCLUSION

Given conflicting evidence, further studies are necessary to investigate vocal fold steroid injections prior to and following the induction of phonotrauma. Prophylactic administration of triamcinolone immediately prior to acute phonotrauma resulted in no significant changes in COX-2, IL-1β, and TGF-β1 gene transcript levels.

Transforming growth factor β3 for the prevention of vocal fold scarring

OBJECTIVES/HYPOTHESIS

Vocal fold scarring poses a therapeutic challenge. It causes hoarseness and decreases the quality of life. Transforming growth factor β3 (TGFβ3) is highly expressed in fetal wounds that heal without scarring, and administration of TGFβ3 has been reported to prevent scarring of the skin and the buccal mucosa. Thus TGFβ3 is considered to be a key molecule in scar-free healing. This study aimed to examine the ability of TGFβ3 to prevent vocal fold scarring, with particular attention paid to the distribution of extracellular matrices and functional outcomes.

STUDY DESIGN

Prospective study using an animal model.

METHODS

Ten beagles were used in this study; 500 μL of TGFβ3 (0.5 μg/mL: 5 beagles) or saline (5 beagles) was injected into the vocal fold lamina propria. Fifteen minutes after injection, vocal folds were injured by stripping off the entire layer of the lamina propria. Six months after surgery, animals were euthanized and the larynges were harvested. Vibratory and histologic examinations were performed.

RESULTS

The administration of TGFβ3 suppressed granulation-tissue formation and scarring. TGFβ3-treated vocal folds showed significantly better vibratory properties, resembling normal vocal folds. Histologic analysis revealed favorable restoration of elastin and hyaluronic acid in the lamina propria. The distribution of collagen was well organized, and collagen deposition was less dense in TGFβ3-treated vocal folds compared to sham-treated vocal folds.

CONCLUSIONS

Administration of TGFβ3 before injury significantly suppressed scar formation and induced favorable restoration of extracellular matrices in the vocal fold lamina propria, resulting in much improved phonatory function.

Effect of Fibrin Glue on Collagen Deposition after Autologous Fascia Grafting in Rabbit Vocal Folds

Objectives:

Fibrin glue (FG) is a reaction product of fibrinogen and thrombin that forms a fibrin clot responsible for tissue adhesion. However, FG and its components may interfere with wound healing by interacting with cytokines such as transforming growth factor–β (TGF-β). The objective of this study was to investigate the effect of FG on collagen deposition after fascia grafting in the vocal folds of rabbits.

Methods:

Eighteen rabbits underwent autologous fascia grafting in both vocal folds, and the left side was fixed with FG. Each animal was painlessly sacrificed after 7, 30, or 90 days. The larynx was removed, and the vocal folds were prepared for histomorphometric analysis by picrosirius red staining to evaluate collagen deposition around the graft.

Results:

There was a significant increase in collagen density around the grafts at 90 days in the vocal folds that were fixed with FG (p = 0.0102) compared with the control vocal folds.

Conclusions:

Application of FG altered collagen deposition around the fascia grafts, leading to significantly increased collagen density after 90 days. Differences found in the composition of the extracellular matrix in later stages of the healing process are a result of changes that occur in the beginning of this process. Therapeutic interventions, such as the use of FG and/or its components, performed in the early stages of wound healing may interfere with the complex interactions of fibroblasts, inflammatory cells, and cytokines (especially TGF-β), thereby modulating the healing process.

Glucocorticoids regulate extracellular matrix metabolism in human vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Given the recent emergence of encouraging efficacy data regarding the utility of intralesional glucocorticoid (GC) injection for a variety of vocal fold pathologies, we sought to describe the location and expression pattern of the GC receptors within the vocal folds and quantify the effects of GCs on vocal fold fibroblasts.

STUDY DESIGN

In vitro, in vivo.

METHODS

Immunolocalization of the GC receptor was performed on normal rat vocal fold tissue. Receptor expression was also assayed in our human vocal fold fibroblast cell line. These cells were then treated with exogenous dexamethasone (DM) to quantify the effects of GCs on receptor expression, proliferation, transforming growth factor (TGF)-β-induced collagen secretion, and matrix protease synthesis.

RESULTS

Positive immunostaining for the GC receptor was found throughout the vocal fold with particularly strong staining in the epithelium and capillaries. Human vocal fold fibroblasts constitutively express the GC receptor, but this expression decreased in response to exogenous DM. DM also decreased fibroblast proliferation and TGF-β-induced collagen synthesis. DM also abrogated TGF-β-mediated effects on enzymes related extracellular matrix turnover.

CONCLUSIONS

Our data are the first to provide mechanistic insight regarding the recently published favorable data regarding the utility of GCs in patients with vocal fold scar. Although further investigation is warranted, both the accessibility of this class of agents and the amenability to office-based procedures are likely to direct patient care models.

Cause of vocal fold scar

PURPOSE OF REVIEW

The prolonged debilitation, loss of income, and decrement in quality of life caused by vocal fold scar is exacerbated by our inability to successfully treat this difficult problem. As technology focuses on developing innovative treatments, we need to fully appreciate and understand the mechanisms giving rise to glottal scar, on both a macroscopic and microscopic level. This review examines recent literature pertaining to the gross and molecular mechanisms which give rise to vocal fold scar.

RECENT FINDINGS

Mechanisms of vocal fold scar production have been examined in both macroscopic and microscopic detail. Trauma and injury involving any aspect of the lamina propria, particularly the deeper layers, may result in epithelial tethering and scar formation. At the molecular level, early inflammatory cytokines activate and recruit fibroblasts which then drive the fibrotic cascade. Transforming growth factor-β enhances fibrosis and is balanced by tissue matrix metalloproteinases and hepatocyte growth factor activity. Molecular signaling offers novel opportunities to intervene in scar formation.

SUMMARY

New work investigating the cause of vocal fold scar identifies complex molecular processes leading to fibrosis in the lamina propria. Improved mechanistic understanding offers insight into prevention strategies and possible targets for antifibrotic therapies that may help prevent or treat this debilitating condition.

Characterization of vocal fold scar formation, prophylaxis, and treatment using animal models

PURPOSE OF REVIEW

To review recent literature on animal models used to study the pathogenesis, detection, prevention, and treatment of vocal fold scarring. Animal work is critical to studying vocal fold scarring because it is the only way to conduct systematic research on the biomechanical properties of the layered structure of the vocal fold lamina propria, and therefore develop reliable prevention and treatment strategies for this complex clinical problem.

RECENT FINDINGS

During the period of review, critical anatomic, physiologic, and wound healing characteristics, which may serve as the bases for selection of a certain species to help answer a specific question, have been described in mouse, rat, rabbit, ferret, and canine models. A number of different strategies for prophylaxis and chronic scar treatment in animals show promise for clinical application. The pathways of scar formation and methods for quantifying treatment-induced change have become better defined.

SUMMARY

Recent animal vocal fold scarring studies have enriched and confirmed earlier work indicating that restoring pliability to the scarred vocal fold mucosa is challenging but achievable. Differences between animal models and differences in outcome measurements across studies necessitate considering each study individually to obtain guidance for future research. With increased standardization of measurement techniques it may be possible to make more inter-study comparisons.