Recruitment patterns of side population cells during wound healing in rat vocal folds

Glycolysis of Tissue Stem Cells in the Macula Flava of Newborn Vocal Fold

OBJECTIVES

There is growing evidence that the cells in the maculae flavae are tissue stem cells and the maculae flavae are a stem cell niche of the human vocal fold mucosa. This study investigated the metabolic activity, especially glycolysis, of the tissue stem cells in the maculae flavae of the human newborn vocal fold.

METHODS

Three normal human newborn vocal folds obtained from autopsy cases were investigated using immunohistochemistry.

RESULTS

Among the three phenotypes of cells (cobblestone-like polygonal cells, vocal fold stellate cell-like cells and fibroblast-like spindle cells) in the newborn maculae flavae, a small number of cobblestone-like polygonal cells strongly expressed glucose transporter-1. All three phenotypes of cells in the newborn maculae flavae expressed glycolytic enzymes (hexokinase II, glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase A). The cells did not express phosphofructokinase-1 (rate-limiting enzyme of regular glucose metabolism pathway) but sparsely express glucose-6-phosphate dehydrogenase (rate-limiting enzyme) indicating the cells relied more on the pentose phosphate pathway. The cells' expression of lactate dehydrogenase A suggests the maculae flavae of the newborn vocal fold is likely to be an anaerobic microenvironment where cells perform anaerobic glycolysis.

CONCLUSIONS

The present study is consistent with the hypothesis that the tissue stem cells in the maculae flavae of the newborn vocal fold seem to rely more on anaerobic glycolysis, especially by the pentose phosphate pathway, for energy supply. Already at birth, the metabolism of the tissue stem cells in the maculae flavae of the newborn vocal fold is likely to prevent the formation of toxic reactive oxygen species and is likely favorable to maintaining the stemness and undifferentiated states of the tissue stem cells in the stem cell system.

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

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

Descriptive proteomics of paired human vocal fold and buccal mucosa tissue

The vast majority of voice disorders is associated with changes of the unique, but delicate, human vocal fold mucosa. The ability to develop new effective treatment methods is significantly limited by the physical inaccessibility and the extremely rare occasions under which healthy tissue biopsies can be obtained. Therefore, the interest in laryngological research has shifted to human oral (buccal) mucosa, a similar and more easily available tissue. The harvesting process is less invasive and accompanied with faster healing and less scarring, compared to vocal fold mucosa. Here we report a descriptive proteomic comparison of paired human buccal and vocal fold mucosa by high‐resolution mass spectrometry (CID‐MS/MS). Our study identified a total of 1575 proteins detected within both tissues that are highly consistent in several crucial biological processes, cellular components, and molecular functions. Hence, our proteomic analysis will provide a fundamental resource for the laryngological research community.

[Molecular laryngology : A new chapter in the understanding of laryngeal diseases]

BACKGROUND

Despite considerable advances in laryngological research, there is still a plethora of (benign) vocal fold pathologies that cannot be treated causally. This is due to the limited accessibility and sensitive microarchitecture of the vocal folds, which cannot be investigated at a cellular level. Consequently, current pathophysiological knowledge is frequently based on macroscopic findings. The impact of interventions is mainly evaluated endoscopically or via indirect diagnostic methods.

OBJECTIVE

The aim of this article is to discuss state-of-the-art biotechnological methods used in laryngological research, illustrated by practical examples.

RESULTS

In recent years, animal and in vitro experiments have significantly contributed to a continuous expansion of knowledge in this field, particularly regarding vocal fold inflammation and scar formation. Vocal fold fibroblasts, the most important cellular component of the lamina propria, can be accredited a central role in these processes.

CONCLUSION

Our knowledge regarding macroanatomy and macropathophysiology of several pathologies has increased considerably in recent years. In vitro trials have shown, e.g., that vocal fold fibroblasts in an inflammatory setting secrete less profibrotic and proinflammatory cytokines when exposed to vibration. Early vocal exercises after surgical interventions on the vocal folds may therefore promote better wound healing and consequently improved phonation. Research in molecular laryngology should create a solid basis of knowledge for subsequent clinical studies.

