COL1A1 and heart failure: TGF-β1 caused an increase in expression of key fibrotic proteins COL1a1 (p = 0.0003, Figure 3), matrix metalloproteinase-2 (MMP2, p = 0.008) and osteoprotegerin (OPG, p = 0.021), and in heart failure-associated proteins insulin-like growth factor binding protein-7 (IGFBP7, p = 0.036) and growth differentiation factor-15 (GDF-15, p = 0.08).