Do different ethnic groups need different sun protection?

Background: In the present study, the transmission of sunlight trough the human skin barrier into the living tissue was investigated in the spectral region between 280 and 700 nm.
Methods: The experiments were performed with a fiber-based spectrometer on sliced skin obtained from volunteers with different skin types. One fiber was positioned directly on the skin surface and the second one underneath the skin samples. The distribution of the sunlight under the epidermis was determined.
Results: Significant differences were found in the absorption properties of the different skin types, which were mainly determined by the variations in melanin concentration and distribution. It was found that sunscreens for specific ethnic groups need different combinations of UV filters, if a balanced relation between ultraviolet B (UVB) and ultraviolet A (UVA) protection is to be obtained. On the other hand, it could be demonstrated that the human skin is also well protected against visible and near-infrared light by melanin.
Conclusions: The higher the skin type category, the better the protection in the visible part of the spectrum of the sun. This stimulates the hot discussion at the present time, as to whether sunscreens should also contain protection compounds in the visible and near-infrared parts of the spectrum.     

Analysis of the absorbance spectra of skin lesions as a helpful tool for detection of major pathophysiological changes

BACKGROUND/AIMS: Although reflectance spectrophotometry is often applied to measurement of skin color, raw data of reflectance spectra of normal and lesional skin are difficult to analyze. The purpose of this pilot study was to determine whether measurement of spectral difference in absorbance (SDA) between various skin lesions and normal skin adjacent to them could yield useful information for clinics in dermatology. METHODS: We studied spectral reflectance of a total of 173 various skin lesions. After converting obtained reflectance into apparent absorbance A (=log(10)(1/reflectance)), we examined the profile of SDA, that is, A(lesion)-A(normal skin) in the range of 400-700 nm, and compared them with the absorbance spectra of melanin and hemoglobin. RESULTS: SDA of epidermal pigmentary disorders was similar to the absorption spectrum of melanin in vitro, but the cases with intradermal melanin deposition showed a different pattern, reflecting the scattering effect of the dermis. SDA of erythematous lesions was similar to the spectra of either oxygenated or reduced hemoglobin, and varied according to the oxygenated level of cutaneous blood. SDA of lesions with a combination of factors appeared as a simple summation of spectra corresponding to each of the factors. CONCLUSIONS: Our method may offer easy and quick detection of major pathophysiological changes in skin lesions.     

Spectral reflectance of human skin in vivo

A newly developed skin reflectance spectrophotometer was evaluated for measurements of both melanin pigmentation and erythema. Physiological changes in blood flow and blood content in normal humans were induced by compression with an arm cuff during recording of skin reflectance spectra. Reflectance spectra of UV-induced erythema were also recorded and compared with laser-Doppler flow measurements. Spectral reflectance measurements were found to be highly sensitive in determining minimal erythema, which was not clinically detectable. The measurements of erythema using reflectance spectroscopy and UV irradiation were very highly correlated (r = 0.996). It was possible to calculate the in vivo absorbance of oxygenized haemoglobin. The melanin pigmentation following UV irradiation was quantified by reflectance spectroscopy and correlates highly with the dose of UV irradiation (r = 0.995). Furthermore, regional variations in skin melanin and haemoglobin were analysed for fair Caucasian skin.     

Noninvasive computerized analysis of skin chromophores in vivo by reflectance spectroscopy

Reflectance spectroscopy in an objective and accurate method for determining skin colour and has been widely used for measuring physiological variations in skin colour and for monitoring dermatological treatment modalities. Previous studies have used pigment indexes to describe changes in skin colour. Using a multiple regression method to calculate reflectance spectroscopic data, it has been possible to calculate the relative amounts of the different chromophores present in the skin. The technique was found reliable in in vitro tests and in experimentally induced variations in pigment content caused by venous congestion or ultraviolet (UV) light irradiation. In developing UV-induced erythema, the primary events seem to be venous dilatation followed by an increase in blood flow.     

