The mechanisms and role of postnatal cerebral vascular remodeling

描述(申请人提供)：大脑血液流动得到严格调节，以满足大脑巨大的能量需求。然而，目前尚不清楚在发育过程中，血管形成程度与局部代谢需求之间如何实现精确匹配。由于大量的突触发生，大脑在出生后早期的能量需求急剧增加。然而，出生后血管重塑的过程，可能是建立足够的血管网络的关键，仍然知之甚少。这一建议旨在增加我们对出生后血管重塑的了解。我们假设神经元的活动通过血管内皮生长因子(VEGF)促进出生后的血管重塑，这一过程的短暂中断对神经元的连接具有永久性的影响。为了测试这一点，我们将使用各种遗传和药理学方法来改变神经元的活动，以及使用双光子显微镜在固定组织和活着的小鼠大脑中进行血管和神经元成像。在具体目标1中，我们通过测量血管生成、发芽和修剪的程度来表征血管重塑的模式，并将其与局部突触密度相关联。在目标2中，我们利用药理学和遗传学的方法，通过改变神经元的活动来确定神经元活动对血管重塑的影响。我们还测量了神经元活动对血管内皮生长因子水平的影响。在目标3中，我们确定了改变出生后血管重塑对神经元结构和连接性的影响。此外，我们测试血管重塑是否发生在一个关键时期内，类似于出生后观察到的神经元连接的精细化。总之，这些研究将极大地促进我们对出生后血管重塑机制的理解，这可能在满足大脑的新陈代谢需求和维持神经元的健康方面至关重要。

DESCRIPTION (provided by applicant): Cerebral blood flow is tightly regulated to meet the brain's large energetic needs. Yet it remains unclear how a precise matching between the degree of vascularization and regional metabolic demands is achieved during development. The brain's energetic needs increase dramatically in the early postnatal period due to massive synaptogenesis. However, the process of postnatal vascular remodeling, which could be critical for establishing an adequate vascular network, remains poorly understood. This proposal aims at increasing our understanding of postnatal vascular remodeling. We hypothesize that neuronal activity promotes postnatal vascular remodeling via vascular endothelial growth factor (VEGF) and that transient disruption of this process has permanent consequences on neuronal connectivity. To test this, we will use a variety of genetic and pharmacological methods to alter neuronal activity as well as vascular and neuronal imaging in fixed tissues and the living mouse brain using two-photon microscopy. In specific aim 1, we characterize the patterns of vascular remodeling by measuring the degree of angiogenesis, sprouting and pruning and correlate it with regional synaptic density. In aim 2, we determine the effects of neuronal activity on vascular remodeling by altering neuronal activity using pharmacological and genetic methods. We also measure the effect of neuronal activity on levels of VEGF. In aim 3, we determine the effects of altering postnatal vascular remodeling on neuronal structure and connectivity. Additionally, we test whether vascular remodeling occurs within a critical period analogous to that observed with postnatal refinement of neuronal connections. Together, these studies will greatly advance our understanding of the mechanisms of postnatal vascular remodeling which may be critically important in meeting the metabolic demands of the brain and maintaining the health of neurons.