Skin autofluorescence as a biological UVR dosimeter

The association between conjunctival and scleral thickness and ocular surface ultraviolet autofluorescence

Ultraviolet autofluorescence (UVAF) imaging is used to visualise ocular surface changes due to sunlight exposure and so is considered to be a biomarker for UV damage. The conjunctival and scleral thicknesses of participants with and without ocular surface UVAF were measured to examine the UVAF associated tissue thicknesses. The presence of UVAF on the ocular surface was associated with significant differences in tissue thickness including thinner conjunctival epitheliums and thicker scleras but predominantly thickening of the conjunctival stroma. Participants were also classified into four groups according to the presence and absence of UVAF on both the temporal and nasal conjunctivas. It was noted that for those that had only nasal UVAF, the temporal conjunctival stroma was significantly thicker even without the presence of UVAF. Some participants with temporal UVAF had signs of pinguecula observed with slit lamp examination and some had OCT SLO enface imaging darkening. These findings highlight the potential of techniques other than slit lamp examination, including tissue thickness measurement and UVAF photography, in the detection of early UV-related changes to the ocular surface.

Which are the main fluorophores in skin and oral mucosa? A review with emphasis on clinical applications of tissue autofluorescence

OBJECTIVES

The present review provides information about which molecules appear to be the main fluorophores in skin and oral mucosa, together with their clinical applications.

DESIGN

The MEDLINE database was searched, using "oral mucosa AND fluorophores", "skin AND fluorophores", "epidermal AND fluorophores", "dermal AND fluorophores" and "cutaneous AND fluorophores" as entry terms. We searched the literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The level of evidence in the studies was assessed using the Classification of the Oxford Centre for Evidence-based Medicine (CEBM) Levels for Diagnosis.

RESULTS

Five papers and 17 were primarily focused on description of fluorophores in oral mucosa and skin Evidence exists that fluorophores of oral mucosa and skin are mainly proteins such as collagen, elastin, keratin and tryptophan. Other possible fluorophores identified are: porphyrins, advanced glycation end products, flavins, lipopigment, nicotinamide adenine dinucleotide, flavin adenine dinucleotide, pheomelanin, eumelanin and components of lipofuscin. Clinical applications of oral mucosal autofluorescence (AF) are related to management of malignant and potentially malignant lesions. In the skin, AF has been used for acne assessment, diagnosis of sweat-gland pathologies, glycemic control and management of malignant lesions and as a marker for skin aging.

CONCLUSION

Fluorophores stimulated through AF devices are implied in different physiologic and pathologic processes. AF seems to be useful for several clinical applications, especially in skin department. Because most of the studies show a low level of evidence, further studies are necessary in such a promising and fascinating field.

Characterization of human cutaneous tissue autofluorescence: implications in topical drug delivery studies with fluorescence microscopy

In pharmacokinetic studies of topical drugs, fluorescence microscopy methods can enable the direct visualization and quantification of fluorescent drugs within the skin. One potential limitation of this approach, however, is the strong endogenous fluorescence of skin tissues that makes straightforward identification of specific drug molecules challenging. To study this effect and quantify endogenous skin fluorescence in the context of topical pharmacokinetics, an integrating sphere-based screening tool was designed to collect fluorescence yield data from human skin specimens. Such information could be utilized to select specific donors in the investigation of drug uptake and distribution. Results indicated human facial skin specimens from a group of more than 35 individuals exhibited an at least 6-fold difference in endogenous fluorescence. In visualizing drug distributions, the negative impact of autofluorescence could be exacerbated in cases where there are overlapping spatial distributions or spectral emission profiles between endogenous fluorophores and the exogenous fluorophore of interest. We demonstrated the feasibility of this approach in measuring the range of tissue endogenous fluorescence and selecting specimens for the study of drug pharmacokinetics with fluorescence microscopy.

Organ transplant recipients express enhanced skin autofluorescence and pigmentation at skin cancer sites

BACKGROUND

Skin autofluorescence and pigmentation can estimate photodamage and sun exposure. These techniques may quantify differences in actinic damage between high-risk organ transplant recipients (OTRs) and immunocompetent patients.

METHODS

Age and gender-matched OTRs (n = 15) and immunocompetent controls (n = 15) with a new keratinocyte carcinoma (KC) were included. We measured skin autofluorescence (370 nm excitation, F370) and skin pigmentation at five standardized body sites; and determined black light-evaluated solar lentigines on the shoulders and photosensitivity to UVA and simulated solar radiation (SSR) as minimal erythema doses (MED).

