Real-time, High-resolution, In Vivo Characterization of Superficial Skin With Microscopy Using Ultraviolet Surface Excitation (MUSE)

November 2016 | Volume 15 | Issue 11 | Original Article | 1344 | Copyright © November 2016

Derek Ho BS,a,b Farzad Fereidouni PhD,c Richard M. Levenson MD,c and Jared Jagdeo MD MSa,b,d

aDermatology Service, Sacramento VA Medical Center, Mather, CA bDepartment of Dermatology, University of California Davis, Sacramento, CA cDepartment of Pathology and Laboratory Medicine, University of California Davis, Sacramento, CA dDepartment of Dermatology, State University of New York Downstate Medical Center, Brooklyn, NY

Abstract
BACKGROUND: Skin care products make up the largest part (36%) of the cosmetic market globally, of which the United States plays the largest role. In 2015, approximately 115 billion USD was spent globally on skin care products. Skin care products, in contradistinction to pharmaceuticals, are not strictly regulated by the FDA. A key factor for evaluation of a skin care product or topical drug is skin barrier function and effect on super cial skin. Thus, it is critical to have quantitative and qualitative methods to study the effects of skin care products on skin barrier and the super cial skin. Currently, no imaging method exists that can evaluate and track super cial skin changes visually in real-time. OBJECTIVE: To report using a novel imaging modality, Microscopy using Ultraviolet Surface Excitation (MUSE), to provide real-time, high- resolution, in vivo characterization of super cial skin and moisturizing properties of topical moisturizer, and to highlight key bene ts of using MUSE to visualize the super cial skin and serve as an excellent complementary tool to current quantitative methods. METHODS AND MATERIALS: The methodology of MUSE is based upon two main principles inherent to ultraviolet (UV) light and uorescent staining agents. In this study, the author’s (JJ) index ngertip was imaged using the MUSE instrument without and with moisturizer. RESULTS: Dermatoglyphics of the fingertip consists of ridges (cristae super ciales) and grooves (sulci super ciales) proved to be straightforward to visualize at high resolution. Desquamation of superficial corneocytes and opening of an acrosyringium (the most superficial portion of eccrine ducts) were visualized in high-resolution. Post-application of a moisturizer, a uniform layer of moisturizer could be seen superficial to the corneocytes along the ridges and CONCLUSIONS: Real-time, high-resolution, in vivo characterization of super cial skin and moisturizing properties of moisturizer using MUSE is feasible. Its utility can be enhanced with downstream quantification using imaging software. J Drugs Dermatol. 2016;15(11):1344-1346.

INTRODUCTION

Skin care products make up the largest part (36%) of the cosmetic market globally, of which the United States plays the largest role.1 In 2015, approximately 115 billion USD was spent globally on skin care products.2 The skin care industry has shifted its consumer focus from the older to younger population, commercializing environmentally friendly, organic anti-aging products to achieve youthfulness and delay signs of aging.2 Skin care products, in contradistinction to pharmaceuticals, are not strictly regulated by the FDA.3 Manufacturers invest significant resources into research and development to demonstrate efficacy, namely to ensure that marketed products yield the desired outcome.Superficial skin is important because it serves as environmental barrier protecting against external (physical, chemical/biochemical) stress and is regulating transdermal water loss.4 A key factor for evaluation of a skin care product or topical drug is skin barrier function and other effects on superficial skin, which includes the ability of a product to penetrate the stratum corneum and to affect the status of skin hydration.5 Thus, it is critical to have quantitative and qualitative methods to study the effects of skin care products on skin barrier and the superficial skin. Various methods (non-invasive, invasive, in vitro) and mathematical models have been developed to study skin barrier function, primarily focusing on transepidermal water loss (TEWL) and skin conductance measurements.6 These measurements are currently employed to assess skin barrier function; however, limitations exist including factors associated with changes in humidity, temperature, circadian rhythms, stress, and device used.7 In addition, penetration properties of topically applied products are related to the vehicle used, and conventional in vitro measurements from tape stripping, skin biopsies, and skin models may not necessarily reflect the actual in vivo condition. More importantly, a significant limitation is that none of these methods capture the visual appearance of superficial skin. Currently, there exists no imaging method that can evaluate and track skin barrier function visually in real-time.Here, we report using a novel imaging modality, Microscopy using Ultraviolet Surface Excitation (MUSE), to provide real-time, high-resolution, in vivo characterization of superficial skin