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DISCUSSION
Müller cells and RPE cells are widely distributed in the retina. When the retina is damaged by mechanical or chemical stimuli, RPE cells migrate across Bruch's membrane to fill the lesion with subsequent scar formation. Müller cells and astrocytes replace the damaged outer nuclear layer of the retina, interdigitating with the migrated RPE cells. Müller cells undergo widespread and longlasting changes after the lesion, including increased expression of glial fibrillary acidic protein associated with hypertrophy migration and scar tissue formation[5]. The normal ability of RPE cells to secrete growth factors can protect the retina from damage; however, irregular growth factor secretion can also be involved in the pathogenesis of retinal diseases. Interestingly, RPE cells produce various growth factors that may induce the mitogenic effects of RPE cells.
Studies have shown that conditioned media of RPE can promote the proliferation of Müller cells under normoxia [6]. In addition, RPE, which is a major source of VEGF, can secret several molecules, including VEGF, basic fibroblast growth factor (bFGF), and angiopoietin1. Under hypoxia, RPE increases the levels of VEGF mRNA and protein synthesis. In contrast, RPE cells cultured under hypoxic conditions show reduced steadystate levels of bFGF mRNA and decreased bFGF protein synthesis[7].
Since hypoxia is a critical process in most pathogenesis, we are interested in knowing whether Müller cells migrate and/or proliferate after being promoted by RPE under both normoxic and hypoxic conditions. In this study, we first used the Transwell chamber system to detect the effect of RPE on Müller cells. Compared to the conditioned media of RPE, the Transwell chamber system can more closely simulate in vivo conditions and thus reveal dynamic changes during the interaction of RPE and Müller cells. Next, we carried out experiments to observe the effect of RPE on Müller cells at various time points and under various culture conditions, as noted above. We expected that cocultured RPE could stimulate the migration and proliferation of Müller cells under both hypoxic and normoxic conditions in a timedependent manner. Considering that both RPE and hypoxia are independent factors stimulating the migration and proliferation of Müller cells, it was intriguing to find that these two factors did not combine in a synergetic manner to produce that result.
In summary, we have demonstrated that hypoxia and RPE coculture are important mediators of migration and proliferation of Müller cells in a timedependent manner. Previous studies have demonstrated that hypoxia could induce upregulation of VEGF, which may partially explain the mechanism of these effects on Müller cells. However, the mechanisms underlying this phenomenon are unclear. Many of the effects of VEGF are mediated by other factors, and the hypoxia that induces VEGF production can initiate a cascade of factors. Since there is a significant difference between two time points, we proposed that some growth factor(s) may be released during this period.This study sheds some insights on the proliferative diseases in the retina. Further work is needed to elucidate the exact mechanisms involved in the pathogenesis.
【参考文献】
1 Song E, Yang W, Cui ZH, Wu JX. Effects of highconcentration insulin on expression of vascular endothelial growth factor in cultured Müller cells in vitro. Int J Ophthalmol(Guoji Yanke Zazhi) 2004;4 (2):201205
2 Feng W, Zheng JJ, Lutz DA, McLaughlin BJ. Loss of RPE phenotype affects phagocytic function. Graefes Arch Clin Exp Ophthalmol 2003;241:232240
3 Wang YL, Hui YN, Guo B, Zhang XG, Hou X, Ma JX. Inhibition of proliferation of retinal microvascular endothelial cells by pericytes through downregulating KDR/FIK1 in a coculture system. Int J Ophthalmol(Guoji Yanke Zazhi) 2006;6(2):256263
4 Allenbach C, Zufferey C, Perez C, Launois P, Mueller C,TacchiniCottier F. Macrophages induce neutrophil apoptosis through membrane TNF, a process amplified by Leishmania major. J Immunol 2006;176:66566664
5 Tretiach M, Madigan MC, Gillies MC. Conditioned mediun from mixed retinal pigmented epithelium and Müller cell cultures reduces in vitro permeability of retina vascular endothelial cells. Br J Ophthalmol 2004;88:957961
6 Jaynes CD,Turner JE.Isolation of a retinal pigment epithelial cellderived fraction which promotes Müller cell proliferation. Brain Res Dev
Brain Res 2000;20(2):267271
7 Strauss O.The retinal pigment epithelium in visual function. Physiol Rev 2005;85:845881
Transwell小室共培养条件下RPE促进 Müller细胞的增殖和迁移
马洪梅，张晓梅，付小玻，李伟军，乌兰，王巍
作者单位：150001 中国黑龙江省哈尔滨市，哈尔滨医科大学第一临床医学院附属<a href="../search/search.php?SearchType=%E6%96%87%E7%AB%A0%3E&SearchKeyWord=%E7%9C%BC%E7%A7%91%E5%8C%BB%E9%99%A2&AS=news" target="_blank">眼科医院a>
作者简介：马洪梅，女，在读硕士研究生，研究方向：眼底病。
摘要 目的：观察在体外共培养系统中RPE对Müller细胞的影响。方法：Transwell小室共培养RPE和Müller细胞，MTT法、细胞计数法，测定Müller增殖和迁移的情况。结果：Müller 细胞增殖的实验：Müller 细胞的增殖，除了3h与6h,24h与48h之外,在其他各时间点之间差别有统计学意义。Müller细胞与RPE共培养组和Müller细胞单独培养组两组之间差别有统计学意义。Müller 细胞迁移的实验：Müller 细胞迁移，除了3h和6h之外,在其他各时间点之间差别有统计学意义。Müller细胞与RPE共培养组和Müller细胞单独培养组两组之间差别有统计学意义。在析因设计实验中，与RPE共培养、缺氧条件，这两个因素都可以分别作为独立的因素促进Müller细胞的增殖和迁移，而两者不存在协同作用。结论：正常和缺氧条件下RPE促进Müller的增殖、迁移，随共培养时间的延长RPE促进Müller增殖、迁移的作用加强。缺氧条件下RPE与Müller细胞间的相互作用在视网膜增殖性疾病中起到了重要的作用。
关键词：Transwell小室；缺氧；视网膜色素上皮细胞；Müller细胞 上一页 [1] [2] |
