Pr Philippe HUMBERT
Abstract
This study highlights the role of photoaging and predominantly lateralized ultraviolet exposure as a determinant of facial asymmetry.
Photoaging is a phenotype of an individual that is considered to be the part of aging related to solar irradiation, which can be summarized as ultraviolet irradiation if we disregard infrared.
More than appearance, photoaging is also about histo-pathological disorders such as dystrophic elastic fibres, reduction in the collagen content of skin tissue and increased activity of prosthetic enzymes such as metalloprotease1 (MMP1).
UVA has the ability to modify skin cells in culture as well as in vivo.
Thus, for the first time it has been possible to quantify in terms of additional age the proportion of ageing due to exposure to ultraviolet radiation.
This part of ageing which is called photoageing is on average six years for 30 years of exposure (number of years of professional activity).
Thus, every five years, each individual can be considered to age an additional year as a result of exposure to the sun.
These findings provide important support for recommendations on photo-protection by any means.
The author concludes this work by insisting on the implementation of adapted preventive and curative methods, both topical and oral, with the administration of nutrients and food supplements with antioxidant properties.
Keywords: photo-aging, face, asymmetry, ultraviolet radiation, UVA, biometrology.
The human body is not symmetrical
It has always been noticed that the human body, despite its great perfection, is not symmetrical.
Seen from the outside, symmetry seems to be one of the characteristics of this body made up of even parts (limbs...) and odd parts (face...).
However, it would have been observed that the breasts of a woman are not totally superimposable, that the scrotum in the man, which the sculptors perfectly noticed (Michel-Angelo), was made up of a lower left bursa.
These are the most remarkable elements.
Inside this body, the asymmetry is even greater.
The lungs have three lobes on the right and two on the left.
The stomach is not medial but shifted to the left and so on...
As for the face, since we take special care in analyzing it, we will have noticed how asymmetrical it is.
This has been the subject of several medical publications, so-called "clinical cases" when it comes to showing the left side of a person who has been exposed to solar radiation for many, many years.
This was the case of a patient of Professor Moulin, who very sympathetically entrusted us with these photographs, as this person is a teacher.
Photoageing of the face due to ultraviolet radiation
The ultraviolet radiation to which the earth's globe is subjected includes:
Ultraviolet B (280-315 nm),
Ultraviolet A (315-400 nm),
Ultraviolet C (100-280 nm), is totally absorbed in the atmosphere. Thus, during a summer day
About 3.5% of the ultraviolet radiation reaching the earth is UVB,
While 96.5% is UVA.
Ultraviolet B rays are almost entirely absorbed by the glass, while almost half of the UVA rays pass through it.
Although 1000 times less energetic than UVB photons, UVA photons are able to induce age-related changes even deep in the dermis due to their great capacity to penetrate deep into the skin.
Photo-aging is a phenotype of an individual that is considered to be the part of aging related to solar irradiation, which can be summarized as ultraviolet irradiation if we disregard infrared.
At least this was the case in recent years, since the role of infrared radiation was underestimated.
If we look at the ageing of a person who has been exposed throughout his or her working life to intense heat, such as people working in front of cauldrons, ovens and fireplaces, particularly in ironwork shops, we cannot ignore the role of this heat in skin ageing.
What is the role of UVA in aging faces
More than appearance, photoaging is also about histopathological disorders such as:
Dystrophic elastic fibres,
Reduction in the collagen content of skin tissue
And increased activity of prosthetic enzymes such as metalloprotease 1 (MMP1).
UVA has the ability to modify skin cells in culture but also in vivo.
These effects are due to reactive oxygen species generated through endogenous chromophores such as trans-urocanic acid and porphyrins that act as photosensitizers.
This oxidative stress leads to damage to the structural proteins, lipids and DNA, especially as we observe in parallel the reduction of these key enzymes in the purification of free radicals such as catalase and superoxide dismutase.
The clinical and biometrological study in facial asymmetry,which quantities photo-ageing due to UVA
The author's team (University of Franche-Comté) carried out an original clinical study under the direction of Mac-Mary S. [2, 4] using people who had noticed a certain asymmetry in their faces.
And so, a wide variety of "responders" were interviewed and each had professional activities that allowed them to be considered as responsible for the asymmetry.
The trades involved were represented by drivers, teachers, store salesmen, sales representatives.
On this basis, a bio-metrological study was conducted to try to determine the amount of radiation needed to observe at a certain age the role of photoageing in the aging of the individual.
