Sustained expression of a therapeutic human microdystrophin protein is achieved after intravenous administration of rAAV6 vectors, without significant cellular infiltration. (a) Anti-dystrophin-labeled tibialis anterior from a treated mdx mouse administered 1 × 1013 vector genomes rAAV6–CK6–microdystrophin and 10 μg VEGF. This treatment significantly (Tmdx compared with mdx, P ≤0.05) reduced serum creatine kinase (CK) levels. Individual data are depicted as dots with group means in red. (b) Anti-dystrophin immunofluorescence microscopy (left) and hematoxylin-stained and eosin-stained sections (right) of tibialis anterior muscles from wild-type, untreated mdx (mdx) and mdx mice treated as in a (Tmdx), respectively. Yellow points function are markers identifying the same muscle fiber in left and right panels. Mice were examined 6 weeks after treatment. Scale bars, 1 mm (a) and 200 μm (b).