Nonmyeloablative bone marrow cells transplantation restores dystrophin synthesis in the muscles of MDX mice

Abstract

Duchenne muscular dystrophy is an X-linked recessive muscular dystrophy associated with a mutations in the dystrophin protein gene. The most common laboratory model of Duchenne muscular dystrophy is mdx mice. The striated muscle fibers of mdx mice are characterized by the absence of dystrophin, the presence of centrally located nuclei, and the high level of renewal of the striated muscle fibers. In addition, mdx mice show a morphological aberrations at neuromuscular junctions, expressed in the breakdown of large clusters of acetylcholine receptors in the form of branches into small clusters in the form of islets. One approach to treating muscular dystrophy in mdx mice may be the nonmyeloablative transplantation of wild-type bone marrow cells after X-ray irradiation of mdx mice at a dose of 3 Gy. The aim of this work is to evaluate the effect of nonmyeloabla-tive transplantation of wild-type bone marrow cells on dystrophin synthesis and the structure of neuromuscular junctions of mdx mice. Mdx mice were irradiated with X-rays at a dose of 3 Gy, after 24 hours was performed intravenous transplantation of bone marrow cells of C57BL/6 mice. The m. quariceps femoris and diaphragm were examined 2, 4, 6, 9, 12 months after transplantation. Muscle studies were performed using immunohisto-chemical methods of study (immunohistochemical staining with antibodies to dystrophin). The neuromuscular junctions were stained with tetramethylrodamine-a-bungarotoxin. After intravenous bone marrow cells transplantation, the part of dystrophin-positive muscle fibers in the muscle quadriceps femoris was shown to increase to a 27,6±6,7% 6 months after transplantation. After 12 months, the part of dystrophin-positive muscle fibers decreased to 5,1±1,1%. There was also an increase in the proportion of striated muscle fibers without centrally located nuclei and a decrease in the part of dead striated muscle fibers. Similar changes were found in the striated muscle fibers of the diaphragm of mdx mice. In addition, transplantation of bone marrow cells after irradiation at a dose of 3 Gy increases the part of neuromuscular junctions with normal structure. Thus, nonmy-eloablative transplantation of wild-type bone marrow cells can be considered as one way to treat monogenic disease of striated muscle fibers muscular dystrophy of mdx mice.