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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
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
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
.
Branco et al
82