Research Article Infant Skin Barrier, Structure, and Enzymatic Activity Differ from Those of Adult in an East Asian Cohort Qiwei Liu, 1 Yanhui Zhang, 1 Simon G. Danby, 2 Michael J. Cork, 2 and Georgios N. Stamatas 3 1 Baby Innovation Platforms, Skin Care R&D, Johnson & Johnson Consumer China, Shanghai, China 2 Te Academic Unit of Dermatology Research, Department of Infection and Immunity, Faculty of Medicine, Dentistry and Health, Te University of Shefeld Medical School, Beech Hill Road, Shefeld, UK 3 Baby Innovation Platforms, Skin Care R&D, Johnson & Johnson Sant´ e Beaut´ e France, Issy-les-Moulineaux, France Correspondence should be addressed to Georgios N. Stamatas; gstamata@its.jnj.com Received 20 March 2018; Revised 8 June 2018; Accepted 27 June 2018; Published 12 July 2018 Academic Editor: Maxim E. Darvin Copyright © 2018 Qiwei Liu et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Skin physiology is dynamically changing over the frst years of postnatal life; however, ethnic variations are still unclear. Te aim of this study was to characterize infant skin barrier function, epidermal structure, and desquamation-related enzymatic activity as compared to that of adult skin in an East Asian population. Te skin properties of 52 infants (3-24 months) and 27 adults (20- 40 years) were assessed by noninvasive methods at the dorsal forearm and upper inner arm. Transepidermal water loss and skin surface conductance values were higher and more dispersed for infants compared to adults. Infant skin surface pH was slightly lower than adult on the dorsal forearm. Te infant SC and viable epidermis were thinner compared to adults with diferences that were site-specifc. Although the chymotrypsin-like activity for infant skin was comparable to adult level, the caseinolytic specifc activity was signifcantly higher for the infant cohort. Tese observations indicate a diferently controlled pattern of corneocyte desquamation in infants. In conclusion, structural and functional diferences exist between infant and adult skin in the East Asian population pointing to dynamic maturation of the epidermal barrier early in life. 1. Introduction As the outermost organ of the body, skin is endowed with multiple functions such as protection, secretion, absorp- tion, and thermoregulation [1]. Tese functions are essential throughout life. Several studies emphasize the importance of the stratum corneum (SC) in providing a protective barrier from an early age [2, 3]. At birth, the skin of term newborns behaves as a competent physical inside-out and outside-in barrier, but not at the capacity of adult skin [4–6]. Te barrier function and the water-handling properties of infant SC have been shown to be diferent from those of adult [7, 8]. Infant SC was found to have higher water content and higher rates of transepidermal water loss (TEWL) at rest, absorb more water, and lose excess water faster than adult SC. Further studies revealed that such functional diferences were associated with diferences in the epidermal microstructure [9, 10]. An important factor for a healthy epidermal barrier is a carefully controlled SC desquamation process [11, 12]. SC desquamation is a proteinase-dependent process that involves complex synergies of enzymatic activities, which are responsible for precisely degrading a variety of intra- cellular and intercellular macromolecules and for providing an inconspicuous shedding of corneocytes [13, 14]. Te corneodesmosomes are critical for the maintenance of the SC integrity and barrier function. A key event that eventually results in normal desquamation is the complete proteolysis of all corneodesmosomes. Four distinct types of proteolytic activity are identifed within the intercellular regions of the SC that are responsible for corneocyte dissociation and desquamation processes [13, 14]: (i) chymotrypsin-like protease activity exhibited by kallikrein (KLK) 7, previously referred to as stratum corneum chymotryptic enzyme (SCCE); (ii) trypsin–like protease Hindawi BioMed Research International Volume 2018, Article ID 1302465, 8 pages https://doi.org/10.1155/2018/1302465