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

Therapeutic Efficacy of Bovine Basic Fibroblast Growth Factor Combined with Ultrapulsed Fractional CO2 Laser in Acne Scars: Randomized Controlled Trial

Objective

To observe the therapeutic efficacy of ultrapulsed fractional CO2 laser combined with bovine basic fibroblast growth factor (bFGF) on acne scars, so as to provide clinical evidence for future treatment of acne scars.

Methods

One hundred and twenty patients with acne scars admitted between October 2021 and August 2022 were selected as the research participants, of which 60 cases treated with bFGF plus ultrapulsed fractional CO2 laser were regarded as the research group (RG) and 60 cases with ultrapulsed fractional CO2 laser therapy alone were set as the control group (CG). The clinical efficacy, Échelle d'évaluation clinique des cicatrices d'acné (ECCA) score, and scar base depth before and after treatment were comparatively analyzed, and changes in skin pore value, texture value and skin barrier function were detected. Finally, the duration of redness, scabbing and erythema after treatment and the incidence of adverse reactions after treatment were counted.

Results

A higher overall response rate was determined in RG versus CG (P<0.05). Besides, RG was lower than CG in post-treatment ECCA score, scar base depth, skin pore value, texture value and transepidermal water loss (TEWL), and higher in skin water and epidermal oil content (P<0.05). Moreover, the duration of redness, scabbing and erythema was shorter and the incidence of adverse reactions was lower in RG than in CG after treatment (P<0.05).

Conclusion

The combination of bFGF and ultrapulsed fractional CO2 laser is highly effective and safe in the treatment of acne scars, which reserves widespread use in clinical practice.

Vocal fold injury models in rats: a literature review on techniques and methodology

This study reviewed the current literature on technical aspects regarding controlled vocal fold injuries in the rat model. Data from PubMed, Embase, and Scopus database for English language literature was collected to identify methodological steps leading to a controlled surgical injury of the rat vocal fold. Inclusion criteria: full disclosure of anesthesia protocol, positioning of the rat for surgery, vocal fold visualization method, instrumentation for vocal fold injury, vocal fold injury type. Articles with partial contribution were evaluated and separately included due to the limited number of original methodologies. 724 articles were screened, and eleven articles were included in the analysis. Anesthesia: ketamine hydrochloride and xylazine hydrochloride varied in dose from 45 mg/kg and 4.5 mg/kg to 100 mg/kg and 10 mg/kg. Visualization: The preferred method was the 1.9 mm, 25-30 degree endoscopes. The widest diameter endoscope used was 2.7 mm with a 0 or 30 degree angle of view. Instruments for lesion induction range from 18 to 31G needles, microscissors, micro forceps to potassium titanyl phosphate, and blue light lasers. Injury types: vocal fold stripping was the main injury type, followed by vocal fold scarring and charring. One article describes scaffold implantation with injury to the superior aspect of the vocal fold. Rats are good candidates for in vivo larynx and vocal folds research. A more standardized approach should be considered regarding the type of vocal fold injury to ease data comparison.

Polycyclic Aromatic Hydrocarbons from Fine Particulate Matter Induce Oxidative Stress and the Inflammatory Response in Human Vocal Fold Fibroblast Cells

Polycyclic aromatic hydrocarbons (PAHs) are toxicants in particulate matter (PM). The vocal fold, part of the larynx and a key structure for voicing, is always in contact with air. In recent epidemic studies, PM was shown to cause laryngitis; however, the basic mechanism has not been evaluated. In the present study, intracellular reactive oxygen species (ROS) and proinflammatory cytokine levels were analyzed after exposing human vocal fold fibroblasts (hVFFs) to PM standard reference material (SRM 2786). Expression levels of the aryl hydrocarbon receptor (AhR) and Cytochrome P450 Family 1 Subfamily A Member 1 (CYP1A1) were also evaluated. PM induced ROS formation and proinflammatory cytokines via the AhR CYP1A1 pathway and caused lipid peroxidation and DNA damage. Blocking AhR or CYP1A1 production using siRNAs significantly decreased ROS production and IL-6 and IL-9 expression in PM-exposed hVFFs, thus protecting the cells against oxidative stress. These results confirm that PAHs in PM play an important role in cell damage and inflammation, confirming a basic pathophysiologic relationship between PM exposure and laryngitis.

In vitro mechanical vibration down-regulates pro-inflammatory and pro-fibrotic signaling in human vocal fold fibroblasts

INTRODUCTION

Voice rest following phonotrauma or phonosurgery has a considerable clinical impact, but clinical recommendations are inconsistent due to inconclusive data. As biopsies of the vocal folds (VF) for molecular biology studies in humans are unethical, we established a new in vitro model to explore the effects of vibration on human vocal fold fibroblasts (hVFF) in an inflammatory and normal state, which is based on previously published models.

