Fig. 5.

Fig. 5.

Transient AT7519 treatment enhances cardiomyocyte number expansion and accelerates the rate of myocardial regeneration following injury. (A) Experimental timeline indicating cardiac injury, transient CDK9i treatment and imaging time points. (B) LSFM images of Tg(myl7:DsRed2-NLS) larvae displaying ventricular cardiomyocytes at 48 hpi following transient treatment with 0.3% DMSO vehicle (left), 50 μM AT7519 (middle) or 3 μM FVP (right). (C) Number of ventricular cardiomyocytes at 24 hpi and 48 hpi following transient treatment with ≤0.3% DMSO vehicle, 50 μM AT7519 (left) or 3 μM FVP (right). Error bars represent s.d., n=29 larvae, experimental n=3. **P<0.01 (one-way ANOVA and Tukey post-hoc test for comparisons between DMSO vehicle or CDK9i treatment groups). (D) Surface-rendered LSFM image of a Tg(myl7:GFP) heart. Dashed line outlines the ventricular apex area that is subject to laser injury. (E) Surface-rendered LSFM image of a Tg(myl7:GFP) wound at the ventricular apex at 24 hpi and 48 hpi, following transient treatment with 0.1% DMSO vehicle (top) or 50 μM AT7519 (bottom). Arrowheads indicate cardiomyocyte protrusions adjacent to the wound (myl7:GFP negative). (F) Myocardial wound area (μm²) at 24 hpi and 48 hpi following transient treatment with 0.1% DMSO vehicle or 50 μM AT7519. Error bars represent s.d., n=27 larvae, experimental n=3. One-way ANOVA and Tukey post-hoc test performed for comparisons between treatment groups. (G) Myocardial wound closure (%) between 24 hpi and 48 hpi following transient treatment with 0.1% DMSO vehicle or 50 μM AT7519. Error bars represent s.d., n=27 larvae, experimental n=3. *P<0.05 (Mann–Whitney U-test for comparison between treatment groups). (H) Surface-rendered LSFM time-lapse-derived images of an injured myl7:GFP ventricle; hpi indicated. Arrowheads indicate myocardial wound (myl7:GFP negative). Asterisk indicates cardiomyocytes bridging across the myocardial wound (myl7:GFP negative). LSFM fluorescence images were acquired in 3D and maximum intensity projections (B) or 3D renders (D,E,H) are displayed. Scale bars: 50 μm (B,H); 20 μm (E). ns, non-significant.