Choi, W.Y., Gemberling, M., Wang, J., Holdway, J.E., Shen, M.C., Karlstrom, R.O., and Poss, K.D. (2013) In vivo monitoring of cardiomyocyte proliferation to identify chemical modifiers of heart regeneration. Development (Cambridge, England). 140(3):660-666.
Adult mammalian cardiomyocytes have little capacity to proliferate in response to injury, a deficiency that underlies the
poor regenerative ability of human hearts after myocardial infarction. By contrast, zebrafish regenerate heart muscle after
trauma by inducing proliferation of spared cardiomyocytes, providing a model for identifying manipulations that block or enhance
these events. Although direct genetic or chemical screens of heart regeneration in adult zebrafish present several challenges,
zebrafish embryos are ideal for high-throughput screening. Here, to visualize cardiomyocyte proliferation events in live zebrafish
embryos, we generated transgenic zebrafish lines that employ fluorescent ubiquitylation-based cell cycle indicator (FUCCI)
technology. We then performed a chemical screen and identified several small molecules that increase or reduce cardiomyocyte
proliferation during heart development. These compounds act via Hedgehog, Insulin-like growth factor or Transforming growth
factor β signaling pathways. Direct examination of heart regeneration after mechanical or genetic ablation injuries indicated
that these pathways are activated in regenerating cardiomyocytes and that they can be pharmacologically manipulated to inhibit
or enhance cardiomyocyte proliferation during adult heart regeneration. Our findings describe a new screening system that
identifies molecules and pathways with the potential to modify heart regeneration.