Transforming growth factor β3 for the prevention of vocal fold scarring

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

II.

Anti-inflammatory and Antioxidant Effects of Japanese Herbal Medicine Kyoseihatekigan on Vocal Fold Wound Healing

OBJECTIVES

The Japanese herbal medicine kyoseihatekigan (KHG) has been used to alleviate the symptoms of croaky voice and globus hystericus, and each of its components has anti-inflammatory and antioxidant effects. However, the mechanisms underlying these beneficial actions of KHG on the vocal folds remain largely unknown. We examined the effects of KHG on rat vocal fold wound healing and assessed its anti-inflammatory and antioxidant properties.

STUDY DESIGN

Animal model.

METHODS

The vocal folds of Sprague-Dawley rats were unilaterally injured under endoscopy. Rats were divided into three groups based on KHG dosing from pre injury day 4 to post injury day 3: 0 mg/kg/day (sham group), 500 mg/kg/day (1% KHG group) and 1000 mg/kg/day (2% KHG group). Histologic changes were examined to assess the degree of inflammation and oxidative stress at day 3, and fibrosis at day 56. In addition, gene expression related to pro-inflammatory cytokines and transforming growth factor-beta1 (TGF-β1) signaling was examined by quantitative real-time polymerase chain reaction (qPCR).

RESULTS

Histologic analysis showed that the 1% and 2% KHG treatments significantly decreased cell infiltration and the 4-hydroxy-2-nonenalx-immunopositive area, and increased hyaluronic acid at day 3. Both KHG treatments significantly decreased fibrosis at day 56. qPCR revealed that mRNA of interleukin-1β and cyclooxygenase-2 were significantly suppressed at day 1 and TGF-β1 mRNA was significantly downregulated at day 5 in both KHG groups.

CONCLUSIONS

The current findings suggest that KHG has anti-inflammatory and antioxidant effects in the early phase of vocal fold wound healing, which can lead to better wound healing with less scar formation.

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

Objective

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

Materials and Methods

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

Results

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

Conclusion

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

Level of evidence

II Prospective case series treatment.

The life-cycle and restoration of the human vocal fold

Objective

To better understand the challenges of designing therapies to treat damaged vocal fold lamina propria, it is essential to understand the biophysical and pathophysiological mechanisms involved in vocal fold development, maintenance, injury, and aging. This review critically analyses these points to try and direct future efforts and new strategies toward science-based solutions.

Data Sources & Review Methods

MEDLINE, Ovid Embase, and Wed of Science databases were used to identify relevant literature. A scoping review was performed following the preferred reporting items for systematic reviews and meta-analyses extension for scoping reviews checklist.

Results

The layered arrangement of the vocal fold, develops during early childhood and is maintained during adulthood unless injury occurs. The stellate cells of the macular flava are likely to be important in this process. The capacity for vocal fold regeneration and growth is lost during adulthood and repair results in the deposition of fibrous tissue from resident fibroblasts. With advancing age, viscoelastic tissue declines, possibly due to cell senescence. Strategies aimed at replacing fibrous tissue within the vocal folds must either stimulate resident cells or implant new cells to secrete healthy extracellular protein. Injection of basic fibroblast growth factor is the most widely reported therapy that aims to achieve this.

Conclusions

The pathways involved in vocal fold development, maintenance and aging are incompletely understood. Improved understanding has the potential to identify new treatment targets that could potentially overcome loss of vocal fold vibratory tissue.

