Architectural characteristics of sun exposed and sun protected south‐east Asian skin
Authors: Jacinto S. , Langle S. , Noblesse E. , Bonnet‐Duquennoy M. , Bernois A. , Bonté F. , Francisco J. 
Published: September 2010

Although some data on the skins of Japanese, Korean and Chinese people have appeared recently, few studies have examined the skin of south‐east Asians.

The population of the Philippines results for centuries of intermarriage between Chinese, Spanish and Malays. Filipino skin is different from that of Malayan Indonesians or Malaysians.

Because little is known about how Filipinos skin changes with aging, we have collected data on the clinical and histological characteristics of the skin of Filipino women living in Manila. We recorded skin colour, pigmentation disorders, skin hydration, firmness, slackness, wrinkle status and carried out a histological and immunochemical evaluation of the difference between skin exposed to and protected from sunlight.

Methods

A total of 30 healthy Filipino women (mean age: 44 years) took part in this study of the clinical and histological features of their skin, and a comparison of areas protected from and exposed to sunlight was performed. All gave their informed consent. The subjects were assigned to one of the five age groups (20–30, 30–40, 40–50, 50–60 and >60). Overall, 52% had a dry skin and 48% had oily skin. Twelve women were in menopause. According to the Fitzpatrick classification [1], 47% of the skins were phototype IV, 50% were phototype V and 3% were phototype VI. Eleven women (37%) were former smokers and five (16%) still smoked.

Facial skin colour, hydration and wrinkles were all assessed by a dermatologist. The overall severity of facial wrinkles and pigmentation brown spots were photograded using the Jin Ho Chung photograding scale [2]. Skin elasticity, firmness and slackening (face ovale shape) were also evaluated on using a scale of 0‐10 [3]. The colour (Mexameter MX18) and hydration (corneometer CM820) of the skin on the left upper cheek were measured and skin replicas (Silflo/silicone resin) of the right eye contour were made. Image analysis was used to measure the number of wrinkles, total wrinkled area (mm²), total length of wrinkles (mm), mean length of wrinkles (mm) and mean depth of wrinkles (μm).

Data were analysed by analysis of variance (anova) and linear regression statistical significance was taken as P < 0.05.

Punch biopsies (4 mm) were taken from photoprotected areas (buttocks) and photoexposed regions (preauricular face). Samples were fixed in formalin and embedded in paraffin for histological and immunohistochemical evaluation. Sections were stained with Fontana Masson, Masson trichrome, orcein, haematoxylin‐phloxin‐safran (HPS) by standard procedures. Immunohistochemistry was carried out to detect type IV collagen and metallothionein expression.

Results

Clinical evaluation

There was a significant change in the severity of facial wrinkles with age between the women of three age groups, 20–30, 31–60 and >60 years. Women aged 20–30 years had very few if any wrinkles (mean grade: 0.7), those aged 31–60 years had a similar degree of wrinkling (mean grade: 2.8), while those aged over 60 years had significantly more severe wrinkles (mean grade: 4.4). The crow's feet area was the major site of wrinkles in all age groups.

Women aged less than 30 years had no facial dyspigmentation (mean grade: 0.2). Those aged 31–50 years had a similar degree of pigmentation spots (mean grade: 1.25). Women over 50 years had significantly more severe dyspigmentation (mean grade: 2.2) (Fig. 1). The patterns of facial dyspigmentation were similar in all the age groups. Women younger than 30 years had no spots on their hands; those aged 31–50 years had a similar degree of pigmentation spots (mean grade: 0.6); while those over 50 years old had significantly more severe dyspigmentation of their hands (mean grade: 1.25). The overall distribution of the spots on the face (cheeks, periocular and forehead) was similar to that found for Asian women. The hands had fewer spots than the face, as found for Chinese women.

Photograding of facial pigmentation.

image

The skin of the women studied showed significantly decreases in elasticity and firmness and increased slackening with age.

Skin features

Mexameter measurements showed no correlation between the erythemal index and age all the women had comparable erythemal indexes. However, the melanin index seemed to increase with age. There was a significant difference in the melanin indexes for 20–30‐year‐old women and women over 60 years (P ?≤ 0.05), but no difference between the indexes for women aged 20–30 and those aged 40–60. Skin hydration measured with corneometer decreased with age, being significantly different between women aged 20–40 and those >60. The total wrinkled area, total length of wrinkles and mean depth of wrinkles all increased significantly with age, while the number and mean length of wrinkles did not.

Histology

The histology of the skin from areas protected from sunlight and areas exposed to sunlight was compared. Masson trichrome staining of protected skin showed a decrease in epidermis thickness with age, which was much more sever in areas exposed to sunlight. In contrast, the stratum corneum was thinner in photo‐exposed areas.

The structure of the keratinocytes appeared to be normal, with the overall organisation and epidermal differentiation being better and more regular in areas protected from sunlight. The basal layer was more continuous and regular and the granulous layer slightly thicker. Fontana Masson staining showed no difference in distribution of melanin in areas exposed to sunlight with aging.

The collagen in dermo epidermal junction (DEJ) was more dense in the sun‐exposed areas of older patients. There was a general flattening of the DEJ in the sun‐protected skin of older patient. This flattening was also increased in skin exposed to sunlight. These findings are similar to those of other skin aging studies [4, 5]. Immunohistochemistry showed that the amount of type IV collagen did not vary with age or exposure to sunlight. There was also no correlation between the amount of type IV collagen and skin elasticity, firmness, slackening, or the number and length of wrinkles. However the dermis of skin exposed to sunlight had heavier deposits of elastotic material (Orcein staining). The network of elastic fibers in the superficial papillary dermis (oxytalan fibers) of skin exposed to sunlight was diminished (­50%) or absent, but it was present in skin protected from sunlight (Fig. 2).

Orcein staining. (A) age: 42 years, sun‐protected; (B) age: 42 years, sun‐exposed; (C) age: 64 years, sun‐protected; (D) age: 64 years, sun‐exposed. e, epidermis; d, dermis.

image

The metallothioneins (MTs) are low molecular weight cysteine‐rich, proteins that bind heavy metals; they are produced in response to a variety of stress signals [6, 7]. There are no published data on the effect of chronic exposure to UV light on metallothioneins. We therefore measured their abundance in the skin of six subjects, in areas protected from sunlight and areas exposed to sunlight (Fig. 3). The six chosen subjects had similar good skin tolerance of sunlight. Metallothionein expression was restricted to the keratinocytes and some dermal cells. The basal layer consistently immunostained more intensely for MT than did the suprabasal layers. There was MT immunoreactivity in both the cytoplasm and nucleus of keratinocytes. The numbers of MT‐positive cells in the epidermis of areas exposed to sunlight and those protected from the sun were significantly different.

Metallothionein in the skin epidermis.

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In conclusion, this study has for the first time described normal skin clinical evaluation, skin biomechanical properties measurements and histological data in relation to aging and pointed out the importance of the skin responses to the chronic photo exposition.

Acknowledgments

The authors thank N. Lachmann, for her support, and M. Juan (LVMH) and P. Gasser (Bio EC, Clamart, France) for technical assistance in the histological studies.

References

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