Elastotic degenerative change and yellowish discolouration in photoaged skin

Age-related changes in cheek skin movement: A case study of Japanese women

BACKGROUND

The majority of conventional studies on skin aging have focused on static conditions. However, in daily life, the facial skin we encounter is constantly in motion due to conversational expressions and changes in facial expressions, causing the skin to alter its position and shape, resulting in a dynamic state. Consequently, it is hypothesized that characteristics of aging not apparent in static conditions may be present in the dynamic state of the skin. Therefore, this study investigates age-related changes in dynamic skin characteristics associated with facial expression alterations.

METHODS

A motion capture system measured the dynamic characteristics (delay and stretchiness of skin movement associated with expression) of the cheek skin in response to facial expressions among 86 Japanese women aged between 20 and 69 years.

RESULTS

The findings revealed an increase in the delay of cheek skin response to facial expressions (r = 0.24, p < 0.05) and a decrease in the stretchiness of the lower cheek area with age (r = 0.60, p < 0.01). An increasing variance in delay and stretchiness within the same age group was also observed with aging.

CONCLUSION

The findings of this study revealed that skin aging encompasses both static characteristics, such as spots, wrinkles, and sagging, traditionally studied in aging research, and dynamic aging characteristics of the skin that emerge in response to facial expression changes. These dynamic aging characteristics could pave the way for the development of new methodologies in skin aging analysis and potentially improve our understanding and treatment of aging impressions that are visually perceptible in daily life but remain unexplored.

Analysis of optical absorption of photoaged human skin using a high-frequency illumination microscopy analysis system

Skin is composed of different layers, including the stratum corneum, epidermal living layer and papillary and reticular dermis. Each has specific optical properties due to differences in their biological components. Alterations in the skin's cutaneous biological components resulting from photoaging caused by chronic exposure to UV light affect the deterioration of appearance associated with the skin's optical properties. Various methods for analysing cutaneous optical properties have been previously proposed, including mathematical models and computer simulations. However, these were insufficient to elucidate changes in each skin layer and comprehensively understand the skin's integrated optical properties. We focused on UV-induced yellowing of the facial skin. We evaluated site-specific optical absorption of human skin tissue sections to investigate the yellowish discoloration, which is suggested to be related to the photodamage process. The method includes our original technique of separating the transmitted and scattered light using high-frequency illumination microscopy, leading to microscopic analysis of the tissue's optical absorption in the regions of interest. In analysing the sun-exposed facial skin tissue sections, we successfully showed that dermal regions of aged skin have increased absorption at 450 nm, where yellowish colours are complemented. Furthermore, we confirmed that elastic fibres with observable histological disorder resulting from photodamage are a prominent source of high optical absorption. We detected changes in the skin's optical absorption associated with dermal degeneration resulting from photodamage using a novel optical microscopy technique. The results provide a base for the evaluation of optical property changes for both yellowing discoloration and other tissue disorders.

Age-related changes in dermal fiber-like structures in facial cheeks

BACKGROUND/PURPOSE

Despite recent progress in non-invasive measurement methods, such as in vivo laser confocal microscopy (CLSM), it is difficult to quantitatively measure age-related changes in dermal fibrous structures in the face using these methods and qualitative characteristics. We used characteristics extracted from the analysis of CLSM images to quantitatively investigate the effects of aging on dermal fibrous structures in the face.

METHODS

CLSM images of dermal fibrous structures were obtained from 90 Japanese females, ranging in age from 20 to 60 years. The feature values of CLSM images were extracted using image analysis methods, such as short-line segment-matching processing and spatial frequency analysis. The qualitative characteristics of the dermal fibrous structures in the CLSM images were obtained by principal component analysis (PCA) of these feature values. The fibrous structures were scored on the basis of qualitative characteristics and then age-related changes in the scores among the subjects were quantitatively evaluated.

RESULTS AND CONCLUSION

The PCA results showed that there were two characteristics in the images of fibrous structures: clearness and directionality. The clearness of fibrous structures decreased and directionality isotropy increased with age.

A combined near-infrared diffuse reflectance spectroscopy and principal component analysis method of assessment for the degree of photoaging and physiological aging of human skin

The phenomenon of skin aging may be categorized broadly into photoaging caused by exogenous factors and physiological aging induced by endogenous factors. A near-infrared diffuse reflectance (NIR-DR) spectroscopy method was recently proposed for non-invasive evaluation of changes that occur within the skin of hairless mice that were divided into an ultraviolet-B (UVB)-irradiated group (photoaging) and a non-irradiated group (physiological aging). In the present study, a non-invasive method to assess changes in human skin was developed and tested. For investigation of photoaging and physiological aging, NIR-DR spectra in the 8000 to 4000 cm(-1) region were measured from the outer forearm (sun-exposed) and the inner upper arm (sun-protected) of 86 females ranging in age from 23 to 69 years. The obtained spectra were subjected to principal component analysis (PCA). PCA results suggested that contributions of both types of aging occurring within the skin can be monitored and quantitatively assessed using the 5990 to 5490 and 5000 to 4480 cm(-1) regions of second derivative NIR-DR spectra, respectively. This study demonstrates that for human skin, NIR-DR spectroscopy and PCA may allow non-invasive assessment of the degree of photoaging and physiological aging due to degenerative changes in protein elasticity and reduction in protein quantity, respectively.

