KLF4 and triple-A syndrome: The current study shows that AB4, a saponin from Pulsatilla chinensis, (1) attenuated AAA pathogenesis, (2) prevented VSMC dedifferentiation and transdifferentiation to macrophage-like cells, (3) decreased vascular inflammation, (4) decreased MMP expression and activity, and (5) mechanistically, KLF4 overexpression attenuated the effects of AB4 on VSMC to macrophage-like cell transition and VSMC inflammation.