Preliminary study of a novel transfection modality for in vivo siRNA delivery to vocal fold fibroblasts

OBJECTIVE

An obstacle to clinical use of RNA-based gene suppression is instability and inefficiency of current delivery modalities. Nanoparticle delivery likely holds great promise, but the kinetics and transfection conditions must be optimized prior to in vivo utility. We investigated a RNA nanoparticle complex incorporating a lipitoid transfection reagent in comparison to a commercially available reagent.

STUDY DESIGN

In vitro.

METHODS

We investigated which variables influence transfection efficiency of lipitoid oligomers and a commercially available reagent across species, in vitro. These variables included duration, dose, and number of administrations, as well as serum and media conditions. The target gene was Smad3, a signaling protein in the transforming growth factor-β cascade implicated in fibroplasia in the vocal folds and other tissues.

RESULTS

The two reagents suppressed Smad3 mRNA for up to 96 hours; lipitoid performed favorably and comparably. Both compounds yielded 60% to 80% mRNA knockdown in rat, rabbit, and human vocal fold fibroblasts (P < 0.05 relative to control). Dose and number of administrations played a significant role in gene suppression (P < 0.05). Suppression was more dose-sensitive with lipitoid. At a constant siRNA concentration, a 50% decrease in gene expression was observed in response to a five-fold increase in lipitoid concentration. Increased number of administrations enhanced gene suppression, ∼45% decrease between one and four administrations. Neither serum nor media type altered efficiency.

CONCLUSION

Lipitoid effectively knocked down Smad3 expression across multiple transfection conditions. These preliminary data are encouraging, and lipitoid warrants further investigation with the goal of clinical utility.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E231-E237, 2017.

Structurally and functionally characterized in vitro model of rabbit vocal fold epithelium

In this paper, we describe a method for primary culture of a well differentiated electrically tight rabbit vocal fold epithelial cell multilayer and the measurement of transepithelial electrical resistance (TEER) for the evaluation of epithelial barrier function in vitro. Rabbit larynges were harvested and enzymatically treated to isolate vocal fold epithelial cells and to establish primary culture. Vocal fold epithelial cells were co-cultured with mitomycin C-treated feeder cells on collagen-coated plates. After 10-14 days in primary culture, cells were passaged and cultured until they achieved 70-90% confluence on collagen-coated plates. Epithelial cells were then passaged onto collagen-coated cell culture inserts using 4.5cm2 membrane filters (1.0μm pore size) with 10% fetal bovine serum or 30μg/mL bovine pituitary extract to investigate the effects of growth-promoting additives on TEER. Additional experiments were performed to investigate optimal seeding density (1.1, 2.2, 4.4, or 8.9×105 cells/cm2), the effect of co-culture with feeder cells, and the effect of passage number on epithelial barrier function. Characterization of in vitro cultures was performed using hematoxylin and eosin staining and immunostaining for vocal fold epithelial cell markers and tight junctions. Results revealed higher TEER in cells supplemented with fetal bovine serum compared to bovine pituitary extract. TEER was highest in cells passaged at a seeding density of 2.2×104 cells/cm2, and TEER was higher in cells at passage two than passage three. Ultrastructural experiments revealed a well-differentiated epithelial cell multilayer, expressing the epithelial cell markers CK13, CK14 and the tight junction proteins occludin and ZO-1.

Clinicopathological parameters associated with histological background and recurrence after surgical intervention of vocal cord leukoplakia