METHODS

By using a phonomimetic bioreactor we were able to apply predefined vibrational stress patterns on hVFF cultured under inflammatory or normal conditions. Inflammatory and pro-fibrotic stimuli were induced by interleukin (IL)1β and transforming growth factor (TGF)β1, respectively. Mechanical stimulation was applied four hours daily, over a period of 72 hours. Outcome measurements comprised assessment of extracellular matrix (ECM)-related components, angiogenic factors, and inflammatory and fibrogenic markers on gene expression and protein levels.

RESULTS

Under inflammatory conditions, the inflammatory cytokine IL11, as well as the myofibroblast marker alpha smooth muscle actin (α-SMA) were significantly reduced when additional vibration was applied. The desirable anti-fibrotic ECM component hyaluronic acid was increased following cytokine treatment, but was not diminished following vibration.

CONCLUSION

Our experiments revealed the effect of vibrational stress on hVFF in an inflammatory state. Elevated levels of certain pro-inflammatory/pro-fibrotic factors could be mitigated by additional vibrational excitation in an in vitro setting. These findings corroborate clinical studies which recommend early voice activation following an acute event.

Effect of Urban Particulate Matter on Vocal Fold Fibrosis through the MAPK/NF-κB Signaling Pathway

Particulate matter (PM) is an environmental exposure factor that adversely affects human health. PM is a risk factor for various diseases. However, the mechanism by which PM affects the vocal folds (VF) has not yet been evaluated. Thus, we investigated the cytotoxic effects of PM on human vocal fold fibroblasts (hVFF) and the underlying signaling pathways. hVFF were isolated from human VF. The effect of PM on hVFF, and the underlying mechanism, were analyzed using Western blot, quantitative real-time polymerase chain reaction, and flow cytometry. In addition, a histological evaluation was performed in animal experiments. Cell proliferation decreased after the PM treatment. PM increased the expression of interleukin (IL)-6 and IL-1β. The generation of reactive oxygen species (ROS) in PM-treated hVFF and subsequent activation of the mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways were confirmed. Furthermore, PM increased the expression of fibrosis-related markers and induced the accumulation of collagen in the extracellular matrix. As a result, PM exposure significantly enhances the inflammatory response on VF through the ROS-mediated activation of the MAPK and NF-κB signaling pathways. In addition, PM promotes differentiation into myofibroblasts and induces fibrosis. These results suggest that PM triggers an inflammatory reaction through ROS production and causes VF fibrosis.

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.

A tissue-specific, injectable acellular gel for the treatment of chronic vocal fold scarring

Gel-based injectable biomaterials have significant potential for treating vocal fold defects such as scarring. An ideal injectable for vocal fold lamina propria restoration should mimic the microenvironment of the lamina propria to induce scarless wound healing and functional tissue regeneration. Most current synthetic or natural injectable biomaterials do not possess the same level of complex, tissue-specific constituents as the natural vocal fold lamina propria. In this study we present a newly-developed injectable gel fabricated from decellularized bovine vocal fold lamina propria. Blyscan assay and mass spectrometry indicated that the vocal fold-specific gel contained a large amount of sulfated glycosaminoglycans and over 250 proteins. Gene Ontology overrepresentation analysis revealed that the proteins in the gel dominantly promote antifibrotic biological process. In vivo study using a rabbit vocal fold injury model showed that the injectable gel significantly reduced collagen density and decreased tissue contraction of the lamina propria in vocal folds with chronic scarring. Furthermore, this acellular gel only elicited minimal humoral immune response after injection. Our findings suggested that the tissue-specific, injectable extracellular matrix gel could be a promising biomaterial for treating vocal fold scarring, even after the formation of mature scar. STATEMENT OF SIGNIFICANCE: Vocal fold lamina propria scarring remains among the foremost therapeutic challenges in the management of patients with voice disorders. Surgical excision of scar may cause secondary scarring and yield inconsistent results. The present study reports an extracellular matrix-derived biomaterial that demonstrated antifibrotic effect on chronic scarring in vocal fold lamina propria. Its injectability minimizes the invasiveness of the delivery procedure and the degree of mucosal violation. In this work we also describe a new methodology which can more accurately identify proteins from the complex mixture of an acellular extracellular matrix gel by excluding interfering peptides produced during the enzymatic digestion in gel fabrication.

Towards a Physiological Scale of Vocal Fold Agent-Based Models of Surgical Injury and Repair: Sensitivity Analysis, Calibration and Verification

Agent based models (ABM) were developed to numerically simulate the biological response to surgical vocal fold injury and repair at the physiological level. This study aimed to improve the representation of existing ABM through a combination of empirical and computational experiments. Empirical data of vocal fold cell populations including neutrophils, macrophages and fibroblasts were obtained using flow cytometry up to four weeks following surgical injury. Random Forests were used as a sensitivity analysis method to identify model parameters that were most influential to ABM outputs. Statistical Parameter Optimization Tool for Python was used to calibrate those parameter values to match the ABM-simulation data with the corresponding empirical data from Day 1 to Day 5 following surgery. Model performance was evaluated by verifying if the empirical data fell within the 95% confidence intervals of ABM outputs of cell quantities at Day 7, Week 2 and Week 4. For Day 7, all empirical data were within the ABM output ranges. The trends of ABM-simulated cell populations were also qualitatively comparable to those of the empirical data beyond Day 7. Exact values, however, fell outside of the 95% statistical confidence intervals. Parameters related to fibroblast proliferation were indicative to the ABM-simulation of fibroblast dynamics in final stages of wound healing.

