Abstract Body (Do not enter title and authors here): Intro: Abdominal aortic aneurysm (AAA) is a prevalent condition in the elderly, with a significant risk of mortality if it ruptures. Despite this, there is currently no effective medical therapy to prevent AAA growth and rupture. The monocyte chemoattractant protein (MCP-1) / C-C chemokine receptor type 2 (CCR2) axis appears to play a role in AAA development. We demonstrated the potential of CCR2 as a theranostic marker for predicting AAA rupture, along with the effectiveness of a CCR2 inhibitor (RS-504393) in mitigating rupture. We further hypothesized that CCR2 inhibition can impact monocytes/macrophages trafficking in aortic tissue.
Mehtods: Sprague-Dawley rats (N=54) underwent intraluminal aortic exposure to porcine pancreatic elastase (PPE) to induce aneurysmal degeneration. To stimulate AAA rupture, rats also recieved β-aminopropionitrile (BAPN). After 3 days of PPE exposure, a group of rats with AAA were administered a CCR2 inhibitor (CCR2i) either daily until the end of the study (CCR2i Full), or discontinued at day 5 (CCR2i Short), while the remaining rats proceeded without intervention (Fig1A). Ultrasound (12MHz) was performed at 7&14 days to assess diameter, while another cohort of animals were euthanized at 6 days, prior to rupture, for single-cell RNA sequencing analysis. The relative content of inflammatory cells within the aortic tissue was analyzed.
Results: Both CCR2i Short and CCR2i Full treated, exhibited a significant reduction in AAA diameter at day 7 and 14 compared to controls (p<0.05; Fig1B&C). Notably, rats treated with CCR2i Full did not experience any AAA ruptures, while controls had a 56% risk of rupture. In contrast, CCR2i Short delayed the occurrence of ruptures without reducing the rupture rate (p<0.01; Fig1D). Single-cell RNA seq analysis of aortic tissue revealed that CCR2 inhibition led to a decrease in the number of recruited monocytes/macrophages. Cell recruitment was also relative to the duration of CCR2i treatment (Fig1E-G).
Conclusions: Our study findings highlight the impact of CCR2-targeting in reducing AAA growth and the risk of rupture. Interestingly, length of CCR2i was a crucial variable for AAA rupture prevention. Furthermore, treatment length impacted the relative recruitment of monocytes/macrophages to AAA tissue, highlighting the role these cells in AAA disease pathology. Future analysis of CCR2+ inflammatory cell subgroups may help elucidate how CCR2 mechanistically modulates AAA progression and rupture risk.