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

Acute Effects of Steroids on Vocal Fold Epithelium Post-injury in a Preclinical Model

INTRODUCTION

Glucocorticoids (GCs) are commonly prescribed for laryngeal indications due to their potent anti-inflammatory properties. However, GCs effect on vocal fold (VF) epithelial morphology and barrier function following injury is overlooked and may be key to efficacy. In this study, the effects of GCs on epithelial morphology and barrier function were quantified in injured VFs. We seek to increase our understanding of biochemical processes underlying GC mechanisms to refine therapeutic strategies.

METHODS

Microflap injury was induced in 65 rabbits. Seven days after injury, animals received bilateral 20 μL intracordal injections of saline, dexamethasone, methylprednisolone, or triamcinolone (n = 15 per condition). Five rabbits in each condition were euthanized 1, 7, or 60 days following treatment. An additional five animals served as non-injured/untreated controls. To quantify transepithelial electrical resistance (TEER), 1 mm epithelial biopsies were placed in an Ussing chamber. The contralateral VF was processed for transmission electron microscopy and epithelial depth analysis.

RESULTS

At 60 days, GC treatment maintained TEER levels similar to non-injured/untreated controls. However, triamcinolone reduced TEER compared with saline-treated conditions. Acutely, epithelial hyperplasia typically persisted in all injured VFs. At 60 days, only dexamethasone and triamcinolone increased epithelial depth in injured VFs; all GCs increased epithelial depth compared with non-injured/untreated controls.

CONCLUSION

Acutely, GCs did not alter TEER. Additionally, GCs did not alter epithelial depth compared with saline treatment, indicating alignment with natural healing responses. At 60 days, GCs exhibited varying degrees of TEER restoration and epithelial hyperplasia, possibly due to distinct pharmacodynamic profiles.

LEVEL OF EVIDENCE

NA Laryngoscope, 2024.

Effect of fenugreek oil on healing of experimentally induced buccal mucosal ulcer by immunohistochemical evaluation of Ki-67 expression

Wound healing involves multiple populations of cells, the extracellular matrix, and soluble mediators' actions like growth factors and cytokines. Wound care was the target of many research, utilizing new therapy techniques and the progression of acute and chronic wound treatments with techniques involving plants to improve healing and decrease the side effects of drugs. When fenugreek is applied to an ulcer, its anti-inflammatory components are released, reducing unnecessary inflammation and accelerating the healing process. Healing is controlled by growth factors that naturally activate and boost the proliferation of cells, such as Ki-67, which is associated with the growth fraction and represents the cell's ability to proliferate. The current study aims to assess the expression of Ki-67 in rat mucosal ulcers treated with fenugreek leave oil. Twenty-four male Wistar albino rats of 350-450 gm weight were used. The rats were grouped as follows; normal group (normal tissue without ulcer induction), control group (tissue with surgical ulcer induction on the right side), and study group (ulcer treated with fenugreek leave oil on the left side), and had been sacrificed at 3- and 7-day healing durations. Thereafter, the tissue specimens were used for immunohistochemical analysis of Ki-67. The obtained outcomes showed that expression of Ki-67 increased in groups where ulcers were induced, with significant differences between control and study groups on the 3rd day. It was concluded that the application of fenugreek oil had an accelerating effect on the healing process of mucosal ulcers, as indicated by the elevated expression level of Ki-67.

Establishing a Mouse Model of Surgical Vocal Fold Injury

OBJECTIVE

Animal models of vocal fold (VF) surgical injury and scar formation provide insight into the wound healing process. The purpose of this study was to establish an alternative model of surgical injury to the mouse VF using materials commonly available in most research laboratories or for purchase and to investigate wound healing of the epithelium (EP) and lamina propria (LP).

METHODS

Mice were anesthetized by isoflurane gas delivery and positioned on a platform so that the larynx could be observed using a laryngoscope and dissection microscope. Unilateral VF injury was created using a wire brush. Mice were euthanized and the larynx evaluated 1-, 3-, 5-, 7-, 14-, and 28-days following injury. Histological and immunofluorescent analysis was used to evaluate thickness of the EP, LP area, proliferative (Ki67+) and basal cells (p63+) in the EP, and collagen III content in the LP.

RESULTS

The depth of injury reached the superficial thyroarytenoid muscle on Day 1. The thickness of the EP of the injured VF was increased on Days 3 and 5, and the LP area was increased on Days 3, 5, and 7 as compared with the uninjured VF. Ki67+ and p63+ cells were increased on Day 3 and collagen III content was increased on Days 5 and 28 as compared with the uninjured VF.

CONCLUSION

We successfully established an alternative method of creating unilateral VF injury in the mouse. This method will be useful for future research regarding VF surgical injury and wound healing.

LEVEL OF EVIDENCE

N/A Laryngoscope, 2024.

Method for Collecting Single Epithelial Cells from the Mouse Larynx

OBJECTIVE

The larynx is lined by specialized epithelial cell populations. Studying molecular changes occurring in individual epithelial cell types requires a reliable method for removing these cells from the larynx. Our objective was to develop a method to harvest individual epithelial cells from the mouse larynx while minimizing contamination from non-laryngeal sites and non-epithelial laryngeal cells.

