From vascular tissue mechanics to Klf2 transcription factor-induced angiogenesis

在血管系统中，机械转导通路响应于由血流或基底膜刚度诱导的机械刺激而被激活，并且在血管组织的发育和体内平衡中起重要作用。内皮细胞具有许多机械转换器，包括细胞-细胞连接处的钙粘蛋白和细胞-基质粘附处的整合素。法国合作伙伴最近证明，CCM复合物，耗尽遗传性和散发性脑血管疾病（脑海绵状血管畸形病理学），作为VE-钙粘蛋白依赖性细胞间相互作用和β 1整合素依赖性细胞-ECM粘附之间的节点。CCM蛋白复合物丢失后，细胞外基质力学因β 1整联蛋白活化而改变，并通过减弱VE-钙粘蛋白介导的细胞间粘附和提高内皮渗透性反馈到内皮细胞上。德国合作伙伴证明，机械敏感性转录因子Klf 2在斑马鱼ccm 2突变胚胎中上调，敲低Klf 2可恢复正常的心血管发育。合作，两个合作伙伴发现，β 1整合素参与Klf 2表达的上调。Klf 2的高表达水平通过诱导Egfl 7（一种ECM相关蛋白，其作为Notch信号传导的负调节剂和β 3整联蛋白信号传导的激活剂）而促成斑马鱼中的ccm突变表型。我们正在进行的合作支持这样一种假设，即CCM蛋白丢失后血管生成程序的激活可能是由β 1和β 3整合素信号传导协调的，这反过来又刺激了促血管生成Klf 2机械敏感性反应。首先，这项资助计划旨在阐明β 1整合素在发育过程中和CCM病理生理条件下调节Klf 2机械转导途径的收缩和信号传导途径。其次，我们将研究Klf 2信号转导调节endoMT过程和内皮稳定性的机制。我们的合作将斑马鱼模型的遗传学和发育生物学的力量与创新生物物理研究相关的体外受控细胞培养的深入机制方法结合在一起。该项目是一个跨学科的方法，旨在研究机械转导在心血管发育和CCM疾病中的作用，CCM疾病是血管系统的相关病理学。

In the vascular system, mechanotransduction pathways are activated in response to mechanical stimuli induced by blood flow or basement membrane stiffness and play important roles during the development and in the homeostasis of vascular tissues. Endothelial cells have numerous mechanotransducers including cadherins at cell-cell junctions and integrins at cell-matrix adhesions. The French partner recently demonstrated that the CCM complex, depleted in a hereditary and sporadic cerebrovascular disease (the Cerebral Cavernous Malformation pathology), functions as a node between VE-cadherin-dependent cell-cell interactions and beta1 integrin-dependent cell-ECM adhesion. Upon loss of the CCM protein complex, extracellular matrix mechanics is changed due to beta1 integrin activation and feeds back onto endothelial cells by weakening VE-cadherin-mediated cell-cell adhesion and by raising endothelial permeability. The German partner demonstrated that the mechanosensitive transcription factor Klf2 is upregulated in zebrafish ccm2 mutant embryos and that knocking down Klf2 restores normal cardiovascular development. Collaboratively, both partners found that beta1 integrin is involved in the upregulation of Klf2 expression. High expression levels of Klf2 contribute to the ccm mutant phenotype in zebrafish through induction of Egfl7, an ECM-associated protein, which functions as a negative regulator of Notch signaling and activator of beta3 integrin signaling. Our ongoing collaboration supports the hypothesis that the activation of an angiogenesis program upon loss of CCM proteins might be orchestrated by beta1 and beta3 integrin signaling, which in turn stimulates the proangiogenic Klf2 mechanosensitive response. First, this grant proposal aims at elucidating the contractile and signaling pathways by which beta1 integrin regulates the Klf2 mechanotransduction pathway during development and under CCM pathophysiological conditions. Secondly, we will investigate the mechanism(s) by which Klf2 signaling regulates endoMT processes and endothelial stability. Our collaboration brings together the power of genetics and developmental biology of the zebrafish model with the in-depth mechanistic approach of in vitro controlled cell culture associated with innovative biophysical studies. This project is an interdisciplinary approach that aims at investigating the role of mechanotransduction in cardiovascular development and in the CCM disease, which is an associated pathology of the cerebrovasculature.