Figure 2. Deletion of CD38 prevented heart dysfunction and reduces spontaneous Ca²⁺ activity in isolated cardiomyocytes of mdx/CD38 ^−/− mice.

• A
  Cardiac function evaluated by echocardiography in mdx/CD38 ^−/− mice: The dot plots show the left ventricular (LV) diastolic (A₁) and systolic (A₂) inner diameters and LV ejection (A₃) fraction in 7‐month‐old WT (n = 5), mdx (n = 6), and mdx/CD38^−/− (n = 10) mice.
• B
  Plasma levels of cardiac stress biomarkers: brain natriuretic peptide (BNP) (B₁) and cardiac troponin I (cTnI) (B₂) in 7‐month‐old WT (n = 7), mdx (n = 6), and mdx/CD38 ^−/− (n = 11) mice.
• C
  Cropped images revealed the collagen (blue) stained by Masson’s trichrome staining in the heart of WT, mdx, and mdx/CD38 ^−/− mice. Dot plot showing the quantification of heart collagen staining area (% total area) in 7‐month‐old WT, mdx, and mdx/CD38 ^−/− mice (n = 4 per group). Scale bars: 200 µm.
• D
  Isoproterenol‐induced heart failure in 3‐month‐old mice. The Kaplan–Meier curve shows the survival rate of mdx mice (NaCl, n = 5), and mdx (n = 19) and mdx/CD38 ^−/− (n = 9) mice following isoproterenol (iso, subcutaneous injection) at 2.5 mg/kg/d for 10 days.
• E
  Histogram showing isoproterenol‐induced heart hypertrophy in mdx NaCl (n = 5) mice, and surviving mdx (isoproterenol, n = 9), mdx/CD38 ^−/− NaCl (n = 9), and mdx/CD38 ^−/− (isoproterenol, n = 9) mice, expressed as heart weight/body weight ratio (HW/BW).
• F
  Plasma levels of cardiac stress biomarkers: brain natriuretic peptide (BNP) (F₁) and cardiac troponin I (cTnI) (F₂) following isoproterenol treatment in mdx NaCl (n = 5), and surviving mdx (isoproterenol, n = 8), mdx/CD38 ^−/− NaCl (n = 5), and mdx/CD38 ^−/− (isoproterenol, n = 8) mice.
• G, H
  Time‐lapse images recorded by confocal microscopy in “line‐scanning mode”, showing Ca²⁺ sparks and waves in cardiomyocytes at rest, extracted from mdx and mdx/CD38 ^−/− mice; scale bars: 10 µM (horizontal), 500 ms (vertical). Bar graphs showing the averaged Ca²⁺ spark (G) and wave (H) frequencies in cardiomyocytes isolated from WT (n = 21 cells), mdx (n = 28 cells), and mdx/CD38 ^−/− (n = 32 cells) mice.
• I
  Bar graph showing the fractional release following caffeine application in cardiomyocytes from WT (n = 24 cells), mdx (n = 33 cells), and mdx/CD38 ^−/− (n = 32 cells) mice.
• J
  Bar graph showing the post‐rest potentiation in cardiomyocytes from WT (n = 24 cells), mdx (n = 28 cells), and mdx/CD38 ^−/− (n = 32 cells) mice.

Data information: A,B,C: Each dot of the graphs represents a mouse. A,F in duplicate; C in triplicate; and D,E one value/mouse. G,H,I,J: experiments performed in three mice of each group. After normality and variance comparison tests, significance was assessed using: A₁,B₁,B₂,C,I: ANOVA followed by Fisher's LSD test; A₂,A₃,G,H,J: the Kruskal–Wallis test followed by Dunn’s test; D: the log‐rank Mantel–Cox test and the log‐rank test for trend and the Gehan–Breslow–Wilcoxon test; E,F₂: the Kruskal–Wallis test followed by the Mann–Whitney tests; and F₁: ANOVA followed by Student’s/ Welch’s t‐tests. Values are expressed as means ± SEM. Significance: *P < 0.05, **P < 0.01, and ***P < 0.001.

Source data are available online for this figure.