JOURNAL OF COSMETIC SCIENCE 422 the iontophoresis of VC derivatives and some medicines directed to not only the skin but other tissues, since the different polarities between skin/target organs and VC derivatives/ medicines can be regulated by bipolar stimulation. CONCLUSION Gunpatsu pulse was effective at increasing the amount of collagen in skin with either unipolar or bipolar stimulation for less than 10 min. Furthermore, in terms of the ionto- phoresis of VC derivatives, bipolar Gunpatsu pulse stimulation for 5 min was most effec- tive. These results suggest that our methods can be used to increase the amount of collagen in skin, particularly in the case of iontophoresis of substances to the target organ, where bipolar stimulation was more effective. Furthermore, Gunpatsu pulse stimulation has much less of an adverse effect compared to ordinary pulse stimulation. This method can be developed as a novel and safe treatment for the application of medicines. This is the fi rst report that substantiates that the amount of collagen in skin is increased by elec- tric stimulation, Gunpatsu pulse. REFERENCES (1) W. D. Tian, R. Gillies, L. Brancaleon, and N. Kollias, Aging and effects of ultraviolet A exposure may be quantifi ed by fl uorescence excitation spectroscopy in vivo, J. Invest. Dermatol., 116(6), 840–845 (2001). (2) T. Quan, T. He, S. Kang, J. J. Voorhees, and G. J. Fisher, Solar ultraviolet irradiation reduces collagen in photoaged human skin by blocking transforming growth factor-beta type II receptor/Smad signaling, Am.J. Pathol., 165(3), 741–751 (2004). (3) L. Reinisch, J. A. Muccini, Jr., and T. Fuller, Quantitative and qualitative evaluation of skin laser, Lasers Surg. Med., 167(Suppl. 11), 41 (1999). (4) J. A. Muccini, Jr., F. E. O’Donnell, Jr., T. Fuller, and L. Reinisch, Laser treatment of solar elastosis with epithelial preservation, Lasers Surg. Med., 23, 121–127 (1998). (5) K. M. Kelly, J. S. Nelson, G. P. Lask, R. G. Geronemus, and L. J. Bernstein, Cryogen sprays cooling in combination with nonabrasive laser treatment of facial rhytides, Arch Dermatol., 135, 691–694 (1999). (6) L. Zhang, S. Lerner, W. V. Rustrum, and G. A. Hofmann, Electroporation mediated topical delivery of vitamin C for cosmetic applications, Bioelectrochem. Bioenerg., 48(2), 453–461 (1999). (7) P. Batheja, R. Thakur, and B. Michniak, Transdermal iontophoresis, Expert Opin. Drug Deliv., 3(1), 127–138 (2006). (8) M. Ebihara, M. Akiyama, Y. Ohnishi, S. Tajima, K. Komata, and Y. Mitsui, Iontophoresis promotes percutaneous absorption of L-ascorbic acid in rat skin, J. Dermatol. Sci., 32(3), 217–222 (2003). (9) M. Kakinuma, Y. Watanabe, Y. Hori, T. Oh-I, and R. Tsuboi, Quantifi cation of hydroxyproline in small amounts of skin tissue using isocratic high performance liquid chromatography with NBD-F as fl uoro- genic reagent, J. Chromatogr. B, 824(1–2), 161–165 (2005). (10) G. Menaker, Treatment of facial rhytides with a nonabrasive laser: A clinical and histologic study, Der- matol. Surg., 25, 440–444 (1999). (11) S. N. Doshi and T. S. Alster, 1,450 nm long-pulsed diode laser for nonablative skin rejuvenation, Der- matol, Surg., 31, 1223–1226 (2005). (12) M. A. Trelles, I. Allones, J. L. Levy, R. G. Calderhead, and G. A. Moreno-Arias, Combined nonablative skin rejuvenation with the 595- and 1450-nm lasers, Dermatol. Surg., 30(10), 1292–1298 (2004). (13) E. F. Rostan, Laser treatment of photodamaged skin, Facial Plast. Surg., 21(2), 99–109 (2005). (14) N. N. Byl, A. L. McKenzie, J. M. West, J. D. Whitney, T. K. Hunt, H. W. Hopf, and H. Scheuenstuhl, Pulsed microamperage stimulation: A controlled study of healing of surgically induced wounds in Yucatan pigs, Phys. Ther., 74(3), 201–218 (1994). (15) L. J. Bernstein, A. N. Kauvar, M. C. Grossman, and R. G. Geronemus, The short- and long-term side effects of carbon dioxide laser resurfacing, Dermatol. Surg., 23(7), 519–525 (1997).

J. Cosmet. Sci., 60, 423–428 (July/August 2009) 423 The effect of N-acetyl-glucosamine on stratum corneum desquamation and water content in human skin T. MAMMONE, D. GAN, C. FTHENAKIS, and K. MARENUS, Estee Lauder Research Laboratory, Melville, NY 11747. Accepted for publication February 11, 2009. Synopsis Alpha-hydroxy acids have been used topically to treat skin for both dermatological and cosmetic problems for many years. Though there are many known benefi ts of the use of alpha-hydroxy acids on skin, there have been recent reports that topical treatments with alpha-hydroxy acids increase skin damage resulting from UVB. Additionally, high concentrations of alpha-hydroxy acids by themselves have also been found to cause skin irritation. In order to fi nd alternatives to alpha-hydroxy acids, we investigated a variety of amino sugar compounds that were previously reported to inhibit the reaggregation of dissociated corneocytes by modulating cellular adhe- sion. In vivo, we observed that topical treatments with a formulation containing N-acetyl-glucosamine (NAG) led to an increase in skin moisturization, a decrease in skin fl akiness, and the normalization of stratum cor- neum exfoliation. In vitro, we observed an upregulation of differentiation markers, keratin 10 and involucrin, in keratinocytes treated with NAG. CD44 is a lectin cell adhesion molecule that is also expressed in kerati- nocytes. Amino sugars such as NAG may competitively bind to CD44, modulating keratinocyte cellular adhesion. We hypothesize that these amino sugars modulate keratinocyte cellular adhesion and differentia- tion, leading to the normalization of stratum corneum exfoliation. We propose the use of amino sugars such as NAG as alternative compounds to replace the use of alpha-hydroxy acids in skin care. INTRODUCTION Alpha-hydroxy acids have been used for a number of years to treat skin for both dermato- logical and cosmetic problems (1). Topical treatments with alpha-hydroxy acids have clearly demonstrated an anti-aging effect (2), photoprotection (3), and anti-infl ammatory activity (3). However, the mechanism by which alpha-hydroxy acids operate is largely unknown. One hypothesis for their mechanism of action is that they lower corneocyte cohesion (4) and thereby enhance the stratum corneum exfoliation process. This mechanism of action suggests, however, a purely denaturing effect on the proteins of the epidermis and repre- sents a low specifi c functionality. This is demonstrated by the fact that high concentra- tions, 5–10%, of alpha hydroxy acids have a direct irritating effect. In order to develop alternatives to the use of alpha-hydroxy acids with higher specifi c activity and fewer side effects, we have been investigating a variety of materials. One such class of compounds is amino sugars. These have been reported by Brysk et al. (5) to inhibit