Following treatment of mdx mice, immunohistochemical staining was performed and this revealed some dystrophin expression in skeletal muscles such as the TA and diaphragm for both these deletion Pip6-PMOs ( Figure 5) . Quantification of the immunohistochemical staining revealed the lowest dystrophin restoration in the quadriceps with Pip6d-treatment, closely followed by Pip6c-PMO when compared to the other Pip6-PMOs (Figure 6a,b and Table 1 ). Similarly, Pip6d-PMO displayed the lowest dystrophin restoration in the diaphragm. The recovery scores for Pip6c-and Pip6d-PMO conjugates in the heart were very low, indicating their poor efficiency (Pip6c %RS -1.06% and Pip6d 2.50%; Figure 6b) .