Feasibility and accuracy of a newly developed hand-held device with a flat-type fluorescent lamp for measuring the minimal erythema dose for narrow-band UVB therapy

Background: Narrow-band ultraviolet B (NB-UVB) for the treatment of refractory skin diseases, such as psoriasis and atopic dermatitis, requires an adequate irradiation protocol based on the minimal erythema dose (MED) to establish an optimal dosage schedule. Although MED can be measured using a systemic-type irradiation unit, there are difficulties associated with this device. There is no standardized device available to determine the MED for NB-UVB. Here, we compared a conventional device with a newly developed device for measuring MED.
Method: MED was measured in 16 psoriasis patients using both a conventional measuring device and the newly developed device, which comprised a hand-held NB-UVB (311–313 nm) flat-type fluorescent lamp with neutral density filters having different transmittances ranging from 10% to 90%. This device was designed to be stably maintained on the skin surface and to provide a highly accurate measurement with only one UV irradiation exposure while also preventing UV radiation from leaking to nonirradiated areas.
Results: The MED values obtained from each patient were the same using both devices.
Conclusion: One-time irradiation using the new hand-held device with the NB-UVB flat-type fluorescent lamp is feasible and accurate for determining the MED to use in calculating the UV irradiation treatment dose.     

Autofluorescence of human skin is age-related after correction for skin pigmentation and redness

When measuring the skin fluorescence in vivo, the absorption of chromophores such as melanin and hemoglobin often contribute predominantly to the changes in fluorescence and obscure the information from the fluorophores. We measured in vivo the collagen-linked 375 nm fluorescence (excitation: 330 nm) and 455 nm fluorescence (excitation: 370 nm) from nonexposed buttock skin of healthy volunteers. Skin pigmentation and redness of the same sites were quantified by reflectance of the skin at 555 nm and 660 nm. Multiple regression analysis was used to find the correlation between the fluorescence and skin pigmentation and redness. The fluorescence was corrected for the impact of pigmentation and redness according to the equation found in the regression analyses. The age-related trend of the fluorescence was evaluated. The 375 nm fluorescence showed positive relation to age, whereas the 455 nm fluorescence showed no significant relation to age. The increasing rate of the 375 nm fluorescence (logarithm transformed) was 2% per year, which is comparable with previously published data. The results suggest that the correction of the autofluorescence intensity for skin pigmentation and redness is valid, and the 375 nm skin autofluorescence may be used as a biologic marker of skin aging in vivo.     

The effects of heating and cooling on ultraviolet radiation-induced erythema and pigmentation in human skin

Background/Purpose: As most biochemical systems are affected by temperature, thermal changes before or after ultraviolet (UV) irradiation could influence skin vascular blood flow changes and inflammatory responses. In this study, our aim was to investigate the influence of thermal changes on UV-induced acute skin reactions, namely, erythema and pigmentation.
Methods: Our volunteers consisted of 10 males, with ages ranging from 22 to 24 years and with Fitzpatrick's skin type III or IV. Skin temperatures were changed with a 45°C heating pad or by ice pack application before or after UV irradiation (control, 1 minimal erythema dose (MED), 2 MED) and then changes in erythema and pigmentation were measured by a Minolta Spectrophotometer CM-2002.
Results: The present study demonstrates that both heating and cooling increase skin erythema and reduce pigmentation, and that the timing of heating and cooling influences the UV-induced skin reaction. Pre-heating and post-cooling groups showed more UV-induced erythema than the post-heating and pre-cooling groups, respectively.
Conclusion: Our results indicate that alteration of skin surface temperature could modulate UV-induced erythema and pigmentation responses.     

Spectroscopic characteristics of human melanin in vivo

In this paper we present the absorption characteristics of human melanin in the visible range of wavelengths and specifically in the range 620-720 nm. The spectroscopy of melanin is studied by measuring remittance spectra of normal skin and vitiligo-involved skin of volunteers-patients. It is assumed that the spectral differences between adjacent areas of normally pigmented skin, and to some degree amelanotic skin, can only be due to the variations of the melanin filter. The ratio of the remittance spectrum of the vitiligo-involved skin with the spectrum of the normal skin in the range 620-720 nm can be fitted with a straight line for all the volunteers. A very strong correlation is obtained between the intercept and the slope for all the volunteers, which leads us to conclude that it is indeed melanin that we are measuring in all the volunteers and that it is the same substance spectroscopically for all the volunteers.     

