Background: Abdominal aortic aneurysm (AAA) formation is associated with by inflammation
and matrix degradation. This study tested the hypothesis that calprotectin, a novel biomarker for
inflammation, as well as established biomarkers such as C-reactive protein (CRP) and matrix metalloproteinase-
9 (MMP-9) could also be indicative inflammatory biomarkers during AAA pathogenesis and
progression. We also evaluated the correlation of serum soluble Receptor for Advanced Glycation End
Products (sRAGE) with AAA diameter and serum calprotectin levels.
Materials and Methods: Rat abdominal aortas were perfused with porcine pancreatic elastase (AAA
Group) or saline (Control Group) and studied on post-perfusion days 7 and 14 (n=11 per treatment
group). Aneurysm was defined as a dilatation of the aorta above 150% of its original diameter. Laparotomy
was performed on days 0 (T0), 7 (T7) and 14 (T14) for aortic diameter measurement. At the same
time intervals, we measured the serum levels of calprotectin, CRP, sRAGE and MMP-9.
Results: All animals developed AAA and no rupture occurred. MMP-9 in AAA group at T14 (p<0.05
compared with T7 and p<0.005 compared with T0) and calprotectin in AAA group at T14 (p<0.001 compared
with T7 and T0) continued to significantly increase at all times. Serum sRAGE was significantly
lower in the AAA group compared with the control group and within AAA group at all time points
(p<0.001). On the other hand, the highest levels of CRP were identified at T7 in both groups. Calprotectin
concentrations in AAA group were significantly higher compared with controls at T7 and T14
(p<0.001 and p<0.001, respectively). Aortic diameter was significantly correlated with MMP-9 and
calprotectin serum concentrations at all time points (r=0.51, p<0.001; r=0.728, p<0.001 respectively).
Serum sRAGE levels were significantly correlated with aortic diameter at all time points (r=-0.48,
p<0.001) and serum calprotectin levels (r=-0.22, p<0.001).
Conclusion: This is the first evaluation of calprotectin as an AAA inflammation biomarker. It seems to
be a promising marker related to AAA natural history. Further experimental and large human studies are
needed to fully elucidate the role of calprotectin in the development and progression of AAAs.