Progressively increasing GFAP stain density (fraction of segmented pixels, left) and mean astrocyte morphology score (right) in different ROIs as a function of age in the disease groups (6, 9, and 12 months) as compared to the control group (6 months). The comparisons with the mean hypertrophy score generally have higher statistical significance. P-value from Dunnett’s T3 multiple comparisons test. * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001; n= 11 (6 month Ctrl), 13 (6 months), 10 (9 months), and 9 (12 months).
Quantifying the results by ROI and mice shows that the GFAP stain density, or the fraction of GFAP-positive pixels, increases progressively over time, from 6 to 12 months-of-age. The mean astrocyte hypertrophy score showed a similar trend, but with more statistically significant changes. For example, in the piriform cortex, the 6 months to control comparison becomes statistically significant, while the other comparisons have increased significance. As such, in the context of a preclinical therapeutic efficacy study, it would be possible to detect a smaller effect size with the same number of mice or a similar effect size with fewer mice using the astrocyte morphological analysis rather than the GFAP stain density alone.