Tyrosine kinase inhibitors (TKIs), despite efficacy as anti-cancer therapeutics, are associated with cardiovascular side effects ranging from induced arrhythmias to heart failure. We used patient-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), generated from 11 healthy individuals and 2 patients receiving cancer treatment, to screen FDA-approved TKIs for cardiotoxicities by measuring alterations in cardiomyocyte viability, contractility, electrophysiology, calcium handling, and signaling. With these data, we generated a “cardiac safety index” to assess cardiotoxicities of existing TKIs. TKIs with low cardiac safety indices exhibit cardiotoxicity in patients. We also derived endothelial cells (hiPSC-ECs) and cardiac fibroblasts (hiPSC-CFs) to examine cell type-specific cardiotoxicities. Using high-throughput screening, we determined that VEGFR2/PDGFR-inhibiting TKIs caused cardiotoxicity in hiPSC-CMs, hiPSC-ECs, and hiPSC-CFs. Using phosphoprotein analysis, we determined that VEGFR2/PDGFR-inhibiting TKIs led to a compensatory increase in cardioprotective insulin and insulin-like growth factor (IGF) signaling in hiPSC-CMs. Upregulating cardioprotective signaling with exogenous insulin or IGF1 improved hiPSC-CM viability during co-treatment with cardiotoxic VEGFR2/PDGFR-inhibiting TKIs. Thus, hiPSC-CMs can be used to screen for cardiovascular toxicities associated with anti-cancer TKIs, correlating with clinical phenotypes. This approach provides unexpected insights, as illustrated by our finding that toxicity can be alleviated via cardioprotective insulin/IGF signaling.

In eukaryotic cells, mitochondrial dysfunction is associated with a variety of human diseases. Delivery of exogenous functional mitochondria into damaged cells has been proposed as a mechanism of cell transplant and physiological repair for damaged tissue. We here demonstrated that isolated mitochondria can be transferred into homogeneic and xenogeneic cells by simple co-incubation using genetically labelled mitochondria, and elucidated the mechanism and the effect of direct mitochondrial transfer. Intracellular localization of exogenous mitochondria was confirmed by PCR, real-time PCR, live fluorescence imaging, three-dimensional reconstruction imaging, continuous time-lapse microscopic observation, flow cytometric analysis and immunoelectron microscopy. Isolated homogeneic mitochondria were transferred into human uterine endometrial gland-derived mesenchymal cells in a dose-dependent manner. Moreover, mitochondrial transfer rescued the mitochondrial respiratory function and improved the cellular viability in mitochondrial DNA-depleted cells and these effects lasted several days. Finally, we discovered that mitochondrial internalization involves macropinocytosis. In conclusion, these data support direct transfer of exogenous mitochondria as a promising approach for the treatment of various diseases.

Background: Molecular targeted chemotherapies have been shown to significantly improve cancer patient outcomes, but often cause cardiovascular side effects that limit their use and impair patients' quality of life. Cardiac dysfunction induced by these therapies, especially trastuzumab, shows a distinct cardiotoxic clinical phenotype compared to cardiotoxicity induced by conventional chemotherapies. Methods: We employed the human induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) platform to determine the underlying cellular mechanisms in trastuzumab-induced cardiac dysfunction. We assessed the effects of trastuzumab on structural and functional properties in iPSC-CMs from healthy individuals and performed RNA-sequencing (RNA-seq) to further examine the effect of trastuzumab on iPSC-CMs. We also generated iPSCs from patients receiving trastuzumab and examined whether patients' phenotype could be recapitulated in vitro using patient-specific iPSC-CMs.