Skin Viscoelasticity Research Articles

A novel imaging technique for skin dermal viscoelasticity and its correlation with dermal density

Human skin consists of three distinct layers’ epidermis, dermis and hypodermis. In the dermis layer, collagen is responsible for the tensile strength, and elastic fibers are interwoven among collagen bundles providing elasticity. For measuring skin viscoelasticity, there have been studies focusing on the epidermis layer. However, the viscoelastic properties are mainly associated with the fiber matrix of dermis layer. Therefore, we measured the viscoelasticity of dermis layer and investigated the correlation with dermal density in this study. In addition, we developed the novel facial images representing the distribution of dermal viscoelasticity. Twenty healthy subjects, aged between 20 and 40 years, participated in the study. Skin Fibrometer® and Skin scanner DUB® were used for the evaluation. As a result, there were significant positive correlations between viscoelasticity parameter of Skin Fibrometer® and dermal density, thickness parameters of Skin scanner DUB® (p < 0.01). As the viscoelasticity of skin increased, the density and thickness of dermis layer both increased. Furthermore, the results of dermal viscoelasticity were represented by visual images not only by numerical values using newly developed analyzing program. For the visualization, 25 areas of each subject's face were evaluated, and the facial images were taken by VISIA-CR®. The visualizing program was developed based on IDW (Inverse Distance Weighting) interpolation principle, which is a deterministic method for interpolation with a known scattered set of measuring points. Conclusively, the correlative relation between parameters of dermis layer was investigated, and the facial images representing the dermal viscoelasticity were newly developed in this study.

Novel in situ forming hydrogel microneedles for transdermal drug delivery.

Novel in situ forming hydrogel microneedles were evaluated for transdermal drug delivery using a biocompatible non-ionic triblock amphiphilic thermosensitive copolymer. The transition property of poloxamer from solution at room temperature to gel at skin temperature (32°C) was utilized in preparation of in situ forming hydrogel microneedles. Methotrexate has been used to treat solid tumors, but because of its narrow safety margin, it requires sustained delivery within the therapeutic window. Formulations with and without poloxamer at different methotrexate concentrations were prepared and evaluated for drug permeation across skin using vertical Franz diffusion cell for 72h. Sol-gel transition, skin resistance and thickness, microneedles geometry, microchannel depth, shape, formation and uniformity, viscoelasticity of skin, and in vitro drug permeation were characterized and tested. An average cumulative drug amount of 32.2±15.76 and 114.54±40.89μg/cm2 for porcine ear skin and 3.89±0.60 and 10.27±6.98μg/cm2 for dermatomed human skin from 0.2% w/w and 0.4% w/w methotrexate formulations was delivered by the in situ forming hydrogel microneedles. These in situ hydrogel microneedles embedded within the porated site of the skin provided a steady and sustained drug delivery.

Relationship between Dermal Structural Changes on Ultrasonographic Images and Skin Viscoelasticity in Overweight and Obese Japanese Males

It has been reported that overweight Japanese males have poorly organised dermis and their skin may be fragile to external forces because of decreased dermal echogenicity. However, it is unknown whether the changes in the dermal structure actually affect the dermal function. The objective of this study was to clarify the relationship between dermal structural parameters and dermal functional parameters in overweight and obese Japanese males. A cross-sectional, observational study was conducted on Japanese male volunteers. Two ultrasound scanners, a 20-MHz Dermascan C® and an 18-MHz MylabTM five® were used to evaluate dermal structure. Echogenicity of the lower dermis and dermal thickness of the participants’ abdomens and thighs were measured. A Cutometer® MPA580 was used to evaluate skin viscoelasticity, skin deformation (R0) and elasticity (R2, R7). The correlation between dermal structural parameters and skin viscoelasticity were validated using Pearson’s correlation coefficient or Spearman’s correlation coefficient by rank test. A total of 79 male volunteers were recruited of which 43 were control subjects with BMI <25 (age, 22 - 63 years), 25 were overweight subjects with BMI ≥ 25 to <30 (age, 23 - 64 years) and the 11 obese subjects had a BMI ≥ 30 (age, 26 - 47 years). There was no correlation between dermal structural parameters and skin viscoelasticity in the abdomens or thighs of all 79 participants. On the other hand, in the 36 overweight and obese participants, thigh dermal echogenicity was significantly and negatively correlated with R0 (r = -0.456, p < 0.01) and dermal thickness in the abdomen was significantly and positively correlated with R0 (r = 0.464, p < 0.01). The dermal functional parameter was significantly correlated with dermal structural parameters in overweight and obese males; in other words, a decrease in dermal function may be caused by structural changes in the dermis during obesity.

