The majority of epidermal Merkel cells are non-proliferative: a quantitative immunofluorescence analysis

Although epidermal Merkel cells (MC) are able to form synapses and synthetize neuromediators, they can be considered as being of epithelial nature because of the presence of cytokeratins in their cytoskeleton and desmosomes on their membranes. Since epidermis is an epithelium undergoing permanent renewal, it was important to determine whether MC were able to renew, as neighbouring keratinocytes do. This was investigated by studying whether S phase nuclei could be found in cells bearing a specific MC marker. The technique consisted of injecting rabbits with bromodeoxyuridine (BrdUrd) and performing double immunofluorescence on skin sections with the antikeratin number 8 monoclonal antibody (MAb) TROMA-I and anti-BrdUrd MAb. The results show that, in contrast to the neighbouring epidermal cells, the great majority of MC were found to be devoid of BrdUrd labelling, indicating that most of these cells are unable to divide, or divide very rarely.