Measurement of dermal water content by confocal RAMAN spectroscopy to investigate intrinsic aging and photoaging of human skin in vivo

Abstract

Background In vivo confocal Raman spectroscopy (CRS) revealed a clear correlation of age and dermal water content, indicating increasing water content of the dermis with increasing age. This enhancement of water has been interpreted as an age‐dependent depletion, of proteins, mainly of collagen. Chronical sun exposure is known to destroy the collagen network of the skin, which leads to the signs of photoaging as the formation of wrinkles. Noninvasive in vivo measuring techniques for photoaging are limited. Therefore, sensitive techniques to quantify even mild degrees of photoaging in a clinical setting are of high interest. We used CRS to measure the water content in human dermis in vivo, assuming that additionally to the increase of water content in intrinsic aging, photoaging would lead to further collagen depletion and an additional increase in water content of the dermis. Materials and Methods A panel of 24 female subjects of different age‐groups and scores of photoaging was recruited. A ranking of high resolution dorsal forearm photographs was used to classify the degree of photoaging with high precision. After that, CRS water content and collagen measurements were performed in the photoexposed dorsal as well as the photoprotected volar dermis of the subjects. Results A positive correlation of water content in the dermis with age could be confirmed (r = .550). Further, a positive correlation between water content of dorsal dermis and photoaging ranks was observed (Pearson's r = .417). Conclusion Assessment of water content in the dermis with confocal Raman spectroscopy was found to be a promising method to measure the degree of photoaging in human subjects in vivo.

Assessment of a 3050/3200 nm fiber laser system for ablative fractional laser treatments in dermatology

“…Table 1 shows laser system‐dependent parameters like wavelength and penetration depth, as well as the thermal confinement time and stress confinement time of water. It is important to highlight that human tissue has water contents from 15%–30% (stratum corneum) to 60%–80% (epidermis and dermis) and that the absorption coefficient also depends on temperature 3,23 …”

“…It is important to highlight that human tissue has water contents from 15%-30% (stratum corneum) to 60%-80% (epidermis and dermis) and that the absorption coefficient also depends on temperature. 3,23 Laser ablation threshold and models…”

“…2 Compared to hemoglobin or melanin, water is not a useful target for SP since it is present at a high concentration throughout the skin (approximately 60%-80% of the epidermis and dermis). 3 To target water as a chromophore and to avoid bulk heating of the skin, fractional photothermolysis (FP) was invented. 4 In FP, short laser pulses with high peak fluences focused into small spots create spatially separated microscopic damage zones, leaving surrounding areas of skin perfectly intact.…”

“…The theory suggests that to obtain permanent thermal damage (thermolysis) of a target, laser light must be absorbed by the target and energy must be confined to the targeted structure, the latter keeping surrounding tissue intact, by keeping the pulse duration shorter than the thermal relaxation time 2 . Compared to hemoglobin or melanin, water is not a useful target for SP since it is present at a high concentration throughout the skin (approximately 60%–80% of the epidermis and dermis) 3 . To target water as a chromophore and to avoid bulk heating of the skin, fractional photothermolysis (FP) was invented 4 .…”

Raman confocal microscopy and biophysics multiparametric characterization of the skin barrier evolution with age

“…Both processes intrinsic and extrinsic have overlapping biological, biochemical and molecular mechanisms [3,4]. In the dermis, aging involves: (a) Degradation of several extracellular matrix proteins, including collagen and elastic fibers [2,3,5] and (b) changes in the hydration state [2,5,6]. Chronological aging alters the collagen of the papillary dermis [5], reduces the hydration and compactness of collagen fibers [2,5], while photoaging causes a decrease in collagen stability by reducing collagen type VII containing anchoring fibrils that contribute to the stabilization of the epidermal-dermal junction [4] and altering proline and hydroxyproline residues in the reticular dermis [5].…”