Synergy between interstitial flow and VEGF directs capillary morphogenesis in vitro through a gradient amplification mechanism
Synergy between interstitial flow and VEGF directs capillary morphogenesis in vitro through a gradient amplification mechanism
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DOI：
10.1073/pnas.0503681102
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发表时间：
2005-11-01
影响因子：
11.1
通讯作者：
Swartz, MA
中科院分区：
文献类型：
--
作者：
Helm, CLE;Fleury, ME;Swartz, MA
细胞组织在很大程度上是由形态发生蛋白的细胞外梯度调控的。VEGF是毛细血管形成的重要因子，储存在细胞外基质中，但它和其他基质结合的形态因子被动员形成空间梯度的机制尚不清楚。在这里，我们提出了一种在毛细管形态发生的体外模型中，由微妙的生物物理力产生形态发生梯度的有效机制。使用纤维蛋白结合的VEGF变体，通过蛋白水解释放来模拟体内情况，我们报告了低水平的间质流动与VEGF协同作用来驱动内皮组织，而单独的每种刺激作用很小。为了帮助解释这种协同作用，我们展示了这些缓慢的流动如何使细胞分泌的蛋白酶分布偏倚，有趣的是，这导致了相对于细胞的VEGF梯度的增加，并在流动方向上倾斜。相反，单独的扩散只能解释对称的、递减的自分泌梯度。事实上，只有在VEGF与血流结合的情况下，毛细血管结构的分支才偏向于血流方向。因此，这项工作证明了形态形成梯度产生和放大的一般机制，由已知存在于体内的普遍存在的小机械力。
Cell organization is largely orchestrated by extracellular gradients of morphogenetic proteins. VEGF, an essential factor for capillary formation, is stored in the extracellular matrix, but the mechanisms by which it and other matrix-bound morphogens are mobilized to form spatial gradients are poorly understood. Here, we suggest an efficient mechanism for morphogen gradient generation by subtle biophysical forces in an in vitro model of capillary morphogenesis. Using a fibrin-bound VEGF variant that is released proteolytically to mimic the in vivo situation, we report that low levels of interstitial flow act synergistically with VEGF to drive endothelial organization, whereas each stimulus alone has very little effect. To help account for this synergy, we show how these slow flows can bias the distribution of cell-secreted proteases, which leads, interestingly, to the creation of an increasing VEGF gradient relative to the cell and skewed in the direction of flow. In contrast, diffusion alone can only account for symmetric, decreasing autocrine gradients. Indeed, branching of capillary structures was biased in the direction of flow only with the combination of VEGF and flow. This work thus demonstrates a general mechanism of morphogen gradient generation and amplification by small ubiquitous mechanical forces that are known to exist in vivo.