Ceramide synthase 4 is highly expressed in involved skin of patients with atopic dermatitis

BACKGROUND

Ceramide is a crucial lipid in the stratum corneum (SC) which maintains the barrier function and hydration of the skin. In atopic dermatitis (AD) patients who have defective skin barrier function, ceramide levels are altered. We previously reported that although the amount of total ceramide was lower in involved skin compared with uninvolved skin of AD patients and with healthy control skin, the amounts of smaller ceramide species of Cer[NS] (<40 total carbons, which are total carbons of both sphingoid base and amide-linked fatty acid), especially Cer[NS] with 34 total carbons (C34-Cer[NS]), were higher. However, the enzyme(s) that produces the higher levels of smaller ceramide species in involved skin of AD patients was unclear.

OBJECTIVE

To identify the enzyme(s) that produces higher levels of smaller ceramide species of Cer[NS] in the involved skin of AD patients.

METHODS

Eight female Caucasian subjects who were diagnosed with AD on their arms (age range: 21-45 years) were enroled in this study. We compared ceramide levels in the SC and the expression levels of enzymes involved in ceramide metabolism using real-time PCR and immunohistochemistry between involved and uninvolved skin of AD patients.

RESULTS

Level of mRNA encoding ceramide synthase 4 (CERS4), which is one of the enzymes that synthesize ceramide from a sphingoid base and an amide-linked fatty acid, was significantly higher in involved skin than in uninvolved skin (P < 0.01). Additionally, the protein expression level of CERS4 in the epidermis was also higher in involved skin compared with uninvolved skin. The expression level of CERS4 correlated with the amount of C34-Cer[NS] (P < 0.01) and the skin hydration value (P < 0.05).

CONCLUSIONS

The elevated expression level of CERS4 contributes to the increase of C34-Cer[NS] and the impaired SC barrier function in involved skin of AD patients.

Age-related changes in the three-dimensional morphological structure of human facial skin

BACKGROUND/AIMS

The human face shows morphological changes with age. Although these changes are generally recognized as wrinkle formation, there have been no quantitative studies of three-dimensional morphological changes with age in each area of the face. The object of the present study, therefore, was to evaluate age-related three-dimensional morphological changes in each area of the face.

METHODS

We obtained replicas using a silicon impression material from eight areas of the face (forehead, eye corners, upper eyelids, lower eyelids, glabella, cheeks, mouth angles, and nasolabial groove) of 136 healthy women, and performed morphological evaluations using a small object type three-dimensional surface morphology measurement system (Voxelan, NKK Co. Ltd., Japan).

RESULTS

All parameters examined, with the exception of sWvin the cheeks, increased with age. The correlation between sWp and age was high in the following order: eye corners > mouth angles > glabella > nasolabial groove > upper eyelids > lower eyelids > forehead > cheeks. sWp in all areas except the eye corners was similar to the mean value in the cheeks in the group aged 18-20 years. However, in the group aged 71-83 years, marked differences were observed among the eye corners, glabella, mouth angles, nasolabial groove, and upper eyelids.

CONCLUSION

Although sunlight is important in the development of three-dimensional changes in surface morphology (wrinkles) in the face, other factors seem to play important roles for the progression of these changes.

The relationship between skin aging and steady state ultraweak photon emission as an indicator of skin oxidative stress in vivo

BACKGROUND/PURPOSE

Ultraweak photon emission (UPE) is one potential method to evaluate the oxidative status of the skin in vivo. However, little is known about how the daily oxidative stress of the skin is related to skin aging-related alterations in vivo. We characterized the steady state UPE and performed a skin survey.

METHODS

We evaluated the skin oxidative status by UPE, skin elasticity, epidermal thickness and skin color on the inner upper arm, the outer forearm, and the buttock of 70 Japanese volunteers.

RESULTS

The steady state UPE at the three skin sites increased with age. Correlation analysis revealed that the steady state UPE only from the buttock was related to skin elasticity, which showed age-dependent changes. Moreover, analysis by age group indicated that b* values of the inner upper arm of subjects in their 20s were inversely correlated with UPE as occurred in buttock skin. In contrast, photoaged skin did not show a clear relationship with steady state UPE because the accumulation of sun-exposure might influence the sensitivity to oxidative stress.

CONCLUSION

These results suggest that steady state UPE reflects not only intrinsic skin aging and cutaneous color but also the current oxidative status independent of skin aging.

Gene transfer in human skin with different pseudotyped HIV-based vectors

Pseudotyping lentiviral vector with other viral surface proteins could be applied for treating genetic anomalies in human skin. In this study, the modification of HIV vector tropism by pseudotyping with the envelope glycoprotein from vesicular stomatitis virus (VSV), the Zaire Ebola (EboZ) virus, murine leukemia virus (MuLV), lymphocytic choriomeningitis virus (LCMV), Rabies or the rabies-related Mokola virus encoding LacZ as a reporter gene was evaluated qualitatively and quantitatively in human skin xenografts. High transgene expression was detected in dermal fibroblasts transduced with VSV-G-, EboZ- or MuLV-pseudotyped HIV vector with tissue irregularities in the dermal compartments following repeated injections of EboZ- or LCMV-pseudotyped vectors. Four weeks after transduction, double-labeling immunofluorescence of beta-galactosidase and involucrin or integrin beta1 demonstrated that VSV-G-, EboZ- or MuLV-pseudotyped HIV vector effectively targeted quiescent epidermal stem cells which underwent terminal differentiation resulting in transgene expression in their progenies. Among the six different pseudotyped HIV-based vectors evaluated, VSV-G-pseudotyped vector was found to be the most efficient viral glycoprotein for cutaneous transduction as demonstrated by the highest level of beta-galactosidase expression and genome copy number evaluated by TaqMan PCR.

