Prolonged Expression of Therapeutic Levels of Human Granulocyte Colony-Stimulating Factor in Rats Following Gene Transfer to Skeletal Muscle

Abstract

Gene transfer to skeletal muscle was examined as a means of gene therapy for neutropenia. A recombinant retrovirus containing a human granulocyte colony-stimulating factor (G-CSF) gene was introduced into primary human or rat myoblasts, which were then shown to produce biologically active G-CSF. Transplantation of G-CSF-producing rat myoblasts into the muscle of syngeneic rats resulted in a 15-fold increase in absolute neutrophil counts. This increase correlated with detection of circulating human G-CSF protein throughout the 6-month duration of the experiment. These results clearly demonstrate long-term production of therapeutically relevant amounts of a human protein by normal cells in vivo.

Overview summary

Currently patients with cyclic neutropenia receive daily injections of recombinant granulocyte colony-stimulating factor (G-CSF) to raise their neutrophil counts and relieve the symptoms of their disease. As an alternative, it may be possible to treat this and other diseases that require chronic protein administration by gene therapy. We have used transplantation of genetically modified primary skeletal muscle cells to demonstrate that this goal can be achieved in an animal model. The G-CSF cDNA was expressed from a retroviral vector in vivo at levels which increased neutrophil counts 15-fold for at least 6 months.