Fig. 4. Aging significantly attenuates the kinetics of the gliovascular structural plasticity response.

In order to determine if the kinetics of endfoot replacement significantly slowed as a result of aging, we ablated astrocytes at penetrating arterioles and acquired continual z-stacks to capture the exact time of endfoot replacement. White asterisks indicate ablated astrocytes (shown in gray, blood vessels are in red) and arrows demarcate replacement processes (as in a and b) or lack thereof (as in c and d). Volumetric reconstruction showing a penetrating arteriole in a 4-month-old mouse (top) and 12-month old mouse (bottom) at a baseline, b the start of apoptosis, c the moment of endfoot retraction, and d one hour later. Scale bar = 10 µm. n = 6 astrocytes across 4 mice. e Average number of minutes to new endfoot replacement post-ablation in 4- versus 12-month old mice. Two-tailed, unpaired t-test, p < 0.0371. f Average number of hours to astrocyte corpse removal post-ablation in 4- versus 12-month old mice. Two-tailed, unpaired t-test, p < 0.03. g Average number of hours to endfoot replacement in 4- versus 12-month-old mice post-ablation. Two-tailed, unpaired t-test, p < 0.0022. n = 6 cells across 4 mice for both age groups. h Average area of eGFP+ endfoot lining around arterioles at ablated location pre- versus post-ablation. Two-tailed paired end t-test, p < 0.0370, n = 18 optical sections/4 mice. i Average post-ablation eGFP+ endfoot vessel lining area expressed as a percentage of baseline. n = Focal PAA ablations at 6 arterioles/4 mice. Note that the data points in h are averaged to give one dot in (i). Data are presented as mean values ± SEM. LUTS have been adjusted to emphasize the replacement astrocytes and associated processes.