Regenerative phonosurgical treatments for vocal fold scar and sulcus with basic fibroblast growth factor

Evaluating Interventions for Sulcus Vocalis or Vocal Fold Scar: A Systematic Review and Meta-analysis

BACKGROUND

Sulcus vocalis reflects varying degrees of vocal cord lamina propria (LP) damage. Many interventions have been discussed in the literature for addressing sulcus vocalis, but there is no universally accepted gold standard for its management.

AIM

We aim in our study to collectively evaluate the effectiveness of different relevant interventions in the literature used for sulcus vocalis or vocal fold scar.

METHODS

We searched five electronic databases to collect all relevant studies. Records were screened for eligibility. Data were extracted from the included studies independently. Our continuous outcomes were pooled in our single-arm meta-analysis as mean change (MC) and with 95% confidence interval (CI).

RESULTS

Our systematic review and meta-analysis included 43 studies encompassing 1302 patients. The jitter parameter indicated that laser degeneration and LP regeneration/scar degradation led to the highest improvements compared to their baseline, with pooled MC of -0.897 and -0.893, respectively. Graft interposition showed a MC of -0.848, while medialization and dissection had less pronounced changes at -0.200. Shimmer parameter results were similar, with medialization and laser degeneration leading to MC of -2.129 and -2.123, while LP regeneration/scar degradation and graft interposition showed smaller changes MC -1.530 and -1.217. For the noise-to-harmonic ratio (NHR) parameter, LP regeneration/scar degradation demonstrated MC = -0.028. In aerodynamics outcomes, graft interposition and LP regeneration/scar degradation showed the highest MCs in mean phonatory time (MPT) (4.214 and 3.467, respectively). Endoscopic outcomes for mucosal wave showed high improvements in medialization and graft interposition (MC = 10.40 and 10.18, respectively). Perceptual outcomes favored graft interposition in various parameters, while laser degeneration performed well in most categories. Graft interposition and LP regeneration/scar degradation had a high voice handicap index (VHI) (MC = -27.195 and -19.269, respectively).

CONCLUSION

Laser degeneration and LP regeneration/scar degradation were particularly effective in improving acoustic parameters. In aerodynamics, graft interposition and LP regeneration/scar degradation improved vocal efficiency compared to their baselines. Medialization and laser degeneration had the largest impact compared to their baseline on shimmer and MPT. Endoscopic assessments showed that medialization and graft interposition had high improvement in mucosal waves, and perceptual outcomes were generally high with graft interposition and laser degeneration.

The use of basic fibroblast growth factor to improve vocal function: A systematic review and meta-analysis

OBJECTIVES

This systematic review and meta-analysis examines if intralaryngeal injection of basic fibroblast growth factor 2 (FGF2) can improve voice outcomes in those with vocal disability.

DESIGN

A Systematic review of original human studies reporting voice outcomes following intra-laryngeal injection of basic fibroblast growth factor 2 in those with vocal dysfunction. Databases searched were Medline (1946-July 2022), Embase (1947-July 2022), Cochrane database and Google Scholar.

SETTING

Secondary or tertiary care centres that undertook the management of voice pathology Hospital.

PARTICIPANTS

Inclusion criteria were original human studies reporting voice outcome measurements following intralaryngeal injection of FGF2 to treat vocal fold atrophy, vocal fold scarring, vocal fold sulcus or vocal fold palsy. Articles not written in English, studies that did not include human subjects and studies where voice outcome measures were not recorded before and after FGF2 injection were excluded from the review.

MAIN OUTCOME MEASURES

The primary outcome measure was maximum phonation time. Secondary outcome measures included acoustic analysis, glottic closure, mucosal wave formation, voice handicap index and GRBAS scale.

RESULTS

Fourteen articles were included out of a search of 1023 and one article was included from scanning reference lists. All studies had a single arm design without control groups. Conditions treated were vocal fold atrophy (n = 186), vocal cord paralysis (n = 74), vocal fold fibrosis (n = 74) and vocal fold sulcus (n = 56). A meta-analysis of six articles reporting on the use of FGF2 in patients with vocal fold atrophy showed a significant increase of mean maximum phonation time of 5.2 s (95% CI: 3.4-7.0) at 3-6 months following injection. A significant improvement in maximum phonation time, voice handicap index and glottic closure was found following injection in most studies assessed. No major adverse events were reported following injection.

CONCLUSIONS

To date, intralaryngeal injection of basic FGF2 appears to be safe and it may be able to improve voice outcomes in those with vocal dysfunction, especially vocal fold atrophy. Randomised controlled trials are needed to further evaluate efficacy and support the wider use of this therapy.

Evaluation of Safety After Intracordal Basic Fibroblast Growth Factor Injection

OBJECTIVES

Although there are many reports of voice improvement with intracordal trafermin (a basic fibroblast growth factor) injections under local anesthesia, few papers have documented the safety of trafermin. Therefore, we aimed to investigate whether trafermin is safer than control drugs (triamcinolone acetonide) early after intracordal injection under local anesthesia.

METHODS

We conducted a retrospective review from the medical records of patients who underwent intracordal injection with trafermin and triamcinolone acetonide under local anesthesia at our institution. Early postinjective complications were defined as changes in vital signs and chief complaints early after intracordal injection.

