Effect of topical mitomycin-C on total collagen deposits on the submucosa of intact vocal folds in swine

OBJECTIVE

To compare the effects of topical mitomycin-C at different concentrations on submucosal collagen deposition on the vocal folds of swine.

METHODS

The animals were divided into three groups according to the composition of the topical solution to be applied to the vocal folds: 0.9% saline solution (control group); 4 mg/ml mitomycin-C (group 1) and 8 mg/ml mitomycin-C (group 2). Thirty days after the application, all animals were sacrificed, their vocal folds were collected and stained by the picrosirius red technique, and submucosal collagen deposition areas were estimated by the Image Pro Plus 4.5 software. Mann-Whitney test was used to compare differences between parameters of each group.

RESULTS

The means of the areas of submucosal collagen deposits on vocal folds were 3110.44 square micrometers (microm(2)), 3115.98 microm(2) and 3105.78 microm(2) for groups control, 1 and 2, respectively. There were no statistical differences across the three groups (p>0.05).

CONCLUSION

Mitomycin-C topically applied to intact vocal folds of swine did not alter submucosal collagen deposition.

[Expression of transforming growth factor beta1 in human vocal fold polyps]

OBJECTIVE

To analyze the expression of transforming growth factor-beta1 (TGF-beta1) in human vocal fold polyps, and explore the pathogenesis of vocal fold polyp.

METHOD

The expression of TGF-beta1 were detected in 37 examples of vocal fold polyps and 11 healthy vocal folds by immunohistochemical staining (SP method). Meanwhile, the positive results were compared.

RESULT

The percent of positive expression of TGF-beta1 was 56.76% and the number of positive cells was 22.55 +/- 27.31 in vocal fold polyps, both of which were significantly increased compared with the percent of positive expression of TGF-beta1 (18.18%) and the number of positive cells (2.53 +/- 3.75) in healthy vocal folds (P<0.05). The positive expression of TGF-beta1 in stroma cells of vocal cord polyps was significantly higher than that in the healthy vocal cords. There was no significant difference of TGF-beta1 between the vocal fold polyps of male and female (P>0.05).

CONCLUSION

TGF-beta1 may participate in some pathologic changes in vocal cord polyps, such as extracellular matrix accumulation, local fibrosis and formation and development of vocal cord polyps. Manipulating the TGF-beta1 expression in vocal cord polyps may supply a new treatment method.

A patient-specific in silico model of inflammation and healing tested in acute vocal fold injury

The development of personalized medicine is a primary objective of the medical community and increasingly also of funding and registration agencies. Modeling is generally perceived as a key enabling tool to target this goal. Agent-Based Models (ABMs) have previously been used to simulate inflammation at various scales up to the whole-organism level. We extended this approach to the case of a novel, patient-specific ABM that we generated for vocal fold inflammation, with the ultimate goal of identifying individually optimized treatments. ABM simulations reproduced trajectories of inflammatory mediators in laryngeal secretions of individuals subjected to experimental phonotrauma up to 4 hrs post-injury, and predicted the levels of inflammatory mediators 24 hrs post-injury. Subject-specific simulations also predicted different outcomes from behavioral treatment regimens to which subjects had not been exposed. We propose that this translational application of computational modeling could be used to design patient-specific therapies for the larynx, and will serve as a paradigm for future extension to other clinical domains.

Side population cells in the human vocal fold

OBJECTIVES

The regenerative processes of the vocal fold, or the existence of stem cells in the folds, are unknown. Side population (SP) cells are defined as cells that have the ability to exclude the DNA binding dye, Hoechst 33342. They are regarded as a cell population enriched with stem cells and can be isolated from non-SP cells by a fluorescence-activated cell sorter. This study was designed to determine whether SP cells exist in the human vocal fold, as a first step in elucidating the regenerative mechanisms of the vocal fold.

METHODS

Seven human excised larynges were used in this study. Two were used for fluorescence-activated cell sorter analysis, and 5 were subjected to immunohistochemical analysis with antibodies against an adenosine triphosphate binding cassette transporter family member, ABCG2, which is expressed in SP cells.

