Aging in Skin of Color: Disruption to Elastic Fiber Organization Is Detrimental to Skin’s Biomechanical Function  Abigail Kate Langton, Sabrina Alessi, Mark Hann, Anna Lien-Lun Chien, Sewon Kang, Christopher Ernest Maitland Griffiths, Rachel Elizabeth Beatrice Watson  Journal of Investigative Dermatology  Volume 139, Issue 4, Pages 779-788 (April 2019) DOI: 10.1016/j.jid.2018.10.026 Copyright © 2018 The Authors Terms and Conditions

Figure 1 Biomechanical testing reveals significantly reduced skin function in aged and photoaged skin of color. Graphic representation of the biomechanical properties obtained from application of the Cutometer (a) and ballistometer (b) to the skin. The biomechanical properties of black African-American buttock and forearm skin were determined using the Cutometer in mode 1 with a 4-mm aperture probe (c, e) and the ballistometer (d, f). Curves generated using these devices indicated that the biomechanical properties of young and intrinsically aged buttock skin were similar (c, d); however, intrinsically aged skin was significantly less resilient, had reduced elasticity and fatigue was apparent. In contrast, the Cutometer and ballistometer curves from young and chronically photoexposed forearm (e, f) reveal significant differences in all biomechanical properties between cohorts. Journal of Investigative Dermatology 2019 139, 779-788DOI: (10.1016/j.jid.2018.10.026) Copyright © 2018 The Authors Terms and Conditions

Figure 2 Epidermal thickness and DEJ convolution are significantly reduced in both intrinsically aged and chronically photoexposed skin of color. Our study cohort demonstrated the diversity of pigmentation levels in black African-American individuals, with skin types ranging from lightest to darkest (a). A Pearson product-moment correlation coefficient was computed to assess the relationship between an individual’s individual typology angle and their epidermal melanin content (b); a negative correlation exists between the two variables (r = –0.598, n = 78, P < 0.001). Furthermore, younger individuals tend to have darker skin than the aged cohort (c). Morphometric measurements of epidermal thickness and DEJ convolution index were analyzed using cryosections from young and aged African-American skin at buttock and forearm anatomic sites (d). Young skin had a significantly thicker epidermis and a more convoluted DEJ compared to intrinsically aged and chronically photoexposed skin (e). Scale bar = 100 μm. ∗ P < 0.05, ∗∗∗P < 0.001. DEJ, dermal–epidermal junction. Journal of Investigative Dermatology 2019 139, 779-788DOI: (10.1016/j.jid.2018.10.026) Copyright © 2018 The Authors Terms and Conditions

Figure 3 Aging impacts the organization and abundance of elastic fibers and collagen I. Elastin (a), fibrillin-rich microfibrils (b), and fibulin-5 (c) were arranged in distinctive candelabra-like arrays in the superficial papillary dermis of young buttock and forearm. In contrast, intrinsically aged buttock and chronically photoexposed forearm showed significant depletion and remodeling of elastic fibers proximal to the dermal–epidermal junction. Picrosirius Red staining viewed under polarized light identified abundant organized fibrillar collagens in young buttock and forearm (d). In aged skin of color, the abundance of organized fibrillar collagen was significantly reduced in both intrinsically aged buttock and chronically photoexposed forearm. Immunofluorescent detection of mature collagen I (e) further confirmed that the overall intensity was significantly reduced in the papillary dermis of aged buttock and forearm. Scale bar = 50 μm. ∗∗P < 0.01, ∗∗∗P < 0.001. Journal of Investigative Dermatology 2019 139, 779-788DOI: (10.1016/j.jid.2018.10.026) Copyright © 2018 The Authors Terms and Conditions

Figure 4 Association between biomechanical properties and skin architecture. An X-Y-Z plot (a) revealed that young African-American buttock (solid black circles) and intrinsically aged buttock (solid red circles) share similar biomechanical properties (F3 parameter) and architectural features as measured by DEJ convolution and elastic fiber abundance. Similarly, young African-American forearm (open black circles) shares these properties. However, chronically photoexposed African-American forearm (open red circles) did not share these properties with the other groups and clustered on the X-Y-Z plot at a position of reduced DEJ convolution, low elastic fiber abundance, and impaired biomechanical function. DEJ, dermal–epidermal junction. Journal of Investigative Dermatology 2019 139, 779-788DOI: (10.1016/j.jid.2018.10.026) Copyright © 2018 The Authors Terms and Conditions