FAK Inhibition Attenuates Corneal Fibroblast Differentiation In Vitro

Corneal fibrosis (or scarring) occurs in response to ocular trauma or infection, and by reducing corneal transparency, it can lead to visual impairment and blindness. Studies highlight important roles for transforming growth factor (TGF)-β1 and -β3 as modulators in corneal wound healing and fibrosis, leading to increased extracellular matrix (ECM) components and expression of α-smooth muscle actin (αSMA), a myofibroblast marker. In this study, human corneal fibroblasts (hCF) were cultured as a monolayer culture (2D) or on poly-transwell membranes to generate corneal stromal constructs (3D) that were treated with TGF-β1, TGF-β3, or TGF-β1 + FAK inhibitor (FAKi). Results show that hCF 3D constructs treated with TGF-β1 or TGF-β3 impart distinct effects on genes involved in wound healing and fibrosis-ITGAV, ITGB1, SRC and ACTA2. Notably, in the 3D construct model, TGF-β1 enhanced αSMA and focal adhesion kinase (FAK) protein expression, whereas TGF-β3 did not. In addition, in both the hCF 2D cell and 3D construct models, we found that TGF-β1 + FAKi attenuated TGF-β1-mediated myofibroblast differentiation, as shown by abrogated αSMA expression. This study concludes that FAK signaling is important for the onset of TGF-β1-mediated myofibroblast differentiation, and FAK inhibition may provide a novel beneficial therapeutic avenue to reduce corneal scarring.

Therapeutic Effect of Human Amniotic Epithelial Cells in Rat Models of Intrauterine Adhesions

As a refractory fibrosis disease, intrauterine adhesions (IUAs) is defined as fibrosis of the physiological endometrium. Although hysteroscopic adhesiolysis is widely recommended as an effective treatment, prognosis and recurrence remain poor in severe cases. Recently, stem cell therapy has been promoted as a promising treatment for IUAs. The ability of human amniotic epithelial cells (hAECs), emerging as a new candidate for stem cell therapy, to treat IUAs has not been demonstrated. To study the potential effects of hAECs on IUAs, we created an IUA rat model using mechanical injury and injected cultured primary hAECs into the rats’ uteri. Next, we observed the morphological structure of endometrial thickness and glands using hematoxylin and eosin staining, and we detected extracellular-matrix collagen deposition using Masson staining. In addition, we performed immunohistochemical staining and reverse-transcription polymerase chain reaction (RT-PCR) to investigate potential fibrosis molecules and angiogenesis factors 7 d after hAECs transplantation. Finally, we detected estrogen receptor (ER) and growth factors via RT-PCR to verify the molecular mechanism underlying cell therapy. In the IUA rat models, endometrial thickness and endometrial glands proliferated and collagen deposition decreased significantly after hAEC transplantation. We found that during the recovery of injured endometrium, the crucial fibrosis marker transforming growth factor-β (TGF-β) was regulated and angiogenesis occurred in the endometrial tissue with the up-regulation of vascular endothelial growth factor. Furthermore, hAECs were shown to promote ER expression in the endometrium and regulate the inflammatory reaction in the uterine microenvironment. In conclusion, these results demonstrated that hAEC transplantation could inhibit the progression of fibrosis and promote proliferation and angiogenesis in IUA rat models. The current study suggests hAECs as a novel stem cell candidate in the treatment of severe IUA.

Characterization of intrauterine growth, proliferation and biomechanical properties of the murine larynx

Current research approaches employ traditional tissue engineering strategies to promote vocal fold (VF) tissue regeneration, whereas recent novel advances seek to use principles of developmental biology to guide tissue generation by mimicking native developmental cues, causing tissue or allogenic/autologous progenitor cells to undergo the regeneration process. To address the paucity of data to direct VF differentiation and subsequent new tissue formation, we characterize structure-proliferation relationships and tissue elastic moduli over embryonic development using a murine model. Growth, cell proliferation, and tissue biomechanics were taken at E13.5, E15.5, E16.5, E18.5, P0, and adult time points. Quadratic growth patterns were found in larynx length, maximum transverse diameter, outer dorsoventral diameter, and VF thickness; internal VF length was found to mature linearly. Cell proliferation measured with EdU in the coronal and transverse planes of the VFs was found to decrease with increasing age. Exploiting atomic force microscopy, we measured significant differences in tissue stiffness across all time points except between E13.5 and E15.5. Taken together, our results indicate that as the VF mature and develop quadratically, there is a concomitant tissue stiffness increase. Greater gains in biomechanical stiffness at later prenatal stages, correlated with reduced cell proliferation, suggest that extracellular matrix deposition may be responsible for VF thickening and increased biomechanical function, and that the onset of biomechanical loading (breathing) may also contribute to increased stiffness. These data provide a profile of VF biomechanical and growth properties that can guide the development of biomechanically-relevant scaffolds and progenitor cell differentiation for VF tissue regeneration.

