Analysis of Inflammatory and Angiogenic Activities in Patients with Abdominal Aortic Aneurysms with the Radiotracers 99mTc-HYNIC-CCR2-L and 99mTc-RGD with Single-Photon Emission Computed Tomography.

BACKGROUND

The C-C chemokine receptor 2 (CCR2) drives macrophage recruitment in the abdominal aortic aneurysm (AAA) wall, and αvβ3 integrin plays a key role in angiogenesis at the aneurysm site. We aimed to evaluate the expression of CCR2 and αvβ3 integrin in patients with AAA utilizing single-photon emission computed tomography (SPECT) with the novel radiotracers technetium-99m-6-hydrazinylnicotinoyl-C-C-chemokine receptor-2 ligand (99mTc-HYNIC-CCR2-L) and technetium-99m-arginine-glycine-aspartic acid (99mTc-RGD).

METHODS

This in vivo pilot study included patients with atherosclerotic, asymptomatic, small AAA, and a history of smoking. Patients were then allocated to one of the 2 groups to analyze inflammation (99mTc-HYNIC-CCR2-L) or angiogenesis (99mTc-RGD). Radiotracer uptake with SPECT was based on the region of interest (ROI), expressed as counts per minute (cpm). We quantified inflammation and angiogenesis at aneurysmal and nondiseased or control aorta, and evaluated with the Wilcoxon signed rank and t-tests using GraphPad Prism software, version 9.0 (GraphPad Software Inc., Boston, MA, United States).

RESULTS

A total of 9 patients (77% males, mean age of 78 ± 8 years) were studied. In the inflammation group (n = 5), the ROI mean value of the aneurysm site was 44,442 cpm (standard error [SE]: 10,309 cpm; median 33,834 and range: 26,950-81,910 cpm), which was higher than that of the nondiseased aorta (mean ROI: 24,633 cpm; SE: 2,141 cpm; median 14,775 and range: 10,514-68,700 cpm) (P = 0.01). In the angiogenesis group (n = 4), we visualized a higher 99mTc-RGD uptake at the aneurysm site (mean ROI: 7,471 cpm; SE: 224 cpm; range: 7,042-8,102 cpm) compared to the control aorta (mean ROI: 7,347 cpm; SE: 238 cpm; range: 6,901-8,002 cpm) (P = 0.0001).

CONCLUSION

We detected increased inflammatory and angiogenic activity at the AAA site compared to the nondiseased aorta, as determined by SPECT. Further research with molecular imaging should address the pathophysiology of aneurysmal progression and rupture.