RESULTS

The number of SP cells in the human vocal fold was about 0.2% of the total number of cells. ABCG2-positive cells were identified in both the epithelium and subepithelial tissue throughout the entire vocal fold.

CONCLUSIONS

This preliminary study demonstrated the existence of SP cells in the human vocal fold. Further studies are warranted to clarify how these cells work in the vocal fold, particularly in the regenerative process.

Atomic Force Microscopy Investigation of Vocal Fold Collagen

OBJECTIVES

Collagen is an important constituent of the vocal fold extracellular matrix and is necessary for providing tensile strength and maintaining tissue geometry. Traditional investigations of vocal fold collagen using light and electron microscopy do not provide information on the organization and mechanical properties of collagen in native topographic state. The primary objective of this study was to use Atomic Force Microscopy (AFM) to examine the surface characteristics and organization of collagen in the deep layer of the lamina propria at nanoscale resolution.

STUDY DESIGN

Experimental in vitro design.

METHODS

Freshly dissected porcine vocal folds were mounted on AFM discs and imaged under contact and tapping mode to obtain information on topographic distribution of collagen.

RESULTS

AFM imaging of the deep layer of the lamina propria revealed dense, abundant collagen fibers with a characteristic banding pattern. The distribution of collagen was heterogeneous, with both hydrophilic and hydrophobic regions within a sample.

CONCLUSIONS

AFM offers a useful tool to obtain topographic information about biologic samples at nanoscale resolution with minimal sample preparation. Mapping the topography and mechanical properties of vocal fold collagen is necessary for designing rheologically compatible bioimplants for the treatment of dysphonia resulting from vocal fold scarring and bowing.

Concentration and Distribution of Hyaluronic Acid in Human Vocal Folds

OBJECTIVE/HYPOTHESIS

To evaluate the concentration and distribution of hyaluronic acid (HA) in human adult vocal folds.

STUDY DESIGN

Experimental study.

METHODS

Histologic samples of the anterior, middle, and posterior regions of the vocal folds were studied to determine the tissue distribution of HA. The HA was traced with hyaluronan-binding proteins (HAPB) from bovine cartilage. Chemical bonds were detected through the avidin-biotin immunoperoxidase method. A control with the specific Streptomyces hyalurolyticus hyaluronidase was conducted to avoid false-positive results. The concentration levels of HA were determined through a fluorescence-based assay method with the same HAPB and europium-labeled streptavidin.

RESULTS

Women presented higher HA concentrations than men in every studied region of the vocal folds and overall HA concentration levels twice as higher. In regard to the distribution of HA, the macula flavae and the vocal fold intermediate and deep layers presented marked staining, with moderate staining around the vessels, on the gland capsules, and the connective tissue surrounding the vocal fold muscular fibers.

CONCLUSIONS

HA is diffusely distributed along the vocal folds; the profuse amounts of HA observed in the female vocal folds may be related to impact absorption, acting as a protective factor against the characteristic high vibration frequency.

Immediate inflammatory response and scar formation in wounded vocal folds

OBJECTIVES

Vocal fold scarring is the major cause of voice disorders after voice surgery or laryngeal trauma. The role of inflammatory factors in vocal fold wound healing and fibrosis has not been adequately investigated. Scarless wound healing has been associated with decreased inflammatory responses. To understand scar formation and develop reliable treatments, it is necessary to control extracellular matrix production and inflammation. Thus, we examined the inflammation profile and extracellular matrix production in wounded vocal folds in the acute phase of wound healing.

METHODS

Vocal fold stripping was performed on 30 Sprague-Dawley rats. Vocal fold tissue was collected at 5 time points (4, 8, 16, 24, and 72 hours). We examined the in vivo messenger RNA expression profile of inflammatory factors interleukin 1beta, interferon gamma, tumor necrosis factor alpha, nuclear factor kappa beta, transforming growth factor beta, and cyclooxygenase 2, as well as hyaluronic acid synthases 1 and 2, procollagen subtypes I and III, and elastin synthase in scarred vocal folds after injury, compared to normal vocal folds, using real-time reverse transcription-polymerase chain reaction.

