الفهرس 
ACKNOWLEDGEMENTSOnly 14 pages are availabe for public view
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Abstract
Animal and human studies have provided converging evidence that dehydration adversely affects vocal fold physiology and voice production. This is consistent with the well-accepted clinical practice of recognizing the importance of vocal fold hydration in maintaining optimal vocal physiology. However, Fisher and his colleagues (2001) have demonstrated bidirectional transepithelial water fluxes toward and away from the airway surface of native vocal folds. A pathway for the flux of water across the wet stratified squamous epithelium of the vocal fold has not been explicitly shown.
The discovery of the Aquaporins “AQP” family of water channel proteins has provided insights into molecular mechanisms of water permeability. Since AQPs are the only channels that are predominantly selective to the osmotic flow of water, these channels may play an important role in the transport of water across vocal fold epithelium.
AQPs expressions in mice larynx
In this study, the immune-fluorescencelocalization of aquaporin (AQP1-9) investigated in the mouse tracheal and laryngeal tissues. Immuno fluorescence stained tissue sections were viewed and imaged for each antibody for different tracheal and laryngeal levels, as most of the studies show localization of AQPs within small portion of the airway.
The immuno-fluorescence localization of aquaporins (AQP 1-8) in the mouse larynx and trachea was reported with no labeling for AQP 9.The localization of AQP1, AQP4, and AQP5 was evident at the vocal fold level.
AQP4 was densely expressed at the anterior commissure in the basal and intermediate layers of the squamous epithelium and was minimally extended Posterior through the vocal fold epithelium to be expressed atbasal layer only. In contrast to AQP4, strong AQP5 expression appeared in the surface and intermediate layers of the vocal fold over the entire length of the epithelium. On the other hand, AQP1 was detected in the subepithelial connective tissue including the perichondrium but not at the vocal fold epithelium.
The unique expression of AQPs throughout the vocal fold length and layer with subepithelial connective tissue forms a network facilitating transcellular water movement. This suggests a potential critical role of AQPs in regulating vocal fold fluid homeostasis.
Expression of AQP1, AQP4, and AQP5 were significantly decreased at the vocal process. However, their biological significance is unclear.
The laryngeal hydration was supplied not only by the transepithelial water flux, but also by serous and mucous secretion from the laryngeal glands.
Immuno-fluorescence staining revealed an extensive network of AQP2, AQP3, AQP5, AQP6, AQP7, and AQP8 expression at the submucosal, saccular, and laryngeal glands. All AQPs were found to be expressed on the apical surface of the glandular epithelium.
Studies have suggested that a neural regulation of AQPs channels in peripheral organs may exist. In order to determine whether this is true for the larynx and trachea or not, unilateral vagotomiezed mice where used for localization of the AQPs.
The results showed that significant decrease of AQP s expression at the glandular tissue (AQP 2, 3, 5, 6, 7, and 8) in vagotomized side in comparison to contralateral side with no significant difference could be detected for AQPs epithelial expression. The significant decreased was evident for mice scarified after three weeks. Thus, AQPs are important molecules for parasympathetic controlled laryngeal gland secretion.
The more striking finding was a significant decrease of the AQPs expressed at the glandular tissue in the aged mice compared with young mice. This decrease in the AQPs could cause the alteration of laryngeal secretion with aging and age related voice changes.
AQPs expressions in Human Vocal Folds
The study continue to involve human vocal fold sample from vocal fold cyst, polyp, and Reinke’s edema to be compared with normal control healthy tissue sample of vocal fold from patients undergoing total laryngectomy.
In healthy vocal fold tissue as well as vocal fold cyst, AQP1 was located in the endothelial cells of microvessels in the lamina propria of the human vocal fold. AQP5 was expressed in the apical side of the vocal fold epithelium. AQP4 couldn’t be detected in the human vocal fold in contrast with animal study.
AQP1 is considered to serve for the water permeability of microvessels in the lamina propria.AQP5 localized on the apical side of vocal fold epithelium might play important roles in water permeability of vocal fold epithelium.
In unhealthy vocal fold sample, AQP5 in the vocal fold epithelium was significantly decreased in Reinke’s edema and central portion of the vocal fold polyp, while subepithelial AQP1 was significantly increased with Reinke’s edema. Altered expression of AQPs might be related with the patho-physiology of Reinke’s edema and vocal fold polyp.
Thus, this study could be the first light for more understanding of the unclear mechanism of vocal fold hydration and could give new understanding for dysphonia patho-physiology hoping better prevention and management.
Conclusion and Recommendations
The animal part of this study demonstrates specific pattern of AQPs expression in the larynx. AQP1, AQP4, and AQP5 were detected to be broadly expressed throughout the vocal fold. While, AQP 2, AQP 3, AQP 5, AQP 6, AQP 7, and AQP 8 were evidently expressed at the airway gland at which their expression was evident to be controlled by vagus nerve. Thus, AQPs showed specific expression in the larynx, which indicates their important roles in vocal fold lubrication.
AQP1, and AQP5 were detected to be broadly expressed in human vocal fold and no expression could be detected for AQP4.
More interesting, AQPs expression in the human vocal fold was altered in the patients with vocal fold polyp and Reinke’s edema. These results suggest the functional importance of AQPs in laryngeal water homeostasis and pathology of laryngeal diseases.
This suggests the functional importance of AQPs in the larynx water homeostasis. However, more information’s still to be known about AQPs in the larynx.
I. Further studies are required to elucidate both the physiological and patho-physiological roles of AQPs in larynx using knockout mice.
II. Also further extended study to examine the expression of AQPs in Vocal fold different lesion with detailed correlation to patient data ”e.g. smoking” and lesion clinical subtype needed.