Heterogeneity of Stem Cells in the Human Vocal Fold Mucosa

1. There is growing evidence to suggest that the cells in the maculae flavae are tissue stem cells of the human vocal fold and maculae flavae are a candidate for a stem cell niche. 2. The latest research shows that the cells in the human maculae flavae are involved in the metabolism of extracellular matrices that are essential for viscoelasticity in the human vocal fold mucosa as a vibrating tissue and are considered to be important cells in the growth, development, and aging of the human vocal fold mucosa. 3. Recent evidence has indicated that the cells including vocal fold stellate cells in the maculae flavae of the human vocal fold mucosa are a functionally heterogenous population. 4. The cells in the human maculae flavae possess proteins of all three germ layers, indicating that they are undifferentiated and have the ability of multipotency. 5. The cell division in the human adult maculae flavae is reflective of asymmetric self-renewal, and cultured cells form a colony-forming unit. Therefore, the phenomenon gives rise to the strong possibility that the cells in the human maculae flavae are putative stem cells. 6. Recent research has suggested that the cells in the human maculae flavae arise from the differentiation of bone marrow cells via peripheral circulation. 7. Cultured cell populations in the human maculae flavae are roughly divided into three groups by morphological features: cobblestone-like polygonal cells, vocal fold stellate cell-like cells, and fibroblast-like spindle cells. However, at the present state of our investigation, it is difficult to clarify the stem cell system and hierarchy of stem cells in the human maculae flavae. 8. Subpopulations of cells in the maculae flavae proliferate extremely slowly and retain stem cell properties. 9. Tension caused by phonation seems to regulate the behavior and heterogeneity of the cells (mechanical regulation) in the maculae flavae of the human vocal fold. 10. The putative stem cells in the maculae flavae appear to differentiate into other kind of cells in the surrounding tissue.

Liquid-type non-thermal atmospheric plasma ameliorates vocal fold scarring by modulating vocal fold fibroblast

Injection laryngoplasty is a widely used therapeutic option for drug delivery into vocal folds (VFs). Efficient injectable materials are urgently needed for treating intractable VF disease. Liquid-type non-thermal atmospheric plasma (LTP) has been found to be useful for various biological applications, including in regenerative medicine. We evaluated the effects of LTP on VF regeneration. Migration and matrix metalloproteinase-2 expression of lipopolysaccharide (LPS)-treated human vocal fold-derived mesenchymal stem cells (VF-MSCs) were enhanced by LTP treatment. LTP treatment not only ameliorated nuclear factor-κB and interleukin-6 activation, induced by LPS treatment, but also the increased manifestation of α-smooth muscle actin and fibronectin, induced by transforming growth factor-ß. In a rabbit VF scarring animal model, histological analyses showed increased hyaluronic acid deposition and decreased collagen accumulation after LTP injection. Videokymographic analysis showed more improved vibrations in LTP-treated VF mucosa compared to those in non-treated group. In conclusion, LTP treatment enhanced the recruitment and activation of VF-MSCs. Regulated extracellular matrix (ECM) synthesis and eventual functional improvement of scarred VFs were observed upon LTP treatment. The results of this study suggest that LTP injection can enhance wound healing and improve functional remodeling following VF injury.

Impact statement

Voice disorder has a significant impact on life quality, and one of the major causes of this voice disorder is vocal fold scarring. Therefore, various approaches have been tried to treat for voice disorder. However, no method has satisfied all requirements until now. Plasma medicine, which involves the medical application of plasma, is a rapidly developing field. We have confirmed that liquid-type plasma improved vocal fold scarring by mobilizing and activating vocal fold fibroblast. In conclusion, liquid-type plasma is a potential therapeutic agent for promoting vocal fold scarring through simple injection and it may be an alternative therapeutic agent for the current situation to treat voice disorder.

