Abstract 12087: KCa3.1 Channels Support Resting Potential and Proliferative Function During Store-Operated Ca2+-Entry in c-kit+ Endogenous Cardiac Stem Cells
Introduction: Adult hearts contain c-kit+ endogenous cardiac stem cells (eCSCs). Cultured eCSCs express a wide range of ion channels, but cell culture is known to affect phenotype. Here we defined ion currents in freshly isolated c-kit+ eCSCs and their potential functional role.
Methods: eCSCs isolated from healthy and heart failure (HF, ventricular tachypacing X 2 wks) dog hearts were magnetically purified with c-kit antibodies. Ion currents and membrane potential were recorded with patch clamp.
Results: Contrary to cultured c-kit+ eCSCs, ion currents were barely detectable with Ca2+i buffered (Fig A). Free Ca2+i activated prominent IKCa3.1 (TRAM34 sensitive, Fig B) in 82% of cells. IKCa3.1 was reduced in eCSCs isolated from HF dogs (Fig C), along with corresponding KCNN4 mRNA (Fig D). Under perforated patch to maintain spontaneous physiological [Ca2+]i, eCSCs had a membrane potential (Vmem) of -73±10 mV. Ca2+i depletion with nominally 0 mM [Ca2+]o strongly depolarized the membrane. After passive Ca2+i depletion, store-operated channel (SOC) mediated Ca2+ entry (SOCE) caused a robust Vmem hyperpolarization (from -21±4 to -79±7 mV, p<0.001). The SOCE effect on Vmem was substantially reduced by both 2-APB (SOC inhibitor) and TRAM34 (Fig E). Inhibiting KCa3.1 (TRAM34, 0.1 μM) or SOCs (2-APB, 50 μM) in culture decreased c-kit+ eCSCs proliferation by 21% (p<0.05) and 55% (p<0.001) respectively.
Conclusions: In contrast to cultured eCSCs, voltage-dependent ion currents are virtually absent from freshly isolated c-kit+ eCSCs. IKCa3.1 is prominent and maintains Vmem in the face of substantial Ca2+ entry from SOCs. This Ca2+ entry would normally depolarize the cell, reduce the gradient for Ca2+ entry and turn off the Ca2+ signal. We hypothesize that the Ca2+-mediated KCa3.1 K+-conductance increase is necessary to maintain Vmem in the face of the Ca2+ entry that activates eCSC proliferation, and that KCa3.1 channels may therefore play an important role in eCSC function.
Author Disclosures: P. Vigneault: None. P. Naud: None. D.R. Davis: None. S. Nattel: None.
- © 2015 by American Heart Association, Inc.