RESULTS

F370 autofluorescence values were enhanced at KC site versus other body sites in OTRs (2208 vs. 1458-1898 AU, p < 0.05). Compared with non-OTRs, OTRs expressed higher F370 autofluorescence at KC site (2208 vs. 1385 arbitrary units AU, p = 0.01) and the shoulder (1898 vs. 1525, p = 0.05). Likewise, OTRs had increased skin pigmentation (25.0 vs. 20.8 pigment%, p = 0.05) and solar lentigines (3.5 vs. 3.0, p = 0.048) on the shoulders. MED tests showed increased UVA photosensitivity in OTRs (2.4 vs. 1.7 times higher than expected, p = 0.03), whereas SSR photosensitivity was similar.

CONCLUSION

Quantified F370 autofluorescence, skin pigmentation, and density of solar lentigines could serve to assess photodamage in OTR. Increased UVA photosensitivity may account for higher skin photodamage.

Conjunctival ultraviolet autofluorescence area, but not intensity, is associated with myopia

BACKGROUND

Conjunctival ultraviolet autofluorescence (CUVAF) has been used as a biomarker of time spent outdoors. Smaller CUVAF area is associated with myopia in southern hemisphere cohorts. Further research is required to determine if this association is replicated in northern latitudes and whether average CUVAF intensity is a valuable metric. This prospective study explored the association between myopia, CUVAF (area and intensity) and additional indicators of sun exposure (vitamin D₃ and self-reported sun exposure preferences) across seasons at a location of 55° north.

METHODS

Young adults (age 18-20) provided blood samples biannually (March/April and September/October) over an 18-month period (four phases) for the assessment of 25-hydroxyvitamin D (25(OH)D₃ ) concentrations (liquid chromatography-tandem mass spectrometry). CUVAF (total area, average intensity) and self-reported sun exposure preferences were recorded at each phase. Axial length and corneal radius were measured. Refractive error was measured by autorefractor and spherical equivalent refraction used to classify participants into refractive groups: myopic (spherical equivalent refraction ≤ -0.50 DS) or non-myopic.

RESULTS

Fifty-four participants (24 myopes, 30 non-myopes) participated. CUVAF area was negatively associated with the presence of myopia (odds ratio = 0.94, 95 per cent confidence interval = 0.90-0.98, p = 0.002). Myopes = 4.5 mm² (interquartile range [IQR] 0.95-6.4 mm² ), non-myopes = 7.0 mm² (IQR = 2.0-10.7 mm² ). No significant association was found between CUVAF intensity and refractive group (p = 0.17). There was no significant association between sun exposure preferences or serum concentration of 25(OH)D₃ and refractive status (all p ≥ 0.21). CUVAF measures were not associated with ocular biometry measures (all p ≥ 0.084). CUVAF area was unaffected by season (all p ≥ 0.45) and variations in CUVAF area over the study period did not exceed the repeatability of the measurement technique.

CONCLUSION

Myopia was associated with smaller areas of CUVAF indicative of less cumulative ultraviolet-B exposure. These findings suggest that CUVAF measures are a useful, non-invasive biomarker of the time spent outdoors in adults in northern hemisphere populations.

Skin cancer detection using non-invasive techniques

Skin cancer is the most common form of cancer and is globally rising. Historically, the diagnosis of skin cancers has depended on various conventional techniques which are of an invasive manner. A variety of commercial diagnostic tools and auxiliary techniques are available to detect skin cancer. This article explains in detail the principles and approaches involved for non-invasive skin cancer diagnostic methods such as photography, dermoscopy, sonography, confocal microscopy, Raman spectroscopy, fluorescence spectroscopy, terahertz spectroscopy, optical coherence tomography, the multispectral imaging technique, thermography, electrical bio-impedance, tape stripping and computer-aided analysis. The characteristics of an ideal screening test are outlined, and the authors pose several points for clinicians and scientists to consider in the evaluation of current and future studies of skin cancer detection and diagnosis. This comprehensive review critically analyses the literature associated with the field and summarises the recent updates along with their merits and demerits.

Skin autofluorescence reflects individual seasonal UV exposure, skin photodamage and skin cancer development in organ transplant recipients

IMPORTANCE

Ultraviolet radiation (UVR)-induced skin cancers varies among organ transplant recipients (OTRs). To improve individual risk assessment of skin cancer, objectively quantified skin photodamage is needed.

OBJECTIVES

We measured personal UVR-exposure dose in OTRs and assessed the relation between individual UVR exposure, skin cancer and objectively measured photodamage in terms of skin autofluorescence, pigmentation, and black light-evaluated solar lentigines.

