Cell Type-Specific Adenoviral Transgene Expression in the IntactOvine Pituitary Gland after Stereotaxic Delivery: An in VivoSystem for Long-Term Multiple Parameter Evaluation of HumanPituitary Gene Therapy**This work was supported by the Medical Research Council, the Biotechnology and Biological Sciences Research Council, and the Royal Society.

Abstract

Ablative therapies for pituitary tumors commonly cause irreversible damage to normal pituitary cells. Toxin gene therapy should therefore ideally be targeted to specific cell types to avoid collateral cell damage. To evaluate cell-type-specific adenoviral gene transfer in the intact pituitary gland we have used stereotaxic transcranial delivery of recombinant adenoviruses in the sheep with continuous assessment of endocrine function. Adenoviral β-galactosidase expression was driven either by the human cytomegalovirus (hCMV) promoter or the human PRL gene promoter. The hCMV promoter directed adenoviral β-galactosidase expression in all pituitary cell types, but the PRL promoter restricted this exclusively to lactotropic cells, indicating that this promoter conferred appropriate cell type specificity in the context of adenoviral transduction in vivo. Serial measurements of plasma hormones showed no disruption of endocrine function over 7 days after intrapituitary injection. In summary, this work shows cell type-specific expression of an adenoviral transgene in the mixed cell population of the intact pituitary gland in vivo in a large animal model and indicates that stereotaxic intrapituitary delivery does not disrupt normal endocrine function.