RESULTS

A total of 699 and 297 patients underwent intracordal injection under local anesthesia with trafermin and triamcinolone acetonide, respectively. Of these, 227 and 130 patients had early postinjective complications with trafermin and triamcinolone acetonide, retrospectively. The most common complications occurring with trafermin was increased blood pressure in 39 cases (5.58%): 17 cases (2.43%) of blood pressure increase of ≥20 mm Hg. Other complications included pharyngeal discomfort in 37 (5.29%), lightheadedness in 33 (4.72%), and phlegm discharge in 29 (4.15%). Triamcinolone acetonide caused pharyngeal discomfort in 28 patients (9.43%), phlegm discharge in 17 patients (5.72%), lightheadedness in 12 patients (4.04%), sore throat in 11 patients (3.70%), increased blood pressure in 10 patients (3.37%): 7 cases (2.36%) of blood pressure increase of ≥20 mm Hg, and dizziness in seven patients (2.36%). Statistical analysis of the complications between trafermin and triamcinolone acetonide showed no significant differences.

CONCLUSIONS

The proportion of early postinjective complications from intracordal injection of trafermin is no significant difference in that of triamcinolone acetonide. The results suggest that the early postinjective complications are not due to the drug action of trafermin, but rather to complications from the intracordal injection procedures. Intracordal trafermin injection may be safe in the short term.

Changes in serum basic fibroblast growth factor concentration following intracordal injection

Objective

Although many studies have reported improvements in voice outcomes with intracordal trafermin injection, there is a lack of data documenting its changes in serum basic fibroblast growth factor (bFGF) blood concentration. This study examined whether serum bFGF concentrations change after intracordal trafermin injection.

Methods

This retrospective study was conducted at Tokyo Voice Center. We investigated serum bFGF concentrations before and after injection in 40 patients who underwent intracordal trafermin injection. There were 26 males and 14 females, with an age ranging from 13 to 88 years (average 53.25 years). They were diagnosed with paralysis (15 patients), atrophy (15 patients), sulcus (8 patients), and others (2 patients: scar and functional), presenting with severe hoarseness that interfered with daily life.

Results

The mean pre- and post-injective serum bFGF concentration of the 40 patients was 6.689 and 4.658 pg/mL, respectively. The difference in mean serum bFGF concentration between pre- and post-injective was -2.031 pg/mL. The Pearson correlation coefficient was calculated to evaluate the correlation between dosage of trafermin and post-injective serum bFGF concentration, and a moderate correlation was found at r = 0.52. Generalized linear model regression analysis was performed for the purpose of adjusting for confounding among variables. The only variable that showed a statistically predominant association with post-injective serum bFGF concentrations was the dosage of trafermin, with an estimated regression coefficient of 0.048.

Conclusion

In this study, the dosage of trafermin we injected and post-injective serum bFGF concentrations were dose-dependent but the amount of changes in the serum bFGF concentration was negligible within the physiological range. Therefore, as with subcutaneous and wound administration, intracordal trafermin injections may be safe.

Level of Evidence

Level IV.

In vivo hamster cheek pouch subepithelial ablation, biomaterial injection, and localization: pilot study

SIGNIFICANCE

The creation of subepithelial voids within scarred vocal folds via ultrafast laser ablation may help in localization of injectable biomaterials toward a clinically viable therapy for vocal fold scarring.

AIM

We aim to prove that subepithelial voids can be created in a live animal model and that the ablation process does not engender additional scar formation. We demonstrate localization and long-term retention of an injectable biomaterial within subepithelial voids.

APPROACH

A benchtop nonlinear microscope was used to create subepithelial voids within healthy and scarred cheek pouches of four Syrian hamsters. A model biomaterial, polyethylene glycol tagged with rhodamine dye, was then injected into these voids using a custom injection setup. Follow-up imaging studies at 1- and 2-week time points were performed using the same benchtop nonlinear microscope. Subsequent histology assessed void morphology and biomaterial retention.

RESULTS

Focused ultrashort pulses can be used to create large subepithelial voids in vivo. Our analysis suggests that the ablation process does not introduce any scar formation. Moreover, these studies indicate localization, and, more importantly, long-term retention of the model biomaterial injected into these voids. Both nonlinear microscopy and histological examination indicate the presence of biomaterial-filled voids in healthy and scarred cheek pouches 2 weeks postoperation.

CONCLUSIONS

We successfully demonstrated subepithelial void formation, biomaterial injection, and biomaterial retention in a live animal model. This pilot study is an important step toward clinical acceptance of a new type of therapy for vocal fold scarring. Future long-term studies on large animals will utilize a miniaturized surgical probe to further assess the clinical viability of such a therapy.

A Systematic Review on Surgical Treatments for Sulcus Vocalis and Vocal Fold Scar

OBJECTIVES/HYPOTHESIS

Vocal fold sulcus and scars are benign vocal fold lesions that present as a challenge to the laryngologist. A number of different surgical techniques have been proposed, aiming at restoring the lamina propria (LP), closing the glottal gap, or both. This study aimed to provide a systematic review of surgical treatment for sulcus and scar and to propose a new classification for these techniques.

STUDY DESIGN

A literature search using MEDLINE and Google Scholar through August 2020.

