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A new example of ectopia: Oral hair in some rodent species

Authors:
  • Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences
ISSN 00124966, Doklady Biological Sciences, 2010, Vol. 431, pp. 117–120. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.S. Baranov, O.F. Chernova, N.Yu. Feoktistova, A.V. Surov, 2010, published in Doklady Akademii Nauk, 2010, Vol. 431, No. 4, pp. 559–562.
117
The term ectopia (heterotopia, tissue aberration)
means the appearance of morphological structures in
regions of the body where they are untypical; e.g.,
three cases of slight hair growth in the human oral cav
ity (in persons that had no hypertrichosis) have been
described [1–3]. Histological analysis has shown the
slightly keratinized gingival epithelium contains deep
hollows, through which “hairlike structures” are likely
to grow into the oral cavity, and follicles that some
what differ from those of normal skin hair. Medical
examination of these three patients did not show any
disease with which oral hair could be related (all the
three persons proved to be physically healthy); there
fore, it was assumed that oral hair growth was caused
by mutations affecting the gingival tissue [3].
It is known that some regions of the oral mucosa
are more or less keratinized in different mammals.
This is why gingival epithelium is capable of producing
derivatives, such as teeth, sebaceous glands, and hair.
Keratinization of the epithelium of the oral cavity may
be induced by mechanic injury during chewing of
food. In many rodent species, the buccal mucosa has
cutaneous cavities sparsely covered with thin, short
hairs associated with hypertrophied sebaceous glands
[4–6]. However, hair had never been found on the gin
gival or palatal mucosa before our study.
When preparing the skulls of hamsters
Phodopus
campbelli
from the vivarium of the Severtsov Institute
of Ecology and Evolution of the Russian Academy of
Sciences, we found an unusual structure, namely an
extremely welldeveloped of gingival and parodontal
pouches (hereinafter, pouches), cleftlike spaces
between the buccal surface of the tooth crown and the
gingival margin filled with “brushes” of vertical kerati
nous outgrowths, which later proved to be true hairs.
Similar structures were found in some other rodents
kept in the vivarium, namely
Ph. sungorus
and
Mus
musculus
(table). At the same time, they were absent in
Ph. robrovskii
, a closely related species of the same
genus, as well as in
Mesocricetus auratus
and
Rattus
norvegicus.
All examined rodents received the standard
diet developed in the Severtsov Institute of Ecology
and Evolution; the food contained oats and com
pound food for rodents.
The gingival and parodontal pouches were more or
less developed in all examined
Ph. campbelli
and
Ph. sungorus.
They were usually located at the internal
or buccal side of the maxillary tooth row, but they were
sometimes also found at the mandibular teeth and on
the palate behind or in front of the tooth row. The
number and sizes of these pouches considerably varied
in different species, in animals of different sexes and
ages, and in different parts of the palate in the same
individual. Some of them were as deep as the tooth
roots; in this case, the tooth row was shifted and the
teeth became loose. Some of these pouches contained
single hairs; others, thick bundles of colorless or pig
mented hairs reaching as high as the chewing surface
of the teeth. Sometimes, the tooth row was surrounded
with a regular brush of hair bundles on both sides. The
hairs grew vertically and had sharp ends, often covered
with lumps of a mucous–sebaceous substance. There
were no symptoms of gingivitis or other inflammations
on the gums or palate. At the same time, we found that
the bone tissue at these places was sometimes
destroyed and richly perforated.
In different individual
Ph. campbelli
, pouches con
taining hair were more often found on the maxilla and
less often, on the mandible. On the maxilla, they were
located on the right and on the left of the tooth row,
usually in the segment between M
1
and M
3
. They
number varied, in different individuals, from one to
five; the thickness of the hair bundles varied from sev
eral hairs to a dense brush tightly adjacent to the tooth.
Hair growth was especially pronounced in the pouches
located on the internal side of the tooth row. In some
cases, the pouches were located between teeth. The
interdental gingival space varied from 2–3 to 0.4–
1.2 mm in width, which was inversely related to the
degree of development of the pouches: if the hair brush
was thick and the pouch was deep and wide, the tooth
row was shifted and deformed. After removal of the
GENERAL
BIOLOGY
A New Example of Ectopia: Oral Hair in Some Rodent Species
A. S. Baranov
a
, O. F. Chernova
b
, N. Yu. Feoktistova
b
, and A. V. Surov
b
Presented by Academician E.I. Vorob’eva September 24, 2009
Received October 1, 2009
DOI:
10.1134/S0012496610020134
a
Kol’tsov Institute of Developmental Biology,
Russian Academy of Sciences, ul. Vavilova 26, Moscow,
119991 Russia
b
Severtsov Institute of Ecology and Evolution, Russian
Academy of Sciences, Leninskii pr. 33, Moscow,
119071 Russia
118
DOKLADY BIOLOGICAL SCIENCES Vol. 431 2010
BARANOV et al.
