| Summary: | <p>Abstract</p> <p>Background</p> <p>Adenovirus (Ad) mediated gene transfer is a well-established tool to transiently express constructs in livers of mice <it>in vivo</it>. In the present study, we determined the specificity and efficiency of Ad vectors expressing short hairpin (sh) RNA constructs to knock-down the estrogen receptor α (ERα).</p> <p>Results</p> <p>Two different shRNA constructs derived from the murine ERα coding sequence were designed (shERα). <it>In vitro</it>, transfection of three mouse cell lines with pSUPER-shERα constructs resulted in up to 80% reduction of endogenous ERα activity. A single mismatch in the target sequence eliminated the reduction of ERα activity, demonstrating the specificity of shERα. The subsequently generated Ad.shERα vectors were equally effective <it>in vitro</it>. <it>In vivo</it>, intravenous administration of Ad.shERα resulted in 70% reduced hepatic mouse ERα mRNA levels. Co-injection of Ad.shERα with an Ad vector containing a luciferase (luc) gene driven by an estrogen responsive element (ERE) containing promoter resulted in a significant (90% on day five) down-regulation of hepatic luciferase activity, as determined by non-invasive optical imaging. Down-regulation was sustained up to day seven post-injection.</p> <p>Conclusion</p> <p>Ad mediated transfer of shERα expression constructs results in efficient and specific knockdown of endogenous ERα transcription both <it>in vitro </it>and <it>in vivo</it>.</p>
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