Biological Sciences, University of Idaho, Moscow, Idaho, USA.
Dev Dyn. 2020 Jun;249(6):723-740. doi: 10.1002/dvdy.163. Epub 2020 Feb 27.
Microglia colonize the developing vertebrate central nervous system coincident with the detection of developmental apoptosis. Our understanding of apoptosis in intact tissue in relation to microglial clearance of dying cells is largely based on fixed samples, which is limiting given that microglia are highly motile and mobile phagocytes. Here, we used a system of microglial depletion and in vivo real-time imaging in zebrafish to directly address microglial phagocytosis of apoptotic cells during normal retinal development, the relative timing of phagocytosis in relation to apoptotic progression, and the contribution of P2RY12 signaling to this process.
The depletion of microglia resulted in accumulation of numerous apoptotic cells in the retina. Real-time imaging revealed precise timing of microglial engulfment with the progression of apoptosis, and dynamic movement and displacement of engulfed apoptotic cells. Inhibition of P2RY12 signaling delayed microglial clearance of apoptotic cells.
Microglial engulfment of dying cells is coincident with apoptotic progression and requires P2RY12 signaling, indicating that microglial P2RY12 signaling is shared between development and injury response. Our work provides important in vivo insight into the dynamics of apoptotic cell clearance in the developing vertebrate retina and provides a basis to understand microglial phagocytic behavior in health and disease.
小胶质细胞与发育性细胞凋亡的检测同时定殖于脊椎动物中枢神经系统的发育过程中。我们对完整组织中凋亡与小胶质细胞清除死亡细胞之间关系的理解在很大程度上基于固定样本，这是有限的，因为小胶质细胞是高度运动和移动的吞噬细胞。在这里，我们使用小胶质细胞耗竭和斑马鱼体内实时成像系统，直接解决正常视网膜发育过程中小胶质细胞吞噬凋亡细胞的问题，吞噬作用与凋亡进展的相对时间以及 P2RY12 信号对这一过程的贡献。
小胶质细胞耗竭导致视网膜中积累了大量凋亡细胞。实时成像揭示了小胶质细胞吞噬作用与凋亡进展的精确时间，并显示了吞噬的凋亡细胞的动态运动和位移。P2RY12 信号的抑制延迟了小胶质细胞对凋亡细胞的清除。
小胶质细胞吞噬死亡细胞与凋亡进展同时发生，需要 P2RY12 信号，表明小胶质细胞 P2RY12 信号在发育和损伤反应中是共享的。我们的工作为理解脊椎动物发育中视网膜中凋亡细胞清除的动力学提供了重要的体内见解，并为理解健康和疾病中小胶质细胞吞噬行为提供了基础。
