Water Distribution and Natural Moisturizer Factor Content in Human Skin Equivalents Are Regulated by Environmental Relative Humidity

Abstract

Human skin equivalents (HSEs) show great similarities to human native skin. However, one of the key processes impaired under in vitro conditions is desquamation. Desquamation involves the degradation of the corneodesmosomes, in which various enzymes participate. Activation of these enzymes is affected by several microenvironmental factors such as pH and water level. The water level is assumed to depend on the presence of natural moisturizing factors (NMF). In this study, the levels of water and one of the prominent NMF components--pyrrolidone carboxylic acid (PCA)--were examined. In HSE generated under normal culture conditions (93% relative humidity (RH)), the water level and PCA content appeared to be much lower than in the native counterpart. To increase the water and PCA levels in HSE, a culture method was established in which HSE was reconstructed under reduced RH. Although at 40% RH the PCA levels in reconstructed and native tissue are similar, the hydration levels in reconstructed tissue remain still lower. Only topical application of water induced marked swelling of corneocytes. This clearly shows that the stratum corneum water level in HSE is regulated by other, still unknown, factors, in addition to NMF.

Confocal Raman spectroscopy: determination of natural moisturizing factor profile related to skin hydration

“…During the aging process of skin, cell renewal is slower, facilitating the action of hydrolytic enzymes that are responsible for breaking the chains of the filaggrin protein. The disruption of these protein chains results in the release of amino acids and their derivatives, such as pyrrolidone carboxylic acid (PCA) and urocanic acid (UCA), which are responsible for composing the NMF (Bouwstra et al, 2008). Urocanic acid is the result of the metabolic degradation of histidine, an amino acid found in human skin that has a high absorption capacity for UVB rays.…”

Lowered Humidity Produces Human Epidermal Equivalents with Enhanced Barrier Properties

“…In a previous report, 41 it was noted that a reduction in environmental humidity increased SC hydration levels in HEEs. Yet TEWL rates were not altered by differences in SC hydration properties.…”

“…The Ca 2 + and pH gradients are involved in maintaining epidermal permeability homeostasis. [48][49][50] There is a link between ambient humidity and enhanced barrier function that has been described in both animals and humans, 25,51 and recapitulated in vitro with neonatal human keratinocytes, 41,52,53 although the exact molecular mechanisms remain unknown.…”

Overcoming antibiotic resistance in treatment of pyoderma

“…Образование компонентов NMF происходит при протеолитическом распаде филаггрина -в ро-говом слое образуются «микстура» из поликарбок-силовых кислот и гигроскопичных аминокислот, мочевины, лактатных соединений и ионов металлов [2]. В детской коже синтез компонентов NMF несо-вершенен и происходит менее интенсивно, чем у взрослых.…”