METHODS

Data on study design were retrieved and outcomes were classified as acoustic, aerodynamic, self-reported, perceptual, and stroboscopic. Methodological quality was assessed using the MINORs criteria. Each technique was classified as direct, indirect, or combined.

RESULTS

Our search included 31 studies with a total of 617 patients. Direct techniques included dissection, graft interposition, or LP regeneration/scar degradation while indirect techniques aimed for glottal gap closure. Only one article performed a comparison between different types of techniques and only eight studied the five types of outcomes. No superiority of any technique was noted in our analysis. Self-reported outcomes were the most frequently improved.

CONCLUSIONS

There seems to not exist a one-fits-all treatment for this clinical picture and no clear decision-making pattern. A recent trend toward sequential approaches, starting with less invasive procedures, can be observed. Laryngoscope, 2021.

Long-term outcomes of basic fibroblast growth factor treatments in patients with vocal fold scarring, aged vocal fold, and sulcus vocalis

OBJECTIVE

Fibrotic changes in the vocal fold mucosa have been observed in patients with vocal fold scarring, aged vocal fold, and sulcus vocalis, which often lead to severe voice disorders. Previous research suggests that the basic fibroblast growth factor (b FGF) improves variations in vocal fold properties [1,2]. Although clinical studies on b FGF treatments have been conducted [3,4,5], these studies only demonstrated the efficacy of this drug over a short period. The present study is the first to investigate the long-term efficacy of b FGF treatment.

METHODS

b FGF injections were performed in six patients from January of 2016 to December of 2017 at our institution. Patient follow-up continued for at least two years after the last injection. Three patients had vocal fold scarring, two had aged vocal fold atrophy, and one patient had sulcus vocalis. Each vocal fold was injected with 10 µg of b FGF four times. Voice and stroboscopic examinations were performed after surgery (at one month, three months, six months, one year, two years). Fundamental frequency, maximum phonation time (MPT), mean flow rate (MFR), amplitude perturbation quotient (APQ), pitch perturbation quotient (PPQ), and noise-to-harmonic ratio (NHR), and voice handicap index-10 (VHI-10) were examined and compared statistically between the pretreatment time and at each posttreatment time point.

RESULTS

The speaking F0 had an obvious decreasing tendency, with significant differences suggesting the increase in volume in the vocal folds. Aerodynamic parameters also showed small improvements. The most remarkable improvement was observed in the acoustic parameters, indicating that the treatment could improve the vocal fold to make vibrations symmetrically and regularly for a long period. Achievement of symmetry and regularity on vocal fold vibrations suggested the property changes had happened in the vocal folds. Consequently, the score of VHI-10 had improved, indicating high patient satisfaction with this treatment.

CONCLUSION

b FGF injections could be a reliable treatment option for diseases that deteriorate the property of vocal fold.

Intracordal Injection of Basic Fibroblast Growth Factor in 100 Cases of Vocal Fold Atrophy and Scar

OBJECTIVES/HYPOTHESIS

Vocal fold atrophy, scar, and sulcus reduce the vibratory function of the vocal fold mucosa, which causes severe refractory dysphonia. We have reported encouraging preliminary results using an intracordal injection of basic fibroblast growth factor (bFGF) and showed improvement in phonatory parameters and voice. The present study summarizes our experience with 100 cases of stiffened vocal folds that were treated with bFGF injections.

STUDY DESIGN

Retrospective chart review with Interstitial Review Board (IRB) approval.

METHODS

Local injection of bFGF was performed in 100 cases of vocal fold pathology, which included 43 cases of vocal fold atrophy, 41 cases with scar, and 16 cases with sulcus. Ten micrograms of bFGF were injected into the vocal folds under topical anesthesia 4 times in each patient. Therapeutic outcomes were examined with maximum phonation time (MPT), voice handicap index-10 (VHI-10), and GRBAS scale.

RESULTS

MPT, VHI-10, and GRBAS scores significantly improved in all pathology groups. An improvement on the VHI-10 greater than five points was observed in 82% of atrophy cases, 78% of scar cases, and 67% of sulcus cases. Improvement on the VHI-10 was significantly better in the atrophy group than the scar or sulcus groups. The mild/moderate cases of scar and sulcus showed better improvement than severe cases.

CONCLUSIONS

The current large case series indicates positive effects of intracordal injection of bFGF for improvement of voice with no severe adverse events. The effects appeared best for cases of atrophy, while the treatment of severe scar and sulcus requires further improvement.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:2059-2064, 2021.

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

OBJECTIVES

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

STUDY DESIGN

Literature review.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Autologous fibroblasts for vocal scars and age-related atrophy: A randomized clinical trial

OBJECTIVES/HYPOTHESIS

To assess the safety and efficacy of autologous cultured fibroblasts (ACFs) to treat dysphonia related to vocal fold scar and age-related vocal atrophy (ARVA).

STUDY DESIGN

Randomized, double-blinded, placebo-controlled, multi-institutional, phase II trial.

