Fig. 3. Mmp13^-/- muscles exhibit hypertrophy in response to IGF-1 but without satellite cell involvement. (A) IGF-I content significantly increases in TA muscles of both WT and Mmp13^-/- mice following injection with AAV-Igf1 (N=3 muscle pairs). (B) MMP-13 activity increased in response to IGF1 AAV in WT muscles, but not in muscles from Mmp13^-/- mice (N=3 muscles pairs). (C) Relative muscle mass increased following AAV-Igf1 injection in TA and EDL muscles compared to contralateral control muscles regardless of genotype (N=6 muscle pairs), but muscles from Mmp13^-/- mice displayed a blunted hypertrophic response. (D) Median fiber areas significantly increased in response to AAV-Igf1 injection in EDL muscles. (E) The percent of CNF increased in WT but not in EDL muscles from Mmp13^-/- mice in response to AAV-Igf1 injection. The * represents p<0.05 between +AAV and non-injected muscles. The † represents p<0.05 between genotypes.