Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Denmark

Correspondence: Dr Robert Gniadecki, Department of Dermatology D92, Bispebjerg Hospital, Bispebjerg bake 23, DK-2400 Copenhagen NV, Denmark; Email: rg01@bbh.hosp.dk

¹Present address: Department of Dermatology, Gentofte Hospital, University of Copenhagen, Denmark.

Received 15 December 2002; Revised 17 January 2003; Accepted 19 February 2003; Published online 18 August 2003.

Abstract

Lipid rafts are dynamic membrane microdomains enriched in cholesterol and sphingolipids and are involved in the regulation of a variety of cellular processes, such as proliferation, apoptosis and cell motility. We have previously described that large lipid raft aggregates are readily detectable on cultured keratinocyte cell line HaCaT by staining with the fluorescein-tagged cholera toxin (CTx-FITC). In this paper we adopted this method for the detection of lipid rafts in human epidermis and keratinocytes in culture. Double labelling of showed the non-overlapping clusters of basal cells in human epidermis: CD29^dimCTx-FITC^bright cells in the deep rate ridges and CD29^brightCTx-FITC^dim cells at the tips of dermal papillae. A similar patchy, non-overlapping staining pattern was observed in cultured keratinocytes in vitro. CTx-FITC^bright cells are mitotically active whereas a large proportion of CTx-FITC^dim cells are quiescent. We conclude that the epidermal stem-like cells, previously shown to occupy the tips of dermal papillae and to exhibit high density of membrane 1 integrin have a low content of lipid rafts. In contrast, the putative transit amplifying cells in deep rate ridges show enrichment in lipid rafts. Thus, lipid rafts may be a factor controlling the mitotic activity of epidermal keratinocytes and possibly the differentiation of stem cells into the transit amplifying cells.