METHODS

Mice were euthanized, and the larynx was carefully exposed and separated from non-laryngeal sites. A small dental brush was inserted into the laryngeal inlet and rotated to obtain epithelial cells. Cells were transferred to collection media, counted, and cytospin preparations stained for laryngeal epithelial (i.e., Pan-Keratin, EpCAM, NGFR, p63, K5, β-tubulin, MUC5AC) and non-epithelial (i.e., vimentin) cell markers. Histopathology was completed on brushed laryngeal tissue sections to evaluate the depth of cell collection. Preliminary Single-cell RNA sequencing (scRNA-seq) was performed to confirm this method can capture diverse laryngeal cell types.

RESULTS

We collected 6000-8000 cells from a single larynx and 35000-40000 cells from combining brushings from three tissues. Histopathology demonstrated brushing removed the epithelial layer of the larynx and some underlying tissue. Immunofluorescence staining demonstrated the phenotype of harvested cells was primarily epithelial. Preliminary scRNA-seq was successfully conducted and displayed nine unique cell clusters.

CONCLUSION

We developed a reliable method of harvesting individual epithelial cells from the mouse larynx. This method will be useful for collection of laryngeal cells for a variety of downstream cellular and molecular assays, including scRNA-seq, protein analyses, and cell-culture-based experiments, following laryngeal injury.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:786-794, 2024.

Introducing a new type of alternative laryngeal mucosa model

Research of human vocal fold (VF) biology is hampered by several factors. The sensitive microstructure of the VF mucosa is one of them and limits the in vivo research, as biopsies carry a very high risk of scarring. A laryngeal organotypic model consisting of VF epithelial cells and VF fibroblasts (VFF) may overcome some of these limitations. In contrast to human VFF, which are available in several forms, availability of VF epithelial cells is scarce. Buccal mucosa might be a good alternative source for epithelial cells, as it is easily accessible, and biopsies heal without scarring. For this project, we thus generated alternative constructs consisting of immortalized human VF fibroblasts and primary human buccal epithelial cells. The constructs (n = 3) were compared to native laryngeal mucosa at the histological and proteomic level. The engineered constructs reassembled into a mucosa-like structure after a cultivation period of 35 days. Immunohistochemical staining confirmed a multi-layered stratified epithelium, a collagen type IV positive barrier-like structure resembling the basement membrane, and an underlying layer containing VFF. Proteomic analysis resulted in a total number of 1961 identified and quantified proteins. Of these, 83.8% were detected in both native VF and constructs, with only 53 proteins having significantly different abundance. 15.3% of detected proteins were identified in native VF mucosa only, most likely due to endothelial, immune and muscle cells within the VF samples, while 0.9% were found only in the constructs. Based on easily available cell sources, we demonstrate that our laryngeal mucosa model shares many characteristics with native VF mucosa. It provides an alternative and reproducible in vitro model and offers many research opportunities ranging from the study of VF biology to the testing of interventions (e.g. drug testing).

Hyperdry Human Amniotic Membrane as a Protective Dressing for Open Wounds With Exposed Bowel in Mice

INTRODUCTION

An enteroatmospheric fistula forms when the exposed bowel is perforated with chronic enteric fistula formation. Currently, there is no established preventative method for this condition. Hyperdry (HD) amniotic membrane (AM) can promote early granulation tissue formation on the exposed viscera and is suitable for dressing intractable wounds as it possesses anti-inflammatory, antibacterial, and immunomodulatory properties. This study investigated whether HD-AM promotes early formation of blood vessel-containing granulation tissue for enteroatmospheric fistula treatment.

METHODS

An experimental animal model of an open wound with exposed bowel was developed. A 15 × 20 mm wound was prepared on the abdomen of Institute of Cancer Research mice, and the HD-AM was placed. The mice were assigned to one of the following groups: HD-AM group, in which the stromal layer of the HD-AM was placed in contact with the exposed bowel; HD-AM UD group, in which the epithelial layer of the HD-AM was placed in contact with the exposed bowel; and the HD-AM (-) or control group, in which the HD-AM was not used.

RESULTS

On postoperative days 7 and 14, granulation tissue thickness significantly increased in the HD-AM and HD-AM UD groups compared with that in the HD-AM (-) group. Macrophages accumulated in the HD-AM epithelium only in the HD-AM group. During HD-AM contact, a subset of invading macrophages switched from M1 to M2 phenotype.

CONCLUSIONS

HD-AM is a practical wound dressing with its scaffolding function, regulation of TGF β-1 and C-X-C motif chemokine 5 (CXCL-5), and ability to induce M1-to-M2 macrophage conversion.

The role of systemic dehydration in vocal fold healing: Preliminary findings

Rationale

Systemic dehydration negatively alters the expression of vocal fold inflammatory and cell junction markers. These biological changes can have downstream effects on the healing processes of injured vocal folds. In the dermis, reduced hydration prolongs inflammation and delays healing. It is unknown whether this biological effect is observed in vocal fold tissue.

Objective

To investigate the effects of systemic dehydration on vocal fold healing outcomes following acute, bilateral vocal fold injury in a rodent model.

Methods

Eighteen systemic dehydrated and 18 euhydrated adult male Sprague Dawley rats experienced bilateral vocal fold injuries or no injury (N = 9/group). Vocal fold gene expression levels of inflammatory mediators and epithelial cell junction markers were measured 24 h post-injury.

Results

Pro-inflammatory gene markers (IL-1β; TNF-α) were differentially expressed in response to systemic dehydration with vocal fold injury compared to non-injury. Epithelial cell junction markers (Cadherin-3, Desmoglein-1) also exhibited divergent trends following systemic dehydration, but these data were not statistically significant.

Conclusions

Systemic dehydration may affect cellular vocal fold healing processes within 24 h. These findings lay the groundwork for further investigation of how hydration status can affect vocal fold tissue recovery and influence clinical care.

