老年 5xFAD 小鼠的认知能力下降、Aβ 病理学和血脑屏障功能。

Cognitive decline, Aβ pathology, and blood-brain barrier function in aged 5xFAD mice.

机构信息

Sanders-Brown Center On Aging, University of Kentucky, 760 Press Ave, 124 HKRB, Lexington, KY, 40536-0679, USA.

Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.

出版信息

Fluids Barriers CNS. 2024 Mar 27;21(1):29. doi: 10.1186/s12987-024-00531-x.

DOI:10.1186/s12987-024-00531-x

PMID:38532486

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC10967049/

Abstract

BACKGROUND

Patients with Alzheimer's disease (AD) develop blood-brain barrier dysfunction to varying degrees. How aging impacts Aβ pathology, blood-brain barrier function, and cognitive decline in AD remains largely unknown. In this study, we used 5xFAD mice to investigate changes in Aβ levels, barrier function, and cognitive decline over time.

METHODS

5xFAD and wild-type (WT) mice were aged between 9.5 and 15.5 months and tested for spatial learning and reference memory with the Morris Water Maze (MWM). After behavior testing, mice were implanted with acute cranial windows and intravenously injected with fluorescent-labeled dextrans to assess their in vivo distribution in the brain by two-photon microscopy. Images were processed and segmented to obtain intravascular intensity, extravascular intensity, and vessel diameters as a measure of barrier integrity. Mice were sacrificed after in vivo imaging to isolate brain and plasma for measuring Aβ levels. The effect of age and genotype were evaluated for each assay using generalized or cumulative-linked logistic mixed-level modeling and model selection by Akaike Information Criterion (AICc). Pairwise comparisons were used to identify outcome differences between the two groups.

RESULTS

5xFAD mice displayed spatial memory deficits compared to age-matched WT mice in the MWM assay, which worsened with age. Memory impairment was evident in 5xFAD mice by 2-threefold higher escape latencies, twofold greater cumulative distances until they reach the platform, and twice as frequent use of repetitive search strategies in the pool when compared with age-matched WT mice. Presence of the rd1 allele worsened MWM performance in 5xFAD mice at all ages but did not alter the rate of learning or probe trial outcomes. 9.5-month-old 15.5-month-old 5xFAD mice had twofold higher brain Aβ and Aβ levels (p < 0.001) and 2.5-fold higher (p = 0.007) plasma Aβ levels compared to 9.5-month-old 5xFAD mice. Image analysis showed that vessel diameters and intra- and extravascular dextran intensities were not significantly different in 9.5- and 15.5-month-old 5xFAD mice compared to age-matched WT mice.

CONCLUSION

5xFAD mice continue to develop spatial memory deficits and increased Aβ brain levels while aging. Given in vivo MP imaging limitations, further investigation with smaller molecular weight markers combined with advanced imaging techniques would be needed to reliably assess subtle differences in barrier integrity in aged mice.

摘要

背景

阿尔茨海默病（AD）患者的血脑屏障功能会出现不同程度的障碍。衰老如何影响 AD 中的 Aβ 病理学、血脑屏障功能和认知能力下降，目前仍知之甚少。在这项研究中，我们使用 5xFAD 小鼠来研究 Aβ 水平、屏障功能和认知能力随时间的变化。

方法

9.5 至 15.5 月龄的 5xFAD 和野生型（WT）小鼠接受 Morris 水迷宫（MWM）测试，以评估其空间学习和参考记忆能力。行为测试后，使用急性颅窗植入和静脉内注射荧光标记的葡聚糖，通过双光子显微镜评估其在体内的分布。对图像进行处理和分割，以获得血管内强度、血管外强度和血管直径，作为屏障完整性的衡量标准。体内成像后，处死小鼠分离大脑和血浆，测量 Aβ 水平。使用广义或累积链接逻辑混合水平模型以及 Akaike 信息准则（AICc）进行模型选择，评估每个测定的年龄和基因型的影响。使用成对比较来确定两组之间的结果差异。

结果

与年龄匹配的 WT 小鼠相比，5xFAD 小鼠在 MWM 测试中表现出空间记忆缺陷，且随着年龄的增长而恶化。与年龄匹配的 WT 小鼠相比，5xFAD 小鼠的逃避潜伏期高出 2-3 倍，到达平台的累计距离高出 2 倍，在水池中重复搜索策略的使用频率高出两倍，表明记忆受损。rd1 等位基因的存在使 5xFAD 小鼠在所有年龄段的 MWM 表现都变差，但不改变学习速度或探测试验结果。与 9.5 月龄的 5xFAD 小鼠相比，9.5 月龄和 15.5 月龄的 5xFAD 小鼠的大脑 Aβ 和 Aβ 水平分别高出 2 倍（p < 0.001）和 2.5 倍（p = 0.007），血浆 Aβ 水平分别高出 2 倍（p < 0.001）和 2.5 倍（p = 0.007）。图像分析显示，与年龄匹配的 WT 小鼠相比，9.5 月龄和 15.5 月龄的 5xFAD 小鼠的血管直径以及血管内和血管外葡聚糖强度没有显著差异。