Figure 1.
Morphological alterations of collagen and elastin fibers in aged human skin. Collagen second harmonic generation (SHG) (blue, total SHG signal, backward + forward, λexc= 820 nm) and elastin autofluorescence (green, λdet = 500–550 nm) of sun-exposed forearm skin samples from individuals aged 25 (top left) and 54 (top right) years, and sun-protected buttocks skin samples from individuals aged 25 (lower left) and 83 (lower right) years. Shown are maximum projections (15-µm thickness). SHG imaging highlights abundant collagen fibers in young skin (top and bottom left), and relatively reduced mature collagen content and increased fragmentation in photoaged (top right) and aged skin (bottom right). In addition, photoaging and chronological aging are characterized by the disappearance of small elastin fibers in the upper dermis. Photoaging is characterized by accumulation of elastotic material composed of aggregated elastin fibers (top right). (Human study guidelines approved by the University of Michigan Institutional Review Board.)