关键词: 皮肤生理学过程, 皮脂, 敏感性皮肤, 角质层屏障, 衰减全反射傅里叶变化红外光谱

Abstract: 【Abstract】 Objective To investigate differences in stratum corneum components between sensitive skin and normal skin by attenuated total reflectance Fourier transform infrared （ATR-FTIR） spectroscopy, and to evaluate the value of ATR-FTIR spectroscopy in the study of pathogenesis of sensitive skin. Methods From December 2018 to February 2019, 148 volunteers were recruited, who had lived in Shanghai for ≥ 6 years. Through questionnaire survey, lactic acid sting test and capsaicin test, the subjects were divided into normal skin group and sensitive skin group; meanwhile, total sting score and total burning score of the subjects were recorded in the lactic acid sting test and capsaicin test respectively. ATR-FTIR spectroscopy was performed to detect stratum corneum components, including natural moisturizing factor （NMF）, stratum corneum lipids, free fatty acids （FFA） and β-sheet/α-helix （β/α） ratio; moreover, other non-invasive techniques were used to measure skin physiological parameters, including transepidermal water loss （TEWL）, stratum corneum hydration （SCH） levels, stratum corneum lipids, skin pH, current perception thresholds of 3 peripheral sensory nerve fibers, and superficial skin blood flow perfusion. Spearman correlation coefficients between stratum corneum components and the total sting score as well as total burning pain score were analyzed, so were Pearson correlation coefficients between the stratum corneum components and skin physiological parameters. Results A total of 73 volunteers completed all tests, including 15 males and 19 females aged 41.8 ± 8.9 years in the sensitive skin group, and 19 males and 20 females aged 42.8 ± 9.4 years in the normal skin group. Compared with the normal skin group, the sensitive skin group showed significantly decreased levels of stratum corneum NMF （30.90 ± 7.38 vs. 37.01 ± 8.77, t = 3.193, P < 0.01） and FFA （14.90 ± 6.75 vs. 20.45 ± 11.76, t = 2.422, P < 0.05）, but significantly increased β/α ratio （3.17 ± 1.03 vs. 2.67 ± 0.56, t = -2.595, P < 0.05）; there was no significant difference in stratum corneum lipid content between the two groups （t = 1.458, P > 0.05）. As far as the skin physiological parameters were concerned, the sensitive skin group showed significantly increased TEWL （t = -3.496, P < 0.001）, but significantly decreased current perception thresholds at a frequency of 5 Hz and epidermal density （both P < 0.05） compared with the normal skin group; no significant difference in stratum corneum lipid content was observed between the two groups （P > 0.05）. Correlation analysis revealed that NMF, FFA and β/α ratio were significantly correlated with TEWL （r = -0.405, -0.562, 0.503, respectively, all P < 0.01） and total sting score （rs = -0.401, -0.285, 0.316, respectively, P < 0.01 or 0.05）; meanwhile, epidermal density was also significantly correlated with NMF （r = 0.402, P < 0.01） and β/α ratio （r = -0.369, P < 0.05）. However, none of NMF, FFA and β/α ratio was correlated with stratum corneum lipid content, current perception thresholds of the 3 sensory nerve fibers, superficial skin blood flow perfusion or epidermal thickness （all P > 0.05）. Conclusions NMF, FFA and β/α ratio in the stratum corneum significantly differed between the sensitive skin and normal skin, and were significantly correlated with some physiological parameters related to stratum corneum barrier function. ATR-FTIR spectroscopy is an effective method for evaluating barrier function of sensitive skin.

Key words: Skin physiological processes, Sebum, Sensitive skin, Stratum corneum barrier, Attenuated total reflectance-Fourier transform infrared