Tissue Engineering as a Promising Treatment for Glottic Insufficiency: A Review on Biomolecules and Cell-Laden Hydrogel

Glottic insufficiency is widespread in the elderly population and occurs as a result of secondary damage or systemic disease. Tissue engineering is a viable treatment for glottic insufficiency since it aims to restore damaged nerve tissue and revitalize aging muscle. After injection into the biological system, injectable biomaterial delivers cost- and time-effectiveness while acting as a protective shield for cells and biomolecules. This article focuses on injectable biomaterials that transport cells and biomolecules in regenerated tissue, particularly adipose, muscle, and nerve tissue. We propose Wharton's Jelly mesenchymal stem cells (WJMSCs), induced pluripotent stem cells (IP-SCs), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), insulin growth factor-1 (IGF-1) and extracellular vesicle (EV) as potential cells and macromolecules to be included into biomaterials, with some particular testing to support them as a promising translational medicine for vocal fold regeneration.

Exposure to e-cigarette vapor extract induces vocal fold epithelial injury and triggers intense mucosal remodeling

Vaping has been reported to cause acute epiglottitis, a life-threatening airway obstruction induced by direct epithelial injury and subsequent inflammatory reaction. Here, we show that we were able to recapitulate this phenomenon in vitro. Exposure of human engineered vocal fold (VF) mucosae to 0.5% and 5% electronic cigarette (e-cigarette) vapor extract (ECVE) for 1 week induced cellular damage of luminal cells, disrupting homeostasis and innate immune responses. Epithelial erosion was likely caused by accumulation of solvents and lipid particles in the cytosol and intercellular spaces, which altered lipid metabolism and plasma membrane properties. Next, we investigated how the mucosal cells responded to the epithelial damage. We withdrew the ECVE from the experimental system and allowed VF mucosae to regenerate for 1, 3 and 7 days, which triggered intense epithelial remodeling. The epithelial changes included expansion of P63 (TP63)-positive basal cells and cytokeratin 14 (KRT14) and laminin subunit α-5 (LAMA5) deposition, which might lead to local basal cell hyperplasia, hyperkeratinization and basement membrane thickening. In summary, vaping presents a threat to VF mucosal health and airway protection, thereby raising further concerns over the safety of e-cigarette use. This article has an associated First Person interview with the first author of the paper.

Topical phenytoin administration accelerates the healing of acetic acid-induced colitis in rats: evaluation of transforming growth factor-beta, platelet-derived growth factor, and vascular endothelial growth factor

Ulcerative colitis (UC), limited to the colon's innermost lining, has become a global health problem. Immunomodulatory and monoclonal antibodies are used to treat UC despite their side effects and limitations. Phenytoin is used to heal wounds owing to its effects on growth factors, collagen, and extracellular matrix synthesis. This study aimed to evaluate the effect of topical phenytoin administration in UC. Phenytoin was administered in two doses during the treatment. Eighty male Wistar rats (230-280 g) were divided randomly into ten groups of sham, control, hydrocortisone, phenytoin 1%, and 3% groups in 6- or 12-day treatment protocols. The UC model was induced by the administration of acetic acid 4% into the colon. Animals were killed on the 7th and 13th postoperative days. The main outcome measures included body weight loss, microscopic score, and ulcer index measured using specific criteria. Growth factors were measured by western blotting. Results illustrated that body weight loss was reversed in the treatment groups. Ulcer index had decreased on 6- and 12-day treatment protocols. Microscopic scores in 6-day enema treatment significantly decreased compared to the control groups. Transforming growth factor-beta (TGFβ) significantly increased in a time-dependent manner and platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) significantly increased in a time- and dose-dependent manner in phenytoin 1% and 3% in the 6- and 12-day protocols. Phenytoin dose- and time-dependently reversed weight loss. In addition, histopathological parameters included microscopic scores, and the ulcer index was decreased through the induction of growth factors TGFβ, PDGF, and VEGF and consequently accelerated ulcer healing.

Singer’s Nodules: Investigating the Etiopathogenetic Markers Progressing Their Pathogenesis and Clinical Manifestations

Simple Summary

Vocal nodules, together with vocal polyps, are the most common benign vocal cord structures that are thought to be caused by extensive vocal abuse (shouting, talking loudly for prolonged periods) and are routinely treated surgically. However, surgical excision of these nodules, does not exclude the possibility of recurrence of these nodules, especially if lifestyle changes are not adapted to prevent phonetic trauma. Furthermore, the etiopathogenetic pathways governing the formation and maintenance of these nodules are not known. Herein, we investigated the etiopathogenetic markers for proliferation, apoptosis, growth, ischemia (tissue hypoxia), inflammation and innervation to elucidate the causative pathways. We found a profound and significant intensification of apoptosis in tissue epithelium, which strongly correlated with proliferative, ischemic, and inflammatory changes, highlighting the underlying complex interactions between various mechanisms on a cellular and tissue level, which occur during the morpho-pathogenesis of vocal nodules.