Effect of ultraviolet adaptation on the ultraviolet absorption spectra of human skin in vivo

Background: The absorption spectrum of human skin provides a basis for the estimation of the possible photobiological impact of ultraviolet (UV) radiation. The optical properties of human skin in the UV spectral range have so far mainly been measured ex vivo due to a lack of an appropriate in vivo technique and the change of optical properties during the course of adaptation to higher UV doses has hardly been addressed. Methods: We have determined the absorption spectra of human skin in vivo in the wavelength range from 290 to 341 nm in 3 nm steps using laser optoacoustics. In this technique, optical properties are derived from the pressure profile generated by absorbed light energy in the sample. Spectra from the volar and dorsal aspects of the forearm of 20 subjects were compared, i.e. sites with native and various facultative pigmentation. Results: UV adaptation shows as an increase in absorption coefficients over the entire measured UV range and especially in short‐range UVB. Subject groups with high vs. low UV exposure can be discriminated by analyzing the difference absorption spectra between dorsal and volar aspects of the forearm. No dependence on the subject's phototype was seen in the degree of adaptation. Conclusion: The difference between native and facultative pigmentation may be explained by the absorption properties of the two prime chromophores responsible for adaptation to higher UV exposure: melanin and keratin. Stronger pigmentation, i.e. a higher melanin concentration, is found as an increase of absorption coefficients over the entire UVA‐II/UVB range. The thickening of the horny layer and accordingly, a higher influence of keratin on the absorption spectra is prominent especially in the UVB region.     

In vivo measurement of skin erythema and pigmentation: new means of implementation of diffuse reflectance spectroscopy with a commercial instrument

Background Various physical, chemical and biological insults, including exposure to ultraviolet (UV) radiation, cause erythema and change in pigmentation in human skin. These reactions provide an important measure of the cutaneous response to the insult. Objectives To present a new implementation of a method for objective in vivo measurement of erythema and pigmentation. Methods The method is based on acquisition of reflectance spectra in the visible range using a commercially available spectrophotometer. The probe of this instrument incorporates an integrating sphere that captures the light remitted from the skin in a wide range of angles. We corrected the acquired reflectance spectra for the contribution of specular reflections by an amount given by the Fresnel equation and verified this correction experimentally. This correction is particularly important when measurements are performed on heavily pigmented skin. The corrected reflectance spectra are then transformed into absorbance spectra. To analyse these spectra, we developed an algorithm which can be used to calculate apparent concentrations of oxyhaemoglobin, deoxyhaemoglobin and melanin. This method was tested in clinical studies of skin reactions induced by exposure to UV radiation. These experiments involved three groups of subjects with progressively darker complexion (constitutive pigmentation). Each group consisted of 10 subjects. Erythema was measured 1 day after UV exposure, and pigmentation (melanin content) 1 week later. Results Distinct apparent absorbance spectra were obtained for dark, intermediate and fair skin. There was good agreement between reconstructed spectra and experimental data at relevant wavelengths. Difference absorption spectra were able to show the dose dependence of UV‐induced responses, and erythema and pigmentation values obtained by the spectroscopic method showed good correlation with those derived by subjective visual grading. Conclusions The results demonstrate that the presented methodology provides an objective noninvasive way of measuring UV‐induced reactions independently of the level of constitutive pigmentation.     

Photoprotection of bacterial-derived melanin against ultraviolet A–induced cell death and its potential application as an active sunscreen

Background  The increase in the incidence of non-melanoma skin tumours, photoaging, and immunosuppression demand for more effective sunscreen on ultraviolet A (UVA) irradiation.
Objectives  The aim of the study is to evaluate the photoprotective effects of a bacterial-derived melanin against UVA-induced damages in vitro and in vivo .
Methods  Human fibroblasts were used to assess the role of the bacterial-derived melanin on cell viability against UVA. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and nuclear morphology were employed to evaluate the photoprotection at the cellular level. Fluorometric assays were performed to detect the formation of reactive oxygen species (ROS) in the cells. Evaluations of the bacterial-derived melanin as a sunscreen were measured by transmission test and persistent pigment darkening on human skin.
Results  Bacterial-derived melanin efficiently scavenged ROS in the fibroblasts after UVA irradiation. The cell viability of xeroderma pigmentosum (XP) fibroblast treated with varied doses of melanin increased dramatically in comparison with untreated control and the treated XP fibroblasts became more resistant to UVA-induced apoptosis than normal fibroblasts. Although the relative transmission didn't change too much with different concentration of bacterial-derived melanin, this melanin could keep UVA-irradiated skin from pigment darkening and act as an active sunscreen on skin.
Conclusions  The bacterial-derived melanin provided significant protection to fibroblast cell and human skin against the UVA radiation. It has the potential to be developed as an active sunscreen for the patients with photosensitivity skin to sun exposure.     

