PEER-REVIEW | SKIN ANALYSIS | Table 1 Techniques available for skin detection


METHOD Fluhr et al (2000)13 Measured skin physiologic parameters from volar forearm of 44 adults (mean 34.6 years) and 44 of their children (mean 3.5 years) and cutaneous blood perfusion using laser Doppler flowmetry LDF-PF2.


Laser Doppler velocimetry (LDV)/laser Doppler flowmetry RESULTS


Transepidermal water loss, stratum corneum hydration, water-holding capacity, skin colour and pH value did not differ significantly. The children and adults differed in the parameters of hygroscopicity, redness, lightness, and cutaneous blood perfusion was significantly higher in children.


Kelly et al (1995)14 Studied 10 young (18–26 years) and 10 old (65–88 years) subjects, using a laser Doppler flowmeter, attaching one probe to the forehead and one to the ventral forearm. They recorded basal flow levels, then blood flow was occluded for 3 minutes, after which pressure was removed, resulting in postischaemic reactive hyperaemia.


LDV–Murine data


METHOD Monteiro-Riviere et al (1991)15 Evaluated the effects of ageing on cutaneous blood perfusion in male Fischer 344 rats (R), aged 1, 2, 3, 8, 12, 16, 20, 24 months and in CB57BL/6N mice (M) at 1, 2, 3, 9, 15, 19, 22 months. Measured blood flow was made on the backs of all animals. Skin biopsies (4 mm) were removed after LDV to assess epidermal and dermal thickness and number of epidermal cell layers.


RESULTS


Blood-flow of mice increased between 1 and 2 months, remaining constant to 19 months and then increasing again at 22 months. Blood flow in rats increased between 1 and 2 months, then decreased at 3 months, and remained constant until 24 months. The number of viable epidermal layers in mice remained, while in rats it decreased with age. Epidermal thickness in both mice and rats decreased from 2–3 months and then remained constant. Dermal thickness decreased from 3 to 22 months in mice, and increased in rats from 1 to 2 months, and then remained constant. Thus age differences in epidermal and dermal thickness, and blood flow of mice and rats occur and should be considered when evaluating cutaneous toxicity studies in different-aged animals. These changes may potentially alter dermal absorption and/or distribution of xenobiotics.


METHOD Kelly et al (1995)14 Studied Caucasian people: 13 old subjects (mean 74.9 years) and 13 young subjects (mean 23.2 years). Studied forehead and ventral forearm using intravital capillaroscopy with fluorescin angiography. They counted dermal papillary loops as dots, representing nutritional exchange vessels and horizontal vessels as lines, representing post-capillary venules, ascending arterioles, and part of the sub-papillary plexus.


Intravital capillaroscopy–fluorescin angiography RESULTS


Dermal papillary loops were significantly reduced in old skin compared with young skin (forehead by 40%; forearm by 37%). Horizontal vessels showed increased volume fraction in elderly forehead and forearm skin. Laser-Doppler studies demonstrated no significant differences between young and old skin; indeed, hyperaemic responsiveness appeared more rapid in the elderly. Colour measurements showed elderly skin, particularly in men, to be significantly darker and redder. They concluded that a marked loss in dermal nutritional vessel density and surface area for exchange is a feature of both chronologic ageing and photoageing.


No significant difference was seen between old and young subjects in either the forehead or forearm in basal flow level, reactive hyperaemic peak flow, time taken to return from the peak to a new baseline, and area under the posthyperaemic curve. Time taken from pressure release to reach posthyperaemic peak was less in the elderly forehead, consistent with more rapid vasodilation. This was not seen in the forearm.


CD31/PECAM immunohistochemistry


METHOD Chung et al (2002)16 This study included 21 Korean males and females, evenly distributed from ages 20–90 years. They obtained 2 and 4 mm punch biopsy specimens from eye corners and buttock. Specimens were stained for the CD31 antigen and histologically analysed.


RESULTS


Chronic photodamage was associated with dramatically reduced numbers of cutaneous vessels that were also reduced in size. Vessel size decreased 30.6% in the 40–69-year age group and 30.8% in the 70–84-year age group compared with the young group. Moderate changes in the cutaneous area covered by the CD31-positive vessels did not reach significance. Eye corners, photoaged: vessel numbers reduced by 43.1% in the 70–84-year age group compared with the young group. Average vessel size decreased 38.1% in 40–69-year age group with a 45.3% decrease after 70 years. Average dermal area covered by vessels decreased 43% in the 40–69-year age group and by 69.5% in the group over 70 years. In conclusion, intrinisic ageing has little effect on cutaneous blood vessels and all vasculature parameters measured in photoaged skin decreased progressively with increased age.


Photoplethysmography METHOD


Leveque et al (1984)17 The authors developed some routine techniques to measure physical properties of the skin both deep in the dermis–epidermis and at the surface (stratum corneum). Measurements on the forearm of 150 people were taken using photoplethysmography.


RESULTS


They yielded the following results: (1) skin thickness begins to decrease at 45 years for men and women, when women’s skin becomes thinner than men’s; (2) torsion extensibility, normalised for a given skin thickness, sharply decreases after 35 years; (3) skin optical properties are modified, for example the photoplethysmographic signal, measured on the forehead, greatly increases after 60 years; (4) at the cutaneous surface level, the main modifications are: increased shedding of stratum corneum after 60 years in parallel with a modification of the stratum corneum cohesivity, altered skin microrelief during the ageing process, and slightly decreased transepidermal water loss, while the corneocyte projected size increases. The alterations of the physical properties and their kinetics suggest various processes according to the different cutaneous sections.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76