soft tissues of the palate, we found that the hair bun
dles were mainly adjacent to the processus alveolaris of
the maxillary bone. If there was a hair brush, the hairs
grew from hollows in the bone lined with mucosa, and
the bone was considerably perforated (Fig. 1). The
number of perforations varied from three or four to
eight or more; their configurations and sizes, from
round (0.08–0.3 mm) to oval (0.2
×
1.5 mm). The per
forated bone area varied from 0.5
×
2.5 to 2.5
×
4.0 mm, when it filled the entire space along the tooth
row and a thick bone ridge (crest) ran along the central
line of the maxillary bone (Fig. 2).
The hairs filling the pouches were not foreign frag
ments and had not been stuffed there during groom
ing; they were typical hairs with welldeveloped roots;
i.e., they grew directly from the keratinized mucosal
lining of the pouches. The number of hairs and the
sizes of the pouches considerably varied in different
individuals and in different pouches of the same indi
vidual. The hair length was usually 1–2 mm; some
times, it reached 2.5 mm. Their color was mostly yel
lowish, but black hairs were also sometimes observed.
The shape of the hair shaft was similar to the shape that
we earlier described in the study on specialized hairs
on the feet and midventral glands of
Phodopus
[6]. The
shaft was of regular cylindrical shape, with a narrower
stem above the root and gradual widening in the upper
third. It had a sharp end, which was sometimes slightly
bent. The medulla stretched along the entire shaft,
from the root to the sharp end (Fig. 3a). All hairs could
be divided into two types: (1) very thin (23.5
×
0.5
µ
m),
long hairs with a poorly developed and strongly pig
mented onelayered ladderlike medulla occupying as
much as 20% of the shaft width and (2) thickened
hairs (55.8
×
0.5
µ
m) with an unpigmented, well
developed (62%) medulla, which looked degenerative:
it consisted of a continuous chord or consisted of sep
arate, irregularly oriented wide septa, with poorly
developed air cavities. The pattern of the cuticle of
palatal hairs was similar to that of the skin hair cover of
Phodopus
[6]. The cuticle was semicircular or circular,
slightly flattened in the middle and at the top of the
(a)
GP A
(b)
Fig. 1.
(a) The external appearance of the oral cavity. Gingival pouches (GP) with thick bundles of hair growing from their mucous
lining are clearly seen. (b) Perforated bone tissue of the teeth of an adult
Ph. campbelli.
Numerous hollows are seen. A, hair.
The occurrence of animals with gingival pouches (percent of the total number of examined animals)
Species
Number of animals examined
Maxilla Mandible Palate
total number those with gingival
pouches, %
Ph. campbelli
50 50 Present Present Present
Ph. sungorus
20 40 The same The same The same
Mus musculus
10 20 Present Not found Not found
DOKLADY BIOLOGICAL SCIENCES Vol. 431 2010
A NEW EXAMPLE OF ECTOPIA: ORAL HAIR IN SOME RODENT SPECIES 119
shaft compared to its base (Fig. 3b). The cuticular
scales were as long as 10
µ
m at the base of the shaft and
shorter (up to 5
µ
m) above the middle of the shaft. The
free edges of the scales were slightly sinuate (Fig. 3d).
The outer surface of some hairs lacked the cuticle, and
its relief was formed by thickened edges of cortical
cells oriented along the shaft (Fig. 3c), which sug
gested that a strong mechanical effect had destroyed
their cuticular layer.
It remains unclear why these hair structures appear
in the oral cavity of mammals. We may only speculate
on the origin of this phenomenon. The gingival
pouches may result from paradontitis and paradonto
sis caused by feeding on compound food in the vivar
ium, i.e., by a suboptimal diet. This pathology may be
exacerbated by elements of the food that are absent in
natural food, such as genetically modified (GM)
ingredients (GM soybean or maize meal) or contami
nants (pesticides, mycotoxins, heavy metals, etc.).
Probably, hair growth in the gingival pouches is a pro
tective reaction of the body suppressing the progress of
gingival pathology, because the hair bundles are so
dense that they prevent food from getting into the
pouches and the resultant inevitable inflammation.
