Skin Types IV-VI Research Articles

Alexandrite Laser Hair Removal is Safe for Fitzpatrick Skin Types IV-VI

Various lasers have been developed for epilation of unwanted hair. Most studies, however, have been done in white patients with minimal reference to dark-skinned individuals. To determine the safety profile of a long-pulsed alexandrite laser for hair removal in patients with Fitzpatrick skin types IV-VI exclusively. Prospective clinical evaluation conducted from June 1998 to April 1999 at a referral private clinic. Prelaser skin testing was performed starting at 16 J/cm2 and energy fluence selected according to response. Complications were recorded at each visit. One hundred and fifty patients are reported (18 men and 132 women) ranging in age from 15 to 50 years, for a total of 550 treatment sites. Complications occurred in only 2% of cases. The long-pulsed alexandrite laser is safe for hair removal in darker skin tones. Prelaser skin testing was not helpful in this study, as there was no relationship between skin reaction and the incidence of complications.

Aging in Epidermal Melanocytes: Cell Cycle Genes and Melanins

With aging, melanocytes become unevenly distributed in the epidermis. In light skin individuals, hypopigmentation is found in association with focal hyperpigmentation (lentigo senilis). Apparently this results from progressive loss of active melanocytes and focal increase in melanocyte proliferation and/or aggregation. This paper summarizes the present knowledge on aging of melanocytes in vivo and in vitro, with a focus on the role of melanin as a determinant for proliferation and terminal differentiation. We describe that excessive melanin deposition by cyclic AMP-inducing agents results in increased expression of the cyclin-dependent kinase inhibitors p27Kp-1 and p21SDI-1/Waf-1, increased binding of p16 to CDK4, and terminal differentiation. Importantly, the efficiency with which the melanocytes exit the cell cycle depends on the melanin background of the donor's cells. Melanocytes from skin types IV-VI that accumulate large amounts of brown black melanin (eumelanin), lose expression of the transcription factors E2F1 and E2F2, two key regulatory proteins, and withdraw from the cell cycle more rapidly than melanocytes from skin types I and II that accumulate red/yellow melanin (pheomelanin). Thus, we propose that terminal differentiation is a tumor suppressor mechanism that becomes less efficient under imperfect eumelanization.