Enhanced skin delivery of vismodegib by microneedle treatment.

The present study investigated the effects of microneedle treatment (maltose microneedles, Admin Pen™ 1200, and Admin Pen™ 1500) on in vitro transdermal delivery of vismodegib with different needle lengths, skin equilibration times, and microneedle insertion durations. The influence of microneedle treatment on the dimensions of microchannels (dye binding, calcein imaging, histology, and confocal microscopy studies), transepidermal water loss, and skin permeability of vismodegib was also evaluated. Skin viscoelasticity was assessed using a rheometer, and microneedle geometry was characterized by scanning electron microscopy. Permeation studies of vismodegib through dermatomed porcine ear skin were conducted using vertical Franz diffusion cells. Skin irritation potential of vismodegib formulation was assessed using an in vitro reconstructed human epidermis model. Results of the in vitro permeation studies revealed significant enhancement in permeation of vismodegib through microneedle-treated skin. As the needle length increased from 500 to 1100 and 1400μm, drug delivery increased from 14.50 ± 2.35 to 32.38 ± 3.33 and 74.40 ± 15.86μg/cm(2), respectively. Positive correlation between drug permeability and microneedle treatment duration was observed. The equilibration time was also found to affect the delivery of vismodegib. Thus, changes in microneedle length, equilibration time, and duration of treatment altered transdermal delivery of vismodegib.

Compressive viscoelasticity of freshly excised mouse skin is dependent on specimen thickness, strain level and rate.

Although the skin’s mechanical properties are well characterized in tension, little work has been done in compression. Here, the viscoelastic properties of a population of mouse skin specimens (139 samples from 36 mice, aged 5 to 34 weeks) were characterized upon varying specimen thickness, as well as strain level and rate. Over the population, we observed the skin’s viscoelasticity to be quite variable, yet found systematic correlation of residual stress ratio with skin thickness and strain, and of relaxation time constants with strain rates. In particular, as specimen thickness ranged from 211 to 671 μm, we observed significant variation in both quasi-linear viscoelasticity (QLV) parameters, the relaxation time constant (τ1 = 0.19 ± 0.10 s) and steady-state residual stress ratio (G∞ = 0.28 ± 0.13). Moreover, when τ1 was decoupled and fixed, we observed that G∞ positively correlated with skin thickness. Second, as steady-state stretch was increased (λ∞ from 0.22 to 0.81), we observed significant variation in both QLV parameters (τ1 = 0.26 ± 0.14 s, G∞ = 0.47 ± 0.17), and when τ1 was fixed, G∞ positively correlated with stretch level. Third, as strain rate was increased from 0.06 to 22.88 s−1, the median time constant τ1 varied from 1.90 to 0.31 s, and thereby negatively correlated with strain rate. These findings indicate that the natural range of specimen thickness, as well as experimental controls of compression level and rate, significantly influence measurements of skin viscoelasticity.

Wpływ mokrego środowiska pracy na wybrane parametry bariery naskórkowej (TEWL i zawartość wody w naskórku) oraz lepkosprężystość skóry u pielęgniarek

