Abstract 18186: Restoration of Impaired Diastolic Function in Induced Pluripotent Stem Cell Derived Cardiomyocytes From Hypertrophic Cardiomyopathy Patients by Re-Balancing the Calcium Homeostasis
Introduction: Diastolic dysfunction, defined as the abnormal filling and elevated pressures of ventricles during diastole phase, is commonly seen in patients with hypertrophic cardiomyopathy (HCM). However, the cellular mechanism of diastolic dysfunction in HCM is not fully understood, and no specific drug so far has been developed.
Hypothesis: We hypothesize here that patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from HCM patients can be used to study cellular mechanisms and to screen for drugs reversing diastolic dysfunctions in HCM.
Methods: We generated beating iPSC-CMs from healthy individuals and HCM patients carrying different mutations (MYH R663H and MYBPC3 R943ter). The contractility and calcium handling of iPSC-CMs were measured by traction force microscopy and Fura-2 AM ratiometric calcium imaging.
Results: Using calcium transient and contractile force simultaneous recording, we found that calcium sensitivity of myofilament, measured as T-C gain factor, was greatly increased in iPSC-CMs with HCM mutations. Also, Fura-2 AM calcium imaging indicated significant elevation of resting cytoplasmic calcium concentration and higher arrhythmia probability in HCM iPSC-CMs compared to WT cells, which were exaggerated by β-adrenergic challenge. Thus, both elevated basal calcium level and increased calcium sensitivity of myofilament contribute to the prolonged diastolic phase in HCM cardiomyocytes (887±36 ms) compared to WT cells (405±23 ms) (P<0.05). Expression profiling of HCM and WT iPSC-CMs indicated that increased expression of calcium channels may underlie the increased basal calcium concentration in HCM cells. Partial blocking of the calcium influx by verapamil and diltiazem reset the basal calcium level, attenuate calcium mishandling, and restore the diastolic function in HCM iPSC-CMs. Finally, cell viability assay show that re-balancing calcium homeostasis benefit long-term survival of HCM iPSC-CMs at both basal level and β-adrenergic stress conditions.
Conclusion: In summary, our studies have revealed novel cellular mechanisms and novel therapeutic targets of diastolic dysfunction in HCM.
Author Disclosures: H. Wu: None. H. Yang: None. T. Seeger: None. C. Lam: None. J.Z. Zhang: None. J.C. Wu: None.
- © 2016 by American Heart Association, Inc.