Bacterial β‐galactosidase and human dystrophin genes are expressed in mouse skeletal muscle fibers after ballistic transfection

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Abstract
Ballistic transfection, based on cell and tissue bombardment by the tungsten and gold microparticles covered with the gene DNA, was used for the delivery of a bacterial β‐galactosidase and a full‐length cDNA copy of the human dystrophin genes into mouse skeletal muscles. CMV‐lacZ, SV40‐lacZ, LTR‐lacZneo and full‐length cDNA dystrophin (pDMD‐1, approximately 16 kb) in eukaryotic expression vector pJ OMEGA driven by mouse leukaemia virus promotor (pMLVDy) were used throughout the studies. Musculus glutaeus superficialis of C57BL/6J and quadriceps femoris of mdx male mice were opened surgically under anesthesia and bombarded by means of the gene‐gun technique originally developed by us. Different mixtures of gold and tungsten particles at ratios of 4:1, 1:1, 1:4 were applied. X‐gal assay revealed marked β‐gal activity, both in total muscles and whole muscle fibers on histological sections, up to three months after transfection. The most intensive staining was observed after SV40‐lacZ delivery. No staining was detected with LTR‐lacZneo DNA as well as in untreated muscles. The higher tungsten particle concentration in the bombardment mixture correlated with more intense X‐gal staining. At the gold/tungsten ratio of 1:4 the microparticles penetrated the musculus glutaeus superficialis and transfected the underlying musculus glutaeus medius as well. Immuno‐cytochemical assay for human dystrophin revealed dystrophin positive myofibers (DPM) in the bombarded area up to two months after transfection. The proportion of DMP varied from 2.5% on day 17 up two 5% on day 60 after bombardment compared to only 0.5% in the control mdx mice. These results suggest the applicability of particle bombardment for gene delivery into muscle fibers.