Nurses are prone to develop hand eczema due to occupational exposure to irritants, including wet work. The aim of the study was to evaluate the impact of wet work on selected skin properties, reflecting epidermal barrier function--transepidermal water loss (TEWL) and stratum corneum hydration--and additionally skin viscoelasticity, in nurses. Study subjects included 90 nurses employed in hospital wards. Measurements were carried out within the dorsal aspect of the dominant hand, using a Cutometer MPA 580 equipped with Tewameter TM 300 and Corneometer CM 825 (Courage & Khazaka, Germany) probes. Examina- tions took place on hospital premises. Similar measurements were performed in the control group of females non-exposed to irritants. In the examined group of nurses, mean TEWL was 15.5 g/h/m2 and was higher than in the control group (12.99 g/h/m2). After rejecting the extreme results, the difference between the groups proved to be statistically significant (p < 0.05). The mean value of stratum corneum hydration was lower in the examined group (37.915) compared with the control group (40.05), but the difference was not sta tistically significant. Also results of viscoelasticity assessment showed no significant differences between studied groups. The results of the assessment of skin biophysical properties show that wet work exerts a moderately adverse impact on skin condition. A higher TEWL value and a lower stratum corneum hydration in workers exposed to irritants reflect an adverse impact of these factors on the epidermal barrier function.

Novel Ideas: The Increased Skin Viscoelasticity - A Possible New Fifth Sign for the Very Early Diagnosis of Systemic Sclerosis.

Diagnosis of systemic sclerosis (SSc) at very early stage could allow starting an appropriate therapy and improving the patient outcome. Skin involvement is often the first non-Raynaud's phenomenon (RP) symptom. Its uncovering may play an important role for the initial diagnosis. To introduce a simplified method for non-invasive evaluation of skin mechanical properties in patients with clinically evident or suspected SSc. A total of 94 patients and 162 healthy subjects were studied. According to clinical and nailfold videocapillaroscopy findings the patients were divided into four groups: 20 with edematous phase of SSc (group 1), 28 with indurative phase of SSc (group 2), 26 with suspected secondary RP (group 3), and 20 with primary RP (group 4). Mechanical properties of the volar forearm skin were evaluated using a non-invasive suction device (Cutometer) equipped with 2-mm diameter probe. The skin mechanical parameters analyzed were distensibility (Uf), elasticity (Ua/Uf) and viscoelasticity (Uv/Ue). Skin distensibility was reduced and skin viscoelasticity increased in group 1-3 compared to age matched healthy controls. There were no significant changes in skin elasticity. Mechanical parameters in group 4 were normal. Comparison of individual patient's values with population 95% confidence intervals of the mean showed increased skin viscoelasticity in group 1 (100%), group 2 (93%), and group 3 (81%), whereas the incidence in group 4 was 10%. Noninvasive method applied is appropriate for objective and quantitative evaluation of sclerodermatous skin. In combination with nailfold videocapillaroscopy it could be predictive in pre-scleroderma patients. The increased skin viscoelasticity parameter could be proposed as the possible new fifth sign for the very early diagnosis of SSc.

Asymmetric facial skin viscoelasticity during climacteric aging.

BackgroundClimacteric skin aging affects certain biophysical characteristics of facial skin. The purpose of the present study was to assess the symmetric involvement of the cheeks in this stage of the aging process.MethodsSkin viscoelasticity was compared on both cheeks in premenopausal and post-menopausal women with indoor occupational activities somewhat limiting the influence of chronic sun exposure. Eighty-four healthy women comprising 36 premenopausal women and 48 early post-menopausal women off hormone replacement therapy were enrolled in two groups. The tensile characteristics of both cheeks were tested and compared in each group. A computerized suction device equipped with a 2 mm diameter hollow probe was used to derive viscoelasticity parameters during a five-cycle procedure of 2 seconds each. Skin unfolding, intrinsic distensibility, biological elasticity, and creep extension were measured.ResultsBoth biological elasticity and creep extension were asymmetric on the cheeks of the post-menopausal women. In contrast, these differences were more discrete in the premenopausal women.ConclusionFacial skin viscoelasticity appeared to be asymmetric following menopause. The possibility of asymmetry should be taken into account in future studies of the effects of hormone replacement therapy and any antiaging procedure on the face in menopausal women.

