Melanogenesis inhibition in mice using a low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser: a pilot study

Abstract

A low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser, or laser toning, has yielded favorable outcomes in various benign pigmented disorders. However, the exact mechanism of action of laser toning has not been fully elucidated. We sought to determine the inhibitory effect of laser toning on melanogenesis and to assess how laser passes influence the outcomes. To produce perceptible pigmentation, nine HRM-2 melanin-possessing hairless mice were treated with ultraviolet (UV) B radiation on the dorsal skin. This was followed by zero, two, four, or six passes of laser toning twice in 2 weeks on each designated quadrant. The spectrophotometric values and pigmentation-related protein expressions were measured. Pigment changes were found in the mice skin using the Fontana-Masson stain for histopathological analysis. Four- and six-pass laser toning significantly improved the lightness compared to that in the unirradiated control (p < 0.002). The Fontana-Masson stain showed that melanin was considerably decreased in laser-irradiated skin. As the number of laser passes increased, the expression of tyrosinase decreased (p < 0.008). The following parameters also decreased in proportion to the number of laser passes: MITF, TRP-1, TRP-2, p-ERK, and p-Akt. In contrast, TGF-β increased in proportion to the number of laser passes. However, the changes in these six proteins were not statistically significant. Our study demonstrates that laser toning improves skin pigmentation with increased number of passes in a dose-dependent manner. This effect is mediated by tyrosinase inhibition.

Laser toning in melasma

“…Melanogenic stimulators, including a-MSH and NGF, were also reduced. Similar results were also reported by Nam et al [16] They also reported that there is a positive correlation between number of passes and pigmentation improvement. Omi et al [17] compared ultrastructural changes after toning with QSL to q-switched ruby laser and concluded that QSL toning offered superior results with less epidermal disruption and cellular damage, thus, confirming the safety of toning with QSL.…”

Five hundred and thirty‐two‐nanometer Q ‐switched Nd:Yag laser with larger fractional spot: A novel and safe technique to treat C afé au lait macule—A case report

“…2 The exact mechanism by which low-fluence 1064-nm Q-switched Nd: Yag laser improves pigmentary lesions is not fully clarified; the induction of "subcellular selective photothermolysis" and the inhibition of melanogenesis, reported in mice, has been proposed as hypothesis. 3,4 Five hundred and thirty-two-nanometer Q-switched neodymiumdoped yttrium aluminum garnet (Nd:Yag) laser does not penetrate deeply into the skin and is suitable for epidermal pigmented lesion. 5 We describe a clinical case of a 16-years-old female patient who presented congenital solitary asymptomatic, polygonal, brown stain (Café-au-lait macule), measuring 8 Â 4 cm, on the zygomatic-temporal area of her right face emilate.…”