The human melanocyte and melanoblast populations per unit area of epidermis in the rete ridge are greater than in the inter-rete ridge.

OBJECTIVE

In human skin, melanocytes and melanoblasts are mostly located in the epidermis in addition to hair follicles. In hairy skin such as mouse skin, the inter-follicular epidermis is generally flat. In contrast, in human skin, the epidermis is wavy and possesses well-developed rete ridges. It is not well understood what difference exists in cell function between melanocytes present in the inter-rete ridge and those in the rete ridge. To clarify this problem, we first tried to determine the melanocyte and melanoblast populations per unit area of epidermis both in the rete ridge and inter-rete ridge epidermis.

METHODS

Thirty-eight samples from normal skin sites of 28 patients (14 males and 14 females) aged from 5 to 76 years were fixed and processed to dopa and combined dopa-premelanin reactions. The numbers of cells positive to the dopa (melanocytes) and combined dopa-premelanin (melanoblasts and melanocytes) reactions were scored.

RESULTS

The average melanocyte population/0.1 mm of the inter-rete ridge was 74 cells, whereas that of the rete ridge was 147 cells. Moreover, the average melanoblast population/0.1 mm in the inter-rete ridge was 43 cells, whereas that of the rete ridge was 131 cells. The melanoblast population in the rete ridge differed between female and male, but the melanocyte populations in the rete ridge and inter-rete ridge and the melanoblast population in the inter-rete ridge did not differ between female and male. However, no age difference in the melanocyte and melanoblast populations was observed between the rete ridge and inter-rete ridge.

CONCLUSION

Human epidermal melanocytes and melanoblasts in the rete ridge exist more numerously than in the inter-rete ridge.