Abstract: Objective To analyze the sensitivity of vitiligo melanocytes to external oxidants and the role of oxidative stress in the pathogenesis ofvitiligo.Methods Melanocytes were isolated from the epidermis of normal-appearing skin of 4 vitiligo patients and from that of 6 normal human controls,and subjected to primary culture.The cultured melanocytes were exposed to 0.5 mmol/L hydrogen peroxide for 1 h.The cell ultrastructural characteristics were observed by transmission electron microscopy.Stereological image analysis was also performed to assess the ultrastructural changes of mitochondria,rough endoplasmic reticulum and melanosome.Results The 0.5 mmol/L hydrogen peroxide had no significant effect on the morphology or ultrastructure of cell organelles of the normal control melanocytes,whereas the number of mitochondria and rough endoplasmic reticulum were significantly decreased in melanocytes after the treatment compared with the melanocytes without any treatment(P<0.05) and the control melanocytes(P<0.01). Partial vacuolization of mitochondria and dilation of endoplasmic reticulum were observed in vitiligo melanocytes treated with hydrogen peroxide.No significant difference was found in the number of melanosomes among the vitiligo melanocytes with and without treatment as well as the control melanocytes (P>0.05),even though the volume increase was found in some melanosomes.Conclusion Our results suggest that hydrogen peroxide could impair the function of melanocytes and induce the development of vitiligo, likely by interfering with the energy metabolism and protein synthesis in these cells.

Key words: Vitiligo, Melanocytes, Microscopy,electron,transmission