Abstract：
Delta like non-canonical Notch ligand 1 (DLK1), as a member of epidermal growth factor-like family, plays a critical role in somatic growth, tissue development and possibly tissue renewal. Though previous studies had indicated that DLK1 contributed to adipogenesis and myogenesis, it\'s still controversial whether DLK1 affects angiogenesis and how it interacts with Notch signaling with numerous conflicting reports from different models. Based on our preliminary finding that DLK1 expression was up-regulated in mice ischemic gastrocnemius and in the border zone of infarcted myocardium, we administered either recombinant DLK1 (rDLK1) or PBS in C57BL/6 mice after establishment of hindlimb ischemia (HLI) and myocardial infarction (MI), respectively. Exogenous rDLK1 administration significantly improved both blood perfusion of mice ischemic hindlimbs and muscle motor function on the 3rd, 7th day after HLI, by promoting neovascularization. Similar effect on neovascularization was verified in mice on the 28th day after MI as well as improvement of cardiac failure. Correspondingly, the number of CD34+KDR+ cells, indicated as endothelial progenitor cells (EPCs), was significantly in mice ischemic gastrocnemius by rDLK1 administration, which was abrogated by DAPT as the specific inhibitor of Notch intracellular domain (NICD). Furthermore, bone marrow mononuclear cells were obtained from C57BL/6 mice and differentiated to EPCs ex vivo. Incubation with rDLK1 triggered Notch1 mRNA and NICD protein expressions in EPCs as exposed to hypoxia and serum deprivation, promoting EPCs proliferation, migration, anti-apoptosis and tube formation. Otherwise, rDLK1 incubation significantly decreased intracellular and mitochondrial reactive oxygen species, increased ATP content and mitochondrial membrane potential, downregulated short isoform of OPA-1 expression whereas upregulated mitofusin (-1, -2) expression in EPCs by Notch1 signaling, which were all abrogated by DAPT. In summary, the present study unveils the pro-angiogenesis and its mechanism of rDLK1 through activation of Notch1 signaling in endothelial progenitor cells.
摘要：
Delta样非规范Notch配体1（DLK1），作为表皮生长因子家族的一员,在体细胞生长中起着关键作用，组织发育和可能的组织更新。尽管以前的研究表明DLK1有助于脂肪生成和肌肉生成，DLK1是否影响血管生成以及它如何与Notch信号相互作用仍有争议，来自不同模型的许多相互矛盾的报道。根据我们的初步发现，DLK1在小鼠缺血腓肠肌和梗死心肌边界区表达上调，在建立后肢缺血（HLI）和心肌梗死（MI）后，我们在C57BL/6小鼠中施用重组DLK1（rDLK1）或PBS，分别。外源性rDLK1显著改善小鼠缺血后肢的血流灌注和肌肉运动功能,HLI之后的第7天，通过促进新血管形成。在MI后第28天在小鼠中证实了对新血管形成的类似作用以及心力衰竭的改善。相应地,CD34+KDR+细胞的数量，表示为内皮祖细胞（EPCs），通过rDLK1给药在小鼠缺血腓肠肌中显著，DAPT作为Notch细胞内结构域（NICD）的特异性抑制剂被废除。此外，从C57BL/6小鼠获得骨髓单核细胞并体外分化为EPCs。暴露于缺氧和血清剥夺时，用rDLK1孵育可触发EPCs中Notch1mRNA和NICD蛋白的表达，促进EPC增殖，迁移,抗凋亡和管形成。否则,rDLK1孵育显著降低细胞内和线粒体活性氧，增加ATP含量和线粒体膜电位，OPA-1表达的短同工型下调，而通过Notch1信号在EPCs中上调mitofusin（-1，-2）表达，都被DAPT废除了。总之,本研究揭示了通过激活内皮祖细胞中的Notch1信号，rDLK1的促血管生成及其机制。
