Inflammation in the anterior visual pathway in multiple sclerosis: what do the animal models teach us?

Abstract

A provocative and overly reductive mantra is that "the back of the eye is the front of the brain". Retinal imaging techniques that take advantage of this "window" to the central nervous system can provide valuable information regarding injury to the nervous system with relative ease and with a limited burden to patients. The retina develops embryonically as part of the neuroectoderm, is made up principally of neurons and their supporting cells, and is synaptically tied to the central nervous system (CNS). This has led to significant interest in using retinal health as a biomarker for brain health-given the relatively limited accessibility of brain tissue in chronic neurodegenerative diseases that progress over decades. The retina is not truly part of the CNS, and as with much of brain imagingthe grounds for asserting the pathological specificity of retinal imaging is limited. Biophotonics-based methods such as optical coherence tomography indirectly provide an opportunity to evaluate retinal neurodegeneration, while autopsy studies, histology and immunohistochemistry predominate as the methods that collect direct pathological data. Our understanding of pathological retinal lesions characteristic of demyelinating diseases, specifically diseases showing anterior visual pathway involvement, has grown significantly in recent years.

Galectin-3 Plays a Role in Neuroinflammation in the Visual Pathway in Experimental Optic Neuritis

“…Unpaired t-tests were employed for pairwise comparisons, and one-way ANOVA followed by Bonferroni tests was used for multiple comparisons. Statistical significance was set at p < 0.05 [6,9,[21][22][23].…”

“…Animals, deeply anesthetized, were sacrificed and perfused with normal saline followed by 4% paraformaldehyde (PFA) in 0.1 M phosphate buffer (PB) [6,9,[21][22][23]. The brain, including the optic nerve, optic chiasm, and the optic tract, was removed and immersed in 30% sucrose in PBS for 1-2 days.…”

“…For immunohistochemistry, sections were pretreated with blocking solution (5% albumin, 2% normal goat serum and 0.3% tritonX-100) for 30 min at room temperature (RT) [6,9,[21][22][23]. Sections were then incubated with primary antibodies overnight at 4 • C. The following antibodies were used as primary antibodies: anti-galectin-3 antibody (1:200; Santacruz Biotechnologies, Dallas, TX, USA), anti-Iba-1 polyclonal antibody (1:2000; WAKO, Osaka, Japan), anti-Iba-1 monoclonal antibody (1:200; WAKO), anti-GFAP antibody (1:2000; Sigma-Aldrich), anti-cathepsin D antibody (1:200; R&D Systems, Minneapolis, MN, USA), anti-NLR family, pyrin domain containing 3 (NLRP3) antibody (1:1000; Adipogen Life Sciences, Füllinsdorf, Switzerland).…”

“…Animals, deeply anesthetized, were sacrificed and perfused with normal saline [6,9,[21][22][23]. Subsequently, the optic nerve, chiasm, and tract were dissected and lysed in cell lysis buffer (Cell lytic M lysis buffer; Sigma-Aldrich).…”

“…Experimental autoimmune encephalomyelitis (EAE) is the most widely used experimental animal model of human inflammatory demyelinating diseases such as MS [6][7][8]. Because the pathogeneses of EAE and MS share similar features and are related to ON and NMO, EAE can be used as a disease model of ON [9,10]. Indeed, accumulating evidence suggests that EAE induces significant retinal ganglion cell (RGC) loss [11][12][13].…”