White David T, Sengupta Sumitra, Saxena Meera T, Xu Qingguo, Hanes Justin, Ding Ding, Ji Hongkai, Mumm Jeff S
Wilmer Eye Institute; Johns Hopkins School of Medicine, Baltimore, MD 21231.
The Center for Nanomedicine; Johns Hopkins School of Medicine, Baltimore, MD 21231.
Proc Natl Acad Sci U S A. 2017 May 2;114(18):E3719-E3728. doi: 10.1073/pnas.1617721114. Epub 2017 Apr 17.
Müller glia (MG) function as inducible retinal stem cells in zebrafish, completely repairing the eye after damage. The innate immune system has recently been shown to promote tissue regeneration in which classic wound-healing responses predominate. However, regulatory roles for leukocytes during cellular regeneration-i.e., selective cell-loss paradigms akin to degenerative disease-are less well defined. To investigate possible roles innate immune cells play during retinal cell regeneration, we used intravital microscopy to visualize neutrophil, macrophage, and retinal microglia responses to induced rod photoreceptor apoptosis. Neutrophils displayed no reactivity to rod cell loss. Peripheral macrophage cells responded to rod cell loss, as evidenced by morphological transitions and increased migration, but did not enter the retina. Retinal microglia displayed multiple hallmarks of immune cell activation: increased migration, translocation to the photoreceptor cell layer, proliferation, and phagocytosis of dying cells. To test function during rod cell regeneration, we coablated microglia and rod cells or applied immune suppression and quantified the kinetics of () rod cell clearance, () MG/progenitor cell proliferation, and () rod cell replacement. Coablation and immune suppressants applied before cell loss caused delays in MG/progenitor proliferation rates and slowed the rate of rod cell replacement. Conversely, immune suppressants applied after cell loss had been initiated led to accelerated photoreceptor regeneration kinetics, possibly by promoting rapid resolution of an acute immune response. Our findings suggest that microglia control MG responsiveness to photoreceptor loss and support the development of immune-targeted therapeutic strategies for reversing cell loss associated with degenerative retinal conditions.
缪勒胶质细胞（MG）在斑马鱼中作为可诱导的视网膜干细胞发挥作用，在损伤后能完全修复眼睛。最近研究表明，固有免疫系统可促进以经典伤口愈合反应为主导的组织再生。然而，白细胞在细胞再生过程中的调节作用——即类似于退行性疾病的选择性细胞丢失模式——尚不清楚。为了研究固有免疫细胞在视网膜细胞再生过程中可能发挥的作用，我们利用活体显微镜观察中性粒细胞、巨噬细胞和视网膜小胶质细胞对诱导的视杆光感受器凋亡的反应。中性粒细胞对视杆细胞丢失无反应。外周巨噬细胞对视杆细胞丢失有反应，形态转变和迁移增加可证明这一点，但未进入视网膜。视网膜小胶质细胞表现出免疫细胞激活的多个特征：迁移增加、向光感受器细胞层移位、增殖以及吞噬死亡细胞。为了测试在视杆细胞再生过程中的功能，我们共同消融小胶质细胞和视杆细胞，或应用免疫抑制，并量化（1）视杆细胞清除的动力学、（2）MG/祖细胞增殖以及（3）视杆细胞替代情况。在细胞丢失前应用共同消融和免疫抑制剂会导致MG/祖细胞增殖速率延迟，并减缓视杆细胞替代速率。相反，在细胞丢失开始后应用免疫抑制剂会导致光感受器再生动力学加速，这可能是通过促进急性免疫反应的快速消退实现的。我们的研究结果表明，小胶质细胞控制MG对视杆细胞丢失的反应性，并支持开发针对免疫的治疗策略，以逆转与退行性视网膜疾病相关的细胞丢失。