Differentiation potential of the cells in the macula flava of the human vocal fold mucosa

The latest research suggests cells in the maculae flavae located at both ends of the lamina propria of the human vocal fold mucosa have stemness. This study investigated the differentiation potential of the cells in the maculae flavae of the human vocal fold mucosa. Four normal human adult vocal folds from surgical specimens were used. After extraction of the anterior maculae flavae located at the anterior end of the lamina propria of the human vocal fold mucosa under microscope, the maculae flavae were minced, cultured and proliferated in mesenchymal stem cell growth medium and morphological features were assessed. Cell surface markers were detected using flow cytometry. Cell differentiation into adipogenic, chondrogenic and osteogenic lineages was performed. Cell's differentiation potential was assessed using a human pluripotent stem cell functional identification kit and immunohistochemistry. Subcultured cells formed a colony-forming unit. Subcultured cells expressed CD90, CD105 and CD73 and lacked expression of CD45, CD34, CD11b, CD19 and HLA-DR. They differentiated into adipogenic, chondrogenic and osteogenic lineages. Consequently, the cell features in the maculae flavae meet the minimal criteria defining mesenchymal stromal cells. In addition, subcultured cells differentiated into ectoderm, mesoderm and endoderm and expressed stage-specific embryonic antigen 3 (SSEA-3). The results of this study are consistent with the hypothesis that the cells in the maculae flavae in the lamina propria of the human vocal fold mucosa are putative stem cells.

Distribution of label-retaining cells and their properties in the vocal fold mucosa

Objective

The latest research suggests cells in the maculae flavae (MFe) are putative stem cells of the vocal fold mucosa and the MFe are a candidate for a stem cell niche. Distribution and properties of label-retaining cells (LRCs) in the vocal fold mucosa were investigated.

Study Design

Histologic analysis of the rat vocal folds.

Methods

Oral administration of bromodeoxyuridine (BrdU) was given to rats and the LRCs in the vocal fold mucosa were observed by immunohistochemistry. Immunoreactivity to antibodies directed to BrdU, Ki67, cytokeratin, vimentin, glial fibrillary acidic protein, desmin, Sox17, CD34, CD45, Type I collagen, and CD44 was studied. Extracellular matrices around LRCs were observed by Alcian blue staining and hyaluronidase digestion study.

Results

LRCs were present in the MFe and were resting cells (G0-phase). They expressed epithelium, muscle, neural, and mesenchymal cell-associated intermediate filament proteins, and an endodermal marker, indicating cells in the MFe are undifferentiated and express proteins of all three germ layers. They expressed hematopoietic markers (CD34, CD45) and Type I collagen, which are the major markers of bone marrow derived circulating fibrocytes. The hyaluronan concentration in the MFe was high and the cells in the MFe expressed the surface hyaluronan receptor CD44, indicating that the MFe were a hyaluronan-rich matrix.

Conclusion

LRCs reside in the MFe and MFe had a hyaluronan-rich matrix. The results of this study are consistent with the hypothesis that the cells in the MFe are putative stem cells and the MFe are a candidate for a stem cell niche.

Level of Evidence

N/A.

Comparative characteristics of laryngeal-resident mesenchymal stromal cell populations isolated from distinct sites in the rat larynx

BACKGROUND

Although tissue-resident mesenchymal stromal cells (MSCs) in the larynx have been described, their distinct characteristics and roles have not been thoroughly explored. Therefore, we investigated stem cell characteristics and regenerative potentials of single clonal populations isolated from rat epiglottic mucosa (EM), lamina propria (LP), and macula flava (MF) to determine whether they comprised laryngeal tissue-resident stem cells.

