Changes In Dendritic Length,proliferation,and Melanogenesis Of Epidermal Melanocytes Exposed To Three Types Of LED Light And UV Radiation

Backgrounds and ObjectivesLight-emitted diode(LED)type phototherapy has been widely used for the treatment of many skin conditions such as acne,skin inflammatory conditions and even hair loss.However,there are sporadic reports of LED lights appearing to cause hyperpigmentation as a side effect of treating skin.Relatively little is known about whether LED phototherapy directly affects phenotypical alteration and melanin production in melanocytes(MC)of the skin.Our aim is to investigate the effect of different types of phototherapies on morphological changes and cell division in MC in the cultured human epidermal sheet model and melanin synthesis in a mouse tail skin.Methods1.Established the model of MC within the epidermis in vitro,Dopa staining was respectively performed at 0h,2h,6h,8h and 12 h after the single irradiation of UVA(320-400nm),308 nm excimer light(308nm EL)and LED-red(630nm),-yellow(585nm),-blue(430nm),then observed the morphological changes of melanocyte.2.The molecular mechanisms involved in dendritic elongation were also studied.The melan-a cells with a single dose of LEDs/UV irradiation were selected to detect the expression of Rac1 and Rho A m RNA which regulate the dendritic related genes of melanocyte.3.The mouse tail was irradiated with LEDs or/UV every other day for a total of three exposures.Fontana–Masson staining was carried out to visualize melanin content and distribution in the tail skin.4.Meanwhile,the melanocytes division labeled with Ed U incorporation and immunostained using a panel of specific antibodies against c-kit(immature MC marker),Tyrp2/Dct(MC stem cell marker)to visualize the mitosis of MC within the epidermis.Results1.There was no significant difference in cell number and dendritic length between treated and untreated groups for the three LED light irradiation therapies.In contrast,significant increases were observed in UVA-and 308 nm excimer light(EL)-treated specimens.The q PCR results showed that when compared with the sham-irradiated control,the Rac1 m RNA levels were significantly elevated in the cells treated with UVA or/ 308 nm EL,whereas the Rho A m RNA expression was only upregulated in the three LED light-treated groups.2.Fontana–Masson staining found a great number of continuous zonal melanin granules can be observed in the basal layer,particularly 308 nm EL group was the greatest one above all(P(27)0.01).while,less pronounced melanin deposits were observed in LEDs groups and the control group(P(29)0.05).3.After tracking the mitotic activity of MC in cultured human epidermal sheet,the results showed that 308 nm EL predominately stimulated immature MC other than mature MC to divide.ConclusionsThe three types of LED light fail to directly stimulate the MC to proliferate and to produce more melanin.308 nm EL exerts a potent photobiostimulation towards immature MC,which can not only prolong the dendrites of immature MC in human epidermis,but also promote MC mitosis and melanogenesis and effectively promoting vitiligo repigmentation.