Ovariectomy is sufficient to accelerate spontaneous skin ageing and to stimulate ultraviolet irradiation-induced photoageing of murine skin

BACKGROUND

Wrinkling and sagging of the skin during photoageing is physiologically associated with diminished elasticity, which can be attributed to increased fibroblast-derived elastase activity. This degrades the dermal elastic fibres needed to maintain the three-dimensional structure of the skin. We previously reported that ovariectomy accelerates ultraviolet (UV)B-induced wrinkle formation in rat hind limb skin by altering the three-dimensional structure of elastic fibres.

OBJECTIVES

In this study, we used hairless mice to assess the effects of ovariectomy with or without chronic UVA or UVB radiation on sagging and wrinkling of skin, on the elasticity of skin, as well as on matrix metalloproteinase activities in the skin.

METHODS

Ovariectomies or sham operations were performed on 6-week-old female ICR/HR hairless mice.

RESULTS

Even in the ovariectomy group without UV irradiation, the skin elasticity was significantly decreased during the 3-13 weeks after ovariectomy, which was accompanied by a significant increase in elastase activity in the skin. After UVA or UVB irradiation, skin elasticity was significantly decreased to a greater extent in the ovariectomy group than in the sham operation group, and this was accompanied by a reciprocal increase in elastase activity but not in the activities of collagenases I or IV in the skin. Consistent with the decreased skin elasticity, UVA irradiation for 12 weeks elicited more marked sagging in the ovariectomy group than in the sham operation group. UVB irradiation for 12 weeks also induced more marked wrinkle formation in the ovariectomy group than in the sham operation group.

CONCLUSIONS

These results suggest that ovariectomy alone is sufficient to accelerate skin ageing and to increase UV sensitivity, which results in the further deterioration of the skin and photoageing, and may account for the accelerated skin ageing seen in postmenopausal women.

Age-related changes in skin wrinkles assessed by a novel three-dimensional morphometric analysis

BACKGROUND

A system has been developed whereby the morphology of the skin surface can be evaluated directly in three dimensions. This system employs a non-invasive device that utilizes white light of halogen origin, and which allows the computation of wrinkle depth and width, and other parameters of skin surface morphology. Using innovative engineering, an optical system has been devised so that light is transmitted via a slit and can be used to measure not only replicas of the skin but also the skin surface directly. The measurement area is 6.4 x 6.4 mm, and the theoretical resolution with a x 50 magnification lens is within 12.5 micro m.

OBJECTIVES

To use this system to study age-related changes in the morphology of wrinkles at the eye corner areas of women of varying ages.

METHODS

One hundred and one healthy women (age range 20-80 years) residing in the Tokyo area were the subjects used in this study.

RESULTS

Wrinkles demonstrated a rapid increase in depth in women aged 40 years or older, and plateaued at the age of 60 years. Surface morphology parameters yielded results similar to those of age-related changes in wrinkles.

CONCLUSIONS

This new analytical system provides a rapid and convenient non-invasive method to evaluate skin surface morphology in three dimensions, especially with respect to wrinkle formation. The results obtained using this system provide a deeper insight into the mechanistic relationship between wrinkles and skin elasticity.

Diurnal variation affects age-related profile in skin thickness

We have previously demonstrated that over the course of each day there are changes in skin thickness that can be measured by B-mode ultrasonography. This suggests that there is a shift in dermal fluid from the face toward the legs by gravity, resulting in a diurnal variation in skin thickness. Therefore, age-dependent profiles in skin thickness were evaluated by B-mode ultrasonography in the morning or in the afternoon for 130 normal Japanese females aged 18-83 years. Three areas of the face (the forehead, the corners of the eye, and the cheeks) were measured as distinctively sun-exposed areas while the flexion side of the forearm was measured as a weakly sun-exposed area. A weak correlation between skin thickness and age was found in all areas measured (positive for the forehead, the corners of the eye, and the cheeks; negative for forearms) in the morning but not in the afternoon, when only a weak positive correlation was observed in the cheek. These results indicate that when measuring skin thickness, an appropriate time for taking measurements should be selected with consideration of the movements of dermal fluid over the course of each day.

Dermal fluid translocation is an important determinant of the diurnal variation in human skin thickness

BACKGROUND

Ultrasonography has been used as a non-invasive approach to measure skin thickness. To date there have been no studies on diurnal variations in skin thickness.

OBJECTIVES

To evaluate diurnal variations in skin thickness and to compare these with corresponding echogenicity and skin elasticity.

