Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA.
J Neuroinflammation. 2024 Mar 25;21(1):74. doi: 10.1186/s12974-024-03062-2.
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 (p≤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.
视网膜色素上皮 (RPE) 维持光感受器的存活和功能，完成视觉循环，并形成外血视网膜屏障 (oBRB)。RPE 功能的丧失会导致几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) 导致神经感觉视网膜与下面的 RPE 分离，破坏了这些层之间的功能和代谢关系。尽管对 RD 引起的视网膜反应进行了广泛的研究，但对于 RPE 如何对这种相互作用的丧失作出反应知之甚少。使用 RNA 测序 (RNA-Seq) 比较了 C57BL6/J 小鼠中的正常和脱离的 RPE。将幼稚的 RPE 转录组与之前发表的 RPE 特征基因列表进行比较，并从这 14 个基因 (Bmp4、Crim1、Degs1、Gja1、Itgav、Mfap3l、Pdpn、Ptgds、Rbp1、Rnf13、Rpe65、Slc4a2、Sulf1 和 Ttr) 的联合中得出了一个核心特征基因集，适用于啮齿动物和人类的 RPE。对小鼠 RPE 转录组的基因本体论富集分析 (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。在视网膜脱离后 1 天 (1 dprd) 和 7 天 (7 dprd) 差异表达的基因 (DEG) 定义为与幼稚 RPE 相比，mRNA 的显著 (p≤0.05) 折叠变化 (FC) 为 0.67≥FC≥1.5。RPE 转录组在 1 dprd 时发生了剧烈变化，鉴定出 2297 个 DEG。与先天免疫反应相关的 KEGG 途径和生物学过程 GO 组显著富集。脂联素 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、视觉循环、吞噬作用和紧密连接，在 1 dprd 时下调。这种反应是短暂的，在 7 dprd 时仅鉴定出 18 个显著的 DEG，包括补体基因 C4b 的上调。验证研究证实了 RNA-Seq 的结果。因此，RPE 在 RD 后迅速下调细胞特异性功能并启动先天免疫防御反应。我们的数据表明，RPE 有助于对 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。
