Abstract 16982: Human Cardiomyocytes Generated From Muliple iPS Cell Lines Exhibit Mature Calcium Handling
Background: Cardiomyocytes (CM) derived from human induced pluripotent stem cells (iPSC) are increasingly used to model human disease phenotypes, but Ca handling of iPSC-CM has not been comprehensively investigated.
Objective: To compare Ca handling of human iPSC-CM generated independently by three labs (Wu lab at Stanford, Hong lab at Vanderbilt, Kamp lab at U. of Wisconsin) with that of acutely isolated adult rabbit ventricular CM under identical experimental conditions.
Methods and Results: Human iPSC-CM (21-25 days post cardiac induction) were plated at low density on matrigel-coated dishes, and studied 3-4 days after plating. Acutely-isolated native adult rabbit CM served as control. CMs were loaded with the ratiometric Ca indicator Fura-2AM and studied at room temperature in Tyrode’s solution (2 mM Ca). The contribution of major Ca removal pathways sarcoplasmic reticulum (SR) Ca ATPase (SERCA), NaCa exchanger (NCX) and plasma membrane Ca ATPase (PMCA) was evaluated using the flux balance method. Importantly, cytosolic Ca buffering was not significantly different between iPSC-CM (Bmax=105±19 μmol/L cytosol, Kd=0.6±0.1 μmol, n=11) and rabbit-CM (Bmax=117±15 μmol/L cytosol, Kd=0.61±0.11 μM, n=9). All 3 iPSC-CM lines exhibited robust caffeine-releasable SR Ca stores. SR Ca content (measured by caffeine spritz and NXC integral) and height of field-stimulated (0.5 Hz) Ca transients were not significantly different from rabbit CM. Ca transient decay rates (tau [s]) were comparable in the 3 iPSC-CM (Vanderbilt 1.09±0.06; Wiconsin 0.99±0.09; Stanford 0.84±0.09; n=12-17), but significantly faster in rabbit CM (0.54±0.04, n=27, p<0.01). However, the relative contribution of SR Ca uptake via SERCA and plasma membrane Ca transport via NCX and PMCA was the same as in native rabbit CM (Figure).
Conclusions: Human iPSC-CM from different labs all exhibit functional SR Ca handling that is characteristic of mature mammalian CM.
- © 2013 by American Heart Association, Inc.