High-Throughput Screening Platform in Postnatal Heart Cells and Chemical Probe Toolbox to Assess Cardiomyocyte Proliferation

Restoring lost heart muscle is an
attractive goal for cardiovascular
regenerative medicine. One appealing strategy is the therapeutic stimulation
of cardiomyocyte proliferation, which inter alia remains
challenging due to available assay technologies capturing the complex
biology. Here, a high-throughput-formatted phenotypic assay platform
was established using rodent whole heart-derived cells to preserve
the cellular environment of cardiomyocytes. Several readouts allowed
the quantification of cycling cardiomyocytes, including a transgenic
H2B-mCherry system for unequivocal, automated detection of cardiomyocyte
nuclei. A chemical genetics approach revealed pronounced species differences
and furnished pan-kinase inhibitors 5 and 36 as potent and robust inducers of endoreplication and acytokinetic
mitosis. Combined profiling of the commonly used p38 MAPK inhibitors
SB203580 (1), SB239063 (2) and a novel set
of skepinone-L (6) derivatives pointed to off-target
effects beyond p38 that might be critical for effective cardiomyocyte
cytokinesis. Kinome-focused screening eventually furnished TG003 (38) as a novel candidate for stimulating cardiomyocyte proliferation.