Age-related blood-brain barrier disruption and cerebromicrovascular rarefaction contribute importantly to the pathogenesis of both vascular cognitive impairment and dementia (VCID) and Alzheimer's disease (AD). Recent advances in geroscience research enable development of novel interventions to reverse age-related alterations of the cerebral microcirculation for prevention of VCID and AD. To facilitate this research there is an urgent need for sensitive and easy-to-adapt imaging methods, which enable longitudinal assessment of changes in BBB permeability and brain capillarization in aged mice, that could be used in vivo to evaluate treatment efficiency. To enable longitudinal assessment of changes in BBB permeability in aged mice equipped with a chronic cranial window, we adapted and optimized two different intravital two-photon imaging approaches. By assessing relative fluorescence changes over the baseline within a volume of brain tissue, after qualitative image subtraction of the brain microvasculature, we confirmed that in 24 month old C57BL/6J mice cumulative permeability of the microvessels to fluorescent tracers of different molecular weights (0.3 kDa to 40 kDa) is significantly increased as compared to that of 5 month old mice. Real-time recording of vessel cross-sections showed that apparent solute permeability of single microvessels is significantly increased in aged mice vs. young mice. Cortical capillary density, assessed both by intravital two-photon microscopy and optical coherence tomography (OCT) was also decreased in aged mice vs. young mice. The presented methods are optimized for longitudinal in vivo assessment of cerebromicrovascular health in preclinical geroscience research.

中文翻译：

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通过双光子显微镜和光学相干断层扫描证实小鼠中与年龄相关的血脑屏障破坏和脑微血管稀疏


与年龄相关的血脑屏障破坏和脑微血管稀疏对血管性认知障碍和痴呆（VCID）以及阿尔茨海默病（AD）的发病机制有重要影响。老年科学研究的最新进展使得能够开发新的干预措施来逆转与年龄相关的大脑微循环改变，从而预防 VCID 和 AD。为了促进这项研究，迫切需要灵敏且易于适应的成像方法，能够对老年小鼠的血脑屏障通透性和脑毛细血管化的变化进行纵向评估，并可用于体内评估治疗效率。为了能够对配备慢性颅窗的老年小鼠的血脑屏障通透性变化进行纵向评估，我们采用并优化了两种不同的活体双光子成像方法。通过评估一定体积脑组织内相对于基线的相对荧光变化，在对脑微血管系统进行定性图像减除后，我们证实，在 24 个月大的 C57BL/6J 小鼠中，微血管对不同分子量（0.3 kDa）的荧光示踪剂的累积渗透性至 40 kDa）与 5 个月大的小鼠相比显着增加。血管横截面的实时记录表明，与年轻小鼠相比，老年小鼠的单个微血管的表观溶质渗透性显着增加。通过活体双光子显微镜和光学相干断层扫描（OCT）评估，老年小鼠的皮质毛细血管密度也比年轻小鼠有所降低。所提出的方法针对临床前老年科学研究中脑微血管健康的纵向体内评估进行了优化。