Plasmid-based expression technology using growth hormone releasing hormone: a novel method for physiologically stimulating long-term growth hormone secretion.
Novel DNA-based technologies were recently introduced for various purposes, such as screening of targets identified from genomic projects, shuffled molecules for vaccination, or to direct the in vivo production of hormones and other peptides for therapeutic or preventative applications. We have used a plasmid-based technology to deliver growth hormone releasing hormone (GHRH) to various animal species for screening, toxicology and therapy. A single intramuscular injection of a low dose of plasmid followed by electroporation can ensure that the target species will produce physiological levels of GHRH for extended periods of time, which would replace costly, frequent injections of the recombinant hormone and improve the quality of life and compliance of patients. This therapeutic modality is of particular importance in circumstances requiring long-term administration of small molecules with naturally short half-life (e.g. treatment of anemia and cachexia associated with renal failure, cancer or other chronic disability). A similar technique was used to create, test and validate protease-resistant analogs of GHRH with significantly longer half-life. Analysis of the characteristics of each of the plasmid components and tissue-specific transcription factors and the choice of target tissue is imperative when designing plasmids for therapeutic applications. Using the species-specific sequences of GHRH or other molecule along with the appropriate choice of plasmid backbone and expression cassette components can result in long and steady expression of the transgene product.