Zhang Cheng, Lam Tim T, Tso Mark Om
Wilmer Eye Institute, Johns Hopkins University School of Medicine, 600 N Wolfe Street, Rm 457, Woods Building, Baltimore, MD 21287-9238, USA.
Exp Eye Res. 2005 Dec;81(6):700-9. doi: 10.1016/j.exer.2005.04.008. Epub 2005 Jun 20.
Activation of Microglia/macrophages has been observed in ischemia-reperfusion injury of the brain. This study was undertaken to investigate the different subpopulations of microglia/macrophages in the normal rat retina and their activation after retinal ischemia. Retinal ischemia was induced by elevation of intraocular pressure to 120 mmHg for 60 min. Microglia/macrophages were identified on frozen retinal sections by four antibodies, namely OX42, 5D4, OX6 and ED1. In the normal retina, there were heterogeneous populations of resident microglia/macrophages as characterized by their differences in morphology, antigen expression and distribution. OX42+ cells had delicate processes and were located in the inner layers of the retina, while 5D4+ cells were highly ramified and mostly scattered in the inner plexiform layer (IPL) and the outer plexiform layer. Few amoeboid ED1+ cells were also seen in the ganglion cell layer and IPL. OX6+ (MHC-II antigen presenting) cells were not detected in the normal retinas. Double labeling with OX42 and 5D4 antibodies on normal retinal sections showed few microglia exhibited positive labeling with both OX42 and 5D4, while the majority of the microglia were labeled with either OX42 or 5D4 antibodies. After retinal ischemia single labeling with these antibodies showed increased number of these antigen-expressing cells, disappearance of normal cellular processes, and rounding or amoeboid like appearance of the cell bodies. At 1 day after ischemia, there was a significant infiltration of round OX42+, ED1+ and OX6+ cells with loss of the cellular processes in the inner retina. From 3 to 14 days, all subpopulations of microglia/macrophages differentiated cellular processes and became dendritic again. Double labeling on retinas after 1 day of recovery showed OX42+ cells were co-labeled with ED1+ or OX6+ cells, but not with 5D4+ cells. Scattered amoeboid OX42+, 5D4+, and ED1+ cells were noted in the subretinal space 3-14 days after ischemia. In summary, there were heterogeneous populations of resident microglia/macrophages in the normal inner retina and they were activated early after ischemia-reperfusion injury and exhibited different antigenic expression which were further altered in the recovery phase.
在脑缺血再灌注损伤中已观察到小胶质细胞/巨噬细胞的激活。本研究旨在调查正常大鼠视网膜中小胶质细胞/巨噬细胞的不同亚群及其在视网膜缺血后的激活情况。通过将眼压升高至120 mmHg持续60分钟诱导视网膜缺血。用四种抗体，即OX42、5D4、OX6和ED1在冷冻视网膜切片上鉴定小胶质细胞/巨噬细胞。在正常视网膜中，存在不同类型的驻留小胶质细胞/巨噬细胞群体，其特征在于形态、抗原表达和分布的差异。OX42+细胞具有纤细的突起，位于视网膜内层，而5D4+细胞高度分支，大多散在于内网状层（IPL）和外网状层。在神经节细胞层和IPL中也可见少数阿米巴样ED1+细胞。在正常视网膜中未检测到OX6+（MHC-II抗原呈递）细胞。用OX42和5D4抗体对正常视网膜切片进行双重标记显示，很少有小胶质细胞同时显示OX42和5D4阳性标记，而大多数小胶质细胞用OX42或5D4抗体标记。视网膜缺血后，用这些抗体进行单标记显示这些抗原表达细胞数量增加，正常细胞突起消失，细胞体呈圆形或阿米巴样外观。缺血后1天，圆形的OX42+、ED1+和OX6+细胞显著浸润到视网膜内层，细胞突起消失。从3天到14天，小胶质细胞/巨噬细胞的所有亚群分化出细胞突起并再次变成树突状。恢复1天后对视网膜进行双重标记显示，OX42+细胞与ED1+或OX6+细胞共标记，但不与5D4+细胞共标记。缺血后3 - 14天，在视网膜下间隙可见散在的阿米巴样OX42+、5D4+和ED1+细胞。总之，正常视网膜内层存在不同类型的驻留小胶质细胞/巨噬细胞群体，它们在缺血再灌注损伤后早期被激活，并表现出不同的抗原表达，在恢复阶段进一步改变。
