Abstract 406: Prevention of Heart Failure in delta-Sarcoglycan Knock-Out Mice after Intravenous Gene Transfer with Targeted Adeno-Associated Viral (AAV) Vectors
Background: Delta-Sarcoglycan (SGCD) is a member of the dystrophin-associated glycoprotein complex. Mutations may result in isolated dilated cardiomyopathy or limb-girdle muscle dystrophy 2F with variable cardiac involvement. A potential gene therapeutic approach requires an efficient myocardial gene transfer. AAV vectors are suitable for cardiac gene transfer. Novel AAV serotypes such as AAV-8 or -9 even enable a systemic gene transfer in rodents. Aim of our study was to establish a vector for efficient systemic cardiac gene transfer and its subsequent use to prevent heart failure by expressing the SGCD cDNA in SGCD knock out mice.
Material and Methods: 1011 genomic particles of AAV-8 and -9 vectors harboring a luciferase reporter gene under control of the CMV-enhanced myosin light chain promoter were intravenously injected into adult NMRI mice (n=6 and n=10, respectively). After 4 weeks, reporter activities were determined in representative organs. Analogous, 2x1011 AAV-9 SGCD and AAV-9 EGFP vectors were intravenously injected in SGCD knock out mice (n=9 and n=7, respectively). Cardiac function (fraction of shortening) was assed by echocardiography at the beginning and the end of the study after 6 months. Running distances were measured using voluntary wheel running.
Results: Reporter gene transfer with AAV-9 vectors resulted in increased cardiac luciferase activities compared to AAV-8 (3.8x108 ±4.4x108 relative light units [RLU]/mg protein versus 0.10x108 ±0.08x108 RLU/mg protein, p=0.05) with increased specificity. In comparison to EGFP controls, AAV-9 delta-sarcoglycan gene transfer resulted in a significant increase in running distance and a significant decrease in decline in fraction of shortening (67.6% to 65.0% versus 69.9% to 58.1%; p=0.04). Immunohistochemical analyses in AAV-9 SGCD treated knock-out mice revealed a transmural reconstitution of more than 90% of cardiomyocytes.
Conclusion: Intravenous injections of AAV-9 SGCD vectors enable an efficient transmural cardiac gene transfer in adult mice and prevent deterioration of left ventricular function in SGCD knock out mice. Therefore, this vector system may be suitable for validation of novel targets for cardiac diseases.