Characterization of ion currents of murine CD117pos stem cells in vitro and their modulation under AT2R stimulation.

Aim Hematopoietic stem cells, especially CD117^pos cells, have been found to possess a regenerative potential in various tissues, in particular cardiac muscle. However, the characterization of the relevant ion currents of stem cells prior to implantation lacks documentation. Activation of angiotensin II type 2 receptor ( AT₂R) can lead to further cell differentiation and receptor auto-expression and might thus influence electrophysiological properties of CD117^pos stem cells. This study was designed to functionally characterize membrane currents of CD117^pos cells under normal and AT₂R-stimulated conditions. Methods CD117^pos murine bone marrow stem cells were isolated with MACS technique and stimulated for the AT₂R with angiotensin II and losartan for 3-5 days prior to patch-clamp measurements. RT- PCR was used to determine channel expression. Endothelial properties were analysed with immunocytochemistry and ac LDL uptake assay. Results A well-expressed inward rectifying current ( I_Kir) was identified in cultured CD117^pos cells. Furthermore, a ZD 7288 ( HCN channel blocker)-sensitive current component was isolated. Voltage-dependent potassium currents and chloride currents were less expressed. A small fraction of cells demonstrated voltage- and time-dependent inward currents. In AT₂R-stimulated cells inward rectifying the hyperpolarization-induced inward currents were slightly attenuated on the translational level but showed increased mRNA expression. Cultured CD117^pos cells express CD31 and VEGFR-2 and significantly increased the uptake of ac LDL. Conclusions CD117^pos cells do not have properties of action potential-generating cells and moderately change their excitability during AT₂R stimulation. Electrophysiological and molecular properties of control and AT₂R-stimulated cells point to a differentiation to vascular endothelial cells. This could increase beneficial vascularization in injured tissues. [ABSTRACT FROM AUTHOR]