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

CoQ10 and Vitamin A Supplementation Support Voice Rehabilitation. A Double-Blind, Randomized, Controlled, Three-Period Cross-Over Pilot Study

Objectives: To evaluate the effectiveness of an adjuvant therapy (CoQ10 in its water-soluble form and vitamin A) in supporting voice rehabilitation in a large group of patients with muscle tension dysphonia (MTD).

Study Design: Twelve-week, double-blind, randomized, controlled, three-period cross-over pilot study. The primary endpoint was the change in the Dysphonia Severity Index (DSI) over the 12-week study period. Secondary endpoints were the changes in the subcomponents of DSI, including MPT, F0-high, I-low, and jitter. Exploratory endpoints were the changes in the Shimmer and in Voice Handicap Index (VHI).

Methods: Patients were randomly assigned in a 1:1 ratio to two counter-balanced arms. Group A (ADJ-PLA) patients were administered QTer 300 mg and Vit A acetate 500.000 Ul/g 1 mg twice daily for a 4-week intervention period, followed by a 4-week period of wash-out, and then were submitted to a last 4-week period of placebo. Patients in Group B (PLB-ADJ) were given the treatment period in reverse order. Both groups received a 45-min voice therapy in a group format once a day for 4 weeks during the first and the second active periods. The therapy was held during the wash-out period.

Results: The analysis of main time effect indicated a trend toward recovery of vocal function regardless of group assignment. A significant time by group effect was found on DSI [F = 3.4 (2.5, 80.5), p = 0.03], F0-high [F = 4.5 (2.6, 82.9), p = 0.008] and Shimmer [F = 3.6 (1.5, 46.9), p = 0.048], under CoQ10 and Vit A treatment, with a small effect size. There was no significant time by group effect on the other study measures, namely MPT, I-low, VHI.

Conclusions: A trend toward recovery of vocal function was observed in all the patients, likely due to voice rehabilitation. The improvement of DSI was greater under CoQ10 and Vitamin treatment, indicating a more pronounced improvement of vocal quality under adjuvant therapy. The study protocol was reviewed and approved by the Ethics Committee of Policlinico Umberto I Hospital, Rome, Italy Rif. 3069/13.02.2014.

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.

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

Objectives

The tension caused by phonation (vocal fold vibration) is hypothesized to stimulate vocal fold stellate cells (VFSCs) in the maculae flavae (MFe) to accelerate production of extracellular matrices. The distribution of hyaluronic acid (HA) and expression of CD44 (a cell surface receptor for HA) were examined in human vocal fold mucosae (VFMe) that had remained unphonated since birth.

Methods

Five specimens of VFMe (3 adults, 2 children) that had remained unphonated since birth were investigated with Alcian blue staining, hyaluronidase digestion, and immunohistochemistry for CD44.

Results

The VFMe containing MFe were hypoplastic and rudimentary. The VFMe did not have a vocal ligament, Reinke's space, or a layered structure, and the lamina propria appeared as a uniform structure. In the children, HA was distributed in the VFMe containing MFe. In the adults, HA had decreased in the VFMe containing MFe. In both groups, the VFSCs in the MFe and the fibroblasts in the lamina propria expressed little CD44.

Conclusions

This study supports the hypothesis that the tensions caused by vocal fold vibration stimulate the VFSCs in the MFe to accelerate production of extracellular matrices and form the layered structure. Phonation after birth is one of the important factors in the growth and development of the human VFMe.

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.

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.

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.

Microenvironment of macula flava in the human vocal fold as a stem cell niche

BACKGROUND

There is growing evidence that the cells in the maculae flavae are tissue stem cells of the human vocal fold mucosa, and that the maculae flavae are a candidate for a stem cell niche. The role of microenvironment in the maculae flavae of the human vocal fold mucosa was investigated.

METHOD

Anterior maculae flavae from six surgical specimens were cultured in a mesenchymal stem cell growth medium or a Dulbecco's modified Eagle's medium.

RESULTS

Using mesenchymal stem cell growth medium, the subcultured cells formed a colony-forming unit, and cell division reflected asymmetric self-renewal. This indicates that these cells are mesenchymal stem cells or stromal stem cells in the bone marrow. Using Dulbecco's modified Eagle's medium, the subcultured cells showed symmetric cell division without a colony-forming unit.

CONCLUSION

A proper microenvironment in the maculae flavae of the human vocal fold mucosa is necessary to be effective as a stem cell niche that maintains 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.

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.

