Figure 5A NAD+ levels in limb muscles of 20-month-old WT (n=7), mdx (n=5) and mdx/CD38-/- (n=6) mice. Data information: Each dot of the graphs represents a mouse. in duplicate; After normality and variance comparison tests, significance was assessed using: ANOVA followed by Fisher's LSD test; Values are expressed as means ± SEM. Significance: *p<0.05, **p<0.01, ***p<0.001. B CD38 expression: western blot analysis of CD38 (B1) protein in limb of WT and mdx mice (n=6 per group). Vinculin is used as housekeeping protein control and the dot plots show the ratio of CD38/vinculin. qPCR analysis of CD38 mRNA (B2) in limb of 20-month-old WT and mdx mice (n=4 per group). Data information: Each dot of the graphs represents a mouse. one value/mouse; After normality and variance comparison tests, significance was assessed using: B1: unpaired Welch's t-test; B2 : unpaired Student's t-test Values are expressed as means ± SEM. Significance: *p<0.05, **p<0.01, ***p<0.001. C Histograms showing the grip duration (latency to fall) (C1) and the limb force (C2) measured by a grip test in WT (n=89), mdx (n=52, 53 respectively) and mdx/CD38-/- (n=58) mice (age: 9 to 26 months old). Data information: C1 one value/mouse; C2 in triplicate. After normality and variance comparison tests, significance was assessed using: : unpaired Student's t-test; Values are expressed as means ± SEM. Significance: *p<0.05, **p<0.01, ***p<0.001. D Images showing muscle fiber typology revealed by immunostaining. Localization of the slow MyHC (Type I) fiber and fast MyHCs (Type IIa and IIb/X) fibers, along with laminin (red) on transverse cross-sections from soleus and tibialis (TA) of WT, mdx and mdx/CD38-/- mice. Scale bars: 100 µm. Histogram showing the percentage of I, IIa and IIb/X fiber type distribution in soleus and TA of WT, mdx and mdx/CD38-/- mice. Experiments performed in WT (n=3), mdx (n=5) and mdx/CD38-/- (n=7) mice for soleus; WT (n=5), mdx (n=6) and mdx/CD38-/- (n=6) mice for TA. Data information: one value/mouse; After normality and variance comparison tests, significance was assessed using: D: Chi-square test; Values are expressed as means ± SEM. Significance: *p<0.05, **p<0.01, ***p<0.001. E Fiber size distribution in soleus from WT, mdx and mdx/CD38-/- mice. Data information: one value/mouse After normality and variance comparison tests, significance was assessed using: E: Kolmogorov-Smirnov test; Values are expressed as means ± SEM. Significance: *p<0.05, **p<0.01, ***p<0.001. F Images displaying the collagen (blue) revealed by Masson's trichrome staining in limb of WT, mdx, and mdx/CD38-/- mice. The dot plot shows the quantification of collagen staining area (% total area) in limb of WT (n=4), mdx (n=5) and mdx/CD38-/- (n=5) mice. Scale bars: 200 µm. Data information: Each dot of the graphs represents a mouse. in triplicate. After normality and variance comparison tests, significance was assessed using: : ANOVA followed by Fisher's LSD test; Values are expressed as means ± SEM. Significance: *p<0.05, **p<0.01, ***p<0.001. G Embryonic myosin expression revealed by immunostaining along with laminin (green) on transverse cross-sections from limb of WT (n=5), mdx (n=8) and mdx/CD38-/- (n=8) mice. Scale bars: 50 µm. Dot plot showing the relative proportion of embryonic myosin area in limb of WT, mdx and mdx/CD38-/- mice. Data information: Each dot of the graphs represents a mouse. one value/mouse; After normality and variance comparison tests, significance was assessed using: G: Welch's ANOVA followed by Welch's t-tests. Values are expressed as means ± SEM. Significance: *p<0.05, **p<0.01, ***p<0.001.