Figure 9.

Heparanase inhibitors PI-88 and OGT2115 rescue remyelination and reduce axonal injury induced by IFN-γ treatment. A–E, Injection of 3 ng of IFN-γ with or without PI-88 (10 μg/ml) or OGT2155 (0.4 μm) directly into demyelinated lesions in mice (8–10 weeks of age). Animals were killed at 14 dpl, and spinal cord tissue was processed for electron microscopy. Representative fields shown within the lesion periphery. F, G, IFN-γ treatment induces various forms of axonal injury and degeneration. H, Several remyelinated axons also exhibit very thin remyelination following IFN-γ treatment. Arrows represent degenerating axons. I–K, The proportions of degenerating axons among total axons (I), the proportion of remyelinated axons among healthy-appearing axons (J), and the g-ratio of normal-appearing remyelinating axons (K) were calculated in each animal (mean ± SEM; n = 3–6 animals/group). I, J, Both PI-88 and OGT2115 treatment rescued the negative effects of IFN-γ on axonal damage (I) and the percentage of remyelination (J) following demyelination. L–O, Relationship between axon diameter and g-ratio (linear regression shown) between groups (L; control vs IFN-γ; M, IFN-γ vs IFN-γ + PI-88; N, control vs OGT2155; and O, IFN-γ vs IFN-γ + OGT2155). P, Q, Frequency distribution of axonal diameter (P) and g-ratio (Q) in lesion (n = 3–6 animals/group, ≥400 axons). Holm–Sidak test: **p < 0.01, ***p < 0.001, ****p < 0.0001 for each pairwise comparison following one-way ANOVA. Scale bar, 2 μm.