Topical application of green and white tea extracts provides protection from solar-simulated ultraviolet light in human skin

Background:  Tea polyphenols have been found to exert beneficial effects on the skin via their antioxidant properties.
Aims:  We sought to determine whether topical application of green tea or white tea extracts would prevent simulated solar radiation-induced oxidative damages to DNA and Langerhans cells that may lead to immune suppression and carcinogenesis.
Methods:  Skin samples were analysed from volunteers or skin explants treated with white tea or green tea after UV irradiation. In another group of patients, the in vivo immune protective effects of green and white tea were evaluated using contact hypersensitivity to dinitrochlorobenzene.
Results:  Topical application of green and white tea offered protection against detrimental effects of UV on cutaneous immunity. Such protection is not because of direct UV absorption or sunscreen effects as both products showed a sun protection factor of 1. There was no significant difference in the levels of protection afforded by the two agents. Hence, both green tea and white tea are potential photoprotective agents that may be used in conjunction with established methods of sun protection.     

1320nm激光对小鼠皮肤组织病理和生理特性的影响

目的:研究1320 nm激光对小鼠皮肤组织病理和部分皮肤生理指标的影响。方法:用该波长激光对小鼠背部皮肤照射,于照射前、照射后1 h3、d7、d、15 d、30 d取皮肤做病理,同时用MPA皮肤多功能测试系统测定其皮肤回声值、黑素含量、皮肤血红蛋白含量、经皮失水量、表皮含水量和皮脂含量。结果:激光照射后1 h,真皮纤维组织排列致密。照射后3 d,真皮炎症细胞和成纤维细胞增多。照射后15 d真皮层增厚、胶原增加。激光照射后短期内对于皮肤弹性、皮肤血红蛋白含量、经皮失水量、皮脂含量、表皮含水量,均有一定程度暂时性影响,对皮肤黑素含量无影响。结论:1320 nm激光可引起小鼠成纤维细胞增生和胶原蛋白合成增加,改善皮肤弹性,但在短期内对皮肤生理状态可产生一定的负面影响。     

Evaluation of dark circles of the lower eyelid: comparison between reflectance meters and image processing and involvement of dermal thickness in appearance

Background/aims: Dark circles of the lower eyelid (DCLE) represent a well-known beauty problem. The pathogenesis of DCLE is obscure, although stasis and hyperpigmentation of the eyelids have been considered to be involved. One reason for the small number of studies on DCLE may be the difficulty in measuring such soft and curved skin as the eyelids using bulky reflectance meters. The purpose of this study was to quantitatively analyze DCLE using various bioengineering methods.
Methods: The lower eyelid and cheek areas of 14 subjects with DCLE and 28 without DCLE were examined using two kinds of reflectance meters and image analysis to measure erythema index (EI), melanin index (MI), and oxygenation index (OX). Ultrasound echo images were also recorded to evaluate the thickness and echo density of the dermis. An in vitro model using collagen gel and hemoglobin solution was also examined as a phantom of eyelid skin.
Results: When contact-type reflectance meters were used, no significant differences in EI, MI, and OX were found between groups with and without DCLE. However, mean values of both MI and EI at eyelids were significantly higher in subjects with DCLE on image analysis, paralleling the results of inspection. Mean dermal thickness was significantly smaller in subjects with DCLE.
Conclusion: Evaluation of EI and MI by image processing methods seems suitable for quantitative evaluation of DCLE, since inadequate contact of the measuring head with the skin is avoided. Whether stasis or hyperpigmentation is more responsible for DCLE remains uncertain. Dermal thickness of eyelid skin may be involved in the appearance of DCLE.     

