[18F]Fluorothymidine Uptake in the Porcine Pancreatic Elastase-Induced Model of Abdominal Aortic Aneurysm

Abstract

The porcine pancreatic elastase (PPE) model is a common preclinical model of abdominal aortic aneurysms (AAA). Some notable characteristics of this model include the low aortic rupture rate, non-progressive disease course, and infra-renal AAA formation. Enhanced [¹⁸F]fluorothymidine ([¹⁸F]FLT) uptake on positron emission tomography/computed tomography (PET/CT) has previously been reported in the angiotensin II-induced murine model of AAA. Here, we report our preliminary findings of investigating [¹⁸F]FLT uptake in the PPE murine model of AAA. [¹⁸F]FLT uptake was found to be substantially increased in the abdominal areas recovering from the surgery, whilst it was not found to be significantly increased within the PPE-induced AAA, as confirmed using in vivo PET/CT and ex vivo whole-organ gamma counting (PPE, n = 7; controls, n = 3). This finding suggests that the [¹⁸F]FLT may not be an appropriate radiotracer for this specific AAA model, and further studies with larger sample sizes are warranted to elucidate the pathobiology contributing to the reduced uptake of [¹⁸F]FLT in this model.

Keywords: abdominal aorta; aneurysm; mice; positron emission tomography; radioactive tracer.

Figure 1

(a) Representative histological images of Ki67-stained aortic tissue from control and the PPE AAA model. Ki67 positivity is indicated by the brown colour, and a blue haematoxylin counterstain has been applied to aid visualisation. (b) Proportion of Ki67-positive nuclei in controls (n = 3) and in the PPE AAA model (n = 7). *** p < 0.001 on one-way ANOVA with post-hoc Bonferroni–Holm correction.

Figure 2

Aortic anterior–posterior diameters and volumes based on three-dimensional USS of 14-day PPE AAA vs. 14-day sham control aortae. ns: not significant on two-sample t test.

Figure 3

Coronal-view PET/CT images of static 14-day uptake of [¹⁸F]FLT 80 min post-radiotracer injection in all animals. Arrows indicate the abdominal aortic region. Colour scale bars indicate SUV thresholding to aid visualisation.

Figure 4

Decay-corrected ex vivo [¹⁸F]FLT counts per mass units. (a) All organs. (b) Uptake in the spleen and abdominal aorta normalised to uptake in the heart.