Stage-specific embryonic antigen-4 as a novel marker of ductal cells of human eccrine sweat glands

Background Different populations of unipotent or multipotent stem cells have been identified in human epidermis and its appendages. It is well documented that these cells maintain tissue homeostasis and actively participate in epidermal regeneration after injury. However, there is no evidence of the presence of pluripotent stem cells in human epidermis. Objectives In this study we investigated whether cells positive for embryonic stem cell marker stage-specific embryonic antigen-4 (SSEA-4) are present in adult human epidermis and, if so, whether they are pluripotent and correspond to the population of primitive stem cells. Methods The expressions of SSEA-4 and pluripotency transcription factors were analysed using flow cytometry. By means of immunohistochemical staining, we studied the exact localization of these cells in sections of human skin. Results We show that a population of SSEA-4(+) cells is present in human epidermis. In contrast to the commonly accepted belief, the expression of SSEA-4 is not connected with the pluripotent character of isolated cells. We found that these SSEA-4(+) cells are localized in the ducts of eccrine sweat glands. Conclusions Our results indicate that SSEA-4 is a novel marker identifying the ductal cells of human sweat glands. The surface character of the antigen provides for a simple method of isolating this cell population and suggests applications of SSEA-4 for future cell therapy research.