The relationship between habitual physical activity and skin mechanical properties.

BACKGROUND: Physical activity (PA) is important for body health. A few reports suggested that PA also influenced skin structure and components. Little data are available on the influence of PA on skin mechanical properties (SMP). Here, we investigated the relationship between PA and SMP. METHODS: Twenty-five healthy Japanese female subjects (31.0 ± 3.3 years) were enrolled in the study. To monitor the 24-hr pulse rate, a wrist watch-type pulse monitor was used. PA intensity was divided into five PA intensity zones (max, anaerobic, aerobic, fat combustion, and warm-up) by the pulse monitor. The average values of the time spent on each intensity for 70 days were calculated. To measure SMP, a Cutometer was used at the end of the monitoring. R0 indicated the height of the maximal skin deformation, and R6 was the ratio between viscoelastic and elastic deformation. RESULTS: R0 was positively correlated with the time spent in four of the five PA intensity zones (max, anaerobic, aerobic, and fat combustion), whereas R6 was negatively correlated with the time spent in these four PA intensity zones. The time of warm-up did not correlate with SMP. CONCLUSION: These results suggest that habitual moderate-to-vigorous PA influences SMP.

Gender- and age-related differences in facial sebaceous glands in Asian skin, as observed by non-invasive analysis using three-dimensional ultrasound microscopy.

BACKGROUND: While determining sebaceous gland morphology is useful in the treatment of skin disorders such as acne, a non-invasive assessment method has not been developed. Since age and gender affect sebum level, differences in sebaceous gland morphology according to these factors were investigated. METHODS: Facial skin was measured using a high-frequency three-dimensional ultrasound microscope. First, the ultrasound images were compared with skin sections. Next, we assessed sebaceous gland morphology. Images of sebaceous gland in the cheeks of young male, young female and elderly female subjects were obtained using ultrasound microscopy, and en face images were processed to measure the sebaceous gland area. RESULTS: In the ultrasound images, sebaceous glands and also thin collagen fibers, which surrounded the glands, could be detected as low-intensity regions. We called them sebaceous units. In young male subjects, the sebaceous unit areas 900-µm beneath the skin surface were larger than those at 700 µm. In contrast, depth-dependent differences in sebaceous unit area were not observed in young female subjects, indicating that males had cauliflower-shaped sebaceous glands while young females had somewhat more cylindrical and smaller sebaceous glands than the young males. Regarding age, the areas of sebaceous units at 900 µm were diminished and the depth of maximum area was shallower in elderly female subjects compared to young female subjects. Hence, sebaceous glands are considered to shrink with age. CONCLUSION: Differences in facial sebaceous unit morphology between genders as well as by age groups could be observed using high-frequency ultrasound microscopy.

In vivo evaluation of human skin anisotropy by polarization-sensitive optical coherence tomography.

We performed an in vivo three-dimensional analysis of anisotropic changes in the dermal birefringence of mechanically deformed human skin using polarization-sensitive optical coherence tomography (PS-OCT). The papillary-dermal birefringence of the forehead increased significantly when the skin was shrunk parallel to the body axis, and decreased significantly when the skin was shrunk perpendicular to the body axis. En-face images of the papillary-dermal birefringence revealed variations among individual subjects, and that both shrinking parallel to and stretching in perpendicular to the body axis promoted the formation of macro rope-like birefringent domains. We found that PS-OCT is useful for understanding anisotropic properties of collagen structure in the skin.

Hydrating effect of potassium lactate is caused by increasing the interaction between water molecules and the serine residue of the stratum corneum protein.

Natural moisturizing factors (NMFs) play an important role in maintaining the physical properties of the stratum corneum (SC). The relationship between SC water content and NMFs has long been investigated. Recently, we demonstrated that potassium lactate as an NMF increased SC water content more than sodium lactate did. The details of the moisturizing mechanism of NMFs, however, were not revealed. We, therefore, investigated the cause of the SC moisturizing effect of potassium lactate in comparison with sodium lactate. Using differential scanning calorimetry, we found that potassium lactate increased the bound water content of plantar SC more than what sodium lactate did. We also found, however, that the bound water content of the potassium lactate solution was less than that of the sodium lactate solution, suggesting that potassium lactate increased the water molecules interacting with SC components. Moreover, potassium lactate increased the ratio of hydrogen/deuterium exchange at 1340/cm, which represents the OH bending mode, of plantar SC spectra obtained by the attenuated total reflectance infrared spectroscopy. We assign this band to the OH group of the serine residue. These results suggest that potassium lactate increases the water-holding capacity of the SC by increasing interaction between water molecules and the OH group of serine in SC keratin.