Abstract

Vocal nodules (or Singer’s nodules) are benign vocal cord structures which are commonly encountered by clinicians. Though phonetic trauma/abuse is thought to be the main cause of the development of vocal nodules, the exact etiopathogenesis remains unknown. Hence, we compared the immunohistochemical markers for proliferation (Ki-67), apoptosis (TUNEL), growth (EGFR), ischemia (VEGF), inflammation (IL-1α and 10), and immunoreactive innervation (PGP 9.5), in vocal nodule tissue samples obtained from 10 females (17–56 years) and vocal cord tissue from seven controls. A statistically significant increase in Ki-67, TUNEL, EGFR, VEGF and IL-1α expression was noted (p < 0.05) between nodule tissue and control tissue in both epithelial and subepithelial layers. However, the difference was non-significant for both IL-10 and PGP 9.5 (p > 0.05). All markers demonstrated moderate to strong positive correlations, except for IL-10. These findings suggest increased cellular growth and proliferation in vocal nodules coupled with a persistent presence of inflammatory and ischemic environment. Furthermore, global prevalence of apoptotic cells and decreased anti-inflammatory cytokines highlight the presence of underlying complex mechanisms in the etiopathogenesis of vocal nodules, with age having a negligible impact on the marker levels. Our results could potentially further our knowledge in understanding the effects of different treatment modalities available at the cellular level.

Mainstream Cigarette Smoke Impacts the Mouse Vocal Fold Epithelium and Mucus Barrier

OBJECTIVES/HYPOTHESIS

Cigarette smoke (CS) is a primary risk factor for the development of numerous benign and malignant laryngeal diseases. The epithelium and mucus lining the vocal folds (VF) are the first barriers against CS. The primary objective of this study was to investigate epithelial and mucus barrier changes in the mouse laryngeal mucosa upon exposure to subacute CS. The secondary objective was to compare mucus barrier changes in mice and human smokers and nonsmokers. Study Design Animal model.

METHODS

Mice were exposed to CS for 4 weeks for 4 hours (N = 12, high dose [HD]) or 1 hour (N = 12, low dose [LD]) per day. Air-exposed mice were used as a control group (N = 10). Larynges were harvested and VF epithelial barrier integrity was evaluated including cellular proliferation and expression of cell junctions. We also investigated mucus production by examining mucus cell area and mucin expression in mice and human smokers and nonsmokers.

RESULTS

HD CS increased VF epithelial cellular proliferation but did not alter the expression of cell junctions. HD CS also induced hypertrophy of the mucus-producing submucosal glands. However, only LD CS increased MUC5AC gene expression. MUC5AC staining appeared elevated in laryngeal specimens from smokers, but this was not significant as compared to nonsmokers.

CONCLUSIONS

These findings help us identify potential adaptive mechanisms to CS exposure as well as set the foundation for further study of key aspects of epithelial and mucus barrier integrity that may be implicated in laryngeal disease development following prolonged smoking.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:2530-2539, 2021.

Hydrogel-Supported, Engineered Model of Vocal Fold Epithelium

There is a critical need for the establishment of an engineered model of the vocal fold epithelium that can be used to gain understanding of its role in vocal fold health, disease, and facilitate the development of new treatment options. Toward this goal, we isolated primary vocal fold epithelial cells (VFECs) from healthy porcine larynxes and used them within passage 3. Culture-expanded VFECs expressed the suprabasal epithelial marker cytokeratin 13 and intercellular junctional proteins occludin, E-cadherin, and zonula occludens-1. To establish the engineered model, we cultured VFECs on a hyaluronic acid-derived synthetic basement membrane displaying fibronectin-derived integrin-binding peptide (RGDSP) and/or laminin 111-derived syndecan-binding peptide AG73 (RKRLQVQLSIRT). Our results show that matrix stiffness and composition cooperatively regulate the adhesion, proliferation, and stratification of VFECs. Cells cultured on hydrogels with physiological stiffness (elastic shear modulus, G' = 1828 Pa) adopted a cobblestone morphology with close cell-cell contacts, whereas those on softer matrices (G' = 41 Pa) were spindle shaped with extensive intracellular stress fibers. The development of stratified epithelium with proliferating basal cells and additional (1-2) suprabasal layers requires the presence of both RGDSP and AG73 peptide signals. Supplementation of cytokines produced by vimentin positive primary porcine vocal fold fibroblasts in the VFEC culture led to the establishment of 4-5 distinct cell layers. The engineered vocal fold epithelium resembled native tissue morphologically; expressed cytokeratin 13, mucin 1, and tight/adherens junction markers; and secreted basement membrane proteins collagen IV and laminin 5. Collectively, our results demonstrate that stiffness matching, cell-matrix engagement, and paracrine signaling cooperatively contribute to the stratification of VFECs. The engineered epithelium can be used as a versatile tool for investigations of genetic and molecular mechanisms in vocal fold health and disease.

Novel immortalized human vocal fold epithelial cell line: In vitro tool for mucosal biology

Study of vocal fold (VF) mucosal biology requires essential human vocal fold epithelial cell (hVFE) lines for use in appropriate model systems. We steadily transfected a retroviral construct containing human telomerase reverse transcriptase (hTERT) into primary normal hVFE to establish a continuously replicating hVFE cell line. Immortalized hVFE across passages have cobblestone morphology, express epithelial markers cytokeratin 4, 13 and 14, induced hTERT gene and protein expression, have similar RNAseq profiling, and can continuously grow for more than 8 months. DNA fingerprinting and karyotype analysis demonstrated that immortalized hVFE were consistent with the presence of a single cell line. Validation of the hVFE, in a three‐dimensional in vitro VF mucosal construct revealed a multilayered epithelial structure with VF epithelial cell markers. Wound scratch assay revealed higher migration capability of the immortalized hVFE on the surface of collagen‐fibronectin and collagen gel containing human vocal fold fibroblasts (hVFF). Collectively, our report demonstrates the first immortalized hVFE from true VFs providing a novel and invaluable tool for the study of epithelial cell‐fibroblast interactions that dictate disease and health of this specialized tissue.