Optical tracking of local surface wave for skin viscoelasticity

Rapid and effective determination of biomechanical properties is important in examining and diagnosing skin thermal injury. Among the methods used, viscoelasticity quantification is one of the most effective methods in determining such properties. This study aims to rapidly determine skin viscoelasticity by optically tracking the local surface wave. New elastic and viscous coefficients were proposed to indicate skin viscoelasticity based on a single impulse response of the skin. Experiments were performed using fresh porcine skin samples. Surface wave was generated in a single impulse using a vibrator with a ball-tipped device and was detected using a laser Doppler vibrometer. The motions along the depth direction were monitored using an ultrasound system. The ultrasound monitoring results indicated the multi-layered viscoelasticity of the epidermis and dermis. The viscoelastic coefficients from four healthy samples show a potential viscoelasticity variation of porcine skin. In one sample, the two coefficients were evidently higher than those in a healthy area if the skin was slightly burned. These results indicate that the proposed method is sensitive, effective, and quick in determining skin viscoelasticity.

Skin viscoelasticity in incipient gravitational syndrome

The gravitational syndrome resulting from venous pressure elevation occasionally develops on the legs during pregnancy. The limb tends to enlarge and become stiffer. The body contours are altered. To assess incipient gravitational edema due to chronic venous insufficiency using measurements of the skin tensile strength. A total of 21 women aged 28-37years were enrolled in the study. Evaluations were made twice in each subject following an alternate use and avoidance of daytime elastic contention. Skin viscoelasticity was measured on the mid portion of the calves using a computerized suction device. The discretely increased consistency of skin showing abnormal rheological characteristics at the site of incipient gravitational edema was significantly improved by contention therapy. Under progressive suction measurements, both skin distensibility, biologic elasticity and hysteresis were increased after wearing tight stockings. The biologic elasticity appears to be the most sensitive parameter pointing to the diagnosis of gravitational syndrome. Noninvasive measurements of the skin viscoelasticity, particularly the biologic elasticity, represent an objective assessment of both early gravitational edema and its control by contention therapy.

Constitution-specific features of perspiration and skin visco-elasticity in SCM

BackgroundHuman skin properties have been used as an important diagnostic component in traditional medicine as they change with health conditions. Sasang constitutional medicine (SCM) puts emphasis on the recognition of the constitution-specific skin features prior to the diagnostic decision of health. In this work, in search of skin-characteristics effectively reflecting SCM features, we compared several skin properties such as perspiration, visco-elasticity, elasticity, and elasticity hysteresis, in several candidate body parts.MethodsWe conducted a clinical study in which a total of 111 healthy females aged 50 – 70 years participated with their Sasang constitution (SC) types determined objectively by the Sasang constitutional analytic tool. Perspiration on the skin surface was estimated by using a capacitance sensor to measure the amount of moisture on the palm, forehead, and philtrum before and after a heating stimulus. We acquired the visco-elasticity, elasticity, and elasticity hysteresis at the forearm by Dermalab’s elasticity sensing device. An analysis of covariance (ANCOVA) was conducted to evaluate the effect of SC on the nine skin features acquired.ResultsThe visco-elasticity of the forearm of the Soeum-in (SE) group was significantly lower than that of the Taeeum-in (TE) group (F = 68.867, p < 0.001), whereas the elasticity hysteresis of the SE group was higher than that of the TE group (F = 10.364, p < 0.01). The TE group had more perspiration on the forehead than the SE group (F = 9.050, p < 0.01). The SE group had a large perspiration difference between the philtrum and the forehead compared with the TE group (F = 7.892, p < 0.01).ConclusionsWe found four significant skin features that reflect the inherent constitutional attributes of the TE and SE groups in accordance with SCM literature; the visco-elasticity, elasticity hysteresis, perspiration on the forehead and philtrum. Our findings are based on a novel interpretation of the SCM literature and will contribute to developing the constitutional health status evaluation system in SCM.

Skin viscoelasticity studied in vitro by microprobe-based techniques

Time-dependent deformation of porcine skin was studied in vitro using specialized microprobe instruments. The deformation behavior of stratum corneum, dermis, and whole skin is examined in the context of results of creep strain, elastic stiffness, and viscoelastic constants obtained in terms of the hold time, loading/unloading rate, and maximum indentation depth (load). Skin time-dependent deformation is significantly influenced by dermis viscoelasticity up to a critical indentation depth (load) beyond which it is controlled by the outermost hard epidermis, particularly stratum corneum. Skin viscoelastic behavior under constant load (creep) and constant displacement (stress relaxation) is interpreted in the light of phenomenological observations and experimental trends.