A noninvasive method for assessing interior skin damage caused by chronological aging and photoaging based on near-infrared diffuse reflection spectroscopy

This paper reports a noninvasive method for evaluating skin aging based on near-infrared diffuse reflectance (NIR-DR) spectroscopy. Skin aging can be attributed to photoaging and chronological aging. Both types of aging are heavily involved in the skin changes that occur as we get older, for example, wrinkles or sagging skin. Our goal is to develop a noninvasive way to assess changes taking place inside the skin for each type of aging by using NIR-DR spectroscopy. Interior skin damages caused by photoaging and chronological aging were studied for an ultraviolet-B (UVB)-irradiated hairless mouse group (24 mice) and a non-irradiated group (29 mice) by using NIR-DR spectroscopy and principal component analysis (PCA). The results suggested the possibility of monitoring the contribution and the quantitative assessment of both types of aging taking place inside the skin by using the 5990-5490 cm(-1) and 5000-4480 cm(-1) regions of NIR-DR spectra. For the photoaging, structural changes in proteins are most clearly reflected by a shift of the band near 4880 cm(-1) due to a combination of amide A and amide II modes. On the other hand, the chronological aging is associated with a change in collagen quantity as is seen in the intensity changes in NIR bands assigned to collagen. NIR-DR spectroscopy and PCA may allow us to noninvasively assess the degree of photoaging and chronological aging as the degeneration of elasticity in collagen protein and the degradation of protein quantity, respectively.

Relationships between changes in mechanical properties of the skin, wrinkling, and destruction of dermal collagen fiber bundles caused by photoaging

BACKGROUND/PURPOSE

Long-term exposure to ultraviolet (UV) radiation induces various cutaneous changes that differ from those because of physiological aging, including structural destruction of dermal collagen fiber bundles (DCFBs), which comprise the major component of the dermis. Wrinkling, a representative change in skin surface associated with photoaging, is often seen at the corners of the eyes and in the space between the eyebrows. These are locations where the skin contracts repeatedly and routinely. Lowered resiliency to skin contraction induced by marked structural changes in DCFBs may represent one cause of photo-induced wrinkles. Using animal models of photoaging, changes in mechanical properties of the skin caused by UV irradiation were measured, and relationships between UV-induced changes were analyzed.

METHODS

Animal models of photoaging were prepared by irradiating hairless mice with UVB light. Dorsal skin surface replicas of animals were taken using silicon rubber, and volume of wrinkles was calculated using an image analyzer. Stress of the skin against horizontal contraction was measured using a new device called the Resiliometer. Three-dimensional organization of dermal collagen structures in skin samples collected from the back of each animal was observed under scanning electron microscopy, and compactness of DCFBs was assessed from electron micrography.

RESULTS

With time and therefore increasing UV dose, deep wrinkles formed on the backs of mice. Volume of wrinkles peaked at 8 weeks. All parameters obtained from Resiliometer measurements were increased by irradiation. DCFB structure was degraded in a radiation dose-dependent manner. DCFB grading was significantly correlated with each Resiliometer parameter. Significant correlations were also observed between each Resiliometer parameter and volume of wrinkles.

CONCLUSION

Stress of the skin against horizontal contraction obtained using the Resiliometer changes following UV irradiation, correlating with photo-induced wrinkling and destruction of DCFBs. These results support the hypothesis that changed force of restitution to skin contraction induced by marked structural changes in DCFBs represents one cause of photo-induced wrinkles. The resiliometric parameter may offer a good indicator for monitoring the condition of DCFB structure, as changes in these would induce failure in restitution to skin contraction, leading to wrinkling.

A study of differences in surface roughness between sun-exposed and unexposed skin with age

BACKGROUND

To understand and separate the roles of age and solar ultraviolet exposure (sun damage) on the surface roughness of skin.

OBJECTIVES

To determine the effects of age and site (sun exposed vs. unexposed) on skin roughness in normal healthy subjects.

SUBJECTS/METHODS

Using a stylus profilometer and silicone skin surface replicas, we have measured skin surface roughness parameters on habitually exposed (back of hand) and habitually unexposed (upper buttock) skin sites from the same individual in a sample of 73 subjects from the normal population. We compared the two sites in order to determine any differences in roughness caused, we postulate, by the effect of solar ultraviolet exposure on the exposed site.

RESULTS

We found that the two sites are indistinguishable in roughness until after 30 years of age. For the over 30 years group, the difference between exposed and unexposed skin roughness correlated strongly with age. For all ages, skin roughness showed a positive correlation with age on the unexposed, but not the exposed, site. On the hand site subjects aged 40 years and older had significantly smoother skin than those aged less than 40 years, as measured by one roughness parameter. On the back, the older group had significantly rougher skin than the younger group measured by two roughness parameters.

CONCLUSIONS

We propose that on the back of the hands, solar damage reverses or reduces the increase in roughness which would otherwise be caused by intrinsic ageing.