10 people were selected: eight women aged 65 on average and two men aged 60 on average living in Eastern France, all of whom had a profession related to driving.
They were therefore subjected almost exclusively to additional UVA irradiation on the left side of their faces.
Clinical scores for wrinkles in the cheeks, eye contour, crow's feet and laxity measurements were rated more severely on the left frame.
Curiously, less heterogeneity in skin color was observed on the most exposed side.
Wrinkles were more pronounced in volume and skin roughness was greater in half of the exposed face.
Results: this study showed the strong impact of cumulative exposure from facial skin to UVA
Since Lowe's work, it has been established that even repeated non-erythematous doses of UVA are capable of inducing photoaging.
The result is a thickening of the epidermis and lysozyme deposits in the elastic fibres.
This study, using computer tools, led to the creation of two new faces for each volunteer:
One consisting of twice the most affected haemiface, i.e. the left haemiface,
And for the other a face consisting of twice the right haemiface,
Thus, for each volunteer there were two faces that could represent two different people, one appearing significantly older than the other,
By randomly presenting its faces to a panel of 98 experts, we were able to observe that the apparent age of the hemi-face reconstructed from half the left face appeared five to seven years older than the other.
Thus, for the first time it has been possible to quantify in terms of additional age the proportion of ageing due to exposure to ultraviolet radiation.
This part of ageing which is called photoageing is on average six years for 30 years of exposure (number of years of professional activity).
Thus, every five years, we can consider that each individual ages an additional year due to exposure to the sun.
Prevention of multiple effects of exposure solar radiation
These findings, not to say these revelations, of course provide important support for the recommendations on photoprotection by whatever means. But sun exposure is not only ageing, it also causes other losses of skin functions such as:
Mechanical functions,
Metabolic functions,
Immunological functions
And protective functions against the development of cancers.
This is why it is important to consider that with age, the skin depletes anti-radical factors, i.e. antioxidant factors such as:
Endogenous antioxidants catalase,
Super Oxide Dismutase, SOD,
And exogenous antioxidants: trace elements, vitamin C.
Preventive treatments for facial photo-ageing
If we consider the main antioxidant of exogenous origin, namely vitamin C, we must know the results of this original study published in 2003, which for the first time quantified the dermis vitamin C content, and was able to demonstrate that at age 60 the amount of vitamin C in the skin, it was not only the skin photos exposed, was half that of 20 years old.
However, considering that vitamin C is the body's:
Main antioxidant factor,
Main factor in collagen synthesis.
It is important to provide the skin, both systemically and topically, with vitamin C, in a form that is not oxidizable and that can be proven to penetrate transcutaneously.
The same is true of the essential need for Super Oxide Dismutase (SOD) intake, given the widely demonstrated need for SOD during aging, and the interest that has also been widely demonstrated in the intake of Glisodine [4, 5].
Conclusion
In aesthetic medicine, we cannot ignore the role of photoaging and ultraviolet exposure as a determining factor in the asymmetry of a face.
Therefore, appropriate preventive and curative methods, both topical and oral, should be implemented and the administration of nutrients and dietary supplements with research-based evidence of their antioxidant properties should be advised.
References
1. Moulin G, Thomas L, Vigneau M, Fiere A. A case of unilateral elastosis with cysts and comedone. Favre-Racouchot syndrome. Ann Dermatol Venereol 1994;121:721-3.
2. Mac-Mary S, Sainthillier JM, Jeudy A, Sladen C, Williams C, Bell M., Humbert P. Assessment of cumulative exposure to UVA through the study of asymmetrical facial skin aging. Clinical Interventions in Aging, 2010;5:277-84.
3. Leveque N, Robin S, Makki S, Muret P, Rougier A, Humbert P. Iron and ascorbic acid concentrations in human dermis with regards to age and body sites. Gerontology 2003;49:117-22.
4. Mac-Mary S, Sainthillier JM, Courderotmasuyer C, Creidi P, Humbert P. Could a photobiological test be a suitable method to assess the anti-oxidant effect of a nutritional supplement Glisodin? Eur J Dermatol 2007;17:254-5.
5. Vouldoukis I, Conti M, Krauss P, Kamate C, Blazquez S, Tefit M, Mazier D, Calenda A, Dugas B. Supplementation with gliadin-combined plant superoxide dismutase extract promotes antioxidant defences and protects against oxidative stress. Phytother Res 2004;18:957-62.