METHODS

Single clonal laryngeal cells were isolated following microdissection of the EM, LP, and MF from the rat larynx. Several clonal populations from the three laryngeal subsites were selected and expanded in vitro. We compared the stem cell characteristics of self-renewal and differentiation potential, as well as the cell surface phenotypes and gene expression profiles, of laryngeal MSC-like cells to that of bone marrow MSCs (BM-MSCs). We also investigated the regenerative potential of the laryngeal cells in a radiation-induced laryngeal injury animal model.

RESULTS

Self-renewing, clonal cell populations were obtained from rat EM, LP, and MF. EM-derived and LP-derived clonal cells had fibroblast-like features, while MF-resident clonal cells had stellate cell morphology and lipid droplets containing vitamin A. All laryngeal clonal cell populations had MSC-like cell surface marker expression (CD29, CD44, CD73, and CD90) and the potential to differentiate into bone and cartilage cell lineages; EM-derived and MF-derived cells, but not LP-derived cells, were also able to differentiate into adipocytes. Clonal cells isolated from the laryngeal subsites exhibited differential extracellular matrix-related gene expression. We found that the mesenchymal and stellate cell-related genes desmin and nestin were enriched in laryngeal MSC-like cells relative to BM-MSCs (P < 0.001). Growth differentiation factor 3 (GDF3) and glial fibrillary acidic protein (GFAP) transcript and protein levels were higher in MF-derived cells than in other laryngeal populations (P < 0.001). At 4 weeks after transplantation, laryngeal MF-derived and EM-derived cells contributed to laryngeal epithelial and/or glandular regeneration in response to radiation injury.

CONCLUSIONS

These results suggest that cell populations with MSC characteristics reside in the EM, LP, and MF of the larynx. Laryngeal MSC-like cells contribute to regeneration of the larynx following injury; further investigation is needed to clarify the differential roles of the populations in laryngeal tissue regeneration, as well as the clinical implications for the treatment of laryngeal disease.

Cell therapy and vocal fold scarring

Vocal fold microstructure is complex and can be affected by laryngeal microsurgery, inducing scarring that prevents mechanical uncoupling of epithelium and muscle, leading to vibration disorder and disabling dysphonia. Treatment options presently are few, and often without efficacy for vibration, having only an impact on volume to reduce glottal closure defect. The present review of the literature had two aims: (i) to report the current state of the literature on cell therapy in vocal fold scarring; and (ii) to analyze the therapeutic interest of the adipose-derived stromal vascular fraction in the existing therapeutic armamentarium. A PubMed^® search conducted in September 2016 retrieved English or French-language original articles on the use of stem cells to treat vocal fold scarring. Twenty-seven articles published between 2003 and 2016 met the study selection criteria. Mesenchymal stem cells were most widely used, mainly derived from bone marrow or adipose tissue. Four studies were performed in vitro on fibroblasts, and 18 in vivo on animals. End-points comprised: (i) scar analysis (macro- and micro-scopic morphology, viscoelastic properties, extracellular matrix, fibroblasts); and (ii) assessment of stem cell survival and differentiation. The studies testified to the benefit of mesenchymal stem cells, and especially those of adipose derivation. The stromal vascular fraction exhibits properties that might improve results by facilitating production logistics.

The Macula Flava of the Human Vocal Fold as a Stem Cell Microenvironment

1. There is growing evidence to suggest that the cells in the maculae flavae are tissue stem cells of the human vocal fold and maculae flavae are a candidate for a stem cell niche. 2. The latest research shows that the cells in the human maculae flavae are involved in the metabolism of extracellular matrices that are essential for the viscoelasticity in the human vocal fold mucosa as a vibrating tissue, and considered to be important cells in the growth, development, and aging of the human vocal fold mucosa. 3. The cells in the human maculae flavae possess proteins of all three germ layers, indicating they are undifferentiated and have the ability of multipotency. 4. The cell division in the human adult maculae flavae is reflective of asymmetric self-renewal and cultured cells form a colony-forming unit. Therefore, the phenomenon gives rise to the strong possibility that the cells in the human maculae flavae are tissue stem cells. 5. Recent research suggests that the cells in the human maculae flavae arise from the differentiation of bone marrow cells via peripheral circulation. 6. The hyaluronan concentration in the maculae flavae is high and contains cells which possess hyaluronan receptors, indicating that the maculae flavae are hyaluronan-rich matrix, which is required for a stem cell niche. 7. A proper microenvironment in the maculae flavae of the human vocal fold mucosa is necessary to be effective as a stem cell niche maintaining the stemness of the contained tissue stem cells.

