Abstract
Two-photon fluorescence (TPF) and second harmonic generation (SHG) microscopy provide direct visualization of the skin dermal fibers in vivo. A typical method for analyzing TPF/SHG images involves averaging the image intensity and therefore disregarding the spatial distribution information. The goal of this study is to develop an algorithm to document age-related effects of the dermal matrix. TPF and SHG images were acquired from the upper inner arm, volar forearm, and cheek of female volunteers of two age groups: 20 to 30 and 60 to 80 years of age. The acquired images were analyzed for parameters relating to collagen and elastin fiber features, such as orientation and density. Both collagen and elastin fibers showed higher anisotropy in fiber orientation for the older group. The greatest difference in elastin fiber anisotropy between the two groups was found for the upper inner arm site. Elastin fiber density increased with age, whereas collagen fiber density decreased with age. The proposed analysis considers the spatial information inherent to the TPF and SHG images and provides additional insights into how the dermal fiber structure is affected by the aging process.
Highlights
AJohnson & Johnson Consumer Inc., Beauty Innovation Platforms, Skillman, New Jersey, United States bJohnson & Johnson Santé Beauté, Global Consumer R&D, Issy-les-Moulineaux, France
Z-stacks of Two-photon fluorescence (TPF) and second harmonic generation (SHG) images were taken at three different body sites including the dorsal forearm, upper inner arm, and cheek
Dermal fibers were identified in the TPF and SHG images of the younger skin group, with elastin fibers shown as thin distinct bundles [Fig. 1(a)], whereas collagen fibers shown as thick intertwined bundles [Fig. 1(b)]
Summary
AJohnson & Johnson Consumer Inc., Beauty Innovation Platforms, Skillman, New Jersey, United States bJohnson & Johnson Santé Beauté, Global Consumer R&D, Issy-les-Moulineaux, France. By analyzing the mean intensity changes of collagen and elastin fibers, the SHG-to-AF aging index of dermis (SAAID) was defined and found to decrease with age.[6] In addition to intrinsic aging, photoaging has been studied by comparing the differences in SAAID between sun-exposed and sun-protected skin regions.[7] this method ignores the information relating to the spatial distribution of the signals.
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