Roles of Functional Ion Channels In Human Cardiac C-Kit+ Progenitor Cells

Abstract

Background and objectives: Cardiac progenitor cells play an important role in cardiac repair and regeneration; however, cellular biology and electrophysiology are not understood. The present study was to investigate the functional ion channel expression in human cardiac c-kit+ progenitor cells and the 53 potential roles of these ion channels in regulating proliferation and migration. Methods: Multiple experimental approaches were employed in this study, including whole-cell patch voltage-clamp, RT-PCR, Western blots, cell proliferation and migration assays, etc. Results: Several ionic currents were heterogeneously expressed in human cardiac c-kit+ progenitor cells, including a large conductance Ca2+-activated K+ current (BKCa) in most (93%) of cells, an inwardly-rectifying K+ current (IKir) in 87% of cells, a transient outward K+ current (Ito) in 39% of cells, a voltage-gated tetrodotoxin-sensitive Na+ currents (INa,TTX) in 76% of cells. Molecular identities of these ionic currents were determined with RT-PCR and Western blot analysis. KCa.1.1 (for BKCa), Kir2.1 (for IKir), Kv4.2, Kv4.3 (for Ito), NaV1.2, NaV1.3, NaV1.6, NaV1.7 (for INa.TTX) were expressed in human cardiac progenitor cells. Inhibition of BKCa with paxilline, Ito with 4-aminopyridine, but not INa.TTX with TTX and IKir with Ba2+, decreased cell proliferation. Silencing of KCa.1.1, Kv4.2 or Kv4.3, but not Kir2.1, with siRNA targeting corresponding channels reduced proliferation. Inhibition of KCa1.1 or Kv4.2 or Kv4.3 channels accumulated cells at G0/G1 phase. Interestingly, down regulation of KCa1.1, Kv4.2 or Kv4.3 channels decreased, while of Kir2.1 channels increased migration in human c-kit+ progenitor cells. Conclusions: These results demonstrate for the first time that multiple ion channels are expressed in human cardiac c-kit+ cells. KCa1.1, Kv4.2, and Kv4.3 channels, but not Na+ channels and Kir 2.1 channels, participate in regulating proliferation. KCa1.1, Kv4.2 or Kv4.3 channels promote, while Kir2.1 channels reduce cell migration in human cardiac c-kit+ progenitor cells.