In vivo measurement of the water content in the dermis by confocal Raman spectroscopy.

BACKGROUND/PURPOSE: Dermal water plays an important role in the physical properties of the skin. Recently, researchers have attempted to directly measure the dermal water content in vivo using magnetic resonance imaging, near infrared spectroscopy, and Raman spectroscopy. However, these methods have limitations. Although confocal Raman spectroscopy has been developed to measure the water content in the skin, no reports have suggested that this instrument can measure the dermal water content. This report describes a method for measuring the dermal water content in vivo using confocal Raman spectroscopy. METHODS: We used a confocal Raman spectrometer and adjusted the laser exposure time and depth increments according to the skin depth. Age-related changes in the dermal water content of the forearm were examined in 30 young and 30 elderly male subjects. Diurnal changes in the dermal water content of the forearm were examined in 12 elderly male subjects. RESULTS: Adjusting the exposure time and depth increment dramatically improved the signal-to-noise ratios of the Raman spectra. Elderly dermis had significantly higher water content than young dermis. Moreover, the dermal water content displayed a diurnal change. CONCLUSION: This study demonstrates that the dermal water content can be measured in vivo using confocal Raman spectroscopy.

Relationship between dermal birefringence and the skin surface roughness of photoaged human skin.

The dermal degeneration accompanying photoaging is considered to promote skin roughness features such as wrinkles. Our previous study demonstrated that polarization-sensitive spectral domain optical coherence tomography (PS-SD-OCT) enabled noninvasive three-dimensional evaluation of the dermal degeneration of photoaged skin as a change in dermal birefringence, mainly due to collagenous structures. Our purpose is to examine the relationship between dermal birefringence and elasticity and the skin morphology in the eye corner area using PS-SD-OCT. Nineteen healthy male subjects in their seventees were recruited as subjects. A transverse dermal birefringence map, automatically produced by the algorithm, did not show localized changes in the dermal birefringence in the part of the main horizontal wrinkle. The averaged upper dermal birefringence, however, showed depth-dependent correlation with the parameters of skin roughness significantly, suggesting that solar elastosis is a major factor for the progress of wrinkles. Age-dependent parameters of skin elasticity measured with Cutometer did not correlate with the parameters. These results suggest that the analysis of dermal birefringence using PS-SD-OCT enables the evaluation of photoaging-dependent upper dermal degeneration related to the change of skin roughness.

In vivo three-dimensional birefringence analysis shows collagen differences between young and old photo-aged human skin.

Polarization-sensitive optical coherence tomography (PS-OCT) permits non-invasive visualization of dermal birefringence, mainly due to collagenous structures. The purpose of this study is to use PS-OCT to assess intrinsic-age-related and photo-age-related differences in three-dimensional dermal birefringence. We measured dermal birefringence of the cheek skin and photo-protected interior upper arm skin from old and young volunteers. The algorithm that we used automatically produces the transversal dermal birefringence map from the polarization-sensitive OCT volume. This allowed quantitative comparison and visualization of the transverse distribution of the dermal birefringence. We found that dermal birefringence of the cheek skin was significantly smaller in the old group than in the young group (young group, 0.295+/-0.037 degrees microm(-1); old group, 0.207+/-0.03 degrees microm(-1); P=0.003), whereas the interior upper arm showed no age-dependent difference. The transversal map of the cheek showed a heterogeneous decrease in dermal birefringence due to photoaging. The maps suggested that the peripheral regions of some infundibula were surrounded by a strong collagen network. Three-dimensional analyses of dermal birefringence using PS-OCT help to quantify the diagnosis of photoaging.

Relationship between NMF (lactate and potassium) content and the physical properties of the stratum corneum in healthy subjects.

Natural moisturizing factor (NMF) of the stratum corneum (SC) has been established to play important roles in the physical properties of the SC. Few studies, however, have investigated the specific influences of NMF components other than the amino acids. In this study, therefore, we focus on the relationship between the ion content and physical properties of the SC in 40 healthy subjects. Changes in the physical properties of the SC induced by the extraction of NMF were equivalent to the changes that took place from summer to winter, demonstrating the important role of NMF in the physical properties of the SC in healthy subjects. The seasonal changes in the physical properties of the SC from summer to winter were accompanied by significant decreases in the levels of lactate, potassium, sodium, and chloride in the SC. Lactate and potassium were the only components found to correlate significantly with the state of hydration, stiffness, and pH in the SC. Interestingly, the levels of lactate and potassium in the SC were also significantly correlated. Moreover, potassium lactate restored the SC hydration state decreased by extraction of NMF. These results suggest that lactate and potassium may play roles in maintaining the physical properties of the SC in healthy subjects.