Global gene expression differences between blood- and lymphatic-specific endothelial colony forming cells

The identification of circulating endothelial progenitor cells has led to speculation regarding their origin as well as their contribution to neovascular development. Two distinct types of endothelium make up the blood and lymphatic vessel system. However, it has yet to be determined whether there are distinct lymphatic-specific circulating endothelial progenitor cells. We isolated circulating endothelial colony forming cells (ECFCs) from whole peripheral blood. These cells are endothelial in nature, as defined by their expression of endothelial markers and their ability to undergo capillary morphogenesis in three-dimensional culture. A subset of isolated colonies express markers of lymphatic endothelium, including VEGFR-3 and Prox-1, with low levels of VEGFR-1, a blood endothelial marker, while the bulk of the isolated cells express high VEGFR-1 levels with low VEGFR-3 and Prox-1 expression. The different isolates have differential responses to VEGF-C, a lymphatic endothelial specific cytokine, strongly suggesting that there are lymphatic specific and blood specific ECFCs. Global analysis of gene expression revealed key differences in the regulation of pathways involved in cellular differentiation between blood and lymphatic-specific ECFCs. These data indicate that there are two distinguishable circulating ECFC types, blood and lymphatic, which are likely to have discrete functions during neovascularization. Overall design: RNA was isolated from 2 blood-specific ECFC cell lines and 2 lymphatic-specific ECFC cell lines 3 separate times each

循环内皮祖细胞（circulating endothelial progenitor cells）的鉴定引发了关于其起源及对新生血管发育贡献的诸多推测。血液与淋巴管系统由两类截然不同的内皮细胞构成，但目前尚未明确是否存在特异性的淋巴系循环内皮祖细胞。我们从全外周血中分离出内皮集落形成细胞（endothelial colony forming cells, ECFCs）。这类细胞具有内皮细胞的固有特性，具体体现为其表达内皮细胞标志物，且能够在三维培养体系中完成毛细血管形态发生。部分分离得到的集落表达淋巴管内皮标志物，包括VEGFR-3与Prox-1，同时仅低水平表达血液内皮标志物VEGFR-1；而大部分分离细胞则高表达VEGFR-1，同时低表达VEGFR-3与Prox-1。不同分离株对淋巴管内皮特异性细胞因子VEGF-C的反应存在显著差异，这强烈提示存在淋巴系特异性与血液系特异性的ECFCs。基因表达的全局分析揭示了血液系与淋巴系特异性ECFC之间细胞分化通路调控的关键差异。上述数据表明，存在两种可区分的循环ECFC亚型——血液系与淋巴系，二者在新生血管形成过程中可能行使截然不同的功能。整体实验设计：分别从2株血液系特异性ECFC细胞系与2株淋巴系特异性ECFC细胞系中分离RNA，各重复实验3次。