The retinal pigment epithelium (RPE) maintains photoreceptor viability and function, completes the visual cycle, and forms the outer blood-retinal barrier (oBRB). Loss of RPE function gives rise to several monogenic retinal dystrophies and contributes to age-related macular degeneration. Retinal detachment (RD) causes separation of the neurosensory retina from the underlying RPE, disrupting the functional and metabolic relationships between these layers. Although the retinal response to RD is highly studied, little is known about how the RPE responds to loss of this interaction. RNA sequencing (RNA-Seq) was used to compare normal and detached RPE in the C57BL6/J mouse. The naïve mouse RPE transcriptome was compared to previously published RPE signature gene lists and from the union of these 14 genes (Bmp4, Crim1, Degs1, Gja1, Itgav, Mfap3l, Pdpn, Ptgds, Rbp1, Rnf13, Rpe65, Slc4a2, Sulf1 and Ttr) representing a core signature gene set applicable across rodent and human RPE was derived. Gene ontology enrichment analysis (GOEA) of the mouse RPE transcriptome identified expected RPE features and functions, such as pigmentation, phagocytosis, lysosomal and proteasomal degradation of proteins, and barrier function. Differentially expressed genes (DEG) at 1 and 7 days post retinal detachment (dprd) were defined as mRNA with a significant (padj≤0.05) fold change (FC) of 0.67 ≥ FC ≥ 1.5 in detached versus naïve RPE. The RPE transcriptome exhibited dramatic changes at 1 dprd, with 2297 DEG identified. The KEGG pathways and biological process GO groups related to innate immune responses were significantly enriched. Lipocalin 2 (Lcn2) and several chemokines were upregulated, while numerous genes related to RPE functions, such as pigment synthesis, visual cycle, phagocytosis, and tight junctions were downregulated at 1 dprd. The response was largely transient, with only 18 significant DEG identified at 7 dprd, including upregulation of complement gene C4b. Validation studies confirmed RNA-Seq results. Thus, the RPE quickly downregulates cell-specific functions and mounts an innate immune defense response following RD. Our data demonstrate that the RPE contributes to the inflammatory response to RD and may play a role in attraction of immune cells to the subretinal space.

中文翻译：

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小鼠视网膜色素上皮在视网膜脱离后产生先天免疫防御反应

视网膜色素上皮 (RPE) 维持光感受器的活力和功能，完成视觉周期，并形成外血视网膜屏障 (oBRB)。 RPE 功能丧失会导致多种单基因视网膜营养不良，并导致年龄相关性黄斑变性。视网膜脱离 (RD) 导致感觉神经视网膜与底层 RPE 分离，破坏这些层之间的功能和代谢关系。尽管视网膜对 RD 的反应得到了深入研究，但对于 RPE 如何应对这种相互作用的丧失却知之甚少。 RNA 测序 (RNA-Seq) 用于比较 C57BL6/J 小鼠中正常和分离的 RPE。将幼稚小鼠 RPE 转录组与之前发布的 RPE 特征基因列表以及这 14 个基因（Bmp4、Crim1、Degs1、Gja1、Itgav、Mfap3l、Pdpn、Ptgds、Rbp1、Rnf13、Rpe65、Slc4a2、Sulf1 和 Ttr）的联合进行比较）代表了适用于啮齿动物和人类 RPE 的核心特征基因集。小鼠 RPE 转录组的基因本体富集分析 (GOEA) 确定了预期的 RPE 特征和功能，例如色素沉着、吞噬作用、蛋白质的溶酶体和蛋白酶体降解以及屏障功能。视网膜脱离（dprd）后1天和7天的差异表达基因（DEG）被定义为在脱离与幼稚RPE中具有显着（padj≤0.05）倍数变化（FC）0.67≥FC≥1.5的mRNA。 RPE 转录组在 1 dprd 时表现出巨大的变化，确定了 2297°。与先天免疫反应相关的KEGG通路和生物过程GO组显着富集。脂质运载蛋白 2 (Lcn2) 和几种趋化因子上调，而许多与 RPE 功能相关的基因，如色素合成、视觉周期、吞噬作用和紧密连接，在 1 dprd 时下调。该反应很大程度上是短暂的，在 7 dprd 时仅识别出 18 个显着的 DEG，包括补体基因 C4b 的上调。验证研究证实了 RNA 测序结果。因此，RPE 会迅速下调细胞特异性功能，并在 RD 之后启动先天免疫防御反应。我们的数据表明，RPE 有助于 RD 的炎症反应，并可能在吸引免疫细胞到视网膜下腔中发挥作用。