RESULTS

The inflammatory factors showed a time-dependent sequence of expression peaks, starting with interleukin 1beta, nuclear factor kappa beta, tumor necrosis factor alpha (4 and 8 hours), and transforming growth factor beta (72 hours). Interferon gamma decreased at 24 hours. Correspondingly, hyaluronic acid synthase 1 expression peaked first (4 and 8 hours), whereas hyaluronic acid synthase 2 expression peaked at 16 hours and again at 72 hours. Procollagen I expression peaked at 72 hours, whereas procollagen III decreased from 8 to 16 hours but peaked at 72 hours. Cyclooxygenase 2 expression was elevated, whereas elastin expression remained constant.

CONCLUSIONS

The results show a clear profile of vocal fold inflammation with corresponding changes in extracellular matrix production.

Effects of Growth Factors on Extracellular Matrix Production by Vocal Fold Fibroblasts in 3-Dimensional Culture

Culturing cells in 3-dimensional (3D) systems is important in tissue engineering and in fundamental studies of cellular mechanisms that are sensitive or specific to the 3D environment. To guide the engineering of artificial vocal fold lamina propria tissue, we developed 3D cultures containing human vocal fold fibroblasts (hVFFs) dispersed in a synthetic peptide hydrogel matrix. Growth factors were added to the culture to examine their influence on extracellular matrix (ECM) synthesis, cell proliferation, and matrix contraction. The hVFF-hydrogel constructs were treated with transforming growth factor-beta 1 (TGF-beta1), basic fibroblast growth factor (bFGF), or hepatocyte growth factor (HGF), and the culture was maintained for 21 days. TGF-beta1 induced matrix contraction and enhanced collagen and sulfated glycosaminoglycan production, bFGF effectively increased cell proliferation, and HGF stimulated synthesis of hyaluronic acid and elastin with less collagen accumulation than other conditions. Of the growth factors tested, HGF appears to be most useful for stimulating essential tissue components for restoring vocal fold pliability. The results also suggest that multiple growth factors might be employed sequentially or in combination to program the makeup of cell-hydrogel constructs for vocal fold tissue repair.

Fine needle aspiration of the vocal fold lamina propria in an animal model

OBJECTIVES

The development of a minimally invasive fine needle aspiration (FNA) technique for vocal fold (VF) biopsy would have far-reaching implications and applicability in laryngology. The objective of this study was to determine whether FNA of the VF lamina propria is feasible and whether it causes injury to the VF.

METHODS

Unilateral VF FNA was performed with a 26-gauge needle on 20 rabbits. The FNA cell collection of the lamina propria was confirmed by cytology. Four weeks after the FNA, the rabbits were painlessly sacrificed and the larynges were harvested. Histologic analysis of the VF lamina propria included Masson's trichrome and elastin-van Gieson stains. The linear viscoelastic shear properties, elastic modulus, and viscous modulus of the tissue were measured.

RESULTS

Compared to the contralateral normal VFs, those VFs that underwent FNA demonstrated no significant differences in levels of collagen (p = .17) and elastin (p = .94). Rheologically, the elastic shear modulus and viscous modulus did not significantly differ between the normal and FNA VFs (p = .9380 and p = .9359, respectively).

CONCLUSIONS

Fine needle aspiration of the VF lamina propria is feasible without injury and offers a potentially promising, less invasive alternative to be developed for future diagnostic and therapeutic management of VF lesions.

Collagen subtypes in human vocal folds

OBJECTIVES

The collagen subtypes in human vocal folds are of particular interest, because each collagen subtype has different features that make it uniquely suited for performing specific tissue tasks and each collagen subtype can affect the tissue properties of the vocal fold lamina propria.