Skin viscoelasticity during hormone replacement therapy for climacteric ageing

Climacteric ageing refers to the period of women's life centred by the perimenopause. This step of life is responsible for initiating skin atrophic withering and slackness responsible for changes in the viscoelasticity of the dermal connective tissue. Some women benefit from hormone replacement therapy (HRT) for controlling some unpleasant internal climacteric changes (osteoporosis, vasomotor instability, …). To investigate some corrective effects of HRT on the functional damages in the dermal tensile strength. This study was performed on 200 healthy Caucasian women. In vivo skin viscoelasticity was assessed using the suction method. Skin distensibility and hysteresis appeared increased at menopause with or without HRT. By contrast, the biological elasticity significantly decreased out of HRT. Some drugs and cosmetics might attempt at improving such viscoelastic attributes of the skin at menopause.

Confirmed efficacy of topical nifedipine in the treatment of facial wrinkles

Introduction: Over the past two decades, there has been increasing demand for aesthetic procedures to reverse the effects of aging, particularly in the facial area. Recently, topical nifedipine has been proposed for its anti-wrinkle efficacy. Objective: To confirm the anti-wrinkle efficacy of a 0.5% nifedipine-based topical formulation. Materials and methods: A randomized study was conducted in 20 healthy female volunteers, aged between 45 and 60 years, with moderate to moderately severe facial wrinkles. 10 volunteers applied a 0.5% nifedipine cream and 10 volunteers applied a good moisturizer twice daily for 90 days. The aesthetic improvement was evaluated by a blinded investigator using the Wrinkle Severity Rating Scale (WSRS). Anti-wrinkles effectiveness was also objectively assessed by measuring transepidermal water loss (TEWL), moisture levels of the stratum corneum, skin viscoelasticity and skin folding capacity by instrumental analysis. Results: Post-treatment WSRS score was significantly lower than the baseline WSRS score only in the nifedipine group. The mean WSRS score at T0 was 3.85 and at T3 1.84 in the nifedipine group, while the mean WSRS score at T0 was 3.78 and at T3 3.36 in the control group. Corneometry showed significant increases in measures of skin hydration and TEWL values decreased in all the patients of both groups, indicating a trend toward improved integrity of skin. Dermolab® recorded significant increases in measures of skin hydration in the nifedipine group and a lower increase in the control group. The colorimetric evaluation showed that use of the tested product resulted in significant overall lightening of the skin during use compared with baseline, while the moisturizer didn't produce any change of skin lightening parameters. Conclusion: The tested topical preparation is effective in reducing facial wrinkles' depth and in increasing skin hydration and elasticity.

Comparative Evaluation of Wrinkle Treatments

Skin wrinkles are one of the most cosmetically concerning signs of aging for women, and improvements in the visual effect of wrinkles become a matter of concern that has an impact on the quality of life. Although various wrinkle treatments are being tried in the area of aesthetics and noninvasive cosmetic surgery, no guideline on how to treat wrinkles exists to date. This study evaluated the clinical effects of four wrinkle treatment methods [fractional erbium yttrium-aluminum-garnet (YAG) laser treatment, intense pulsed light (IPL) therapy, CD-atRA external application, and nutritional therapy with intake of amino acid supplements]. These four methods were selected as promising candidates in a pilot case study to improve wrinkles by following the consensus guideline (Task Force Committee for Evaluation of Anti-Aging Function, J Jpn Cosmet Sci Soc 31:411-431, 2007) for the evaluation of anti-wrinkle effects issued by the Japan Cosmetic Industry Association. The wrinkle area fraction and skin viscoelasticity were measured by objective evaluation. Furthermore, a satisfaction survey of the subjects was conducted on the basis of subjective evaluations using the visual analog scale (VAS) method and in accordance with the guideline for the evaluation of antiwrinkle effects. Fractional erbium YAG laser treatment showed statistically significant improvement in both of the objective evaluations (wrinkle area and skin elasticity). The IPL method showed statistically significant improvement in both of the objective evaluations (wrinkle area and skin elasticity), and it especially demonstrated a more significant difference in skin elasticity. The CD-tretinoin external application method showed statistically significant improvement in both of the objective evaluations (wrinkle area and skin elasticity), and it especially demonstrated a more significant difference in wrinkle area. Nutritional therapy showed statistically significant improvement in wrinkle area, whereas IPL, CD-tretinoin external application, and nutritional therapy demonstrated statistically significant improvement in the degree of wrinkle. As for the subjective assessment of VAS, all four treatments demonstrated equivalent satisfaction. All four minimally invasive procedures (fractional erbium YAG treatment, IPL therapy, CD-atRA external application, and intake of amino acid supplements) showed significant improvement of wrinkles. Comparative evaluation of wrinkles using the same criteria is important. The findings clearly showed that an evidence-based approach to wrinkle treatments supported by validation of their effectiveness is required. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Porcine model to evaluate local tissue tolerability associated with subcutaneous delivery of protein

