CDKN1A and cardiac hypertrophy: When control siRNA-treated hCMs were stimulated with Ang II, a known inducer of myocardial hypertrophy and premature senescence44, significantly increased gene expression of key senescence markers TP53 (p53) and CDKN1a (p21) was observed, whereas knockdown of IGFBP7 by siRNA abolished the increases (Fig. 6a).