Histological examination of biopsy shows usefulness in the diagnosis of vocal cord leukoplakia; however, in considerable amount of cases, the examination cannot provide definitive diagnosis of malignancy from benign conditions such as hyperplasia and dysplasia. The present work therefore was aimed to identify clinicopathological factors and molecular markers predictive of recurrence and malignant transformation of vocal cord leukoplakia.Clinical data of 555 cases of vocal cord leukoplakia enrolled from July 1999 to June 2014 were analyzed. The cohort consisted of keratosis (n = 137), hyperplasia (n = 139), dysplasia (n = 177), and primary (n = 10) and invasive (n = 46) carcinoma. Correlations between patients' backgrounds, clinicopathological factors, molecular markers (p53, p16, Ki67, cytokeratin, and proliferating cell nuclear antigen), and histology backgrounds were examined using by Pearson Chi-squared or Fisher exact test. Reflux symptom index (RSI) and reflux finding score (RFS) before and after treatment were compared using Wilcoxon signed-rank test. Risk factors for disease recurrence were identified using Cox proportional hazards models of multivariate analysis. Time to recurrence was analyzed using log-rank test of Kaplan-Meier method.In the present cohort, alcohol drinking was found associated with GRBAS grade (P = .0258) and the site (P = .0298) of leukoplakia. For the different disease types, chief complaint (P = .0179), GRBAS grade (P = .0101), mucosal wave (P < .0001), and molecular markers p53 (P < .0001) and Ki67 (P < .0001) were identified as correlates. RSI and RFS were significantly lowered by surgical intervention. A single side of leukoplakia was predictive of a lower risk of recurrence (odds ratio, 0.378; 95% confidence interval, 0.197-0.723; P = .0033). Absence of mucosal wave was associated with a shorter time-to-recurrence (P = .0357).The present work identified clinicopathological factors and molecular markers associated with the different histology of vocal cord leukoplakia, and also the prognostic factor for the low risk of recurrence after surgery.

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.

Vitamin A-Storing Stellate Cells in the Human Newborn Vocal Fold

Objectives:

Vocal fold stellate cells (VFSCs) in the newborn vocal fold were examined and compared with VFSCs in the adult vocal fold.

Methods:

Light and electron microscopic investigation of VFSCs was carried out on 5 human newborn larynges.

Results:

The VFSCs were distributed in human newborn maculae flavae. They were stellate or oval in shape, and possessed cytoplasmic processes. The VFSCs in some cells formed a gap junction with each other. A few lipid droplets were present in the cytoplasm, but they were much fewer than those of an adult. The nucleus-cytoplasm ratio was high, and the intracellular organelles were not very well developed. Free ribosomes were well developed in the cytoplasm. The VFSCs in some cells showed strong cytoplasm staining with periodic acid-Schiff stain and type III collagen. There were vesicles along the periphery of the cytoplasm of the VFSCs, and newly released amorphous materials were seen, but fewer were observed on the cell surface. The newborn VFSCs had started to synthesize extracellular matrices such as collagenous fibers, reticular fibers, elastic fibers, and glycosaminoglycan.

Conclusions:

The VFSCs in the newborn maculae flavae were immature, but had already started the synthesis of extracellular matrices essential for the viscoelastic properties of the vocal fold mucosa.

Histologic Characterization of Rat Vocal Fold Scarring

This study aimed to clarify the characteristics of rat vocal fold scarring by examining the alteration of key components in the extracellular matrix: hyaluronic acid, collagen, and fibronectin. Under monitoring with a 1.9-mm-diameter telescope, unilateral vocal fold stripping was performed, and larynges were harvested at 2, 4, 8, and 12 weeks after operation. The vocal folds were histologically analyzed with Alcian blue stain, trichrome stain, and immunofluorescence of collagen type I, collagen type III, and fibronectin. The scarred vocal folds showed less hyaluronic acid and more collagen types I and III than did the controls at all time points. Type III was stable for 12 weeks, while type I declined until 8 weeks and thereafter remained unchanged. Fibronectin increased for 4 weeks and then decreased; it was close to the control level at 8 and 12 weeks. These results suggest that the tissue remodeling process in scarred vocal folds slows down around 2 months after wounding.

