Dose-dependent effects and mechanisms of exercise-like stimulation on cardiac injury and contractile function: outcomes of the MICRO-ATHLETE study.

Figures

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  Fig. 1. Schematic overview of the MICRO-ATHLETE experimental procedures. A EHTs were created using hiPSC-derived cardiomyocytes and cardiac fibroblasts. EHTs were used as non-stimulated controls, electrically stimulated for 2 or 4 h, or treated with Doxorubicin, and analyzed for biomarker concentrations, contractile function, markers of cell death and tissue integrity by imaging. B EL-EPS was applied by carbon electrodes in the platform. C EL-EPS increased spontaneous beating frequency to 2.5 Hz

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  Fig. 2. High-sensitivity cardiac troponin T (hs-cTnT) concentrations in non-stimulated controls, after 2 or 4 h of exercise-like electrical pulse stimulation (EL-EPS) or doxorubicin (DOX) treatment. Data are presented as median ± IQR, *p < 0.05, **p < 0.01 and ***p < 0.001

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  Fig. 3. Lactate Dehydrogenase (LDH) concentrations in non-stimulated controls, after 2 or 4 h of exercise-like electrical pulse stimulation (EL-EPS) or doxorubicin (DOX) treatment. Data are presented as median ± IQR, *p < 0.05, **p < 0.01 and ***p < 0.001

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  Fig. 4. Release of mitochondrial and nuclear DNA at recovery as a marker of cell death. A mtDNA copy number and B HBB copy number in non-stimulated controls, after 2 or 4 h of exercise-like electrical pulse stimulation (EL-EPS) or doxorubicin (DOX) treatment, measured following 20 h of recovery. Data are presented as median ± IQR. Statistical significance: *p < 0.05, **p < 0.01, ***p < 0.001

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  Fig. 5. Changes in contractile function in non-stimulated controls, after 2 or 4 h of exercise-like electrical pulse stimulation (EL-EPS) or doxorubicin (DOX) treatment. Alterations in contractile function relative to baseline were assessed by A Force of Contraction, B Contractile Velocity, and C Relaxation Velocity. Data are presented as median ± IQR, *p < 0.05, **p < 0.01 and ***p < 0.001

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  Fig. 6. Correlation of relative changes in force of contraction (FoC) following exposure with (A) hs-cTnT and (B) LDH concentrations following recovery

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  Fig. 7. Morphological analysis of non-stimulated controls, 2 and 4 h EL-EPS or doxorubicin (DOX)-exposed EHTs. Representative whole-mount tissue immunostaining of A control; B 2 h EL-EPS; C 4 h EL-EPS; and D DOX-exposed EHTs following 20 h of recovery. Sections were immunostained for cardiac troponin T (cTnT, red), Phalloidin (F-actin, green), and DAPI (nuclei, blue). White arrowheads depict the presence of actin aggregates