Keratocytes synthesize stromal proteins and participate in wound healing through successive differentiation into corneal fibroblasts and myofibroblasts. Cultured keratocytes or corneal fibroblasts are also known as non-professional phagocytes and innate immune cells. However, whether the corneal fibroblasts phagocytize their dead cells and whether the associated innate immunity is enhanced remains unknown. We initially characterized immortalized corneal fibroblast cells with the expression of specific genes. The corneal fibroblasts strongly expressed extracellular matrix molecules (FN and COL1A1) and low or medium levels of macrophage markers (CD14, CD68, and CD36), inflammatory cytokines (IL1A, IL1B, and IL6), and chemokines (IL8 and CCL2), but not CD11b, suggesting that corneal fibroblasts are macrophage-like fibroblasts. We confirmed the phagocytic activity of the corneal fibroblasts with fluorescent dye labeled-dead E. coli and S. aureus bacteria using confocal microscopy and flow cytometry. To test corneal fibroblast phagocytosis of apoptotic and necrotic cells we co-cultured corneal fibroblasts with fluorescent dye labeled-apoptotic and -necrotic cells and analyzed their uptake using fluorescence and confocal microscopy. We observed that corneal fibroblasts can engulf digested or processed cellular debris and entire dead cells. Co-cultured dying and dead cells strongly enhanced the expression of cytokine (IL1A, IL1B, and IL6), chemokine (CCL2, CCL5, CCL20, IL8, and CXCL10), and MMP (MMP1, MMP3, and MMP9) genes through the NF-κB signaling pathway. Our findings suggest that dying and dead cells stimulate corneal fibroblasts to further induce inflammatory factors and that corneal fibroblasts contribute to the clearing of cell debris as non-professional phagocytes.

中文翻译：

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响应角膜成纤维细胞中死细胞，细胞碎片的吸收和炎性因子的表达增强。

角质形成细胞合成基质蛋白并通过连续分化为角膜成纤维细胞和成肌纤维细胞参与伤口愈合。培养的角膜细胞或角膜成纤维细胞也称为非专业吞噬细胞和先天免疫细胞。然而，角膜成纤维细胞是否吞噬其死细胞以及相关的先天免疫是否增强尚不清楚。我们最初用特定基因的表达来表征永生的角膜成纤维细胞。角膜成纤维细胞强烈表达细胞外基质分子（FN和COL1A1）和低或中等水平的巨噬细胞标志物（CD14，CD68和CD36），炎性细胞因子（IL1A，IL1B和IL6）和趋化因子（IL8和CCL2），但不是CD11b，这说明角膜成纤维细胞是巨噬细胞样成纤维细胞。我们使用共聚焦显微镜和流式细胞术证实了荧光染料标记的死大肠杆菌和金黄色葡萄球菌对角膜成纤维细胞的吞噬活性。为了测试凋亡和坏死细胞的角膜成纤维细胞吞噬作用，我们将角膜成纤维细胞与荧光染料标记的凋亡和坏死细胞共培养，并使用荧光和共聚焦显微镜分析了它们的摄取。我们观察到角膜成纤维细胞可以吞噬消化或加工的细胞碎片和整个死细胞。共培养的垂死细胞和死细胞通过NF大大增强了细胞因子（IL1A，IL1B和IL6），趋化因子（CCL2，CCL5，CCL20，IL8和CXCL10）和MMP（MMP1，MMP3和MMP9）基因的表达-κB信号通路。