Shifts in Biochemical Markers Associated with Wound Healing in Laryngeal Secretions following Phonotrauma: A Preliminary Study

The current study sought to determine whether shifts in key components of the inflammatory process could be detected from laryngeal secretions sampled before and after vocal loading. A healthy 44-year-old woman served as the subject. The vocal folds were swabbed to collect baseline secretions. Ten and 20 minutes after nearly constant loud phonation for 1 hour, the vocal folds were swabbed again. The findings indicated strong shifts in several key inflammatory mediators: interleukin-1beta, tumor necrosis factor alpha, and matrix metalloproteinase 8. The concentrations of those mediators continued to increase from the 10- to 20-minute postloading time-points. Transforming growth factor beta and prostaglandin E2 did not demonstrate clear shifts. In summary, mediators reflecting the acute inflammatory process could be detected from laryngeal secretions in an awake human. The upward slope of the curves at the 20-minute time interval indicates the need for longer follow-up sampling to determine the full biological response of the vocal folds to acute phonotrauma.

Expression and Distribution of CD44 and Hyaluronic Acid in Human Vocal Fold Mucosa

Objectives:

Expression of CD44 (a cell surface receptor for hyaluronic acid) and the distribution of hyaluronic acid were examined in the human vocal fold mucosa.

Methods:

Light microscopic investigation was carried out on 10 normal larynges of newborn, infant, younger adult, and older adults with Alcian blue staining, a hyaluronidase digestion study, and immunohistochemistry for CD44.

Results:

Before the appearance of hyaluronic acid in the newborn vocal fold mucosa, CD44 was expressed on the stellate cells in the macula flava and on the fibroblasts in Reinke's space. During infancy, hyaluronic acid appeared and was distributed in the vocal fold mucosa. Many more stellate cells in the macula flava showed CD44 expression, and a large amount of hyaluronic acid was present around the infant stellate cells; however, the fibroblasts in Reinke's space expressed little CD44. During adulthood, hyaluronic acid was distributed in the vocal fold mucosa. Almost all of the stellate cells in the macula flava showed CD44 expression, and much hyaluronic acid existed around the stellate cells in the adult macula flava. However, fibroblasts in the adult Reinke's space expressed little CD44, and hyaluronic acid density in that space was lower than that in the macula flava.

Conclusions:

Stellate cells in the macula flava and CD44 cooperatively play important roles in maintaining hyaluronic acid in the human vocal fold mucosa as a vibrating tissue.

Age-Related Changes in Vitamin A-Storing Stellate Cells of Human Vocal Folds

Light and electron microscopic investigation of age-related changes in vocal fold stellate cells (VFSCs) of the human vocal fold mucosa was carried out on 10 excised human adult larynges from autopsy and surgical cases. The results are summarized as follows. Aged VFSCs were stellate in shape and possessed slender cytoplasmic processes. Aged VFSCs also possessed lipid droplets in the cytoplasm and stored vitamin A. Basically, the morphological characteristics of the aged VFSCs were the same as those of younger adults. The number of VFSCs had decreased. There were fewer intercellular organelles than in younger adults. Some components of the cytoplasm had degenerated. The nuclei of the VFSCs were dense and cleaved. There were few vesicles at the periphery of the cytoplasm of aged VFSCs, and few newly released amorphous materials. Some aged VFSCs had degenerated, and an accumulation of glycogen particles was seen in the cytoplasm. The number of fibers synthesized by these inactivated cells had decreased. These findings were recognized to various degrees. The aged VFSCs in the maculae flavae appear to have decreased activity, have abnormal metabolism, and undergo degeneration. Age-related changes in the VFSCs of the maculae flavae are postulated to influence the metabolism of extracellular matrices in the vocal fold mucosa, as well as the viscoelasticity of the aged vocal fold mucosa, and are one of the causes of aging of the voice.

[Expression and clinical pathological implications of carbonic anhydrase 9 and P glycoprotein in laryngeal squamous cell carcinoma]

OBJECTIVE

To identify the difference of CA IX and P-gp expression level between laryngeal squamous cell carcinoma (LSCC) and benign tissues, evaluate the relationship of these two proteins in LSCC, and their correlation with clinical and pathological features.