Protein Substrate Alters Cell Physiology in Primary Culture of Vocal Fold Epithelial Cells

The basement membrane interacts directly with the vocal fold epithelium. Signaling between the basement membrane and the epithelium modulates gene regulation, differentiation, and proliferation. The purpose of this study was to identify an appropriate simple single-protein substrate for growth of rabbit vocal fold epithelial cells. Vocal folds from 3 New Zealand white rabbits (Oryctolagus cuniculus) were treated to isolate epithelial cells, and cells were seeded onto cell culture inserts coated with collagen I, collagen IV, laminin, or fibronectin. Transepithelial electrical resistance (TEER) was measured, and phase contrast microscopy, PanCK, CK14, and E-cadherin immunofluorescence were utilized to assess for epithelial cell-type characteristics. Further investigation via immunofluorescence labeling was conducted to assess proliferation (Ki67) and differentiation (Vimentin). There was a significant main effect of substrate on TEER, with collagen IV eliciting the highest, and laminin the lowest resistance. Assessment of relative TEER across cell lines identified a larger range of TEER in collagen I and laminin. Phase contrast imaging identified altered morphology in the laminin condition, but cell layer depth did not appear to be related to TEER, differentiation, or morphology. Ki67 staining additionally showed no significant difference in proliferation. All conditions had confluent epithelial cells and dispersed mesenchymal cells, with increased mesenchymal cell numbers over time; however, a higher proportion of mesenchymal cells was observed in the laminin condition. The results suggest collagen IV is a preferable basement membrane substrate for in vitro vocal fold epithelial primary cell culture, providing consistent TEER and characteristic cell morphology, and that laminin is an unsuitable substrate for vocal fold epithelial cells and may promote mesenchymal cell proliferation.

Short-term whole body cigarette smoke exposure induces regional differences in cellular response in the mouse larynx

The larynx is an essential organ in the respiratory tract and necessary for airway protection, respiration, and phonation. Cigarette smoking is a significant risk factor associated with benign and malignant laryngeal diseases. Despite this association, the underlying mechanisms by which cigarette smoke (CS) drives disease development are not well elucidated. In the current study, we developed a short-term murine whole body inhalation model to evaluate the first CS-induced cellular responses in the glottic [i.e. vocal fold (VF)] and subglottic regions of the larynx. Specifically, we investigated epithelial cell proliferation, cell death, surface topography, and mucus production, at various time points (1 day, 5 days, 10 days) after ∼ 2 h exposure to 3R4F cigarettes (Delivered dose: 5.6968 mg/kg per cigarette) and following cessation for 5 days after a 5 day CS exposure (CSE). CSE elevated levels of BrdU labeled proliferative cells and p63 labeled epithelial basal cells on day 1 in the VF. CSE increased proliferative cells in the subglottis at days 5, 10 and following cessation in the subglottis. Cleaved caspase-3 apoptotic activity was absent in VF at all time points and increased at day 1 in the subglottis. Evaluation of the VF surface by scanning electron microscopy (SEM) revealed significant epithelial microprojection damage at day 10 and early signs of necrosis at days 5 and 10 post-CSE. SEM visualizations additionally indicated the presence of deformed cilia at days 5 and 10 after CSE and post-cessation in the respiratory epithelium lined subglottis. In terms of mucin content, the impact of short-term CSE was observed only at day 10, with decreasing acidic mucin levels and increasing neutral mucin levels. Overall, these findings reveal regional differences in murine laryngeal cellular responses following short-term CSE and provide insight into potential mechanisms underlying CS-induced laryngeal disease development.

Transcriptomic and Morphological Analysis of Cells Derived from Porcine Buccal Mucosa-Studies on an In Vitro Model

Simple Summary

Domestic pigs express high phylogenetic similarity to humans and are often used as a compatible model in biomedical research. Porcine tissues are used as an accessible biomaterial in human skin transplants and tissue architecture reconstruction. We used transcriptional analysis to investigate the dynamics of complex biological system of the mucosa. Additionally, we performed computer analysis of microscopic images of cultured cells in vitro. Computer analysis of images identified epithelial cells and connective tissue cells in in vitro culture.

Abstract

Transcriptional analysis and live-cell imaging are a powerful tool to investigate the dynamics of complex biological systems. In vitro expanded porcine oral mucosal cells, consisting of populations of epithelial and connective lineages, are interesting and complex systems for study via microarray transcriptomic assays to analyze gene expression profile. The transcriptomic analysis included 56 ontological groups with particular focus on 7 gene ontology groups that are related to the processes of differentiation and development. Most analyzed genes were upregulated after 7 days and downregulated after 15 and 30 days of in vitro culture. The performed transcriptomic analysis was then extended to include automated analysis of differential interference contrast microscopy (DIC) images obtained during in vitro culture. The analysis of DIC imaging allowed to identify the different populations of keratinocytes and fibroblasts during seven days of in vitro culture, and it was possible to evaluate the proportion of these two populations of cells. Porcine mucosa may be a suitable model for reference research on human tissues. In addition, it can provide a reference point for research on the use of cells, scaffolds, or tissues derived from transgenic animals for applications in human tissues reconstruction.