Mechanical Regulation of Human Vocal Fold Stellate Cells

Objective:

It is generally accepted that tensile and compressive strains have direct effects on cell morphology and structure, including changes in cytoskeletal structure and organization. Cytoskeletons play the role of mechanoreceptor of the cells. Vocal fold stellate cells (VFSCs) in the human maculae flavae (MFe) are inferred to be involved in the metabolism of extracellular matrices essential for the viscoelasticity of the vocal fold mucosa. Our previous studies have supported the hypothesis that the tension caused by phonation (vocal fold vibration) regulates the behavior of the VFSCs. The microstructure of the intermediate filaments and the expression of their proteins were investigated in VFSCs in the MFe, which had remained unphonated since birth.

Methods:

Three adult vocal fold mucosae that had remained unphonated since birth were investigated by immunohistochemistry and electron microscopy.

Results:

The intermediate filaments of the VFSCs were fewer in number. The expression of their characteristic proteins (vimentin, desmin, and glial fibrillary acidic protein) was also reduced.

Conclusion:

Vocal fold vibration seems to affect VFSC morphology and structure, such as cytoskeletal structure and organization. This supports the hypothesis that vocal fold vibration regulates VFSC behavior in the human MFe. In addition to chemical factors, mechanical factors also appear to modulate VFSC behavior.

Cytoskeleton of newborn vocal fold stellate cells

OBJECTIVES/HYPOTHESIS

Vocal fold stellate cells (VFSCs) in the human maculae flavae located at both ends of the vocal fold mucosa are inferred to be involved in the metabolism of extracellular matrices of the vocal fold mucosa. Tension caused by phonation (vocal fold vibration) likely regulates the behavior of the VFSCs in the human maculae flava. Tensile and compressive strains have direct effects on cell morphology and structure, including changes in cytoskeletal structure and organization. Cytoskeletons play a role as mechanoreceptors for the cells. The microstructure of the intermediate filaments and the expression of their characteristic proteins were investigated regarding the human newborn VFSCs.

STUDY DESIGN

Histopathologic analysis of the human newborn vocal fold.

METHODS

Three newborn vocal fold mucosae were investigated by immunohistochemistry and electron microscopy.

RESULTS

The intermediate filaments in the cytoplasm of the newborn VFSCs were few in number. However, their characteristic proteins (vimentin, desmin, GFAP [Glial fibrillary acidic protein], cytokeratin) had already expressed.

CONCLUSION

The function and fate of VFSCs are regulated by various microenvironmental factors. Not only chemical factors but also mechanical factors could also modulate VFSC behaviors. The cytoskeletal structure of the newborn VFSCs is under development. And the newborn VFSCs have not acquired mechanical regulation.

LEVEL OF EVIDENCE

N/A.

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.

The effect of retinyl palmitate on healing of benign vocal fold lesions

The leading cause of vocal fold lesions such as nodules and polyps is phonotrauma, which causes microhematoma formation in the vocal fold cover that can initiate an inflammatory process. Vitamin A (Vit A) is essential for immunity, cellular differentiation and maintenance of respiratory epithelium. The aim of this study is to investigate the effect of Vit A (retinyl palmitate) on healing of vocal fold lesions, including vocal polyps and nodules. Eighteen patients with vocal fold lesions were included in the study. Of the patients, 13 had vocal polyps and 5 had vocal nodules. Patients received 90,000 IU oral Vit A in palmitate form daily for 2 months. In addition to Vit A treatment, only vocal hygiene recommendations were given to the patients, without any other medication or specific voice therapy. Pre- and post-treatment acoustic analysis [jitter % (jitt %), shimmer % (shim %), normalized noise energy (NNE), maximum phonation time (MPT), etc.] were performed. Lesion dimensions and stroboscopic findings were evaluated. Voice handicap index (VHI) was applied. Statistical analysis was performed between pre- and post-treatment measurements. Of the 18 patients, 8 had immature lesions (6 polyp-like lesions and 2 immature nodules) and 10 had mature lesion (7 polyps and 3 nodules). None of the patients showed complete healing. Partial response was seen in four patients with immature lesions. There were minimal changes in lesion dimensions, but this difference did not reach statistical significance. MPT of patients with immature lesions were close to significance level but overall MPT revealed no significant improvement (p = 0.051). Jitt %, shim % and NNE did not change significantly. In this study, the only statistically significant finding was VHI of the patients with immature lesions. Three of the patients complained of weight gain. Our data showed that Vit A at a given level of dose and duration seems to be ineffective in the treatment of benign vocal fold lesions. On the other hand, whether Vit A is effective on mature and immature lesions of vocal folds at higher doses and/or longer duration of treatment or not requires further studies.

Vocal Fold Stellate Cells in the Human Macula Flava and the Diffuse Stellate Cell System

Objectives:

Hepatic stellate cells (HSCs) are desmin-positive cells with perinuclear vitamin A droplets that play important roles in liver fibrogenesis. Morphologically similar cells have been found at many extrahepatic sites. Consequently, the concept of a diffuse stellate cell system has been proposed. Vocal fold stellate cells (VFSCs) in the human maculae flavae (MFs) are starlike in shape and possess lipid droplets and store vitamin A. In this study, the relationship between the VFSCs in the human MFs and the diffuse stellate cell system was investigated.

