Growth Hormone Gene Therapy Using Encapsulated Myoblasts

Increasing numbers of gene therapy protocols are being accepted for human clinical trials both for somatic and Mendelian genetic disorders. For monogenic diseases, the goal is to provide a normal level of the previously missing gene product in vivo (Morgan and Anderson 1993, Morsy et al 1993). However, for these gene products, which are subject to intricate metabolic control, treatment with somatic gene therapy protocols has not yet progressed to the clinical stage, either because our knowledge about the regulatory control of the product in question is limited, or because the technical capability to reproduce the control pathway is not available. Hence, although the gene coding for insulin was one of the first human genes cloned, treatment of diabetes with somatic gene therapy is still an unrealized goal. Secretion of insulin is tightly controlled through interaction with several metabolic pathways, and its unregulated release by implanting insulin-secreting recombinant cells could lead to severe hypoglycemia and death (Selden et al 1987).