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.

Antioxidant Properties of Tonsil-Derived Mesenchymal Stem Cells on Human Vocal Fold Fibroblast Exposed to Oxidative Stress

The therapeutic potential of tonsil-derived mesenchymal stem cells (TMSCs) has been proved in several in vitro and in vivo models based on their antioxidative capacity. Oxidative stress is involved in the formation of vocal fold scars and the aging of vocal folds. However, few studies have examined the direct correlation between oxidative damage and reconstitution of extracellular matrix (ECM) in the vocal fold fibrosis. We, therefore, sought to investigate the impact of oxidative stress on cell survival and ECM production of human vocal fibroblasts (hVFFs) and the protective effects elicited by TMSCs against oxidative damages in hVFFs. hVFFs were exposed to different concentrations of tert-butyl hydroperoxide in the presence or absence of TMSCs. Cell viability and reactive oxygen species (ROS) production were assessed to examine the progression of oxidative stress in vitro. In addition, expression patterns of ECM-associated factors including various collagens were examined by real-time PCR and immunocytochemical analysis. We found that both cell viability and proliferation capacity of hVFFs were decreased following the exposure to tBHP in a dose-dependent manner. Furthermore, tBHP treatment induced the generation of ROS and reactive aldehydes, while it decreased endogenous activity of antioxidant enzymes in hVFF. Importantly, TMSCs could rescue these oxidative stress-associated damages of hVFFs. TMSCs also downregulated tBHP-mediated production of proinflammatory cytokines in hVFFs. In addition, coculture with TMSC could restore the endogenous matrix metalloproteinase (MMP) activity of hVFFs upon tBHP treatment and, in turn, reduce the oxidative stress-induced ECM accumulation in hVFFs. We have, therefore, shown that the changes in hVFF proliferative capacity and ECM gene expression induced by oxidative stress are consistent with in vivo phenotypes observed in aging vocal folds and vocal fold scarring and that TMSCs may function to reduce oxidative stress in aging vocal folds.

Effects of phenytoin injection on vocal cord healing after mechanical trauma: An experimental study

Background/aim

Phenytoin is an anticonvulsant drug which causes fibroblast proliferation, collagen synthesis, and an increase in epidermal growth factor. Therefore, the aim of the present study is to evaluate the effect of phenytoin injection on the wound healing process in rats with vocal cord injury by histopathological methods.

Materials and methods

The vocal cords of 10 albino Wistar rats were damaged bilaterally; the left vocal cord was kept as the control group. Phenytoin was injected in the right vocal cord. Ten rats were sacrificed. The thickness of the lamina propria and density of the fibroblast and collagen were evaluated histopathologically.

Results

Thickness of the lamina propria was 18.0 ± 7.1 µm in the control group, 65.5 ± 10.7 µm in the phenytoin group. The density of fibroblast and collagen were statistically lower in the control group compared the phenytoin group (P < 0.05).

Conclusion

Phenytoin injection in rats after vocal cord injury significantly increased the thickness of the lamina propria and density of fibroblast and regular and mature collagen in the lamina propria. The findings in our study provide a feasible scientific view for adding phenytoin treatment to vocal cord surgeries in otolaryngology practice, but further studies are needed in order to evaluate the use of phenytoin in preventing the formation of scar tissue and possible effects on vocal cord vibration in humans after vocal cord injury.

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.

