Correlations between Skin Condition Parameters and Ceramide Profiles in the Stratum Corneum of Healthy Individuals

Abstract

Ceramides are essential lipids for skin barrier function, and various classes and species exist in the human stratum corneum (SC). To date, the relationship between skin conditions and ceramide composition in healthy individuals has remained largely unclear. In the present study, we measured six skin condition parameters (capacitance, transepidermal water loss, scaliness, roughness, multilayer exfoliation, and corneocyte cell size) for the SC of the cheeks and upper arms of 26 healthy individuals and performed correlation analyses with their SC ceramide profiles, which we measured via liquid chromatography-tandem mass spectrometry. In the cheeks, high levels and/or ratios of two free ceramide classes containing an extra hydroxyl group in the long-chain moiety and a protein-bound ceramide class containing 6-hydroxysphingosine correlated with healthy skin conditions. In contrast, the ratios of two other free ceramide classes, both containing sphingosine, and a protein-bound ceramide class containing 4,14-sphingadiene correlated with unhealthy skin conditions, as did shortening of the carbon chain of the fatty acid portion of two ceramide classes containing non-hydroxy fatty acids. Thus, our findings help to elucidate the relationship between skin conditions and ceramide composition.

Keywords: ceramide; lipids; skin; skin barrier; sphingolipids.

Figure 1

Skin condition parameters. The parameters ((A), capacitance; (B), transepidermal water loss [TEWL]; (C), multilayer exfoliation; (D), corneocyte cell size; (E), roughness; (F), scaliness) were measured for the cheeks and upper arms of healthy women (31–49 years old; n = 26) in winter. Boxes indicate the interquartile range (IQR), and lines in boxes represent the median. Whiskers indicate minimum and maximum values within 1.5 times the IQR. Circles and crosses represent outliers and means, respectively (** p < 0.01; Welch’s t-test). AU, arbitrary unit.

Figure 2

Skin condition parameters for the cheek in the dry and non-dry groups. The parameters ((A), capacitance; (B), transepidermal water loss [TEWL]; (D), multilayer exfoliation; (E), corneocyte cell size; (G), roughness; (H), scaliness) were measured in winter and were compared between the dry and non-dry groups (n = 13 each). Bars and whiskers indicate means and standard deviations (* p < 0.05; ** p < 0.01; Welch’s t-test). AU, arbitrary unit. (C) After collecting the stratum corneum by tape stripping, samples were subjected to brilliant green/gentian violet staining. The images are typical examples from each of the groups. Scale bars, 200 μm. (F) Images of the skin surface were obtained using Visioscan VC98. The images are typical examples from each of the groups. Scale bars, 1 mm.

Figure 3

Ceramide profiles. Stratum corneum samples were collected from the cheeks and upper arms of healthy women (31–49 years old; n = 26) by tape stripping in winter, and ceramides were quantified via liquid chromatography coupled with tandem mass spectrometry. Quantities of free ceramides (A), protein-bound ceramides (B), and total ceramides (C) are shown in box-and-whisker plots. Boxes indicate the interquartile range (IQR), and lines in boxes represent the median. Whiskers indicate minimum and maximum values within 1.5 times the IQR. Circles and crosses represent outliers and means, respectively (** p < 0.01; Welch’s t-test). AU, arbitrary unit. The proportions of free ceramides (D) and protein-bound ceramides (E) comprised by each ceramide class are shown in pie charts.

Figure 4

Ceramide class composition of cheek samples from the dry and non-dry groups. Quantities of ceramides ((A), free ceramide classes; (B), protein-bound ceramide classes; (C), total ceramides) and ratios of ceramide classes to total ceramides ((D), free ceramide classes; (E), protein-bound ceramide classes) in the cheeks in winter were compared between the dry and non-dry groups (n = 13 each). Bars and whiskers represent means and standard deviations (* p < 0.05; ** p < 0.01; Welch’s t-test).

Figure 5

Correlations between ceramide class ratios and skin condition parameters. Correlations were analyzed between seven ceramide classes (NS, NP, AS, EOS, EOH, PB-H, and PB-SD) and six skin condition parameters (capacitance, transepidermal water loss [TEWL], scaliness, roughness, multilayer exfoliation, and corneocyte cell size) for samples taken from the cheeks in winter. (A) The strength of each correlation is indicated in the heatmap. Red and blue indicate correlations with healthy and unhealthy skin conditions, respectively. The numbers are the correlation coefficients (R). (B) Representative scatter plots of the ceramide class ratios and skin condition parameters (magenta, dry group; light blue, non-dry group).

Figure 6

Ceramide chain lengths for the cheek in the dry and non-dry groups. Weighted averages of the chain lengths of free ceramide classes (A) and fatty acid composition of NS (B) and NH (C) for the cheeks in winter were compared between the dry and non-dry groups (n = 13 each). Bars and whiskers represent means and standard deviations (* p < 0.05; Welch’s t-test). (D) Analysis of correlations in the NS and NH classes between FA chain length and skin condition parameters (capacitance, transepidermal water loss [TEWL], scaliness, roughness, multilayer exfoliation, and corneocyte cell size) for the cheeks in winter. The strength of each correlation is indicated in the heatmap. Red and blue indicate correlation with healthy and unhealthy skin conditions, respectively. The numbers are the correlation coefficients (R). (E) Representative scatter plots of the fatty acid chain lengths of NS and NH and skin condition parameters (magenta, dry group; light blue, non-dry group).

Figure 7

Differences in ceramide levels and class composition in the cheeks between seasons. Stratum corneum samples were collected from the cheeks of healthy women (31–49 years old; n = 26) by tape stripping in summer and winter, and ceramides were quantified via liquid chromatography coupled with tandem mass spectrometry. (A) Bars and whiskers represent means and standard deviations of total ceramide quantities (** p < 0.01; paired Student’s t-test). (B) The ratios of the ceramide classes are shown in pie charts.