Human microglia differentially respond to ß-amyloid, tau, and combined Alzheimer's disease pathologies in vivo

Recent studies have identified important species-dependent differences in the response of microglia to beta-amyloid pathology. Yet, whether human microglia also interact differently with the pathognomonic combination of amyloid and tau pathologies that occurs in Alzheimer's Disease (AD) remains unclear. We generated a xenotolerant mouse model of AD that develops both plaque and tangle pathologies, transplanted stem cell derived microglial progenitors and examined the interactions between human microglia and AD pathologies with scRNA sequencing, immunohistochemistry, and in vitro modeling. Combined amyloid and tau pathologies induced robust type-I interferon and proinflammatory cytokine responses, as well as an increased adoption of a distinct “rod” morphology in human microglia. The Rod morphology could be induced with type-I interferon treatment in vitro. We provide new insights into human microglial responses to combined AD pathologies and a novel platform to investigate and manipulate human microglia in vivo. Overall design: Cultured human iPSC-derived microglia were treated with DPBS or Interferon alpha (50 ng/ml), interferon beta (50 ng/ml), interferon gamma (100 ng/ml) for 48 hours. Cells were then collected, washed and pelleted and RNA was extracted using a standard Trizol protocol.

既往研究已揭示，小胶质细胞（microglia）对β淀粉样蛋白病理的应答存在显著的物种依赖性差异。然而，人类小胶质细胞是否同样会与阿尔茨海默病（Alzheimer's Disease, AD）中出现的特征性淀粉样蛋白与tau蛋白病理组合产生差异化相互作用，目前仍未明确。本研究构建了可同时形成淀粉样斑块与神经原纤维缠结病理的异种耐受型AD小鼠模型，移植干细胞来源的小胶质细胞前体，并通过单细胞RNA测序（single-cell RNA sequencing, scRNA sequencing）、免疫组织化学与体外模型，探究人类小胶质细胞与AD病理的相互作用。研究发现，联合存在的淀粉样蛋白与tau蛋白病理可诱导人类小胶质细胞产生强烈的I型干扰素与促炎细胞因子应答，同时显著增加其呈现独特“杆状”形态的比例；体外实验证实，通过I型干扰素处理即可诱导产生该杆状形态。本研究为解析人类小胶质细胞对联合AD病理的应答提供了新视角，并构建了可在体内探究与调控人类小胶质细胞的全新实验平台。整体实验设计：培养的人类诱导多能干细胞（induced pluripotent stem cell, iPSC）来源小胶质细胞分别经杜氏磷酸盐缓冲液（DPBS）、α干扰素（50 ng/ml）、β干扰素（50 ng/ml）与γ干扰素（100 ng/ml）处理48小时，随后收集细胞、洗涤并离心沉淀，采用标准Trizol提取流程提取总RNA。