Skin parameters in cosmetic medicine: a new point of care

Mercoledì, 01 Luglio 2015

Skin biological parameters are usually measured with scales or digital photographs, but in recent years new devices based on physical and chemical principles have been developed to better define the effectiveness of drugs and instrumental therapies. The authors recruited 20 patients to perform a dermatologic evaluation with a new skin measuring device (Skin Tester). Skin Tester is a reliable and useful tool for clinical investigations in different medical and surgical branches, and provides the opportunity to stardardise skin pathology in different clinical environments. 

Characteristics of the skin and changes as a result of ageing are usually measured using scales or digital photographs, with data comparison before and after a specific treatment. In recent years, however, some instruments based on different physical and chemical principles have been developed, in order to have a more reliable evaluation to define the effectiveness of drugs and therapies.

To identify specific pathological skin parameters, it is important to be cognisant of the changes which the skin undergoes during ageing. Waller and Maibach1,2 described the features of the different layers of the skin and their biochemical alterations during the ageing process (proteins, glycosaminoglycans, water, lipids).

Skin components and photoageing

Collagen

The age-related changes of the skin have been analysed on the basis of biochemical modifications. Proteins are investigated using spectroscopy, which analyses molecular compound conformation and aspartic acid racemisation to detect skin proteins, such as collagen and elastin accumulation. Collagen, which includes approximately 70–80% of the dry weight of the dermis, is responsible for the skin's tensile strength. Each collagen molecule consists of three polypeptide chains, containing approximately 1000 amino acids in their primary sequence. In collagen molecules, the α-chains are wrapped around each other to achieve a triple helical formation2. The ratio of types I and III collagen fibres in the skin remain constant throughout childhood and young adult life. However, as we age, the proportion of type III collagen in the dermis increases and the bundle width changes significantly, reflecting an impaired synthesis of type I collagen in older skin3. Oikarinen4 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. On the contrary, an excessive exposure to sunlight may cause severe photoageing as early as the second decade of life.

Figure1_new-300x208.jpg

Figure 1 Skin Tester (manufactured by Selenia Italia and distributed by Dermal Institute)

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.

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.

Lipids

The stratum corneum is rich in corneocytes, which are embedded in a matrix of ceramides, cholesterol, fatty acids and smaller amounts of cholesterol sulphate, glucosylceramide and phospholipids in multilamellar sheets2. They create a waterproof barrier for the epidermis and quantitative variation of the ischaemic compounds induces xerosis and possible atopic dermatitis10. Many authors agree that the overall lipid content of human skin decreases with age10–12.

Skin detection and ageing

The techniques available for skin examination and its follow-up include histological analysis and more recently, direct immunohistochemical studies with regard to CD31 antigen and platelet endothelial cell adhesion molecule (PECAM) staining. Immunohistochemistry is preferred to synthase phosphatase evaluation as it supplies semi-quantitative results. Intravital capillaroscopy can be performed either ex vivo or in vivo with luminescence microscopy and fluorescent angiography, photoplethysmography, and laser Doppler flowmetry for the arterial or dermal plexus.Some dynamic tests such as finger immersion in cold water and finger circulation measurement show a blood-flow reduction with age progression, while in vivo fluorescine angiography showed an age-related decrease to the papillary dermis and little change in horizontal vessels.

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Figure 2 Skin Tester evaluation after filler injection

Epidermal thickness has been measured using confocal miscroscopy, or with ultrasound by Richard et al18, who performed an ultrasound analysis in 30 elderly women. Electrical conductance, colour, microrelief, skin thickness and subepidermal non-echogenic band (SENEB) were measured on the neck skin, which was damaged as a result of exposure to sunlight and on an adjacent part not exposed to the sun. Changes in SENEB, skin thickness, skin extensibility and elasticity, and colour heterogeneity were more evident in the sun-exposed skin, demonstrating that the cumulative effect of sun exposure can be the cause of atrophy or solar elastosis in older people. Pellacani and Seidenari19 enrolled 40 women (aged 25–90 years) in order to study 12 different facial skin sites with a 20 mHz B echographic scanner, demonstrating an increase in facial skin thickness in old patients compared with the younger subjects.To demonstrate a significant variation of skin parameters between different age groups, Seidenari et al20 performed an echographic evaluation of skin modifications on 48 patients (24 aged 27–30 years, and 24 over 60 years) with a 20 mHz B scanner at six different sites, showing an important regional variation of ultrasound reflection in older skin compared with the young skin. A consistent shift from low-intensity ultrasound echoes in the dermis of young subjects, to intermediate or high reflection amplitudes in older skin, was observed.Gniadecka et al21 enrolled 10 older individuals (five men and five women; age range 74–87 years) and 10 control individuals (five men and five women; age range 22–29 years) to identify the role of structural protein ageing modifications to induce wrinkles, loss of elasticity and dryness. There was evidence that protein-specific amide I, amide III, and carbon–hydrogen stretching bands were shifted in photoaged forearm skin, suggesting an increase in protein folding. In contrast, significant changes were seen only in the amide I peak in chronologically aged skin. The intensity of the stretching band was increased in photoaged skin, but not in chronologically aged skin.The same authors21 alsoinvestigated the water content and found that in young skin and chronologically aged skin, water was detectable in the bound form. In the photoaged skin, however, there was an increase in intensity, which reflects an increase in the non-protein-bound water (tetrahedron water clusters), concluding that proteins in photoaged skin are more compact and interact with water to a limited degree.