METHOD

Immunohistochemical detection of CA IX and P-gp were performed in 47 cases of LSCC and 20 cases of vocal cord polyps.

RESULT

Overexpression of CA IX and P-gp both in LSCC and in vocal cord polyp (P < 0.05) were confirmed, with a correlation between the two proteins in LSCC (r = 0.324, P < 0.05). The expression of CA IX was related to clinical staging and lymph node metastasis in LSCC (P < 0.05). While P-gp was related to clinical staging and histological grading in LSCC (P < 0.05).

CONCLUSION

The overexpression of CA IX and P-gp may play a role in LSCC progression.

The histological components of the phoniatrical body-cover model in minipigs of different ages

Pigs are models in human phoniatry. However, features of maturation and ageing have not been considered with regard to the so-called body-cover model in this species. Therefore, the glottis of “young” (2–3 months; n = 6) and “old” (4–7 years; n = 6) minipigs was investigated. Their cranial (CraF) and caudal (CauF) vocal folds were histomorphometrically and stratigraphically analysed with emphasis on their amounts of collagen structures and elastic fibres. A dense subepithelial layer (SEL) was a distinct feature of CraF and CauF of both age groups; it was spread upon the underlying loose, flexible “cover” like a fibro-elastic membrane. The “cover” was characterised by the so-called superficial layer (SL), which was distinctly loose in the “young” minipigs, but had a much denser texture in the “old” minipigs. Here, the SL was dominated by elastic fibres in the CraF, but was of mixed qualities (collagenous and elastic) in the CauF. The structural requirements for the SL’s function as a loose “cover” were thus met only in the “young” animals. A clearly demarcated intermediate layer (IL)—characterised by high amounts of elastic fibres (as in humans)—was only found in the CraF of the “young” animals. In the “old” animals, it had lost its demarcation. In the depth of the CraF of the “old” animals, many thick collagen fibre bundles were detected in a location equivalent to that of the vocal muscle in the CauF. The development of their large diameters was interpreted as part of the maturation process, thereby supporting the hypothesis of their functional importance as a component of the “body.” In the CauF, the amounts of collagen structures increased throughout the entire lamina propria, resulting in a loss of demarcated stratigraphical subdivisions in the “old” minipigs. This situation resembled that described in the vocal fold of geriatric humans.

Characterization of extracellular matrix proteins during wound healing in the lamina propria of vocal fold in a canine model: a long-term and consecutive study

The characterization of vocal fold wound healing can be reflected by the changes of extracellular matrix (ECM) proteins in the lamina propria. Although the expression of ECM proteins after vocal fold injury has been widely studied, such observations have lacked time continuity and integrity of marker proteins. In this study, we observed the morphology of injured vocal folds in a canine model. We used immunofluorescence staining to evaluate the expression and distribution of ECM proteins, such as collagen, elastin, hyaluronic acid, decorin and fibronectin, from 15 days to 6 months after injury. The results showed that large amounts of ECM proteins were secreted 15-40 days after injury. Collagen and fibronectin secretion increased significantly, and were disorderly deposited. The secretion of decorin and elastin increased slightly, while hyaluronic acid decreased. The 15-40 day post-injury period may be the critical intervention stage in wound healing of vocal folds. From 3 to 6 months after injury, the secretion of ECM proteins declined. However, collagen and fibronectin secretion were still significantly higher than normal with irregular arrangement, while the secretion of elastin, hyaluronic acid and decorin decreased significantly at 6 months. This led to vocal fold inelasticity and stiffness, which required effective long-term interventions to treat scar formation.

