Abstract: Objective To investigate the interaction between human epidermal melanocytes (EMCs) and follicular keratinocytes (FKCs) in direct contact co-culture.Methods Single-cell suspension was obtained by treating the isolated hair follicles and preputial epidermis with pancreatin,then FKCs and EMCs were respectively purified at the second passage.The third passage of FKCs was seeded in 6-well dishes and cultured for 48 hours,then EMCs were seeded into the same dishes in three different ratios (i.e.,melanocyte:keratinocyte ratios of 1:2,1:10 and 1:20).α-melanocyte-stimulating hormone (α-MSH) and nicotinamide were respectively put into the co-culture system with an initial seeding ratio of 1:10.On the sixth day,the cells were stained by NKI/beteb monoclonal antibody.Results EMCs and FKCs both proliferated quickly after EMCs were seeded in wells in which FKCs had colonized,and an initial seeding ratio of 1:10 was ideal for simulating physiological condition.The system with a ratio of 1:20 provided observation of distinct contact between melanocytic dendrites and keratinocytes.The co-culture with a ratio of 1:2 could product a great quantity of melanocytes,α-MSH had little effect on the proliferation rates of the two types of cells,but markedly increased and elongated the melanocytic dendrites in co-cultures and in melanocyte mono-cultures.Incubation with nicotinamide had no effect on morphology of melanocytes in mono-culture,but it resulted in the retraction of the melanotic dendrites and the distribution of melanosome in the periphery of cell body in co-cultures of FKCs and EMCs.Conclusion Contact co-culture of FKCs and EMCs is a sutiable model for the investigation of human pigmentary system.

Key words: Cells,cultured, Melanocytes, Keratinocytes, Niacinamide