Partial Rescue of Growth Failure in Growth Hormone (GH)-Deficient Mice by a Single Injection of a Double-Stranded Adeno-Associated Viral Vector Expressing the GH Gene Driven by a Muscle-Specific Regulatory Cassette

Growth hormone (GH) deficiency (GHD) causes somatic growth impairment. GH has a short half-life and therefore it must be administered by daily subcutaneous injections. Adeno-associated viral (AAV) vectors have been used to deliver genes to animals, and double-stranded AAV (dsAAV) vectors provide widespread and stable transgene expression. In the present study we tested whether an intramuscular injection of dsAAV vector expressing GH under the control of a muscle creatine kinase regulatory cassette would ensure sufficient systemic GH delivery in conjunction with muscle-specific expression. Virus-injected GHD mice showed a significant (p < 0.05) increase in body length and body weight, without reaching full normalization, and significant (p < 0.05) reduction in absolute and relative visceral fat. Quantitative RT-PCR showed preferential GH expression in skeletal muscles that was confirmed by qualitative fluorescence analysis in mice injected with a similar virus expressing green fluorescent protein. The present study shows that systemic GH delivery to GHD animals is possible via a single intramuscular injection of dsAAV carrying a muscle-specific GH-expressing regulatory cassette.