TGFB1 and peripheral arterial disease: Separate analysis of the PAD patients alone (PAD-II and PAD-IV; N = 45) and the CTRL subjects alone (N = 20) revealed a significant correlation between TGF-β1 and collagen density in the PAD group (r = 0.854, p < 0.001), but not in the CTRL group (r = 0.119, p = 0.618), indicating that the pathological fibrosis in PAD is driven by TGF-β1 expression.