METHODS

ACFs were expanded from punch biopsies of the postauricular skin in each subject; randomization was 2:1 (treatment vs. placebo). Three injections of 1-2 × 10⁷ cells or placebo saline was performed at 4-week intervals for each vocal fold. Follow-up was performed at 4, 8, and 12 months. The primary outcome was improved mucosal waves. Secondary outcomes included Voice Handicap Index (VHI)-30, patient reported voice quality outcomes, and perceptual analysis of voice.

RESULTS

Fifteen subjects received ACF and six received saline injections. At 4, 8, and 12 months after ACF treatments, a significant improvement in mucosal wave grade relative to baseline was observed in both vocal scar and ARVA groups. Relative to control group, mucosal waves were significantly improved in the ARVA group at 4 and 8 months. Perceptual analysis significantly improved in the vocal scar group 12 months after ACF treatments compared to controls. Vocal scar group reported significantly improved vocal quality from baseline. VHI and expert rater voice grade improved in both groups, but did not achieve significance. No adverse events related to fibroblast injections were observed.

CONCLUSIONS

In this cohort, injection of ACFs into the vocal fold lamina propria (LP) was safe and significantly improved mucosal waves in patients with vocal scar and ARVA. ACF may hold promise to reconstruct the LP.

LEVEL OF EVIDENCE

1 Laryngoscope, 130:2650-2658, 2020.

Endoscopic Sealing With a Polyglycolic Acid Sheet for Restoration of Vocal Fold Mucosa in Dogs

OBJECTIVES/HYPOTHESIS

Voice outcomes of cordectomy for early glottic cancer are often poor due to vocal fold scarring and tissue defects. Improvements in this aspect could make cordectomy a more acceptable treatment option than radiotherapy. We hypothesized that a polyglycolic acid (PGA) sheet could be used to cover vocal fold defects. The present study aimed to prevent vocal fold scarring after cordectomy using the PGA sheet.

STUDY DESIGN

Animal experiment.

METHODS

Nine male beagles were divided into three groups including a control group (n = 3). Following cordectomy, the vocal fold defect was covered with the PGA sheet plus fibrin glue (PGA group; n = 3) or with the PGA sheet plus fibrin glue containing basic fibroblast growth factor (bFGF; the PGA-bFGF group, n = 3). Vocal folds were chronologically observed, and larynges were removed 6 months after surgery. Mucosal amplitude was measured using a high-speed camera, and histological analysis was performed.

RESULTS

The re-epithelialization process was delayed in the PGA and PGA-bFGF groups compared with the control group. The mucosal amplitude was significantly more normalized and the thickness ratio significantly higher in the PGA and PGA-bFGF groups compared with the control group. The PGA-bFGF group had the highest elastic fiber density, followed by the PGA group and then the control group, with a significant difference between the PGA-bFGF and control groups.

CONCLUSIONS

The PGA sheet plus fibrin glue could serve as an effective regenerative scaffold for reconstructing vocal fold morphology and function after cordectomy, with the potential benefit of establishing an endoscopic sealing method for vocal fold defects.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:E436-E443, 2020.

Regenerative potential of basic fibroblast growth factor contained in biodegradable gelatin hydrogel microspheres applied following vocal fold injury: Early effect on tissue repair in a rabbit model

Introduction

Postoperative dysphonia is mostly caused by vocal fold scarring, and careful management of vocal fold surgery has been reported to reduce the risk of scar formation. However, depending on the vocal fold injury, treatment of postoperative dysphonia can be challenging.

Objective

The goal of the current study was to develop a novel prophylactic regenerative approach for the treatment of injured vocal folds after surgery, using biodegradable gelatin hydrogel microspheres as a drug delivery system for basic fibroblast growth factor.

Methods

Videoendoscopic laryngeal surgery was performed to create vocal fold injury in 14 rabbits. Immediately following this procedure, biodegradable gelatin hydrogel microspheres with basic fibroblast growth factor were injected in the vocal fold. Two weeks after injection, larynges were excised for evaluation of vocal fold histology and mucosal movement.

Results

The presence of poor vibratory function was confirmed in the injured vocal folds. Histology and digital image analysis demonstrated that the injured vocal folds injected with gelatin hydrogel microspheres with basic fibroblast growth factor showed less scar formation, compared to the injured vocal folds injected with gelatin hydrogel microspheres only, or those without any injection.

Conclusion

A prophylactic injection of basic fibroblast growth factor -containing biodegradable gelatin hydrogel microspheres demonstrates a regenerative potential for injured vocal folds in a rabbit model.

Collagen-binding basic fibroblast growth factor improves functional remodeling of scarred endometrium in uterine infertile women: a pilot study

Intrauterine adhesion (IUA) is a common cause of uterine infertility and one of the most severe clinical features is endometrial fibrosis namely endometrial scarring for which there are few cures currently. Blocked angiogenesis is the main pathological change in the scarred endometrium. The fibroblast growth factor 2 (bFGF), a member of FGF family, is usually applied to promote healing of refractory ulcer and contributes to angiogenesis of tissues. In this study, the sustained-release system of bFGF 100 µg was administrated around scarred endometrium guiding by ultrasound every 4 weeks in 18 patients (2-4 times). Results showed that after treatment, the menstrual blood volume, endometrial thickness and the scarred endometrial area were improved. Histological study showed blood vessel density increased obviously. Three patients (3/18) achieved pregnancy over 20 gestational weeks. Therefore, administrating the bFGF surrounding scarred endometrium may provide a new therapeutic approach for the patients with endometrial fibrosis.

