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The results of this study demonstrate that suppression of inflammation by dexamethasone attenuates the host immune response against adenoviral-mediated gene transfection and thereby prolongs transgene expression in murine nasal mucosa.Gene transfer using a recombinant adenovirus is a good tool for research and clinical applications, but the immune response to adenoviral vectors can induce inflammation and loss of transgene expression in transfected tissues. In this study we investigated the effects of dexamethasone-induced immunosuppression on adenovirus gene transfer in the nasal mucosa of the mouse.We administered the recombinant adenovirus Ax1CAlacZ, which encodes Escherichia coli beta-galactosidase (lacZ gene), to the nasal mucosa of mice treated with or without i.p. dexamethasone and evaluated the expression of the lacZ gene on Days 2, 4, 7, 14 and 28. The nasal mucosa was dissected out, and the mRNA level was measured using a LightCycler. The expression of the exogenous beta-galactosidase was detected by means of histochemistry.Dexamethasone treatment significantly increased the mRNA level compared with that in the controls at Days 4, 7 and 14. Histochemistry showed that the expression of beta-galactosidase protein persisted in the dexamethasone-treated mice at Days 7 and 14 but had diminished almost to nothing in the control group.

The expression of adenoviral vector (Ad)-mediated lacZ and brain-derived neurotrophic factor (BDNF) in mouse olfactory epithelium (OE) was examined, and the effect of BDNF on the survival of the bulbectomized OE was evaluated. A recombinant adenovirus, Ax1CAlacZ, was administrated into the mouse OE after bulbectomy, and the expression of a transferred E. coli beta-galactosidase (beta-gal) gene was confirmed by X-gal staining. The expression and effects of exogenous BDNF in the OE after bulbectomy were examined using immunohistochemistry and the TUNEL method. The adenoviral vector-mediated expression of beta-gal in the mouse OE was detectable for up to 14 days after bulbectomy in vivo. The Ad-mediated expression of BDNF was also observed in the OE after bulbectomy. Exogenously induced BDNF suppressed the degenerative changes of bulbectomized OE. TUNEL staining indicated that the exogenous BDNF enhanced the survival of the bulbectomized OE by inhibiting apoptosis. Ad-mediated expression of BDNF in the mouse nasal mucosa alleviated degenerative changes in bulbectomized OE. Ad-mediated transfer of neurotrophic factors might be applicable in the treatment of olfactory disorders.

Adenovirus is a good tool for transferring exogenous genes into various organs because the virus has a wide spectrum of infection. In this report, we demonstrate that a recombinant adenovirus, Ax1CAlacZ, can transfer an exogenous lacZ gene into murine nasal mucosa in vivo. The efficiency of the exogenous gene expression varied for different cell types and was improved by optimizing the method of administration. In the olfactory region, the olfactory epithelia, sustentacular cells and olfactory nerve efficiently expressed lacZ gene transferred by Ax1CAlacZ using either of two administration methods, dripping or injecting. In contrast, in the respiratory region, the respiratory epithelia but not the subepithelial tissues expressed lacZ gene transferred by Ax1CAlacZ, and the efficiency of the gene transfer, which was low when the virus was administered by nasal drops, was improved when the virus was administered by injection. Our study demonstrated that gene transfer mediated by adenovirus is more efficient in the olfactory epithelia than in the respiratory epithelia, and may be applicable to nasal or paranasal diseases such as olfactory epithelial disturbances.