Figure 4. In vivo co-administration of AAV-shRNA3X and AAV-optPABPN1 diminishes muscle fibrosis and myofibre atrophy and improves the functionality of treated muscles.

(a,b) Morphometric evaluation of Sirius red staining (a) or collagen VI immunostaining (b) in treated muscles of 30-week-old mice shows a significant reduction in fibrosis in muscles treated with AAVs expressing a combination of shRNA3X and optPABPN1 compared to saline-treated muscles. (c) The average of myofibre sizes per group shows that myofibres of muscles treated with AAV-optPABPN1 only or in combination with AAV-shRNA3X are larger than myofibres of muscles treated with saline. (d) Eighteen weeks after AAVs injection no difference was detected in the muscle weight of AAV-treated muscles compared to saline-injected TA of A17 mice. (e) Maximal force generated by TA muscles of treated mice was measured by in situ muscle physiology, co-injecting AAV-shRNA3X and AAV-optPABPN1 significantly increased the absolute maximal tetanic force generated by TA muscles. (f) Normalization of maximal force by muscle weight provides a measure of the muscle strength per unit of skeletal muscle called specific maximal force. The co-injection of the two AAVs normalized the specific maximal force of TA muscles to the level detected by wild-type muscles. Data are represented as mean±s.e.m. a–c: n=6 (saline-treated A17 or FvB muscles) or n=8 (all the other groups). d–f: n=8 (saline-treated A17 or FvB muscles) or n=10 (all the other groups). One-way ANOVA test with Bonferroni post-hoc test, *P<0.05, ***P<0.001, NS, not significant.