Non-invasive tracking of disease progression in young dystrophic muscles using multi-parametric MRI at 14T

Fig 1. Cross-sectional area for GA, SOL, and TA muscles. Comparisons of muscle maximum cross-sectional area (CSAmax) between mdx4cv and control groups for GA, SOL, and TA muscles at each time point.

Fig 2. T2, T1, and MTR values analyzed for TA, GA, and SOL muscles. Graphs displaying the average longitudinal values of the mdx4cv and control mice muscles in the T2, T1, and MTR measures. T2 values for the mdx4cv mice were significantly higher at all time points versus age-matched controls. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, and ****p ≤ 0.0001. Significant higher T2 values were detected in ctrl mice at 3 weeks of age compared to other time-points. ‡p ≤ 0.05.

Fig 3. Representative T2, T1, and MTR color maps acquired from lower hind limbs of a mdx4cv mouse followed longitudinally over 11 weeks. The T2, T1 and MTR maps are overlaid onto T2 weighted images to display the change in values for each time point.

Fig 4. Fractional Anisotropy (FA), Mean Diffusivity (MD) and Radial Diffusivity (RD) of TA, GA, and SOL muscles. Graphs displaying average longitudinal FA, MD, and RD values for mdx4cv and control muscles. FA values from GA muscles of mdx4cv mice are significantly lower at all time points versus age-matched controls. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, and ****P ≤ 0.0001.

Fig 5. Eigenvalues analyzed for TA, GA, and SOL muscles. Graphs displaying average longitudinal eigenvalues λ1, λ2, and λ3 of mdx4cv and control mouse muscles. λ1 values for mdx4cv mice were significantly lower at the 3- and 5-week time points versus age-matched controls in all muscles (top panels), while λ3 values for mdx4cv mice were significantly higher at 9 and 11 weeks (bottom panels). λ2 values were not significantly different between groups until the 11-week time point in the TA muscle (middle panels). *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, and ****P ≤ 0.0001.

Fig 6. Average muscle fiber area, and λ3 versus average muscle fiber area for TA and GA muscles. Individual muscle fiber areas were measured for the TA and GA muscles and then averaged for comparison between groups. Mdx4cv mice exhibit significantly reduced average individual muscle fiber area for both TA and GA muscles. This data was then plotted against the λ3 values for correlation of diffusivity across single muscle fibers and average fiber size. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, and ****P ≤ 0.0001.

Fig 7. Histogram Analysis for individual muscle fiber area of TA and GA muscle fibers in 11-week old mdx4cv and control mice. Muscle fiber areas measured for the TA and GA muscle differences between groups. Area values were binned into intervals of 500 μm2 and overlaid for both frequency and distribution comparisons.

Fig 8. Longitudinal tissue analysis for mdx4cv mice at each timing point (3, 5, 7, 9, and 11 weeks of age) at 10x and 20x magnification. Representative H&E histology images of the TA muscle in mdx4cv mice. Images are taken from the same area of muscle for both 10x and 20x images (scale bar represents 100 μm).

Fig 9. 11-week comparison of TA and GA muscles of control and mdx4cv mice (both H&E and trichrome staining) at 20x magnification. Comparisons of representative histology images for both groups of animals (scale bar represents 100 μm).