METHODS

Measurements by ultrasonography B-mode and by Cutometer SEM 575 were carried out in the morning and in the afternoon on 20 men and 20 women (mean age 30 years) on three areas of the face (forehead, corner of the eye and cheek), the forearm and the upper arm, and the flank, thigh and calf.

RESULTS

From the morning to the afternoon, the skin thickness in both sexes significantly decreased on three areas of the face, the forearm and the upper arm, but significantly increased on the thigh and calf. In parallel, the echogenicity significantly increased from the morning to the afternoon on the three areas of the face, the forearm and the upper arm, but decreased significantly on the thigh and calf. Measurements of mechanical properties at four sites demonstrated that from the morning to the afternoon, the major parameters of skin elasticity Ue* and Uf* increased significantly in both sexes on two areas of the face and slightly on the forearm, but decreased significantly on the calf.

CONCLUSIONS

The diurnal profiles of skin thickness and skin elasticity in the upper half of the body are the reverse of those in the lower half of the body. These findings suggest that shifts of dermal fluid from the face to the leg by gravity during the day cause the diurnal variation in skin thickness.

Selective inhibition of skin fibroblast elastase elicits a concentration-dependent prevention of ultraviolet B-induced wrinkle formation

We previously reported that wrinkle formation in the skin following long-term ultraviolet B irradiation is accompanied by decreases in skin elasticity and the curling of elastic fibers in the dermis. We further showed that wrinkles could be repaired by treatment with retinoic acid and that this was concomitant with the recovery of skin elasticity ascribed to the repair of damaged elastic fibers. Those studies suggested that decreasing the tortuosity of dermal elastic fibers is an important factor involved in inhibiting or repairing wrinkle formation. Therefore, it is of particular interest to determine whether the inhibition of elastase activity in vivo would prevent the damage of dermal elastic fibers and might abolish wrinkle formation associated with the loss of skin elasticity. Because the major elastase in the skin under noninflammatory conditions is skin fibroblast elastase, we used a specific inhibitor of that enzyme to assess its biologic role in wrinkle formation. The hind limb skins of Sprague-Dawley rats were irradiated with ultraviolet B at a suberythemal dose three times a week for 6 wk. During that period, 0.1-10.0 mM N-phenetylphosphonyl-leucyl-tryptophane, an inhibitor of skin fibroblast elastase, was applied topically five times a week. N-phenetylphosphonyl-leucyl-tryptophane application at concentrations of 0.1-1.0 mM abolished wrinkle formation in a concentration-dependent manner, with a peak for inhibition at 1.0 mM. This inhibition was accompanied by a continued low tortuosity of dermal elastic fibers and a maintenance of skin elasticity. Measurement of elastase activity after 6 wk of ultraviolet B irradiation demonstrated that whereas phosphoramidon-sensitive elastase activity was significantly enhanced in the ultraviolet B-exposed skin, there was no significant increase in that activity in the ultraviolet B-exposed, N-phenetylphosphonyl-leucyl-tryptophane-treated skin. These findings suggest that skin fibroblast elastase plays an essential part in the degeneration and/or tortuosity of elastic fibers induced by cumulative ultraviolet B irradiation.

Inhibitory effect of an extract of Sanguisorba officinalis L. on ultraviolet-B-induced photodamage of rat skin

We previously reported that chronic Ultraviolet-B (UVB) irradiation causes wrinkle formation, decreases skin elasticity, and damages/curls dermal elastic fibers. Those UVB-induced wrinkles can be improved by treatment with retinoic acid or with a CO2 laser which results in a recovery of skin elasticity and a repair of elastic fiber linearity. We showed further that topical application of N-phenetyl-leucyl-tryptophane, an agent that specifically inhibits fibroblast-derived elastase, immediately after UVB irradiation inhibited UVB-induced wrinkle formation, maintained skin elasticity, and inhibited changes in the three-dimensional structure of dermal elastic fibers in a dose-dependent manner. In this study, the effects of an extract of Sanguisorba officinalis L., which also inhibits fibroblast-derived elastase, was evaluated for possible inhibition of UVB induced wrinkle formation, maintenance of skin elasticity, and prevention of damage to the 3-dimensional structure of dermal elastic fibers. Hind limb skins of 3-week-old Sprague-Dawley rats were irradiated with UVB at a suberythemal dose 3 times a week for 6 weeks. Simultaneously, an extract of Sanguisorba officinalis L. (at 0.2% (v/v) or 1% (v/v)) was topically applied 5 times per week immediately following each UVB irradiation and 1 d later. The extract of Sanguisorba officinalis L. inhibited wrinkle formation, maintained skin elasticity, and inhibited the decrease of dermal elastic fiber linearity in the rat hind limb skin in a dose-dependent manner. We have confirmed that the inhibition of elastase activity in fibroblasts immediately after UVB irradiation using an extract of Sanguisorba officinalis L. prevents chronic photodamage following UVB irradiation.

Analytical method to examine the effects of carbon dioxide lasers on skin: a study using wrinkles induced in hairless mice

BACKGROUND AND OBJECTIVE

Investigation of the wrinkle smoothing process elicited by CO(2) laser treatment is important for understanding the mechanism involved in their repair.

