In Alzheimer’s disease (AD), microglia are affected by disease processes, but may also drive pathogenesis. AD pathology-associated microglial populations have been identified with single-cell RNA-Seq, but have not been validated in human brain tissue with anatomical context. Here, we quantified myeloid cell markers to identify changes in AD pathology-associated microglial populations. We performed fluorescent immunohistochemistry on normal (n = 8) and AD (n = 8) middle temporal gyri, co-labelling the pan-myeloid cell marker, Iba1, with one of 11 markers of interest (MOIs): CD45, HLA-DR, CD14, CD74, CD33, CD206, CD32, CD163, P2RY12, TMEM119, L-Ferritin. Novel image analyses quantified the single-cell abundance of Iba1 and each MOI. Each cell was gated into one Iba1-MOI population (Iba1low MOIhigh, Iba1high MOIhigh, or Iba1high MOIlow) and the abundance of each population was compared between AD and control. Triple-labelling of L-Ferritin and Iba1 with a subset of MOIs was performed to investigate L-Ferritin-MOI co-expression on Iba1low cells. Iba1low MOIhigh myeloid cell populations delineated by MOIs CD45, HLA-DR, CD14, CD74, CD33, CD32, and L-Ferritin were increased in AD. Further investigation of the Iba1low MOIhigh populations revealed that their abundances correlated with tau, but not amyloid beta, load in AD. The Iba1low microglial population highly expressed L-Ferritin, reflecting microglial dysfunction. The L-Ferritinhigh CD74high HLA-DRhigh phenotype of the Iba1low population mirrors that of a human AD pathology-associated microglial subpopulation previously identified using single-cell RNA-Seq. Our high-throughput immunohistochemical data with anatomical context support the microglial dysfunction hypothesis of AD.

中文翻译：

---

使用新型单细胞组织学图像分析鉴定人类阿尔茨海默病皮层中功能失调的小胶质细胞群

在阿尔茨海默病 (AD) 中，小胶质细胞受疾病过程的影响，但也可能驱动发病机制。AD 病理学相关的小胶质细胞群已用单细胞 RNA-Seq 鉴定，但尚未在具有解剖学背景的人脑组织中得到验证。在这里，我们量化了骨髓细胞标记物，以识别 AD 病理学相关小胶质细胞群的变化。我们对正常 (n = 8) 和 AD (n = 8) 颞中回进行了荧光免疫组化，共标记泛髓细胞标记物 Iba1，与 11 个感兴趣的标记物 (MOI) 之一：CD45、HLA-DR 、CD14、CD74、CD33、CD206、CD32、CD163、P2RY12、TMEM119、L-铁蛋白。新的图像分析量化了 Iba1 和每个 MOI 的单细胞丰度。每个细胞都被分为一个 Iba1-MOI 群体（Iba1low MOIhigh、Iba1high MOIhigh、或 Iba1high MOIlow)，并比较 AD 和对照之间每个种群的丰度。使用 MOI 子集对 L-铁蛋白和 Iba1 进行三重标记，以研究 L-铁蛋白-MOI 在 Iba1low 细胞上的共表达。由 MOIs CD45、HLA-DR、CD14、CD74、CD33、CD32 和 L-铁蛋白描绘的 Iba1low MOIhigh 骨髓细胞群在 AD 中增加。对 Iba1low MOIhigh 种群的进一步调查显示，它们的丰度与 AD 中的 tau 负荷相关，但与淀粉样蛋白 β 负荷无关。Iba1low 小胶质细胞群高度表达 L-铁蛋白，反映小胶质细胞功能障碍。Iba1low 群体的 L-Ferritinhigh CD74high HLA-DRhigh 表型反映了先前使用单细胞 RNA-Seq 鉴定的人类 AD 病理相关小胶质细胞亚群的表型。