Priming of human iPSCs with doxorubicin causes genome-wide transcriptional reprogramming and functional impairments in iPSC-derived cardiomyocytes.

How Doxorubicin (Dox) mediated damage to stem cells or cardiomyocytes contributes to cardiotoxicity and cardiac regeneration is unclear. Using a human iPSC-based model together with corresponding iPSC-derived cardiomyocytes (iCMs) revealed that iPSCs are much more sensitive against single short pulse-treatments with Dox than iCMs. Major mitochondrial impairments such as increased mitochondrial fragmentation, loss of mitochondrial membrane potential, reduced ATP levels, and altered mitochondrial DNA (mtDNA) organization, yet neither increased ROS formation, nuclear DNA damage response, nor apoptosis were detected in Dox-treated iPSCs. Whole genome transcriptome profiling revealed major differences in the transcriptional response to Dox including downregulation of genes regulating cellular homeostasis and energy metabolism. Dox exposure at the iPSC stage, termed priming here, shifts the global transcriptional landscape of iCMs towards reduced cardiac muscle regeneration, energy metabolism, muscle contraction, and increased fibrosis. Functionally, priming caused iCMs to 'memorize' this early Dox treatment resulting in reduced ATP levels, altered mtDNA organization, and in impaired contractility and oscillating Ca2+ handling. We propose that Dox-induced mitochondrial dysfunction and transcriptional priming in stem cells alters durably cardiac and bioenergetic properties of its progeny which may impair the regenerative capacity after differentiation. This may be of particular relevance for children and teenagers undergoing chemotherapy.