Avon Products Inc, Suffern, New York.
Photodermatol Photoimmunol Photomed. 2019 Nov;35(6):408-414. doi: 10.1111/phpp.12470. Epub 2019 Apr 29.
The epidermis is the outermost layer of skin and is composed of cells primarily containing keratin. It consists of about ten layers of living cells (keratinocytes) and ten layers of dead cells (corneocytes). Thinning of the epidermis and decreased proliferation of its cells are associated with aging related changes in skin, including wrinkling and laxity. Fluorescence excitation spectroscopy is a noninvasive method of monitoring characteristic excitation-emission peaks in skin that have been related to the epidermal and dermal composition. The magnitude of the peak that occurs at 295nm excitation (F295) has been linked to changes in epidermal thickness, proliferation, and skin aging.
The goal of this study is to correlate changes in the F295 signal with proliferation of cells and thickening of the epidermis induced by cosmetic formulations. We hypothesize that two commonly used cosmetic ingredients, retinol and glycolic acid, will increase these markers that have been implicated in skin anti-aging.
In a placebo-controlled study subjects' forearms were treated with formulations containing retinol or glycolic acid under occlusive patch for a period of 21 days. Skin fluorescence was measured at baseline and after treatment, and biopsies were taken following treatment for histological analysis of epidermal thickness and cell proliferation.
After 21 days of treatment retinol and glycolic acid formulas significantly increased F295 (by 265.1±33.5% and 162.2±18.7% respectively), whereas the placebo control formula did not induce a change from baseline. Furthermore, retinol and glycolic acid treatments significantly increased epidermal thickness (by 63.1% and 7.8% respectively) and keratinocyte proliferation (by 236.9% and 62.8% respectively) versus placebo control.
Increases in F295 were found to correlate with epidermal renewal, but more so with increased cell proliferation than epidermal thickness. We conclude that the F295 signal is a fast and reliable early indicator of epidermal remodeling in skin that can be used to distinguish between formulations with different cosmetic ingredients.
表皮是皮肤的最外层，主要由角蛋白组成。它由大约十层活细胞（角质形成细胞）和十层死细胞（角质细胞）组成。表皮变薄和细胞增殖减少与皮肤衰老相关变化有关，包括皱纹和松弛。荧光激发光谱是一种非侵入性监测皮肤特征激发-发射峰的方法，这些峰与表皮和真皮成分有关。在 295nm 激发下出现的峰（F295）的幅度与表皮厚度、增殖和皮肤老化的变化有关。
本研究的目的是将 F295 信号的变化与化妆品配方诱导的细胞增殖和表皮增厚相关联。我们假设两种常用的化妆品成分，视黄醇和乙醇酸，将增加这些与皮肤抗衰老有关的标志物。
在一项安慰剂对照研究中，研究对象的前臂在闭塞贴剂下用含有视黄醇或乙醇酸的制剂处理 21 天。在基线和治疗后测量皮肤荧光，并在治疗后进行活检，用于表皮厚度和细胞增殖的组织学分析。
经过 21 天的治疗，视黄醇和乙醇酸配方显著增加了 F295（分别增加了 265.1±33.5%和 162.2±18.7%），而安慰剂对照配方则没有从基线开始变化。此外，视黄醇和乙醇酸处理显著增加了表皮厚度（分别增加了 63.1%和 7.8%）和角质形成细胞增殖（分别增加了 236.9%和 62.8%），而安慰剂对照处理则没有。
F295 的增加与表皮更新有关，但与细胞增殖的相关性大于表皮厚度。我们得出结论，F295 信号是皮肤表皮重塑的快速可靠的早期指标，可以用来区分具有不同化妆品成分的配方。
