Osseiran Sam, Cruz Jomer Dela, Jeong Sinyoung, Wang Hequn, Fthenakis Christina, Evans Conor L
Wellman Center for Photomedicine, Harvard Medical School, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129, USA.
Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue E25-518, Cambridge, MA 02139, USA.
Biomed Opt Express. 2018 Nov 26;9(12):6425-6443. doi: 10.1364/BOE.9.006425. eCollection 2018 Dec 1.
The most superficial layer of the epidermis, the stratum corneum, plays a crucial role in retaining hydration; if its structure or composition is compromised, dry skin may result as a consequence of poor water retention. Dry skin is typically treated with topical application of humectant agents that attract water into the skin. Corneometry, the industry standard for measuring skin hydration, works by assessing the bulk electrical properties of skin. However, this technique samples a large volume of tissue and thus does not resolve the biochemical changes that occur at the cellular level that may underlie mechanisms of dry skin. These limitations can be addressed using coherent Raman scattering (CRS) microscopy to probe the intrinsic vibrational modes of chemical groups such as lipids and water. In the present study, human skin explants undergoing dehydration and humectant-induced rehydration were measured via CRS imaging and corneometry. Corneometry data and chemically specific images were obtained from the stratum corneum of each patient sample at each timepoint. The resulting data was statistically analyzed using linear mixed effect model regression analysis. The cellular imaging data revealed water loss in the stratum corneum during dehydration that was correlated with corneometer readings. Interestingly, the imaging data and corneometer readings show differences under the experimental rehydration conditions. The rehydration results suggest that hydration restored by the humectant agents may not be retained by the corneocytes in the model system. Given the complementary nature of corneometry, a bulk assessment tool, and CRS microscopy, a modality with subcellular resolution implemented here in an en-face tissue imaging setup, these techniques can be used to measure uptake and efficacy of topical compounds in order to better understand their mode of action and improve therapeutic applications.
表皮的最外层，即角质层，在保持皮肤水分方面起着关键作用；如果其结构或成分受到损害，可能会因保水能力差而导致皮肤干燥。皮肤干燥通常通过局部涂抹保湿剂来治疗，保湿剂可将水分吸引到皮肤中。角质层水合测量法是测量皮肤水合作用的行业标准，其工作原理是评估皮肤的整体电学性质。然而，这项技术对大量组织进行采样，因此无法解析在细胞水平上发生的可能是皮肤干燥机制基础的生化变化。使用相干拉曼散射（CRS）显微镜来探测脂质和水等化学基团的固有振动模式，可以解决这些局限性。在本研究中，通过CRS成像和角质层水合测量法对经历脱水和保湿剂诱导再水化的人体皮肤外植体进行了测量。在每个时间点从每个患者样本的角质层获得角质层水合测量数据和化学特异性图像。使用线性混合效应模型回归分析对所得数据进行统计分析。细胞成像数据显示脱水过程中角质层的水分流失与角质层水合测量仪读数相关。有趣的是，成像数据和角质层水合测量仪读数在实验再水化条件下显示出差异。再水化结果表明，在模型系统中，保湿剂恢复的水合作用可能无法被角质形成细胞保留。鉴于角质层水合测量法（一种整体评估工具）和CRS显微镜（一种在本研究中以表面组织成像设置实现的具有亚细胞分辨率的方法）的互补性质，这些技术可用于测量局部化合物的摄取和功效，以便更好地理解其作用模式并改善治疗应用。
