Bioluminescence in vivo imaging of autoimmune encephalomyelitis predicts disease

Abstract

Background: Experimental autoimmune encephalomyelitis is a widely used animal model to understand not only multiple sclerosis but also basic principles of immunity. The disease is scored typically by observing signs of paralysis, which do not always correspond with pathological changes.

Methods: Experimental autoimmune encephalomyelitis was induced in transgenic mice expressing an injury responsive luciferase reporter in astrocytes (GFAP-luc). Bioluminescence in the brain and spinal cord was measured non-invasively in living mice. Mice were sacrificed at different time points to evaluate clinical and pathological changes. The correlation between bioluminescence and clinical and pathological EAE was statistically analyzed by Pearson correlation analysis.

Results: Bioluminescence from the brain and spinal cord correlates strongly with severity of clinical disease and a number of pathological changes in the brain in EAE. Bioluminescence at early time points also predicts severity of disease.

Conclusion: These results highlight the potential use of bioluminescence imaging to monitor neuroinflammation for rapid drug screening and immunological studies in EAE and suggest that similar approaches could be applied to other animal models of autoimmune and inflammatory disorders.

Figure 1

Bioluminescence imaging of GFAP-dependent transcription in EAE. EAE was induced in GFAP-luc mice with MOG_35–55 emulsified in CFA plus pertussis toxin and bioluminescence was recorded in living mice injected with luciferin (150 mg/kg) 1 day before (-1) and at indicated time points after immunization. (a) Time course of bioluminescence recorded in a representative mouse. (b) Bioluminescence was expressed as fold induction and plotted with clinical score (n = 23). (c) Time course of EAE-associated neuropathology. GFAP-luc mice were sacrificed at indicated time points. Neuroinflammation was assessed by immunohistochemistry as a function of astrogliosis (GFAP), microgliosis (CD68) and T lymphocyte infiltration (CD4). Scale bar = 100 μm.

Figure 2

Astrocyte activation in response to adjuvant or MOG_35–55 peptide. GFAP-luc mice were injected with PBS, CFA, PT, MOG_35–55 peptide or combinations. Bioluminescence was recorded in living mice 1 day before and day 14 after injection and expressed as fold induction over baseline. Bars are mean ± SEM (n = 3–4 mice per group). *: P < 0.01 as compared with PBS by ANOVA and Tukey's post-hoc test.

Figure 3

Bioluminescence recorded at day 10 correlates strongly with clinical score at day 14. GFAP-luc mice were immunized with MOG_35–55 emulsified in CFA plus pertussis toxin. Bioluminescence was recorded in living mice and expressed as fold induction over baseline measured 1 day before immunization. Each dot represents one mouse. The correlation was assessed by Pearson correlation analysis (n = 10 mice). R: correlation coefficient.