Modeling fibrosis using fibroblasts isolated from scarred rat vocal folds

Following injury, pathologically activated vocal fold fibroblasts (VFFs) can engage in disordered extracellular matrix (ECM) remodeling, leading to VF fibrosis and impaired voice function. Given the importance of scar VFFs to phenotypically appropriate in vitro modeling of VF fibrosis, we pursued detailed characterization of scar VFFs obtained from surgically injured rat VF mucosae, compared with those obtained from experimentally naïve, age-matched tissue. Scar VFFs initially exhibited a myofibroblast phenotype characterized by increased proliferation, increased Col1a1 transcription and collagen, type I synthesis, increased Acta2 transcription and α-smooth muscle actin synthesis, and enhanced contractile function. These features were most distinct at passage 1 (P1); we observed a coalescence of the scar and naïve VFF phenotypes at later passages. An empirical Bayes statistical analysis of the P1 cell transcriptome identified 421 genes that were differentially expressed by scar, compared with naïve, VFFs. These genes were primarily associated with the wound response, ECM regulation, and cell proliferation. Follow-up comparison of P1 scar VFFs and their in vivo tissue source showed substantial transcriptomic differences. Finally, P1 scar VFFs responded to treatment with hepatocyte growth factor and transforming growth factor-β3, two biologics with reported therapeutic value. Despite the practical limitations inherent to working with early passage cells, this experimental model is easily implemented in any suitably equipped laboratory and has the potential to improve the applicability of preclinical VF fibrosis research.

Molecular insights on the effect of TGF-β1/-β3 in human corneal fibroblasts

Transforming growth factor β (TGF-β) plays a critical role in wound healing and the pathogenesis of fibrosis (scarring). Three isoforms of TGF-β have been identified in mammals. Previous studies have shown that the addition of TGF-β1 (T1) or -β2 (T2) to human corneal fibroblasts (HCF) cultured in a 3-dimensional construct resulted in a fibrotic matrix, while the addition of TGF-β3 (T3) resulted in the production of enhanced non-fibrotic matrix as compared to control (Vitamin C [VitC] only). In the current investigation, we undertook the molecular comparison of fibrosis-related gene expression in T1 or T3-treated HCF to gain further insights into the regulation and roles of these two isoforms on the fibrotic response. HCF were cultured in 100 mm dishes in basic medium (Eagles minimum essential medium [EMEM] with 10% fetal bovine serum [FBS]). At 70-80% confluency, cells were exposed to basic medium with 0.5 mM 2-O-α-d-glucopyranosyl-l-ascorbic acid (VitC) ± 2 ng/ml of T1 or T3. After 4 h or 3 days, cells were harvested, and mRNA or protein was isolated. Fibrosis related mRNA levels were assayed using a commercial qRT-PCR Array. Selected proteins were examined using Western blotting (WB). Experiments were performed 6 times for the qRT-PCR and 4 times for WB for each condition. qRT-PCR results showed that most of the fibrosis-related genes were up or downregulated in HCF exposed to T1 or T3 as compared with VitC control. At 4 h, only Smad7 expression was significantly altered in T3-treated HCF, compared to T1, and at 3 days, five genes were altered. WB confirmed that T1 significantly decreased Smad7 expression compared to T3 and control, and that the expression of thrombospondin-1 in T3-stimulated HCF was enhanced compared to T1-treated cells. Finally, both T1 and T3 decreased Smad3 expression dramatically at both time points. At early time points, T1 and T3 have similar effects on expression of fibrosis related genes; however, with a longer exposure, an increasing number of genes were differentially expressed. Interestingly, most of the differentially expressed gene products are secreted by the cells and may be related to the modulation of extracellular matrix.

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.

Novel experimental rabbit model of anterior glottic web formation

CONCLUSION

The rabbit model of anterior glottic web (AGW) formation using the laryngofissure technique resulted in reproducible and stable AGW formation that may facilitate research into this area.