MATERIALS AND METHODS

Danish OTRs with (n=15) and without a history of skin cancer (n=15) kept sun diaries from May to September and wore personal dosimeters recording time-stamped UVR doses in standard erythema doses (SED). Photodamage was quantified as skin autofluorescence with excitation at 370nm (F370) and 430nm (F430), skin pigmentation (pigment protection factor, PPF), and black light-evaluated solar lentigines.

RESULTS

OTRs with skin cancer received a higher UVR dose than OTRs without skin cancer (median 116 SED vs. 67 SED, p=0.07) and UVR exposure doses were correlated with increased PPF (p=0.052) and F370 on the shoulder (F370_shoulder) (p=0.04). We found that skin cancer was associated with F370_shoulder (OR 10.53, CI 3.3-31,938; p=0.018) and time since transplantation (OR 1.34, CI 0.95-1.91, p=0.097). A cut-off at 7.2 arbitrary units, 89% of OTRs with skin cancer had F370_shoulder values above 7.2 arbitrary units and F370_shoulder was additionally related to patient age (p=0.09) and black light-evaluated solar lentigines (p=0.04).

CONCLUSION

F370 autofluorescence indicates objectively measured photodamage and may be used for individual risk assessment of skin cancer development in OTRs.

The use of conjunctival ultraviolet autofluorescence (CUVAF) as a biomarker of time spent outdoors

PURPOSE

Conjunctival ultraviolet autofluorescence (CUVAF) has been used in previous Southern Hemisphere myopia research as a marker for time spent outdoors. The validity of CUVAF as an indicator of time spent outdoors is yet to be explored in the Northern Hemisphere. It is unclear if CUVAF represents damage attributed to UV exposure or dry eye. This cross-sectional study investigated the association between CUVAF measures, self-reported time spent outdoors and measures of dry eye.

METHODS

Participants were recruited from University staff and students (n = 50, 19-64 years; mean 41). None were using topical ocular medications (with the exception of dry eye treatments). Sun exposure and dry eye questionnaires (Ocular Surface Disease Index and McMonnies) were completed by the participant. Dryness was also assessed using slit lamp biomicroscopy and invasive tear break up time. Images of the temporal and nasal conjunctiva from the right and left eye were captured using a bespoke photography system. The total CUVAF area, average CUVAF pixel intensity per mm(2) and total CUVAF pixel intensity were analysed using MATLAB R2013a (The MathWorks Inc).

RESULTS

Of the 50 participants, 42% were classified as having dry eye. Self-reported sunglasses use was negatively associated with all CUVAF measures (Kruskal Wallis total CUVAF area, p = 0.04, ptrend  = 0.03, average CUVAF pixel intensity p = 0.02, ptrend  = 0.02, total CUVAF pixel intensity: p = 0.04, ptrend  = 0.02). Time spent outdoors was positively associated with all CUVAF measures (Spearman's correlation coefficients, total CUVAF area: r = 0.37, p = 0.01, average CUVAF pixel intensity: r = 0.36, p = 0.01, total CUVAF pixel intensity: r = 0.37, p = 0.01) and remained significant when sunglasses use was controlled for (partial correlation, total CUVAF area: r = 0.32, p = 0.03, average CUVAF pixel intensity: r = 0.39, p = 0.01, total CUVAF pixel intensity: r = 0.39, p = 0.03). Neither CUVAF area nor intensity measures were associated with any dry eye measure (Ocular Surface Disease Index: all p ≥ 0.41, corneal staining: all p ≥ 0.38, McMonnies: all r ≤ 0.09 all p ≥ 0.52, slit lamp biomicroscopy: all r ≤ 0.20 all p ≥ 0.17, invasive tear break up time: all r ≤ -0.07 all p ≥ 0.31).

CONCLUSIONS

CUVAF area and intensity were not associated with clinical measures of dry eye. Greater CUVAF area and intensity were associated with wearing sunglasses less frequently and spending more time outdoors. If sunglass wear is accounted for, CUVAF may be a useful biomarker of time spent outdoors in future myopia studies.

Pilot study on the correlation between skin auto-fluorescence and serum antioxidant enzyme: skin auto-fluorescence is negatively associated with levels of malondialdehyde

BACKGROUND/PURPOSE

Various methods have been used to objectively record skin changes. However, estimating the intrinsic and extrinsic aging of skin remains a challenge. Our objective was to study intrinsic skin aging with respect to patient age and extrinsic photo-aging of human dorsal (photo-exposed) and volar (photo-protected) forearm in vivo through skin auto-fluorescence (AF). We also examined the correlations between serum antioxidant enzyme, malondialdehyde(MDA), and skin AF.