IntroductionThe conversion from intravenous (IV) to subcutaneous (SC) delivery of biotherapeutics has increased in recent years. Some of the reasons for this shift in route of delivery are due to patient convenience, reduced adverse systemic effects, lack of a need for vascular access, and reduced cost of patient care, which ultimately lead to improved patient quality of life. One caveat to SC delivery is the limited volumes that can be administered at a single site and the associated local tolerability. To characterize factors that affect subcutaneous delivery of large volumes of therapeutic proteins, a porcine model was developed. Model endpoints included measurement of interstitial pressure, assessment of local skin visco-elasticity, and the qualitative assessment of local infusion sites. MethodsImmunoglobulin G (IgG) was subcutaneously infused into the abdominal region of Yucatan miniature swine. Changes in interstitial pressure were measured, using an in-line pressure transducer, during and after infusions. Additionally, pre- and post-infusion changes in local skin visco-elasticity were measured using a Cutometer®. Lastly, infusion sites were assessed for post-infusion local skin reactions such as erythema and swelling. Similar assessments were made following SC IgG delivery with the permeation enhancer recombinant human hyaluronidase PH20 (rHuPH20). ResultsSubcutaneous infusions of IgG, in the presence of rHuPH20, significantly reduced average interstitial pressures by 55% during the infusion period and by 67% during the post-infusion period, compared to the control. Infusions in the presence of rHuPH20 also maintained better local skin elasticity as seen by a 42% increase in local skin pliability compared to the control. Finally, infusions with rHuPH20 resulted in an 80% reduction in swelling area compared to the control. DiscussionA large animal model was developed that incorporates both quantitative and qualitative assessment methods to aid in understanding SC delivery of proteins.

The influences of skin visco‐elasticity, hydration level and aging on the formation of wrinkles: a comprehensive and objective approach

Various skin parameters including skin visco-elasticity and hydration level affect the formation of wrinkles. The aim of this study was to investigate the comprehensive and objective relationship between age, skin visco-elasticity, hydration level, and the occurrence of wrinkles using bioengineering equipments for the first time. A total number of 97 healthy women were included in this study. Age, Fitzpatrick skin type, skin mechanical parameters obtained with Cutometer(R0~R9), hydration level measured with Corneometer, as well as wrinkle parameters (SEsm, SEr, SEsc, and SEw) assessed with Visioscan, were analyzed with the Pearson's correlation test. The skin fluidity (R6) increased while the elastic recovery ratio (R7) decreased with the age. The wrinkle parameter (SEw) also increased with the age. The higher skin hysteresis values (R4 and R9) coincided with the higher SEw values. Skin hydration significantly lowered the hysteresis (R9), the wrinkles (SEw), and the depth of wrinkle furrows (R3mr). The elderly have less elastic skin and more wrinkles. Skin hysteresis most closely related with the degree of wrinkles. Drier skin showed more wrinkles and deeper furrows, with wider intervals. On the basis of these objective findings, we propose several skin parameters associated with wrinkles, and hypothesize the mechanism of wrinkle generation.