STUDY DESIGN/MATERIALS AND METHODS

Hairless mice with wrinkles induced in their dorsal skin by long-term exposure to ultraviolet radiation in the wavelength range of 290-320 nm were treated with a CO(2) laser. By using this model, we investigated the external appearance, histologic changes, and the mechanical properties of the skin during the wrinkle repair.

RESULTS

Laser treatment with an appropriate intensity caused wrinkles to smooth completely. In the healing process, reepithelialization and collagen tissue regeneration in the upper dermis was observed. However, marked changes in the skin were noted, such as increases in the collagen layer and in the skin thickness, and changes in the mechanical properties of the skin, despite the favorable external appearance.

CONCLUSIONS

An abnormal state characterized by excessive collagen regeneration and other changes in the dermis occur concomitantly with wrinkle smoothing.

The role of elastases secreted by fibroblasts in wrinkle formation: implication through selective inhibition of elastase activity

We have previously demonstrated that decreases in skin elasticity, accompanied by increases in the tortuosity of elastic fibers, are important early events in wrinkle formation. In order to study the role of elastases in the degeneration of elastic fibers during wrinkle formation we examined the effects of an inhibitor of skin fibroblast elastase, N-phenethylphosphonyl-L-leucyl-L-tryptophane (NPLT), on wrinkle formation in hairless mice skin following UV irradiation. Dorsal skins of hairless mice were exposed daily to UV light for 18 weeks at doses of 65-95 mJ/cm2 and treated topically with 100 microL of 1 mM NPLT immediately after each UV irradiation. Wrinkles on dorsal skins were evaluated from week 6 through week 18. The daily exposure of mouse skin to UV light with less than 1 minimal erythemal dose significantly enhanced the activity of elastase in the exposed skin by week 4, and the elevated levels of elastase activity were significantly reduced by the in vitro incubation with NPLT in a dose-dependent manner to a level similar to that in unexposed mice skin, indicating that NPLT can efficiently inhibit the UV-inducible elastase activity. Topical application of NPLT significantly suppressed wrinkle formation when compared with vehicle controls by week 15 of treatment (P < 0.05). Histochemistry of elastic fibers with Orcein staining demonstrated that there were no obvious decreases of the fine elastic fibers in UV-exposed NPLT-treated skin in contrast to their marked decreases in the UV-exposed vehicle-treated skin. These findings suggest that skin fibroblast elastase plays a decisive role in wrinkle formation through the degeneration of elastic fiber.

The inhibitory effect of an extract of Sanguisorba officinalis L. on ultraviolet B-induced pigmentation via the suppression of endothelin-converting enzyme-1alpha

Endothelin-1 (ET-1) has been reported to be expressed in human epidermis at both the gene and protein levels. ET-1 plays a pivotal role in ultraviolet B (UVB)-induced pigmentation due to its accentuated secretion after UVB irradiation and its function as a mitogen and as a melanogen for human melanocytes. We have recently found that endothelin-converting enzyme (ECE)-1alpha plays a constitutive role in the secretion of ET-1 by human keratinocytes and that an extract of Sanguisorba officinalis L. inhibits ECE activity in human endothelial cells, which predominantly express ECE-1alpha. In this report, to clarify the potential use of this botanical extract as a whitening agent, we examined whether this extract inhibits UVB-induced pigmentation in vivo. When this extract was applied to human keratinocytes after UVB irradiation, secretion of ET-1 by those cells was reduced, and this was accompanied by a concomitant increase in the secretion of inactive precursor Big endothelin-1. When hairless mice were exposed to UVB light and were treated with the extract, it suppressed the induction of ET-1 in the UVB-irradiated epidermis. In the course of UVB-induced pigmentation of brownish guinea pig skin, this extract significantly diminished pigmentation in UVB-exposed areas. These findings indicate that ECE-1alpha in keratinocytes plays a pivotal role in the induction of pigmentation following UVB irradiation and that an extract of S. officinalis, which inhibits ET-1 production in human keratinocytes, is a good ingredient for a whitening agent.

The paracrine role of stem cell factor/c-kit signaling in the activation of human melanocytes in ultraviolet-B-induced pigmentation

The interaction of stem cell factor with its receptor, c-kit, is well known to be critical to the survival of melanocytes. Little is known about the role(s) of the stem cell factor/c-kit interaction in epidermal pigmentation, however. To clarify whether the stem cell factor/c-kit signaling has a paracrine role in ultraviolet-B-induced pigmentation, we determined whether the exposure of human keratinocytes, melanocytes, and the epidermis to ultraviolet B light stimulates the expression of stem cell factor or c-kit at the gene and/or protein levels. We further examined whether interrupting the binding of stem cell factor to c-kit by subepidermal injection of a monoclonal antibody to c-kit affects ultraviolet-B-induced pigmentation in brownish guinea pig skin. When human keratinocytes and melanocytes in culture were exposed to ultraviolet B light, transcripts of stem cell factor and c-kit (as assessed by reverse transcription polymerase chain reaction) and expression of those proteins (by enzyme-linked immunosorbent assay and western blotting) increased significantly and peaked at a dose of 20-40 mJ per cm2. In ultraviolet-B-exposed human epidermis, stem cell factor transcripts and protein expression were also markedly enhanced compared with the nonexposed epidermis. Immunohistochemistry with antibodies to stem cell factor revealed an increased staining in the ultraviolet-B-exposed epidermis, which was accompanied by a slight epidermal hyperplasia. In the course of ultraviolet-B-induced pigmentation of brownish guinea pig skin, the subepidermal injection of c-kit inhibitory antibodies completely abolished the induction of pigmentation in the ultraviolet-B-exposed area, and there was no increase in the number of dihydroxyphenylalanine-positive melanocytes. These findings indicate that the stem cell factor/c-kit signaling is critically involved in the biologic mechanism of ultraviolet-B-induced pigmentation.