METHODS

37 healthy volunteers were enrolled. We measured skin AF and its heterogeneity on the dorsal and volar forearms. We also examined serum concentration of catalase, superoxide dismutase, vitamin E, and MDA levels in every participant.

RESULTS

In photo-protected areas, skin AF intensity in the 40 years or older group was significantly higher compared to the group less than 40 years-old. On the other hand, heterogeneity value was significantly higher in the less than 40 years-old group in photo-protected area. With respect to serum antioxidant enzyme and MDA level, only MDA level showed a negative correlation with skin AF intensity in photo-exposed area.

CONCLUSION

We determined that skin AF intensity of the photo-protected area reflects intrinsic skin aging. In addition, degree of photo-aging could be indirectly inferred by skin AF of photo-exposed area and serum MDA level.

Iridoids are natural glycation inhibitors

Glycation of amino acid residues in proteins leads to the eventual formation of advanced glycation end products (AGEs). AGE formation significantly influences human health and the aging process. AGE accumulation rates may be slowed by modifications to lifestyle or by pharmacological strategies. But the use of therapeutic drugs is not an appropriate means of controlling AGEs within the general population. However, phytochemical constituents in plant-based foods exhibit anti-glycation activities and may be more appropriate for general consumption. Among these phytochemicals are iridoids. The anti-AGE potential of iridoids has been demonstrated in vitro and in vivo, while also revealing possible mechanisms of action. Inclusion of iridoid food sources in the diet may be a useful component of strategies intended to mitigate AGE accumulation within the body.

A new gender-specific model for skin autofluorescence risk stratification

Advanced glycation endproducts (AGEs) are believed to play a significant role in the pathophysiology of a variety of diseases including diabetes and cardiovascular diseases. Non-invasive skin autofluorescence (SAF) measurement serves as a proxy for tissue accumulation of AGEs. We assessed reference SAF and skin reflectance (SR) values in a Saudi population (n = 1,999) and evaluated the existing risk stratification scale. The mean SAF of the study cohort was 2.06 (SD = 0.57) arbitrary units (AU), which is considerably higher than the values reported for other populations. We show a previously unreported and significant difference in SAF values between men and women, with median (range) values of 1.77 AU (0.79-4.84 AU) and 2.20 AU (0.75-4.59 AU) respectively (p-value « 0.01). Age, presence of diabetes and BMI were the most influential variables in determining SAF values in men, whilst in female participants, SR was also highly correlated with SAF. Diabetes, hypertension and obesity all showed strong association with SAF, particularly when gender differences were taken into account. We propose an adjusted, gender-specific disease risk stratification scheme for Middle Eastern populations. SAF is a potentially valuable clinical screening tool for cardiovascular risk assessment but risk scores should take gender and ethnicity into consideration for accurate diagnosis.

Antiglycation Activity of Iridoids and Their Food Sources

Iridoids are dietary phytochemicals that may have the ability to inhibit the formation of advanced glycation end products (AGEs). Three studies were conducted to investigate this anti-AGE potential. First, the inhibition of fluorescence intensity by food-derived iridoids, after 4 days of incubation with bovine serum albumin, glucose, and fructose, was used to evaluate in vitro antiglycation activity. Next, an 8-week open-label pilot study used the AGE Reader to measure changes in the skin autofluorescence of 34 overweight adults who consumed daily a beverage containing food sources of iridoids. Finally, a cross-sectional population study with 3913 people analyzed the relationship between daily iridoid intake and AGE accumulation, as measured by skin autofluorescence with the TruAge scanner. In the in vitro test, deacetylasperulosidic acid and loganic acid both inhibited glycation in a concentration-dependent manner, with respective IC₅₀ values of 3.55 and 2.69 mM. In the pilot study, average skin autofluorescence measurements decreased by 0.12 units (P < 0.05). The cross-sectional population survey revealed that, for every mg of iridoids consumed, there is a corresponding decline in AGE associated age of 0.017 years (P < 0.0001). These results suggest that consumption of dietary sources of iridoids may be a useful antiaging strategy.

A novel approach for the detection of early gastric cancer: fluorescence spectroscopy of gastric juice

OBJECTIVE

This study aimed to investigate the efficacy of fluorescence spectroscopy of gastric juice for early gastric cancer (EGC) screening.

