Aspects Of The Retinal Pigment Epithelial Cell

RPE细胞在维持神经视网膜的结构和生理完整性方面起着基本的作用。其结构和功能的改变会导致光感受器和视力的丧失。我们对RPE细胞作为眼后极重要的免疫调节细胞进行了广泛的研究。我们对RPE细胞的研究活动可分为三类：正常细胞功能研究、细胞因子相互作用研究和感染过程研究。该项目致力于研究细胞因子与免疫系统的细胞以及眼部微环境中的细胞相互作用的方式。这些研究表明，细胞因子介导的RPE细胞活化可能是眼免疫的一个基本组成部分，也是RPE细胞移植的一个重要方面。在过去的一年里，我们对RPE细胞的Toll样受体(TLR)、血小板衍生生长因子(PDGF)的产生和ATP结合盒(ABC)进行了研究。TLR是天然免疫的重要组成部分，参与宿主对微生物病原体的防御。我们研究了TLRs在人视网膜色素上皮(RPE)细胞中的表达和功能。实时荧光定量聚合酶链式反应显示TLR1~7、9、10基因在RPE细胞中有表达。TLR1和TLR3是最高表达的TLRs。TLR3是病毒复制的中间体dsRNA的受体。由于RPE细胞表达TLR3，并且经常是病毒在视网膜内复制的部位，我们评估了TLR3信号。Poly I：C处理的RPE细胞产生干扰素-β，但不产生干扰素-α，而抗TLR3抗体处理的RPE细胞则抑制这种作用。重组人干扰素-β通过抑制病毒复制对RPE细胞具有生物活性。Poly I：C处理RPE后，IL-6、IL-8、MCP-1和sICAM-1的产生增加。RPE细胞上TLRs的存在以及由此产生的RPE细胞中的TLR信号表明，这些分子可能在视网膜内的先天和获得性免疫反应中发挥重要作用。 在我们对RPE细胞中细胞因子相互作用的持续研究中，我们观察到血小板衍生生长因子(PDGF)的基因表达和蛋白产生在转化生长因子-β处理后上调。这些研究表明，RPE细胞来源的PDGF促进间充质细胞的增殖和迁移，可能促进增生性玻璃体视网膜病变(PVR)相关的纤维血管组织的形成。 三磷酸腺苷结合盒(ABC)转运蛋白在生理和病理中发挥着重要作用。在合作研究中，我们发现两种mRNA亚型(ABCB5a和ABCB5b)在正常黑素细胞和RPE细胞中表达。这些研究表明，ABCBa/b的表达是色素细胞特异性的，可能参与黑素的形成。

The RPE cell plays a basic role in maintaining the structural and physiological integrity of the neural retina. Alterations in its structural and functional actions can result in loss of photoreceptors and vision. We have studied the RPE cell extensively as an important immunoregulatory cell within the posterior pole of the eye. Our research activities on RPE cells can be subdivided into three categories: normal cell function studies, cytokine interactions and infectious processes. This project has concentrated on studying the ways in which cytokines interact with cells of the immune system and with cells in the ocular microenvironment. These studies indicate that cytokine-mediated activation of RPE cells may be a basic component of ocular immunity and an important aspect of RPE cell transplantation. During the past year, we have studied the Toll-Like receptors (TLR), production of platelet derived growth factors (PDGF), and ATP-binding cassette (ABC) in RPE cells. TLRs are crucial components of innate immunity that participate in host defense against microbial pathogens. We evaluated the expression and function of TLRs in human retinal pigment epithelial (RPE) cells. Real time PCR analysis revealed gene expression for TLR 1 to 7, 9 and 10 in RPE cells. TLR 1 and 3 were the most highly expressed TLRs. TLR 3 is the receptor for dsRNA, an intermediate of virus replication. Since RPE cells express TLR 3 and are frequently the site of virus replication within the retina, we evaluated TLR 3 signaling. RPE cells treated with poly I:C produced IFN-beta but not IFN-alpha, and this was inhibited by treatment of RPE cells with anti-TLR 3 antibody. Human recombinant IFN-beta was shown to be biologically active on RPE cells by inhibiting viral replication. Poly I:C treatment of RPE resulted in an increase in the production of IL-6, IL-8, MCP-1 and sICAM-1. The presence of TLRs on RPE cells and the resultant TLR signaling in RPE cells suggest that these molecules may play an important role in innate and adaptive immune responses within the retina. In our continued studies on cytokine interactions in RPE cells we observed that platelet derived growth factor (PDGF) gene expression and protein production was up-regulated in response to TGF-beta treatment. These studies indicate that the promotion of the proliferation and migration of mesenchymal cells by RPE cell derived PDGF may facilitate the formation of fibrovascular tissues associated with proliferative vitreo-retinopathy (PVR). ATP-binding cassette (ABC) transporters play a pivotal role in physiology and pathology. In collaborative studies we identified two mRNA isoforms (ABCB5a and ABCB5b) are expressed in normal melanocytes and in RPE cells. These studies suggest that ABCBa/b expression is pigment cell-specific and might be involved in melanogenesis.