Mohler Emile R, Fang Yun, Shaffer Rebecca Gusic, Moore Jonni, Wilensky Robert L, Parmacek Michael, Levitan Irena
Department of Medicine, Cardiovascular Division, Section of Vascular Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
Biochem Biophys Res Commun. 2007 Jun 22;358(1):317-24. doi: 10.1016/j.bbrc.2007.04.138. Epub 2007 Apr 30.
Inwardly-rectifying K(+) (Kir) channels are responsible for maintaining membrane potentials in a variety of cell types including endothelial cells where they modulate endothelium-dependent vasorelaxation. The goal of this study is to determine the functional expression of Kir channels in porcine bone marrow-derived side population (BM-SP) cells that demonstrate phenotypes of endothelial progenitor cells (EPCs). We further asses the hypercholesterolemia sensitivity of Kir channels in BM-SP cells, which may play a key role in hypercholesterolemia-mediated regulation of EPCs.
To assess the effect of hypercholesterolemia on Kir channels in BM-SP, Kir currents were recorded in SP cells sorted from the bone marrow of healthy or hypercholesterolemic animals.
We found Kir channels constitute the major conductance in porcine bone marrow-derived side population (BM-SP) cells. These cells are defined by their efficiency of Hoechst dye efflux and have been reported to differentiate into multiple cell lineages including endothelium in vivo. We demonstrate here that porcine BM-SP cells differentiate to an endothelial lineage (CD31(+), vWF(+)) supporting the hypothesis that these cells are endothelial progenitor cells. Also, BM-SP cells express Kir with biophysical properties recapitulating those in mature endothelial cells, but with a much higher current density. Flow cytometric (FACS) analysis indicated that the number of SP cells was unaffected by hypercholesterolemia. However, hypercholesterolemia significantly inhibited Kir channels in BM-SP cells.
We successfully demonstrate that BM side population cells represent an origin of endothelial progenitor cells. This study further shows, for the fist time, that the functional expression of Kir channels in bone marrow (BM)-derived SP. Moreover, we demonstrate that hypercholesterolemia condition significantly suppresses the Kir channels in BM-SP cells, suggesting that hypercholesterolemia-mediated regulation of Kir channels may be an important factor not only in dysfunction of mature endothelium but also in dysfunction of BM-SP cells.
内向整流钾（Kir）通道负责维持多种细胞类型的膜电位，包括内皮细胞，在这些细胞中它们调节内皮依赖性血管舒张。本研究的目的是确定猪骨髓来源的侧群（BM-SP）细胞中Kir通道的功能表达，这些细胞表现出内皮祖细胞（EPC）的表型。我们进一步评估了BM-SP细胞中Kir通道对高胆固醇血症的敏感性，这可能在高胆固醇血症介导的EPC调节中起关键作用。
为了评估高胆固醇血症对BM-SP中Kir通道的影响，在从健康或高胆固醇血症动物骨髓中分离的SP细胞中记录Kir电流。
我们发现Kir通道构成猪骨髓来源的侧群（BM-SP）细胞中的主要电导。这些细胞通过其Hoechst染料外排效率来定义，并且据报道在体内可分化为多种细胞谱系，包括内皮细胞。我们在此证明猪BM-SP细胞分化为内皮谱系（CD31(+)，vWF(+)），支持了这些细胞是内皮祖细胞的假设。此外，BM-SP细胞表达的Kir具有与成熟内皮细胞中相似的生物物理特性，但电流密度更高。流式细胞术（FACS）分析表明，SP细胞的数量不受高胆固醇血症的影响。然而，高胆固醇血症显著抑制了BM-SP细胞中的Kir通道。
我们成功证明BM侧群细胞代表内皮祖细胞的一个来源。本研究首次进一步表明，骨髓（BM）来源的SP中Kir通道的功能表达。此外，我们证明高胆固醇血症状态显著抑制BM-SP细胞中的Kir通道，表明高胆固醇血症介导的Kir通道调节可能不仅是成熟内皮功能障碍的重要因素，也是BM-SP细胞功能障碍的重要因素。