Culture of Mesenchymal Stem Cells in a Hydrogel Model of Vocal Fold Lamina Propria

Stem cell injection has been proposed as an alternative approach for the restoration of vocal fold (VF) function in patients with VF scarring. To assess the therapeutic efficacy of this treatment strategy, we evaluated the behaviors of human mesenchymal stem cells (hMSCs) in hydrogels derived from thiolated hyaluronic acid (HA-SH) and poly(ethylene glycol) diacrylate (PEG-DA) entrapping assembled collagen fibrils (abbreviated as HPC gels). Three hydrogel formulations with varying amounts of collagen (0, 1 and 2 mg/mL) but a fixed HA-SH (5 mg/mL) and PEG-DA (2 mg/mL) concentration, designated as HPC0, HPC1 and HPC2, were investigated. The HPC gels exhibit similar pore sizes (35-50 nm) and AFM indentation moduli (~175 Pa), although the elastic shear modulus for HPC1 (~32 Pa) is lower than HPC0 and HPC2 (~55 Pa). Although HPC1 and HPC2 gels both promoted the development of an elongated cell morphology, greater cell spreading was observed in HPC2 than in HPC1 by day 7. At the transcript level, cells cultured in HPC1 and HPC2 gels had an increased expression of fibronectin and integrin β1, but a decreased expression of tissue inhibitor of metalloproteinase-1, collagen types I/III and HA synthase-1 when compared to cells cultured in HPC0 gels. Cellular expression of connective tissue growth factor was also elevated in HPC1 and HPC2 cultures. Importantly, the HPC2 hydrogels promoted a signficant up-regulation of matrix metalloproteinase 1, transforming growth factor β1, and epithelial growth factor receptor, indicating an increased tissue turnover. Overall, hMSCs cultured in HPC2 gels adopt a phenotype reminiscent of cells involved in the wound healing process, providing a platform to study the effectiveness of therapeutic stem cell treatments for VF scarring.

Mechanisms underlying the wound healing and tissue regeneration properties of Chenopodium album

In the current study, aerial parts (leaves, stem and shoots) of C. album were extracted with methanol and subjected to phytochemical and HPLC analysis. Agar well diffusion method was used for anti-bacterial activity against Gram-negative strains Escherichia coli, Salmonella typhi, Klebsiella, Pseudomonas aeruginosa and Gram-positive Bacillus cereus, Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus. Burn was induced through flame heated metal rod on mice. C. album ointment (2% w/w), Vaseline (vehicle) and silver sulfadiazine (standard) were topically applied thrice daily for 15 days. Wound area was measured on day 0, 5, 10 and 15. On last day, the wound tissues were excised and subjected to histopathological, quantitative PCR and immunohistochemical analysis. Phenols, alkaloids, phytosterols, tannins, saponins, flavonoids, carbohydrates and glycosides were detected in phytochemical analysis. HPLC chromatogram displayed peaks for rutin, quercetin, ascorbic acid, gallic acid and various other phyto-constituents. The extract exhibited zone of inhibition in millimeter (mm) against E. coli (12.3 ± 0.57), S. typhyi (14.6 ± 1.52), Klebsiella (11.8 ± 0.76), P. aeruginosa (12.3 ± 0.57), B. cereus (12.5 ± 1.29), S. aureus (18.3 ± 2.08), and MRSA (11.8 ± 0.76). The wound area in C. album group was significantly (60%) reduced as compared to vehicle group (11%). Histological analysis showed complete re-epithelialization and fine tissue in extract treated group. qPCR data revealed up-regulation of EGF, PDGF and TGF-β1 genes in extract treated group. Similarly, immunohistochemistry results confirmed heightened EGFR expression in extract treated group. Our findings suggest that C. album can promote wound healing and tissue regeneration through control of burns related infection and modulation of growth factors and its receptors.

Hyperdry human amniotic membrane application as a wound dressing for a full-thickness skin excision after a third-degree burn injury

Background

Severe burn injuries create large skin defects that render the host susceptible to bacterial infections. Burn wound infection often causes systemic sepsis and severe septicemia, resulting in an increase in the mortality of patients with severe burn injuries. Therefore, appropriate wound care is important to prevent infection and improve patient outcomes. However, it is difficult to heal a third-degree burn injury. The aim of this study was to investigate whether hyperdry human amniotic membrane (HD-AM) could promote early granulation tissue formation after full-thickness skin excision in third-degree burn injury sites in mice.

Methods

After the development of HD-AM and creation of a third-degree burn injury model, the HD-AM was either placed or not placed on the wound area in the HD-AM group or HD-AM group, respectively. The groups were prepared for evaluation on postoperative days 1, 4 and 7. Azan staining was used for granulation tissue evaluation, and estimation of CD163, transforming growth factor beta-1 (TGF-β1), vascular endothelial growth factor (VEGF), CD31, alpha-smooth muscle actin (α-SMA) and Iba1 expression was performed by immunohistochemical staining. Quantitative reverse-transcription polymerase chain reaction (PCR) was used to investigate gene expression of growth factors, cell migration chemokines and angiogenic and inflammatory markers.

Results

The HD-AM group showed significant early and qualitatively good growth of granulation tissue on the full-thickness skin excision site. HD-AM promoted early-phase inflammatory cell infiltration, fibroblast migration and angiogenesis in the granulation tissue. Additionally, the early infiltration of cells of the immune system was observed.

Conclusions

HD-AM may be useful as a new wound dressing material for full-thickness skin excision sites after third-degree burn injuries, and may be a new therapeutic technique for improving the survival rate of patients with severe burn injuries.

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.

