Leukaemia inhibitory factor is expressed by normal human keratinocytes in vitro and in vivo

Leukaemia inhibitory factor (LIF) is a pleotropic cytokine, regulating differentiation, cell growth, cachexia and inflammation. Using the reverse transcription-polymerase chain reaction (RT-PCR) we found that, in culture, normal human keratinocytes (KC) expressed mRNA transcripts for both LIF and the LIF receptor. In the conditioned medium (CM), constitutive LIF protein production was barely detectable but stimulation of KC with 10 ng/ml of either interleukin (IL)-1 alpha, or IL-8, for 24 h, resulted in small but significant increases (P < 0.05) in LIF protein, as measured by enzyme-linked immunosorbent assay. After culture in media containing 1.5 mmol/l calcium, a time-dependent increase in LIF mRNA was seen up to 72 h (an 8.5-fold increase), over levels in cells cultured in 0.05 mmol/l calcium. A large increase in LIF protein in the CM (from 1.15 +/- 0.15 pg/ml to 178.7 +/- 75.7 pg/ml) was seen 72 h after a switch to media containing 1.5 mmol/l calcium (P = 0.05). Twenty-four hours after stimulation of human KC in culture with 10 ng/ml recombinant LIF, a twofold increase in both IL-1 alpha and IL-8 protein in the CM (P < 0.05) was observed. In normal human scalp and foreskin, the epidermis was shown to contain LIF protein by immunostaining. LIF staining was found throughout the epidermis, and in the cells of the outer layer of the root sheath. Thus, KC synthesize LIF in vitro and in vivo.