Table_2_Transcriptomic Remodelling of Fetal Endothelial Cells During Establishment of Inflammatory Memory.xlsx

Inflammatory memory involves the molecular and cellular ‘reprogramming’ of innate immune cells following exogenous stimuli, leading to non-specific protection against subsequent pathogen exposure. This phenomenon has now also been described in non-hematopoietic cells, such as human fetal and adult endothelial cells. In this study we mapped the cell-specific DNA methylation profile and the transcriptomic remodelling during the establishment of inflammatory memory in two distinct fetal endothelial cell types – a progenitor cell (ECFC) and a differentiated cell (HUVEC) population. We show that both cell types have a core transcriptional response to an initial exposure to a viral-like ligand, Poly(I:C), characterised by interferon responsive genes. There was also an ECFC specific response, marked by the transcription factor ELF1, suggesting a non-canonical viral response pathway in progenitor endothelial cells. Next, we show that both ECFCs and HUVECs establish memory in response to an initial viral exposure, resulting in an altered subsequent response to lipopolysaccharide. While the capacity to train or tolerize the induction of specific sets of genes was similar between the two cell types, the progenitor ECFCs show a higher capacity to establish memory. Among tolerized cellular pathways are those involved in endothelial barrier establishment and leukocyte migration, both important for regulating systemic immune-endothelial cell interactions. These findings suggest that the capacity for inflammatory memory may be a common trait across different endothelial cell types but also indicate that the specific downstream targets may vary by developmental stage.

炎症记忆（Inflammatory memory）指先天免疫细胞（innate immune cells）在受到外源性刺激（exogenous stimuli）后发生分子与细胞层面的“重编程”，进而对后续病原体暴露产生非特异性保护作用。目前该现象也在非造血细胞（non-hematopoietic cells）中被报道，例如人类胎儿及成人内皮细胞（endothelial cells）。本研究针对两种不同的胎儿内皮细胞类型——祖细胞（ECFC）与分化细胞（HUVEC）群体，绘制了其在炎症记忆建立过程中的细胞特异性DNA甲基化谱（DNA methylation profile）与转录组重塑（transcriptomic remodelling）图谱。研究发现，两种细胞类型在初次接触病毒样配体（viral-like ligand）Poly(I:C)后均会产生核心转录应答，其特征为干扰素应答基因（interferon responsive genes）的表达上调。此外ECFC还存在特异性应答，该应答以转录因子（transcription factor）ELF1为标志，提示祖内皮细胞中存在非经典的病毒应答通路。随后，本研究证实ECFC与HUVEC均可在初次病毒暴露后建立记忆，进而改变其后续对脂多糖（lipopolysaccharide）的应答模式。尽管两种细胞在致敏或耐受特定基因集诱导的能力上较为相似，但祖细胞ECFC的记忆建立能力更强。在被耐受的细胞通路中，包含参与内皮屏障构建与白细胞迁移（leukocyte migration）的相关通路，这两类过程均对调控全身免疫-内皮细胞互作（immune-endothelial cell interactions）具有重要意义。本研究结果表明，炎症记忆的能力或许是不同内皮细胞类型共有的特征，但同时也提示其具体的下游效应靶点可能随发育阶段不同而存在差异。