There are three isoforms of TGF-β, which all have effects on cell differentiation, proliferation, and apoptosis.45 Stimulation of VSMCs with TGF-β upregulates the mRNA and protein expression of α-SMA, SMMHC, and CNN while reducing proliferation.46 The mainstream view is that TGF-β is a protective factor for AAA. This evidence concerns the gene TGFB1 and triple-A syndrome.