Efficient Gene Expression System Using the RTP801 Promoter in the Corpus Cavernosum of High-Cholesterol Diet-Induced Erectile Dysfunction Rats for Gene Therapy

Authors


Jun-Kyu Suh, MD, PhD, Department of Urology, Inha University Hospital, 7-206, 3rd St. Shinheung-Dong Jung-Gu, Incheon, Korea 400-711. Tel: 82-32-890-3441; Fax: 82-32-890-3097; E-mail: jksuh@inha.ac.kr

ABSTRACT

Introduction.  The application of gene therapy for a nonlife-threatening disease, such as erectile dysfunction (ED), requires a higher safety level and more efficacious systems for gene transfer.

Aim.  To establish a novel technique for gene expression in a rat model of hypercholesterolemic ED that uses the RTP801 promoter, a hypoxia-inducible promoter.

Methods.  Two-month-old male Sprague–Dawley rats were fed a diet containing 4% cholesterol and 1% cholic acid, and age-matched control animals were fed a normal diet, for 3 months.

Main Outcome Measures.  Cavernous expression of hypoxia-inducible factor (HIF)-1α was evaluated by Western blot. After intracavernous injection of pSV-Luc or pRTP801-Luc, gene expression was evaluated by luciferase assay, and the gene expression area was evaluated by immunohistochemistry.

Results.  HIF-1α was up-regulated in the corpus cavernosum of hypercholesterolemic rats. Although pSV-Luc did not induce gene expression in either the control or the cholesterol group, pRTP801-Luc significantly induced gene expression in the cholesterol group and resulted in higher luciferase activity than did pSV-Luc up to 14 days after injection. Immunohistochemistry showed that the gene expression area was also greater in the pRTP801-Luc group than in the pSV-Luc group, but the difference was not as great as that in luciferase activity. This suggests that pRTP801-Luc exerts its effect mainly by inducing promoter activity under hypoxia, not by increasing the number of transfected cells.

Conclusion.  The RTP801 promoter-driven gene expression system increased gene expression in the corpus cavernosum tissue of rats with cholesterol-induced ED. This may be a useful system for the development of gene therapy in vasculogenic ED. Lee M, Ryu J-K, Piao S, Choi MJ, Kim HA, Zhang L-W, Shin H-Y, Jung HI, Kim I-H, Kim SW, and Suh J-K. Efficient gene expression system using the RTP801 promoter in the corpus cavernosum of high-cholesterol diet-induced erectile dysfunction rats for gene therapy. J Sex Med 2008;5:1355–1364.

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