PROLIFERATIVE MERKEL CELLS WERE NOT DETECTED IN HUMAN SKIN

The fetal development of Merkel cells - neuroendocrine cells of the sk in - has been a matter of debate for a long time. Recent results have helped to confirm their intraepidermal development in humans. Simple e pithelial cytokeratins (CK) nos, 8, 18, 19 and 20 are well established markers at the light microscopic level. These cells could be detected from fetal week 8 within the epidermis with an enormous increase duri ng the following weeks, This gives rise to the question as to whether Merkel cells are undergoing mitoses or whether they are derived from b asal keratinocytes. We studied fetal and adult skin using antibodies t o simple epithelial CK and to Ki67, a human nuclear cell proliferation -associated antigen in an attempt to answer these questions. In human adult and fetal skin of various stages me could not detect any Merkel cells undergoing cell division. These results suggest that Merkel cell s are postmitotic cells to be renewed from undifferentiated keratinocy tes with stem cell characteristics.