MMP2 and achalasia-alacrima syndrome: They provided fresh insights into AAA experimental design and guidelines for AAA prevention.[12–14] The authors from green clusters such as Thompson, RW and Newman, KM focused on the immune responses, and pathogenesis of AAA formation.[15–17] The authors from bule clusters such as Longo, Gm and Newby mainly focused on the role of MMPs in AAA research.[18,19] They found that deficiency of MMP-2 and MMP-9 could not result in AAA formation and prolonged administration of doxycycline was safe and reduced MMP-9 plasma level in patients with small asymptomatic AAAs.