TGF-β-inhibitor treatment reduced the incidence of clonal expansion in Confetti mice 7 days after MI in the border zone by 79 ± 19% compared to infarcted controls (p = 0.03; Supplementary Fig. 9), suggesting that mesenchymal activation contributes to endothelial expansion. Here, TGFB1 is linked to myocardial infarction.