Materials and methods

For an objective assessment of the quality of the skin in cosmetic medicine, it is relevant to perform qualified clinical investigations with pre- and post-treatment comparisons in order to support the patient’s judgement with the instrumental detection of skin parameters. Therefore, the authors developed a non-invasive multi-parametric point of care diagnostic tool (Skin Tester, manufactured by Selenia Italia and distributed by Dermal Institute), to provide an evaluation of a number of skin parameters, such as hydration, pH, elasticity, and sebometry.

Skin Tester

Skin Tester is a new device originally planned and validated by the authors in comparison with the currently available skin analysers for the diagnostic qualitative analysis of facial skin. It analyses a number of parameters to monitor pre- and post-treatment variations. An ultrasound emitted beam is reflected by the dermal tissues, according to its stromal density and vascular tone. Furthermore, impedance variation as related to intracellular and interstitial water content and photoplethysmography, a reflectometric method to evaluate vascular network dynamics, are encompassed by the diagnostic device. Therefore, the following skin parameters can be detected:

  • Total and intracellular water to correctly evaluate hydration
  • Extracellular water and water retention to detect tissue fluid engulfment and drain impairment. The stratum corneum has a water content which is balanced by general skin and subcutaneous tissue hydration
  • Skin pH, related to sebaceous and sweat gland secretion. Skin pH is usually slightly acidic as a result of lactic acid, amino acids and fatty acids coming from sweat, sebum, and degradation products of the corneal layer, which supplied amino acid and pyrrolidinecarboxylic acid.

The pH measuring device is a potentiometer with an electrode sensor, with selective hydrogen ion sensitivity. The small amount of water lying between the electrode and the skin surface is adequate to solubilise ions on the skin’s surface and create adequate measuring conditions.

When the pH probe is in contact with a solution containing H3O+ ions, a flux of electrons moves between the active electrode and the reference electrode. The potentiometer then measures the difference in potential, which is directly proportional to the pH of the solution used during examination:

  • Thickness of the horny layer
  • Sebum epidermic concentration, a thin hydrolipidic film produced by the sebaceous glands
  • Skin elasticity and tonicity parameters, related to elastin, collagen and GAG imbalance
  • Vascular network adaptations.

The Skin Tester works very quickly (30 seconds) and records the operative data through a touch-screen display. It has a flat transducer to be applied over the skin surface and requires a gel film to achieve ultrasound delivery. Analysis results are printed on a ticket with the reference values, so the doctor and patient can keep a record of the cosmetic treatment variations.

Investigation of dermatological and cosmetic parameters

Filler injections

The authors report on their first clinical experience using the Skin Tester device in cosmetic medicine, investigating on a series of cases, the individual healing process of which could be adequately monitored.

Twenty patients (14 females and six males) aged between 19 and 67 years were admitted to this dermatologic evaluation, before and after the injection of dermal fillers (specifically Aliaxin GP, Ibsa Farmaceutici, Italia). This study was performed in accordance with the Helsinki declaration and local internal review board (IRB) rules. All patients signed an informed consent after reading the standard information sheet and discussing the procedure with the clinician. Doses of 1–2 ml of hyaluronic acid were injected at different facial areas, according to the individual patient’s needs, including nasolabial folds, upper lips, chin, periorbital area and cheeks. The injection volume was selected at the discretion of the specialist, administering the compound until full correction was achieved.

A pre- and post-treatment measure of skin parameters (hydration, elasticity, pH and sebum levels) helped the authors to define the real amount of filler required to reach an optimal cosmetic effect, by evaluating the skin response immediately after the procedure.

Results

Total water content (hydration), elasticity, pH and sebum levels were selected as the most representative indices of beneficial effects. It is well known that hyaluronic acid can bind with up to 6 L of water in vitro to a point of maximal saturation, thus becoming fundamental for biology and a functional determinant in cellular water homeostasis.

The statistical analysis evidenced a significant positive effect of filler treatment and a significant improvement of all the parameters measured with Skin Tester before and after the procedure.

The results suggest that filler injection significantly improved the quality of the skin, mainly in terms of total water content, elasticity and sebum, with a slight increasing trend after treatment.

In particular, pH decreased from basic values to neutral values in all the subjects except for two people who had the same parameters before and after the procedure. Skin elasticity increased significantly in all 20 patients owing to the action of hyaluronic acid, which instigates collagen production and consequently, a significant change in skin tensile strength. Skin hydration reached optimal values as hyaluronic acid attracts and holds water molecules. Finally, a sebum improvement was also observed and it was correlated with a decrease of pores squeeze and inaesthetic skin.

A limitation of this study was the absence of a follow-up over a long-term period (at 6 months, for example). With this in mind, the authors plan to undertake further studies to include long-term follow-up.

However, this study has demonstrated that hyaluronic acid injection can actually significantly improve skin parameters such as hydration, elasticity, pH and sebum.

Discussion and conclusions

The Skin Tester system is very easy to use, quick and gives accurate computer-assisted information that can be stored and printed at any time. It is a reliable and useful tool for clinical investigations in different medical and surgical branches (e.g. dermatology, vascular surgery, gerontology, gynaecology, plastic surgery).

The tested instruments gave the authors the opportunity to standardise skin pathology in different clinical conditions, with the chance to record all the relevant data measured on each patient at planned time intervals, or after medical surgical treatment.

Skin Tester represents an updated, exhaustive functional and rational solution compared with some of the other devices, as it is based on modern physical principles such as diagnostic ultrasound and plethysmography and therefore, it meets all the required criteria to perform a simplified and standardised holistic investigation.

 

Acknowledgements

Declaration of interest: None

Figures 1,2 © Palmieri et al

References

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