Fig. 2

Regional distribution, density and morphology of corneal sensory nerves in WT and rTg4510 mice at 2, 6, 8, and 11 months. a–d Representative images of the superficial nerve terminals (SNT) in the corneas of WT and rTg4510 mice at 11 months. β-tubulin III⁺ SNTs can be abundantly seen in the central and peripheral cornea of WT mice (a, b), while rTg4510 mice had a relatively sparse distribution in the central cornea but were spared in the peripheral cornea (c, d). e, f Percentage area demonstrates a significantly lower density of SNTs in the central cornea of rTg4510 compared to WT mice at 11 months (P < 0.05), while the peripheral cornea showed no significant intergroup difference across the age groups (P > 0.05). g–n Representative images of the sub-basal nerve plexus (SBNP) in corneas of WT and rTg4510 mice showing a lower abundance of SBNPs that appeared in a beaded morphology in the central and peripheral areas of rTg4510 mouse corneas (m, n; yellow arrowheads). o, p The density of SBNPs was significantly lower in the central cornea of rTg4510 compared to WT mice at 11 months (P < 0.05), while the lower SBNP density occurred in the peripheral cornea from 8 months and persisted to 11 months (P < 0.05). q, r The extent of nerve beading that characterizes the morphology of SBNPs was analyzed; the percentage of beaded nerves was remarkably higher in both central and peripheral regions of rTg4510 mouse corneas at 11 months (P < 0.05) but not in the younger age cohorts (P > 0.05). Data are shown as mean ± SEM, where * indicates P ≤ 0.05 (n = 6 per group) as demonstrated using two-way ANOVA and Tukey’s multiple comparisons. Scale bars represent 100 μm for all images except for f–n where the scale bars are 10 μm