Abstract: Objective To investigate the ultrastructural characteristics of amelanotic melanocytes (AMMCs). Methods Individual hair follicles from normal human scalp were digested with collagenase type V, then washed in phosphate buffer saline. Hair-follicle cell suspensions were prepared by trypsin and cultured in a medium suitable for melanocyte growth. The keratinocytes were removed by differential trypsinization. Geneticin (100μg/mL) was used to eliminate contaminating fibroblasts. After 3 passages the cells were trypsinized, washed in phosphate buffer saline, and finally processed for transmission electron microscopy. Results Under transmission electron microscope, the cultured cells were round or oval-shaped with a single large nucleus and double-layered karyotheca. Abundant euchromosome but sparse heterochromosome was observed within the nucleus. There were various organelles in the cytoplasm, including mitochondria, rough endoplasmic reticulum (RER), ribosomes and abundant melanosomes of nearly uniform size. The electronic density granules distributed in a concentric pattern in most of the melanosomes. Colgi complexes were inconspicuous in the cells. Conclusions Compared to epidermal melanocytes, AMMCs from human hair follicles have different ultrastructural characteristics which implies their functional immaturity. AMMCs may serve as the depot for mature melanocytes.

Key words: Melanocytes, Melanosomes, Microscopy,electron