Abstract: Objective To investigate the effect of bone marrow stem cell transplantation (BMT) on the diaphragm muscles of mdx mice, a mouse model of Duchenne muscular dystrophy (DMD). Methods The bone marrow-derived stem cells form male SD rats was transplanted through the tail vein into 18 female 8-week-old mdx mice, which were sacrificed at 4, 8 and 12 weeks after BMT (6 at each time point), respectively. The diaphragm muscles of the mice were subjected to HE staining, im-munofluorescence detection of dystrophin, reverse transcription (RT)-PCR analysis of dystrophin mRNA transcripts and PCR analysis of Sry (sex-determining region on the Y chromosome) gene, with age-matched female C57 mice and untreated mdx mice as the controls. Results The proportion of centrally nucleated fibers (CNF) in the diaphragm muscle of the recipient mdx mice was (15.58±0.91)%, (12.50±1.87)% and (10.17±1.17)% at 4, 8 and 12 weeks after BMT, respectively, significantly smaller than that of untreated mdx mice [(19.5±1.87)%], and the fibers after BMT showed less inflammatory infiltration. Compared with the untreated mice, the recipient mdx mice showed green fluorescence on significantly more diaphragm muscle cell membranes [with the proportion of dystrophin-positive fibers of (1.00±0.32)%, (6.00±1.05)% and (11.92±1.11)% at 4, 8, and 12 weeks after BMT]. RT-PCR of dystrophin mRNA also demonstrated significantly higher relative levels of dystrophin in the recipient mdx mice (0.19±0.05, 0.26± 0.06 and 0.36±0.04 at 4, 8 and 12 weeks after BMT) than in untreated mdx mice, and Sry gene was present in the recipient mice. Conclusions BMT can partially restore dystrophin expression and ameliorate the pathology in the diaphragm muscles of mdx mice, and has great potential to produce general therapeutic effect in patients with DMD.