Center for Frontier Science and Engineering, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, 182-8585, Tokyo, Japan.
Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan.
Adv Exp Med Biol. 2013;789:15-20. doi: 10.1007/978-1-4614-7411-1_3.
To better understand cellular interactions of the cerebral angiogenesis induced by hypoxia, a spatiotemporal dynamics of cortical microvascular restructuring during an exposure to continuous hypoxia was characterized with in vivo two-photon microscopy in mouse cortex. The mice were prepared with a closed cranial window over the sensory-motor cortex and housed in 8-9 % oxygen room for 2-4 weeks. Before beginning the hypoxic exposure, two-photon imaging of cortical microvasculature was performed, and the follow-up imaging was conducted weekly in the identical locations. We observed that 1-2 weeks after the onset of hypoxic exposure, a sprouting of new vessels appeared from the existing capillaries. An average emergence rate of the new vessel was 15 vessels per unit volume (mm(3)). The highest emergence rate was found in the cortical depths of 100-200 μm, indicating no spatial uniformity among the cortical layers. Further, a leakage of fluorescent dye (sulforhodamine 101) injected into the bloodstream was not detected, suggesting that the blood-brain barrier (BBB) was maintained. Future studies are needed to elucidate the roles of perivascular cells (e.g., pericyte, microglia, and astroglia) in a process of this hypoxia-induced angiogenesis, such as sprouting, growth, and merger with the existing capillary networks, while maintaining the BBB.
为了更好地理解缺氧诱导的大脑血管生成的细胞相互作用，我们采用活体双光子显微镜在小鼠大脑皮层中对暴露于持续缺氧时皮质微血管结构重排的时空动力学进行了研究。在准备实验时，在感觉运动皮层上方放置了一个封闭的颅窗，并将小鼠饲养在 8-9%的氧气环境中 2-4 周。在开始缺氧暴露之前，对皮质微血管进行了双光子成像，并且在相同位置每周进行后续成像。我们观察到，在缺氧暴露开始后的 1-2 周内，新血管从现有的毛细血管中出现了分支。新血管的平均出现率为每单位体积（mm(3)）出现 15 个血管。在皮层深度为 100-200 μm 的部位出现的新血管出现率最高，这表明各皮层层之间没有空间均匀性。此外，未检测到注入血流中的荧光染料（磺基罗丹明 101）的渗漏，这表明血脑屏障（BBB）得以维持。未来的研究需要阐明周细胞（例如，周细胞、小胶质细胞和星形胶质细胞）在缺氧诱导的血管生成过程（例如发芽、生长和与现有毛细血管网络融合）中的作用，同时保持 BBB 的完整性。
