Variable sensitivity to complement-dependent cytotoxicity in murine models of neuromyelitis optica

Abstract

BackgroundStudies of neuromyelitis optica (NMO), an autoimmune disease of the central nervous system (CNS), have demonstrated that autoantibodies against the water channel aquaporin-4 (AQP4) induce astrocyte damage through complement-dependent cytotoxicity (CDC). In developing experimental models of NMO using cells, tissues or animals from mice, co-administration of AQP4-IgG and normal human serum, which serves as the source of human complement (HC), is required. The sensitivity of mouse CNS cells to HC and CDC in these models is not known.MethodsWe used HC and recombinant monoclonal antibodies (rAbs) against AQP4 to investigate CDC on mouse neurons, astrocytes, differentiated oligodendrocytes (OLs), and oligodendrocyte progenitors (OPCs) in the context of purified monocultures, neuroglial mixed cultures, and organotypic cerebellar slices.ResultsWe found that murine neurons, OLs, and OPCs were sensitive to HC in monocultures. In mixed murine neuroglial cultures, HC-mediated toxicity to neurons and OLs was reduced; however, astrocyte damage induced by an AQP-specific rAb #53 and HC increased neuronal and oligodendroglial loss. OPCs were resistant to HC toxicity in neuroglial mixed cultures. In mouse cerebellar slices, damage to neurons and OLs following rAb #53-mediated CDC was further reduced, but in contrast to neuroglial mixed cultures, astrocyte damage sensitized OPCs to complement damage. Finally, we established that some injury to neurons, OLs, and OPCs in cell and slice cultures resulted from the activation of HC by anti-tissue antibodies to mouse cells.ConclusionsMurine neurons and oligodendroglia demonstrate variable sensitivity to activated complement based on their differentiation and culture conditions. In organotypic cultures, the protection of neurons, OLs, and OPCs against CDC is eliminated by targeted astrocyte destruction. The activation of human complement proteins on mouse CNS cells necessitates caution when interpreting the results of mouse experimental models of NMO using HC.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0767-4) contains supplementary material, which is available to authorized users.

Myelin-specific multiple sclerosis antibodies cause complement-dependent oligodendrocyte loss and demyelination

“…By comparison, there was a minor, but statistically significant loss (about 10%) of oligodendrocyte cells following treatment with Iso + HC from 24 h (Fig. 2e, f), which is consistent with our previous finding that HC causes some modest oligodendrocyte loss in cerebellar slices after 24 h treatment [14]. No changes in oligodendrocyte morphology or viability were noted following treatment with MS#30 in the absence of HC with preservation of 95.8 ± 2.7 and 101.9 ± 16.5% of eGFP+ oligodendrocyte cell bodies respectively at 24 h and 48 h when compared to Iso treatment (Fig.…”

“…Purkinje neuron death was monitored by co-labeling with calbindin and propidium iodide (PI). Consistent with previous reports [14], exposure to HC (Iso + HC) induced a low level of Purkinje cell death at 48 h post-treatment. Whereas no notable increase of Purkinje cell death was detected in MS#30 + HC-treated slices when compared to Iso + HC, Purkinje cell death in the slices treated with NMO#53 + HC was significantly elevated as previously described (Fig.…”

“…Instead, C3d was on cells presumed to be astrocytes (Fig. 6q–t; arrows) as previously demonstrated for NMO#53-mediated astrocyte cytotoxicity [14]. These results demonstrate that complement activated by MS#30 or NMO#53 is specifically targeted to oligodendrocytes or astrocytes based on their respective antigenic specificities.…”

“…Whereas no notable increase of Purkinje cell death was detected in MS#30 + HC-treated slices when compared to Iso + HC, Purkinje cell death in the slices treated with NMO#53 + HC was significantly elevated as previously described (Fig. 4g–r) [14]. Furthermore, neuronal death was not limited to Purkinje cells, as coincident NeuN and PI staining demonstrated a general loss of neurons throughout the cerebellum of NMO#53 + HC-treated slices, including the granule cell layer [14].…”

“…4g–r) [14]. Furthermore, neuronal death was not limited to Purkinje cells, as coincident NeuN and PI staining demonstrated a general loss of neurons throughout the cerebellum of NMO#53 + HC-treated slices, including the granule cell layer [14]. Even with extended treatment (72 h), the morphology and survival of astrocytes and neurons remained unaffected in MS#30 + HC treated slices (data not shown).…”