METHODS

Human vocal folds from 5 autopsy cases (less than 65 years old) were examined by immunohistochemistry for collagen types I, III, IV, and V and elastin.

RESULTS

Collagen type III was distributed throughout the whole lamina propria. Type I was found just beneath the basal membrane, in the deep layer of the lamina propria and in the anterior and posterior maculae flavae. Types IV and V were present in the epithelial and endothelial basal membrane. Three-dimensional images from thick specimens reconstructed with confocal microscopy showed 2 distinct patterns: type III fibers were wavy, collagenous fibers, as previously observed in the vocal folds, and type I fibers were thinner than type III fibers. These results suggest that type III fibers help maintain the lamina propria structure and that type I fibers provide the tensile strength required around the basal membrane and vocal ligament to maintain the vocal fold shape while withstanding vibratory forces.

Differential cell adhesion to vocal fold extracellular matrix constituents

The human vocal folds are a complex layering of cells and extracellular matrix. Vocal fold extracellular matrix uniquely contributes to the biomechanical viscoelasticity required for human phonation. We investigated the adhesion of vocal fold stellate cells, a novel cell type first cultured by our laboratory, and fibroblasts to eight vocal fold extracellular matrix components: elastin, decorin, fibronectin, hyaluronic acid, laminin and collagen types I, III and IV. Our data demonstrate that these cells adhere differentially to said substrates at 5 to 120 min. Cells were treated with hyaluronidase and Y-27632, a p160ROCK-specific inhibitor, to test the role of pericellular hyaluronan and Rho-ROCK activation in early and mature adhesion. Reduced adhesion resulted; greater inhibition of fibroblast adhesion was observed. We modulated the fibronectin affinity exhibited by both cell types using Nimesulide, an inhibitor of fibronectin integrin receptors alpha5beta1 and alphavbeta3. Our results are important in understanding vocal fold pathologies, wound healing, scarring, and in developing an accurate organotypic model of the vocal folds.

Postnatal development of rat vocal folds

OBJECTIVES

In this study we aimed to determine the feasibility of using a rat model for the study of postnatal vocal fold (VF) development.

METHODS

Eighteen male rats that were 3 days old, 3 weeks old, or 8 months old were analyzed histologically with Alcian blue stain used for detecting hyaluronic acid, elastin-van Gieson stain for elastin, Oil Red O and gold chloride stains for vitamin A-containing lipid droplets, and immunohistochemistry for vimentin (general fibroblast marker) and collagen types I and III.

RESULTS

The macula flava (MF) was observed as a mass of cells that expressed vimentin intensively in the cytoplasm. The MF showed denser hyaluronic acid and collagen type I than did the midmembranous portion of the VF lamina propria. Clear developmental changes were evident in the MF and other regions. The vimentin-positive cells of the 3-day-old MF were mainly oval-shaped and had less cytoplasm, whereas those of the 8-month-old MF were spindle- and stellate-shaped and had more cytoplasm, similar to that reported in humans. Vitamin A-containing lipid droplets were limited to the 3-week-old and 8-month-old MFs and were not present in the 3-day-old VF.

CONCLUSIONS

These results suggest that a rat model is useful in studying VF development and that vitamin A is related to the maturity of the VF.

Quantitative and comparative studies of the vocal fold extracellular matrix II: collagen

OBJECTIVES

This study examines the collagen content and turnover in the midmembranous vocal fold laminae propriae (LPs) of humans, dogs, pigs, and ferrets.

METHODS

The LP collagen levels were assessed by quantifying tissue hydroxyproline. Quantitative histology allowed evaluation of the collagen content in specific LP regions. Several collagen types and two markers of collagen turnover were examined immunohistochemically.