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.

Single, high-dose local injection of bFGF improves thyroarytenoid muscle atrophy after paralysis

OBJECTIVES/HYPOTHESIS

Unilateral vocal fold paralysis (UVFP) induces hoarseness due to progressive atrophy of the denervated thyroarytenoid (TA) muscle. Therefore, treatments aimed at regenerating the atrophied TA muscle are required. Basic fibroblast growth factor (bFGF) is involved in muscle development and regeneration. This study aimed to elucidate the effects of bFGF injection on atrophied TA muscle.

STUDY DESIGN

Animal research.

METHODS

A recurrent laryngeal nerve-paralysis rat model was established, and low- (200 ng) or high-dose (2,000 ng) bFGF or saline (control) was injected into the TA muscle 28 days later. The larynges were excised on day 1, 3, 7, 14, and 28 after treatment. The cross-sectional area of the TA muscle in normal and paralyzed sides was compared, and the Ki67-positive (Ki67⁺ ) dividing cells, paired box 7-positive (Pax7⁺ ) satellite cells (SCs), and myogenic differentiation-positive (MyoD⁺ ) myoblasts were counted.

RESULTS

The TA muscle area of animals administered high-dose bFGF increased with time and was significantly larger than that of the saline-injected controls 28 days after treatment (P < .05). The counts of Ki67⁺ and Pax7⁺ cells were the highest on day 1, whereas the MyoD⁺ myoblast count was highest on day 7. These results suggest that bFGF administration into the denervated TA muscles compensated for the atrophied TA muscles by inducing proliferation of SCs and their differentiation to myoblasts.

CONCLUSIONS

A single injection of high-dose bFGF augmented regeneration and differentiation of the atrophied TA muscle by enhancing proliferation and differentiation of muscle SCs, suggesting its possible clinical application in humans with UVFP.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:159-165, 2020.

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

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

Regenerative Effects of Basic Fibroblast Growth Factor on Restoration of Thyroarytenoid Muscle Atrophy Caused by Recurrent Laryngeal Nerve Transection

OBJECTIVES

Vocal fold atrophy following unilateral vocal fold paralysis is caused by atrophy of the thyroarytenoid (TA) muscle and remains a challenge. Medialization procedures are popular treatment options; however, hoarseness often remains due to the reduction in mass or tension of the TA muscle. Therefore, in addition to medialization procedures, TA muscle reinnervation is desirable. In vivo studies have shown the potential for basic fibroblast growth factor (bFGF) to affect muscular and nerve regeneration. The present study aimed to examine the regenerative effects of bFGF on restoration of TA muscle atrophy caused by recurrent laryngeal nerve transection.

STUDY DESIGN

Prospective animal experiments with controls.

METHODS

TA muscle atrophy was induced by unilateral transection of the recurrent laryngeal nerve. One month after transection, different doses (200 ng, 100 ng, 10 ng) of bFGF in 50 µL were repeatedly injected into the TA muscle four times with an interval of 1 week between injections. Saline only was injected in the sham group. Larynges were harvested for histologic and immunohistochemical examination 4 weeks after the final injection.

RESULTS

The cross-sectional TA muscle area was significantly larger in the bFGF-treated groups compared with the sham-treated groups. Immunohistochemistry indicated that bFGF significantly increases the number of neuromuscular junctions and satellite cells in the TA muscle.

CONCLUSIONS

These results suggest that local application of bFGF to the TA muscle may improve TA muscle atrophy caused by recurrent laryngeal nerve paralysis. Furthermore, bFGF may have regenerative effects on both nerves and muscles.

Injection of basic fibroblast growth factor for unilateral vocal cord paralysis. Acta Otolaryngol 2017;137:962-967. [PMID: 28434284 DOI: 10.1080/00016489.2017.1314550]

OBJECTIVE

Unilateral vocal cord paralysis (UVCP) not only induces severe dysphonia, but aspiration as well. Although laryngeal framework surgery is usually performed to treat this condition, the procedure is not tolerated by some patients. In the previous study, basic fibroblast growth factor (bFGF) injections for vocal cord scarring and sulcus have been reported to provide favorable outcomes while being minimally invasive. In this study, the authors retrospectively investigated phonological outcomes after bFGF injection in patients with UVCP.

METHODS

This study was registered in University hospital Medical Information Network - Clinical Trials Registry (UMIN000019347). Nineteen patients with unilateral cord paralysis were treated with bFGF injection. The treatment regimen involved a single injection of 50 μg of bFGF into the muscle layer. More than six months after the injection, aerodynamic and acoustic outcomes were examined.

RESULTS

The voice handicap index, maximum phonation time, mean airflow rate, and pitch range improved significantly after injection of bFGF. No sex-related differences were observed in any phonological parameter.

CONCLUSION

bFGF injection, an easy method and suitable as an office procedure, significantly improved the hoarseness caused by UVCP. It is expected to be widely adopted and effective adjunctive drugs, and procedures are anticipated to be developed.

