Fig. 5
RAS modulation reduced microglial accumulation, offset sustained activation and prevented chronic reactive microgliosis, in SHRs post-stroke. a Representative immunofluorescent images depicting microglial morphology/ramification status changes as illustrated Iba-1 positive (red stained) microglia with blue dapi nuclear staining, scale bar represents 50 and 20 μm for 20× and 63× images, respectively. Hypertensive controls (saline) subjected to tMCAO had, in the ischemic hemisphere, a significantly higher proportion of b total microglia (F(4,14) = 13.18, P < 0.05) and c active, inflammatory microglia (F(4,14) = 249.1, P < 0.0001) at 30 days post-stroke relative to shams and C21/candesartan-treated animals. These saline-treated controls also showed d increased circularity (F(4,14) = 33.52, P < 0.0001), e reduced Feret’s maximum diameter (F(4,14) = 7.314, P < 0.05), and f reduced transformation index (TI) (F(4,14) = 14.02, P < 0.0001), all consistent with a transformation of microglia from ramified to reactive amoeboid forms, at 30 days post-stroke relative to both sham and C21/candesartan-treated animals. However, C21 and candesartan-treated animals showed indices not much different from those of shams (n = 3–4 animals/group, error bars indicate SEM). Statistical significance for post hoc comparisons between groups using Tukey’s multiple comparison procedure are denoted by *P < 0.05 for differences in proportion of total microglia and Feret’s maximum diameter and *P < 0.0001 for differences in all other parameters. Feret’s (maximum) diameter, a measure of cell length, is the greatest distance between any two points along the cell perimeter [51]. Circularity = 4π × [cell area (μm2)]/[cell perimeter (μm)]2 is unitless value that ranges from 0 (infinitely elongated)-1 (perfect circle) [51]. Transformation index (TI) = [perimeter of cell (μm)]2/4π [cell area(μm2)] [51]