Mitochondrial Dysfunction Drives Age-Related Degeneration of the Thoracic Aorta

Figures

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  Figure 1:. Age-related changes in the thoracic aorta. (A) Representative echo image of the murine aorta showing the aortic root, ascending aorta, mid-aortic arch, and distal aortic arch. (B) Comparison of maximal aortic diameter between young (6–8 mo, n=19) and aged mice (24–27 mo, n=25). Histologic comparisons of elastin breaks (C), collagen content (D), and media thickness (E) between young (n=5) and aged (n=6–7) mice. Multiple t-tests (with Holm-Sidak correction) and student’s t-test, * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001.

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  Figure 2:. Complex II-linked respiration declines with age but is rescued with ELAM. (A) Schematic of the electron transport system; note the uncoupler, which breaks the link between aerobic respiration and ATP production. Oxygen consumption rate (OCR) of complex I (B), complex II (C), maximal coupled respiration (D), and maximal uncoupled respiration (E) in the ascending aorta and aortic arch of young NT (n=14), young ELAM (n=9), aged NT (n=17), and aged ELAM (n=13) mice. Oxygen consumption rate (OCR) of complex I (F), complex II (G), maximal coupled respiration (H), and maximal uncoupled respiration (I) in the descending thoracic aorta (DTA) of the same mice. 2-way ANOVA, Fisher’s least significant difference, * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001. (A) was created with BioRender.com.

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  Figure 3:. Phosphorylative capacity is rate-limiting with age and improves with ELAM treatment. Relative phosphorylative capacity in the ascending aorta and arch (A) and DTA (B). Young NT (n=14), young ELAM (n=9), aged NT (n=17), and aged ELAM (n=13). 2-way ANOVA, Fisher’s least significant difference, * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001.

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  Figure 4:. Canonical senescent markers and the inflammatory enzyme MMP9 increase with age, and ELAM treatment reduces MMP9 expression. RT-qPCR of the murine thoracic aorta for the senescent markers p16 (A) and p21 (B). (C) Schematic of MMP9’s mechanism of action in the vascular extracellular matrix. (D) Expression level of MMP9 in the murine thoracic aorta. n=6 for all groups. 2-way ANOVA, Fisher’s least significant difference, * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001. (C) was created with BioRender.com.

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  Figure 5:. ELAM improves elastin breaks with age. Relative change of the aortic root (A) and ascending aorta (B) over the 8 week study period in young NT (n=10), young ELAM (n=9), aged NT (n=12), and aged ELAM mice (n=13). Histologic assessment of the frequency of elastin breaks (C) in the four treatments groups (n=5–6 per group) reveals a significant improvement in elastin breaks with ELAM treatment. 2-way ANOVA, Fisher’s least significant difference, * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001.

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  Figure 6:. ELAM affects the aortic transcriptome in an age-dependent manner. (A) Principal component (PC) analysis of the aortic transcriptome across the four treatment groups (n=6 per group). (B) Heat map showing the clustered expression level of genes with significant age by treatment interaction (ANOVA, FDR<0.05). Note the SenMayo genes demarcated by black hashes on the left side, and the significant difference between the aged control (NT) mice and the other treatment groups. The mean expression level of each of the SenMayo genes in young and aged mice are connected by lines in (C), and the mean expression level of each of the SenMayo genes in ELAM and control mice are connected by lines in (D). (E) The top ten most significant GO terms enriched by genes with age-treatment interaction.

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  Figure 7:. Proposed mechanism of age-related disease in the aorta. Bioenergetic derangements with age drive senescent expression and consequential inflammatory destruction of the aorta. ELAM blunts these inflammatory changes by improving the bioenergetic profile of the aging aorta. Created with BioRender.com.