MMP9 and triple-A syndrome: Mice lacking MMP-9 or MMP-2 are protected in elastase/CaCl2 models with preservation of matrix; deficiency or inhibition of cysteine cathepsins (K and S) likewise reduces elastin fragmentation and AAA burden; and deleting neutrophil elastase/proteinase-3 also suppresses AAAs and dampens downstream NET-driven inflammation [87,88,89,90].