Attempting gene transfer in muscle raises difficult problems: the nuclei of mature muscle fibers do not undergo division, thus excluding strategies involving replicative integration of exogenous DNA. As adenovirus has been reported to be an efficient vector for the transfer of an enzyme encoding gene in mice, we decided to explore its potential for muscle cells. Advantages of adenovirus vectors are their independence of host cell replication, broad host range, and potential capacity for large foreign DNA inserts. We constructed a recombinant adenovirus containing the fi-galactosidase reporter gene under the control of muscle-specific regulatory sequences. This recombinant virus was able to direct expression of the 3-galactosidase in myotubes in vitro. We report its in vivo expression in mouse muscles up to 75 days after infection. The efficiency and stability of expression we obtained compare very favorably with other strategies proposed for gene or myoblast transfer in muscle in vivo.The eventual correction of muscle diseases, and especially Duchenne muscular dystrophy (DMD), raises very difficult problems. As much as 50% ofDMD cases are sporadic (1) and thus cannot be prevented by current genetic counseling and prenatal diagnosis approaches; this frequency is even higher in mitochondrial myopathies (2). It is thus necessary to actively explore therapeutic strategies. The main problems to overcome are the large number of muscles to be treated and the nondividing nature of mature muscle cells. Moreover, the size of the sequences coding for dystrophin [11,056 base pairs (bp)] is incompatible with most vectors used for gene transfer; in addition, dystrophin is an intracellular protein thought to have a structural role in the muscle cells, whereas most of the current gene therapy approaches concern circulating proteins such as a1-antitrypsin (3), or diseases due to an enzymatic defect, where a very partial restoration of the activity might be sufficient, such as adenosine deaminase (4).Two strategies have been proposed to date: myoblast transplantation (5) and direct DNA injection (6). We decided to explore a third route using adenovirus as a vector for gene expression in muscle cells. Such a vector has already been used to correct postnatally an ornithine transcarbamoylase deficiency in mouse (7,8)
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