METHODS

Gastric juice was collected from 101 participants who underwent endoscopy in the Outpatient Endoscopy Center of Peking University Third Hospital. The participants were divided into three groups: the normal mucosa or chronic non-atrophic gastritis (NM-CNAG) group (n = 35), advanced gastric cancer (AGC) group (n = 33) and EGC group (n = 33). Fluorescence spectroscopic analysis was performed in all the gastric juice samples and the maximum fluorescence intensity of the first peak (P1 FI) was measured.

RESULTS

The mean fluorescence intensity of P1 FI of gastric juice in AGC (92.1 ± 10.7) and EGC (90.8 ± 12.0) groups was significantly higher than that in the NM-CNAG group (55.7 ± 7.5) (AGC vs NM-CNAG, P = 0.006 and EGC vs NM-CNAG, P = 0.015, respectively). The areas under the receiver operating characteristic curves for the detection of AGC and EGC were 0.681 (95% confidence interval [CI] 0.553-0.810, P = 0.010) and 0.655 (95% CI 0.522-0.787, P = 0.028). With the P1 FI of ≥47.7, the sensitivity, specificity and accuracy for detecting EGC were 69.7%, 57.1% and 63.2%, respectively.

CONCLUSIONS

The enhancement of P1 FI of gastric juice occurs at the early stage of gastric cancer. Fluorescence spectroscopy of gastric juice may be used as a novel screening tool for the early detection of gastric cancer.

Multimodal fundus imaging in choroidal osteoma

PURPOSE

To describe the morphologic features of calcified and decalcified choroidal osteomas using multimodal imaging and correlate these findings with a previous histopathologic study.

DESIGN

Retrospective observational case series.

METHODS

Three patients with choroidal osteoma underwent complete ophthalmologic examination, fundus photography, and multimodal fundus imaging, including Fourier-domain optical coherence tomography (FD-OCT) and blue-light fundus autofluorescence (bAF).

RESULTS

FD-OCT imaging of calcified tumors revealed a distinctive latticework pattern of reflectivity resembling the spongy bone structure seen histopathologically. On bAF the fluorescence was relatively well preserved overlying calcified tumors. In decalcified areas 2 patterns of reflectivity were identified: the first consisted of areas of relative hyperreflectivity with a lamellar appearance while the second was characterized by heterogeneous, hyperreflective, mound-like irregular areas associated with some posterior optical shadowing. Decalcified tumor areas had reduced overall fluorescence on bAF.

CONCLUSION

FD-OCT demonstrated different reflectivity patterns in both calcified and decalcified portions of the choroidal osteoma, which may correspond to different stages of tumor evolution. A distinctive latticework pattern of reflectivity similar to spongy bone was seen in calcified tumors. These observations improve our knowledge of the in vivo structure of choroidal osteomas and may have implications for the diagnosis and management of this tumor.

Two fluorescent wavelengths, 440(ex)/520(em) nm and 370(ex)/440(em) nm, reflect advanced glycation and oxidation end products in human skin without diabetes

BACKGROUND

Advanced glycation end products (AGEs) and oxidation products (OPs) play an important role in diabetes complications, aging, and damage from sun exposure. Measurement of skin autofluorescence (SAF) has been promoted as a noninvasive technique to measure skin AGEs, but the actual products quantified are uncertain. We have compared specific SAF measurements with analytically determined AGEs and oxidative biomarkers in skin collagen and determined if these measurements can be correlated with chronological aging and actinic exposure.

METHODS

SAF at four excitation (ex)/emission (em) intensities was measured on the upper inner arm ("sun protected") and dorsal forearm ("sun exposed") in 40 subjects without diabetes 20-60 years old. Skin collagen from the same sites was analyzed by liquid chromatography-tandem mass spectrometry for three AGEs-pentosidine, carboxymethyllysine (CML), and carboxyethyllysine (CEL)-and the OP methionine sulfoxide (MetSO).

RESULTS

There was poor correlation of AGE-associated fluorescence spectra with AGEs and OP in collagen, with only pentosidine correlating with fluorescence at 370(ex)/440(em) nm. A little-studied SAF (440(ex)/520(em) nm), possibly reflecting elastin cross-links, correlated with all AGEs and OPs. Levels of CML, pentosidine, and MetSO, but not SAF, were significantly higher in sun-exposed skin. These AGEs and OPs, as well as SAF at 370(ex)/440(em) nm and 440(ex)/520(em) nm, increased with chronological aging.

CONCLUSIONS

SAF measurements at 370(ex)/440(em) nm and 335(ex)/385(em) nm, except for pentosidine, which correlated with fluorescence at 370(ex)/440(em), correlate poorly with glycated and oxidatively modified protein in human skin and do not reflect actinic modification. A new fluorescence measurement (440(ex)/520(em) nm) appears to reflect AGEs and OPs in skin.

