Compounding Effects of Aging and Sex on Cerebrovascular Endothelial Mitochondria

Abstract

Despite the increasing burden of age-related neurological diseases such as vascular cognitive impairment and dementia or Alzheimer’s disease, the underlying mechanisms of these pathologies are not clear. Nonetheless, structural and functional changes in the microvasculature represent probable pathological aspects of these age-associated diseases. The silent and cumulative changes in endothelial mitochondria with subsequently compromised cerebral vascular function are thought to play a central role in neurological disease development. We tested the hypothesis that mitochondrial morphological changes in endothelial cells facilitate the distinct aging- and sex-related differences in the cerebral microvascular proteome and energetics. Mito-dendra2 (mt-D2) labeled endothelial mitochondria were imaged in vivo via a cranial window using two-photon microscopy at 875 nm in young and old, male and female, mito-Dendra2 mice (YM, YF, OM, and OF, respectively). Mt-D2 associated signal was analyzed in 3D stacks using the Huygens Pro CE 23.04.0p3 object analyzer (160 images, originated from 4-5 mt-D2 mice/groups). We also measured mRNA copy numbers of mitochondrial fission and fusion genes in isolated, cortical microvessels (<70 μm) from YM, YF, OM, and OF C57Bl/6J mice (n=7-11/age/sex) using ddPCR. Kruskal-Wallis test with Dwass-Steel-Critchlow-Fligner post-hoc comparisons were used to compare mt-D2 signal among YM, YF, OM, and OF, whereas Mann-Whitney U test determined changes across age and sex strata. p<0.05 was considered statistically significant. mRNA copy numbers were normalized to housekeeping genes (GAPDH, β-actin, and HPRT-1) and compared with one-way ANOVA based on data distribution. Analysis of four object parameters revealed that object surface was smaller in old vs. young that was significant in YM vs. OM. We found significantly greater corrected lateral width in OM vs. YM, OF vs. YF, and in YF vs. YM. The lateral aspect ratio was significantly greater in YM vs. OM, in YF vs. OF, as well as in YM vs. YF. Accordingly, the axial sphericity of the principal box was significantly greater in OM vs. YM, in OF vs. YF, and in YF vs. YM. Normalized mRNA copy numbers of mitochondrial fission and fusion genes were not statistically different in our samples for DRP-1, Fis-1 or Mfn-1/2, Opa-1, respectively. These results suggest that aging driven morphological differences, such as the shortening of endothelial mt-D2 signal are, at least in part, facilitated by altered fission/fusion protein abundances and/or activity rather than transcriptional changes in our samples. Although we are still analyzing other morphological parameters, by assessing the effect sizes and their physiological relevance, we postulate that these morphological differences contribute to the vulnerability of the aged cerebral microvasculature to injury. AG083567, 3P30GM145498-01, U54GM104940, HL148836. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.