Melanocyte stem cells as potential therapeutics in skin disorders.

INTRODUCTION: Melanocytes produce pigment granules that color both skin and hair. In the hair follicles melanocytes are derived from stem cells (MelSCs) that are present in hair bulges or sub-bulge regions and function as melanocyte reservoirs. Quiescence, maintenance, activation and proliferation of MelSCs are controlled by specific activities in the microenvironment that can influence the differentiation and regeneration of melanocytes. Therefore, understanding MelSCs and their niche may lead to use of MelSCs in new treatments for various pigmentation disorders. AREAS COVERED: We describe here pathophysiological mechanisms by which melanocyte defects lead to skin pigmentation disorders such as vitiligo and hair graying. The development, migration and proliferation of melanocytes and factors involved in the survival, maintenance and regeneration of MelSCs are reviewed with regard to the biological roles and potential therapeutic applications in skin pigmentation diseases. EXPERT OPINION: MelSC biology and niche factors have been studied mainly in murine experimental models. Human MelSC markers or methods to isolate them are much less well understood. Identification, isolation and culturing of human MelSCs would represent a major step toward new biological therapeutic options for patients with recalcitrant pigmentary disorders or hair graying. By modulating the niche factors for MelSCs, it may one day be possible to control skin pigmentary disorders and prevent or reverse hair graying.