Nehls V, Herrmann R, Hühnken M
Medizinische Klinik, Institut für Klinische Biochemie und Pathobiochemie der Universität Würzburg, Germany.
Histochem Cell Biol. 1998 Apr;109(4):319-29. doi: 10.1007/s004180050232.
To investigate mechanisms of capillary network remodeling, we developed a serum-free angiogenesis in vitro system in three-dimensional fibrin matrices which allows the study of directional growth of endothelial sprouts, anastomosis, and remodeling ('pruning') of the primitive plexus toward more elaborated capillary trees. To follow the movements of living endothelial cells by inverse-fluorescence microscopy, we cocultured unlabeled endothelial cells with endothelial cells labeled with the carbocyanine dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI). We show that elongation and retraction of neighboring capillary sprouts occurs simultaneously, resembling a tug-of-war by which endothelial cells are withdrawn from shortening sprouts to become incorporated in other sprouts nearby. For the first time, we directly demonstrate the long-suspected parallel sliding movement of endothelial cells. We show that cell migration persists within immature capillaries even after sprouts have merged to continuous capillary loops, leading to overlapping growth of opposing sprout tips. As a novel concept of capillary remodeling, we distinguish two types of endothelial cell migration: sprouting and guided migration. Sprouting is the de novo invasion of a matrix by endothelial cells, and guided migration is the locomotion of cells along preexistent capillary-like structures. We show that guided migration leads to remodeling of immature capillary networks and to the retraction of sprouts. We describe a method for quantification of sprouting versus guided migration in DiI-mosaic-labeled capillary networks, and we present evidence that endothelial cell-derived basic fibroblast growth factor serves as a chemotactic signal for other cells to migrate along a preestablished capillary-like structure.
为了研究毛细血管网络重塑的机制，我们在三维纤维蛋白基质中开发了一种无血清体外血管生成系统，该系统可用于研究内皮芽的定向生长、吻合以及原始血管丛向更复杂的毛细血管树的重塑（“修剪”）。为了通过反向荧光显微镜追踪活内皮细胞的运动，我们将未标记的内皮细胞与用碳氰染料1,1'-二辛基-3,3,3',3'-四甲基吲哚碳菁高氯酸盐（DiI）标记的内皮细胞共培养。我们发现相邻毛细血管芽的伸长和回缩同时发生，类似于一场拔河比赛，内皮细胞从缩短的芽中撤出，并入附近的其他芽中。我们首次直接证明了长期以来怀疑的内皮细胞平行滑动运动。我们发现，即使芽合并成连续的毛细血管环后，细胞迁移仍在未成熟的毛细血管内持续，导致相对芽尖的重叠生长。作为毛细血管重塑的一个新概念，我们区分了两种类型的内皮细胞迁移：芽生和引导迁移。芽生是内皮细胞对基质的从头侵袭，引导迁移是细胞沿着预先存在的毛细血管样结构的运动。我们发现引导迁移导致未成熟毛细血管网络的重塑和芽的回缩。我们描述了一种在DiI镶嵌标记的毛细血管网络中定量芽生与引导迁移的方法，并且我们提供证据表明内皮细胞衍生的碱性成纤维细胞生长因子作为一种趋化信号，促使其他细胞沿着预先建立的毛细血管样结构迁移。