Fluorescence spectroscopy as a tool to detect and evaluate glucocorticoid-induced skin atrophy

Topical glucocorticoid (GC) therapy has been successfully used in the treatment of several common cutaneous diseases in clinical practice for a long time, and skin atrophy is one of the most typical cutaneous side effects of this therapy. The aim of this study was to evaluate the potential of noninvasive fluorescence spectroscopy (FS) technique in the detection and classification of GC-induced skin atrophy. A total of 20 male Wistar rats were used in the experimental protocol under controlled environmental conditions and with free access to food. One group received topical application of clobetasol propionate 0.05% for 14 days to induce cutaneous atrophy (atrophic group) and the other (control) group received only vehicle application following the same protocol and schedule. Histological analyses and FS measurements with laser excitation at both 532 nm and 408 nm were obtained on days 1 and 15. The FS results were classified as "normal" or "atrophic" according by histological analysis. Fluorescence spectra obtained with excitation at 408 nm allowed a clear distinction between the control and atrophic groups, and were more informative than the those obtained at 532 nm. Our results reveal that, if correctly applied, FS allows noninvasive evaluation of corticosteroid-induced skin atrophy, and thus represents an important step towards better monitoring of undesirable side effects of cutaneous therapy.

The minimal melanogenesis dose/minimal erythema dose ratio declines with increasing skin pigmentation using solar simulator and narrowband ultraviolet B exposure

PURPOSE

To investigate the relation between pre-exposure skin pigmentation and the minimal melanogenesis dose (MMD)/minimal erythema dose (MED) ratio after a single narrowband ultraviolet B (nUVB) and solar simulator (Solar) exposure.

BACKGROUND

In fair-skinned individuals, it is well known that the UV dose to give pigmentation (MMD) after a single exposure to UVB is larger than the UV dose to elicit erythema (MED) (MED<MMD), but it remains to be established if this is true also in dark-skinned individuals.

METHODS

Eighty-four volunteers with a wide variation in skin pigmentation (Fitzpatrick skin types I-V) were included.

RESULTS

After a single Solar or nUVB exposure we found that the ratio MMD/MED depends on skin pigmentation. In light-pigmented individuals, up to 1.9 MED is required to induce pigmentation (MMD). The MMD/MED ratio is about 1.5 in medium-pigmented and dark-pigmented individuals. In very brown-pigmented individuals the MMD/MED ratio is 1 (MED=MMD). This connection was most pronounced for facultative skin at wintertime. The ratio was almost stable for constitutive pigmentation with MMD/MED=1.3. The ratios were almost independent of skin type.

CONCLUSION

The ratio MMD/MED is highly dependent on skin pigmentation after a single exposure to Solar or nUVB and is independent of skin type.

Lifestyle factors and visible skin aging in a population of Japanese elders

Background

The number of studies that use objective and quantitative methods to evaluate facial skin aging in elderly people is extremely limited, especially in Japan. Therefore, in this cross-sectional study we attempted to characterize the condition of facial skin (hyperpigmentation, pores, texture, and wrinkling) in Japanese adults aged 65 years or older by using objective and quantitative imaging methods. In addition, we aimed to identify lifestyle factors significantly associated with these visible signs of aging.

Methods

The study subjects were 802 community-dwelling Japanese men and women aged at least 65 years and living in the town of Kurabuchi (Takasaki City, Gunma Prefecture, Japan), a mountain community with a population of approximately 4800. The facial skin condition of subjects was assessed quantitatively using a standardized facial imaging system and subsequent computer image analysis. Lifestyle information was collected using a structured questionnaire. The association between skin condition and lifestyle factors was examined using multivariable regression analysis.

Results

Among women, the mean values for facial texture, hyperpigmentation, and pores were generally lower than those among age-matched men. There was no significant difference between sexes in the severity of facial wrinkling. Older age was associated with worse skin condition among women only. After adjusting for age, smoking status and topical sun protection were significantly associated with skin condition among both men and women.

Conclusions

Our study revealed significant differences between sexes in the severity of hyperpigmentation, texture, and pores, but not wrinkling. Smoking status and topical sun protection were significantly associated with signs of visible skin aging in this study population.