Cell origin in the macula flava of the human newborn vocal fold

BACKGROUND

There is growing evidence to suggest that cells in the maculae flavae are tissue stem cells of the human vocal fold and maculae flavae are a stem cell niche.

METHODS

Three newborn vocal folds were investigated. Immunoreactivity to antibodies directed to cytokeratin, desmin, glial fibrillary acidic protein, vimentin, cluster of differentiation 34, cluster of differentiation 45, collagen type I, telomerase reverse transcriptase, SOX17 and stage-specific embryonic antigen 3 was investigated.

RESULTS

The cells in the newborn maculae flavae expressed haematopoietic markers (cluster of differentiation 34, cluster of differentiation 45) and collagen type I, which are the major makers of bone marrow derived circulating fibrocytes. The cells expressed epithelium, muscle, neural and mesenchymal cell associated proteins, and endodermal marker, indicating that they are undifferentiated and express proteins of all three germ layers. The cells also expressed stage-specific embryonic antigen 3 and telomerase reverse transcriptase.

CONCLUSION

The cells in the newborn maculae flavae are undifferentiated cells arising from the differentiation of bone marrow cells. The results of this study are consistent with the hypothesis that the cells in maculae flavae are tissue stem cells.

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.

Stem cell approaches for vocal fold regeneration

OBJECTIVES/HYPOTHESIS

Current interventions in the management of vocal fold (VF) dysfunction focus on conservative and surgical approaches. However, the complex structure and precise biomechanical properties of the human VF mean that these strategies have their limitations in clinical practice and in some cases offer inadequate levels of success. Regenerative medicine is an exciting development in this field and has the potential to further enhance VF recovery beyond conventional treatments. Our aim in this review is to discuss advances in the field of regenerative medicine; that is, advances in the process of replacing, engineering, or regenerating the VF through utilization of stem cells, with the intention of restoring normal VF structure and function.

DATA SOURCES

English literature (1946-2015) review.

METHODS

We conducted a systematic review of MEDLINE for cases and studies of VF tissue engineering utilizing stem cells.

RESULTS

The three main approaches by which regenerative medicine is currently applied to VF regeneration include cell therapy, scaffold development, and utilization of growth factors.

CONCLUSION

Exciting advances have been made in stem cell biology in recent years, including use of induced pluripotent stem cells. We expect such advances to be translated into the field in the forthcoming years. Laryngoscope, 126:1865-1870, 2016.

Origin of Vocal Fold Stellate Cells in the Human Macula Flava

Objectives:

There is growing evidence that vocal fold stellate cells (VFSCs) in the human maculae flavae are tissue stem cells of the human vocal fold and that the maculae flavae are a stem cell niche. The origin of the cells in the human maculae flavae (CHMF) and the relationship with bone marrow–derived cells were investigated.

Methods:

Five human adult vocal fold mucosae were investigated. The CHMF were subcultured and morphological features were assessed. Immunoreactivity to antibodies directed to cytokeratin, desmin, GFAP, vimentin, CD34, CD45, and collagen type I was investigated.

Results:

Cultured CHMF formed a colony-forming unit, indicating they are mesenchymal stem cells or stromal stem cells in the bone marrow. The CHMF expressed hematopoietic markers (CD34, CD45) and collagen type I, which are the major makers for bone marrow–derived circulating fibrocytes. The cultured CHMF expressed epithelium-associated, muscle-associated, neural-associated, and mesenchymal cell–associated proteins, indicating the CHMF are undifferentiated and express proteins of all 3 germ layers.

