Gene transfer of arginine kinase to skeletal muscle using adeno-associated virus

In this study we tested the feasibility of non-invasively measuring phosphoarginine (PArg) after gene delivery of arginine kinase (AK) using an adeno-associated virus (AAV) to murine hindlimbs. This was achieved by evaluating the time course, regional distribution, and metabolic flux of PArg using (31) phosphorus magnetic resonance spectroscopy ((31)P-MRS). AK gene was injected into the gastrocnemius of the left hindlimb of C57Bl10 mice (age 5wk, male) using self-complementary AAV, type 2/8 with desmin promoter. Non-localized (31)P-MRS data were acquired over nine months after injection using 11.1-T and 17.6-T Bruker Avance spectrometers. In addition, (31)P 2-D chemical shift imaging and saturation transfer experiments were performed to examine the spatial distribution and metabolic flux of PArg, respectively. PArg was evident in each injected mouse hindlimb after gene delivery, increased until 28 weeks, and remained elevated for at least nine months (p<.05). Furthermore, PArg was primarily localized to the injected posterior hindimb region with the metabolite being in exchange with ATP. Overall, the results show the viability of AAV gene transfer of AK gene to skeletal muscle, and provide support of PArg as a reporter that can be utilized to non-invasively monitor the transduction of genes for therapeutic interventions.