Methods:

Light and electron microscopic investigations and immunohistochemical studies were performed in 5 samples of human adult vocal fold mucosa.

Results:

The VFSCs showed the morphological features of the HSCs (ie, they were desmin-positive cells with perinuclear vitamin A droplets). Glial fibrillary acidic protein and vimentin were identified in the VFSCs in the MFs.

Conclusions:

The VFSCs in the human adult MFs express the neural and muscle-associated proteins seen in HSCs. Our present and previous investigations suggest that the VFSCs in the human MFs are a member of the diffuse stellate cell system. The VFSCs are considered a new category of cells in the human vocal fold. The MFs are proposed to be special microenvironments, known as niches, that nurture a pool of VFSCs.

Challenges and opportunities in the management of the aging voice

Presbyphonia, or age-related dysphonia, is a diagnosis of exclusion, and other comorbidities must be considered in a complete evaluation of elderly patients with dysphonia. The aging voice can have a significant effect on the quality of life of the patient. In addition to the molecular effects of aging on the laryngeal tissues, the etiology of presbyphonia is often multifactorial because of comorbidities in the other organ systems involved in phonation. After a comprehensive evaluation, presbyphonia may be treated conservatively with voice therapy or with a range of interventions. Research into tissue engineering and electrical reanimation offers future options for treatment of presbyphonia. Currently, a multidisciplinary approach offers the most complete improvement in the vocal quality of life in this patient population.

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

Objectives:

The tension caused by phonation (vocal fold vibration) is hypothesized to stimulate vocal fold stellate cells (VFSCs) in the maculae flavae (MFe) to accelerate production of extracellular matrices. The distribution of hyaluronic acid (HA) and expression of CD44 (a cell surface receptor for HA) were examined in human vocal fold mucosae (VFMe) that had remained unphonated since birth.

Methods:

Five specimens of VFMe (3 adults, 2 children) that had remained unphonated since birth were investigated with Alcian blue staining, hyaluronidase digestion, and immunohistochemistry for CD44.

Results:

The VFMe containing MFe were hypoplastic and rudimentary. The VFMe did not have a vocal ligament, Reinke's space, or a layered structure, and the lamina propria appeared as a uniform structure. In the children, HA was distributed in the VFMe containing MFe. In the adults, HA had decreased in the VFMe containing MFe. In both groups, the VFSCs in the MFe and the fibroblasts in the lamina propria expressed little CD44.

Conclusions:

This study supports the hypothesis that the tensions caused by vocal fold vibration stimulate the VFSCs in the MFe to accelerate production of extracellular matrices and form the layered structure. Phonation after birth is one of the important factors in the growth and development of the human VFMe.

Characteristics of age-related changes in cultured human vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Normal human vocal fold fibroblast (hVFF) primary cell lines are unavailable commercially and are very difficult to acquire, subsequently little is known about their characteristics. The purpose of this study was to compare the morphological and proliferation characteristics and gene expression of hVFFs from different aged donors.

STUDY DESIGN

In vitro.

METHODS

We developed three normal hVFF primary cell lines from donors aged 21 (21T), 59 (59T) and 79 (79T) years. We characterized their morphological features, proliferative abilities, telomere lengths, and their functional gene expression by quantitative real-time PCR.

RESULTS

The 21T line maintained a typical spindle shape until passage 14 whereas 59T and 79T changed morphology to wider, shorter cells at passage 7. Proliferation rates were constant for the 21T through passage 14; 59T's proliferative half-life was passage 9, whereas 79T maintained lower proliferation rates from passage 4. Gene expression levels for fibronectin, collagen I, collagen VI, procollagen I and elastin demonstrated similar patterns for all lines, however, relative amounts decreased with the age of donor. Telomere lengths did not show differences related with donor age.

CONCLUSIONS

hVFF primary cultures have limited proliferative capacity. The morphology, proliferation, differentiation, and gene expression levels of VFF can be affected by age, but senescence patterns were similar across the ages.

Irradiated macula flava in the human vocal fold mucosa

PURPOSE

There have been no investigations regarding radiation-induced damage on human maculae flavae (MFs) in the vocal fold mucosa (VFM) and on stellate cells (SC) in the MF. The VFM, especially MF, after irradiation was investigated histologically.

MATERIALS AND METHODS

The lamina propria of the irradiated VFM was investigated in 5 human adult vocal folds by light and electron microscopy.

