Fig 2: Dose-dependent restoration of dystrophin-associated protein complex proteins at the sarcolemma(A) Sarcolemma expression of a-sarcoglycan, ß-sarcoglycan, and d-sarcoglycan for mice systemically treated with low dose (8.94 × 1010 vg total dose; 4.63 × 1012 vg/kg), mid dose (3.63 × 1011 vg total dose; 1.85 × 1013 vg/kg), or high dose (1.26 × 1012 vg total dose; 7.41 × 1013 vg/kg) of SRP-9005 (n = 6/group) shown in the tibialis anterior muscle. Scale bar, 100 µm. (B) Quantitative analysis of positive fiber DAPC expression. Data represent the mean ± SEM. DAPC, dystrophin-associated protein complex; SGCG-/-, ?-sarcoglycan gene deficient; WT, wild type.

Fig 3: Serum chemistries(A) Liver enzyme (ALT and AST) levels were analyzed for toxicity (n = 6/group). Dotted lines indicate normal limits in WT mice. (B) CK levels in serum decreased in all treated groups compared with untreated SGCG−/− and WT controls; mid and high doses only (low-dose data were not collected due to insufficient sample volume). Data were analyzed by one-way ANOVA for all blood chemistries and represent the mean ± SEM. ALT, alanine aminotransferase; AST, aspartate aminotransferase; CK, creatine kinase; SGCG−/−, γ-sarcoglycan gene deficient; WT, wild type.

Fig 4: Functional benefits in SGCG−/− mice treated with SRP-9005(A) Following 12 weeks of SRP-9005 treatment, specific force of tibialis anterior muscles (both left and right) was measured (data were normalized to tibialis anterior weight). Specific force increased in all SRP-9005-treated SGCG−/− mice (with minimal difference between doses) compared with vehicle-treated (SGCG−/−) and WT mice (n = 6/group, average of both legs used for analysis [total n = 12]). (B) Diaphragm muscle strips were harvested to measure specific force. Following 12 weeks of SRP-9005 treatment, the force was significantly increased in treated mice compared with SGCG−/− and WT mice. (C) Following 12 weeks of treatment, improvement was seen in analysis of activity cage ambulation and vertical activity through open-field analysis in vector-treated mice compared with SGCG−/− and WT mice (n = 6/group). One-way ANOVA with Tukey’s multiple comparisons test was performed for analysis of tibialis anterior and diaphragm physiology and for analysis of cage activity. Data represent the mean ± SEM. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001 versus SGCG−/−; +p < 0.05, ++p < 0.01, +++p < 0.001 versus WT. SGCG−/−, γ-sarcoglycan gene deficient; WT, wild type.

Fig 5: Improvement in muscle morphology by SRP-9005 is independent of dose in SGCG−/− mice(A) H&E images of tibialis anterior and diaphragm muscles as well as heart from SGCG−/− mice systemically treated with low dose (8.94 × 1010 vg total dose; 4.63 × 1012 vg/kg), mid dose (3.63 × 1011 vg total dose; 1.85 × 1013 vg/kg), or high dose (1.26 × 1012 vg total dose; 7.41 × 1013 vg/kg) of SRP-9005 (n = 6/group). Representative 20× images show a dramatic reduction in centralized nuclei and an overall normalization of fiber size independent of treatment dose. Scale bar, 100 μm. (B) Quantification of centrally located nuclei in left and right muscles (TA, GAS, QD, GLUT, TRI, PSO, DIA) from treated mice compared with SGCG−/− and WT controls (n = 6/group; four images per section). Data were analyzed by two-way ANOVA followed by Tukey’s multiple comparisons test and represent the mean ± SEM. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001 versus SGCG−/−. (C) Quantification confirming myofiber diameter normalization of tibialis anterior, gastrocnemius, and triceps muscles in vector-treated groups compared with vehicle-treated mice (SGCG−/−) and WT controls (n = 6/group). DIA, diaphragm; GAS, gastrocnemius; GLUT, gluteus; HRT, heart; PSO, psoas major; QD, quadriceps; SGCG−/−, γ-sarcoglycan gene deficient; TA, tibialis anterior; TRI, triceps; WT, wild type.