Vocal fold ion transport and mucin expression following acrolein exposure

The vocal fold epithelium is exposed to inhaled particulates including pollutants during breathing in everyday environments. Yet, our understanding of the effects of pollutants on vocal fold epithelial function is extremely limited. The objective of this study was to investigate the effect of the pollutant acrolein on two vocal fold epithelial mechanisms: ion transport and mucin (MUC) synthesis. These mechanisms were chosen as each plays a critical role in vocal defense and in maintaining surface hydration which is necessary for optimal voice production. Healthy, native porcine vocal folds (N = 85) were excised and exposed to an acrolein or sham challenge. A 60-min acrolein, but not sham challenge significantly reduced ion transport and inhibited cyclic adenosine monophosphate-dependent, increases in ion transport. Decreases in ion transport were associated with reduced sodium absorption. Within the same timeline, no significant acrolein-induced changes in MUC gene or protein expression were observed. These results improve our understanding of the effects of acrolein on key vocal fold epithelial functions and inform the development of future investigations that seek to elucidate the impact of a wide range of pollutant exposures on vocal fold health.

The posterior cricoarytenoid muscle is spared from MuRF1-mediated muscle atrophy in mice with acute lung injury

Background

Skeletal muscle wasting in acute lung injury (ALI) patients increases the morbidity and mortality associated with this critical illness. The contribution of laryngeal muscle wasting to these outcomes is unknown, though voice impairments and aspiration are common in intensive care unit (ICU) survivors. We evaluated the intrinsic laryngeal abductor (PCA, posterior cricoarytenoid), adductor (CT, cricothyroid) and limb (EDL, extensor digitorum longus) muscles in a mouse model of ALI.

Methods

Escherichia coli lipopolysaccharides were instilled into the lungs of adult male C57Bl6J mice (ALI mice). Limb and intrinsic laryngeal muscles were analyzed for fiber size, type, protein expression and myosin heavy chain (MyHC) composition by SDS-PAGE and mass spectroscopy.

Results

Marked muscle atrophy occurred in the CT and EDL muscles, while the PCA was spared. The E3 ubiquitin ligase muscle ring finger-1 protein (MuRF1), a known mediator of limb muscle atrophy in this model, was upregulated in the CT and EDL, but not in the PCA. Genetic inhibition of MuRF1 protected the CT and EDL from ALI-induced muscle atrophy. MyHC-Extraocular (MyHC-EO) comprised 27% of the total MyHC in the PCA, distributed as hybrid fibers throughout 72% of PCA muscle fibers.

Conclusion

The vocal cord abductor (PCA) contains a large proportion of fibers expressing MyHC-EO and is spared from muscle atrophy in ALI mice. The lack of MuRF1 expression in the PCA suggests a previously unrecognized mechanism whereby this muscle is spared from atrophy. Atrophy of the vocal cord adductor (CT) may contribute to the impaired voice and increased aspiration observed in ICU survivors. Further evaluation of the sparing of muscles involved in systemic wasting diseases may lead to potential therapeutic targets for these illnesses.

Regulation of wound healing by granulocyte-macrophage colony-stimulating factor after vocal fold injury

Objectives

Vocal fold (VF) scarring remains a therapeutic challenge. Granulocyte-macrophage colony-stimulating factor (GM-CSF) facilitates epithelial wound healing, and recently, growth factor therapy has been applied to promote tissue repair. This study was undertaken to investigate the effect of GM-CSF on VF wound healing in vivo and in vitro.

Methods

VF scarring was induced in New Zealand white rabbits by direct injury. Immediately thereafter, either GM-CSF or PBS was injected into the VFs of rabbits. Endoscopic, histopathological, immunohistochemical, and biomechanical evaluations of VFs were performed at 3 months post-injury. Human vocal fold fibroblasts (hVFFs) were cultured with GM-CSF. Production of type I and III collagen was examined immunocytochemically, and the synthesis of elastin and hyaluronic acids was evaluated by ELISA. The mRNA levels of genes related to ECM components and ECM production-related growth factors, such as HGF and TGF-ß1, were examined by real time RT-PCR.

