Ocular Angiogenesis Group, Department of Ophthalmology and Department of Cell Biology and Histology, University of Amsterdam, Academic Medical Center, PO Box 22660, 1100 DD Amsterdam, The Netherlands.
Angiogenesis. 2012 Mar;15(1):151-63. doi: 10.1007/s10456-011-9251-z. Epub 2012 Jan 17.
The functional shift of quiescent endothelial cells into tip cells that migrate and stalk cells that proliferate is a key event during sprouting angiogenesis. We previously showed that the sialomucin CD34 is expressed in a small subset of cultured endothelial cells and that these cells extend filopodia: a hallmark of tip cells in vivo. In the present study, we characterized endothelial cells expressing CD34 in endothelial monolayers in vitro. We found that CD34-positive human umbilical vein endothelial cells show low proliferation activity and increased mRNA expression of all known tip cell markers, as compared to CD34-negative cells. Genome-wide mRNA profiling analysis of CD34-positive endothelial cells demonstrated enrichment for biological functions related to angiogenesis and migration, whereas CD34-negative cells were enriched for functions related to proliferation. In addition, we found an increase or decrease of CD34-positive cells in vitro upon exposure to stimuli that enhance or limit the number of tip cells in vivo, respectively. Our findings suggest cells with virtually all known properties of tip cells are present in vascular endothelial cell cultures and that they can be isolated based on expression of CD34. This novel strategy may open alternative avenues for future studies of molecular processes and functions in tip cells in angiogenesis.
静息内皮细胞向迁移的顶尖细胞和增殖的 stalk 细胞的功能转变是血管生成中发芽的关键事件。我们之前曾表明，唾液酸糖蛋白 CD34 在培养的内皮细胞中的一小部分细胞中表达，这些细胞伸出丝状伪足：这是体内顶尖细胞的标志。在本研究中，我们在体外内皮单层中鉴定了表达 CD34 的内皮细胞。与 CD34 阴性细胞相比，我们发现 CD34 阳性的人脐静脉内皮细胞显示出低的增殖活性和所有已知顶尖细胞标记物的 mRNA 表达增加。对 CD34 阳性内皮细胞的全基因组 mRNA 分析表明，与增殖相关的功能相关的生物学功能富集，而 CD34 阴性细胞富集与增殖相关的功能。此外，我们发现，在体外暴露于分别增强或限制体内顶尖细胞数量的刺激物后，CD34 阳性细胞的数量增加或减少。我们的研究结果表明，血管内皮细胞培养物中存在具有几乎所有已知顶尖细胞特性的细胞，并且可以基于 CD34 的表达来分离这些细胞。这种新策略可能为未来在血管生成中顶尖细胞的分子过程和功能的研究开辟替代途径。
