Comparative analysis of intrinsic skin aging between Caucasian and Asian subjects by in vivo harmonic generation microscopy

• Main Authors: Kuan-Hung Lin, 林冠宏
• Other Authors: 孫啟光
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/txh6us

碩士 === 國立臺灣大學 === 生醫電子與資訊學研究所 === 106 === Intrinsic skin aging is defined as an inalterable process that is associated with the cellular and sub-cellular structural change of epidermis and dermis. Phenotypical and functional differences in the intrinsic skin aging process of individuals between Caucasians and Asians have generated considerable interest in dermatology and cosmetic industry. Some recent works describing racial differences in structural skin aging properties have been reported. However, most of these studies have been focused on stratum corneum and in some other studies interindividual differences in skin quality overwhelm the racial difference. Therefore, there has been a demand for more detailed studies to address various cellular and sub-cellular epidermal/dermal parameters together with age differences among different racial groups. This study investigates the morphological changes related to intrinsic skin aging in the viable epidermis and the dermal papilla zone (DPZ) between Caucasians and Asians. In contrast to other microscopies, harmonic generation microscopy (HGM) is an optimal tool to study skin aging because of the ability to distinguish the epidermis from dermis by different harmonic generation phenomena. A 1230 nm femtosecond chromium-forsterite laser was used for excitation to lessen skin attenuation and a sub-micron and 1-micron resolution in lateral and axial directions and a greater than 300 μm penetrability were previously achieved. In this study, we recruited 31 Caucasian subjects and obtained in vivo HGM images on the sun-protected volar forearm. In combination with our previous results on Asian skin, these studies allow us to comparatively analyze the difference of intrinsic aging between Caucasian and Asian skin. In comparative analysis between Caucasians and Asians, Caucasian subjects have on average larger scale in the viable epidermis thickness, the cellular size, nuclear size and NC ratio of granular cells, the depth of DPZ, the DP volume per unit area, the collagen volume per unit area, the DP volume ratio and the 3D interdigitation index. The cellular and nuclear sizes of basal cells in Caucasians increase with age with the same trend as in Asians, and the maximum viable epidermis thickness, the depth of DPZ and the DP volume per unit area in Caucasians decrease with age with highly significant difference respect to Asians. Our present findings suggest that the primary factor to result in different aging outlook between Caucasians and Asians is the DPZ-related parameters while the cellular, nuclear size of basal cells can serve as scoring indices for intrinsic skin aging due to their consistency between Caucasians and Asians.