OBJECTIVE

To introduce and validate a novel experimental animal model of AGW formation using the rabbit.

METHODS

The inner larynges of eight New Zealand white rabbits were exposed through the laryngofissure technique. The mucosa of the bilateral true vocal fold was stripped off using the bevel of a needle tip. On the basis of the laryngoscopic findings at 8 weeks postoperatively, the extent of AGW was measured, and the success of this procedure was validated. Laryngeal specimens were sampled at 8 weeks for high-speed recording and histological analysis.

RESULTS

In seven (87.5%) rabbits, laryngoscopic examination revealed the formation of a scar band involving the anterior commissure. The mean extent of AGW ratio on the left and right sides was 0.58 ± 0.073 and 0.55 ± 0.075, respectively. The symmetric formation of AGW (p = 0.655, p = 0.128) and stability of the AGW procedure (p = 0.491, left; p = 0.501, right) were statistically validated. On high-speed recording, the vocal mucosal wave was hindered by AGW formation. Histologically, fibro-connective tissue, especially collagen fiber, was observed in the anterior commissure.

Scarless wound healing: chasing the holy grail

Over 100 million patients acquire scars in the industrialized world each year, primarily as a result of elective operations. Although undefined, the global incidence of scarring is even larger, extending to significant numbers of burn and other trauma-related wounds. Scars have the potential to exert a profound psychological and physical impact on the individual. Beyond aesthetic considerations and potential disfigurement, scarring can result in restriction of movement and reduced quality of life. The formation of a scar following skin injury is a consequence of wound healing occurring through reparative rather than regenerative mechanisms. In this article, the authors review the basic stages of wound healing; differences between adult and fetal wound healing; various mechanical, genetic, and pharmacologic strategies to reduce scarring; and the biology of skin stem/progenitor cells that may hold the key to scarless regeneration.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Epithelial cells are active participants in vocal fold wound healing: an in vivo animal model of injury

Vocal fold epithelial cells likely play an important, yet currently poorly defined, role in healing following injury, irritation and inflammation. In the present study, we sought to identify a possible role for growth factors, epidermal growth factor (EGF) and transforming growth factor-beta 1 (TGFβ1), in epithelial regeneration during wound healing as a necessary first step for uncovering potential signaling mechanisms of vocal fold wound repair and remodeling. Using a rat model, we created unilateral vocal fold injuries and examined the timeline for epithelial healing and regeneration during early and late stages of wound healing using immunohistochemistry (IHC). We observed time-dependent secretion of the proliferation marker, ki67, growth factors EGF and TGFβ1, as well as activation of the EGF receptor (EGFR), in regenerating epithelium during the acute phase of injury. Ki67, growth factor, and EGFR expression peaked at day 3 post-injury. Presence of cytoplasmic and intercellular EGF and TGFβ1 staining occurred up to 5 days post-injury, consistent with a role for epithelial cells in synthesizing and secreting these growth factors. To confirm that epithelial cells contributed to the cytokine secretion, we examined epithelial cell growth factor secretion in vitro using polymerase chain reaction (PCR). Cultured pig vocal fold epithelial cells expressed both EGF and TGFβ1. Our in vivo and in vitro findings indicate that epithelial cells are active participants in the wound healing process. The exact mechanisms underlying their roles in autocrine and paracrine signaling guiding wound healing await study in a controlled, in vitro environment.

Hyaluronic acid behavior in the lamina propria of the larynx with advancing age

OBJECTIVES

To analyze the hyaluronic acid behavior in the lamina propria of the larynx with advancing age.

STUDY DESIGN

Prospective study.

SETTING

UNESP-Univ Estadual Paulista, Botucatu Medical School, Brazil.

SUBJECTS AND METHODS

Thirty vocal folds were obtained at necropsy from 10 adult males (30-50 years old) and 20 geriatric males (10: 60-75 years old; 10: over 76 years old). Midmembranous vocal fold sections were subjected to immunohistochemical reactions. Digital imaging software (ImageJ) was used to quantify the hyaluronic acid distribution over the lamina propria of vocal folds, from superficial to deep layers.

