Doxorubicin (Adriamycin) is an anthracycline chemotherapy agent effective in treating a wide range of malignancies with a well–established dose–response cardiotoxic side effect that can lead to heart failure. At present, it is not possible to predict which patients will be affected by doxorubicin-induced cardiotoxicity (DIC). Here we demonstrate that patient–specific human induced pluripotent stem cell–derived cardiomyocytes (hiPSC–CMs) can recapitulate individual patients’ predilection to DIC at the single cell level. hiPSC–CMs derived from breast cancer patients who suffered clinical DIC are consistently more sensitive to doxorubicin toxicity, demonstrating decreased cell viability, mitochondrial and metabolic function, calcium handling, and antioxidant pathway activity, along with increased reactive oxygen species (ROS) production compared to hiPSC–CMs from patients who did not experience DIC. Together, our data indicate that hiPSC–CMs are a suitable platform for identifying and verifying the genetic basis and molecular mechanisms of DIC.

Background Despite the promise shown by stem cells for restoration of cardiac function following myocardial infarction (MI), the poor survival of transplanted cells has been a major issue. Hypoxia inducible factor-1 (HIF-1) is a transcription factor that mediates adaptive responses to ischemia. Here we hypothesize that co-delivery of cardiac progenitor cells (CPCs) with a nonviral minicircle plasmid carrying HIF-1 (MC-HIF1) into the ischemic myocardium can improve the survival of transplanted CPCs. Methods and Results Following MI, CPCs were co-delivered intramyocardially into adult NOD/SCID mice with either saline, MC-GFP, or MC-HIF1 versus MC-HIF1 alone (N=10/group). Bioluminescence imaging (BLI) demonstrated better survival when CPCs were co-delivered with MC-HIF1. Importantly, echocardiography showed mice injected with CPCs + MC-HIF1 had the highest ejection fraction 6 weeks post-MI (57.1±2.6%) followed by MC-HIF1 alone (48.5±2.6%), with no significant protection for CPCs + MC-GFP (44.8±3.3%) compared to saline control (38.7±3.2%, P<0.05). In vitro mechanistic studies confirmed that cardiac endothelial cells (ECs) produced exosomes which were actively internalized by recipient CPCs. Exosomes purified from ECs overexpressing HIF-1 had higher contents of miR-126 and miR-210. These microRNAs activated pro-survival kinases and induced a glycolytic switch in recipient CPCs, giving them increased tolerance when subjected to in vitro hypoxic stress. Inhibiting both of these miRs blocked the protective effects of the exosomes. Conclusions In summary, HIF-1 can be used to modulate the host microenvironment for improving survival of transplanted cells. The exosomal transfer of miRs from host cells to transplanted cells represents a unique mechanism that can be potentially targeted for improving survival of transplanted cells.

Left ventricular non-compaction (LVNC) is the third most prevalent cardiomyopathy in children and its pathogenesis has been associated with the developmental defect of the embryonic myocardium. We show that patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) generated from LVNC patients carrying a mutation in the cardiac transcription factor TBX20 recapitulate a key aspect of the pathological phenotype at the single-cell level and was associated with perturbed transforming growth factor beta (TGFβ) signaling. LVNC iPSC-CMs have decreased proliferative capacity due to abnormal activation of TGFβ signaling. TBX20 regulates the expression of TGFβ signaling modifiers including a known genetic cause of LVNC, PRDM16, and genome editing of PRDM16 caused proliferation defects in iPSC-CMs. Inhibition of TGFβ signaling and genome correction of the TBX20 mutation were sufficient to reverse the disease phenotype. Our study demonstrates that iPSC-CMs are a useful tool for the exploration of pathological mechanisms underlying poorly understood cardiomyopathies including LVNC.