PARP1 overexpression promotes heart regeneration in neonatal mice. (A) Representative western blot and statistical analysis of PARP1 protein expression in control mice and PARP1CKI mice. GAPDH was used as a loading control (n=7 per group). ***P < 0.001 by unpaired Student's t-test. (B) Statistical analysis of EF and FS of echocardiography at P28 in control mice and PARP1CKI mice (n=4 per group). (C and D) WGA staining and statistical analysis of WGA staining and HW/BW ratio in control mice and PARP1CKI mice at P7 (n=5-6 per group), **P < 0.01 by unpaired Student's t-test. (E and F) Representative immunostaining images and statistical analysis of pH3+ (red) cardiomyocyte number in control mice and PARP1CKI mice at P7 (n=4 per group). Scale bars, 10μm. ***P < 0.001 by unpaired Student's t-test. (G and H) WGA staining and statistical analysis of WGA staining and HW/BW ratio in control mice and PARP1CKI mice at P28 (n=4-7 per group). **P < 0.01 by unpaired Student's t-test. (I and J) Representative immunostaining images and statistical analysis of pH3+ (red) cardiomyocyte number in control mice and PARP1CKI mice at P28 (n=4 per group). Scale bars, 10μm. ***P < 0.001 by unpaired Student's t-test. (K and L) Representative immunostaining images and statistical analysis of pH3+ cardiomyocytes (red) in control mice and PARP1CKI mice at 7 dpr (n=6 per group). Scale bars, 10 μm. ***P < 0.001 by unpaired Student's t-test. (M and N) Representative immunostaining images and statistical analysis of Ki67+ cardiomyocytes (red) in control mice and PARP1CKI mice at 7 dpr (n=6 per group). Scale bars, 10 μm. ***P < 0.001 by unpaired Student's t-test. (O and P) Masson staining images and statistical analysis of heart regeneration and scar size in control mice and PARP1CKI mice (n=5-6 per group). Scale bars, 500 μm. ***P < 0.001 by unpaired Student's t-test. (Q) Statistical analysis of EF and FS of echocardiography in control mice and PARP1CKI mice at 21 dpr (n=5 per group), *P < 0.05, **P < 0.01 by unpaired Student's t-test.