Results

The GM-CSF-treated VFs showed reduced collagen deposition in comparison to the PBS-injected controls (P<0.05). Immunohistochemical staining revealed lower amounts of type I collagen and fibronectin in the GM-CSF-treated VFs (P<0.05 and P<0.01, respectively). Viscous and elastic shear moduli of VF samples were significantly lower in the GM-CSF group than in the PBS-injected group (P<0.001 and P<0.01, respectively). Mucosal waves in the GM-CSF group showed significant improvement when compared to the PBS group (P = 0.0446). GM-CSF inhibited TGF-β1-induced collagen synthesis by hVFFs (P<0.05) and the production of hyaluronic acids increased at 72 hours post-treatment (P<0.05). The expressions of HAS-2, tropoelastin, MMP-1, HGF, and c-Met mRNA were significantly increased by GM-CSF, although at different time points (P<0.05).

Conclusion

The present study shows that GM-CSF offers therapeutic potential for the remodeling of VF wounds and the promotion of VF regeneration.

Pipette aspiration applied to the characterization of nonhomogeneous, transversely isotropic materials used for vocal fold modeling

The etiology and treatment of voice disorders are still not completely understood. Since the vibratory characteristics of vocal folds are strongly influenced by both anatomy and mechanical material properties, measurement methods to analyze the material behavior of vocal fold tissue are required. Due to the limited life time of real tissue in the laboratory, synthetic models are often used to study vocal fold vibrations. In this paper we focus on two topics related to synthetic and real vocal fold materials. First, because certain tissues within the human vocal folds are transversely isotropic, a fabrication process for introducing this characteristic in commonly used vocal fold modeling materials is presented. Second, the pipette aspiration technique is applied to the characterization of these materials. By measuring the displacement profiles of stretched specimens that exhibit varying degrees of transverse isotropy, it is shown that local anisotropy can be quantified using a parameter describing the deviation from an axisymmetric profile. The potential for this technique to characterize homogeneous, anisotropic materials, including soft biological tissues such as those found in the human vocal folds, is supplemented by a computational study.

[Expression and significance of MCM2, Ki-67 and Rb protein in laryngeal squamous cell carcinomas]

OBJECTIVE

To investigate the expression of MCM2, Ki-67 and Rb and its biological characteristic in human laryngeal squamous cell carcinomas(LSCC).

METHOD

The expression of MCM2 protein and Rb protein were detected in 60 cases of LSCC, 10 cases of precarcinoma, 10 cases of vocal cord polyps and 10 cases of normal laryngeal tissues, and Ki-67 protein were detected in 60 cases of LSCC and 10 cases of normal laryngeal tissues by Elivision plus immunohistochemical staining, and analyze their relations with clinicopathological characteristics.

RESULT

The positive expression rate of MCM2 in LSCC was significantly higher than that in precarcinoma and normal laryngeal tissues (P < 0.05), and was positively correlated with pathological grades, clinical stages and lymph node metastases (P < 0.05) of LSCC. The positive expression rate of Rb protein in LSCC was significantly lower than that in precarcinoma and normal laryngeal tissues (P < 0.05). The expression level of MCM2 in LSCC was negatively corelated with Rb (r = -0.542, P < 0.05), the expression level of Ki-67 in LSCC (76.67%) was significantly higher than that in normal laryngeal tissues (30.00%) (P < 0.01) and the expression level of MCM2 in LSCC was positively corelated with Ki-67(r = 0.596, P < 0.01). The LI of MCM2 in the 3-year survival rate of LSCC was significantly lower than that in Ki-67 (P < 0.05).

CONCLUSION

Over expression of MCM2 and loss of Rb protein were related to the carcinogenesis and development of LSCC. The determination of MCM2 can be an index for estimating the level of malignancy and prognosis of LSCC.

