Figure 3

NOS2 deficiency does not alter glaucomatous neurodegeneration. (A, B) There were no gross anatomical differences between young Nos2^+/+ (A) and Nos2^-/- (B) nerves. (C) Eventually 80% of the optic nerves of DBA/2J mice develop severe optic nerve degeneration (Nos2^+/+). (D) The complete absence of NOS2 did not prevent glaucomatous neurodegeneration as many Nos2^-/- nerves had severe axonal damage. (E) Nos2 genotype had no effect on the distribution of nerve damage. Numbers of nerves by age, genotype and disease state were: (given as total number analyzed, genotype, number of that genotype with mild, moderate, severe glaucoma) 3.5 months 6 Nos2^+/+ 6,0,0; 7 Nos2^+/- 7,0,0;11 Nos2^-/- 11,0,0; 10–12 months 53 Nos2^+/+ 23,3,27; 53 Nos2^+/- 21,9,23; 56 Nos2^-/- 17,3,36 (P value for all comparisons > 0.3). F) Average counts of RGC layer neurons from Nos2 mice of each genotype with either severe glaucomatous damage or no detectable glaucomatous damage (total number of cells of the 8 fields counted per retina; see methods). Nos2 genotype conferred no differential protective effect to RGCs in eyes with different degrees of axon loss. RGCs comprise 45–50% of cells in the RGC layer [71] and so almost all RGCs were lost in mice with severe axon loss independent of Nos2 genotype. Percentage of surviving cells; Nos2^+/+, 54.4% ± 1.5; Nos2^+/-, 54.6% ± 1.5; Nos2^-/-, 58.0% ± 2.5; P values for all comparisons > 0.28. Number of retinal flat mounts counted, (given as genotype, mild, severe) Nos2^+/+ 9, 7; Nos2^+/- 12, 8; Nos2^-/- 8, 13. Bar = 100 μm.