| SKIN ANALYSIS | PEER-REVIEW sunlight may cause severe photoageing as early as the
second decade of life. Gniadecka et al5
also investigated the subepidermal
low-echogenic band, a consistent echostructural band found in the aged and photodamaged skin of 23 older, healthy volunteers (75–100 years old), with a high-frequency ultrasound scanner (B-mode, 20 mHz). The thickness of this band may reflect the degree of cutaneous ageing and can be used to monitor the severity of photoageing. The authors collected images from the volar forearm twice per day, in the morning and 12 hours later. A significant inter-individual and circadian variability of the band echostructure was demonstrated, suggesting that it is involved in the redistribution of fluids in the aged dermis. According to Uitto6
, two independent factors — innate
ageing and solar exposure — are responsible for cutaneous ageing and consequently, degenerative changes. Furthermore, a decrease in collagen biosynthesis and fibroblast proliferative capacity caused a reduction of collagen deposition, with the development of dermal atrophy related to poor wound healing in the elderly. At the same time, alterations in the molecular organisation of the elastic fibre network lead to changes in skin mechanical properties, with consequent reduced skin resilience and elasticity.
Elastin This protein is present in 2–4% of the dermis volume and dramatically changes between 30 and 70 years of age2 Photoageing increases elastin storage owing to gene
.
upregulation, which leads to a 5.3-fold increase in elastin expression7
. This phenomenon is enhanced by reduced
elastin degradation identified by the amount of racemised aspartic acid over time. From an immunohistochemical point of view, skin elastin and fibrillin are located in the papillary dermis, just below the basement membrane, and are small, oriented perpendicular to the epidermis. In the deep dermis, elastic fibres are thick and surround the vessels and annexa. With age, a rearrangement of these fibres is often observed2
. Fragmentation of elastic fibres induces a decrease in
their number and diameter, and a biochemical modification of the fibres in polar amino acids, carbohydrates, lipids and calcium composition8
.
Other proteins Protein structure modifications are very common during ageing, with an increase in protein folding and a decrease in their aliphatic remnants exposed to water,
especially in photoaged skin9 . Amino acid composition
of protein and free amino acids in aged skin differ significantly from that of young skin, and in older patients, an increase in their overall hydrophobicity is quite common.
Oikarinen showed that collagen synthesis gradually declines in
chronologically aged skin, and in protected skin the epidermis
becomes thinner, especially after the seventh decade of life.
Glycosaminoglycans Glycosaminoglycans (GAGs) are specifically disaccharide units bound to a core protein (proteoglycans) or not (hyaluronic acid), and chondroitin sulfates, namely dermatan sulphate. They bind up to 1000 times their volume in water. With photoageing there is a paradoxical increase of GAGs, which stratify abnormally on the elastoic material of the superficial dermis, and not between collagen and elastic fibres as in normal skin. This phenomenon might explain the dry and leathery appearance of photoaged skin7
. Figure 2 Skin
Tester evaluation after filler injection
Figure 1 Skin Tester (manufactured by Selenia Italia and
distributed by Dermal Institute)
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