RESULTS

Fibroblasts in the irradiated Reinke's space (RS) showed no morphological changes. Irradiated RS was composed of fibrous tissue with increased collagenous fibers. Most of the SC in the irradiated MF had dark cytoplasm. The nucleus-cytoplasm ratio was relatively small, but there were few intracellular organelles in the cytoplasm. Some SC showed degeneration. Fewer vesicles were present at the periphery of the cytoplasm. The MF was rather deficient in fibrous components. Elastic and collagenous fibers immediately surrounding SC in the irradiated MF were lower in number than usual, but elastic fibers and collagenous fibers composed of irregular collagen fibrils could be detected at a distance from SC. It was suggested that precursors of collagenous and elastic fibers synthesized by SC were damaged by irradiation. Radiation sensitivity of SC was higher than that of conventional fibroblasts in RS, and SC appeared to decrease their level of activity.

CONCLUSIONS

Radiation sensitivity of SC was different from that of conventional fibroblasts. Radiation induced not only changes in the lamina propria of the VFM but also dysfunction of the SC in the MF, and is one of the causes of voice disorders after irradiation.

Histopathologic investigations of the unphonated human vocal fold mucosa

CONCLUSION

Vocal fold vibration (phonation) after birth is one of the important factors in the growth and development of the human vocal fold mucosa.

OBJECTIVES

Stellate cells in the maculae flavae located at both ends of the vocal fold mucosa are inferred to be involved in the metabolism of extracellular matrices. Maculae flavae are also considered to be an important structure in the growth and development of the human vocal fold mucosa. Tension caused by phonation (vocal fold vibration) is hypothesized to stimulate stellate cells to accelerate production of extracellular matrices. Vocal fold mucosae unphonated since birth were investigated histologically.

SUBJECTS AND METHODS

Vocal fold mucosae, which were unphonated since birth, of three younger adults (17, 24, 28 years old) were investigated by light and electron microscopy.

RESULTS

Vocal fold mucosae were hypoplastic and rudimentary and did not have a vocal ligament, Reinke's space or a layered structure. The lamina propria appeared as a uniform structure. Some stellate cells in the maculae flavae showed degeneration. Not many vesicles were present at the periphery of the cytoplasm. The stellate cells synthesized fewer extracellular matrices, such as fibrous protein and glycosaminoglycan. Cytoplasmic processes of the stellate cells were short and shrinking. The stellate cells appeared to have decreased activity.

Cultured stellate cells in human vocal fold mucosa

Objectives:

Stellate cells in the maculae flavae, located at both ends of the human vocal fold mucosa, have been considered an independent category of cells. We aimed to isolate and subculture these stellate cells, and to observe their morphological characteristics.

Methods:

Stellate cells from the maculae flavae and fibroblasts from Reinke's space were cultured in three normal, adult human vocal fold mucosa preparations.

Results:

The subcultured cells from Reinke's space were conventional fibroblasts. The subcultured cells from the maculae flavae were stellate in shape and had cytoplasmic processes. They were larger than conventional fibroblasts, and lipid droplets in the cytoplasm disappeared in the second culture. These stellate cells proliferated by attaching their cytoplasmic processes to each other. During the seven to 10 month subculture period, each cell type continued to exhibit its own morphological characteristics.

Conclusion:

This study demonstrated that such stellate cells form an independent cell category, which should be considered as a new category of cells within the human vocal fold.

Changes in expression of extracellular matrix genes, fibrogenic factors, and actin cytoskeletal organization in retinol treated and untreated vocal fold stellate cells

The regulation of extracellular matrix (ECM) constituency is critical in maintaining vocal cord biomechanical viscoelasticity required for phonation. Recently our laboratory successfully isolated and cultured a novel cell called a vocal fold stellate cell (VFSC), thought to play a central role in laryngeal ECM metabolism, aging, scarring and cancer. Our laboratory has shown that these cells undergo transdifferentiation that is partially reversed by exposure to all-trans retinol (ATROH). Here we make the first report on the expression of various ECM components, MMPs, TIMPs, pro-fibrogenic cytokines, and other ECM modulators in transdifferentiated and deactivated VFSCs. We show that VFSCs maintain an ECM expression pattern similar to laryngeal cancer and scars but distinct from tracheal fibroblasts. Exposure to ATROH differentially affects the VFSC expression of ECM components, matrix-regulating enzymes, and fibrogenic factors suggesting that the inhibitory effects of this synthetic cofactor should be studied further in laryngeal fibrosis and scarring. We also show that increased exposure to retinol induces sequential reorganization of the actin cytoskeleton in activated VFSCs. Our findings demonstrate that VFSCs are capable of regulating vocal fold ECM constituency important throughout normal laryngeal development. Furthermore, our results implicate VFSC activation in ECM misregulation which is a hallmark of several laryngeal pathologies.

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.