Investigating Pericyte Roles in Blood-Brain Barrier Formation

摘要 血脑屏障(BBB)在血液和脑之间起着信号和运输接口的作用。这个 血脑屏障在胚胎发育早期就开始形成，因为中胚层来源的血管系统侵入 不成熟的中枢神经系统(CNS)，并获得血脑屏障特征，如紧密连接和缺乏 栅栏。成人血脑屏障在进一步成熟后，具有极低的通透性和丰富的分子 运输系统是通过与神经血管单位(NVU)的支持细胞相互作用来维持的。近期 研究表明，中枢神经系统周细胞在血脑屏障形成中的重要性，周细胞触发减少 跨细胞，白细胞黏附分子表达减少，紧密连接组织正常。 然而，在血脑屏障形成过程中能够引起这些重要变化的周细胞衍生因子的同一性 都是未知的。因此，我们对血脑屏障形成的分子机制的理解是 在这个方案中，我们的目标是进一步研究脑周细胞撞击的机制。 血脑屏障队形。探索血脑屏障形成的一种强大而创新的方法是使用人类诱导 多能干细胞(IPSC)技术模拟NVU的血脑屏障和相关的支持细胞。我们会 证明脑周细胞不仅可以区别于IPSCs，它们还可以调节关键的血脑屏障 IPSC来源的脑内皮细胞(BMECs)的特性。同时，使用基因组学方法，我们有 确定了一组周细胞来源的分泌因子，其中几种可以诱导IPSC的BBB特性- 来源的BMEC。结合这些方法，我们将研究周细胞衍生的机制 分泌因子可不同程度地调节IPSC来源的BMECs血脑屏障的形成。初步数据显示 周细胞衍生的分泌因子之一，BMP5，可以影响已知的标志性血脑屏障特性 由脑周细胞调节。也就是说，BMP5可以减少细胞转运，改善脑内紧密连接结构。 IPSC来源的BMEC。进一步研究BMP5调节血脑屏障形成的机制 在开发过程中，我们将使用遗传小鼠模型来探索BMP5信号是否对BBB是必需的 构成和功能。最后，我们将评估补充BMP5是否对小鼠有治疗作用 多发性硬化症的模型。了解周细胞衍生的血脑屏障形成调节因子可以产生许多 关于具有明显周细胞参与的脑部疾病的新的机械论见解。了解以下内容 屏障的形成途径也为恢复BBB衰弱功能开辟了新的途径 神经系统疾病。

ABSTRACT The blood-brain barrier (BBB) acts as a signaling and transport interface between the blood and brain. The BBB begins to form early in embryonic development as the mesoderm-derived vasculature invades the immature central nervous system (CNS) and acquires BBB characteristics such as tight junctions and a lack of fenestrae. After further maturation, the adult BBB, with its very low permeability and a wealth of molecular transport systems, is maintained by interactions with supporting cells of the neurovascular unit (NVU). Recent studies have indicated the importance of CNS pericytes in BBB formation, with pericytes triggering reduced transcytosis, reduced expression of leukocyte adhesion molecules and proper tight junction organization. However, the identity of pericyte-derived factors that can elicit these important changes during BBB formation are not known. Thus, our understanding of the molecular mechanisms underpinning BBB formation is incomplete; and in this proposal, we aim to further examine the mechanisms by which brain pericytes impact BBB formation. A powerful and innovative approach to explore BBB formation is the use of human induced pluripotent stem cell (iPSC) technology to model the BBB and the associated support cells of the NVU. We will demonstrate that not only can brain pericytes be differentiated from iPSCs, they can also regulate key BBB properties in iPSC-derived brain endothelial cells (BMECs). In parallel, using genomics approaches, we have identified a cohort of pericyte-derived secreted factors, several of which can induce BBB properties in iPSC- derived BMECs. Combining these approaches, we will examine the mechanisms whereby pericyte-derived secreted factors can differentially regulate BBB formation in iPSC-derived BMECs. Preliminary data indicate that one of the pericyte-derived secreted factors, BMP5, can influence hallmark BBB properties known to be regulated by brain pericytes. Namely, BMP5 can reduce transcytosis and improve tight junction structures in iPSC-derived BMECs. To further examine the mechanism by which BMP5 regulates BBB formation during development, we will use genetic mouse models to explore whether BMP5 signaling is necessary for BBB formation and function. Finally, we will assess whether BMP5 supplementation can be therapeutic in a mouse model of multiple sclerosis. Understanding the pericyte-derived regulators of BBB formation could yield many new mechanistic insights regarding brain diseases that have demonstrable pericyte involvement. Knowledge of the barrier formation pathways could also open new avenues for restoring BBB function in debilitating neurological disease.