Skin autofluorescence for the risk assessment of chronic complications in diabetes: a broad excitation range is sufficient

Skin autofluorescence (AF) is becoming an accepted clinical method for assessing the risk of chronic complications in diabetes mellitus (DM). In this study, the role of the excitation wavelength in the recognition of increased risk of diabetes-related chronic complications was investigated. An Excitation Emission Matrix Scanner (EEMS) was used to perform noninvasive measurements in four age-matched groups of patients with type 1 and type 2 DM, with and without chronic complications, as well as in a control group (N=97 in total). AF was calculated for excitation wavelengths in the range 355 - 405 nm. Mean spectra were assessed per group. AF values in both type 1 and type 2 DM patients with complications were increased compared to the control subjects (p < 0:01); this ratio remained practically constant, independent of the excitation wavelength. No emission peaks were distinctive for specific patient groups. We conclude that in these groups, no characteristic fluorophores dictate the use of a specific wavelength or set of wavelengths. The results show the validity of applying a broad excitation wavelength range for risk assessment of chronic complications in diabetes.

New device for real-time bioluminescence imaging in moving rodents

Bioluminescence imaging (BLI) allows detection of biological functions in genetically modified cells, bacteria, or animals expressing a luciferase (i.e., firefly, Renilla, or aequorin). Given the high sensitivity and minimal toxicity of BLI, in vivo studies on molecular events can be performed noninvasively in living rodents. To date, detection of bioluminescence in living animals has required long exposure times that are incompatible with studies on dynamic signaling pathways or nonanaesthetised freely moving animals. Here we develop an imaging system that allows: 1. bioluminescence to be recorded at a rate of 25 images/s using a third generation intensified charge-coupled device (CCD) camera running in a photon counting mode, and 2. coregistration of a video image from a second CCD camera under infrared lighting. The sensitivity of this instrument permits studies with subsecond temporal resolution in nonanaesthetized and unrestrained mice expressing firefly luciferase and imaging of calcium signaling in transgenic mice expressing green fluorescent protein (GFP) aequorin. This imaging system enables studies on signal transduction, tumor growth, gene expression, or infectious processes in nonanaesthetized and freely moving animals.

Ultraviolet fluorescence photography: patterns in established pterygia

PURPOSE

To investigate established pterygia using our newly developed ultraviolet fluorescence photography (UVFP) system.

DESIGN

Prospective observational case series.

METHODS

setting: Prince of Wales Hospital, Sydney, Australia. study population: Fourteen patients (both eyes) attending the Ophthalmology Clinic at Prince of Wales Hospital for assessment of their established pterygia. There were eight men and six women, with an age range of 26 to 62 years. A total of 15 (75%) of 20 had primary pterygia, and five (25%) of 20 had recurrent pterygia. There were no specific exclusion criteria. observation procedures: Ultraviolet and standard (control) photographs were taken of the nasal and temporal interpalpebral regions bilaterally. main outcome measures: The presence of established pterygia detected by standard photography and the corresponding presence and patterns of areas of fluorescence detected by UVFP.

RESULTS

In the 14 patients, 20 established pterygia were identified on standard photography. On UVFP, four patterns of fluorescence of established pterygia were identified. Of the 20 pterygia, six (30%) of 20 demonstrated fluorescence at the leading edge of the pterygium, seven (35%) of 20 demonstrated fluorescence at the limbus, three (15%) of 20 demonstrated fluorescence at both the leading edge and the limbus, and four (20%) of 20 demonstrated no visible fluorescence.

CONCLUSIONS

In this study, we describe patterns of fluorescence in established pterygia by UVFP. We hypothesize that the areas of fluorescence represent areas of cellular activity within the pterygium. The patterns of fluorescence may be useful to further understand of pterygium growth and pathogenesis.

Steady-state directional diffuse reflectance and fluorescence of human skin

We present numerical simulations predicting the directional diffuse reflectance and autofluorescence from human skin. Skin is modeled as a seven-layered medium, with each layer having its own optical properties and fluorophore concentrations. Both collimated and diffuse monochromatic excitation at 442 nm are considered. In addition, the effect of an index-matching cream used to eliminate total internal reflection within the skin is assessed. We compute the intensity distributions of the excitation and fluorescence light in the skin by solving the radiative transfer equation using the modified method of characteristics. It was found that the use of an index-matching cream reduces the directional fluorescence signal while increasing the directional diffuse reflectance from the skin for collimated excitation. On the other hand, both the fluorescence and diffuse reflectance increase for diffuse excitation with an index-matching cream. Moreover, the directional fluorescence intensity obtained by use of collimated excitation is larger than that obtained by use of diffuse excitation light. This computational tool could be valuable in designing optical devices for biomedical applications.