Ion homeostasis and transport are regulated by genes differentially expressed in porcine buccal pouch mucosal cells during long-term culture in vitro – a microarray approach

The oral mucosa is a compound tissue composed of several cells types, including fibroblasts and keratinocytes, that are characterized by different morphology, as well as biochemical and metabolomic properties. The oral mucosal cells are the most important factors mediated between transport and drugs delivery. The changes in cellular ion homeostasis may significantly affect the bioavailability of administrated drugs and their transport across the mucous membrane. Therefore we investigated the expression profile of genes involved in ion transport and homeostasis in porcine buccal pouch mucosal cells.

The oral mucosa was separated surgically and isolated enzymatically. The cells were examined during long-term in vitro culture (IVC). The cultured cells were collected at 7, 15 and 30 days of IVC and subsequently transferred to RNA isolation and next, the gene expression profile was measured using Affymetrix microarray assays.

In the results, we can extract genes belonging to four ontology groups: “ion homeostasis”, “ion transport”, “metal ion transport”, and “inorganic ion homeostasis”. For TGFB1 and CCL2, we observed up-regulation after 7 days of IVC, down-regulation after 15 days of IVC and upregulation again after 30 days of IVC. The ATP13A3, ATP1B1, CCL8, LYN, STEAP1, PDPN, PTGS2, and SLC5A3genes showed high activity after day 7 of IVC, and in the days 15 and 30 of IVC showed low activity.

We showed an expression profile of genes associated with the effects of ion influence on the porcine normal oral mucosal cell development in IVC. These studies may be the starting point for further research into oral diseases and will allow for the comparison of the gene expression profile of normal and disease altered cells.

Wound-healing effects of 635-nm low-level laser therapy on primary human vocal fold epithelial cells: an in vitro study

Low-level laser therapy (LLLT) has been promoted for its beneficial effects on tissue healing and pain relief for skin and oral applications. However, there is no corresponding literature reporting on vocal fold wound healing. Our purpose was to assess the potential wound-healing effects of LLLT on primary human vocal fold epithelial cells (VFECs). In this study, normal vocal fold tissue was obtained from a 58-year-old male patient who was diagnosed with postcricoid carcinoma without involvement of the vocal folds and underwent total laryngectomy. Primary VFECs were then cultured. Cells were irradiated at a wavelength of 635 nm with fluences of 1, 4, 8, 12, 16, and 20 J/cm² (50 mW/cm²), which correspond to irradiation times of 20, 80, 160, 240, 320, and 400 s, respectively. Cell viability of VFECs in response to varying doses of LLLT was investigated by the Cell Counting Kit-8 (CCK-8) method. The most effective irradiation dose was selected to evaluate the cell migration capacity by using the scratch wound-healing assay. Real-time polymerase chain reaction (RT-PCR) was used to detect the gene expression of TGF-β1, TGF-β3, EGF, IL-6, and IL-10. Irradiation with doses of 8 J/cm² resulted in 4% increases in cell proliferation differing significantly from the control group (p < 0.05). With subsequent doses at 48 and 72 h after irradiation, the differences between the experimental and the control groups became greater, up to 9.8% (p < 0.001) and 19.5% (p < 0.001), respectively. It also increased cell migration and the expression of some genes, such as EGF, TGF-β1, TGF-β3, and IL-10, involved in the tissue healing process. This study concludes that LLLT at the preset parameters was capable of stimulating the proliferation and migration of human vocal fold epithelial cells in culture as well as increase the expression of some genes involved in tissue healing process. Additionally, successive laser treatments at 24 h intervals have an additive beneficial effect on the healing of injured tissues.

Expression of tenascin-C in a rat vocal fold injury model and its regulation of fibroblasts

OBJECTIVES/HYPOTHESIS

Tenascin-C (Tnc) is an extracellular matrix (ECM) glycoprotein that plays a vital role in wound healing and fibrotic disease. Tnc is highly upregulated soon after vocal fold injury, but its function in the vocal fold has not yet been defined. In this study, we investigated Tnc expression in a rat vocal fold injury model in vivo and its roles in fibroblasts in vitro.

STUDY DESIGN

In vivo and in vitro.

METHODS

Tnc mRNA and protein expression levels were quantified on days 3, 7, 14, 28, and 56 after vocal fold injury in Sprague-Dawley rats. In vitro, immunocytochemistry, Western blot, and quantitative real-time polymerase chain reaction (qRT-PCR) analyses were performed in primary rat vocal fold fibroblasts following Tnc or transforming growth factor (TGF)-β1 stimulation to investigate the phenotypic effects.

RESULTS

Tnc mRNA and protein expression was upregulated dramatically on days 3 and 7 after injury, and significant differences were observed by qRT-PCR (P < .01). In vitro, Tnc significantly stimulated the migration of primary vocal fold fibroblasts. Following incubation with Tnc for 72 hours, α-smooth muscle actin, collagen I, and fibronectin expression was significantly upregulated (P < .05). TGF-β1 increased Tnc expression in a time-dependent manner, and a mothers against decapentaplegic homolog 3 (SMAD3) inhibitor attenuated this TGF-β1-induced stimulation.

CONCLUSIONS

Tnc was highly upregulated during the early postinjury period in vivo and promoted vocal fold fibroblast migration, transdifferentiation, and ECM protein synthesis in vitro. Tnc was induced by TGF-β1 in a SMAD3-dependent manner. Transient expression of Tnc is likely to promote regeneration, but its potential role in fibrosis requires further study.

LEVEL OF EVIDENCE

NA Laryngoscope, 128:E316-E322, 2018.