Carbon dioxide laser treatment promotes repair of the three-dimensional network of elastic fibres in rat skin

BACKGROUND

We have previously reported that ultraviolet (UV) B irradiation induces a loss of linearity in the three-dimensional structure of dermal elastic fibres, which results in the reduction of elastic properties of the skin and leads to wrinkle formation. We further reported that repair of wrinkles by all-trans retinoic acid is accompanied by recovery of the linearity of elastic fibres. Carbon dioxide (CO2) lasers are widely used for treating wrinkles in cosmetic surgery.

OBJECTIVES

To perform CO2 laser treatment of wrinkles induced in rat skin by UVB irradiation and to evaluate changes in the three-dimensional structure of dermal elastic fibres during wrinkle repair.

METHODS

Wrinkles were induced in the hind limb skin of Sprague-Dawley rats by UVB irradiation (130 mJ cm-2 three times weekly for 6 weeks), followed by CO2 laser treatment (11.3 J cm-2). The surface appearance of the skin was evaluated by replica observation 6 and 10 weeks after CO2 laser treatment followed by measurement of mechanical properties using a Cutometer. Subsequently, perfusion fixation and digestion with formic acid were performed and elastic fibres were observed by scanning electron microscopy (SEM). Image analysis of SEM micrographs was carried out to evaluate the linearity in the three-dimensional structure of elastic fibres.

RESULTS

Six weeks after CO2 laser treatment, all parameters of skin mechanical properties in the UVB-irradiated group recovered to levels of the control non-irradiated group, accompanied by repair of wrinkles and a significant increase in linearity of the three-dimensional structure of elastic fibres.

CONCLUSIONS

These findings indicate that CO2 laser treatment has a therapeutic potential to repair wrinkles to non-irradiated levels through recovery of the three-dimensional structure of elastic fibres.

Ovariectomy Accelerates Photoaging of Rat Skin¶

We have previously reported the formation of wrinkles, a decrease in skin elasticity and a loss in the linearity of dermal elastic fibers in rat hind limb skin irradiated with ultraviolet radiation in wavelength ranging 290-320 nm (UVB) at a suberythemal dose for 6 weeks. Estrogens are considered effective in preventing photoaging in postmenopausal females, but the role of estrogen in the skin remains unclear. In this study we have evaluated the influence of short-term chronic UVB irradiation at a suberythemal dose on the skin of ovariectomized rats. An ovariectomy or a sham operation was performed on each 3 week-old female Sprague-Dawley rat. Starting 1 week after the operation the hind limb skin of each rat was irradiated with UVB at a suberythemal dose (130 mJ/cm2) three times a week for 3 or 6 weeks. Decreases in elasticity and wrinkle formation in the skins of ovariectomized animals were induced more quickly than in the skins of sham-operated animals following UVB irradiation. The linearity of elastic fibers in the ovariectomy group decreased significantly compared with the sham-operation group, but erythema in the ovariectomy group was induced more readily than in the sham-operation group following UVB irradiation. These findings suggest that decreases in the estrogen levels after ovariectomy accelerate photoaging in terms of the morphology and physical properties of the skin surface and the three-dimensional structure of elastic fibers.

Epidermal change can alter mechanical properties of hairless mouse skin topically treated with 1alpha, 25-dihydroxyvitamin D(3)

Wrinkle formation caused by photoaging clearly involves changes of extracellular matrix components and mechanical properties of the skin. Recently, it was reported that the topical application of 1alpha, 25-dihydroxyvitamin D(3) to hairless mouse skin induced wrinkling. Here we have evaluated the effect of topical application of 1alpha, 25-dihydroxyvitamin D(3), which causes skin wrinkling, on the mechanical properties of the hairless mouse (HR/ICR) skin, using a commercially available non-invasive in vivo instrument. The elasticity element of the skin was unchanged, but the viscosity element significantly increased. Histologically, the epidermis became remarkably thick, but no conspicuous changes were observed in the dermis. Changes in the mechanical properties of the skin after 1alpha, 25-dihydroxyvitamin D(3) treatment take place through epidermal physical variation, especially changes of viscosity elements. It is suggested that the visco-elastic properties of the epidermis are also attributable to the morphology as well as the mechanical properties of the skin.

