Characterization of cryopreserved human Langerhans cells

Potential efficacy of imiquimod on immunity-related cytokines in murine skin in vivo and in human Langerhans cells in vitro

INTRODUCTION

Imiquimod, an immune-response modifier, has been proven to be clinically effective in the treatment of viral infections and skin cancers, but its mechanism of action remains poorly understood. This study aimed to assess the effects of imiquimod on the expression of three immunity-related cytokines, TNF-α, IL-1β, and IL-6.

MATERIALS AND METHODS

Female BALB/C mice were treated for seven days with topical 1% imiquimod cream; they were then killed and skin samples were snap-frozen. In the in vitro studies, both purified LCs and HaCaT cells were incubated with 5 μg/ml imiquimod for four hours. In all samples, the mRNA levels of TNF-α, IL-1β, and IL-6 were then detected by reverse transcription polymerase chain reaction, and the secretion levels were determined by an enzyme-linked immunosorbent assay.

RESULTS

Imiquimod upregulated the mRNA and protein expression levels of TNF-α, IL-1β, and IL-6 in the skin of imiquimod-treated BALB/C mice and in human LCs, compared with untreated controls (P<0.05). However, there was no significant difference in the expression of these cytokines in imiquimod-treated and untreated HaCaT cells.

CONCLUSIONS

These findings indicate that imiquimod increased the expression of TNF-α, IL-1β, and IL-6 in skin and that the target cell of imiquimod may be the LCs but is unlikely to be the epidermal keratinocytes.

Defective TPA signalling compromises HaCat cells as a human in vitro skin carcinogenesis model

HaCat cells, a human keratinocyte line, are commonly utilised as an in vitro cell model for toxicity testing and the discernment of processes of chemically induced skin carcinogenesis. Here, as part of an ongoing program of carcinogenesis research, we tested the genomic transcriptional response of two keratinocyte cell lines HaCat (human) and Pam212 (mouse) to 12-O-tetradecanoylphorbol 13-acetate (TPA), one of the most studied skin carcinoma promoting agents, and compared this with the response in primary keratinocytes. Differences in the genomic response profile indicated an insufficiency in the MEK/ERK pathway signalling in HaCat but not Pam212 cells compared to primary keratinocytes. TPA can also activate NFkappaB and so we tested whether this was also deficient in the HaCat cells using TNFalpha which signals directly to NFkappaB. By this method NFkappaB was found to be equally active in both HaCat and Pam212 cells. Analysis of ERK phosphorylation showed that while TPA mediated ERK phosphorylation occurred in both cell lines it was more robust and difficult to inhibit in Pam212 cells suggesting that there may be an insufficiency in this step in HaCat cells leading to a reduced response. Overall these data indicate that caution should be employed when using HaCat cells as an in vitro skin model for biochemical research or toxicological evaluation.

Liver Transplantation Using Liver Grafts Preserved Under High Pressure

To extend organ preservation time, we attempted to establish a unique method of maintaining a preservation solution in a stable unfrozen state below its freezing point by pressurizing the solution. Livers removed from Lewis rats (RT1l) were stored in UW solution pressurized at the prescribed pressure. After the termination of preservation, orthotopic liver transplantation was performed. Experiment 1: Liver grafts were pressurized up to 30, 40, 50, and 70 MPa and preserved at 0 degrees C for 60 min. Experiment 2: Liver grafts were compressed at a rate of 1.32 or 0.04 MPa/s to 35 MPa and preserved for 60 min at 0 degrees C. Experiments 3 and 4: Liver grafts were pressurized up to 5, 10, 20, and 30 MPa and preserved at -2 degrees C (Exp. 3), -3 degrees C or -4 degrees C (Exp. 4) for 5 h. All rats transplanted with livers pressurized up to 30 MPa (Exp. 1), all rats in the 5 MPa and control groups at -2 degrees C (Exp. 3), and all rats in the 5 MPa group at -3 degrees C (Exp. 4) survived for 2 weeks. In light microscopy, diffuse hemorrhage and vacuolar degeneration of hepatocytes were observed in a pressure-dependent manner. Liver grafts preserved under pressurized, subzero nonfrozen condition have sufficient function to sustain the life of rats after orthotopic transplantation.