Tight junction-related barrier contributes to the electrophysiological asymmetry across vocal fold epithelium

Electrophysiological homeostasis is indispensable to vocal fold hydration. We investigate tight junction (TJ)-associated components, occludin and ZO-1, and permeability with or without the challenge of a permeability-augmenting agent, histamine. Freshly excised ovine larynges are obtained from a local abattoir. TJ markers are explored via reverse transcriptase polymerase chain reaction (RT-PCR). Paracellular permeabilities are measured in an Ussing system. The gene expression of both TJ markers is detected in native ovine vocal fold epithelium. Luminal histamine treatment significantly decreases transepithelial resistance (TER) (N = 72, p<0.01) and increases penetration of protein tracer (N = 35, p<0.001), respectively, in a time-, and dose-dependent fashion. The present study demonstrates that histamine compromises TJ-related paracellular barrier across vocal fold epithelium. The detection of TJ markers indicates the existence of typical TJ components in non-keratinized, stratified vocal fold epithelium. The responsiveness of paracellular permeabilities to histamine would highlight the functional significance of this TJ-equivalent system to the electrophysiological homeostasis, which, in turn, regulates the vocal fold superficial hydration.

Acute stress to excised vocal fold epithelium from reactive oxygen species

OBJECTIVES/HYPOTHESIS

Vocal fold epithelium is exposed to reactive oxygen species from the inhaled environment and from tissue inflammation. The objective of this study was to explore the functional and structural consequences of reactive oxygen species exposure on vocal fold epithelium.

STUDY DESIGN

In vitro, prospective study design.

METHODS

Hydrogen peroxide (H(2)O(2)), a common reactive oxygen species, was utilized in this study. Freshly excised, viable porcine vocal fold epithelia (N = 32) were exposed to H(2) O(2) or sham challenge for 2 hours. Electrophysiology, western blotting, and light microscopy were used to quantify the functional and structural effects of reactive oxygen species on vocal fold epithelia.

RESULTS

Exposure to reactive oxygen species did not significantly alter transepithelial resistance. There was a small, nonsignificant trend for decreased concentration of epithelial junctional complex protein with reactive oxygen species challenge. Minimal changes to the gross structural appearance of vocal fold epithelia were also noted.

CONCLUSIONS

The stratified squamous epithelia of the vocal folds effectively defend against an acute reactive oxygen species challenge. The current study lays the groundwork for future investigations on the effects of reactive oxygen species on vocal fold epithelia that are compromised from phonotrauma.

Cross-sample validation provides enhanced proteome coverage in rat vocal fold mucosa

The vocal fold mucosa is a biomechanically unique tissue comprised of a densely cellular epithelium, superficial to an extracellular matrix (ECM)-rich lamina propria. Such ECM-rich tissues are challenging to analyze using proteomic assays, primarily due to extensive crosslinking and glycosylation of the majority of high M_r ECM proteins. In this study, we implemented an LC-MS/MS-based strategy to characterize the rat vocal fold mucosa proteome. Our sample preparation protocol successfully solubilized both proteins and certain high M_r glycoconjugates and resulted in the identification of hundreds of mucosal proteins. A straightforward approach to the treatment of protein identifications attributed to single peptide hits allowed the retention of potentially important low abundance identifications (validated by a cross-sample match and de novo interpretation of relevant spectra) while still eliminating potentially spurious identifications (global single peptide hits with no cross-sample match). The resulting vocal fold mucosa proteome was characterized by a wide range of cellular and extracellular proteins spanning 12 functional categories.

Morphological properties of collagen fibers in porcine lamina propria

OBJECTIVES

Collagen influences the biomechanical properties of vocal folds. Altered collagen morphology has been implicated in dysphonia associated with aging and scarring. Documenting the morphological properties of native collagen in healthy vocal folds is essential to understand the structural and functional alterations to collagen with aging and disease. Our primary objective was to quantify the morphological properties of collagen in the vocal fold lamina propria. Our secondary exploratory objective was to investigate the effects of pepsin exposure on the morphological properties of collagen in the lamina propria.

STUDY DESIGN

Experimental, in vitro study with porcine model.

METHODS

Lamina propria was dissected from 26 vocal folds and imaged with atomic force microscopy (AFM). Morphological data on d-periodicity, diameter, and roughness of collagen fibers were obtained. To investigate the effects of pepsin exposure on collagen morphology, vocal fold surface was exposed to pepsin or sham challenge before lamina propria dissection and AFM imaging.