RESULTS

Hyaluronic acid distribution was homogeneous for the larynges, at both superficial and deep layers (41.6 and 38.5, respectively). For both 30- to 50-year-old men geriatric age groups, hyaluronic acid level was lower at both layers.

CONCLUSION

Hyaluronic acid level in the lamina propria of the larynx of geriatric men decreases with advancing age at both layers of the lamina.

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.

Mechanotransduction and fibrosis

Scarring and tissue fibrosis represent a significant source of morbidity in the United States. Despite considerable research focused on elucidating the mechanisms underlying cutaneous scar formation, effective clinical therapies are still in the early stages of development. A thorough understanding of the various signaling pathways involved is essential to formulate strategies to combat fibrosis and scarring. While initial efforts focused primarily on the biochemical mechanisms involved in scar formation, more recent research has revealed a central role for mechanical forces in modulating these pathways. Mechanotransduction, which refers to the mechanisms by which mechanical forces are converted to biochemical stimuli, has been closely linked to inflammation and fibrosis and is believed to play a critical role in scarring. This review provides an overview of our current understanding of the mechanisms underlying scar formation, with an emphasis on the relationship between mechanotransduction pathways and their therapeutic implications.

Preliminary results of antiscarring therapy in the prevention of postendoscopic esophageal mucosectomy strictures

BACKGROUND

Esophageal endoscopic submucosal dissection (ESD) is an effective minimally invasive therapy for early esophageal cancer and high-grade Barrett dysplasia. However, esophageal stricture formation after circumferential or large ESD has limited its wide adoption. Mitomycin C (MMC), halofuginone (Hal), and transforming growth factor β3 (TGF-β3) exhibits antiscarring effects that may prevent post-ESD stricture formation.

METHODS

Using endoscopic mucosectomy (EEM) technique, an 8- to 10-cm-long circumferential esophageal mucosal segment was excised in a porcine model. The site was either untreated (control, n = 6) or received 40 evenly distributed injections of antiscarring agent immediately and at weeks 1 and 2. High and low doses were used: MMC 5 mg (n = 2), 0.5 mg (n = 2); Hal 5 mg (n = 2), 1.5 mg (n = 2), 0.5 mg (n = 2); TGF-β3 2 μg (n = 2), 0.5 μg (n = 2). The degree of stricture formation was determined by the percentage reduction of the esophageal lumen on weekly fluoroscopic examination. Animals were euthanized when strictures exceeded 80 % or the animals were unable to maintain weight.

RESULTS

The control group had a luminal diameter reduction of 78.2 ± 10.9 % by 2 weeks and were euthanized by week 3. Compared at 2 weeks, the Hal group showed a decrease in mean stricture formation (68.4 % low dose, 57.7 % high dose), while both TGF-β3 dosage groups showed no significant change (65.3 % low dose, 76.2 % high dose). MMC was most effective in stricture prevention (53.6 % low dose, 35 % high dose). Of concern, the esophageal wall treated with high-dose MMC appeared to be necrotic and eventually led to perforation. In contrast, low dose MMC, TGF-β3 and Hal treated areas appeared re-epithelialized and healthy.

CONCLUSIONS

Preliminary data on MMC and Hal demonstrated promise in reducing esophageal stricture formation after EEM. More animal data are needed to perform adequate statistical analysis in order to determine overall efficacy of antiscarring therapy.

