HSC Section 6 Nov2016 Green Book

Branco et al

Figure 3. Vocal folds. (A) Control group: collagen I staining the basement membrane and the superficial layer. (B, C) Elderly groups: dense collagen I staining the superficial and deep layers of the lamina propria. Immunohistochemical reaction, 20 3 .

Figure 4. Vocal folds. (A) Control group: collagen III staining the basement membrane and the superficial layer. (B, C) Elderly groups: col- lagen III staining the superficial (B) and deep layers (C) of the lamina propria. Immunohistochemical reaction, 20 3 .

to Ohno et al, 25 the collagen increase in the elderly larynx affects the mucosal wave, resulting in decreases of phona- tory intensity and fundamental frequency, especially in women. The voice becomes failing and weak, a vocal pat- tern known as phonasthenia. 26 In an attempt to better understand what causes the abnor- mal production of collagen in the elderly larynx, Koszty 1 a- Hojna et al 27 studied the ultrastructure of vocal folds retrieved at elderly autopsies or from total laryngectomies due to supra- glottic larynx carcinomas, without damage to the actual vocal folds. Using transmission electronic microscopy, the authors observed the destruction of epithelial cells, a vacuolar degen- eration of the cell’s cytoplasm, a considerable increase of col- lagen fibers, a vacuolar degeneration of fibroblasts, an increase of the endoplasmic reticulum, and an increase of blood vessels. These authors suggest that the increase of collagen fibers is connected to the cytoplasmatic alterations observed in fibro- blasts. This possibility is insufficiently supported by the litera- ture and therefore requires additional studies. Although the mechanisms are not yet understood, the elderly larynx fibroblasts produce collagen in an excessive and irregular way, as well as a lower amount of hyaluronic acid and elastic fibers. In a study of young and elderly rat larynx fibroblast cultures, Hirano et al 12 observed in the latter lower amounts of hyaluronic acid and higher concentrations of collagen I. They observed the opposite when the fibro- blasts were exposed to fibroblast growth factor, which was thus considered by the authors a potential therapeutic tool for

correlate the alterations in the vocal folds of the elderly population with the rest of the body’s epithelial covering, Ximenes Filho et al 18 performed the simultaneous histomor- phometric analysis of vocal folds and inguinal skin from 20 elderly cadavers (10 male and 10 female), finding similar alterations in both locations such as lamina propria and epithelial atrophy. The immunohistochemical staining revealed that this net- work is mainly formed by collagen I and III ( Table 1 ; Figures 3 and 4 ) with a significant decreased in density of elastin in the elderly larynx ( Table 1 ; Figure 7 ). These structural changes in the vocal fold cover are responsible for the hardening of the vocal folds, 6,19,20 clinically mani- fested by symptoms of hoarseness, vocal fatigue, and vocal range restriction, having a direct impact on speech in higher frequencies. 21,22 Keeping the proportion of elastic and collagen fibers in the lamina propria of the larynx is important for this organ to retain local resistance, provided by collagen fibers, and distensibility, given by the elastic fibers. Studies of the larynx in animals 23 and in humans 24 have confirmed the role of collagen I in resistance and that of collagen III and elastin in flexibility and elasticity. These parameters work as a ‘‘balance,’’ whose equilibrium determines the relative participation of the different vocal fold layers in phonation. When collagen fibers start to predominate in the lamina pro- pria, as seen in our study, the vocal folds become more rigid, which negatively affects voice qualities. 19 According

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