Background Podoplanin (PDPN)/T1/aggrus/PA2.26 antigen, a transmembranous glycoprotein, is a well-known lymphatic endothelial marker. Recent evidence indicates that PDPN is also expressed in keratinocytes especially of sebaceous glands.Objective To verify expression-pattern and the regulatory mechanism of PDPN in human epidermal keratinocytes Methods PDPN-expression pattern was analyzed in normal and psoriatic epidermis by immunostaining. The regulatory mechanism of PDPN-expression of keratinocytes by cytokines was analyzed using specific inhibitors, siRNA, and adenoviral shRNA of signaling pathways.Results In normal skin, PDPN was expressed on the basal cell layer of sebaceous glands and on the outer root sheath of hair follicles. While no expression was detected in the normal interfollicular epidermis, PDPN was detected in the basal cell layer of wound and hyperproliferative psoriatic epidermis, where the granular layer is lacking.