RESULTS

The d-periodicity, diameter, and roughness values for native vocal fold collagen are consistent with literature reports of collagen fibers in other body tissues. Pepsin exposure on vocal fold surface did not appear to change the morphological properties of collagen fibers in the lamina propria.

CONCLUSIONS

Quantitative data on collagen morphology were obtained at nanoscale resolution. Documenting collagen morphology in healthy vocal folds is critical for understanding the physiological changes to collagen with aging and scarring and for designing biomaterials that match the native topography of lamina propria.

Treatment of acute vocal fold scar with local injection of basic fibroblast growth factor: a canine study

CONCLUSIONS

Results of the current study revealed improved phonation threshold pressure (PTP), normalized mucosal wave amplitude (NMWA), and less contraction of the lamina propria in injured larynges treated with basic fibroblast growth factor (bFGF).

OBJECTIVES

We investigated the effects of local injection of bFGF for treatment of acute vocal fold injury in a canine model.

METHODS

Vocal folds of eight beagles were unilaterally injured by removal of the mucosa under direct laryngoscopy. Four beagles received local injections of bFGF delivered to the scarred vocal fold at 1 month after injury. The remaining four beagles received local injections of saline and served as a sham-treatment group. Larynges were harvested 5 months after treatment and excised larynx experiments were performed to measure PTP, NMWA, and normalized glottal gap (NGG). Histologic staining was performed to evaluate structural changes of the extracellular matrix.

RESULTS

Excised larynx measurements revealed significantly lower PTP and increased NMWA in bFGF-treated vocal fold. Elastica Van Gieson staining revealed less contraction of the bFGF-treated vocal fold. Histologic measurements revealed that the thickness of the lamina propria was significantly greater in the bFGF-treated vocal fold. Alcian blue staining revealed improved restoration of hyaluronic acid in the bFGF-treated vocal fold.

In Vivo engineering of the vocal fold ECM with injectable HA hydrogels-late effects on tissue repair and biomechanics in a rabbit model

OBJECTIVES

To determine if the utilization of injectable chemically modified hyaluronan (HA) derivative at the time of intentional vocal fold resection may facilitate wound repair and preserve the unique viscoelastic properties of the extracellular matrix (ECM) and lamina propria 6 months after treatment.

STUDY DESIGN

Prospective, controlled animal study.

METHODS

Twelve rabbit vocal folds were biopsied bilaterally, and the left side of vocal fold was treated with Extracel, an injectable, chemically modified HA derivative, and the right side of vocal fold was injected with saline as control at the time of resection. Animals were sacrificed 6 months after biopsy and injection. Outcomes measured include transcription levels for procollagen, fibronectin, fibromodulin, transforming growth factor beta one (TGF-β1), HA synthase, and hyaluronidase, and tissue biomechanics-viscosity and elasticity.

RESULTS

Extracel-treated vocal folds were found to have significantly less fibrosis than saline-treated controls. Extracel-treated vocal folds had significantly improved biomechanical properties of elasticity and viscosity. Significantly decreased levels of fibronectin, fibromodulin, TGF-β1, procollagen I, and HA synthase were measured.

CONCLUSIONS

Prophylactic in vivo manipulation of the ECM with an injectable HA hydrogel appears to induce vocal fold tissue regeneration to yield improved tissue composition and biomechanical properties at 6 months.

[Potentialities of the vegetative resonance test for diagnostics of hyperplastic processes in vocal folds]

The objective of the present study was to evaluate potentialities of the vegetative resonance test (VRT) for the elucidation of metabolic aspects of the inflammatory process in different forms of chronic vocal fold hyperplasty. The proposed diagnostic criteria characterize the inflammatory process in the larynx, specific features of metabolism in patients presenting with catarrhal and oedematopolypous laryngitis, characteristic changes in oedematofibrous and fibrous polyps. The use of VRT allowed diagnostic criteria for precarcinogenic conditions in the larynx to be developed.