Figure 5

Natural history of cell death in a chronic ocular hypertensive (OHT) model of neurodegeneration. (a–f) Cells were retrogradely labelled using DiI (a), and analysed at intervals over 8 weeks. The higher magnification image (green box in (a)) taken at time zero (b) shows the normal density of RGCs, with little change at 3 weeks (c). However, there was marked RGC dropout 8 weeks after surgical induction of elevated IOP (d). When the data were analysed with respect to the identification of apoptosis in these same cells, it was clear that those RGCs that were annexin V positive at 3 weeks (e) were no longer identifiable at 8 weeks (f), confirming that cells originally classified as undergoing apoptosis degenerated 5 weeks later. (g) Only a small proportion of RGCs was identified in early-phase apoptosis (annexin V only) compared with late-phase apoptosis (both annexin V and PI staining) at 3 weeks. (h) MK801 treatment of animals at the time of surgery significantly reduced the number of both apoptotic and necrotic cells 3 weeks after treatment. (i) Quantitative analysis of the co-localisation data for PI and annexin V confirmed that significantly more cells were in late-phase apoptosis (P>0.05, yellow, Anx+/PI+) than in necrosis (red, PI+). Treatment with MK801 led to a significant reduction (P<0.05) in the number of dying cells (total), mostly because of a significant decrease in the levels of necrosis (P>0.05, red, PI+) and late apoptotic (P>0.05, yellow, Anx+/PI+) cell death. Scale bar 100 μm as indicated, error bars represent 95% confidence intervals, ^*P<0.05