Influence of Oral Administration of Soybean Peptide on Water Content of the Stratum Corneum, Transepidermal Water Loss and Skin Viscoelasticity

Soybean Peptide (SP) increases collagen content in fibroblasts, but no previous studies have investigated the effects of SP on skin properties such as water content of the stratum corneum, Transepidermal Water Loss (TEWL) and skin viscoelasticity. Thus, we orally administered SP to ultraviolet (UV)-irradiated mice in order to investigate the effects on skin. Hairless mice were irradiated with a daily dose of 22.3 J/cm2 of UVA and a 20% aqueous solution of SP or Collagen Peptide (CP) was administered via oral gavage to achieve a daily dose of 2 mg/g. UVA radiation and oral samples were administered for 25 consecutive days. Water content of the stratum corneum and TEWL were measured daily and skin viscoelasticity was measured every other week. Skin was collected and prepared as frozen sections after the conclusion of the study for use in histological observation with hematoxylin and eosin staining. Oral administration of SP and CP to UVA-irradiated mice resulted in no significant differences in body weight in any of the groups. Water content of the stratum corneum and TEWL improved over time in all groups. TEWL recovered more quickly in the SP group than the CP group. Skin viscoelasticity improved in all groups. The values in the SP group were almost identical to those in the normal group, which did not receive UVA irradiation or oral treatment. Histological observations revealed suppression in UVA-induced epidermal thickening in the SP group. The findings of this study indicate that oral administration of CP and SP improves the barrier function of skin and skin viscoelasticity in UV-irradiated mice.

A study on the alterations in skin viscoelasticity before and after an intradermal administration of growth factor

Background:While photo-aging is believed to be preventable by the complete blockage of ultraviolet rays, there is no epoch-making method except sing fillers or autologous fat injection, for rejuvenating the skin once it has aged.Objective:Our group developed a new method for rejuvenating aged skin by the direct intradermal injection of basic fibroblast growth factor, the first method of its kind in the world. In this paper we report the results of long-term follow-up observations and alterations in skin viscoelasticity before and after this treatment.Materials and Methods:A single dose of growth factor was injected directly into aged skin of the dorsal surface of the hand intradermally. The skin viscoelasticity of 50 treated cases was measured by a cutometer just before the treatment and at 1, 3, 6, and 9 months after treatment, respectively.Results:We observed the following rejuvenating effects: improved skin softness, gradual improvement of turgor, improved thickness of atrophied skin, and greatly improved viscoelasticity which reveals the improvement of biomechanical properties of the treated aged skin. According to the comparisons of viscoelasticity between pre- and post-treatment, the rejuvenated changes of R2 and R7 values were comparable to an age difference of more than 20 years.Conclusion:This method was confirmed to have excellent effects in rejuvenating aged skin safely and reliably including biomechanical properties. With this advance, we expect conventional non-physiological skin rejuvenating treatments to be replaced by a much more fundamental method using one-time injections of the growth factor.

Quantitative assessment of scleroderma by surface wave technique

Scleroderma is a multisystem disease characterized by cutaneous and visceral fibrosis. Skin disease is both a disabling feature of scleroderma and a predictor of visceral involvement. The established method of skin assessment is the modified Rodnan skin score (MRSS) which uses semi-quantitative manual skin scoring. However, the Rodnan method is subjective. We have developed a technique and system for assessing skin health by producing and analyzing surface waves in the skin to determine the skin viscoelastic properties. Viscoelasticity of human skin is measured on 30 healthy volunteers and 10 scleroderma patients at six anatomic sites. A small force, monitored by a force transducer, is applied to the skin using a ball-tipped device attached to a mechanical shaker. The skin motion is measured by a scanning laser vibrometer. The surface wave speed is measured by the phase gradient method. The viscoelasticity is inversely estimated by the wave speed dispersion. A typical measurement of the surface wave speed is 3.25 ± 0.19 m/s on the forearm of a volunteer at 200 Hz. With the wave speed dispersion from 100 Hz to 400 Hz, the shear elasticity μ 1 and shear viscosity μ 2 are estimated, respectively, 7.86 ± 1.86 kPa and 5.03 ± 0.60 Pa on the forearm. Statistical analyses suggest that there are significant differences of viscoelasticity between scleroderma patients and healthy subjects. Scleroderma can be effectively and quantitatively evaluated based on human skin viscoelasticity.