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

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

Comparative proteomics of paired vocal fold and oral mucosa fibroblasts

Injuries of the vocal folds frequently heal with scar formation, which can have lifelong detrimental impact on voice quality. Current treatments to prevent or resolve scars of the vocal fold mucosa are highly unsatisfactory. In contrast, the adjacent oral mucosa is mostly resistant to scarring. These differences in healing tendency might relate to distinct properties of the fibroblasts populating oral and vocal fold mucosae. We thus established the in vitro cultivation of paired, near-primary vocal fold fibroblasts (VFF) and oral mucosa fibroblasts (OMF) to perform a basic cellular characterization and comparative cellular proteomics. VFF were significantly larger than OMF, proliferated more slowly, and exhibited a sustained TGF-β1-induced elevation of pro-fibrotic interleukin 6. Cluster analysis of the proteomic data revealed distinct protein repertoires specific for VFF and OMF. Further, VFF displayed a broader protein spectrum, particularly a more sophisticated array of factors constituting and modifying the extracellular matrix. Conversely, subsets of OMF-enriched proteins were linked to cellular proliferation, nuclear events, and protection against oxidative stress. Altogether, this study supports the notion that fibroblasts sensitively adapt to the functional peculiarities of their respective anatomical location and presents several molecular targets for further investigation in the context of vocal fold wound healing.

BIOLOGICAL SIGNIFICANCE

Mammalian vocal folds are a unique but delicate tissue. A considerable fraction of people is affected by voice problems, yet many of the underlying vocal fold pathologies are sparsely understood at the molecular level. One such pathology is vocal fold scarring - the tendency of vocal fold injuries to heal with scar formation -, which represents a clinical problem with highly suboptimal treatment modalities. This study employed proteomics to obtain comprehensive insight into the protein repertoire of vocal fold fibroblasts, which are the cells that predominantly synthesize the extracellular matrix in both physiological and pathophysiological conditions. Protein profiles were compared to paired fibroblasts from the oral mucosa, a neighboring tissue that is remarkably resistant to scarring. Bioinformatic analyses of the data revealed a number of pathways as well as single proteins (e.g. ECM-remodeling factors, transcription factors, enzymes) that were significantly different between the two fibroblast types. Thereby, this study has revealed novel interesting molecular targets which can be analyzed in the future for their impact on vocal fold wound healing.

Practice variations in voice treatment selection following vocal fold mucosal resection

OBJECTIVES/HYPOTHESIS

To characterize initial voice treatment selection following vocal fold mucosal resection in a Medicare population.

STUDY DESIGN

Retrospective analysis of a large, nationally representative Medicare claims database.

METHODS

Patients with > 12 months of continuous Medicare coverage who underwent a leukoplakia- or cancer-related vocal fold mucosal resection (index) procedure during calendar years 2004 to 2009 were studied. The primary outcome of interest was receipt of initial voice treatment (thyroplasty, vocal fold injection, or speech therapy) following the index procedure. We evaluated the cumulative incidence of each postindex treatment type, treating the other treatment types as competing risks, and further evaluated postindex treatment utilization using the proportional hazards model for the subdistribution of a competing risk. Patient age, sex, and Medicaid eligibility were used as predictors.

RESULTS

A total of 2,041 patients underwent 2,427 index procedures during the study period. In 14% of cases, an initial voice treatment event was identified. Women were significantly less likely to receive surgical or behavioral treatment compared to men. From age 65 to 75 years, the likelihood of undergoing surgical treatment increased significantly with each 5-year age increase; after age 75 years, the likelihood of undergoing either surgical or behavioral treatment decreased significantly every 5 years. Patients with low socioeconomic status were significantly less likely to undergo speech therapy.

CONCLUSION

The majority of Medicare patients do not undergo voice treatment following vocal fold mucosal resection. Further, the treatments analyzed here appear disproportionally utilized based on patient sex, age, and socioeconomic status. Additional research is needed to determine whether these observations reflect clinically explainable differences or disparities in care.

LEVEL OF EVIDENCE

2c. Laryngoscope, 126:2505-2512, 2016.

The Efficacy of Fibroblast Growth Factor for the Treatment of Chronic Vocal Fold Scarring: From Animal Model to Clinical Application

Objectives

This study assessed the regenerative efficacy of basic fibroblast growth factor (FGF) in a rabbit model of chronic vocal fold scarring and then confirmed its utility and safety in a prospective trial of patients with this condition.

Methods

FGF was injected three times, at 1-week intervals, into a chronic vocal fold scar created in a rabbit model. After 1 month, mRNA level of procollagen I, hyaluronic acid synthetase 2 (HAS 2), and matrix metalloproteinase 2 (MMP 2) were analyzed by real-time polymerase chain reaction. The relative densities of hyaluronic acid (HA) and collagen were examined 3 months post-injection. From April 2012 to September 2014, a prospective clinical trial was conducted at a tertiary hospital in Korea. FGF was injected into the mild vocal fold scar of 17 consecutive patients with a small glottic gap. The patients underwent perceptual, stroboscopic, acoustic aerodynamic test, and Voice Handicap Index (VHI) survey prior to and 3, 6, and 12 months after FGF injection.

