Shinsuke Ina

In vivo gene introduction into keratinocytes using jet injection

Successful keratinocyte gene therapy requires the development of efficient methods of gene transfer to keratinocytes. Jet injection of a solution containing DNA can be used to transfer genes to several tissues in vivo. In this article, we tried to introduce DNA into rat and human keratinocytes using this method. First, we fired a β-gal expression vector into rat skin at several distances using a jet injector and examined β-gal activity in the epidermal keratinocytes. The highest activity in keratinocytes was found when the plasmid was fired at 10 cm from the skin surface; the activity lessened as the firing distance became shorter than 10 cm. Next, we transplanted human skin on to a nude rat, fired the vector into the human skin from a distance of 10 cm and examined the β-gal activity. We also injected the same amount of plasmid with a needle to compare jet with needle injections. The results showed that jet injection of the naked DNA could introduce and express DNA in human keratinocytes in vivo and that jet injection exhibited much higher activity than needle injection. Jet injection of the naked DNA will provide a method for keratinocyte gene therapy in the future.

In vivo introduction of the interleukin 6 gene into human keratinocytes: induction of epidermal proliferation by the fully spliced form of interleukin 6, but not by the alternatively spliced form.

Abstract The achievement of keratinocyte gene therapy in clinical practice requires fundamental experiments using human keratinocytes or skin. We have recently demonstrated that the in vivo introduction of the interleukin 6 (IL-6) gene into rat keratinocytes induces epidermal proliferation and lymphocyte infiltration into the skin. In this study, we first amplified the human IL-6 cDNA from oligo-dT-primed keratinocyte cDNA and then detected the fully spliced (FS) form and the alternatively spliced (AS) form of IL-6 cDNA. Sequence analysis showed that the AS form, which was composed of the IL-6 coding region with all of exon II deleted except for the first guanine, was identical to that reported to be present in lymphocytes. We constructed the expression vectors phIL6 of the FS form and phIL6S of the AS form. We transplanted human skin onto nude rats and introduced phIL6 and phIL6S into the human keratinocytes using the naked DNA method. Keratinocytes prepared 24 h after introduction from the areas treated with them were examined by reverse transcriptase (RT)-PCR and enzyme linked immunosorbent assay (ELISA). RT-PCR showed that the amounts of FS IL-6 mRNA and AS IL-6 mRNA were similar, whereas the ELISA showed that the amount of FS IL-6 peptide was four times that of the AS IL-6 peptide. Histological examination 48 h after introduction showed that the FS form had induced epidermal proliferation, whereas the AS form had not. The epidermal thickening without lymphocyte infiltration induce by the FS form indicates that keratinocyte proliferation is caused by a direct effect of overexpressed IL-6, and not by a secondary effect of infiltrating lymphocytes. This is the first report of the introduction of a human gene into human keratinocytes to produce a biologically active transgenic gene product in human skin using the naked DNA method.

Keratinocyte gene therapy: cytokine gene expression in local keratinocytes and in circulation by introducing cytokine genes into skin

Abstract: Using the plasmid DNA injection method, we introduced cytokine genes into skin to determine whether systemic expression of cytokine genes is possible. Eight human cytokine [interleukin‐4 (IL‐4), IL‐6, IL‐10, transforming growth factor β1 (TGF‐β1), monocyte chemotactic and activating factor (MCAF), granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), tumor necrosis factor α (TNF‐α) and interferon γ (IFN‐γ)] gene expression vectors were constructed and injected into rat skin. Transgenic cytokines in local keratinocytes and in the sera were assayed with ELISA. Our results showed that transgenic cytokines were markedly increased in keratinocytes at the injection site. The serum concentrations of IL‐4, 6, 10 and ΤGF‐β1 reached levels high enough to have systemic biologic effects. However, other cytokines used in this study could not be detected in the sera. Moreover, the serum transgenic IL‐10 level after subcutaneous injection was significantly higher than after intramuscular injection. We suggest that keratinocytes can be used as a bioreactor to achieve systemic expression of cytokine genes by DNA injection, but the transgenic protein level in circulation depends on different kinds of cytokine. This level also depends on different target cells used for gene transfer.

Expression vector with DNA of bovine papilloma virus 1 for keratinocyte gene therapy.

Although there are several methods for introducing the genes to keratinocytes in vivo, expression of transgene does not last long enough for effective keratinocyte gene therapy. In this study, we added bovine papilloma virus 1 (BPV) DNA into expression vectors with the lacZ gene driven by metallothionein and keratin 10 promoters, and we transferred them into keratinocytes in vivo using the naked DNA method, and measured beta-gal activity in keratinocytes. The results showed that beta-galactosidase activity of vectors with the BPV DNA was clearly higher than that without the DNA. Moreover, time-course experiment disclosed that the activity of the BPV vector declined at a lower rate than that of the control vector, suggesting this fragment prolonged transgene expression. These results should prove useful for understanding gene regulation in keratinocytes in vivo and for developing potential expression vectors for keratinocyte gene therapy.

In Vivo Gene Transfer Method in Keratinocyte Gene Therapy: Intradermal Injection of DNA Complexed with High Mobility Group-1 Protein in Rats

In order to develop a more efficient method of introducing genes into keratinocytes in vivo, we intradermally injected DNA bound to high mobility group 1 protein, thereby taking advantages of the naked DNA and hemagglutinating virus of the Japan-liposome method reported previously. First we performed a gel mobility shift assay, which confirmed DNA binding to high mobility group 1. Then we injected beta-galactosidase expression vector complexed with high mobility group 1 into the rat skin and the activity of sample with the protein was 2-3 times higher than that without the protein as control. Semiquantification of transferred-DNA content using polymerase chain reaction and a time course of transgene expression in keratinocytes suggested that high mobility group 1 protein increased transfer of the DNA from the cytoplasm to the nucleus. Direct injection of the DNA-high-mobility-group-1 complex is a highly efficient method for introducing genes into keratinocytes in connection with gene therapy.