RESULTS

Collagen made up 43.4% +/- 2.6% of human LP total protein (TP), with men having approximately 30% higher collagen content than women (p < .024). The collagen levels in pigs (52.6% +/- 1.9% of TP) and ferrets (29.8% +/- 3.7% of TP), but not that in dogs (45.3% +/- 1.2% of TP), varied significantly from that in humans (pigs, p < .016; ferrets, p < .011). Quantitative histology indicated marked interspecies differences in total collagen distribution. Collagen types I, III, and IV were detected in the LP, and spatially complex staining patterns were observed for the two markers of collagen turnover studied.

CONCLUSIONS

The collagen content of the human LP is approximately 60% to 70% of that of human dermis. Although canine LP collagen levels are most similar to those of humans, quantitative histology indicates that the collagen distribution of the human LP is best matched by the porcine LP. Collagen types I and III seem to be the dominant LP collagens. Spatial variations in collagen turnover appear to exist that may contribute to normal LP physiology.

Towards the expression of sex hormone receptors in the human vocal fold

BACKGROUND

The human larynx is assumed to be a steroid receptor target organ. There are only very limited data on the evidence of steroid receptors in the vocal folds, although voice alterations due to hormonal influence and treatment have been found.

GOAL OF THE STUDY

To investigate the expression of estrogen alpha, progesterone, and androgen receptors in human vocal folds (vocalis muscle, glands, lamina propria, epithelium).

METHODS

Immunohistochemically, vocal fold cadaver specimens of 15 autopsied patients (6 women, 9 men), which were taken approximately 4 to 8 hours postmortem were investigated. Furthermore, one (male) vocal fold biopsy obtained intraoperatively during a laryngectomy was tested.

RESULTS

No specific immunohistochemical staining for the different types of steroid hormones investigated could be observed in either the postmortem taken biopsies nor the intraoperatively one. However, several unspecific staining patterns could be observed.

CONCLUSION

The results of this study contradict recently published data and question the expression of sex hormone receptors in the vocal folds. Main causes of false interpretations of unspecific staining are discussed.

Biochemical markers associated with acute vocal fold wound healing: a rabbit model

This study seeks to determine the ability of enzyme-linked immunosorbent assays (ELISAs) of vocal fold secretions to detect and describe the acute tissue response to injury in a rabbit vocal fold model. Vocal fold secretions were collected before the induction of a unilateral surgical injury to the vocal fold and at 6 timepoints after injury (1, 5, 7, 10, 14, and 21 days). Secretions were then subjected to ELISAs to assess concentrations of interleukin-1 beta (IL-1beta) and prostaglandin-E2 (PGE-2). The results indicate that ELISAs may be useful in documenting fluctuations in these markers associated with the wound healing process in the rabbit model. The temporal expression of both IL-1beta and PGE-2 was consistent with their proposed roles in the wound healing cascade in other systems, pointing to the potential that surface secretions may be at least partial indicators of wound healing events within the tissue.

Current treatment of vocal fold scarring

PURPOSE OF REVIEW

Vocal fold scarring still remains a therapeutic challenge, with the most problematic issue being the histologic changes that are primarily responsible for altering the viscoelasticity of the vocal fold mucosa. Optimal treatment for vocal fold scarring has not yet been established. To restore or regenerate damaged vocal folds, it is important to investigate the changes to the layer structure of the lamina propria. Tissue engineering and regenerative medicine may provide new strategies for the prevention and treatment of vocal fold scarring. Recent developments in this field are reviewed in the present article.

RECENT FINDINGS

Histologic studies have revealed that hyaluronic acid, fibronectin, decorin, and various other extracellular matrix components, as well as collagen, may contribute to determining the vibratory properties of the vocal fold mucosa. Changes of these molecules are thought to affect the viscoelasticity of the scarred vocal folds. Based on such histologic findings, innovative approaches have been developed, including administration of hyaluronic acid into injured or scarred vocal folds. Other strategies that have recently shown advances include growth factor therapy and cell therapy using stem cells or mature fibroblasts. The effects of these new treatments have not fully been confirmed clinically, but there seems to be great therapeutic potential in such regenerative medical strategies.

