Figure 5: Dystrophin exon-skipping and protein expression following i.m. administration of 2′-OMePSE23 with and without polymers in TA muscle of mdx mice (aged 4-5 weeks) 2 weeks after treatment. Muscles were treated by local injection with 2′-OMePSE23 (2 μg) and polymer (5 μg) in 40 μL saline. 2′-OMePSE23 (2 μg) alone and PEI 25k were used as controls: a) Restoration of dystrophin in TA muscles was detected by immunohistochemistry with rabbit polyclonal antibody P7 against dystrophin. Blue nuclear staining with DAPI (4,6-diamidino-2-phenylindole). Original magnification, x 40. b) The numbers of dystrophin-positive fibers. The maximum numbers of dystrophin-positive fibers were counted in a single cross-section (n = 5, two-tailed t-test, *p ≤ 0.05 compared with 2 μg 2′-OMePSE23). c) Detection of exon 23 skipping by RT-PCR. Total RNA of 100 ng from each sample was used for amplification of dystrophin mRNA from exon 20 to exon 26. The upper bands (indicated by E22+E23+E24) correspond to the normal mRNA and the lower bands (indicated by E22+E24) correspond to the mRNA with exon E23 skipped. d) Western blotting demonstrate the expression of dystrophin protein from treated mdx mice in comparison with C57BL/6 and untreated mdx mice. Dys, dystrophin detected with monoclonal antibody Dys 1. α-Actin was used as the loading control.