Conclusions:

The CHMF are undifferentiated cells derived from the differentiation of bone marrow cells. The results of this study are consistent with the hypothesis that the VFSCs are tissue stem cells or progenitor cells of the human vocal fold mucosa.

Age effects on extracellular matrix production of vocal fold scar fibroblasts in rats

Vocal fold (VF) fibroblasts are the central subject of interest in fibrogenesis and wound healing after VF injury. Scar fibroblasts (SF) exhibit an aberrant production of several extracellular matrix (ECM) components which lead either to VF fibrosis or scarless wound healing. This study aimed to investigate the role of age at the time of injury on ECM production of SF. This is designed as an animal study. VF injury was established unilaterally in eight male Sprague-Dawley rats [3 months of age (n = 4), 11 months of age (n = 4)], while the other side was left intact. Three months after injury the larynges were excised and fibroblasts were extracted from VF [normal fibroblasts (NF)–scar fibroblasts (SF)] and cultured in vitro. After first passage, VF fibroblasts were plated in 24-well plates and levels of hyaluronic acid (HA) and collagen type I were determined enzymatically from supernatant after 24 and 72 h. Cultured SF from younger animals produced significantly higher levels of HA compared to NF fibroblasts from the same animals. HA concentrations of the older animals did not differ significantly between the NF and SF cultures, but the range in SF cultures was large. In contrast to previous studies, we found that even 3 months after VF injury cultured SF from young animals expressed higher levels of HA in comparison to SF from older animals. No difference in collagen levels were observed between the younger and older animals. Age of animals is an essential factor during VF healing and has to be considered for study design.

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.

Experimental methods for the characterization of the frequency-dependent viscoelastic properties of soft materials

A characterization method based on Rayleigh wave propagation was developed for the quantification of the frequency-dependent viscoelastic properties of soft materials at high frequencies; i.e., up to 4 kHz. Planar harmonic surface waves were produced on the surface of silicone rubber samples. The phase and amplitude of the propagating waves were measured at different locations along the propagation direction, which allowed the calculation of the complex Rayleigh wavenumbers at each excitation frequency using a transfer function method. An inverse wave propagation problem was then solved to obtain the complex shear/elastic moduli from the measured wavenumbers. In a separate, related investigation, dynamic indentation tests using atomic force microscopy (AFM) were performed at frequencies up to 300 Hz. No systematic verification study is available for the AFM-based method, which can be used when the dimensions of the test samples are too small for other existing testing methods. The results obtained from the Rayleigh wave propagation and AFM-based indentation methods were compared with those from a well-established method, which involves the generation of standing longitudinal compression waves in rod-shaped test specimens. The results were cross validated and qualitatively confirmed theoretical expectations presented in the literature for the frequency-dependence of polymers.

Vocal fold scars: current concepts and future directions. Consensus report of the Phonosurgery Committee of the European Laryngological Society

Scarring of the vocal folds leads to a deterioration of the highly complex micro-structure with consecutively impaired vibratory pattern and glottic insufficiency. The resulting dysphonia is predominantly characterized by a reduced vocal capacity. Despite the considerable progress in understanding of the underlying pathophysiology, the treatment of scarred vocal folds is still an unresolved chapter in laryngology and phonosurgery. Essential for a successful treatment is an individual, multi-dimensional concept that comprises the whole armamentarium of surgical and non-surgical (i.p. voice therapy) modalities. An ideal approach would be to soften the scar, because the reduced pliability and consequently the increased vibratory rigidity impede the easiness of vibration. The chosen phonosurgical method is determined by the main clinical feature: Medialization techniques for the treatment of glottic gap, or epithelium freeing techniques for improvement of vibration characteristics often combined with injection augmentation or implantation. In severe cases, buccal mucosa grafting can be an option. New developments, include treatment with anxiolytic lasers, laser technology with ultrafine excision/ablation properties avoiding coagulation (Picosecond infrared laser, PIRL), or techniques of tissue engineering. However, despite the promising results by in vitro experiments, animal studies and first clinical trials, the step into clinical routine application has yet to be taken.