SUMMARY

Recent research has revealed the detailed histologic and rheologic changes related to vocal fold scarring. Based on these findings, various new therapeutic strategies have been developed in animal models using tissue engineering and regenerative medicine. However, no clinical trials have been performed, and more studies are necessary to establish the optimum modality.

Midmembranous vocal fold lamina propria proteoglycans across selected species

OBJECTIVES

We examined the proteoglycan (PG) and associated sulfated glycosaminoglycan (GAG) content of the midmembranous vocal fold lamina propria (LP) of humans, dogs, pigs, and ferrets.

METHODS

The LP PG levels were assessed indirectly by quantifying the associated sulfated GAGs, and immunohistochemical analyses of specific PGs and/or GAGs (PGs/GAGs) were conducted.

RESULTS

Sulfated GAGs constituted approximately (average +/- SEM) 14.7 +/- 2.1 microg per milligram of tissue total protein in the human LP--similar to levels in canine, porcine, and ferret LPs (p > .05). Immunohistochemical analysis identified versican, chondroitin 4- and 6-sulfate, and heparan sulfate in the LP extracellular matrix--PGs/GAGs previously believed to be localized only intracellularly and in the basement membrane. Observations of PG/GAG staining patterns resulted in identification of microstructurally based subdivisions of canine, porcine, and ferret LPs.

CONCLUSIONS

The sulfated GAG concentration in human LP was similar to that of dermis. In contrast to the interspecies similarity in LP sulfated GAG levels, immunohistochemical analysis indicated notable interspecies differences in specific PG/GAG distributions. Moreover, spatial variations in the presence of several PGs/GAGs were observed--variations that may be integral in maintaining normal LP physiology. Finally, the noted canine, porcine, and ferret LP subdivisions may yield insight into the adaptation of LP microstructure to the phonatory needs of each species.

Transdifferentiation of vocal-fold stellate cells and all-trans retinol-induced deactivation

The maculae flavae of the human vocal folds include dense extracellular matrices and compacted cells with a stellate morphology. These vocal-fold stellate cells are thought to participate in the metabolism of extracellular matrices essential in maintaining vocal-fold viscoelasticity required for phonation. We have isolated and cultured these new cells and have tested the hypothesis that they maintain a distinct cellular and biochemical phenotype. We have compared proliferation rates, changes on immunophenotype, and intracellular lipid and vitamin A storage. Vocal-fold stellate cells undergo culture-induced transdifferentiation to a myofibroblast-like phenotype with an altered phenotype resembling, but not identical to, activated hepatic and pancreatic stellate cells. Our results reveal that these cells are capable of responding to exogenous all-trans retinol in culture. Exposure to this synthetic co-factor causes deactivation characterized by decreased proliferation, loss of the activated stellate cell marker, alpha-smooth muscle actin, and restoration of intracellular lipid and vitamin A metabolite storage. These data establish a new and distinct cellular target for future investigations of the viscoelastic properties of the vocal-fold mucosa during normal phonation, aging, vocal-fold scarring, laryngeal fibrosis, and myofibroblastoma.

Acute histologic effects of extraesophageal reflux on vocal fold healing

This study evaluates how extraesophageal reflux affects membranous vocal fold healing in a canine model. We created membranous vocal fold injuries in the animals and randomly assigned them to topical application of acid and pepsin at pH 2 or pH 6 or of normal saline solution every other day for 12 days. The experimental vocal folds were compared to uninjured, control vocal folds from animals painlessly sacrificed for other reasons. Hematoxylin and eosin, fibronectin, and procollagen I staining were performed for histologic analysis. The injured specimens had three times greater cellular infiltrate (p < or = .001, analysis of variance) and twice as much fibronectin and procollagen I (p < or = .001, analysis of variance) as did the specimens from the control animals. No significant differences or trends were identified for cellular infiltrate, fibronectin, or procollagen I within the injured groups (p > .05, Bonferroni t-test). Acute wound healing did not appear to be influenced by the presence of acid and pepsin at pH 2 or 6 as compared to saline solution.

