Functional BKCa Channel in Human Resident Cardiac Stem Cells Expressing W8B2

Abstract

The adult human heart harbors several populations of cardiac/progenitors stem cells that express specific markers. Recently, a new population of resident cardiac stem cells was identified. These cells are positive for W8B2 marker (called also mesenchymal stem cell antigen-1). W8B2 positive cardiac stem cells (W8B2+ CSCs) exhibit a strong therapeutic potential when transplanted into a chronic myocardial infarction rat model. However, the functional characterization (electrophysiology and calcium signaling) of these cells has not been studied yet. We first establish the conditions of isolation and expansion of W8B2+ CSCs from human heart biopsies by magnetic cell sorting system followed by flow cytometry cell sorting. These cells have a self-renewal capacity demonstrated by their ability to form colonies. In addition, our preliminary results of RT-qPCR show an induction of transcripts encoding contractile proteins such as actin and cardiac troponin-T after in vitro differentiation of W8B2+ CSCs. This differentiation is accompanied by the appearance of cyclic calcium activity assessed by the calcium protein sensor GCaMP protein. The analysis of calcium activity shows that calcium oscillations profile change during differentiation. Using patch-clamp in whole cell configuration, we show for the first time the electrophysiological signing of BKCa channel. In addition, RT-PCR analysis reveals the presence of KCNMA1 (BKCa) mRNA in W8B2+ CSCs. Interestingly, BKCa channel inhibition by paxilline decreases cell proliferation in a concentration-dependent manner and abolishes calcium activity after W8B2+ CSCs differentiation. Taken together, our results are consistent with an important role of BKCa channels on cell cycle progression and on calcium activity during stem cell differentiation.