Acute exposure of human skin to ultraviolet or infrared radiation or heat stimuli increases mast cell numbers and tryptase expression in human skin in vivo

Background  Mast cells are key effector cells in diverse immunological and pathological processes. It is still unclear why there are more mast cells at peripheral and sun-exposed skin sites than at sun-protected sites.
Objectives  To investigate changes in mast cell numbers associated with natural ageing and photoageing, and to observe the effects of ultraviolet (UV) and infrared (IR) radiation and heat on the prevalence of mast cells and tryptase expression in human skin in vivo .
Methods  Sun-exposed and sun-protected skin samples were taken from individuals in four different age groups. UV, IR or heat-treated buttock skin of young volunteers was also obtained. Mast cells were quantified by immunohistochemical staining of mast cell-specific tryptase and chymase. The expression of tryptase was determined by Western blotting.
Results  Both sun-exposed and sun-protected skin showed a gradual decrease in total mast cells (MC_Total) number with ageing. The number of mast cells in sun-exposed skin was significantly higher than that in sun-protected skin. After UV irradiation (2 minimal erythema doses), MC_Total and mast cells expressing tryptase and chymase were significantly increased at 24 and 48 h postirradiation. After IR irradiation (3 minimal heating doses) and heat treatment (43 °C for 90 min), MC_Total reached peak induction at 8 and 48 h after stimulation, respectively. Tryptase expression was also clearly upregulated by UV, IR and heat.
Conclusions  Our data demonstrate that mast cell numbers decreased with ageing in human skin. Also, mast cells may be activated and recruited by UV, IR and heat. These findings should further our understanding of the reason for the high prevalence of mast cells at peripheral sun-exposed skin sites.     

Pretreatment with long-wave ultraviolet light inhibits ultraviolet-induced skin tumor development in hairless mice

The carcinogenic effects of long-wave ultraviolet radiation (UV-A) (320 to 400 nm) irradiation followed by exposure to broad-spectrum ultraviolet (UV) irradiation were studied in 200 lightly pigmented, hairless, hr/hr C3H/Tif mice. No skin tumors were observed in the group irradiated with UV-A for four weeks (total dose, 4050 kJ/m2, observed for 57 weeks). Ultraviolet exposure induced skin tumors in a dose-dependent manner. In a group exposed to UV irradiation for 13 weeks, 35% of the mice had developed tumors after 57 weeks. Twenty-six weeks of exposure resulted in 88% of the animals being affected. In contrast it was found that treatment with UV-A irradiation (four weeks, total dose up to 4200 kJ/m2) preceding exposure to UV irradiation (13 or 26 weeks) resulted in a significantly delayed tumor development. Exposure with UV-A induced no visible changes of the skin, and subsequent microscopic examination revealed no measurable changes in epidermal thickness or melanin content. Our results suggest that, depending on the exposure schedule, UV-A in addition to previously reported carcinogenic properties also may act as an antitumor agent.     

Imaging of melanin distribution using multiphoton autofluorescence decay curves

Background/purpose: Multiphoton fluorescence lifetime imaging (FLIM) is a technique that produces an image based on differences in the decay rate of fluorescence from a sample. Based on this method, the DermaInspect was developed to observe human skin components non-invasively. In this study, we used the DermaInspect to study melanin in skin.
Methods: A human three-dimensional skin model containing melanocytes was embedded in an OCT compound, frozen and sectioned at 10 μm. The melanin distribution in each section was visualized by the DermaInspect using time-resolved single-photon counting and near-infrared femtosecond laser pulse excitation. The melanin distribution of the same sections was then visualized using the Fontana-Masson staining method.
Results: High-resolution images were generated from the ratio of a ₁/ a ₂ ( a ₁e^{− t /120}+ a ₂e^{− t /1100} was chosen to express the exponential fluorescent decay curve) obtained using the DermaInspect. Granules with a high a ₁/ a ₂ ratio, approximately 1 μm in diameter, were observed. Fontana-Masson staining identified these granules as melanin. This new technique was then applied for in vivo observation of melanin in human skin. 'Melanin caps' were visualized in the basal cell layer around the nuclei in images derived from the a ₁/ a ₂ ratio.
Conclusion: Our study confirms that FLIM can non-invasively provide data of the melanin distribution with almost the same quality as the conventional Fontana-Masson staining method, and demonstrates that FLIM is useful for in vivo observation of melanin granules in human skin.     