Advances in our understanding of the Reinke space

PURPOSE OF REVIEW

Normal vocal fold vibration depends critically upon the composition of the Reinke space or the lamina propria extracellular matrix. Alterations in the normal composition of the extracellular matrix result in a loss of normal vibratory function. In this article, the present literature on the Reinke space in normal and disease states is reviewed including publications in the multidisciplinary fields of biomechanics, histology, molecular biology, and tissue engineering.

RECENT FINDINGS

With recent technology advances, the etiology for benign lesions has been investigated with computer models and bioreactors. Particular extracellular matrix constituents in various benign vocal fold lesions--fibronectin, fibromodulin and hyaluronan--appear to be involved in altering the viscoelastic properties of the Reinke space. Significant basic science approaches to the investigation of the characterization of the Reinke space in vocal fold scarring has produced several potential future treatment avenues. Tissue-engineering approaches for regeneration of the Reinke space are the most recent addition to the literature showing promising research directions.

SUMMARY

Voice disorders represent a significant clinical problem. Research attempting to discover the underlying molecular and genetic regulation and homeostasis of the extracellular matrix of the Reinke space are essential. Effective future clinical interventions must be based upon the knowledge of how genetic and biologic features are disturbed in vocal diseases and how they relate to vocal symptoms.

Detecting synchronizations in an asymmetric vocal fold model from time series data

A nonlinear modeling approach is presented for the reconstruction of the synchronization structure in an asymmetric two-mass model from time series data. The asymmetric two-mass model describes a variety of normal and pathological human voices associated with synchronous and desynchronous oscillations of the two asymmetric vocal folds. Our technique recovers the synchronization diagram, which yields the regimes of synchronization as well as desynchronization, which are dependent upon the asymmetry parameter and the subglottal pressure. This allows the prediction of the regime of pathological phonation associated with desynchronization of the vocal folds from a few sets of recorded time series. It is shown that the modeling is quite effective when the time series data are chaotic and if they are taken from a regime of desynchronization. We discuss the applicability of the present approach as a diagnostic tool for voice pathologies.

Polydimethylsiloxane versus polytetrafluoroethylene for vocal fold medialization: histologic evaluation in a rabbit model

The objective is to study the tissue reaction of the paralyzed vocal cord in response to the injection of particulate plastics in a rabbit model. Forty-five New Zealand rabbits with surgical vocal-fold paralysis were used in the study. Histologic reactions of the larynx and the regional lymph nodes were analyzed by a single blinded pathologist at 6 weeks and 6 months after a vocal-cord injection of Teflon or of silicone elastomer. Macroscopic studies of the liver, lungs, spleen, kidney, and brain were performed. The histological study showed a greater proportion of chronic granulomatous inflammation in animals injected with silicone than in those injected with Teflon. The immunohistochemical study showed a higher degree of phagocytosis of Teflon particles than of the silicone particles. The silicone group presented a more severe fibrous reaction than the Teflon group, but the difference was not significant. No migration particles were found. It is concluded that silicone, having a greater viscosity than Teflon because of the size of its particles, induces more fibrosis and a larger proportion of foreign giant cells in the host. Due to this histological reaction, silicone particles present greater anchorage and stability.

TFF peptides in the human false vocal folds of the larynx

TFF peptides (formerly P domain peptides, trefoil factors) are typical secretory products of mucin-producing cells and are thought to influence the rheological properties of mucous gels. We investigated the localization of these peptides in the human false vocal folds of the larynx, also known as the ventricular folds or vestibular folds. An analysis of TFF peptide mRNA by RT-PCR and TFF protein by Western blot detected TFF1 and TFF3, but not TFF2. Immunohistochemistry revealed TFF1 to be associated with the secretory product of goblet cells and mucous parts of subepithelial seromucous glands. TFF3 occurred in columnar epithelial cells of the mucosa and in serous cells and excretory duct cells of seromucous glands. These peptides may play a role in the rheological function of mucus secreted onto the true vocal folds and are thus important constituents of vocal production.