Results

FGF injection of the vocal fold scar decreased the density of collagen and increased mRNA level of HAS 2 and MMP 2 expression significantly compared to the control group injected with phosphate buffered solution in a rabbit model (P<0.05). In the clinical trial, significant improvements in the majority of the subjective and objective voice parameters were registered 3 months after FGF injection and were maintained at 12 months. Complications associated with the FGF injections, such as granuloma, were not observed during the follow-up period.

Conclusion

Based on the animal model and the prospective clinical trial, vocal fold injections of FGF in patients with mild chronic vocal fold scarring can significantly improve voice quality for as long as 1 year and without side effects. Our results recommend the use of FGF vocal fold injection as an alternative treatment modality for mild chronic vocal fold scarring.

The use of injectable calcium hydroxylapatite in the surgically pretreated larynx with glottal insufficiency

OBJECTIVES/HYPOTHESIS

To evaluate the efficacy of vocal fold (VF) augmentation with calcium hydroxylapatite (CaHA) microspheres in the surgically pretreated larynx with glottal insufficiency.

STUDY DESIGN

Prospective clinical pilot study.

METHODS

After several prior reconstructive attempts (following tumor resection, VF paralysis, in sulcus vocalis, and VF scarring), CaHA was injected under general anaesthesia using a transoral microlaryngoscopic approach in 10 patients with residual glottal insufficiency ≤1.5 mm. The postinterventional result was assessed after 1 day, and 1 and 3 months. Evaluation of augmentation comprised intraoperative video/photo documentation, pre-/postoperative videolaryngostroboscopy, as well as established subjective and objective voice function diagnostics (Grade, Roughness, Breathiness [GRB] Scale; Voice Handicap Index; voice range profile; and acoustic-aerodynamic analysis).

RESULTS

In the pretreated VF with no or minimal lamina propria remaining, the exact placement of CaHA was not possible due to unpredictable propagation into the scarred tissue. The results showed an insufficient postoperative augmentation. Accordingly, the voice function did not improve. However, a significant increase of the vocal range from 6.2 ± 3.2 to 8.7 ± 3.9 semitones was observed in the speaking voice profile (P =.02). All other acoustic and aerodynamic parameters remained on the whole unchanged; the slight differences between pre- and postoperative findings were not significant.

CONCLUSIONS

The application of CaHA in the surgically pretreated scarred larynx is not reliable to achieve a sufficient glottal closure and a satisfactory improvement of voice. Though CaHA is a welcome addition to our armamentarium against glottal insufficiency, the suitability for augmentation of scar tissue in the larynx must be considered carefully in each individual case.

LEVEL OF EVIDENCE

4 Laryngoscope, 127:1125-1130, 2017.

Histological Effect of Basic Fibroblast Growth Factor on Chronic Vocal Fold Scarring in a Rat Model

OBJECTIVES

Vocal fold scarring is one of the most challenging laryngeal disorders to treat and there are currently no consistently effective treatments available. Our previous studies have shown the therapeutic potential of basic fibroblast growth factor (bFGF) for vocal fold scarring. However, the histological effects of bFGF on scarred vocal fold have not been elucidated. The aim of this study was to examine the histological effects of bFGF on chronic vocal fold scarring.

METHODS

Sprague-Dawley rats were divided into phosphate buffered saline (sham) and bFGF groups. Unilateral vocal fold stripping was performed and the drug was injected into the scarred vocal fold for each group 2 months postoperatively. Injections were performed weekly for 4 weeks. Two months after the last injection, larynges were harvested and histologically analyzed.

RESULTS

A significant increase of hyaluronic acid was observed in the vocal fold of the bFGF group compared with that of the sham group. However, there was no remarkable change in collagen expression nor in vocal fold contraction.

CONCLUSION

Significant increase of hyaluronic acid by local bFGF injection was thought to contribute to the therapeutic effects on chronic vocal fold scarring.

Stem cell approaches for vocal fold regeneration

OBJECTIVES/HYPOTHESIS

Current interventions in the management of vocal fold (VF) dysfunction focus on conservative and surgical approaches. However, the complex structure and precise biomechanical properties of the human VF mean that these strategies have their limitations in clinical practice and in some cases offer inadequate levels of success. Regenerative medicine is an exciting development in this field and has the potential to further enhance VF recovery beyond conventional treatments. Our aim in this review is to discuss advances in the field of regenerative medicine; that is, advances in the process of replacing, engineering, or regenerating the VF through utilization of stem cells, with the intention of restoring normal VF structure and function.

DATA SOURCES

English literature (1946-2015) review.

METHODS

We conducted a systematic review of MEDLINE for cases and studies of VF tissue engineering utilizing stem cells.

RESULTS

The three main approaches by which regenerative medicine is currently applied to VF regeneration include cell therapy, scaffold development, and utilization of growth factors.

CONCLUSION

Exciting advances have been made in stem cell biology in recent years, including use of induced pluripotent stem cells. We expect such advances to be translated into the field in the forthcoming years. Laryngoscope, 126:1865-1870, 2016.

