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Degree

PhD, University of Cincinnati, Pharmacy : Pharmaceutical Sciences, 2009.

Abstract

Natural moisturizing factor (NMF) is essential for stratum corneum hydration, barrier homeostasis, desquamation and plasticity. It is formed from filaggrin proteolysis to small, hygroscopic molecules including individual amino acids, lactic acid, urea, etc. Although NMF levels have been extensively studied in normal and abnormal skin conditions, the effects of perturbations such as water exposure, barrier damage and repair, even variations across the body surface, are poorly understood. Biophysical measurements such as TEWL (transepidermal water loss) or MAT (moisture accumulation test) are commonly used in cosmetic laboratories without a clear understanding of what these instruments are measuring in the skin. The detrimental effects to the skin of long water exposure are well known. Soak baths of relatively brief duration, up to 20 minutes in length, have been shown to temporarily increase skin hydration and reduce scaling, while extended water exposure causes maceration, disruption of the skin barrier, and a dry flaky appearance once the excess water evaporates. The boundary between therapeutic and damaging effects of water exposure is unknown, as is the etiology of the resulting damage. Conversely, NMF itself relies on water; NMF production depends on ambient humidity levels, with an optimal humidity range of 80-95%. We hypothesized that minor perturbations of the skin and differing anatomical locations generate differences in NMF levels, and that these changes in NMF are reflected by alterations in the biophysical properties of the skin. To this end, a novel method of quantifying the amino acid components of NMF, using D-Squames® for stratum corneum (SC) sampling is presented and validated. This method was used in conjunction with conventional bioengineering methods (MAT, TEWL, pH) to investigate the relationships between skin biophysical properties and NMF levels. The work focused on the effects of water on NMF, both as soaking and occlusion, and also explored the effect of regional variation on NMF and biophysical measurements. Studies were conducted on the effects on NMF of soaking the skin with and without lipid extraction, barrier damage and repair under various humidities, and regional variation. Increased NMF was found with increased SC depth. Also, combining extraction and soaking increased NMF loss relative to control or to extraction or soaking alone. In studies on the effect of water alone, replacement of NMF over a four hour time period after soaking occurred, corresponding to a recovery in SC pH. Two studies on the effect of humidity on barrier integrity showed significant suppression of barrier repair by wet dressings, with barrier damage also occurring due to occlusion alone. Smaller than expected differences in NMF levels were found between body sites, although SC cohesiveness measurements agreed with published results. NMF levels were weakly correlated to MAT and negatively correlated to SC pH. In sum, the NMF is a complex mixture whose effects on skin condition as measured visually and biophysically is entangled with many other factors and thus difficult to isolate. NMF is clearly a significant determinant of the condition of skin but our results indicate that other factors play important roles.

Subject Headings

Biochemistry; Biomedical research; Occupational safety; Pharmaceuticals

Keywords

natural moisturizing factor; skin; pH; body sites; skin barrier

Committee / Advisors

R. Randall Wickett, PhD (Committee Chair)
Gerald Kasting, PhD (Committee Member)
Marty Visscher, PhD (Committee Member)
Steven Hoath, MD (Committee Member)
Pankaj Desai, PhD (Committee Member)

Pages

1166p.

Document number: ucin1243351990
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=ucin1243351990

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