Label-free stimulated Raman scattering microscopy visualizes changes in intracellular morphology during human epidermal keratinocyte differentiation

Abstract

Epidermal keratinocyte (KC) differentiation, which involves the process from proliferation to cell death for shedding the outermost layer of skin, is crucial for the barrier function of skin. Therefore, in dermatology, it is important to elucidate the epidermal KC differentiation process to evaluate the symptom level of diseases and skin conditions. Previous dermatological studies used staining or labelling techniques for this purpose, but they have technological limitations for revealing the entire process of epidermal KC differentiation, especially when applied to humans. Here, we demonstrate label-free visualization of three-dimensional (3D) intracellular morphological changes of ex vivo human epidermis during epidermal KC differentiation using stimulated Raman scattering (SRS) microscopy. Specifically, we observed changes in nuclei during the initial enucleation process in which the nucleus is digested prior to flattening. Furthermore, we found holes left behind by improperly digested nuclei in the stratum corneum, suggesting abnormal differentiation. Our findings indicate the great potential of SRS microscopy for discrimination of the degree of epidermal KC differentiation.

Changes in facial moisture distribution and feelings of moisture/dryness among various environmental temperatures and humidities in summer and winter

“…Perhaps it would also be necessary to compare the epidermal morphology. 24,25 As the skin's environmental conditions vary depending on the area of residence, residential building, season, and clothing, our results indicate the importance of environmental conditions when skin conditions are being measured. We usually evaluate skin conditions at 23-25°C and 40%-50% RH.…”

Three-Dimensional Analysis of Water Dynamics in Human Skin by Stimulated Raman Scattering

“…16−18 SRS microscopy has also been used to examine the intracellular morphology of epidermal cells and the differentiation process of keratinocytes. 19,20 In a previous study, we focused on C−H stretching vibrations in the spectral range of 2800−3100 cm −1 to study lipids and proteins. In a recent study, multiplex CARS imaging was used to visualize water retention in intercellular lipids, 21 but the temporal change of water distribution in skin tissue has not yet been investigated.…”

Three-dimensional analysis of water dynamics in human skin by stimulated Raman scattering imaging

“…These coherent Raman scattering microscopes have been widely applied to biological research, including dermatology, for imaging mouse, pig, and human skin [16][17][18]. SRS microscopy has also been used to examine the intracellular morphology of epidermal cells and the differentiation process of keratinocytes [19,20]. Previous studies have used C-H stretching vibrations in the spectral range of 2800-3100 cm -1 to study lipids and proteins, and multiplex CARS imaging has been used to visualize water retention in intercellular lipids [21].…”