ARTICLE
Connective tissues, especially the skin, undergo alterations during aging.
This has led to the hypothesis that cells in the extra cellular matrix,
as well as the extra cellular matrix itself, are involved in the aging process.
Moreover, ultraviolet radiation is thought to induce adverse reactions in
the skin, leading to photodamage. The UV-induced lesions are due to, in
part, reactive oxygen species.
Vitamin C (L-ascorbic acid) is essential for life in humans. Since the
discovery in the 1930s that vitamin C is the antiscorbutic factor, much
work has been undertaken to elucidate its mechanisms of action. In relation
to dermatology, the roles of vitamin C are as a reductant and in collagen
synthesis. Ascorbic acid is an important regulator of collagen expression
and increases the expression of type I mRNAs in some fibroblasts. Thus,
it stimulates procollagen synthesis in cultured human skin fibroblasts.
Moreover vitamin C levels of the skin can be severely depleted after W
irradiation.
On the basis of in vitro and in vivo studies, it has been
postulated that vitamin C could be used topically for prevention and correction
of skin aging. However, only a small amount of work deals with the interest
of topical application of vitamin C in chronic skin damage in which oxidative
stress and collagen synthesis play a determinant role. Moreover, to be
biologically active, vitamin C must remain in a free form and be stable.
Thus, a formulation (5% vitamin C w/o emulsion) corresponding to these
two important criteria was assessed in 20 female volunteers (55-60 years),
with photoaged skin (low neck) during a 6 month daily application. The
study was conducted in double blind versus placebo. Topographical, biophysical
and mechanical properties of the skin were measured, and biochemical analyses
of the collagen metabolism under treatment were performed on skin biopsies.
The study was conducted in agreement with the "Declaration of Helsinki"
and approved by the ethical committee of the University hospital Saint-Jacques,
in Besançon, France. [The method that examined the skin relief
is a new one in terms of result expression.] It involved a negative replica
of the skin areas before and 6 months after treatment with either the
5% vitamin C cream or the placebo. The relief of the replicas was measured
using a three-dimensional laser microscope allowing a resolution of 1
mm. The 3D image obtained was then analysed using a new approach of skin
surface morphology which allowed us to classify skin furrows according
to their depth, width and orientation. The furrow families can be represented
as a three-dimensional tree which permitted us to classify the organisation
of skin relief in 3 main categories, i.e., microrelief (0-10 mum
depth), medium (10-20 mum) and deep furrows (> 20 mum).
Results showed that compared to placebo there exists a highly significant
increase in the density of skin microrelief as well as a decrease of the
deep furrows on the side of the low neck treated with the vitamin C cream.
Clinical examination by the dermatologist as well as self assessment by
the patients confirmed the improvement of the skin relief, especially
of the fine wrinkles; thus, confirming the relevance of the new approach
of the measurement of skin surface morphology used in this study.
Moreover, ten patients accepted a skin biopsy on their forearms, each
being treated with either the vitamin C emulsion, or the placebo. So,
at the termination of the treatment two 5 mum punch biopsies up to the
hypodermis were collected under local anesthesia at the site of the topical
application. One biopsy was used for classical morphology and electron
microscopy reported elsewhere (manuscript in preparation). The second
biopsy was used for measurement of the mRNAs coding for different proteins
and enzymes involved in collagen synthesis process.
The aim of the present study was to evaluate the effect on the dermal
cells of vitamin C administered by topical application on the skin of
normal human volunteers by measuring the steady state level of the mRNAs
of procollagens, their post-translational processing enzymes, the fibrillar
structures-associated proteoglycan, decorin, the main components of the
elastic fibers, elastin and fibrillins 1 and 2 and the enzymes involved
in the degradation of these matrix components. Such investigations performed
on small biopsies were made possible by the use of quantitative RT-PCR
controlled by original newly created internal standards of synthetic RNA.
The mRNAs were measured by RT-PCR made quantitative by simultaneous amplification
of internal standards of synthetic RNA. [Betty Nüsgens and Charles
Lapière, *Laboratory of Connective Tissues Biology, Tour de Pathologie,
University of Liège, Belgium.]
The mRNA of collagen type I and type III were increased to a similar
extent by vitamin C. The mRNA of three post-translational enzymes, procollagen
N- and C-proteinases and lysyloxidase were similarly increased. The mRNA
of decorin was also stimulated but elastin, fibrillin 1 and 2, MMP1, 2
and 9 were not modified by the vitamin. The stimulating activity of topical
vitamin C was most conspicuous in the women with the lowest dietary intake
of the vitamin. The results demonstrate that vitamin C penetrates up to
the dermis and further indicate that collagen synthesis not maximal in
postmenopausal women and can be increased. These data clearly show that
topically applied vitamin C can have a beneficial effect for treatment
of skin aging, the mechanism of action being related to an activation
of the collagen metabolism.
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