Recovery of Vocal Fold Epithelium after Acute Phonotrauma

We investigated the timeline of tissue repair of vocal fold epithelium after acute vibration exposure using an in vivo rabbit model. Sixty-five New Zealand white breeder rabbits were randomized to 120 min of modal- or raised-intensity phonation. After the larynges were harvested at 0, 4, 8, and 24 h, and at 3 and 7 days, the vocal fold tissue was evaluated using electron microscopy and quantitative real-time polymerase chain reaction. There was an immediate decrease in the microprojection depth and height following raised-intensity phonation, paired with upregulation of cyclooxygenase-2. This initial 24-h period was also characterized by the significant downregulation of junction proteins. Interleukin 1β and transforming growth factor β1 were upregulated for 3 and 7 days, respectively, followed by an increase in epithelial cell surface depth at 3 and 7 days. These data appear to demonstrate a shift from inflammatory response to the initiation of a restorative process in the vocal fold epithelium between 24 h and 3 days. Despite the initial damage from raised-intensity phonation, the vocal fold epithelium demonstrates a remarkable capacity for the expeditious recovery of structural changes from transient episodes of acute phonotrauma. While structurally intact, the return of functional barrier integrity may be delayed by repeated episodes of phonotrauma and may also play an important role in the pathophysiology of vocal fold lesions.

An in vitro scaffold-free epithelial-fibroblast coculture model for the larynx

OBJECTIVES/HYPOTHESIS

Physiologically relevant, well-characterized in vitro vocal fold coculture models are needed to test the effects of various challenges and therapeutics on vocal fold physiology. We characterize a healthy state coculture model, created by using bronchial/tracheal epithelial cells and immortalized vocal fold fibroblasts. We also demonstrate that this model can be induced into a fibroplastic state to overexpress stress fibers using TGFβ1.

STUDY DESIGN

In vitro.

METHODS

Cell metabolic activity of immortalized human vocal fold fibroblasts incubated in different medium combinations was confirmed with an MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide) assay. Fibroblasts were grown to confluence, and primary bronchial/tracheal epithelial cells suspended in coculture medium were seeded directly over the base layer of the fibroblasts. Cells were treated with transforming growth factor β1 (TGFβ1) to induce myofibroblast formation. Cell shape and position were confirmed by live cell tracking, fibrosis was confirmed by probing for α smooth muscle actin (αSMA), and phenotype was confirmed by immunostaining for vimentin and E-cadherin.

RESULTS

Fibroblasts retain metabolic activity in coculture epithelial medium. Live cell imaging revealed a layer of epithelial cells atop fibroblasts. αSMA expression was enhanced in TGFβ1-treated cells, confirming that both cell types maintained a healthy phenotype in coculture, and can be induced into overexpressing stress fibers. Vimentin and E-cadherin immunostaining show that cells retain phenotype in coculture.

CONCLUSIONS

These data lay effective groundwork for a functional coculture model that retains the reproducibility necessary to serve as a viable diagnostic and therapeutic screening platform.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:E185-E192, 2017.

Distribution and characteristics of slow-cycling cells in rat vocal folds

OBJECTIVES/HYPOTHESIS

Stem cells are known to proliferate at a slow rate in adult organs, and thus slow-cycling cells exhibiting pluripotency are considered tissue-specific stem cells in some organs. Slow-cycling cells in the vocal fold (VF) have not been well documented. Here we sought to clarify the distributions and characteristics of slow-cycling cells in rat VFs.

METHODS

We applied double-labeling technique to detect the distribution of slow-cycling cells. We injected the exogenous proliferation marker 5-bromo-2'-deoxyuridine (BrdU) into Sprague-Dawley rats. After a chasing period, VFs were immunostained with antibodies to BrdU and the second endogenous proliferation marker, Ki-67. BrdU (+) Ki-67(+) cells were regarded as slow-cycling cells and counted by VF regions. To reveal slow-cycling cells' characteristic, their immunophenotypes were histologically investigated and their kinetics in injured VFs were evaluated.

RESULTS

Most slow-cycling cells were detected in the basal layer of the epithelium. Slow-cycling cells in the epithelium displayed a low positive ratio of E-cadherin and CK5 and a high positive ratio of vimentin and CD31 as compared with the other epithelial cells. The expression of S100A4 was low in slow-cycling cells of the lamina propria and the macula flava. FGFR1, HAS1, HAS2, and HAS3 were not detected in the slow-cycling cells. A time-dependent reduction of slow-cycling cells was observed in injured VFs.

CONCLUSION

Most slow-cycling cells resided in the epithelium, exhibiting various phenotypes in a relatively undifferentiated condition, and they are suspected to contribute to the tissue repair of the injured VFs.

LEVEL OF EVIDENCE

N/A.

Wound repair: role of immune-epithelial interactions

The epithelium serves as a highly selective barrier at mucosal surfaces. Upon injury, epithelial wound closure is orchestrated by a series of events that emanate from the epithelium itself as well as by the temporal recruitment of immune cells into the wound bed. Epithelial cells adjoining the wound flatten out, migrate, and proliferate to rapidly cover denuded surfaces and re-establish mucosal homeostasis. This process is highly regulated by proteins and lipids, proresolving mediators such as Annexin A1 protein and resolvins released into the epithelial milieu by the epithelium itself and infiltrating innate immune cells including neutrophils and macrophages. Failure to achieve these finely tuned processes is observed in chronic inflammatory diseases that are associated with non-healing wounds. An improved understanding of mechanisms that mediate repair is important in the development of therapeutics aimed to promote mucosal wound repair.

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.