Increase in dermal collagen fibril diameter and elastogenesis with UVB exposure: an optical and ultrastructural study in albino Balb/c mice.
Cutaneous aging is a complex biological phenomenon, dependent not only on the innate or intrinsic process ("biological clock"), but also on extrinsic elements, primarily chronic sun exposure (photoaging). In order to verify dermal morphological changes in the elastic fiber system and collagen associated with aged skin, we performed a light and electron microscopic study on exposed-shaved albino mice, which were exposed to UVB radiation. The experimental group consisted of 48 exposed animals, randomly distributed in three groups and submitted to different radiation doses (A, 28800 J/m2; B, 57600 J/m2; and C, 86400 J/m2) and studied 0, 30, 60 and 90 days of exposure discontinuation. Nonexposed-shaved and nonexposed-nonshaved animals were included as controls. From the day of exposure discontinuation and subsequently, the elastic system and collagen network were progressively modified. The increase in collagen fibril diameter was prominent in the 60 and 90 day groups (p<0.05), as noticed on electron microscopy. Elastic fiber density also increased after irradiation (p<0.05). On electron microscopy, elastogenesis was seen in the deep dermis. The comparative study among the groups disclosed clear relationship between doses and "elastotic changes". It also showed that chronological aging of mice skin was apparently intensified after UVB exposure. Skin elastogenesis seems to be a major consequence of UVB exposure, apart from elastolysis, and occurs not only in humans but also in hairless mice submitted to continuous, long-term UVB exposure.
Carneiro
Sueli Coelho
SC
HUCFF/UFRJ and School of Medicine, Federal University of Rio de Janeiro, Brazil. sueli@hucff.ufrj.br
Cassia
Flavia de Freire
Fde F
Pascarelli
Bernardo Miguel
BM
Souza
Sonia Oliveira
SO
Ramos-e-Silva
Marcia
M
Filgueira
Absalom Lima
AL
Japiassu
Maria Augusta
MA
Takiya
Christina Maeda
CM
D000818:Animals; D020405:Dermis / Q000503:physiopathology / Q000528:radiation effects* / Q000648:ultrastructure; D004548:Elasticity / Q000528:radiation effects; D024022:Fibrillar Collagens / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure; D051379:Mice; D008807:Mice, Inbred BALB C; D011829:Radiation Dosage; D015595:Skin Aging / Q000528:radiation effects; D013997:Time Factors; D014466:Ultraviolet Rays
D024022:Fibrillar Collagens