Spectral responses of melanin to ultraviolet A irradiation

The purpose of this investigation was to study the ultraviolet A-induced effects on melanin pigmentation both in an in vitro model system and in vivo. Ultraviolet-Vis absorbance spectra of L-3,4-dihydroxyphenylalanine-melanin solutions at different concentrations were measured before and after ultraviolet A exposure (10-120 J per cm2). The difference spectra reveal that following ultraviolet A exposure the absorbance increases exponentially from 800 nm to 450 nm accompanied by a prominent decrease of absorbance in the ultraviolet A range. This change of spectral features depends on both ultraviolet A doses and melanin concentrations. The photo-bleaching effect observed in the ultraviolet A range also depends on oxygen. Human subjects were irradiated with ultraviolet A (40-80 J per cm2) on their back and diffuse reflectance spectra were collected at both irradiated and untreated sites. The absorption spectra of ultraviolet A-induced pigment were calculated as the difference of the two. The ultraviolet A-induced pigment in vivo has similar spectral characteristics and dose dependency as the in vitro system. Photo-oxidation of pheomelanin solutions presents distinctively different spectral and dose-response characteristics from eumelanin. After ultraviolet A irradiation pheomelanin absorbance decreases both in the visible and the ultraviolet A range. We conclude that irradiation with ultraviolet A induces significant photochemical alterations in the skin witnessed by increased photoprotection in the visible spectral range and reduced protection in the ultraviolet A range. We suggest that soluble melanin plays an important part in ultraviolet A-induced pigment in skin and two distinct absorption mechanisms of melanin may be involved in ultraviolet A photo-oxidation. We also propose that eumelanin and pheomelanin could be differentiated according to their spectral responses to ultraviolet A irradiation.     

Melanin differentially protects from the initiation and progression of threshold UV-induced erythema depending on UV waveband

BACKGROUND/PURPOSE: This study aimed to determine the relationship between various measures of constitutive skin pigmentation and erythema caused by solar-simulated UV (ssUV), 290 and 310 nm UV. METHODS: Skin pigmentation was assessed clinically by skin typing as well as objectively by measurement of the melanin index (MI) by reflectance spectroscopy. Subjects having Fitzpatrick skin types I-IV were exposed to graded doses of ssUV and either narrowband 310 nm (n=70) or 290 nm (n=69) UV, and assessed 24 h after exposure. Minimal erythema dose (MED) was assessed visually as the lowest dose that caused minimally perceptible erythema. Susceptibility to further development of erythema with higher exposure doses was measured by the gradient of erythema dose-response curves. This was determined by linear regression using reflectance spectrometry data beyond the MED. RESULTS: Although there was considerable variation within each skin type, MI and ssUV MED increased with increasing Fitzpatrick skin type. MI correlated with ssUV MED and 310 nm UV MED, but not 290 nm UV MED. There was also a significant negative correlation between MI and erythema dose-response gradients caused by ssUV, 310 and 290 nm UV. CONCLUSION: Melanin situated near the basal epidermis may not protect from the initial development of threshold erythema caused by 290 nm UV because it penetrates poorly past the stratum corneum and is not well absorbed by melanin in vivo compared with 310 nm UV. Higher erythemal 290 nm UV doses may reach basal epidermal melanin, which may then afford protection against further 290 nm UV erythema.     

Increased expression of TRPV1 channel in intrinsically aged and photoaged human skin in vivo

Abstract:  Transient receptor potential vanilloid type 1 (TRPV1) is activated by various stimuli including capsaicin, heat and acid. While TRPV1 has been localized in the epidermis, little is known about the physiological role of TRPV1 in the skin, especially in skin ageing. In this study, we investigated the effect of acute UV irradiation on TRPV1 expression in human skin and the changes in TRPV1 mRNA and protein in intrinsic ageing and photoageing using human sun-protected (upper inner arm) and sun-exposed (forearm) skin of young and elderly subjects.
Western blot analysis of UV-irradiated young buttock skin revealed that the expression of TRPV1 protein was increased at 24 h (2.3-fold) and 48 h (2.4-fold) after UV irradiation. Real-time PCR analysis also showed that the mRNA level of TRPV1 was augmented by 2.4-fold at 4 h after UV irradiation. TRPV1 protein was expressed at higher levels by 2.6-fold in the sun-protected skin of the elderly subjects than in that of young people according to western blotting, real-time PCR analysis and immunohistochemical staining. In addition, the photoaged skin of elderly showed increased expression of TRPV1 mRNA and protein compared with that of the sun-protected skin of the same individuals. Also, we found increased expression of TRPV1 in nerve fibres of elderly persons using double staining of TRPV1 and nerve fibres.
Based on the above results, our data suggest that the expression of TRPV1 is affected by both the intrinsic ageing and photoageing processes.