Noninvasive monitoring of therapeutic gene transfer in animal models of muscular dystrophies

Muscular dystrophies are a genetically and phenotypically heterogeneous group of degenerative muscle diseases. A subset of them are due to genetic deficiencies in proteins which form the dystrophin-associated complex at the membrane of the myofibers. In this report, we utilized recombinant adeno-associated virus containing a U7 cassette carrying an antisense sequence aimed at inducing exon skipping of the dystrophin gene or containing the alpha-sarcoglycan gene to alleviate the dystrophic phenotype of the mdx and Sgca- null mice, respectively. As these diseases are characterized by cycle of degeneration/regeneration, we postulated that a reporter gene coadministered at the time of the treatment would make it possible to follow the extent of muscle repair. We observed that the murine secreted alkaline phosphatase (muSeAP) level was very much lower in these animal models than in normal mice. Upon treatment of the dystrophic muscle by gene transfer, the level of muSeAP was restored and correlated with the expression of the therapeutic transgene and with the level of muscle improvement. The system described here provides a simple and noninvasive procedure for monitoring the outcome of a therapeutic strategy involving cell survival.