Youth solar ultraviolet radiation exposure, concurrent activities and sun-protective practices: a review

To assist standardization of procedures, facilitate comparisons, and help guide research efforts to optimally inform development of appropriately targeted interventions, there is a need to review methods used to quantify child and adolescent solar ultraviolet radiation (UV) exposure, related outdoor activities and sun-protective practices. This holistic approach is essential for comprehensive research that will provide all-inclusive, informative and meaningful messages for preventive measures of harmful UV exposure. Two databases were searched and 29 studies were retrieved, and these studies report measurement or assessment techniques documenting UV exposure patterns and related outdoor activities. Polysulfone film badges were the main measurement instrument used in 10 studies, with questionnaire, survey data, observation, a model, electronic dosimeters, biological dosimeters, colorimeter and UV colouring labels used in the remaining studies. Methods used to record activities included self-report, parental report, a logbook and observation. Measurement duration and unit of UV exposure varied in most studies, but a method common to 15 studies was measured UV exposure as a percentage of ambient UV. The studies reviewed do not provide sufficient information for the development and evaluation of targeted youth sun protection programs. Studies are required which document precise UV exposure, concurrent activities and sun protection usage for children and adolescents.

Facial skin fluorescence as a marker of the skin's response to chronic environmental insults and its dependence on age

BACKGROUND

Throughout life facial skin is exposed to a variety of adverse environmental conditions and is constantly required to repair itself. The rate of epidermal cell proliferation is indicative of the skin's repair rate and can be monitored noninvasively in vivo using skin intrinsic fluorescence markers.

OBJECTIVES

The goal of the present study was to assess the effects of ageing, geographical region, ethnic origin and season on the ability of facial skin to repair itself in the presence of chronic environmental insults using in vivo fluorescence spectroscopy.

METHODS

Skin fluorescence emission was measured on the cheeks of 522 individuals in winter and repeated in summer in five different geographical locations in the Asia-Pacific region. Fluorescence emission was also measured from 80 caucasians of fair complexion in the United States (New Jersey area) on the face and on a relatively protected area (upper inner arm). The age range of the participants was 14-75 years.

RESULTS

We found that epidermal proliferation rates decrease monotonically with age, while the fluorescence of collagen and elastin cross-links increases with age indicating accumulation of advanced glycation end-products. These trends were independent of geographical region, ethnic origin and season of measurement. Epidermal proliferation rates of facial skin were higher than those of unexposed sites; they may be 10 times higher in younger (second decade) than in older (seventh decade) individuals, and they decrease with age at rates 10 times faster compared with those of unexposed sites.

CONCLUSIONS

This is the first time that epidermal proliferation and its dependence on ageing have been measured noninvasively on the human face. The higher tryptophan fluorescence values on the face vs. the protected site are indicative of accelerated rates of epidermal proliferation in the presence of chronic environmental insults. The repair potential of facial skin, i.e. its ability to maintain high proliferation rates, is maximal in younger populations and gradually decreases with age.

Ultraviolet fluorescence photography to detect early sun damage in the eyes of school-aged children

PURPOSE

To develop a method to detect precursors of ocular sun damage using ultraviolet fluorescence photography (UVFP).

DESIGN

Observational cross-sectional study

METHODS

settings: Preschool, primary, and high school in Sydney, Australia. study population: 71 children ages 3 to 15 years old (both eyes). Inclusion criteria were children attending the schools who gave consent. There were no exclusion criteria. observation procedures: UV and standard (control) photographs were taken of the nasal and temporal interpalpebral regions bilaterally. main outcome measures: Presence of areas of increased fluorescence detected by UVFP, or presence of pinguecula detected by standard photography.

RESULTS

Established pingueculae, on standard photography, were seen in seven of 71 (10%) children; all were 13 years of age or older. On UVFP, all of these pingueculae demonstrated fluorescence. In total, 23 of 71 (32%) had increased fluorescence detected on UVFP, including the seven of 23 (30%) with pingueculae. Of the remaining 16 of 23 (70%), the changes were only detectable using UVFP. Fluorescence on UVFP was seen in children ages 9 years and above, with prevalence increasing with age. The presence of fluorescence (in at least one region) was 0 of 15 (0%) for children ages 3 to 5 years, 0 of 12 (0%) of children ages 6 to 8 years, 6 of 23 (26%) for those ages 9 to 11 years, and 17 of 21 (81%) of those ages 12 to 15 years.

CONCLUSIONS

We hypothesize that the areas seen to fluoresce on UVFP but not detectable on control photography represent precursors for ophthalmohelioses. Our preliminary data strongly suggests that UVFP is a sensitive method for detecting early ocular sun damage occurring many years before clinical manifestations.