Vocal fold stem cells and their niche in the human vocal fold

OBJECTIVES

Vocal fold stellate cells (VFSCs) in the maculae flavae have many morphological differences from conventional fibroblasts in the human vocal fold mucosa. It is uncertain whether the VFSCs are derived from the same embryonic source as conventional fibroblasts. The purpose of this study was to investigate the stemness of the VFSCs and whether the pericellular matrices in the maculae flavae are a hyaluronan-rich matrix, which is required for a stem cell niche.

METHODS

Paraffin-embedded specimens were stained with Alcian blue (pH 2.5) for a hyaluronidase digestion study. Immunoreactivity to antibodies directed to CD44, CD133, Oct-4, Ki67, and telomerase was investigated in 5 human adult vocal fold mucosae.

RESULTS

The VFSCs were resting cells (G0-phase) and expressed a mesenchymal stem cell marker. The VFSCs did not express hematopoietic or embryonic stem cell markers. Telomerase resided in the VFSCs. The hyaluronan concentration in the maculae flavae was high and the VFSCs expressed hyaluronan receptors, indicating that maculae flavae are characterized by a certain criterion of hyaluronan-rich matrix.

CONCLUSIONS

There is growing evidence that the VFSCs in the human maculae flavae are somatic (mesenchymal) stem cells of the vocal fold, and that the maculae flavae may be a candidate for a stem cell niche that is a microenvironment nurturing a pool of VFSCs.

[Vocal fold scars: pathogenesis, diagnosis, therapy]

Scarring of the vocal folds leads to a deterioration of the highly complex microstructure with consecutively impaired vibratory pattern and glottic insufficiency. The resulting dysphonia is predominantly characterized by a reduced vocal capacity. Despite considerable progress in the understanding of the underlying pathophysiology, treatment of scarred vocal folds is still an unresolved chapter in laryngology and phonosurgery. Decisive for successful treatment is an individual, multidimensional concept that comprises the whole armamentarium of surgical and nonsurgical (e.g. voice therapy) modalities. The chosen phonosurgical method is determined by the main clinical feature: medialization techniques for treatment of glottic insufficiency, or epithelium-freeing techniques for improvement of vibration characteristics often combined with injection augmentation or implantation. In severe cases, buccal mucosa grafting can be an option. New developments include treatment with angiolytic lasers [pulse dye laser, PDL; potassium titanyl phosphate (KTP) laser], or techniques of tissue engineering. However, despite promising results with in vitro experiments, animal studies and first clinical trials, application in clinical routine has not yet been achieved.

Regenerative medicine of the larynx. Where are we today? A review

Tissue engineering is a multidimensional process combining cells, scaffold matrices, and chemical signals to produce a structure similar to a target tissue. These techniques have opened a completely new field in diagnosis and therapy in numerous fields, including that of laryngology. Laryngeal tissue engineering has emerged in the last decade, although clinical applications are rare. The reasons therefore are numerous including ethical reasons, as well as the extremely complex anatomical structure of the vocal fold. The search for new treatment options has also enlarged our knowledge about the microphysiology and micropathophysiology of the vocal fold. To date, only specific growth factors are in clinical use for treatment of vocal fold atrophy. Big advances have been made in creating state-of-the-art scaffolds with various techniques including biomaterials as well as fully synthetic polymers. These scaffolds are supposed to provide an optimal environment for residual or implanted cells. Several in vitro settings showed practicability of these scaffolds, also in studying effects of growth factors. Cell therapy is a powerful tool in regenerative medicine but bears the uncertainty of possible malignant transformation. The aim of this review was to give a comprehensive overview about current knowledge in the field of laryngeal tissue engineering and regenerative medicine, including restoration of both vocal folds and laryngeal cartilage, and furthermore to elucidate further trends in this fascinating field.