The effects of UVA and UVB irradiation on the viscoelastic properties of hairless mouse skin in vivo

BACKGROUND

Age-related changes in the elasticity of the human skin have been demonstrated as well as those due to proto ageing.

AIMS AND METHODS

To investigate if UV irradiation causes similar changes in the elastic properties of skin, hairless mice (HR/ICR) were irradiated chronically with suberythemal doses of UVA or UVB. Using a recently designed, commercially available noninvasive in vivo instrument, we compared skin thickness and elasticity after 8 weeks of UV exposure with age-matched control mice.

RESULTS

Skin thickness increased significantly after UVB irradiation. Skin elasticity (Ur/Uf) decreased significantly after UVA and UVB irradiation, and the ratio of viscosity to elasticity (Uv/Ue) increased significantly after UVA irradiation. Intrinsic immediate strain (Ue*) and intrinsic delayed strain (Uv*) decreased significantly after UVB and UVA exposure. These changes were similar to those reported previously in an in vivo study on human face skin using the same instrument.

CONCLUSION

This finding suggests that the Ue* and Uv* changes observed in human facial skin are associated with actinic ageing caused by chronic UV exposure.

Fucoidan is the active component of fucus vesiculosus that promotes contraction of fibroblast-populated collagen gels

The fibroblast-populated collagen gel culture method has been evaluated as a dermal model of wound contraction and granulation in tissues during the wound healing process and as an in vitro model of dermal tissue. We previously reported that an extract of Fucus vesiculosus promoted fibroblast-populated collagen gel contraction and that the promotion of the gel contraction was due to the increased expression of integrin alpha2beta1 on the surface of the fibroblasts. In this study, we investigated the active component of the extract of this alga using extraction and fractionation techniques. Water extraction of the alga was followed by precipitation with excess ethanol and then gel filtration with the boundary molecular weight of 30,000. The high molecular weight fraction obtained from gel filtration was fractionated by ion exchange chromatography on diethylaminoethyl cellulose column to give active fractions that have more polar properties. These polar, high molecular weight fractions which contained molecules with fucose and sulfate groups showed significant gel contraction-promoting activity and integrin expression-enhancing activity, and were estimated to be the sulfated-polysaccharide fucoidan. Commercially available fucoidan showed similar activities to the above-described fraction of this alga. Although it remains necessary to precisely identify the specific active component, the above results indicate that fucoidan is the active component which promotes collagen gel contraction, and also indicate the possibility that it dose so by enhancing the integrin alpha2beta1 expression.

Age-related alterations of echogenicity in Japanese skin

BACKGROUND

Ultrasonic methods are commonly used for the noninvasive measurement of skin thickness. The effects of ageing on the skin have been reported to differ between Asians and Caucasians. Therefore, it is possible that the echogenicity of the skin on ultrasonographic images reflects differences in the skin architecture and properties that may vary among races and environments.

OBJECTIVE AND METHODS

Since there have been a few reports on ageing-related changes in ultrasonic echogenicity in Caucasian skin, but not in Asian skin, we evaluated age-related changes in the echogenicity of ultrasonographic images by the ultrasonic B mode at 3 sites on the face (forehead, eye corners, cheeks) considered as sun-exposed areas and on the ventral forearms considered as weakly sun-exposed areas in 130 Japanese females aged from 18 to 83 years. The dermis was divided into 3 layers (upper, middle, lower), and echogenicity was evaluated in each area.

RESULTS

No age-related change in echogenicity was observed in the entire dermis. When the dermis was divided into 3 layers (upper, middle and lower dermis), the echogenicity was decreased in the upper layer and increased in the lower layer with age in all skin areas tested. In contrast, there were no age-related changes of echogenicity in the middle dermis.

CONCLUSION

These findings suggest that, as for Caucasians, echogenicity in the upper and lower dermis is a useful tool for evaluating skin ageing in the Japanese.

Effects of natural product extracts on contraction and mechanical properties of fibroblast populated collagen gel

Fibroblast-populated collagen gel cultures have been used as a dermal model of wound contraction and granulation in the wound healing process and as an in vitro model of dermal tissue. We evaluated the effects of various natural product extracts on collagen gel contraction-promoting activity and mechanical properties (relaxation time) using this model, and observed that some natural product extracts, such as Hibamata extract (from Fucus vesiculosus) promoted gel contraction and increased the relaxation time of the gels. In addition, we investigated the mechanism of the promotion of the gel contraction, noting increased expression of integrin alpha2 and beta1 subunit molecules on the surface of the fibroblasts, suggesting that some extracts, such as Hibamata extract, promote gel contraction by increasing the expression of integrin molecules on the fibroblasts surface. For other types of natural product extracts, other mechanisms of the gel contraction-promoting activity, which were independent of an increase of integrins, were suggested. Although the mechanisms of promotion of gel contraction by these extracts are still unclear, it is at least clear that, more than one mechanism appears to be present. Therefore, more effective drug regimens for improving dermal tissues and wound healing may be achieved by combining drugs which increase integrin molecules and drugs with other mechanisms of action.

