In the adult retina, ramifying microglia interact with the outer plexiform layer (OPL) monitoring the synaptic integrity between photoreceptors and post-synaptic target cells. Microglia are reactive during photoreceptor diseases, but their disease-related function(s) are not fully understood. Retinal explant cultures are model systems used to study degenerative events including photoreceptor degeneration and gliosis. Our culture paradigm, with adult porcine retinas subjected to coculture with human A-retinal pigment epithelia-19 (ARPE) cells, is an experimental approach resulting in improved photoreceptor survival and reduced gliosis. Under the in vitro pathological conditions with photoreceptor degeneration, reactive Iba1-and CD11b-immunoreactive microglia and their processes positioned in proximity with the OPL and among photoreceptor outer segments. Coculture for 3 days with ARPE-cells resulted in a significantly increased density of microglia at the OPL. After 5 days of culture, the density of microglia at the OPL was similar between coculture and control specimens. Electron microscopy revealed the presence of two subtypes of microglia: one exhibiting a dark nucleus and cytosol with dilated endoplasmic reticulum, vacuoles, endosomes and mitochondrial variations. This subtype localized close to synaptic structures in the OPL. The other subtype appeared as pale phagocytic microglia localized among degenerating outer segments. The Iba1-and CD11b-immunoreactive microglia in degenerating retina may be of two separate subtypes, which differ in localization, subcellular morphology and perhaps function.

在成年视网膜中，分枝小胶质细胞与外丛状层（OPL）相互作用，监控感光器和突触后靶细胞之间的突触完整性。小胶质细胞在光感受器疾病中具有反应性，但与疾病相关的功能尚不完全清楚。视网膜外植体培养物是用于研究退化事件的模型系统，包括光感受器变性和神经胶质变性。我们的培养范例是将成年猪视网膜与人A视网膜色素上皮细胞19（ARPE）细胞共培养，这是一种实验方法，可提高感光细胞的存活率并减少神经胶质变性。在体外感光细胞变性，反应性Iba1和CD11b免疫反应性小胶质细胞的病理状况及其过程，其位置靠近OPL并位于感光细胞外部。与ARPE细胞共培养3天导致OPL小胶质细胞密度显着增加。培养5天后，共培养样品和对照样品的OPL小胶质细胞密度相似。电子显微镜检查显示存在两种小胶质细胞亚型：一种表现为暗核和胞质溶胶，内质网，液泡，内体和线粒体变异较大。该亚型位于OPL的突触结构附近。其他亚型表现为位于退化的外节段之间的淡吞噬小胶质细胞。