Abstract
Purpose :
Aging affects the eyes and is a major risk factor for many eye diseases. The purpose of the current study was to elucidate the effect of aging on retinal oxygen and blood flow metrics in healthy aging mice.
Methods :
Forty-seven C57BL/6 mice in four age groups (3-month-old (mo): N=18, 9mo: N=13, 15mo: N=8, and 21mo: N=8) were included in the study. Using our previously established custom-made multimodal imaging systems, retinal arterial and venous diameters (DA, DV), venous blood velocity (V), and arterial and venous oxygen contents (O2A, O2V) were measured in one eye of each animal, and average blood flow (BF), oxygen delivery (DO2), metabolism (MO2), and extraction fraction (OEF) were calculated. ANOVA, and Tukey post-hoc analyses were performed to determine the effect of age on these variables. The difference between groups were calculated as percent change of variable means.
Results :
There was a significant difference in V, BF, O2A, O2V, and DO2 among the age groups. V was significantly lower in the 21mo group (p = 0.004) and marginally lower in 15mo group (p = 0.06) compared to the 3mo group, representing reductions of 41% and 30%, respectively. Similarly, BF was lower in the 21mo group than the 3mo group (p = 0.007), a 42% reduction. Additionally, O2A and O2V were significantly lower in 21mo group compared to the 9mo group (p <= 0.05), indicating reductions of 30% and 65%, respectively. DO2 was significantly decreased in the 21mo group compared to 15mo (p = 0.05) and 9mo (p = 0.04) groups, representing reductions of 46% and 44%, respectively. MO2 was lower in the 21mo group than the other groups, however the difference did not reach statistical significance (p > 0.2). OEF was highest in the 21mo group, but was marginally different among the groups (p = 0.07). DA and DV were not significantly different among the groups (p > 0.1).
Conclusions :
Our results show that retinal vascular oxygen content, oxygen delivery rate, and blood flow were significantly reduced in older mice. These findings establish baselines for retinal oxygen metrics which are essential for differentiating normal aging from disease abnormalities, and evaluating experimental preventative/therapeutic interventions. More studies are necessary to validate our results and evaluate the basis for these findings.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.