Hair grows in the parts of the mucosa that, being
affected by mechanical factors, acquire the capacity
for keratinization. However, this assumption does not
explain why oral hair has not been found in rats or
other animals from the vivarium, including hamsters
(
Ph. robrovskii
and
M. auratus
). It is unknown whether
this phenomenon occurs in natural populations of
rodents and, if so, how common it is.
It is noteworthy that this phenomenon has been
found in representatives of phylogenetically remote
taxa (rodents and humans). Further research is
required to determine the cause and mechanism of the
phenomenon of oral hair in mammals.
ACKNOWLEDGMENTS
We are grateful to D.M. Shchepotkin (Kol’tsov
Institute of Developmental Biology of the Russian
Academy of Sciences) for the assistance in preparing
the photographs.
This study was supported by the Grant of the Presi
dent of the Russian Federation for Leading Scientific
Schools (project no. NSh7522.2010.4), Russian Foun
dation for Basic Research (project no. 0904000 701),
10
µ
m
a
b
Fig. 2.
Different parts of hairs of the gingival pouches of an
adult male
Ph. campbelli.
The hairs are of two types: a large
guard hair with a continuous pigmented medulla that has a
degenerative structure and a small guard hair with a pig
mented onelayered ladderlike medulla; the medulla
reached (
a
) almost the very end of the hair and (
b
) the hair
root.
(a) 10
µ
m
10
µ
m
10
µ
m
10
µ
m
(b)
(c) (d)
Fig. 3.
(a) Cross sections and (b–d) the cuticle of hairs of
the gingival pouches of an adult male
Ph. campbelli.
(b) A
cylindrical or slightly deformed hair shaft with a central
medulla canal running along the middle of the shaft or
slightly shifted; the medulla is poorly developed. (c) A
destroyed cuticular layer; rough edges of cortical cells are
seen.
120
DOKLADY BIOLOGICAL SCIENCES Vol. 431 2010
BARANOV et al.
and the Program of the Presidium of the Russian
Academy of Sciences “Biological Diversity” (project
no. NOTs 02.740.11.02.82).
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Genus
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... Hypertrichosis in humans is regarded as a developmental anomaly. HC can underlie this phenomenon (premature development of hair coat in children), heterotopy (hair coat atypical body parts, up to gingival pocket in hamsters and rats (Baranov et al., 2010)), and heterogeny (male-type hair coat in women, e.g., beard and mustache) (Chernova, 2006a). The postembryonic development of hair has a growth cycle that includes three stages: stage of hair follicle formation (anagen), resting stage (telogen), and involution stage (katagen). ...
... [29]. Baranov ve arkadaşları tarafından yapılan çalışmada ise; genetiği değiştirilmiş soya ile beslenen farelerin ağız boşluğu içinde kontrol grubuna göre daha sıklıkla tüy oluşumunun gözlendiği bildirilmiştir [30]. Ermakova çalışmasında; genetiği değiştirilmiş soyadan elde edilen yem hammaddeleri ile beslenen çiftlik hayvanlarında; sperm sayısı düşüklüğü, embriyo gelişiminde önemli değişiklikler ve infant mortalitesinde artış olduğunu bildirmiştir [31]. ...
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A proven case of true hair occurring naturally in the mouth has been reported only once previously. A second case of this rare anomaly is reported here. In this case a single hair was found at the base of the attached gingiva in the mandibular cuspid region of a 45-year old white man.
Kozhnye zhelezy mlekopitayushchikh (Skin Glands of Mammals)
  • V E Sokolov
  • O F Chernova
Sistematika, filogeografiya, ekologiya, fiziologiya, povedenie, khimicheskaya kommunikatsiya (Hamsters of the Genus Phodopus: Phylogeography
  • N Feoktistova
  • Yu
  • Khomyachki Roda Phodopus
  • A E W Miles
  • Proc
  • Roy
Miles, A.E.W., Proc. Roy. Soc. Med., 1960, vol. 53, pp. 527–528.
  • R A Baughman
  • D Paul
  • Jr Heidrieh
  • Oral Surg
Baughman, R.A., Paul, D., and Heidrieh, Jr., Oral Surg. Med. Oral Pathol., 1980, vol. 49, pp. 530–531.
  • F Aghaahosseini
  • F Etesam
AghaaHosseini, F., Etesam, F., and Rohani, B., Med. Oral. Pathol. Oral Cir. Bucal., 2007, vol. 12, no. 5.
  • R A Baughman
  • D Paul
  • Heidrieh
Baughman, R.A., Paul, D., and Heidrieh, Jr., Oral Surg. Med. Oral Pathol., 1980, vol. 49, pp. 530-531.