Fig 1. Rougher collagen fibril surface in aged dermis.

(a) Histological image of young (left, 28 years) and aged (right, 82 years) human skin. Skin sections are obtained from sun-protected hip and stained with H&E (upper) and Sirius red (bottom). Images are representative of six young (25±5 years) and six aged (75±8 years) subjects. Bar = 100μm. (b) Skin dermal collagen alterations in aged human skin. The morphological characteristics of dermal collagen fibers were assessed based on three criteria reflecting alterations in dermal collagen fibers: (i) inter-fiber spacing, (ii) fiber thinness, and (iii) disorder in fiber arrangement. Each of these factors was assessed using a numerical scale that ranged from 1 (minimally evident) to 9 (highly evident).Results are expressed as the mean ± SEM. (c) Representative bright field image shows the AFM cantilever positioned on the dermis. AFM images were obtained from the reticular and papillary dermis (rectangles, 5×5μm scan size). (d) AFM nanoscale images of the collagen fibrils from young (left, 28 years) and aged (right, 82 years) human skin. White and red arrows indicate intact and fragmented collagen fibrils, respectively. Images are representative of six young and aged subjects. Bar = 1μm (insert = 500nm). (e) Representative image for quantification of collagen fibril surface roughness. Lateral dimension is 2.5x2.5 μm². Height is given in black and white brightness. The lines indicate cross sections that are displayed by graph. Each line (blue, red, and green) height fluctuations in the graph indicate corresponding collagen surface roughness of the image. Bar = 200nm. (f) The roughness of collagen fibril surface is increased in aged human skin. The roughness of collagen fibrils was analyzed using Nanoscope Analysis software (Nanoscope_Analysis_v120R1sr3, Bruker-AXS, Santa Barbara, CA). Each group comprised six subjects. Results are expressed as the mean ± SEM.