Correlation among MRI, treadmill performance and quantity/quality of AChR clusters in mdx mice.
The same set of mdx mice were included in a cohort analyzed by: magnetic resonance imaging (MRI); treadmill performance and AChR clusters analysis. a. MRI was used to monitor changes in the transverse relaxation time constant (T2) muscle. On the top representative MRI images of the fourth of 16 consecutive NMR sections of the lower hind limbs for all experimental groups are shown. Alterations in muscle T2 are correlated to muscle damage, edema, inflammatory infiltration and fibrosis. T2 MRI changes in mdx mice lower hind limb muscles in untreated wt and untreated or treated mdx mice with mAAV8-Jazz or mAAV8-JZif1 at 5 days. All experimental groups were examined at the times indicated before and after an exhaustive treadmill exercise until the age of about 3 months. Statistical analysis with ‘unpaired t-test’ showed a significant difference in T2 relaxation time between untreated and treated mdx mice indicated by (*P < 0.05). The lighter areas indicate the presence of inflammatory infiltration or muscle damage. b. The table shows the correlation between treadmill running times and counts of AChR clusters. c. Maximum z-stack projections of whole diaphragm in mdx mice, untreated and treated with mAAV8-JZif1 ormAAV8-Jazz, analyzed post-treadmill. Muscles were stained with alpha-bungarotoxin to visualize and count AChR clusters at the postsynaptic membrane (right panel). Data represent the average ±SEM of 3 mice/group and statistically significant differences were calculated by Student t-test. (*P < 0.05 JZif1 vs mdx, Jazz vs mdx). d. The AChR clusters analysis, performed in mdx diaphragm reveals that JZif1 and Jazz improve also the morphology of postsynaptic membrane, as indicated by an increase number of continuous (not fragmented) AChR clusters. Approximately, a total of 200 AChR clusters were examined for each diaphragm. Data represent the average ±SEM of three mice per group and statistically significant differences were calculated by Student t-test. (*P < 0.05 JZif1 vs mdx, Jazz vs mdx).