Neuroblasts have a clustered phenotype critical for their unidirectional migration, which in part is dependent on signaling from microvascular endothelial cells (EC) and pericytes (PC). Diffusible signals secreted by vascular cells have been demonstrated to increase survival, proliferation, and differentiation of subventricular zone resident neural stem cells (NSC); however, the signals that promote the necessary initiating step of NSC clustering are undefined. To investigate the role of vascular cells in promoting NSC clustering and directing migration, we created a 3-D hydrogel that mimics the biomechanics, biochemistry, and architectural complexity of brain tissue. We demonstrate that EC, and not PC, have a crucial role in NSC clustering and migration, further verified through microfluidic chamber systems and traction force microscopy. Ablation of the extended NSC aggregate arm halts aggregate movement, suggesting that clustering is a prerequisite for migration. When cultured with EC, NSC clustering occurs and NSC coincidentally increase their expression of N-cadherin, as compared to NSC cultured alone. NSC-presented N-cadherin expression was increased following exposure to EC secreted metalloproteinase-2 (MMP2). We demonstrate that inhibition of MMP2 prevented NSC N-cadherin surface expression and subsequent NSC clustering, even when NSC were in direct contact with EC. Furthermore, with exogenous activation of EGFR, which serves as a downstream activator of N-cadherin cleavage, NSC form clusters. Our results suggest that EC secretion of MMP2 promotes NSC clustering through N-cadherin expression. The insight gained about the mechanisms by which EC promote NSC migration may enhance NSC therapeutic response to sites of injury.

中文翻译：

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内皮细胞分泌的金属蛋白酶-2 增强神经干细胞 N-钙粘蛋白的表达、聚集和迁移

神经母细胞具有对其单向迁移至关重要的聚集表型，这部分依赖于来自微血管内皮细胞 (EC) 和周细胞 (PC) 的信号传导。血管细胞分泌的可扩散信号已被证明可以增加脑室下区驻留神经干细胞 (NSC) 的存活、增殖和分化；然而，促进 NSC 聚类的必要启动步骤的信号是不确定的。为了研究血管细胞在促进 NSC 聚集和引导迁移中的作用，我们创建了一种 3-D 水凝胶，可以模拟脑组织的生物力学、生物化学和结构复杂性。我们证明 EC 而不是 PC 在 NSC 聚集和迁移中起着至关重要的作用，通过微流体室系统和牵引力显微镜进一步验证。延长 NSC 聚合臂的消融会停止聚合运动，这表明聚类是迁移的先决条件。与单独培养的 NSC 相比，当与 EC 一起培养时，会发生 NSC 聚类，并且 NSC 恰巧增加了它们的 N-钙粘蛋白表达。暴露于 EC 分泌的金属蛋白酶-2 (MMP2) 后，NSC 呈递的 N-钙粘蛋白表达增加。我们证明 MMP2 的抑制阻止了 NSC N-钙粘蛋白表面表达和随后的 NSC 聚集，即使 NSC 与 EC 直接接触。此外，外源性激活作为 N-钙粘蛋白裂解下游激活剂的 EGFR，NSC 形成簇。我们的结果表明 MMP2 的 EC 分泌通过 N-钙粘蛋白表达促进 NSC 聚集。