The unsolved chapter of vocal fold scars and how tissue engineering could help us solve the problem

Vocal fold scarring is a relatively small field in scar research with prerequisites found nowhere else. The deterioration of the delicate tri-layered micro-structure of the epithelium of the vocal folds leads to impaired vibration characteristics resulting in a permanent hoarse and breathy voice. Tissue engineering approaches could help to restore the pre-injury status. Despite a considerable progress in this field during the last years, routine clinical applications are not available so far. One reason might be that vocal fold fibroblasts, as the responsible cell type for fibrogenesis, have very particular properties that are only poorly characterized. Moreover, in vivo trials are costly and time consuming and a representative in vitro model does not exist so far. These particular circumstances lead to innovative in vitro strategies and concepts such as macro-molecular crowding that can also be applied in adjacent fields.

Single injection of basic fibroblast growth factor to treat severe vocal fold lesions and vocal fold paralysis

Objectives/Hypothesis

Severe vocal fold lesions such as vocal fold sulcus, scars, and atrophy induce a communication disorder due to severe hoarseness, but a treatment has not been established. Basic fibroblast growth factor (bFGF) therapies by either four‐time repeated local injections or regenerative surgery for vocal fold scar and sulcus have previously been reported, and favorable outcomes have been observed. In this study, we modified bFGF therapy using a single of bFGF injection, which may potentially be used in office procedures.

Study Design

Retrospective chart review.

Methods

Five cases of vocal fold sulcus, six cases of scars, seven cases of paralysis, and 17 cases of atrophy were treated by a local injection of bFGF. The injection regimen involved injecting 50 µg of bFGF dissolved in 0.5 mL saline only once into the superficial lamina propria using a 23‐gauge injection needle. Two months to 3 months after the injection, phonological outcomes were evaluated.

Results

The maximum phonation time (MPT), mean airflow rate, pitch range, speech fundamental frequency, jitter, and voice handicap index improved significantly after the bFGF injection. Furthermore, improvement in the MPT was significantly greater in patients with (in increasing order) vocal fold atrophy, scar, and paralysis. The improvement in the MPT among all patients was significantly correlated with age; the MPT improved more greatly in younger patients.

Conclusions

Regenerative treatments by bFGF injection—even a single injection—effectively improve vocal function in vocal fold lesions.

Level of Evidence

4 Laryngoscope, 125:E338–E344, 2015

Evaluation of the Poly(lactic-co-glycolic acid)/Pluronic F127 for Injection Laryngoplasty in Rabbits

Objective

Poly(lactic-co-glycolic acid) (PLGA) is an aliphatic polyester and one of the most commonly used synthetic biodegradable polymers for tissue engineering. The objectives of this study were to evaluate the biocompatibility of PLGA/Pluronic F127 in the vocal fold.

Study Design

A randomized, prospective, controlled animal study.

Setting

University laboratory.

Subjects and Methods

We used 18 New Zealand white rabbits, which were divided into 5% PLGA solution (n = 9) and 10% PLGA solution (n = 9) groups. The PLGA/Pluronic F127 solutions were injected into the rabbit vocal fold. Laryngoscopic exams were performed at 1, 4, and 8 weeks after implantation; then larynx specimens were sampled. High-speed video camera examination was performed for functional analysis of vocal mucosa vibration at 8 weeks after implantation. Also, we evaluated the amplitude of the mucosal wave from the laryngeal midline on high-speed recording. Histologic study of larynx specimen was performed at 4 and 8 weeks.

Results

All animals survived until the scheduled period. Laryngoscopic analysis showed that both 5% and 10% PLGA/Pluronic F127 maintained after 8 weeks after injection without significant inflammatory response. On functional analysis, high-speed camera examination revealed regular and symmetric contact of vocal fold mucosa without a distorted movement by injected PLGA/Pluronic F127. Histologically, no significant inflammation was observed in the injected vocal fold.

Conclusion

As a vocal fold injection material, PLGA/Pluronic F127 showed a good bio-compatibility without significant inflammatory response. Further experiment will follow to elucidate its role for drug or gene delivery into the vocal fold.

Biocompatibility and efficacy of collagen/gelatin sponge scaffold with sustained release of basic fibroblast growth factor on vocal fold fibroblasts in 3-dimensional culture

OBJECTIVE

Treatment of vocal fold scarring remains challenging. We have previously reported the therapeutic effects of local injection of basic fibroblast growth factor (bFGF) in animal models and humans. A novel collagen/gelatin sponge (CGS) is capable of sustained release of bFGF, which compensates for its quick absorption in vivo, avoiding multiple injections. This study aimed to evaluate the biocompatibility and efficacy of the CGS in rat vocal fold fibroblasts prior to human trials.

METHODS

Fibroblasts extracted from Sprague-Dawley rat vocal folds were seeded onto a CGS and then cultivated with bFGF at concentrations of 0, 10, and 100 ng/mL. Vocal fold fibroblast morphology, adhesion, proliferation, and gene expression were measured under these 3-dimensional conditions.

RESULTS

Cells adhered to the CGS from day 1. Although no significant differences in cell morphology were detected, cell proliferation was accelerated by bFGF administration. Expression of endogenous bFGF and hepatocyte growth factor was significantly up-regulated at 10 ng/mL bFGF. The expression of procollagen I and procollagen III was significantly suppressed, whereas HAS-1 and HAS-2 were up-regulated at 10 and 100 ng/mL bFGF.

CONCLUSION

The collagen/gelatin sponge is biocompatible with vocal fold fibroblasts and may be useful as a bFGF drug delivery system for the treatment of scarred vocal folds.