All-trans retinoic acid promotes the repair of tortuosity of elastic fibres in rat skin

To elucidate the repair effects of all-trans retinoic acid (t-RA) on ultraviolet (UV)-induced tortuosity of elastic fibres in rat skin, the hind limbs of Sprague-Dawley rats were irradiated at a suberythemal dose of UV (three times/week for 6 weeks) and 0.025% t-RA in ethanol was applied topically five times/week for 6 weeks. The three-dimensional arrangement of elastic fibres with special reference to their linearity was quantified by image analysis using a scanning electron microscope following a combination of intravascular resin injection and selective digestion using formic acid. When t-RA was topically applied for 6 weeks on wrinkles formed by 6 weeks' exposure of the skin of rat hind limbs to UV radiation, the wrinkles disappeared to control levels, concomitant with an improvement in skin elasticity. The linearity of the elastic fibres was significantly (P < 0.01) increased compared with age-matched UV-irradiated controls. These findings suggest that the degeneration and deposition of elastic fibres accompanied by an increase in their linearity is involved in the process of wrinkle repair by topical application of t-RA.

Age-related discontinuous changes in the in vivo fluorescence of human facial skin

We measured the 325-nm laser-induced fluorescence of the skin of the face and ventral forearm in seventy Japanese female volunteers, and evaluated the effects of age and exposure to sunlight. The subjects were arbitrarily grouped into 10-year age-groups. In slightly exposed areas such as the ventral forearm, the average laser-induced intensity ratio at 390 nm to 430 nm showed no significant differences with the age group. In areas markedly exposed to sunlight such as the corners of the eyes and mouth, the average laser-induced intensity ratio showed a discontinuous decrease with age. These findings suggested that dermal fluorophore changes differ with the skin areas and are affected by sunlight exposure.

Unusual wrinkle formation after temporary skin fixation followed by UVB irradiation in hairless mouse skin

Generally, many wrinkles form on the human face, and temporary wrinkles eventually become permanent. We evaluated the effects of temporary skin fixation on wrinkle formation after UVB irradiation using the back skin of hairless mice. In the group treated with UVB irradiation immediately after production using cyanoacrylate resin of an artificial groove parallel to the midline, wrinkles formed parallel to the midline, an uncommon direction for wrinkle formation in this mouse model. These wrinkles did not disappear even when the skin was stretched. No such changes were observed in the group in which only the temporary groove alone was produced without UVB irradiation. In 3-D surface parameter analysis, all roughness parameters in the group treated with UVB irradiation immediately after production of an artificial groove were significantly increased relative to the age-matched control group. In contrast, no differences were observed between the group in which only the temporary groove alone was produced without UVB irradiation and age-matched controls. The results of this study suggest that both a temporary groove in the skin and UVB irradiation are necessary for wrinkle formation in the back skin of hairless mice.

The relationship between quantitative changes in collagen and formation of wrinkles on hairless mouse skin after chronic UV irradiation

Female albino hairless mice were irradiated chronically with sub-erythemal doses of UVB radiation. Collagen extracted from the irradiated or non-irradiated dorsal skin of mice was fractionated into neutral salt-soluble (NSC), acid-soluble (ASC) and insoluble fractions (ISC). An age-related exponential decrease in the content and proportion of acid-soluble collagen was found in each group. The contents and the proportions of ASC from irradiated mice were always significantly lower than those from age-matched control animals. Age-related slight decreases were observed in the contents (per fresh weight of tissues) of NSC, ISC and total collagen in the control group but decreases in these collagen contents after UVB irradiation were marked. A dramatic decrease in ASC occurred nearly concomitantly with wrinkle formation in the irradiated mice. The decrease of acid-soluble skin collagen in irradiated mice may play a role in the formation of wrinkles on hairless mouse dorsal skin.

Degree of ultraviolet-induced tortuosity of elastic fibers in rat skin is age dependent

To elucidate differential effects of ultraviolet (UV) exposure on three-dimensional networks of elastic fibers during maturation of rat skin, Sprague-Dawley rat hind limbs were irradiated with suberythemal doses of UV light (UVB, 130 mJ/cm2, or UVA, 27 J/cm2) in three different time courses of exposure: 3-9 weeks old, 9-15 weeks old, and 3-15 weeks old. Three-dimensional arrangement with special reference to linearity of elastic fibers was quantified by image analysis using a scanning electron microscope after a combination of intravascular resin injection and selective digestion technique using formic acid. Among the three irradiation groups, the group irradiated with UVB or UVA between 3 and 15 weeks old (UVB, three times per week; UVA, five times per week) elicited the most marked decrease in the linearity of elastic fibers. Despite the same irradiation period, there was a significant difference in the decreased linearity between the two irradiation groups of 3-9 and 9-15 weeks old, with the former irradiation group exhibiting greater loss of linearity than the latter irradiation group. The magnitude of the decreased linearity was greater in the UVB-exposed groups than in the UVA-exposed group. These findings indicate that the three-dimensional linearity of elastic fibers is more susceptible to disruption by UV exposures during the growth period than that after the growth period.