Treatment of intractable oral ulceration with an oral mucosa equivalent

The current use of steroids or pharmacological immunomodulators for the treatment of intractable oral ulceration is ineffective, necessitating newer cell-based therapeutic approaches. We examined the potential efficacy of an oral mucosa equivalent developed in this study in an in vivo model of repeat major oral ulceration mimicking the intractable oral ulceration observed clinically. Oral mucosal samples and plasma fibrin were obtained from Sprague-Dawley rats. The oral mucosa equivalents were prepared with cultured mucosal keratinocytes and plasma fibrin mixed with cultured fibroblasts. Ulcers were chemically induced on the rat buccal mucosa thrice in 3 weeks and covered with or without mucosa equivalents. Gross and microscopic findings and mRNA expression levels were compared between the ulcer control and mucosa equivalent groups. Oral mucosal keratinocytes and fibroblasts were cultured in vitro to achieve high viability and colony-forming efficiency. The equivalents showed epithelial and subepithelial structures similar to those of oral mucosa and exhibited high p63 positivity. In the in vivo study, ulceration was resolved earlier without significant granulation or scarring in the equivalent group than in control group (p < 0.05). Microscopic examinations revealed rapid re-epithelialization and less fibrosis in the equivalent group than in the control group (p < 0.05). Mucosa equivalent-covered ulcers showed histological characteristics similar to those of the normal buccal mucosa and exhibited lower expression of TGFB1, ACTA2, and FN1 mRNAs than the control group. The in vitro-engineered oral mucosa equivalent promotes ulcer healing without scarring and functional deficits. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1779-1785, 2019.

Protective effect of biodegradable nerve conduit against peripheral nerve adhesion after neurolysis

OBJECTIVE Peripheral nerve adhesion caused by extraneural and intraneural scar formation after neurolysis leads to nerve dysfunction. The authors previously developed a novel very flexible biodegradable nerve conduit composed of poly(L-lactide) and poly(ε-caprolactone) for use in peripheral nerve regeneration. In the present study, they investigated the effect of protective nerve wrapping on preventing adhesion in a rat sciatic nerve adhesion model. METHODS Rat sciatic nerves were randomly assigned to one of the following four groups: a no-adhesion group, which involved neurolysis alone without an adhesion procedure; an adhesion group, in which the adhesion procedure was performed after neurolysis, but no treatment was subsequently administered; a nerve wrap group, in which the adhesion procedure was performed after neurolysis and protective nerve wrapping was then performed with the nerve conduit; and a hyaluronic acid (HA) group, in which the adhesion procedure was performed after neurolysis and nerve wrapping was then performed with a 1% sodium HA viscous solution. Six weeks postoperatively, the authors evaluated the extent of scar formation using adhesion scores and biomechanical and histological examinations and assessed nerve function with electrophysiological examination and gastrocnemius muscle weight measurement. RESULTS In the adhesion group, prominent scar tissue surrounded the nerve and strongly adhered to the nerve biomechanically and histologically. The motor nerve conduction velocity and gastrocnemius muscle weight were the lowest in this group. Conversely, the adhesion scores were significantly lower, motor nerve conduction velocity was significantly higher, and gastrocnemius muscle weight was significantly higher in the nerve wrap group than in the adhesion group. Additionally, the biomechanical breaking strength was significantly lower in the nerve wrap group than in the adhesion group and HA group. The morphological properties of axons in the nerve wrap group were preserved. Intraneural macrophage invasion, as assessed by the number of CD68- and CCR7-positive cells, was less severe in the nerve wrap group than in the adhesion group. CONCLUSIONS The nerve conduit prevented post-neurolysis peripheral nerves from developing adhesion and allowed them to maintain their nerve function because it effectively blocked scarring and prevented adhesion-related damage in the peripheral nerves.

Tissue engineering in the larynx and airway

PURPOSE OF REVIEW

Tissue engineering is a rapidly expanding field in medicine and involves regeneration and restoration of many organs, including larynx and the airways. Currently, this is not included in routine practice; however, a number of clinical trials in humans are ongoing or starting. This review will cover publications during the past 2 years and the focus is on larynx and trachea.

RECENT FINDINGS

Recent reports concern the development and investigations of cell therapies, including biological factors such as growth factors which promote healing of damage and increased vascular support of the tissue. A separate section concerns studies of stromal cells and stem cells in tissue engineering. Cell therapies and treatment with biological active factors are often combined with the development of scaffolds to support or reconstruct the soft tissue in the larynx or the cartilages in trachea or larynx. New techniques for scaffold construction, such as 3D printing, are developed. The trend in the recent publications is to combine these methods.

SUMMARY

Recent advances in tissue engineering of the larynx and trachea include the development of cell therapies or treatment with biological active factors often in combination with scaffolds.