Abstract
.Skin wrinkling is a typical symptom of cutaneous photoaging; however, the skin wrinkling depends on not only the actual age but also exposure history to ultraviolet B (UVB) rays in individuals. Therefore, there is considerable need for its assessment technique in vivo in skin cosmetics and antiaging dermatology. Wrinkles always appear as linear grooves in the skin, and dermal collagen fibers play an important role to determine the morphology and mechanical properties of the skin. Therefore, an optical probe sensitive to dermal collagen fiber and its orientation will be useful. Polarization-resolved second-harmonic-generation (SHG) microscopy is a promising approach for in vivo evaluation of collagen fiber orientation because the efficiency of SHG light is sensitive to collagen fiber orientation when the incident light is linearly polarized. We investigate orientation change of dermal collagen fiber in prewrinkled and wrinkled skins of the UVB-exposed mouse model using polarization-resolved SHG microscopy. A polarization anisotropic image of the SHG light indicates that the change of collagen fiber orientation starts in the prewrinkled skin of UVB-exposed mice, then the wrinkle appears. Furthermore, the dominant direction of collagen fiber orientation in the prewrinkled skin is significantly parallel to the wrinkle direction in the wrinkled skin. This result implies that the change of collagen fiber orientation is a trigger of wrinkling in cutaneous photoaging.
Highlights
Cutaneous aging is an age-related skin change and is closely related to a balance change of production and decomposition of dermal collagen fibers
Decomposition of dermal collagen fibers is more dominant than production of them because the ultraviolet B (UVB)-damaged collagen fibers are decomposed by active secretion of collagenase
The image contrast is given by scattering in tissue: mainly melanin pigment deposited on a boundary between the epidermis layer and the dermis layer
Summary
Cutaneous aging is an age-related skin change and is closely related to a balance change of production and decomposition of dermal collagen fibers. Exposure of the skin to ultraviolet B (UVB) rays in sunlight often accelerates skin aging and causes morphological changes in the skin, such as mottled pigmentation, leathery texture, laxity, sallowness, and deep wrinkle. This is called cutaneous photoaging.[1] In the cutaneous photoaging, decomposition of dermal collagen fibers is more dominant than production of them because the UVB-damaged collagen fibers are decomposed by active secretion of collagenase. The need exists for an in vivo assessment technique to estimate the degree of cutaneous photoaging for studies in fields such as skin cosmetics and antiaging dermatology
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