Targeted Complement Inhibition at Synapses Prevents Microglial Synaptic Engulfment and Synapse Loss in Demyelinating Disease

• Published in: Immunity (Cambridge, Mass.) Mass.), 2020-01, Vol.52 (1), p.167-182.e7
• Main Authors: Werneburg, Sebastian, Jung, Jonathan, Kunjamma, Rejani B., Ha, Seung-Kwon, Luciano, Nicholas J., Willis, Cory M., Gao, Guangping, Biscola, Natalia P., Havton, Leif.A., Crocker, Stephen J., Popko, Brian, Reich, Daniel S., Schafer, Dorothy P.
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Animal models; Animals; Autoimmune diseases; Callithrix; Cell Line, Tumor; Central nervous system; Complement; Complement C3 - antagonists & inhibitors; Complement C3 - immunology; Complement component C1q; Complement component C3; Complement inhibitors; Crry protein; Degeneration; Demyelinating diseases; Demyelination; Disease; Disease Models, Animal; Encephalomyelitis, Autoimmune, Experimental - pathology; engulfment; Female; gene therapy; Gliosis; Gliosis - pathology; Humans; Male; Mice; Mice, Inbred C57BL; Microglia; Microglia - pathology; Middle Aged; Monkeys & apes; Multiple sclerosis; Multiple Sclerosis - pathology; Myelin; neural-immune; Neurodegeneration; Neurodegenerative diseases; neuroinflammation; Optic nerve; Receptors, Complement 3b - metabolism; synapse; Synapses; Synapses - pathology; Thalamus - pathology; Visual perception; Visual system; West Nile virus
• ISSN: 1074-7613; 1097-4180
• DOI: 10.1016/j.immuni.2019.12.004

Multiple sclerosis (MS) is a demyelinating, autoimmune disease of the central nervous system. While work has focused on myelin and axon loss in MS, less is known about mechanisms underlying synaptic changes. Using postmortem human MS tissue, a preclinical nonhuman primate model of MS, and two rodent models of demyelinating disease, we investigated synapse changes in the visual system. Similar to other neurodegenerative diseases, microglial synaptic engulfment and profound synapse loss were observed. In mice, synapse loss occurred independently of local demyelination and neuronal degeneration but coincided with gliosis and increased complement component C3, but not C1q, at synapses. Viral overexpression of the complement inhibitor Crry at C3-bound synapses decreased microglial engulfment of synapses and protected visual function. These results indicate that microglia eliminate synapses through the alternative complement cascade in demyelinating disease and identify a strategy to prevent synapse loss that may be broadly applicable to other neurodegenerative diseases. [Display omitted] [Display omitted] •Microglia engulf and eliminate synapses in the visual thalamus of MS patients•MS-relevant animal models show synapse engulfment and loss occur early in disease•Complement C3, but not C1q, localizes to synapses in demyelinating disease•AAV-Crry inhibits C3 and microglia-mediated synapse loss and preserves function The mechanisms underlying synaptic changes in multiple sclerosis (MS) remain unclear. Werneburg et al. identify microglia-mediated synapse engulfment and synapse loss in MS patients and multiple MS-relevant animal models. Synapse loss can occur early and prior to other MS-relevant pathology and is associated with synapse-localized complement C3. An AAV approach to inhibit C3 protects synapses and preserves circuit function.