INTRODUCTION
With an estimated prevalence of 9.4% globally, acne vulgaris (hereafter referred to as acne) is one of the most common cutaneous diseases worldwide, with one of the highest disease burdens of disease.1 Mechanistically speaking, acne is a complex, multifactorial skin condition associated with reduced levels of filaggrin2 and aquaporin-33 proteins, impaired barrier function,4 and increased transepidermal water loss (TEWL),5 which can lead to skin dryness, sensitivity, and irritation.4 Furthermore, prescription and over-the-counter (OTC) actives commonly used to treat and prevent acne, such as retinoids and benzoyl peroxide, help accelerate skin cell turnover and suppress sebum production via keratolytic, comedolytic, sebostatic, and/or bactericidal mechanisms of action,6,7 thereby causing skin dryness and irritation4,6 and affecting patients' compliance with treatment.8,9 Moreover, harsh cleansers formulated with traditional small-monomer surfactant micelles can also cause skin dryness and irritation by washing away essential natural moisturizing factor (NMF) compounds naturally present in the skin. A lightweight moisturizer that provides long-lasting skin hydration without a greasy residue is an ideal adjunctive product for acne patients who may have excess sebum but also suffer from acne-related dryness and irritation.4,10
Stratum corneum (SC) moisture levels are critical for enzymatic processes involved in surface desquamation,11-14 which help maintain proper barrier function. Low SC moisture content can inhibit the desquamation process, causing non-viable skin cells to accumulate and clog pores, which leads to the formation of acne lesions.15,16 SC corneocytes contain various hygroscopic molecules (e.g., amino acids, urea, saccharides, and electrolytes) that comprise the NMF and efficiently bind water to support moisture retention and barrier function.17-19 Epidermal proteins such as filaggrin and aquaporin-3 play a critical role in sustaining SC hydration and barrier integrity.20-24 Through enzymatic metabolism, for example, filaggrin breaks down into free amino acids that constitute a significant proportion of the NMF residing in the SC corneocytes.20-22,24 Moreover, filaggrin deficiency has been associated with increased TEWL2,20-22,24 and acne.2 Aquaporin-3 supports the transport of water molecules (among others) from the deeper epidermal layers to the surface SC layer, and deficiency has been shown to decrease the SC's water-holding capacity (capacitance).3,25,26
Stratum corneum (SC) moisture levels are critical for enzymatic processes involved in surface desquamation,11-14 which help maintain proper barrier function. Low SC moisture content can inhibit the desquamation process, causing non-viable skin cells to accumulate and clog pores, which leads to the formation of acne lesions.15,16 SC corneocytes contain various hygroscopic molecules (e.g., amino acids, urea, saccharides, and electrolytes) that comprise the NMF and efficiently bind water to support moisture retention and barrier function.17-19 Epidermal proteins such as filaggrin and aquaporin-3 play a critical role in sustaining SC hydration and barrier integrity.20-24 Through enzymatic metabolism, for example, filaggrin breaks down into free amino acids that constitute a significant proportion of the NMF residing in the SC corneocytes.20-22,24 Moreover, filaggrin deficiency has been associated with increased TEWL2,20-22,24 and acne.2 Aquaporin-3 supports the transport of water molecules (among others) from the deeper epidermal layers to the surface SC layer, and deficiency has been shown to decrease the SC's water-holding capacity (capacitance).3,25,26
