ABSTRACT
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 (AT2 R) 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 AT2 R-stimulated conditions. METHODS: CD117(pos) murine bone marrow stem cells were isolated with MACS technique and stimulated for the AT2 R 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 acLDL uptake assay. RESULTS: A well-expressed inward rectifying current (IKir ) 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 AT2 R-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 acLDL. CONCLUSIONS: CD117(pos) cells do not have properties of action potential-generating cells and moderately change their excitability during AT2 R stimulation. Electrophysiological and molecular properties of control and AT2 R-stimulated cells point to a differentiation to vascular endothelial cells. This could increase beneficial vascularization in injured tissues.