Age-related changes in the elastic properties and thickness of human facial skin

Using recently designed, commercially available, non-invasive instruments, we measured the thickness and elasticity of the skin of the face and ventral forearm in 170 women, and evaluated the effects of age and exposure to sunlight. Skin thickness decreased with age in ventral forearm skin, which has limited exposure to sunlight, but increased significantly in the skin of the forehead, corners of the eyes, and cheeks, which are markedly exposed to sunlight. Skin elasticity (Ur/Uf) decreased with age on both the face and forearm. The ratio of viscosity element to elasticity element (Uv/Ue) increased with age at all sites. However, delayed distension (Uv), immediate retraction (Ur), final distension (Uf), and immediate distention (Ue), as individual elements, decreased on the face and increased on the forearm with age. This tendency was more marked after correction for skin thickness. These results suggested the specificity of skin thickness and elasticity in the facial skin. Analysis using a four-element model showed no changes in the elasticity coefficient of Maxwell element on the forearm, but an increase on the face. This indicates quantitative or qualitative changes in elastic fibres in facial skin. Thus, sunlight appears to have a considerable effect on the thickness and physical properties of facial skin.

Ultraviolet-B irradiation deforms the configuration of elastic fibers during the induction of actinic elastosis in rats

We used scanning electron microscopy combined with perfusion fixation, resin injection and a selective digestion procedure to determine the effects of ultraviolet-B (UVB) radiation on the three-dimensional architecture of elastic fibers of rat skin. Chronic irradiation with a suberythematous dose of UVB (3 times/week for 12 weeks) produced a tortuous deformation of the superficial elastic fibers in the skin of the rat sole which normally are linearly arranged. Using computer analysis, we evaluated 40 individuals elastic fibers every 3 weeks for 12 weeks following the irradiation. This procedure confirmed the increasing tortuosity of the fibers, which was related to a decline in the elastic property of the skin in situ. Fine elastic branches developed among the deformed fibers and eventually anastomosed to produce an irregular network in the superficial dermal connective tissue, which may correspond to the development of actinic elastosis, that is, the UV-related accumulation of elastic fiber material.

Two genetically distinct molecular species of octopus muscle collagen

The arm muscular tissue of an octopus, Octopus vulgaris, was subjected to limited proteolysis with pepsin and the solubilized tissue collagen was separated into two fractions by selective salt precipitation. Biochemical characterization of the major collagen fraction precipitating at 0.45 M NaCl (pH 2.6) has demonstrated that it comprises almost a single type of molecular species with structure (alpha 1)2 alpha 2, which was identified by its CNBr-peptide pattern as being similar to Type I-like collagen of octopus skin. On the other hand, the minor collagen fraction precipitating at 0.90 M NaCl (pH 2.6) was found to contain a unique gamma-chain-sized component cross-linked by disulfide bonds. Sepharose CL-4B gel filtration of the reduced gamma component revealed the presence of an alpha component, which is virtually identical in amino acid composition to the original gamma protein and bears a close resemblance to known basement membrane collagens. This unique alpha component was genetically distinct from alpha 1 and alpha 2 chains of the major muscle collagen as judged by their CNBr-peptide patterns.

Octopus skin collagen. Isolation and characterization of collagen comprising two distinct alpha chains

A major collagenous component of octopus skin was isolated from limited pepsin digests by selective salt precipitation in acidic and neutral solvents. Chromatography on Cm-cellulose of the denatured collagen and sodium dodecyl sulfate-gel electrophoresis, agarose gel filtration, and chemical analysis of the chromatographic fractions revealed that two distinct alpha chains, alpha 1 and alpha 2, are present in a molar ratio of 2:1. The formaldehyde-cross-linked collagen yielded a large proportion of gamma chain, which was identified as gamma 112 by its chromatographic behavior and amino acid composition. Moreover, cyanogen bromide peptide mapping suggested a structural relationship between octopus skin collagen and calf skin Type I collagen. These composite results led us to the conclusion that the native collagen molecules are designated by the formula (alpha 1)2 alpha 2 and correspond to type I collagen in higher vertebrate tissues. On the basis of these findings, we assume that Type I or Type I-like collagen might have evolved along independent phylogenetic lines in protostomian and deuterostomian animals.

Lower vertebrate collagen. Evidence for type I-like collagen in the skin of lamprey and shark

The soluble skin collagens of the lamprey, Entosphenus japonicus, and the great blue shark, Prionace glauca, have been isolated and characterized with respect to their chain composition. Chromatography on CM-cellulose of the denatured skin collagens and agarose gel filtration, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and chemical analysis of the chromatographic fractions revealed that the two distinct subunits, alpha 1 and alpha 2, were present in a molar ratio of about 2:1. Thus, the chain composition of both lower vertebrate collagens is designated by the formula (alpha 1)2 alpha 2, similar to that of Type I collagen in higher vertebrate tissues. However, electrophoresis of the collagens in sodium dodecyl sulfate showed mostly a single type of alpha component. This seems to be due to the preferential crosslinking of alpha 1 into beta 11 dimers for the lamprey collagen and of alpha 2 into beta 12 dimers for the shark protein. These composite findings indicate that Type I-like collagen is widely distributed in the skin of vertebrates ranging from cyclostomes to mammalians.