Age-related macular degeneration (AMD) is the principal cause of permanent blindness among elderly individuals worldwide. Chronic inflammation in the subretinal space is associated with a progression of exudative AMD. Progranulin (PGRN) is a growth factor secreted from myeloid cells and plays an important role in controlling the lysosomal function. A deficiency in PGRN leads to inflammation of the neurons in the central nervous system. The purpose of this study was to investigate the role played by PGRN in the size of the choroidal neovascularization (CNV) in laser-induced CNV mice. CNVs were induced in C57BL/6J mice by laser photocoagulation of the retina. The expression of PGRN and the accumulation of Iba-1+ cells around the sites of the CNVs were determined. Grn−/−, Grn+/−, and Grn+/+ mice with laser-induced CNVs were also studied. To evaluate the effect of macrophages on the inflammation, we used a macrophage cell line (RAW264.7) in which the expression of PGRN was knocked down by RNA interference and peritoneal macrophages derived from Grn−/− and Grn+/+ mice. These cells were incubated under hypoxic conditions (1% O2). Iba-1+ myeloid cells migrated and accumulated in the photocoagulation-induced CNV areas, and the CNV lesions secreted high levels of PGRN in Grn+/+ mice. The size of the CNVs was larger in Grn−/− mice than in Grn+/− and Grn+/+ mice. In Grn−/− mice, the number of ocular-infiltrating Iba-1+ cells around the CNV was higher, and these cells produced more VEGF-A than the cells in the Grn+/+ mice. PGRN-silencing of RAW264.7 cells led to abnormal activation of the cells. In addition, hypoxic conditions promoted the production of proangiogenic and proinflammatory cytokines from PGRN-deficient macrophages. Interestingly, the expression level of lysosome-associated proteins and the number of activated lysosomes increased in PGRN-deficient macrophages. These findings indicate that PGRN deficiency in Iba-1+ cells activates the lysosomal function that then leads to abnormal inflammation. The aberrant activation of Iba-1+ myeloid cells might contribute to the progression of the CNV and the regulation of these cells might be a novel therapeutic target for exudative AMD.

中文翻译：

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Iba-1+骨髓细胞中颗粒蛋白前体缺乏通过扰乱溶酶体功能和异常炎症加剧脉络膜新生血管形成

年龄相关性黄斑变性 (AMD) 是全球老年人永久性失明的主要原因。视网膜下腔的慢性炎症与渗出性 AMD 的进展有关。颗粒蛋白前体 (PGRN) 是骨髓细胞分泌的一种生长因子，在控制溶酶体功能中起重要作用。PGRN 的缺乏会导致中枢神经系统中的神经元发炎。本研究的目的是研究 PGRN 在激光诱导的 CNV 小鼠脉络膜新生血管 (CNV) 大小中所起的作用。通过视网膜的激光光凝术在 C57BL/6J 小鼠中诱导 CNV。测定了 PGRN 的表达和 CNV 位点周围 Iba-1+ 细胞的积累。还研究了具有激光诱导的 CNV 的 Grn-/-、Grn++/- 和 Grn++/+ 小鼠。为了评估巨噬细胞对炎症的影响，我们使用了巨噬细胞系 (RAW264.7)，其中 PGRN 的表达被 RNA 干扰和源自 Grn-/- 和 Grn+/+ 小鼠的腹膜巨噬细胞敲低。这些细胞在低氧条件（1% O2）下培养。Iba-1+ 骨髓细胞在光凝诱导的 CNV 区域迁移和积累，Grn+/+ 小鼠的 CNV 病变分泌高水平的 PGRN。Grn-/- 小鼠中 CNV 的大小比 Grn++/- 和 Grn+/+ 小鼠中的大。在 Grn-/- 小鼠中，CNV 周围的眼部浸润性 Iba-1+ 细胞数量较多，这些细胞比 Grn+/+ 小鼠中的细胞产生更多的 VEGF-A。RAW264.7 细胞的 PGRN 沉默导致细胞异常激活。此外，缺氧条件促进了 PGRN 缺陷巨噬细胞产生促血管生成和促炎细胞因子。有趣的是，在 PGRN 缺陷型巨噬细胞中，溶酶体相关蛋白的表达水平和活化溶酶体的数量增加。这些发现表明 Iba-1+ 细胞中的 PGRN 缺乏会激活溶酶体功能，然后导致异常炎症。Iba-1+ 骨髓细胞的异常激活可能有助于 CNV 的进展，这些细胞的调节可能是渗出性 AMD 的新治疗靶点。这些发现表明 Iba-1+ 细胞中的 PGRN 缺乏会激活溶酶体功能，然后导致异常炎症。Iba-1+ 骨髓细胞的异常激活可能有助于 CNV 的进展，这些细胞的调节可能是渗出性 AMD 的新治疗靶点。这些发现表明 Iba-1+ 细胞中的 PGRN 缺乏会激活溶酶体功能，然后导致异常炎症。Iba-1+ 骨髓细胞的异常激活可能有助于 CNV 的进展，这些细胞的调节可能是渗出性 AMD 的新治疗靶点。