RIPK1 and aneurysm: Interestingly, after treating Nec-1 for another 7 days, at the 8th day of elastase perfusion, smaller mean aortic expansion and marked reduction of macrophage infiltration and MMP9, which was produced primarily by inflammatory cells and plays important roles in aneurysm pathogenesis was observed, suggesting inhibition of RIPK1 can block progression in mice with pre-existing small AAAs.