TGF-β3 modulates the inflammatory environment and reduces scar formation following vocal fold mucosal injury in rats

Transforming growth factor (TGF)-β1 and TGF-β3 have been reported to exert differential effects on wound healing, and possibly even account for tissue-specific differences in scar formation. Scarring is particularly detrimental in the vocal fold mucosa (VFM), where destruction of the native extracellular matrix causes irreparable biomechanical changes and voice impairment. Here, in a series of in vitro and in vivo experiments, we identified differences in TGF-β1 and TGF-β3 transcription and immunolocalization to various cell subpopulations in naïve and injured rat VFM, compared with oral mucosa (which undergoes rapid healing with minimal scar) and skin (which typically heals with scar). Treatment of cultured human vocal fold fibroblasts with TGF-β3 resulted in less potent induction of profibrotic gene transcription, extracellular matrix synthesis and fibroblast-myofibroblast differentiation, compared with treatment with TGF-β1 and TGF-β2. Finally, delivery of exogenous TGF-β3 to rat VFM during the acute injury phase modulated the early inflammatory environment and reduced eventual scar formation. These experiments show that the TGF-β isoforms have distinct roles in VFM maintenance and repair, and that TGF-β3 redirects wound healing to improve VFM scar outcomes in vivo.

Coexistence of elastic fibers with hyaluronic acid in the human urethral sphincter complex: a histological study

PURPOSE

To promote the prevention and treatment of urethral sphincteric dysfunction, we examined the distribution of elastic fibers around the urethral sphincter complex and the histological localization of hyaluronic acid in relation to elastic fiber architecture.

MATERIALS AND METHODS

Using elastica-Masson staining as well as biotinated hyaluronic acid binding protein, we examined specimens of the urethral sphincter complex obtained from 14 elderly Japanese cadavers, including 10 men and 4 women. As a control, we also observed other striated muscles in male cadavers.

RESULTS

Elastic fibers were densely distributed throughout the submucosal and smooth muscle layers along the entire length of the male urethra, including the prostatic urethra. The levator ani fascia and rhabdosphincter also contained abundant elastic fibers. An intramuscular elastic net was seen in the rhabdosphincter but not in other striated muscles. Strong staining for hyaluronic acid was evident in the submucosa and smooth muscle sphincter of the urethra but not in the levator ani fascia or rhabdosphincter, suggesting that elastic fibers and hyaluronic acid might interact at the former sites. Gender related differences in the distribution of elastic fibers and hyaluronic acid were noted with a much lower density of elastic fibers and hyaluronic acid staining in women than in men.

CONCLUSIONS

Urethral sites where elastic fibers and hyaluronic acid coexist could be targeted for the prevention and treatment of urethral sphincteric insufficiency. These findings should improve our understanding of the human urethral sphincter complex.

Elastic fiber-mediated enthesis in the human middle ear

Adaptation to constant vibration (acoustic oscillation) is likely to confer a specific morphology at the bone-tendon and bone-ligament interfaces at the ear ossicles, which therefore represent an exciting target of enthesis research. We histologically examined (i) the bone attachments of the tensor tympani and stapedius muscles and (ii) the annular ligament of the incudostapedial joint obtained from seven elderly donated cadavers. Notably, both aldehyde-fuchsin and elastic-Masson staining demonstrated that the major fibrous component of the entheses was not collagen fibers but mature elastic fibers. The positive controls for elastic fiber staining were the arterial wall elastic laminae included in the temporal bone materials. The elastic fibers were inserted deeply into the type II collagen-poor fibrocartilage covering the ear ossicles. The muscle tendons were composed of an outer thin layer of collagen fibers and an inner thick core of elastic fibers near the malleus or stapes. In the unique elastic fiber-mediated entheses, hyaluronan, versican and fibronectin were expressed strongly along the elastic fibers. The hyaluronan seemed to act as a friction-reducing lubricant for the elastic fibers. Aggrecan was labeled strongly in a disk- or plica-like fibrous mass on the inner side of the elastic fiber-rich ligament, possibly due to compression stress from the ligament. Tenascin-c was not evident in the entheses. The elastic fiber-mediated entheses appeared resistant to tissue destruction in an environment exposed to constant vibration. The morphology was unlikely to be the result of age-related degeneration.