The integrity of the human stratum corneum (SC) is crucial for maintaining skin barrier function, primarily facilitated by a lipid matrix composed of ceramides, cholesterol, and free fatty acids. Among these lipids, ceramides exhibit the most molecular diversity, and their composition and quantity significantly impact the epidermal barrier’s permeability. While ceramide NP has been widely utilized in skincare for its barrier-repairing properties, the functional roles of less abundant ceramide subclasses, such as 1-O-acylceramides, are still being elucidated. This study6 addressed the knowledge gap regarding phytosphingosine-based 1-O-acylceramide (CerENP), which, despite prior identification of other 1-O-acylceramides like CerENS and CerEAS, had not been reported in human skin. Given in vitro evidence suggesting CerENP’s potential to enhance lipid lamellar organization, this research aimed to identify CerENP in the human SC and investigate its physiological role in skin barrier function, particularly in synergy with CerNP, as a potential strategy for improving moisturizers.
Methods
The researchers employed a combination of analytical and in vivo techniques. Human stratum corneum samples were obtained through tape stripping, and the presence of CerENP was confirmed using liquid chromatography/high-resolution mass spectrometry (LC-HRMS). Subsequently, a double-blind, vehicle-controlled human study involving 20 volunteers was conducted. Test creams containing a fixed concentration of CerNP (0.2%) and varying concentrations of CerENP (0.02%, 0.05%, 0.2%, and 0.5%) were applied to the forearms of participants for four weeks, and skin hydration, moisture retention, and SC cohesion were measured. Additionally, the formation and stability of Maltese crosses in the test creams were observed using cross-polarized microscopy.
Key Findings:
•Identification of 1-O-Stearoyl-Ceramide NP (18:0-t18:0/18:1) in Human Stratum Corneum: The study successfully identified 1-O-stearoyl-ceramide NP (18:0-t18:0/18:1) in human stratum corneum extracts using LC-HRMS, matching its fragmentation pattern with a synthetic standard.
•Profiling of 1-O-Acylceramide NP (CerENP) in Human Stratum Corneum: Further LC-HRMS analysis revealed the presence of nine different species of CerENP in the human SC, with saturated N-acyl chains being predominantly observed. Multiple isobaric isomers were also detected for most CerENP species.
•Effects of CER 1-O-ENP on Multilamellar Formation and Its Stability: In vitro observations showed that the addition of CerENP to CerNP-containing creams enhanced the formation of Maltese crosses, indicating improved lipid lamellar organization. Notably, CerENP also significantly increased the long-term stability of these lamellar structures over six months.
•The Influence of CER 1-O-ENP on Skin Hydration: The human study demonstrated that incorporating a small percentage (0.02% or 0.05%) of CerENP into a CerNP (0.2%) cream led to a significant increase in skin hydration after four weeks compared to the CerNP cream alone. Moreover, the combination of CerENP and CerNP resulted in superior and long-lasting moisture retention after the cessation of cream application.
•CER 1-O-ENP Fostered SC Cohesion: Measurements of transepidermal water loss (TEWL) after tape stripping indicated that test creams containing CerENP significantly improved stratum corneum cohesion, making the skin more resistant to physical stress, with 0.02% CerENP showing notable effects.
This research provides the novel finding of the presence and characterization of phytosphingosine-based 1-O-acylceramide (CerENP) in the human stratum corneum. The key innovation lies in demonstrating that a surprisingly small amount of CerENP can significantly boost the skin barrier functions of CerNP, leading to enhanced hydration, prolonged moisture retention, and improved SC cohesion in human skin. These results highlight a new understanding of the synergistic interactions between different ceramide classes and suggest that optimizing the relative ratio of CerENP and CerNP could be a promising strategy for developing more effective moisturizers, particularly for individuals with dry and atopic skin. Future studies should delve deeper into the molecular mechanisms underlying CerENP’s boosting effects and explore its potential interactions with other lipid components and skin structures like natural moisturizing factors and corneodesmosomes. This research opens new avenues for formulating advanced dermatological and cosmetic products with enhanced skin barrier repair and hydration capabilities.
Link to the study: https://www.mdpi.com/2079-9284/12/2/47
