LRP1 and triple-A syndrome: Since the evidence for dysregulated LRP1–PDGFR-β signaling in aortic disease primarily derives from murine studies, we examined pathway activity and noted moderately higher levels of activated (Tyr1021-phosphorylated) PDGFR-β in AAA, compared with omental and tibial arteries, the caveat of different artery comparisons notwithstanding (Figure 4C, quantified in Supplemental Figure 6).