Congestive Heart Failure Upregulates Volume-Dependent Chloride Currents in c-Kit(+) Endogenous Cardiac Stem Cells

Introduction: Adult hearts contain c-Kit + endogenous cardiac stem cells (eCSCs) that are being studied for regenerative therapy. eCSCs express volume-dependent Cl - channels ( I Cl,vol ) activated under hemodynamic stress. Here, we examined the changes in eCSC Cl - channels caused by experimental congestive heart failure (CHF). Methods: c-Kit + eCSCs isolated from healthy (CTL) and CHF (tachypaced) dog hearts were magnetically purified with c-Kit antibodies. Cl - channel expression in freshly isolated cells was studied with patch clamp and qPCR. Results: Under isotonic conditions, ionic currents were barely detectable in CTL eCSCs (Fig. A). The current observed was time-independent and reversed at values close to the calculated Cl - equilibrium potential ( E Cl - ≈ -40 mV). This current was insensitive to TEA-Cl but inhibited by the Cl - channel blocker DIDS. When cells were superfused with hypo-osmotic solution (0.7T), an outward current with unchanged reversal potential was activated, and completely inhibited by DIDS (Fig. B). CHF eCSCs had much larger DIDS-sensitive currents under isotonic conditions vs CTL (Fig. C), and were significantly smaller than CTL (membrane capacitance 4.2±2.1 pF vs 5.5±1.9 pF). Among DIDS-sensitive Cl - channels known to be expressed on plasma membranes, only Clcn3 was present in c-Kit + eCSCs. Consistent with patch-clamp data, Clcn3 expression was greater in CHF eCSCs vs CTL (Fig. D). Inhibiting Cl - currents in vitro with DIDS (100 μM) or NPPB (50 μM) decreased eCSC proliferation by 17% (p Conclusions: In contrast to CTL c-Kit + eCSCs, I Cl,vol is strongly activated under basal conditions in CHF. Transient activation of Cl - channels is required to initiate cell proliferation, but sustained Cl - channel activation and cell-shrinkage as seen in CHF c-Kit + eCSCs is associated with programmed cell death. Therefore, the up-regulation of Cl - currents in CHF c-Kit + eCSCs may have pathophysiological significance.